JP2696640B2 - Photomultiplier tube protection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection mechanism for a photomultiplier tube in a wafer surface inspection apparatus.

[0002]

2. Description of the Related Art A semiconductor IC is manufactured by forming a wiring pattern on a silicon wafer. If unevenness or foreign matter is present on the surface of the material wafer, it becomes a defect and the quality of the IC deteriorates. Therefore, the wafer is inspected by a wafer surface inspection apparatus. In the wafer surface inspection device, the size of the defect to be detected gradually becomes smaller with the miniaturization of the wiring pattern,
Recently, an apparatus capable of inspecting a minute defect of 0.1 μm or less has been developed.

FIG. 2 shows a basic configuration of a main part of the above-mentioned wafer surface inspection apparatus (hereinafter simply referred to as an inspection apparatus). Fig. 2 (a)
In the inspection apparatus, a spindle 22 for mounting and rotating the wafer 1 to be inspected, a rotation mechanism 2 including a drive unit 21 for driving the spindle 1, and a moving table for moving the rotation mechanism 2 in the direction of the radius R of the wafer 1 3 is provided. On the other hand, a light projecting system 4 including a laser light source 41 and a light projecting lens 42,
Each is provided with a light receiving system 5 including a plurality of condenser lenses 51 and a photomultiplier tube 52. In the inspection,
A predetermined voltage is applied to the laser light source 41 and each photomultiplier tube 52 to stabilize each operation. The rotation mechanism 2 is stopped at the wafer mounting / detaching position indicated by the dotted line, the wafer 1 is mounted on the spindle 22, and the driving unit 21 rotates the wafer 1 by θ. While moving the wafer 1 in the direction of the radius R by moving table 3, projects vertically the laser beam L _T to the surface of the wafer 1. the surface of the wafer 1 by the rotation and R moving θ is scanned spirally by the laser beam L _T,
Scattered light L _R is each focusing lens of the light receiving system 5 due to defects in the surface
The light is condensed by 51 and is received by each photomultiplier tube 52 to output a defect detection signal. FIG. 2B is a plan view showing the configuration of the light receiving system 5, wherein the scattered light L due to a surface defect of the wafer 1 is shown.
_Since the directivity of _R varies depending on the shape of the defect, it is necessary to receive light in as many directions as possible.
In the figure, four condenser lenses 51a, 51b, 51c, and 51d, respectively,
Photomultiplier tubes 52a, 52b, 52c, and 52 d, are symmetrically arranged with respect to the projection point of the laser beam L _T. In this case, the directions of the optical axes of the condenser lenses 51 and the photomultiplier tubes 52 are set at appropriate angles with respect to the surface of the wafer 1 so that defects can be detected well.

[0004]

In FIG. 3, it is assumed that the rotating mechanism 2 is stopped at the wafer mounting / detaching position. Since the laser light source 41 is always operated, the laser beam L _T output from this rotation mechanism 2 is stopped in the detachable position, reflecting the projected by reflected light L _s to the surface of the moving table 3. To one of the condenser lens 51 of the reflected light L _s is the light receiving system 5, type directly, or indirectly input through the other components of the optical system is focused, photomultiplier The light enters the tube 52. Originally, the performance of the photomultiplier tube 52 deteriorates due to incident light regardless of whether voltage is applied or not. Therefore, in order to prevent deterioration, the use of unnecessary light is minimized except during inspection. It is absolutely necessary to avoid. For this purpose, various methods have been tested, such as processing the surface of the moving table 3 into a diffusely reflecting surface such as satin finish, providing a light diffusing plate, or painting a black non-reflective surface. However, since very strong intensity of the laser beam L _T is also how many minutes, the anti-reflection method above various Any incomplete, it was found that deterioration preventing effect is not rise. Therefore, in front of the moving table 3, a method for reflecting the laser beam L _T in a direction not incident to the light receiving system 5 is considered valid. However, it is necessary not to hinder the inspection of the wafer. According to the present invention, the rotation mechanism 2
There does not interfere with the wafer inspection when in the test position, when in the mounting and dismounting position, the protection to reflect the laser beam L _T in a direction not incident to the light receiving system 5, to prevent unnecessary deterioration of the photomultiplier tube 52 The purpose is to provide a mechanism.

[0005]

According to the present invention, there is provided a protection mechanism for a photomultiplier tube which achieves the above-mentioned object. A reflector that receives a laser beam and reflects the laser beam in a horizontal direction that does not enter the light receiving system is attached to a drive unit of a rotating mechanism.

[0006]

In the above protection mechanism, the reflector attached to the drive unit of the rotation mechanism receives the laser beam in the vertical direction and reflects the laser beam in the horizontal direction when the rotation mechanism is at the wafer mounting / removing position. On the other hand, since the light receiving system is above, the reflected light does not enter and the deterioration of the photomultiplier is prevented.
In wafer inspection, the reflector moves together with the driving unit, and the laser beam is projected on the wafer at the inspection position, so that the reflector does not hinder the inspection.

[0007]

FIG. 1 shows an embodiment of the present invention. The wafer surface inspection apparatus in FIG. 3A is the same as that in FIG. 2 described above, and is assumed to be at the mounting / detaching position of the wafer 1 as in FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals, and the description of the operation of each part is omitted.

In FIG. 1A, a driving unit 21 of the rotating mechanism 2 is used.
Is provided with a bracket 23, and the laser beam L near its tip is provided.
_The reflector 6 is mounted at a position corresponding to _T. (b) is a vertical sectional view of the reflector 6, showing two examples (a) and (b). In both cases, an appropriate metal cylinder was used, and a laser beam L
_The entrance hole 61 into which _T enters is pierced. For (b), the reflection plane 62 having an inclination angle of 45 ° to the central axis in the lower part of the entrance aperture 61 is formed, for reflecting the laser beam L _T in a horizontal direction. In the case of (b), a reflection curved surface 63 such as a spherical surface is used, and the light is also reflected in the horizontal direction. These reflection plane 62, reflection curved surface
63 does not need good reflectivity, but does not need to reflect diffusely. Because, if it is irregularly reflected,
This is because there is a danger that a part of the light will enter the light receiving system 5 upward. When the rotation mechanism 2 is in the mounting and dismounting position by more than, the laser beam L _T is mostly reflected in the horizontal direction by the reflector 6, a part is Saegigi is the entrance aperture 61 upward photomultiplier 52 And the deterioration is prevented. In the inspection of the wafer 1, the reflector 6 moves in the radius R direction (right direction) together with the rotating mechanism 2, so that the inspection does not hinder the inspection.

[0009]

As described above, in the photomultiplier tube protection mechanism according to the present invention, the reflector is attached to the drive unit of the rotation mechanism of the wafer surface inspection apparatus, and when the rotation mechanism is at the wafer mounting / removing position. Since the reflector receives the laser beam in the vertical direction and reflects it in the horizontal direction, unnecessary light does not enter the light receiving system, preventing deterioration of the photomultiplier tube. The instrument moves together with the rotating mechanism and does not hinder the inspection, and greatly contributes to ensuring the reliability of the inspection apparatus.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of the present invention, in which FIG. 1A is a view showing how a reflector is attached to a wafer surface inspection apparatus, and FIG. 1B is a vertical sectional view showing the reflector.

FIG. 2 shows a basic configuration of a wafer surface inspection apparatus, and (a)
Is a vertical sectional view, and (b) is a plan view of a light receiving system.

FIG. 3 is an explanatory diagram of unnecessary deterioration of a photomultiplier tube caused by a laser beam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Rotating mechanism, 21 ... Drive part, 22 ... Spindle, 23 ... Bracket, 3 ... Moving table, 4 ... Light emitting system,
41: Laser light source, 42: Projection lens, 5: Light receiving system, 51, 51
a, 51b, 51c, 51d: condenser lens, 52, 52a, 52b, 52c, 52d: photomultiplier tube, 6: reflector, 61: entrance hole, 62: reflection plane,
63… Reflection curved surface.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Mitomo 2-6-1, Otemachi, Chiyoda-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd. (72) Inventor Hidetoshi Hosono 2-6-1, Otemachi, Chiyoda-ku, Tokyo No. Hitachi Electronics Engineering Co., Ltd. (56) References JP-A-62-11135 (JP, A) JP-A-61-17050 (JP, A) JP-A-4-151547 (JP, A) JP-A-3-153 100446 (JP, A) JP-A-62-13547 (JP, A)

Claims (1)

(57) [Claims] 1. A spindle for horizontally mounting and rotating a wafer to be inspected, a rotation mechanism including a drive unit for rotating the spindle, and moving the rotation mechanism between a mounting / detaching position of the wafer and an inspection position. A light projection system, comprising: a moving table, mounted on the spindle at the attachment / detachment position, and vertically projecting a laser beam onto the surface of the wafer moved to the inspection position; and a foreign substance present on the surface. And a light receiving system having a plurality of photomultiplier tubes that respectively receive scattered light in a plurality of directions. A protection mechanism for a photomultiplier tube, comprising: a reflector that receives a laser beam from the light projecting system when in a position, and reflects the laser beam in a horizontal direction that does not enter the light receiving system.