JPH06281409A - Automatic external appearance inspecting device and inspecting method using same - Google Patents

Abstract

PURPOSE:To improve defect detecting precision by arranging plural focus offsets optionally. CONSTITUTION:Firstly, a focus is automatically adjusted in a reference focus position 14 by an automatic focusing offset unit. Secondly, focus offset values A, B are set and a focus position is switched sequently from 15 to 16, so that a focus can be adjusted properly to respective layers such as a wiring part 18 and a contact part, 19, and consequently, a failure to find a defect is eliminated and defect detecting precision is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for automatically inspecting a semiconductor wafer, and more particularly to an apparatus capable of multiple setting of a focus offset and an inspection method using the apparatus.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of an automatic semiconductor wafer visual inspection apparatus.

FIG. 2 is a schematic diagram showing a chip on which comparative inspection is performed and its inspection area.

FIG. 4 is a schematic diagram showing a cross-sectional view of a surface portion of a semiconductor wafer under inspection in a conventional semiconductor wafer automatic visual inspection apparatus.

As shown in FIGS. 1 and 2, this type of automatic semiconductor wafer visual inspection apparatus has two chips 1 to be inspected on a semiconductor wafer 3 fixed to a stage 2.
The information of the inspection areas 12 and 13 at the same coordinate points in 0 and 11 is recognized as an image by the TV camera 4 through the optical microscope 1, and the signal is recognized by the ultra-high-speed image processing dedicated computer 6
After pixel division and gradation classification by, the values are further digitized and overlay comparison is performed to detect defects.

Conventionally, the focus control during the inspection of this apparatus is performed by controlling the height position of the stage 2 by the autofocus unit 5 and the operation computer 8. As shown in FIG. It is put in according to 14. Subsequently, according to the only focus offset value set in the system computer 7 from the terminal 9 when the inspection condition designation file is created, the stage 2 is performed by the operation computer 8 in the same manner as above.
The inspection has been performed with a certain fixed focus 21 different from the reference focus 14 by the autofocus by moving the height position in the plus or minus direction.

The focus offset value is set according to the position to be observed. If the focus control operation is performed for each inspection point 12 and 13 and the inspection is performed on the entire surfaces of the chips 10 and 11, the inspection points 12 and 13 are moved and the focus control operation is performed at each point. Is done.

[0008]

By the way, in the above-described conventional inspection method using the semiconductor wafer automatic visual inspection apparatus, the focus offset is always constant according to the preset value, and the depth of focus at that time is not deep, so the observable range is limited. As a result, it is not possible to sufficiently observe each layer of the semiconductor wafer formed in multiple layers, and there is a drawback that defects are overlooked.

[0009]

SUMMARY OF THE INVENTION The semiconductor wafer automatic visual inspection apparatus of the present invention can set only one focus offset in the prior art so as to cope with complicated surface states of semiconductor wafers formed in multiple layers. It is an inspection apparatus in which a computer for a system that could not be used is a computer for a system capable of arbitrarily setting a plurality of focus offsets.

Further, the inspection method according to the present invention is a method of continuously inspecting one inspection region on the surface of a semiconductor wafer having a multi-layer structure with different focuses according to the setting of arbitrary and a plurality of focus offsets using the above apparatus. is there.

[0011]

According to the above apparatus and method, each layer on the surface of a semiconductor wafer having a multi-layer structure can be inspected with an independent focus. Therefore, it is possible to improve the detection sensitivity of micro defects over a multi-layer structure as compared with the conventional method. it can.

[0012]

First Embodiment The present invention will be described below with reference to the drawings.

Since the configuration diagram of the inspection apparatus is the same as that of the conventional apparatus (FIG. 1), the same figure and the reference numerals in the figure are used for the description. In the figure, 1 is an optical microscope, 2 is a stage,
3 is a semiconductor wafer, 4 is a TV camera, 5 is an autofocus unit, 6 is a computer for ultra-high-speed image processing, 7 is a system computer, 8 is an operation computer, 9 is a terminal, and 10 is a chip to be inspected.

Next, the operation of the above-mentioned semiconductor wafer automatic visual inspection apparatus will be described. In the semiconductor wafer automatic visual inspection apparatus of the present invention, instead of using the conventional apparatus in which the system computer 7 shown in FIG. 1 can set only one focus offset, arbitrary and plural focus offsets are set. Since it is the same as the conventional device except that it can be used, the operation computer 8 can operate the stage 2 in multiple stages according to the setting, and fine focus adjustment is possible. There is.

FIG. 3 is a schematic view showing a cross section of the surface of a semiconductor wafer under inspection when the apparatus of Example 1 is used. In the figure, 14 is a reference focus position by autofocus, 15 is a focus position according to the focus offset value A, 16 is a focus position according to the focus offset value B, 17 is a semiconductor wafer, 18 is a wiring part, and 19 is The contact portion, 20 is a stage.

In the present embodiment, the depth of observing the surface of a multi-layered semiconductor wafer with respect to one inspection region is set by applying an arbitrary and a plurality of focus offsets using the apparatus of the first embodiment. Instead, it is a multiple inspection method. For example, the focus offset setting is 2
If there is one (focus offset value A, B),
First, the autofocus unit 5 automatically adjusts the focus to the position indicated by 14, and then the focus positions are sequentially switched to 15 and 16 by setting the focus offset values A and B, and the wiring portion 18, the contact portion 19 and the like are changed. Since it is possible to accurately focus on different layers, there is an advantage that defects are not overlooked.

[0017]

As described above, according to the present invention, in the semiconductor wafer automatic visual inspection apparatus, the focus offset value can be set arbitrarily and a plurality of values can be set. Since they are aligned with each other, the accuracy of defect detection is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an automatic visual inspection apparatus for semiconductor wafers according to the present invention.

FIG. 2 is a schematic diagram showing a test chip and a test area.

FIG. 3 is a schematic diagram showing a cross-sectional view of a semiconductor wafer surface portion under inspection when the apparatus of the present invention is used.

FIG. 4 is a schematic view showing a cross-section of a semiconductor wafer surface portion under inspection when using a conventional apparatus.

[Explanation of symbols]

1 Optical Microscope 2 Stage 3 Semiconductor Wafer 4 TV Camera 5 Auto Focus Unit 6 Computer for Ultra High-speed Image Processing 7 Computer for System 8 Computer for Operation 9 Terminal (CRT, Keyboard) 10, 11 Inspection Chip 12 Inspection Area (with Defect) 13 Inspection Area 14 Focus Position as Reference by Auto Focus 15 Focus Position According to Focus Offset A 16 Focus Position According to Focus Offset B 17 Semiconductor Wafer 18 Wiring Section 19 Contact Section 20 Stage

Claims (2)

[Claims] 1. A microscope to which an image processing apparatus for visual inspection is in contact, an autofocus means for automatically adjusting the distance between the microscope and an object to be observed, and an arbitrary amount based on the autofocus point. An automatic visual inspection apparatus having a focus offset setting function for observing points at different distances between a microscope and an object to be observed, wherein the focus offsets can be set in multiple stages and are automatically switched. 2. A method for inspecting the surface appearance of a semiconductor wafer having a multi-layered film formed on the surface, wherein focus offsets are set in multiple stages by using the automatic appearance inspection apparatus according to claim 1, and different depths are set. An inspection method characterized by observing.