JP2594685B2 - Wafer slip line inspection method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface appearance inspection of a wafer, and more particularly to an automatic inspection method for a slip line generated on a wafer.

[Conventional technology]

Conventionally, this kind of inspection of a slip line has been carried out by visual inspection by a human or selective etching for crystal defects, measuring the length of the slip line by visual observation and microscopic observation, sketching and photographing.

[Problems to be solved by the invention]

Since the above-described conventional inspection method of the slip line is a visual inspection by a human, there is a disadvantage that the length of the slip line and the position in the wafer are not constant due to individual differences in detection and reproducibility and differences in the inspection environment. For example, FIG. 7 shows an example, in which (a) and (b) show slip lines observed by different persons under the same microscope, and (c) shows slip lines observed by different persons under (a) and (b) under different microscopes.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic slip line inspection method which eliminates indefiniteness by visual observation with a microscope as described above.

[Means for solving the problem]

The method for inspecting a wafer slip line according to the present invention includes detecting a reflected light by irradiating the wafer with light at a specific angle at which a slip line is generated, corresponding to a crystal plane orientation of the wafer, and detecting a lattice plane assumed on the wafer. Then, the position and length of the slip line are automatically measured from the position and the number of gratings where the reflected light is detected.

(Operation)

An orientation flat is provided on the wafer in a specific crystal plane orientation. Therefore, since the direction at which the slip line of the wafer is generated is determined, the intensity of the reflected light from the slip line can be increased by determining the incident angle of the light in accordance with the direction. This reflected light is detected, and the slip line can be automatically measured from the grid position and the number of grids on the grid surface that exceed a certain level. The direction of reflection from the slip line will be described in detail in Examples.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an apparatus for implementing this embodiment. The wafer 4 is irradiated with the circularly polarized laser light 2 emitted from the laser oscillator 1 while performing a raster scan in the X direction by the scanning mirror 3. At this time, in order to distinguish the scattered light 6 due to the foreign matter 5 and the reflected light 7 in a specific direction from the slip line, the angle θ and the angle rotation direction γ determined by the crystal plane orientation and the orientation flat direction of the wafer 4 are rotated. The position is set by the variable arm 9 and the position of the wafer 4 is determined. The reflected light 7 in a specific direction is squeezed by the objective lens 10, received by the photoelectric element 11, converted into a voltage, input to the comparator 12, and compared with the slip line detection voltage 13 set according to the detection sensitivity in the comparator 12. And outputs a detection signal as a slip line. The wafer 4 has θ,
The γ, Y stage 15 tilts to the angle θ by the angle rotation variable arm 9 and advances in the Y direction. When the slip line detection signal is output from the comparator 12, the X ·
The Y coordinate is stored in the memory 14. In addition, each position coordinate of the reflected light detected at the time when the measurement is performed again and the scanning of the entire wafer is completed is stored in the memory 14 after being rotated by the fixed angle γ.

FIG. 2 is a front view showing a main part of the inspection apparatus according to the embodiment, which determines an incident angle of the laser beam with respect to the wafer 4. The wafer 4 is supported by a vacuum chuck 8 at the tip of a variable angle rotation arm 9. As described above, the angle rotation variable arm 9 determines θ and sets the angle γ around the axis.
The entire surface of the wafer 4 is scanned by rotating the wafer 4 in the Y direction and further moving in the Y direction.

FIG. 3 is a schematic diagram showing a method for measuring the length of a slip line. (A) illustrates data stored in the memory 14 of the slip line inspection device of the present invention. The slip line 18 mainly exists in the wafer 4, but the foreign matter 5 and the scratch 20 also exist. As described above, the slip line 18 is determined by the crystal plane orientation and the orientation flat direction, and has a feature that exists linearly in a specific direction and has a length. (B), the foreign matter 5 and the flaw 20 existing as points, or as straight lines, curves or irregular shapes having a width are removed from the coordinates as shown in FIG. Then, the slip line coordinates (b) from which the foreign matter 5 and the flaw 20 have been removed are input to the slip line measuring circuit 17,
The wafer shown in (c) is superimposed on a lattice plane 19 divided into a chip matrix of 0.5 mm × 0.5 mm and deformed into a slip line map of (d), and the slip line measuring circuit 17 obtains one of the slip line maps (d). The slip line existing in the chip is counted as 0.5 mm, and the slip line on the chip that is not a square around the wafer is 0.
It counts as 25 mm and outputs the sum of these as the slip line length.

Next, the principle of slip line determination will be described.
Fig. 4 shows foreign matter 5 on the wafer, slip line
This shows the state of scattering and reflection when the laser beam 21 is irradiated on 18. When the laser beam 21 is applied to the foreign matter 5 in (a), the reflected light becomes isotropic and becomes scattered light 6. When the laser beam 21 is applied to the slip line 18 in (b), since the laser beam 21 has a linear length in a specific direction according to the crystal plane direction and the orientation flat direction, the slip line 18 shows anisotropy and becomes the reflected light 7.

FIG. 5 shows a slip line occurrence position of the crystal plane orientation (111). (A) shows a unit cell of the crystal structure, and a slip line 1 having a crystal plane orientation (111) is shown.
The slip surface existing as 8 is enclosed in the [110] direction (1
1) 22, (11) 23, and (11) 24. From this, drawing a circle centered on the origin of the unit cell reveals that three planes appear at 120 ° C each, and that the angle θ is tilted to 60 ° C. The slip line direction of the crystal plane orientation (111) can be detected. (B) shows the slip line direction that occurs when the crystal plane orientation is (111) and the orientation flat direction is <10>. As described above, the slip line 18 is set to <10> 25, <1>
0> 26, <01> 27, <10> 28, <01> 29, <01>
There are six of thirty. Although the position in the wafer is different, the direction of the slip line is the above six directions,
And the slip line 18 can be distinguished.

Next, a second embodiment will be described. FIG. 6 is a front view of a main part of the second embodiment. The X direction of the laser beam 2 and the stage angle rotation γ direction are the same as in the first embodiment. The difference from the first embodiment is that the detection system of the objective lens 11 and the photoelectric element 12 for receiving the reflected light of the slip line is of a variable angle type. In this embodiment, only the movement of the .theta., .Gamma., And Y stages 15 in the Y direction and the rotation of a certain angle in the .gamma. Direction are performed. There is an advantage that can be measured.

〔The invention's effect〕

As described above, the present invention detects a reflected light of a slip line by irradiating a laser beam to a wafer surface in a slip line inspection of a semiconductor wafer such as an IC and an LSI, and detects a length of the slip line, By measuring the position, human errors such as conventional human visual inspection, microscopic inspection, and skill can be eliminated, and there is an effect that measurement can be performed with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for implementing the slip line inspection method of the present invention, FIG. 2 is a front view of a main part of the slip line inspection apparatus, and FIG. 3 explains the measurement and output operation of the length of the slip line. FIG. 4 is a view showing the reflection direction of the foreign matter and the slip line on the wafer, FIG. 5 is a view showing the slip plane of the slip line having the crystal plane orientation (111), and FIG. The figure is a front view of a main part of the slip line inspection device of the second embodiment. FIG. 7 is a sketch diagram after a visual inspection to explain the length of the slip line, individual differences in the position in the wafer, and differences in the environment. 1 laser oscillator, 2 laser light (circularly polarized light), 3 scanning mirror, 4 wafer, 5 foreign matter, 6 scattered light, 7 reflected light, 8 vacuum chuck, 9: Variable angle rotation arm, 10: Objective lens, 11: Photoelectric element, 12: Comparator, 13: Slip line detection voltage, 14: Memory, 15: θ, γ, Y stage, 16 …… Slip line position coordinate output circuit, 17… Slip line measurement circuit, 18… Slip line, 20… Scratch.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein the reflected light is detected by irradiating the wafer with light at a specific angle at which a slip line is generated in accordance with the crystal plane orientation of the wafer, and the reflected light is detected on a lattice plane assumed on the wafer. An inspection method that automatically measures the position and length of a slip line from the position and number of grids that have been set.