JP2002047569A - Method for depositing transmission element silicide thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for depositing a transition element silicide thin film of high film quality, being free from contamination with silicon carbide. SOLUTION: In this film deposition method, gaseous organometallic compound containing a carbonyl group and a gaseous silicon starting material are mixed in an introduction tube 20, this mixture is thereafter charged into a vacuum tank 2, and a metallic silicide thin film is vapor-phase-grown on the surface of a preheated silicon substrate 12. At the time of using the gaseous organometallic compound containing a carbonyl group as a source gas in this way, carbon atoms in the gas are made into gaseous carbon monoxide, are absorbed into a vapor phase and are discharged to the outside of the vacuum tank without being deposited on the surface of the silicon substrate 12. Thus the metallic silicide thin film of high quality without contamination with silicon carbide can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a transition element silicide thin film, and more particularly to an improvement of a method of manufacturing an iron silicide thin film used for a light emitting / receiving element or the like.

[0002]

2. Description of the Related Art In recent years, a light-emitting / light-receiving element in which a light-emitting element and a light-receiving element serve as one element has been proposed. An example of the light emitting / receiving element is indicated by reference numeral 115 in FIGS. 5A and 5B. FIG. 5A is a plan view of the light emitting / receiving element 115, and FIG. 5B is a cross-sectional view taken along line AA of FIG. The light emitting / receiving element 115 has an n-type silicon substrate 112. An iron silicide thin film 113 is formed on the entire surface of the silicon substrate 112. As shown in FIG. 5B, a surface electrode 114 made of a ring-shaped metal thin film is formed on the surface of the iron silicide thin film 113, while a back electrode made of metal is formed on the entire back surface of the silicon substrate 112. 111 is formed.

In such a light emitting / receiving element 115, the silicon substrate 112 is an n-type, while the iron silicide thin film 1
13 is a p-type, so that a pn junction is formed between the iron silicide thin film 113 and the silicon substrate 112. The surface electrode 114 is formed in a ring shape, and the iron silicide thin film 113 is exposed.

In such a light emitting / receiving element 115, when sunlight is incident on the iron silicide thin film 113 in a state where a load (not shown) is connected between the front electrode 114 and the back electrode 111, the n-type is formed by the photovoltaic effect. Silicon substrate 11
A current flows from 2 to the p-type iron silicide thin film 113, and the current is supplied to the load. In this case, the light-emitting / light-receiving element 115 functions as a light-receiving element that receives light and generates electromotive force.

On the other hand, when a positive voltage is applied to the front electrode 114 and a negative voltage is applied to the back electrode 111, holes are injected from the p-type iron silicide thin film 113 into the n-type silicon substrate 112, and electrons are injected. And the bond energy is converted into light to emit light. In practice, a p-type silicon layer may be formed on the iron silicide thin film 113, and holes may be injected from the p-type silicon layer. In this case, the light emitting / receiving element 115 functions as a light emitting element. Thus, the light emitting / receiving element 115
Is an element having both functions of a light emitting element and a light receiving element.

In order to manufacture the light emitting / receiving element 115 having the above structure, it is necessary to form an iron silicide thin film on the surface of a silicon substrate. The method of forming iron silicide on the surface of the silicon substrate includes vapor deposition of iron on the surface of the silicon substrate, and a method of forming silicide by heating and holding this at about 400 ° C., or implantation of iron ions on the surface of the silicon substrate,
There is an implantation method or the like in which silicide is formed by a subsequent heat treatment. However, in these vapor deposition methods and injection methods,
Iron silicide does not form a thin film because it is agglomerated or formed into islands on the silicon substrate surface. For this reason, a CVD method is used to form a thin film.

[0007] Reference numeral 101 in FIG. 6 shows an example of a CVD film forming apparatus used for forming an iron silicide thin film. This CVD film forming apparatus 101 has a vacuum chamber 102.
A vacuum exhaust system 108 is connected to the vacuum chamber 102,
It is configured so that the inside thereof can be evacuated.

A mounting table 107 is disposed below the inside of the vacuum chamber 102. The mounting table 107 has a heater inside and has a flat surface, so that the substrate can be heated while the substrate is mounted on the surface.

In the vacuum chamber 102, gas introduction pipes 105, 1
06 is connected to one end. Gas inlet pipe 105, 10
The other end of 6 is connected to gas introduction devices 103 and 104, respectively. The gas introduction pipes 105 and 106 are provided with valves 121 and 122, respectively.
In 03 and 104, monosilane (SiH ₄ ) gas and
It is filled with a metallocene (Fe (C ₅ H ₅ ) ₂ ) gas, and is configured such that a monosilane gas and a metallocene gas can be introduced into the vacuum chamber 102 from the gas introduction pipes 105 and 106, respectively. The gas introduction pipes 105 and 106 are provided with flow controllers 133 and 134, respectively, so that the flow rates of the monosilane gas and the metallocene gas introduced into the vacuum chamber 102 can be adjusted respectively. .

In order to form an iron silicide thin film on the surface of a silicon substrate by using the CVD film forming apparatus 101, first, the inside of the vacuum chamber 102 is evacuated, and the silicon substrate is evacuated while maintaining a vacuum state inside. It is carried into the tank 102 and mounted on the surface of the mounting table 107. The silicon substrate in this state is indicated by reference numeral 112 in FIG.

The mounting table 107 is previously heated by a heater. When the silicon substrate 112 is mounted on the surface of the mounting table 107, the temperature of the silicon substrate 112 rises. When the temperature of the silicon substrate 112 is raised to a predetermined temperature, the gas introduction pipe 105 and the gas introduction pipe 105 are respectively adjusted while adjusting the monosilane gas and the metallocene gas to appropriate flow rates with the flow rate adjusters 133 and 134.
From 106, it is introduced into the vacuum chamber 102.

Then, iron silicide is vapor-grown on the surface of the silicon substrate 112, and an iron silicide thin film is formed on the surface of the silicon substrate 112. Using such a CVD method,
A large-area thin film can be formed on a silicon substrate surface.

However, in the above-mentioned CVD method, a metallocene gas is used as a raw material gas. During the growth of the thin film, carbon contained in the metallocene gas is mixed into the iron silicide and silicon carbide is contained in the iron silicide thin film. Will be formed. As a result, the quality of the thin film deteriorates,
There has been a problem that a film quality sufficient to withstand the use of the light emitting / receiving element cannot be obtained.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned disadvantages of the prior art, and has as its object to form a transition element silicide thin film having good film quality. It is to provide a method.

[0015]

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to a method in which a transition element source gas containing a metal atom belonging to a transition element and a silicon source gas containing silicon atoms are mixed in a reaction chamber. A method for forming a transition element silicide thin film in which a transition element silicide thin film is vapor-phase grown on the surface of the silicon substrate, wherein at least one carbonyl is added to the metal atom as the transition element source gas. It is characterized in that a gas of an organometallic compound formed by bonding groups is used. The invention according to claim 2 is the method for forming a transition element silicide thin film according to claim 1, wherein a gas containing at least one of silane gas, disilane gas, and organic silicon gas is used as the silicon source gas. Features. The invention according to claim 3 is the method for forming a transition element silicide thin film according to claim 1 or claim 2, wherein the gas of the organometallic compound is Fe (CO) ₅ gas or Fe (CO) ₁₂ gas. It is characterized in that either one or both are used. The invention according to claim 4 is the method for forming a transition element silicide thin film according to any one of claims 1 to 3, wherein the transition element raw material gas and the silicon raw material gas are mixed. , And introduced into the reaction chamber.

In the present invention, an organic metal compound gas in which one or more carbonyl groups are bonded to a metal atom, such as Fe (CO) ₅ gas, and a silicon source gas, such as silane gas, are used. The transition element silicide is vapor-phase grown on the surface of the silicon substrate by heating the substrate as a source gas.

The carbonyl group contains a carbon atom, which becomes a carbon monoxide gas during the vapor phase growth, is absorbed in the gas phase, and is discharged out of the reaction chamber. Does not adhere to the surface. Therefore, unlike the conventional method using a metallocene gas which is an organometallic gas containing no carbonyl group, no silicon carbide is mixed into the silicide thin film. Therefore, it is possible to form a thin film of good film quality that does not contain silicon carbide.

In the film forming method of the present invention, Fe (CO)
_{When a} gas of an organometallic compound having one or more carbonyl groups, such as ₅ gases, is introduced into the reaction chamber through an introduction port provided in the reaction chamber, the temperature near the introduction port to the reaction chamber is high. Therefore, metal may be deposited on the inner wall surface of the reaction chamber near the introduction port.However, in the film forming method of the present invention, the silicon source gas and the gas of the organometallic compound are mixed beforehand into the reaction chamber. Has been introduced. In this case, the silicon source gas and the organometallic compound gas are mixed with each other and react with each other to produce an intermediate product that maintains a gas state even at a high temperature. An iron silicide thin film can be formed without depositing and adhering iron on the surface.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Reference numeral 1 in FIG. 1A shows an example of an apparatus for performing the film forming method of the present embodiment, which is an example of a CVD film forming apparatus used for forming an iron silicide thin film.

The CVD film forming apparatus 1 has a vacuum chamber 2 which is an example of a reaction chamber used in the film forming method of the present invention. A vacuum evacuation system 8 is connected to the vacuum chamber 2 so that the inside thereof can be evacuated.

A mounting table 7 is disposed below the inside of the vacuum chamber 2. The mounting table 7 is provided with a heater (not shown) therein and has a flat surface, so that the substrate can be heated while the substrate is mounted on the surface.

Outside the vacuum chamber 2, two gas introducing devices 3, 4 are provided. Each gas introduction device 3, 4
Each is filled with a silicon source gas containing silicon atoms and a transition element source gas containing metal atoms belonging to the transition element. In the present embodiment, monosilane (SiH ₄ ) gas is used as the silicon source gas, and iron pentacarbonyl (Fe (CO) ₅ ) gas is used as the transition element source gas.
Of these, the gas introduction device 4 on the side filled with iron pentacarbonyl gas has a cooling device inside, and the iron pentacarbonyl gas filled therein is reduced by −5.
It has been cooled to ℃.

One end of each of gas discharge tubes 5 and 6 is connected to each of the gas introduction devices 3 and 4. The other ends of the gas discharge tubes 5 and 6 are both connected to one end of the introduction tube 20,
Valves 21 and 22 are provided in the gas release tubes 5 and 6, respectively. When the valves 21 and 22 are opened, monosilane gas and iron pentacarbonyl gas are introduced through the gas release tubes 5 and 6, respectively. It is configured so that it can be introduced into the tube 20. The other end of the introduction pipe 20 is connected to an introduction port 31 provided in the vacuum chamber 2, and when the monosilane gas and the iron pentacarbonyl gas are introduced into the introduction pipe 20, they are mixed inside the introduction pipe 20. Later, the inlet 31
And into the vacuum chamber 2. Each gas discharge pipe 5, 6 has a flow controller 3
3 and 34 are provided so that the monosilane gas and the iron pentacarbonyl gas can be introduced into the vacuum chamber 2 through the introduction pipe 20 after the flow rates are adjusted to appropriate flow rates.

In order to form an iron silicide thin film on the surface of a silicon substrate using the CVD film forming apparatus 1 having the above-described structure, first, the inside of the vacuum chamber 2 is evacuated to vacuum and the silicon is kept in a vacuum state. The substrate is carried into the vacuum chamber 2 and mounted on the surface of the mounting table 7. The silicon substrate in that state is indicated by reference numeral 12 in FIG.

The mounting table 7 is previously heated by a heater, and when the silicon substrate 12 is mounted on the surface of the mounting table 7, the temperature rises. Silicon substrate 1 up to predetermined film formation temperature (500 ° C)
When the temperature of 2 rises, the valves 21 and 22 are opened, and the flow controllers 33 and 34 are activated to introduce monosilane gas and iron pentacarbonyl gas into the introduction pipes 20 while adjusting them to appropriate flow rates. I do. Then, the monosilane gas and the iron pentacarbonyl gas are mixed in the introduction pipe 20, and the mixed gas is introduced into the vacuum chamber 2. At this time, the flow rates of the monosilane gas and the iron pentacarbonyl gas are respectively adjusted by the flow rate controllers 33 and 34, and the flow ratio of the monosilane gas to the iron pentacarbonyl gas is 2: 1.
And the pressure inside the vacuum chamber 2 is set to 3 × 10 ⁻² Pa.

Then, iron silicide is vapor-grown on the surface of the silicon substrate 12, and an iron silicide thin film is formed on the surface of the silicon substrate 12. Fig. 1 shows the iron silicide thin film.
Reference numeral 13 in FIG.

Thereafter, the inside of the vacuum chamber 2 is evacuated to 1 × 10 ⁻¹
The substrate temperature is cooled to 100 ° C. or less in a hydrogen atmosphere of about Pa. Thereafter, the inside of the vacuum chamber 2 is returned to the atmospheric pressure, and the silicon substrate 12 is taken out of the vacuum chamber 2.

In the film forming method of this embodiment, iron pentacarbonyl gas is used as a transition element raw material gas, and carbon atoms are mixed in the iron pentacarbonyl gas. Group 5
I have Therefore, during the growth of the thin film, the carbon atoms are absorbed in the gas phase as carbon monoxide gas, and are exhausted to the outside of the vacuum chamber without adhering to the substrate surface, so that silicon carbide is not mixed into the thin film. In addition, a thin film having good film quality can be formed.

The inventors of the present invention formed an iron silicide thin film on a silicon substrate surface with a growth time of one hour and examined the characteristics of the iron silicide thin film in order to confirm the effect of the above-described film forming method. .

FIG. 2 is a graph showing the evaluation results of X-ray diffraction of the iron silicide thin film. The horizontal axis in FIG. 2 indicates the diffraction position 2θ, and the vertical axis indicates the scattering intensity in the 2θ direction. The curve (A) in FIG. 2 shows the evaluation result of the iron silicide thin film formed by the CVD method of the present embodiment, and the curve (A) in FIG.
(B) shows a conventional C using metallocene gas as a source gas.
4 shows evaluation results of an iron silicide thin film formed by a VD method. Also, in FIG.
7, 48, 50, 56, 57, and 58 all indicate the spectra of silicon atoms in the iron silicide thin film, and reference numerals 45 and 55 all indicate the spectra of iron silicide. Reference numerals 41, 42, 43, and 44 indicate spectra of silicon carbide.

Spectra of silicon atoms 40, 46, 4
7, 48, 50, 56, 57 and 58 are curves (A) and (B)
However, while the spectrums 41, 42, 43, and 44 of silicon carbide appear on the curve (B), the spectrum of silicon carbide does not appear on the curve (A) at all. Further, the peak value of the iron silicide spectrum 55 in the curve (A) is larger than that of the iron silicide spectrum 45 in the curve (B). From the above, it can be seen that the CVD method of the present embodiment does not involve silicon carbide and can form an iron silicide thin film having better film quality than the conventional method.

The inventors of the present invention analyzed the iron silicide thin film formed on the silicon substrate surface by the film forming method of the present embodiment by Auger electron spectroscopy. FIG.
FIG. 3 is a graph showing the results of an Auger electron spectroscopic analysis of an iron silicide thin film formed by the film forming method of the present embodiment.

The horizontal axis in FIG. 3 shows the sputtering time.
This sputtering time corresponds to the depth in the thickness direction of the iron silicide thin film. The vertical axis indicates the spectral intensity of Auger electrons, which corresponds to the element concentration in the thin film.

The curve (C) in FIG. 3 shows the spectrum of silicon atoms, and the curve (D) shows the spectrum of iron atoms. Curve (E) shows the spectrum of an oxygen atom, and curve (F) shows the spectrum of a carbon atom.

As shown in FIG. 3, in the iron silicide thin film of this embodiment, the curves (C) and (D) appear with almost constant intensity, whereas the curves (E) and (F) appear. Appears only slightly near the surface and hardly appears.
As described above, in this iron silicide thin film, iron atoms and silicon atoms are present at a substantially constant ratio, but even if they are present, the amount of carbon atoms and oxygen atoms is less than the detection limit. Understand. This also confirms that the CVD method of this embodiment hardly mixes carbon atoms into the iron silicide thin film.

Further, the inventors of the present invention have found that when a surface of an iron silicide thin film formed on a silicon substrate surface is irradiated with a laser beam by the film forming method of the present embodiment, the intensity of surface light emission generated on the surface of the thin film is reduced. The distribution was examined.

FIG. 4 is a diagram showing a light emission intensity distribution when the surface of the iron silicide thin film is irradiated with a laser beam to emit surface light. The horizontal axis of FIG. 4 indicates the measurement wavelength of the emitted light,
The vertical axis indicates the light emission intensity. Curve (H) in FIG.
The spectrum of the emission intensity of the iron silicide thin film formed by the film forming method of the present embodiment is shown, curve (I), ferrocene (C ₅ H ₅ ) Fe (C ₅ H ₅ ) gas as a source gas The spectrum of the emission intensity of the iron silicide thin film formed by the conventional film forming method is shown.

In the curve (I) corresponding to the iron silicide thin film formed by using the ferrocene gas, the spectrum is constant, the spectrum of the emission intensity does not appear at all, and no surface emission occurs. In the curve (H), when the measurement wavelength is around 15600 nm, the peak 50
Appears, indicating that strong surface light emission appears. In addition, as described above, iron pentacarbonyl gas is supplied to the vacuum chamber 2
When only iron pentacarbonyl gas is introduced into the vacuum chamber 2 alone when introduced into the inside, the temperature near the inlet through which iron pentacarbonyl gas is introduced into the vacuum chamber becomes a high temperature of 200 ° C. or more, In some cases, iron precipitates and adheres to the inner wall surface of the vacuum chamber 2 near the inlet, but in the film forming method of the present embodiment, after mixing iron pentacarbonyl gas and monosilane gas in the inlet tube 20, , Into the vacuum chamber 2. For this reason, the iron pentacarbonyl gas and the monosilane gas react inside the introduction pipe 20 to form an intermediate product gas. This intermediate product is kept in a gaseous state at a temperature (about 200 ° C.) inside the vacuum chamber 2 near the gas inlet 31 which is higher than room temperature and lower than the substrate temperature during film formation. An iron silicide thin film can be formed without depositing and attaching iron to the opening 31.

In this embodiment, iron pentacarbonyl gas (Fe (CO) ₅ ) is used as the transition element source gas, but the transition element source gas used when forming the iron silicide thin film is the same as this. It is not limited, and for example, iron dodecanecarbonyl (Fe (CO) ₁₂ ) gas may be used.

In the present embodiment, the iron silicide thin film is formed. However, the transition element silicide thin film of the present invention is not limited to this, and can be applied to, for example, tungsten silicide or titanium silicide. is there. At this time,
When a tungsten silicide thin film is formed, tungsten hexacarbonyl (W (C
O) ₆ ) gas may be used, and when a titanium silicide thin film is formed, titanium hexacarbonyl (Ti (CO) ₆ ) gas may be used as a transition element source gas.

Further, monosilane is used as a silicon source gas.
Although (SiH ₄ ) gas was used, the silicon source gas of the present invention is not limited to this, and for example, other silane-based gas such as disilane (Si ₂ H ₆ ) gas may be used, or Organic silicon gas may be used.

Further, in the present embodiment, the gas discharge pipe 5,
6 and the introduction pipe 20 are directly connected, and the monosilane gas released from each of the gas release pipes 5 and 6 and the iron pentacarbonyl gas are mixed inside the introduction pipe 20. However, the present invention is not limited to this. A mixing chamber is provided between the gas discharge tubes 5 and 6 and the introduction tube 20, and after mixing monosilane gas and iron pentacarbonyl gas in the mixing chamber, the mixed gas is introduced from the introduction tube 20 into the vacuum chamber 2. May be introduced.

[0043]

As described above, a transition element silicide thin film having good film quality can be formed.

[Brief description of the drawings]

FIG. 1A is a view for explaining a configuration of a CVD apparatus for carrying out a method for forming a transition element silicide thin film according to an embodiment of the present invention; FIG. Sectional view for explaining a state in which an iron silicide thin film is formed.

FIG. 2 is a graph showing evaluation results of X-ray diffraction of a film forming method according to an embodiment of the present invention and each iron silicide thin film formed by a conventional film forming method.

FIG. 3 is a graph showing the results of Auger spectroscopy analysis of the iron silicide thin films formed by the film forming method according to one embodiment of the present invention and the conventional film forming method.

FIG. 4 is a graph illustrating the spectrum intensity of surface light emission when a surface of each iron silicide thin film formed by a film forming method according to an embodiment of the present invention and a conventional film forming method is irradiated with laser light.

5A is a plan view illustrating an example of a light emitting / receiving element; FIG. 5B is a cross-sectional view illustrating an example of a light emitting / receiving element;

FIG. 6 is a diagram illustrating a configuration of a film forming apparatus that performs a conventional film forming method.

[Explanation of symbols] 2 ... Vacuum tank (reaction chamber) 3,4 ... Gas introduction device
5, 6: gas release pipe 20: introduction pipe

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 AA09 AA12 BA07 BA18 BA20 BA48 CA04 CA12 FA10 LA18 5F041 AA31 CA22 CA33 CA46 5F045 AA04 AB30 AC01 AC07 AD08 AD09 AE13 AF03 CA09 CA13 5F051 AA20 BA11 CB12 GA06 GA03

Claims (4)

[Claims] A transition element source gas containing metal atoms belonging to a transition element and a silicon source gas containing silicon atoms are introduced into a reaction chamber, and a transition element silicide thin film is vapor-phase grown on the surface of the silicon substrate. A method for forming a transition element silicide thin film, wherein a gas of an organometallic compound in which at least one carbonyl group is bonded to the metal atom is used as the transition element source gas. A method for forming an elemental silicide thin film. 2. The method for forming a transition element silicide thin film according to claim 1, wherein a gas containing at least one of silane gas, disilane gas and organic silicon gas is used as said silicon source gas. 3. The gas of said organometallic compound is Fe (CO)
3. The method for forming a transition element silicide thin film according to claim 1, wherein one or both of a _five gas and a Fe (CO) ₁₂ gas are used. 4. The transition element silicide according to claim 1, wherein the transition element source gas and the silicon source gas are mixed and then introduced into the reaction chamber. A method for forming a thin film.