JPS63140525A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid the delay of signal propagation and reduce the burden of a manufacturing process on a semiconductor device even if it is precisely structured and highly integrated by a method wherein, after a thin film layer containing silicon is patterned into a required form beforehand, a heat treatment is carried out in an atmosphere containing halide of high melting point metal to induce chemical reaction. CONSTITUTION:Before the gate electrode of a MOS field effect transistor is formed, a silicon substrate 1 on which a residual polycrystaline silicon thin film 3 is provided is placed in a furnace into which WF6 diluted by inert gas such as argon is supplied, The residual thin film 3 whose surface is exposed is heated in the atmosphere maintained at predetermined temperature and pressure reducing reaction expressed by a following equation is induced: 2WF6+3Si 2W+3SiF4. By this reaction, silicon is converted into halide and volatilized from the substrate and a high melting point metal film is formed as substitution. By increasing the temperature in the furnace and making the exposing time longer, the thickness of the high melting point metal film is increased and the gate electrode composed of a double-layer structure in which the surface polycrystalline silicon film 3 is successively substituted by the high melting point metal film 4 can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device using a high melting point metal film as a conductive material.

<Prior Art> In recent years, semiconductor devices, particularly MO5LSIs, have become increasingly finer and more densely packed, and as a result delays in signal propagation caused by determining the resistance of electrodes and wiring have become a major problem.

For example, in gate electrodes,
In order to lower the resistance of polycrystalline silicon, which has been widely used in the past, attempts have been made to use refractory metals or refractory metal silicides with low resistance values. Among the 25SDRAM products that are in practical use, a two-layer structure of molybdenum silicide or tungsten silicide and polycrystalline silicon is adopted.

In the manufacturing process of the two-layer gate electrode having the above-mentioned high melting point metal film, the surface of the substrate silicon is
Thermal oxidation is performed at a depth of 0λ, followed by low pressure CVD on the oxide film.
Polycrystalline silicon is deposited to a thickness of about 2000λ using the method.

Next, the polycrystalline silicon is doped with impurities such as phosphorus or arsenic to make it conductive, and then tungsten silicide or molybdenum silicide is formed to a thickness of about 3000λ by kcVD or sputtering. After that, the polycrystalline silicon and high-melting point metal silicide are processed by RIE (React) to form the gate electrode shape.
ive Ion Etching) There is a method of etching.

Furthermore, apart from the above manufacturing method, recently titanium is formed on polycrystalline silicon formed on an oxide film by a sputtering method, and a part of the polycrystalline silicon is turned into titanium silicide by heat treatment at 700 to 900°C. A method of forming a gate electrode having a two-layer structure of crystalline silicon and titanium silicide has also been proposed.

<Problem that the invention seeks to solve> Where are high melting point metals and high melting point metal silicides?

It has the specific resistance value (μΩ) shown in the table below. Therefore, when a gate electrode is formed by the former method, the resistance of the high-melting point metal silicide film is much higher than that of the high-melting point metal film. The purpose of speeding up signal propagation cannot be achieved.

Furthermore, it is difficult to accurately pattern the laminated silicide film and polycrystalline silicon film at the same time, and the gate length changes in the actual product, causing problems in the stability and reproducibility of transistor characteristics. Furthermore, there is a large difference in the coefficient of thermal expansion between polycrystalline silicon and silicide, as shown in the table below, and the silicide layer is likely to peel off due to the natural oxide film that forms at the laminated interface, causing reliability problems.

In the latter gate electrode production method that forms titanium silicide, the purity of the titanium target is low, and Ni,
Contains many impurities such as Cr and Fe.

This causes problems in the reliability of semiconductor devices.

In addition, titanium compounds have the property of dissolving in hydrofluoric acid, so
The hydrofluoric acid cleaning process used in current manufacturing processes cannot be used, and a new cleaning method and cleaning line will be required. Furthermore, since titanium silicide has a higher coefficient of thermal expansion than silicon, there are problems such as the semiconductor substrate itself becoming warped, reducing pattern accuracy, and making it difficult to continue the manufacturing process. It could not be said that it was sufficient for manufacturing integrated circuit devices.

Means for Solving the Problems The present invention eliminates the drawbacks of the above conventional methods and provides a method for manufacturing a semiconductor device using a high melting point metal film as a conductive material.
For a thin film layer containing at least silicon, such as a polycrystalline silicon or amorphous silicon thin film, the thin film layer is patterned in advance into a desired shape, and then heated in an atmosphere containing a high melting point metal halide to cause a chemical reaction. According to
A semiconductor device is manufactured in which silicon is replaced with a high melting point metal and the high melting point metal film is used as a conductive material.

The conductor on the semiconductor substrate is not only made of a material with relatively high resistance, such as a polycrystalline silicon thin film, but also made of a low-resistance, high-melting-point metal that replaces silicon through chemical change. This makes it possible to prevent high resistance due to microfabrication and prevent delays in signal propagation in integrated circuits. Also, is the conductor a thin film containing silicon? Since the metal is replaced with a high melting point metal after being patterned into a desired shape in advance, etching of layers of the same material is sufficient, compared to the process of etching a multilayer structure.

<Example> First, an example of a specific chemical reaction for replacing silicon (Si)' with a high melting point metal (W, Mo) is given by the following formula % formula % (1
) Figure 1 shows that in the reaction of equation (1) above, when argon is supplied as a diluent gas and the reaction is carried out under a pressure of 1 torr, silicon is consumed and the high melting point metal (W) is
The relationship between silicon consumption or formed W film thickness and reaction time when IC is replaced is shown. As can be seen from FIG. 9, at a reaction temperature of 300° C., 100 to 200 W films grow at the initial stage, but the film growth almost stops thereafter. On the other hand 4
At 00°C, the W film thickness reaches 5,000 layers in 10 minutes from the start of the reaction, and the W film grows at a rate of -75°C. Therefore, the reaction temperature is preferably 400°C or higher.

Figure 2 shows that the high melting point metal is MO as shown in the above formula +211c.
Reaction time, silicon film consumption, and MO
It shows the relationship between film growth thickness. Even in the unreacted state, the atmosphere was maintained at about 400° C. and the pressure was 1 torr.

(Example 1) Next, a process for creating a gate electrode of an MO5 field effect transistor using the above chemical reaction will be described.

In FIG. 3 fal, the surface of the silicon substrate 1 is thermally oxidized to form a gate oxide film 2 having a total thickness of about 200 to 800 λ. A polycrystalline silicon pattern 3 having a thickness of 3,000 to 4,000 wafers is formed on the gate oxide film 2 using a low pressure CVD method. The polycrystalline silicon film 3 is etched into a desired shape corresponding to gate electrodes, inter-device wiring, etc., to form a residual thin film region having exposed silicon on the silicon substrate 1 as shown in FIG. 3 (bK). Residual polycrystalline

Impurities such as phosphorus or arsenic are ion-implanted into the drain region and the like to impart conductivity. Note that it is not necessary to make the polycrystalline silicon 3 conductive if silicon is completely replaced with a high melting point metal in the step of replacing the polycrystalline silicon 3 with a high melting point metal, which will be described later. However, complete 17i: difficult to replace,
Furthermore, when completely replaced, the adhesion between the high melting point metal and the oxide film is not necessarily good. Therefore, as in this embodiment, it is desirable to make the silicon component conductive and leave it on the gate oxide film.
, WFs k using an inert gas such as argon as a diluent gas.
Install it in the supplied furnace. The temperature in the furnace is maintained at about 400° C. and the pressure is about 1 torr and 7 C, and the residual thin film 3 whose surface is exposed is treated in this atmosphere to cause a reduction reaction shown by the linear equation.

2 W F 6 + 8 Si → 2 W + 35
i F a By the above reaction, silicon becomes a halide and scatters from the substrate, forming a high melting point metal film. By increasing the temperature in the furnace and prolonging the holding time, the thickness of the high melting point metal film becomes thicker, and as shown in FIG.
A gate electrode consisting of a two-layer structure replaced with is formed,
By further advancing the reaction, a gate electrode almost completely replaced by the high melting point metal film is formed as shown in FIG. 3fdl.

Electrical i with polycrystalline silicon remaining in the core as shown in Figure 3 (m)
Even in terms of structure, the resistance value is significantly reduced compared to electrodes made solely of polycrystalline silicon.

(Example 2) An example applied to forming an electrode in ohmic contact with an uninvented gold or silicon semiconductor substrate will be described.

@Figure 4 (alF!) Then, an oxide film 12 is formed on the surface of the silicon substrate 110 by thermal oxidation or CVD.

A preliminary contact hole 18'lr for electrical connection to the oxide film 12 is formed by etching or the like to expose the surface of the silicon substrate 11. contact hole 18
Figure 4 (
Polycrystalline silicon 14 is formed on the entire surface of the substrate as shown in bl, and the holes 13 are filled.

Next, polycrystalline silicon other than the polycrystalline silicon filling hole 1B'Z is removed by RIE or the like, and at least contact hole 18 is filled with polycrystalline silicon 14 as shown in FIG. 4IC). The above semiconductor substrate Ilk is set in a WF6 gas atmosphere diluted with argon, a chemical reaction is caused under a pressure of about 400°C, and the polycrystalline silicon 14' is replaced with a high melting point metal 15, making ohmic contact with the silicon substrate. (Fig. 4 (dl)) 0 When the high melting point metal is M, the reducing action by hydrogen is weak as a characteristic of 1Mo, so the dilution gas is an inert gas. Alternatively, hydrogen gas may be used.

FIG. 5 shows the resistance and atmosphere (390° C., 1 torr) of the wire formed by replacing polycrystalline silicon (Si) with molybdenum (Mo) K through the above steps.

(MoF6/H2=0.07, 800 sec) is a diagram showing the relationship with retention time. As is clear from the figure, the resistance value, which was 35QKΩ in the polycrystalline silicon state before the molybdenum layer grows, decreased to 6Ω by being exposed to the M o F 6 atmosphere for about 30 minutes. ing.

Effects> As described above, according to the present invention, it is possible to create a semiconductor device by using a high melting point metal film with a low resistance value as a conductive part on a semiconductor substrate, and it is also possible to create a semiconductor device that is miniaturized and highly integrated. , it is possible to prevent delays in signal transmission. In addition, when forming a high melting point metal film with a desired shape, the silicon contained in the pre-patterned area is replaced with a high melting point metal film, so there is no need to etch the high melting point metal film, reducing the burden on the manufacturing process. significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the change in film thickness of Si and W and time-varying relationship to explain the uninvented state, and Fig. 2 is a diagram of the time-slope relationship between the film thickness of Si and W to explain the uninvented state.
, Mo film thickness change amount and time relationship diagram. 3 and 4 are cross-sectional views showing the manufacturing process of the semiconductor device according to the present invention, and FIG. 5 is a diagram showing the reaction time and the change in resistance value over time. 1.11: Silicon substrate. 2.12 Dioxide film. 3.14: Polycrystalline silicon, 4.15: High-melting point metal film Representative Patent attorney Takeshi Sugiyama (and 1 other person) 1st time closing [Force @begi] Figure 2 (c) (C) Figure 3
Ward 4 OIQ 2o Type 30 Closed (departure) Figure 5

Claims (1)

[Claims] 1) A step of patterning the deposited thin film layer containing silicon into a desired shape; A step of placing the remaining thin film layer in a heated atmosphere containing a halide of a high melting point metal; A method for manufacturing a semiconductor device, comprising the step of substituting the silicon with a high melting point metal through a chemical reaction while maintaining the semiconductor device in the atmosphere. 2) The semiconductor device according to claim 1, wherein the thin film layer is made of polycrystalline silicon deposited on an insulating layer, and the polycrystalline silicon is replaced with a high melting point metal through a chemical reaction. manufacturing method. 3) The thin film layer is made of polycrystalline silicon that fills the openings formed in the insulating film deposited on the semiconductor substrate layer, and the polycrystalline silicon is replaced with a high melting point metal through a chemical reaction to form an electrode. A method for manufacturing a semiconductor device according to claim 1, characterized in that: