JPS59116191A - Vapor growth method of semiconductor crystal of in base iii-v group compound - Google Patents

Abstract

PURPOSE:To obtain the titled high-quality crystal at atmospheric pressure by connecting a piping system mixing the vapors of org. In compd. and the org. V group compd. and a piping of the V group hydride to a piping system in which a gaseous raw material is sent and controlling the pipe wall temps. of respective piping systems. CONSTITUTION:Hydrogen gas is bubbled in an org. In compd. 401 and an org. Vgroup compd. 402 put in containers 404, 405 and the generated vapors are sent to a mixing vessel 412 together with H2. The mixed gas is sent from the first piping system 414 to the second piping system 413 in which H2 gas for transportation is guided via an entrance 415. Further, the V group hydride 403 is sent from the entrance 420 to the system 413, and the pipe wall temps. of respective systems 414, 413 are controlled independently by heating elements 416, 421 to carry out the vapor growth of a semiconductor crystal of a desired compd. on a substrate crystal 423 in a growth furnace 418. In this manner, the low-temp. decomposition of the org. In compd. and condensation and accumulation of the reaction products in the pipes caused by contact and mixing of gaseous raw materials are prevented, and the titled uniform product of high quality is obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is suitable for growing In-based compound semiconductor thin films such as Ink, InGaAs, and InGaP by pyrolysis vapor phase growth using an organic In compound as a starting material. Concerning vapor phase growth methods.

[Technical background of the invention and its problems]

Recently, the development of elements that can operate at high speed in a high frequency band has been progressing. The matrix material used in these devices is required to have characteristics such as a high electron saturation rate and high electron mobility under a low electric field.

In-based compounds such as InP and InGaAs have higher electron saturation velocity and lower field electron mobility than GaAs, which is currently used as a material for microwave devices, and are suitable as materials for high-speed operation devices. It is attracting attention as One of the methods for growing these In-based group IV compound semiconductor crystal thin films is the pyrolytic vapor phase growth method using an alkyl compound of In and a hydride of a group Ⅰ element as the starting materials for the group V and group V elements, respectively. FIG. 1 shows a layout of a vapor phase growth apparatus for In-based compound semiconductor crystals which is generally used in this case. In the figure, (101) is an organic In compound that is a starting material for In, and (102) is a group V hydride that is a starting material for group V. The steam and gas of these starting materials are
The transport gas (carrier cassette) flowing through the transport pipe (103) is both introduced into the growth reactor (104). Growth furnace (1
The starting material vapor or gas introduced into the 04) is thermally decomposed in the growth temperature range where it is heated to a desired temperature by, for example, a high frequency coil (105), and then placed in the growth temperature range. The structure is such that a compound semiconductor growth layer is deposited on a substrate crystal (106). For example, in the pyrolytic vapor phase growth method of indium phosphide (Ink), organic In compounds (
101) as trimethyl In((CI4s)sIn
), or 1 sip of triethyl ((CtHs)sIn
), and phosphine (FT(3)) is often used as the hydride (to2) of group (2).

However, these organic In compounds used in the pyrolytic vapor phase growth of InT' are easily dissociated and decomposed at low temperatures, and the first
As shown in the figure, before the vapor of the organic In compound (101) reaches the growth temperature region, it decomposes in the low temperature region near the gas inlet (107) to the growth furnace (104).

Therefore, organic In is placed in the low temperature area near the waste inlet (107)
A decomposition product (108) of the compound is deposited and the substrate crystal (1
06) Disturb the compositional stability of the overlying Chenling Formation. Also, the substrate crystal (
106) The deposition rate of the growth layer on J- is low and the reproducibility is low. When the vapor of these organic In compounds and the vapor of Group V hydride come into contact, a low-volatile substance is generated, and this low-volatility substance is absorbed into the piping system, for example, in the transport pipe shown in Figure 1. The particles deposited within (103) also contribute to the difficulty in crystal growth of a uniform, high-quality InP thin film.

In order to eliminate such drawbacks of the pyrolysis vapor phase growth method of In-based compounds, the pressure inside the reactor is lowered, and I
Attempts have also been made to perform vapor phase growth of n-based compounds. FIG. 2 shows the configuration of a typical vapor phase growth apparatus used when performing vapor phase growth under reduced pressure. In the same figure (201) is organic I
(202) represents a group V hydride.

The growth furnace (203) is evacuated using a vacuum pump (204). The pressure inside the growth furnace (203) is adjusted by controlling the degree of opening and closing of the gate pulp (205). A filter (206) for removing harmful substances is provided at the rear of the vacuum pump (204).

In order to perform vapor phase growth of InP, for example, using the reduced pressure vapor phase growth apparatus having the above configuration, triethyl I n ((C2H'5)3 In ) is used as the organic In compound (201), and V
It is common to use phosphine as the group hydride (202). The steam and gas of these starting materials are evacuated by a vacuum pump (204) and introduced into a growth furnace (203) whose pressure is regulated by a gate valve (205), where the substrate is heated by a high frequency coil (207) etc. Crystal (208)
The growth layer accumulates on top. The main advantage of this method of vapor phase growth of In-based compound films under reduced pressure is that the mean free path of gas molecules is generally longer under reduced pressure. The substrate crystal inside (2
08) It is possible to reduce the unnecessary decomposition of the organic In compound in the low temperature region as described above by transporting it to the vicinity in a short time.

However, in order to grow In-based compounds, such as InP crystals, with good reproducibility using the reduced pressure vapor phase growth apparatus configured as described above, it is necessary to
It is required that the pressure (degree of pressure reduction) in the growth reactor (203) be stable for each growth cycle, and that fluctuations in the pressure in the growth reactor (203) during growth be suppressed. However, the vacuum oil sealed in the exhaust vacuum pump (204) deteriorates due to a reaction with harmful gases such as phosphine gas (102), and the filter for removing harmful substances (particles) (206) becomes clogged. Considering the accompanying fluctuations in displacement, etc., extremely complicated operation and maintenance of the vapor phase growth apparatus is required to fully meet the above requirements.

It is expected that the complicated operation methods and the maintenance and upkeep of the vacuum system included in the vapor-phase growth apparatus during vapor-phase growth under reduced pressure can be avoided by using the vapor-phase growth method under atmospheric pressure. However, regarding the growth of In-based compound crystals, as mentioned above, the inability to sufficiently prevent the decomposition of organic In compounds hinders the production of high-quality crystals. A method for pyrolytic vapor phase growth of In-based compound crystals in which low-temperature decomposition of organic In compounds is suppressed under normal pressure is desired. Currently, in order to prevent low-temperature decomposition of organic In compounds, attempts are being made to add small amounts of organic compounds of group V elements to the starting material gas system for growing In-based compound semiconductor crystals. FIG. 3 shows a typical example of equipment used in such an attempt.

In the figure, (301) is an organic In compound, (302) is a hydride of a group II element, or (303) is an organic group compound. The steam and gas of these starting materials are each independently introduced into a gas transport pipe (304) through which a transport gas (carrier gas) flows, and then transported into a growth furnace (305).

The vapor of the starting material transported into the growth furnace (305) together with the transport gas is thermally decomposed near the substrate crystal (307), which is heated and maintained at a desired growth temperature by, for example, a high frequency coil (306), and the substrate crystal is (307) Semiconductor crystal is grown in vapor phase on top.

To perform vapor phase growth of TnP crystal using this method, for example, trimethyl In ((C)
Is)sin), phosphine (PITR) as a group hydride (302), and trimethylarsine ((CH3)3) as an organic compound (303) of a group
As ) is used. By adding this organic group V compound to the reaction gas system, the organic In compound can be grown in the low temperature region in the growth reactor (305), compared to the above-mentioned normal pressure vapor phase growth method that does not use the organic group V compound. Decomposition product accumulation can be reduced. However, due to the contact in the transport pipe (304) between the organic group I compound added to the reaction gas system and the starting material other than the organic In compound, especially the group V hydride, the low-volatile substance (308) is These are the transport pipes (304)
There are still problems such as the accumulation of water on the surface. The accumulation of this low volatility product in the transport pipe is a major factor that inhibits the vapor phase growth of high quality InP crystals. Therefore, even in the atmospheric pressure pyrolysis vapor phase growth method using organic compounds of group Ⅰ, there are problems that need to be solved, such as mixing organic group V compounds into the reaction gas system and preventing the accumulation of low-volatile substances in the reaction tube. There are many.

[Purpose of the invention]

The present invention aims to eliminate the above-mentioned drawbacks and provides a vapor phase growth method that suppresses low-temperature decomposition of organic In compounds under normal pressure and enables vapor phase growth of In-based compound semiconductor crystals.

[Summary of the invention]

That is, in this invention, the vapor of an organic indium compound, which is an indium raw material, is brought into contact with and mixed with the vapor of an organic group II compound in advance, and passed through a first piping system, and then the mixed vapor is
The transport gas is mixed into a second piping system that guides the transport gas, and the second piping system further mixes Group III main source hydrogen compound vapor, and the pipe wall temperature of the first piping system and the second piping system increases. This method is for vapor phase growth of an In-based 1-V group compound semiconductor crystal in which each raw material gas reaches a growth furnace through independently controlled piping systems and is grown in a vapor phase.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows an example of an In-based 1-V group vapor phase growth apparatus used in this example. In the figure, (401) represents an organic In compound used as a starting material for In, and (402) represents an organic group V compound such as trimethylarsine ((CH,), As). (403) is a hydrogen compound of group V element, which is the main source of group Ⅰ element. The organic In compound (401) and the organic group V compound (402) were stored in a stainless steel bubbler container (
404) and (405), respectively. Organic In
The vapor pressure of the compound (,101) and the organic compound (402) is controlled using a stainless steel bubbler container (404),
The temperature of (405) may be adjusted using constant temperature baths (406) and (407). In this vapor phase growth apparatus, a flowmeter (410
), (411) to precisely control the flow rate of hydrogen (H7)
Organic In compound (401) by bubbling with gas
and the organic compound (402), and the generated vapors are conveyed together with hydrogen gas etc. through the pipes (408) and (409), respectively, and are thoroughly mixed with each other in the gas mixer (412). The mixed gas is transferred to a gas mixer (41
2) through the first piping system (414) and introduced into the second piping system (413) through which the transport gas is flowing through the inlet (415), and this piping system (413) and flows into the growth furnace (418) through a connecting joint (419) between the growth furnace (418) and the growth furnace (418). The temperature of the outer tube wall of the first piping system (414) is determined by the resistance heating element (4
16) can be adjusted with a transformer (417). The group V hydrogen compound (403) is the above organic In compound (401) and the organic group II compound (402)
An inlet (420) provided at a position further closer to the connecting joint (419) of the growth furnace (418) than the inlet (415) provided to introduce the mixed steam with the second piping system (413).
is introduced into this piping system (413) via. The temperature of the outer pipe wall of the second piping system (413) between the inlet (415) and the connection joint (419) is determined by the voltage applied to the resistance heating element (421) provided around the pipe body. The first piping system (414) is adjusted by a transformer (422).
) can be controlled independently from the temperature of the outer tube.

A substrate crystal (423) placed in a growth furnace (4N()) is heated by a high frequency coil (424).

This vapor phase growth apparatus is used to perform vapor phase growth of InP crystal. First, as an organic In compound (401), trimethyl Jn
((CIls)sln) as an organic compound (402)
Trimethylphosphine ((CHs)sP ) is used as the hydride (403) of a group V element, and phosphine (PH3) gas is used as the group V element hydride (403). Trimethyl I n (401
), and stainless steel bubblers ((404) and (405) containing trimethylphosphine (402)
) is the temperature of the constant temperature bath ((,406) and (407))
and maintained at 30°C and 20°C, respectively.

Trimethyl In, trimethylphosphine is purified hydrogen (
H2) Bubble gas and bubble trimethyl In H
The second flow rate was 30 cc/min, and the flow rate was set to 25 cc/min, respectively.

Phosphine (PH,) gas diluted with H2 with a concentration of 10% is used, and the flow rate of pHs gas is set at 650 ec/min. H2 gas is used as the transportation gas, and its flow rate is:
6. Set it to 71/min. Substrate crystal (423) L and 41
Iron (Fe) added (
100) Using InP crystal, the temperature of this substrate is 650
Keep set at ℃. Gas mixture again? The outer wall temperature of the second piping system (413) from the gas inlet (412) to the gas inlet (415) is set to 55°C, and the connecting joint (4
The outer wall temperature of the first piping system (414) leading to 19) was set to 60
Heat and maintain at ℃.

Under these growth conditions, In'P crystal was continuously grown in a vapor phase, and the change in the growth rate of the InP crystal with the number of times of growth was investigated. The results are shown in FIG. The numerical values indicated by circles in the figure are the results obtained with the apparatus configuration and method based on this example. On the other hand, the numerical values indicated by marks in the figure were obtained by the above-mentioned conventional normal pressure vapor phase growth method in which organic In compound vapor and organic Group V compound vapor are grown without being mixed with each other in advance. This is the result. In the conventional normal pressure vapor phase growth method, the growth rate of InP crystals is not stable from growth to growth, and the growth rate is
It tends to decrease as the number of growth increases and is unstable. On the other hand, in the vapor phase growth apparatus with the apparatus configuration based on the present invention, a growth rate of 0.11 μm/min, which is approximately twice that of the conventional method described above, can be obtained, and even if the number of growths is increased, the acid amount rate remains almost the same. No change is observed and it remains constant.

Also, the results of investigating the distribution of the thickness of the deposited layer within the wafer surface for an InP wafer obtained when an InP vapor phase growth layer was deposited on an InP crystal substrate for 20 minutes.

While the average film thickness was 22 μm, the standard deviation of the film thickness variation was 0.18 μm, and a grown layer having a uniform thickness was deposited. As described above, according to this embodiment, it is possible to maintain the growth rate of the InP vapor phase growth layer stably and with good reproducibility, and it is possible to vapor phase grow an InP crystal having a uniform film thickness.

Next, we will discuss the effect of heating the outer wall of the pipe on the surface quality of the InP vapor growth layer. When the outer wall of the pipe is not heated, a solid substance that is likely to be produced by contact with the group V hydride in the vapor of the organic In compound is observed inside the transport pipe (413).

A portion of these deposited minute solid substances are transported to the vicinity of the substrate crystal (423) placed in the growth furnace (418) by a large amount of transport gas flowing within the second piping system (413). , these fine particles are taken into the raw material gas,
This adversely affects the surface quality of the grown film, such as inducing abnormal growth such as the formation of pyramid-shaped protrusions in the resulting vapor-phase grown film. On the other hand, by heating the outer wall of the piping as shown in the example, the solid substance as described above condenses inside the piping.

To prevent deposition and to obtain a vapor-phase grown film having good surface quality. Further, the second piping system (413) includes the first piping system (
414), a large amount of H2 gas with good thermal conductivity flows. Therefore, from the outer wall temperature of the first piping system (414) provided to introduce the mixed vapor of the organic group II compound and the organic group II compound into the second piping system (413), the second piping system Setting the outer wall temperature of (413) a little higher is more effective in preventing solid substances from condensing and depositing inside the pipe.

Therefore, by heating the piping system as described above and controlling the temperature independently for each piping system, the vapor of the organic In compound and the vapor of the Sv-containing compound are mixed in advance, and the low-temperature decomposition of the organic In compound is prevented. This prevention also prevents condensation and deposition of reaction products in the piping due to contact and mixing of starting material gases, resulting in uniform and high-quality vapor phase growth of InT' crystals.

The vapor phase growth apparatus used in the above example is a ternary one containing In.

Alternatively, it can also be applied to vapor phase growth of quaternary semiconductor mixed crystal thin films.

For example, in order to grow a TnGaAs ternary mixed crystal thin film in the vapor phase, trimethyl In is used as an organic compound, and trimethylarsine ((CHs)s
As) is converted into arsine (A) as a hydrogen compound of group V element.
s H3) may be used. In addition, organic Ga is used as a Ga source.
The compound trimethyl Ga ((CHs)sGa) can be used. In order to introduce trimethyl Ga into the reaction gas system, a piping system may be configured as shown in FIG. (601) in the figure is an organic In compound ((CHs)sIn
), (602) is an organic group compound ((cr(3
)sAS), (603) is 1! la compound ((CHs
)30a), (604) are hydrogen compounds of group ■ elements (A
sHs). Even when using an organic Ga compound in addition to the organic In compound as a starting material, the organic In compound ((CL)sin) (601) and the organic group V compound ((
CH3)3AS) (!: Preliminary gas mixer (605)
) and then this mixed gas is introduced into the transport gas reaction tube (606) through the inlet (607). (CH3) 30a (603) steam is introduced into the inlet (
The transport gas reaction tube (606)
) is mixed with the transport gas flowing through it.

AsH3 gas is further supplied to the growth furnace (60) from the inlet (609).
8) is mixed with the transport gas through the inlet (610) located on the side.

Even in the above case, the organic In compound and the organic Group V compound are brought into contact and mixed in advance, and this mixed gas is mixed with other organic metal compounds or the vapor of the hydrogen compound of the Group V element,
If the organic In compound is introduced into the transportation gas through an inlet arranged as shown in FIG. 6 without contacting the gas, decomposition of the organic In compound can be suppressed. Also, as mentioned above, a gas mixer (
The first piping system (605) to the inlet (607)
11), and the temperature of the outer wall of the second piping system (612) from the inlet (607) to the growth furnace (608) is heated and maintained at 35°C and 40°C by resistance heating elements (613) and (614), respectively. By doing so, it is possible to prevent unnecessary condensate that is expected to be generated by the gas phase reaction in the piping systems (6] 1) and (612) from accumulating in the piping systems (611) and (612), and to prevent organic In High-quality I n G with suppressed decomposition of compounds
To achieve vapor phase growth of an A s ternary mixed crystal thin film with good reproducibility.

In this example, a case has been described in which InP and TnGaAs are vapor-phase grown using trimedel T n ((CI(s)sIn) as a raw material, but the raw material for In is not limited to (CHs)sIn). Other organic In compounds such as triethyl I n ((C2Hs) + T n
) but that's fine. In addition, the organic group V compound used for the purpose of suppressing the decomposition of organic In compounds is trimethylphosphine c
(CH3)P), trimethylarsine (((J
ls)sA-8), and other organic Group V compounds may be used. In addition, in the embodiment, fn(]aA
Trimethyl O is used as an organic Ga compound to grow s.
Although a is used, other organic Ga compounds may also be used. Furthermore, although a resistance heating element was used in the embodiment to adjust the temperature of the outer wall of the piping, the method of heating the piping system is not limited to this method.

〔Effect of the invention〕

As described above, according to the present invention, the temperature of the outer wall of each pipe of the first piping system and the second piping system can be independently controlled and vapor phase growth is performed, thereby forming an organic In compound. In addition to suppressing the necessary decomposition, it also prevents organic In from entering the pipes.
The deposition of low-volatile substances based on the decomposition reaction of the compound is also prevented, and high-quality semiconductor crystals of In-based compounds can be grown with good reproducibility.

[Brief explanation of the drawing]

Figure 1 shows an example of a vapor phase growth apparatus conventionally used for vapor phase growth of Tn-based compound crystals under normal pressure.
The figure shows an example of a vapor phase growth apparatus used for vapor phase growth of In-based compound crystals under reduced pressure.
FIG. 4 is an example of a vapor phase growth apparatus for In-based compound semiconductor crystals used in the present invention, and FIG. 5 is an example of a vapor phase growth apparatus for using a group compound as one of the starting materials. Comparison of the growth rate of InP crystal grown in vapor phase by the method based on the method based on the growth number (%) Figure 6 is a diagram showing another example of a vapor phase growth apparatus for In-based compound semiconductor crystal used in the present invention. . In Figure 1, (101)...organic In compound (102)...hydride of group ■ element (103)...gas transport pipe (104)
)...Growth furnace (105)--Heating high-frequency coil (106)...Substrate crystal (107)...Gas inlet (201)...Organic In compound (202)...V group Elemental hydride (203)...Growth reactor (2
04)... Vacuum pump for exhaust (205)... Gate valve (206)... Filter for removing harmful substances (207)...
... Heating high-frequency coil (208) ... In the substrate crystal diagram 3 (301) ... Organic In compound (302) ... Hydride of group ■ element (303) ... Organic group compound (3
04)...Gas transport pipe (305)...Growth furnace
(306)...Heating high frequency coil (307)
...Substrate crystal (308)...Low emissive substance In Figure 4 (401)...Organic In compound (402)...Organic V
Group compound (403)...Group hydride (404)...Stainless steel baffler container (405)
... (406) ... Constant temperature chamber (407) ... Constant temperature chamber (408) ... Piping (409) ... Piping (410) ... Flowmeter (411) ... Flowmeter (412) ...Gas mixer (413)...Second piping system (414)...First piping system (415)...
・Gas inlet (416)...Resistance heating element (417
)...Transformer (418)...Growth furnace (419
)...Connection joint (420)...Inlet (
421)...Resistance heating element (4, 22)...Transformer
(423)...Substrate crystal (424)...High frequency coil for heating In Fig. 6 (601)...Organic In compound (602)...Organic Group II compound (603)...Organic Ga compound (6
04)...Hydride of group ■ element (605)...Gas mixer (606)...Gas reaction tube for transportation (607)
)...Inlet (for organic In compound) (608')...
・Growth furnace

Claims (1)

[Claims] The vapor of an organic indium compound, which is an indium raw material, is
The vapor of the organic Group V compound is brought into contact and mixed with the vapor of the organic group V compound and passed through the first piping system, and then the mixed vapor is mixed into the second piping system that guides the transport gas (carrier gas). The second piping system further mixes hydrogen compound vapor, which is the main supply of the group ■, and the temperature of the tube wall of the first piping system and the second piping system is controlled independently.Each raw material gas grows through the piping system. A method for vapor phase growth of In-based 1-V group compound semiconductor crystal, characterized by vapor phase growth in a furnace.