JP3124129B2 - Thin film formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film,
Particularly, the present invention relates to a method effective for forming an Al alloy thin film to be used as a wiring of a semiconductor integrated circuit device or the like.

[0002]

2. Description of the Related Art As semiconductor devices become finer and higher in density, the diameters of contact holes and via holes become 1 μm or less, and their aspect ratio (depth / diameter) is 1.0.
It's getting more. For this reason, it is not possible to sufficiently fill holes having a large aspect ratio with an alloy film of Al or Al-Si-Cu by a conventional sputtering method, which leads to disconnection of wiring and the like, which leads to lower reliability of LSI. Become.

In order to solve the above-mentioned problem caused by the sputtering method, recently, a blanket tungsten CVD method has been used.
The embedding of the connection hole by the use has begun to be practically used. However, there are various problems such as complicated processes and high resistance.

[0004] On the other hand, selective Al-CV
Research using D has been conducted. According to this method, A
Since l is densely embedded in the connection hole, the above-mentioned problem with tungsten is considered to be temporarily solved.
However, it is anticipated that the solid solution alloying of Al and Si in the contact portion locally progresses and breaks the pn junction. Further, since Cu, Mg, etc. are not contained, there is a problem that the electromigration resistance of the wiring is weakened.

As a method for solving the above-mentioned problem,
JP-A-3-111568 discloses Al-Cu or A
It describes an l-Si-Cu alloy CVD method.
Among the examples in this, dimethyl aluminum hydride
Bisacetyl as raw material gas containing DMAH and Cu
Luacetonate copper (Cu (C_FiveH₇O_Two)_Two) Such as copper organic containing oxygen
Al-Si-Cu alloy is formed using compound
ing. However, DMAH, which is the source gas for Al, is strong.
Cu (C), which is a source gas containing Cu, has a reducing property.
_FiveH₇O_Two)_Two And DMAH react during mixing to produce aluminum oxide
Um (Al_TwoO _Three) Is generated and this is taken into the membrane
(That is, if oxygen is mixed into the synthesized thin film)
Expected). Material containing halogen in Cu source gas
Material, for example, bishexafluoroacetylacetonate
Copper (Cu (C_FiveF₆HO_Two)_TwoThe same can be said when using)
You.

Japanese Patent Application Laid-Open No. 1-179416 describes a method of forming an aluminum alloy thin film by a CVD method using a metal alkoxide compound containing an alloying element to be alloyed with an aluminum alkoxide as a source gas. However, when the triisopropoxide aluminum (Al (O-iC ₃ H ₇ ) ₃ ) of this embodiment is used, the ordinary low pressure CVD
In the method, a large amount of oxygen is mixed in the film.

Further, Japanese Patent Application Laid-Open No. Hei 2-170419 discloses that cyclopentadienyltriethylphosphine copper ((η ⁵ -C ₅ H ₅ ) Cu (P (C ₂ H ₅ ) ₃ ) is used as a Cu material. It is said that this material gas contains neither oxygen nor halogen, but when the alloy film is formed, a large amount of impurities such as phosphorus are mixed in, and the resistance becomes larger. Another disadvantage is that a harmful phosphorus compound is generated during the film formation, which involves danger in the maintenance of the exhaust system, and as described above, it is difficult to form an Al alloy thin film by the conventional method. Yes, even if a film can be formed, resistance, purity and the like become problems.

[0008]

As described above, in the above-mentioned prior art, it was difficult to bury the connection hole reliably and to obtain a low-resistance wiring. An object of the present invention is to solve the above-mentioned technical problems and to provide a thin film forming method capable of forming a high-quality Al-based alloy film as a conductor with good controllability.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to an alkylaluminum hydride gas and an organometallic compound of copper or magnesium containing no oxygen, halogen, and phosphorus , wherein the organic group is 2-butyne or 2-pentyne. , Shiku
Lopentadienyl, methylcyclopentadienyl, cyclo
Looctadienyl, vinyltrimethylsilane and tri
A thin film forming method characterized by forming an aluminum alloy film on a semiconductor substrate by a chemical vapor deposition method using a gas of one or more methylsilylacetylenes and a hydrogen gas. .

The present invention is also directed to an alkylaluminum hydride gas and an organometallic compound of copper or magnesium free of oxygen, halogen, and phosphorus ,
The organic group is 2-butyne, 2-pentyne, cyclopentadie
Nil, methylcyclopentadienyl, cyclooctadie
Nyl, vinyltrimethylsilane and trimethylsilyl
A thin film forming method comprising forming an aluminum-silicon alloy film on a semiconductor substrate by a chemical vapor deposition method using a gas of at least one of acetylene, a gas containing silicon, and hydrogen gas. Is provided.

[0011]

According to the thin film forming method of the present invention, a reaction system of an alkyl aluminum hydride gas, a gas of an organometallic compound containing no oxygen, halogen, and phosphorus, a hydrogen gas, or a gas further containing Si. In the above, a dense Al alloy film with low resistance can be deposited on the substrate. When the Al alloy film obtained according to the present invention is used for filling the connection hole, a wiring having improved electromigration resistance can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the present invention, a high-quality Al alloy film is grown on a semiconductor substrate by a CVD method. FIG. 1 shows a CVD apparatus used to carry out the Al alloy thin film forming method according to the present invention. The apparatus includes a substrate holder 3 having a heater 4 built in a reaction tube 2. The temperature of the substrate surface can be raised to 500 ° C. by the heater 4.
The inner wall of the reaction tube 2 can be water-cooled. The substrate 1 on which a film is to be formed is placed on the substrate holder 3 through the load lock 8, and about 1 × 10
Exhaust to ^-8 Torr. After that, the substrate temperature is raised to 200 to 400 ° C. by the heater 4. Exhaust unit 5
Consists of a turbo molecular pump and a rotary pump.

As a raw material for Al, DMAH, which is widely used in Al-CVD, is used. Since DMAH is a colorless liquid having a relatively high vapor pressure, bubbling with hydrogen gas from the gas line 10 using the bubbler 6 is necessary to introduce the DMAH into the reaction tube. Its chemical properties are strong reducing properties, so it reacts with water and oxygen. Therefore, the raw material gas is introduced after paying sufficient attention to the cleanliness of the gas pipe, the reaction and the carrier gas.

As a raw material of the organometallic compound containing an alloying element to be alloyed, an organometallic compound containing no oxygen, halogen and phosphorus in the molecule is used in order to prevent a direct reaction with DMAH. The compound has two atoms per metal atom.
It is one in which the functional groups are bonded. The following table shows typical examples of usable source gases for each element. In the above formula, R ₁ and R ₂ are η ⁸ -C ₈ H ₈ (cyclooctadienyl, COD), η ⁵ -C ₅ H ₅ (cyclopentadienyl, Cp), 2-butyne (2 -butyne) ) ,
2-pentyne (2- pentyne), C ₅ H ₁₂ Si
(Vinyl trimethylsilane, VTMS), C ₈ H ₁₈ Si
₂ (bistrimethylsilylacetylene) and the like, which may be the same or different.

For example, in the case of Mg, biscyclopentadienyl magnesium (Mg (η ⁵ -C ₅ H ₅ ) ₂ ) or bismethylcyclopentadienyl magnesium (Mg (η ⁵ -CH ₃ C ₅ H ₄ ) ₂ ) Can be used. The raw materials listed in these tables are liquids or sublimable solids. To introduce them into the reaction tube, the bubbler 7 filled with the raw materials and the gas line to the reaction tube are heated. Gas line 11 for transport to reaction tube 2
Bubbling with hydrogen.

As a material gas containing Si, tetramethylsilane (Si (CH ₃ ) ₄ ) or trimethylsilane (SiH (CH ₃ ) ₃ ) having a low decomposition temperature is used.
These gases are diluted with hydrogen and introduced into the reaction tube 2 from the gas line 12.

Using the above three kinds of source gases, an Al alloy film is synthesized by the following two methods. One of the methods is to form a film by sufficiently mixing the above-mentioned raw material gas with hydrogen as a reaction gas before being introduced into the reaction tube 2. This reaction gas is introduced from a gas line 9. The other is a method in which a thin film of pure Al is first synthesized, a metal film to be alloyed is formed, and the metal to be alloyed is diffused into the Al film by an annealing treatment and alloyed. At this time, the thickness of the metal film to be alloyed is preferably as thin as possible.

As a method of cleaning the substrate before film formation, 0.5%
It is immersed in a pure hydrofluoric acid aqueous solution for 1 to 2 minutes, and then immediately washed with pure water and dried. This is performed to remove a natural oxide film in the connection hole on the semiconductor substrate. This cleaning selectively embeds the alloy film only in the connection hole. In addition, when the pretreatment with the titanium solution is performed, the entire surface can be formed non-selectively.

Immediately after drying, the substrate 1 is set on the substrate holder 3 in the thin film forming apparatus through a load lock. Before and after the film formation, the inside of the reaction tube is evacuated to about 1 × 10 ⁻⁸ Torr.

Next, hydrogen as a reaction gas is supplied to the reaction tube 2, the pressure in the reaction tube is maintained at about 2 Torr, and each raw material gas is introduced to make the total pressure in the range of 1 to 3 Torr.
The film is formed for 5 to 10 minutes. The resulting deposition rate is 500
Å2000 ° / min.

The selective growth of the Al alloy film with respect to the connection hole of the substrate will be described with reference to FIG. FIG. 2 (a)
Is a cross-sectional view of an n-type silicon substrate 21 on which patterning for depositing an oxide film 23 has been performed and ap ⁺ diffusion layer 22 has been formed by ion implantation. After washing the substrate with the above 0.5% hydrofluoric acid pure aqueous solution,
When the 1 alloy film is formed, as shown in FIG. 2B, the Al alloy film is selectively embedded only in the connection hole, not on the oxide film 23.

As described above, the Al alloy film obtained by the above-described thin film forming method can be buried sufficiently densely in the connection hole on the semiconductor substrate. Thereby, a low-resistance and highly reliable wiring for a semiconductor device can be obtained.

Example 1 A film of an Al—Cu alloy was formed using the above-described CVD apparatus. DMAH is used as a source gas for Al, and cyclooctadienyl-2-butyne copper ((η ⁸ -C ₈
H ₈ ) Cu (2-butyne)) was used. The reaction gas is hydrogen. When the total pressure of the reaction tube 2 was maintained at about 2.0 to 3.0 Torr and the substrate temperature was changed in the range of 240 to 280 ° C., the film formation was performed, and the film formation rate was 1000 to 2000 ° / min. The flow rate of the carrier gas supplied to the bubbler is Al, Cu
The material was 100 sccm, the bubbler temperature was about 50 ° C. for DMAH, and 60 ° C. for cyclooctadienyl-2-butyne copper.
１２０120 ° C. As a result of examining the film composition of the film obtained by Auger electron spectroscopy or the like, impurities such as oxygen were hardly mixed. Further, the content of Cu is 0.1 to 0.1.
5%. The specific resistance was about 3.0 μΩcm. This value is the value of the bulk of pure Al (about 2.
7 μΩcm). Further, the electromigration life of the wiring in the case of using each of the wiring obtained by the alloy CVD and the wiring formed by the Al-CVD was examined for the wiring formed by depositing a film on a substrate and patterning the entire surface. Table 1 shows the results. That is, the wiring of the Al-Cu alloy was about 36 times longer than the wiring by Al-CVD, and it was found that its reliability was high.

(Embodiment 2) Using the same CVD apparatus as in Embodiment 1, a film of an Al-Si-Cu alloy was formed. Al
As the raw material gas use DMAH, cyclopentadienyl vinyltrimethylsilane copper as a material containing Cu to alloying ^{_{((η 5 -C 5 H 5}} ) Cu (VTMS)), tetramethylsilane as the gas containing Si (Si (CH ₃ ) ₄ ) was used.
The reaction gas is hydrogen. The total pressure of the reaction tube 2 is about 2.0 to
When the film was formed while maintaining the pressure at 3.0 Torr and changing the substrate temperature in the range of 240 to 280 ° C., the film formation speed was 500.
１1200 ° / min. The flow rate of the carrier gas supplied to the bubbler and the bubbler temperature are the same as those in Example 1 (the flow rate of tetramethylsilane is 10 to 20 sccm). As a result of examining the film composition of the film obtained by Auger electron spectroscopy or the like, impurities such as oxygen and carbon were hardly mixed.
The contents of Cu and Si are each 0.1 to 0.5.
%, 0.5 to 0.8%. The specific resistance was about 3.5 μΩcm. This value is very close to the bulk value of pure Al (about 2.7 μΩcm). Also,
A substrate having a structure as shown in FIG. 2 (b) was manufactured in order to examine the junction leak failure rate of the film obtained by the alloy CVD. The result is expressed as Al-C
The results are shown in Table 2 together with those by VD. That is, the leak failure rate of the Al-Si-Cu alloy did not change even after the annealing treatment as compared to immediately after the film formation, and no junction breakdown due to solid solution alloying occurred.

(Embodiment 3) Using the same CVD apparatus as in Embodiment 1, a film of an Al--Mg alloy was formed. DMAH was used as a source gas for Al, and biscyclopentadienyl magnesium (Mg (η ⁵ -C ₅ H ₅ ) ₂ ) was used for Mg. The reaction gas is hydrogen. The total pressure of the reaction tube 2 is about 1.0
While maintaining the pressure at -2.0 Torr, pure Al was first deposited to a film thickness of about 5000 °, and then pure Mg was deposited to a thickness of 100 °. This is 300
After hydrogen annealing at 30 ° C. for 30 minutes, an Al—Mg alloy was obtained. As a result of examining the composition of this film, impurities such as oxygen were hardly mixed, and the content of Mg was 0.2 to 1%.
%Met. The specific resistance was about 3.2 μΩcm. The electromigration life of the wiring when each of the wiring obtained by alloy CVD and the wiring by Al-CVD was used was examined in the same manner as in Example 2. Table 3 shows the results. That is, Al-
The wiring of Mg alloy is about 2 times larger than the wiring by Al-CVD.
It was 0 times longer, indicating that its reliability was high.

(Embodiment 4) Using the same CVD apparatus as in Embodiment 1, a film of an Al-Cu alloy was formed. DMAH was used as the source gas for Al, and cyclooctadienyl-2-butyne copper ((η ⁸ -C ₈ H ₈ ) Cu (2-butyne)) was used for Cu, and oxygen and halogen were used as comparison targets. Bishexafluoroacetylacetonate containing copper (Cu (C ₅ F ₆ HO ₂ )
₂ ) was also used. The reaction gas is hydrogen. The total pressure of the reaction tube 2 was maintained at about 1.0 to 2.0 Torr, and both gases were introduced at the same time. When the former cyclooctadienyl-2-butyne copper was used, an Al—Cu alloy containing almost no impurities such as oxygen and carbon was obtained.
AH and the Cu raw material reacted directly, and a film containing a large amount of oxygen was synthesized. When the specific resistance was measured, the former was about 3 μΩcm, and the latter was a very high value of about 15 μΩcm. That is, it was found that the use of the former copper cyclooctadienyl-2-butyne free of oxygen and halogen gave a more reliable product.

[0027]

According to the formation method of the present invention, a low-resistance, dense Al alloy film is formed on a substrate by using an alkylaluminum hydride gas and an organometallic compound containing no oxygen, halogen and phosphorus as raw materials. Can be deposited on top. As another effect, an Al alloy film having improved electromigration resistance can be deposited on a substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a thin film forming apparatus to which the present invention can be applied.

FIG. 2 is a cross-sectional view of a substrate before and after film formation in an example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate 2 Reaction tube 3 Substrate holder 4 Heater 5 Exhaust unit 6 Bubbler of raw material A 7 Bubbler of raw material B 8 Load lock 9 Reaction gas line 10 Carrier gas line 11 Carrier gas line 12 Gas line of raw material C 21 n-type silicon substrate 22 p ⁺ diffusion layer 23 oxide film 24 Al alloy film

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yamamoto 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Headquarters, Kawasaki Steel Works Co., Ltd. (72) Inventor Tadashi Nakano 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Address Kawasaki Steel Corp. Technical Research Division (56) References JP-A-3-110838 (JP, A) JP-A-4-214868 (JP, A) JP-A-6-2722042 (JP, A) JP-A-4-355965 (JP, A) JP-A-3-111568 (JP, A) JP-A-2-170419 (JP, A) JP-A-1-179416 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/285 301 H01L 21/285 C23C 16/20

Claims (3)

(57) [Claims] An alkylaluminum hydride gas and a copper or copper gas containing no oxygen, halogen, and phosphorus .
An organometallic compound of gnesium , wherein the organic group is 2-butane.
Tin, 2-pentyne, cyclopentadienyl, methyl
Clopentadienyl, cyclooctadienyl, vinyl
One of trimethylsilane and trimethylsilylacetylene
A thin film forming method, wherein an aluminum alloy film is formed on a semiconductor substrate by a chemical vapor deposition method using at least one gas and hydrogen gas. 2. An alkylaluminum hydride gas and oxygen or halogen or phosphorus-free copper or copper.
An organometallic compound of gnesium , wherein the organic group is 2-butane.
Tin, 2-pentyne, cyclopentadienyl, methyl
Clopentadienyl, cyclooctadienyl, vinyl
One of trimethylsilane and trimethylsilylacetylene
A thin film forming method, comprising forming an aluminum-silicon alloy film on a semiconductor substrate by a chemical vapor deposition method using at least one gas, a gas containing silicon, and a hydrogen gas. (3) The organometallic compound is copper or magnesium;
2-butyne, 2-pentyne, cyclopentadi
Enyl, methylcyclopentadienyl, cyclooctadi
Enyl, vinyltrimethylsilane and trimethylsilyl
Two identical or different organics selected from ruacetylene
Wherein the groups are bonded.
The method for forming a thin film according to claim 2.