JPH0234909A - Compound semiconductor vapor growth method and device - Google Patents

Abstract

PURPOSE:To prevent generation of crystal defects by arranging a material- storing boat at the upper part of a bell jar type reaction vessel whose top is closed and a susceptor capable of rotating below it, and heating the susceptor to the specified temperature, and letting reaction gas flow while heating a material gas transport part and a material boat arranged part. CONSTITUTION:An electric resistance furnace 11 is arranged around a part of the small diameter part 1a, the taper part 1c, and the large diameter part 1b of a reaction tube 1 which becomes a guide path for reaction gas discharged from nozzles 7a and 7b, and the temperature of the vicinity of a material storing boat 10 is kept stable at about 800 deg.C. Also, the entire small diameter part 1a as a material-strong boat arranged part and as a material transport part is heated so that the temperature distribution along the axial direction may be constant temperature gradient. Also, the heating of a GaAs substrate 20 is done by partial heating by means of a high frequency coil 5 arranged below a susceptor 3a inside a rection vessel. Hereby, an epitaxial growth layer small in crystal defects can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor substrate manufacturing technology and a vapor phase epitaxial growth method for compound semiconductors, and particularly relates to a method for growing a compound semiconductor layer such as gallium arsenide (GaAs) on a plurality of substrates ( This technology relates to effective techniques for epitaxial growth on wafers.

[Prior art] Formation of a gallium arsenide semiconductor layer by a conventional vapor phase growth method involves placing a quartz boat containing gallium (Ga) as a source in a quartz reaction vessel placed horizontally, and a quartz boat containing gallium (Ga) as a source. Epitaxial growth was performed by placing a growth substrate (wafer) and heating the outer periphery of the reaction vessel in a resistance heating furnace.

In this way, when the reaction vessel is heated with a resistance heating furnace, it takes 2 to 3 hours to reach a temperature around 750 T, which is the vapor phase growth temperature of GaAs.

However, when a GaAs growth substrate (wafer) is heated in a high-purity carrier gas (e.g. H2) or in a vacuum, thermal decomposition begins at about 600°C, and the surface of the growth substrate (wafer) decomposes in a short time. If a vapor phase epitaxial growth layer is formed on a substrate (wafer) with such a rough surface, a large number of crystal defects will be generated in the layer, making it impossible to put it to practical use. Therefore, it is not preferable to heat the growth substrate (wafer) in the reaction vessel for a long time until it reaches a predetermined growth temperature in a resistance heating furnace.In order to eliminate this drawback, For example, the inventions described in Japanese Patent Application Laid-Open No. 51-76968 shown in FIG. 3 and Japanese Patent Application Laid-Open No. 60-109222 shown in FIG. 4 have been proposed. That is, instead of using a resistance heating furnace, the growth substrate is rapidly heated by a high-frequency coil from outside the reaction vessel and cooled in a short time.

However, in this method, when attempting to simultaneously heat a large number of GaAs crystal substrates (wafers) using a large heating substrate support, the following undesirable problem occurs.

That is, as shown in FIG.
When a large substrate support 3 is heated from the outside of the quartz reaction tube 1, the distance from the high-frequency coil 5 is greatly different between the center of the support 3 and the outer circumference near the wall of the reaction tube. It is unavoidable that the temperature profile inside the substrate support 3 becomes non-uniform along the tube diameter direction.

As a result, large variations occur in the thickness and resistivity of the epitaxially grown layer within a substrate (wafer) and between each substrate (wafer), resulting in a problem of reduced yield.

Furthermore, in the apparatus shown in FIG. 4, it is necessary to prevent the substrate (wafer) 20 from falling off the substrate support 3, so a holding device such as a claw must be provided. Not only is it impossible to obtain a desired epitaxial growth layer at the contact portion with the holder and its vicinity, but the occurrence rate of crystal defects is high, which has the drawback of lowering the yield of the product. A method using a vacuum chuck may be considered to prevent the yield from decreasing due to the holder, but this requires a vacuum pump and piping, which increases the size and cost of the device. Furthermore, in a horizontal epitaxial growth apparatus as shown in FIG. Even with rotation, it is difficult to obtain a uniform vapor phase growth layer.

Furthermore, as shown in FIG. 5, as a silicon vapor phase growth apparatus, a nozzle 7 is provided in the vertically placed reaction tube 1 to penetrate through the center of a graphite susceptor 30 and its rotating shaft 3b. There is one in which a wafer 20 is heated by a high-frequency coil 5 disposed below, a raw material is flowed through the nozzle 7, and single crystal silicon is grown on the wafer 20. However, in a silicon vapor phase growth apparatus, it is sufficient to flow the raw material through one nozzle 7.
Unlike GaAs vapor phase growth equipment, two nozzles are provided to supply the Ga compound and As compound to be reacted on the wafer surface, and there is no need to flow the reaction gases separately, and it is also possible to prevent the reaction from occurring on the wafer surface. All you have to do is control it properly. Therefore, it is not necessary to pay much attention to the temperature profile throughout the reaction tube. In other words, heating by the high-frequency coil 5 is sufficient, and heating of the entire reaction tube by a resistance heating furnace is unnecessary.

Furthermore, if the apparatus shown in Fig. 4, which combines the high-frequency heating method and the resistance heating method, is simply made vertical, the heating body that heats the reaction vessel is hollow and cylindrical, so Air flow occurs in the gap between the body and the body due to the chimney effect,
This makes precise control of the temperature profile along the axis of the container extremely difficult.

The purpose of this invention is to prevent surface roughness and crystal defects in an epitaxially grown layer formed on a substrate, and to grow an epitaxially grown layer with uniform thickness and electrical characteristics over the entire surface of the substrate with good reproducibility and yield. An object of the present invention is to provide a compound semiconductor vapor phase growth method and an apparatus for the same.

[Means for Solving the Problems] Therefore, the present invention provides a method in which a raw material storage boat is arranged above a bell jar type reaction vessel with a closed top and arranged vertically, and a rotatable substrate support is arranged below the boat. A spiral high-frequency coil or heating lamp is provided directly below, and a resistance heating furnace is provided so as to cover the periphery and upper part of the raw material gas transport section and the raw material storage boat placement section of the reaction vessel, and the high-frequency coil or heating lamp The substrate support is uniformly and rapidly heated to a predetermined temperature, and the raw material gas transport section and the raw material storage boat arrangement section are constantly heated by an electric resistance heating furnace so that the temperature distribution is approximately uniform or constant along the axial direction. A compound semiconductor layer is epitaxially grown on the surface of the wafer on the substrate support by flowing a reactive gas from a double-structured nozzle that protrudes upward from the center of the rotation axis of the support while heating to create a temperature gradient of . It is something.

[Function] A bell jar type reaction vessel is installed vertically, and the reaction gas discharged from the nozzle is configured to flow from the top to the bottom of the reaction vessel, and a combination of high frequency or lamp heating and resistance heating is used to heat the raw material gas. The transport section is heated by resistance heating, and the GaAs substrate is heated by local heating using a high-frequency coil or heating lamp installed at the bottom of the substrate heating table inside the reaction vessel chamber, so that the axial direction of the raw material gas transport section is heated. The temperature distribution becomes uniform or has a predetermined temperature gradient during steady state, and it is possible to rapidly heat and cool the substrate and to make the in-plane temperature distribution uniform. Moreover, since the flow of air outside the reaction vessel is minimized, the temperature stability and controllability of the raw material gas transport section are improved.

Moreover, there is no Ga As precipitation on the wall surface of the container at the same location, and epitaxial growth on the substrate can be stably performed. Furthermore, the support base on which the board is placed has a concave counterbore to prevent the board from sliding or shifting, and can be held horizontally, so the board can be stably fixed without the need for special board holders. Therefore, it is possible to form an epitaxially grown layer that is uniform over the entire surface of the substrate and has few crystal defects. This makes it possible to efficiently perform vapor phase growth with few defects and good uniformity, thereby achieving the above-mentioned objective of improving product yield and productivity.

[Example] FIG. 1 shows an example of a compound semiconductor vapor phase growth apparatus that realizes the present invention.

In this embodiment, a bell jar-shaped quartz reaction tube 1 with one end closed is arranged on a base 2 so as to maintain a vertical posture with the closed end facing upward.

The reaction tube 1 has a small diameter part 1a in the upper half and a large diameter part 1b in the lower half.
A disk-shaped graphite support stand 3a is disposed within the large diameter portion 1b. If the upper half has the same diameter as the lower half, the volume of the space above the substrate increases, resulting in an increase in the amount of reaction gas stagnation, and the doping distribution of impurities in the thickness direction within the epitaxial growth layer does not become steep. '', which has a negative effect on electrical characteristics when used as a device such as a transistor.For this reason, it is preferable to make the diameter of the upper half as small as possible as long as the function allows. It is fixed to the upper end of a freely attached cylindrical support body 3b.

Further, on the upper surface of the support stand 3a, a plurality of accommodation recesses 3c on which wafers 2o, which are GaAs growth substrates, are placed are formed at equal intervals, similar to the support stand 3 shown in FIG. 3(b). At the same time, a coating of about 0.3 m made of silicon carbide or the like is formed on the surface of the support base 3a. This coating seals impurities generated from the graphite forming the support base and prevents contamination within the reaction tube, and also facilitates aqua regia cleaning of GaAS deposited on the surface of the support base 3a due to epitaxial growth.

Further, a spiral high-frequency coil 5 is disposed below the support base 3a via a reaction gas shielding tube 4 made of quartz, and by passing a high-frequency current through the coil 5, the support base 3a is heated by induction. The wafer placed on top can be heated indirectly.

On the other hand, around the support stand 3a, inside the reaction tube, an inner bell jar 6 having an open upper end is arranged at a predetermined distance from the wall of the reaction tube. The inner bell jar 6 corresponds to the large diameter part 1b and the tapered part 1c of one reaction tube 1, and the small diameter part 1
An exhaust hole 2a is formed in the base 2 so as to substantially match the height of the lower end of the inner bell jar 6, and is located inside the inner bell jar 6. With this, the support base 3
Excessive GaAs can be prevented from being deposited on the wall of the reaction tube 1 in the low temperature section below a. In other words, the reaction gas flowing down from above is guided exclusively to the inside of the inner belljar 6, and is directed to the inner wall of the inner belljar 6.
Even if s is precipitated, it is prevented from being deposited on the wall of the reaction tube 1. After the "epitaxial growth" process, the inner bellger 6 is removed from the reaction tube 1 and cleaned with aqua regia or the like, making handling easier than when cleaning the reaction tube itself.

Furthermore, a nozzle 7 is provided so as to pass through the center of the support body 3b, which is the rotation axis of the support table 3a, and protrude toward the small diameter portion 1a of the reaction tube 1.

This nozzle 7 includes an inner nozzle 7a and an outer nozzle 7b.
The inner nozzle 7a has a double tube structure, and the inner nozzle 7a projects further upward than the tip of the outer nozzle 7b. Above the outer nozzle 7b, a stopper 8 is fixed to the outer periphery of the inner nozzle 7a for forcibly changing the flow of gas flowing therefrom downward.

Further, the tip of the inner nozzle 7a projects upwardly from a raw material storage boat 10 made of quartz and supported by a support 9 fixed to the upper end of the inner bell jar 6. The raw material storage boat 10 is formed in a donut shape, and gallium Ga, which is a raw material for a group III raw conductor, is stored therein.

An electric resistance heating furnace 11 is disposed around a portion of the small diameter portion 1a, tapered portion 1c, and large diameter portion 1b of the reaction tube 1, which serve as guide paths for the reaction gas flowing out from the nozzles 7a and 7b. The temperature in the vicinity of the raw material storage boat 10 can be maintained at a stable temperature of around 800°C. Moreover, in this example.

The upper part of the reaction tube 1 is covered by the electric resistance heating furnace 11, which prevents the flow of air from the bottom to the top caused by the chimney effect around the reaction tube 1. The entire small-diameter portion 1a serving as the accommodation boat arrangement portion and the raw material gas transport portion can be heated so that the temperature distribution along the axial direction constantly becomes approximately -like or has a constant temperature gradient.

Note that a heat shield plate 12 is disposed below the high frequency coil 5 to block the high heat generated in the support stand 3a from being transmitted to the base 2.
An introduction pipe 13 for introducing a gas such as H2 or He is provided inside the shielding cylinder 4 for shielding the high frequency coil 5 and the power supply line from the corrosive reaction gas in the reaction tube 1.

By introducing gases such as H2 and He into the inside of the shielding tube 4, corrosion and oxidation damage to parts such as the high frequency coil 5 and G
Precipitation of aAs can be prevented.

FIG. 2 shows a second embodiment of a compound semiconductor vapor phase growth apparatus for realizing the present invention.

In this embodiment, a spiral heating lamp 5a or a plurality of rod-shaped heating lamps 5a and a reflecting mirror 5b are disposed below the substrate support 3a via a reactive gas shielding cylinder 4 instead of a high-frequency coil, and by passing a current through the lamp 5a, The support table 3a is heated by radiation, and the wafer placed thereon can be indirectly heated. At this time, by appropriately adjusting the relative positions of the lamp and the support base 3a along the radial direction, the in-plane temperature distribution of the support base 3a can be made uniform. Further, below the heating lamp 5a, there is a reflection fi5b that prevents the radiant heat generated by the lamp 5a from being transmitted to the base 2 and reflects it toward the substrate support side so that all the generated heat can be effectively used. is located.

On the other hand, the cylindrical inner bell jar 6 arranged around the shielding cylinder 4 and inside the reaction tube has a height that is equal to or higher than that of the substrate support stand.
It is formed to approximately match the height of a. The inner bell jar 6 is provided for the same purpose as in the first embodiment, and is designed to deposit excess GaAs on the inner wall surface of the inner bell jar 6 and transfer GaAs to the reaction tube 1.
It works to prevent the precipitation of. Although not shown, for the same purpose, a cylinder that can be divided into two and easily removed is provided in close contact with the outer periphery of the shielding cylinder 4 to prevent the precipitation of GaAs on the surface of the outer wall of the shielding cylinder 4. You can also do it.

Further, in this second embodiment, the inner nozzle 7a is
An auxiliary nozzle 17, which is shorter than that of the embodiment and is continuous with the inner nozzle 7a above the stopper 8, is connected by a connecting pipe 16. A flange 17a is formed at the upper end of this auxiliary nozzle 17.
A doughnut-shaped raw material storage boat 10 is placed on top of the boat 7a. Further, above the raw material storage boat 1o, an edge 18a and a baffle plate 1 are provided at a relatively narrow interval.
A disc-shaped baffle 18 with 8b is arranged.

As a result, the gas flowing out from the auxiliary nozzle 17 collides with the baffle 18 and the baffle plate 18b, changes the flow direction downward, comes into contact with the surface of the gallium Ga in the raw material storage boat 10, and the raw material gas and gallium are separated. The reaction is now sufficiently carried out. Note that the baffle 18 is supported by several protrusions 10a formed at the peripheral edge of the boat 1o.

Next, a method of growing a GaAs epitaxial layer on a wafer using the vapor phase growth apparatus configured as described above will be described.

First, gallium Ga as a raw material is put into the raw material storage boat 10 in the reaction tube 1, and a growth substrate 20 such as a GaAs wafer is placed in the storage recess 3c on the support stand 3a. Then, the inner nozzle 7a and the outer nozzle 7
A predetermined amount of nitrogen and hydrogen are flowed from b to replace the gas in the reaction tube. Subsequently, while hydrogen is flowing out from the nozzles 7a and 7b, the power switch of the high frequency coil 5 or the heating lamp 5a is turned on to heat the wafer support stand 3a.

At the same time, the resistance heating furnace 11, which has already been sufficiently heated, is placed over the reaction tube 1 to heat the raw material storage boat section and the raw material gas transport section. At this time, the support stand 3a is rotated at a slow speed of about 10 ppm via the support body 3b.

Due to the above heating, the temperature of the gallium storage part is 800℃~900℃
Furthermore, HCQ (hydrogen chloride) is flowed out together with hydrogen at a rate of several square meters per minute from the inner nozzle 7a until the growth substrate reaches a temperature of 600 DEG C. to 750 DEG C. As a result, GaA
The surface of the s-growth substrate is etched and cleaned, and surface roughening caused by hydrogen as a carrier gas can be prevented. In other words, when a GaAs substrate is heated to about 750°C and exposed to hydrogen for a long time, As will volatilize due to thermal decomposition and the surface will become rough, but etching by HCR is more effective than volatilization of As. Because it is quick, it is possible to prevent surface roughness. However, HCΩ is flowed for about 30 minutes until the gallium storage area reaches a predetermined temperature (800 to 9'OoC), and the amount of the GaAs substrate etched during this period is only about 5 to 10 μm. . Ga
The A s substrate reaches a predetermined temperature in several minutes by lamp heating.

When the Ga storage section reaches a predetermined temperature, the outer nozzle 7
Hydrogen (or arsenic trichloride A s Cfl, using hydrogen as a carrier gas) is flowed from b at a rate of several Q per minute, and AsCf1 is flowed from inna nozzle 7a using hydrogen as a carrier gas.
．． will be introduced. Then, the gallium Ga in the raw material storage boat 10 and the introduced AsCQ3 react to form GaCQ.
and As gas are generated, which flow downward and become Ga.
GaA is grown on the surface of the As growth substrate through a reduction reaction with hydrogen.
s is produced and a single crystal is epitaxially grown.

According to the method and apparatus of the above embodiment, one reaction tube 1 is installed vertically and one reaction gas is ejected from the nozzle tip and flows from top to bottom, so it is similar to when installed horizontally. There is no difference in gas flow between the top and bottom sides of the tube, and the gas flow is uniform throughout the reaction tube. Furthermore, since the support table 3a is rotated, the reaction gas is evenly supplied to the surface of each substrate (wafer).

Furthermore, the substrate (wafer) is evenly heated by the high frequency coil 5 or heating lamp 5a.

Unlike the conventional method of heating the support from the outside of the reaction tube 1, there is no temperature difference between the outside and the center, so the GaAs precipitation reaction progresses evenly and a uniform GaAs growth layer is formed. Formed on a substrate (wafer).

Furthermore, in the above embodiment, the resistance heating furnace 11 is provided so as to cover the upper part of the reaction tube 1 from the periphery of the raw material gas transport section, so that no upward air current is generated around the reaction tube 1 due to the chimney effect. Therefore, the temperature distribution along the axial direction of the raw material gas transport section can be maintained at a substantially -like temperature gradient or at a constant temperature gradient.

Moreover, the temperature stability and controllability are good, and since GaAs is not applied to the wall surface of the container at the same location, epitaxial growth on the substrate crystal can be stably performed. Furthermore, since the disk-shaped support base on which the substrate crystal is placed is held horizontally, the substrate (wafer) can be stably fixed without the need for a special substrate holder, allowing uniform crystallization over the entire surface of the substrate. Epitaxially grown layers with fewer defects can be formed - as a result, the uniformity of the grown film's thickness and electrical properties (resistance) is 3.
It has become possible to efficiently grow an epitaxial growth layer on a wafer with good reproducibility of less than %.

In the above embodiment, the surface of the graphite support 3a is coated with a silicon carbide film, but instead of silicon carbide, silicon nitride (Si, N), boron nitride (BN), or aluminum nitride (A Support stand 3a with coating of uN)
The surface of the substrate may be coated.

Further, the present invention can be utilized when a compound semiconductor layer other than a GaAs semiconductor layer is epitaxially grown on a wafer surface.

[Effects of the Invention] According to the present invention, a good epitaxial growth layer with few crystal defects and a uniform thickness and electrical characteristics can be grown on a wafer with high reproducibility and efficiently. The yield and productivity of wafers can be improved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of a vapor phase growth apparatus implementing the present invention, FIG. 2 is a front view showing a second embodiment of a vapor phase growth apparatus implementing the present invention, and FIG. FIG. 4(A) is a front sectional view showing an example of a conventional vapor phase growth apparatus; FIG. 4(A) is a schematic front view showing another example of the conventional vapor phase growth apparatus. FIG. 4(B) is a plan view showing an example of the configuration of a wafer support in the reaction tube of the same apparatus. FIG. 5 is a front view showing an example of a vapor phase growth apparatus for silicon wafers. DESCRIPTION OF SYMBOLS 1... Reaction tube, 3a... Support stand, 4... Shield tube, 5... High frequency coil, 5a... Heat lamp, 5b... Reflector, 7a, 7b... nozzle,
10...Raw material storage boat, 11...Resistance heating furnace, 2゜Representative Patent Attorney Tomio Ohinata6)...Growth substrate (wafer). No.! Figure diagram

Claims (6)

[Claims] (1) A group III raw material storage boat is placed on top of a bell jar type reaction vessel that is vertically installed with one end of the top closed, and a rotatable substrate support is placed below this storage boat to support the substrate. In a vertical vapor phase growth apparatus in which a plurality of reaction gas supply nozzles are mounted upward from the bottom of a base of a reaction vessel having an exhaust hole so as to pass through the center of the rotation axis of the table, the first heating means The upper part of the bell jar type reaction vessel is heated so that the temperature distribution is constantly almost uniform or constant in the vertical direction, and the substrate support is heated by the second heating means so that the temperature distribution on the upper surface thereof is horizontal. A compound semiconductor characterized in that the raw material gas is caused to flow out from the nozzle while being locally heated uniformly along the direction, and reacts on the surface of the wafer on the substrate support to grow an epitaxial layer. Vapor phase growth method. (2) A group III raw material storage boat is placed on top of a bell jar type reaction vessel that is vertically installed with one end of the top closed, and a rotatable substrate support is placed below this storage boat to support the substrate. Multiple types of reaction gas supply nozzles are provided so as to pass through the center of the rotation axis of the table, and
A compound semiconductor vapor phase growth apparatus comprising: an electric resistance heating means for heating the group III raw material storage boat placement section; and a high frequency heating means or a radiation heating means for heating the substrate support. (3) The compound semiconductor vapor phase growth apparatus according to claim 2, wherein the electric resistance heating means is provided to cover the periphery and top of the reaction vessel. (4) Claim 2 or 3, characterized in that the high-frequency heating means is a spiral coil disposed below the substrate support in the reaction vessel and running along the lower surface of the support. The compound semiconductor vapor phase growth apparatus described above. (5) Claim 2 or 3, characterized in that the radiation heating means is a lamp-shaped heating element disposed below the substrate support in the reaction vessel and running along the lower surface of the support. The compound semiconductor vapor phase growth apparatus described in Section 1. (6) The cross-sectional area of the group III raw material storage boat placement portion of the bell jar type reaction vessel is smaller than the cross-sectional area of the lower substrate wafer support placement portion. The compound semiconductor vapor phase growth apparatus according to item 1, 3, 4, or 5.