# Patent

## Title
Monosilane or disilane derivatives and method for low temperature deposition of silicon-containing films using the same

## Abstract

This invention relates to silicon precursor compositions for forming silicon-containing films by low temperature (e.g., <550° C.) chemical vapor deposition processes for fabrication of ULSI devices and device structures. Such silicon precursor compositions comprise at least a silane or disilane derivative that is substituted with at least one alkylhydrazine functional groups and is free of halogen substitutes.

## Background
FIELD OF THE INVENTION
The present invention relates generally to the formation of silicon-containing films in the manufacture of semiconductor devices, and more specifically to compositions and methods for forming such films, e.g., films comprising silicon, silicon nitride (Si3N4), siliconoxynitride (SiOxNy), silicon dioxide (SiO2), etc., low dielectric constant (k) thin silicon-containing films, high k gate silicate films and low temperature silicon epitaxial films.
DESCRIPTION OF THE RELATED ART
Silicon nitride (Si3N4) thin films are widely employed in the microelectronic industry as diffusion barriers, etch-stop layers, sidewall spacers, etc.
Deposition of silicon nitride films by chemical vapor deposition (CVD) techniques is a highly attractive methodology for forming such films. CVD precursors currently used include bis(tert-butylamino)silane (BTBAS) or silane/ammonia, but such precursors usually require deposition temperature higher than 600° C. for forming high quality Si3N4 films, which is incompatible with the next generation IC device manufacturing, where deposition temperature of below 500° C., and preferably about 450° C., is desired. Therefore, development of low-temperature silicon-containing CVD precursors is particularly desired.
Presently, hexachlorodisilane, Cl3Si—SiCl3, is being studied as a candidate precursor for low-temperature CVD formation of silicon nitride thin films upon reaction with amnmonia gas. The drawbacks of using hexachlorodisilane in CVD processes include: (i) formation of large amount of NH4Cl during the process, which leads to the particle contamination and solid build-up in vacuum system and exhaust lines; (ii) possible chlorine incorporation in the chips, which could significantly reduce their life time and long-term performance; and (iii) the reaction by-products are known to be explosive. It is therefore desirable to develop new chlorine-free precursors that can be used for low-temperature CVD formation of silicon nitride thin films.
SUMMARY OF THE INVENTION
The present invention relates generally to the formation of silicon-containing films, such as films comprising silicon, silicon nitride (Si3N4), siliconoxynitride (SiOxNy), silicon dioxide (SiO2), etc., silicon-containing low k films, high k gate silicates, and silicon epitaxial films, among which silicon nitride thin films are preferred, in the manufacture of semiconductor devices, and more specifically to compositions and methods for forming such silicon-containing films.
The present invention in one aspect relates to a group of halogen-free silane or disilane derivatives that are substituted with at least one alkylhydrazine functional groups and can be used as CVD precursors for deposition of silicon-containing thin films.
The silane derivatives of the present invention can be represented by the general formula of:




wherein R1 and R2 may be the same as or different from each another and are independently selected from the group consisting of H, C1-C7 alkyl, aryl, and C3-C6 cycloalkyl, or R1 and R2 together may form C3-C6 heterocyclic functional group with N, and wherein X, Y, and Z may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, alkylamino, dialkylamino, and alkylhydrazido (e.g., R1R2NNH—, wherein R1 and R2 are same as described hereinabove).

Preferably, X, Y, and Z are all identical functional groups. More preferably, X, Y, and Z are all C1-C7 alkyl, such as methyl or ethyl. Alternatively but also preferably, X, Y, and Z are all alkylhydrazido (e.g., R1R2NNH—, wherein R1 and R2 are same as described hereinabove), such as N,N′-dimethylhydrazido or N,N′-diethylhydrazido.
The disilane derivatives of the present invention can be represented by the general formula of:




wherein R1, R2, R3, and R4 may be the same as or different from each another and are independently selected from the group consisting of H, C1-C7 alkyl, aryl, and C3-C6 cycloalkyl, or R1 and R2 together may form C3-C6 heterocyclic functional group with N, or R3 and R4 together may form C3-C6 heterocyclic functional group with N, and wherein X1, X2, Y1, and Y2 may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, alkylamino, dialkylamino, and alkylhydrazido (e.g., R1R2NNH—, wherein R1 and R2 are same as described hereinabove).

Preferably, the disilane derivative compound of the present invention is characterized by functional groups that are symmetrically distributed in relation to the Si—Si bond.
Preferred silane or disilane derivative compounds of the present invention include, but are not limited to, Me3Si(HNNMe2), Si(HNNMe)4, Me2(HNNMe2)Si—Si(HNNMe2)Me2, and (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2, wherein Bu and Me are consistently used as the respective abbreviations of butyl and methyl throughout the text hereinafter.
Another aspect of the present invention relates to a method for forming a silicon-containing film on a substrate, comprising contacting a substrate under chemical vapor deposition conditions including a deposition temperature of below 550° C., preferably below 500° C., and more preferable below 450° C., with a vapor of a silane or disilane derivative compound that is substituted with at least one alkylhydrazine functional group.
Still another aspect of the present invention relates to a method of making such silane or disilane derivative compounds, by reacting silane or disilane compounds comprising one or more halogen groups (i.e., halosilane or halodisilane) with alkylhydrazine in the presence of NEt3, to substitute the one or more halogen groups of such silane or disilane compounds with alkylhydrazine functional groups.
A still further aspect of the present invention relates to a method of making Me3Si(HNNMe2), by reacting Me3SiCl with approximately one molar ratio of H2NNMe2 in the presence of NEt3, according to the following reaction:




A still further aspect of the present invention relates to a method of making Si(HNNMe2)4, by reacting SiCl4 with approximately four molar ratio of H2NNMe2 in the presence of NEt3, according to the following reaction:




A still further aspect of the present invention relates to a method of making Me2(HNNMe2)Si—Si(HNNMe2)Me2, by reacting Me2(Cl)Si—Si(Cl)Me2 with approximately two molar ratio of H2NNMe2 in the presence of NEt3, according to the following reaction:




A still further aspect of the present invention relates to a method of making, by reacting (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2, by reacting (HNBut)2(Cl)Si—Si(Cl)(HNBut)2 with approximately two molar ratio of LiHNNMe2, according to the following reaction:




Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a STA plot for Si(HNNMe2)4.
FIG. 2 is an X-ray crystal structure of the compound Si(HNNMe2)4.
FIG. 3 is a STA plot for Me2(HNNMe2)Si—Si(HNNMe2)Me2.
FIG. 4 is a STA plot for (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2.



DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF
The present invention relates to silicon precursors for CVD formation of films on substrates, such as silicon precursors for forming low k dielectric films, high k gate silicates, low temperature silicon epitaxial films, and films comprising silicon, silicon oxide, silicon oxynitride, silicon nitride, etc., as well as to corresponding processes for forming such films with such precursors.
Silane or disilane derivatives that contain one or more alkylhydrazine functional groups, free of any halogen substitutes, are found particularly suitable for low-temperature deposition of silicon nitride thin films, since the bond-strength of the nitrogen-nitrogen single bond in the hydrazine functional group relatively weak. Moreover, use of such halogen-free silicon precursors avoids the various problems involved in previous CVD processes using hexachlorodisilane.
Preferred silane derivatives of the present invention can be represented by the general formula of:




wherein R1 and R2 may be the same as or different from each another and are independently selected from the group consisting of H, C1-C7 alkyl, aryl, and C3-C6 cycloalkyl, or R1 and R2 together may form C3-C6 heterocyclic functional group with N, and wherein X, Y, and Z may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, alkylamino, dialkylamino, and alkylhydrazido (e.g., R1R2NNH—, wherein R1 and R2 are same as described hereinabove).

Preferred disilane derivatives of the present invention can be represented by the general formula of:




wherein R1, R2, R3, and R4 may be the same as or different from each another and are independently selected from the group consisting of H, C1-C7 alkyl, aryl, and C3-C6 cycloalkyl, or R1 and R2 together may form C3-C6 heterocyclic functional group with N, or R3 and R4 together may form C3-C6 heterocyclic functional group with N, and wherein X1, X2, Y1, and Y2 may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, alkylamino, dialkylamino, and alkylhydrazido (e.g., R1R2NNH—, wherein R1 and R2 are same as described hereinabove).

Disilane derivative compounds that are substantially symmetrical in structure in relation to the Si—Si bond, i.e., all functional groups of such compounds being symmetrically distributed in relation to the Si—Si bond, are particularly preferred for practicing of the present invention. For example, such disilane derivative compounds may contain two identical alkylhydrazine functional groups and four identical C1-C5 alkyl functional groups that are symmetrically distributed in relation to the Si—Si bond, such as Me2(HNNMe)Si—Si(HNNMe)Me2.
The silane or disilane derivative compounds as described hereinabove are advantageously characterized by a vaporization temperature of less than 300° C. Moreover, such compounds can be transported in vapor form at less than 300° C. and under atmospheric pressure, with no or little (≦2%) residual material. The silicon-containing films that can be formed using such disilane precursor compounds include Si3N4 thin films, high k gate silicates and silicon epitaxial films. In a particularly preferred embodiment of the invention, the films formed using such silane or disilane precursors comprise silicon nitride.
Preferred silane or disilane compounds of the above-described formulas include, but are not limited to, Me3Si(HNNMe2), Si(HNNMe2)4, Me2(HNNMe2)Si—Si(HNNMe2)Me2, and (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2.
Synthesis and characterization of the above-listed preferred compounds is described in the following examples:
EXAMPLE 1
Synthesis and Characterization of Me3Si(HNNMe2)
A 3 L flask was filled with a solution comprising 2.5 L hexanes, 54.0 grams (0.53 mol) NEt3, and 30 grams (0.50 mol) of H2NNMe2. 58 grams (0.53 mol) Me3SiCl, as dissolved in 500 mL of hexanes, was slowly added into the 3 L flask at 0° C. White precipitate was observed during the addition of Me3SiCl. After the completion of the reaction, the mixture was warmed to room temperature, stirred overnight, and then filtered. The crude yield was in 80%. Regular distillation procedure was used to purify the end product, which has a boiling point of approximately 100° C. 1H NMR (C6D6): δ 0.15 (s, 9H,—SiCH3), 1.73 (br, 1H, —NH), 2.22 (s, 6H, —NCH3). 13C{1H} NMR (C6D6): δ −0.54 (—SiCH3), 52.4 (—NCH3). Mass spectrum: m/z 132 [M+], 117 [M+−Me)], 102 [M+−2Me)], 88 [M+−3Me)], 73 [M+−(—HNNMe2)].
Me3Si(HNNMe2) is a liquid at room temperature.
EXAMPLE 2
Synthesis and Characterization of Si(HNNMe2)4 
A 250 mL flask was filled with a solution comprising 200 mL hexanes, 12.2 grams (120.7 mmol) NEt3, and 7.25 grams (120.7 mmol) HNNMe2. 5.0 grams (29.4 mmol) SiCl4, as dissolved in 15 mL of hexanes, was slowly added into the 250 mL flask at 0° C. White precipitate was observed during the addition of SiCl4. After the completion of the reaction, the mixture was stirred overnight and then filtered at room temperature. All volatile materials were removed from the filtrate under vacuum. The crude yield was in 65% (5.0 g, 19.0 mmol). Purified end product was obtained by recrystallization in hexanes at −5° C. 1H NMR (C6D6): δ 2.42 (s, 24H,—CH3), 2.47 (br, 4H, —HN). 13C{1H} NMR (C6D6): δ 52.7 (—CH3). C8H28N8Si: Found (calculated) C: 36.15% (36.34%), H: 11.02% (10.67%), N: 42.66% (42.37%).
Si(HNNMe2)4 is a solid material having a melting temperature of approximately 73° C. The thermal stability of Si(HNNMe2)4 in solution at 100° C. was monitored by proton NMR study for 7 days, and no significant decomposition was detected.
FIG. 1 is a STA plot for Si(HNNMe2)4, indicating that Si(HNNMe2)4 can be transported completely with very little (<2%) residual material at 500° C.
FIG. 2 shows the X-ray crystal structure of Si(HNNMe2)4.
EXAMPLE 3
Synthesis and Characterization of Me2(HNNMe2)Si—Si(HNNMe2)Me2
A 3 L flask was filled with a solution comprising 2.5 L hexanes, 57 grams (561 mmol) anhydrous NEt3, and 50 grams (267 mmol) of Me2(Cl)Si—Si(Cl)Me2. 34 grams (561 mmol) H2NNMe2, as dissolved in 100 mL of diethyl ether, was slowly added into the 3 L flask at room temperature. White precipitate was observed during the addition of H2NNMe2. After the completion of the addition of H2NNMe2, the mixture was stirred overnight, and then filtered. All volatile materials were removed from the filtrate under vacuum. The crude yield was in 86% (54 g, 230 mmol). Vacuum distillation procedure was used to purify the end product, which has a boiling point of approximately 45° C. at 35 mTorr. 1H NMR (C6D6): δ 0.33 (s, 12H,—CH3Si), 1.90 (br, 2H, —HN), 2.27 (s, 12H,—CH3N). 13C{1H} NMR (C6D6): δ −0.68 (—SiCH3), 52.6 (—NCH3). Mass spectrum: m/z 175 [M+−(—HNNMe2)], 132 [M+−(—HNNMe2)−(—NMe2)], 116 [M+−(—SiMe2(HNNMe2)]. C8H26N4Si2: Found (calculated) C: 40.81% (40.98%), H: 10.99% (11.18%), and N: 23.67% (23.89%).
FIG. 3 shows the STA plot for Me4Si2(HNNMe2)2, which is a liquid at room temperature and can be transported in its vapor form completely with very little (<1%) residual material at about 350° C. The thermal stability of Me4Si2(HNNMe2)2 in solution at 100° C. was monitored by proton NMR study for 7 days, and no significant decomposition was detected.
EXAMPLE 4
Synthesis and Characterization of (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2 
A 250 mL flask filled with a solution comprising 120 mL of hexanes and 15.8 mL (1.6M, 25.3 mmol) of methyllithium ether solution. 1.52 grams (25.3 mmol) of H2NNMe was slowly bubbled into the 250 mL flask at 0° C. Upon completion of the addition, the reaction flask was allowed to warm to room temperature and stirred for an additional hour. To this flask, a 50 mL of diethyl ether solution containing 5 grams (12 mmol) of (HNBut)2(Cl)Si—Si(Cl)(HNBut)2 was slowly added at 0° C. The mixture was stirred overnight, and then refluxed for an additional four hours. After it was cooled to room temperature, it was filtered. All volatile materials were removed from the filtrate under vacuum. The crude yield was in 72% (4.0 grams, 8.64 mmol). Purified end product was obtained by recrystallization in hexanes at −20° C. 1H NMR (C6D6): δ 1.40 (s, 36H, —C(CH3)3), 1.55 (br, 4H, —HHC(CH3)3), 2.13 (br, 2H, —NHN(CH3)2), 2.43 (s, 12H, —NHN(CH3)2). 13C{1H} NMR (C6D6): δ 34.3 (—NHC(CH3)3), 49.5 (—NHC(CH3)3), 52.6 (—NHN(CH3)2). C20H54N8Si2: Found (calculated) C: 51.76% (51.90%), H: 12.14% (11.76%), N: 24.28% (24.21%).
FIG. 4 shows the STA plot for (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2, which is a solid at room temperature and can be transported completely with very little ( ̃0.03%) residual material at about 500° C.
Such silane or disilane derivative compounds as described hereinabove can be used for low-pressure CVD deposition of various silicon-containing films, including silicon nitride thin films, consistent with the disclosure in U.S. patent application Ser. No. 10/294,431 for “Composition and Method for Low Temperature Deposition of Silicon-Containing Films Including Silicon Nitride, Silicon Dioxide and/or Silicon-Oxynitride” filed on Nov. 14, 2002, published on May 20, 2004 as U.S. Patent Application Publication No. 2004/0096582, and now allowed, the content of which is incorporated by reference in its entirety for all purposes.
While the invention has been described herein with reference to various specific embodiments, it will be appreciated that the invention is not thus limited, and extends to and encompasses various other modifications and embodiments, as will be appreciated by those ordinarily skilled in the art. Accordingly, the invention is intended to be broadly construed and interpreted, in accordance with the ensuing claims.

## Claims

1. A disilane compound of the formula:




wherein R1, R2, R3, and R4 may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, aryl, and C3-C6 cycloalkyl, or R1 and R2 together may form a C3-C6 heterocyclic functional group with N, or R3 and R4 together may form a C3-C6 heterocyclic functional group with N, and wherein X1, X2, Y1, and Y2 may be the same as or different from one another and are independently selected from the group consisting of H, C1-C7 alkyl, alkylamino, dialkylamino, and alkylhydrazido having the formula R1R2NNH—, wherein R1 and R2 are as described above, and wherein R1, R2, R3, R4, X1, X2, Y1, and Y2 are not all methyl.

2. The disilane compound of claim 1, characterized by a substantially symmetrical structure in relation to the Si—Si bond.

3. The disilane compound of claim 1, having functional groups symmetrically distributed in relation to the Si—Si bond.

4. The disilane compound of claim 1, wherein X1, X2, Y1, and Y2 are all C1-C7 alkyl.

5. The disilane compound of claim 1, wherein X1 , X2, Y1, and Y2 are all methyl or ethyl.

6. The disilane compound of claim 1, characterized by a melting temperature of less than 100° C.

7. The disilane compound of claim 1, characterized by a vaporization temperature of less than 300° C.

8. (HNBut)2(HNNMe2)Si—Si(HNNMe2)(HNBut)2.