JP2004176127A - Film deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a silicide film in which silicon and a metal are bonded in a desired ratio. <P>SOLUTION: In the film deposition method, among particles in a vapor depositing material, only micro-electrically charged particles 83 having a high charge mass ratio reach a treating object 52. The micro-electrically charged particles 83 have extremely high reactivity to reaction gas, and have high bonding reaction efficiency with the reaction gas, so that, a silicide film having a higher silicon concentration can be deposited as the concentration of the reaction gas is made higher. Thus, the partial pressure of the reaction gas and the bonding ratio between the silicon and metal are previously obtained per film deposition condition such as the kind of the vapor depositing material 31 and the kind of the reaction gas, and the partial pressure of the reaction gas is controlled on the basis of the result, so that the silicide film having a desired bonding ratio can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a film forming method, and more particularly, to a method for forming a silicide film.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an SRAM (Static Random Access Memory) has been widely used as a storage device.
In an SRAM, the gate electrode of a MOS (Metal Oxide Semiconductor) type IC is formed by forming a low-resistance silicide (metal silicide) film on the surface of a medium-resistance polysilicon film. Is formed by a sputtering method using a target made of silicide.
[0003]
However, it has been difficult to control the bonding ratio between metal and silicon in the silicide film formed by the sputtering method. When the thickness of the gate electrode is as thin as 30 nm to 50 nm, the accuracy of the bonding ratio between metal and silicon in the silicide film is required, and it is difficult to form such a silicide film by a conventional film forming method. Was.
[0004]
[Patent Document 1]
JP-A-11-150238 (Pages 6-7, FIG. 1)
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-mentioned disadvantages of the prior art, and an object of the present invention is to provide a film forming method capable of controlling a bonding ratio between metal and silicon when forming a silicide film. is there.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes disposing a deposition material, an anode electrode, and a processing object in a vacuum chamber, forming a vacuum atmosphere in the vacuum chamber, and then forming the vacuum atmosphere. While supplying the reaction gas into the tank, an arc discharge is generated between the vapor deposition material and the anode electrode to flow an arc current, and the charged particles of the vapor deposition material are released from the vapor deposition material. In the generated magnetic field, the traveling direction of the charged particles is bent in a direction in which the object to be processed is arranged, the charged particles reach the surface of the object to be processed, and the charged particles and the reaction gas react with each other, and the processing is performed. A method for forming a film on an object surface by arc discharge, wherein a metal is used as the vapor deposition material, and the following chemical formula (1) is used as the reaction gas:
[0007]
_{Si x H 2x + 2 ...... (} 1)
(In the above chemical formula (1), x represents an integer of 1 or more and 3 or less)
This is a film formation method for forming a silicide film using a silane gas represented by
[0008]
The invention according to claim 2 is the film forming method according to claim 1, wherein one or both of tungsten and tantalum are used as a metal constituting the vapor deposition material.
According to a third aspect of the present invention, there is provided the film forming method according to any one of the first and second aspects, wherein the reactive gas is represented by the following chemical formula (2):
[0009]
SiH ₄ (2)
[0010]
This is a film formation method using a monosilane gas represented by
The invention according to claim 4 is the film forming method according to any one of claims 1 to 3, wherein the pressure in the vacuum chamber is reduced to 6.5 × 10 ⁻⁷ Pa or less. This is a film forming method for generating arc discharge.
[0011]
The present invention is configured as described above, and since the vapor deposition material is composed of a conductive material such as a metal, a trigger electrode is arranged near the vapor deposition material, and a voltage is applied between the anode electrode and the vapor deposition material. When applied, a trigger discharge occurs between the trigger electrode and the deposition material.
[0012]
When the particles of the vapor deposition material are released from the vapor deposition material by the trigger discharge, the pressure between the anode electrode and the vapor deposition material increases, the dielectric strength between the vapor deposition material and the anode electrode decreases, and the anode electrode and the vapor deposition material are reduced. An arc discharge occurs between the surface and the surface. At this time, when an arc current for maintaining the arc discharge is caused to flow away from the object to be processed, the magnetic field induced by the current causes particles of the positive charge emitted from the surface of the deposition material to be exposed to the object to be processed. It exerts a bending force in the direction.
[0013]
Particles emitted from the surface of the deposition material include neutral particles and positively charged particles. Of the neutral particles and the positively charged particles, the charged particles having a small charge-to-mass ratio (charge / mass) do not fly in the direction of the processing object because the rate of bending by the magnetic field is small. Here, the anode electrode is formed in a cylindrical shape, the vapor deposition material is formed in a columnar shape, and if the side surface of the vapor deposition material is covered with the anode electrode, the neutral particles and the charged particles having a large charge mass ratio adhere to the inner peripheral surface of the anode electrode. It does not reach the object to be processed.
[0014]
That is, the charged particles that reach the object to be treated are only ions having a large charge-mass ratio and high chemical activity. Therefore, when silane gas is used as the reaction gas, the reactivity between the charged particles reaching the object to be treated and the silane gas is very high, and the efficiency of the binding reaction with the silane gas is high. A silicide film having a high silicon concentration can be obtained.
[0015]
For example, when a tungsten silicide film is formed using a monosilane gas, A tungsten and B monosilane all react to form a silicide film in which the bonding ratio of tungsten to silicon is A: B. If the number A is constant, B is proportional to the partial pressure of the silane gas in the vacuum chamber.
[0016]
Therefore, without changing the number of charged particles emitted from the evaporation material, the bonding ratio between silicon and metal in the silicide film can be changed by changing the partial pressure of the silane gas in the vacuum chamber. If the pressure in the vacuum chamber is set to 6.5 × 10 ⁻⁷ Pa or less, a high-purity silicide film can be obtained because impurities such as oxygen are not mixed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Reference numeral 1 in FIG. 1 indicates a film forming apparatus used in the film forming method of the present invention. The film forming apparatus 1 includes a vacuum chamber 2, an evaporation source 3, a substrate holder 50, and a nozzle 63.
[0018]
The evaporation source 3 is arranged on the bottom wall side of the vacuum chamber 2, and the substrate holder 50 is arranged on the ceiling side of the vacuum chamber 2. The nozzle 63 is located at a position between the substrate holder 50 and the deposition source 3 and near the substrate holder 50.
[0019]
The evaporation source 3 has a mounting plate 37, an anode electrode 32, an evaporation material 31, a trigger electrode 34, and an arc electrode 39. A hole is formed in the bottom wall of the vacuum chamber 2, and the mounting plate 37 is mounted horizontally so as to hermetically close the hole.
[0020]
The anode electrode 32 has a cylindrical shape and stands upright on the mounting plate 37 inside the vacuum chamber 2. A rod-shaped mounting member 36 is inserted through the inside of the anode electrode 32, the lower end portion is fixed on a mounting plate 37, and the trigger electrode 34 is mounted on the upper portion via a first insulating member 35. .
[0021]
The vapor deposition material 31 is attached to the distal end position of the attachment member 36 via a second insulating member 33 arranged above the trigger electrode 34. The vapor deposition material 31 is located below the opening 38 at the upper end portion of the anode electrode 32, that is, inside the anode electrode 32.
[0022]
The deposition material 31 is formed in a columnar shape having a diameter smaller than the inner diameter of the anode electrode 32, and the deposition material 31 is placed on the center axis 8 of the anode electrode 32. Therefore, there is a gap between the inner peripheral surface of the anode electrode 32 and the side surface of the deposition material 31.
The arc electrode 39 is rod-shaped and arranged in a gap, the upper end is connected to the vapor deposition material 31, and the lower end is air-tightly led out of the vacuum chamber 2 via the insulating material 41 of the mounting plate 37. It is electrically connected to a power supply device 40 disposed outside.
[0023]
The trigger electrode 34 is also electrically led out of the vacuum chamber 2 and is connected to the same power supply device 40. On the other hand, the anode electrode 32 and the vacuum chamber 2 are each connected to a ground potential.
[0024]
The vacuum chamber 2, the trigger electrode 34, the deposition material 31, and the anode electrode 32 are insulated from each other by first and second insulating members 33 and 35. Is applied, and a higher negative voltage than the vapor deposition material 31 is applied to the trigger electrode 34.
[0025]
The center of the substrate holder 50 is located on the central axis 8 of the anode electrode 32. When a processing target, which will be described later, is disposed on the surface of the substrate holder 50 on the bottom wall side of the vacuum chamber 2, the processing target is an anode. It faces the opening 38 of the electrode 32.
[0026]
The nozzle 63 is arranged in the vacuum chamber 2, and the ejection port at the tip thereof is arranged near the object to be processed, and the nozzle 63 is connected to the cylinder of the gas introduction system 61 arranged outside the vacuum chamber 2. . The cylinder is filled with a silane gas such as monosilane gas (SiH ₄ ) as a reaction gas, and is configured so that the silane gas can be ejected from an ejection port of a nozzle toward an object to be treated.
[0027]
A heater 68 and a cold water pipe 69 are wound around the outer wall of the vacuum chamber 2 so that the temperature inside the vacuum chamber 2 is maintained at a predetermined temperature in a film forming process described later.
A process of forming a silicide film on a processing target using the film forming apparatus 1 will be described. As the processing target 52, a substrate in which a polysilicon film described later is formed on one surface is prepared.
[0028]
The vacuum evacuation system 62 connected to the vacuum chamber 2 is started to form a vacuum atmosphere of 6.5 × 10 ⁻⁷ Pa or less inside the vacuum chamber 2, and then, while maintaining the vacuum atmosphere, the processing target 52 is maintained. Is loaded into the vacuum chamber 2, and the processing object 52 is held by the substrate holder 50 with the polysilicon film facing downward, so that the surface of the polysilicon film is directed toward the opening 38 of the anode electrode 32.
[0029]
The silane gas is ejected from the ejection port of the nozzle 63, the flow rate of the silane gas is adjusted while continuing the evacuation, and when the partial pressure of the silane gas in the vacuum chamber 2 reaches a predetermined pressure, the power supply device 40 is started to activate the anode electrode 32. A pulse-like voltage (here, 3.4 kV) is applied to the trigger electrode 34 with a voltage of about 100 V applied between the trigger electrode 34 and the deposition material 31.
[0030]
Here, the vapor deposition material 31 is formed of a column made of a refractory metal such as tungsten (W) or tantalum (Ta), and is arranged such that the bottom surface thereof is substantially horizontal. That is, since the side surface of the vapor deposition material 31 faces the inner peripheral surface of the anode electrode 32, particles of the high melting point metal are released from the side surface of the vapor deposition material 31 by the trigger discharge, and the pressure in the anode electrode 32 increases. When the insulation resistance decreases, an arc discharge is induced between the anode electrode 32 and the deposition material 31.
[0031]
The power supply device 40 is equipped with a large-capacity capacitor, which is charged in advance. When an arc discharge is induced between the anode electrode 32 and the vapor deposition material 31, the capacitor discharges the arc current. Is supplied. The arc current has a maximum value immediately after the arc discharge. If the maximum value is a peak current value, the capacitance of the capacitor is 8800 μF and the peak current value is 1200 A or more and 1400 A or less.
[0032]
The arc electrode 39 is disposed parallel to and near the center axis 8 of the anode electrode 32, and an arc current flows through the arc electrode 39 from the vapor deposition material 31 toward the bottom surface of the vacuum chamber 2. A magnetic field is formed about the axis 8.
[0033]
On the other hand, when an arc current flows through the vapor deposition material 31 due to the arc discharge, the side surface of the vapor deposition material 31 is melted, and a fixed amount of high melting point metal particles are emitted at each pulse of the trigger discharge. The released high melting point metal particles include positively or negatively charged particles and neutral particles.
[0034]
Reference numeral 81 in FIG. 2 indicates neutral particles, reference numeral 84 indicates a giant charged particle having a smaller charge (lower charge-to-mass ratio) than mass, and reference numerals 82 and 84 indicate larger charge (larger charge-to-mass ratio) than the mass. (Large) microcharged particles are shown.
[0035]
Of these, the neutral particles 81 and the giant charged particles 84 are not affected by the electric field between the anode electrode 32 and the deposition material 31, and when emitted from the deposition material 31, linearly move toward the anode electrode 32. When it flies and collides with the inner peripheral surface of the anode electrode 32, it adheres there.
[0036]
On the other hand, among the minutely charged particles 82 and 84, the minutely charged particles 82 (including electrons) having a negative charge repel the vapor deposition material 31 and are attracted to the positive voltage anode electrode 32, so that the negative charge Fly toward electrode 32. At this time, a force in the direction of the opening 38 is received by the magnetic field formed by the arc current, and the flight direction is bent toward the opening 38, and the airplane flies toward the processing object 52.
[0037]
Further, the positive fine charged particles 83 having a positive charge are released from the vapor deposition material 31, and are pushed back by the positive voltage anode electrode 32 on the way to the anode electrode 32, and are attracted to the negative voltage vapor deposition material 31, It flies in the opposite direction toward the direction of the deposition material 31.
[0038]
During the flight in the opposite direction, the positive fine charged particles 83 receive a force toward the opening 38 from the magnetic field formed by the arc current, and are attracted to the negative fine charged particles 82 flying toward the processing object 52. Then, the flight direction is bent toward the opening 38.
[0039]
The positive fine charged particles 83 whose flight direction is bent toward the opening 38 are emitted from the opening 38 toward the processing target 52 and reach the surface of the processing target 52. Therefore, in the film forming method of the present invention, only the minute charged particles 83 having a large charge-to-mass ratio and high reactivity reach the processing target 52.
[0040]
Since the surface of the processing target 52 on which the polysilicon film is formed faces the opening 38 and the silane gas is jetted to the processing target 52 as described above, the minute charged particles reaching the surface of the polysilicon film 83 reacts with the silane gas to grow a tungsten silicide film which is a silicide film.
[0041]
During the growth of the thin film, the substrate holder 50 is relatively rotated with respect to the opening 38 of the anode electrode 32 by the moving means (not shown), and the object 52 to be processed is rotated together with the substrate holder 50. A metal silicide film (silicide film) having a uniform thickness distribution grows on the surface of the film.
[0042]
Reference numeral 57 in FIG. 3 indicates an example of a silicide film formed on the processing target 52, and the polysilicon film 56 and the silicide film 57 constitute a stacked body 55. A silicide film composed of a metal silicide such as tungsten silicide has a lower electric resistance than a medium resistance film such as a polysilicon film. Therefore, if the surface on the polysilicon film 56 side of the laminate 55 is brought into close contact with the surface of the gate insulating film, the laminate 55 can be used as a gate electrode.
[0043]
Next, the film forming method of the present invention will be described more specifically.
<Silicon concentration>
A monosilane gas was used as a reaction gas, and a partial pressure of the reaction gas in the vacuum chamber 2 before film formation was changed to form a silicide film. Note that the ultimate pressure before film formation immediately before the supply of the reaction gas into the vacuum chamber 2 was 1 × 10 ⁻⁹ Torr (1.33 × 10 ⁻⁷ Pa).
[0044]
Auger analysis was performed on each silicide film to measure the atomic concentration of silicon contained in the silicide film. FIG. 4 shows the measurement results.
The horizontal axis of the graph in FIG. 4 indicates the partial pressure of the monosilane gas, and the vertical axis indicates the atomic concentration of silicon. As is clear from FIG. 4, the higher the partial pressure of the monosilane gas, the higher the silicon concentration of the silicide film, and it was confirmed that the partial pressure of the silane gas as the reaction gas was proportional to the silicon concentration.
[0045]
Therefore, the relationship between the partial pressure of the reaction gas and the silicon concentration is determined for each film forming condition such as the type of the reaction gas and the vapor deposition material, and the partial pressure of the reaction gas is set based on the relationship. It can be seen that a silicide film having a bonding ratio can be obtained.
[0046]
<Auger analysis>
A silicide film is formed under the condition that the partial pressure of the monosilane gas in the vacuum chamber 2 is 5 × 10 ⁻³ Torr (6.65 × 10 ⁻¹ Pa), Auger analysis is performed on the silicide film, and a depth direction of the silicide film is obtained. Was determined. The result is shown in FIG.
[0047]
The vertical axis in FIG. 5 indicates the atomic concentration, and the horizontal axis indicates the sputtering time (etching time). Symbols A, B, and C in FIG. 5 indicate silicon of a polysilicon film, silicon of a silicide film, and tungsten of a silicide film, respectively.
As can be seen from FIG. 5, the ratio of silicon to tungsten in the silicide film is substantially constant at a depth where the silicide film is etched away and silicon in the polysilicon film starts to be detected.
[0048]
From this, from the time when the minute charged particles 83 start to adhere to the surface of the polysilicon film, tungsten is combined with silicon to be silicified, and a silicide film having a constant composition ratio of elements with respect to the depth is obtained. You can see that.
[0049]
The case where a monosilane gas is used as the reaction gas has been described above. However, the present invention is not limited to this. For example, a disilane gas (Si ₂ H ₆ ), trisilane Silane gas (Si ₃ H ₈ ) can be used. These silane gases may be used alone or as a mixture of two or more.
[0050]
The constituent material of the vapor deposition material is not limited to tungsten, and various silicide films such as tantalum silicide and titanium silicide can be formed using various refractory metals such as tantalum (Ta) and titanium (Ti).
The shape of the anode electrode 32 is not limited to a cylindrical shape, and various shapes such as a hollow rectangular parallelepiped can be used. The shape of the vapor deposition material 31 is not limited to a cylinder, and various shapes such as a rectangular parallelepiped can be used.
[0051]
【The invention's effect】
In the present invention, only particles of the ionized deposition material reach the surface of the processing object. Such particles have very high reactivity, and the higher the concentration of the silane gas, the reactive gas, the greater the bonding ratio between silicon and metal. Therefore, by controlling the partial pressure of the reaction gas in the vacuum atmosphere, it is possible to obtain a metal silicide film bonded at a desired bonding ratio. In addition, since the ionized particles of the evaporation material react with the reaction gas without heating the object, the object is not damaged by heating. If the object to be treated and the vacuum chamber are not heated, the water adhering to the inner wall of the vacuum chamber will not be decomposed, and the decomposed products of water, oxygen and hydrogen will not be generated, and such impurities will not form. Since it is not mixed into a thin film in the film, a silicide film having a low impurity concentration can be obtained. Further, since the film thickness can be controlled by the number of pulses of the trigger discharge, the film thickness can be easily controlled, and a thin silicide film having a film thickness of about 10 nm to 50 nm can be manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of a film forming apparatus used in a film forming method of the present invention. FIG. 2 is a cross-sectional view illustrating the principle of an evaporation source used in the film forming apparatus of the present invention. FIG. 4 is a cross-sectional view for explaining a silicide film formed by the film forming method of FIG. 4. FIG. 4 is a graph showing a relationship between a partial pressure of a reaction gas and a silicon concentration in the silicide film. Graph showing the atomic concentration distribution in the direction [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus 2 ... Vacuum tank 3 ... Vapor deposition source 32 ... Anode electrode 38 ... Opening 31 ... Vapor deposition material 34 ... Trigger electrode 52 ... Processing object 55 ... Laminated body 56 ... Poly Silicon film 57: Silicide film 83: Positive charged particles

Claims (4)

A deposition material, an anode electrode, and a processing object are arranged in a vacuum chamber,
After forming a vacuum atmosphere in the vacuum chamber, while supplying a reaction gas into the vacuum chamber, an arc current is generated by generating an arc discharge between the deposition material and the anode electrode,
Discharging charged particles of the deposition material from the deposition material,
In the magnetic field generated by the arc current, the traveling direction of the charged particles is bent in a direction in which the object to be processed is arranged,
A film forming method by arc discharge in which the charged particles reach the surface of the processing target, react the charged particles and the reaction gas, and form a film on the surface of the processing target,
Using a metal as the deposition material,
The following chemical formula (1) is used as the reaction gas:
_{Si x H 2x + 2 ...... (} 1)
(In the above chemical formula (1), x represents an integer of 1 or more and 3 or less)
A film forming method for forming a silicide film using a silane gas represented by the formula: The film forming method according to claim 1, wherein one or both of tungsten and tantalum are used as a metal constituting the vapor deposition material. The following chemical formula (2) is used as the reaction gas.
SiH ₄ (2)
The film forming method according to claim 1, wherein a monosilane gas represented by the following formula is used. 4. The film forming method according to claim 1, wherein the arc discharge is generated after the pressure in the vacuum chamber is reduced to 6.5 × 10 ⁻⁷ Pa or less. 5.

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