JPS6376875A - Vapor growth method - Google Patents

Abstract

PURPOSE:To inhibit the erosion of a silicon substrate by feeding a source gas mixed with an inert gas in the early stage of growth and specifying the internal pressure of a reaction chamber, the ratio in flow rate between the gases and the speed of the flow of the gases. CONSTITUTION:When a layer of a high m.p. metal such as W is selectively grown on a silicon substrate by a chemical vapor growth method, a source gas such as WF6 is mixed with an inert gas such as N2, fed to a reaction chamber 11 and blown on the substrate 11 to grow a film on the substrate 11 at 260-420 deg.C. The chamber 11 is evacuated beforehand to 0.1-1.5Torr pressure, the ratio in flow rate between the N2 and source gas is regulated to 10<2>-10<3> and the speed of the flow of the gases to 10<3>-10<4>cm/min. H2 is then fed in place of N2 and a film is grown in the second stage. By this method, the erosion of the silicon substrate can be inhibited in the early stage of growth and the selective growth of a film in a contact hole can be satisfactorily carried out.

Description

Detailed Description of the Invention [Summary] In the initial growth of tungsten, a large amount of inert gas is flowed and the flow rate is increased to form a tungsten thin film with a uniform thickness of 100 mm.

[Industrial application field]

The present invention relates to a vapor phase growth method, and more specifically, in a method of selectively growing tungsten (W), titanium (Ti), molybdenum (Mo), etc. by chemical vapor deposition (CVD), the initial stage is The present invention relates to a method for growing a thin film of the metal while minimizing erosion (cutting in) of a silicon substrate.

[Conventional technology]

Referring to FIG. 4, a contact hole 33 is formed in an insulating film (5iOz film) 32 provided on a silicon substrate 31, and a wiring layer 35 is formed to make contact with, for example, a device formed on the substrate through this contact hole 33.
For example, aluminum (AI) is deposited to fill the contact hole 33 to form the wiring layer 35. However, if Al adheres poorly to the side wall of the contact hole, the contact resistance increases, or There is a problem that wire breakage occurs at the stepped portion of the contact hole.

In order to solve this problem, a technique has been developed in which a tungsten layer 34 is selectively grown in the contact hole 33 to fill the contact hole 33 with tungsten, and then a wiring layer 35 is formed. The advantage of this technique is that contact resistance can be suppressed to a low level, and the surface of the wiring layer 35 is formed flat, so that the glabella insulating film, the second wiring, etc. on the wiring layer 35 are flat. Scales are formed on the surface.

[Problem that the invention seeks to solve]

When growing tungsten on a silicon substrate,
Using the apparatus shown in FIG. 1, ridge gas is blown onto the heated substrate.

WFs + 3/2 Si-+W+ 3/25ip, 4
generates a reduction reaction. Since 5iF1 has a low evaporation point, it evaporates at a temperature of about 300° C., and tungsten is deposited on the substrate.

However, in the early stages of the reaction described above, 5iF1
As the tungsten is formed, the underlying silicon is eroded (eaten into), and the thickness of the deposited tungsten matches the reduction in the silicon substrate.

In the conventional method, in the initial reaction, when 200-500 tungsten films are formed, the substrate has 300-7
50 people are attacked. In very large scale integrated circuit (VLSI) devices, junctions in silicon substrates are formed shallowly, so when selectively growing tungsten in contact holes, it is required to suppress erosion of the silicon substrate during the initial reaction. There is.

The present invention was created in view of these points, and an object of the present invention is to provide a vapor phase growth method capable of suppressing encroachment of a silicon substrate during the initial reduction reaction of tungsten or the like on a silicon base.

[Means for solving problems]

The present invention is a sectional view of an apparatus for carrying out the method of the present invention, in which 11 is a chamber, 12 is a substrate (for example, a silicon wafer), 13 is a susceptor, 14 is a heater, 15 is a gas supply section, and 16 is an exhaust pipe. It is.

In the present invention, the initial (first stage) growth of tungsten is performed under the following conditions.

1st stage pressure crab 0.1-1.5 Torr Growth temperature = 260-420°C N2 flow rate: 1000 cc/5inWP6 flow rate:
2cc/win N2/Wh (flow rate ratio): 50ON2 flow rate=10cm2Cnl/lll1n Next, the second stage of growth is performed under the following conditions.

2nd stage pressure crab 1.5 Torr Growth temperature: 260-420°C H2 flow Ml: 1000 cc/5hinWF6 flow rate: 2cc/s+1n H2/WFs (flow rate ratio): 500H2 flow rate: 1
0 幡c+s/sin [Function] According to the inventor's experiments, when N2 is used in the reduction reaction of tungsten using the ridge 6, the temperature decreases from 260 to 420°C.
The thickness of the tungsten film grown within the range of 10% is stable at approximately 50%.
The tungsten film that grows when the temperature is maintained at 4 to 10'Icm/5h is also on the order of 50 nm, and therefore the depth of the silicon substrate eroded by the evaporated SiH can be suppressed to less than 100 Å.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

The present inventor performs two-step growth in selective growth of tungsten using WF6. The first stage of growth occurs in the reaction chamber (
The pressure inside the chamber is 0.1 to 1.5 Torr, and the gas is supplied together with the source gas WF6, for example, N2 + Ar+
Regarding He, etc., experiments were conducted on the relationship between the growing tungsten film thickness and temperature, and the results shown in the diagram of FIG. 2 were obtained.

In Figure 2, the horizontal axis shows the temperature in ('C), and the vertical axis shows the thickness of the grown tungsten film in [people]. As can be understood from the results of this experiment, when N2 gas is supplied, the thickness of the tungsten that grows in the range of 260°C to 420°C is extremely low (and
Shows a stable value. On the other hand, when Ar or Ile is supplied, the tungsten film thickness increases quite rapidly from around 350°C. For this reason, the present inventor supplied N2 together with the total 6 for the initial growth of tungsten (or initial reduction reaction), and set the temperature in the range of 260 to 420°C.

Next, regarding the flow rate ratio of N2 and ridge 6, set N2 to 102~
It is better to supply a large amount within the range of 104, specifically, the flow rate of N2 is 1000cc/min, and the flow rate of WF6 is 1000cc/min.
The flow rate of is 2 cc/min, thus N2/WF+;
It was confirmed that preferable results were obtained when the flow rate ratio was set to 500. If the flow rate ratio is made smaller than 102, the effect of the present invention cannot be obtained, and even if it is made larger than 103, no significant change is observed.

Regarding the above-mentioned N2 flow rate, the present inventor obtained the results shown in the diagram of FIG. 3 through experiments. In the figure, the horizontal axis represents the flow rate in cn+/n+in, and the vertical axis represents the thickness of the grown tungsten film.

According to experiments, when the flow rate is lower than 103, the tungsten film thickness is large and the silicon substrate is eroded by that amount, and when the flow rate is over 10'Icm/win, the tungsten W film thickness is It was found that the value was almost constant, and the practical flow rate was 103 to 104.
cm/sin.

In the method described above, that is, in the initial stage using the apparatus shown in FIG.
．． 5 Torr into the chamber 11 and the heater 14
About 50 pieces of tungsten were initially grown over a period of 6 to 12 seconds on a substrate 12 placed on a susceptor 13 heated to 350°C. During this initial growth, if the pressure is too high, the reaction between silicon and tungsten will increase, but if the pressure is too low (too much), the tungsten will grow unevenly and the underlying silicon will be partially exposed, which is undesirable. .

Thereafter, as a two-step growth, N2 was supplied in place of N2, and a reaction of F6+3H2→W+6HF occurred in the usual manner to grow tungsten to a desired thickness. The growth conditions in the second stage are as described above: pressure crab: 1.5 Torr, growth temperature: 260-420°C.
, N2 flow rate: 1000cc/min, WF6
Flow rate: 2 cc/min% N2/WF6 flow rate ratio: 500, N2 flow rate: 10''cm/min.

〔Effect of the invention〕

As described above, according to the present invention, in the initial growth of tungsten using WF6, by supplying a large amount of N2 at a high flow rate,
■The reduced amount of silicon that is bitten into 5iFa is small, so it passes through the shallow junction.■It has a uniform film thickness and has a smooth surface, so it is easy to reduce when tungsten is further grown in the subsequent process. There are effects such as becoming. Although the above description has been made regarding the growth of tungsten, the scope of the present invention is not limited to that case, and the growth of titanium (Ti) and molybdenum (Mo) using metal halides such as TiC1!4 and MOα5 is This also applies to growth.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an example of the present invention. Figure 2 is a diagram showing the relationship between the growth temperature and the thickness of the grown tungsten. Figure 3 is the relationship between the flow rate of the reactant gas and the thickness of the grown tungsten. FIG. 4 is a cross-sectional view showing an example of selective growth of tungsten into a contact hole. 1 and 4, 11 is a chamber, 12 is a substrate, 13 is a susceptor, 14 is a heater, 15 is a gas supply section, 16 is an exhaust pipe, 31 is a silicon substrate, 32 is an SiO+ film, 33 is a contact hole , 34 is a tungsten layer, and 35 is a wiring layer. Agent: Moto Kuki, Patent Attorney: Akifuku, Patent Attorney: Yoshiyoshi Osuga

Claims (1)

[Claims] In selectively growing a high melting point metal layer (34) on a silicon base (31) by chemical vapor deposition, in the initial growth, an inert gas is added to the source gas and supplied; The pressure of the reaction chamber (11) is 0.1 to 1.5 Torr, the growth temperature is 260 to 420°C, the flow rate ratio of nitrogen and source gas is 10^2 to 10^3, and the flow rate of the gas is 10^3 to 10
A vapor phase growth method characterized by growing at a rate of 4 cm/min.