JP2735525B2 - Chemical vapor deposition 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 chemical vapor deposition method for various thin films used for manufacturing electronic devices such as integrated circuits, and more particularly to a chemical vapor deposition method suitable for forming a wiring material. .

[0002]

2. Description of the Related Art Sputtering and vapor deposition have been widely used as a method for forming a wiring material such as Al. However, chemical vapor deposition using organic Al as a source has attracted attention because of its excellent step coverage. I have. In addition, a vapor growth method using WF ₆ as a source is used for a selective growth technique such as a W plug.

[0003] In the conventional film forming technique, as shown in a gas supply sequence of FIG. 3, a vapor phase growth is performed while supplying a reactant gas to a reaction chamber at a constant flow rate (hereinafter, a first conventional example). ). However, when forming a thick metal film by this method, even if the flow rate of the reactant gas is constant,
As shown in FIG. 3, the film forming speed gradually decreases. And
In the case of a thick film formed by continuous growth, unevenness occurs on the surface, and a good surface morphology cannot be obtained. Although the cause of such film quality deterioration is not always clear, it is thought that the presence of the reaction product has an adverse effect.

In order to eliminate the adverse effect of continuously supplying the source gas, a method of intermittently supplying the source gas (hereinafter referred to as a second conventional example) has been proposed. FIG.
FIG. 1 is a gas supply sequence diagram of a vapor phase growth method proposed in Japanese Patent Application Laid-Open No. 4-64223. In this method, the substrate temperature is raised to a predetermined temperature, H ₂ as a carrier gas is supplied, and WF ₆ and SiH ₄ as source gases are supplied intermittently. In this embodiment, the source gas supply period (t) is set to about 15 seconds with a rest period (Tt) of about 30 seconds interposed therebetween. According to this growth method, fluorine taken into the W film can be diffused outward during the suspension of the supply of the source gas, so that a low-resistance W plug can be formed. A similar technique is disclosed in
Japanese Patent Application Laid-Open No. 215668/1992 and Japanese Patent Application Laid-Open No. 4-263072.

[0005]

In the above-mentioned first conventional example, when a thick film is formed, the film forming speed is reduced, and a metal film having good film quality cannot be obtained. Also, the second
In the prior art, since the reactant gas is intermittently supplied by opening and closing a valve provided in the reactant gas supply system, the frequency of opening and closing the valve is significantly increased, and the quality of the deposited film is deteriorated due to an increase in dust generation. In addition, there is a problem that the deterioration of the valve is accelerated and the operation time of the CVD apparatus is reduced due to an increase in the frequency of replacing the valve.

When the raw material gas has a low vapor pressure such as an organometallic compound and needs to be supplied by bubbling the reaction raw material gas with a carrier gas, the reaction gas is reacted with a bypass system for directly supplying the carrier gas to the reaction chamber. It is often used by switching to a bubbling system supplied through a bubbling container for the raw material. In such a case, when the carrier gas is switched from the bypass system to the bubbling system, as shown in the gas supply sequence in FIG. When switching to the bubbling system, the reactant gas, which has been completely vaporized and trapped inside the bubbling vessel, is supplied all at once, so that the source gas pressure and the total pressure in the reaction chamber temporarily rise, If both the bypass system and bubbling system valves are closed, the carrier gas pressure rises and bubbling occurs. When the carrier gas is supplied by opening the valve, a transient change occurs, such as a sudden increase in the flow rate including the reactant and a sudden increase in the pressure of the carrier gas in the reaction chamber. There was a problem that controllability deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide a high-quality conductive film by a growth method with good controllability. Another object of the present invention is to reduce the chance of replacing parts in a gas supply system that requires complicated operations.

[0008]

In order to achieve the above object, a chemical vapor deposition method according to the present invention intermittently controls the amount of exhaust gas from an exhaust system while supplying a source gas to a reaction chamber at a constant flow rate. The film formation is performed while increasing and decreasing the pressure in the reaction chamber while decreasing and increasing the pressure.

[0009]

FIG. 1 is a schematic diagram showing an outline of a vapor phase growth apparatus for performing a vapor phase growth method according to the present invention. As shown in FIG. 1, a sample table 8 having a built-in heater is arranged in the reaction chamber 1, and a sample 9 is mounted thereon. The reaction chamber 1 is provided with a reaction material gas supply system 2 through which various gases required for film formation are supplied. The reaction chamber 1 further includes a main exhaust system 3 having a main exhaust valve 4.
And an auxiliary exhaust system 5 having a variable auxiliary conductance (opening degree) and a small-capacity auxiliary exhaust valve 6. The exhaust system exhausts the gas in the reaction chamber through an exhaust pump 7.

FIG. 2A is a process sequence diagram showing a source gas supply flow rate and an exhaust gas flow rate showing the growth method according to the present invention, and FIG. 2B is a reaction sequence corresponding to the gas flow rate. It is a figure which shows the change of the pressure in a room. As shown in the figure, in the growth method of the present invention, a constant amount of source gas is continuously supplied, but the amount of exhaust gas is intermittently increased or decreased. When the displacement increases, the pressure in the reaction chamber decreases and the growth of the film substantially stops. At this time, unnecessary reaction products in the reaction chamber are removed outside the apparatus by the exhaust system. Therefore, when the amount of exhaust gas is reduced and film formation is started, the growth rate returns to the initial value. And this growth rate is
Since the continuous growth time is relatively short, a substantially constant value is maintained. Also, by sandwiching this period of increasing the displacement, even when a thick metal film is formed, a good surface morp can be obtained.
You can get hology membrane.

It is desirable that the time for increasing the exhaust gas flow rate be short in order not to lower the effective growth rate. By setting the continuous time during which the exhaust gas flow rate increases to one-third or less of the continuous time during which the exhaust gas flow rate decreases, the growth rate can be increased as compared with the case where continuous growth is performed at a constant source gas supply flow rate. . The exhaust amount is adjusted by adjusting the conductance between the main exhaust valve 4 and the auxiliary exhaust valve 6. For example, the conductance of the auxiliary exhaust valve is kept constant, and the exhaust amount is increased or decreased by opening and closing the main exhaust valve. can do.

According to the present invention, but not limited to, dimethyl aluminum hydride (AlH (OCH ₃ ))
₂ ) or triisobutyl aluminum (Al
Using ((CH ₃ ) ₂ CHCH ₂ ) ₃ as a reaction raw material gas and hydrogen gas as a carrier gas, an Al film is formed on copper hexafluoroacetylacetonate (Cu [(CO) ₂ CH (C
Using F ₃ ) ₂ ] ₂ ) as a reaction raw material gas and argon as a carrier gas, a Cu film is formed. Tetrakis-methylaminotitanium (Ti [N (CH ₃ ) ₂ ] ₄ ) and ammonia are used as a reaction raw material gas, and nitrogen is used as a carrier. TiN used as gas
A W film can be grown by using the film as a reaction source gas with tungsten hexafluoride and hydrogen as a carrier gas.

In the present invention, the pressure of the reaction by-product in the reaction chamber is intermittently controlled by opening and closing a valve of a downstream exhaust system, not by opening and closing a valve of a reaction material gas supply system located upstream of the reaction chamber. Therefore, the effect of dust generation due to the opening and closing of the valve can be significantly reduced, and the film quality can be improved. Furthermore, it is possible to suppress an increase in the maintenance frequency of the equipment of the source gas supply system that is complicated to handle, and to prevent a decrease in controllability of the supply amount of the reaction source gas.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. As a sample 7, a silicon oxide film having a thickness of 0.6 μm was formed on a silicon substrate for an integrated circuit by thermal oxidation or CVD, and fine holes having a diameter of 0.4 μm were formed in the silicon oxide film by a standard photoetching process. An open one was used. After evacuating the inside of the reaction chamber 1 to the order of 10 ^-4 Pa,
The sample is heated to 170 ° C. using a sample heater (not shown) provided on the sample stage, and hydrogen as a carrier gas is supplied to the reaction chamber 1 from the reaction material gas supply system 2. Next, the auxiliary exhaust valve 6 is opened, the main exhaust valve 4 is closed, and the conductance of the auxiliary exhaust valve 6 is adjusted so that the pressure in the reaction chamber becomes 1.6 × 10 ² Pa. The reaction chamber 1 was prepared using dimethylaluminum hydride (hereinafter abbreviated as DMAH), which is an organoaluminum compound, as a source gas and hydrogen gas as a carrier.
To start the growth of the aluminum film. DMAH
One minute after the start of the supply, the main exhaust valve 4 is also opened and the exhaust in the main exhaust system 3 is also added, and the pressure in the reaction chamber 1 is temporarily reduced to about 6 Pa. After the exhaust in the main exhaust system 3 is continued for 15 seconds, the main exhaust valve 4 is closed again, the pressure in the reaction chamber 1 is increased to 1.6 × 10 ² Pa, and the vapor phase growth is continued. After the closing and opening of the main exhaust valve 4 were repeated 10 times at such time intervals, the growth of the aluminum film was terminated.

When comparing the aluminum film formed by the method of this embodiment with the film formed by the conventional method in which the main exhaust valve 14 is not opened during the vapor phase growth, the film thickness is proportional to the growth time in the conventional method. In contrast, when the growth time was prolonged, the deposition rate was reduced, whereas in the method of the present invention, the film thickness was almost proportional to the growth time, and the deposition rate was not reduced. Also, in the film formed by the conventional method, although the film deposited for a long time has a remarkable unevenness on the surface in spite of the fact that the film thickness is thinner than that according to the method of the present invention, and voids are generated in the micropores, According to the method of the present invention, the surface was excellent in smoothness, and it could be uniformly and reproducibly deposited in the fine pores.

[0016]

As described above, the chemical vapor deposition method according to the present invention supplies the reactant gas at a constant flow rate and intermittently increases or decreases the exhaust gas flow rate. The pressure in the reaction chamber during film formation is intermittently reduced without causing a decrease in the controllability of the gas, the pressure of the reaction by-product gas is intermittently reduced, the reduction in the deposition rate is suppressed, and the surface smoothness is reduced. And the properties of deposition into the micropores can be improved. In addition, the intermittent reduction of the pressure of the reaction by-product gas in the reaction chamber is controlled by the opening and closing of the reactant gas supply valve located on the upstream side of the sample on which the film is to be deposited, regardless of whether the valve of the exhaust system on the downstream side is opened or closed. Since this is achieved by opening and closing, the effect of dust generation due to opening and closing of the valve can be reduced, the film quality can be improved, and an increase in the maintenance frequency of the reaction material supply system that is complicated to handle can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a vapor phase growth apparatus for describing an embodiment and an example of the present invention.

FIG. 2 is a sequence diagram of a gas flow rate and a reaction chamber pressure for describing an embodiment of the present invention.

FIG. 3 is a source gas supply sequence diagram of a first conventional example.

FIG. 4 is a source gas supply sequence diagram of a second conventional example.

FIG. 5 is a source gas supply sequence diagram for explaining a problem of the conventional example.

[Explanation of symbols]

 Reference Signs List 1 reaction chamber 2 reaction material gas supply system 3 main exhaust system 4 main exhaust valve 5 auxiliary exhaust system 6 auxiliary exhaust valve 7 exhaust pump 8 sample table 9 sample

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shunji Kishida 5-7-1 Shiba, Minato-ku, Tokyo Within NEC Corporation (72) Inventor Akiko Kobayashi 5-2-1, Yotsuya, Fuchu-shi, Tokyo Anelba Inside the corporation

Claims (4)

(57) [Claims] In a chemical vapor deposition method in which a source gas is supplied to a reaction chamber to form a film on a substrate, the pressure in the reaction chamber is decreased and increased by intermittently increasing and decreasing the amount of exhaust by an exhaust system. A chemical vapor deposition method characterized by performing film formation while performing. 2. The chemical vapor deposition method according to claim 1, wherein the material of the source gas contains a metal compound, and a metal film or a metal compound film is formed. 3. The chemical vapor deposition method according to claim 1, wherein the duration of the state in which the displacement is increased is not more than one third of the duration of the state in which the displacement is reduced. 4. An exhaust system of a vapor phase growth apparatus comprising a main exhaust valve and an auxiliary exhaust valve, wherein the auxiliary exhaust valve is opened at a fixed opening, and the main exhaust valve is opened and closed to increase or decrease the exhaust amount. The chemical vapor deposition method according to claim 1, wherein: