JPS5974627A - Method and apparatus for inspecting photo-mask - Google Patents

Abstract

PURPOSE:To detect the defect of a pattern accurately by detecting the photo- mask by using every eight measuring units in which directions are changed at a 45 deg. angle unit with the half length of a picture element row. CONSTITUTION:The photo-mask 1 is moved by an X-Y stage by an automatic feeder 2, and the pattern of the mask 1 is projected by an optical device 3, and outputted as a picture data by a scanner 4. The data is binary-coded 5, and memorized 6 as a picture data. A detector 5 consists of a plurality of AND gates and OR gates, the data is read in succession and the defect of the pattern is detected, and the positional coordinates of the defect are recorded when the section is discriminated as a defective section, and outputted after the whole mask 1 is inspected completely. The positional coordinates discriminated as the defective section are displayed on an X-Y plotter 8. Accordingly, the defective section of the photo-mask is corrected by comparing an output drawing displaying the defective position and the photo-mask.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for inspecting patterns on photomasks for printed circuit boards.

Conventionally, printed circuit boards are created by creating a photomask from an original plate and then subjecting it to development and fixing processing. In this case, defects such as small conductor width, small conductor spacing, black spots, pinholes, protrusions, and chips occur on the photomask due to dust in the developer or contact with the substrate during pattern formation on the pattern.

Conventionally, such defects have been detected and corrected by visual inspection using a stereomicroscope or the like. However, as photomask patterns have become increasingly finer and denser in recent years, conventional visual inspections are no longer sufficient to detect defects, and inspections using scanning light beams, electron beams, etc., have become necessary. . A method of more accurately carrying out inspection by scanning with a light beam, an electron beam, etc. is being sought.

SUMMARY OF THE INVENTION In view of the above-mentioned background, an object of the present invention is to more accurately perform scanning with a light beam, especially by using a form of local area processing.

According to the present invention, the purpose of this is to provide the length of a pixel column for inspecting the minimum conductor width and minimum conductor spacing, which are the inspection standards of the photomask, using the image data obtained by reading the photomask with a scanner. A state in which eight measurement units each having a length of 45 degrees are used, and each of the opposing measurement units has a value corresponding to a conductor part or a non-conductor part? A photomask inspection method, which is characterized by detecting? Further, according to the present invention, automatic feeding means for moving a photomask in the X-Y direction, and scanning a pattern of the photomask projected by an optical means, a scanner that outputs image data corresponding to brightness and darkness; a binarization unit that binarizes the image data output by the scanner; and a binarization unit that converts the binarized image data into a storage means for storing bit/pixel data;
71. composed of a predetermined number of pixels from among the bit/pixel data stored in the storage means. The measuring unit is 8 pixels each with the length of the bar of the pixel row changed in 45° increments. The present invention is characterized by comprising a detection means for detecting a state having a value corresponding to , a display means for displaying a result detected by the detection means, and a control section for controlling the operation of the scanner and each means. This is achieved by providing a photomask inspection device that performs the following steps.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is a block diagram showing an apparatus for carrying out a photomask inspection method according to the present invention. In Fig. 1, 1 indicates a photomask which is a sample to be inspected, 2 indicates an automatic feeding means for moving the photomask on an X-Y stage, and 6 indicates an optical means for projecting a turn on the photomask. 4 is a scanner that outputs the photomask pattern projected by the optical means as image data corresponding to the brightness and darkness of the turn, and for example, a line scan type solid-state image sensor is used. 5 is a binarization means that binarizes the image data outputted by the scanner after correcting the variation between the solid-state image sensors since it contains the variation, and 6 is a binarization means that is used by the binarization means. #) A storage means for storing binarized 1-bit/pixel image data as bit/pixel data, and 7 is a storage means that sequentially reads out the bit/pixel data and detects defects in the pattern and determines that it is a defective part. In some cases, the detection means records the position coordinates and outputs them after the entire inspection of the photomask 1 is completed, and is composed of a plurality of AND gates and an OR gate.

8 is a position b determined to be a defective part by the detection means.
For example, an XY block is used as a display means for displaying the mark. Reference numeral 9 denotes a control unit that controls the operation of each means in 2 to B-1 described above. In such a configuration
- The defective portion of the photomask is corrected by comparing the output diagram showing the defective portion finally shown on the Y plotter 8 with the aforementioned photomask.

FIG. 2 is a diagram showing the arrangement of pixels in the photomask inspection method according to the present invention. In Figure 2, each square indicates bit/pixel data stored in the storage means, and the measurement unit changes direction in 45° angle units with a length corresponding to the minimum conductor width and minimum conductor spacing. 8 each
It consists of one pixel row. The pixel range corresponding to each measurement unit is as follows.

al is 10 pixels from (1-10,j) to (i-1,j),
C2 has 1D pixels from (i+10.j) to (1,011.j), C3 has 7 pixels from (i-7,j) to (i-1,,+), and a has 1D pixels from (1+6.j) to (i+1.j)
6 pixels, bl is (i, j-10) ~ (i,
j-1) (7D 10 pixels, bl is (i, j+10
) ~ (i, j+1) - 10 pixels, b3 is (i, j
-7) ~ (i, j-1) 7 pixels, b4 is (i,
j+6) to (1, j+1), C1 is (i-
7 pixels from 7,j+7) to (i-1,j+1), C2
has 7 pixels from (1+7.j-7) to (i+1.j 1), and C3 has 7 pixels from (i-4,j-1-4) to (i-1,j
+1), C4 is (1+5.j-5)~(
1+1. j-1) 5 pixels, dl is B-7, j-7
) to (Sat-1, j-1), dz is (i+7
．． j+7) ~ (i+1. j+1 ) 7 pixels, C3 is (4-s, j-5) ~ (1-1, j-1)
The 5 pixels of C4 are (i+4.j+4) to (t+1.
j+1) 4 pixels. Among these measurement units, al, C2, bl, bl, clsC2, dl, C2
For inspection of conductor width, C3, 84% b3, b4, C3,
C4, C3, and C4 are used to inspect conductor spacing. Note that these two positions are not limited to the positions shown in FIG. 2 because they are performed independently in logical analysis. In this example, the minimum conductor width of 200 μm and the minimum conductor spacing of 130 μm are set as inspection standards, so the image data is
In the case of 0 μm/pixel, defects occur when the conductor width is 19 pixels or less and the conductor interval is 12 pixels or less.

In the diagonal direction, the conductor width is 19/ρf: 13 pixels or less, and the conductor interval i1: 12/8 pixels or less in the medium is considered defective. However, the number of pixels is the reading unit of image data (μm
/pixel) and inspection standards. In this embodiment, as shown in FIG. 2, the measurement unit is the sum of two pixels. However, if the number of pixels is even, the center position (i, j) will be shifted. Further, it is assumed that 1 in the image data corresponds to a conductor portion and 0 corresponds to a non-conductor portion.

Regarding the conductor width in the vertical direction of the drawing, each measuring unit of al and C2 is inspected. There is a change of 0 → 1 from the periphery (1-10゜j) of C2 to the center (1-1, j), and from the periphery (i+1o, )) of C2 to the center (i
+1. j) When there is a change from 0 to 1, the conductor width can be determined to be 19 pixels or less.

Also, regarding the conductor spacing in the vertical direction, the measurement units of C3 and C4 are inspected. Peripheral part of C3 (1-7, D to central part (i
-1,j), and 1→0 from the periphery (1+6.j) to the center (i+1.j) of C4.
When there is a change of 0, it can be determined that the conductor spacing is 12 pixels or less.

Defects in other directions can be similarly determined by inspecting the measurement units b1 to d4.

FIG. 6 is a circuit diagram of the detection means 70 in the photomask inspection apparatus according to the present invention. Figure 3 is a circuit diagram for one measurement unit, and in this case, the length of the measurement unit, that is, the number of pixels, is shown as 5 pixels, but the number of pixels is set to an appropriate value according to the conditions described above. Ru. In the same figure, in the case of inspecting the conductor spacing, the area located above five pixels is located at the periphery, and as it moves downward, it becomes the center area.

On the other hand, when inspecting the conductor width, this direction is reversed. The AND gate 11 outputs 1 when adjacent upper and lower pixels of the measurement unit 10 change from 1 to 0. The OR gate 12 outputs 1 if even one AND gate 11 becomes 1.

The results of inspection by the photomask inspection method according to the present invention will be explained with reference to FIGS. 4(a), (b), and (O). In FIG. 4, the shaded portions indicate conductor portions, and the other portions indicate non-conductor portions.

In FIG. 4(a), the conductor width is small (19 pixels) in the horizontal direction of the drawing. Both measurement units b1 and bl change from 0 to 1 from the periphery to the center, which can be determined as a defect.

Figure 4(b) shows "small conductor spacing" (12 pixels) in the horizontal direction.
It becomes. For both measurement units b3 and b4, a change from 1 to 0 from the periphery toward the center can be identified as a defect.

Figure 4 (0) shows "small conductor width" in diagonal direction (16 pixels)
It becomes. The measurement unit (11, dz) can be identified as a defect if there is a change from 0 to 1 from the periphery to the center.

In FIG. 4(d), the conductor spacing is small (8 pixels) in the diagonal direction.

Measurement unit d3.6.4: 1 from the periphery to the center
→A change of 0 can be identified as a defect.

FIG. 4(θ)d shows a case where a protrusion corresponding to IXl pixels is generated due to binarization. The conductor width of this protrusion is 19 pixels or less, which meets the criteria for a defect, but is not a defect. Unit of measurement b! , in b2, 0 → 1 from the periphery to the center
Since there is no change in , it can be excluded as a defect. Also, if the position of the protrusion deviates from (1°j) in the horizontal direction, bl p
Since only a change from 0 to 1 occurs on one side of b2, it can be excluded from defects.

FIG. 4(f) shows a portion corresponding to the bend of the lead or the corner of the land. The protrusions resulting from binarization are combined, and there is a change of 1→0.0→1 in the measurement units b1 and C1. However, since there is no change from 1 to 0 in b2 and C2, which are opposing units of measurement, they can be excluded from defects.

As described in detail above, by using the photomask inspection method and apparatus according to the present invention, it is possible to accurately detect pattern defects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a photomask inspection apparatus according to the present invention. FIG. 2 is a diagram showing pixel arrangement 6 in the photomask inspection method according to the present invention. The detection circuit of the detection means in the photomask inspection device, and FIGS. 4(a) and 4(b)
), ((J, (d), (e), and (f) are diagrams explaining the photomask inspection method according to the present invention. (Explanation of symbols) 1... Photomask 2... Automatic feeding Means 6...Optical means 4...Scanner 5...Binarization means 6...Storage means 7...Detection means 8...Display means 9...Control unit 10...Measurement Unit 11...AND gate group 12...OR gate al ゞa4 p bl ゞb4 HC1"""C
4* (11ゞa. ...Measurement unit No. 1 Fig. 2 ↓-IQ j-7j le◆6 1Ryo10尤-10几-7j
, jφ6 1 out of 10 Fig. 4 (b) Fig. 4 (c) Destination −+o i−7尤 ↓會6
L Middle 10 Figure 4 (d) 1-10 Top-7 Top 1.
6 1++. Figure 4(e)

Claims (1)

[Claims] 1. The length of the pixel row used to inspect the minimum conductor width and minimum conductor spacing, which are the inspection standards for the photomask, with respect to the image data obtained by scanning the photomask with a scanner. Using eight measuring units each with a length of 45° and whose direction is changed in 45° increments, it is possible to detect a state in which the opposing measuring units both have values corresponding to conductive parts and non-conductive parts. Characteristic photomask inspection method. Z: automatic feeding means for moving the photomask 1 in the x-y direction; a scanner for scanning the pattern of the photomask projected by an optical means and outputting image data corresponding to the brightness and darkness of the pattern; a binarizing means for binarizing the image data;
The digitization means converts the binarized image data into bits.
A storage means for storing pixel data, and an angle 45 having the length of a pixel row composed of a predetermined number of pixels from among the bit/pixel data stored in the storage means.
Detection means for detecting a state in which each eight pixel rows whose direction is changed in degrees is used as a measurement unit, and the opposing measurement units of the pixel rows have values corresponding to a conductor portion and a non-conductor portion. A photomask inspection apparatus comprising: a display means for displaying a result detected by the detection means; and a control section for controlling the operation of the scanner and each means.