JPH0660409B2 - Method of forming metal film - Google Patents

Description

The present invention relates to a method for forming a metal film by chemical vapor deposition,
Particularly, the present invention relates to a chemical vapor deposition method suitable for forming a metal film for semiconductors.

[Conventional technology]

As is well known, the conventional metal film forming methods include a physical vapor deposition method and a chemical vapor deposition method.

In the physical vapor deposition method, the vapor deposition has directivity, and the film thickness uniformity of the formed film is poor with respect to a pattern having a step. It was difficult. For this reason, technological development of chemical vapor deposition, which has excellent step coverage, has become popular. However, in the formation of a metal film by this chemical vapor deposition method, for example, Applied Physics Letter by R. Solanki et al. (R. Solanki et al, Appl. Phys. Lett)
As described in Volume 41 (1983), page 1041, organometallics are mainly used. Therefore, there is a problem that carbon remains in the formed metal film and electric resistance is not sufficiently lowered. To avoid this, for example, Journal of Applied Physics (SD Allen, J. Appl. Phys.) Volume 54 (1983), by S. D. Allen et al.
As described on page 041, a device using a metal halide as a source has been devised, but other than metal fluorides, they are solid at room temperature and are difficult to handle, so they are used as a source in chemical vapor deposition. I can't. For this reason, metal fluorides are often used. However, when a metal fluoride is used, fluorine or hydrogen fluoride is generated in the reaction system, and this reacts with silicon oxide (such as SiO ₂ ) and silicon nitride (such as Si ₃ N ₄ ) which are insulators, It was difficult to form a metal film on the surface of these insulators.

Also, J. Less-Common Metals, Vol. 33 (1973), pages 209 to 218, by G. M. Neumann et al. The method of forming a vapor of the above and reacting this with arsine to form a GaAs crystal is described, but this is a method of forming a compound semiconductor, not a method of forming a metal film. This is completely different from the technical idea of the present invention described in.

[Problems to be solved by the invention]

As described above, the conventional technique is a chemical vapor deposition method in which an organic metal or a metal fluoride is sent in a gaseous state, and thermal energy is applied to the gas to cause a decomposition reaction to deposit a metal. For this reason, there have been problems that impurities such as carbon and oxygen are contained in the metal film, or metal cannot be deposited on the insulating film such as silicon oxide and silicon nitride. However, in the physical vapor deposition method for avoiding these problems, there is a problem that the metal film formation has directivity and the coverage of the metal film at the pattern step portion on the substrate is poor.

An object of the present invention is to oxidize a high-purity metal film containing no impurities that lowers the electrical conductivity of metal by chemical vapor deposition, which has a good step coverage and reacts with fluorine or hydrogen fluoride. It is an object of the present invention to provide a high-quality metal film forming technique for semiconductors, which can efficiently form a metal film on an insulating film such as silicon or silicon nitride.

[Means for solving problems]

In order to achieve the above-mentioned object of the present invention, a metal film is formed on the surface of an insulator such as an element such as carbon or oxygen that lowers the electric conductivity of the metal film, or an oxide such as silicon oxide or silicon nitride formed on a substrate. When forming a film, it is desirable to use a metal source that does not contain an element such as fluorine that reacts with the insulator. In the usual case, the problem can be basically solved by using metal chloride as the source. However,
Chloride is a solid in most metals, making it unsuitable as a metal source for conventional vapor deposition.

According to the present invention, a metal member for forming a desired metal film and a substrate on which the desired metal film is to be formed and on which a metal film is to be formed are arranged in an appropriate positional relationship in a reaction vessel of a chemical vapor deposition apparatus (first
Fig.), A gas containing a halogen gas, for example, a gas containing chlorine gas, is first reacted with the metal member to generate a metal chloride, and the metal chloride is placed on the substrate arranged in the vicinity of the metal member. This is accomplished by causing a chemical decomposition reaction above to deposit the metal on the substrate.

According to the chemical vapor deposition method of the present invention, the metal used for forming the metal film may be any one as long as it reacts with a gas containing a halogen gas such as chlorine, bromine, iodine or fluorine to produce a metal halide, For example, W, Mo, V, Cr, Ni, etc., or Al, Cu, Ag, Pd, Zr, etc. can be mentioned in large numbers, and the kind of metal used is not particularly limited. Fluorine in the halogen gas that reacts with the above-mentioned metals reacts when the substrate material or insulating material is silicon oxide or silicon nitride, and is not preferable. It can be applied only when forming a metal film. In the formation of the metal film by the chemical vapor deposition method of the present invention, it is most preferable to use chlorine as a reaction gas in terms of its reactivity and handling.

In the case of reacting a metal member for forming a desired metal film with a halogen in the reaction vessel of the chemical vapor deposition method of the present invention, if the reaction is performed under photoexcitation, the metal halide production efficiency is further improved. Also, in the case of chemically decomposing a metal halide on a substrate to deposit a metal to form a metal film, the decomposition reaction efficiency can be increased and the decomposition concentration can be reduced by performing the reaction under photoexcitation. .

[Action]

When a metal member for forming a desired metal film and a gas containing a halogen gas, for example, a gas containing chlorine gas are introduced and the temperature is raised to an appropriate temperature, they react with the introduced chlorine gas to chlorinate the metal. Produce things. The chloride of this metal sublimes and reaches the surface of the substrate. When the substrate temperature is still at an appropriate temperature, the metal chloride undergoes a thermal decomposition reaction to deposit the metal on the surface of the substrate to form a metal film. Then, the presence of reducing gas such as hydrogen further improves the efficiency of thermal decomposition. At this time, in order to more efficiently react the metal member with chlorine, chlorine may be used in a photodecomposed state, and if the generated metal chloride is decomposed using a photochemical reaction, metal deposition efficiency is increased. Is even better and has the effect of lowering the decomposition temperature of metal chlorides.

〔Example〕

An embodiment of the present invention will be described below in more detail with reference to the drawings.

Example 1 In this example, an example of forming a tungsten metal film will be described.

Using the chemical vapor phase reactor having the structure shown in FIG. 1, first, the inside of the reaction vessel 11 is evacuated by the vacuum exhaust system 12. When the pressure in the reaction vessel reached the level of 10 ⁻⁶ Torr, the heaters 2 and 4 of the metal bulk 1 of tungsten and the substrate 3 were energized, and the temperature of the metal bulk 1 was 500 ° C. and the temperature of the substrate 3 was 4 ° C.
Control at 00 ℃. When each temperature is sufficiently stable, first, the excitation light beam, Zenon chloride (XeC
l) Excimer laser 7 and Argon Fluorine (ArF)
Irradiating the excimer laser 8 of the
More chlorine gas is introduced, and hydrogen gas is introduced from the reaction gas supply nozzle 9. The irradiation conditions of the excimer laser are as follows: XeCl excimer laser 7 is 200 mJ / p (millijoules / pulse), 20
Hz, Argon Fluorine (ArF) excimer laser 8 150mJ
It was / p, 20Hz. The laser beam at this time was applied without passing through the lens system. On the other hand, chlorine gas and hydrogen gas were introduced into the reaction vessel 11 with a mass flow controller for chlorine gas and hydrogen gas at 25 sccm and 800 sccm, respectively. The pressure in the reaction vessel 11 at this time was about 0.25 Torr. After continuing the reaction for 15 minutes in this state, the supply of chlorine gas and hydrogen gas was stopped and the irradiation of the excimer laser was stopped. Next, the power supply to the heater 2 of the metal bulk 1 and the heater 4 of the substrate 3 was stopped, the temperature was lowered to room temperature, and the substrate 3 was taken out.

A tungsten film was formed on a substrate 3 made of a silicon wafer coated with silicon dioxide (SiO ₂ ), and its resistivity was 10 μΩ · cm, which was about twice that of bulk tungsten. The tungsten film was 600 nm. When the adhesion between SiO ₂ and the obtained tungsten film was evaluated by a so-called tape test, the formed tungsten film was SiO ₂
It was found that the adhesiveness was extremely good without peeling off from the surface. Moreover, when the Auger electron spectroscopy spectrum of the obtained tungsten film was investigated, as shown in the analysis result in FIG. 2, no peaks corresponding to carbon and oxygen were observed, and these impurities were also present in the tungsten film. I found that I didn't.

Example 2 Next, the case of forming an aluminum film will be described. In FIG. 1, except that the metal bulk 1 is replaced with aluminum, the same procedure as in Example 1 is performed except that the set temperatures of the heater 2 of the metal bulk 1 and the heater 4 of the substrate 3 are respectively set.
The temperature was 450 ℃ and 300 ℃. Also, the XeCl excimer laser increased the output and irradiated at 400 mJ / p, 20 Hz. Other conditions are the same as in Example 1.

By doing so, an aluminum film could be obtained on SiO ₂ , and the thickness was 700 nm. The electrical resistivity was 6 μΩ · cm, which was twice as low as that of bulk. The presence of carbon and oxygen in the aluminum film was not confirmed by Auger electron spectroscopy, but a small amount of chlorine remained. However, also in this case, the chlorine peak in the aluminum film disappeared when the substrate temperature was lowered to 350 ° C or lower.

〔The invention's effect〕

As described in detail above, according to the method of forming a metal film by the chemical vapor deposition method of the present invention, the coverage of the pattern steps on the substrate is further improved as compared with the physical vapor deposition method, and the source of organic metal or the like is used. Since it is not used, impurities such as carbon and oxygen that deteriorate electric conductivity are not mixed, and a high-purity and high-quality metal film can be formed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of a metal film forming apparatus by the chemical vapor deposition method used in the embodiment of the present invention, and FIG. 2 is an Auger electron spectrum analysis of the tungsten film obtained in the embodiment of the present invention. It is a graph shown. Explanation of symbols 1 ... Metal bulk, 2 ... Heater 3 ... Substrate, 4 ... Heater 5,6 ... Window, 7, 8 ... Excimer laser 9, 10 ... Reactant gas supply nozzle 11 ... Reaction Vessel, 12 …… Vacuum exhaust system 13 …… Tungsten peak position 14 …… Carbon peak position, 15 …… Oxygen peak position

Claims (2)

[Claims] 1. In a chemical vapor deposition method for forming a metal film on a substrate arranged in a vapor phase reaction container, the reaction container is provided with a metal member as a raw material for forming a desired metal film. A high-purity metal chloride is placed in an appropriate positional relationship with the substrate, a gas containing chlorine gas and a reducing gas are introduced near the metal member, and the excimer laser is locally irradiated on the metal member. Of the metal chloride is generated, the vapor of the metal chloride is brought into contact with the surface of the substrate under photoexcitation by an excimer laser to decompose, and a desired metal film is deposited on the substrate or an insulating film provided on the substrate. A method for forming a metal film, which is characterized by the above. 2. The method for forming a metal film according to claim 1, wherein the excimer laser is a Zenon chloride excimer laser or an argon fluorine excimer laser.