JPH04234110A - Method of selectively growing compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To enable an excellent crystal of ternary or more compound semiconductor to grow selectively on a substrate by a method wherein a pressure is specified when a compound semiconductor crystal is made to grow can a semiconductor crystal substrate through an organic metal vapor growth method. CONSTITUTION:A crystal of ternary or more compound semiconductor is made to grow selectively on the limited region of a semiconductor crystal substrate 3 through an organic metal vapor growth method, where a pressure is set to 15-30Torr when the compound semiconductor crystal concerned is made to grow. For instance, an SiN film is formed on an InP substrate 3, which is formed into a required pattern through a photolithography method. Then, TEG, TMI, and AsH3 are used as Ga, In, and As material respectively, hydrogen is made to serve as carrier gas, and these materials are fed to a reaction oven 1. The substrate 3 is kept at a temperature of 650 deg.C, the growing pressure is set to 15-30Torr, and a GaInAs crystal is selectively grown through an organic metal vapor growth method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively growing compound semiconductors. More specifically, the present invention relates to a method for growing high-quality compound semiconductor crystals in a limited area on a semiconductor crystal substrate.

0002

2. Description of the Related Art With the development of optical communication technology, optoelectronic integrated circuits in which optical elements and electronic elements are integrated have come into use. Examples of optoelectronic integrated circuits include those in which a light emitting element and its driving circuit are integrated, and those in which a light receiving element and an amplifier circuit are integrated. Optoelectronic integrated circuits differ from general semiconductor devices in that they integrate elements with completely different crystal structures, such as optical elements and electronic elements.

[0003] The manufacturing method of an integrated circuit including elements with completely different crystal structures, such as the above-mentioned optoelectronic integrated circuit, is different from that of general semiconductor devices. That is, a typical semiconductor element is manufactured by processing a semiconductor substrate itself or a semiconductor crystal epitaxially grown on the entire surface of a semiconductor substrate. On the other hand, in an optoelectronic integrated circuit, two types of semiconductor layers, a semiconductor crystal layer having a crystal structure of an optical device and a semiconductor crystal layer having a crystal structure of an electronic device, are laminated over the entire surface of a semiconductor substrate. and,
In the area of devices that use only the lower semiconductor layer, a method of removing the upper semiconductor layer by etching or the like has often been used.

However, in the above method, the properties of the upper semiconductor crystal layer deteriorate due to the influence of the lower semiconductor crystal layer having a different crystal structure. In addition, since two types of semiconductor crystal layers are stacked, the thickness of the resulting device becomes large, and since a portion of the upper semiconductor crystal layer is removed, there are problems such as the inability to flatten the device surface. be.

[0005] Recently, therefore, selective growth techniques are sometimes used when producing integrated circuits such as optoelectronic integrated circuits. Selective growth is a technique for selectively growing a crystal with a crystal structure different from that of the surrounding area only in a limited area on a substrate. By using this crystal growth technique, it is possible to create any three-dimensional crystal structure on a substrate. Therefore, the functionality of integrated circuits including elements with completely different crystal structures, such as optoelectronic integrated circuits, can be greatly enhanced. Furthermore, the surface can be made flat by performing so-called embedded selective growth in which the region to be selectively grown is etched and recessed in advance. For example, metal organic chemical vapor deposition (MO-CVD) has been used for selective growth of semiconductor crystals.

[0006]

[Problems to be Solved by the Invention] When selectively growing compound semiconductor crystals on a semiconductor substrate using metal organic vapor phase epitaxy, a dielectric film such as SiN or SiO2 is formed on a portion of the substrate. and use it as a mask. At this time, the raw material supplied on the mask may diffuse into the unmasked area and increase the crystal growth rate in the unmasked area (Journal of
Crystal Growth 77 (1986)
p334-339).

The crystal to be selectively grown is GaInAs, A
In the case of crystals of ternary compound semiconductors such as lInAs and GaInP, or crystals of quaternary compound semiconductors such as GaInAsP and AlGaInP, in particular, the diffusion rates of group III element source gases such as Al, Ga, and In are different from each other. The difference becomes a problem. That is, if the above-mentioned compound semiconductor crystal is selectively grown on a part of the substrate surface under normal conditions, the crystal will have a different composition than when it is grown on the entire surface of the substrate. This is I
It is thought that this is because the organometallic raw material gases of Group II elements have a large difference in diffusion rate within the boundary layer formed directly above the substrate. Therefore, since a raw material with a fast diffusion rate easily diffuses into an unmasked area, the concentration of the raw material in an unmasked area becomes higher as the rate of diffusion of the raw material is faster. In other words, I supplied to the crystal growth region
The proportion of group II elements is determined by the partial pressure ratio of the raw material gas (ratio of supply amount)
It will be different.

As a result, the crystal composition of the selectively grown ternary compound semiconductor or quaternary compound semiconductor deviates from the predetermined composition, the lattice constant changes, and lattice mismatch with the substrate occurs, resulting in poor crystal quality. There were problems such as a decline in If the selective growth region and mask pattern are uniform, this lattice mismatch can be improved to some extent by correcting the supply amount of the source gas. However, if the shape of the selective growth region is not uniform over the entire surface of the substrate, the partial pressure ratio of the raw material gas that can grow a predetermined compound semiconductor crystal differs from region to region. Therefore, lattice matching cannot be achieved simply by correcting the total supply amount of source gas. Furthermore, even if the shape of the selective growth region is uniform over the entire substrate,
When the selective growth region is large, the composition of the source gas has a distribution within that region, so lattice matching cannot be achieved simply by correcting the supply amount of the source gas.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for selectively growing high-quality crystals of ternary or higher compound semiconductors on a substrate, which solves the problems of the prior art described above.

0010

[Means for Solving the Problems] According to the present invention, a ternary or higher compound semiconductor crystal is selectively deposited in a limited area on a semiconductor crystal substrate by an organometallic vapor phase epitaxy method. A method for selectively growing a compound semiconductor crystal is provided, the method comprising growing the compound semiconductor crystal at a pressure of 15 to 30 Torr.

The method of the present invention is effective, for example, when selectively growing a GaInAs compound crystal on an InP crystal substrate or when selectively growing a GaInAsP compound crystal on an InP crystal substrate.

0012

[Function] The method of the present invention provides three
The main feature is that the pressure is set at 15 to 30 Torr when selectively growing compound semiconductor crystals of a higher than elementary type. In organometallic vapor phase epitaxy, the diffusion constant of the source gas is determined by the temperature,
Changes depending on pressure etc. Further, the raw material gas undergoes thermal decomposition within the boundary layer, resulting in a change in molecular weight, which also changes the diffusion constant. Therefore, in the present invention, the pressure is set to 15 to 30 Torr.
By setting r, it is possible to optimize the diffusion rates of all source gases of group III elements to be equal, and it is possible to eliminate variations in composition during selective growth.

[0013] The present invention will be explained in more detail with reference to examples below, but the following disclosure is merely an example of the present invention and is not intended to limit the technical scope of the present invention in any way.

[0014]

EXAMPLE In order to confirm the effectiveness of the present invention, GaInAs crystal was selectively grown on an InP substrate while changing the pressure of the reactor. FIG. 1 shows a schematic diagram of an apparatus used to grow compound semiconductor crystals on a semiconductor substrate by metal organic vapor phase epitaxy. The apparatus shown in FIG. 1 includes a reactor 1 that can maintain an airtight interior, a susceptor 2 that fixes a semiconductor substrate 3 therein, a reactor 1 that can heat the semiconductor substrate 3, and a high vacuum inside the reactor 1. It includes a vacuum pump 4 capable of evacuation, and a regulating valve 5 that controls the displacement of the vacuum pump 4. The reactor 1 is supplied with raw material gas together with a carrier gas from cylinders 7 and 8 and bubblers 9 and 10 through a pipe 6 having a flow rate regulating valve 61 . Cylinder 7, 8, Bubbler 9
, 10 have regulating valves 71, 81, 91 and 1, respectively.
01 is provided, and the supply amount of each raw material gas can be adjusted.

First, a SiN film is formed on the InP substrate 3, and a width of 8 is formed by photolithography as shown in FIG.
A pattern in which 00 μm masks 31 are arranged at 200 μm intervals, and a 200 μm wide mask 32 is 800 μm wide.
A pattern was formed that was arranged at intervals of . TEG for Ga raw material
(triethylgallium), TMI (trimethylindium) as the In raw material, AsH3 (asine) as the As raw material, and hydrogen was used as a carrier gas and supplied to the reactor 1. The supply amount of each is shown below. TEG 2.9×10-6mol/minTM
I 3.4 x 10-6 mol/min AsH3
The temperature of the 4.5×10 −4 mol/min substrate 3 was fixed at 650° C., and the growth pressure was varied in the range of 10 Torr to 60 Torr. Grown GaI
The difference (lattice mismatch) between the lattice constant of nAs and the lattice constant of the InP substrate was evaluated by two-crystal X-ray diffraction.

FIG. 3 shows the growth pressure dependence of lattice mismatch. The solid line indicates the lattice mismatch in the pattern area where masks with a width of 800 μm are arranged at intervals of 200 μm, and the dashed line indicates the width
The figure shows the lattice mismatch in the pattern area of 200 μm masks arranged at 800 μm intervals. The dotted line indicates lattice mismatch when crystals are grown over the entire surface of the substrate. As can be seen from FIG. 3, the lattice constant of the selectively grown GaInAs crystal is largely dependent on the growth pressure. In this case, GaInAs
The lattice constant of the crystal is correlated with the crystal composition, and as mentioned above, the crystal composition is related to the diffusion constant of the source gas, so the ratio of the diffusion constant of the Ga source gas to the diffusion constant of the In source gas is This shows that the growth pressure changes with the growth pressure. Furthermore, from FIG. 3, it is clear that the GaInAs crystal grown selectively at a pressure of 15 to 30 Torr is different from the GaInAs crystal grown on the entire surface of the substrate.
It can be seen that the lattice constant is approximately equal to that of InAs crystal. Therefore, if the pressure inside the reactor is set within this range, G
The diffusion constant of the source gas for a is equal to the diffusion constant for the source gas for In, and no mismatch in lattice constant occurs with the InP substrate.

When a GaInAsP crystal is selectively grown using the method of the present invention, PH3 (phosphine) may be added as a P raw material to the above-mentioned apparatus. In general, in the organometallic vapor phase epitaxy method, a raw material gas of group V elements such as P and As is supplied in an amount several to several hundred times in excess of the raw material gas of group III elements such as Ga and In. Even when selective growth is performed, there is an excess of group V element source gas directly above the substrate regardless of the presence or absence of a mask, and like group III element source gas, the source gas is transferred from the masked area to the unmasked area. Gas cannot diffuse. Therefore, even when selectively growing GaInAsP, only group III elements such as Ga and In are related to lattice mismatch, and by setting the growth pressure to 15 to 30 Torr, as in the case of GaInAs, the InP substrate No lattice mismatch occurs between

0010

[Effects of the Invention] As explained above, according to the present invention,
A ternary or higher compound semiconductor crystal that is lattice-matched to the substrate can be formed in a region of any shape and size on the substrate. According to the present invention, an element such as an optoelectronic integrated circuit that requires the integration of a plurality of semiconductors having different crystal structures can be easily manufactured.

[Brief explanation of the drawing]

1 is a schematic diagram of an example of a device implementing the method of the invention; FIG.

FIG. 2 is a perspective view of a mask pattern formed on an InP substrate used in an experiment conducted to confirm the effectiveness of the method of the present invention.

FIG. 3 is a graph showing the relationship between growth pressure and lattice mismatch when a GaInAs compound semiconductor crystal is selectively grown on an InP substrate.

[Explanation of symbols]

1 Reactor 2 Susceptor 3 Substrate 4 Vacuum pump 5, 61, 71, 81, 91, 101 Regulating valve 7
, 8 cylinder 9, 10 bubbler

Claims (3)

[Claims] 1. A method for selectively growing a ternary or higher compound semiconductor crystal in a limited region on a semiconductor crystal substrate by metal organic vapor phase epitaxy, wherein the compound semiconductor crystal 1. A method for selectively growing a compound semiconductor crystal, the method comprising growing a compound semiconductor crystal at a pressure of 15 to 30 Torr. 2. The method for selectively growing a compound semiconductor crystal according to claim 1, wherein the semiconductor crystal substrate is an InP crystal substrate, and the compound semiconductor crystal is a GaInAs crystal. 3. The method for selectively growing a compound semiconductor crystal according to claim 1, wherein the semiconductor crystal substrate is an InP crystal substrate, and the compound semiconductor crystal is a GaInAsP crystal.