JPS6233768A - Selective growing method for tungsten film - Google Patents

Abstract

PURPOSE:To grow W films having required film thicknesses selectively on semiconductor substrates by admitting a reactive gas consisting of WF6 and H2 into a reaction chamber, executing thermal cracking and intermittently stopping the inflow of the reactive gas to increase the vacuum degree in the reaction chamber. CONSTITUTION:An Si substrate 11 is disposed in the reaction furnace 12 subjected to vacuum evacuation 14 and WF6 and H2 are admitted through respective introducing ports 15, 16 into the furnace. The reactive gas admitted into the furnace is heated by a heating element 13 and is thermally cracked. The W formed by the reaction WF6+3H2 W+6HF is selectively grown on the above-mentioned Si substrate 11. The admission of the reactive gas in the above-mentioned operation is intermittently stopped and the inside of the furnace 12 is evacuated to a vacuum to once suck and remove the excess HF formed by the above-mentioned reaction. The admission and thermal cracking of the reactive gas are thereafter executed and the same operation is subsequently repeated. The W films having the required film thicknesses are thereby grown selectively on the Si substrates 11.

Description

[Detailed Description of the Invention] [(Existing) A reaction gas of tungsten hexafluoride and hydrogen is thermally decomposed,
A tungsten film is selectively grown, then the flow of reactant gas is stopped and the product gas is removed by vacuum suction. By repeating these operations, a tungsten film of a desired thickness is selectively grown.

[Industrial Application Field] The present invention relates to a method for selectively growing a tungsten film used in manufacturing semiconductor devices.

In a semiconductor device such as an IC, semiconductor elements and other circuit elements are formed on a semiconductor substrate, and a large number of electrode wirings leading out from these areas are provided on the upper surface.

Up until now, aluminum films or aluminum alloy films have been used for these electrode wirings, but the disadvantage of aluminum is that it has a low melting point, which limits the formation of an insulating film between the eyebrows when forming multilayer wiring. There are drawbacks. Therefore,
As an alternative wiring material, a conductive polycrystalline silicon film is widely used, but this has the problem of not having very good conductivity.Recently, high-melting point metal films with good electrical conductivity or their silicide films have been used for electrode wiring. The method used is adopted.

However, in the process of investigating various methods for depositing such high-melting point metal films, it has been found that tungsten films can be selectively grown on semiconductor substrates without applying a photo process. However, the selective growth method is not yet sufficient, and there is a need to establish a fully satisfactory selective growth method.

[Prior art and problems to be solved by the invention] The selective growth method of such a tungsten film is, of course, a growth method using chemical vapor deposition (CVD). ) and hydrogen (N2) are thermally decomposed and deposited, and the reaction formula is as shown below.

WF+, +3H2→W+6HF As seen from this reaction equation, hydrofluoric acid ()IF) gas is generated, and the HF gas is silicon dioxide (SiO2
) It is believed that selective growth occurs in which the tungsten film grows only on the silicon substrate and not on the 5i02 film by etching the film surface.

However, when the selective growth film thickness becomes about 3000 or more,
There is no longer any selectivity and the tungsten film is deposited even on top of the 5i02 film. For example, as shown in the cross-sectional view of FIG.
If an electrode window 3 is formed in the 5i02 film 2 of m and a tungsten film 4 is deposited on the electrode window, the electrode window 3 cannot be buried only by selective growth. Therefore, at present, only about 5,000 people or less are selectively growing tungsten films.

In this example, burying the electrode window with a conductive film is important for flattening the wiring layer, and if the amount of deposition is small as described above, the electrode window will be covered with another conductive film. must be buried.

The present invention proposes a growth method for selectively growing a tungsten film of a desired thickness by eliminating the above-described selective growth of a tungsten film that has a limited growth thickness.

[Means for solving the problem] The purpose is to thermally decompose a reactive gas consisting of tungsten hexafluoride and hydrogen to selectively grow a tungsten film on a semiconductor substrate. This is achieved by a selective tungsten film growth method in which the introduction is stopped intermittently and the vacuum level of the reaction chamber is increased.

[Operation] That is, in the present invention, in order to prevent the generated HF from damaging the base, the introduction of the reaction gas is stopped during the selective growth process, and the excessively generated HF is removed by vacuum suction. By performing selective growth intermittently in this manner, a tungsten film can be selectively grown without any limit to the film thickness.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a schematic diagram of a CVD apparatus to which the present invention is applied, in which 11 is a silicon substrate, and 12 is a reaction chamber.

13 is a heating element, 14 is a vacuum exhaust port, 15 is a WF6 gas inlet, and 16 is a N2 gas inlet.

The reaction chamber 2 of such a CVD apparatus is heated to a constant temperature between 300 and 325°C, and the gas inlets 15 and 16 are
The interior of the reaction chamber 12 is maintained at a reduced pressure of about 0.3 Torr by introducing WF6 gas and N2 gas from the other end and drawing vacuum from the other end. For example, the gas inflow rate is 30cc/min for WF6 gas and 400cc/min for N2 gas.
Make it about a minute. Also, at this time, the WF6 gas is nitrogen (N2)
Another method is to dilute it with gas and then flow it in.

Then, the WF6 gas is thermally decomposed in the reaction chamber, and a tungsten film grows. At this time, as shown in the cross-sectional view of FIG. 3, the tungsten film 4 is not deposited on the 5i02 film 2, but only on the silicon substrate 1 of the electrode window 3.

In this way, after reacting for 30 minutes and growing a film with a thickness of about 1000, the inflow of WF6 gas and N2 gas is stopped. However, since the vacuum suction continues, the degree of depressurization increases and the reaction chamber 2 reaches 0. The degree of vacuum is approximately I Torr. Then, WF6 gas and N2 gas are introduced again and reacted for 30 minutes to further grow a tungsten film with a thickness of about 1,000.

By repeating such operations and performing selective growth, the electrode window 3 can be buried in the tungsten film 4 as shown in the cross-sectional view of FIG. In this way, the selective growth film thickness is no longer limited because excessively generated HF is removed by vacuum suction, and the 5i02 film surface is not damaged by excessive HF.

In the above example, we explained the process of burying the electrode window and planarizing the WAN, but being able to selectively grow the desired film thickness in this way also has various positive effects on other manufacturing processes. This goes without saying.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, a tungsten film of a required thickness can be selectively grown, and rcO high performance and
This greatly contributes to higher quality and higher density.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a CVD apparatus to which the present invention is applied, Fig. 2 is a cross-sectional view of an electrode window in which a tungsten film according to the present invention is selectively grown, and Fig. 3 is a cross-sectional view of an electrode window in which a conventional tungsten film is selectively grown. FIG. In the figure, 1.11 is a silicon substrate, 2 is a 5i02 film, 3 is an electrode window, 4 is a tungsten film, 12 is a reactor,
13 is a heating element, 14 is a vacuum exhaust port, 15
is the WF6 gas inlet, 16 is the H2 gas inlet

Claims (1)

[Claims] In the growth process in which a reactive gas consisting of tungsten hexafluoride and hydrogen is thermally decomposed to selectively grow a tungsten film on a semiconductor substrate, the flow of the reactive gas is intermittently stopped to maintain the vacuum level of the reaction chamber. A selective growth method for a tungsten film characterized by adding an operation to increase the height.