JP3215898B2 - Plasma CVD method and plasma CVD apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD method for forming a thin film of metal or the like on a substrate by a chemical reaction in a gas phase, and a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In recent years, the density of semiconductor devices has been remarkably increased by the progress of fine processing technology, and semiconductor devices having a submicron structure are now on the market. Meanwhile, research and
In development, the practical application of a semiconductor device having a half-micron or quarter-micron structure has been targeted. Such a reduction in size (scaling down) speeds up the operation of the semiconductor device and greatly enhances reliability by increasing the density.

By the way, in MOS transistors and the like, if the channel length of the transistor is shortened due to this reduction, a short channel effect occurs and the operation of the transistor is hindered. Efforts have been made to reduce the depth of the junction between the source and drain of a transistor (shallow junction). On the other hand, even if the two-dimensional size of the transistor or wiring is reduced by the reduction, the electrical resistance of the wiring and the capacitance between the wirings must be kept small. Cannot be reduced. for that reason,
The aspect ratio (aspect ratio) of the contact hole formed in the insulating film connecting the source / drain and the wiring increases, and the high concentration silicon surface of the source / drain at the bottom of the contact hole and the metal buried in the contact hole In the meantime, it is becoming difficult to obtain a low contact resistance.

Furthermore, when the dimensions of these patterns have been large, the electrical resistance of high-concentration silicon has not been a problem in the design of the device. However, these problems have become noticeable due to their shallow junction and miniaturization. It has become In order to solve this new problem, research on forming a silicide film of a refractory metal on high-concentration silicon such as a source / drain layer and a gate electrode to lower the resistance has been actively conducted in recent years. Conventionally, this silicide film is formed by depositing a metal film on a silicon layer by sputtering or the like, heating the metal film to react the deposited metal with silicon to silicide the metal, and depositing the metal on the insulating film. The unreacted metal film that has not been silicided is removed by washing, and a silicide film is selectively formed only on the silicon layer.

However, in forming a metal film by sputtering, it is difficult to form a metal film having a required thickness at the bottom of a contact hole having a high aspect ratio. On the other hand, as described above, in the method of depositing a metal and then reacting it with the underlying silicon by heat to silicify the metal, the silicidation proceeds too much at the boundary between the silicon surface and the insulating film surface, and the silicide generated by the reaction is There has been a problem that it crawls on the insulating film or penetrates into the silicon layer in a spike shape.

In order to solve such a problem, attempts have been made to form a silicide film by a CVD method. In the film formation by the CVD method, a raw material gas is sent onto a solid on which a film is to be formed, and the gas is reacted on the surface of the solid on which the film is to be formed, and molecules reacted in a gas phase are diffused to the surface of the solid on which the film is to be formed. Since the film is deposited on the solid surface of the film, it is possible to deposit a film having a necessary thickness on the bottom surface of the contact hole having a high aspect ratio. As an example, there is CVD for forming a titanium silicide film using titanium tetrachloride gas. This C
In the deposition of titanium silicide by VD, a titanium silicide film can be selectively grown only on the silicon surface. The feature of this film formation is that the silicide film does not creep over the insulating film other than the silicon layer, and the silicide film does not penetrate deeply into the silicon layer.

However, this CVD method also has some disadvantages described below. One is that the grown film has a large crystal grain size and the surface morphology of the film is poor. Second, there is a variation in the time from the supply of a source gas as a film forming material to the growth of the film (latent period: incubation time). This variation becomes a phenomenon of the presence or absence of partial film growth when depositing a thin film, and becomes a variation in thickness when depositing a thick film. These problems may be fatal when the CVD method is formed on a source / drain layer or an electrode having a shallow junction.

Here, the prior art of the plasma CVD method and the apparatus will be described. The plasma CVD method has a feature that a film can be deposited at a temperature lower than a thermal decomposition temperature of a source gas, and has been conventionally used for manufacturing a semiconductor device. Here, plasma enhanced door
C VD (PECVD) or plasma assisted CVD
(PACVD), etc., which perform film deposition by promoting thermal decomposition of source gas with plasma
Is referred to as plasma CVD.

Conventionally, the plasma CVD method is mainly used for depositing an insulating film, and is hardly used for depositing a semiconductor film or a metal film. The main reason is that, when a semiconductor film or a metal film is formed by a plasma CVD method, a film deposited between the walls of the reaction vessel and the electrodes for plasma generation causes an electrical short circuit between the electrodes and causes plasma. This makes it impossible to perform a discharge. Therefore, in order to form a semiconductor film or a metal film by plasma CVD, a device specially designed to prevent a short circuit between electrodes is required.

Although there are few examples of such devices devised in this way, one example of such a conventional device will be introduced below. FIG. 5 shows a hot wall type PECVD apparatus developed for depositing an insulating film, a semiconductor film, and a conductor film.
This device is described in Document 1 (Journal of Vacuum
Science and Technology, Volume B2, No. 4, 7
33, 1984).

FIG. 5 (a) is a structural view of the apparatus viewed from the side, and FIG. 5 (b) is a cross-sectional view showing a cross section of the structural view of FIG. 5 (a). This device connects an electrode 82 and an electrode 83 provided alternately inside a quartz tube 81 to a high-frequency power supply 84, and applies a high-frequency voltage to the electrodes 82 and 82 by the high-frequency power supply 84.
A voltage is applied between the electrodes 83 to generate plasma between the electrodes 82, 83, and a film is deposited on the surface of the wafer 85 mounted on the surfaces of the electrodes 82 and 83. The inside of the quartz tube 81 is depressurized by a vacuum exhaust system 86, and a source gas 87 is supplied from the other end of the quartz tube 81. The electrodes 82 and 83 and the wafer 85 inside the quartz tube 81 are supported by a boat (not shown), and the boat has a special structure such that the electrodes 82 and 83 are not short-circuited by deposition of a conductive film or the like. It has become. However, the exact structure is not well known.

Next, a conventional method of depositing a semiconductor film or a conductor film with this plasma CVD apparatus will be described, but there are few examples. It described in the literature 1, using PEVCD device, an amorphous silicon film, an example in which a polycrystalline film and a titanium silicide (TiSi _x) film have been reported. The deposition of the titanium silicide film described in Reference 1 will be briefly introduced.

The wafer 85 loaded on the electrodes 82 and 83 in the quartz tube 81 is heated to 300 to 500 ° C., and titanium tetrachloride (TiCl ₄ ) gas and monosilane (S
iH ₄ ) gas, using argon (Ar) gas as a diluting gas, titanium tetrachloride gas at 25 to 100 cc / min.
(Hereafter, the volume of the gas at the gas flow rate is assumed to be the volume at 0 ° C. and 1 atm.)
/ Min, 800 to 4000 cc / mi of argon gas
n, the pressure in the quartz tube 81 is set to 100 to 266 Pa, and a high frequency of 50 kHz and 100 W is applied to grow an amorphous titanium silicide film at a rate of 60 to 80 ° / min. The titanium silicide film thus formed grows non-selectively (blanket) almost uniformly.

[0014]

Since the apparatus described in the prior art 1 is constructed as described above, the surface of the wafer becomes a part of the high-frequency electrode for generating plasma, and the surface of the wafer is Is exposed to a strong plasma, and the deposition of the film becomes a blanket (non-selective), and there is a problem that selective growth cannot be performed. In addition, when a silicide film made of a high melting point metal is formed in the process of manufacturing a semiconductor device, there is a problem that the surface of the wafer is often damaged by plasma.

[0015]

SUMMARY OF THE INVENTION A plasma CV according to the present invention is provided.
The D method is intended to solve the above problems ,
A reaction chamber on which a substrate including a recon
It must be in communication and have multiple holes at its boundary with the reaction chamber.
A plasma generation chamber with an aperture plate
Vacuum evacuation, heating the substrate, and plasma
When the inert gas, hydrogen gas, or inert gas is
Supply a first gas selected from a mixed gas with hydrogen gas
And a predetermined pressure difference between the plasma generation chamber and the reaction chamber.
Providing, and applying a high frequency to the plasma generation chamber to perform the first
Gas plasma and the plasma generation chamber
Of the first gas into the reaction chamber by the high frequency applied to
The process of producing zuma and titanium tetrachloride in the reaction chamber,
Is a gas mixture of titanium tetrachloride and silicon hydride
Supply one of the source gases and mix the first gas and the source gas.
A plasma of the combined gas is generated, and only on the silicon surface of the substrate
And a step of selectively growing titanium silicide.
It is characterized by having done.

On the other hand, the plasma CVD apparatus of the present invention
Substrate placement for placing the substrate to be deposited in the reaction chamber
A table, a heating means for heating the substrate, and a place communicating with the reaction chamber.
A plasma generation chamber for generating a plasma of
Equipped with multiple holes located at the boundary between the
Aperture plate and exhaust means for evacuating the reaction chamber
And a gas for supplying a predetermined gas in communication with the plasma generation chamber.
Source supply means and a source gas serving as a film forming source in the reaction chamber.
Source gas supply means and high frequency power to the plasma generation chamber.
A high frequency source for applying a force, and the aperture plate has a plurality of
Made of insulator with holes, applied to plasma generation chamber
High-frequency structure leaks into the reaction chamber.
Each of the diameters allows the plasma generated in the plasma generation chamber to pass through.
The size of the holes and the number of holes
When a specified gas is supplied to the reaction chamber,
The diameter and number that cause a predetermined pressure difference.
A predetermined gas is introduced into the reaction chamber by the high frequency applied to the living room.
A plasma of a mixed gas with the source gas is generated.
It is characterized by that .

[0017]

For example, a plasma such as an inert gas or a reducing gas is supplied to the reaction chamber.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a configuration diagram of a plasma CVD apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a plasma generation chamber, which is a discharge tube 2 made of PBN or quartz glass having a diameter of about 10 cm, a high-frequency coil 3 wrapped around the discharge tube 2, and an inert gas provided on the discharge tube 2. And a gas supply port 4 for reducing gas, and a thickness 1 provided at a lower portion of the discharge tube 2.
A hole (aperture) with a size of 2 mm and a diameter of 2 mm
It comprises an aperture plate 5 of about 10 cm in diameter made of individually opened PBN or quartz glass. Reference numeral 6 denotes a reaction chamber, 7 denotes a wafer, 8 denotes a heater disposed in the reaction chamber 6 for heating the wafer 7, 9 denotes a source gas supply port for supplying a source gas or a reducing gas into the reaction chamber 6, and 10 denotes a reaction gas. An exhaust port 11 for exhausting indoor gas is a high-frequency power supply for supplying a high-frequency voltage to the high-frequency coil 3.

The aperture plate 5 restricts the flow of the gas supplied to the plasma generation chamber 1 and provides a gas pressure difference between the plasma generation chamber 1 and the reaction chamber 6. The supply of gas is controlled by a mass flow controller (not shown), and the exhaust is preferably performed by a pump capable of evacuating to a high vacuum such as a turbo molecular pump or an oil diffusion pump.
Is preferably loaded into the reaction chamber 6 by a load lock mechanism that prevents oxygen and moisture from entering the reaction chamber 6. This apparatus is a cold-wall type single-wafer processing plasma CVD apparatus, and it is easier to automate the loading of the wafer 7 into the reaction chamber 6 than a batch processing type apparatus.

In order to operate this apparatus, an inert gas such as argon or a gas such as hydrogen is decomposed from the gas supply port 4 so that the pressure in the plasma generation chamber 1 becomes a pressure sufficient to generate plasma. A reducing gas that does not generate deposits is supplied, and a high-frequency voltage is applied to the coil 3 to generate plasma. The plasma of the inert gas generated in the plasma generation chamber 1 leaks into the reaction chamber 6 unless the aperture diameter of the aperture plate 5 is extremely small. In addition, since the aperture plate 5 is an insulator, a high frequency leaks into the reaction chamber 6 and generates low-density plasma in the reaction chamber 6.

For example, 50 cc of gas is supplied from the gas supply port 4.
/ Min, and when the gas is exhausted from an exhaust port 10 having a pipe diameter of about 10 cm by a pump having an exhaust capacity of about 1000 l / s, the pressure in the plasma generation chamber 1 becomes about 7.2 Pa, and the pressure in the reaction chamber 6 becomes The pressure amounts to about 0.35 Pa. When plasma is generated by a normal plasma generator, 0.3
At a low pressure of about 5 Pa, the plasma is unstable and may be extinguished. However, in the apparatus of the present invention, the pressure in the plasma generation chamber 1 is sufficient to stabilize the plasma state. The reaction chamber 6 is supplied to the reaction chamber 6 through the
In this case, low-density plasma can be generated stably. When the source gas is supplied into the reaction chamber 6 where the low-density plasma is stably generated, the decomposition of the source gas is promoted by the action of the plasma.

When the diameter of the aperture of the aperture plate 5 is extremely small, for example, 1 mm or less, the pressure in the reaction chamber 6 becomes too low, and the plasma in the aperture is cut off. Plasma may not be generated. In this case, no reactive ions exit from the aperture of the aperture plate 5 to the reaction chamber 6 side.
Only neutral atoms, atoms and radicals come out. In such a state, the plasma generation chamber 1 acts as an atom / radical beam source. In order to promote the decomposition of the source gas in CVD, the effect cannot be obtained unless low-density plasma is generated in the reaction chamber 6, and the effect cannot be obtained by the atom / radical beam source.

On the other hand, if the diameter of the aperture is too large, the conductance becomes too large, the pressure difference between the plasma generation chamber 6 and the reaction chamber 1 becomes small, and the gas flow becomes slow, so that the source gas becomes large. It is easy to enter the plasma generation chamber 6. For example, the aperture diameter of the aperture plate 5 is 4 mm, and 5
When a gas of 0 cc / min is supplied and exhausted by the above-described exhaust system, the pressure in the plasma generation chamber 1 is about 1.8 Pa and the pressure in the reaction chamber 6 is 0.35 Pa. The pressure ratio between the plasma generation chamber 1 and the reaction chamber 6 was 20 times when the aperture diameter was 2 mm, but dropped 5 times when the aperture diameter was 4 mm. Since the pressure ratio between the plasma generation chamber 1 and the reaction chamber 6 is substantially proportional to the conductance of the aperture, the pressure ratio fluctuates in a form substantially inversely proportional to the square of the ratio of the aperture diameter of the aperture plate 5.

As described above, when the source gas enters the plasma generation chamber 1, a film is deposited in the plasma generation chamber 1, contaminating the inside of the plasma generation chamber 1, and depositing a film on the electrode. As a result, a discharge for generating plasma becomes difficult to occur. Therefore, according to the present invention, the aperture diameter of the aperture plate 5 cannot be made too large. In this device, the source gas is less likely to enter the plasma generation chamber due to the gas flow in the aperture of the aperture plate 5, so that the plasma can be generated stably.

The surface of the aperture plate 5 on the side of the reaction chamber 6 is exposed to the source gas. However, the aperture plate 5 is not heated except by heating by high frequency or copying from a heater. Film deposition is low. If the film growth on the wafer 7 is set to the condition of the selective growth, the surface of the aperture plate 5 is also likely to be the condition of the selective growth, so that the film does not grow. Under such conditions, it can be used stably without fluctuation for a long time. When a film is deposited on the surface of the aperture plate 5 and the high-frequency matching conditions fluctuate, for example, chlorine trifluoride (ClF ₃ ) gas is supplied to the reaction chamber to generate plasma. If done, it can be easily cleaned.

(Embodiment 2) FIG. 2 is a block diagram showing a second embodiment of the plasma CVD apparatus of the present invention. Reference numeral 2a denotes a discharge tube, and 6a denotes a reaction chamber. As shown in FIG. 2, the discharge tube 2a and the reaction chamber 6a are connected via an aperture plate 5, and unlike the first embodiment shown in FIG. The tube 2a is exposed to the atmosphere. In such a configuration, the discharge tube 2
The side wall a is made of quartz glass or the like thicker than the discharge tube 2 of the first embodiment so as to withstand the atmospheric pressure. In this structure, the outside of the discharge tube 2a and the high-frequency coil 3 are connected to the reaction chamber 6a.
, The film does not accumulate on that portion or is not contaminated with deposits.

(Embodiment 3) By the way, in the above embodiment, high frequency was used for plasma generation. However, the present invention is not limited to this, and microwaves are guided to a plasma generation chamber by a waveguide to generate plasma. May be. Further, a magnetic field is applied to the plasma generation chamber to satisfy the ECR condition,
The same effect as that of generating plasma at a high frequency can be obtained as a plasma source.

(Embodiment 4) Next, the plasma C of the present invention
An example of the VD method will be described. This method can be carried out using the plasma CVD apparatuses of the first and second embodiments or another plasma CVD apparatus capable of generating low-density plasma CVD on the wafer surface. An example performed using the plasma CVD apparatus of the first embodiment will be described.

Before the gas is supplied, the plasma generating chamber 1 and the reaction chamber 6 are evacuated by a pump having an exhaust capacity of 1000 l / s connected to the exhaust port 10 to reduce the partial pressure of unnecessary gases such as moisture and oxygen. It was evacuated to a high vacuum of 1 × 10 ⁻⁴ Pa or less. The wafer 7 is previously heated to about 720 by the heater 8.
° C, and 30 g of argon was supplied through the gas supply port 4.
cc / min, 20 cc / min of hydrogen as reducing gas
Supplied. Here, argon was supplied to facilitate plasma generation, and the supply amount was adjusted according to the size of the aperture diameter of the aperture plate 5 and the exhaust capacity. As a result, the pressure in the reaction chamber 6 became about 0.35 Pa.

In this state, when a high frequency of 50 to 1000 W is applied to generate plasma, low density plasma is also generated in the reaction chamber 6 due to the argon plasma leaked from the plasma generation chamber 1 and the high frequency, and the wafer 7 A little light was emitted from the plasma near the surface of the sample. However,
In the following film growth, the high frequency power was fixed at 200 W.

Next, when titanium tetrachloride gas was supplied as a source gas at about 0.4 cc / min from the source gas supply port 9, a titanium silicide film was selectively grown only on the silicon surface of the wafer 7. The change in the plasma generation state due to the supply of the titanium tetrachloride gas was slight. The growth rate of the titanium silicide film is about 100 ° / min,
The titanium silicide film was formed in a form in which crystal grains were connected. The crystal grain size was smaller than in the case of growing only by heat without generating plasma, and the unevenness (surface morphology) of the grown film surface was also small. Further, the selectivity of the growth of the titanium silicide film was extremely good, and no growth occurred on the silicon oxide film despite the use of plasma.

The selective growth of titanium silicide is possible not only under the above conditions but also under various conditions. For example, if the heating temperature of the wafer is set to 600 ° C. or higher, a titanium silicide film having a low resistance can be obtained. Change. That is,
At a relatively high temperature of 700 ° C. or more, C54 type or C4
Nine-type TiSi ₂ is easy to grow, its grain size is large, and the resistance of the film is small. Also, 600-700
At a relatively low temperature of ° C., Ti ₅ Si ₃ grows easily, the crystal grain size is slightly smaller, and the resistance of the film becomes higher.

The supply amounts of argon and hydrogen for generating plasma may be determined in accordance with the conductance of the gas flow by the aperture plate 5 and the exhaust capacity so that plasma can be generated stably. It is not limited to. For example, hydrogen has a reducing effect even at a flow rate of 5 cc / min, and if it is supplied at a flow rate of 100 cc / min or more, discharge is continued without supplying argon, and plasma is generated.

The higher the RF power, the higher the plasma density and the higher the ability to excite the source gas and the reducing gas. However, the input power is not directly used for generating low-density plasma in the reaction chamber 6. Therefore, the plasma density of the reaction chamber 6 is orders of magnitude lower than that of the plasma generation chamber 1 even when large power is applied. Therefore, it is possible to selectively grow a titanium silicide film even with a power of 500 W or more, and by using low power, damage to the wafer surface by plasma is small.

By the way, the supply amount of titanium tetrachloride changes the growth rate, the film quality, and the consumption amount (bite amount) of silicon, and particularly has a great influence on the growth rate of the titanium silicide film. The supply amount of titanium tetrachloride gas is 0.05
Even if it is reduced to about cc / min, the titanium silicide film is selectively grown, but the growth rate is considerably reduced. Although the upper limit of the supply amount of the titanium tetrachloride gas for selectively growing the titanium silicide film is not clear, the selectivity does not collapse at least when the supply amount is about 0.5 cc / min. If the supply amount of the titanium chloride gas is increased without increasing the density of the plasma, the effect of the plasma is weakened, the temperature becomes closer to that of thermal CVD, and the growth rate of the titanium silicide film is also increased.

As long as titanium tetrachloride gas is used as the source gas and hydrogen gas is used as the reducing gas, even in the case of plasma CVD, there is a strong tendency that titanium is not deposited unless it is combined with silicon. Therefore, even if the above conditions such as the flow rate of titanium tetrachloride gas are greatly changed, the selectivity does not easily collapse. According to this embodiment, in order to obtain a desired growth rate and film quality of the titanium silicide film, it is preferable to grow the film in advance by changing the conditions and evaluate the film to determine the optimum film growth conditions. .

Generally, in the selective growth of a metal film, very high cleanliness is required on the surface for selective growth, except for those using fluorine gas as a source gas.
This is natural because the selective growth of the titanium silicide film is caused between the semiconductor, the conductor and the insulator. On a surface where the silicon surface to be selectively grown is not clean and a natural oxide film is growing, the film does not grow or grows in an island shape. However, according to the plasma CVD method of the present invention, a film having good morphology can be selectively grown even if a natural oxide film is slightly grown on the silicon surface.

For example, the natural oxide film on the silicon surface is removed by immersion in dilute hydrofluoric acid to make the silicon surface hydrophobic, rinsed with pure water, and then immersed in a hydrogen peroxide solution to oxidize the silicon surface. Even if the plasma CVD of the present invention is applied to a wafer which has been made hydrophilic by rinsing with pure water and dried, a titanium silicide film having good surface morphology is selectively grown on the silicon surface. It is considered that the natural oxide film on the silicon surface grown by being oxidized with the hydrogen peroxide solution is taken into the titanium silicide film. Such a property that is not affected by the natural oxide film is important in manufacturing a semiconductor device .

(Embodiment 5) Plasma C shown in Embodiment 4
Under the condition of VD, a small amount of monosilane (SiH ₄ ) gas, for example, 2 cc / min of monosilane gas may be simultaneously supplied from the source gas supply port 9 to the reaction chamber. Monosilane gas is a stronger reducing gas than hydrogen gas, and has the function of reducing chlorine in titanium tetrachloride gas. However, care must be taken when the supply amount of the monosilane gas is increased more than necessary, since high-resistance silicon or titanium silicide is deposited. While the supply amount of the monosilane gas is relatively small, high-resistance silicon or titanium silicide is selectively grown, but when the supply amount is relatively large, the blanket grows over the entire surface of the wafer 7.

Although the monosilane (SiH ₄ ) gas is used here, the invention is not limited to this, and disilane (S
silanes such as i ₂ H ₆ ) and trisilane (Si ₃ H ₈ )
The same effect can be obtained even if one is used.

(Embodiment 6) In the above embodiment, the titanium silicide film is selectively deposited on the silicon surface.
By setting the conditions of the plasma CVD shown in the fifth embodiment to specific conditions, a titanium silicide film can be selectively epitaxially grown on a silicon surface. (0
01) was heated to 680 to 720 ° C., and argon was supplied to the plasma generation chamber at 30 cc / min.
Hydrogen is supplied at 20 cc / min, plasma is generated with high frequency power of 50 to 100 W, and titanium tetrachloride gas is supplied at 0.1 to 0.5 cc / min and silane gas is supplied at 1 to 0.5 cc / min.
When supplied at 3 cc / min, a C49-type TiSi ₂ film is selectively epitaxially grown on the silicon (001) plane of the wafer. This epitaxially grown titanium silicide film has a flat and smooth surface, and the crystal orientation relationship determined by reflection electron diffraction is C49TiSi ₂ (01
0) // Si (001).

In order to cause epitaxial growth, it is necessary that the supply flow rates of titanium tetrachloride gas and silane gas are in an appropriate ratio. For example, silane gas is added to titanium tetrachloride gas at 0.4 cc / min. 0.5-2.
Supply 5 cc / min. The mechanism by which epitaxial growth occurs is not clear, but during the growth of the film, a proper amount of silicon is supplied from the gas phase to the titanium silicide film, so that the titanium silicide becomes a C49 type TiSi.
_It is thought to be ₂ . For this reason, the optimal value of the flow rate ratio between titanium tetrachloride and silane gas slightly changes depending on the power of the plasma and the wafer temperature.

(Embodiment 7) When plasma CVD is performed for a short period of time of about 30 seconds under the conditions shown in Embodiment 4 or Embodiment 5, and then the supply of high frequency is stopped, the generation of plasma is stopped and the thermal CVD is performed. A titanium silicide film grows more selectively. In this case, the first plasma CVD
The growth rate of the titanium silicide film is higher in the case of thermal CVD after the case of (1).

As an effect of performing plasma CVD for a short time before thermal CVD, firstly, when only thermal CVD is performed, there is a latent period from gas supply to film growth, and there is a difference in silicon surface and a difference in CVD conditions. Due to the variation, the incubation period varies depending on the portion on the wafer where the film is to be formed, and the thickness of the film to be formed varies or the film does not grow. However, these problems are solved. Secondly, the thermal CVD alone causes the film to grow in an island shape strongly influenced by the natural oxide film on the silicon surface. However, even if the film is hardly grown by the plasma CVD, the thermal CVD is continued. Thus, the film grows all at once on the silicon surface, so that the uniformity of the film thickness and the surface morphology are remarkably improved.

By the way, the hydrogen and argon supplied from the gas supply port 4 may be stopped when switching to the thermal CVD, but even if they are not stopped, there is no problem because the hydrogen and the argon are hardly involved in the thermal CVD reaction. Further, as in the above embodiment, thermal CVD can be performed using only titanium tetrachloride gas. However, since silicon wafer on the wafer surface reacts with titanium tetrachloride, the consumption of silicon increases. In order to reduce the silicon consumption of the wafer 7, it is preferable to supply monosilane gas to the reaction chamber 6 at 5 to 100 cc / min when switching to thermal CVD.

Since the silicon consumption and the resistance of the titanium silicide film depend on the flow rate ratio between the titanium tetrachloride gas and the monosilane gas, in order to obtain the desired film quality, it is necessary to evaluate the film with the changed flow rate in advance. It is necessary to put. Even if a silane gas such as a disilane gas or a trisilane gas is used instead of the monosilane gas, the silicon consumption of the wafer 7 can be similarly reduced.

(Embodiment 8) Next, an embodiment of a plasma CVD method of a titanium silicide film at a relatively low temperature will be described. The eighth embodiment is basically the same as the plasma CVD shown in the fourth embodiment.
In this method, the heating temperature of the wafer 7 is set to 600 ° C. or lower. When the heating temperature of the wafer 7 is set to 600 ° C. or lower under the film growth conditions shown in the fourth embodiment, the film quality and growth rate of the film to be grown are greatly different from those grown at 600 ° C. or higher. That is, when a film is grown under the condition of 600 ° C. or less, a film in a crystal chamber having extremely small crystal grains is formed except for the initial growth state, or a uniform film without crystal grains is formed. Form selectively. The crystallinity and stoichiometry of these films are not yet clear.

Next, specific examples will be described below. Before the gas is supplied, the plasma generation chamber 1 and the reaction chamber 6 are 1 ×
After evacuating to 10 ⁻⁴ Pa or less, the wafer 7 was loaded on the heater 8 and heated. 22c of argon gas from gas supply port 4
c / min, hydrogen gas was supplied at 20 cc / min, and a high frequency of 300 W was applied to generate plasma. Next, titanium tetrachloride gas was supplied from the source gas supply port 9, and the pressure in the reaction chamber 6 at this time was about 0.27 Pa. When the wafer is heated to about 550 ° C. under the above growth conditions and plasma CVD is performed for 7 to 8 minutes by supplying a titanium tetrachloride gas at 0.3 cc / min, titanium is deposited on the silicon surface of the wafer 7 on the silicon surface. The titanium silicide film penetrates and grows.

When the film was observed with a scanning electron microscope, 1
A film was grown in which very small crystal grains of 00 to 300 ° were observed almost in a single layer. The silicon surface on which the film has grown has a low sheet resistance of about 1000 Ω / □. On the other hand, neither the crystal grains nor the film grow on the silicon oxide film on the surface of the wafer 7. When Auger spectroscopic analysis is performed on the silicon surface and the silicon oxide film surface of the wafer 7, the titanium signal slightly appears on the silicon oxide film surface, but the silicon surface is larger, and the difference is remarkable in the depth analysis while etching. It has become.

Next, an example in which the wafer is heated to about 490 ° C. to perform plasma CVD will be described. Plasma CVD by supplying titanium tetrachloride at 0.3 cc / min for 7 to 8 minutes
Was done. Observation of the film with a scanning electron microscope revealed that there was no crystal grain on the silicon surface and a uniform film having a thickness of less than 100 ° was grown. The sheet resistance of the silicon surface is 1
It became about 000Ω / □. The result of Auger analysis of the silicon surface and the silicon oxide film surface of the wafer 7 is about 550
As in the case of heating to ° C., the signal of titanium was larger on the silicon surface than on the silicon oxide film surface, and the difference was remarkable in the depth analysis.

As described above, the example in which the titanium silicide film is selectively grown using plasma at a relatively low temperature has been described. However, there is a feature that an extremely thin titanium silicide film can be formed at such a low temperature. The plasma CVD at this low temperature is 6
There is a feature different from plasma CVD at a high temperature of 00 ° C. or higher. One is the difference in the action of chlorine supplied from titanium tetrachloride. The chlorine supplied by the decomposition of titanium tetrachloride combines with the silicon on the surface of the wafer 7 to generate silicon chloride (SiCl _n : n = 1, 2, 3, 4) gas, thereby etching Si. There is.

By the way, in plasma CVD at a high temperature of 600 ° C. or more, chlorine is almost uniformly combined with silicon over the entire silicon surface or titanium silicide surface to generate silicon chloride, so that silicon consumption is substantially uniform. At 600 ° C. or lower, etching may proceed locally to generate etch pits depending on the film growth conditions. Etch pits tend to be easily generated when the supply amount of titanium tetrachloride is increased, when the high-frequency power is reduced, or when the growth time is lengthened. However, the above two growth conditions at about 550 ° C. and about 490 ° C. are conditions under which etch pits are unlikely to appear during growth in a relatively short time.

The selective growth of the titanium silicide film by low temperature plasma CVD is not limited to the above embodiment. In plasma CVD using a titanium tetrachloride gas and a hydrogen gas, it is difficult to grow titanium as a film on a silicon surface or an insulating film even when using a considerably changed condition. The growth of the film occurs only in the form of forming titanium silicide. For this reason, the titanium silicide film with good surface morphology can be selectively grown under various conditions, as long as care is taken not to generate etch pits. In this low-temperature plasma CVD, the titanium silicide film can be selectively grown even when a small flow rate of silane is supplied to the reaction chamber 6, as in the high-temperature plasma CVD. However, if too much is supplied, titanium silicide grows on the insulating film and the selectivity is broken.

(Embodiment 9) In Embodiment 9, Embodiment 4
Alternatively, tungsten (W) is selectively grown on the titanium silicide film selectively grown in Example 8 by using tungsten hexafluoride (WF ₆ ) gas. In the plasma CVD method of the present invention, the titanium silicide film is selectively grown despite the fact that the titanium silicide film is formed by using plasma. The selective growth of tungsten is maintained.

A titanium silicide film is selectively grown on a wafer having a silicon surface and a silicon oxide film surface by the method described in the fourth or eighth embodiment, and the wafer is taken out of the reaction chamber 6 into the air to form a tungsten film. It was loaded into the reaction chamber of the CVD apparatus. In the reaction chamber of the tungsten film CVD apparatus, the partial pressure thereof is set to 1 × 1 so that residual gas such as moisture or oxygen does not affect the growth of the tungsten film.
The ^air is exhausted so as to be 0 ^-4 Pa or less.

There are two types of tungsten film formation by CDV, a silane reduction method and a hydrogen reduction method. First, tungsten film formation by the silane reduction method will be described below.
First, a wafer on which a titanium silicide film is selectively formed is heated to about 330 ° C., and tungsten hexafluoride gas 1 is heated.
0 cc / min, 5 cc / min of monosilane gas, and 1 l / min of hydrogen gas were respectively supplied to the reaction chamber of the tungsten CVD apparatus, and the pressure in the reaction chamber was set to 13 Pa to grow tungsten on the wafer. At this time, the growth rate of tungsten was about 800 ° / min.

Next, tungsten film formation by the hydrogen reduction method will be described. In this case, the wafer was heated to about 420 ° C., and tungsten fluoride gas was supplied to the reaction chamber at 10 cc / min and hydrogen gas at 2 l / min, and the pressure in the reaction chamber was set to 23 Pa to grow tungsten on the wafer.
At this time, the growth rate of tungsten is about 400 ° / m.
was in.

As described above, even when tungsten is grown on the titanium silicide film selectively grown by the method of Embodiments 4 to 8, the selective growth of tungsten is ensured by either method. As described above, a two-layer film of titanium silicide / tungsten can be selectively formed by the CVD method.

Here, the features of this film forming method will be described below. When tungsten is selectively grown on a silicon surface without a titanium silicide film by the above-described method, the silicon of the wafer is locally eroded by the action of fluorine generated by the decomposition of tungsten hexafluoride as a source gas, and encroachment and It is known that wormholes can occur. Further, even when tungsten is deposited on silicon under such a condition that such erosion does not occur, the silicon is consumed uniformly by this deposition, so that the tungsten film is formed in a state in which the silicon film is etched.
In the hydrogen reduction method, this penetration is large, while in the silane reduction method, this penetration is improved.However, in the silane reduction method, if there is a difference between the silicon surface and the type and concentration of impurities, the penetration amount varies. Occurs.

Further, since the incubation period of tungsten film growth varies greatly depending on the difference in silicon composition and the like,
The thickness of the growing tungsten varies widely. That is, it has the same disadvantage as the selective CVD method of the titanium silicide film by heat. This defect may be fatal when manufacturing a fine and high-density semiconductor device .

However, when the titanium silicide layer is provided on the silicon surface, the titanium silicide film is not eroded during the growth of the tungsten film, so that the silicon under the titanium silicide film is not eroded. This is the same even if a tungsten film is formed by the hydrogen reduction method, and a thin titanium silicide layer formed by low-temperature plasma CVD has an excellent effect. The amount of silicon erosion during the formation of these titanium silicide films and tungsten films is determined by plasma CVD of the titanium silicide layer and thermal CVD of the tungsten layer. The amount can be reduced.

The growth conditions of the tungsten film for obtaining the above effects are not limited to the above two examples.
For example, the heating temperature of the wafer is ± 50 to
Even in the range of 100 ° C., selective growth of tungsten is possible. Further, the gas supply flow rate and the pressure also have a range, and if each condition satisfies the condition for selective growth of the tungsten film, this effect can be expected.

Embodiment 10 Next, an example of a method for manufacturing a semiconductor device by using the selective growth of a two-layer film of titanium silicide and tungsten shown in Embodiment 9 will be described below. The tenth embodiment uses a MOS
By selectively growing a titanium silicide layer on the source / drain layer and the gate electrode of the transistor,
An ohmic contact hole having a low resistance is formed, and the contact hole is filled with a tungsten selective growth film.

Hereinafter, this manufacturing method will be described with reference to FIG. FIG. 3 is a cross-sectional view schematically showing a cross-sectional structure during a manufacturing process of the MOS transistor. First, a structure as shown in FIG. 3A is formed on a wafer by a normal MOS transistor manufacturing method. In FIG. 3A, reference numeral 31 denotes a low-concentration silicon layer having a relatively low impurity concentration, 32 denotes an oxide film for element isolation, and 33 denotes a high-concentration impurity whose conductivity type is relatively higher than that of the low-concentration silicon 31. A source / drain layer made of silicon; a gate electrode made of polysilicon doped with impurities at a high concentration;
5 is an interlayer insulating film, and 36 is a contact hole formed in the interlayer insulating film 35.

This wafer was used in Example 1 or Example 2
Is loaded into the reaction chamber 6 of the plasma CVD apparatus shown in FIG.
3B by the method described in the seventh to seventh embodiments.
As shown in FIG. 7, a titanium silicide film 37 is selectively grown on the surfaces of the source / drain layers 33 and the gate electrode 34. The titanium silicide film 37 grows so as to uniformly erode the surfaces of the source / drain layers 33 and the gate electrode 34. Therefore, in order to obtain a low contact resistance between the source / drain layer 33 and the titanium silicide film 37, the titanium silicide film 37 is formed so that the lower surface of the titanium silicide film 37 contacts the high concentration portion of the source / drain layer 33. Grow thinly.

Next, as shown in FIG. 3C, a tungsten film 38 is selectively grown on the titanium silicide film 37 by the method described in the ninth embodiment, so that the contact hole 36 is made of metal (tungsten). Can be embedded. In the subsequent steps, the semiconductor device can be completed by commonly used steps. By using the film forming method including the plasma CVD method described in the tenth embodiment, a film can be grown almost uniformly on the surface of silicon having different crystallinity, conductivity, impurity concentration and surface cleanliness. Therefore, it is convenient to manufacture a semiconductor device in which various types of silicon exist, such as different impurity concentrations.

(Embodiment 11) Next, a description will be given of another embodiment, which is different from the embodiment 10 and in which a semiconductor device is manufactured by using the method shown in the ninth embodiment. FIG. 4 is a cross-sectional view schematically showing a cross-sectional structure during a manufacturing process of the MOS transistor. First, a structure as shown in FIG. 4A is formed on a wafer by a normal semiconductor device manufacturing method. FIG.
4A, reference numeral 41 denotes a low-concentration silicon layer having a relatively low impurity concentration, reference numeral 42 denotes an oxide film for element isolation, and reference numeral 43 denotes a high-concentration silicon having a conductivity type opposite to that of the low-concentration silicon 41 and a relatively high impurity concentration. A source / drain layer 44 is a gate electrode made of polysilicon doped with impurities at a high concentration, and 44 is an insulating film formed around the side wall of the gate electrode 44.

This wafer is loaded into the reaction chamber 6 of the plasma CVD apparatus of the first or second embodiment, and the source / drain layer is formed by the method of the third or seventh embodiment as shown in FIG. A titanium silicide film 47 is selectively grown on the surfaces of 43 and the gate electrode 44. Next, FIG.
A tungsten film 48 is selectively grown on the titanium silicide film 47 as shown in FIG. Next, as shown in FIG. 4D, an interlayer insulating film 49 is deposited. At this time,
In order to prevent the reaction between the underlying silicon and the titanium silicide film 47 and the tungsten film 48, the interlayer insulating film 49 is deposited at a temperature of 600 ° C. or less. Thereafter, as shown in FIG. 4E, a contact hole 50 is opened in the interlayer insulating film 49, and as shown in FIG.
Is buried with tungsten 51 as in the tenth embodiment.

In the method according to the eleventh embodiment, first, a two-layer film of titanium silicide and tungsten is selectively formed. There is an advantage that no erosion such as cracking occurs, and even if the titanium silicide film is thinned, the sheet resistance can be reduced by increasing the thickness of the tungsten film.

When the contact hole 46 is opened by etching the interlayer insulating film 49, the underlying tungsten serves as an etching stopper layer, so that the titanium silicide film is not etched by over-etching, and Since the titanium silicide film which is easily attacked by the solution containing acid is covered with the tungsten film which is hardly attacked by hydrofluoric acid, the contact hole can be washed with the solution containing hydrofluoric acid after opening the contact hole. When the contact hole 46 is buried by selective growth of tungsten,
Since the base is tungsten, tungsten is more likely to grow on it.

[0071]

As described above, according to the present invention, since CVD is performed with the aid of low-density plasma of a source gas, the selectivity of forming a film only on a silicon surface on a substrate containing silicon is impaired. In addition, there is an effect that the silicide formed of the composition of the source gas can be uniformly formed in a state where the substrate is hardly damaged by the plasma.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a plasma CVD apparatus according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a plasma CVD apparatus showing another embodiment of the present invention.

FIG. 3 is a sectional view illustrating a method of manufacturing a semiconductor device according to another embodiment of the present invention;

FIG. 4 is a sectional view showing a method for manufacturing a semiconductor device according to another embodiment of the present invention;

FIG. 5 is a configuration diagram showing a configuration of an example of a conventional plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation chamber 2 Discharge tube 3 High frequency coil 4 Gas supply port 5 Aperture plate 6 Reaction chamber 7 Wafer 8 Heater 9 Source gas supply port 10 Exhaust port

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-108381 (JP, A) JP-A-63-166971 (JP, A) JP-A-60-96763 (JP, A) JP-A-3-3 224223 (JP, A) JP-A-2-260420 (JP, A) JP-A-2-8132 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 C23C 16 / 42 H05H 1/46

Claims (2)

(57) [Claims] A substrate including a silicon surface to be formed is placed on the substrate.
With the reaction chamber and the reaction chamber.
Plate made of insulator with multiple holes at the boundary of
Evacuation of a plasma generation chamber in which is disposed, heating of the substrate, inert gas, hydrogen gas, or
Selected from a mixture of inert gas and hydrogen gas
Supplying a first gas, the plasma generation chamber and the reaction chamber;
Providing a predetermined pressure difference between the first gas and the first gas by applying a high frequency to the plasma generation chamber.
And generate plasma in the plasma generation chamber.
The first gas is introduced into the reaction chamber by the applied high frequency.
Generating a plasma of titanium tetrachloride or titanium tetrachloride or silicon tetrachloride in the reaction chamber.
Either the raw material gas of the mixed gas with the hydride of Recon
And a mixed gas mixture of the first gas and the source gas.
Plasma is generated and silicide is applied only to the silicon surface of the substrate.
A step of selectively growing tin. 2. A substrate for film formation, which is placed in a reaction chamber.
A substrate mounting table for mounting, a heating unit for heating the substrate, and a plasma of a predetermined gas generated by communicating with the reaction chamber;
A plasma generation chamber , disposed at a boundary between the plasma generation chamber and the reaction chamber;
An aperture plate having a plurality of holes; an exhaust unit for evacuating the reaction chamber; and supplying the predetermined gas in communication with the plasma generation chamber.
Gas supply means, and a raw material for supplying a raw material gas serving as a film forming raw material into the reaction chamber.
Gas supply means, a high-frequency source for applying high-frequency power to the plasma generation chamber,
Comprising, the aperture plate is made of an insulator having a plurality of holes,
The high frequency applied to the plasma generation chamber leaks into the reaction chamber.
And the diameter of each of the plurality of holes is
Large enough to allow plasma generated in the plasma generation chamber to pass through
The diameter of the plurality of holes and the number thereof are determined beforehand in the plasma generation chamber.
When a predetermined gas is supplied, a predetermined gas is supplied to the reaction chamber.
The diameter and the number that cause a pressure difference, and the high frequency applied to the plasma generation chamber causes the reaction.
The mixed gas of the predetermined gas and the source gas is injected into the room.
A plasm characterized in that plasma is generated
Ma CVD equipment.