Substrate support for a thermal processing chamber

Details Substrate support for a thermal processing chamber Substrate support for a thermal processing chamber

1998-02-11

2001-03-13

Lund, Jeffrie R. (Department: 1763)

Coating apparatus

Gas or vapor deposition

Work support

C118S500000, C156S345420

Reexamination Certificate

active

06200388

ABSTRACT:

BACKGROUND
This invention relates to a substrate support for a thermal processing chamber.
In many semiconductor device manufacturing processes, the required high levels of device performance, yield, and process repeatability can only be achieved if the temperature of the substrate (e.g., a semiconductor wafer) is tightly monitored and controlled during processing of the substrate.
Rapid thermal processing (RTP), for example, is used for several different fabrication processes, including rapid thermal annealing (RTA), rapid thermal cleaning (RTC), rapid thermal chemical vapor deposition (RTCVD), rapid thermal oxidation (RTO), and rapid thermal nitridation (RTN). The temperature in an RTP chamber, however, may exceed 1100° C. and is subject to rapid change, thereby making precise control of the substrate temperature more complicated and more difficult.
Additionally, although it is desirable to provide a substantially uniform temperature throughout the substrate during many manufacturing processes, the support on which the substrate rests can affect the manufacturing system's ability to achieve such uniformity. In susceptorless systems, for example, the substrate is usually only supported around its perimeter with an edge ring. In some situations, however, the edge ring acts as a thermal load which removes heat from the edge of the substrate, thereby making it difficult to provide a uniform temperature across the substrate and interfering with temperature measurements.
SUMMARY
In general, in one aspect of the invention, a semiconductor wafer support includes a shelf for receiving a semiconductor wafer. The support is formed of a silicon carbide substrate, a polysilicon layer disposed on the silicon carbide substrate, and a silicon nitride layer disposed on the polysilicon layer. In one implementation, the wafer support is an edge ring that includes an annular support for receiving a semiconductor wafer.
In another aspect, a method of forming a semiconductor wafer support includes forming a silicon carbide substrate, providing a polysilicon layer on the substrate, and providing a silicon nitride layer on the polysilicon layer. The substrate can be annular-shaped.
Various implementations include one or more of the following features. The edge ring or other wafer support can be disposed in a thermal semiconductor processing chamber. The polysilicon layer, which can include intrinsic or doped polysilicon, can be disposed directly on the silicon carbide substrate. Similarly, the silicon nitride layer can be disposed directly on the polysilicon layer. The polysilicon and silicon nitride layers can cover substantially the entire surface of the silicon carbide substrate.
In one implementation, the silicon nitride layer has a thickness in the range of 1800-2000 angstroms, and the polysilicon layer has a thickness of approximately 100 microns. Other thicknesses, however, can be used for either or both of the layers. Thus, the silicon nitride layer can have thicknesses of less than or more than 2000 angstroms. The silicon nitride layer can form an anti-reflective coating.
Although the wafer support or edge ring can be made using many different techniques, according to one technique, the polysilicon layer is grown in an epitaxial reactor, and the silicon nitride layer is grown using a low pressure chemical vapor deposition process.
Various implementations include one or more of the following advantages. The addition of the silicon nitride layer can improve the emissivity of the edge ring or other substrate support. In some systems, an RTP temperature controller measures the chamber temperature and determines the power required to affect a temperature change. The higher emissivity of the edge ring allows it to absorb or emit the radiation from a heating element more quickly. The edge ring can, therefore, respond more quickly to temperature changes.
The silicon nitride layer also can prevent formation of an oxide layer during processing, thereby resulting in a more uniform temperature across the semiconductor substrate and more accurate temperature measurements. In addition, the silicon nitride layer can help reduce the occurrence of a failures to a heating element in the chamber. Furthermore, the silicon nitride layer can act as a diffusion barrier to prevent impurities that may be present in the poly-Si layer from contaminating a semiconductor substrate supported by the edge ring.
Use of the silicon nitride layer allows the edge ring to behave like an extension of the substrate so that the temperatures and temperature changes of the edge ring and substrate coincide more closely with one another. As a result, the energy entering the chamber in which the edge ring is disposed can be more balanced throughout different parts of the chamber, and groups of lamps in the heating element can be more easily controlled by the RTP temperature controller.
Additional features and advantages will be readily apparent from the following detailed description, drawings and claims.


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