JP2004241676A - Method of manufacturing compound semiconductor, semiconductor material, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make even an in-plane carrier concentration distribution of an InGaP film formed on a semiconductor substrate. <P>SOLUTION: When carriers are doped into a GaAs single crystal substrate 1 using an n-InGaP layer 2 expressed by formula In<SB>X</SB>Ga<SB>1-X</SB>and using phosphine as a p-source for vapor phase growth, a V/III ratio is set at 100 or less as its growth conditions. Consequently, the in-plane carrier concentration distribution of the resultant InGaP film becomes uniform to such an extent as practically negligible. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a compound semiconductor having an InGaP film on a semiconductor substrate, a semiconductor material using the compound semiconductor, and a semiconductor device manufactured using the same.
[0002]
[Prior art]
Various electronic devices such as bipolar transistors and high-mobility field-effect transistors are manufactured using compound semiconductors, and each of these electronic devices is a compound semiconductor formed by laminating a required semiconductor thin film layer on a semiconductor substrate. It is manufactured using a wafer. Therefore, for example, a GaAs single crystal plate is prepared as a semiconductor substrate, and a required single crystal thin film layer made of a material such as GaAs, AlGaAs, InGaAs, or InGaP is formed on the semiconductor substrate by an appropriate thin film forming method such as a vapor phase growth method. It is formed by using.
[0003]
Among these various compound semiconductor materials, InGaP has not only excellent electron transport characteristics but also a characteristic that the energy gap can be largely changed depending on the In composition. Recently used as a Group 3-5 compound semiconductor material used for the semiconductor device.
[0004]
When an InGaP layer is to be formed on a semiconductor substrate by, for example, an organometallic thermal decomposition method (hereinafter referred to as MOCVD method), phosphine (PH ₃ ) is generally used as a phosphorus supply source (P source). In the growth conditions of the InGaP layer using GaN, the V / III ratio is set to a high value, for example, about 200 because the decomposition rate of phosphine is low, and the InGaP layer is grown as a single crystal thin film (for example, J. Crystal Growth 221 ( 2000) 509).
[0005]
Here, the V / III ratio is a supply ratio of the group 5 raw material and the group 3 raw material during the growth of the group 3-5 compound semiconductor crystal. Generally, in the metal organic chemical vapor deposition method, a raw material is supplied in a gas state from a gas cylinder or a bubbler. The amount of gas supplied from the gas cylinder is controlled by a flow rate control device such as a mass flow controller installed in the supply line, and the (gas concentration in the cylinder) × (gas flow rate) is the actual flow rate of the raw material. The amount of gas supplied from the bubbler is controlled by a flow control device such as a mass flow controller installed in the carrier gas supply line that flows through the bubbler. Is the actual flow rate. The actual flow rate of the raw material supplied by these methods, which is the ratio of the supply amount of the Group 5 raw material to the Group 3 raw material, is generally referred to as the V / III ratio. The term V / III ratio is also used herein according to the above definition.
[0006]
[Problems to be solved by the invention]
However, when the InGaP layer is grown under the above conditions using phosphine, if an n-type InGaP layer doped with an n-type carrier such as silicon (Si) is to be grown, the n-type carrier is uniformly doped. Very difficult to let. Therefore, it is difficult to make the carrier concentration distribution of the completed InGaP layer uniform over the surface, and it is difficult to improve the in-plane distribution of the carrier concentration in the grown n-InGaP layer. When, for example, a heterojunction bipolar transistor (HBT) is manufactured using a semiconductor wafer having a large in-plane distribution of the carrier concentration in the n-InGaP layer, a high resistance or a low resistance in the layer is obtained, and the quality is varied. However, there arises a problem that only an HBT having a large value is obtained.
[0007]
An object of the present invention is to provide a method of manufacturing a compound semiconductor, a semiconductor material, and a semiconductor element which can solve the above-described problems in the conventional technology.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, when vapor-phase growing an InGaP film on a semiconductor substrate using n-type impurities by using phosphine as a P source, the V / III ratio is set to 100 or less as a growth condition. By doing so, the carrier concentration distribution in the plane of the completed InGaP film has a uniformity that does not hinder practical use.
[0009]
According to the present invention, the general formula In X _Ga 1-X _P represented by a compound semiconductor layer for manufacturing by vapor phase growth using an organic metal thermal decomposition method of a compound semiconductor containing at least one layer a method, said in X _Ga 1-X _P layer during growth with use of phosphine as the source of phosphorus so as to dope the carrier, the manufacture of compound semiconductor of the V / III ratio, characterized in that 100 or less A method is proposed.
[0010]
According to the invention of claim 2, in the invention of claim 1, wherein the In X _Ga 1-X _P layer is a compound semiconductor manufacturing process to be doped to n-type is proposed.
[0011]
According to the invention of claim 3, in the invention of claim 1 or 2, wherein an In X _Ga compound semiconductor manufacturing method so as to dope the silicon as a dopant to 1-X _P layer during growth is suggested.
[0012]
According to the invention of claim 4, in the invention of claim 1, 2 or 3, and characterized in that the growth of the _{In X Ga 1-X} P layer, trimethyl gallium, trimethyl indium, by the MOCVD method using phosphine Is proposed.
[0013]
According to a fifth aspect of the present invention, there is provided a semiconductor material manufactured by using the method of manufacturing a compound semiconductor according to the first, second, third, or fourth aspect.
[0014]
According to a sixth aspect of the present invention, there is provided a semiconductor device manufactured using the semiconductor material of the fifth aspect.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a layer structure diagram showing an example of an embodiment of an epitaxial substrate according to the present invention. In the epitaxial substrate 10 shown in FIG. 1, in order to form an InGaP layer having desired characteristics when fabricating a semiconductor device, a supply ratio of In and Ga, a supply amount of a dopant gas, and an accurate growth rate of InGaP are checked. It is for the purpose. That is, the epitaxial substrate 10 is what is called a so-called check epi, and an epitaxial substrate as a product is manufactured based on the growth conditions obtained by using the epitaxial substrate 10. The epitaxial substrate 10 is obtained by forming an n-InGaP layer 2 and an n-GaAs layer 3 on a GaAs single crystal substrate 1 in this order. In the epitaxial substrate 10, the target film thickness, carrier concentration, and In composition of the n-InGaP layer 2 are 2000 °, 1 × 10 ¹⁷ cm ⁻³ , and 0.5, respectively. The target film thickness and carrier concentration of the n-GaAs layer 3 are 3000 ° C. and 3 × 10 ¹⁷ cm ⁻³ , respectively. The n-GaAs layer 3 is provided in order to prevent the n-InGaP layer 2 from being deteriorated, for example, to prevent the removal of P from the surface of the InGaP after the growth of the n-InGaP layer 2.
[0017]
The n-InGaP layer 2 is a single-crystal semiconductor thin-film layer which is grown on the GaAs single-crystal substrate 1 by the MOCVD method using phosphine as a phosphorus source (P source) and n as a dopant using Si as a dopant. It is formed as an InGaP layer represented by the general formula In _X Ga _1- XP doped with n-type impurities.
[0018]
Next, an embodiment of a method for producing the epitaxial substrate 10 having the layer structure shown in FIG. 1 will be described. First, a GaAs single crystal substrate 1 is prepared. The GaAs single-crystal substrate 1 is a high-resistance semi-insulating GaAs single-crystal substrate, and is manufactured by an LEC (Liquid Encapsulated Czochralski) method, a VB (Vertical Bridgeman) method, a VGF (Vertical Gradient Freezing) single crystal A method, and the like. Preferably, a substrate having an inclination of about 0 ° to 10 ° from one crystallographic plane orientation is prepared, regardless of the method of manufacture.
[0019]
After the surface of the GaAs single crystal substrate 1 prepared as described above is degreased and cleaned, etched, washed with water, and dried, the GaAs single crystal substrate 1 is placed on a heating table of a MOCVD growth furnace. After sufficiently replacing the inside of the MOCVD growth furnace with high-purity hydrogen, heating is started. When stabilized at an appropriate temperature, phosphine is introduced into the MOCVD growth furnace as a phosphorus material. Further, a gallium raw material and an iridium raw material are introduced. The n-InGaP layer 2 is grown by controlling the supply amount and time of each raw material. When the n-InGaP layer 2 is formed as an n-type InGaP layer containing an n-type impurity, Si is introduced as a dopant into a MOCVD growth furnace.
[0020]
In this manner, the n-InGaP layer 2 is grown by the MOCVD method, and the in-plane distribution of the carrier concentration in the n-InGaP layer 2 thus obtained is significantly reduced as compared with the conventional one. The V / III ratio is set to 100 or less, and the n-InGaP layer 2 is vapor-phase grown. Preferably it is 1 to 100, more preferably 15 to 90, most preferably 30 to 80. On the InGaP layer 2, a GaAs layer 3 is grown to protect the InGaP layer 2 by using AsH3 as an As source, using TMG as a Ga source, and using Si as a dopant. The carrier concentration of the GaAs layer 3 is set to a value similar to that of the InGaP layer 3.
[0021]
The optimum growth temperature is about 600 ° C., but the same effect can be obtained even if the growth temperature is different as long as the reaction state of growth is the same. However, the growth temperature is not critical, but is preferably about 550C to 600C. Further, in this type of semiconductor material, the carrier concentration in the n-InGaP layer 2 is often about 0.8 × 10 ¹⁷ cm ^{−3 to} 1.2 × 10 ¹⁷ cm ^−3, but the carrier concentration distribution is , The carrier concentration can be set to an arbitrary value.
[0022]
Finally, the supply of each material is stopped to stop the crystal growth, and after cooling, the epitaxial substrate 10 stacked as shown in FIG. 1 is taken out of the MOCVD growth furnace to complete the crystal growth. The substrate temperature during crystal growth is usually in the range of about 500 ° C to 800 ° C.
[0023]
In addition, as the carrier, for example, in addition to silicon, an n-type dopant such as a hydrogen compound such as germanium, tin, sulfur, or selenium or an alkylated compound having an alkyl group having 1 to 3 carbon atoms can be used.
[0024]
When the n-InGaP layer 2 is grown as described above, as the V / III ratio decreases, the degree of decrease in the carrier concentration at the substrate edge decreases, and the in-plane uniformity of the carrier is improved. Since this change has a certain direction, the smaller the V / III ratio, the better the uniformity of the carrier concentration.
[0025]
From the results of various experiments, it is considered that the lower the V / III ratio, the better the in-plane distribution of carriers. However, in the growth of the InGaP layer, the decomposition efficiency of phosphine, which is the P material, is poor. Therefore, when the V / III ratio is extremely reduced, the supply of the P material to the substrate surface becomes insufficient, and the In and Ga metals are not sufficiently supplied. Care must be taken that the lower limit does not fall below 1 because precipitation occurs and InGaP cannot be grown due to the shortage of the P material.
[0026]
【Example】
Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments described below.
[0027]
(Example 1)
The stacked structure shown in FIG. 1 was epitaxially grown on a VGF semi-insulating GaAs substrate by MOCVD using a reduced-pressure barrel type MOCVD furnace. The GaAs single crystal substrate 1 used here was 2.0 ° off. Then, the growth temperature was set to 600 ° C., and the n-InGaP layer 2 was grown by introducing silicon into the furnace so as to have a thickness of 2000 ° and a carrier concentration of 1.0 × 10 ¹⁷ cm ⁻³ . By changing the V / III ratio during this growth to 158, 79, and 39, three samples were manufactured.
[0028]
For the growth of InGaP, trimethylindium and trimethylgallium, which are organometallic compounds, were used as group III raw materials. Phosphine gas was used as the group 5 raw material. The carrier was prepared by supplying Si using Si ₂ H ₆ gas and by MOCVD.
[0029]
For these three samples, the in-plane distribution of the carrier concentration of the epitaxial substrate 10 was measured. FIG. 2 shows the measured values. In FIG. 2, the abscissa indicates the distance from the center of the epitaxial substrate 10 to the edge starting from the center, and the ordinate indicates the carrier concentration normalized with the carrier concentration at the center of the epitaxial substrate 10 as 1.
[0030]
FIG. 2 shows that the smaller the V / III ratio is, the smaller the in-plane distribution of the carrier concentration of the epitaxial substrate 10 is.
[0031]
As the V / III ratio is reduced to 158, 79, and 39, the degree of decrease in the carrier concentration on the outer peripheral side of the substrate is reduced, and the in-plane uniformity of the carrier is improved. Since this change has a certain direction, it is obvious that the uniformity can be further improved by further reducing the V / III ratio. The smaller the V / III ratio, the better the uniformity of the carrier concentration.
[0032]
(Example 2)
Except that the off angle of the GaAs single crystal substrate 1 was set to 0.4 degrees, another three samples were prepared by changing the V / III ratio to 158, 79, and 39 in the same manner as in Example 1. Produced. Then, the in-plane distribution of the carrier concentration was measured for these samples. FIG. 3 shows the measured values. In FIG. 3 as well, the horizontal axis represents the distance from the center of the epitaxial substrate 10 to its edge, and the vertical axis represents the carrier concentration value normalized with the carrier concentration at the center of the epitaxial substrate 10 as 1. .
[0033]
FIG. 3 shows that even if the off-angle of the substrate is small, the smaller the V / III ratio is, the smaller the in-plane distribution of the carrier concentration of the epitaxial substrate 10 is.
[0034]
FIG. 4 shows the tolerance of the in-plane carrier concentration distribution obtained from the experimental results shown in FIGS. FIG. 4 shows that when the V / III ratio is set to 100 or less, the in-plane tolerance becomes about 3% or less. When fabricating a semiconductor device from an MOCVD substrate, an in-plane distribution of 5 to 3% or less is generally required. Therefore, when the V / III ratio is 100 or less, in-plane uniformity of carrier concentration sufficient to obtain a practical epitaxial substrate can be obtained.
[0035]
From the results shown in FIGS. 2, 3 and 4, it is apparent that the lower the V / III ratio, the better the in-plane distribution of carriers. However, in the growth of the InGaP layer, the decomposition efficiency of phosphine, which is a P raw material, is low. Therefore, if the V / III ratio is less than 30, the supply of the P raw material to the substrate surface becomes insufficient, and In, Ga, etc. There is a tendency for segregation and precipitation of metals. It should be noted that if the V / III ratio is less than 1, growth of InGaP itself may not be possible.
[0036]
(Example 3)
A heterojunction bipolar transistor (HBT) was produced as follows. First, a semi-insulating GaAs substrate was prepared, a required thin film layer was formed thereon as follows, and a compound semiconductor wafer for forming an HBT was formed. That is, a collector layer composed of an n ⁺ -GaAs layer (carrier concentration of about 10 ¹⁸ cm ⁻³ units) and an i-GaAs layer was formed on a semi-insulating GaAs substrate. A base layer was formed on the collector layer. Approximately, the base layer was composed of ap ⁺ -GaAs layer (with a carrier concentration of about 10 ¹⁹ cm ⁻³ ), and the carrier concentration and the film thickness were adjusted so that the base sheet resistance was 270 Ω / □. On the base layer, an n-InGaP layer (about 10 ¹⁷ cm ⁻³ carrier concentration), an n-GaAs layer (about 10 ¹⁷ cm ⁻³ carrier concentration), and an n ⁺ -GaAs layer (about 10 ¹⁷ cm ⁻³ carrier concentration) ^An emitter layer of about ¹⁸ cm ⁻³ was formed. Here, the n-InGaP layer forming the emitter layer was formed under the conditions of Example 1 with a V / III ratio of 39.
[0037]
An HBT was manufactured using the compound semiconductor wafer obtained as described above, and its characteristics were measured. As a result, a good result was obtained with a base sheet resistance of 270 Ω / □ and a current amplification factor β of 116. . As described above, by applying the present invention to an HBT thin film, not only the in-plane uniformity can be improved, but also a high-performance HBT having excellent electric characteristics can be realized.
[0038]
【The invention's effect】
According to the present invention, as described above, an InGaP thin film having a significantly small in-plane distribution of carrier concentration can be grown, and a high-performance semiconductor element can be manufactured.
[Brief description of the drawings]
FIG. 1 is a layer structure diagram illustrating an example of an embodiment of the present invention.
FIG. 2 is a graph showing a measurement result of an in-plane distribution of a carrier concentration according to one embodiment of the present invention.
FIG. 3 is a graph showing a measurement result of an in-plane distribution of a carrier concentration according to another embodiment of the present invention.
FIG. 4 is a graph showing the in-plane tolerance of the carrier concentration in the example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 GaAs single crystal substrate 2 n-InGaP layer 10 Epitaxial substrate

Claims (6)

A general formula an In X _Ga process for the preparation by vapor phase growth using 1-X _P metal organic decomposition method of a compound semiconductor containing at least one layer of a compound semiconductor layer represented by, said an In _X Ga _A method for producing a compound semiconductor, wherein phosphine is used as a phosphorus supply source and a carrier is doped at the time of growing a _1- XP layer, and the V / III ratio is 100 or less. The _{In X Ga 1-X} P layer is a compound semiconductor manufacturing method according to claim 1, wherein the n-doped. The In X _Ga 1-X _P layer according to claim 1 or 2 method of producing a compound semiconductor according to as doped silicon as a dopant during the growth of the. The _In the growth of _{X Ga 1-X} P layer, trimethyl gallium, trimethyl indium, claim 2 or 3 method of producing a compound semiconductor according and performing by the MOCVD method using phosphine. A semiconductor material produced by using the method for producing a compound semiconductor according to claim 1, 2, 3, or 4. A semiconductor device manufactured using the semiconductor material according to claim 5.

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