CVD syntheses of silicon nitride materials

Details CVD syntheses of silicon nitride materials CVD syntheses of silicon nitride materials

2001-04-26

2003-10-07

Cuneo, Kamand (Department: 2829)

Semiconductor device manufacturing: process

Radiation or energy treatment modifying properties of...

C438S758000, C438S775000, C438S780000, C438S781000, C438S789000, C438S790000, C438S791000

Reexamination Certificate

active

06630413

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to silicon nitride materials useful in the semiconductor industry, and more particularly to deposition methods for making silicon nitride materials having a low hydrogen content.
2. Description of the Related Art
Silicon nitride materials are widely used in the semiconductor industry as gate dielectrics for amorphous silicon and III-V compound semiconductor transistors, insulators between metal levels, masks to prevent oxidation and diffusion, etch masks in multilevel photoresist structures, passivation layers and as spacer materials in transistors.
Silicon nitride materials are typically deposited onto the substrate by decomposing chemical precursors in the presence of the substrate. The properties of the deposited silicon nitride material generally depend upon the deposition method. For a number of semiconductor applications, low hydrogen content (“H-content”) is desirable. Conventional silicon nitride is said to contain 20-30 atomic % hydrogen, see U.S. Pat. No. 4,854,263.
A number of methods are used to deposit silicon nitride films, including thermal chemical vapor deposition (“thermal CVD”) and plasma-enhanced chemical vapor deposition (“PECVD”). It is generally recognized that low H-content silicon nitride can be deposited by thermal CVD using high deposition temperatures. For example, U.S. Pat. No. 5,326,649 discloses the use of NH
3
(ammonia) as the nitrogen source and SiH
4
(silane) as the silicon source to make low-H content silicon nitride materials at temperatures in the range from 900° to 1500° C. Thermal CVD methods that utilize ammonia and silane are apparently favored because those precursors are widely available and relatively inexpensive. However, such high temperature methods may be incompatible with many process steps in the semiconductor manufacturing process. Thermal CVD using ammonia and silane at lower temperatures generally results in relatively high H-content silicon nitride films. U.S. Pat. No. 4,720,395 discloses the use of NF
3
(nitrogen trifluoride) and H
3
SiSiH
3
(disilane) in a mole ratio of about 0.5 to about 3.0 to deposit silicon nitride at a temperature in the range of 250°-500° C. The H-content of the films produced by this process is not disclosed, but is likely to be relatively high because of the low deposition temperatures and the relatively high H-content of disilane.
Various PECVD techniques utilize precursors that contain significant amounts of hydrogen. JP 62253771A discloses a PECVD technique for depositing silicon nitride using H
n
Si(NH
2
)
4-n
, where n is 1, 2 or 3. U.S. Pat. No. 5,731,238 employs jet vapor deposition using silane and N
2
(nitrogen) as precursors to make silicon nitride. The PECVD method of JP 6338497A utilizes (SiH
3
)
3
N (trisilylamine) and ammonia to make silicon nitride and oxynitride films. When ammonia is used as the nitrogen source, PECVD has been found to produce silicon nitride having generally higher levels of hydrogen. For example, U.S. Pat. No. 4,854,263 notes that, as a consequence of using ammonia to obtain acceptable deposition rates and throughput, the concentration of hydrogen in the deposited silicon nitride can be quite high, as much as 25-30 atomic percent.
Attempts have been made to reduce H-content by eliminating ammonia from the deposition process. For instance, U.S. Pat. No. 4,854,263 discloses a method for making a silicon nitride film having a hydrogen content of 5-7 atomic percent by using SiH
4
/N
2
/NF
3
in a PECVD process that utilizes a particular inlet gas manifold. U.S. Pat. No. 4,854,263 also discloses a similar process for making silicon oxynitride films having a hydrogen content of less than six atomic percent using SiH
4
/N
2
/N
2
O. WO 00/03425 discloses a PECVD process that utilizes silane and nitrogen. The PECVD method disclosed in U.S. Pat. No. 5,508,067 utilizes a precursor gas mixture that contains an inorganic silane, a nitrogen-containing organosilane and a nitrogen-containing gas. A variety of precursors are mentioned, some of which contain hydrogen and some of which do not, but the deposition of silicon nitride using a hydrogen-containing precursor mixture of (CH
3
)
3
NN(CH
3
)
3
(hexamethyldisilazene), silane, ammonia and nitrogen is exemplary.
Problems have been encountered when entirely hydrogen-free precursors are used to make low H-content silicon nitride. U.S. Pat. No. 4,481,229 discusses the etching problems encountered when attempting to make hydrogen-free films using halogenide silicon gases such as SiF
4
, SiCl
4
, SiF
3
Cl, or SiBr
4
in place of SiH4 and purports to provide a solution in the form of a particular plasma technique. That patent discloses the deposition of a Si—N film using SiF
4
and N
2
or NF
3
as precursors. However, U.S. Pat. No. 4,737,379 states that practical deposition systems utilizing this art will require the creation and control of a uniform, large magnetic field throughout the plasma volume. U.S. Pat. No. 4,737,379 also states that such a system will require the use of microwave tuning and applicator technology capable of coupling microwave energy into a plasma impedance which is changing rapidly near the resource condition. According to U.S. Pat. No. 4,737,379, the additional technological complications brought about by these requirements have significant economic consequences for manufacturing machines employing this art. Thus, the art does not appear to recognize U.S. Pat. No. 4,481,229 as providing a satisfactory method for making low-H content silicon nitride materials. The PECVD method disclosed in U.S. Pat. No. 4,737,379 for making low-H content films utilizes a feedstock gas that is hydrogen-free, i.e., free of combined hydrogen, silanes, partially halogenated silanes, and partially substituted hydrocarbons. Hydrogen-free silicon nitride is not always desirable, however, so that patent discloses the use of molecular hydrogen (H
2
) to modify the properties of the deposited film.
There remains a need for low-H content silicon nitride materials having better properties more suitable for use in microelectronics manufacturing, and for processes for producing such materials that can be readily integrated into fabrication process flows.
SUMMARY OF THE INVENTION
The inventor has discovered various ways of depositing silicon nitride materials onto surfaces. In preferred embodiments, the deposited silicon nitride materials have a relatively low content of hydrogen. Such silicon nitride materials and processes are particularly useful for making microelectronic devices such as integrated circuits.
In one embodiment, a process is provided for depositing a silicon nitride material from vapor phase precursors on a surface, comprising providing a deposition chamber having disposed therein a substrate; and introducing a chemical precursor to the chamber, wherein the chemical precursor is comprised of one or more N—Si chemical bonds, thereby depositing a silicon nitride material onto the substrate by thermal decomposition.
In another embodiment, a thermal chemical vapor deposition process is provided, comprising placing an integrated circuit into a chemical vapor deposition chamber, heating the integrated circuit to a temperature in the range of about 500° C. to about 650° C., and adding a chemical precursor to the chemical vapor deposition chamber to thereby deposit a material onto the integrated circuit, wherein the chemical precursor is selected from the group consisting of (X
3
Si)
3
N, (X
3
Si)
2
N—N(SiX
3
)
2
, (X
3
Si)N═N(SiX
3
), and (R
3-m
SiX
m
)
3
N; wherein m is 0, 1 or 2; wherein each X is individually selected from the group consisting of F, Cl, Br, H and D; and wherein each R is individually selected from the group consisting of methyl, ethyl, phenyl and tertiary butyl.
In another embodiment, a process is provided for depositing a silicon nitride material, comprising creating a mixture comprised of a N-containing chemical precursor and a Si-containing chemical precursor, wherein the mixture is created in the presence o

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