CMP-apparatus retainer ring and manufacturing method thereof, and CMP apparatus

Abstract

A retainer ring is provided which is capable of, effectively in practice, restraining the time taken for a break-in polish to the minimum. This retainer ring 8: is disposed inside of a holding head 4 in a CMP apparatus 1 which polishes a wafer W chemically and mechanically; has a ring shape so as to surround the periphery of the wafer W; presses a polish surface 3a of a polish pad 3; is made of an engineering plastic material such as PPS; and has a pressure surface 8a for pressing the polish surface 3a of the polish pad 3 whose surface roughness is a center-line average roughness (Ra) of 0.01 μm or below.

Description

TECHNICAL FIELD

The present invention relates to a CMP (or chemical mechanical polishing) apparatus which polishes a wafer chemically and mechanically. Particularly, it relates to a retainer ring which is provided on (attached to) the inside of a holding head of the CMP Apparatus and surrounds the periphery of the wafer.

BACKGROUND ART

As a semiconductor device has more highly integrated and has performed better, its measurements in the horizontal directions (on the plane) have shortened and the structure in the vertical directions has been fined down and multi-layered. In order to realize such a fine and multi-layered structure, a semiconductor substrate (such as a silicon substrate) needs to have a high flatness (evenness). Hence, the flatness has to be heightened at the stage of a wafer, and in response to this demand, a CMP Apparatus is used.

This CMP Apparatus is configured by, for example: a rotary base; a polish pad disposed on this base; and a holding head which holds a wafer and presses it onto the polish pad; a slurry supply nozzle; and the like. The holding head is formed by: a retainer ring which surrounds the periphery of the wafer; for example, an elastic film which pushes (presses) the upper surface of the wafer; an air chamber which is enclosed with this elastic film, the retainer ring and a head body; an air supply path which supplies air for pressurization into this air chamber. The retainer ring surrounds the periphery of the wafer and prevents the wafer from popping out. It also presses the polish surface of the polish pad, and flattens and fines down (suits) the polish surface of the polish pad which polishes the wafer. Hence, the retainer ring's pressure surface (surface for pressing the polish pad) needs to have a low surface roughness.

On the other hand, since such a retainer ring presses the polish pad, its pressure surface itself is supposed to be polished and worn off by the polish pad. This requires that the retainer ring be regularly replaced. However, if the retainer ring's pressure surface is rough, then a predetermined polishing performance, or a desirable flatness of a wafer, cannot be obtained. In the case where the retainer ring has been exchanged, therefore, before a product wafer (a wafer which is manufactured as a product) begins to be polished, a break-in (preparatory) polish needs to be given using a newly-attached retainer ring. Specifically, this new retainer ring is attached to the holding head of the CMP Apparatus and dozens of dummy wafers (break-in wafers) are polished. After it is ascertained that a suitable polishing performance has been obtained, for the first time, a polish is given to the product wafer. This break-in polishing requires a great deal of time and labor, thus lowering the production availability of wafers.

Taking this into account, in order to shorten the time taken for the break-in polishing, a retainer ring whose pressure surface is subjected to surface working (machining) so that it has a predetermined smoothness is known (e.g., refer to Patent Document 1). Specifically, in this retainer ring, its pressure surface is designed to have a surface roughness of 0.8 μm or below at the maximum height (Rmax). This makes it possible to dispense with such break-in polishing.

• Patent Document 1: Japanese Patent Laid-Open No. 2002-126995 specification

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, an extremely high flatness is necessary for a wafer, and such a high flatness cannot be satisfied with the retainer ring given in Patent Document 1 described above. Specifically, the pressure surface's surface roughness is some 0.8 μm at the maximum height, and thus, the polish pad's polish surface cannot be flattened and fined down desirably (up to a high level). Even if a wafer is polished with this polish pad, an extremely high flatness cannot be obtained. This requires, in practice, a break-in polish which takes a long time equivalent to the time taken conventionally. Besides, in terms of the surface roughness described in Patent Document 1, the smallest value is 0.6 μm at the maximum height. If the surface roughness is such a roughness level, a long-time break-in polish has to be given in the same way as the case of 0.8 μm. Incidentally, according to Patent Document 1, the pressure surface's surface roughness is set to 0.8 μm or below at the maximum height, so that a polishing rate and the polishing rate's uniformity within the surface can be enhanced. However, the polishing rate only expresses how fast (mm/min) a wafer can be polished, and thus, it is not supposed to indicate that a wafer can be polished so as to have a high flatness.

In addition, the flatness of a wafer polished by the CMP Apparatus depends upon the material of a retainer ring and its pressure surface's surface roughness. In other words, if the retainer ring's material and its pressure surface's surface roughness are specified, that makes it possible to polish a wafer to a high flatness. However, in Patent Document 1, no mention is made of a retainer ring's material. Hence, it is unclear whether a retainer ring made of a specific material can enjoy the advantage in that its pressure surface is set to have a surface roughness of 0.8 μm or below at the maximum height so that break-in polishing can be dispensed with.

As described so far, according to the retainer ring and disclosure contents given in Patent Document 1, not only break-in polishing cannot be saved, but also effectively in practice, the time taken for such break-in polishing cannot be kept down to the minimum.

Therefore, it is an object of the present invention to provide a retainer ring and a manufacturing method thereof which are capable of, effectively in practice, restraining the time taken for a break-in polish to the minimum.

Means for Solving the Problems

In order to attain the above described object, a CMP-apparatus retainer ring according to claim 1 which, in a CMP apparatus that includes a polish pad disposed on a base and a holding head holding a wafer and pressing the wafer against the polish pad and that polishes the wafer chemically and mechanically: is provided inside of the holding head; has a ring shape so as to surround the periphery of the wafer; and presses the polish surface of the polish pad, characterized in that: the retainer ring is made of an engineering plastic material; and the surface roughness of a pressure surface for pressing the polish surface of the polish pad is a center-line average roughness (arithmetic average roughness) of 0.01 μm or below.

A CMP-apparatus retainer ring according to claim 2, characterized in that, in the CMP-apparatus retainer ring according to claim 1: in the back surface of the retainer ring located at the back surface of the pressure surface, a portion to be held is formed; and the pressure surface is polished.

A CMP-apparatus retainer-ring manufacturing method according to claim 3 for, in a CMP apparatus that includes a polish pad disposed on a base and a holding head holding a wafer and pressing the wafer against the polish pad and that polishes the wafer chemically and mechanically, manufacturing an engineering-plastic retainer ring which is provided inside of the holding head, has a ring shape so as to surround the periphery of the wafer and presses the polish surface of the polish pad, characterized by including the steps of: working a shaped surface other than a pressure surface for pressing the polish surface of the polish pad so that the shaped surface has a predetermined measurement; holding the retainer ring without applying an external-circumference pressure and an internal-circumference pressure to the retainer ring; and machining the pressure surface in this state, and polishing the pressure surface until the surface roughness thereof becomes a center-line average roughness of 0.01 μm or below.

A CMP-apparatus retainer-ring manufacturing method according to claim 4, characterized in that, in the CMP-apparatus retainer-ring manufacturing method according to claim 3: the polish pad disposed on the base, a pressing means for rotating the retainer ring and pressing the pressure surface thereof against the polish pad and a slurry supplying means for supplying slurry to the polish pad are provided; and the polishing is conducted by a polishing apparatus which regulates a pressure and a rotational speed given by the pressing means and a slurry supply given by the slurry supplying means.

A CMP-apparatus retainer-ring manufacturing method according to claim 5, characterized in that, in the CMP-apparatus retainer-ring manufacturing method according to claim 4, before the polishing is conducted, break-in working is conducted by attaching a break-in retainer ring to the polishing apparatus.

A CMP-apparatus retainer-ring manufacturing method according to claim 6, characterized in that, in the CMP-apparatus retainer-ring manufacturing method according to any one of claims 3 to 5, the machining and the polishing are conducted with holding only the side of the back surface of the retainer ring located at the back surface of the pressure surface.

A CMP-apparatus retainer-ring manufacturing method according to claim 7, characterized in that, in the CMP-apparatus retainer-ring manufacturing method according to claim 6: a portion to be held is formed in the back surface of the retainer ring; the retainer ring is held by a machining jig which includes a holding portion that holds this portion to be held; and the machining is conducted in this state.

A CMP-apparatus retainer-ring manufacturing method according to claim 8, characterized in that, in the CMP-apparatus retainer-ring manufacturing method according to claim 7: the machining jig holding the retainer ring is supported by a polishing jig which supports the side of the back surface of the machining jig located at the back surface of the holding portion; and the polishing is conducted in this state.

A CMP-apparatus retainer-ring machining jig according to claim 9 which is the machining jig used in the CMP-apparatus retainer-ring manufacturing method according to claim 7, characterized in that the machining jig: has a flat-board shape; and in an attachment surface which comes into surface contact with the back surface of the retainer ring, includes the holding portion which holds the portion to be held that is formed in the back surface of the retainer ring.

A CMP-apparatus retainer-ring machining jig according to claim 10 which is the polishing jig used in the CMP-apparatus retainer-ring manufacturing method according to claim 8, characterized in that the polishing jig: has a flat-board shape; and includes a concave supporting portion which houses the side of the back surface of the machining jig located at the back surface of the attachment surface, is fitted to the peripheral surface of the machining jig and supports the back surface of the machining jig.

A CMP apparatus according to claim 11 which: includes a polish pad disposed on a base and a holding head that holds a wafer and presses the wafer against the polish pad, this holding head having a retainer ring which has a ring shape so as to surround the periphery of the wafer and presses the polish surface of the polish pad; and polishes the wafer chemically and mechanically, characterized in that: the retainer ring is made of an engineering plastic material; and the surface roughness of a pressure surface of the retainer ring for pressing the polish surface of the polish pad is set at a center-line average roughness of 0.01 μm or below.

Advantages of the Invention

In the CMP-apparatus retainer ring according to claim 1, which is made of engineering plastics, its pressure surface's surface roughness is a center-line average roughness of 0.01 μm or below. Therefore, in practice, the time taken for a break-in polish can be effectively restrained to the minimum. Specifically, in this retainer ring, the pressure surface's surface roughness indicates an extremely small value of 0.01 μm or below. Thereby, from immediately after the retainer ring has been attached to the holding head of the CMP apparatus, the polish pad's polish surface is flattened and fined down desirably (up to a high level) with the retainer ring's pressure surface. This helps obtain a suitable polishing performance, in other words, polish a wafer to an extremely high flatness, without giving any break-in polish or only by giving a short-time (minimal) break-in polish. As a result, the time and labor taken for such a break-in polish can be kept down to the minimum. Effectively in practice, this makes it possible to enhance the production availability of wafers. Besides, the time taken for a break-in polish comes to the minimum, so that polish scrap produced through the break-in polish can be reduced, scratches on a wafer by such polish scrap are less likely, or impurities are less likely to adhere to a wafer. Consequently, the production quality of a wafer becomes higher and more stable, thus decreasing the number of defective products and enhancing the productivity further.

In the CMP-apparatus retainer ring according to claim 2, the portion to be held of the back surface is held, so that the retainer ring can be held without deforming the pressure surface. Therefore, polishing is conducted with held in this state, thus helping make the pressure surface's surface roughness extremely fine.

In the CMP-apparatus retainer-ring manufacturing method according to claim 3, after the shaped surface other than the pressure surface is wrought so as to have a predetermined measurement, the pressure surface is machined and polished (lapped). Therefore, the pressure surface which has undergone machining or the like is not deformed in the following working. Furthermore, it is subjected to machining or the like in a state where the retainer ring is held without given an external-circumference pressure and an internal-circumference pressure. This prevents such a hold from deforming the pressure surface. Moreover, through machining (such as cutting and grinding), the pressure surface's flatness and surface roughness reach a specific measurement (level), and thereafter, polishing is conducted. This helps conduct such polishing desirably. As a result, the pressure surface can be finished off so as to have a high flatness and an extremely-low surface roughness.

In the CMP-apparatus retainer-ring manufacturing method according to claim 4, in accordance with the material or size of the retainer ring, the kind of slurry (abrasive) or the like, the pressure or the rotational speed by the pressing means, or the slurry supply, is regulated. Therefore, the retainer ring's pressure surface can be polished to a high flatness and an extremely-low surface roughness.

In the CMP-apparatus retainer-ring manufacturing method according to claim 5, break-in working is conducted, so that the polish pad (such as a cloth) of the polishing apparatus is suited (flattened and fined down) and stabilized. Therefore, in the following polishing, the retainer ring's pressure surface can be wrought well (so as to have a high flatness and an extremely-low surface roughness).

In the CMP-apparatus retainer-ring manufacturing method according to claim 6, the machining and the polishing are conducted with holding only the side of the back surface of the retainer ring. Therefore, this hold can be prevented from deforming the pressure surface, thus working the pressure surface desirably.

In the CMP-apparatus retainer-ring manufacturing method according to claim 7, the portion to be held which is formed in the back surface of the retainer ring is held, and in this state, the pressure surface is machined. Therefore, the retainer ring's hold can be prevented from deforming the pressure surface, thus machining the pressure surface desirably.

In the CMP-apparatus retainer-ring manufacturing method according to claim 8, the side of the back surface of the machining jig which holds the retainer ring is supported by the polishing jig. Therefore, this support can be prevented from deforming the retainer ring's pressure surface. Besides, the polishing can be conducted in a state where the retainer ring is held on the machining jig. In other words, the machining and the polishing can be continuously conducted without removing the retainer ring from the machining jig. This helps maintain the machining jig's holding accuracy and holding stability. As a result, the pressure surface can be properly polished.

In the CMP-apparatus retainer-ring machining jig according to claim 9, the portion to be held which is formed in the back surface of the retainer ring is held by the machining jig. Therefore, this hold can be prevented from deforming the retainer ring's pressure surface. In addition, the back surface of the retainer ring comes into surface contact with the attachment surface of the machining jig, and in this state, the retainer ring is held on the machining jig. Consequently, at the time of machining, the retainer ring's pressure surface becomes more stable. As a result, the pressure surface can be appropriately machined.

In the CMP-apparatus retainer-ring polishing jig according to claim 10, the side of the back surface of the machining jig which holds the retainer ring is supported by the polishing jig. Therefore, this support can be prevented from deforming the retainer ring's pressure surface. Besides, the polishing can be conducted in a state where the retainer ring is held on the machining jig. Besides, the supporting portion is fitted to the peripheral surface of the machining jig, so that the machining jig (the retainer ring) can be prevented from shifting sideward. Simultaneously, it supports the back surface of the machining jig (the back surface of the retainer ring), so that a working force applied to the retainer ring's pressure surface is properly supported. This helps stabilize the pressure surface at the time of polishing. As a result, the pressure surface can be suitably polished.

In the CMP apparatus according to claim 11, in terms of the retainer ring, its pressure surface's surface roughness is set to a center-line average roughness of 0.01 μm or below. Therefore, in practice, the time taken for a break-in polish can be effectively restrained to the minimum. Specifically, in this retainer ring, the pressure surface's surface roughness indicates an extremely small value of 0.01 μm or below. Thereby, from immediately after the retainer ring has been attached to the holding head, the polish pad's polish surface is flattened and fined down desirably with the pressure surface. This helps obtain a suitable polishing performance, without giving any break-in polish or only by giving a short-time break-in polish. As a result, the time and labor taken for such a break-in polish can be kept down to the minimum. Effectively in practice, this makes it possible to enhance the production availability of wafers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a CMP apparatus according to an embodiment of the present invention, showing a schematic configuration thereof.

FIG. 2 is a schematic sectional view of a holding head of the CMP apparatus according to the embodiment of the present invention.

FIGS. 3(a) and 3(b) are a plan view and a side sectional view, respectively, of a CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 4 is a table, showing a manufacturing process flow for the CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 5 is a front view (partial sectional view) of a machining jig for working ahead of polishing (machining) the CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 6 is a sectional view of a polishing jig for polishing the CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 7 is a table, showing a measurement result or the like of the surface roughness of a pressure surface of the CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 8 is an illustration, showing measurement points for the surface roughness of the pressure surface of the CMP-apparatus retainer ring according to the embodiment of the present invention.

FIG. 9 is a table, showing a measurement result of the surface roughness of the pressure surface of the CMP-apparatus retainer ring according to the embodiment of the present invention.

BEST MODE FOR IMPLEMENTING THE INVENTION

Hereinafter, a CMP-apparatus retainer ring according to an embodiment of the present invention will be described with reference to the attached drawings.

FIG. 1 is a front view of a CMP apparatus 1 according to the embodiment of the present invention, showing a schematic configuration thereof. This CMP apparatus 1 has a configuration equivalent to a CMP apparatus which is widely used in general, apart from a retainer ring 8 (described later). Herein, a detailed description is omitted. It includes: a base 2 which can be rotated; a polish pad 3 (such as a cloth) which is disposed on this base 2; a holding head 4; a slurry supply nozzle 5 (a slurry supplying means); and a dresser 6 (a dressing means). It polishes a wafer W chemically and mechanically.

The holding head 4 holds the wafer W and presses its surface W1 to be polished against the polish pad 3. It is designed to move on the polish pad 3 while rotating. This holding head 4 is, as shown in FIG. 2, provided with: a head body 7; the retainer ring 8 which is disposed under this head body 7; and an elastic film 9 which is located inside of this retainer ring 8 and presses an upper surface W2 of the wafer W. Then, an air chamber 10 is enclosed with the head body 7, the retainer ring 8 and the elastic film 9, and air for pressurization is supplied into this air chamber 10. Via the elastic film 9, the holding head 4 presses the wafer W onto the polish pad 3.

The retainer ring 8 surrounds the periphery of the wafer W and prevents the wafer W from popping out of the holding head 4. It also presses a polish surface 3a of the polish pad 3, and flattens and fines down (suits) the polish surface 3a (the part which comes into surface contact with the polished surface W1 of the wafer W) of the polish pad 3 which polishes the wafer W. Specifically, the polish surface 3a of the polish pad 3 becomes so as that its flatness is low and the surface roughness is rough with using slurry 5a (abrasive). Hence, the retainer ring 8 enhances this polish surface 3a's flatness and lowers the surface roughness.

In consideration of chemical resistance, mechanical properties or the like, this retainer ring 8 is made of a PPS (polyphenylene sulfide, engineering plastic) material. It has, as shown in FIG. 3, a ring shape. In a pressure surface 8a for pressing the polish surface 3a of the polish pad 3, a plurality of slits 8b are formed which are each shaped like a groove for allowing polish scrap to escape (discharge). In a back surface 8c of the retainer ring 8 located at the back surface of the pressure surface 8a, a plurality of screw inserts 8d (portions to be held) each of which has a female thread 8e are inserted. In other words, such a screw insert 8d is substantially cylindrical, and a male thread is formed in its external-circumference part and the female thread 8e is formed in its internal-circumference part. In addition, the pressure surface 8a's surface roughness is set (the surface is polished) to a center-line average roughness (arithmetic average roughness, Ra) of 0.01 μm or below.

Next, the method of manufacturing the retainer ring 8 having such a configuration will be described based on a process flow shown in FIG. 4.

First, in a first process, a PPS blank is roughly cut into a shape near the final shape and measurements. Next, tapping (female-thread formation) is conducted on the side of the back surface 8c (Process 2), and into this tap, the screw insert 8d is screwed (inserted, Process 3). Sequentially, cutting is conducted so that the internal diameter becomes a predetermined measurement (Process 4). Thereafter, cutting is conducted on the sides of the pressure surface 8a and the back surface 8c so that the retainer ring 8's height (thickness) becomes a predetermined measurement (Process 5). Afterward, cutting is conducted so that the external diameter becomes a predetermined measurement (Process 6) and milling is conducted so that the slits 8b are formed on the side of the pressure surface 8a (Process 7). Then, burrs produced in such working are removed (Process 8) and cutting is conducted again on the side of the back surface 8c (Process 9). At this time, in the cutting, it is shallowly cut so that the flatness becomes higher on the side of the back surface 8c. Through Process 1 to Process 9 described above, the shaped surfaces other than the pressure surface 8a are wrought so as to have the predetermined measurements.

Sequentially, using such a machining jig 11 as shown in FIG. 5, the pressure surface 8a of the retainer ring 8 is wrought ahead of a polish (machined) (Process 10). This machining jig 11 is made of stainless steel and is shaped like a disk (a flat board). Its external diameter is almost equal to the external diameter of the retainer ring 8. Besides, bolt holes 11c are formed in the same positions (at the same pitch) as the screw inserts 8d of the retainer ring 8. Through such a bolt hole 11c, a bolt 12 (a holding portion) is inserted from the side of a back surface 11b to the side of an attachment surface 11a. With this attachment surface 11a of the machining jig 11, the back surface 8c of the retainer ring 8 comes into surface contact, and the bolt 12 is tightened on the screw inserts 8d. Thereby, without applying an external-circumference pressure and an internal-circumference pressure to the retainer ring 8, the retainer ring 8 is held by the machining jig 11. Next, the peripheral part of the machining jig 11 is grasped by the chuck of a lathe, and the pressure surface 8a of the retainer ring 8 is subjected to surface cutting in the lathe. At this time, it is shallowly cut and the rotation is slowed in the lathe so that the pressure surface 8a has a high flatness and a low surface roughness. Incidentally, in this embodiment, the pressure surface 8a is cut by the lathe, but in accordance with the retainer ring 8's material, hardness or the like, some other machining such as grinding may also be conducted.

After this, without detaching the retainer ring 8 from the machining jig 11, using such a polishing jig 13 as shown in FIG. 6, the pressure surface 8a of the retainer ring 8 is polished (Process 11). This polishing jig 13 is made of poly-vinyl chloride and is shaped like a disk (a flat board). In its central part, a concave supporting portion 13a is formed. This supporting portion 13a's internal diameter is almost equal to the machining jig 11's external diameter, so that it can be fitted exactly to the machining jig 11's peripheral surface. In this supporting portion 13a, the side of the back surface 11b of the machining jig 11 is housed (inserted). Thereby, the back surface 11b of the machining jig 11 is supported on a bottom surface 13b of the supporting portion 13a. On this bottom surface 13b, a protective cloth 14 is provided which protects the machining jig 11. This polishing jig 13 supports the machining jig 11 holding the retainer ring 8, and in this state, the pressure surface 8a is polished.

This polishing is conducted by a polishing apparatus (a lapping machine, a polishing machine) which has a configuration equivalent to the above described CMP apparatus 1. Specifically, this polishing apparatus includes: a polish pad (equivalent to the polish pad 3) which is disposed on a base; a pressing means (equivalent to the holding head 4) which presses the pressure surface 8a against the polish pad while rotating the retainer ring 8; and a slurry supplying means (equivalent to the slurry supply nozzle 5) which supplies slurry to the polish pad. It is designed to regulate a pressure and a rotational speed given by the pressing means, a slurry supply given by the slurry supplying means, and the like. In accordance with the retainer ring 8's material quality (such as hardness) or size, the kind of slurry (abrasive) or the like, polishing conditions are regulated such as the pressure or the rotational speed by the pressing means and the slurry supply. Then, the pressure surface 8a of the retainer ring 8 is polished. As those polishing conditions, an example is specifically given below.

Slurry 5a; CO (diluent is a cerium system) and the particle diameter is 2 μm

• • Supply of slurry; 500-1000 ml/min.
  • Temperature of a base; 24-26□ (the cooling-water temperature of a base)
  • Pressure by the pressing means; 0.2 kgf/cm²
  • Rotational speed by the pressing means; 50 rpm

In this polishing apparatus, before the retainer ring 8 is polished, break-in working is conducted by attaching a break-in retainer ring (a dummy retainer ring) thereto. Through this break-in working, the polish pad of the polishing apparatus is suited (flattened and fined down) and stabilized. After this break-in working, the retainer ring 8 is polished on the above described polishing conditions until the pressure surface 8a's surface roughness becomes a center-line average roughness of 0.01 μm or below.

After this polishing, polish scrap is cleared away by means of an air blow, and each part is measured (Process 12). Then, the retainer ring 8 which has the predetermined measurements and surface roughness undergoes an ultrasonic cleaning (Process 13). This puts an end to the manufacturing process.

Next, in the retainer ring 8 which has been produced through the above described manufacturing process, a measurement result of the pressure surface 8a's surface roughness will be described. FIG. 7 shows this measurement result, and the measurement is conducted in the following measuring instrument and under measurement conditions. Herein, measurement points A, B are positions shown in FIG. 8.

Measuring instrument; Surftest SV-3000S4 (a contact-point type surface-roughness measuring instrument) by Mitsutoyo Corporation

• • Standard; OLDMIX
  • Evaluation curve type; R
  • Reference length; 0.8 mm
  • Interval function; 5
  • Ac (a cut-off value); 0.8 mm
  • Filter type; Gaussian
  • Evaluation length; 4.0 mm
  • Entrance length; 0.4 mm
  • Exit length; 0.3985 mm
  • Smooth connection; Off
  • Average line correction at the time of a parameter calculation; Off

In FIG. 7, the values of Sample 1 are a measurement result of this retainer ring 8, and at both the measurement points A, B, the surface roughness is a center-line average roughness (Ra) of 0.01 μm. In terms of the maximum height (Ry), it is 0.080 μm at the measurement point A and 0.108 μm at the measurement point B. Hence, in this retainer ring 8, the pressure surface 8a's surface roughness is far lower than the retainer ring's surface roughness (some 0.8 μm at the maximum height) given in Patent Document 1 described above. On the other hand, when the pressure surface of the same retainer ring (with the same material, the same measurements) as this retainer ring 8 is polished (lapped) by hand, a measurement result of its surface roughness is given by the values of Sample 2 in FIG. 7. In respect of the center-line average roughness, it is 0.220 μm at the measurement point A and 0.201 μm at the measurement point B. In respect of the maximum height, it is 1.776 μm at the measurement point A and 1.923 μm at the measurement point B. Incidentally, in the case of a metal product (metal working), if its surface roughness is a center-line average roughness of 0.01 μm or below, this surface is said to be mirror-finished. In this retainer ring 8, the pressure surface 8a's surface roughness is 0.01 μm or below, and thus, it is supposed to be a mirror-finished surface in a metal product. In FIG. 7, a surface roughness “Rq” is a square average square-root roughness; “Rz” is a ten-point average roughness; “Rc” is an average concave-convex height; “Rp” is a maximum peak height; “Rv” is a maximum valley depth; and “Rt” is a maximum section height.

As described above, in this retainer ring 8, the pressure surface 8a's surface roughness is a center-line average roughness of 0.01 μm or below. It is extremely low, and thus, when this retainer ring 8 is attached to a CMP apparatus, in practice, the time taken for a break-in polish can be effectively restrained to the minimum. Specifically, because the pressure surface 8a's surface roughness is extremely low, from immediately after this retainer ring 8 has been attached to the holding head 4 of the CMP apparatus 1, the polish pad 3's polish surface 3a is flattened and fined down desirably (up to a high level) with the pressure surface 8a. This helps obtain a suitable polishing performance, in other words, polish the polished surface W1 of the wafer W to an extremely high flatness, without giving any break-in polish or only by giving a short-time (minimal) break-in polish. As a result, the time and labor taken for such a break-in polish can be kept down to the minimum. Effectively in practice, this makes it possible to enhance the production availability of the wafer W.

For example, in a conventional retainer ring whose pressure surface is rough, before the product wafer W (a wafer which is manufactured as a product) begins to be polished, external preparation and a break-in polish have to be given. Specifically, in the external preparation, this retainer ring is roughly cut for approximately ten minutes by a dedicated polishing apparatus (a polishing machine). Thereafter, it is polished and finished for about fifteen minutes by another dedicated polishing apparatus and is cleaned for some twenty minutes with ultrasonic waves. Then, in a break-in polish, the retainer ring is attached to the holding head 4, and twenty or more dummy wafers (break-in wafers) are polished. Then, it has to be ascertained that a suitable polishing performance has been obtained. In contrast, in the retainer ring 8 according to the present invention, the pressure surface 8a's surface roughness is extremely low, and thus, there is no need to conduct such external preparation. Besides, even though it depends somewhat upon the CMP apparatus l's working accuracy (processing precision), the polish pad 3's type or conditions (such as a flatness) or the like, without giving any break-in polish or only by giving a break-in polish for several minutes immediately after this retainer ring 8 has been attached to the holding head 4, the polished surface W1 of the wafer W can be polished to an extremely high flatness. Incidentally, the conventional retainer ring's pressure surface is cut, for example, only by a lathe. Hence, its surface roughness is a center-line average roughness of around 3.0 μm.

Furthermore, the time taken for a break-in polish is minimized. Therefore, polish scrap produced through the break-in polish is reduced, scratches on the wafer W by such polish scrap are less likely, or impurities are less likely to adhere to it. Consequently, the production quality of the wafer W becomes higher and more stable, thus decreasing the number of defective products and enhancing the productivity further.

Herein, in this retainer ring 8, the pressure surface 8a's surface roughness is a center-line average roughness of 0.01 μm or below. It is extremely low because of such a manufacturing process as described earlier. Specifically, first, through Process 1 to Process 9, the shaped surfaces other than the pressure surface 8a are wrought so as to have the predetermined measurements. Thereafter, the pressure surface 8a is wrought ahead of a polish (Process 10) and is polished (Process 11). This prevents the pressure surface 8a after wrought from undergoing some change in its shape. In other words, if another shaped surface is wrought after the pressure surface 8a has been wrought so as to have a predetermined measurement or the like, the pressure surface 8a may be deformed to change its measurements or the like. In this manufacturing process, however, such a deformation can be evaded.

Moreover, with holding the retainer ring 8 without applying any external-circumference pressure and internal-circumference pressure to the retainer ring 8, it is wrought ahead of a polish and is polished. Thereby, some hold can be prevented from deforming the pressure surface 8a. Specifically, in the working ahead of polishing (pre-polish working, Process 10), the bolt 12 of the machining jig 11 is tightened on the screw inserts 8d of the retainer ring 8, so that the retainer ring 8 can be held on the machining jig 11. Therefore, the pressure surface 8a will not be deformed by this hold. Besides, the back surface 8c of the retainer ring 8 is supported on the attachment surface 11a of the machining jig 11. This stabilizes the pressure surface 8a of the retainer ring 8 while being wrought ahead of a polish. As a result, the pressure surface 8a is wrought ahead of a polish desirably (up to a high flatness and a low surface roughness). Then, through this working ahead of polishing, the pressure surface 8a's flatness and surface roughness reach a specific measurement (level), and thereafter, polishing is conducted. This makes it possible to finish off (polish) the pressure surface 8a so that it has a high flatness and an extremely-low surface roughness.

In addition, in the following polishing (Process 11), the side of the back surface 11b of the machining jig 11 holding the retainer ring 8 is supported on the polishing jig 13. Therefore, the pressure surface 8a of the retainer ring 8 will not be deformed by this hold. Besides, the supporting portion 13a of the polishing jig 13 is fitted to the machining jig 11's peripheral surface. This helps prevent the machining jig 11 (the retainer ring 8) from slipping laterally. Besides, the back surface 11b of the machining jig 11 (the back surface 8c of the retainer ring 8) is supported on the bottom surface 13b of the supporting portion 13a. Thereby, a working force (a polishing force) applied to the retainer ring 8's pressure surface 8a is appropriately supported. This helps stabilize the pressure surface 8a at the time of polishing. Further, the polishing can be conducted in a state where the retainer ring 8 is held on the machining jig 11. In other words, the working ahead of polishing and the polishing can be continuously conducted without removing the retainer ring 8 from the machining jig 11. This helps maintain the machining jig 11's holding accuracy and holding stability. As a result, the pressure surface 8a can be polished up to a high flatness and an extremely-low surface roughness.

Furthermore, in the polishing, as described earlier, in accordance with the material or size of the retainer ring 8, the kind of the slurry 5a or the like, the pressure or the rotational speed by the pressing means, the slurry supply or the like is regulated. Therefore, the retainer ring 8's pressure surface 8a can be polished to a high flatness and an extremely-low surface roughness. Besides, before the retainer ring 8 is polished, break-in working is conducted using a break-in retainer ring. Through this break-in working, the polish pad of the polishing apparatus is suited (flattened and fined down) and stabilized. After the break-in working, the retainer ring 8's pressure surface 8a is polished, and thus, the pressure surface 8a can be wrought well (so as to have a high flatness and an extremely-low surface roughness).

As a result, in the retainer ring 8, the pressure surface 8a's surface roughness can be polished (finished off) up to an extremely low value, or a center-line average roughness of 0.01 μm or below.

Incidentally, in this embodiment, the retainer ring 8 is made of PPS, but it may also be another kind of engineering plastics, such as PEEK (polyether etherketone), PET (polyethylene terephthalate), POM (polyacetals) and PI (polyimide). In the same way as the retainer ring 8 according to this embodiment, its pressure surface's surface roughness can be set to a center-line average roughness of 0.01 μm or below. For example, a retainer ring is made of a PEEK material, is subjected to the same manufacturing process as described earlier, and its pressure surface's surface roughness is measured. This measurement result is shown in Sample 3 of FIG. 7. Consequently, at both the measurement points A, B, the surface roughness is a center-line average roughness of 0.009 μm. In terms of the maximum height, it is 0.076 μm at the measurement point A and is 0.074 μm at the measurement point B. Hence, in the retainer ring 8 made of a PEEK material, its surface roughness is slightly lower than the retainer ring 8 according to this embodiment which is made of a PPS material. Because the hardness of a PEEK material is a little higher (harder) than that of a PPS material. The values of Sample 4 in FIG. 7 indicate a measurement result of the PEEK-made retainer ring's surface roughness when the pressure surface is polished by hand.

Moreover, if a pressure surface is polished using slurry whose particle diameter is smaller, the pressure surface's surface roughness becomes lower. For example, in a retainer ring made of a PPS material, its pressure surface is polished with slurry which has a particle diameter of 1.2 μm. In this case, as shown in FIG. 9, a lower surface roughness is obtained. For example, in terms of the center-line average roughness, it is 0.004 μm at the measurement point A and is 0.005 μm at the measurement point B. In terms of the maximum height, it is 0.049 μm at the measurement point A and is 0.051 μm at the measurement point B. Hence, if the particle diameter of slurry is set to be smaller in accordance with the material or hardness of a retainer ring, its pressure surface's surface roughness can be reduced further. In FIG. 9, measurement points C, D, E are measurement positions shown in FIG. 8.

INDUSTRIAL APPLICABILITY

As describe so far, a CMP-apparatus retainer ring according to the present invention is extremely useful as a retainer ring which is capable of restraining the time taken for a break-in polish to the minimum, as well as enhancing and stabilizing the production quality of a wafer.

Claims

1. A CMP-apparatus retainer ring which, in a CMP apparatus that includes a polish pad disposed on a base and a holding head holding a wafer and pressing the wafer against the polish pad and that polishes the wafer chemically and mechanically: is provided inside of the holding head; has a ring shape so as to surround the periphery of the wafer; and presses the polish surface of the polish pad, characterized in that:

the retainer ring is made of an engineering plastic material; and the surface roughness of a pressure surface for pressing the polish surface of the polish pad is a center-line average roughness of 0.01 μm or below.

2. The CMP-apparatus retainer ring according to claim 1, characterized in that: in the back surface of the retainer ring located at the back surface of the pressure surface, a portion to be held is formed; and the pressure surface is polished.

3. A CMP-apparatus retainer-ring manufacturing method for, in a CMP apparatus that includes a polish pad disposed on a base and a holding head holding a wafer and pressing the wafer against the polish pad and that polishes the wafer chemically and mechanically, manufacturing an engineering-plastic retainer ring which is provided inside of the holding head, has a ring shape so as to surround the periphery of the wafer and presses the polish surface of the polish pad, characterized by including the steps of:

working a shaped surface other than a pressure surface for pressing the polish surface of the polish pad so that the shaped surface has a predetermined measurement;

holding the retainer ring without applying an external-circumference pressure and an internal-circumference pressure to the retainer ring; and

machining the pressure surface in this state, and polishing the pressure surface until the surface roughness thereof becomes a center-line average roughness of 0.01 μm or below.

4. The CMP-apparatus retainer-ring manufacturing method according to claim 3, characterized in that: the polish pad disposed on the base, a pressing means for rotating the retainer ring and pressing the pressure surface thereof against the polish pad and a slurry supplying means for supplying slurry to the polish pad are provided; and the polishing is conducted by a polishing apparatus which regulates a pressure and a rotational speed given by the pressing means and a slurry supply given by the slurry supplying means.

5. The CMP-apparatus retainer-ring manufacturing method according to claim 4, characterized in that before the polishing is conducted, break-in working is conducted by attaching a break-in retainer ring to the polishing apparatus.

6. The CMP-apparatus retainer-ring manufacturing method according to any one of claims 3 to 5, characterized in that the machining and the polishing are conducted with holding only the side of the back surface of the retainer ring located at the back surface of the pressure surface.

7. The CMP-apparatus retainer-ring manufacturing method according to claim 6, characterized in that: a portion to be held is formed in the back surface of the retainer ring; the retainer ring is held by a machining jig which includes a holding portion that holds this portion to be held; and the machining is conducted in this state.

8. The CMP-apparatus retainer-ring manufacturing method according to claim 7, characterized in that: the machining jig holding the retainer ring is supported by a polishing jig which supports the side of the back surface of the machining jig located at the back surface of the holding portion; and the polishing is conducted in this state.

9. A CMP-apparatus retainer-ring machining jig which is the machining jig used in the CMP-apparatus retainer-ring manufacturing method according to claim 7, characterized in that,

the machining jig: has a flat-board shape; and in an attachment surface which comes into surface contact with the back surface of the retainer ring, includes the holding portion which holds the portion to be held that is formed in the back surface of the retainer ring.

10. A CMP-apparatus retainer-ring polishing jig which is the polishing jig used in the CMP-apparatus retainer-ring manufacturing method according to claim 8, characterized in that,

the polishing jig: has a flat-board shape; and includes a concave supporting portion which houses the side of the back surface of the machining jig located at the back surface of the attachment surface, is fitted to the peripheral surface of the machining jig and supports the back surface of the machining jig.

11. A CMP apparatus which: includes a polish pad disposed on a base and a holding head that holds a wafer and presses the wafer against the polish pad, this holding head having a retainer ring which has a ring shape so as to surround the periphery of the wafer and presses the polish surface of the polish pad; and polishes the wafer chemically and mechanically, characterized in that:

the retainer ring is made of an engineering plastic material; and the surface roughness of a pressure surface of the retainer ring for pressing the polish surface of the polish pad is set at a center-line average roughness of 0.01 μm or below.