JPS6072222A - Method for growing semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain the good-quality growth layer in a thin film growing device for growing compound semiconductor thin films by a method wherein a pedestal supported by a supporting member is arranged in a vertical tube reactor and a partion wall arranged around a semiconductor substrate put on said pedestal screens it and a flow path restrain spacer is arranged on the pedestal to expose the substrate to a material gas introduced from a gas inlet of the top through a space between the spacer and the reactor, after which the gas after use is carried to the gas outlet of the upper part through an opening of the center of the spacer. CONSTITUTION:A pedestal 10 for carrying a compound semiconductor 8 is inserted in a tube reactor 2 surrounded by a water-cooled outer tube 3 with being supported by a supporting member 9 and the periphery of the substrate 8 is screened by a partition wall 37. Above the substrate 8, an exhaust opening for the gas 29 after use is arranged in the center and a flow path restrain spacer 23 having a space for passing a material gas 30 is arranged in the periphery. The material gas 30 is introduced from the inlets 21 both of which are arranged in the upper part and the substrate 8 is exposed to this gas and is mixed sufficiently in a gas mixing and dispersing chamber 34. After that the gas is led to an outlet 22 through the central part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a semiconductor thin film growth apparatus suitable for growing semiconductor thin films, particularly compound semiconductor thin films.

(Description of Prior Art) As a method for epitaxially growing a compound semiconductor film 11 such as GaAs or AlAs, an organometallic compound thermal decomposition method, which is different from the conventional liquid phase epitaxial growth method, has been proposed. This method is called the MO-CVD method, and is a method of crystal-growing a compound semiconductor thin film by thermally decomposing an organic metal. The basic characteristics of this MO-CVD method include that the composition and growth rate of the grown film can be controlled using the raw material transport law, and that it is an irreversible reaction and does not have the negative effects of substrate etching. Therefore, it has recently attracted much attention as a core technology for optical semiconductor devices and ultra-high frequency/ultra-high speed devices.

However, many phenomena are unclear because the theories of thermal decomposition and growth reactions of organic metals are still underdeveloped. In particular, the quality of the grown epitaxial layer tends to be greatly influenced by the structure of the reaction tower, the method of supplying various scraps, etc., which has been a major problem.

FIG. 1 is a cross-sectional view schematically showing a typical structure of a conventional reaction tower used in the MO-CVD method.

In this structure, the reaction tower 1 has a double structure made of quartz glass, with an outer tube 3 provided around the outer periphery of an inner reaction tube 2, and inlet/outlet ports 4.5 provided above and below the outer tube 3. The structure includes a cooling device that cools the outer wall of the reaction tube 2 by flowing cooling water through the tube.

A gas inlet 6 is provided in the upper part of the reaction tube 2, and a waste discharge lower is provided in the lower part.
A (CH3) 3, A (C413) 3, etc. gas) and hydride residue (e.g., AsH3, PH3, etc. gas) are fed into the reaction tube together with a carrier gas (e.g., H2, Ar, etc. gas), Unnecessary gas after the reaction is discharged from the gas outlet pipe 7.

Further, a compound semiconductor substrate 8 on which an epitaxial growth layer is to be grown is mounted on the upper surface 10a of a carbon pedestal 10 installed on a support 9t in the reaction tube 2,
Is this outside? It has a structure in which it is heated to 600 to 800°C by a high frequency induction coil 11, which is a heating device provided on the outer periphery of the cylinders 6 and 3. In order to uniformly supply gas to this substrate 8, a mesh part tjA12 made of quartz glass is provided below the gas inlet 6, thereby mixing and dispersing the mixing force flow from the gas inlet 6. ing.

(Disadvantages of the prior art) In order to obtain a homogeneous growth layer using the MO-CVD method, it is necessary to carry out the thermal decomposition reaction at an appropriately low temperature so that no harmful reactions occur. In the conventional reaction tower structure described above, due to the temperature R of the pedestal at one stage during epitaxial growth, the temperature of the compound semiconductor substrate and the gas near the pedestal doubles, which causes convection of the mixed gas flow. is generated intensely, and the mixed gas flow 14 that has passed through the waste inlet 6 or the mixing and dispersing mesh member 12 is stirred vigorously, and as a result, the reaction tube? The temperature of the mixed gas inside will rise excessively. Because of this, before the mixed gas involved in epitaxial growth reaches the vicinity of the compound semiconductor 8, each component undergoes a decomposition reaction. This thermal decomposition reaction has a significant effect on the ratio of each component element in the mixed gas that reaches the surface of the compound semiconductor substrate 8, so the convection of the mixed gas flow causes in-plane unevenness on the substrate surface. Including uniformity, this poses an extremely large obstacle to achieving a high-quality epitaxial growth layer.

(Purpose of the invention) The purpose of the invention is to radically solve such conventional drawbacks,
The raw material mixed gas is supplied to the compound semiconductor substrate while being maintained at a low temperature, and the high temperature spent gas or other unnecessary waste after the reaction in 5 is reliably separated from the raw material mixed gas and exhausted. Another object of the present invention is to provide a semiconductor thin film growth apparatus having a structure in which harmful fine powder generated by a high-temperature mixed gas falls onto the surface of a compound semiconductor.

(Structure of the Invention) In order to achieve this object, according to the present invention 1, a gas flow regulating device is provided in the reaction tube to fundamentally improve the relative relationship between the mixed gas in the reaction tube and the compound semiconductor substrate. Therefore, according to the semiconductor thin film growth apparatus of the present invention, a waste inlet for supplying raw material waste and a gas loss outlet for discharging rising exhaust gas are provided at the upper end of the reaction tube, Furthermore, a gas flow path regulating device is provided within the reaction tube,
This waste flow path regulating device has a gas flow path regulating device that allows the raw material waste supplied from the gas inlet to descend along the inner wall of the reaction tube, and also to separate it from the raw material gas and discharge the rising exhaust gas. A flow path regulating spacer is provided between the outlet and the upper surface of the pedestal, and includes a gas suction section that sucks rising exhaust gas and a neck section that discharges the rising exhaust gas to the gas exhaust port. do.

In a preferred embodiment of the invention, the gas flow regulating device includes:
A partition wall can be provided near the upper surface of the pedestal to partition the space within the reaction tube.

Furthermore, in carrying out the present invention, it is preferable that the flow path regulating spacer is provided with an enlarged portion that is provided between the aforementioned neck portion and the lower end portion of the gas suction portion and forms a gas convection space. It is.

Furthermore, in the present invention, it is preferable to insert cotton-like fibers into the gas convection space of this ampulla.

(Description of Examples) Examples of the present invention will be described below with reference to FIG. In these figures, the same components as those shown in FIG. 1 are indicated by the same reference numerals, and detailed explanation thereof will be omitted. Further, these figures are only shown schematically with some parts omitted to the extent that the structure of the present invention can be understood.

FIG. 2 is a schematic cross-sectional view showing one embodiment of the reaction tower of the semiconductor thin film growth apparatus of the present invention.

According to the present invention, as is clear from FIG. 2, raw material gas is supplied from one or more waste inlets 21 provided at the upper end of the reaction tube 2, and is discharged from the gas outlet 22 also provided at the upper end. The structure is such that A gas flow regulating device is disposed within this reaction tube 2. Various gases involved in evixaxial growth include Ga(,CH3)3, AI(CH3), and AI(CH3).
3) Organometallic compound scum such as 3, AsH3, PH3
etc., scum for impurity addition, carrier gas such as H2, At, etc. are used, and these raw material gases are mixed in several sub-groups and then passed from the gas inlet 21 to the reaction tube 2. supplied inward. The above-mentioned gas flow path regulating device includes a flow path regulating spacer 23 made of quartz glass, for example, in order to regulate the flow paths of these raw material gases.

This spacer 23 connects the gas υ[outlet 22 and the pedestal l
The attachment/detachment 11 is inserted and disposed between O and O.

In the illustrated example, the spacer 23 includes a neck 24 arranged to communicate with the gas discharge port 22, an enlarged part 25 continuous to the neck 24, and a lower end of the enlarged part 25 connected to the neck 24. gas outlet 2 in the center of the reaction tube 2.
2 side and a gas suction part 27 extending obliquely in three directions and having a groove 26 formed above the semiconductor substrate 8. This gas suction part 27 has a shape that is constricted on the upper side and widens towards the lower side, and collects a gas flow near the central axis of the reaction tube 2.

In addition, the enlarged portion 25 has a central portion that is, for example, a cylindrical portion, and the raw material gas that has flowed therein is cooled. $
It has a guiding function so that it can descend near the wall surface along the inner wall of No. 2. It is preferable that the enlarged portion 25 and the gas suction portion 27 form a gas convection space 28 inside the spacer 23 . Alternatively, a structure may be adopted in which the neck portion 24 is directly communicated with the central opening 26 of the gas suction portion 27 in a chimney-like manner without providing the enlarged portion 25. In this case, the gas suction part 27 is appropriately spaced apart from the pedestal 10 and the semiconductor substrate 8 to provide a gap between them, so that the gas is supplied into the tube from the gas inlet 21 at the upper part of the reaction tube 2. The configuration is such that the source gas can pass through the outside of the spacer 23 and be effectively supplied to the compound semiconductor substrate 8 mounted on the center surface of the pedestal 10.

Further, the spacer 23 acts to completely separate the rising exhaust gas 29, which is heated near the upper surface 10a of the pedestal 10 and is at a high temperature, from the raw material mixed gas 30 supplied from the waste inlet 21.

In addition, in the case of a structure in which this spacer 23 is provided with an enlarged portion 25, the gas to be discharged is locally −kJ 3Gf 31 ,I) #f within the gas convection space 28, or
This convection flow 31 does not adversely affect the original ascending exhaust gas flow 29 and raw material gas flow 3o. This waste canal space 28 is filled with the high temperature mixed gas, that is, the rising exhaust gas 2.
A produced when 9 reacts with a small amount of residual impurity residue in the system.
It acts to provide a place for collecting fine powders such as oxides of S or Ga, and prevents these harmful fine powders from falling onto the surface of the compound semiconductor substrate. In this way, it is possible to prevent fine pit-like roughness of the epitaxial growth surface caused by fine powder adhering to the semiconductor surface serving as a nucleus. For example, cotton fibers 32 made of quartz glass may be inserted into this local gas convection space 28 to further effectively enhance the filtering effect of the fine powder.

Further, it is preferable that the spacer 23 is provided with a partition plate 35 having an opening 33 of an appropriate size and forming a gas distribution space 34 for combining and dispersing the source gas. Although the shape and arrangement of the partition plate 35 can be arbitrarily determined,
In the illustrated example, it is formed integrally with the neck portion 24. This partition plate 35 is used as a fixing member, and is detachably supported and fixed by a flange-like projection 38 provided inside the reaction tube 2.

Further, the gas flow path regulating device can include, as a component thereof, a partition wall 37 made of, for example, quartz glass, which is separate from the spacer 23 described above. As shown,
This partition wall 37 is located near the pedestal 10, for example, on the second surface 10a of the pedestal 10, and surrounds the semiconductor substrate 8 mounted thereon at an appropriate interval.
It is preferable that the reaction tube 2 is detachably supported and fixed by a collar-shaped projection 38 provided on the inner wall of the reaction tube 2. This partition wall 37 divides the space inside the reaction tube into upper and lower parts, and the space above the pedestal 10!
-1'+110 The gas heated in contact with a surface other than a is this l! It is possible to prevent the It debris from rising above the position of the FI+ wall 37 and mixing with the debris flow around the spacer, and to effectively direct the original It debris that has descended along the tube wall toward the semiconductor substrate surface. It acts to induce. The gas below the partition wall 37 is discharged from the waste outlet 37.

The device of the present invention also has a double pipe structure like the conventional device, and is cooled by water or other cooling medium.
It is designed to be able to cool the reaction tower, and is also equipped with a high frequency induction wire ring 11 which is a heating device, and a pedestal 1
The compound semiconductor substrate 8 mounted on the surface of the semiconductor substrate 8 can be heated to an epitaxial growth temperature, for example, 600 to 800°C.

(Description of Operation) Next, the characteristic operating principle of the present invention in the reaction tower structure of the embodiment of the present invention described above will be explained.

In the present invention, the gas inlet 21 at the upper part of the reaction tower 20
The various raw material scraps supplied to the inside of the reaction tube 2 through
First, after being well R-combined and dispersed in the gas mixing and dispersion space 34, the gas passes through the opening 33 of the final Jfi 35 and is guided near the wall surface (=1) of the reaction tube 2, which is being cooled by the outer wall of the flow path regulating spacer 23. In this region, the mixed gas flow of the raw material 3
Since the 0 is guided from the periphery of the pedestal 1O to the compound semiconductor substrate 8 while maintaining a sufficiently low temperature, good epitaxial growth onto the substrate 8 is performed.

At this time, the mixed gas flow whose temperature has increased near the surface IQa of the pedestal 10 is collected by the gas suction part 27 of the spacer 23, and with the addition of the chimney effect within this spacer 23, it becomes an ascending exhaust gas flow 29. The waste is rapidly discharged from the waste discharge port 22. For this reason, the flow path regulating spacer 23
Accordingly, the low temperature region streamline 30 of the raw material gas flow and the high temperature region streamline 28 of the rising gas flow can be completely separated so that they do not flow together. Therefore, the temperature of the mixed gas until it reaches the surface of the compound semiconductor substrate 8 can be maintained low, and the harmful thermal decomposition reaction of each component gas of the mixed gas can be suppressed to a minimum. can solve the biggest drawback of

In this way, II+ is maintained in this low temperature state! The combined raw material gas flow 30 can be supplied to the compound semiconductor substrate 8 mounted in the center of the pedestal 10, and therefore, together with the mud flow prevention effect of the gas flow described above, harmful thermal decomposition of each component gas can be prevented. The reaction can be suppressed more effectively.

Further, in one embodiment of the present invention shown in FIG. 2, the partition wall 37 provided near the pedestal 10 is
This is provided in order to prevent the temperature of the flow path regulating spacer 21 from rising due to debris heated by surfaces other than the surface 10a of the spacer 21. This partition wall 29 allows the above-described effects of the present invention to be more reliably and effectively exerted.

(Effects of the Invention) As explained in the embodiment shown in FIG. 2, according to the semiconductor thin film growth apparatus of the present invention, a mixed gas of various raw material gases is It prevents harmful thermal decomposition reactions from occurring before reaching the surface of the compound semiconductor substrate, quantitatively ensuring the ratio of each component element involved in epitaxial growth, and also prevents harmful fine powder generated by high-temperature mixed gases. This method effectively prevents the compound semiconductor from falling onto the surface of the compound semiconductor substrate, making it possible to grow an epitaxial layer with good crystallinity, surface flatness, and electrical conductivity with good reproducibility, which is not possible with conventional equipment. It can produce excellent effects.

The semiconductor thin film growth apparatus of the present invention improves the crystal properties of epitaxial crystal layers used as constituent materials for high-efficiency light-emitting devices, ultra-high-speed FET devices, and integrated devices thereof, so that device performance can be improved and device performance can be improved. This can greatly contribute to improving manufacturing yields, etc.

It is clear that the present invention is not limited only to the embodiments described above. For example, the structure of the gas flow path regulating device may be another structure. In this way, the used or unnecessary gas flow whose temperature has been raised is effectively separated from the raw material gas flow, and the raw material gas flow is lowered along the inner wall of the reaction tube being cooled to reach the surface of the semiconductor substrate. It is sufficient if the structure is such that it can be supplied to

Furthermore, this reaction tower can be constructed using a glass plate other than quartz glass.

Furthermore, the partition plate may be integrated with the flow path regulating spacer, or may be formed separately from the flow path regulating spacer.

Further, as a matter of course, the cooling device and the heating device may be devices other than those described in the embodiments described above.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a conventional semiconductor thin film growth apparatus, and FIG. 2 is a schematic cross-sectional view showing an embodiment of the semiconductor thin film growth apparatus of the present invention. l...Reaction tower, 2...Reaction tube 3...Outer tube, 4.5...Inflow/discharge pipe 6...
Gas inflow pipe, 7... Gas υ1 outlet pipe 8... Compound semiconductor substrate, 9... Support body 10... Pedestal, 1
0a...Pedestal surface 11...High frequency guide wire ring, 12...Mesh member 13...Convection of mixed gas flow, 14...Mixed gas flow 20...Reaction tower, 21.
...Gas inlet 22.38...Dus discharge port 23...Flow path regulating spacer 24...Neck of canal regulating spacer 25...Enlarged portion 26 of canal regulating spacer...Opening 27. ... Gas suction part 28 of flow path regulating spacer ... Gas convection space 28 ... Rising exhaust gas (flow) 30 ... Raw material (mixed) gas (flow) 31 ... Convection, 32 ... Fluffy Fiber 33...opening, 34...gas mixing space 35...partition plate, 36
．． 38... Flange-like process 37... Partition. Figure 2

Claims (1)

[Scope of Claims] 1. A reaction tube having a waste inlet and a gas outlet; a pedestal disposed inside the reaction tube and having a surface on which a compound semiconductor substrate can be mounted facing the gas inlet; Semiconductor integrated film growth for organometallic compound pyrolysis method, comprising: a cooling device provided outside the reaction tube for cooling the reaction tube; and a heating device for heating the compound semiconductor substrate. In the apparatus, an upper end of the reaction tube is provided with one gas inflow port for supplying raw material gas and a gas outlet for discharging rising exhaust gas, and further comprising a gas flow path regulating device disposed in the reaction tube. The gas flow regulating device causes the raw material gas supplied from the gas inflow port to descend near the inner wall along the inner wall of the reaction tube, and separates it from the raw material gas and discharges the rising exhaust gas. a flow-path regulating spacer disposed between the gas outlet and the upper surface of the pedestal, the spacer including a gas inlet for inhaling the rising exhaust gas and a neck for discharging the rising exhaust gas to the gas outlet; A semiconductor thin film growth apparatus characterized by having: 2. The gas flow path regulating device has a partition wall that divides the space inside the reaction tube into two at a position near the upper surface of the pedestal, as set forth in claim 1. Semiconductor thin film growth equipment. 3. The flow path regulating spacer has an enlarged portion that is provided between the neck portion and the lower end portion of the gas suction portion and forms a gas convection space. A semiconductor thin film growth apparatus according to claim 1, characterized in that: 4. The semiconductor thin film growth apparatus according to claim 3, further comprising flocculent fibers in the gas convection space of the ampulla.