JP2665093B2 - Evaluation method of epitaxial crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating an epitaxial crystal by observing the thickness of the epitaxial crystal without breaking the crystal.

[0002]

2. Description of the Related Art FIG.
pplied Physics vol.25, No.6 (1986) pp.L498-L500 is a diagram showing a conventional method for measuring each layer thickness of an epitaxial crystal layer having a semiconductor laser structure. , 1 is a GaAs substrate, 2 is GaAs
An all-epitaxial crystal layer formed on the s-substrate 1, wherein the all-epitaxial crystal layer 2 is formed of an AlGaAs first
The cladding layer 3, the AlGaAs active layer 4, the AlGaAs second cladding layer 5, and the GaAs cap layer 6 are laminated.

Next, the working procedure will be described. First, FIG.
As shown in FIG. 1A, an all-epitaxial crystal layer 2 including an AlGaAs first cladding layer 3, an AlGaAs active layer 4, an AlGaAs second cladding layer 5, and a GaAs cap layer 6 is formed on a GaAs substrate 1 having a diameter of 2 inches by MOCVD. Grow by law. Thereafter, the wafer is cleaved as shown in FIG. 3 (b) to produce a strip-shaped sample. And FIG.
As shown in (c), the cross section is SEM (Scanning electro
The thickness of each epitaxial layer is determined by observing with a microscopy (scanning electron microscope) and taking photographs.

[0004]

The conventional method for evaluating an epitaxial crystal has been performed as described above, and it is necessary to destroy the wafer to form a cleavage plane. There is a problem that the wafer is contaminated due to dust at the time and adhesion of oil by manual operation, and measurement accuracy is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for evaluating an epitaxial crystal which can determine the thickness of each epitaxial crystal layer without breaking a wafer. I do.

[0006]

A method for evaluating an epitaxial crystal according to the present invention comprises growing an epitaxial crystal layer on a semiconductor substrate having a concave portion having a side wall formed vertically on the surface of the substrate, and growing the epitaxial crystal layer along the side wall. This is to observe the epitaxial crystal layer formed by observation from the surface.

Further, an epitaxial crystal layer formed on a cleavage side surface of the cleavage portion of the wafer perpendicular to the substrate surface is observed from the wafer surface.

[0008]

According to the present invention, an epitaxial crystal layer is grown on a semiconductor substrate having a concave portion having a vertical side wall surface on the surface thereof. A crystal layer is formed on the side wall surface of the concave portion, and the layer thickness can be measured by observing the cross-sectional shape from the substrate surface.

Further, crystal growth is performed using a substrate having a cleavage plane perpendicular to the surface, and the cleavage side surface or the cross section of the epitaxial crystal layer formed on the substrate surface is observed at the cleavage part of the substrate. Measurement of the layer thickness can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for evaluating an epitaxial crystal according to an embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same reference numerals as those in FIG. 3 denote the same or corresponding parts, and 1 denotes a GaAs substrate having a diameter of, for example, 2 inches, and a recess 7 in the (001) plane in a region surrounded by <010> and <001> directions. Are formed. 8 is the (1) of the substrate 1
1) Show the surface.

Next, the working procedure will be described. First, Figure 1
As shown in (a), the (1) of the GaAs substrate 1 having a diameter of 2 inches is used.
The <00) surface was subjected to <01 by photoengraving and wet etching.
Only the region surrounded by the <0> and <001> directions is recessed. Then, the dent 7 has a {011} surface that is neither a normal mesa shape nor a reverse mesa shape ({010} and {0}).
It has a side wall perpendicular to the surface (inclined at 45 ° with respect to the 01 ° plane) (see FIG. 1B).

Thereafter, as shown in FIGS. 1 (c) and 1 (d), an epitaxial crystal 2 having a semiconductor laser structure is formed on the (100) 1 surface of the GaAs substrate 1 in which the recess 7 is formed by MOC.
It grows by the VD method. Then, the growth rate on each surface of the recess 7 is almost equal to the growth rate on the substrate surface.
Further, the {111} plane 8 is completely exposed (see FIGS. 1 (e) and 1 (f)). Therefore, SEM from the substrate surface
The thickness of each layer of the epitaxial crystal 2 can be read simply by observation.

Further, by forming four recesses 7 in the substrate 1, the distribution of the thickness of each layer in the wafer can be measured.

As described above, according to the present embodiment, the concave portion 7 having the {010} surface and the {001} surface exposed to the (001) surface of the substrate 1 is provided, and the epitaxial crystal is formed on the substrate. 2 and the cross section of the epitaxial crystal 2 grown along the side wall surface of the concave portion
Since the thickness of each layer is read by observing from the 1｝ surface 8 with an SEM, it is not necessary to break the wafer, the operation is simple, and the wafer is not contaminated.

In the above-described embodiment, the recess 1 is previously formed in the substrate 1.
Is formed, and the epitaxial layer is grown thereon. However, the cross section of the epitaxial layer formed at the cleavage portion of the wafer may be observed. That is, FIG. 2 is a diagram showing a method for evaluating an epitaxial crystal according to the second embodiment of the present invention. In FIG. 2, reference numeral 9 denotes a cleavage portion.

Next, the working procedure will be described. Fig. 2 (a)
As shown in (1), epitaxial growth is performed on the (001) plane of the GaAs substrate 1. Then, as shown in FIG.
An epitaxial crystal layer 2 a is formed on the surface of the GaAs substrate 1, and the epitaxial crystal layer 2 a
b is formed. And this epitaxial crystal layer 2b
Is formed on the cleavage side surface perpendicular to the surface of the GaAs substrate 1 as shown in FIG.
1｝ plane 8 appears, and from this plane 8, epitaxial crystal layer 2b
By observing, the thickness of each layer can be read in the same manner as in the above example. In this case, the thickness of each layer can be read by observing the epitaxial crystal layer 2a formed on the surface of the GaAs substrate 1. In this case, there is no need to provide a recess or the like on the substrate, and the operation can be further simplified.

In the above embodiment, the case where a laser is constituted as an epitaxial crystal layer has been described as an example.
It goes without saying that an epitaxial crystal layer other than a laser may be used.

As the substrate used in each of the above embodiments, it is desirable to use a substrate having an inclination within 5 ° from the (100) plane.

[0019]

As described above, according to the method for evaluating an epitaxial crystal layer according to the present invention, epitaxial growth is performed also in the direction perpendicular to the substrate surface, and the cross-sectional structure exposed at the end face is removed from the surface. Since the thickness of each layer of the epitaxial layer is measured by observation, crystal evaluation can be performed by a simple operation procedure without destroying the wafer, and dust at the time of cleavage and adhesion of oil due to manual work can be evaluated. There is an effect that the influence is removed and improvement in measurement accuracy can be expected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a principle of measuring a layer thickness in an epitaxial crystal evaluation method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a principle of measuring a layer thickness in a method for evaluating an epitaxial crystal according to another embodiment of the present invention.

FIG. 3 is a process chart showing a layer thickness measuring procedure of a conventional method for evaluating an epitaxial crystal.

[Explanation of symbols]

 Reference Signs List 1 GaAs substrate 2 Total epitaxial crystal layer 3 AlGaAs first cladding layer 4 AlGaAs active layer 5 AlGaAs second cladding layer 6 GaAs cap layer 7 Substrate surface depression 8 {111} plane 9 Cleaved part

Claims (2)

(57) [Claims] 1. A method for measuring and evaluating the thickness of an epitaxial layer formed on a substrate, comprising: using a substrate having a recess having a vertical inner wall surface, growing the epitaxial layer on the substrate; A method for evaluating an epitaxial crystal, comprising: evaluating a crystal by measuring a layer thickness of an exposed cross section of an epitaxial layer grown along the inner wall surface. 2. A method for measuring and evaluating the thickness of an epitaxial layer formed on a substrate, comprising: using a substrate having a cleavage plane perpendicular to the surface thereof, growing the epitaxial layer on the substrate, Crystallographic evaluation by measuring the thickness of the exposed cross section of the epitaxial layer grown along the cleavage plane of the substrate or the thickness of the exposed cross section of the epitaxial layer grown on the surface of the substrate viewed from the cleavage plane A method for evaluating an epitaxial crystal.