JP2753523B2 - (III) -Epitaxial growth method of group V compound semiconductor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor wafer manufacturing technique, and more particularly to a technique that is effective when used in a vapor phase epitaxial growth method of a III-V compound semiconductor.

[Prior Art] Generally, GaAs, GaP, InP, InAs doped with impurities
For example, a vapor phase epitaxy apparatus shown in FIG. 6 is used to vapor-grow a III-V group compound semiconductor such as above on a substrate.

This vapor-phase growth apparatus comprises a cylindrical quartz reaction tube 1 having both ends closed, and an electric furnace 2 for heating the reaction tube 1 from the outside. It is configured so that the temperature distribution can be controlled. When GaAs is vapor-phase epitaxially grown by this vapor-phase growth apparatus,
In the reaction tube 1, a raw material boat 4 containing a gallium 3 as a material source is arranged on the upstream side (left side in the figure), and a gGaAs substrate 5 for vapor-phase growth is arranged on the downstream side.

On the other hand, a first gas introduction pipe 6a and a second gas introduction pipe 6b for supplying gas upstream of the substrate 5 by bypassing the raw material boat 4 are connected to the upstream end of the reaction tube 1. A third gas introduction pipe 6c for supplying gas to the raw material boat 4 is connected to the upstream end of the reaction tube 1.

In the middle of the gas introduction pipes 6b and 6c, AsC
l ₃ of entering the bubbler 8b, 8c is interposed. Gas inlet pipe 6
H ₂ gas is introduced into b and 6c, and a mixture gas of AsCl ₃ + H ₂ can be supplied into the reaction tube 1 by blowing H ₂ gas into AsCl ₃ in the bubblers 8b and 8c. I have. Bubblers 8b and 8c are temperature controlled thermostats (not shown)
And controlling the temperature to control the evaporation amount of AsCl ₃ . Reference numeral 9 denotes an exhaust pipe connected to the downstream end of the reaction tube 1.

In the following description, the gas supply system including the gas introduction pipe 6a is referred to as A
The gas supply system including the bubbler 8b and the gas introduction pipe 6b is referred to as a B system, and the gas supply system including the bubbler 8c and the gas introduction pipe 8c is referred to as a C system.

Conventionally, to perform GaAs vapor phase growth using the vapor phase growth apparatus having the above configuration, first, supply of a mixed gas of AsCl ₃ + H ₂ is started from the C system. Next, after the elapse of a predetermined time, As
At the same time as the supply of the mixed gas of Cl ₃ + H _2, the supply of the doping gas from the system A is started to perform the vapor phase growth. Then, after the growth was completed, the gas supply to all the A, B, and C systems was stopped at the same time.

However, if the gas supply is stopped simultaneously, the decrease in the partial pressure of the doping gas is delayed, so that the partial pressure of the doping gas is relatively increased, and the carrier concentration becomes high in the final formation portion (surface portion) of the epitaxial growth film. There was a problem that would be. When the carrier concentration fluctuates on the surface of the epitaxially grown film, it becomes difficult to obtain a normal metal-semiconductor electrode when manufacturing a device such as an FET.

Therefore, as disclosed in, for example, JP-A-62-202515, after the supply of the doping gas of the A system and the supply of the epitaxial growth gas of the C system are simultaneously stopped, 5 to 10
A technique has been proposed in which the supply of the B-system gas is stopped after a lapse of about seconds to make the carrier concentration uniform within the epitaxial growth film. This is the B system AsCl
_This is because the mixed gas of ₃ + H ₂ has the function of increasing the partial pressure of As ₄ in the reaction tube 1 to lower the partial pressure of the doping gas, thereby lowering the impurity concentration.

[Problems to be Solved by the Invention] However, in the vapor phase epitaxial growth method disclosed in the above-mentioned publication, although the carrier concentration can be made uniform to some extent, it is difficult to control the gas concentration for the homogenization. However, complete uniformity between the surface portion of the epitaxially grown film and other portions could not be achieved.

The present invention has been made in view of such a conventional problem, and by etching a portion having a non-uniform carrier concentration on the surface of a grown epitaxial growth film,
It is an object of the present invention to provide a vapor phase epitaxial growth method of a III-V compound semiconductor capable of obtaining an epitaxial growth film of a III-V compound semiconductor having a uniform carrier concentration throughout the thickness direction of the epitaxial growth film.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a III-V compound semiconductor by supplying an epitaxial growth gas and a doping gas into a reaction tube containing a group III raw material and a substrate. In a vapor-phase epitaxial growth method for vapor-phase growing an epitaxially-grown film of a group III-V compound semiconductor doped with an impurity on a substrate, the impurity-doped epitaxial growth layer may be formed to a thickness greater than a desired thickness while maintaining a constant supply of the doping gas. After the growth, the growth gas supplied to the reaction tube is changed to an etching gas to etch a portion where the impurity concentration changes near the surface of the impurity-doped epitaxial growth layer.

[Operation] In the above-described method for vapor-phase epitaxial growth of a group III-V compound semiconductor, the surface of an epitaxially-grown film whose carrier concentration tends to be non-uniform is removed by an etching gas introduced after stopping the vapor-phase growth. The carrier concentration can be made uniform over the entire thickness of the epitaxial growth film on the surface.

Embodiment FIG. 2 shows an example of a vapor phase growth apparatus used in the vapor phase epitaxial growth method according to the present invention.

This vapor phase growth apparatus is almost the same as that shown in FIG. 7, except that the electric furnace 2 is movable in the axial direction of the reaction tube 1 and the reaction tube 1 can be rapidly cooled at room temperature. Have been. The gas introduction pipes 6b, 6c have three-way valves 10b, 1c.
0c, 11c is interposed, respectively, the H ₂ gas bubbler 8b, 8
It is provided so that a mixed gas of AsCl ₃ + H ₂ may be blown into AsCl ₃ in c, or H ₂ gas may be directly supplied into the reaction tube 1.

In this embodiment, the first gas phase growth apparatus
By starting and stopping the supply of the A, B, and C system gases according to the procedure shown in the figure, a Si-doped GaAs layer is grown on the GaAs substrate 5 in a vapor phase.

That is, from time T _{0 to} T _1, N ₂ gas is supplied from the B and C systems to temporarily replace the inside of the reaction tube 1 with N ₂ gas, and then H ₂ gas is supplied from time T _{1 to} T _2. The inside of the reaction tube 1 was replaced with H ₂ , the electric furnace 2 was operated, and the temperature distribution in the reaction tube 1 was changed to the third.
As shown in the figure, the Ga source is maintained at 820 ° C., and the substrate 5 is maintained at 750 ° C.

Then, from time T _2, and supplies the H ₂ gas containing AsCl ₃ through B and C strains. Then, first, As ₄ dissolves in the Ga to the solubility limit in the boat portion 4 to generate a GaAs crust, and the HCl generated at this time moves downstream to etch the surface of the substrate 5. When the Ga source 3 is completely covered with the GaAs film, the GaAs and HCl react to react with G
aCl and As ₄ are generated and supplied to the downstream substrate 5,
GaAs is deposited on the surface of the substrate 5 and a GaAs layer grows. At this time, the AsCl ₃ + H ₂ gas supplied from the B system acts to suppress the incorporation of Si into the grown buffer layer.

When the buffer layer has grown to a predetermined thickness, B at time T ₃
The supply gas of the system is switched to H _2, and SiH ₄ (hydrogen dilution: 10 ppm) is supplied as a doping gas from the system A, and the GaAs active layer is etched on the substrate 5 after the desired film thickness while doping impurities. Epitaxial growth is made thicker by the amount to be removed. At this time, H supplied from the B system
No. ₂ acts to make the incorporation of Si constant.

Next, at time T ₄ stops the supply of the doping gas of system A (SiH _4), switch the feed gas C line from the epitaxial growth gas (AsCl ₃ + H ₂₎ to H ₂ gas, B
The mixed gas of AsCl ₃ + H ₂ is started to be supplied from the system instead of the H ₂ gas, and etching of the surface of the epitaxially grown film formed on the substrate 5 is started with HCl obtained by thermal decomposition. However, after stopping the doping, instead of immediately switching the supply gas of the B system from H ₂ gas to AsCl ₃ + H ₂ , the H ₂ gas is continuously supplied from the B system for a while (several seconds), and the time T ₅
, The H ₂ gas may be switched to a mixed gas of AsCl ₃ + H ₂ .

Then, switching the feed gas B line in H ₂ at time T _6, the etching gas in the reaction tube 1 was replaced with H _2, axially upstream side of the electric furnace 2 the reaction tube 1 at time T ₇ (second (Left side in FIG. 2) and quenched at room temperature. And time T ₈
In switching the feed gas B and C strains in N _2, the reaction tube 1 was replaced with N _2, the substrate 5 was epitaxially grown at time T ₉
And exit.

In the above embodiment, the temperature of the bubblers 8b and 8c was set to 2
The temperature was set to 0 ° C.

The carrier concentration distribution of the vapor phase epitaxial growth film obtained as described above was measured by CV measurement. The result is shown in FIG. FIG. 4 shows the depth from the surface of the epitaxial growth film on the horizontal axis and the carrier concentration on the vertical axis. As can be seen from the figure, 0.05 to 0 from the surface.
At a depth of 5 μm, the carrier concentration was constant at 6 × 10 ¹⁷ cm ⁻³ , and the carrier concentration did not change near the surface.

In the above embodiment, at time T ₆ the feed gas B lineage
It switched to H _2, the etching gas in the reaction tube 1 was replaced with H _2, so it was decided to quench at room temperature by moving the electric furnace 2 from the reaction tube 1 at time T _7, the predetermined for each growth The thickness of the epitaxially grown film could be obtained with good reproducibility, and the in-plane uniformity was also good.

FIG. 5 shows the relationship between the etching time (T ₆ −T ₅ ) and the in-plane uniformity. The horizontal axis represents the position in the wafer (substrate), and the vertical axis represents the film thickness distribution (1 / sheet). The resistance x 10 ³ ) is taken. In FIG. 5, the solid lines 11 to 15 are obtained by changing the etching time.
Seconds, solid line 12 is 30 seconds, solid line 13 is 40 seconds, solid line 14 is 50 seconds, solid line
15 is a case where it is set to 60 seconds. The average values (Ω / □) of the sheet resistance measurement results are 99.2 for the solid line 11, 107.6 for the solid line 12, and 1 for the solid line.
3 was 141.5, solid line 14 was 195.2, and solid line 15 was 274.7. The standard deviation / average value (%) was 2.8 for the solid line 11 and 12 for the solid line.
Was 3.0, the solid line 13 was 3.1, the solid line 14 was 5.3, and the solid line 15 was 14.5. When the etching time is 60 seconds or more, the variation in the film thickness distribution becomes large, and when the etching time is 10 seconds or less, the effect of the etching does not appear.
It is selected in a range of less than seconds, preferably 20 seconds or more and 50 seconds or less. Corresponding etching thickness exceeds 0.05μm and 0.30μ
m, preferably from 0.10 μm to 0.25 μm.

In the above embodiment, the etching gas is
AsCl ₃ + but using a mixed gas of H _2, the present invention is not limited to such embodiments, for example, H instead of AsCl ₃
A gas containing AsCl ₃ for applying Cl and As partial pressure may be used, and is not limited to a gas as long as it can etch the surface of the epitaxially grown film.
Electropolishing may be used.

Further, the present invention is not only applied to the vapor phase epitaxial growth method of GaAs, but is also applicable to the vapor phase epitaxial growth method of GaP, InP, InAs and the like.

[Effects of the Invention] As described above, according to the method of the present invention for vapor-phase epitaxial growth of a group III-V compound semiconductor, a gas for epitaxial growth and a doping gas are supplied into a reaction tube to form a group III-V compound on a substrate. After growing the semiconductor layer thicker than a desired thickness, the growth gas supplied to the reaction tube is switched to an etching gas to etch an impurity concentration change portion generated near the surface of the impurity epitaxial growth layer. Accordingly, an epitaxially grown film having a uniform carrier concentration over the entire thickness direction can be obtained.

[Brief description of the drawings]

FIG. 1 is a gas control timing chart in one embodiment of a vapor phase epitaxial growth method for a III-V compound semiconductor according to the present invention, and FIG. 2 is a longitudinal sectional view showing a vapor phase growth apparatus used in one embodiment of the present invention. FIG. 3, FIG. 3 is a graph showing a temperature distribution in a reaction tube in one embodiment of the present invention, FIG. 4 is a graph showing a carrier concentration distribution of an epitaxially grown film obtained in one embodiment of the present invention, and FIG. FIG. 6 is a vertical sectional front view showing a vapor phase growth apparatus used in a conventional vapor phase epitaxial growth method for a group III-V compound semiconductor when the time is changed. FIG. 1 ... Reaction tube, 2 ... Electric furnace, 3 ... Ga source, 4 ... Raw material boat, 5 ... Substrate, 6,6a, 6b, 6c ... Gas introduction tube, 8b, 8
c ... Bubbler.

Claims (1)

(57) [Claims] 1. An epitaxial growth gas and a doping gas are supplied into a reaction tube containing a group III raw material and a semiconductor substrate, and impurities are doped on the semiconductor substrate.
In the vapor phase epitaxial growth method of a group III-V compound semiconductor, wherein the group III-V compound semiconductor layer is vapor-phase grown, the impurity-doped epitaxial growth layer is grown to a thickness larger than a desired thickness while keeping the supply amount of the doping gas constant. After that, the growth gas supplied to the reaction tube is switched to an etching gas to etch a portion where the impurity concentration changes near the surface of the impurity-doped epitaxial growth layer, thereby etching the III-V compound semiconductor. Method.