JP2729310B2 - Apparatus for forming thin film on semiconductor substrate surface - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for forming a thin film on a surface of a semiconductor substrate, and more specifically, to an excellent control of an interface structure between the semiconductor substrate and the thin film. The present invention relates to an apparatus for forming a thin film.

[Prior Art] Since the characteristics of an electronic device are extremely strongly affected by the presence of impurities introduced in a deliberate or unintentional accident during fabrication, the cleanliness of the fabrication environment is maintained at a very high level throughout the entire process. It is necessary to use advanced cleaning technology and high-purification technology in the materials used, the processing atmosphere, the forming method, and the like.

2. Description of the Related Art In a semiconductor device, its manufacturing process is roughly divided into a thin film forming process and a circuit pattern forming process. The thin film forming process is further subdivided into various processes depending on the type of film and the forming method, and a unique or partially common cleaning technology has been developed. An important and basic cleaning operation common to all of these is substrate pretreatment before thin film formation.

In the pretreatment step, water washing, acid washing or alkali washing, chemical oxidation, dilute hydrofluoric acid treatment and the like are usually performed for the purpose of degreasing, removing heavy metals and removing natural oxide films. These solution cleaning methods are now widely adopted as established processes, but the decisive problem is that the substrate after processing is always exposed to air between immediately after the completion of processing and the start of thin film formation. Therefore, when an active semiconductor or metal is exposed on the substrate, some natural oxide film growth occurs without exception. Therefore, solution cleaning is effective for removing impurities such as organic substances and heavy metals, but is not necessarily a means for obtaining an intrinsic surface.

The growth of the native oxide film has a detrimental effect on the quality of the thin film in the subsequent thin film forming process. Examples of thin film formation include epitaxial growth, formation of a refractory metal film (so-called polycide structure) on polysilicon,
There are wiring formation for forming an electrical contact on the substrate, formation of an ultra-thin insulating film, and the like, and these formation steps will be increasingly important in the future with high integration. Therefore, there is a strong demand for a method of forming a thin film in which the interface structure between the thin film and the substrate is well controlled in order to improve the quality of the thin film while removing harmful impurities taken into the film.

FIG. 15 is a cross-sectional view of a conventional single-wafer sputtering apparatus. Referring to FIG. 15, a conventional single-wafer sputtering apparatus has the following configuration.
Chamber 20, which includes a lock valve 21
a, lock valve 21b, lock valve 21c, loader chamber 2
2, etching chamber 23, depot chamber 24, unloader chamber 25
It is divided into.

The loader chamber 22 has a nitrogen gas inlet 26a and an exhaust port 9a. In the loader chamber 22, a transport system 27a such as a belt conveyor is provided.

The etching chamber 23 has an argon gas inlet 28a for introducing an argon gas, and an exhaust port 9b. Etching room 2
Inside 3, a transfer system 27b is provided. Etching room 23
Includes a substrate support 29a. A tray 30 is placed on the substrate support table 29a, and a semiconductor substrate such as a silicon substrate 4 is placed on the tray 30. A high frequency power supply 31 is connected to the silicon substrate 4 via a matching circuit 32. The substrate support 29a and the chamber 20 are insulated by an insulating part 33a.

The deposition chamber 24 is provided with an argon gas introduction port 28 for introducing an argon gas and an exhaust port 9c. A transport system 27c is provided in the deposition chamber 24. Depot room 24 is substrate support table 2
Contains 9b. Further, the deposition chamber 24 includes a target 34. A DC power supply 35 is connected to the target 34, and a high voltage is applied between the target 34 and the argon gas. The substrate support 29b and the chamber 20 are insulated by the insulating part 33b, and the target 34 and the chamber 20 are insulated by the insulating part 33b.

The unloader chamber 25 has a nitrogen gas inlet 26 and an outlet 9d. A transfer system 27d is provided in the unloader chamber 25.

Next, a method of forming a thin film on a substrate using this apparatus will be described.

First, each of the loader chamber 22, the etching chamber 23, the deposit chamber 24, and the unloader chamber 25 is brought into a high vacuum state. Next, the nitrogen gas inlet 26a is inserted into the vacuum-held loader chamber 22.
More nitrogen gas is introduced and the room is returned to atmospheric pressure. Next, a door (not shown) is opened, the plurality of silicon substrates 4 placed on the tray 30 are introduced into the loader chamber 22, and the door is closed again. Subsequently, the inside of the loader chamber 22 is evacuated from the exhaust port 9a by a vacuum pump (not shown), and the inside is brought into a high vacuum state. Next, the lock valve 21a is opened, and the motor of the transport system 27a is driven to move the silicon substrate 4 placed on the tray 30 into the etching chamber 23. Then, the lock valve 21a is closed. The opening and closing of the lock valve 21a and the operation of the transport system 27a are performed by, for example, externally provided switch means (not shown). The etching chamber 23 is maintained in a high vacuum state of about 10 ^-7 to 10 ^-8 Torr. And the etching chamber
Argon gas of 10 ^-3 to 10 ^-1 Torr is introduced into 23 through an argon gas inlet 28a. Subsequently, the high frequency power supply 31 causes several hundreds to several ones between the silicon substrate 4 and the argon gas.
Apply a bias of 000 volts to create a plasma. The argon ions in the plasma collide with the silicon substrate 4 on the negative and high pressure side with high energy, and sputter-etch a natural oxide film and contaminants adhering to the surface of the silicon substrate 49. When the sputter etching is completed, the introduction of the argon gas and the application of the bias are stopped. Then, the argon gas in the etching chamber 23 is exhausted, and the etching chamber 23 is exhausted.
The inside of 23 is made a high vacuum state. Subsequently, the lock valve 21b is opened, the motor of the transport system 27b is driven, and the silicon substrate 4 placed on the tray 30 is moved into the deposition chamber 24. And
Close the lock valve 21b. At this time, the second silicon substrate 4 has moved to the etching chamber 23. Depot room 24
Is maintained in a high vacuum state of about 10 ^-7 to 10 ^-8 Torr.
Then, an argon gas of 10 ^-3 to 10 ^-1 Torr is introduced into the deposition chamber 24 from the argon gas inlet 28b. Subsequently, a voltage of several hundreds to several thousand volts is applied between the target 34 and the argon gas by the DC power supply 35. This allows
Plasma is created. The argon ions in the plasma collide with the target 34 on the negative and high pressure side with high energy, and sputter the material of the target 34. This substance is deposited on the silicon substrate 4 to form a thin film. When the formation of the thin film having the desired film thickness, uniformity and film quality is completed, the introduction of the argon gas and the application of the voltage are stopped, and the inside of the deposition chamber 24 is evacuated to a high vacuum state.

Subsequently, the lock valve 21c is opened, the motor of the transfer system 27c is driven, and the silicon substrate 4 placed on the tray 30 is moved to the unloader chamber 25. And lock valve 21c
Close. At this time, the second substrate 1 has been moved to the deposition chamber 24 and the third substrate 1 has been moved to the etching chamber 23. The silicon substrate 4 which is sequentially etched and subsequently deposited is
It is stored in a cassette in the unloader room 25. When the last silicon substrate 4 is stored in the cassette, the unloader chamber 25
The internal pressure is returned to the atmospheric pressure, and the silicon substrate 4 on which the desired thin film is formed is taken out together with the cassette and sent to the next step.

[Problem to be Solved by the Invention] A conventional sputtered thin film forming apparatus is configured as described above. Therefore, it is necessary to apply a high bias between the silicon substrate 4 and the argon gas in order to remove a natural oxide film and contaminants by sputter etching using plasma of an inert gas such as argon. Therefore, there is a problem that damage is introduced to the silicon substrate 4 by the argon plasma.

There is also known a method in which a natural oxide film or contaminants are removed by gas etching by a high-temperature hydrogen reduction method, and a thin film is continuously formed thereon. However, this high-temperature hydrogen reduction method requires a high temperature (usually 1000 ° C. or higher), causing a droop of the PN junction, and has a problem that the applicable range is limited.

As a method for removing a natural oxide film, Japanese Patent Laid-Open No.
No. 27621 discloses a technique for removing a natural oxide film by heating a substrate temperature to 800 to 1000 ° C. in a hydrogen gas flow.
However, such a high-temperature treatment not only causes the above-mentioned heat dripping, but also changes the amorphous silicon into polysilicon with advanced crystallization as described by Kinsbron (E. Kinsbron, M. Stenbeim, and R.Knoel
l, Appl.Phys.Lett., Vol.42, No.9,835,1 May (198
3)). As a recent tendency in device fabrication, it is desired that polysilicon have as small a crystal grain size as possible, that is, an amorphous material. Therefore, it is a problem that polysilicon having advanced crystallization is generated.

Japanese Patent Application Laid-Open No. 61-124123 discloses a substrate surface treatment method in which a reactive gas is adsorbed on a substrate, the substrate is irradiated with light, and the substrate is etched with the reactive gas. In this prior art, what kind of light is used, what kind of reaction gas is used, and how much the temperature of the substrate is used are not specifically described, so the details are unknown. . However, if this technique is applied as it is to a method for removing a natural oxide film or the like attached to a semiconductor substrate, the following problems occur.

That is, in the above-described technology, the reaction gas is adsorbed on the substrate, and the adsorbed reaction gas etches the substrate, so that not only the natural oxide film on the substrate is removed, but also the semiconductor substrate itself is etched. The problem arises.

The present invention has been made in order to solve the above problems, and removes a natural oxide film or a contaminant attached to a semiconductor substrate surface at a sufficiently low temperature and without damaging the semiconductor substrate surface. It is another object of the present invention to provide a thin film forming apparatus capable of forming a thin film on the surface of the semiconductor substrate without exposing the semiconductor substrate to the atmosphere.

Means for Solving the Problems A thin film forming apparatus according to the present invention removes a natural oxide film or a contaminant adhered to a surface of a semiconductor substrate, and then forms a thin film on the clean surface by a sputter deposition method. And a chamber accommodating the semiconductor substrate to be processed, a reaction gas introducing means for introducing a gas capable of reacting with the natural oxide film or the contaminant into the chamber, and the semiconductor substrate at a temperature of 200 to 700 ° C. Heating means for heating to a temperature within the range, and when heating the semiconductor substrate, at a temperature within the range of 200 to 700 ° C., the reaction gas introduced into the chamber and the semiconductor substrate surface A light source for irradiating the reaction gas with light having a wavelength that causes a photochemical reaction with a natural oxide film or a contaminant attached to the natural gas film or a contaminant; A target that provides a component of a thin film formed on the surface of the semiconductor substrate from which the object has been removed; and a substrate moving unit that is provided in the chamber and moves the semiconductor substrate. The substrate moving unit includes: When removing a natural oxide film or a contaminant attached to the semiconductor substrate, the semiconductor substrate is moved so that the surface of the semiconductor substrate faces the light source, and when a thin film is formed on the semiconductor substrate, And moving the semiconductor substrate so that the surface of the semiconductor substrate faces the target.

[Operation] As described above, in the present invention, light and heat are used in combination in removing a natural oxide film or a contaminant attached on the surface of a semiconductor substrate with a reaction gas. When, for example, HCl gas is used as the reaction gas, for example, a natural oxide film is removed from the substrate according to the following reaction formula.

SiO ₂ + 4HCl → SiCl ₄ + 2H ₂ O The present invention makes use of the fact that this reaction is promoted by the synergistic effect of light energy and heat energy. Therefore, even if a reaction gas that cannot be activated only by light is used, it is possible to remove a natural oxide film or contaminants with the reaction gas. Even if the natural oxide film or the contaminant cannot be removed unless it is placed at a high temperature, the natural oxide film or the contaminant can be removed at a lower temperature with the help of light energy.

Therefore, a natural oxide film or a contaminant attached to the semiconductor substrate surface can be removed at a sufficiently low temperature without damaging the semiconductor substrate surface. Then, a thin film is formed on the intrinsic surface of the semiconductor substrate obtained in this manner by a sputter deposition method without continuously exposing the semiconductor substrate to the atmosphere, so that a natural oxide film or the like intervenes at the interface between the semiconductor substrate and the thin film. Disappears. Therefore, the interface structure between the semiconductor substrate and the thin film is suppressed to a favorable state.

[Embodiment] A method of forming a thin film on the surface of a semiconductor substrate using the thin film forming apparatus according to the present invention has two main steps, namely, a step of removing a natural oxide film or a contaminant attached to the surface of the semiconductor substrate ( Hereinafter, a first step) and a step of removing a natural oxide film or a contaminant attached to the surface of the semiconductor substrate and subsequently forming a thin film on the surface of the semiconductor substrate without exposure to the air (hereinafter, referred to as a second step). Process)
Consists of

First, how much a natural oxide film or a contaminant is actually removed from the surface of the semiconductor substrate in the first step will be described with reference to experimental data.

Experimental apparatus used: FIG. 1 is a sectional view of the experimental apparatus used.

Referring to FIG. 1, the experimental apparatus includes a chamber 3. The chamber 3 is provided with an HCl gas inlet 6, a SiH ₂ Cl ₂ gas inlet 7, an NH ₃ gas inlet 8, and an outlet 9. Further, the chamber 3 is provided with an ultraviolet ray entrance window 2 for irradiating the chamber 3 with ultraviolet rays. A low-pressure mercury lamp 1 is installed opposite the ultraviolet light entrance window 2. A substrate support 5 is set in the chamber 3, and a semiconductor substrate, for example, a silicon substrate 4 is set on the substrate support 5. The substrate support 5 has a heating means 5a. Thereby, the silicon substrate 4 can be heated via the substrate support 5.

Outline of Method for Removing Natural Oxide Film or Contaminant Adhered on Semiconductor Substrate Surface: Next, an outline of a method for removing the natural oxide film or contaminant adhered to the surface of the semiconductor substrate using the above-described experimental apparatus will be described. State.

The silicon substrate 4 is placed on the substrate support 5. Although this silicon substrate 4 has been subjected to the solvent treatment, it has already been exposed to the atmosphere and a natural oxide film has been formed on the surface thereof.
Next, an HCl gas is introduced into the chamber 3 from the HCl gas inlet 6, and the HCl gas is supplied to the surface of the silicon substrate 4. Next, by lighting the low-pressure mercury lamp 1,
The surface of the silicon substrate 4 is irradiated with ultraviolet light from the ultraviolet light incident window 2. Simultaneously with this ultraviolet irradiation, the silicon substrate 4
Heat to 0-700 ° C. Then, due to the synergistic effect of light and heat, for example, the following reaction is promoted, and the natural oxide film on the silicon substrate 4 is removed.

SiO ₂ + 4HCl → SiCl ₄ + 2H ₂ O Method for confirming whether or not the natural oxide film has been removed: The natural oxide film is removed as described above, and whether or not the natural oxide film has been removed It is necessary to devise to confirm whether it is. Because silicon is an extremely oxidizable substance, even if the natural oxide film is removed according to the method described above, when the silicon substrate is taken out of the device to confirm the effect, the surface is oxidized again at that moment. It is because. Therefore, in the evaluation, two clever techniques have been devised here.

First Confirmation Method: A first confirmation method is to remove a natural oxide film from the surface of a silicon substrate, deposit a thin film containing no oxygen atoms such as a silicon nitride film on the silicon oxide film as it is, This is a method of observing an element profile in a film thickness direction by electron spectroscopy or the like. According to this method, the presence or absence of a natural oxide film is determined based on whether or not an oxygen signal is detected near the interface between the silicon substrate (Si) and the deposited film (Si ₃ N ₄ ).

FIG. 2A shows that a silicon nitride film is chemically deposited (hereinafter referred to as CVD) immediately after removing a native oxide film from the surface of a silicon substrate.
This is an Auger profile in the film thickness direction of a sample obtained by deposition according to the method described above. The sample subjected to the Auger electron spectroscopy was prepared as follows.

Referring to FIG. 1, silicon substrate 4 after solution cleaning was placed on substrate support 5. This silicon substrate 4
In contact with the atmosphere, a natural oxide film had already formed. Next, HCl gas was introduced into the chamber 3 from the HCl gas inlet 6, and the HCl gas was supplied to the surface of the silicon substrate 4. Next, at the same time as irradiating the surface of the silicon substrate 4 with ultraviolet rays, the substrate is heated to a temperature in the range of 200 to 700 ° C.
A removal process of the natural oxide film was performed. The exposure time of HCl gas was several minutes. Next, HCl gas is exhausted from the exhaust port 9, then SiH ₂ Cl ₂ gas is introduced from the SiH ₂ Cl ₂ gas inlet 7, NH ₃ gas is introduced from the NH ₃ gas inlet 8, and A silicon nitride film was deposited by a CVD method. This was subjected to an Auger electron spectroscopic analysis. In FIG. 2A, the horizontal axis is the sputtering time, and the vertical axis is the Auger signal. As is clear from FIG. 2A, no oxygen signal was detected near the interface between Si and Si ₃ N ₄ when the natural oxide film was removed (HCl treated).

FIG. 2B is an element profile in the film thickness direction when Si ₃ N ₄ is deposited without performing a natural oxide film removal process (without HCl treatment). As is clear from FIG. 2B, Si and Si
Near the interface of ₃ N _4, oxygen signal is detected.

From the above results, it is confirmed that the natural oxide film is surely removed by performing the first process of removing the natural oxide film.

Second Confirmation Method: A second confirmation method of the effect of the natural oxide film removal treatment is to irradiate the silicon substrate with ultraviolet light before and after the natural oxide film removal treatment to cause photoelectrons to be emitted, and the amount of emitted electrons This is a method of measuring a change in (photocurrent). In this method, as described later, the presence or absence of the natural oxide film has a significant effect on the photoelectric flow rate, and thus can be a good means for determining the presence or absence of the natural oxide film.

Further, in this method, the ultraviolet light used for removing the natural oxide film can be used as it is as the ultraviolet light for causing photoelectron emission. Therefore, by tracking the photocurrent, the natural oxide film is removed. There is an advantage that the situation can be monitored.

The relationship between photocurrent and the presence or absence of a native oxide film is shown in FIG.
This will be described with reference to FIG. 3B. In these figures, the substrate temperature was set to 550 ° C in an argon atmosphere, and after the start of UV irradiation,
It tracks the current of emitted photoelectrons. FIG. 3A shows data when a silicon substrate exposed to HCl gas under ultraviolet irradiation at 550 ° C. for 15 minutes is used, and corresponds to FIG. 2A. FIG. 3B shows data obtained when a silicon substrate not subjected to this processing is used, and corresponds to FIG. 2B.

As is clear from these figures, when the natural oxide film is removed, the photocurrent is significantly reduced.
Therefore, it can be concluded that the decrease in photocurrent is a phenomenon that occurs due to the removal of the native oxide film.

It will also be readily appreciated that by tracking the degree of photocurrent reduction, the situation in which the native oxide is being removed can be monitored.

Proof that the natural oxide film has been removed by the synergistic effect of the thermal reaction and the photoreaction in the first step: Removal of the natural oxide film in the first step, taking into account the results of FIGS. 3A and 3B Is due to a synergistic effect of thermal reaction and photochemical reaction.

FIGS. 4A, 4B, 4C, and 4D show changes in the photocurrent during the removal process of the native oxide film at each substrate temperature shown in the figure. is there. That is, the method of removing the natural oxide film in the first step is based on the temperature dependence of the method. FIG. 4A shows a change in photocurrent when the substrate temperature is set to 250 ° C. FIG. 4B shows a change in photocurrent when the substrate temperature is set to 450 ° C. FIG.4C shows that the substrate temperature is 50
The change in photocurrent at 0 ° C. is shown.
FIG. 4D shows a change in photocurrent when the substrate temperature is set to 550 ° C. In these figures, the horizontal axis represents time (minutes) and the vertical axis represents photocurrent (μA). The photocurrent measurement was performed by placing the semiconductor substrate in an HCl atmosphere at each temperature, opening the shutter for the ultraviolet irradiation time, and tracking the current value over time. The following findings were obtained from FIGS. 4A to 4D.

At each temperature, the photocurrent decreases with ultraviolet irradiation.

The rate of decrease in photocurrent increases rapidly with increasing substrate temperature.

The reduced photocurrent settles at a constant value regardless of the substrate temperature.

As described above, the decrease in photocurrent can be related to the removal of the native oxide film, and the above results suggest that the removal rate of the native oxide film is higher at higher temperatures and accelerated by heat. Is done. According to the data book, HCl at normal temperature and normal pressure absorbs only ultraviolet light having a wavelength of about 150 nm or less. Therefore, light emitted from a low-pressure mercury lamp (ultraviolet rays having wavelengths of 1849Å and 2537Å)
Then, originally, HCl is not excited, and thus this H
Cl will not be able to remove the native oxide. However, by heating the substrate to a temperature in the range of 200-700 ° C., the native oxide film is actually removed, as shown in FIGS. 4A-4D. Therefore, also from this point, it can be concluded that the removal of the natural oxide film in the first step is a result of a synergistic effect of heat and light.

4A to 4D show that a substrate temperature of about 500 ° C. or more is desirable under the time constraint of pre-treatment before forming a thin film. Compared with the case described above, remarkable lowering of the temperature has been achieved, and it can be said that the practical significance is very large.

FIG. 5 shows the ultraviolet irradiation effect of the natural oxide film removal treatment in the first step. The experimental apparatus used was the apparatus shown in FIG. 1 provided with a photoelectron collector electrode. This photoelectron collector electrode is a mesh-shaped electrode, and is disposed at a position between the silicon substrate 4 and the ultraviolet light incident window 2 with reference to FIG.

In this experiment, the substrate temperature was set to 500 ° C in an Ar atmosphere,
The photocurrent was measured by changing the voltage applied to the photoelectron collector electrode.

The following four types were selected as substrates for measurement.

A substrate exposed to HCl at 500 ° C. for 15 minutes while being irradiated with ultraviolet rays (the substrate subjected to the treatment in the first step).

A substrate obtained by exposure to HCl at 500 ° C. for 15 minutes while irradiating ultraviolet rays, and at the same time, continuously applying a voltage of +250 V to the photoelectron electrode.

A substrate exposed to HCl at 500 ° C for 15 minutes without UV irradiation.

 A substrate that was not exposed to HCl at all.

As apparent from FIG. 5, the photocurrent characteristics were clearly divided into a group consisting of and a group consisting of. From this, the following matters became clear. That is, as is clear from comparison with
Even at a high temperature of about 0 ° C., without UV irradiation, the HCl treatment has no effect. As is clear from comparison with the above, exposure to HCl is indispensable for removing the native oxide film. 2A, 2B, 3A and FIG.
Since the explanation has been given in the explanation of FIG. 3B, the explanation is omitted here.

Referring only to the results in FIGS.4A to 4D, there is a question whether HCl plasma is generated by the external electric field applied during the photocurrent measurement and the natural oxide film is removed by the plasma. Such a question may be resolved because there is no difference in the photocurrent value as compared with and.

Referring to FIG. 5, the increase in the photocurrent with an increase in the applied voltage is due to the electron multiplication effect in Ar, which is the measurement atmosphere gas, and has no significant meaning for the present discussion. From the above, it can be concluded that the removal of the natural oxide film is only possible by the synergistic effect of light and heat. Therefore, even if a reaction gas that cannot be activated only by light is used, the natural oxide film can be removed.
Even if the natural oxide film cannot be removed unless it is placed at a high temperature, the natural oxide film can be removed at a lower temperature with the help of light energy.

In the first step, the heating temperature of the semiconductor substrate is 200 to 700 ° C.
Next, an experiment was performed to find a desirable substrate temperature range in the natural oxide film removal process.

FIG. 6 is an Arrhenius plot (log (etching rate) vs. 1 / T) showing the relationship between etching rate and temperature when a silicon substrate is etched by UV-HCl.
It is. Here, the etching rate of the silicon substrate is used instead of the removal rate of the natural oxide film. This is for the following reason. That is, since the natural oxide film is too thin to determine the removal rate, the etching rate of the silicon substrate is determined, and the removal rate of the natural oxide film is estimated from the etching rate of the silicon substrate. Before explaining the results of FIG. 6, how to determine the etching rate will be described with reference to FIGS. 7A, 7B and 7C. First, referring to FIG. 7A, a mask of a silicon oxide film is formed.
A semiconductor substrate 16 on which 15 is formed is prepared. Semiconductor substrate 16
Used was a p-type (100) silicon substrate having a resistance of 1 to 100 Ω · cm. Next, referring to FIG. 7B, etching is performed under predetermined etching conditions (100% HCl: 700 sccm, atmospheric pressure:
7.2 Torr, with and without irradiation of low pressure mercury lamp)
Performed below. Next, referring to FIG. 7C, the mask 15 was removed, and the etching depth d was determined. The etching rate was determined from the etching depth d.

According to the above-described method, the etching rate was obtained at various temperatures separately for the case where UV irradiation was performed and the case where UV irradiation was not performed. FIG. 6 is an Arrhenius plot of the etching rate thus determined as a function of temperature.

Referring to the upper plot of FIG. 6, it was found that when there was UV irradiation, the etching rate gradually increased from room temperature to 200 ° C., and rapidly increased at a bending point of 200 ° C. This indicates that effective etching does not occur at a temperature of 200 ° C. or less, and that effective etching occurs only at a temperature of 200 ° C. or more. In addition, the lower plot of FIG. 6 shows that without UV irradiation, even if the substrate temperature is increased to 600 ° C., the etching rate does not increase so much and effective etching does not occur.

Since these etching conditions are the same as the natural oxide film removal processing conditions employed in the first step of the present invention,
The result of FIG. 6 can be directly applied to the removal rate of the native oxide film.

Based on the above results, set the substrate temperature to 200 ° C or higher, and
For the first time, it was clarified that an effective natural oxide film removal treatment could be performed by the synergistic effect of heat and light.

By the way, as is clear from FIG. 6, if the temperature is 200 ° C. or more, the removal rate of the natural oxide film increases as the temperature increases. However, it has been reported that increasing the substrate temperature to 600 ° C. or higher changes amorphous silicon to polysilicon (E. Kinsbron, M. Sternheim, a.
nd R.Knoell, Appl.Phys.Lett., Vol.42, No.9,835,1 Ma
y (1983)).

As a recent trend in device fabrication, it is desired that the poly-Si has as small a crystal grain size as possible, that is, an amorphous one, and the substrate temperature is desirably 600 ° C. or less as described above. Even if the treatment is carried out at the above temperature, there is an advantage that a material which can sufficiently withstand use is obtained practically, and the removal rate of the natural oxide film for raising the temperature is increased. However, above 700 ° C., the disadvantage of changing from amorphous silicon to polysilicon becomes more emphasized than the above-mentioned advantages. Therefore, the processing temperature of the semiconductor substrate is preferably set to a temperature in the range of 200 to 700 ° C.

Reference Example of the Present Invention Hereinafter, a reference example (first step + second step) of the present invention will be described.

FIG. 8A is a sectional view of an apparatus for realizing a thin film forming method according to a first reference example of the present invention, which is an apparatus for forming a thin film by a chemical deposition method (hereinafter, referred to as a CVD method).

Referring to FIG. 8A, the processing apparatus includes a chamber 3. The chamber 3 is provided with an HCl gas inlet 6, a film forming gas inlet 36, and an exhaust port 9. Further, the chamber 3 is provided with an ultraviolet ray entrance window 2 for irradiating the chamber 3 with ultraviolet rays. A low-pressure mercury lamp 1 is installed opposite the ultraviolet light entrance window 2. Chamber 3
A substrate support 5 is provided therein, and the silicon substrate 4 is placed on the substrate support 5. The substrate support 5 is a heating means
5 a, and is configured to be able to heat the silicon substrate 4 via the substrate support 5.

Next, a method for forming a thin film on a semiconductor substrate surface by a CVD method using the above-described apparatus will be described.

Referring to FIG. 8A, a silicon substrate 4
Put. This silicon substrate 4 has been subjected to a solvent treatment, but has already been in contact with air to form a natural oxide film. Next, referring to FIG. 8B, HCl gas is introduced into the chamber 3 from the HCl gas inlet 6 and the silicon substrate 4 is introduced.
HCl gas to the surface of. Next, the surface of the silicon substrate 4 is irradiated with ultraviolet light from the ultraviolet light incident window 2 by turning on the low-pressure mercury lamp. Simultaneously with the ultraviolet irradiation, the silicon substrate 4 is heated to 200 to 700 ° C. Then
By the synergistic effect of light and heat, for example, the following reaction is promoted, and the natural oxide film adhered on the silicon substrate 4 is removed.

SiO ₂ + 4HCl → SiCl ₄ + 2H ₂ O Subsequently, a thin film is formed on the surface of the semiconductor substrate by a CVD method without being exposed to the air. That is, referring to FIG. 8C, the HCl gas is exhausted from the exhaust port 9. Next, the heating means 5a is operated to heat the semiconductor substrate 4,
A film forming gas (for example, SiH ₂ Cl
₂ + NH ₃ ). Then, a predetermined thin film is formed on the surface of the semiconductor substrate 4.

The natural oxide film or contaminant attached to the semiconductor substrate surface is removed at a sufficiently low temperature and without damaging the semiconductor substrate surface, and thereafter, a thin film is formed thereon without being exposed to the atmosphere. Therefore, a natural oxide film or the like does not intervene at the interface between the semiconductor substrate and the thin film. Therefore, a semiconductor device in which the interface structure between the semiconductor substrate and the thin film is controlled in a favorable state can be obtained.

Second Reference Example of the Present Invention (CVD Method) In the above reference example, a chamber for removing a natural oxide film or the like (hereinafter, referred to as a pretreatment chamber) and a chamber for forming a thin film (hereinafter, referred to as a pretreatment chamber). A thin film forming apparatus in which a thin film forming chamber is integrally formed and a natural oxide film and the like can be removed and a thin film is formed in the same chamber has been described. However, the preprocessing chamber and the thin film forming chamber may be configured separately. The device shown in FIG. 9 is an example thereof and is a second reference example of the present invention. It is represented in a sectional view.

In FIG. 9, the apparatus has one chamber 20. This chamber 20 is controlled by a lock valve 21a.
The chamber is divided into a pretreatment chamber 37 and a thin film formation chamber. The pretreatment chamber 37 is provided with an HCl gas inlet 6. Further, the pretreatment chamber 37 is provided with an ultraviolet ray entrance window 2 for irradiating the inside of the pretreatment chamber 37 with ultraviolet rays. Facing the ultraviolet light entrance window 2,
A low-pressure mercury lamp 1 is provided. Pretreatment chamber
A substrate support 5 is provided in 37, and the silicon substrate 4 is placed on the substrate support 5. The substrate support 5 is provided with a heating means 5a, and is configured to be able to heat the silicon substrate 4 via the substrate support 5. A transfer system 27 such as a belt conveyor is provided in the pretreatment chamber 37.
a is provided.

The thin film forming chamber 38 includes film forming gas inlets 36a, 36a.
b and an exhaust port 9 are provided. Chamber for thin film formation 3
In 8, a substrate support 5 'is provided. The substrate support 5 'has a heating means 5a'. The transfer system 27b is provided in the thin film forming chamber.

Next, a method for forming a thin film on the surface of a semiconductor substrate using the above-described apparatus will be described.

Referring to FIG. 9, silicon substrate 4 is placed on substrate support table 5 in pretreatment chamber 37. This silicon substrate 4
Is after the solvent treatment, but has already been in contact with air to form a natural oxide film. Next, HCl gas is introduced into the pretreatment chamber 37 from the HCl gas inlet 6, and hydrochloric acid gas is supplied to the surface of the silicon substrate 4. Next, by turning on the low-pressure mercury lamp 1, the ultraviolet light entrance window 2 is turned on.
From above, the surface of the silicon substrate 4 is irradiated with ultraviolet rays. Simultaneously with the ultraviolet irradiation, the silicon substrate 4 is heated to 200 to 700 ° C. Then, a natural oxide film adhered on the silicon substrate 4 is removed by a synergistic effect of light and heat.

Next, the lock valve 21a is opened, the transfer systems 27a and 27b are operated, the semiconductor substrate 4 is introduced into the thin film forming chamber 38, and the silicon substrate 4 is placed on the substrate 4 support 5 '. Opening and closing of lock valve 21a and transfer system 27a, 27b
May be performed by, for example, externally provided switch means (not shown). Next, the exhaust port 9
Thus, the gas in the thin film forming chamber 38 is exhausted. Next, the heating means 5a 'is operated to heat the semiconductor substrate, and at the same time, the thin film forming chamber 3 is supplied from the film forming gas inlets 36a and 36b.
A film forming gas is introduced into 8. Then, a desired thin film is formed on the surface of the semiconductor substrate.

Examples of the thin film formed by the CVD method include a single crystal silicon film (ie, an epitaxial silicon film) on a silicon substrate, a polycrystalline silicon film, an amorphous silicon film, and the like.
In forming an epitaxial silicon film, it is possible to form an epitaxial silicon film without a natural oxide film at the interface with the semiconductor substrate at a low substrate temperature of about 600 ° C. Thereby, a contact resistance sufficiently small can be obtained. Also, in the formation of the polycrystalline silicon film, the natural oxide film, which has caused the contact resistance to be significantly increased, does not intervene with the substrate.
Therefore, it is possible to stably form a polycrystalline silicon wiring having sufficiently small contact resistance. Also, CVD
As a thin film formed by the method, for example, a gate insulating film, a silicon oxide film used as a capacitor insulating film, and an ultra-thin insulating film such as a silicon nitride film can also be formed.
A high-quality ultra-thin insulating film without a natural oxide film at the interface with the semiconductor substrate can be obtained. Unlike a silicon oxide film formed by intentionally oxidizing at a high temperature, a natural oxide film has a very low withstand voltage because the film is not dense and has many defects. When a silicon oxide film or a silicon nitride film is formed by a CVD method after removing the natural oxide film, the insulating characteristics are significantly improved because there is no extremely incomplete natural oxide film as an insulating film. Also in the formation of the silicon nitride film, since a natural oxide film does not exist, it is possible to provide a thin film having an excellent insulating property without a decrease in dielectric constant. Note that the silicon nitride film has a higher dielectric constant than the silicon oxide film, and thus is preferably used as a capacitor insulating film.

After removing the natural oxide film, a thin film of a refractory metal such as tungsten, molybdenum, tantalum, or titanium, or a thin film of a silicide compound thereof may be formed by a CVD method. In any case, since a film having no natural oxide film at the interface is obtained, a film having an extremely low contact resistance can be obtained without heat treatment.

Third Embodiment of the Present Invention (CVD Method) FIG. 10 is a sectional view of a third embodiment of the thin film forming apparatus.

The apparatus comprises one chamber 20,
20 is divided into a pretreatment chamber 37, a pre-film formation chamber 39, and a thin film formation chamber 38 by a lock valve 21a and a lock valve 21b. Referring to FIG. 10, a pretreatment chamber 37 is provided with an HCl gas inlet 6 and an exhaust port 9. Further, the pretreatment chamber 37 is provided with an ultraviolet ray entrance window 2 for irradiating the inside of the pretreatment chamber 37 with ultraviolet rays. A low-pressure mercury lamp 1 is installed opposite the ultraviolet light entrance window 2. The substrate support 5 is set in the pretreatment chamber 37, and the silicon substrate 4 is set on the substrate support 5. The substrate support 5 is a heating means
5 a, and is configured to be able to heat the silicon substrate 4 via the substrate support 5. A transfer system 27a for transferring the silicon substrate 4 is provided in the pretreatment chamber 37.

The transport system 27b is also provided in the pre-film formation chamber 39. The thin film forming chamber 38 is provided with a film forming gas inlet 36 and an exhaust port 9. A substrate support 5 'is set in the thin film forming chamber 38, and the silicon substrate 4 is set on the substrate support 5'. The substrate support 5 'is provided with heating means 5a', and is configured to heat the silicon substrate 4 via the substrate support 5 '. Also,
A transfer system 27c for transferring the semiconductor substrate 4 is provided in the thin film forming chamber 38.

Next, a method for forming a thin film on a semiconductor substrate using this apparatus will be described.

The silicon substrate 4 is placed on the substrate support 5 in the pretreatment chamber 37. This silicon substrate 4 has been subjected to a solvent treatment, but has already been in contact with air to form a natural oxide film. Next, HCl gas is introduced into the pretreatment chamber 37 from the HCl gas inlet 6, and
Supply HC1 gas. Next, the surface of the silicon substrate 4 is irradiated with ultraviolet light from the ultraviolet light incident window 2 by turning on the low-pressure mercury lamp 1. Simultaneously with the ultraviolet irradiation, the silicon substrate 4 is heated to 200 to 700 ° C. Then, a natural oxide film on the silicon substrate 4 is removed by a synergistic effect of light and heat.

Next, the lock valve 21a is opened, and the transport systems 27a and 27b are opened.
To guide the semiconductor substrate 4 into the chamber 39 before film formation. In the pre-film formation chamber 39, the gas atmosphere is controlled so that a natural oxide film is not formed again on the surface of the semiconductor substrate. Next, the lock valve 21a is closed. Thereafter, the lock valve 21b is opened, and the transfer systems 27b and 27c are operated to guide the semiconductor substrate 4 to the substrate support 5 'in the thin film forming chamber 38. At this time, if the lock valve 21a and the lock valve 21b are controlled so as not to be opened at the same time, the pretreatment chamber due to the residual gas in the pretreatment chamber 37 and the residual gas in the thin film formation chamber 38.
Internal contamination of the chamber 37 and the thin film forming chamber 38 can be prevented.

Subsequently, in the thin film forming chamber 38, heating means
5a 'is operated to heat the silicon substrate 4. At the same time, a thin film formation chamber
A film forming gas is introduced into the inside. Then, a desired thin film is formed on the surface of the semiconductor substrate 4.

Fourth Embodiment of the Present Invention (Sputter Deposition Method) FIG. 11 is a sectional view of a fourth embodiment of the thin film forming apparatus. The apparatus includes a single chamber 20. The chamber 20 includes a lock valve 21a, a lock valve 21b, and a lock valve 21c.
It is partitioned into a thin film forming chamber 38 and an unloader chamber 41.

The loader chamber 40 is provided with a nitrogen gas introduction port 26 and an exhaust port 9a. The transfer system 27a is provided in the loader room 40.

The pretreatment chamber 37 is provided with an HCl gas introduction port 6 and an exhaust port 9b. Further, the pretreatment chamber 37 is provided with an ultraviolet ray entrance window 2 for letting ultraviolet rays enter the pretreatment chamber 37. A low-pressure mercury lamp 1 is provided opposite to the ultraviolet incident window 2. The substrate support 5 is provided in the pre-processing chamber 37, and the substrate support 5 is provided.
A tray 30 is placed on the tray, and the silicon substrate 4 is placed on the tray 30. The substrate support 5 is provided with a heating means 5a.
And a silicon substrate 4 via a substrate support 5.
Is configured to be heated. A transfer system 27b for transferring the silicon substrate 4 is provided in the pretreatment chamber 37.

The thin film forming chamber 38 is a deposition chamber for forming a thin film by a sputter deposition method. In the thin film forming chamber 38,
Argon gas inlet 28 for introducing argon gas and exhaust port
9c is provided. The chamber 38 for forming a thin film includes a substrate support 5 '. A target 34 is provided in the thin film forming chamber 38. A DC power supply 35 is connected to the target 34 so that a high voltage can be applied between the target 34 and the argon gas. The substrate support 5 'and the chamber 20 are insulated by an insulating part 33, and the target 34 and the chamber 20 are insulated by the insulating part 33. A transfer system 27c is provided in the thin film forming chamber.

The unloader chamber 41 has a nitrogen gas inlet 26 and an outlet 9d. In the unloader chamber 41, a transfer system 27d is provided. The chamber 20 is airtight, and has an exhaust port 9a, an exhaust port 9b,
The inside can be brought into a high vacuum state by sucking the air through the exhaust port 9c and the exhaust port 9d with a vacuum pump.

Next, a method for forming a thin film on a semiconductor substrate using this apparatus will be described.

First, each of the loader chamber 40, the pretreatment chamber 37, the thin film forming chamber 38, and the unloader chamber 41 is brought into a high vacuum state.

Next, nitrogen gas is introduced into the vacuum-loaded loader chamber 40 from the nitrogen gas inlet 26a, and the inside of the loader chamber 40 is returned to atmospheric pressure. Next, a plurality of silicon substrates 4 placed on the tray 30 are put into the loader chamber 40 using a cassette, and the door is closed.
Subsequently, the inside of the loader chamber 40 is evacuated from the exhaust port 9a by a vacuum pump, and the inside is brought into a high vacuum state. Next, the lock valve 21a
Is opened, the motor of the transport system 27a is driven, the silicon substrate 4 placed on the tray 30 is moved into the pretreatment chamber 37, and the lock valve 21a is closed. The inside of the pretreatment chamber 37 is in a high vacuum state of about 10 ^-7 to 10 ^-8 Torr. Next, HCl gas at a reduced pressure of 10 ⁻⁷ Torr is introduced into the pretreatment chamber 37 from the HCl gas inlet 6, and the HCl gas is supplied to the surface of the silicon substrate 4. Next, the surface of the silicon substrate 4 is irradiated with ultraviolet light from the ultraviolet light incident window 2 by turning on the low-pressure mercury lamp 1. Simultaneously with the ultraviolet irradiation, the silicon substrate 4 is heated to 200 to 700 ° C. Then, due to the synergistic effect of light and heat, for example, the following reaction is promoted, and the natural oxide film on the silicon substrate 4 is removed.

SiO ₂ + 4HCl → SiCl ₄ + 2H ₂ O When the removal of the natural oxide film or the contaminants attached to the surface of the silicon substrate 4 is completed, the introduction of the HCl gas and the irradiation of the low-pressure mercury lamp are stopped, and the HCl in the pretreatment chamber 37 is removed. The gas is exhausted, and the inside of the pretreatment chamber 37 is brought into a high vacuum state.

Subsequently, the lock valve 21b is opened, the motor of the transport system 27b is driven, and the silicon substrate 4 placed on the tray 30 is moved into the thin film forming chamber 38. Then, the lock valve 21b is closed. At this time, the second silicon substrate 4
Has moved into the pretreatment chamber 37. The thin film forming chamber 38 is also in a high vacuum state of about 10 ^-7 to 10 ^-8 Torr. Then, 10 ^-3 to 10
^-1 Torr of argon gas was introduced, and a DC power supply 35
A voltage of several hundred to several thousand volts is applied between the target 34 and the argon gas to create a plasma. The argon ions in the plasma collide with the target 34 on the negative and high pressure side with high energy to sputter the material of the target 34. This substance is deposited on the silicon substrate 4 to form a thin film. When the formation of the thin film having the desired film thickness, uniformity and film quality is completed, the introduction of the argon gas and the application of the voltage are stopped, the argon gas in the thin film forming chamber 38 is exhausted, and the inside of the thin film forming chamber 38 is raised. Apply vacuum. Subsequently, the lock valve 21c is opened, the motor of the transport system 27c is driven, the silicon substrate 4 placed on the tray 30 is moved to the unloader chamber 41, and the lock valve 21c is closed. At this time, the second silicon substrate 4 is a thin film forming chamber.
The third silicon substrate 4 has moved into the pretreatment chamber 37. Thus, the silicon substrate 4 on which the sputter deposition has been performed successively after the removal of the natural oxide film is stored in a cassette (not shown) in the unloader chamber 41. When the last silicon substrate 4 is stored in the cassette, the pressure in the unloader chamber 41 is returned to the atmospheric pressure. The silicon substrate treated in this way is in the unloader chamber
Removed from 41 and sent to the next step.

Embodiment of the Present Invention (Sputter Deposition Method) In the fourth reference example, a thin-film forming apparatus in which a pretreatment chamber and a thin-film forming chamber are separated from each other has been described. Are integrally formed.

12A and 12B are cross-sectional views of a thin film forming apparatus for sputter deposition in which a preprocessing chamber and a thin film forming chamber are integrally formed.

Referring to these figures, chamber 20 has an HCl gas inlet 6, an argon gas inlet 28, and an exhaust port 9. The chamber 20 is provided with an ultraviolet incident window 2 for irradiating the inside of the chamber 20 with ultraviolet rays. A low-pressure mercury lamp 1 is installed opposite the ultraviolet light entrance window 2. The chamber 20 includes the substrate support 5. The substrate support 5 has a heating means 5a. Target 34 in chamber 20
Is provided, and the target 34 and the chamber 20 are insulators.
Insulated by 33. DC power supply 35 for target 34
Is connected. A platen 42 is installed in the chamber 20, and the platen 42 can rotate around a rotation shaft 43. The tray 30 is fixed to the platen. The tray 30 is provided with slightly raised protrusions 44, 44 '. The silicon substrate 4 is placed on the tray 30 so as to be sandwiched between the convex portions 44 and 44 '.

Referring to FIG. 12A, when chamber 20 is used as a pretreatment chamber, platen 42 is supported by support shaft 45 and horizontally oriented. At this time, the silicon substrate 4 and the low-pressure mercury lamp 1 face each other.

Referring to FIG. 12B, when the chamber 20 is used as a thin film forming chamber, the platen 42 is connected around the rotation shaft 43, and the silicon substrate 4 and the target 34 are opposed to each other. When the platen 42 rotates, the silicon substrate 4 tries to slide down diagonally in the plane of the platen 42,
The projection 44 prevents further drop.

Next, a method for forming a thin film on the surface of a semiconductor substrate using this apparatus will be described.

Referring to FIG. 12A, platen 42 is supported on support shaft 45, and platen 42 is horizontally oriented. Subsequently, the silicon substrate 4 is placed on the tray 30. In this case, the silicon substrate 4 is placed so as to be sandwiched between the convex portions 44 and the convex portions 44 '. At this time, the silicon substrate 4 and the low-pressure mercury lamp 1 face each other. Although the silicon substrate 4 has been subjected to a solvent treatment, it has already been exposed to air and a natural oxide film has been formed. Next, an HCl gas is introduced into the chamber 20 from the HCl gas inlet 6, and the HCl gas is supplied to the surface of the silicon substrate 4. Next, the surface of the silicon substrate 4 is irradiated with ultraviolet light from the ultraviolet light incident window 2 by turning on the low-pressure mercury lamp 1. Simultaneously with this ultraviolet irradiation, the silicon substrate 4
Is heated to 200-700 ° C. Then, for example, the following reaction is promoted by the synergistic effect of light and heat, and the natural oxide film on the silicon substrate 4 is removed.

When the removal of the SiO ₂ + 4HCl → SiCl ₄ + 2H ₂ O natural oxide film is completed, the introduction of the HCl gas and the irradiation of the low-pressure mercury lamp 1 are stopped, the HCl gas in the chamber 20 is exhausted, and the inside of the chamber 20 is brought into a high vacuum state. I do.

Subsequently, referring to FIG. 12B, the platen 42 is
And the silicon substrate 4 and the target 34 are opposed to each other. In this state, argon gas is introduced from the argon gas inlet 28, and a high voltage is applied between the argon gas and the target 34 by the DC power supply 35 to generate plasma. Argon ions in this plasma are the target
The material 34 collides with high energy to sputter the material of the target 34, and deposits this material on the silicon substrate 4.
Then, a thin film is formed on the surface of the silicon substrate 4. When the formation of the thin film is completed, the introduction of the argon gas and the application of the high voltage by the DC power supply 35 are stopped, the argon gas in the chamber 20 is exhausted, and the inside of the chamber 20 is brought into a high vacuum state.
Subsequently, the platen 42 is oriented in the horizontal direction to return to the original state, and then the lock valve (not shown) is opened, and the silicon substrate is moved to the unloader chamber (not shown). Even by such a method, a thin film with a well-controlled interface between the semiconductor substrate and the thin film can be formed.

13A and 13B show an apparatus for realizing a fifth embodiment of the present invention. FIG. 13A is a front sectional view, and FIG. The figure is a sectional view taken along the line BB in FIG. 13A.

This apparatus is a batch type processing apparatus capable of processing a large amount of silicon substrates. The processing apparatus has a chamber 20. A boat 46 capable of holding a plurality of silicon substrates 4 is arranged in the chamber 20. The boat 46 has a cylindrical shape, and a groove 46a extending in the vertical direction is formed on a side wall of the boat 46.
Are formed at intervals. Each of the grooves 46a has a holding groove for holding the silicon substrate 4 horizontally.
A plurality of 46b are formed at intervals in the vertical direction. The boat 46 can rotate around its axis. The chamber 20 has an HCl gas inlet 6 and an outlet 9.

Further, the chamber 20 is provided in the ultraviolet incident window 2, and the ultraviolet incident window 2 is arranged so as to be able to irradiate the silicon substrate 4 with light in parallel. A light source, for example, a low-pressure mercury lamp 1 is arranged opposite to the ultraviolet incident window 2.

Next, a method for forming a thin film on the surface of a semiconductor substrate using this apparatus will be described.

The boat 46 holds a plurality of silicon substrates 4. This silicon substrate 4 has been subjected to a solvent treatment,
It has already been exposed to the atmosphere and has a natural oxide film formed on its surface. Next, the inside of the chamber 20 is evacuated. Subsequently, a reactive gas such as HCl gas is introduced from an HCl gas inlet 6 and, at the same time, ultraviolet rays emitted from a light source such as a low-pressure mercury lamp 1 are passed through the ultraviolet incident window 2 to the chamber.
Irradiation is performed on the surface of the silicon substrate 4 in 20 and the introduced reaction gas such as hydrogen chloride gas. At this time, the silicon substrate 4
Is 200 to 7 due to the heat generated by light irradiation
The temperature is raised to 00 ° C. The natural oxide film and the like adhering to the semiconductor substrate are removed by the heat, the subsequently irradiated light, and the introduced HCl gas. After that, after the HCl gas is evacuated from the exhaust port 9, if a thin film is continuously formed in the same apparatus without exposing to air (thin film forming means is not shown), an interface structure between the silicon substrate 4 and the thin film is obtained. The thin film formation can be controlled with good control. The thin film forming means is not shown, but can be realized by forming a gas inlet for introducing a gas for forming a thin film into the chamber 20 on the side wall of the chamber 20.

Sixth Embodiment FIGS. 14A and 14B show an apparatus for realizing a sixth embodiment of the present invention, and FIG. 14A is a cross-sectional view when viewed from above. FIG. 14B is a sectional view taken along the line AOA in FIG. 14A.

This apparatus is also a batch type processing apparatus capable of processing a large amount of silicon substrates. The device includes a chamber 20. A turret 46 capable of holding a plurality of silicon substrates 4 is disposed in the chamber 20. Turret
Reference numeral 46 denotes a truncated cone, and a plurality of pins 46a for holding the silicon substrate 4 are provided on a side wall thereof. The turret 46 can rotate around its axis. The chamber 20 includes an HCl gas inlet 6, an exhaust port 9, and a film forming gas inlet. Chamber
The low pressure mercury lamp 1 and the argon arc lamp 100 are disposed around the periphery of the lamp 20, and light from the low pressure mercury lamp 1 and light from the argon arc lamp 100 are introduced into the chamber 20. Argon arc lamp 100
Is a lamp for raising the temperature of the silicon substrate to 200 ° C. to 700 ° C.

Next, a method for forming a thin film on the surface of a semiconductor substrate using this apparatus will be described.

The turret 46 holds a plurality of silicon substrates 4. Although this silicon substrate 4 has been subjected to a solvent treatment, it has already been exposed to the atmosphere and a natural oxide film has been formed on its surface. Next, the inside of the chamber 20 is evacuated through the exhaust port 9. Subsequently, a reaction gas such as HCl gas is introduced into the chamber 20 from the HCl gas inlet 6 and, at the same time, a light source emitted from the low-pressure mercury lamp 1 and the argon arc lamp 100 is applied to the surface of the silicon substrate 4 in the chamber 20. . At this time, the silicon substrate 4 is heated to 200 to 700 ° C. by the heat generated by the argon arc lamp 100. The heat, the ultraviolet rays emitted from the low-pressure mercury lamp 1, and the introduced HCl gas remove the natural oxide film and the like adhering to the semiconductor substrate. Then, after the HCl gas is evacuated from the exhaust port 9, a CVD reaction gas is introduced into the chamber 20 from the film forming gas inlet 36. Then, a thin film can be formed on a clean surface of the silicon substrate 4. As described above, in this apparatus, after the surface of the silicon substrate 4 is cleaned, a thin film can be continuously formed on the surface without exposing the silicon substrate 4 to the air. Can be formed.

In the above reference example, the case where HCl gas is used as the reaction gas is illustrated, but any gas that absorbs in the ultraviolet region, such as chlorine gas and hydrogen gas, may be used.

Further, although the case where a low-pressure mercury lamp is used as the light source is illustrated, a high-pressure mercury lamp, a mercury xenon lamp, an argon-arc lamp, an ArF excimer laser, a KrF excimer laser, and an XeCl excimer laser may be used. Further, a light source having a light source that emits ultraviolet light and a light source that emits infrared light is also preferably used. Further, although the description has been made using the silicon substrate as the semiconductor substrate, the present invention is not limited to this.

As described above, the thin film forming apparatus of the present invention has been described with reference to the specific embodiments. However, the present invention can be implemented in other various forms without departing from the spirit or main features. Therefore, the above-described embodiments are merely illustrative in every respect and should not be construed as limiting.
The scope of the present invention is defined by the appended claims, and is not limited by the specification. Furthermore, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

[Effects of the Invention] As described above, according to the present invention, a natural oxide film or a contaminant adhered to a semiconductor substrate surface can be removed at a sufficiently low temperature without damaging the semiconductor substrate surface. . Then, a thin film is continuously formed on the surface of the semiconductor substrate subjected to such treatment without being exposed to the air by the sputter deposition method, so that a natural oxide film or the like does not exist at the interface between the semiconductor substrate and the thin film. As a result, a semiconductor substrate in which the interface structure between the semiconductor substrate and the thin film is controlled in a favorable state can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an experimental apparatus for removing a natural oxide film. FIGS. 2A and 2B are diagrams for explaining a first confirmation method for confirming whether or not a native oxide film has been removed. FIGS. 3A and 3B are diagrams for explaining a second confirmation method for confirming whether or not the native oxide film has been removed. FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D are diagrams showing the temperature effect of the first step of the present invention. FIG. 5 is a view showing an ultraviolet irradiation effect in the first step of the present invention. FIG. 6 is an Arrhenius plot of the relationship between the etching rate and the temperature of the silicon substrate. No.
FIGS. 7A, 7B and 7C are diagrams showing a method for determining the etching rate of a silicon substrate. FIG. 8A is a sectional view of an apparatus for realizing the first embodiment of the present invention. 8B and 8C are views showing a method of removing a native oxide film using the device according to the first reference example.
FIG. 9 is a sectional view of an apparatus according to a second embodiment of the present invention. FIG. 10 is a sectional view of an apparatus according to a third embodiment of the present invention. FIG. 11 is a sectional view of an apparatus according to a fourth embodiment of the present invention. 12A and 12B are cross-sectional views of the device according to the embodiment of the present invention. 13A and 13B are cross-sectional views of a device according to a fifth embodiment of the present invention. FIG. 14A and FIG. 1
FIG. 4B is a sectional view of an apparatus according to a sixth embodiment of the present invention.
FIG. 15 is a sectional view of a conventional thin film forming apparatus. In the figure, 1 is a low-pressure mercury lamp, 3 is a chamber, 4 is a silicon substrate, 5a is a heating means, 6 is an HCl gas inlet, 7
Is a SiH ₂ Cl ₂ gas inlet, and 8 is an NH ₃ gas inlet. In the drawings, the same reference numerals indicate the same or corresponding parts.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H01L 21/3065 H01L 21/302 B (72) Inventor Akira Tokui 4-1-1 Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Inside LSI Research Institute Co., Ltd. (72) Katsuyoshi Mitsui 4-1-1 Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Corporation Inside LSI Laboratory (72) Inventor Katsuhiro Tsukamoto 4, Mizuhara, Itami-shi, Hyogo 1-chome, Mitsubishi Electric Corporation LSI Research Institute (56) References JP-A-62-42530 (JP, A) JP-A-57-149748 (JP, A) JP-A-57-87120 (JP) JP-A-57-13743 (JP, A) JP-A-63-120428 (JP, A)

Claims (1)

(57) [Claims] An apparatus for removing a natural oxide film or a contaminant adhered to a surface of a semiconductor substrate, and thereafter forming a thin film on the clean surface by a sputter deposition method, wherein the semiconductor substrate to be processed is accommodated. A chamber; a reaction gas introducing unit for introducing a gas capable of reacting with the natural oxide film or the contaminant into the chamber; a heating unit for heating the semiconductor substrate to a temperature in a range of 200 to 700 ° C .; While heating the semiconductor substrate, 200 ~ 7
At a temperature in the range of 00 ° C., the reaction gas is irradiated with light having a wavelength that allows a photochemical reaction between the reaction gas introduced into the chamber and a natural oxide film or a contaminant attached to the surface of the semiconductor substrate. A light source, a target provided in the chamber, and providing a component of a thin film formed on the surface of the semiconductor substrate from which the natural oxide film or the contaminant has been removed; and a target provided in the chamber, A substrate moving means for moving the semiconductor substrate, wherein the substrate moving means is configured such that, when a natural oxide film or a contaminant attached to the semiconductor substrate is removed, the semiconductor substrate is arranged such that a surface of the semiconductor substrate faces the light source. When a thin film is formed on the semiconductor substrate, the semiconductor is placed such that the surface of the semiconductor substrate faces the target. An apparatus for forming a thin film on the surface of a semiconductor substrate for moving a substrate.