Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
1999-09-15
2001-05-22
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S680000, C438S784000, C257S632000, C257S636000
Reexamination Certificate
active
06235652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to methods for chemical vapor deposition (CVD) of silicon dioxide, and more particularly to a method for CVD of silicon dioxide at a high deposition rate and low reaction chamber pressure using a reactant gas including silane and oxygen.
2 . Description of the Prior Art
Silicon dioxide is one of the most commonly used materials in the manufacturing of semiconductor devices, and can be “grown” or “deposited” onto silicon substrates. Silicon dioxide is grown by subjecting the silicon substrate to oxygen or water vapor at high temperature, i.e. >900° C. (as documented in S. Wolf and R. N. Tauber,
Silicon Processing for the VLSI Era
, Volume 1
Process Technology
, Lattice Press (1986), pages 198, 210). Deposited silicon dioxide is typically done by Chemical Vapor Deposition (CVD) at lower temperatures, i.e. °600° C. (See A. Sherman,
Chemical Vapor Deposition for Microelectronics
, Noyes Publications, Park Ridge, N.J. (1987), pages 66-77.)
Deposited oxides, because of the low temperature process, are used extensively as the insulating layer between multilayer metallization of today's integrated circuits. Silicon dioxide has been deposited by PVD (as disclosed in U.S. Pat. No. 4,624,859) and various CVD processes, both at atmospheric pressure (see U.S. Pat. No. 5,360,646) and at low pressures (see Sherman, pages 66-77). Low-pressure depositions have superior film qualities over depositions at atmospheric pressure and are therefore usually the process of choice (see Sherman, pages 66-77). Low pressure depositions are accomplished by placing a substrate in a vacuum chamber, heating the substrate and introducing silane (as disclosed in U.S. Pat. No. 4,900,591), or any similar silicon precursor such as dichlorosilane, silicon tetrachloride, TEOS (see U.S. Pat. No. 3,934,060) and the like, with oxygen or any similar oxygen precursor, e.g. nitrous oxide, ozone (see U.S. Pat. No. 5,000,113), etc. Deposition rates of approximately 20 to 30 angstroms per minute are typical for low pressure processes (<1 Torr) (see Sherman, page 70), and 50 to 140 angstroms per minute are typical for high pressure processes (>1 Torr) (see U.S. Pat. No. 4,900,591). Higher deposition rates of 2,000 angstroms per minute have been reported for plasma enhanced depositions (see U.S. Pat. No. 5,000,113). Although all of these CVD processes have been used in manufacturing of microelectronics, they all have disadvantages. For example, the process may have a very low rate of deposition, or poor uniformity across the silicon substrate, or high tensile stress (see Sherman, pages 68-77), or the process may incorporate unwanted by-products such as moisture, which degrades the film properties.
U.S. Pat. No. 5,551,985 by Brors et al. describes a CVD reactor that provides improved uniformity in heating a wafer, and a highly uniform gas flow across the surface of a wafer. U.S. Patent. No. applications Ser. Nos. 08/909,461 filed on Aug. 11, 1997, and 09/228,835 and 09/228,840 filed on Jan. 12,1999, the disclosures of which are incorporated herein by reference, describe wafer chambers in which related processes may also be used.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved method of depositing silicon dioxide.
It is another object of the present invention to provide a method of depositing silicon dioxide that results in a high rate of deposition.
It is a further object of the present invention to provide a method of depositing silicon dioxide at a high rate of deposition without the use of plasma enhancement.
It is a still further object of the present invention to provide a method of chemical vapor deposition of silicon dioxide resulting in a high rate of deposition and good film uniformity.
It is another object of the present invention to provide a method of rapid deposition of silicon dioxide at a low chamber pressure that avoids moisture inclusion and gas phase nucleation.
Briefly, a preferred embodiment of the present invention includes a method of depositing silicon dioxide providing a high rate of deposition at a low process chamber pressure, yielding a film with excellent uniformity, and with an absence of moisture inclusion and gas phase nucleation. According to the method, a wafer is placed in a reaction chamber wherein a reactant gas flow of silane and oxygen is directed in parallel with the wafer via a plurality of temperature-controlled gas injectors, and confined to a narrow region above the wafer. The gas is injected at a high velocity resulting in the deposition rate being limited only by the rate of delivery of unreacted gas to the wafer surface and the rate of removal of by-products. The high velocity gas stream passing across the wafer has the effect of thinning the layer adjacent the wafer surface containing reaction by-products, known as the “boundary layer,” which results in faster delivery of the desired reactant gas to the wafer surface. The high velocity gas flow causes a very low gas residence time in the area of interest (i.e. above the substrate surface). The gas flow sweeps out unwanted reaction by-products resulting in a further increase in the relative concentration of the desired reactant species and reduced incorporation of unwanted reaction by-products in the deposited film.
An advantage of the present invention is that it provides an improved method of rapid deposition of silicon dioxide.
A further advantage of the present invention is that it provides a method of rapidly depositing a silicon dioxide film with improved film surface uniformity.
A still further advantage of the present invention is that it provides a method of depositing silicon dioxide at a high rate with a corresponding film of improved uniformity while avoiding moisture inclusion and gas phase nucleation.
REFERENCES:
patent: 5551985 (1996-09-01), Brors et al.
Wolf et al., Silicon Processing for the VLSI Era: vol. 1-Process Technology, 1986, pp. 169-170.
Brors Daniel L.
Cook Robert C.
Chaudhari Chandra
Jaffer David H.
Kilday Lisa
Pillsbury & Winthrop LLP
Torrex Equipment Corporation
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