JPH0666740A - Method for evaluating surface layer of single crystal - Google Patents

Abstract

PURPOSE:To make the intruding depth of X rays shallower and, at the same time, to change the intruding depth in the depth direction from a small area by horizontally arranging the surface layer of a single crystal and changing the illuminating angle of the X rays against the single crystal by adjusting the angle of the surface layer from the horizontal plane and angle of rotation in a plane of reflection. CONSTITUTION:A sample crystal 1 is slightly inclined by an angle alpha against the horizontal plane and the sample 1 is rotated in the horizontal direction by an angle beta under a condition where a reflecting surface is obtained. As a result, the illuminating angle thetai against the surface of the sample 1 becomes smaller. The angle thetai is expressed by sinthetai=sinalpha.sinthetaB-cosalpha.costhetaB.sinbeta, where thetaB represents the Bragg angle of the used reflecting surface. The expression shows that the angle thetai changes when the angle beta is changed and, as a result, the intruding depth of X rays changes. Therefore, the surface layer of the crystal 1 can be continuously evaluated in the depth direction by continuously changing the very shallow surface layer and angle beta. This method can be effectively used for evaluating the working distortion of a crystal or the crystallinity of a thin film formed on a substrate by epitaxial growth.

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 a single crystal surface layer by an X-ray double crystal method.

[0002]

2. Description of the Related Art Conventionally, as a method for evaluating a crystal surface layer by an X-ray diffraction method, for example, Extended Abstracts of the 1
6th Conference on Solid Stste Devices and Material
s, Kobe, 1984, pp. 201-204, a rocking curve is drawn and evaluated using a specific wavelength and a diffraction line.
In this method, the penetration depth of X-rays is determined by the constituent elements of the sample, the crystal structure, the plane orientation of the sample, the reflection surface and the wavelength of the X-rays.
Crystallinity that reflects the magnitude of strain in the region from the surface to the depth and the concentration of lattice defects and the like is measured. In particular,
Using (100) plane GaAs as a sample, CuKα as X-ray
_{When one} line is used, the penetration depth of X-ray is 15 μm for the (400) diffraction line, 5.5 μm for the (422) diffraction line, and (31
1) The diffraction line was 1.5 μm, and it was impossible to make the penetration depth of X-ray smaller than this value or continuously change it during this period.

Therefore, in order to evaluate in the depth direction,
The surface of the sample was etched to a certain depth, X-ray diffraction was performed, and etching was performed again to obtain X-ray diffraction. Etching and measurement were alternately repeated to evaluate in the depth direction. This method is a destructive inspection method in which a sample is destroyed and measured.

Further, by using SR (synchronized light), the wavelength of X-ray can be continuously changed, and by selecting a desired wavelength, a diffraction line having a desired penetration depth can be obtained. However, the device is large and not easy to use. This method is complicated because it is necessary to adjust the monochromator of the diffractive device each time the wavelength is changed.

[0005]

As described above, the conventional X
In the line diffraction method, the penetration depth of X-rays is determined by the constituent elements of the sample, the crystal structure, the plane orientation of the sample surface, the reflecting surface, and the wavelength of the X-rays, and the penetration depth should be smaller than that. Was impossible. Further, in order to obtain continuous information in the depth direction, it was necessary to alternately repeat etching using a specific diffraction line and measurement. Therefore, the present invention solves the above problems and further reduces the penetration depth of X-rays and can change the depth from the small region in the depth direction, such as processing strain of the single crystal surface layer and crystallinity of the epitaxial layer. It is intended to provide a method for evaluating a non-destructive inspection method.

[0006]

The present invention relates to a method for evaluating a single crystal surface layer by an X-ray double crystal method, in which a reflecting surface is obtained after the surface layer of the single crystal to be evaluated is arranged horizontally. Below, the angle from the horizontal plane and the rotation angle in the plane of the reflecting surface of the single crystal are adjusted to change the X-ray irradiation angle with respect to the single crystal. Is.

[0007]

FIG. 1 is a view showing the arrangement of single crystal samples when the method of the present invention is carried out. That is, the sample crystal 1 is inclined at a slight alpha ^O with respect to the horizontal, under conditions in which the reflective surface is obtained by rotating the sample in the transverse direction to the angle beta ^O, to reduce the irradiation angle theta _i with respect to the sample surface Especially. The irradiation angle θ _i is given by the equation (1).
Here, θ _B is the Bragg angle of the reflection surface used. By changing the rotation angle β by _{sinθ i = sinαsinθ B -cosαcosθ B sinβ} (1) formula, the irradiation angle θ
_i changes, and as a result, the penetration depth of X-rays changes, and it is possible to evaluate continuously from the shallow sample surface in the depth direction by changing β in a very shallow sample surface layer continuously. Becomes The penetration depth d of X-rays is expressed by equation (2) according to the kinematic theory. d = [(μ / 2) (1 / γ _O + 1 / γ _h )] ⁻¹ (2) where μ is a linear absorption coefficient, γ _O = sin θ _i , γ _h = s
in θ _r . Note that θ _r is a reflection glancing angle.

[0008]

【Example】

 (Example 1) CuKα as X-ray₁, The first crystal (monoc
(111) method using Si as the sample
X-ray was applied to the surface layer of (100) GaAs which was tilted 2 degrees toward
It was investigated by the double crystal method. The GaAs surface was previously chemically polished.
Grinding with a diameter of 0.016μm by removing machining strain completely
Wrap each with grain and 0.05μm diameter abrasive grain
It was It is possible to set the X-ray irradiation angle (glancing angle) to the sample surface.
The (022) reflection was used to make it as small as possible. This and
Mushroom α is 2^OAnd the change in half-width with β is shown in Fig. 2.
It was exactly as it was. The horizontal axis is based on kinematic theory.
The calculated penetration depth of X-rays is also shown. Fig. 2 (Half value by β
Change in width Si (022) -GaAs (022) α = 2.
0 ^O, Θ_B= 22.6^O) As is clearer, the penetration depth
The strain introduced to the sample surface by reducing the
Was found to appear sensitively.

(Example 2) In Example 1, GaAs was used as the first crystal, and (1) was used instead of (022) reflection.
33) Using reflection, the irradiation angle dependence was examined under the other conditions in the same manner as in Example 1, and FIG.
s (004) -GaAs (133) α = 15.1 ^O , θ
_B = 36.3 ^O ). As is clear from FIG.
It was found that the strain introduced into the sample surface appeared sensitively by reducing the penetration depth.

[0010]

According to the present invention, by adopting the above-mentioned constitution, the single crystal surface layer can be evaluated by a non-destructive inspection method while changing the depth, so that the processing strain of the crystal and the thin film epitaxially grown on the substrate can be evaluated. It is effective for evaluating crystallinity.

[Brief description of drawings]

FIG. 1 is a diagram showing the arrangement of sample crystals when carrying out the method of the present invention.

FIG. 2 is a diagram showing the measurement results of the sample rotation angle dependence of the full width at half maximum of (022) reflection in Example 1.

FIG. 3 is a diagram showing a measurement result of a sample rotation angle dependency of a half width of (133) reflection in Example 2.

Claims (1)

[Claims] 1. A method for evaluating a single crystal surface layer by an X-ray double crystal method, comprising arranging a surface layer of a single crystal to be evaluated horizontally, and then, under a condition that a reflecting surface is obtained, an angle from a horizontal plane, A method for evaluating a single crystal surface layer, which comprises adjusting an in-plane rotation angle of the reflecting surface of the single crystal to change an X-ray irradiation angle with respect to the single crystal.