JPS6217745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mask repair method and an apparatus used in the mask repair method, and more particularly to a method for automatically inspecting and repairing a mask, and an apparatus equipped with the function.

A reticle used when forming a large number of identical patterns on a semiconductor substrate or a mask substrate uses a pattern generator to create a mask on a dry plate.
Draw and form a pattern. However, when writing, an emulsion dry plate is usually used, which has high sensitivity and is suitable for high-speed writing. However, since the emulsion layer has low hardness and the pattern is easily damaged, reticles made from the emulsion dry plate are used directly in the production of photomasks or semiconductor devices. Not suitable for use in manufacturing. Therefore, in the actual manufacturing process described above, a reticle made of a hard mask is used, which is transferred from a reticle made of an emulsion mask as an original plate. However, if there is an abnormality in the reticle made of the hard mask, the manufacturing yield of photomasks or semiconductor devices will be significantly impaired. Inspection is performed by comparing it with the mask pattern on the original plate, and abnormal areas are corrected.

Conventionally, however, in the above-mentioned correction, the pattern of the original reticle consisting of an emulsion mask and the pattern of the reticle consisting of a hard mask are optically superimposed, and a visual inspection is performed using a microscope, etc., to identify the abnormal area for each abnormality item. The method used is to create a map and perform separate laser burning or spot exposure based on the map to correct abnormal patterns.The correction process is complicated and requires a lot of man-hours and steps. There was a problem that it took a lot of time and at the same time correction errors occurred.

In view of the above-mentioned problems, the present invention provides a mask repair method in which pattern inspection and correction are all automatically performed, thereby preventing the occurrence of correction errors, and a mask repair apparatus having the automatic correction function.

That is, the present invention combines standard mask patterns and photo
One of the mask patterns to be inspected coated with a resist layer is projected with red light and the other with green light, and both projected patterns are superimposed and imaged on the same screen, and the superimposed pattern image is is scanned with a photoelectric conversion camera to capture the change in color tone of the superimposed pattern image as an electrical signal, the position and type of the abnormal pattern are determined based on the level of the electrical signal, and laser burning is performed based on the determination. Alternatively, a mask repair method characterized by automatically correcting abnormal patterns by either spot exposure, a servo motor-driven XY stage on which a standard mask and a mask to be inspected are set, and a standard mask and a mask to be inspected. A red light source and a green light source that project separately, an optical system that superimposes the projected image of the red light and the projected image of the green light and form them on the same screen, and a photoelectric conversion camera that scans the superimposed image. It has a comparison and identification device for classifying the electric signal level of the photoelectric conversion camera, and a laser burning system and a spot exposure system that are driven by the signals given from the comparison and identification device, and has a function of automatically making corrections. The present invention relates to a mask correction device characterized by:

The present invention will be described in detail below with reference to an explanatory diagram of an apparatus structure of an embodiment shown in FIG. 1, a schematic diagram of an overlapping pattern shown in FIG. 2, and a configuration diagram of a control system in the same embodiment shown in FIG.

For example, as shown in FIG. 1, the apparatus used in the mask repair method of the present invention places and fixes a standard mask 1 and a mask to be inspected 2 coated with a photoresist layer on a transparent window (not shown). arrows X and Y
It has an XY stage 3 movable in the direction of , and below the stage is a white light source 4 for mask projection, a red filter 5 for forming, for example, red light for projecting the standard mask, and a green light for projecting the mask to be inspected. A green filter 6 is provided to allow the laser beam to pass, and mirrors 7 and 7' are provided to vertically irradiate these lights onto the standard mask 1 and the mask to be inspected 2, respectively. A window 8 is formed.

The red projection light 9 vertically transmitted through the standard mask 1 via the mirror 7 is reflected by the half mirror 11, and a standard mask image is formed on the screen 12. The green projected light 10 transmitted through the half mirror 1
1', and further transmits through the half mirror 11 to form an image of the mask to be inspected on the screen 12, superimposed on the standard mask image, and a photoelectric conversion camera 13 that scans the superimposed image.
It has an inspection function section with

The superimposed image projected onto the screen 12 by the optical system is, for example, a standard mask having a triangular light-transmitting pattern on the light-shielding film and a mask to be inspected having the same pattern, as shown in FIG. In the area where the light-shielding film is provided, neither the red light irradiating the standard mask nor the green light irradiating the mask to be inspected is transmitted, resulting in a black pattern 14, and the triangular light-transmitting pattern is protected from the red light irradiating the standard mask. Since the green light irradiated onto the inspection mask is also transmitted, these colors are superimposed to form the yellow pattern 15.

However, if there is a pinhole in the light-shielding film of the mask to be inspected, green light will pass through the pinhole, so a green pinhole pattern 16 will be projected onto the screen, and the triangular shape of the mask to be inspected will be projected onto the screen. If there is a light-shielding film residue in the light-transmitting pattern, green light is blocked in the light-shielding film residue, so a red light-shielding film residue pattern 17 is projected onto the screen. The voltage level converted by the photoelectric conversion camera varies depending on these changes in light intensity, for example, about 0.5 [V] for yellow, about 0.3 [V] for green, and about 0.2 for red.
[V] In black, it is almost 0 [V].

Therefore, in the apparatus of the present invention, as shown in FIG. 1 again, in addition to the above-mentioned inspection function section, there is a correction function section consisting of a spot exposure system 18 and a laser burning system 19, which operate according to the voltage level of the photoelectric conversion camera. The system is configured so that mask correction is automatically performed. And spot exposure system 18
For example, it consists of an ultraviolet light source 20, a slit 21 that determines the size of the ultraviolet light spot, prism mirrors 23 and 23' that displace the spot exposure position, and a shutter 24, and a laser burning system 19.
For example, it is made up of a YAG laser 25, mirrors 26 and 26' for displacing the laser beam irradiation position, and a shutter 27.

As shown in FIG. 3, the control system of the apparatus of the present invention includes an image circuit system 28 of the photoelectric conversion camera 13, an amplifier circuit 29 following it, a differentiation circuit 30 following it, a comparison circuit 31 following it, and a comparison circuit 31 following it. a type identification logic circuit 32 (the comparison circuit 31 and the type identification logic circuit 32 are collectively referred to as a comparison identification device 33); a stage control circuit 34 connected to the first output line of the comparison identification device 33; It has a spot exposure control circuit 35 connected to the second output line of the identification device 33, and a laser control circuit 36 connected to the third output line of the comparison identification device 33, and the stage control circuit 34 and the spot exposure The control circuit 35 and the laser control circuit 36 are separately connected to a position determination circuit 37 connected to the photoelectric conversion camera signal amplification circuit 29, and the position determination circuit is connected to the fourth output line of the comparison identification device 33. are connected and connected. The output side of the control system is from the stage control circuit 34 to the stage drive device 3.
8, the spot exposure control circuit 35 is connected to a prism mirror drive device 39, a slit drive device 40, and an exposure shutter drive device 41, and the laser control circuit 36 is connected to a mirror drive device 42 and a laser shutter drive device 43, respectively.

However, when inspecting a mask coated with a photoresist layer using the above-mentioned apparatus, when a photoelectric conversion camera scans the overlapping pattern on the screen and detects a green pattern, the corresponding When the scanning of one screen (meaning one screen of a photoelectric conversion camera, which is usually about 2 mm square) having a green pattern is completed, the information signal from the position determination circuit 37 and comparison identification device 33 1
As shown in the figure, the movement of the XY stage 3, the displacement of the prisms 23 and 23' of the exposure system 18, the movement of the slit 21, and the opening and closing of the shutter 24 are performed to produce a photo on the pinhole portion of the mask 2 to be inspected, passing through the half mirror 11'. Spot exposure is performed on the resist film. In addition, if there is a light-shielding film residue on the mask to be inspected, the red pattern projected on the screen 12 is detected by the photoelectric conversion camera 13, and the same position determination circuit (FIG. 3, 37) and comparison identification device (FIG. 3) are used. 33), the XY stage 3 is moved and the YAG laser 25 of the laser burning system 19 is
is driven, the mirrors 26 and 26' are displaced, and the shutter 27 is opened and closed, and the laser beam is irradiated onto the light-shielding film residue of the mask 2 to be inspected through the laser beam passing window 8 of the projection mirror 7', thereby burning the light-shielding film residue. leaving is done.

In the above embodiment, the standard mask was projected with red light and the inspected mask was projected with green light, but the colors of the two projection lights may be reversed. However, in this case, conversely to the above, the pinhole is projected in red and the light shielding film residue is projected in green.

As explained above, according to the present invention, a photomask is electrically inspected by a photoelectric conversion camera, and based on the electrical information, alignment of the correction position and correction operation according to the type of abnormality are automatically performed. Therefore, the number of man-hours and hands for inspection and correction can be greatly reduced, and at the same time, the occurrence of correction errors can be prevented. Therefore, the photomask is extremely effective in improving the manufacturing yield of semiconductor devices and reducing the cost.

[Brief explanation of the drawing]

FIG. 1 is a structural explanatory diagram of the apparatus of the present invention, FIG. 2 is a schematic diagram of overlapping patterns, and FIG. 3 is a configuration diagram of the control system of the apparatus of the present invention. In the figure, 1 is a standard mask, 2 is a mask to be inspected, 3 is an XY stage, 4 is a white light source, 5 is a red filter, 6 is a green filter, 7 and 7' are mirrors, 8 is a laser beam passing window, and 9 is a red projection light,
10 is a green projection light, 11 and 11' are half mirrors, 12 is a screen, 13 is a photoelectric conversion camera,
14 is a black pattern, 15 is a yellow pattern, 16
17 is a pinhole pattern, 17 is a light shielding film residue pattern, 18 is a spot exposure system, 19 is a laser burning system, 20 is an ultraviolet light source, 21 is a slit, 23 and 23' are prism mirrors, 24 is a shutter, 25
26 and 26' are mirrors, 27 is a shutter, 28 is an image circuit, 29 is an amplifier circuit,
30 is a differentiation circuit, 31 is a comparison circuit, 32 is a type identification logic circuit, 33 is a comparison identification device, 34 is a stage control circuit, 35 is a spot exposure control circuit, 3
6 is a laser control circuit, 37 is a position determination circuit, 38
39 is a prism mirror drive device, 40 is a slit drive device, 41 is an exposure shutter drive device, 42 is a mirror drive device, and 43 is a laser shutter drive device.

Claims (1)

[Claims] 1. Either a standard mask pattern or a mask pattern to be inspected coated with a photoresist layer is projected with red light and the other with green light, and both projected patterns are overlapped to form the same image. An image is formed on a screen, and the superimposed pattern image is scanned with a photoelectric conversion camera to capture the change in color tone of the superimposed pattern image as an electrical signal.The position of the abnormal pattern and the abnormal pattern can be determined based on the level of the electrical signal. 1. A mask repair method characterized by determining the type and automatically correcting the abnormal pattern by laser burning or spot exposure based on the determination. 2. A servo-motor-driven XY stage on which the standard mask and the mask to be inspected are set, a red light source and a green light source that project the standard mask and the mask to be inspected separately, and a projected image by the red light and a projected image by the green light. an optical system that superimposes the images on the same screen, a photoelectric conversion camera that scans the superimposed images, a comparison identification device that categorizes the electrical signal level of the photoelectric conversion camera, and a signal provided by the comparison identification device. 1. A mask repairing device comprising a laser burning system and a spot exposure system driven by a signal, and having a function of automatically carrying out correction.