JPH10173019A - Semiconductor inspection method - Google Patents

Abstract

(57) [Abstract] [Problem] To improve inspection sensitivity. SOLUTION: In an inspection method for comparing an image signal or a scattered / diffracted light signal with a predetermined threshold in a semiconductor device manufacturing process and extracting foreign matter / defect, the foreign matter / defect detection threshold is set to a distance r from the center of the wafer. , The function of the rotation angle θ is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for inspecting a semiconductor device.

As an inspection apparatus for detecting a defect such as a circuit pattern using comparative image processing in a semiconductor device manufacturing process, there is an automatic appearance inspection apparatus WI880 manufactured by Hitachi Tokyo Electronics Co., Ltd. As an inspection device for detecting a circuit pattern or the like, in particular, a particle using a diffracted light, an IS2 manufactured by Hitachi Electronics Engineering Co., Ltd.
300 and others.

The former inspection apparatus irradiates a wafer with white light and captures a grayscale image of a pattern into a detector. The difference between this image signal and the image signal of the adjacent chip or shot stored in the delay memory is obtained, and the difference is compared with a predetermined threshold value. This processing is performed by performing an xy scan (scan in the x direction and step feed in the y direction) of the inspection stage.
This is performed on the entire surface of the wafer.

The latter inspection device irradiates a wafer with monochromatic light and takes in scattered and diffracted light of a pattern into a detector. The difference between this signal and the signal of an adjacent chip or shot stored in the delay memory is obtained, and the difference is compared with a predetermined threshold value.
This process is performed on the entire surface of the wafer by performing an xy scan (scan in the x direction and step feed in the y direction) of the inspection stage.

[0005]

In actual processing, film formation and polishing processes, the film thickness often has a concentric distribution from the center of the wafer. That is, the pattern signal level and the color tone also change concentrically, and in particular, the former tends to increase near the wafer. To cope with this problem, in the conventional inspection technique, the inspection is performed using a single threshold value within the wafer surface. Therefore, the threshold value is limited at the position where the pattern signal is highest, and the inspection sensitivity cannot be increased. Further, the difference signal between the adjacent chip and the shot also becomes large in the peripheral portion of the wafer where the color tone changes drastically, and the inspection sensitivity is limited. An object of the present invention is to improve inspection sensitivity.

[0006]

According to the first aspect of the present invention, there is provided an inspection method comprising:
A stage control unit and a stage driving unit that scan the stage over the entire surface of the wafer, an image signal processing unit that stores the image signal incident on the detector in a memory, and that obtains a difference signal, and converts the signal distribution to an r-θ coordinate system. This is achieved by an operation unit that performs the inspection and an inspection condition setting unit that sets the inspection threshold from the signal distribution.

According to a second aspect of the present invention, there is provided an inspection method comprising: a stage control unit and a stage driving unit for scanning a stage over the entire surface of a wafer; and an image signal processing unit for taking a difference image between chips or shots having the same distance r from the center of the wafer. Achieved.

In the inspection method according to the present invention, the pattern signal foreign matter / defect detection threshold is determined by the distance r from the wafer center and the rotation angle θ in the inspection condition setting unit for setting the inspection threshold from the signal distribution. It is possible to set an optimal threshold value in each area without being limited by a signal at a high place, and it is possible to increase the inspection sensitivity.

According to the inspection method of the present invention, it is possible to compare chips or shots having the same color tone by an image signal processing section which takes a difference image between chips or shots having the same distance r from the center of the wafer. In addition, the influence of the process can be reduced and the inspection sensitivity can be improved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the relationship between a chip 2 on a wafer 1, a conventional xy orthogonal coordinate system, and an r-θ rotation coordinate system. FIG. 2 is an apparatus configuration diagram of the present invention. The example shown here is a visual inspection device using white light. The light from the white light source 3 is bent by the mirror 4 and irradiates the wafer 1 on the stage 5. The image of the pattern on the wafer passes through the objective lens 6,
The light enters the detector 7. The incident light is photoelectrically converted and stored in the signal storage unit 8. The arithmetic unit 9 calculates the difference between this signal and the signal of the same pattern stored in advance, compares the difference signal with the value of the threshold table 10, and detects a signal that is equal to or larger than the threshold as a foreign substance or a defect. The stage controller 12 is driven by the stage controller 11, and the processing is performed on the entire surface of the wafer. The determination of the threshold is performed as follows. A part or the whole surface of the wafer is scanned to obtain the relationship between the position and the difference signal level. At this time, an r-θ coordinate system is used as the coordinate system. FIG. 3 shows the results. A value obtained by adding an offset to the signal level at each position is set as a threshold value at that position. This example is shown in FIG.
Shown in The setting of such a threshold is one for each process.
It may be performed only once or for each wafer. The input of the inspection condition is performed by the operation unit 15.

FIG. 5 shows an example of a comparative chip according to the second aspect. The chip comparison unit is equidistant from the center of the wafer. A and B are compared.

[0012]

According to the present invention, a high-sensitivity inspection can be performed without being affected by a pattern signal and a color tone which change concentrically.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a relationship between an xy coordinate system and an r-θ coordinate system.

FIG. 2 is a block diagram of the device.

FIG. 3 is an explanatory diagram of a relationship between a position in a wafer and a level of a difference signal.

FIG. 4 is an explanatory diagram of a threshold table.

FIG. 5 is an explanatory diagram of a comparative chip example of the second embodiment.

[Explanation of symbols]

1 ... wafer, 2 ... chip, 3 ... white light source, 4 ... mirror,
5 stage, 6 objective lens, 7 detector, 8 signal storage unit, 9 arithmetic unit, 10 threshold value table, 11 stage control unit, 12 stage drive unit, 13 image signal processing unit, 14 ... Control unit.

Claims (2)

[Claims] In an inspection method for extracting an extraneous matter / defect by comparing an image signal or a scattered / diffracted light signal with a predetermined threshold value in a manufacturing process of a semiconductor device, the extraneous / defect detection threshold is set to a distance from the center of the wafer. A semiconductor inspection method, wherein a function of r and a rotation angle θ is set. 2. The method according to claim 1, wherein the chips or shots at a distance r from the wafer center are compared with each other.
Defect inspection method.