JPH01218009A - Crystal growing method - Google Patents

Abstract

PURPOSE:To reduce the warpage of a substrate and any crack produced in a grown layer by forming grooves in the thin grown layer to form a plurality of islands in the same, and further growing the layer by a vapor phase epitaxy process. CONSTITUTION:GaAs is grown on a Si substrate 11 by an ordinary process to form a GaAs layer 12a. Grooves 16 are formed in the GaAs layer 12a by etching with use of a resist mask to provide the GaAs layer in a plurality of islands. After the mask 15 is removed, the GaAs is further grown by a vapor phase epitaxy process, for example by a MOCVD process to form a GaAs layer 12b. The GaAs layer 12 is divided along the grooves 16 and forms island- like regions. Hereby, warpage of the substrate 11 and any crack in the grown layer, i.e., in the GaAs layer 12 are reduced.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for crystal-growing a compound semiconductor to a predetermined thickness on a substrate of a group III conductor, the substrate For the purpose of reducing warpage and cracks in the grown layer, first, the grown layer is grown to a thickness thinner than the predetermined thickness, grooves are formed in the grown layer to form a plurality of islands, and then vapor phase epitaxy or The structure is configured to continue growth by molecular beam epitaxy, and grooves are formed in advance on the surface of the substrate to form a surface layer into a plurality of islands, and then by vapor phase epitaxy or molecular beam epitaxy. Configure to grow.

[Industrial application field]

The present invention relates to a method for crystal-growing a compound semiconductor to a predetermined thickness on a substrate of a group (III) raw conductor.

Compound semiconductors can be used to form elements of semiconductor devices and can impart excellent characteristics to the elements, such as GaAs increasing the speed of transistors.

However, compound semiconductor substrates (wafers) are slower to grow in size than substrates made of group II raw conductors, such as Si, and are weaker in strength, which hinders improvements in the production efficiency of semiconductor devices.

Therefore, a compound semiconductor is grown as a crystal on a substrate of a group Ⅰ raw conductor, and for example, GaAs is grown as a crystal on a Si substrate.
Consideration is being given to increasing the size and strength of the substrate on which the aAs element is formed.

[Conventional technology]

When growing GaAs crystals on a Si substrate, Si and G
Due to the difference in the lattice constant of aAs, it was necessary to interpose an appropriate buffer layer to achieve lattice matching, which was complicated, but it has since become possible to directly grow GaAs crystals on Si substrates. Reference: “Growth technology of GaAs on Si substrate” by Sayama et al., Oki Electric Research and Development,
April 1988, No. 134, Vol. 54° No. 2
．． p57).

In that case, a large number of dislocations occur in the grown layer due to the influence of lattice mismatch between St and GaAs. However, as the growth layer becomes thicker, dislocations decrease on the surface side [Reference: Grow
th and characterization o
f Ga/Geepilayers grown on
St 5ubstrates by molecule
Arbeam epitaxy (Growth and properties of Ga/Ge layer on Si substrate by molecular beam epitaxy)'P,
5heldon, et al., J.

Appl, Phys, 58(11), I Dec
, 1985. p4186).

The situation is shown in the side sectional view (a) of FIG.

In the figure, 1 is a Si substrate, 2 is a grown GaAs layer, and 3 is a dislocation. When the thickness of the GaAs element 2 is increased to about 4 .mu.m or more, dislocations on the surface side become so small that they do not adversely affect the formed element.

[Problem to be solved by the invention]

However, when the substrate 1 is made large and the GaAs layer 2 is made thick as described above, when the substrate 1 is taken out after growth, the substrate 1 is warped as shown in FIG. 3(b). This may even cause a crank 4 to occur in the GaAs layer 2.

This is because the growth takes place at high temperatures, and the thermal expansion coefficient of GaAs (6,8 x 10-'/°C) is similar to that of St (2,8 x 10-'/°C).
8X 10-"/°C), so when the substrate 1 returns to room temperature, tensile stress occurs in the GaAs layer 2 in the plane direction, and the thick GaAs layer 2 This is because the stress is connected to the entire area of the substrate 1 and causes the substrate 1 to curve.

This phenomenon is not limited to the case where GaAs is grown on a Si substrate, but is common when a compound semiconductor is grown on a substrate of a group III conductor.

This warping of the substrate causes trouble in the subsequent process of forming the device, and the cranking of the growth layer causes device failure.

Therefore, an object of the present invention is to provide a crystal growth method that reduces the above-mentioned warping of the substrate and cranking of the grown layer.

[Means to solve the problem]

The above purpose is to first grow thinner crystals of a compound semiconductor to a predetermined thickness on a substrate of a group III conductor, and then form grooves in the grown layer to form a plurality of islands. This is achieved by the crystal growth method of the present invention in which the crystal growth is continued using a vapor phase epitaxy method or a molecular beam epitaxy method. After that,
This is achieved by the crystal growth method of the present invention in which growth is performed by vapor phase epitaxy or molecular beam epitaxy.

[For production]

The growth layer grown in this way is separated by the grooves and connected only in the island-like regions.

For this reason, the above-mentioned stress generated in the growth layer due to the difference in thermal expansion coefficient between the group III raw conductor and the compound semiconductor is severed between the island-like regions, so the substrate is made larger and the growth layer is made thicker. However, the warpage that occurs on the substrate will be minimal. In addition, as a result, the cracks described above are less likely to occur in the island-like regions.

In this way, it is possible to eliminate the warpage of the substrate that interferes with the post-process of forming elements, and by aligning the island-shaped area with the element forming area, it is possible to prevent the occurrence of cranks that cause element defects. can.

〔Example〕

Examples of the crystal growth method according to the present invention will be described below with reference to FIGS. 1 and 2. Fig. 1 is a side sectional view (a) to (C1) showing the first embodiment in the order of steps and a plan view (d), and Fig. 2 is a side sectional view in the order of steps (al (b) showing the second embodiment
l and a plan view (el).

In FIG. 1 showing the first embodiment, first [see FIG. FA], GaAs is crystal-grown on a St substrate 11, which is a Si wafer, by a conventional method to form a GaAs layer 12 with a thickness of about 1 μm.
form a. For example, the size of the board 11 is 5! It is.

Next, as shown in the figure (bl), grooves 16 are formed in the GaA layer 112a by etching using a resist mask 15, so that the GaAs layer 12a has a plurality of island shapes as shown in the figure (dl).

Each of the island-like regions is, for example, approximately 5 mm square to match the area for forming elements in a subsequent process, and the width of the groove 15 is, for example, approximately 1 mm square.
It is 0 μm.

Next, as shown in FIG. c (see C1), after removing the resist mask 15, the vapor phase epitaxy method, for example, MOCVD method, is performed.
Or GaA by molecular beam epitaxy method (MBE method)
Continuing the crystal growth of s, GaAs1i1 with a thickness of about 3 μm
2b to complete the desired growth. GaAs layer 12
The combined thickness of a and 12b is about 4pr on the St substrate ll.
s GaAs1i12.

The GaAs layer 12 has grooves 1 formed by the growth of the GaAs layer 12b.
Although the portions 6 appear to be connected, because the growth is by vapor phase epitaxy or molecular beam epitaxy, the ranges that are separated by the grooves 16 and connected become the island-like regions.

The substrate 11 on which the GaAs layer 12 has been grown shows almost no warpage even at room temperature, and the size of the warpage is at most several micrometers. Also,
In each island region of GaAs1i12, the dislocations 3 explained in Fig. 3 are distributed in the same way as in the case of GaAsN2, and are hardly observed on the surface side, and the existence of the crank 4 explained in Fig. 3 is not observed. .

In Fig. 2 showing the second embodiment, first [Fig.
1], the surface of the Si substrate 21 (Si wafer) is etched to a depth of 1 to 3 μm using a resist mask 25.
The surface layer of the substrate 21 is formed by forming grooves 26 of approximately
Make it into multiple islands as shown. The size of the substrate 21 is, for example, 5 mm, each of the island regions is, for example, about 5 square meters to match the area for forming elements in a subsequent process, and the width of the groove 26 is, for example, about 10 micrometers.

Next, after removing the resist mask 25 [see figure (bl)], a vapor phase epitaxy method such as MOCVD method is performed.
Alternatively, GaAs is crystal grown by molecular beam epitaxy to form GaAsN22 with a thickness of about 4 .mu.m to complete the desired growth.

The GaAs layer 22 is GaAs1i in the first embodiment.
12, the range that is separated and connected by the groove 26 is the island-shaped region.

The substrate 21 on which the GaAs layer 22 has been grown shows almost no warpage even at room temperature, as in the case of the first embodiment, and the size of the warpage is approximately several microns at most. . Furthermore, in each island region of the GaAs layer 22, the dislocations 3 explained in FIG. existence is not recognized.

Note that the above example is a case in which GaAs is crystal-grown to a predetermined thickness on an S+ substrate, but the method of the present invention is also applicable to crystal growth of an MV group or III group compound semiconductor on a substrate of a group (III) conductor. It can be easily inferred from the above explanation that it is effective in some cases.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in the method of crystal-growing a compound semiconductor to a predetermined thickness on a substrate of a group III raw conductor, the It is possible to reduce warpage of the substrate and cracks in the grown layer, and has the effect of making it possible to stably improve the production efficiency of, for example, compound semiconductor devices.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view and plan view in the order of steps showing the first embodiment, Fig. 2 is a sectional side view and plan view in the order of steps showing the second embodiment, and Fig. 3 is the side showing the conventional problem. This is a cross-sectional view. In the figure, 1, 11, and 21 are St-based heat resistors, and 2.12.12a, 12b, and 22 are GaAs layers (
growth layer), 3 is a dislocation, 4 is a crack, 15.25 is a resist mask, and 16.26 is a groove. A certain 1 K 2nd Daien Iku・IE shows L rare 111 moxibustion 1 sectional view and plane basket 2nd figure

Claims (1)

[Claims] 1) When crystal-growing a compound semiconductor to a predetermined thickness on a group IV semiconductor substrate, first, the compound semiconductor is grown thinner than the predetermined thickness, and a groove is formed in the grown layer to separate the grown layer. A crystal growth method characterized by forming a plurality of islands in the form of crystals and then continuing to grow them by vapor phase epitaxy or molecular beam epitaxy. 2) When crystal-growing a compound semiconductor on a group IV semiconductor substrate, grooves are formed in advance on the surface of the substrate to form a surface layer in the form of multiple islands, and then vapor phase epitaxy or molecular beam epitaxy is performed. A crystal growth method characterized by performing crystal growth.