JP2005167044A - Forming method of low dielectric constant film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a low dielectric constant film which is excellent in the reproducibility of a formed film thickness in a film formation process and has a uniform property by preventing the lowering of film formation velocity in the film formation process and stabilizing film formation velocity. <P>SOLUTION: A borazine compound has a borazine frame expressed by a chemical formula (1). In the formula, X<SB>1</SB>, X<SB>2</SB>and X<SB>3</SB>can be the same or differ from one another and are hydrogen atoms, an amino group, a 1-4 C alkyl group, an alkenyl group, an alkynyl group, and a monoalkyl amino group or a dialkyl amino group, Y<SB>1</SB>, Y<SB>2</SB>and Y<SB>3</SB>can be the same or differ from one another and are hydrogen atoms, a 1-4 C alkyl group, an alkenyl group, an alkynyl group or a 3-12 C trialkylsilyl group each, and all of X<SB>1</SB>, X<SB>2</SB>, X<SB>3</SB>, Y<SB>1</SB>, Y<SB>2</SB>and Y<SB>3</SB>are not hydrogen atoms. The compound is dissolved and a film is formed by chemical vapor deposition by using a mixture with liquid which does not react with the compound and whose boiling temperature under atmospheric pressure is less than a gasification temperature of the compound as a raw material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low dielectric constant film formed by a chemical vapor deposition (hereinafter abbreviated as CVD) method for a low dielectric constant film used for an insulating film used between layers of a semiconductor element or a substrate of an electric circuit component. The present invention relates to a forming method.

As the speed and integration of semiconductor devices increase, the problem of signal delay is becoming serious. The signal delay is expressed by the product of the wiring resistance and the capacitance between the wirings and between the layers. In order to minimize the signal delay, in addition to reducing the wiring resistance, the dielectric of the interlayer insulating film Lowering the rate is an effective means.
Recently, a method for forming an interlayer insulating film including a B—C—N bond on a surface of an object to be processed by plasma CVD in an atmosphere including a hydrocarbon gas, a borazine, and a plasma gas has been disclosed. It is also disclosed that the interlayer insulating film has a low dielectric constant (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-354958 (first page)

  However, in the above conventional method, since borazine is used as a CVD raw material, a film having a low dielectric constant and a high mechanical strength can be formed. However, since the water resistance is poor, there is a problem that these characteristics are not sustained.

  The present invention has been made to solve such a problem, and can stably obtain a low dielectric constant and a high mechanical strength over a long period of time, and prevents a decrease in film formation rate during the film formation process. It is an object of the present invention to provide a method for forming a low dielectric constant film, which is excellent in the reproducibility of the film thickness during the film forming process and can obtain a low dielectric constant film having uniform characteristics by stabilizing the speed.

  The first low dielectric constant film forming method according to the present invention includes a compound having a borazine skeleton represented by the following chemical formula (1):

（上式中、Ｘ_１、Ｘ_２、Ｘ_３は同一でも異なっていてもよく、それぞれ水素原子、アミノ基、炭素数１〜４のアルキル基、アルケニル基、アルキニル基、モノアルキルアミノ基またはジアルキルアミノ基、Ｙ_１、Ｙ_２、Ｙ_３は同一でも異なっていてもよく、それぞれ水素原子、炭素数１〜４のアルキル基、アルケニル基、アルキニル基または炭素数３〜１２のトリアルキルシリル基で、Ｘ_１、Ｘ_２、Ｘ_３、Ｙ_１、Ｙ_２およびＹ_３の全てが水素原子ではない。）
と、この化合物を溶解し、かつこの化合物と反応せず、大気圧下の沸点が上記化合物の気化温度未満である液体との混合物を原料として、化学的気相成長法により成膜することを特徴とするものである。

(In the above formula, X ₁ , X ₂ and X ₃ may be the same or different, and each is a hydrogen atom, amino group, alkyl group having 1 to 4 carbon atoms, alkenyl group, alkynyl group, monoalkylamino group or dialkyl. The amino group, Y ₁ , Y ₂ and Y ₃ may be the same or different, and each is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group, an alkynyl group or a trialkylsilyl group having 3 to 12 carbon atoms. , X ₁ , X ₂ , X ₃ , Y ₁ , Y ₂ and Y ₃ are not all hydrogen atoms.)
And a chemical vapor deposition method using, as a raw material, a mixture of the compound with a liquid that dissolves the compound and does not react with the compound and has a boiling point under atmospheric pressure that is lower than the vaporization temperature of the compound. It is a feature.

  The first method for forming a low dielectric constant film of the present invention comprises a compound having a borazine skeleton represented by the above chemical formula (1), a compound that dissolves the compound and does not react with the compound, and has a boiling point under atmospheric pressure. Film formation by chemical vapor deposition using a mixture of the above compound with a liquid having a temperature lower than the vaporization temperature as a raw material prevents a decrease in film formation rate during the film formation process and stabilizes the film formation rate. As a result, the reproducibility of the film thickness during the film formation process is excellent, and a low dielectric constant film having uniform characteristics can be obtained.

Embodiment 1 FIG.
A film formed by CVD using a compound having a borazine skeleton represented by the above chemical formula (1) {hereinafter abbreviated as borazine compound (1)} as a raw material has a low dielectric constant, high mechanical strength, and excellent water resistance. Therefore, the above characteristics can be maintained for a long time. However, in the CVD method, when the solid borazine compound (1) is used as a CVD raw material and the vapor obtained by heating and melting it is introduced into a reaction vessel to form a film, Degradation of the borazine compound (1) occurs, and the film formation rate decreases during the film formation process, so that a film having uniform characteristics cannot be obtained.

  Therefore, the method for forming a low dielectric constant film according to the first embodiment of the present invention is to form a film using a mixture obtained by dissolving borazine compound (1) in the following liquid as a CVD raw material. By doing so, the temperature necessary for vaporizing the borazine compound (1) can be made lower than the temperature at which the borazine compound (1) solid is directly melted and vaporized, so that the borazine compound ( 1) can be prevented from being decomposed, the film forming speed during the film forming process is prevented from being lowered, and the characteristics of the formed film can be kept constant.

Therefore, the liquid according to the present embodiment is one that dissolves the borazine compound (1) and does not react with the borazine compound (1), and has a boiling point under atmospheric pressure that is lower than the vaporization temperature of the compound. By using this, the above effect can be obtained.
Although the liquid does not react with the borazine compound (1), specifically, the compound (1) easily undergoes a decomposition reaction under acidic conditions. A solvent that does not contain an attractive group (CO group, CN group, NO ₂ group, etc.), and a liquid that does not contain a group that becomes active hydrogen (for example, an OH group) that increases the acidity can be used. That is, as the liquid, carboxylic acids such as acetic acid and propionic acid, ester compounds thereof, α, γ-diketone compounds such as acetylacetone, and alcohols cannot be used.
Based on the above, liquids according to the present embodiment include aromatic hydrocarbons, aliphatic hydrocarbons, cycloaliphatic hydrocarbons, aliphatic ethers, alkyl-substituted amines, alkyl-substituted boranes, and alkylamino-substituted boranes. When arbitrarily selected from the above, for example, tetrahydrofuran, xylene, cyclohexane, hexane, triethylamine, or trisdimethylaminoborane is used as a material that satisfies the above conditions.

  The CVD raw material according to the present embodiment is obtained by dissolving the borazine compound (1) in the liquid according to the present embodiment, but the borazine compound (1) is dissolved in a concentration range of 1 to 10 mol / l. It is desirable to use those that have been prepared. If it is less than 1 mol / l, a sufficient film formation rate cannot be obtained, or the dielectric constant increases, and if it exceeds 10 mol / l, the viscosity of the solution increases, so that the material supply rate becomes unstable.

In the CVD method according to this embodiment, helium, argon, nitrogen, or the like is used as a carrier gas, and a raw material in which the borazine compound (1) is dissolved is introduced into the pipe through which the carrier gas flows, and the borazine compound (1). Is moved to the vicinity of the substrate on which the film is formed.
At this time, the characteristics of the film formed by mixing the carrier gas with a compound of methane, ammonia or an alkylamine can be controlled to a desired value.
The flow rate of the carrier gas is arbitrarily set in the range of 100 to 1000 sccm, and the flow rate of methane or amines gas is in the range of 5 to 100 sccm. Here, when the flow rate of the carrier gas is less than 100 sccm, the time for obtaining a desired film thickness becomes extremely slow, and the film formation may not proceed. On the other hand, if it exceeds 1000 sccm, the film thickness uniformity in the substrate surface tends to deteriorate. When the flow rate of methane or amine gas exceeds 100 sccm, the dielectric constant of the obtained film increases.

The gasified raw material carried in the vicinity of the substrate as described above is deposited on the substrate with a chemical reaction to form a film, but in order to cause the chemical reaction efficiently, heat, plasma or Laser light or the like can be used, and these may be used in combination. When heat is used, the gas temperature and substrate temperature are controlled between room temperature and 400 ° C. Here, if the source gas and the substrate temperature exceed 400 ° C., the time for obtaining a desired film thickness becomes extremely slow, and the film formation may not proceed.
When plasma is used, a substrate is placed in a parallel plate type plasma generator, and the source gas is introduced into the substrate. The RF frequency used at this time is 13.56 MHz or 400 kHz, and the power can be arbitrarily set within a range of 5 to 1000 W. It is also possible to use a mixture of RFs having different frequencies. Here, if the RF power used for plasma CVD exceeds 1000 W, the frequency of decomposition of the borazine compound (1) by plasma increases, and it becomes difficult to obtain a film having a desired borazine structure.
Further, when using light, deep UV light obtained from a KrF excimer laser or a low-pressure mercury lamp is used in the introduction path of the source gas or on the substrate surface.

In the borazine compound (1) according to the present embodiment, the group substituted with a hydrogen atom on boron is an amino group, an alkyl group having 1 to 4 carbon atoms, an alkenyl group, an alkynyl group, or a monoalkylamino group. Or a dialkylamino group is mentioned, and when the number of carbon atoms in a group containing carbon is larger than 4, the carbon atom content in the formed film increases, and the heat resistance and mechanical strength of the film deteriorate.
On the other hand, examples of the group substituted with a hydrogen atom on the nitrogen atom include an alkyl group having 1 to 4 carbon atoms, an alkenyl group, an alkynyl group, and a trialkylsilyl group having 3 to 12 carbon atoms. In the group containing carbon as in the substituent on the boron atom, if the carbon number is larger than the number of carbons described, the carbon atom content in the formed film increases, and the heat resistance and mechanical strength of the film deteriorate. .

Example 1.
A substrate was placed through a heated introduction tube with a CVD raw material solution comprising a tetrahydrofuran solution in which B, B, B-triethylborazine was dissolved to a concentration of 1 mol / l using nitrogen gas as a carrier gas. The film is introduced into the reaction vessel for 5 minutes to form a film (this is referred to as one film formation), and the film thickness and characteristics (dielectric constant) of the film formed on the substrate are shown in Table 1. It is shown in the column. At this time, the piping temperature to reach the reaction vessel was 23 ° C., the substrate temperature was heated to 300 ° C., and the vapor temperature of B, B, B-triethylborazine was 150 ° C. in the reaction vessel. The flow rate of the source gas was 100 sccm, and the reaction gas was turned into plasma by operating RF with a frequency of 13.56 MHz at 100 W in the reaction vessel.
Next, 29 more substrates were prepared, and in the reaction vessel, the above-mentioned “one film formation” was successively performed on each of the above substrates, and the substrates formed on the second, tenth, and thirty times. Table 1 shows the film thickness and characteristics (dielectric constant) thereof.

Comparative Example 1
In Example 1, the raw material gas was introduced in the same manner as in Example 1 except that the vapor of the borazine obtained by evaporating the B, B, B-triethylborazine simple substance to 150 ° C. was used as the carrier gas. The results are shown in Table 1.

As is apparent from Table 1, in Example 1, the borazine compound (1) is introduced into the reaction vessel in a solution state, so that stable film formation can be achieved even when film formation is repeatedly performed. .
On the other hand, in the method in which the borazine compound (1) is heated and directly introduced into the reaction vessel as in Comparative Example 1, characteristics such as film formation rate and dielectric constant change when film formation is repeated. I understand that. This indicates that the borazine compound (1) reacts with heat and changes in the raw material composition cause stable film formation.

Examples 2-6.
As shown in Table 2, film formation was performed on the substrate in the same manner as in Example 1 except that each borazine compound dissolved in each liquid at a predetermined concentration was used as a raw material for the CVD method. The film thickness and characteristics are measured and shown in the table above.

Comparative Examples 2-4.
As shown in Table 3, a film was formed on a substrate in the same manner as in Example 1 except that each borazine compound (1) dissolved in each liquid at a predetermined concentration was used as a raw material for the CVD method. Similarly to the above, the film thickness and characteristics are measured and shown in the above table.

As is clear from Tables 2 and 3, in Examples 2 to 6, stable film formation is possible even when the film formation is repeated, but in Comparative Examples 2 to 4, the borazine compound reacts with the solvent and decomposes. Therefore, during the film forming process, it is shown that the film thickness to be formed greatly decreases and the characteristics also deteriorate.
Further, Example 2 and Comparative Examples 2 to 4 use the same borazine compound, but it is also shown that Example 2 has a lower dielectric constant than Example 1 from the first film formation. This is considered to be due to partial decomposition of the borazine compound by active hydrogen contained in the solvent.

Example 7
As shown in Table 4, the film was formed once on the substrate in the same manner as in Example 1 except that B, B, B-triethylborazine was diluted with cyclohexane in various concentrations to obtain a CVD raw material. The film thickness and characteristics were measured in the same manner as in Example 1 and shown in the above table. However, in this example, the film was formed with RF of 300 W.

  For the B, B, B-triethylborazine that has not been diluted with the solvent, the same film formed once is also shown as “no dilution” in Table 4.

In Table 4, the film thickness uniformity is shown as the standard deviation value x3 of the in-plane film thickness, but the borazine compound dissolved in the solvent has a more uniform film thickness than that obtained by heating and vaporizing the borazine alone. It can be seen that the uniformity is particularly excellent in the concentration range of 1 to 10 mol / l.

Claims (4)

A borazine compound having a borazine skeleton represented by the following chemical formula (1)

(In the above formula, X ₁ , X ₂ and X ₃ may be the same or different, and each is a hydrogen atom, amino group, alkyl group having 1 to 4 carbon atoms, alkenyl group, alkynyl group, monoalkylamino group or dialkyl. The amino group, Y ₁ , Y ₂ and Y ₃ may be the same or different, and each is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group, an alkynyl group or a trialkylsilyl group having 3 to 12 carbon atoms. , X ₁ , X ₂ , X ₃ , Y ₁ , Y ₂ and Y ₃ are not all hydrogen atoms.)
And a chemical vapor deposition method using, as a raw material, a mixture of the compound with a liquid that dissolves the compound and does not react with the compound and has a boiling point under atmospheric pressure that is lower than the vaporization temperature of the compound. A method for forming a low dielectric constant film. 2. The method for forming a low dielectric constant film according to claim 1, wherein the liquid does not contain an electron withdrawing group in its molecular structure. 2. The method of forming a low dielectric constant film according to claim 1, wherein the liquid does not contain a group that generates active hydrogen in its molecular structure. 4. The method for forming a low dielectric constant film according to claim 1, wherein the concentration of the borazine compound in the mixture is 1 to 10 mol / l.