Plasma enhanced cyclic chemical vapor deposition of silicon-containing films

Abstract

The present invention is a process of plasma enhanced cyclic chemical vapor deposition of silicon nitride, silicon carbonitride, silicon oxynitride, silicon carboxynitride, and carbon doped silicon oxide from alkylaminosilanes having Si—H3, preferably of the formula (R1R2N)SiH3 wherein R1 and R2 are selected independently from C2 to C10 and a nitrogen or oxygen source, preferably ammonia or oxygen has been developed to provide films with improved properties such as etching rate, hydrogen concentrations, and stress as compared to films from thermal chemical vapor deposition.

Description

BACKGROUND OF THE INVENTION

The electronic device manufacturing industry has used chemical vapor deposition (CVD), cyclic chemical vapor deposition (CCVD), or atomic layer deposition (ALD) of silicon nitride, silicon carbonitride, and silicon oxynitride in making integrated circuits. Examples of this industry use include: US 2003/0020111; US 2005/0048204 A1; U.S. Pat. Nos. 4,720,395; 7,166,516; Gumpher, J., W. Bather, N. Mehta and D. Wedel. “Characterization of Low-Temperature Silicon Nitride LPCVD from Bis(tertiary-butylamino)silane and Ammonia.” Journal of The Electrochemical Society 151(5): (2004) G353-G359; US 2006/0045986; US 2005/152501; US 2005/255714; U.S. Pat. No. 7,129,187; U.S 2005/159017; U.S. Pat. Nos. 6,391,803; 5,976,991; US 2003/0059535; U.S. Pat. No. 5,234,869; JP2006-301338; US 2006/087893; US 2003/26083; US 2004/017383; U.S. 2006/0019032; US 2003/36097; US 2004/044958; U.S. Pat. Nos. 6,881,636; 6,963,101; US 2001/0000476; and US2005/129862. The present invention offers an improvement over this prior industry practice for CVD or ALD of silicon-containing films such as silicon nitride, silicon carbonitride, silicon oxynitride, and silicon carbon oxide, and carbon doped silicon oxide on a substrate, as set forth below.

BRIEF SUMMARY OF THE INVENTION

The present invention is a process to deposit silicon-containing films such as silicon nitride, silicon carbonitride, silicon oxynitride, and carbon doped silicon oxide on a substrate.

One embodiment of the present invention is a process to deposit silicon nitride, silicon carbonitride, silicon oxynitride, and silicon carboxynitride on a semi-conductor substrate comprising:

• • a. contacting a nitrogen-containing source with a heated substrate under remote plasma conditions to absorb at least a portion of the nitrogen-containing source on the heated substrate,
  • b. purging away any unabsorbed nitrogen-containing source,
  • c. contacting the heated substrate with a silicon-containing source having one or more Si—H₃ fragments to react with the absorbed nitrogen-containing source, wherein the silicon-containing source has one or more H₃Si—NR⁰₂ (R⁰=SiH₃, R, R¹ or R², defined below) groups selected from the group consisting of one or more of:

• • • wherein R and R¹ in the formulas represent aliphatic groups having from 2 to 10 carbon atoms, wherein R and R¹ in formula A may also be a cyclic group, and R² selected from the group consisting of a single bond, (CH₂)_n, a ring, or SiH₂, and
  • d. purging away the unreacted silicon-containing source.

Another embodiment of the present invention is a process to deposit silicon oxynitride, silicon carboxynitride, and carbon doped silicon oxide on a substrate comprising:

• • a. contacting a oxygen-containing source with a heated substrate under remote plasma conditions to absorb at least a portion of the oxygen-containing source on the heated substrate,
  • b. purging away any unabsorbed oxygen-containing source,
  • c. contacting the heated substrate with a silicon-containing source having one or more Si—H₃ fragments to react with the absorbed nitrogen-containing source, wherein the silicon-containing source has one or more H₃Si—NR⁰₂ (R⁰=SiH₃, R, R¹ or R², defined below) groups selected from the group consisting of one or more of:

• • • wherein R and R¹ in the formulas represent aliphatic groups having from 2 to 10 carbon atoms, wherein R and R¹ in formula A may also be a cyclic group, and R² selected from the group consisting of a single bond, (CH₂)_n, a ring, or SiH₂, and
  • d. purging away the unreacted silicon-containing source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scheme of typical plasma enhanced cyclic chemical vapor deposition for silicon nitride, silicon carbonitride, silicon oxynitride, and silicon carboxynitride.

FIG. 2 is a Deposition Rate vs Pulse Time graph for DIPAS with the following PEALD experimental conditions: 5 sccm NH₃ with plasma power of 1.39 kW, 10 sccm N₂ as sweeping gas, substrate temperature of 400° C., DIPAS at 40° C. in a stainless steel container.

FIG. 3 is a scheme of typical plasma enhanced cyclic chemical vapor deposition for silicon oxynitride and carbon doped silicon oxide.

FIG. 4 is the FTIR spectrum for the films of Example 1 and discussed in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a process of plasma enhanced cyclic chemical vapor deposition of silicon nitride, silicon carbonitride, silicon oxynitride, silicon carboxynitride, and carbon doped silicon oxide from alkylaminosilanes having Si—H₃, preferably of the formula (R¹R²N)SiH₃ wherein R¹ and R² are selected independently from C₂ to C₁₀ and a nitrogen source, preferably ammonia has been developed to provide films with improved properties such as etching rate, hydrogen concentrations, and stress as compared to films from thermal chemical vapor deposition. Alternately, the process can be performed as atomic layer deposition (ALD), plasma assisted atomic layer deposition (PAALD), chemical vapor deposition (CVD), low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD) or spin on deposition (SOD).

A typical cycle of plasma enhanced cyclic chemical vapor deposition is given FIG. 1.

The remote plasma chamber is a Litmas RPS manufactured by Advanced Energy Industries, Inc. The Litmas RPS is a cylindrical inductive plasma source (quartz chamber) integrated with a solid-state RF power delivery system. Water cooled coils are wrapped around the chamber to provide cooling for the chamber and to form the RF antenna. The frequency operating range is between 1.9 MHz and 3.2 MHz. The DC output power range is 100 W to 1500 W.

The ALD system is a Savannah 100 manufactured by Cambridge NanoTech, Inc. The ALD reactor is anodized aluminum and accommodates a 100 mm silicon substrate. The ALD reactor has an embedded disk-shaped heating element which heats the substrate from the bottom. There is also a tubular heater embedded in the reactor wall. The precursor valve manifold is enclosed within a heating block, and heating jackets are used to heat the precursor vessels. The ALD valves in the precursor valve manifold are three-way valves, which continuously supply 10-100 sccm of inert gas to the ALD reactor.

The deposition process for silicon nitride, silicon carbonitride, silicon oxynitride, and silicon carboxynitride is described in the following.

In the first step of the process, ammonia plasma is generated in a remote plasma chamber installed approximately 12 inches upstream of the deposition chamber and is supplied to the deposition chamber at a predetermined volume flow rate and for a predetermined time. Typically, the ammonia plasma is supplied to the ALD chamber by opening the gate valve between the remote plasma head and the ALD reactor for a period of 0.1 to 80 seconds to allow the ammonia radicals to be sufficiently adsorbed so as to saturate a substrate surface. During deposition, the ammonia flow rate supplied to the inlet of the remote plasma chamber is typically in the range of 1 to 100 sccm. The RF power in the plasma chamber is variable between 100 W and 1500 W. Deposition temperatures are conventional and range from about 200 to 600° C., preferably from 200 to 400° C. for atomic layer deposition and 400 to 600° C. for cyclic chemical vapor deposition. Pressures of from 50 mtorr to 100 torr are exemplary. In addition, to ammonia, other nitrogen-containing source can be nitrogen, hydrazine, monoalkylhydrozine, dialkylhydrozine, and mixture thereof.

In the second step of the process, an inert gas, such as Ar, N₂, or He, is used to sweep unreacted ammonia radicals from the chamber. Typically in a cyclic deposition process, a gas, such as Ar, N₂, or He, is supplied into the chamber at a flow rate of 10 to 100 sccm, thereby purging the ammonia radicals and any byproducts that remain in the chamber.

In the third step of the process, an organoaminosilane, such as diethylaminosilane (DEAS), di-iso-propylaminosilane (DIPAS), di-tert-butylaminosilane (DTBAS), di-sec-butylaminosilane, di-tert-pentylamino silane and mixtures thereof, is introduced into the chamber at a predetermined molar volume. e.g., from 1 to 100 micromoles for a predetermined time period, preferably about 0.005 to 10 seconds. The silicon precursor reacts with the ammonia radicals adsorbed on the surface of the substrate resulting in the formation of silicon nitride. Conventional deposition temperatures of from 200 to 500° C. and pressures of from 50 mtorr to 100 torr are employed.

In the fourth step of the process, an inert gas, such as Ar, N₂, or He, is used to sweep unreacted organoaminosilane from the chamber. Typically in a cyclic deposition process, a gas, such as Ar, N₂, or He, is supplied into the chamber at a flow rate of 10 to 100 sccm, thereby purging the organoaminosilane and any byproducts that remain in the chamber.

The four process steps described above comprise a typical ALD process cycle. This ALD process cycle is repeated several times until the desired film thickness is obtained.

FIG. 2. exhibits a typical ALD saturation curve at a substrate temperature of 400° C.

A typical cycle of plasma enhanced cyclic chemical vapor deposition for silicon oxynitride and carbon doped silicon oxide given FIG. 3.

In the first step of the process, oxygen plasma is generated in a remote plasma chamber installed approximately 12 inches upstream of the deposition chamber and is supplied to the deposition chamber at a predetermined volume flow rate and for a predetermined time. Typically, the oxygen plasma is supplied to the ALD chamber by opening the gate valve between the remote plasma head and the ALD reactor for a period of 0.1 to 80 seconds to allow the oxygen containing radicals to be sufficiently adsorbed so as to saturate a substrate surface. During deposition, the oxygen flow rate supplied to the inlet of the remote plasma chamber is typically in the range of 1 to 100 sccm. The RF power in the plasma chamber is variable between 100 W and 1500 W. Deposition temperatures are conventional and range from about 200 to 600° C., preferably from 200 to 400° C. for atomic layer deposition and 400 to 600° C. for cyclic chemical vapor deposition. Pressures of from 50 mtorr to 100 torr are exemplary. In addition to oxygen, other oxygen-containing source can be ozone, nitrous oxide, and mixture thereof.

In the second step of the process, an inert gas, such as Ar, N₂, or He, is used to sweep unreacted oxygen containing radicals from the chamber. Typically in a cyclic deposition process, a gas, such as Ar, N₂, or He, is supplied into the chamber at a flow rate of 10 to 100 sccm, thereby purging the oxygen containing radicals and any byproducts that remain in the chamber.

In the third step of the process, an organoaminosilane, such as diethylaminosilane (DEAS), di-iso-propylaminosilane (DIPAS), di-tert-butylaminosilane (DTBAS), di-sec-butylaminosilane, di-tert-pentylamino silane and mixtures thereof, is introduced into the chamber at a predetermined molar volume. e.g., from 1 to 100 micromoles for a predetermined time period, preferably about 0.005 to 10 seconds. The silicon precursor reacts with the oxygen containing radicals adsorbed on the surface of the substrate resulting in the formation of silicon nitride. Conventional deposition temperatures of from 200 to 500° C. and pressures of from 50 mtorr to 100 torr are employed.

In the fourth step of the process, an inert gas, such as Ar, N₂, or He, is used to sweep unreacted organoaminosilane from the chamber. Typically in a cyclic deposition process, a gas, such as Ar, N₂, or He, is supplied into the chamber at a flow rate of 10 to 100 sccm, thereby purging the organoaminosilane and any byproducts that remain in the chamber.

The four process steps described above comprise an ALD process cycle. This ALD process cycle is repeated several times until the desired film thickness is obtained.

EXAMPLE 1

In an ALD reactor, the said silicon precursor was introduced along with NH₃ after the reactor was pumped down to a vacuum level of ˜40 mT and purged with 10 sccm N₂. The deposition was performed at a temperature of 400° C. A remote plasma was also used to reduce the required deposition temperature. The said silicon precursor was pre-heated to 40° C. in a bubbler wrapped with a heat jacket before being introduced into the reactor. The results are summarized in Table 1.

Since only very small amount of chemical was used during one deposition, the flow rate (amount per unit time) of the said silicon precursor out of the bubbler can then be considered to be constant at a given temperature. Therefore, the amount of the said silicon precursor added into the ALD reactor is linearly proportional to the pulse time used to introduce the said silicon precursor.

As can be seen from Table 1, the rate of forming silicon nitride films changes as the amount of the said silicon precursor added into the reactor changes even when the deposition temperature and the amount of nitrogen precursor are kept the same.

It can also be seen from Table 1, when other processing conditions are kept the same, the rate of forming silicon nitride films increases initially from 0.156 A/cycle as the pulse time (or amount) of the said silicon precursor increases from 0.01 seconds to 0.05 seconds. Then, however, the rate remains almost unchanged after even more silicon precursor is added. This suggests that the films formed using the Si precursor are indeed ALD films.

TABLE 1
Temperature	NH3 pulse	Silicon precursor	Deposition Rate
(° C.)	(second)	pulse time (second)	(A/cycle)
400	3	0.01	0.156
400	3	0.025	0.272
400	3	0.05	0.318
400	3	0.1	0.307
400	3	0.2	0.3

EXAMPLE 2

The deposited ALD films were analyzed using FTIR. The FTIR spectrum for the films is shown in FIG. 4. As can be seen from FIG. 4 there is an absorbance peak at 1046 cm⁻¹, suggesting oxide presence in the film. The peak at 3371 is an N—H stretch (with some O—H) and has the corresponding rock at the shoulder near 1130 cm−1. The 2218 peak is from Si—H and its broad shape indicates a low stress film. The 813 peak is near Si—N. An EDX analysis of the deposited films also confirmed the presence of Si and N in the films.

The embodiments of the present invention listed above, including the working examples, are exemplary of numerous embodiments that may be made of the present invention. It is contemplated that numerous other configurations of the process may be used, and the materials used in the process may be selected from numerous materials other than those specifically disclosed. In short, the present invention has been set forth with regard to particular embodiments, but the full scope of the present invention should be ascertained from the claims as follow.

Claims

1. A process to deposit silicon oxynitride, silicon carboxynitride, and carbon doped silicon oxide on a semi-conductor substrate comprising: a. contacting a heated substrate with an oxygen-containing plasma comprising oxygen-containing radicals to absorb at least a portion of the oxygen-containing radicals on the heated substrate, wherein the oxygen-containing plasma was generated at a location remote relative to the substrate;b. purging away any unabsorbed oxygen-containing radicals;c. contacting the heated substrate with a silicon-containing source having one or more Si—H3 fragments to react with the absorbed oxygen-containing radicals, wherein the silicon-containing source is selected from the group consisting of di-iso-propylaminosilane (DIPAS), di-tert-butylaminosilane (DTBAS), di-sec-butylaminosilane, di-tert-pentylamino silane and mixtures thereof; andd. purging away any unreacted silicon-containing source.

2. The process of claim 1 wherein the process is repeated until a desired thickness of film is established.

3. The process of claim 1 wherein the process is an atomic layer deposition.

4. The process of claim 1 wherein the process is a plasma enhanced cyclic chemical vapor deposition.

5. The process of claim 1 wherein the substrate temperature is in the range of 200 to 600° C.

6. The process of claim 1 wherein the oxygen-containing radicals are generated by subjecting an oxygen-containing gas to plasma energy, wherein the oxygen-containing gas is selected from the group consisting of oxygen, nitrous oxide, ozone, and mixture thereof.