JPS597252A - Method and apparatus for measuring inclined angle of crystal surface - Google Patents

Abstract

PURPOSE:To measure the inclined angle of the crystal surface with high precision, by rotating the crystal in a plane in parallel to the crystal surface, diffracting X-rays, and halving the angle difference between the 2 X-ray intensity peaks obtained from the specified grating faces. CONSTITUTION:The crystal wafer 1 to be measured is fixed to a disc 2, and the disc 2 is rotated with a motor 3 so as to allow the central axis of the disc 2 to coincide with the rotation axis. An X-ray flux 4 narrowed through holelike slits 5, 6 is allowed to fall on the disc through its central axis, and a relative incident angle beta with respect to the flux 4 is changed in the horizontal face of the disc 2. The intensity of the reflected X-rays is detected with an X-ray detector located at the position almost satisfying the Bragg condition. The inclined angle of the crystal surface is obtained by halving the angle difference between the 2 X-ray intensity peaks obtained from the specified grating faces of the crystal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the angle of inclination of a single crystal surface from a specific plane direction.

Conventionally, as a method for measuring the crystallographic plane orientation (hereinafter simply referred to as the 1st self-force orientation) of a single crystal, a narrow beam of characteristic X-rays (hereinafter referred to as the incident beam) is irradiated onto the crystal surface, and There is a method that uses Bragg repulsion from the crystal lattice a+ (hereinafter referred to as lattice plane J). That is, for the incident ray flux of the characteristic XffM, the surface orientation that causes Bragg diffraction is searched, and the surface orientation and the incident direction where the intensity of the narrow beam reflected by the Bragg diffraction (hereinafter referred to as "reflected ray flux J") is maximized are determined. It is common practice to determine the crystal plane index for the plane orientation by measuring the angle (Bragg angle) formed with the reflected ray flux.

On the other hand, when cutting a parallel plate-shaped single crystal (hereinafter referred to as a 1-wafer), such as a semiconductor wafer, from a single crystal ingot, the surface of the wafer is processed to be inclined from the desired plane direction, The degree of the slope may become a problem. For example, if a wafer with a (100) surface is cut from a ready-to-crystal ingot grown with a <100> growth axis, the processed surface will have a deviation of about ±1° unless special care is taken. It is often dismissed from the crystallographic (100) aspect. If it becomes necessary to measure the inclination of such a wafer again with higher precision, it is generally possible to measure the inclination of the wafer by using the Bragg diffraction of X-rays.
．． Measurement can be performed with an accuracy of 10° or less (using a monochromator) [0001° or less in the crystal method].

However, in order to measure the inclination of the wafer surface from the % constant plane orientation, the perpendicular line erected at the irradiation position of the incident beam on the wafer surface must be tilted toward the divine direction and the Bragg diffraction condition described above must be satisfied. The operation to find the solid angle is j#:
iced. This operation has the disadvantage that it is not easy to determine a spatial position that satisfies the Bragg diffraction conditions because the degree of spatial freedom in the direction in which the vertical axis is tilted is large.

The purpose of the present invention is to eliminate these drawbacks and provide a force method for measuring the tilt angle of a crystal surface, which can easily measure the tilt angle from the surface direction of a single crystal wafer with commercial accuracy, and a measuring device therefor. It is about providing.

The method of measuring the angle of crystal light m'ftM of this invention involves continuously rotating a parallel plate-shaped single crystal in a plane parallel to its surface, performing x6 diffraction, and then The X bag i intensity from a specific lattice area on the crystal surface is measured, and this
By bisecting the angular difference between the two peak values of leg strength, the inclination angle is measured l:t! It is assumed to be an rf signal.

The crystal surface inclination angle measuring device of the present invention includes a name plate Z-shaped body supporting a parallel root-shaped single crystal, a rotation means for continuously rotating this plate-shaped body in a plane parallel to the plate surface, and @i''N+i 1#
The apparatus includes an X-ray return means for irradiating the crystal with X-rays without changing the incident angle to cause diffraction and measuring the intensity of the X-rays.

The present invention will be described in detail below with reference to the drawings.

In FIG. 1, the diagonal 1 of the 8i (001) wafer used in the present invention is j. In this example, as a Si wafer, the inclination (
The angle of (0
01] The angle α with the axis is 041°, O, O, respectively.
Wafers with three glazes having temperatures below So, o, and oi° are used.

FIG. 2 is a perspective view showing the configuration of an embodiment of the invention.

In the figure, a wafer 1 to be measured is fixed to a suitable disk 2, and a motor 3 is used to move the disk 2 so that the center axis 1 of the disk 2 (parallel to the perpendicular line t of the wafer) coincides with the rotation axis. Rotate. The central axis of this disk 2 has a diameter of 05 ψ
Hole-like slit 5 and hole-like slit 6 with a diameter of 30 μmψ
Inject the beam 4 narrowed down by the disk 2.
The relative incident angle β with respect to the incident string bundle 4 is changed within the horizontal plane of . The reflection intensity of Xh at this time is X&! placed at a position that satisfies the Bragg condition. It is detected by a detector 7 and its output is recorded by a percentage amplifier and a recorder.

The principle of this invention is as follows. Angle β of the incident ray bundle with respect to the axis of rotation. is the Bragg complementary angle for the 004 reflection and satisfies 2 dou S'' (l-β.)=λ. Therefore, the following two equations hold true in the vicinity of this incident angle β.

2dsin(-1β.-α)2λ (1)2d
stn(-1β.+α)=λ (2) In other words, at such an angular position, a reflected ray flux that satisfies the Bragg condition can be obtained, so β1=Tori+α.

β, = β. -α, the inter-peak distance Δβ in FIG. 3 satisfies the following equation.

Δβ=β, −β,=2α (3) Therefore, when the peak-to-peak distance Δβ in FIG. 3 is measured, the following equation can be directly obtained from it.

Figures 3 (al, b), and (c) are characteristic diagrams measured for the three types of wafers shown in Figure 1 using the apparatus of this example.
Kα.

(wavelength λ = 1.54A), measured near β255.4°, where x is the angle of incidence on the vertical axis relative to the incident angle β on the horizontal axis.
3 strong iI is shown. This figure 3 (a), fb)
In this case, two symmetrical peaks were obtained. In this characteristic diagram, the peak-to-peak angle is △β and the deviation is △β = 082° in Figure 3 1 (a), t'' in Figure 3 tb), △β 2 0.16°, still in Figure 3 fc), the peak was clear and Δβ-%-00. In this combination, since wafer 1 is in h-turn, the intensity of the two peaks is almost ltt.
It is measured in the same way. In this example, from the relationship of equation (4), in Fig. 3 1a) (X = 0.41°, +b
) with r, i: α=0.08°.

fc), α=0. It can be measured as less than 015° (resolution of this example).

In this example, the tilt angle α is not specified in any crystal zone within the wafer, but if you want to know the direction of the tilt within the wafer, d
1. It can be measured using the device shown in the 8+ diagram in Figure 4. That is, a wafer 1 is placed on a disk 2 which has a slit 21 through which a ray of light incident parallel to the rotation axis 1 can pass.
161, and the phase relationship between the optical axis pulse that breaks through the slit 21 and is detected by the photodetector 22 when the disk 2 rotates, and the X-ray pulse detected by the X-ray detector 7. , the measurement may be performed using an appropriate circuit such as the amplifier 23 and the lock-in amplifier 24.

[Brief explanation of drawings]

The first dino is used in this invention and has a crystal surface of (001)W.
Perspective view of a wafer with a surface inclined by α from l, 2nd
The figure is a perspective view showing an embodiment of the present invention, and FIG.
(b), (cl is a characteristic diagram showing the measurement results for three wafers with different tilt angles in this example, the fourth
The figure is a perspective view showing the configuration of another embodiment of the present invention. In the figure, 1... wafer, 2...
Disc, 3...Motor, 4...Incidence X
i bundle, 5, 6...slit, 7...X
Ray detector, 11...Light ray, 21...Disc slit, 22...Photodetector, 23...
...Amplifier, 24... Mouth, Quin Ambu. ) Spear-21? J Otsuβ=0.82'6β-0,1(,' Fig. 3

Claims (1)

[Claims] 1) A parallel plate-like single crystal is continuously (
b) Perform X-ray diffraction while rotating, measure back the X-ray intensity from a specific lattice plane on the crystal surface with respect to the Xh incident angle, and divide the angular difference between the two peak values of the XIti1 intensity into two. A method for measuring a crystal surface tilt angle, characterized by measuring a tilt angle. 2) A plate-shaped body supporting a parallel plate-shaped single crystal, a rotation means for continuously rotating the plate-shaped body in a plane parallel to the plate surface, and an incident angle to the parallel plate-shaped single crystal. Shivering while irradiating X-rays and causing diffraction, the diffraction XfFJ! 1. An apparatus for measuring a crystal surface tilt angle, comprising an X-ray diffraction means for measuring intensity.