JP2006179526A - Movpe growth apparatus and method for growing compound semiconductor crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an MOVPE growth apparatus capable of keeping mirror surface state without contaminating the surface condition of an epitaxial wafer after growing, and to provide a method for manufacturing the same. <P>SOLUTION: To remove a residual gas or particles left within a reaction furnace after growth of a group III-V compound semiconductor crystal, a large quantity of high-temperature inert gas is introduced into the reaction furnace, and then the growth sequence of semiconductor crystal is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a MOVPE growth apparatus (metal organic vapor phase growth apparatus) and a compound semiconductor crystal growth method using the same.

Conventionally, in order to epitaxially grow a III-V compound semiconductor, for example, a thin film crystal of AlGaInP on a GaAs substrate by metal organic vapor phase epitaxy (MOVPE method), trimethylgallium ( A carrier gas containing an organic metal vapor such as TMG), trimethylindium (TMI), or trimethylaluminum (TMA) and a phosphine (PH ₃ ) group V source gas is supplied, and these source gases are supplied to the crystal substrate. Thermal decomposition reaction.

  This crystal growth is performed by repeating a growth sequence in which the steps of depressurization → temperature increase → growth → temperature decrease → return to normal pressure as shown in FIG. 4 are repeated in the same reactor.

When the growth sequence is continuously performed as shown in FIG. 4, phosphine (PH ₃ ) as a group V raw material remains in the reaction furnace, or phosphorus and its compound are adsorbed on jigs and furnace walls in the reaction furnace. To do. It is easy to adsorb especially in the cold part. Further, when the amount of deposits in the reaction furnace increases, peeling or the like occurs, which causes foreign particles (particles).

  When particles adhere to the substrate surface, the substrate surface after epitaxial growth is soiled or clouded, resulting in poor appearance. In order to prevent these problems, the conventional technology does not flow the source gas for the purpose of removing the residual gas by making the inside of the reactor high vacuum before growth or removing phosphorus and its compounds adsorbed on the furnace wall and jig. Bakeout is performed to raise the temperature in the reactor in this state.

  However, it is difficult to remove the adsorbed gas only by making the reactor high vacuum. On the other hand, when baking is performed, it is possible to discharge the remaining gas and particles, but at a high temperature, the deposits are more easily peeled off, and the number of particles is increased. Further, since a process called “baking out” is added, productivity is lowered.

  Accordingly, an object of the present invention is to provide a MOVPE growth apparatus and a method for growing a compound semiconductor crystal that can solve the above-described problems and can keep the surface state of the grown compound semiconductor crystal in a mirror surface without being contaminated. .

  In order to achieve the above object, the present invention is configured as follows.

  The MOVPE growth apparatus (metal organic vapor phase growth apparatus) according to the invention of claim 1 is a MOVPE growth apparatus for growing a III-V compound semiconductor crystal, for removing residual gas and particles in the reactor after the growth. Further, it is characterized in that means for flowing a large amount of high-temperature inert gas into the reaction furnace before the start of growth is provided.

  According to a second aspect of the present invention, there is provided a compound semiconductor crystal growth method comprising: growing a III-V group compound semiconductor crystal using a MOVPE growth apparatus (metal organic vapor phase growth apparatus); In order to remove residual gas and particles in the reaction furnace, a large amount of high-temperature inert gas is flowed into the reaction furnace, and then a growth sequence is started.

According to claim 1 or 2, wherein the residual gas is, for example, phosphine (PH _3).

The invention of claim 3 is the compound semiconductor crystal growth method according to claim 2, wherein the group III-V compound semiconductor crystal is (Al _x Ga _{1 -x} ) _y In _{1 -y} P (0 ≦ x ≦ 1, 0 <y <1) crystals, and the residual gas is phosphine (PH ₃ ).

  According to a fourth aspect of the present invention, in the compound semiconductor crystal growth method according to the second or third aspect, the inert gas is any one of helium, nitrogen, and argon.

  A fifth aspect of the present invention is the compound semiconductor crystal growth method according to any one of the second to fourth aspects, wherein the temperature of the inert gas is 100 ° C. or higher.

<Key points of the invention>
The main point of the present invention is to remove the gas remaining in the reactor or the adsorbed gas raw material and its compound before starting the growth. Furthermore, it is to suppress the generation of particles. Therefore, in the present invention, a large amount of nitrogen or argon gas, which is an inert gas heated to a high temperature, is allowed to flow in the reaction furnace to exhaust the gas remaining in the reaction furnace together with the inert gas. Further, by bringing the inert gas heated to 100 ° C. or more into contact with the inner wall of the reaction furnace, the adsorbed gas raw material and its compound are peeled off, and the peeled deposits are discharged simultaneously.

  According to the present invention, the following excellent effects can be obtained.

  (1) Since the residual gas and particles in the reactor after the growth are effectively removed, the surface of the compound semiconductor crystal after the growth of the III-V compound semiconductor crystal is not contaminated even if the growth is repeated. Can be kept in.

  (2) Since the residual gas and the adsorbed residual gas raw material and its compound can be easily removed, a mirror-finished compound semiconductor crystal surface can be obtained stably.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  FIG. 1 shows a method for growing a III-V compound semiconductor crystal according to this embodiment. Here, a case where an AlGaInP thin film crystal is epitaxially grown on a GaAs substrate as a group III-V compound semiconductor crystal using a MOVPE (metal organic vapor phase epitaxy) method will be described.

   The reaction furnace of the embodiment is provided with a supply system for supplying a raw material gas and an exhaust system for exhausting the inside of the reaction furnace. This supply system is provided with an inert gas supply means capable of introducing a large amount of a high-temperature inert gas. The exhaust system is provided with an exhaust means for exhausting a large amount of inert gas introduced into the reaction furnace.

  In FIG. 1, first, in order to remove residual gas and particles in the grown reaction furnace, a pretreatment is performed to flow a large amount of high-temperature inert gas into the reaction furnace. Specifically, a large amount of inert gas such as helium, nitrogen, and argon having a high temperature of 100 ° C. or higher is flowed for a predetermined time to heat the inside of the reaction furnace to a high temperature (step S0). By flowing a large amount of inert gas heated to a high temperature into the reaction furnace, the gas (phosphine) remaining in the reaction furnace is forcibly exhausted together with the inert gas. Moreover, the inert gas heated to a high temperature is brought into contact with the inner wall of the reactor to separate the adsorbed gas raw material (phosphorus) and its compound, and the peeled deposits are simultaneously discharged with a large amount of inert gas. .

  After the pretreatment described above, the substrate (wafer) is set on a tray, and the substrate is transferred to a reaction furnace in a nitrogen atmosphere. Then, after reducing the pressure in the reaction furnace with a vacuum pump (step S1) and replacing the reaction furnace with hydrogen, the temperature of the reaction furnace is raised to 700 ° C., the growth temperature of AlGaInP (step S2).

Next, trimethylgallium (TMG), trimethylaluminum (TMA), and trimethylindium (TMI) are used as semiconductor crystal source gases, Ga, Al, and In, respectively, at a predetermined growth temperature (substrate temperature during growth) 700 ° C. Further, phosphine (PH ₃ ) is flowed as a raw material of P, and semiconductor crystal AlGaInP is grown on the substrate (step S3).

  When the growth of the predetermined semiconductor crystal AlGaInP is completed, the temperature of the reaction furnace is lowered to, for example, 50 ° C. (step S4), and the pressure is returned to normal pressure (step S5). Then move the tray from the reactor to the glove box and take out the substrate from the tray.

  In order to confirm the effect of the present invention, a prototype of the conventional example and the example were made.

<Conventional example>
As a conventional example, an AlGaInP multilayered epitaxial wafer was fabricated using a MOVPE apparatus. Growth is performed on a GaAs substrate heated to 700 ° C. using a MOVPE growth apparatus, using trimethylgallium (TMG), trimethylaluminum (TMA), and trimethylindium (TMI) as Ga, Al, and In materials, respectively. The phosphine (PH ₃ ) was used as a raw material. Hydrogen (H ₂ ) was used as a carrier gas during growth.

The growth thickness was 4 μm in one growth. Growth was carried out 50 times continuously, and the surface of the grown wafer was subjected to a surface foreign matter measuring device each time to measure the number of foreign matters. The count of foreign matters was measured by the number of particles having a scattering cross section of 0.9 μm ² or more.

  FIG. 2 shows the transition of the number of foreign objects. A dot with a circle is the case of the conventional example. It can be seen that the number of foreign substances increases as the number of growth times increases. In some cases where the number of times of growth exceeds 40 times, a large amount of foreign matter is generated on the surface so as to be visually recognized under a fluorescent lamp.

<Example>
As an example, an AlGaInP multilayer epitaxial wafer was grown under the same growth conditions as those of the conventional example described above. That is, the growth is carried out using trimethylgallium (TMG), trimethylaluminum (TMA), and trimethylindium (TMI) as Ga, Al, and In materials on a GaAs substrate heated to 700 ° C. using a MOVPE growth apparatus, and The phosphine (PH ₃ ) was used as a P raw material. Hydrogen (H ₂ ) was used as a carrier gas during growth. The growth thickness was set to 4 μm by one growth as in the conventional example, and the growth was performed 50 times continuously.

  However, in this example, as described in step S0 of FIG. 1, before starting growth, nitrogen heated to 150 ° C. was supplied into the reactor at 50 L / min for 10 minutes, and residual / adsorbed gas and particles were removed. Exhausted.

The grown wafer surface was measured for the number of foreign matters using a surface foreign matter measuring device every time. The measurement conditions were the same as those described in the conventional example, and the number of foreign matters was measured by the number of scattering cross-sections of 0.9 μm ² or more.

  FIG. 2 shows the transition of the number of foreign objects. The triangular dots are the case of the present embodiment (the present invention). In the case of this example, the number of foreign substances increases with the increase in the number of growths, but the slope thereof is smaller than in the case of the conventional example. No. When the surface condition of the wafer was confirmed by visual observation under a condenser, the surface of the epitaxial wafer grown by the method of this example was very clean.

<Reason for optimum conditions>
In this example, the temperature of the heated nitrogen gas flowing before growth was changed to investigate how the number of foreign matters changed. FIG. 3 shows the relationship between the gas temperature to be introduced and the number of foreign substances. In order to clarify the effect, the inside of the reactor was in a state after 50 growths. As the introduced gas temperature is gradually raised from room temperature, the number of foreign substances decreases, and the number of foreign substances decreases rapidly around 100 ° C. From this result, the gas introduction temperature is preferably 100 ° C. or higher.

<Usage method, application system, etc.>
(1) In the above embodiment, an (Al _x Ga _1-x ) _y In _1-y P (0 ≦ x ≦ 1, 0 <y <1) crystal is used as a semiconductor crystal by MOVPE (metal organic chemical vapor deposition). Although the growth method has been described, the present invention can be used for a gas source molecular beam epitaxy method in addition to a metal organic vapor phase epitaxy method (MOVPE method) using phosphorus (P) as a raw material.

(2) In the above embodiment, phosphine (PH ₃ ), which is a group V raw material, is used as a residual gas. However, the present invention is also effective for removing a dopant gas such as zinc, magnesium, and selenium used for growth.

It is process drawing which showed the growth method of the III-V group compound semiconductor crystal of this invention. It is the figure which represented the relationship between the frequency | count of growth concerning the Example of this invention, and the number of foreign materials in contrast with the prior art example. It is a figure showing the relationship between introduction gas temperature and the number of foreign materials showing the basis of optimal conditions. It is the schematic showing the growth sequence of a semiconductor crystal.

Claims (5)

In a MOVPE growth apparatus for growing a III-V compound semiconductor crystal,
An MOVPE growth apparatus comprising means for flowing a large amount of a high temperature inert gas into a reaction furnace before the start of growth in order to remove residual gas and particles in the reaction furnace after growth. In a compound semiconductor crystal growth method for growing a group III-V compound semiconductor crystal using a MOVPE growth apparatus,
A method for growing a compound semiconductor crystal, comprising: flowing a large amount of high-temperature inert gas into a reaction furnace in order to remove residual gas and particles in the reaction furnace after growth, and then starting a growth sequence. In the growth method of the compound semiconductor crystal of Claim 2,
The III-V group compound semiconductor crystal is an (Al _x Ga _{1 -x} ) _y In _{1 -y} P (0 ≦ x ≦ 1, 0 <y <1) crystal, and the residual gas is phosphine (PH ₃ ). A method for growing a compound semiconductor crystal, comprising: In the growth method of the compound semiconductor crystal of Claim 2 or 3,
A method for growing a compound semiconductor crystal, wherein the inert gas is helium, nitrogen, or argon. In the growth method of the compound semiconductor crystal in any one of Claims 2-4,
A method for growing a compound semiconductor crystal, wherein the temperature of the inert gas is 100 ° C. or higher.

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