THIN EDGE CARRIER RING

Abstract

A PECVD deposition chamber with a circular pedestal with a recessed portion in the outer top surface of the pedestal. A PECVD deposition chamber with a circular wafer carrier ring with a recessed portion in the outer top surface of the wafer carrier ring.

Description

FIELD OF THE INVENTION

This invention relates to the field of integrated circuit processing. More particularly, this invention relates thin film PECVD deposition.

BACKGROUND OF THE INVENTION

During the manufacturing of an integrated circuit a number of dielectric films may be deposited. One technique used to deposit dielectric films at temperatures less than approximately 550 C is PECVD (plasma-enhanced chemical vapor deposition). Some PECVD tools are single wafer tools which a deposit dielectric thin film onto one wafer at a time. One important deposition criteria for the dielectric thin film is thickness uniformity across the wafer including the edges of the wafer. In order to provide uniform thickness out to and including the edges of a wafer the deposition may extend beyond the wafer edge. In PECVD deposition processes using pressures greater than about 12 Torr, a ring of deposited dielectric (also called a deposition fence) may form just outside the edge of the wafer on the pedestal or the wafer carrier ring upon which the wafer is positioned. The deposition fence typically presents a particle problem when the thickness builds up after dielectric deposition upon multiple wafers. The deposition fence may peel due to accumulated film stress or the deposition fence may become sufficiently thick to come into contact with the robot slider which transfers wafers into and out of the chamber. When the robot slider comes into contact with the deposition fence, pieces of the deposition fence may break off and redeposit on the wafer resulting in depressed yield.

Several methods have been developed to deal with the deposition fence. One method is to open the chamber and remove the deposition fence after a specified number of wafers have been processed. Another method is to periodically run a plasma clean step such as a NF3 plasma step to etch away the dielectric fence. Both solutions reduce the time that the deposition tool is available for manufacturing thus increasing manufacturing cost.

SUMMARY OF THE INVENTION

The following presents a simplified summary in order to provide a basic understanding of one or more aspects of the invention. This summary is not an extensive overview of the invention, and is neither intended to identify key or critical elements of the invention, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later.

A PECVD deposition chamber with a circular pedestal with a recessed portion in the outer top surface of the pedestal. A PECVD deposition chamber with a circular wafer carrier ring with a recessed portion in the outer top surface of the wafer carrier ring.

DESCRIPTION OF THE VIEWS OF THE DRAWING

FIG. 1 is a cross-section of a PECVD deposition chamber illustrating the deposition plasma.

FIG. 2. is a cross-section of a PECVD deposition chamber illustrating a deposition fence.

FIG. 3 is a cross-section of a PECVD deposition chamber with a wafer carrier ring formed according to embodiments.

FIGS. 4A and 4B are a top down view and cross-sectional illustrations of a wafer carrier ring.

FIGS. 5A and 5B are a top down view and a cross-sectional illustration of a wafer carrier ring formed according to embodiments.

DETAILED DESCRIPTION

The present invention is described with reference to the attached figures, wherein like reference numerals are used throughout the figures to designate similar or equivalent elements. The figures are not drawn to scale and they are provided merely to illustrate the invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of the invention. One skilled in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the invention. The present invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present invention.

Single wafer PECVD dielectric deposition tools come in a variety of designs. A dielectric tool may have a single chamber which processes a single wafer at a time or may have multiple chambers. A dielectric tool may also have a single chamber with multiple deposition stations for processing multiple wafers at a time. Multiple deposition stations may provide a more uniform film thickness by averaging out deposition nonuniformity that may occur in one of the deposition stations. In a multi-station deposition tool the wafer typically is placed on a carrier ring which transports the wafer from station to station.

The inside of a typical multi-station, single wafer deposition chamber is shown in FIG. 1. Wafer 1008 sits atop pedestal 1004. Carrier ring, 1006, which is used to transport the wafer from one deposition station to the next, surrounds the wafer 1008 providing an extended surface beyond the edge of the wafer. This extended surface facilitates uniform thin film deposition out to and including the edge of the wafer 1008. Reactants are dispensed from top electrode and showerhead, 1010, into the plasma 1012 and recombine at the plasma 1012/wafer 1008 interface to deposit dielectric on the wafer 1008 and recombine along the plasma edge 1016/chamber ambient interface to form a dielectric fence 1014 on the wafer carrier ring 1006. The deposition fence 1014 may increase in thickness as additional wafers are processed.

As is illustrated in FIG. 2, the deposition fence 2014 may build up to a thickness where the robot slider 2018 which transports wafers into and out of the chamber, comes into contact with the deposition fence causing pieces of the deposition fence, 2014, to be broken off resulting in particles that may redeposit on wafer 2008 and depress yield.

An embodiment is illustrated in FIG. 3 which addresses the deposition fence problem. Pedestal 3004 has a central region 3005 surrounded by an outer region 3003, which is recessed with respect to central region 3005. Carrier ring 3006 surrounds central region 3005 and sits over outer region 3003 of pedestal 3004. Carrier ring 3006 includes a central region 3007, which surrounds and has an upper surface that is substantially coplanar with the upper surface of central region 3005 of pedestal 3004, a second region 3008, which surrounds central region 3007 and has an upper surface that is substantially coplanar with the upper surface of wafer 3010 when wafer 3010 is positioned on regions 3005 and 3007, and a third or outer region 3009, which surrounds and is recessed with respect to region 3008. Reactants dispensed from the top electrode and showerhead in a deposition chamber recombine along the interface between the plasma edge and chamber ambient to form dielectric deposition fence 3014 on outer region 3009 of carrier ring 3006. Outer region 3009 of the carrier ring 3006 where the deposition fence 3014 forms is recessed with respect to region 3008 so that the distance from the top of the deposition fence 3014 to the robot slider 3018 is increased. This increased distance, permits more wafers to be processed between plasma chamber cleans or openings thus increasing the time to process product wafers and reducing manufacturing cost.

Top down and side views of a typical carrier ring 4000 are shown in FIGS. 4A and 4B. As shown in FIG. 4B the typical carrier ring 4000 has a center recess region 4004 in which the wafer rests, which is surrounded by region 4002. Region 4002 is of a uniform thickness 4018 out to the edge of the carrier ring. Thickness 4018 of region 4002 exceeds the thickness of center recess region 4004 by the thickness of wafers to be transported by carrier ring 4000.

A top down and side view of a carrier ring 5000 according to an embodiment which addresses the deposition fence problem are shown in FIGS. 5A and 5B. As shown in FIG. 5B, carrier ring 5000 has a center recess region 5004 in which the wafer rests. Center recess region 5004 is surrounded by region 5002, which has a thickness that exceeds the thickness of center recess region 5004 by the thickness of wafers to be transported by carrier ring 5000. Carrier ring 5000 also has an outer portion 5006 where a deposition fence may form. Outer portion 5006 is recessed with respect to region 5002 to provide an increased distance between a deposition fence that forms in this area and a robot slider arm that transports a wafer into and out of the deposition chamber or transports the carrier ring plus the wafer from one deposition station to the next.

In an example embodiment, the multi-station deposition chamber is a Novellus Vector deposition chamber for the deposition of organo-silicate glass (OSG). As shown in FIG. 5B an outer portion of the wafer carrier ring 5006 is recessed. The ring recess 5006 may be in the range of 0.5 to 0.8 inches wide and 0.03 to 0.06 inches deep. In a preferred embodiment the ring recess is about 0.6+/−0.005 inches wide and about 0.0425+/−0.005 inches deep. Using the preferred embodiment, the ratio of the number of wafers able to be processed using a wafer carrier ring with the preferred embodiment recess to the number of wafers able to be processed without a recess prior to a chamber clean is approximately 1.6. This 60% increase in the number of wafers processed between chamber cleans may significantly reduce manufacturing cost.

Although the example embodiment used for illustration is a Novellus Vector, other Novellus PECVD deposition equipment may also benefit. In addition, other multi-station deposition tools and other single wafer, single station deposition tools may benefit. Although the example embodiment used for illustration is an OSG dielectric deposition, other films that are deposited with a pressure greater than about 12 Torr and may form deposition fences may also benefit.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.

Claims

1. A PECVD deposition chamber, comprising:

a circular wafer pedestal with a top surface diameter larger than a wafer diameter and with an outer recessed portion of said top surface where said recessed portion is outside said wafer diameter and where said recessed portion underlies an interface between a plasma edge and chamber ambient in said PECVD deposition chamber.

2. The chamber of claim 1 where said circular wafer pedestal further comprises a wafer carrier ring and where said outer recessed portion is the outer portion of said wafer carrier ring.

3. The chamber of claim 2 where a width of said outer recessed portion is in the range of 0.5 to 0.8 inches and a depth of said outer recessed portion is in the range of 0.03 to 0.06 inches.

4. The chamber of claim 3 where said width is about 0.6+/−0.005 inches and said depth is about 0.0425+/−0.005 inches.

5. The chamber of claim 1 where a pressure during a deposition in said PECVD deposition chamber is greater than 12 Torr.

6. The chamber of claim 1 where a deposition in said PECVD deposition chamber is an OSG deposition.

7. A PECVD deposition chamber, comprising:

a wafer carrier ring with a recessed portion on the outer top side of said wafer carrier ring and where said recessed portion underlies an interface between a plasma edge and chamber ambient in said PECVD deposition chamber.

8. The chamber of claim 7 where a width of said recessed portion is in the range of 0.5 to 0.8 inches and a depth of said recessed portion is in the range of 0.03 to 0.06 inches.

9. The chamber of claim 8 where said width is about 0.6+/−0.005 inches and said depth is about 0.0425+/−0.005 inches.

10. The chamber of claim 7 where a pressure during a deposition in said PECVD deposition chamber is greater than 12 Torr.

11. The chamber of claim 7 where a deposition in said PECVD deposition chamber is an OSG deposition.