JP3700657B2 - Vapor phase growth method of boron phosphide-based semiconductor layer and boron phosphide-based semiconductor layer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor phase growth technique for vapor phase growth of a boron phosphide-based semiconductor layer that is excellent in surface flatness and excellent in continuity without a gap on an underlying surface such as a silicon single crystal substrate.
[0002]
[Prior art]
Conventionally, boron phosphide (BP) has been known as a kind of III-V group compound semiconductor (Akira Teramoto, “Introduction to Semiconductor Devices” (March 30, 1995, first published by Bafukan Co., Ltd., page 28). A crystal layer made of a boron phosphide-based semiconductor containing boron (B) such as boron phosphide and phosphorus (P) as constituent elements is used as a buffer layer, for example, to construct a light emitting device (US) Patent No. 6,069,021) Alternatively, it is used as a contact layer for forming an ohmic electrode (see JP-A-2-288388) and a laser diode (LD). ) And boron phosphide (BP) / aluminum nitride / gallium (Ga) forming the active layer (light emitting layer)_XAl_1-XN: 0.ltoreq.X.ltoreq.1) is used to construct a superlattice layer (see the above-mentioned JP-A-2-288388). Such a superlattice layer composed of a group III nitride semiconductor layer containing boron (N) as a constituent element and boron phosphide is also used as a clad layer for the light emitting layer (see the above-mentioned Japanese Patent Laid-Open No. 2-288388).
[0003]
The boron phosphide-based semiconductor layer is formed, for example, by vapor phase growth means such as metal organic chemical vapor deposition (MOCVD method) using silicon (Si) single crystal (silicon) as a substrate (the above-mentioned US Patent). 6,069,021). For example, to form boron phosphide by MOCVD means, triethylboron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) Is used as a raw material (see (1) above US Pat. No. 6,069,021). The halide phosphorus trichloride (PCl_Three) Or boron trichloride (BCl)_Three(1) J. Crystal Growth, 13/14 (1972), pages 346 to 349, and (2) “Journal of Japanese Society for Crystal Growth” Vol. 25, No. 3 (1998), page A28). In addition, diborane (B₂H₆) And a hydride vapor phase growth method using phosphine ((1) J. Appl. Phys., 42 (1) (1971), pages 420 to 424, and (2) J .. Crystal Growth, 70 (1984), pages 507-514).
[0004]
Formation of a boron phosphide-based semiconductor layer on a silicon single crystal substrate has been conventionally carried out in a vapor phase growth reactor (vapor phase growth reactor) made of quartz material or the like (1) Katsufumi Shono "Semiconductor Technology (above)" (see June 25, 1992, 9th edition of the University of Tokyo Press, pages 74-76) on the susceptor inside the vapor deposition reactor. After the silicon single crystal substrate is mounted, the temperature of the mounting table or the silicon single crystal substrate is raised to a temperature suitable for forming the boron phosphide-based semiconductor layer. (For example, the above-mentioned “Semiconductor Technology (above), see page 76”) Gas materials of Group III elements such as boron and gases of Group V elements such as phosphorus are disclosed. Boron phosphide-based semiconductor layer is distributed through the vapor deposition furnace The formation of the conventional phosphide-based boron phosphide-based semiconductor layer is started by a conventional method (Inst. Phys, Conf. Ser., No. 129 (IPO Pub. Ltd., 1993, UK). ) Refer to pages 157 to 162) As the gas for transporting and supplying the above gas raw material into the vapor phase growth furnace, hydrogen gas (H₂) Is used (see the above Inst. Phys, Conf. Ser., No. 129).
[0005]
On the other hand, silicon nitride (Si_ThreeN_Four) Or silicon dioxide (SiO2)₂) Is known as, for example, a coating material for preventing the growth of gallium nitride (GaN) (1) J. Crystal Growth, 230 (2001), pages 341 to 345, and (2). (See the same magazine, pages 346-350). Thus, the silicon nitride or silicon oxide film is used for selective growth means for forming a group III nitride semiconductor layer containing nitrogen as a constituent element limited to a selected region on the substrate surface. It is used as a coating material for the substrate surface (see “Group III Nitride Semiconductor” (December 8, 1999, published by Baifukan Co., Ltd.), pages 122 to 124).
[0006]
[Problems to be solved by the invention]
In the conventional technology for forming a boron phosphide-based semiconductor layer, for example, the above-described BP / Ga_XAl_1-XThe N (0 ≦ X ≦ 1) superlattice layer is formed in the same vapor phase growth furnace with the BP crystal layer and Ga_XAl_1-XN (0 ≦ X ≦ 1) crystal layers are alternately stacked. By forming such a superlattice layer with a group III nitride semiconductor layer containing nitrogen in the same vapor phase growth furnace, a group III nitride semiconductor crystal is formed on the inner wall or mounting table of the vapor phase growth furnace. Decomposition product containing will adhere. Nitrogen composing the group III nitride semiconductor layer is easily volatilized at a temperature of about 1000 ° C. or higher, which is a conventional formation temperature of a boron phosphide-based semiconductor layer (J. Phys. Chem. 69 (10) (1965), pages 3455-3460). Therefore, nitrogen is released from the decomposition product containing the group III nitride semiconductor crystal to the inside of the vapor phase growth furnace at the time of temperature rise for forming the boron phosphide-based semiconductor layer. In particular, since the sublimation temperature of indium nitride (InN) is as low as about 620 ° C. in vacuum (edited by the Japan Society for the Promotion of Industrial Technology, New Material Technology Committee, “Compound Semiconductor Device” (September 15, 1973, Ltd.) Published by the Industrial Research Council) (see page 397), the decomposition products containing indium nitride significantly release nitrogen into the vapor phase growth furnace.
[0007]
At a high temperature, part of the nitrogen released into the vapor phase growth reactor reacts on the surface of the silicon single crystal substrate to form a silicon nitride film. The silicon nitride film formed on the surface of the silicon single crystal substrate by nitrogen existing in the vapor phase growth furnace in the same manner that the normal formation of the group III nitride semiconductor semiconductor layer is inhibited by the silicon nitride film. Hinders the formation of a boron phosphide-based semiconductor layer. This results in a boron phosphide-based semiconductor layer that lacks rugged continuity. If the boron phosphide-based semiconductor layer formed on the surface of the silicon single crystal substrate lacks surface flatness and continuity in the first place, it is a crystal with excellent surface flatness on it. The layer cannot be formed. Even if an attempt is made to construct a light emitting diode (LED) from such a laminated structure including a discontinuous crystal layer, a forward voltage (so-called “so-called”) is generated due to discontinuity of the crystal layer or non-planarity of the pn junction interface. , Vf) is low, and an LED having excellent current rectification characteristics cannot be obtained.
[0008]
The present invention has been made to solve the above-described problems in the prior art, and covers the inner wall of a vapor deposition reactor that inhibits the formation of a boron phosphide-based semiconductor layer on the surface of a silicon single crystal substrate. Vapor phase growth for forming a boron phosphide-based semiconductor layer having excellent surface flatness and continuity on the surface of a silicon single crystal substrate by presenting means for suppressing release of substances from the deposited decomposition products A method is provided.
[0009]
[Means for Solving the Problems]
That is, the present invention
(1) A vapor phase of a boron phosphide-based semiconductor layer in which a boron phosphide-based semiconductor layer is grown in a vapor phase on a silicon (Si) single crystal substrate (silicon) by a vapor phase growth means in a vapor phase growth furnace. In the growth method, a gas containing boron (B) and phosphorus (P) and a carrier gas accompanying the gas are circulated in a vapor phase growth furnace, and boron and phosphorus are formed on the inner wall of the vapor phase growth furnace. And then forming a boron phosphide-based semiconductor layer on a silicon single crystal substrate by vapor-phase growth.
(2) The vapor phase growth method for a boron phosphide-based semiconductor layer according to (1), wherein the carrier gas is a gas containing argon (Ar) in a volume fraction of 60% or more. .
(3) The method for vapor phase growth of a boron phosphide-based semiconductor layer according to (1) or (2) above, wherein the gas containing boron is a gas containing an organic boron compound and containing no halogen element.
(4) The vapor phase growth method for a boron phosphide-based semiconductor layer according to the above (1) to (3), wherein the gas containing phosphorus is a gas containing a phosphorus hydride compound and containing no halogen element .
(5) Arranging a substrate mounting table on which a silicon single crystal substrate is not mounted inside the vapor phase growth furnace, and maintaining the substrate mounting table at a temperature of 500 ° C. or higher and 1200 ° C. or lower, boron (B) A film containing boron and phosphorus is formed on the inner wall of the vapor phase growth furnace by circulating a gas containing oxygen and phosphorus (P) and a carrier gas accompanying the gas in the vapor phase growth furnace. The vapor phase growth method for a boron phosphide-based semiconductor layer according to any one of (1) to (4) above, wherein:
(6) After vapor-depositing a group III nitride semiconductor in a vapor deposition furnace, a film containing boron and phosphorus is formed on the inner wall of the vapor deposition furnace, and then in the same vapor deposition furnace. The vapor phase growth method for a boron phosphide-based semiconductor layer according to any one of (1) to (5) above, wherein the boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the silicon single crystal substrate.
(7) After forming a coating film containing boron and phosphorus on the inner wall of the vapor phase growth furnace, the silicon single crystal substrate is placed on the substrate mounting table and placed inside the vapor phase growth furnace. The temperature of the mounting table is raised to a temperature in the range of 250 ° C. to 1200 ° C., and the boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the silicon single crystal substrate. The vapor phase growth method for a boron phosphide-based semiconductor layer according to (6).
It is. Furthermore, the present invention provides
(8) A boron phosphide-based semiconductor layer manufactured by the vapor phase growth method for a boron phosphide-based semiconductor layer described in (1) to (7) above.
It is.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a vapor phase growth in which a decomposition product containing nitrogen (N) or oxygen (O) is present regardless of the growth means such as MOCVD method, halogen vapor phase growth method or hydride vapor phase growth method. This is particularly effective when a boron phosphide-based semiconductor layer is vapor-phase grown on the surface of a silicon single crystal substrate inside the furnace. Here, a silicon single crystal (silicon) having a {100} crystal face, a {110} crystal face, or a {111} crystal face can be used for the substrate. A silicon single crystal whose surface is a crystal plane inclined in a specific crystal direction can also be used as a substrate. For example, a silicon single crystal whose surface is a {111} crystal plane inclined by about 7 degrees (°) with respect to the <110> crystal direction can be used as the substrate. If an n-type or p-type conductive silicon single crystal is used as a substrate, an ohmic electrode having either positive or negative polarity can be laid on the back surface of the substrate, so that a light-emitting element or a light-receiving element can be easily configured. Can contribute. In particular, a low resistivity (= resistivity) conductive single crystal substrate with a resistivity of 1 milliohm (mΩ) or less, more preferably 0.1 mΩ or less results in an LED with a low forward voltage (so-called Vf). To contribute. In addition, since it has excellent heat dissipation, it is effective in constructing an LD that provides stable oscillation.
[0011]
The boron phosphide-based semiconductor layer provided on the surface of the silicon single crystal substrate includes boron and phosphorus as constituent elements, for example, B_AAl_BGa_CIn_DP_{1- δ}As_δ(0 <A ≦ 1, 0 ≦ B <1, 0 ≦ C <1, 0 ≦ D <1, A + B + C + D = 1, 0 ≦ δ <1). For example, B_AAl_BGa_CIn_DP_{1- δ}N_δ(0 <A ≦ 1, 0 ≦ B <1, 0 ≦ C <1, 0 ≦ D <1, A + B + C + D = 1, 0 ≦ δ <1). The present invention is applied regardless of the configuration of the boron phosphide-based semiconductor layer provided on the surface of the silicon single crystal substrate, that is, amorphous, polycrystalline, or single crystal. In addition, the conductivity of the boron phosphide-based semiconductor layer, the kind of impurities intentionally added to control the conductivity, the carrier concentration, the layer thickness, etc. Can be demonstrated. Furthermore, the present invention is not limited to the case where the boron phosphide-based semiconductor layer is grown in a vapor phase so as to be bonded to the surface of the silicon single crystal substrate. In particular, a group III nitride semiconductor layer containing nitrogen (N) is used. The effect can also be exhibited when a boron phosphide-based semiconductor layer is provided on the same layer in the same vapor phase growth furnace as that used for vapor phase growth.
[0012]
In the first embodiment of the present invention, vapor phase growth made of a quartz material, a stainless steel material, or a ceramic material such as boron nitride (BN) before placing the substrate made of a silicon single crystal on the mounting table as described above. The operation of coating the inner wall of the furnace with a film containing boron and phosphorus is performed. The inner wall of the vapor phase growth furnace refers to the inner wall surface facing the substrate of the member disposed around the substrate closest to the substrate. Specifically, the coating is made of a gas containing boron and phosphorus while holding a mounting table made of a high temperature resistant material such as graphite or silicon carbide (SiC) at a temperature of 500 ° C. or higher and 1200 ° C. or lower. It is formed by circulating a gas for transport accompanying it in a vapor phase growth furnace. Thereby, the coating of the decomposition product containing nitrogen (N) deposited on the inner wall of the vapor phase growth furnace is coated.
[0013]
For the gas containing boron, triethylboron ((C₂H_Five)_ThreeB), borane (BH_Three) And diborane (B₂H₆), Phosphine (PH_Three) Can be illustrated respectively. In order to form a coating film containing boron and phosphorus on the inner wall of the vapor phase growth furnace, the concentration of phosphorus atoms circulated in the vapor phase growth furnace is preferably higher than the concentration of boron atoms. For example, it is preferable to supply phosphorus atoms having a concentration of about 5 times or more, preferably 10 times or more, to the concentration of boron atoms in the vapor phase growth furnace. If the concentration of phosphorus atoms does not exceed the concentration of boron atoms in forming the film, phosphorus is absorbed by the film rich in Group III constituent elements such as boron when actually growing the boron phosphide-based semiconductor layer. Therefore, there arises a disadvantage that a boron phosphide-based semiconductor layer excellent in terms of an equivalence ratio stoichiometrically balanced cannot be stably obtained.
[0014]
The mounting table is heated by means such as a high-frequency heating method, a resistance heating method, or an infrared heating method. The reason for heating the mounting table is to thermally decompose a gas containing boron or phosphorus supplied into the vapor phase growth furnace to generate boron and phosphorus that form a film. There is also a means of thermally decomposing gas containing boron or phosphorus with a dedicated heating device newly attached to the vapor phase growth furnace, but it can be easily done by heating the mounting table provided in the vapor phase growth furnace. Thermal decomposition can occur. In general, at a low temperature of less than about 250 ° C., the gas containing boron or phosphorus is not sufficiently pyrolyzed, and therefore, it is inconvenient for efficiently depositing the coating containing boron and phosphorus on the inner wall of the vapor deposition furnace. is there. In order to efficiently form a film containing boron and phosphorus, it is preferable to promote thermal decomposition of a gas containing boron and a gas containing phosphorus after setting the temperature of the mounting table to 500 ° C. or higher. Conversely, at a high temperature exceeding 1200 ° C., highly volatile group V elements such as phosphorus evaporate, resulting in a film rich in group III elements, and boron phosphide with a balanced composition in terms of equivalent ratio. This will hinder obtaining a semiconductor layer.
[0015]
In the above temperature range of 500 ° C. or more and 1200 ° C. or less suitable for forming a film, the supply amount of the gas containing phosphorus into the vapor phase growth furnace is increased as the temperature of the mounting table is set higher. It is desirable to increase the supply amount of the gas containing boron. This is in order to avoid deposition of a film rich in Group III elements on the inner wall of the vapor phase growth furnace in consideration of volatilization of phosphorus in a high temperature environment. Another reason is to form a film containing boron and phosphorus that can sufficiently cover the surface of the decomposition product containing nitrogen (N) or the like. The film thickness of the film containing boron and phosphorus is about 2 times or more, more preferably about 4 times or more, as compared with the average thickness of the decomposition product containing nitrogen (N) or the like. When the coating becomes thick, it becomes easy to peel off from the inner wall of the vapor phase growth furnace. Boron phosphide-based semiconductor that peels off from the inner wall of the vapor-phase growth furnace during the vapor phase growth of the boron phosphide-based semiconductor layer, for example, jumps to the surface of the silicon single crystal substrate and results from the small pieces of the coating The surface condition of the layer is impaired. Therefore, the film thickness is preferably less than about 10 times the average thickness of the decomposition products. The film thickness of the coating can be adjusted by controlling the flow time of the gas containing boron or phosphorus into the vapor phase growth furnace when the mounting table is heated. Alternatively, a coating with a larger film thickness can be obtained particularly when the supply amount (= concentration) of the gas containing boron is increased in a predetermined distribution time.
[0016]
In the second embodiment of the present invention, when a film containing boron and phosphorus is formed, a gas containing these elements is transported into the vapor phase growth furnace with a gas mainly composed of argon (Ar). And This carrier gas is supplied into the vapor deposition furnace together with a gas containing boron or phosphorus, and constitutes an atmosphere in the vapor deposition furnace. In other words, a feature of the second embodiment of the present invention is that a film containing boron and phosphorus is formed in an atmosphere mainly composed of argon. The main body means containing 60% or more of argon in terms of volume fraction. This includes argon alone (volume fraction of argon = 100%), argon (volume fraction = 70%) and hydrogen (H₂) (Volume fraction = 30%) and the like. The argon volume fraction can be expressed by the ratio of the volume of argon to the total volume of gas. For the purpose of the present invention to suppress the concentration of nitrogen (N) or oxygen (O) released into the vapor phase growth furnace, argon and nitrogen (N₂), Argon and ammonia (NH_Three), Or argon and oxygen (O₂A mixed gas of argon and nitrogen-containing gas or oxygen-containing gas such as) cannot be preferably used. This is because a masking film made of silicon nitride or silicon oxide which prevents normal vapor phase growth of the boron phosphide-based semiconductor layer is formed on the surface of the silicon single crystal substrate.
[0017]
For example, in a mixed gas of argon and hydrogen, the volume fraction of argon can be changed by adjusting the flow rate of argon with respect to the total flow rate of argon gas and hydrogen gas per unit time. For example, in a mixed gas of argon and hydrogen, when the volume fraction of argon is less than 60%, hydrogen and phosphorus contained in the coating combine to deviate as a hydride of phosphorus with a high vapor pressure, and the coating Is rapidly eroded. As a result, the film thickness of the coating is reduced, the surface of the decomposition product containing nitrogen or the like cannot be sufficiently covered, and nitrogen and the like are released into the vapor phase growth furnace. Helium (He) and neon (Ne), which are inert gases belonging to the same family as argon, can also be used as a carrier gas. However, from an economical viewpoint, the most suitable inert gas for forming a film containing boron and phosphorus. The carrier gas made of active gas is a gas made of argon alone (argon volume fraction = 100%).
[0018]
In the third embodiment of the present invention, a non-halogen compound that does not contain a halogen element such as chlorine (Cl) or bromine (Br) as a gas containing boron when forming a film containing boron and phosphorus. Select and use. In particular, trimethylboron ((CH_Three)_ThreeB), triethylboron ((C₂H_Five)_ThreeAn organic boron compound containing no halogen element such as B) is used. Thereby, erosion of the coating film due to halogen radicals or halogen gas generated during the thermal decomposition of the boron compound containing halogen can be avoided. Since it is an aliphatic saturated compound of boron and triethylboron has an appropriate vapor pressure at room temperature, the flow rate ratio with the gas containing phosphorus to be circulated in the vapor phase growth furnace can be appropriately and adjusted, which is convenient. is there. In addition, an organic boron compound to which a functional group containing a nitrogen (N) atom or an oxygen (O) atom is added cannot be suitably used for forming a film. This is because the formation of a film containing nitrogen (N) or oxygen (O) is led to become a release source of nitrogen or oxygen into the vapor phase growth furnace.
[0019]
In the fourth embodiment of the present invention, a non-halogen compound that does not contain a halogen element such as chlorine (Cl) or bromine (Br) as a gas containing phosphorus when forming a film containing boron and phosphorus. Select and use. In particular, phosphine (PH_Three) And other phosphorus hydrides that do not contain halogen elements. The halogenated phosphorous compound containing halogen is not preferably used because it generates a halogen during the thermal decomposition, which erodes the coating to make it thin and imperfectly coats the surface of the decomposition product. In addition, although phosphine exhibits Lewis basic properties, it does not remarkably cause a complex (polomer) reaction with a Lewis acidic compound such as trimethylboron or triethylboron. However, there is an advantage that it can be fed into the vapor phase growth furnace with a substantially desired concentration. Phosphorous hydrides containing nitrogen (N) atoms or oxygen (O) atoms in addition to hydrogen cannot be suitably used to form a film. This is because the formation of a film containing nitrogen (N) or oxygen (O) is led to become a release source of nitrogen or oxygen into the vapor phase growth furnace.
[0020]
When phosphine is used as a gas containing phosphorus, hydrogen gas (H) is generated by thermal decomposition according to the following chemical reaction formula (1).₂) Will occur in the vapor phase growth furnace.
PH_Three  → P + 3/2 · H₂  ---- Chemical reaction formula (1)
That is, the chemical reaction formula (1) is PH_ThreeIt is shown that 1.5 mol of hydrogen gas is generated when 1 mol (mol.) Of is completely pyrolyzed. Therefore, when the above mixed gas of argon and hydrogen is used as a carrier gas, the volume fraction of the argon gas is determined by the argon gas constituting the mixed gas, the hydrogen gas, and the hydrogen gas generated by the thermal decomposition of phosphine. It is necessary to be 60% or more with respect to the total volume. The amount of hydrogen generated by the thermal decomposition of phosphine is generally (PH_ThreeOf hydrogen generated due to complete pyrolysis of_ThreeIt is appropriate to estimate 1.5 moles of hydrogen per mole (mol.).
[0021]
After the film containing boron and phosphorus is formed on the inner wall of the vapor phase growth furnace, the temperature of the mounting table is lowered to, for example, a temperature near room temperature in order to place the silicon single crystal as a substrate on the mounting table. . After placing the silicon single crystal at a predetermined position of the cooled mounting table up to a temperature at which the substrate can be mounted, the mounting table is finally positioned at a predetermined position in the vapor deposition furnace with the substrate mounted. Insert into. The predetermined position referred to here is a position in the vapor phase growth furnace that is convenient for uniformly heating the boron phosphide-based semiconductor layer to a temperature for vapor phase growth. Thereafter, the temperature of the mounting table is raised to a temperature suitable for vapor phase growth of the boron phosphide-based semiconductor layer. Vapor growth of a boron phosphide-based semiconductor layer on a silicon single crystal substrate can be performed by MOCVD, halogen vapor deposition, hydride vapor deposition, or gas-source molecular beam epitaxy (J. Solid). State Chem., 133 (1997), see pages 269 to 272).
[0022]
A temperature of 250 ° C. to 750 ° C. is suitable for vapor phase growth of an amorphous or polycrystalline boron phosphide-based semiconductor layer. A temperature of 750 ° C. to 1200 ° C. is suitable for vapor phase growth of the single crystal boron phosphide-based semiconductor layer. At high temperatures exceeding 1200 ° C, B₆P or B₁₃P₂Therefore, it is inconvenient for vapor phase growth of a compositionally uniform boron phosphide-based semiconductor layer. The temperature of the mounting table can be measured and adjusted by a temperature measuring device such as a thermocouple or a radiation thermometer. When raising the temperature of the mounting table, and thus the temperature of the silicon single crystal substrate mounted on the mounting table, to a temperature suitable for vapor phase growth of the boron phosphide-based semiconductor layer, vapor phase growth is performed. It is preferable that the atmosphere in the furnace is composed of a mixed gas containing an inert gas such as argon in a volume fraction of 60% or more. It is optimal to construct an atmosphere at the time of temperature rise from simple argon (volume fraction = 100%). Although it is possible to raise the temperature in a hydrogen atmosphere that has been generally used in the past, before the boron phosphide-based semiconductor layer is vapor-phase grown, boron and phosphorus deposited on the inner wall of the vapor-phase growth furnace can be used. This is not preferable because the film thickness of the film is reduced due to the reaction between the film containing hydrogen and hydrogen.
[0023]
In accordance with an embodiment of the present invention, an analysis result showing the effectiveness of forming a film containing boron and phosphorus in advance in a vapor deposition furnace is illustrated. The sample for analysis is a gallium nitride / indium mixed crystal (Ga) having a layer thickness of 620 nm by the MOCVD method._0.90In_0.10N) Vapor phase growth of the layer, and using a vapor phase growth furnace in which a decomposition product having an average layer thickness of less than about 100 nm is deposited on the inner wall of the vapor phase growth furnace, particularly around the mounting table. did. In accordance with the prior art, that is, the substrate surface after heating a silicon single crystal substrate having a {111} crystal face to 1050 ° C. without previously forming a film containing boron and phosphorus on the inner wall of the vapor phase growth furnace The elemental analysis results are shown in FIG. Formation of a thin film is not clearly visible on the substrate surface after heating, but according to Auger spectroscopic analysis (AES), in addition to nitrogen (N), as seen in the spectroscopic spectrum of FIG. The presence of carbon (C) and oxygen (O) can be confirmed. Thus, it is difficult to vapor-phase grow a boron phosphide-based semiconductor layer having continuity and excellent surface flatness on the surface of a silicon single crystal mainly contaminated with nitrogen. Usually, the boron phosphide-based semiconductor layer having a rough surface in which spherical crystals are randomly stacked is only resulted.
[0024]
On the other hand, in accordance with the present invention, after a film having a thickness of about 300 nm containing boron and phosphorus is formed in advance on the inner wall of the vapor phase growth furnace, a silicon single crystal substrate having a {111} plane is formed at 1050 ° C. FIG. 2 illustrates the results of elemental analysis of the substrate surface when the heat treatment is performed in FIG. From the spectrum of AES shown in FIG. 2, in addition to the AES signal of silicon (Si) derived from the silicon single crystal of the substrate, only an AES signal due to carbon (C) can be seen. Further, boron and phosphorus AES signals derived from a film containing boron and phosphorus are observed. Boron or phosphorus existing on the surface of the silicon single crystal substrate provides a “growth nucleus” in the growth of the boron phosphide-based semiconductor layer, and facilitates vapor phase growth of the boron phosphide-based semiconductor layer. It becomes effective. Thus, the coating according to the present invention prevents the contamination of the surface of the silicon single crystal substrate caused by nitrogen (N) and oxygen (O) originating from decomposition products deposited on the inner wall of the vapor deposition reactor. It is clear that it has the effect | action which carries out. The action of preventing the surface contamination of nitrogen (N) and oxygen (O) due to such a film of the present invention can be achieved, for example, by vapor-growing a group III nitride semiconductor layer and then forming a boron phosphide-based semiconductor layer. This is also manifested in vapor phase growth. In this case, after the vapor phase growth of the layer containing nitrogen such as the group III nitride semiconductor layer is completed, a film containing boron and phosphorus is formed prior to the vapor phase growth of the boron phosphide-based semiconductor layer. There is a need.
[0025]
[Action]
Prior to vapor phase growth of the boron phosphide-based semiconductor layer, the coating containing boron and phosphorus formed on the inner wall of the vapor phase growth furnace prevents normal growth of the boron phosphide-based semiconductor layer. It has the effect of preventing contamination of the surface of the substrate originating from the decomposition products in the phase growth furnace.
[0026]
Prior to vapor phase growth of the boron phosphide-based semiconductor layer, a carrier gas containing 60% or more of argon in volume fraction used for forming a film containing boron and phosphorus on the inner wall of the vapor phase growth furnace is In addition, an atmosphere containing argon is created in the vapor phase growth furnace, and the film thickness of the coating film is suppressed from decreasing.
[0027]
Before the boron phosphide-based semiconductor layer is vapor-grown, the organic boron compound, which is a non-halogen compound used to form a film containing boron and phosphorus on the inner wall of the vapor-phase growth furnace, is caused by thermal decomposition. In addition to supplying boron constituting the film, the film has a function of avoiding a decrease in the film thickness of the formed film.
[0028]
Before vapor-depositing a boron phosphide-based semiconductor layer, a phosphorus hydride compound, which is a non-halogen compound, used to form a film containing boron and phosphorus on the inner wall of a vapor deposition furnace is used for thermal decomposition. Therefore, it has the effect | action which avoids that the film thickness of the formed coating film reduces while supplying the phosphorus which comprises a coating film.
[0029]
【Example】
(Example)
Taking as an example the case where a monomeric boron phosphide layer is vapor-phase grown directly on the surface of a silicon single crystal substrate having a p-type {111} crystal plane doped with boron by MOCVD. The contents of the present invention will be specifically described. The structure of the MOCVD vapor phase growth apparatus used in this example is schematically shown in FIG.
[0030]
In the vapor phase growth apparatus shown in FIG. 3, the vapor phase growth furnace 11 is composed of a high purity quartz tube for use in the semiconductor industry. A columnar mounting table 12 made of high-purity graphite for mounting a substrate is disposed in the approximate center of the circular vapor phase growth furnace 11. A high-frequency coil 13 used for high-frequency induction heating of the mounting table 12 is disposed on the outer periphery of the vapor deposition furnace 11 around the mounting table 12. At one end of the vapor phase growth furnace 11, an inlet 14 for supplying a gas containing boron or phosphorus and a carrier gas used for forming a film containing boron and phosphorus or vapor phase growth of a boron phosphide layer into the furnace. Is provided. Further, the other end of the vapor deposition furnace 11 is supplied into the furnace, and the gas flowing around the mounting table 12 along the inner wall 11a of the vapor deposition furnace 11 is discharged to the outside of the furnace together with the carrier gas. An exhaust port 15 is provided.
[0031]
In forming the coating according to the present invention, first, argon gas was supplied as a carrier gas into the vapor phase growth furnace 11 through the inlet 14 at a flow rate of 12 liters per minute. After about 20 minutes have passed since the start of the argon gas flow, a high-frequency power source is turned on to the high-frequency coil 13, and the temperature of the mounting table 12 on which the silicon single crystal substrate is not placed is raised from room temperature to 900 ° C. Warm up. After observing the stability of the temperature measured by the thermocouple 16 inserted in the mounting table 12, the triethyl boron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) Was supplied into the vapor phase growth furnace 11. The supply amount of triethylboron was set to about 4 cc / min in flow rate, and the flow rate of phosphine was set to about 220 cc / min. Thus, while maintaining the pressure inside the vapor phase growth furnace 11 at substantially atmospheric pressure, triethylboron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) Was continuously supplied into the vapor phase growth furnace 11 for 60 minutes, and a film 17 containing boron and phosphorus having a thickness of about 400 nm was formed on the inner wall 11a of the vapor phase growth furnace 11. As the gas containing boron or phosphorus, a gas containing an organic boron compound which is a non-halogen compound and a phosphorus hydride compound was used, so that the film was not significantly etched, and the film thickness was triethylboron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) Increased substantially in proportion to the supply time.
[0032]
After that, triethyl boron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) To the inside of the vapor phase growth furnace 11 was stopped, and only argon gas as a carrier gas was continuously supplied into the furnace from the introduction port 14 at the above flow rate. Next, high frequency induction heating of the mounting table 12 was stopped, and the temperature of the mounting table 12 was lowered. After the temperature is lowered, the mounting table 12 is once taken out of the vapor phase growth furnace 11, and the Si single crystal substrate having the p-type {111} crystal plane is mounted as the substrate 101 at the center of the upper surface of the mounting table 12. I put it. Thereafter, the mounting table 12 on which the substrate 101 was mounted was again inserted into a predetermined position of the vapor phase growth furnace 11. After the insertion, argon was again supplied from the inlet 14 into the vapor phase growth furnace 11 at a flow rate of 12 liters per minute. Thereafter, the temperature of the mounting table 12 was raised to 850 ° C. by an induction heating means in an atmosphere composed of argon. Immediately after the temperature of the mounting table 12 reaches 850 ° C., the flow rate of argon gas used as the carrier gas is reduced from 12 liters per minute to 10 liters per minute prior to vapor phase growth of the boron phosphide layer. It was. At the same time, hydrogen gas at a flow rate of 2 liters per minute is added to the argon gas so that the argon volume fraction is about 83.3%.₂The mixed gas was newly used as a carrier gas.
[0033]
For a while, Ar-H₂After the mixed gas is circulated inside the vapor phase growth furnace 11, triethylboron ((C₂H_Five)_ThreeB) and phosphine (PH_Three) And added. Triethyl boron ((C₂H_Five)_ThreeThe amount of B) added is 4 cc / min, and phosphine (PH_Three) Was 430 cc per minute. Vapor growth of the monomeric boron phosphide layer 102 was started by the flow of the carrier gas accompanying the gas containing boron and (P) into the vapor phase growth furnace 11. A carrier gas accompanying the gas containing boron and phosphorus was circulated continuously for 8 minutes to vapor-phase grow the monomeric boron phosphide layer 102 having a layer thickness of 300 nm. After the addition of the gas containing boron and phosphorus to the carrier gas was stopped and the vapor phase growth of the boron phosphide layer 102 was terminated, the high frequency induction heating of the mounting table 12 was stopped. Ar-H above₂After the temperature of the mounting table 12 is lowered to a temperature near room temperature in an atmosphere composed of a mixed gas (Ar volume fraction≈83.3%), the mounting table 12 is pulled out from the vapor phase growth furnace 11, and a silicon single crystal substrate is obtained. 101 was taken out.
[0034]
The surface of the boron phosphide layer 102 vapor-deposited on the surface of the silicon single crystal substrate 101 in accordance with the present invention was a flat surface having no projections or the like and having no irregularities. Further, a boron phosphide layer having excellent continuity was obtained.
[0035]
(Comparative example)
Using the vapor phase growth furnace 11 described in the above (Example) and without forming a film containing boron and phosphorus in advance on the inner wall 11a of the vapor phase growth furnace 11, a {111} crystal plane is formed. The vapor phase growth of a continuous film made of monomeric boron phosphide having excellent surface flatness was tried on the surface of a silicon single crystal substrate. That is, the vapor phase growth of the boron phosphide layer was attempted in a state where the gas containing boron and phosphorus and the carrier gas were in direct contact with the inner wall 11a of the vapor phase growth furnace 11.
[0036]
As described in the above (Example), in order to accurately compare with the case where a film containing boron and phosphorus is provided in advance on the inner wall 11a of the vapor phase growth furnace 11, in this comparative example, a silicon single crystal substrate is used. The vapor phase growth conditions for vapor phase growth of the boron phosphide layer onto the layer were exactly the same as in the above (Example).
[0037]
However, a continuous layered boron phosphide layer was not formed on the silicon single crystal substrate, and a rough boron phosphide layer with severe irregularities formed by substantially spherical crystal grains overlapping each other. FIG. 4 is a schematic cross-sectional view of the boron phosphide layer 102 grown in a vapor phase on the silicon single crystal substrate 101 in this comparative example. As shown in FIG. 4, the substantially spherical crystal grains 103 did not grow uniformly on the surface of the silicon single crystal substrate 101, but grew in a partial region. Further, the substantially spherical crystal grains 103 did not exist in close contact with each other, and the presence of voids 104 was observed between the adjacent crystal grains 103.
[0038]
Further, according to elemental analysis in the depth direction (layer thickness direction) of the boron phosphide layer 102 using general secondary ion mass spectrometry (SIMS), the silicon single crystal substrate 101 and the boron phosphide layer In the region near the interface with 102, particularly in the region where the crystal grains 103 are not grown, the atomic concentration is about 7 × 10 × 10.¹⁸Atom / cm^ThreeIt was shown that more than oxygen (O) atoms accumulated. This was about one digit higher than the oxygen atom concentration in the region in the vicinity of the interface between the boron phosphide layer grown in the above (Example) and the silicon single crystal substrate. The analysis result showing the remarkable difference in the oxygen atom concentration on the surface of the silicon single crystal substrate 101 suggests that the presence or absence of the coating containing boron and phosphorus according to the present invention is related to the oxygen atom concentration. . That is, even if there is no decomposition product containing nitrogen (N) or the like on the inner wall 11a of the vapor phase growth furnace 11, contamination of the surface of the silicon single crystal due to oxygen from the vapor phase growth furnace 11 made of quartz material. As a result, it was taught that the coating containing boron and phosphorus according to the present invention is effective.
[0039]
【The invention's effect】
According to the present invention, when a boron phosphide-based semiconductor layer is vapor-phase grown on a silicon single crystal substrate or the like by vapor phase growth means, a film containing boron and phosphorus is formed on the inner wall of the vapor phase growth furnace. Therefore, it is possible to avoid contamination of the underlying surface such as a silicon single crystal substrate which hinders the normal vapor phase growth of the boron phosphide-based semiconductor layer. It is effective in providing a boron phosphide-based semiconductor layer having excellent surface flatness and having continuity.
[Brief description of the drawings]
FIG. 1 is a diagram showing a result of elemental analysis of a surface of a silicon single crystal substrate according to a conventional technique.
FIG. 2 is a diagram showing the results of elemental analysis on the surface of a silicon single crystal substrate according to the technique of the present invention.
FIG. 3 is a schematic view showing the structure of a vapor phase growth apparatus according to an embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing a configuration of a boron phosphide layer according to a comparative example of the present invention.
[Explanation of symbols]
11 Vapor growth furnace
11a inner wall
12 Mounting table
13 High frequency coil
14 Introduction
15 outlet
16 Thermocouple
17 Coating
101 Silicon single crystal substrate
102 Boron phosphide layer
103 crystal grains
104 Gaps between grains

Claims (7)

In a vapor phase growth method of a boron phosphide-based semiconductor layer in which a boron phosphide-based semiconductor layer is vapor-grown on a silicon (Si) single crystal substrate (silicon) in a vapor phase growth furnace by vapor phase growth means. And a gas containing boron (B) and phosphorus (P) and a carrier gas accompanying the gas containing argon (Ar) in a volume fraction of 60% or more are circulated in the vapor phase growth furnace. A boron phosphide-based semiconductor characterized in that after a film containing boron and phosphorus is formed on the inner wall of a vapor phase growth furnace, a boron phosphide-based semiconductor layer is vapor-phase grown on a silicon single crystal substrate Vapor phase growth method of layer. 2. The method for vapor phase growth of a boron phosphide-based semiconductor layer according to claim 1 , wherein the gas containing boron is a gas containing an organic boron compound and not containing a halogen element. The method for vapor phase growth of a boron phosphide-based semiconductor layer according to claim 1 or 2 , wherein the gas containing phosphorus is a gas containing a phosphorus hydride compound and containing no halogen element. A substrate mounting table on which the silicon single crystal substrate is not mounted is disposed inside the vapor phase growth furnace, and while maintaining the substrate mounting table at a temperature of 500 ° C. or higher and 1200 ° C. or lower, boron (B) and phosphorus ( P) and a carrier gas accompanying it are circulated in the vapor phase growth furnace to form a film containing boron and phosphorus on the inner wall of the vapor phase growth furnace. The method for vapor phase growth of a boron phosphide-based semiconductor layer according to any one of claims 1 to 3 . After the group III nitride semiconductor in a vapor phase growth furnace was vapor deposited on the inner wall of the vapor phase epitaxy reactor, to form a coating comprising boron and phosphorus, followed, silicon in the same vapor phase growth furnace vapor deposition method boron-phosphide-based semiconductor layer according to claim 1, characterized in that the boron-phosphide-based semiconductor layer is grown in vapor phase on the surface of the single crystal substrate. A film containing boron and phosphorus is formed on the inner wall of the vapor deposition furnace, and then a silicon single crystal substrate is placed on the substrate mounting table and placed inside the vapor deposition furnace. by elevating the temperature of the temperature to a temperature in the range of 1200 ° C. or less at 250 ° C. or higher, wherein the boron-phosphide-based semiconductor layer on the surface of the silicon single crystal substrate to claims 1 to 5, characterized in that vapor-phase growth Vapor phase growth method of boron phosphide-based semiconductor layer. Boron-phosphide-based semiconductor layer manufactured in claims 1 to boron-phosphide-based semiconductor layer according to 6 vapor deposition method.

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