JPH05259081A - Vapor growth device and thin film forming method - Google Patents

Abstract

PURPOSE:To enable a thin film to be formed on a wafer uniform in thickness and resistivity and high in reproducibility and to be easily controlled in impurity concentration and a doping source to be kept high in safety and not to be easily exhausted. CONSTITUTION:Wafers 5 serving as growth substrates and fixed source substrates 5a and 5b serving as doping sources are mounted on a wafer holder 4, and a first nozzle pipe 7a which feeds film forming reaction gas to a region where the wafers 5 are mounted and a second nozzle pipe 7b which feeds etching gas to a region where the fixed source substrates 5a and 5b are mounted are installed, where etching gas is controlled in flow rate to change impurities in concentration for controlling a thin film in resistivity. A fixed source substrate is renewed by this etching gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film by vapor phase growth and an apparatus therefor, and more particularly to a vapor phase growth apparatus for forming a thin film on a surface of a substrate by chemical vapor reaction and doping the thin film with an impurity and a thin film for the same. It relates to a forming method.

[0002]

2. Description of the Related Art In recent years, thin film forming techniques have been used for semiconductors, metals,
Alternatively, it has become an important technology in many industrial fields such as the ceramics industry. Particularly in a semiconductor device manufacturing process using silicon as a main raw material, a process of forming an epitaxial film or a polycrystalline silicon film doped with P-type or N-type impurities on a wafer surface which is a semiconductor substrate is one of important processes. ing. Also, recently, super high speed L
In the field of SI, an alloy of Si and Ge crystals (Si _1-x
The development of LSI devices using Ge _x ) thin films is becoming active.

As a method for forming these thin films, there are a chemical vapor deposition method (CVD), a molecular beam epitaxy method (MBE) and the like. The chemical vapor deposition method is mainly used because of the advantages of high throughput and easy production of high-quality films by these methods. And many chemical vapor deposition apparatuses have been developed. For example, as a growth apparatus for polycrystalline Si that is grown at a relatively low temperature, there is a low pressure vapor phase growth (LPCVD) apparatus using a hot wall type reaction furnace. Also, although there are various types of these reactors, since the oxygen entrainment is small and the wafer rotation is easy,
Vertical furnaces are the mainstream.

On the other hand, there is a vapor phase growth apparatus using a cold wall type reaction furnace in which epitaxial growth is carried out at a high temperature. The reaction furnaces of these apparatuses use barrel type and pancake type reaction furnaces. I came. However, although these devices have the advantage that the amount of silicon deposited on the wall surface of the reactor is small, it is becoming difficult to meet the current requirements in terms of throughput as the diameter of processed wafers increases.

Various new-type devices have been prototyped for processing a large-diameter wafer with high throughput. For example, a hot wall system using a vertical reaction tube has been proposed as an apparatus capable of processing a large amount of 6-inch diameter large-diameter wafers (Japanese Patent Laid-Open No. 63-63).
0086424).

13 (a) to 13 (c) show an example of a conventional vapor phase growth apparatus, (a) is a schematic sectional view, (b) is a side view of a nozzle tube, and (c) is a cross section of an inner tube. It is a side view.
This growth apparatus has a cylindrical outer tube 1 as shown in FIG.
And a reaction vessel having a double structure with the inner tube 2, a resistance heating furnace 6 mounted around the outer tube 1, a wafer holder 4 accommodating a plurality of wafers 5 side by side, and a reaction gas on the surfaces of these wafers 5. Nozzle tube 7 to supply, outer tube 1 and inner tube 2
And a rotation shaft for airtightly penetrating the mount on which the wafer holder 4 is mounted and rotating the wafer holder 4. Further, the reaction gas supplied from the nozzle pipe 7 passes over the surface of the wafer 5 and the inner pipe 2
The gas is discharged through a large number of gas discharge holes provided in the cylindrical surface of.

In order to form a thin film on the wafer 5 with this growth apparatus, the pressure in the reaction vessel is reduced and the wafer is, for example, 900
It was carried out by heating to ℃ -1200 ℃, supplying the reaction gas for forming a film from the nozzle tube 7 into the reaction tube. Further, as a method of forming a thin film on a wafer with this apparatus and performing impurity doping in the film formation, PH ₃ , B
A doping gas (gas source) such as ₂ H ₆ or AsH ₃ and a silane-based reaction gas such as SiH ₂ Cl ₂ related to growth are mixed and supplied to the wafer surface to form an epitaxial film and to dope the film. There is a method (gas source method). Another method is to use a solid source in which P-type or N-type impurities are diffused in high concentration on the wafer surface and perform doping with impurities that evaporate from the wafer surface during epitaxial growth (solid source method). For film formation of alloys such as Si _1-x Ge _x or compound semiconductors, the MBE method using a solid source has been used because of the need for precise control of the composition ratio. However, since the MBE method has extremely poor throughput, it cannot be applied to product production due to the problem of manufacturing cost.

Therefore, recently, a vapor phase growth apparatus capable of growing a Si _1-x Ge _x alloy at a relatively low cost is being prototyped. For example, as a growth apparatus by the CVD method,
[Proc. 11th Int. Conf. CVD
p. 229-239 (1990)]. This vapor phase growth system is compatible with high vacuum (base vacuum degree 1
0 has a growth furnace of ^-9 Torr), 500-8 the substrate temperature
The temperature was set to 00 ° C., and GeH ₄ gas was supplied at the same time as a silane-based reaction gas such as SiH ₄ to grow a Si _1-x Ge _x alloy.

[0009]

In the first vapor phase growth method by the gas source method described above, in order to perform uniform film growth on the wafer surface, various reactive species generated by thermal decomposition of the reactive gas are used. Must be uniformly supplied to the entire growth area. For example, if described using the aforementioned N-type Si epitaxial growth using a reaction gas of SiH ₂ Cl ₂ -H ₂ -PH ₃ system as an example, SiCl ₂ relating to film growth caused by the thermal decomposition of SiH ₂ Cl ₂ It is necessary to uniformly supply a reaction gas such as PH _i (i = 1, 2, 3) related to doping generated by thermal decomposition of PH ₃ and PH ₃ to the entire wafer growth region. For this purpose, the flow velocity of the gas ejected from the nozzle tube and the ejection direction are optimized, but the thermal decomposition process of SiH ₂ Cl ₂ related to film growth and the PH related to doping are performed.
_Since the thermal decomposition process of ₃ is different in terms of decomposition temperature, it is difficult to find conditions that satisfy both film thickness uniformity and resistivity uniformity at the same time. In particular, it is becoming more difficult as the diameter of wafers increases. In addition, the aforementioned Si _1-x Ge
The same is true for _x alloy growth. That is, Si
Since the thermal decomposition temperature and reaction process of the silane-based gas such as SiH ₂ Cl ₂ which is the source and the GeH ₄ gas which is the Ge source are different, the alloy ratio (x) of Si and Ge is made uniform over the entire growth surface. Difficult to do.

Next, the danger of the conventional vapor phase growth apparatus will be described. In conventional vapor phase growth apparatus as described above uses a _{PH 3, AsH 3, B 2} H 6, GeH 4 such as a gas or liquefied gas. Many of these gases are extremely toxic and pyrophoric, which makes them difficult to handle and highly dangerous. In particular, GeH ₄ gas is a highly dangerous reaction gas because it has spontaneous explosive properties and there are many unclear matters regarding its properties. For this reason,
Care must be taken in handling these reaction gases, and in order to ensure their safety, safety measures such as installation of gas detectors and leak warning devices, construction of fail-safe systems, and maintenance of the film-forming factory itself are required. It takes a lot of money and time to establish and maintain it. Also, it goes without saying that once an accident occurs, much cost is required for restoration. In particular, it can be said that the dangerous potential of a gas such as GeH ₄ gas, which has not been used in mass production until now, is extremely high.

On the other hand, the second method using a solid source (solid source method) described above can grow a Si epitaxial film having a uniform film thickness and resistivity in the plane of a wafer even on a large-diameter wafer, or an alloy ratio. Uniform Si _1-x Ge
_x There are advantages such as the ability to form thin films. However, this method also has the following problems.

FIGS. 14A and 14B are views showing the profile of the depth from the surface of the wafer and the impurity concentration.
Regarding this problem, Si epitaxial growth will be described first. The first problem is the Si epitaxial film-
There is a deterioration in the impurity profile at the substrate interface. The impurity profile at the epitaxial film-substrate interface is shown in FIG.
As shown in FIG. 14, it is ideal that it is steep, but in reality, due to impurity thermal diffusion during epitaxial growth and autodoping (a phenomenon in which impurities evaporated from the substrate surface are reincorporated into the epitaxial film), As shown in b), it is known to have a gentle profile. The depth Δt until this smooth rise is called the transition width, and it is desirable that this value is small. This is particularly important for a thin epitaxial film having a thickness of 2 μm or less.
In order to reduce this Δt, it is necessary to reduce the impurity partial pressure in the reaction container immediately before the epitaxial growth and at the initial stage of the epitaxial growth. However, in the case of the above-mentioned second method, the high-concentration dopant diffused on the surface of the solid source is used as a pre-process (eg, H ₂
Since a large amount of vapor has already evaporated in the reaction vessel in the baking step), it is difficult to reduce the impurity partial pressure immediately before the epitaxial growth and at the initial stage of the growth, and the transition width Δt cannot be sufficiently narrowed.

Next, the second problem related to Si epitaxial growth will be described. In the case of the second method described above,
The impurity concentration in the epitaxial film is controlled by adjusting the amount of impurities evaporated from the solid source source during the epitaxial growth. That is, by changing the growth temperature,
A method of adjusting the vapor pressure of impurities and a method of adjusting the amount of impurities diffused in the solid source in advance have been used. However, a change in the growth temperature causes a problem that the growth rate of the epitaxial film changes and it becomes difficult to control the film thickness. Further, extremely low temperature causes deterioration of crystallinity, and high temperature makes it difficult to secure uniformity of film thickness. Further, the method of adjusting the amount of impurities in the solid source has a problem that it is necessary to prepare the solid sources having different amounts of impurities for each resistivity specification of the epitaxial film.

A third problem with the second method described above is that
The solid source substrate is that only one batch of growth can be used (lack of durability as a solid source). That is, it is necessary to replace the solid source substrate for each growth. this is,
This is because the epitaxial film or the polysilicon film grown on the solid source substrate lowers the impurity concentration on the surface of the solid source substrate, so that the amount of evaporated impurities decreases and the desired resistivity cannot be obtained.

For the same reason, also in the growth of Si _1-x Ge _x alloy, the conventional method has a problem of control of the alloy ratio (x) measured in the depth direction of the film or sustainability.

An object of the present invention is to form a film with uniform thickness and resistivity on the wafer surface with good reproducibility, to easily control the impurity concentration of this film, and to use a safe and easy doping source. It is an object of the present invention to provide a vapor phase growth apparatus and a thin film forming method thereof that are not depleted.

[0017]

A vapor phase growth apparatus of the present invention includes a wafer holder for accommodating a plurality of growth substrates and a plurality of plate-like solid sources doped with impurities in one direction, and a wafer holder for the wafer holder. A reaction tube that houses the holder,
A first nozzle tube having a plurality of gas discharge holes for flowing a reaction gas for growth in the reaction tube in a direction substantially parallel to the surface of the substrate to be grown, and a gas for etching the solid source is provided on the surface of the solid source substantially. A second nozzle tube having gas discharge holes that flow in parallel.

The first thin film forming method of the present invention is characterized in that a reaction gas relating to film growth is supplied to the growth substrate and a gas for etching a solid source is supplied to the fixed source.

The second thin film forming method of the present invention is characterized in that the supply of the gas for etching the solid source is a part of the thin film forming process time.

The third thin film forming method of the present invention is characterized in that the solid source is a silicon substrate doped with either N-type or P-type impurities.

The fourth thin film forming method of the present invention is characterized in that when the thin film formed on the growth substrate is a Si _1-x Ge _x alloy film, the solid source is germanium.

[0022]

The first problem in the Si epitaxial growth (increase in impurity transition width) by the means according to the invention described above.
Can be solved by reducing the impurity concentration in the solid source. That is, by reducing the impurity concentration in the solid source, the amount of impurity evaporation in the pre-epitaxial growth step is reduced, and thus the impurity transition width is significantly improved. Moreover, during the epitaxial growth, the surface of the solid source is etched to forcibly evaporate the impurities, so that it is possible to dope the epitaxial film with a sufficient amount of impurities even if the impurity concentration on the surface of the solid source is reduced. ..

The control of the impurity concentration in the Si epitaxial film, which is the second problem, can be easily solved by adjusting the etching rate of the solid source surface. That is,
By utilizing the difference in the amount of impurities generated per unit time due to the change in etching rate, the amount of impurities taken into the epitaxial film can be controlled. At this time, the etching rate can be easily controlled by changing the concentration or flow rate of the etching gas supplied to the solid source. In this method, it is not necessary to change the growth temperature or the impurity concentration in the solid source.

Further, the third problem will be described. In the case of this method, since the surface of the solid source is etched in the epitaxial growth step, no single crystal silicon or polysilicon film grows on the surface of the solid source. Therefore, even after the epitaxial growth process, the impurity concentration on the surface of the solid source cannot be reduced,
The surface concentration can always be kept constant. Therefore, it is not necessary to replace the solid source for each epitaxial growth batch as in the conventional method.

On the other hand, in the case of Si _1-x Ge _x alloy growth,
A silane-based reaction gas such as SiH ₂ Cl ₂ is supplied, and at the same time, an etching gas is supplied on the Ge crystal that is a solid source to form a Si _1-x Ge _x alloy. Therefore, it is not necessary to use the dangerous gas GeH ₄ gas described in the conventional example, and the safety is high. Further, the alloy ratio (x) can be controlled by changing the concentration or flow rate of the etching gas to change the Ge solid source etching rate.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

1 (a) to 1 (c) show a main part of an embodiment of the vapor phase growth apparatus of the present invention, and FIGS. 1 (a) and 1 (b) show a wafer holder and a nozzle tube in an inner tube, (C) is a cross-sectional view of the inner pipe. As shown in FIG. 1, a vapor phase growth apparatus according to an embodiment of the present invention includes a wafer holder 4 on which a wafer 5 as a growth film substrate and solid source substrates 5a and 5b for generating impurities for doping the wafer are mounted. , Solid source substrates 5a and 5b
A second nozzle pipe 7b for supplying a reaction gas having an etching action is provided. Other than this, it is the same as the conventional example.

The operation of the vapor phase growth apparatus is performed by supplying the reaction gas necessary for epitaxial growth to the wafer 5 mounted on the wafer holder 4 from the first nozzle tube 7a and at the same time from the second nozzle tube 7b to the solid source. Substrate 5a,
5b to etch the surfaces of the solid source substrates 5a and 5b to evaporate impurities and dope the epitaxial film of the wafer 5. Further, the concentration of the impurities can be freely controlled by a mass flow controller (not shown) for controlling the etching gas flow rate that changes the etching rate.

FIG. 2 is a view showing a wafer holder for explaining the first embodiment of the thin film forming method by vapor phase epitaxy of the present invention, FIG. 3 is a graph showing the film thickness within the wafer surface, and FIG. 4 is a wafer. FIG. 5 is a graph showing the in-plane resistivity, and FIG. 5 is a graph showing the relationship between the etching gas flow rate and the wafer resistivity. Next, a first embodiment of the method for forming a thin film by vapor phase epitaxy of the present invention will be described by taking an example of growing a low concentration P-type epitaxial film on a P-type Si single crystal substrate having a relatively high concentration. The substrate with this structure has high resistance to soft errors due to latch-up and α rays, so in the future CMO
It is a promising substrate for S devices.

First, as shown in FIG. 2, a resistivity of 0.01
Ω-cm boron-doped P-type Si single crystal substrate (P1 to P
5) and a phosphorus-doped Si single crystal substrate (N1 to N5) having a resistivity of 10 Ω-cm are mounted on the intermediate portion of the wafer holder 4, and a solid source substrate (S1 to S4) having a boron-doped resistivity of 0.001 Ω-cm is mounted. It is mounted above and below the wafer holder 4. Next, the inside of the reaction tube is evacuated to a vacuum degree of about 10 Torr and the temperature is set to 1080 ° C. And rotated at 5 rotations per minute of the wafer holder 4, and H ₂ than the first nozzle tube 20 LSM, the SiH ₂ Cl ₂ 200 S
At the same time as supplying the CCM to the surface of the wafer other than the solid source, the second nozzle tube is used to generate H ₂ on the surface of the solid source substrate.
20 SLM and HCl 200 SCCM are supplied for 30 minutes to form a P-type Si epitaxial film on the wafer surface.
It grew to 0 μm.

As a result, when the film thickness was measured on the P1-P5 wafers by FTIR, as shown in FIG.
Good film thickness uniformity of ± 5% or less was obtained for all wafers. Moreover, when the sheet resistance was measured for the wafers N1 to N5 by the 4-probe method and the film thickness was corrected to calculate the resistivity, the resistivity was ± 5% or less as shown in FIG. Good uniformity was obtained.

HC to be supplied to the solid source substrate crystal
The l gas flow rate is set from the graph shown in FIG. 5 in order to obtain the desired resistivity of the epitaxial film. As described above, the resistivity of the epitaxial film can be easily controlled by changing the flow rate of the HCl gas that is the etching gas. FIG. 6 is a graph showing the impurity concentration distribution measured in the depth direction of the epitaxial film in comparison with the case of the conventional method. Further, while the impurity concentration in the epitaxial film grown by the conventional method is gradually reduced from the substrate-epitaxial interface toward the epitaxial surface, in the method of the present invention, the impurity concentration in the epitaxial film is ideal. Shows a wide range of impurity profiles. Further, FIG. 7 is a graph showing the change in the resistivity of the epitaxial film when the same solid source substrate is used for the epitaxial growth over 20 batches. The change in the resistivity by this method is ± 5% or less. The solid source persistence was confirmed, which was not possible by law.

Next, an example in which the method of the present invention is applied to the growth of an N-type Si epitaxial film will be described. This epitaxial growth was carried out using the same vapor phase growth apparatus as used in the first embodiment. Further, a Si single crystal having a high-concentration impurity-embedded region on its surface was used as a substrate for growth. And its structure is bipolar or Bi-CM
This is an essential structure for OS devices. Further, arsenic ion implantation is performed in advance on the surface of a P-type Si wafer having a boron-doped resistivity of 10 Ω-cm, which is a substrate to be grown, at an acceleration voltage of 70 keV and a dose of 5E14 to grow an N-type high concentration buried region in the surface layer. Created on the substrate.

FIG. 8 is a view showing a wafer holder for explaining a second embodiment of the thin film forming method by vapor phase epitaxy of the present invention. First, as shown in FIG. 8, a substrate to be grown (B1-B5), a P-type Si wafer (P6-P10) having a boron-doped resistivity of 10 Ω-cm, and a solid source substrate (S5 having an arsenic-doped resistivity of 0.01 Ω-cm). -S8) is mounted on each wafer holder and the temperature in the reaction tube is adjusted to 10
The degree of vacuum was 80 ° C. and the degree of vacuum was 10 Torr. Next, the wafer holder is rotated at a speed of 5 revolutions per minute, and H ₂ 20 SLM and SiH ₂ Cl ₂ 200 are first fed through the first nozzle tube.
SCCM is supplied onto the wafer surface other than the solid source for 2 minutes, then all gas supply is stopped, the inside of the reaction tube is evacuated to the base pressure for 1 minute, and then HCM is again supplied from the first nozzle tube.
₂ 20 SLM and SiH ₂ Cl ₂ 200 SCCM were supplied, and H ₂ 20 SLM and HCl 200 SCCM were supplied from the second nozzle tube onto the surface of the solid source substrate for 6 minutes to grow an N-type Si epitaxial film. The reason for delaying the supply of the etching gas onto the solid source is that the impurity transition width at the epitaxial-substrate interface is increased due to the arsenic autodoping phenomenon from the high-concentration buried region on the surface of the substrate (B1-B5) to be grown. This is to prevent it.

FIG. 9 is a graph showing the impurity profile with respect to the depth from the epitaxial film surface of the wafer.
FTIR and 4 for this grown epitaxial film
As a result of measuring the film thickness and the resistivity by the probe method, the film thickness uniformity and the resistivity uniformity were good in the case of the present example as well as the first example. Further, the profile of important dopant impurities (carrier concentration profile measured in the direction perpendicular to the substrate surface) in a thin epitaxial film (2 μm) as in this example was measured. As a result, as shown in FIG. 9, a sharp concentration change was observed at the epitaxial-substrate interface (impurity transition width Δt was small), and a constant concentration could be maintained in the epitaxial film. Further, comparing the carrier concentration profile of the epitaxial film grown by the method of the present invention with that by the conventional method, the impurity transition width Δt of the conventional method is 1.3 μm, whereas the carrier transition profile of the conventional method is 1.3 μm. Δt was 0.5 μm, and the impurity profile was significantly improved by this growth method. Furthermore, it was confirmed that in the conventional method, the impurity concentration in the epitaxial film gradually decreased toward the surface of the epitaxial film, but it was almost constant in the case of the present invention.

A third embodiment described below relates to a technique for growing a Si _1-x Ge _x single crystal thin film by the method of the present invention. This Si _1-x Ge _x single crystal thin film is expected to be applied as a base material of a hetero bipolar transistor (HBT), which is promising as an ultra-high speed LSI. Then, this epitaxial growth was performed using the same vapor phase growth apparatus as in the first embodiment. But S
In i _1-x Ge _x growth, the film forming temperature is required to be lower than that in Si epitaxial growth. Therefore, a load lock chamber is provided in the vapor phase growth apparatus described above, and a device compatible with high vacuum is used by using a turbo pump. did. In addition, the reaction gas is purified to make the inside of the growth chamber highly clean, and the impurity level (H
₂ O level) was set to 10 ppb or less.

First, a P-type Si wafer having a boron-doped resistivity of 10 Ω-cm, which is a substrate to be grown, was washed with a mixed solution of sulfuric acid and hydrogen peroxide, and then treated with 1% hydrofluoric acid for 30 seconds to be formed on the surface of the substrate. The natural oxide film was removed. Next, after washing with water for 1 minute, the substrate crystal was mounted on the wafer holder while purging with nitrogen gas. At the same time, the solid source Ge
The single crystal substrate was also mounted on the wafer holder. Next, this wafer holder was introduced into the load lock chamber of the apparatus, the atmosphere in the load lock chamber was sufficiently replaced with nitrogen, the gate valves of the load lock chamber and the growth chamber were released, and the substrate crystal was moved to the growth chamber. It was Then, the substrate temperature was set to 600 ° C., and the degree of vacuum in the growth chamber was set to 1 × 10 ⁻⁸ To using a high vacuum exhaust system.
rr. Next, the growth exhaust system was switched to, the degree of vacuum in the growth chamber was set to 5 Torr, the substrate holder was rotated at a speed of 5 revolutions per minute, and the H ₂ 5 SLM, Si was supplied from the first nozzle tube.
H ₂ Cl ₂ 200 SCCM is supplied onto the wafer surface other than the solid source, and at the same time, H ₂ 5 SLM and HCl 200 SCCM are supplied from the second nozzle tube onto the solid source for 10 minutes to form a Si _1-x Ge _x thin film of 500 A. I grew it.

When the surface of the thin film thus formed was observed by a scanning electron microscope (SEM), a very flat surface morphology was observed and the thin film thus formed had good crystallinity. Also, in the observation with this transmission electron microscope, lattice defects such as misfit dislocations were not observed. Further, as a result of measuring the alloy ratio of the Si _1-x Ge _x thin film by Rutherford backscattering analysis (RBS), the alloy ratio (x) under the present growth conditions was 0.2. The same effect was obtained even when an amorphous Ge substrate was used as the substrate for the solid source.

FIG. 10 shows Si _1-x Ge against HCl flow rate.
It is a graph which shows the alloy ratio of _x film _| membrane.

Next, in order to investigate the controllability of the Si / Ge alloy ratio, a growth experiment was attempted while changing the flow rate of the HCl gas as the solid source etching gas. The growth conditions other than the HCl flow rate were the same as the growth described above. As a result, as shown in FIG. 10, the alloy ratio (x) increases almost in proportion to the increase in the HCl flow rate. As described above, it was confirmed that the Si _1-x Ge _x thin film having good crystallinity can be grown by controlling the alloy ratio by this growth method.

The fourth embodiment described below relates to a technique for growing a Si _1-x Ge _x polycrystalline thin film by the method of the present invention. This Si _1-x Ge _x polycrystalline thin film is expected to be used as a thin film transistor (TFT) for driving a liquid crystal display element or an amorphous Si optical sensor. Further, the Si _1-x Ge _x polycrystalline thin film is CMO.
Application as a gate electrode of an S device is also under consideration.

This thin film growth was performed using the same vapor phase growth apparatus as used in the third embodiment. First, as in the case of the third embodiment described above, a P-type Si wafer having a boron-doped resistivity of 10 Ω-cm as a growth substrate is washed with a mixed solution of sulfuric acid and hydrogen peroxide, and then a thermal oxide film of about 100 nm is formed. Has grown up. Next, after cleaning this substrate again, it was mounted on a wafer holder together with a Ge single crystal substrate which is a solid source. Then, the growth substrate was moved to the reaction chamber in the same manner as in the third embodiment. As in the third embodiment, the temperature inside the growth chamber was 600 ° C., the degree of vacuum was 5 Torr, the wafer holder was rotated at a speed of 5 revolutions per minute, and the H nozzle was rotated from the first nozzle tube.
_{2 5 SLM, SiH 2 Cl 2} 200 at the same time the SCCM supplied onto the wafer surface except for a solid source second
From nozzle tube onto solid source H ₂ 5 SLM, HCl
Si _1-x Ge by supplying 0.1-3 SLM for 40 minutes
_{The x} thin film was grown to 200 nm. In this example, since the growth of the polycrystalline film was performed, the high vacuum as in the third example was not necessary.

FIG. 11 shows Si _1-x Ge against HCl flow rate.
₇ is a graph showing an alloy ratio of a polycrystalline film of _x . The film thus formed was measured by X-ray photoelectron spectroscopy (XPS), and an experiment was conducted to obtain the alloy ratio (x) of Si and Ge with respect to the HCl flow rate. As a result, as shown in FIG.
It was confirmed that the alloy ratio (x) can be controlled by changing the 1 flow rate.

FIG. 12 is a diagram showing an X-ray diffraction pattern of the Si _1-x Ge _x thin film. In addition, the obtained Si _1-x Ge _x
As a result of measuring an X-ray diffraction pattern on the thin film by the θ-2θ scanning method, as shown in FIG.
It can be seen that it is located between the diffraction angle in the case of i polycrystal and the diffraction angle in the case of Ge polycrystal. This indicates that the obtained polycrystalline thin film is not formed as a mixture of Si polycrystalline and Ge polycrystalline but as an alloy of Si and Ge. Above has dealt with the Si _1-x Ge _x film growth of non-doped, using a Ge crystal doped with P-type or N-type impurity as a solid source, Si _1-x Ge _x of P-type or N-type, respectively It is possible to form a thin film.

[0045]

As described above, according to the present invention, a plurality of substrates (wafers) to be grown are held in a wafer holder in a reaction tube so as to be stacked substantially horizontally at predetermined intervals, and a plurality of reaction gases are provided in the longitudinal direction. A reaction gas is caused to flow from the plurality of nozzle tubes having the emission holes substantially parallel to the respective growth surfaces of the plurality of growth substrates, and N is deposited on the growth substrates by a vapor phase growth method.
As a method for forming a P-type or P-type thin film, a non-doped substrate or a P-type or N-type impurity-doped substrate (fixed source wafer) is used as a film material or a doping source for forming a thin film The wafer is mounted on the wafer holder at the same time as the substrate to be grown, and the reaction gas related to film growth is supplied to the growth substrate and the reaction gas having an etching action is supplied to the solid source. ing. Therefore, as a first effect, it is possible to form a thin film having a uniform alloy ratio, film thickness and resistivity on a large diameter wafer. Further, as a second effect, since the impurity doping amount of the solid source can be reduced, a steep impurity profile can be obtained at the thin film-substrate interface. further,
As a third effect, the resistivity can be easily controlled by changing the HCl flow rate. As a fourth effect, the impurity concentration on the surface of the solid source can be kept constant at all times, so that the solid source is durable and the same solid source can be used for a long time. Fifth, it is safer than using dangerous high pressure gas because of using a solid source.

[Brief description of drawings]

FIG. 1 shows a main part of an embodiment of a vapor phase growth apparatus of the present invention, (a) and (b) showing a wafer holder and a nozzle tube in an inner tube, and (c) a cross section of the inner tube. FIG.

FIG. 2 is a view showing a wafer holder for explaining the first embodiment of the thin film forming method by vapor phase growth of the present invention.

FIG. 3 is a graph showing a film thickness within a wafer surface.

FIG. 4 is a graph showing in-plane resistivity of a wafer.

FIG. 5 is a graph showing the relationship between the flow rate of etching gas and the resistivity of a wafer.

FIG. 6 is a graph showing an impurity concentration distribution measured in the depth direction of an epitaxial film in comparison with the case of a conventional method.

FIG. 7 is a graph showing the resistivity of the epitaxial film for each use of the same solid source.

FIG. 8 is a view showing a wafer holder for explaining a second embodiment of the thin film forming method by vapor phase growth of the present invention.

FIG. 9 is a graph showing the impurity profile with respect to the depth from the epitaxial film surface of the wafer.

FIG. 10 is a graph showing the alloy ratio of the Si _1-x Ge _x film with respect to the HCl flow rate.

FIG. 11 is a graph showing the alloy ratio of the Si _1-x Ge _x polycrystalline film with respect to the HCl flow rate.

FIG. 12 is a diagram showing an X-ray diffraction pattern of a Si _1-x Ge _x thin film.

13A and 13B show an example of a conventional vapor phase growth apparatus. FIG. 13A is a view showing a cross section of a main part, FIG. 13B is a side view of a nozzle tube, and FIG. 13C is a cross sectional view of an inner tube.

FIG. 14 is a diagram showing a depth from a surface of a wafer and an impurity concentration profile.

[Explanation of symbols]

 1 Inner Tube 2 Outer Tube 3 Stand 4 Wafer Holder 5 Wafer 5a, 5b Solid Source Substrate 6 Resistance Heating Furnace 7 Nozzle Tube 7a First Nozzle Tube 7b Second Nozzle Tube 8 Gas Discharge Hole 9 Exhaust Ports 10, 10a, 10b Gas release hole

Claims (5)

[Claims] 1. A wafer holder for accommodating a plurality of growth substrates and a plurality of plate-shaped solid sources doped with impurities in one direction, a reaction tube for accommodating the wafer holder, and a reaction tube in the reaction tube. And a first nozzle tube having a plurality of gas discharge holes for flowing a reaction gas for growth substantially parallel to the surface of the substrate to be grown, and a gas discharge for flowing a gas for etching the solid source substantially parallel to the surface of the solid source. A second nozzle tube having a hole and a vapor phase growth apparatus. 2. A thin film forming method comprising supplying a reaction gas for film growth to the substrate to be grown and supplying a gas for etching the solid source to the solid source. 3. The thin film forming method according to claim 2, wherein the supply of the gas for etching the solid source is a part of a thin film forming process time. 4. The thin film forming method according to claim 2, wherein the solid source is a silicon substrate doped with either N-type or P-type impurities. 5. The thin film formed on the growth substrate is Si
The thin film forming method according to claim 2, wherein the solid source is germanium when the film is a _1-x Ge _x alloy film.