JPS60157008A - Pattern inspecting device - Google Patents

Abstract

PURPOSE:To detect a defect of a pattern easily and accurately by providing a means which changes the direction of scanning lines of a scanning means by 90 deg., and performing a read scan in two orthogonal directions. CONSTITUTION:Image rotators 24 and 26 arranged between an X-Y stage 14 and a flying spot scanner 20 consists of the 2nd and the 3rd mirrors 24 and 26 which cross the 1st mirror parallel to an optical axis at mutually opposite angles and are can be rotated by 45 deg.. When the image rotators 24 and 26 are rotated by 45 deg., scanning directions of beams on photomasks 10 and 12 rotate by 90 deg. and change from an X direction to a Y direction. Consequently, the pattern is scanned in the two orthogonal directions and the ability in defect detection is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a main turn inspection device for inspecting f-turn shaped defects in photomasks and the like.

In recent years, along with the mass production of integrated circuits, photomasks have also been mass produced. Here, 79 of the manufactured photomask
To inspect turns for defects, line up the photomask to be inspected and the original standard photomask, and
In this method, the turns are read and scanned at the same time, and the difference between the two scanning outputs is calculated. Generally, multiple reading scans are performed on a mask in one direction using a flying spot scanner. Here, if the scanning direction is the X direction, the resolution along the Y direction is lower than the ability (resolution) to detect pattern defects along the X direction. Therefore, defects may be overlooked depending on how the photomask is positioned.

The present invention has been made in order to cope with the above-mentioned circumstances, and an object of the present invention is to provide a mother turn inspection device that has equally high defect detection ability not only in one direction but also in a direction orthogonal thereto.

Hereinafter, an embodiment of a pattern inspection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of this embodiment, where the object to be inspected is a pattern on a photomask. An original standard photomask 1o and a photomask to be inspected 12 are fixed to an XY stage 14.

Photodetectors 16 and 18 are fixed on the XY stage 14 below the locations where the photomasks 1θ and 12 are fixed, respectively. Lenses 28, 30 corresponding to the photomasks 10, 12 are provided above the XY stage 14, respectively.

The scanning beams of the flying spot scanner 20 installed above the X-Y stage 14 (approximately 1.!M71) are transmitted onto the photomasks 1θ and 12 via the image rotators 24 and 26 and lenses 28 and 30, respectively. be projected. The beam scanning direction C of the flying spot scanner 20 is the X direction when a coordinate system is set on the photomask 10.12 as shown in FIG. Here, as the photomask 10.12, a so-called multi-sided mask in which the same pattern is arranged in a matrix is used.

The image rotators 24, 26 include a first mirror parallel to the optical axis and a second mirror parallel to the optical axis at opposite angles to each other. The principle diagram of the three mirrors of the third mirror is shown in Fig. 3 (aL (b)). The image is rotated by 1800 degrees. When the image rotator rotates by 45 degrees around the optical axis as shown in Fig. 3, the passing image becomes a mirror image of the real image F rotated by 90 degrees. That is, by rotating the image rotator by 45 degrees, the passing image can be rotated by 90 degrees. Accordingly, in the case of Fig. 1, by rotating the image rotator by 45 degrees,
The scanning direction of the beam on the photomask changes from the X direction to the Y direction.
change in direction.

As shown in Fig. 2, the photomask 10.12 has different light transmittance between the part where the pattern is formed and the part where the pattern is not formed. can be recognized.

Photo detector 16. The output signals of Ill are input to both input terminals of a differential amplifier 36 via video amplifiers 32 and 34, respectively. The output signal of the video amplifier 32.34 is also supplied to a CRT monitor 38.40. The output signal of the differential amplifier 36 is also supplied to a CRT monitor 42 and a microprocessor 46 via a contour pseudo signal removal circuit 44. The microprocessor 46 controls the flying spot scanner 20 via a two-axis/blanking angle 48 and deflection circuit 50, and synchronously controls the XY stage 14 via a stage drive circuit 52. Further, a printer 54 for recording test results is also connected to the microprocessor 46.

Next, the operation of this embodiment will be explained. With the image rotators 24 and 26 in the state shown in FIG. let

At this time, the difference between the output signals from the photodetectors 16 and 18 is iJ? of the photomask 12 to be inspected. This is displayed as a turn defect on the CRT monitor 42 and is input to the microprocessor 46. Next, when the image rotator 24.26 is set to the state shown in FIG. 3(b), even though the scanning direction of the flying spot scanner 20 does not change, the scanning direction of the beam on the photomask 10.12 is 90°.
Rotate in the Y direction. That is, the pattern is read and scanned multiple times along a direction perpendicular to the previous scanning direction. In this way, since the pattern is scanned in two orthogonal directions, by adding up the results of the two scans, the defect detection ability in the two orthogonal directions can be equally improved. For photomasks, Nocturna, usually Y
Since it consists only of straight line parts parallel to the axis and Y axis,
All defects can be detected by performing two readings and nine scans along the Y direction. Since the photomask is a multi-sided mask, when the inspection of one pattern is completed, the x-y stage 1
4 moves in the X direction, and the adjacent pattern is inspected in the same way.

FIG. 4 shows a second embodiment in which the beam scanning direction of the flying spot scanner is electrically changed. Deflection circuit 50
-1 generates a horizontal (X direction) scanning voltage, and the deflection circuit 50
-2 generates a vertical (Y direction) scanning voltage. The outputs of the deflection circuits 50-1 and 50-2 are supplied to a horizontal deflection coil 64 and a vertical deflection coil 66 of a flying spot scanner 62 via a two-power/two-output switch 60. Thus, by switching the inch 60, the scanning direction of the beam of the shifting flying spot scanner can be changed by 900 degrees. Therefore, the switch 60 is
Pattern inspection may be performed for each of the states shown in (b).

The scanning direction of this flying spot scanner can be changed not only by switching the scanning signal, but also by rotating the flying spot scanner itself by 90 degrees around the optical axis. Furthermore, since the scanning direction is determined by the relative relationship between the flying spot scanner and the photomask, it can also be changed by rotating the X-Y stay 14 itself by 90 degrees and by rotating the photomask 10.12 by 90 degrees.

As explained above, according to the present invention, the d' turn to be measured is read along the scanning line. The turn inspection device has a means for rotating the scanning direction by 90 degrees, and has two orthogonal
By performing reading υ scanning along the direction, it is easy to
Moreover, pattern defects can be detected accurately. Furthermore, since the scanning direction can be easily changed, inspection can be carried out efficiently and in a short time. Note that the object to be inspected may not be two multi-sided photomasks, but one multi-sided mask may be two patterns of photomasks, or two single pattern masks.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a pattern inspection apparatus according to the present invention, FIG. 2 is a diagram showing the coordinate system of a photomask on an X-Y stage, and FIGS. FIGS. 4(a) and 4(b) are diagrams showing the principle of operation of the image rotator used in the embodiment. FIGS. 4(a) and 4(b) are diagrams showing the deflection system of the flying spot scanner, which is the main part of the second embodiment. No. 0,12...Photomask, 14...X-Y stage, 16.18...Photodetector, 20...Flying spot scanner, 24.26...Image rotator, 28.30. ... Lens, 36 ... Differential amplifier, 42 ... CRT monitor, 46 ... Microprocessor, 50 ... Deflection circuit, 52 ... Stage movement circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 1 fi 2

Claims (1)

[Claims] A scanning means for scanning the pattern to be inspected and the standard Noreen along a plurality of scanning lines parallel to each other and reading the main turn, and a scanning output of the inspected/4' turn and a scanning output of the standard/flat turn from the scanning means. A lean inspection device comprising: means for inspecting defects in a pattern to be inspected according to the difference between the two; and means for changing the direction of the scanning line of the scanning means by 90 degrees.