JPH05243161A - Vapor growth device and method of growing epitaxial film - Google Patents

Abstract

PURPOSE:To realize a vapor growth device and an epitaxial film growth method, where a film uniform in thickness and resistivity is formed on a wafer of large diameter. CONSTITUTION:A nozzle pipe is composed of a first nozzle pipe 7A of high pure quartz used for feeding silane reactive gas for the growth of film and a second nozzle pipe 7B of material which contains P or N-type impurities which serve as a solid doping an epitaxial film at a certain concentration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth apparatus and an epitaxial film growth method.

[0002]

2. Description of the Related Art Thin film forming technology has become an important technology in many industrial fields such as semiconductor, metal or ceramics industries. Particularly in the manufacturing process of a semiconductor device using a silicon wafer, a technique for uniformly growing an epitaxial film doped with P-type or N-type impurities or a polycrystalline silicon film on the wafer surface is required. Conventionally,
In response to this demand, a chemical vapor deposition (CVD) method, which has a high throughput and can obtain a high quality film, is industrially used, and many apparatuses have been developed.

As a CVD apparatus for growing a polycrystalline silicon film which is grown at a relatively low temperature, an LPCVD apparatus using a hot wall type reaction furnace is used.
Nowadays, a vertical furnace is becoming the mainstream because it has less oxygen entrainment during wafer loading and allows easy wafer rotation.
Further, as a CVD apparatus for growing an epitaxial film, a cold wall type reaction furnace called a barrel type or a pancake type, which hardly deposits silicon on a reaction tube, has been conventionally used because epitaxial growth is a high temperature process.

However, these cold wool CVs
In the D device, it is becoming difficult to meet the current requirements in terms of throughput as the diameter of the processed wafer is increased, and recently, various new system devices have been prototyped. For example, Japanese Patent Application Laid-Open No. 63-0086424 proposes a CVD apparatus capable of processing a large-diameter 6-inch wafer in a large amount by a hot wall method using a vertical reaction tube. 8A and 8B are a longitudinal sectional view and a lateral sectional view of this CVD apparatus.

The reaction container has a double structure, and a wafer holder 4 that holds a vacuum and rotates with an outer tube 1 provided on a pedestal 3 is used.
The gas introduction hole 10 of the nozzle tube 7 in the wafer 5 held by
The reaction gas is supplied from. The reaction gas passes through the growth surface of the wafer 5 and is discharged through a large number of gas discharge holes 8 provided in the cylindrical surface of the inner tube 2. In the conventional epitaxial growth, a wafer is heated to 900 to 1200 ° C. under reduced pressure, and a silane-based reaction gas is supplied to the wafer surface using a nozzle tube 7 to grow an epitaxial film. As a method for doping P-type or N-type impurities into the epitaxial film, a gas source method in which a gas source such as PH ₃ , AsH ₃ , B ₂ H ₆ is used for doping, and P-type or N-type for the wafer holder 4 are used. There is a solid source method in which a solid source substrate containing type impurities is mounted and doping is performed by impurities generated during epitaxial growth from this solid source.

[0006]

In order to grow an epitaxial film having a uniform film thickness and resistivity over all the substrates to be grown by the above-mentioned gas source method, various kinds of gases generated by thermal decomposition of the reaction gas are required. It is necessary to uniformly supply the reactive species in the whole growing region.

[0007] SiH ₂ Cl ₂ -H _{2 -} To describe an example of the growth of a silicon epitaxial film using a PH ₃ based reactive gas, SiCl ₂ relating to film growth caused by the thermal decomposition of SiH ₂ Cl ₂ , And reactive gas species such as PH _i (i = 1, 2, 3) generated by the thermal decomposition of PH ₃ must be uniformly supplied to the growth region of all wafers.
For this reason, the flow velocity of the gas ejected from the nozzle tube and the ejection direction are optimized, but SiH ₂ Cl related to film growth is optimized.
_Since the thermal decomposition process of No. _{2 and} the thermal decomposition process of PH ₃ related to doping are different in the decomposition temperature and the like, it is difficult to find a condition that satisfies both the film thickness uniformity and the resistivity uniformity. Also, the recent increase in the diameter of wafers makes this more and more difficult.

In contrast to the gas source doping method described above, the solid source method has an advantage that a large-diameter wafer can grow an epitaxial film having uniform film thickness and resistivity in the plane of the wafer. This is because in the case of the solid source method, the optimization of growth conditions can be focused only on improving the film thickness uniformity. In fact, this way
As shown in FIG. 9, for a 0 mm wafer, an epitaxial film having good uniformity in film thickness and resistivity (± 5% or less in film thickness and resistivity distribution) was obtained.

However, this solid source method also has a problem that a large amount of wafers cannot be processed at one time because of a problem in the resistivity uniformity between wafers, as described below.

That is, in the impurity doping by the solid source method, the dopant or its hydride or chloride evaporated from the solid source as the diffusion source is diffused in the reaction tube and is transported and doped on the wafer surface. Therefore, the dopant concentration in the reaction tube is high in the vicinity of the solid source and gradually decreases as the distance from the source increases. this is,
The result is that the wafer has a low resistivity near the solid source and the resistivity increases as the distance from the source increases.

As described above, according to the conventional CVD method, it is difficult to grow an epitaxial film having a uniform resistivity on a large number of wafers. FIG. 10 shows an experimental investigation of the relationship between the distance from the solid source and the resistivity of the epitaxial film. From FIG. 10, it can be seen that the range of good resistivity uniformity (range of resistivity distribution ± 5% or less) in the conventional CVD method is a region 150 mm from the solid source (15 wafer regions; wafer interval 10 mm). confirmed.

Even in the conventional CVD method, it is possible to make the dopant concentration in the reaction tube uniform by using a plurality of solid source wafers and devising the mounting position on the wafer holder. It is extremely difficult to achieve a perfectly uniform concentration distribution in the tube by means of measures. In addition, increasing the number of wafers mounted on the solid source reduces the number of wafers to be processed, which causes a new problem of lowering the throughput of the apparatus.

[0013]

A vapor phase growth apparatus according to a first aspect of the present invention comprises a vertical reaction tube and a holder provided in the reaction tube for holding a plurality of growth substrates substantially horizontally at predetermined intervals. A plurality of nozzle tubes provided in the reaction tube and having in the longitudinal direction a plurality of gas introduction holes for flowing a reaction gas substantially parallel to the surface of the substrate to be grown, The nozzle tube is composed of a first nozzle tube made of quartz for introducing a silane-based reaction gas and a second nozzle tube serving as a solid source formed of a material containing impurities to be introduced into the epitaxial film. There is something.

In the epitaxial film growth method of the second invention, the silane-based reaction gas relating to film growth is supplied onto the growth surface of the substrate to be grown from the first nozzle tube, and the solid film is supplied from the second nozzle tube. The etching gas for etching the source is supplied in the direction in which the stream line of the etching gas avoids the growth surface of the growth substrate.

It will be described below that the above-mentioned problems can be solved.

The problem with the conventional method is that each processed substrate (wafer)
And a solid source which is an impurity diffusion source are different in distance. If this problem is solved, it becomes possible to grow an epitaxial film having good resistivity uniformity on a large number of wafers. In the vapor phase growth apparatus of the present invention, the solid source as the impurity diffusion source is installed along the longitudinal direction of the reaction tube, that is, along the wafer loading direction. This results in all processed wafers being loaded approximately equidistant from the solid source. As a result, the amount of dopant transported on each wafer surface is made uniform, and the uniformity of resistivity between wafers can be improved.

[0017]

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

FIGS. 1 (a) and 1 (b) are a longitudinal sectional view and a lateral sectional view of a CVD apparatus according to a first embodiment of the present invention. The apparatus configuration excluding a nozzle tube is the conventional one shown in FIG. It is the same as the CVD apparatus of.

That is, in the vapor phase growth apparatus, a reaction tube composed of a vertical outer tube 1 and an inner tube 2 provided on a pedestal 3 and a plurality of wafers 5 provided in the reaction tube are substantially horizontal at predetermined intervals. Wafer holder 4 so as to hold it and first and second nozzle tubes 7 having a plurality of gas introduction holes in the longitudinal direction.
It is mainly composed of A and 7B and a resistance heating furnace 6.

In the first embodiment, in addition to the first nozzle tube 7A made of high-purity quartz for performing such film growth, the second nozzle tube as a solid source for doping impurities is used. 7B, and in particular, the second nozzle tube 7B is formed of As-doped polycrystalline silicon as shown in FIG. And this second nozzle tube 7B
The direction of the gas introduction hole 10 is defined as the direction to avoid the wafer 5. This is to prevent the surface of the wafer 5 from being etched by the etching gas emitted from the second nozzle tube 7B.

The growth of the silicon epitaxial film by the growth apparatus of the first embodiment will be described below. First, as shown in FIG. 3, Sb having a resistivity of 0.01 Ω · cm
Doped N ⁺ type silicon substrate (N1 to N30) and 10Ω ・
cm P-type silicon substrate (P1 to P30) 3 each
0 wafers are alternately mounted (60 wafers in total) on the wafer holder 4,
The temperature inside the reaction tube was 1080 ° C., and the degree of vacuum was 10 Torr. Next, the wafer holder 4 is rotated at a speed of 5 revolutions per minute, and the H ₂ 20SLM, S is supplied from the first nozzle tube 7A.
200 sccm of iH ₂ Cl ₂ is supplied onto the surface of the wafer 5 and at the same time, H _{2 20} SL is supplied to the second nozzle tube 7B.
M and HCl 100 sccm were supplied for 10 minutes to grow an N-type silicon epitaxial film to a thickness of 2 μm. At this time, at the same time that the epitaxial film grows by the silane-based reaction gas supplied from the first nozzle tube 7A,
The second nozzle tube is etched by HCl gas from the inside of the tube so that the As dopant is released from the gas introduction hole 10 into the reaction tube. At this time, the HCl gas release direction,
That is, the streamline of the HCl gas is directed to avoid the wafer 5 to prevent etching of the wafer surface. The As dopant released into the reaction tube is diffused on the surface of the wafer 5 and taken into the epitaxial film.

For the grown epitaxial film, N1 to
Ferry conversion infrared absorption method (FTIR) for N30
Was used to measure the epitaxial film thickness. In addition, P1
For P30, the sheet resistance was measured by the four-point probe method, and then the resistivity was calculated corresponding to N1 to N30. FIG. 4 shows the wafer-to-wafer distribution of the resistivity obtained by the above method in comparison with the case of the conventional CVD apparatus. Conventional CV
In the case of the D apparatus, the range in which the uniformity of ± 5% is obtained is the range of the wafer mounting position of 150 mm (corresponding to 15 wafers), while the CVD apparatus of the present embodiment has a range of 600 mm.
mm (corresponding to 60 wafers). This is C
This means that the throughput of the VD device has improved almost four times.

In the case of the first embodiment as well, there is a tendency that the higher the wafer mounted on the upper part of the wafer holder, the higher the resistivity, which is due to the pressure loss of the carrier gas in the source nozzle tube and HCl. This is due to the decrease in gas concentration. However, this increase in resistivity is much less than that of conventional CVD equipment.

In the first embodiment, the case where one nozzle tube is used as the first nozzle tube 7A for forming a film has been described, but a plurality of nozzle tubes are used for the purpose of improving the film thickness uniformity. Nozzle tube may be used. Also in this case, good resistivity uniformity of the epitaxial film is obtained. In addition, in the first embodiment, the second nozzle tube 7B
As the nozzle tube formed by processing the As-doped polycrystalline silicon material, a nozzle tube in which the inside of a high-purity quartz tube is coated with As-doped polycrystalline silicon may be used. Also in this case, good resistivity uniformity was obtained as in the first embodiment.

FIG. 5 is a sectional view of a second nozzle tube used in the second embodiment of the present invention. The configuration of the apparatus except for this second nozzle tube is the same as that of the first embodiment. The feature of the second nozzle tube in the second embodiment is that the solid source column 11 made of As-doped single crystal silicon is installed inside the quartz nozzle tube 12.

Also in the case of the second embodiment, as shown in FIG. 4, an epitaxial film having good resistivity uniformity was obtained in the 60-sheet region as in the case of the first embodiment. Further, in the case of the second embodiment, there is an advantage that a material that is difficult to process into a nozzle shape, such as single crystal silicon, can be used as a solid source.

Next, as a third embodiment of the present invention, a method for growing an epitaxial film using a vapor phase growth apparatus will be described. The third embodiment is a case where an N type silicon epitaxial film is grown, and the growth apparatus of the first embodiment is used. A silicon substrate having a high-concentration impurity-embedded region on its surface was used as a substrate for growth. This structure is essential for bipolar or Bi-CMOS devices.

First, As ions are implanted into the surface of a boron-doped P-type silicon wafer having a resistivity of 10 Ω · cm at an acceleration voltage of 70 keV and a dose amount of 5 × 10 ¹⁴ cm ⁻² , and an N-type high-concentration buried region is formed in the surface layer. Wafer (B1-B
5) was created. Next, as shown in FIG. 6, this wafer (B1 to B5) and boron-doped resistivity 10 Ω · cm
P type silicon wafers (P101 to P105) and S
b-doped N ⁺ substrate with resistivity of 0.01 Ω · cm (N10
1 to N105) are respectively mounted on the wafer holder 4, the temperature inside the reaction tube is 1080 ° C., and the degree of vacuum is 10 Torr.
And Next, the wafer holder 4 is rotated at a speed of 5 revolutions per minute, and first the H ₂ 20SL is supplied from the first nozzle tube 7A.
200 sccm of M, SiH ₂ Cl ₂ was supplied onto the surface of each wafer for 2 minutes. Next, after stopping the supply of all the gas and evacuating the inside of the reaction tube to the base pressure for 1 minute, the first gas was again supplied.
From nozzle tube 7A of H _{2 20} SLM, SiH ₂ Cl ₂ 2
At the same time as supplying 00 sccm, the second nozzle tube 7B
H _{2 20} SLM and HCl 200 sccm were supplied for 8 minutes to grow an N-type silicon epitaxial film. The reason for delaying the supply of the etching gas to the second nozzle tube 7B, which is a solid source, is that As from the high-concentration embedded region on the surface of the wafer (B1 to B5) having the embedded region.
This is to prevent an increase in transition of impurities at the interface between the epitaxial film and the substrate due to the autodoping phenomenon.

FTI is applied to the grown epitaxial film.
As a result of measuring the film thickness and the resistivity by the R and four-probe methods, the film thickness uniformity and the resistivity uniformity were good in the case of the third embodiment as well as shown in FIG. .. Furthermore, a thin epitaxial film (2 μm) formed in the third embodiment.
The impurity profile (the carrier concentration profile measured in the direction perpendicular to the substrate surface) was measured. This profile generally exhibits a sharp change in concentration at the interface between the epitaxial film and the substrate (impurity transition width Δt is small), and it is desirable to maintain a constant concentration in the epitaxial film.

FIG. 7 shows the carrier concentration profile of the epitaxial film grown in the third embodiment in comparison with that grown by the conventional method. In contrast to the impurity transition width Δt of the conventional method of 1.3 μm, Δt in the present embodiment.
Is 0.5 μm, which means that the impurity profile is significantly improved by this growth method. Further, in the conventional method, the impurity concentration in the epitaxial film gradually decreased toward the surface of the epitaxial film, but in the case of this example, it was confirmed that the impurity profile had an almost constant ideal profile.

[0031]

As described above, according to the present invention, a plurality of substrates to be grown (semiconductor wafers) are held in a wafer holder so as to be stacked substantially horizontally at a predetermined interval in a reaction tube,
A plurality of nozzle tubes having a plurality of reaction gas emission holes in the longitudinal direction are used to flow a reaction gas substantially parallel to the respective growth surfaces of the plurality of growth substrates, and the reaction gas is grown on the growth substrates by a vapor phase growth method. In the epitaxial growth apparatus for forming a P-type or N-type epitaxial film, the plurality of nozzle tubes are made of high-purity quartz for the purpose of supplying a silane-based reaction gas for film growth. A second nozzle tube (solid state) formed of a material containing a P-type or N-type impurity at a predetermined concentration for the purpose of doping the nozzle tube group and the epitaxial film with a P-type or N-type impurity at a predetermined concentration. It is characterized in that it is composed of a group of source nozzle tubes.

Therefore, an epitaxial film having good film thickness uniformity and resistivity uniformity can be grown on a large number of wafers. As a result, there is an effect that the apparatus throughput is significantly improved as compared with the conventional vapor phase growth apparatus.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view and a lateral sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a second nozzle tube of the first embodiment.

FIG. 3 is a diagram showing a wafer mounting position when an epitaxial film is grown using the first embodiment.

FIG. 4 is a diagram showing resistivity distributions of epitaxial films grown in Examples and Conventional Examples.

FIG. 5 is a sectional view of a second nozzle tube according to the second embodiment of the present invention.

FIG. 6 is a diagram showing a wafer mounting position in the second embodiment.

FIG. 7 is a diagram showing an impurity profile at the interface between the epitaxial film grown in the second embodiment and the substrate.

FIG. 8 is a vertical sectional view and a lateral sectional view of a conventional vapor phase growth apparatus.

FIG. 9 is a diagram showing the film thickness and resistivity of an epitaxial film obtained by a conventional device.

FIG. 10 is a diagram showing a film thickness and a resistivity distribution of an epitaxial film obtained by a conventional device.

[Explanation of symbols]

 1 Outer Tube 2 Inner Tube 3 Frame 4 Wafer Holder 5 Wafer 6 Resistance Heating Furnace 7 Nozzle Tube 7A First Nozzle Tube 7B Second Nozzle Tube 8 Gas Discharge Hole 9 Exhaust Port 10 Gas Inlet Hole 11 Solid Source Column 12 High Purity Quartz tube

Claims (7)

[Claims] 1. A vertical reaction tube, a holder provided in the reaction tube for holding a plurality of substrates to be grown substantially horizontally at a predetermined interval, and a holder provided in the reaction tube on the surface of the substrate to be grown. In a vapor phase growth apparatus equipped with a plurality of nozzle tubes having a plurality of gas introduction holes for flowing reaction gas in parallel in a longitudinal direction, the plurality of nozzle tubes are made of quartz for introducing a silane-based reaction gas. And a second nozzle tube which is made of a material containing an impurity to be introduced into the epitaxial film and serves as a solid source. 2. The vapor phase growth apparatus according to claim 1, wherein the second nozzle tube is formed of polycrystalline silicon containing one kind of element among As, P, Sb and B as an impurity. 3. The vapor phase growth apparatus according to claim 1, wherein the second nozzle tube is made of quartz and the surface thereof is covered with a polycrystalline silicon film containing impurities. 4. The vapor phase growth apparatus according to claim 1,
A vapor phase growth apparatus using a quartz nozzle tube in which a solid source containing impurities is installed in an etching gas passage as a second nozzle tube. 5. The vapor phase growth apparatus according to claim 4, wherein the solid source is polycrystalline silicon containing one kind of element among As, P, Sb and B as an impurity. 6. A method for growing an epitaxial film by using one of the vapor phase growth apparatus according to claim 1, wherein a silane-based reaction gas relating to film growth is supplied from the first nozzle tube. An epitaxial film characterized in that an etching gas for supplying a solid source to a growth surface of a growth substrate and etching a solid source is supplied from a second nozzle tube in a direction in which a streamline of the etching gas avoids the growth surface of the growth substrate. How to grow. 7. The method for growing an epitaxial film according to claim 6, wherein the etching gas is supplied to the second nozzle tube within a time when a reaction gas relating to film growth is supplied to the first nozzle tube.