JPS6220539B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to white spot defects (missing defects) of photomasks.
Regarding repair equipment Among the defects that occur in photomasks, black spot defects (residual defects) can be repaired using a laser (Japanese Patent Publication No. 52-9508), which significantly shortens the process. On the other hand, a lift-off method is used for missing defects, that is, defects in which a part of a normal pattern is missing. This lift-off method consists of (1) applying a positive resist to the entire surface of the photomask that has the missing defect, (2) exposing only the missing defect using a partial exposure method, and (3) removing the missing defect using a development process. (4) process of forming a metal film on the missing defect and its surroundings or the entire photomask using vacuum evaporation technology; (5) removing the resist and also removing the metal film formed on the resist at the same time. It has the drawback that it requires a large number of steps and time.

A method using partial vapor deposition using a laser has also been proposed, but there are many practical problems such as accuracy, film strength, and film uniformity.

As a defect repair method that eliminates these defects and forms a uniform film with high precision in fewer steps and time, a metal complex is applied to the entire surface of a photomask having a defect or only to the defective part and its surrounding area, and A method has been proposed in which defects are corrected by depositing metal by irradiating only the portion with a laser beam. The present invention relates to an improvement in a method for repairing missing defects using this metal complex.

That is, an object of the present invention is to eliminate the above-described drawbacks of the prior art and to provide an apparatus for correcting photomask defects with high quality.

By the way, when repairing a defect (a defect where a part of a normal pattern is missing) by irradiating a coated metal complex salt with laser light to precipitate metal, depending on the size of the laser irradiation area (i.e. the size of the defect), The optimal laser irradiation power density is different.

Therefore, the present invention provides a mechanism for detecting the size of the laser irradiation area and setting conditions optimal for the size, thereby performing high-quality defect repair.

The present invention will be explained in detail below with reference to the drawings. First, FIG. 1 shows a process of correcting defects by irradiating a metal complex with a laser to precipitate a metal, metal oxide, or a mixture thereof.

(a) Mask pattern 2 formed of chromium, chromium oxide, or a multilayer thereof on a glass substrate 1
A metal complex is applied and dried so as to cover the missing defect 3 generated in the process, thereby forming a metal complex film 4.

(b) Laser light 5 is irradiated to the metal complex film 4 in the region including at least the missing defect portion, and a precipitated film 6 of metal, metal oxide, or a mixture thereof is deposited in the region irradiated with the laser light 5.

(c) After laser irradiation, remove the undeposited metal complex. Thereafter, cleaning, heat treatment, etc. are performed as necessary.

The metal complex material used here is a solution prepared by adding silver nitrate, carboxylic acid, and additives to an organic solvent. At this time, carboxylic acid silver salt is formed in a dissolved state in the solution. Among the silver salts, carboxylic acid silver salts are preferably used because they dissolve well in organic solvents and form good films even when the organic solvents are evaporated. Various types of carboxylic acids can be used, but among dicarboxylic acids having two carboxylic acid groups, citraconic acid has particularly excellent film-forming properties. In addition, as an organic solvent, in addition to alcohol-based, cellosolve-based, carbitol-based, and glycol-based organic solvents, dimethyl sulfoxide, dimethylacetamide, dimethyl formamide, etc. can be used, and a mixed solution of methyl cellosolve, acetonitrile, acetylacetone, and dimethyl sulfoxide can be used. is optimal.

Furthermore, in order to improve the adhesion between the deposited metal film, metal oxide film, or mixture thereof and the substrate, the objective can be achieved by adding titanium alcoholate, but titanium tetrabutyrate is most suitable. Apply the above solution as a coating liquid and dry it to 0.1 to 1
A μm-thick complex film is formed, and a predetermined portion is irradiated with a laser. After depositing a metal film, metal oxide film, or mixture film by laser irradiation, the complex film other than the deposited portion can be completely removed by cleaning with methyl cellosolve, acetonitrile, or a mixture of both. Thereafter, the strength of the deposited film and the adhesive strength to the substrate can be improved by baking it in an ultraviolet oven for 30 seconds to 5 minutes.

Here, the laser irradiation is performed by shaping the laser beam 5 emitted from a laser oscillator (not shown) into a rectangular shape by means of a variable slit 7 that can be changed to any size as shown in FIG.
Laser light is focused into a rectangular shape with a size that is the reciprocal of the magnification of the objective lens 8 on the photomask 10 having the defect 9 placed at the position where the real image is focused.

The optical system shown in FIG. 2 allows the complex film to be
Figure 3 shows the results of depositing on a sample formed to a thickness of 0.2 μm by varying the size of the irradiated area and the power density at the irradiated area. In the figure, the area above the solid line is where the power density is too high and the deposited film will be damaged by the laser, and the area below the broken line is where the power density is too low and there is a high risk that the deposited film will fall off during cleaning. It is. That is, the area surrounded by the solid line and the broken line was the appropriate condition range, and the conditions shown by the dashed-dotted line were optimal. Here, the horizontal axis is the dimension of the irradiation area (the length of one side when irradiating a square), and the vertical axis is the laser power density of the irradiation area. When the size (S) of the irradiation area is in the range of 2 μm to 30 μm, the optimum condition is that the laser power density (P) satisfies the constant relationship S×P=.

Figure 3 shows the results when a square area is irradiated, but when the irradiation area is rectangular, the power density is optimal when the square root of the area of the irradiation area is taken as the dimension (S). Ta. However, in the case of a rectangular irradiation area with a ratio of short side to long side of 1:5 or more, it was better to divide the irradiation area into several areas and sequentially irradiate the area.

Figure 3 shows the results when a solution of silver nitrate, carboxylic acid, and additives added to an organic solvent was used to form a film with a thickness of 0.2 μm, and the appropriate power density changes depending on the composition of the complex and the film thickness. .

Furthermore, although a solution prepared by adding silver nitrate, a carboxylic acid, and an additive to an organic solvent has been described as a metal complex solution, the present method is not limited thereto, and the present method is not limited to that, but can be used to prepare a metal complex in a narrow sense, that is, one or more metal complexes. A concept that includes metal salts produced in normal solution reactions in addition to the atomic group when the metal is the central atom and other atoms or atomic groups, that is, ligands, are bonded to it to form one atomic group. It can also be applied to things.

An example of a correction device for carrying out the correction method described above will be shown.

The defect correction device of the embodiment shown in FIG.
Laser oscillator 11, mirror 12 for bending the optical path of laser beam 5, shutter 13, zoom optical system 1
4 and its driving device 31, the laser beam is transferred to the objective lens 8.
A dichroic mirror 15 that bends in the direction of , a rectangular aperture slit 7 arranged on the optical path of the laser beam 5 toward the objective lens 8 and its driving device 16, a detection device 17 for detecting the slit position, a half mirror 18, and an objective. Lens 8, Photomask 10
An illumination light source 19, a half mirror 20, and an observation optical system 2 for observing and aligning the mask pattern 2 of
1, a laser cut filter 22, a slit illumination light source 23, an interference filter 24, a half mirror 25 for observing and displaying the projected image of the pattern 2 of the photomask 10 and the rectangular opening slit 7, a laser cut filter 26, an imaging device 27, and a monitor TV 28. It controls the X-Y table 29 on which the photomask 10 is placed, its drive device 30, the drive device 30 of the X-Y table 29, and the shutter 13, and also controls the drive device 16 of the rectangular opening slit 7 to create a rectangular shape at that time. The control device 32 determines the size of the laser irradiation area based on a signal from the detection device 17 that detects the size of the aperture, and controls the drive device of the zoom optical system 14 to control the beam diameter to obtain the optimum power density. It is configured.

The laser beam 5 emitted from the Ar laser oscillator 11 has an optical path bent by a dichroic mirror 15, reaches a rectangular opening slit 7 whose width in both the X and Y directions can be set independently, and is shaped into a rectangle of any size. be done.

The laser beam 5 formed into an arbitrary rectangle by the rectangular opening slit 7 passes through the half mirrors 25 and 18, is focused by the objective lens 8, and is irradiated onto the photomask 10 having a missing defect. Here, the photomask 10 and the rectangular opening slit 7 are
The image of the rectangular aperture slit 7 is placed in a positional relationship where it is projected by the objective lens 8 with a size that is the reciprocal of the magnification of the objective lens 8, that is, when the magnification of the objective lens 8 is M times, it is reduced to 1/M.

To observe and align the pattern 2 of the photomask 10, light from the illumination light source 19 is transferred to the half mirror 2.
This can be done by the observation optical system 21 by coupling at 0 and 18. In addition, the observation optical system 21 includes a laser beam cut filter 22 for the safety of workers.
is located.

Furthermore, the light from the slit illumination light source 23 is transmitted through an interference filter 24 with only a specific wavelength, transmitted through a dichroic mirror 15, and then passed through a rectangular aperture slit 7.
is formed on the photomask 10 by the objective lens 8 as a projected image. Here, the dichroic mirror 15 has a characteristic of reflecting only the wavelength of the laser beam 5 and transmitting a specific wavelength of the slit illumination light. The rectangular opening slit 7 is formed by this slit illumination light.
The image can also be observed by the observation optical system 21.

Furthermore, a projected image of the pattern 2 of the photomask 10 and the rectangular aperture slit 7 can be observed on the monitor TV 28 using the half mirror 25, the laser cut filter 26, and the imaging device 27.

A metal complex solution is applied onto the photomask 10 having the missing defect 33, and a metal complex film 4 is formed by drying. The missing defect portion 33 can be adjusted using the XY table 29 so that it matches the projected image of the rectangular slit 7. Also, X-Y
The table 29 can be driven manually and by a drive 30.

The width of the rectangular opening slit is adjusted while observing with the observation optical system 21 or the monitor TV 28 to make the projected image match the size of the missing defect portion 33. At this time, the slit width in both the X and Y directions is detected by the slit position detection device 17, and the control device 32 calculates the optimum power density at that width.
The beam diameter is adjusted to obtain the optimum power density by driving the drive device 31 of No. 4.

When all settings are completed, the shutter 13 is opened and the laser beam 5 is irradiated onto the missing defective portion 33. At this time, the laser beam 5 is irradiated onto exactly the same area as the projected image of the rectangular opening slit 7 by the slit illumination light.

Here, the shutter 13 is used to turn the laser beam 5 ON and OFF, but the same operation can be performed using an electro-optic or acousto-optic modulator, and the power source for the Ar laser beam oscillator 11 can also be used. This can also be done by controlling the

The control device 32 has the following functions. That is, it has a function of reading the positional information detected by the defect inspection device from a magnetic medium or the like, driving the drive device 30 of the XY table 29 to reproduce the missing defect position, and receiving a signal from the slit position detection device 17. Dimensions of the rectangular opening slit 7 (that is, M times the rectangular shape projected onto the photomask 10: M
is the magnification of the objective lens) and calculates the optimum power density from its dimensions, and calculates the beam diameter necessary to obtain the optimum power density to drive the drive device 31 of the zoom optical system 14. It has a function of adjusting the beam diameter to a predetermined beam diameter, and a function of turning on and off the laser beam 5 by controlling the shutter 13, modulator, and power supply under appropriate conditions. Furthermore, if the size of the missing defective portion 33 is known in advance, it is also possible to set the slit width by driving the drive device 27 for changing the width of the rectangular opening slit 7.

Here, the appropriate conditions for turning on and off the laser beam 5 are obtained by, for example, detecting the amount of light transmitted through the photomask 10 of the irradiated laser beam 5, and determining the state of precipitation of metal etc. from the change in the amount of transmitted light. It includes conditions.

Next, one aspect of a method for correcting the missing defect 33 of the photomask 10 using the defect correction apparatus shown in FIG. 4 will be described. The entire surface of the photomask 10 having the missing defect portion 33 or the missing defect 33
After applying a metal complex solution such as a silver complex solution to the surrounding area and drying it to form a metal complex film 4,
It is placed on the table 29, and the table driving device 30 is driven by the control device 32 based on the position information from the defect inspection device so that the missing defect portion is at least within the field of view of the observation optical system 21 or the imaging device 27. Make it. Next, while observing the projected image of the rectangular opening slit 7 by the slit illumination light source 23,
Precise positioning is performed using the table 29 and the slit width is set by driving the slit drive device 16.
At this time, adjustment is made so that the projected image of the rectangular opening slit 7 does not protrude from the normal pattern and sufficiently covers the missing defective portion 33. Here, the slit position detection device 17 sends, for example, a signal corresponding to the distance from the optical axis (center of the optical system) to the slit tip position to the control device 32, and
The dimensions of the rectangular opening are calculated from the signal and two signals in the Y direction. Next, the control device 32 determines the optimum power density for this dimension by determining it from an approximation formula or a table stored in the memory section. That is, in the example shown in Fig. 3, between the optimum power density P and the slit size (dimension on the projection plane) S, P×S=
Since there is a certain relationship, if you set the power density at 10μm opening to be 4000W/ ^cm2 , the slit size will be 20μm opening (twice that of 10μm opening).
In this case, the power density is 2000 W/cm ² , that is, the zoom drive device 31 can be driven to widen the beam diameter to √2. (The power density is inversely proportional to the square of the beam diameter.) After all settings are completed, the shutter 13 is opened automatically or according to the operator's instructions.
Laser light 5 oscillated from laser oscillator 11 is irradiated onto missing defective portion 33 . Next, after irradiating for a certain period of time or while monitoring the deposition state of metal etc., a signal is sent to the shutter 13 under appropriate conditions and the laser beam 5
irradiation.

As described above, the missing defect 33 of the photomask 10 is corrected by irradiating the metal complex film 4 with the laser beam 5 and depositing a metal film.

This completes the correction of one missing defect 33, and after observing if necessary, when the operator issues a signal indicating completion of correction, the XY table 29 is driven to the next defect position. After the metal film is deposited on all the missing defective parts 33, the photomask 10 is cleaned to remove the metal complex film 4 other than the parts where the metal has been deposited, and after heat treatment is applied as necessary, the repair work is completed. do.

FIG. 5 shows another example of the photomask missing defect correction apparatus. The correction device shown in FIG. 5 differs from the correction device shown in FIG. 4 in the following points. That is, an aperture plate 35 having a predetermined size and a light amount detector 36 are provided on the back side of the dichroic mirror 34. The dichroic mirror 34 has the characteristic of reflecting most of the laser beam 5, transmitting a portion of it, for example 1%, and transmitting the light from the slit illumination light source 23 selected to have a specific wavelength by the interference filter 24. dichroic mirror 3
A portion 5' of the laser beam transmitted through the laser beam 4 is received by a photodetector 36 through which only the center portion of the beam passes through a plate 35 having an aperture having a constant area. Here, if the transmittance of the dichroic mirror 34 to the laser beam 5 and the area of the aperture 35 are known, the power density on the slit 7 surface, that is, the power density on the photomask 10 can be calculated. From this, the slit dimensions of the rectangular aperture slit 7 are detected, and the control device 32 determines the optimum power density for that dimension from an approximate formula or a table stored in memory, and then compares it with the signal from the light amount detector 36. At the same time, the zoom optical system 14 is driven by the zoom drive device 31 to change the beam diameter, and the signal from the light amount detector 36 and the optimum power density match or are within a certain error (for example, ±5%). It is only necessary to stop the zoom drive device 31 when this occurs. As described above, the irradiation power density of the laser beam 5 on the photomask 10 can be set to an optimal value.

Next, the zoom optical system 1 used in the correction device shown in FIGS. 4 and 5 will be explained. FIG. 6 shows an example of the zoom optical system 14 with a concave lens 3.
8, a convex lens 39, a concave lens 40, and a convex lens 41, forming an afocal zoom system (when parallel light is incident, it is output as parallel light).

As shown in FIG. 6A, a convex lens 39 and a concave lens 4
0, the incident laser beam 5 is output with the maximum beam diameter. On the other hand, when the convex lens 39 and concave lens 40 are combined with the concave lens 38 and convex lens 41, respectively, as shown in B, the beam is output with the minimum beam diameter. By continuously changing the convex lens 39 and the concave lens 40 between the positions shown in FIGS. 6A and 6B, the diameter of the output beam changes continuously. Of course, the beam diameter can also be reduced by selecting the focal length of each lens.

In addition to the above-mentioned afocal zoom system, the exact same function can be obtained by combining, for example, a camera zoom lens and a condensing lens with a fixed focal length.

Furthermore, in the correction apparatus shown in FIGS. 4 and 5, a case has been described in which the zoom optical system 14 is used as a means for changing the power density, but as shown in FIG. A filter whose transmittance is continuously changed by a thin film formed by vapor deposition or the like of a metal such as chromium, aluminum, nichrome, or chromel with varying thickness in the circumferential direction, or a transparent flat plate 44, 44' as shown in FIG. is installed so that it is plane symmetrical with respect to the plane 45 perpendicular to the optical axis, so that the incident angle of the laser beam 5 changes continuously (however, the plane symmetrical relationship with respect to the plane 45 perpendicular to the optical axis is maintained). This objective is achieved by using a filter whose transmittance is continuously varied by rotating it in the direction indicated by the arrow while holding the filter in place.
It is also clear that the same function can be obtained by using the zoom optical system 14 and the filter shown in FIG. 7 or 8 in combination. Figures 7 and 8
When using the filter shown in the figure, the laser beam 5
It is necessary to take measures such as enlarging the beam diameter in advance so that a sufficiently uniform beam power distribution can be obtained up to the maximum area that can be irradiated.

Continuous wave laser light is preferable as a laser for carrying out the present invention, and in the examples, the case where an Ar laser oscillator is used has been explained, but lasers with near-infrared, visible, and ultraviolet wavelengths may also be used. Good. This includes the fundamental wave, second harmonic, and third harmonic of YAG laser, Kr laser, He-Cd laser, continuous wave laser pumped DYe laser, and Ar laser. area is preferred.

As explained above, the device of the present invention can repair missing defects in fewer steps and in 1/10 of the time compared to conventional lift-off methods, and can repair metal films and metal oxides deposited on missing defects. The adhesion strength between the film or its mixture film and the substrate is high, and the light shielding property can be sufficiently corrected with high precision, which has the effect of greatly improving the production yield of semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the process of implementing the present invention, FIG. 2 is an explanatory diagram of an optical system for implementing the present invention, and FIG.
The figure shows the relationship between the dimensions of the laser beam irradiation area and the optimum power density when repairing a missing defect according to the present invention, FIG. 4 is a system diagram showing the missing defect repairing device according to the first invention, and FIG. 5 6 is a diagram showing an example of a zoom optical system as a power density adjusting means for carrying out the present invention, and FIGS. It is a figure explaining the transmittance continuously variable filter similarly as a power density adjustment means. 5... Laser light, 7... Rectangular opening slit, 8
...Objective lens, 10...Photomask, 11...
...Ar laser oscillator, 13...Shutter, 14...
...Zoom optical system, 15...Dichroic mirror, 29...XY table, 17...Slit position detection device, 32...Control device, 36...Light amount detection device.

Claims (1)

[Claims] 1. A means for generating a laser beam, a rectangular opening slit for shaping the laser beam generated by the means into a rectangular shape of an arbitrary size, and a rectangular opening slit for shaping the laser beam into a rectangular shape with the rectangular opening slit. an objective lens for condensing and imaging a reduced image of the rectangular aperture slit;
X-Y to place a photomask with missing defects
a table; a means for detecting the dimensions of the rectangular aperture slit; a means for arbitrarily changing the power density of the laser beam focused and imaged as a reduced image of the rectangular aperture slit; and turning the laser beam ON and OFF. Using the means and defect position information, the X-
A function of controlling the position of the Y table and a function of determining the dimensions of the rectangular opening slit using information from the means for detecting the dimensions of the rectangular opening slit, and a function of calculating the optimum power density for that dimension, and obtaining the calculated optimum power density. The function of controlling the means for changing the power density of the laser beam as well as the laser beam
What is claimed is: 1. A photomask missing defect correction device comprising: a control device having a function of controlling means for turning ON and OFF; 2. A means for generating a laser beam, a rectangular aperture slit for shaping the laser beam generated by the means into an arbitrary rectangle, and a laser beam formed into a rectangle by the rectangular aperture slit as a reduced image of the rectangular aperture slit. An objective lens for condensing and imaging, an XY table on which a photomask with a missing defect is placed, means for detecting the dimensions of the rectangular aperture slit, and condensing and imaging as a reduced image of the rectangular aperture slit. a means for arbitrarily changing the power density of the laser beam, a means for detecting the changed power density of the laser beam, and a means for turning the laser beam on and off.
X
- A function for controlling the position of the Y table, a function for determining the dimensions of the rectangular opening slit based on information from the means for detecting the dimensions, and calculating the optimum power density for that dimension, and a function for detecting the power density. and a function for controlling a means for changing the power density of the laser beam so that the information on the laser beam and the calculated optimum power density are matched or within a certain error range;
What is claimed is: 1. A photomask missing defect correction device comprising: a control device having a function of controlling a means for turning ON and OFF; 3. The control device stores the relationship between the dimensions of the rectangular opening slit and the optimum power density as an approximate expression,
Claim 3 or 4, characterized in that it has a function of calculating, from the approximate expression, the optimum power density for the dimensions of the slit determined based on the information from the means for detecting the dimensions of the rectangular opening slit. Photomask missing defect correction device. 4. The control device stores the relationship between the dimensions of the rectangular opening slit and the optimum power density as a table, and calculates the optimum power density for the slit dimensions determined based on the information from the means for detecting the dimensions of the rectangular opening slit. 5. The photomask missing defect correcting apparatus according to claim 3, further comprising a function of making a determination by referring to the table. 5. The photomask missing defect correction apparatus according to claim 3 or 4, further comprising a zoom optical system as means for changing the power density of the laser beam. 6. The photomask missing defect correction apparatus according to claim 3 or 4, further comprising a continuously variable transmittance filter as means for changing the power density of the laser beam. 7 Continuous oscillation as means for generating the laser beam
5. The photomask missing defect correction apparatus according to claim 3, further comprising an Ar laser oscillator.