Backing plate assembly

Abstract

In certain embodiments, the invention comprises a backing plate for accommodating large area sputtering targets is disclosed. The backing plate assembly has cavities carved into the back surface of the backing plate. The backing plate may further include cooling channels that run through the backing plate to control the temperature of the backing plate and the target. The cavities may be filled with a material that has a lower density than the backing plate. Additionally, the entire back surface may be covered with the material to produce a smooth surface upon which a magnetron may move during a PVD process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/426,271 (APPM/011105), filed Jun. 23, 2006, which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a backing plate assembly for a physical vapor deposition (PVD) apparatus.

2. Description of the Related Art

PVD using a magnetron is one method of depositing material onto a substrate. During a PVD process a target may be electrically biased so that ions generated in a process region can bombard the target surface with sufficient energy to dislodge atoms from the target. The process of biasing a target to cause the generation of a plasma that causes ions to bombard and remove atoms from the target surface is commonly called sputtering. The sputtered atoms travel generally toward the substrate being sputter coated, and the sputtered atoms are deposited on the substrate. Alternatively, the atoms react with a gas in the plasma, for example, nitrogen, to reactively deposit a compound on the substrate. Reactive sputtering is often used to form thin barrier and nucleation layers of titanium nitride or tantalum nitride on the substrate.

Direct current (DC) sputtering and alternating current (AC) sputtering are forms of sputtering in which the target is biased to attract ions towards the target. The target may be biased to a negative bias in the range of about −100 to −600 V to attract positive ions of the working gas (e.g., argon) toward the target to sputter the atoms. Usually, the sides of the sputter chamber are covered with a shield to protect the chamber walls from sputter deposition. The shield may be electrically grounded and thus provide an anode in opposition to the target cathode to capacitively couple the target power to the plasma generated in the sputter chamber.

To deposit thin films over large area substrates such as glass substrates, flat panel display substrates, solar panel substrates, and other suitable substrates, a sputtering target, and hence, the backing plate must be of substantial size. As backing plates increase in size, the weight of the backing plate may also increase.

Therefore, there is a need in the art for large area backing plates that can be used in PVD chambers for large area substrates.

SUMMARY OF THE INVENTION

In certain embodiments, the invention comprises a backing plate for accommodating large area sputtering targets is disclosed. The backing plate assembly has cavities carved into the back surface of the backing plate. The backing plate may further include cooling channels that run through the backing plate to control the temperature of the backing plate and the target. The cavities may be filled with a material that has a lower density than the backing plate. Additionally, the entire back surface may be covered with the material to produce a smooth surface upon which a magnetron may move during a PVD process.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 is a top view of a backing plate assembly 100 having cavities 102 formed therein.

FIG. 2 is a cross sectional view of a backing plate assembly 200 according to another embodiment of the invention.

FIG. 3 is a top view of a backing plate assembly 300 with cavities 304 filled with material 312.

FIG. 4 is a cross sectional view of a backing plate assembly 400 according to another embodiment of the invention.

FIG. 5 is a cross sectional view of a backing plate assembly 500 having a magnetron plate 514 positioned behind the backing plate.

FIG. 6 is a cross sectional view of an apparatus 600 according to another embodiment of the invention.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized in other embodiments without specific recitation.

DETAILED DESCRIPTION

In certain embodiments, the invention comprises a backing plate for accommodating large area sputtering targets is disclosed. The backing plate assembly has cavities carved into the back surface of the backing plate. The backing plate may further include cooling channels that run through the backing plate to control the temperature of the backing plate and the target. The cavities may be filled with a material that has a lower density than the backing plate. Additionally, the entire back surface may be covered with the material to produce a smooth surface upon which a magnetron may move during a PVD process.

The invention is illustratively described and may be used in a physical vapor deposition system for processing large area substrates, such as a PVD system, available from AKT®, a subsidiary of Applied Materials, Inc., Santa Clara, Calif. However, it should be understood that the backing plate may have utility in other system configurations, including those systems configured to process large area round substrates. An exemplary system in which the present invention can be practiced is described in U.S. patent application Ser. No. 11/225,922, filed Sep. 13, 2005, which is hereby incorporated by reference in its entirety.

As the size of substrates increases, so must the size of the sputtering target and hence, the backing plate. For flat panel displays and solar panels, backing plates having a length of greater than 1 meter are not uncommon. As the size of the backing plate increases, so does the weight. Therefore, a backing plate spanning a length of greater than 1 meter may bow due to the significant weight of the backing plate. Additionally, the backing plate may have cooling channels formed therein to control the temperature of the backing plate and the sputtering target. The cooling channels and fluid flowing therein may add to the weight of the backing plate.

Placing an additional support member in the middle of the backing plate to compensate for any bowing is not practical and may interfere with the cooling channels. Any magnetron movement behind the backing plate may be impeded by the support structure. The support structure may impede the movement of the magnetron because the support structure may be positioned in the location where bowing is most likely to occur (i.e., the middle of the backing plate). The bowing is most likely to occur in the middle of the backing plate because the middle is the location furthest away from the edges of the backing plate where the backing plate is supported. The magnetron may be placed behind a backing plate to create a uniform plasma across a sputtering target and hence, uniformly erode the sputtering target. An additional support structure within the chamber is also not practical. The support structure within the chamber greatly increases the likelihood of non-uniform deposition on a substrate positioned opposite the target because the support structure may be placed between the target and the substrate. It would be beneficial to increase the size of the backing plate while not increasing the weight of the backing plate.

One manner of increasing the size of the backing plate while not increasing the weight of the backing plate is to remove a portion of the backing plate material. FIG. 1 is a top view of a backing plate assembly 100 having cavities 102 formed therein. In one embodiment, the cavities 102 are formed by removing backing plate material from the backing plate. In another embodiment, the cavities 102 are formed by pouring backing plate material into a mold having a cavity forming protrusion and allowing the backing plate material to harden. In another embodiment, the cavities 102 are formed by positioning cooling channels within backing plate material to form backing plate hills and then positioning the hills across the back surface of the backing plate with cavities 102 spaced therebetween. The backing plate assembly 100 may have a plurality of cooling fluid inlets/outlets 104 and a power coupling interface 106 positioned adjacent the cavities 102. It is to be understood that while five cavities 102 have been shown, more or less cavities 102 may be present.

In one embodiment, the backing plate comprises aluminum, copper, stainless steel, titanium, or alloys thereof. By having cavities 102 in the backing plate assembly 100, the weight of the backing plate assembly 100 is reduced. The weight of the backing plate assembly 100 is reduced by an amount equal to the weight of the backing plate material that would normally be present within the cavities 102. Thus, a backing plate assembly 100 that has at least one cavity 102 will be lighter and hence, less likely to bow.

FIG. 2 is a cross sectional view of a backing plate assembly 200 according to another embodiment of the invention. The backing plate assembly 200 comprises a sputtering target 202 bonded to a backing plate 206 using a bonding material layer 204. Within the backing plate 206, cavities 208 have been formed. Cooling channels 210 may also be present within the backing plate 206. The cavities 208 and cooling channels 210 alternate along the back surface of the backing plate 206. While only three cooling channels 210 have been shown, it is to be understood that the number of cooling channels 210 may be greater or less than three. Additionally, the shape of the cavities 208 is not restricted. The cavities 208 are shown with a rectangular cross section, but other shapes including dovetail, half-circle, triangular, etc. may be used.

A magnetron may be placed behind a backing plate in order to confine the plasma created during sputtering. The magnetron confines the plasma across the sputtering target to ensure that the sputtering target erodes uniformly. Uniform target erosion maximizes a target's useful life and reduces processing downtime. A non-uniform back surface of a backing plate may present a problem for a magnetron to move smoothly across the backing plate. A cavity may limit the pattern of movement for a magnetron across a backing plate. It should be noted, however, that a magnetron may be beneficially used with a backing plate that has a cavity formed therein. The magnetron may be suspended just above the backing plate so that the magnetron may move across the, back surface of the backing plate without interference by the cavity.

FIG. 3 is a top view of a backing plate assembly 300 with the cavities 304 filled with a filling material 312. The filling material 312 covers the entire back surface of the backing plate 302 except for an interface opening 310. The interface opening 310 permits a technician to easily access the cooling inlets/outlets 306 and a power coupling interface 308. In between the cavities 304, cooling channels are present within the backing plate 302. The fill material 312 covers the backing plate 302 both within the cavities 304 and on top of the backing plate 302 through which the cooling channels are positioned. In one embodiment, the fill material 312 is a single, unitary piece.

When fill material 410 is formed into the cavities 412 of a backing plate 406, it is also formed across the backing plate 406 where cooling channels 408 are positioned so that a smooth, planar surface of fill material 410 covers a portion of the backing plate. FIG. 4 is a cross sectional view of a backing plate assembly 400 according to another embodiment of the invention. A sputtering target 402 is bonded to the backing plate 406 by a bonding material layer 404. The fill material 410 should have a lower density than the backing plate 406. Thus, the backing plate assembly 100 with fill material 410 formed within cavities 412 of the backing plate 406 has a lower weight than a backing plate 406 of the same thickness, but without cavities 412 formed therein.

In one embodiment, the fill material 410 is a polymer. The polymer may be any polymer having a density less than the density of the backing plate 406. In another embodiment, the fill material 410 is a metal having a density lower than the backing plate 406 material. The fill material 410 is not restricted, but should have a lower density than the backing plate 406. Additionally, the fill material 410 should comprise a material that does not interfere with the magnetic field generated by a magnetron that may be placed behind the backing plate 406. By having a lower density than the backing plate 406, the fill material 410 weighs less when filling the cavity 412 than backing plate material remaining in the cavity 412.

FIG. 5 is a cross sectional view of a backing plate assembly 500 having a magnetron plate 514 positioned behind the backing plate 506. An exemplary magnetron that may be used is described in U.S. patent application Ser. No. 11/347,667, filed Feb. 3, 2006, which is hereby incorporated by reference in its entirety. The backing plate assembly 500 comprises a sputtering target 502 bonded to the backing plate 506 using a bonding material layer 504. Cooling channels 508 are positioned within the backing plate 506. Fill material 510 is deposited into cavities 512 formed into the backing plate 506. The fill material 510 fills the cavities 512 and also is present on the backing plate 506 where the cooling channels 506 are positioned. The surface of the fill material 510 that is opposite the backing plate 506 is smooth to permit a magnetron plate 514 to move across the fill material 510.

The fill material 510 may be smoothed by conventional techniques well known in the art and is not restricted to any particular smoothing technique. The fill material 510 may be smoothed so that any friction between the fill material 510 and the rollers 526 upon which the magnetron plate 514 rests is minimal. The rollers 526 may move across the fill material 510 to adjust the location of the magnetic field across the target 502. The rollers 526 are coupled with roller ball assemblies 516. It is to be understood that the invention is not to be limited to rollers 526 for moving the magnetron plate 514 across the fill material 510. Low friction sliding contact pads may also be used either in place of the rollers 526 or in addition to the rollers 526.

The magnetron plate 514 may be partially supported from above by coupling it to rails 520 and rolling on cylindrical roller assemblies 518 through multiple spring-loaded stud assemblies 522. Each stud assembly 522 includes a threaded stud 524 screwed into a tapped hole in the magnetron plate 514. The rollers 526 provide additional support for the magnetron plate 514 as it moves across the fill material 510. A ball transfer Model NSMS ¼, available from Ball Transfer Systems of Perryopolis, Pa., may be used as the rollers 526. The rollers 526 may contact a back surface of the fill material 510.

FIG. 6 is a cross sectional view of an apparatus 600 according to another embodiment of the invention. Within the apparatus 600, a plurality of sputtering targets 614a-f are positioned opposite a substrate 604. The substrate 604 is positioned on a susceptor 602. The processing area 616 is between the substrate 604 and the plurality of sputtering targets 614a-f. The apparatus 600 has chamber walls 606 which are shielded by a shield 608 during sputtering. The targets 614a-f may be sealed with the chamber walls 606 by a sealing surface 612 present on the targets 614a-f and a sealing member 610. In one embodiment, the sealing member 610 is an O-ring. The targets 614a-f are coupled with a backing plate 626 by a bonding material layer 624. Cooling channels 622 may be positioned within the backing plate 626. The cavities may be filed with filling material 620 to provide a smooth surface upon which a magnetron 618 may move. Anodes 628 are positioned between the adjacent sputtering targets 614a-f and may be grounded.

It should be understood that while FIG. 6 shows six separate, isolated targets 614a-f with a corresponding backing plate 626 and magnetron 618, more or less sputtering targets 614a-f may be present. The targets 614a-f may be individually powered. An exemplary power coupling for the targets 614a-f is described in U.S. patent application Ser. No. 11/428,226, filed Jun. 30, 2006, which is hereby incorporated by reference in its entirety. The targets 614a-f may comprise target strips or target tiles placed adjacent one another to create a target strip in a manner described in U.S. patent application Ser. No. 11/424,467, filed Jun. 15, 2006 and U.S. patent application Ser. No. 11/424,478, filed Jun. 15, 2006, both of which are hereby incorporated by reference in their entirety.

The number of backing plates 626 need not equal the number of sputtering targets 614a-f. In one embodiment, a single backing plate 626 is coupled to a plurality of targets 614a-f. Additionally, the number of magnetrons 618 need not correspond to the number of targets 614a-f or backing plates 626. In one embodiment, a single backing plate 626 is used and a single magnetron 618 is used while a plurality of targets 614a-f are used. In another embodiment, a single backing plate 626 may be used while a plurality of magnetrons 626 and a plurality of targets 614a-f may be used. In yet another embodiment, a plurality of backing plates 626 may be used with a plurality of sputtering targets 614a-f and a plurality of magnetrons 618 may be used. In still another embodiment, a plurality of sputtering targets 614a-f may be coupled to a plurality of backing plates 626 with a single magnetron 618 positioned in back of the backing plates 626.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A backing plate assembly, comprising:

a backing plate comprising a front surface and a back surface having at least one cavity; and

a fill material formed over the back surface and within the at least one cavity, the fill material having a substantially smooth back surface.

2. The assembly of claim 1, wherein the fill material is a polymer.

3. The assembly of claim 1, wherein the backing plate comprises a material selected from the group consisting of aluminum, copper, stainless steel, titanium, and alloys thereof.

4. The assembly of claim 1, further comprising:

at least one cooling channel within the backing plate, wherein the at least one cooling channel is adjacent to the at least one cavity.

5. The assembly of claim 1, wherein the fill material has a lower density than the backing plate.

6. A backing plate assembly, comprising:

a backing plate having a front surface and a back surface, the back surface comprising one or more cavity portions and one or more raised portions; and

a fill material formed over the one or more cavity portions and the one or more raised portions.

7. The assembly of claim 6, wherein the fill material is a polymer.

8. The assembly of claim 6, wherein the backing plate comprises a material selected from the group consisting of aluminum, copper, stainless steel, titanium, and alloys thereof.

9. The assembly of claim 6, further comprising:

at least one cooling channel within the backing plate.

10. The assembly of claim 6, wherein the fill material has a lower density than the backing plate.

11. An apparatus, comprising:

a backing plate, the backing plate comprises: a front surface and a back surface; and at least one cavity formed in the back surface;

a sputtering target coupled with the front surface of the backing plate;

a fill material within the at least one cavity and covering the back surface of the backing plate; and

a magnetron movable between a first position and a second position along the fill material.

12. The apparatus of claim 11, wherein the fill material has a lower density than the backing plate.

13. The apparatus of claim 11, further comprising:

at least one cooling channel within the backing plate and adjacent the at least one cavity.

14. The apparatus of claim 13, further comprising:

a plurality of cavities and a plurality of cooling channels, wherein the cavities and cooling channels alternate along the back surface of the backing plate.

15. The apparatus of claim 11, wherein the fill material that is within the at least one cavity and covering the back surface of the backing plate is a single, unitary piece of polymer.

16. The apparatus of claim 11, further comprising:

a plurality of backing plates, wherein each backing plate comprises: a front surface and a back surface; and at least one cavity formed in the back surface;

a fill material within the at least one cavity and covering each backing plate.

17. The apparatus of claim 16, further comprising:

a plurality of magnetrons, wherein each backing plate has a corresponding magnetron.

18. The apparatus of claim 11, further comprising:

a plurality of sputtering targets.

19. The apparatus of claim 11, wherein the magnetron is coupled with at least one roller ball for moving the magnetron.

20. The apparatus of claim 11, wherein the magnetron is coupled with at least one low friction sliding contact pad for moving the magnetron.

21. A sputtering target assembly, comprising:

a backing plate, the backing plate comprising: a front surface and a back surface; at least one cavity formed in the back surface of the backing plate;

a sputtering target coupled with the front surface of the backing plate; and

fill material within the at least one cavity and across the back surface of the backing plate, the fill material has a lower density than the backing plate.

22. The assembly of claim 21, wherein the fill material comprises a polymer.

23. The assembly of claim 21, further comprising:

at least one cooling channel within the backing plate, wherein the at least one cooling channel is adjacent the at least one cavity.

24. The assembly of claim 23, further comprising:

a plurality of cavities and a plurality of cooling channels, wherein the cavities and cooling channels alternate along the back surface of the backing plate.

25. The assembly of claim 21, wherein the backing plate comprises a material selected form the group consisting of aluminum, copper, stainless steel, titanium, and alloys thereof.

26. A sputtering method, comprising:

providing a backing plate having a front surface and a back surface with at least one cavity, the at least one cavity is filled with a material that has a lower density than the backing plate;

providing a target coupled to the front surface of the backing plate; and

applying a bias to the sputtering target assembly.

27. The method of claim 26, further comprising:

moving a magnetron across the back surface of the backing plate.

28. The method of claim 27, wherein the magnetron is moved by rolling the magnetron on at least one roller ball that is coupled with the magnetron.

29. The method of claim 27, wherein the magnetron is moved by moving at least one low friction sliding contact pad that is coupled with the magnetron.