JPH0612250B2 - Scribe line pattern detection method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a scribe line pattern on a wafer, and more specifically, a scribe line pattern that rarely misidentifies other patterns on the wafer with the scribe line pattern. The present invention relates to a line pattern detection method.

[Prior Art] In a micro-dimension measuring device that measures the dimensions of a pattern on a wafer or the alignment accuracy, prior to those measurements,
The tilt of the coordinate system of the wafer with respect to the coordinate system of the XY stage on which the wafer is set is measured. In this measurement, scribe line recognition processing is performed.

Conventionally, the width of the pattern existing in the field of view of the pattern detection optical system is checked with the XY stage positioned at the reference point of the wafer, and if a pattern having the width of the scribe line exists, the scribe line is detected. Have recognized as.

[Problems to be Solved] In such a scribe line detection method focusing only on the pattern width, if a pattern having the same width as the scribe line exists in the field of view, the pattern is erroneously recognized as a scribe line. was there.

[Object of the Invention] An object of the present invention is to provide a method for detecting a scribe line pattern, which is suitable for recognizing the scribe line as described above and is less likely to be misidentified.

[Means for Solving Problems] A feature of the scribe line pattern detection method of the present invention that achieves the above-mentioned object and solves the above problems is as follows.
The chip area along the scribe line pattern whose width is to be detected by the one-dimensional image sensor in the direction in which the width of the scribe line pattern is detected on the surface of the wafer divided by the scribe line pattern when positioned at the reference point of the wafer. Of the width corresponding to the width of the scribe line pattern is detected based on the output data of the image sensor, which is scanned to detect whether or not there is a width corresponding to the scribe line pattern. The length in the direction is calculated, and this length is adjacent to the visual field of the chip area around the reference point, and is determined to be the scribe line pattern when the length is equal to or longer than the longest pattern inside the chip area in the direction of the target scribe line pattern. It is a thing.

[Operation] By the way, in order to detect the length of the scribe line pattern, it may be considered to detect it corresponding to the length of the chip region. However, since the pattern width is detected by comparing it with a predetermined threshold value, the accurate length of the scribe line pattern cannot be detected, and the determination cannot be performed sufficiently. However, if it is compared with the longest internal pattern adjacent to the visual field in the chip area around the reference point, there is a relatively large difference between this and the length of the scribe line pattern. Even if an error occurs in the detection of, the scribe line pattern can be surely separated from other patterns and detected.

Therefore, as in the above-described configuration, the length of the width of the scribe line pattern is detected based on the output data of the image sensor which is sequentially scanned and imaged corresponding to the width of the chip area along the scribe line pattern to detect the surrounding area. If the determination is made by comparing with the longest internal pattern in the chip area, whether or not it is a scribe line pattern can be reliably determined only by scanning for the width of the chip area, and the scribe line pattern can be detected.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a minute dimension measuring apparatus to which the scribe line pattern detecting method of the present invention is applied. This minute dimension measuring device precisely measures the dimension of a pattern of a wafer, a mask, etc., the alignment accuracy of patterns formed in the preceding and following steps.

In FIG. 1, 10 is an XY stage mechanism. The wafer 12 loaded into the chuck portion of the XY stage mechanism 10 by a loader / unloader (not shown) is positioned and held with the orientation flat (orientation flat) 13 as a reference. Thus, the coordinate system of the wafer 12 and the coordinate system of the XY stage mechanism are made to coincide with each other, but some offset is inevitable. In this wafer offset,
Since the influence of the tilt is large, the tilt is detected,
The scribe line pattern detection method according to the present invention is applied to the processing.

The upper surface of the wafer 12 is provided with a halogen lamp 16, a mirror 18, an achromatic lens 20 and a half mirror 2.
Illuminated via 2. The local bright and dark image on the upper surface of the wafer 12 illuminated in this way is detected by the pattern detection optical system 2.
Observed by 4.

The pattern detection optical system 24 includes an objective lens 26, the half mirror 22, the half mirror 28, and a slit 30.
X, 30Y, relay lenses 32X, 32Y, mirror 3
4. Cylindrical lenses 36X and 36Y, CCD linear image sensor 38 which is a one-dimensional image sensor
It is composed of X and 38Y. The bright and dark images in the visual field on the wafer surface determined by the objective lens 26 are the slits 30X, 3
The field of view is further narrowed through 0Y and the images are picked up by the CCD linear image sensors 38X and 38Y. Slit 30X
The aperture is parallel to the X axis of the coordinate system of the XY stage mechanism 10, and an image in the elongated X direction passing through the center of the field of the objective lens 26 is formed on the CCD linear image sensor 38X. Similarly, the field of view of the other CCD linear image sensor 38X is narrowed down by the slit 30Y to an elongated area in the Y direction passing through the center of the field of view of the objective lens 26, and the wafer image in the field of view is formed on the CCD linear image sensor 38X. To be done. The CCD linear image sensors 38X and 38Y pixel-separate and read the bright and dark patterns formed on the CCD linear image sensors, and serially output analog image signals.

Reference numeral 40 is a processing control system. The processing control system 40 includes a gain / offset optimization circuit 42, an analog / digital converter 44, an image memory 46, a microprocessor 48,
It comprises a RAM 50, a keyboard 52 and its interface circuit 54, an XY stage drive circuit 56 and its interface circuit 58. Although there are circuits related to driving control of the CCD linear image sensors 38X and 38Y and the analog / digital converter 44, they are not shown.

The XY stage drive circuit 56 is the microprocessor 4
8 drives the X-Y direction drive motor (not shown) of the XY stage mechanism 10 in accordance with control information given from the interface circuit 58. XY
The stage mechanism 10 is provided with a position encoder (not shown) for detecting the position in the X and Y directions, and the output signal of the position encoder is the interface circuit 5
It is adapted to be inputted to the microprocessor 48 side via the No. 8.

The analog image signals output from the CCD linear image sensors 38X and 38Y are input to the analog / digital converter 44 via the gain / offset optimizing circuit 42 and converted into digital image signals (referred to as image data) therein. Are input to the image memory 46. The microprocessor 48 can access the image memory 46,
Further, writing of image data in the image memory 46 can be controlled.

Here, two reference points A and B are preset on the wafer surface as shown in FIG. An enlarged view of the wafer surface in the vicinity of the reference point A is shown in FIG. As shown in this figure,
Chip regions 60 are formed on the wafer surface in order in the X and Y directions (X and Y directions of the wafer coordinate system), and each chip region 60 is divided by linear grooves in the X and Y directions, that is, scribe lines 62. ing. Generally, the upper right corner of a specific chip area 60 is set as a reference point. Similarly, the reference point B is also set as the upper right corner of the other specific chip area 60.

Next, the wafer tilt detection operation will be described with reference to the flowchart shown in FIG.

When the wafer 12 is positioned and held on the chuck portion of the XY stage mechanism 10, the microprocessor 48 operates in the RAM.
The tilt detection program 50A stored in 50 starts to be executed.

First, the microprocessor 48 determines the coordinates (X ₁ , X _{1 of} the reference point A set in the register 50 B on the RAM 50).
Positioning information obtained by adding a predetermined value to Y ₁ ) is given to the XY stage drive circuit 56 via the interface circuit 58. The XY stage drive circuit 56 drives the drive motor of the XY stage mechanism 10 according to the positioning control information. As a result, if the tilt of the wafer 12 with respect to the X axis of the XY stage mechanism 10 (θ shown in FIG. 2) is zero, the approximate center of the field of view 64 (FIG. 3) of the objective lens 26 is at the reference point A. The wafer 12 is positioned so that it substantially coincides with the intersection of the closest scribe lines 62 (step 105).

If the inclination θ of the wafer 12 is larger than a predetermined upper limit value,
If the positional deviation between the center of 4 and the reference point A is excessive, the tilt cannot be detected normally. Therefore, in order to confirm that the positional deviation is within the allowable range, the scribe line 6
The recognition process 2 is performed.

First, the CCD linear image sensor 38 at the current position
The image data obtained by X is stored in the image memory 46 for one scanning line (step 110). For example, if the CCD linear image sensor 38X is positioned as shown in FIG. 3, the field of view 66 is electronically scanned, and the bright and dark image within the field of view is pixel-decomposed and read to obtain an electrical signal. It is converted and serially output in pixel order. Image data obtained by analog-digital converting this image signal is stored in the image memory 46. After this storage,
The microprocessor 48 uses the I counter 5 on the RAM 50.
0C (cleared in step 100 in advance)
Is incremented by 1 (step 115), and it is compared and judged whether the value of the I counter is equal to or larger than a predetermined value IM (step 120).
This IM is a value corresponding to the dimension of the chip region 60 in the Y direction.

If the I counter value is less than IM, the microprocessor 4
8 moves the wafer 12 in the Y direction (downward in FIG. 3) by one step, in other words, moves the visual field 66 of the CCD linear image sensor 38X upward by 1 step in FIG. Then, the XY stage drive circuit 56 is instructed (step 125), and the process returns to step 110.

In this way, the field of view 66 changes from the position of the solid line to the imaginary line 66.
The chip area 60 is step-moved to the position A by the dimension in the Y direction, and the digital image signal at each position is stored in the image memory 46.

When this operation is completed, the microprocessor 48 reads the image data for one scanning line IM stored in the image memory 46 for one scanning line, and detects the pattern having the width corresponding to the scribe line 62 (step 130). .

More specifically, for example, in FIG.
Only the image data corresponding to the shaded area 6 is read by the microprocessor 48 and compared with a predetermined threshold value. It is assumed that the scribe line 62 exists within the shaded area. In that case, since both sides of the scribe line 62 are edge portions of the chip region 60 and the illumination light is scattered,
At that portion, the level of the analog image signal sharply drops.
The image data is compared with a predetermined threshold value, and such a level drop point, that is, a valley point of the analog image signal waveform is extracted. Then, the interval between adjacent valley points is compared with the interval corresponding to the scribe line width. If there is a scribe line, the spacing between the valley points at both ends should be approximately equal to the scribe line width. When such a pair of valley points is detected, "1" is set to the bit corresponding to the scanning line of the table 50D on the RAM 50 (each bit has been cleared in advance in step 100). The pattern detection method described here is an example until the user gets tired.

Next, the microprocessor 48 decrements the value of the I counter by 1 (step 135) and makes a zero determination of the I counter (step 140). If the value of the I counter is not zero, the process returns to step 130 and the same pattern detection is performed for the next scanning line.

When the pattern detection for the IM scanning lines is completed in this way, the microprocessor 48 refers to the table 50D and continues the "1" bit, that is, the pattern corresponding to the detected scribe line width in the Y direction. The sex is checked (step 145). The continuity here is "1"
The total number of bits of the above is converted into the length, and corresponds to the length of the chip area 60 minutes of the actual scribe line pattern. If the scribe line exists in the movement locus range of the perspective portion of the visual field 66, the pattern having a width corresponding to the scribe line width is in the same direction as the scribe line pattern adjacent to the visual field of the chip region 60 around the reference point A. Must be continuously detected over the length of the longest internal pattern of.

The microprocessor 48 compares the length of the pattern continuous section obtained in step 145 with the length of the longest internal pattern (step 150), and if the former is less than the latter (no scribe line exists), the above processing is performed. Since the validity cannot be guaranteed, the processing ends abnormally at this stage. If the former is the latter or more, the pattern detected continuously is recognized as a scribe line, and step 155 is performed.
Proceed to the subsequent positional deviation detection processing.

In this way, not only the width of the pattern but also the continuity of the pattern is checked to recognize the scribe line. Therefore, misrecognition of the pattern in the vicinity of the scribe line can be prevented and the scribe line can be surely recognized.

Note that only the Y-direction scribe line was recognized here, but similarly, only the X-direction scribe line,
Alternatively, scribe lines in both X and Y directions may be recognized.

Now, in the positional deviation detection process, first, the microprocessor 48 controls the XY stage mechanism 10 via the XY stage drive circuit 56, and thereby the step 105 is performed.
The field of view 6 near the field of view 66 when positioned by
CCD linear image sensor 38 while moving 6
The image data obtained by X, 38Y is stored in the image memory 46.
Are sequentially read through and the pattern of the reference point A is searched.
For example, the pattern of the upper edge and the lower edge of the chip area 60 in which the reference point A is set is searched, and the intersection is recognized as the reference point A. However, this is an example until the user gets tired, and another method may be used. When the reference point A is found,
The microprocessor 48 controls the center of the visual field 62 and the reference point A.
The XY stage mechanism 10 is controlled so that and are matched (stage 155).

After matching the center of the visual field 62 with the reference point A, the microprocessor 48 recognizes the coordinates of the XY stage mechanism 10 from the output signal of the position encoder of the XY stage mechanism 10 at that time (step 160). These coordinates are the actual coordinates of the reference point A. The microprocessor 48
By using this coordinate and the reference point coordinate (X ₁ , Y ₂ ) set in the register 50B, the deviation amount ΔX ₁ , Δ between the two.
Y ₂ is calculated and the result is stored in the register 50 on the RAM 50.
It is stored in E (step 165).

Next, the same processing as the processing from step 100 to step 165 is performed on the other reference point B (step 1
70). However, the coordinates (X ₂ , Y ₂ ) of the reference point B are RA
It is set in the register 50F on the M50, and the positional shift amounts ΔX ₂ and ΔY ₂ of the reference point B are stored in the register 50G on the RAM 50. Also in step 170, if no scribe line is detected, the process ends abnormally.

When the positional deviation amount between the reference points A and B is obtained, the microprocessor 48 calculates the inclination θ according to the following equation, stores the result in the register 50H on the RAM 50, and ends the process = step 175.

tan ⁻¹ θ = [(Y ₂ + ΔY ₂ ) − (Y ₁ + ΔY ₁ )] / [(X ₂ + ΔX ₂ ) − (X ₁ + ΔX ₁ )] ... (1) The inclination thus obtained θ is used for wafer coordinate correction in pattern dimension measurement, pattern alignment accuracy measurement, and the like. The description of the pattern dimension measurement and the alignment accuracy measurement is omitted.

Although one embodiment has been described above, the present invention is not limited to this.

For example, the one-dimensional image sensor may be something other than a CCD linear image sensor.

Although the wafer as the object is moved in the above embodiment, the wafer may be fixed and the one-dimensional image sensor may be moved, or both may be moved.

Further, the surface of the object may be imaged using a two-dimensional image sensor.

Further, the method of detecting the pattern having the specific width and the method of determining the continuity of the pattern may be appropriately changed.

Furthermore, the present invention can be similarly applied to recognition of line patterns other than scribe lines.

[Effects of the Invention] As described above, according to the present invention, the width of the scribe line pattern is determined based on the output data of the image sensor which is sequentially scanned and imaged corresponding to the width of the chip region along the scribe line pattern. Since the length is detected and compared with the longest internal pattern in the surrounding chip area to make the determination, the scribe line pattern can be reliably detected.

As a result, the scribe line pattern is not mistaken for another pattern.

[Brief description of drawings]

FIG. 1 is a schematic view of the configuration of a minute dimension measuring apparatus to which the method for detecting a scribe line pattern according to the present invention is applied, and FIG. 2 is a plan view for explaining a wafer tilt and a reference point,
FIG. 3 is a partially enlarged plan view for explaining the recognition of the scribe line near the reference point, and FIG. 4 is a schematic flowchart of wafer tilt detection processing. 10 ... XY stage mechanism, 12 ... Wafer (object), 16 ... Halogen lamp, 24 ... Pattern detection optical system, 26 ... Objective lens, 30X, 30Y ... Slit, 38X, 38Y ... CCD linear image sensor (one-dimensional image sensor), processing control system, 44 ... Analog / digital converter, 46 ... Image memory, 48 ...
Microprocessor, 50 ... RAM, 56 ... XY
Step drive circuit.

Front page continuation (72) Inventor Nobuyuki Iriki 1450, Kamimizuhonmachi, Kodaira, Tokyo Inside the Musashi Factory, Hitachi, Ltd. (72) Takayoshi Osakaya, 1450, Kamimizuhonmachi, Kodaira, Tokyo Hitachi, Ltd. Musashi, Ltd. In the factory (56) References JP-A-57-168105 (JP, A)

Claims (1)

[Claims] 1. A surface of a wafer divided by a scribe line pattern in a state of being positioned at a reference point of the wafer is a target for detecting the width by a one-dimensional image sensor in a direction of detecting the width of the scribe line pattern. Based on the output data of the image sensor that is sequentially scanned and imaged corresponding to the width of the chip area along the scribe line pattern, it is compared with a predetermined threshold whether or not there is a width corresponding to the scribe line pattern. The chip in the direction of the scribe line pattern of the object, the length in the scanning direction is calculated with respect to the detected width, and the length is adjacent to the visual field of the chip area around the reference point. A scribe line characterized by being judged as a scribe line pattern when the pattern is longer than the longest pattern inside the area. Method of detecting a turn.