JPH06291042A - Selective vapor growth method and device - Google Patents

Abstract

PURPOSE:To extremely suppress the damage to a substrate, at the same time enhance adhesion property and selectively grow a uniform and improved metal film which is not affected by the contamination on the substrate surface and the difference in dopants CONSTITUTION:A first reaction bath 1 is provided with a means 7 for heating a substrate to 300 deg.C, or higher, an exhaust means 8, a means 9 for introducing at least a feed gas in a short pulsive shape, and a control means 10 for maintaining the product of a film-forming time and the pressure of the feed gas to 1X10<-2>sec.Torr by controlling either or both of the gas introduction means 9 and the exhaust means 8. In the first reaction bath, a ground film is allowed to grow selectively at a contact hole, etc., out the substrate. In the second reaction bath 2, a metal film with a desired film thickness is obtained on the ground film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective vapor deposition method (selective CVD method) for selectively growing a metal film in a contact hole on the surface of a semiconductor substrate.

[0002]

2. Description of the Related Art In response to the ever-increasing demand for higher integration of semiconductors, circuit patterns formed on the surface of a substrate are becoming finer. Along with this, the patterns of contact holes and through holes have been miniaturized, but only the pattern size has been reduced while the film thickness of the thin film for window opening has been kept substantially constant, resulting in an increased aspect ratio. Therefore, it has become impossible to obtain good connection between elements simply by sputtering aluminum, which is a wiring metal. Therefore, in order to cope with such a situation, there has been a need for a technique of filling a contact hole or the like with a refractory metal which is not etched during the processing of aluminum wiring and then providing wiring between elements with aluminum or the like.

The technique of burying the above-mentioned contact hole is a blanket CVD + in which a metal is once grown on the entire surface of the substrate and then an unnecessary portion of the metal is removed by etching.
There are an etch-back method and a selective CVD method in which a metal film is grown only on a necessary portion from the beginning, but it is said that the selective CVD method is advantageous from the viewpoints of mass productivity and economical efficiency.

The wiring material used for filling such contact holes is doped polysilicon,
Although aluminum, tungsten, molybdenum, silicide, etc. have been used, it is said that tungsten is excellent among the above wiring materials from the viewpoint of resistance to electromigration and stress migration.

By the way, the selective CVD method requires a technique for selectively growing the embedded metal only on the portion of the substrate surface where connection is desired to be obtained without growing on the insulator. By selecting an appropriate reducing agent, the selectivity is obtained by utilizing the difference in reaction mechanism between the insulator part and the connection part in the substrate and the difference in adsorption probability of the reaction gas.

As the chemical reaction in the selective CVD method, silicon reduction, hydrogen reduction and silane reduction are generally known. Taking tungsten as an example, it is considered that the reaction mechanism is as follows.

Silicon reduction using silicon 3Si + 2WF ₆ → 3SiF ₄ + 2W Hydrogen reduction using hydrogen 3H ₂ + WF ₆ → 6HF + W Silane reduction using silane 3SiH ₄ + 2WF ₆ → 3SiF ₄ + 2W
+ 6H ₂

[0008]

Although a metal film obtained by silicon reduction or hydrogen reduction has a strong adhesion to a substrate, silicon reduction consumes silicon, which is a member of the substrate, and the film thickness exceeds a certain value. There is a problem that the reaction stops and the metal film does not grow anymore, and HF is generated as a reaction by-product in the hydrogen reduction, which causes damage to the substrate called wormholes or encroachment.

On the other hand, the silane reduction does not cause the above-mentioned problems, but the resulting metal film has poor adhesion to the substrate,
There is a problem that it is easily peeled off. Furthermore, selective CVD
The film-forming reaction by the method has a problem that the reaction rate varies depending on the difference in the dopants implanted on the substrate surface and the degree of contamination. There were also problems such as troublesome processing.

In view of the above points, the present invention selectively selects a uniform and high-quality metal film that suppresses damage to the substrate as much as possible and enhances adhesion, and is not affected by contamination of the substrate surface or difference in dopant. Its purpose is to be able to grow into.

[0011]

In order to achieve the above object, the present invention selects a film of a metal element at a desired portion on the surface of a substrate by reacting a source gas containing the desired metal element as a composition. In the selective vapor deposition method of growing the substrate selectively, the substrate is heated to 300 ° C. or higher, the source gas is introduced for a short time, and the reaction atmosphere is set to 1 × 10 ⁻² Tor.
A first step of selectively growing a metal film on the surface of the substrate while maintaining a pressure of r or less to obtain a base film, and introducing a reducing gas into the reaction atmosphere to selectively form a metal film on the base film. And a second step of growing to obtain a metal film having a desired film thickness.

[0012]

In the first step, since the substrate is heated to a high temperature of 300 ° C. or higher, the organic substances on the substrate are burned out. or,
As will be described later, since this step is mainly a silicon reduction utilizing a reduction reaction with a silicon substrate, it is usually 300
The reaction is carried out at a temperature of ℃, but the reaction is accelerated by raising the temperature to a higher temperature, and the influence of stains becomes negligible.

Further, in the selective CVD method, generally, the reaction atmosphere pressure is set to about 0.1 Torr, whereas in the present invention, the pressure is set to a low pressure of 1 × 10 ^-2 or less, and the product of the film formation time and the source gas pressure is set. Since it is a short-time film formation in which the source gas is introduced in a pulsed manner under the condition of 1 × 10 ^-2 sec · Torr or less, metal deposition can be sufficiently controlled even if the substrate is heated to 300 ° C. or more, and a thin base film can be uniformly formed Can be formed into a film.

Further, in order to improve the adhesion to the substrate in the film forming reaction in the first step, even if silicon reduction or hydrogen reduction or a composite reaction of these is used, the reaction is controlled by introducing a pulsed short-time gas. Therefore, the consumption of silicon as a substrate material and the damage to the substrate can be minimized. Then, by forming the base film in the first step, a constant film growth rate that is not affected by the type of substrate and the degree of contamination can be obtained during the growth of the metal film in the second step. Further, since the metal film and the base film are bonded to each other because they are bonded to each other, the metal film and the base film have good adhesiveness. Since the base film also functions as a barrier layer, damage to the substrate can be suppressed to some extent even if the film formation reaction in the second step is carried out by hydrogen reduction.
In order to avoid damage, it is desirable to carry out the film formation reaction in the second step by silane reduction.

By the way, although it is possible to carry out the first step and the second step in the same reaction tank, a first reaction tank for the first step and a second reaction tank for the second step By providing a transfer means for transferring the substrate from the first reaction tank to the second reaction tank, the substrate processing can be continuously performed from the first step to the second step, and the film forming work can be performed efficiently. You can do it. In this case, in the first reaction tank, an evacuation unit, a heating unit for heating the substrate to a temperature higher than 300 ° C., a gas introduction unit for introducing a source gas containing at least a desired metal element as a composition, and the gas introduction unit. One or both of the means and the exhaust means are controlled so that the product of film formation time and source gas pressure is 1 ×.
A control means for keeping the condition of 10 ^-2 seconds · Torr or less is provided. However, if the gas introduction means is constituted by a gas introduction valve capable of opening and closing the pulse and the gas is introduced in a pulsed manner, the film thickness control of the underlying film can be performed. It will be easier.

[0016]

EXAMPLES Referring to FIG. 1, 1 is a first reaction tank and 2 is a second reaction tank.
A buffer chamber 4 which is a reaction tank and is connected between the reaction tanks 1 and 2 via gate valves 3a and 3b is provided between the reaction tanks 1 and 2, and a gate valve 3c is provided in the chamber 4. A loading / unloading chamber 5 connected to the substrate is provided, and the substrate is loaded by a transporting means (not shown) as indicated by an arrow 6, the loading / unloading chamber 5, the buffer chamber 4, the first reaction tank 1, the buffer chamber 4, 2 reaction tanks 2,
The buffer chamber 4 and the loading / unloading chamber 5 are conveyed in this order.

When the substrate is loaded into the loading / unloading chamber 5, the gate valve 3c is closed and the first reaction tank 1, the buffer chamber 4 and the second reaction tank 2 are kept in a vacuum state. After loading the substrate, the loading / unloading chamber 5 is closed, the atmosphere is exhausted by an exhaust means (not shown), the chamber 5 is evacuated, and then the gate valve 3c is opened to place the substrate in the buffer chamber 4 and then the gate valve. 3a is opened and it is conveyed to the first reaction tank 1.

In the first reaction tank 1, heating means 7 such as an infrared lamp for heating the substrate, exhaust means 8 and gas introduction means 9 are provided.
And an exhaust means 8 and a gas introduction means 9 are provided.
There is provided a control means 10 for controlling one or both of the above and to control the internal pressure of the first reaction tank 1.

The exhaust means 8 is constructed by combining a turbo molecular pump, an oil rotary pump and a mechanical booster pump so as to obtain a high vacuum of 1 × 10 ^-5 Torr or less. It should be noted that the second reaction tank 2 is also provided with the same heating means 11 and, further, although not shown, similar exhaust means and gas introduction means.

After the substrate is loaded into the first reaction tank 1,
The gate valve 3a is closed and the substrate is heated to 3 by the heating means 7.
Heat to a temperature above 00 ° C. When the temperature of the substrate reaches a predetermined temperature, the gas introducing means 9 introduces a raw material gas, which is a raw material of the metal film, to start the growth of the base film. As the raw material gas, besides WF ₆ , a desired gas such as MoF ₆ can be used.

During the growth of the base film, the control means 10 is activated to
The product of film formation time and source gas pressure is 1 × 10 ^-2 seconds · Torr
The film growth is maintained under the following stable conditions.

When hydrogen gas is not added to the raw material gas,
The base film is obtained by a reduction reaction between a source gas and a substrate material. At that time, it is possible to form a film without using a diluting gas such as argon. In that case, the pressure of the raw material gas is a value indicating the pressure in the first reaction tank, that is, the degree of vacuum.

The film thickness of the base film to be obtained in the first reaction tank must be such that it does not damage the substrate during the selective growth of the metal film carried out in the second reaction tank. The reaction time required to obtain the thickness is determined by the substrate temperature and the pressure of the source gas. For example, when a film is formed by using WF ₆ gas as a source gas and keeping the substrate temperature at 400 ° C.,
1 second at a pressure of × 10 ^-3 Torr, 5 × 10 ^-5 Torr
At a pressure of 20 seconds, a reaction time of 20 seconds is sufficient for a base film.
A tungsten film having a thickness of 00Å can be obtained.

In the case of performing silicon reduction in which a tungsten film is selectively grown on a silicon substrate using WF ₆ , about 1.5 times the thickness of the produced tungsten film is consumed. The adhesion between the film and the substrate, the leak current observed when the film is grown on the shallow junction, and the like can be said to be due to the consumption of silicon. In Figure 2, WF ₆ was used as the source gas and 2 × was formed on the silicon substrate.
The relationship between the substrate temperature and the depth of indentation of tungsten into the substrate when a base film is formed by reacting for 10 seconds under a pressure of 10 ⁻⁴ Torr is shown. A peel test was carried out using an adhesive tape. In the film in which the tungsten film with a film thickness of 1 μm was formed in the second step on the base film having a film thickness of 30 Å or more obtained at the film forming temperature of 300 ° C. or more in the first step. Practically sufficient adhesion was obtained and no leak current was observed.

FIG. 3 shows the depth of tungsten penetration into the silicon single crystal substrate when the pressure of the source gas and the reaction time were changed at a reaction temperature of 500 ° C. In all cases, the adhesion was good and no leak current was observed.

The present invention is not limited to using only the raw material gas, but hydrogen gas may be added to the raw material gas to form the base film. In that case, the underlying film growth reaction depends on hydrogen reduction and silicon reduction. However, even if the gas introduction means 5 introduces the raw material gas and the hydrogen gas into the reaction tank separately, the hydrogen gas is added to the raw material gas. It may be introduced into the reaction tank 1 after the addition. In any case, the gas introduction means 9 may be a gas introduction valve which is a responsive electromagnetic valve and is capable of opening and closing pulses. According to this, the base film can be continuously formed by introducing the gas in a pulsed manner for several times in a short time, as compared with the case where the film is formed once for a long time. It is possible to more accurately perform minute film thickness control.

When a plurality of substrates are processed continuously, the inside of the first reaction tank is cleaned with hydrogen plasma before the substrates are loaded into the first reaction tank, and the substrates are processed. Removal of source gas such as WF ₆ gas that is adsorbed on the inner wall of the reaction tank during the previous substrate underlayer growth operation or remains in the reaction tank after the substrate is unloaded after the growth operation By doing so, the residual gas partial pressure of the raw material gas during the subsequent underlayer growth can be reduced,
Further, it is possible to perform stable film forming work with good film thickness controllability and reproducibility.

When the base film having a desired film thickness is obtained in the first reaction tank 1, the heating of the substrate and the introduction of the raw material gas are stopped, and the base film growth reaction is completed. After completion of the reaction, the substrate is cooled while the first reaction tank 1 is kept in a high vacuum state of 1 × 10 ⁻⁵ Torr or less. This cooling may be performed in the buffer chamber 4. After cooling the substrate to a predetermined temperature, the gate valve 3a is opened, and the substrate is unloaded from the first reaction tank by the carrying means and loaded into the buffer chamber 4. Next, the gate valve 3b is opened, and the buffer chamber 4
Then, the substrate is loaded into the second reaction tank 2. At this time, a continuous process is possible in which the inside of the first reaction tank 1 is cleaned with hydrogen plasma or the like, if necessary, and then the next substrate is loaded into the first reaction tank to form a base film.

The heating means 11 heats the substrate carried into the second reaction tank 2 to a temperature at which a predetermined reaction occurs, and a metal halide gas, which is a source gas such as WF6, and silane are heated by a gas introducing means (not shown). A reducing gas such as (SiH ₄ ) and, if necessary, a diluent gas such as argon are introduced, and an efficient film forming operation is performed by a generally known selective CVD method.

When the metal film having a desired thickness is obtained in the second reaction tank 2, the gate valve 3b is opened, and the substrate is carried out by the carrying means and carried into the buffer chamber 4. The gate valve 3c is opened with the gate valves 3a and 3b closed, and the substrate is unloaded into the loading / unloading chamber 5.

As described above, since the substrate is not exposed to the atmosphere or an extra step such as etching is not required from the loading of the substrate to the completion of the film forming operation, continuous processing of the substrate can be executed and it can be automated. Easy to handle.

The film thickness and the growth time of the obtained metal film in the case of performing the selective vapor phase growth by providing the underlayer film by the above method and in the case of performing the selective vapor phase growth without providing the underlayer film 4 shows the relationship. The substrate was a <100> silicon single crystal wafer, an n + -p wafer prepared by implanting As + of 4 × 10 ¹⁵ cm ⁻² on a p-type substrate, and BF ₂ on the n-type substrate.
A p + -n wafer prepared by implanting + with 4 × 10 ¹⁵ cm ⁻² was used. SiO ₂ was once deposited on the substrate to a thickness of 1 μm and contact holes were formed in the film to grow a metal film. WF ₆ was used as the source gas.

After the dry pretreatment with the fluorine-based gas plasma, the wafer has a substrate temperature of 4 when the base film is provided.
The underlying film was formed at 00 ° C., pressure of 2 × 10 ⁻⁴ Torr, and reaction time of 10 seconds.

In the case of a wafer using a base film, after the base film is formed, in the case of a wafer not using a base film, after the dry pretreatment, the substrate temperature is set to 300 ° C. and hydrogen gas is set to 1000 s.
ccm, WF ₆ and SiH ₄ were introduced at a flow rate ratio of WF ₆ / SiH ₄ = 2, and a tungsten film was grown by silane reduction under a total pressure of 0.1 Torr. As is apparent from FIG. 4, the film thickness difference between the n + -p wafer and the p + -n wafer is smaller when the underlayer film is used. Further, even when the same dry pretreatment as described above is performed on the wafer by exposing it to the organic gas plasma to intentionally contaminate the wafer and perform the film growth, the film thickness difference between the wafers is smaller when the base film is used. It has been confirmed.

Although the present invention is mainly used for a silicon substrate, if there is an oxide film portion where a metal film such as SiO ₂ does not grow and a portion where metallic silicon atoms are present on the substrate surface, metal silicon is used. Since the film can be selectively grown on the portion, the substrate itself is not limited to the silicon substrate as long as this is the case.

[0036]

As described above, according to the present invention, damage to the substrate can be suppressed as much as possible, and a metal film having good adhesion can be formed. Therefore, the contact hole or the like can be buried without causing junction breakage or the like. Wiring can be done. Furthermore,
Since the film growth can be performed at a constant rate without being affected by the difference in the surface state of the substrate, pretreatment and film thickness control are facilitated, and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a substrate temperature and a depth at which a tungsten film bites into a silicon substrate.

FIG. 3 is a diagram showing a relationship between a reaction pressure and a reaction time and a depth at which a tungsten film bites into a silicon single crystal substrate.

FIG. 4 is a diagram showing a relationship between a film formation time and a film thickness of a tungsten film.

[Explanation of symbols]

1 1st reaction tank 2 2nd reaction tank 6
Substrate transfer sequence 7 Heating means 8 Exhaust means 9
Gas introduction means 10 Control means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Komatsu 523 Yokota, Yamatake-cho, Yamatake-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Super Materials

Claims (5)

[Claims] 1. A selective vapor deposition method for selectively growing a film of a metal element at a desired portion on a surface of a substrate by reacting a source gas containing a desired metal element as a composition, wherein the substrate is 300 ° C. or higher. The first step of obtaining a base film by selectively growing a metal film on the surface of the substrate while heating the raw material gas for a short time and maintaining the reaction atmosphere at a pressure of 1 × 10 ⁻² Torr or less. A second step of introducing a reducing gas into a reaction atmosphere to selectively grow a metal film on the underlayer film to obtain a metal film having a desired thickness. How to grow. 2. The gas introduced in the first step is introduced in pulses under the condition that the product of film forming time and source gas pressure is 1 × 10 ⁻² sec · Torr or less. The selective vapor phase growth method described. 3. The reducing gas introduced in the second step is S
iH ₄ or a derivative thereof, i.
The selective vapor phase growth method described. 4. An apparatus used for carrying out the method according to claim 1, wherein a first reaction tank for performing the first step, a second reaction tank for performing the second step, and the second reaction tank The first reaction tank is provided with an evacuation means, a first heating means for heating the substrate to 300 ° C. or higher, and at least the raw material. The product of film formation time and source gas pressure is controlled to 1 × 10 ^-2 sec · Torr or less by controlling gas introduction means for introducing gas and / or one or both of the gas introduction means and the exhaust means. A selective vapor phase growth apparatus provided with a control means for maintaining the same. 5. The selective vapor phase growth apparatus according to claim 3, wherein the gas introduction unit is composed of a gas introduction valve capable of opening and closing a pulse.