JPH05281149A - Apparatus and method for inspecting micro-crack - Google Patents

Abstract

PURPOSE:To obtain a micro-crack inspecting apparatus, which can accurately detect the micro-cracks of a wafer based on automatic control with regard to the inspecting apparatus for inspecting the micro-cracks generated when the rear surface of the wafer is polished. CONSTITUTION:This apparatus is constituted of a light-beam generating device 1, a light-beam scanning means 3, which scans the light beam generated in the light-beam generating device 1 on a wafer 5, a photodetector 7, which detects the image focusing position of the reflected light of the light beam that is scanned on the wafer 5 with the light beam scanning means 3, and a micro-crack-judging means 8, which detects the recess part on the wafer 5 and detects the micro-crack based on the deviation of the image focusing position of the light beam that is detected by the photodetector 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus and an inspection method for microcracks generated during polishing of the back surface of a wafer.

In recent years, the back surface polishing process of a wafer is carried out by attaching a tape to the surface of the wafer and fixing the wafer to the wafer chuck through the tape. Even if it is sandwiched, it has an effect of preventing cracks from being generated in the wafer due to the polishing residue penetrating into the tape, and the number of cracks is reduced, but it is not yet extinct. Therefore, the inspection of microcracks is one of the important steps in the semiconductor manufacturing process.

[0003]

2. Description of the Related Art Conventionally, microcracks are inspected by the naked eye. This method utilizes the fact that light is scattered at the part where the crack is generated, and the operator observes the wafer surface while tilting the wafer to search for the part where the crack is generated, and further corresponds to the part where the crack is generated. The position of the chip is specified.

[0004]

Relying on human inspection for microcracks may overlook the cracks or make different judgments depending on the operator. Further, it is extremely difficult to specify the position of the chip corresponding to the site where the microcracks are generated, and skill is required.

An object of the present invention is to eliminate these drawbacks, and it is an object of the present invention to provide a microcrack inspection apparatus and a detection method capable of accurately detecting microcracks on a wafer by automatic control.

[0006]

Among the above-mentioned objects, a microcrack inspecting apparatus comprises a light beam generator (1) and a light beam generated by the light beam generator (1) scanning on a wafer (5). A light beam scanning means (3) for performing the above-mentioned wafer (5) by the light beam scanning means (3).
The photodetector (7) for detecting the image forming position of the reflected light of the light beam scanned above and the deviation of the image forming position of the light beam detected by this photodetector (7) are used to detect the image on the wafer (5). This is achieved by a microcrack inspecting apparatus having a microcrack determining means (8) for detecting the concave portion of the above and determining it as a microcrack.

Among the above-mentioned objects, the micro-crack inspection method uses the micro-crack inspection device described above to scan the entire surface of the wafer (5) with a light beam to form an image of reflected light from the wafer (5). The position is detected by the photodetector (7), and the image formation position on the photodetector (7) is remarkably changed in the recess formed in the wafer (5) as compared with the peripheral portion. This is achieved by a microcrack inspection method in which the crack determination means (8) determines a microcrack.

[0008]

As shown in FIG. 5, when the back surface of the wafer is polished,
When the foreign matter 10 is sandwiched between the wafer 5 to which the tape 14 is attached and the chuck 9, a convex portion is generated on the back surface of the wafer 5. In this state, when the back surface is cut flat by the cutter 11 and the wafer 5 is removed from the chuck 9, a recess 12 is formed in the wafer 5 as shown in FIG.

The inventor of the present invention has found that the thickness of the wafer is locally thinned in this concave portion and a great stress is applied to this during cutting, so that the concave portion 12 has cracks 13 as shown in FIG. It has been found that cracks are likely to occur at the stage of passing through a process such as heat treatment even if they do occur or if they do not occur.

The present invention applies the results of this research, and detects a microcrack occurrence site or a site with a high probability of microcrack occurrence by detecting a recess formed on the wafer surface.

As shown in FIG. 1, when the light beam is scanned on the wafer 5 and the image forming position of the reflected light is detected by the photodetector 7, the reflection angle of the light beam in the concave portion is different from the other portions. As shown in FIG. 2, the image formation position of the reflected light is significantly shifted compared with the peripheral portion of the recess, so that the recess on the wafer surface can be detected by detecting this shift. Even if the entire wafer has a large undulation, it can be easily detected because the image forming position is significantly displaced in the concave portion as shown in FIG.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A microcrack inspection apparatus and inspection method according to an embodiment of the present invention will be described below with reference to the drawings.

See FIG. 3. FIG. 3 shows a block diagram of the microcrack inspection apparatus. In the figure, 1 is a laser beam generator, 2 is an expander for adjusting the laser beam diameter, 3 is a light beam scanning means such as a polygon mirror for scanning a laser beam, 4 is a mirror, 5 Is a wafer, 6 is an objective lens, and 7 is, for example, PSD (position sense).
A photodetector such as a detector), and 8 is a microcrack determining means for processing the detection waveform of the photodetector 7 to detect a concave portion and determining a microcrack.

The laser beam is scanned in the X-axis direction of the wafer 5 by rotating the polygon mirror 3, and
The laser beam is scanned over the entire surface of the wafer 5 by moving the wafer 5 in the Y-axis direction. The photodetector 7 detects the image formation position of the reflected light from the wafer 5 formed by the objective lens 6.

4 and 2, when the wafer 5 has a concave portion, the reflection angle θ ₁ of the reflected light from the concave portion is the reflection angle θ of the reflected light from the location where the concave portion does not exist as shown in the optical path diagram of FIG. Since it is different from ₀ , the image forming position of the reflected light on the photo detector 7 is displaced. The situation is shown in FIG. The gentle shift in FIG. 2 is due to the waviness of the wafer.

FIG. 8 shows a block diagram of the microcrack determining means.
An image forming position signal of the reflected light from the wafer 5 by the photodetector 7 is amplified by an amplifier 15, low-frequency and high-frequency noise is removed through a bandpass filter 16, and then binarized by a binarizing device 17. The pulse from the polygon mirror rotation angle pulse generator 18 for generating a pulse corresponding to the rotation angle of the polygon mirror 3 and the binarized image forming position shift signal are input to the recess X direction position determining device 19. Then, the position of the recess in the X direction is determined. In addition,
The position of the recess in the Y direction can be obtained from the moving distance of the stage (not shown). The position of the recess thus detected is determined as the position of the microcrack as described in the section of the action.

By combining the microcrack position data with the stepper exposure data, the chip position corresponding to the microcrack position can be easily determined.

[0018]

As described above, in the microcrack inspecting apparatus and the inspecting method according to the present invention, the concave portion on the wafer is detected from the deviation of the image formation position of the reflected light by scanning the light beam on the wafer. Since it is determined to be a microcrack, the microcrack can be reliably inspected by automatic control without relying on human hands.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle.

FIG. 2 is an output waveform at an image forming position of reflected light from the wafer surface.

FIG. 3 is a configuration diagram of a microcrack inspection device.

FIG. 4 is an optical path diagram for explaining a change in reflection angle at a concave portion.

FIG. 5 is an explanatory diagram of a microcrack generation mechanism.

FIG. 6 is a view showing a concave portion formed on a wafer.

FIG. 7 is a correspondence diagram between a concave portion of a wafer and a crack.

FIG. 8 is a block diagram of a microcrack determining means.

[Explanation of symbols]

 1 Light Beam Generator 2 Expander 3 Light Beam Scanning Means (Polygon Mirror) 4 Mirror 5 Wafer 6 Objective Lens 7 Photo Detector 8 Micro Crack Judging Means 9 Chuck 10 Residue 11 Cutter 12 Recess 13 Crack 14 Tape 15 Amplifier 16 Band Pass Filter 17 Binarization device 18 Polygon mirror rotation angle pulse generator 19 Positioning device for recess X direction

Claims (2)

[Claims] 1. A light beam generator (1), a light beam scanning means (3) for scanning a light beam generated by the light beam generator (1) onto a wafer (5), and the light beam scanning means. The wafer (5) according to (3)
The photodetector (7) for detecting the image forming position of the reflected light of the light beam scanned upward, and the deviation of the image forming position of the light beam detected by the photodetector (7) from the photodetector (7) on the wafer (5) A microcrack inspecting device, comprising: a microcrack determining means (8) for detecting a recess to determine a microcrack. 2. The microcrack inspection device according to claim 1, wherein a light beam is scanned over the entire surface of the wafer (5), and the image formation position of reflected light from the wafer (5) is detected by a photodetector (7). The micro-crack determining means (8) uses the fact that the image formation position on the photodetector (7) changes remarkably in the concave portion formed on the wafer (5) as compared with the peripheral portion. A method for inspecting microcracks, characterized in that it is judged as a crack.