JP3948577B2 - Manufacturing method of semiconductor single crystal thin film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a so-called semiconductor epitaxial wafer by forming a semiconductor single crystal thin film on the surface of a semiconductor substrate.
[0002]
[Prior art]
As the miniaturization and high integration of electronic devices have advanced at a high level as in recent years and the amount of charge handled by devices has decreased, the influence of minute defects in semiconductor substrates has become more prominent. There is a strong need for defect-free products.
A so-called epitaxial wafer in which a semiconductor single crystal thin film is further epitaxially grown on a semiconductor substrate is known as a technique capable of realizing such defect-free in the surface layer portion of the semiconductor substrate. According to the epitaxial growth technology, it is relatively easy to form a steep impurity concentration gradient inside the epitaxial wafer or to form a low concentration layer on top of the high concentration layer. It is essential for the production of barrier diodes.
[0003]
As for the semiconductor single crystal thin film of an epitaxial wafer, further thinning and highly uniform film thickness and resistivity are required with the miniaturization of electronic devices. However, as the size of the device chip increases, the semiconductor substrate becomes larger in diameter and the area of the semiconductor single crystal thin film to be formed is also increasing. Therefore, it is becoming difficult to meet this demand year by year.
As an epitaxial growth apparatus for growing a semiconductor single crystal thin film on a large-diameter semiconductor substrate, a semiconductor substrate horizontal mounting type single wafer epitaxial growth apparatus is mainly used. In Japanese Patent Laid-Open No. 4-233723, as a measure for making the film thickness uniform in such an epitaxial growth apparatus, an elongated hole-like gas inlet provided adjacent to the end of the semiconductor substrate in a plane parallel to the semiconductor substrate is provided. There is disclosed a gas supply manifold that is divided into a plurality of grooves and in which the gas concentration or gas flow rate in each groove can be controlled.
[0004]
By the way, normally, in a reaction vessel of an epitaxial growth apparatus for manufacturing a semiconductor epitaxial wafer, in order to prevent unintended deposition of a semiconductor thin film in a region below a semiconductor substrate placed in the reaction vessel, the epitaxial growth is affected. A gas not supplied, typically the same gas as the carrier gas, is supplied as the purge gas.
FIG. 5 is a configuration example of a conventional general epitaxial vapor phase growth apparatus.
This apparatus has a flat reaction vessel 21 provided with a gas supply port 22 at one end in the longitudinal direction and an exhaust port 23 at the other end, and is located below the reaction vessel 21 for mounting a semiconductor substrate W. A susceptor accommodating portion 24 that accommodates the susceptor 25, a leg portion 30 that is connected to the center of the bottom of the susceptor accommodating portion 24 and allows the rotation shaft 26 of the susceptor 25 to pass therethrough, and a middle portion of the leg portion 30. A rotary assembly 27 connected to the rotary shaft 26 and capable of rotating the rotary shaft 26 in the direction of arrow e, and a first purge gas supply pipe 28 connected to the leg portion 30 for introducing purge gas therein. The second purge gas supply pipe 29 connected to the susceptor accommodating portion 24 for introducing the purge gas therein and arranged outside the ceiling surface of the reaction vessel 21 to uniformly heat the semiconductor substrate W Main components are a plurality of infrared lamps 31 and a radiation thermometer 32 that is disposed outside the bottom surface of the susceptor housing 24 and detects the temperature of the semiconductor substrate W by measuring the temperature of the surface of the susceptor 25. And
[0005]
When a silicon single crystal thin film is grown on the semiconductor substrate W in the above apparatus, for example, H 2 is introduced into the reaction vessel 21 from the gas supply port 22.₂Carrier gas represented by (hydrogen) and SiHCl diluted with this carrier gas_ThreeSource gas such as (trichlorosilane) and B supplied as required₂H₆A reaction gas obtained by mixing with a dopant gas such as is flow-controlled by a mass flow controller (MFC) and then introduced in the direction of arrow a to form a gas flow substantially parallel to the main surface of the semiconductor substrate W. .
The gas supply manifold disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-233723 corresponds to a gas supply port 22 in which the shape of the gas supply port 22 is an elongated hole divided into a plurality of grooves. By controlling the gas flow rate individually for the grooves, a predetermined gas concentration distribution is given in the plane of the semiconductor substrate.
[0006]
On the other hand, in the susceptor accommodating portion 24, for example, H is used as a purge gas.₂After the flow of gas is controlled by a mass flow controller (MFC), the gas is introduced through the first purge gas supply pipe 28 and the second purge gas supply pipe 29. The susceptor accommodating portion 24 has a diameter slightly larger than the diameter of the susceptor 25, and there is a slight annular gap between the inner wall surface and the outer edge of the susceptor 25. Therefore, the purge gas introduced from the first purge gas supply pipe 28 and the second purge gas supply pipe 29 passes through the gap from the susceptor accommodating portion 24 as indicated by arrows b and c, respectively. 21 is reached. The purge gas then merges with the gas stream containing unreacted reaction gas and reaction byproducts, and is exhausted from the exhaust port 23 along the direction of arrow d.
[0007]
The gas flow of the purge gas as described above prevents the reaction gas in the reaction vessel 21 from flowing into the susceptor accommodating portion 24 side, and a polycrystalline silicon thin film is deposited on the inner wall surface of the susceptor accommodating portion 24. Plays a role in preventing.
Prevention of the deposition of the polycrystalline film on the inner wall surface of the susceptor accommodating portion 24 is important for the following two reasons.
One is to improve the film quality of the silicon single crystal thin film by suppressing the particle level in the apparatus, and to improve productivity by reducing the frequency of maintenance of the apparatus as a result.
The other is maintenance of temperature measurement accuracy by the radiation thermometer 32. Since the radiation thermometer 32 calculates the temperature of the semiconductor substrate based on the light emission luminance of the back surface of the susceptor 25 observed through the wall of the susceptor housing portion 24, if the wall of the device becomes clouded due to the deposition of a silicon thin film, the radiation thermometer 32 emits light. This is because the brightness is observed to be lower than actual and the temperature of the semiconductor substrate is erroneously calculated to be low.
[0008]
[Problems to be solved by the invention]
Although it is a purge gas that plays an important role as described above, it has been empirically known that if the flow rate of this purge gas is increased too much, the thickness of the semiconductor single crystal thin film in the semiconductor substrate surface is prevented from being uniform. ing. For this reason, the purge gas flow rate is usually kept to the minimum necessary.
However, depending on the conditions, the uniformity of the film thickness distribution and resistivity distribution of the semiconductor single crystal thin film may be impaired even under a minimum purge gas flow rate. In such a case, if the flow rate of the reaction gas is not changed and the purge gas flow rate is further reduced, an unintended polycrystalline film is deposited on the inner wall surface of the susceptor accommodating portion 24, and the reaction vessel 21. As a result, the productivity decreases due to an increase in the maintenance frequency such as replacement, and the management accuracy of the temperature of the semiconductor substrate by the radiation thermometer 32 decreases.
[0009]
Therefore, the present invention does not cause the deposition of the polycrystalline film on the inner wall surface of the susceptor accommodating portion 24, and at the same time, achieves a good film thickness distribution and resistivity distribution of the semiconductor single crystal thin film on the surface of the semiconductor substrate. The object is to provide a method that makes it possible.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventors have conducted a hydrodynamic analysis on the influence of the purge gas supplied to the susceptor housing portion 24 on the reaction gas concentration in the reaction vessel 21, particularly in the vicinity of the surface of the semiconductor substrate. went. As a result, even if the source gas is supplied so as to have a predetermined concentration distribution in the surface of the semiconductor substrate, the reaction gas concentration on the outer peripheral side of the semiconductor substrate mainly varies depending on the purge gas depending on the flow rate of the purge gas. I found out.
In addition, when the silane-based gas is used as the source gas, the present inventors can obtain a uniform film thickness distribution by setting the source gas concentration relatively higher in the peripheral portion than in the central portion of the semiconductor substrate. Furthermore, it has been found that the resistivity distribution can be made highly uniform by removing the natural oxide film and the deposited organic film on the main surface of the silicon-based semiconductor substrate at low temperatures.
[0011]
The method for manufacturing a semiconductor single crystal thin film of the present invention is proposed based on such knowledge, and the source gas involved in the formation of the semiconductor single crystal thin film has a predetermined concentration distribution along the diameter direction of the semiconductor substrate. Thus, the concentration distribution is optimized in accordance with the flow rate of the purge gas when being supplied in a direction substantially parallel to the main surface of the semiconductor substrate.
At this time, it is also preferable to optimize the total flow rate of the reaction gas according to the flow rate of the purge gas together with the concentration distribution of the source gas.
[0012]
As a practical method for creating the concentration distribution of the source gas as described above, the semiconductor substrate is placed on a susceptor accommodated in a susceptor accommodating portion located below the reaction vessel, and the purge gas is After being introduced into the susceptor housing portion, the reaction gas is merged with the reaction gas in the reaction vessel from the back side of the semiconductor substrate via the outer edge of the semiconductor substrate, and the concentration distribution of the source gas is determined by the width of the reaction vessel. It is convenient to independently set the concentration of the source gas for a plurality of gas supply ports arranged along the direction.
It is important to adjust the flow rate of the purge gas at this time to a flow rate that can suppress the deposition of the semiconductor polycrystalline film on the inner wall surface of the susceptor housing.
The concentration distribution of the source gas is set so that the concentration is relatively low in the central portion in the width direction of the reaction vessel and relatively high in the peripheral portion in the width direction. This is effective in canceling out the dilution effect caused by.
[0013]
When a silicon-based semiconductor substrate is used as the semiconductor substrate and a silane-based gas is used as the source gas, the silicon single crystal thin film can be epitaxially grown. At this time, as a pretreatment prior to the growth of the semiconductor single crystal thin film, HF and H in a temperature range of 0 ° C. or more and less than 100 ° C. are applied to one main surface of the silicon-based semiconductor substrate.₂Of natural oxide film using a mixed gas of HCl and HCl and H in a temperature range of 500 ° C. or higher and lower than 800 ° C.₂When the attached organic substances are removed in this order using the mixed gas, an extremely uniform silicon single crystal thin film can be grown in the next step.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the concentration distribution of the source gas can be achieved by setting the concentration of the source gas independently for a plurality of gas supply ports arranged along the width direction of the reaction vessel. Such a gas supply method can be realized by using, for example, an epitaxial vapor phase growth apparatus as shown in FIG.
[0015]
This apparatus has a flat reaction vessel 1 provided with a gas supply pipe 2 at one end in the longitudinal direction and an exhaust port 3 at the other end, and is positioned below the reaction vessel 1 for mounting a semiconductor substrate W. A susceptor accommodating portion 4 that accommodates the susceptor 5, a leg portion 10 that is connected to the center of the bottom portion of the susceptor accommodating portion 4 and through which the rotating shaft 6 of the susceptor 5 is inserted, and a middle portion of the leg portion 10 A rotary assembly 7 connected to the rotary shaft 6 and capable of rotating the rotary shaft 6 in the direction of arrow G; a first purge gas supply pipe 8 connected to the leg portion 10 for introducing purge gas therein; In order to detect the temperature of the semiconductor substrate W, the second purge gas supply pipe 9 is connected to the susceptor accommodating portion 4 to introduce a purge gas into the susceptor accommodating portion 4 and is disposed outside the bottom surface side of the susceptor accommodating portion 4. The main structure of the radiation thermometer 11 As an element.
[0016]
The width direction of the reaction vessel 1, that is, the length in the short direction is selected to be slightly larger than the diameter of the semiconductor substrate W. As a result, the gas flow in the reaction vessel 1 passes along the main surface of the semiconductor substrate W in an approximately laminar flow state. Assuming processing for a semiconductor substrate W having a diameter of 300 mm, the width of the reaction vessel 1 is set to about 380 mm, for example.
A plurality of infrared lamps for uniformly heating the semiconductor substrate W are arranged outside the reaction vessel 1 on the ceiling surface side. Here, in order to avoid complication, the illustration is omitted, Only the incident direction is indicated by an arrow L. An infrared lamp for heating the semiconductor substrate W may be arranged outside the reaction container 1 on the bottom side.
[0017]
The gas supply pipe 2 has, for example, a flow path divided into three in parallel, and the end of each flow path, that is, the open end connected to the reaction vessel 1 is flat along the width direction of the reaction vessel 1. The gas inlets 2a, 2b and 2c have rectangular shapes. In the illustrated example, the central gas inlet 2b occupies 2/3 of the entire opening area, and the left and right gas inlets 2a, 2c occupy 1/6 each. The gases released from the gas inlets 2a, 2b, and 2c form a gas flow substantially parallel to the main surface of the semiconductor substrate W as indicated by arrows A, B, and C, respectively. Flows toward the exhaust port 3.
[0018]
FIG. 1 schematically shows two gas supply systems assuming epitaxial growth of a silicon single crystal thin film on a silicon single crystal substrate.
One of them is diborane (B₂H₆), SiHCl as the source gas_Three, HCl for pretreatment gas, and H for carrier gas₂Are the first gas supply systems 12A, 12B, 12C. B₂H₆Is a dopant for growing a p-type silicon single crystal thin film. Further, HCl gas is a gas for removing adhering organic substances on the surface of the silicon single crystal substrate prior to epitaxial growth.₂Supplied in a diluted state. This pretreatment using HCl gas will be described later in Example 2.
The first gas supply systems 12A, 12B, and 12C use a mass flow controller (MFC) group 13A, 13B, and 13C provided independently to adjust a mixed gas, that is, a reaction gas having a composition according to the purpose. The reaction gas is supplied into the reaction vessel 1 from the gas inlets 2a, 2b, and 2c at desired flow rates, respectively.
[0019]
In addition, as the source gas for forming the silicon single crystal thin film, the above-mentioned SiHCl_ThreeBesides, various silane-based gases can be used, for example, SiH_Four, SiH₂Cl₂, SiCl_FourAnd monosilane derivatives such as disilane and trisilane derivatives. Here, when disilane or trisilane is used, low temperature growth is possible as compared with the case of using a monosilane derivative.
Moreover, as a dopant, said B₂H₆In addition, phosphine (PH_Three) And other known chemical substances can be used.
[0020]
On the other hand, the second gas supply system 14 converts hydrogen fluoride (HF) into H.₂This is a system for diluting and supplying with gas. This HF is used to remove the natural oxide film on the surface of the silicon single crystal substrate prior to epitaxial growth. This preprocessing using HF will be described later in Example 2. Although HF is a liquid at normal temperature, the vapor pressure is high and vaporizes easily.₂And supplied to the reaction vessel 1.
[0021]
In the susceptor accommodating portion 4 of this apparatus, for example, H is used as a purge gas.₂Gases are introduced from the first purge gas supply pipe 8 and the second purge gas supply pipe 9 through flow control by the MFCs 17 and 18, respectively. The susceptor accommodating portion 4 has a diameter larger than the diameter of the susceptor 5, and a slight annular gap exists between the inner wall surface and the outer edge of the susceptor 25. The width of this gap was 5 mm, for example. H introduced from the first purge gas supply pipe 8₂As shown by an arrow E, the gas passes through the inside of the rotary assembly 7 and the leg 10 and reaches the reaction vessel 1 through the gap, and is exhausted from the exhaust port 3 as shown by an arrow D. Further, H introduced from the second purge gas supply pipe 9₂As shown by the arrow F, the gas also passes through the gap and reaches the reaction vessel 1 and is similarly exhausted.
[0022]
In such an apparatus configuration, since the lowering of the source gas concentration due to the dilution effect of the purge gas is predicted, particularly in the outer peripheral portion of the semiconductor substrate W, the concentration distribution of the source gas is relative to the central portion of the semiconductor substrate in the present invention. It is preferable to set it to be relatively low and relatively high at the outer peripheral portion.
[0023]
By the way, it is known that the success or failure of the epitaxial growth largely depends on the surface state of the semiconductor substrate. In particular, when a silicon single crystal thin film is epitaxially grown on a silicon single crystal substrate, it is necessary to sufficiently remove and clean a natural oxide film and attached organic substances on the surface of the silicon single crystal substrate. As a cleaning method, first, HF and H in a temperature range of 0 ° C. or more and less than 100 ° C.₂After removing the natural oxide film using a mixed gas (HF mixed gas), HCl and H in a temperature range of 500 ° C. or higher and lower than 800 ° C.₂It is extremely preferable to remove the adhering organic substances using the mixed gas (HCl mixed gas).
The HF concentration in the HF mixed gas is preferably about 0.5% or more. If it is less than 0.5%, the removal rate of the natural oxide film is remarkably reduced. On the other hand, there is no great difference in the time required for removing the natural oxide film at 1 to 100%.
Further, it is preferable that the treatment time with the HF mixed gas be in the range of about 0.5 to 5 minutes. If the time is shorter than 0.5 minutes, the natural oxide film is not sufficiently removed, and if the time is longer than 5 minutes, there is almost no difference in effect, which causes a decrease in throughput. In practice, about 3 minutes is sufficient.
[0024]
The above-mentioned method for removing the natural oxide film was proposed by the applicant of the present invention on the basis of another research result, and the water originally adsorbed on the natural oxide film is used as a reaction initiation catalyst at a low temperature. In this method, the natural oxide film is removed. If the temperature is lower than 0 ° C., the natural oxide film may not be removed, or the etching reaction rate may decrease and the throughput may be reduced. Conversely, if the temperature is higher than 100 ° C., the natural oxide film may be removed. Since the sorbed moisture is desorbed and the reaction initiation catalyst disappears, the etching reaction does not proceed.
On the other hand, if the temperature when removing the adhering organic substance with the HCl mixed gas is 500 ° C. or less, the removal does not proceed. Is big. The concentration of the HCl mixed gas is preferably about 0.1 to 10%. If it is less than 0.1%, the effect of removing adhering organic matter is small, and if it is 10% or more, minute irregularities may occur on the surface of the silicon single crystal substrate. The treatment time with the HCl mixed gas is preferably in the range of about 1 second to 10 minutes. Adhering organic substances are not sufficiently removed in a time shorter than 1 second, and if the time is longer than 10 minutes, there is almost no difference in effect, which causes a decrease in throughput.
[0025]
【Example】
Hereinafter, specific examples of the present invention will be described.
[0026]
Example 1
In this example, in the epitaxial growth of a non-doped silicon single crystal thin film using the epitaxial vapor phase growth apparatus shown in FIG.₂SiHCl from the central gas inlet 2b and the left and right gas inlets 2a, 2c with a constant gas flow rate_ThreeThe change in film thickness distribution due to the difference in gas supply concentration ratio was investigated.
The single crystal substrate W used is a p-type low resistance substrate (resistivity = 0.01 Ω · cm) made of silicon and having a diameter of 300 mm.
In this embodiment, the pressure in the reaction vessel 1 is always maintained at 1 atm throughout the process, and the total flow rate of the purge gas introduced from the first purge gas supply pipe 8 and the second purge gas supply pipe 9 at this time. Was always 16 liters / minute.
[0027]
First, the pretreatment of the semiconductor substrate W was performed. That is, the semiconductor substrate W is placed on the susceptor 5 and the first gas supply system 12A, 12B, 12C is used to make the H₂Gas was introduced. In this state, an infrared lamp (not shown) was energized to raise the temperature of the semiconductor substrate W to 1100 ° C. and held at that temperature for 1 minute. Thereby, the silicon oxide film and organic substances adhering to the surface of the silicon single crystal substrate were reduced and removed.
[0028]
Next, the temperature of the semiconductor substrate W is adjusted to 1000 ° C. by adjusting the amount of energization of the infrared lamp, and the reaction gas, SiHCl, is immediately generated._ThreeAnd H₂The mixed gas was introduced from the gas introduction pipe 2 for 1 minute. The composition of the mixed gas is H₂SiHCl 12 g / min for 75 liters / min of gas_ThreeIt was set as the composition which added.
Here, Cl from the central gas inlet 2b and the left and right gas inlets 2a and 2c._ThreeSupply ratio (hereinafter referred to as “left: center: right”) is left: center: right = 1: 1: 1, left: center: right = 4: 1: 4, In addition, three experiments were conducted when the same concentration was applied only to the left and right, that is, left: center: right = 1: 0: 1. At this time, the amount of reaction gas supplied to each inlet was controlled using the MFC groups 13A, 13B, and 13C so that the flow velocity of the mixed gas flowing out from each gas inlet 2a, 2b, 2c was uniform.
After the film formation for 1 minute is finished, the infrared lamp is turned off and at the same time SiHCl_ThreeIs stopped, H₂With only the gas flowing, the temperature of the substrate was lowered to room temperature and taken out of the reaction vessel 1. What is obtained is an epitaxial wafer in which a silicon single crystal thin film is formed on a silicon single crystal substrate.
[0029]
FIG. 2 shows the above three types of SiHCl._ThreeThe measurement result of the film thickness distribution in gas supply concentration ratio is shown. In the figure, the horizontal axis represents the distance (mm) from the epitaxial wafer center, and the vertical axis represents the growth rate (μm / min) of the non-doped silicon single crystal thin film. This growth rate is a direct indicator of the film thickness distribution. That is, the film thickness is thin at a place where the growth rate is low, and the film thickness is thick at a place where the growth rate is high. In addition, the result in the case of left: center: right = 1: 1: 1 is graph I, the result in case of left: center: right = 4: 1: 4 is graph II, and the case of only left and right, that is, left: center : Right = 1: 0: 1 The results are shown in graph III.
SiHCl from the center and left and right_ThreeWhen the supply concentration ratio is uniform (graph I), the growth rate is remarkably reduced on the outer peripheral side of the epitaxial wafer, and when supplied from only the left and right sides (graph III), the growth rate at the center of the epitaxial wafer is Decreased significantly.
On the other hand, in the case of left: center: right = 4: 1: 4 (graph II), the growth rate is uniform in the plane of the epitaxial wafer, and a uniform film thickness distribution is achieved. Yes. At this time, a slight amount of polycrystalline silicon was deposited on the back surface of the susceptor 5, but the deposition range remained within a range of 1 mm from the outer peripheral end toward the inside.
[0030]
In the present embodiment, the best result is obtained when the supply gas source concentration ratio from the central gas inlet 2b and the left and right gas inlets 2a and 2c is left: center: right = 4: 1: 4. However, the supply concentration ratio that yields the best results varies depending on conditions such as the width of the gap formed between the susceptor housing 4 and the susceptor 5 and the flow rate of the purge gas. However, since the concentration of the source gas is reduced by the purge gas in the outer peripheral portion of the semiconductor substrate W, the concentration distribution of the source gas is relatively low in the central portion of the semiconductor substrate W and relatively high in the outer peripheral portion. It is important to optimize the supply concentration ratio so that the concentration is the same.
[0031]
Note that when the purge gas flow rate on the lower side of the semiconductor substrate W is reduced to 2 liters / minute or less, a uniform film thickness distribution is obtained even when left: center: right = 1: 1: 1. Further, deposition of polycrystalline silicon occurred over the entire inner wall of the susceptor accommodating portion 4, which hindered temperature measurement by the radiation thermometer 11.
From the above results, if the concentration distribution of the source gas is optimized as in the present invention, the growth rate on the epitaxial wafer surface becomes uniform even if the purge gas flow rate is large. It is obvious that unnecessary deposition on the back side of the epitaxial wafer can be surely prevented.
[0032]
Example 2
In this example, p⁺In the epitaxial growth on silicon-type silicon single crystal substrate, the change of resistivity distribution due to the difference in pretreatment method was examined.
The single crystal substrate W used was a 300 mm diameter p made of silicon.⁺Type low resistance substrate (resistivity = 0.01 Ω · cm).
In this embodiment, H is used as the reactive gas.₂SiHCl 12 g / min for 75 liters / min of gas_ThreeAnd a very small amount of B₂H₆The one to which was added was used. Other conditions, that is, the pressure in the reaction vessel 1 (1 atm) and the total flow rate of purge gas (16 liters / min) are all the same as those in the first embodiment. SiHCl_ThreeAnd B₂H₆And H₂The supply gas concentration ratio of the reaction gas obtained by mixing was adjusted to left: center: right = 4: 1: 4 in response to good results obtained in Example 1.
[0033]
The pretreatment of the semiconductor substrate W was performed by the following two methods.
The first method is the same as in Example 1 except that H₂Heat treatment is performed at 1100 ° C. for 1 minute in a gas atmosphere.
The second method uses the second gas supply system 14 to convert HF to H.₂The HF mixed gas diluted to 1% is supplied at 23 ° C. for 3 minutes, and then the first gas supply system 12A, 12B, 12C₂The HCl mixed gas diluted to 1% is supplied at 700 ° C. for 1 minute.
Thereafter, a p-type silicon single crystal thin film was epitaxially grown in the same manner as in Example 1.
[0034]
FIG. 3 shows the measurement results of the resistivity distribution of the p-type silicon single crystal thin film formed through the two pretreatments. In the figure, the horizontal axis represents the distance (mm) from the epitaxial wafer center, and the vertical axis represents the resistivity (Ω · cm) of the p-type silicon single crystal thin film. In addition, the result when the pretreatment is performed by the first method is represented by a graph IV, and the result when the pretreatment is performed by the second method is represented by a graph V.
In the case where the pretreatment was performed by the first method (graph IV), the film thickness distribution was uniform, but the resistivity decreased within a range of 3 to 5 mm on the outer peripheral side. This tendency cannot be eliminated by changing the supply concentration ratio of the source gas on the left: center: right, and the uniformity of the resistivity distribution sets the target value of the resistivity high (ie, the doping amount) It was more difficult to reduce.
On the other hand, when the pretreatment is performed by the second method (graph V), the film thickness distribution is uniform, and the resistivity is not lowered at the outer peripheral portion of the epitaxial wafer, and the whole is almost uniform. Resistivity distribution was achieved.
[0035]
The difference in the resistivity distribution described above is due to the heating temperature of the semiconductor substrate W during the pretreatment.
In the first method, since the pretreatment temperature is high, boron atoms in the low-resistance substrate are diffused outward into the gas phase and are carried by the purge gas and stay on the outer periphery of the semiconductor substrate W. This boron atom is SiHCl_ThreeIs still in the gas phase even when the epitaxial growth is started and this is taken into the film during the epitaxial growth, so that a low resistance region is formed on the outer periphery of the silicon single crystal thin film. is there.
In contrast, the second method has a lower pretreatment temperature than the first method.⁺The vaporization of boron, which is a dopant atom of the type low resistivity substrate, into the gas phase can be effectively suppressed. Accordingly, it has been found that the dopant concentration in the gas phase is made uniform, and thereby the resistivity distribution of the silicon single crystal thin film is made uniform.
[0036]
Example 3
In this example, changes in the film thickness distribution due to the difference in flow rate ratio between the carrier gas and the purge gas, which dominate the reaction gas, were studied in the epitaxial growth of the non-doped silicon single crystal thin film.
The used semiconductor substrate W is a 300 mm diameter p made of silicon.⁺Type low resistance substrate (resistivity = 0.01 Ω · cm).
As a reaction gas, H₂SiHCl 12 g / min per 75 liters / min of gas_ThreeAdded SiHCl_ThreeA mixed gas was used. SiHCl_ThreeThe gas supply concentration ratio was adjusted to left: center: right = 4: 1: 4 in response to good results obtained in Example 1.
The pressure in the reaction vessel 1 was always 1 atm.
Furthermore, the pretreatment was in accordance with the second condition described in Example 2.
[0037]
Epitaxial growth was performed based on the following combinations of gas flow VI to IX. However, in this embodiment, the flow rate of the reaction gas is H₂It is regarded as the gas flow rate and this is the carrier H₂I will call it. The purge gas flow is corresponding to the purge H₂Is written.
VI: Career H₂= 50 l / min, purge H₂None
VII: Carrier H₂= 75 liters / minute, purge H₂= 32 liters / minute
VIII: Carrier H₂= 50 l / min, purge H₂= 16 liters / minute
IX: Carrier H₂= 100 l / min, purge H₂= 16 liters / minute
[0038]
FIG. 4 shows the measurement results of the film thickness distribution for the above four combinations of flow rates. In the figure, the horizontal axis represents the distance (mm) from the epitaxial wafer center, and the vertical axis represents the growth rate (μm / min) of the non-doped silicon single crystal thin film. This growth rate is a direct indicator of the film thickness distribution. Further, the names VI to IX of the respective graphs correspond to the above combinations of flow rates.
In the case of graph VI, the thickness of the silicon single crystal thin film was increased on the outer peripheral side of the epitaxial wafer. Further, since there was no purge gas flow, deposition of polycrystalline silicon occurred over the entire inner wall of the susceptor housing 4.
In graph VII, carrier H₂Purge H with the same as graph VI₂Carrier H at once₂Was increased to nearly half of the₂The ratio of SiHC is too high, and SiHCl is formed on the outer peripheral side of the epitaxial wafer._ThreeAs a result, the film thickness was significantly reduced on the outer peripheral side. However, the deposition of polycrystalline silicon in the susceptor housing 4 was not observed.
[0039]
In graph VIII, carrier H is higher than in graph VII.₂Purge H₂Overall, but the purge H₂Is career H₂Therefore, the tendency for the film thickness to decrease on the outer peripheral side was the same as before. However, deposition of polycrystalline silicon in the susceptor housing 4 was not observed.
In graph IX, purge H₂Is the same as Graph VIII₂When the flow rate was increased twice as much as that, the film thickness was slightly increased at the outer peripheral portion, but an almost good film thickness distribution was achieved. Further, silicon deposition on the susceptor housing 4 was only slightly recognized within a range of about 1 mm inward from the outer peripheral edge on the back surface of the susceptor 5.
[0040]
Thus, if the purge gas flow rate is relatively insufficient, the film thickness tends to increase on the outer peripheral side due to the thermal diffusion phenomenon of the reaction gas. Conversely, if the purge gas flow rate is relatively excessive, the reaction gas is diluted. Therefore, the film thickness on the outer peripheral side tends to decrease. In this example, it was confirmed that the flow rate ratio between the reaction gas and the purge gas had a great influence on the film thickness distribution of the semiconductor single crystal thin film, and the importance and effectiveness of controlling the concentration distribution of the source gas as in the present invention was confirmed. Sex has been demonstrated.
[0041]
As mentioned above, although this invention was demonstrated based on three specific Examples, this invention is not limited to these Examples at all. For example, as an epitaxial vapor phase growth apparatus used in the present invention, not only a single wafer type apparatus as shown in FIG. 1 but also an apparatus of a type for simultaneously processing a plurality of semiconductor substrates can be used.
When vapor-phase-growing a silicon single crystal thin film on a silicon single crystal substrate using a silane-based gas, the epitaxial growth temperature is set to 1000 ° C., but it may be slightly shifted from this. However, if it is 800 ° C. or lower, the growth rate is too low to be industrially useful, and if it exceeds 1200 ° C., the semiconductor substrate is deformed due to thermal stress, which is not appropriate.
In the above embodiment, the case where a non-doped or p-type silicon single crystal thin film is formed as the semiconductor single crystal thin film has been described. However, an n-type silicon single crystal thin film may be used. The film is not limited to a thin film, and may be a germanium-based semiconductor thin film.
Furthermore, the present invention can also be applied to the formation of a single crystal thin film of a compound semiconductor by MOCVD.
[0042]
【The invention's effect】
As apparent from the above description, according to the present invention, the concentration distribution of the source gas is adjusted according to the flow rate of the purge gas, so that the uniformity of the film thickness and resistivity distribution of the semiconductor single crystal thin film is not impaired. Unintentional deposition on the back side of the epitaxial wafer can be prevented. The concentration distribution of the source gas can be easily and accurately achieved by independently setting the gas flow rate for a plurality of gas supply ports arranged along the width direction of the reaction vessel.
By setting the concentration distribution relatively low at the central portion in the width direction of the reaction vessel and relatively high at the outer peripheral portion, it becomes easy to make the film thickness and resistivity distribution uniform.
[0043]
In the present invention, by using a silicon single crystal substrate as a semiconductor substrate and a gas mainly containing a silane-based gas as the reaction gas, it is possible to epitaxially grow a very good silicon single crystal thin film. Prior to the epitaxial growth of the silicon single crystal thin film, the uniformity of the resistivity distribution can be improved by removing the silicon oxide film and the organic film in advance in a temperature range lower than the growth temperature.
Therefore, the present invention greatly contributes to manufacturing an epitaxial semiconductor substrate indispensable for forming a certain kind of fine electronic device with excellent quality and productivity.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a configuration example of an epitaxial vapor phase growth apparatus used in the present invention.
FIG. 2 shows SiHCl in epitaxial growth of a non-doped silicon single crystal thin film._ThreeIt is a graph showing the change of the film thickness distribution by the difference in concentration distribution of gas.
FIG. 3 is a graph showing a change in resistivity distribution due to a difference in a pretreatment method in epitaxial growth of a p-type silicon single crystal thin film.
FIG. 4 shows the carrier H in the epitaxial growth of a non-doped silicon single crystal thin film.₂And purge H₂It is a graph showing the change of the film thickness distribution by the difference in flow rate ratio.
FIG. 5 is a schematic cross-sectional view showing a configuration example of a conventional general epitaxial vapor phase growth apparatus.
[Explanation of symbols]
1 reaction vessel
2 Gas introduction pipe
2a, 2c Gas inlet (left and right)
2b Gas inlet (center)
3 Exhaust port
4 Susceptor housing
5 Susceptors
6 Rotating shaft
7 Rotating assembly
8 First purge gas supply pipe
9 Second purge gas supply pipe
10 Radiation thermometer
12A, 12B, 12C First gas supply system
13A, 13B, 13C, 15 MFC group
14 Second gas supply system
W Semiconductor substrate

Claims (4)

The unidirectional flow of the reaction gas containing the source gas is flowed with respect to the main surface of the semiconductor substrate so that the source gas involved in the formation of the semiconductor single crystal thin film has a predetermined concentration distribution along the diameter direction of the semiconductor substrate. After the semiconductor single crystal thin film is grown on the main surface while being formed substantially in parallel, the purge gas supplied from the back side of the semiconductor substrate is merged with the reaction gas via the outer edge of the semiconductor substrate. A method for producing a semiconductor single crystal thin film to be exhausted, comprising:
The semiconductor substrate is placed on a susceptor accommodated in a susceptor accommodating portion located on the lower side of the reaction vessel, and after introducing the purge gas into the susceptor accommodating portion, the semiconductor substrate is introduced from the back side of the semiconductor substrate. The reaction gas is joined in the reaction vessel via the outer edge of
While adjusting the flow rate of the purge gas to a flow rate that can suppress the deposition of the semiconductor polycrystalline film on the inner wall surface of the susceptor accommodating portion,
Concentration distribution of the raw material gas with respect to a plurality of gas supply ports arranged along the width direction of the reaction vessel, the concentration of the raw material gas at a relatively low concentration at the center portion in the width direction of the reaction vessel, and A method for producing a semiconductor single crystal thin film, wherein the peripheral portion in the width direction is set to have a relatively high concentration .   2. The method for producing a semiconductor single crystal thin film according to claim 1, wherein the total flow rate of the reaction gas is optimized in accordance with the flow rate of the purge gas together with the concentration distribution of the source gas. 2. The method of manufacturing a semiconductor single crystal thin film according to claim 1 , wherein a silicon-based semiconductor substrate is used as the semiconductor substrate, and a silane-based gas is used as the source gas. Prior to the growth of the semiconductor single crystal thin film, removal of a natural oxide film using a mixed gas of HF and H ₂ in a temperature range of 0 ° C. or higher and lower than 100 ° C. with respect to one main surface of the silicon-based semiconductor substrate; 4. The semiconductor unit according to claim 3 , wherein the main surface is cleaned by performing removal of adhering organic substances using a mixed gas of HCl and H ₂ in this order in a temperature range of 500 ° C. or higher and lower than 800 ° C. A method for producing a crystalline thin film.

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