JPH11288077A - Manufacture of photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a very high precision photomask with a high yield in a short time by dividing and enlarging and then reducing and synthesizing the mask. SOLUTION: In the proposed manufacturing method of a photomask, photomask patterns 21 -24 are divided into plural patterns A-E and divided photomasks obtained by enlarging the divided patterns by a prescribed magnification factor, four to five times, for example, are manufactured. The divided photomasks are pattern-synthesized on an original mask substrate at the same time as reduction projection at the magnification factor reciprocal to the magnification factor. Then, development and etching are executed and a desired reticle is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI,
In particular, the present invention relates to a method for manufacturing a photomask for forming fine semiconductor patterns at high density.

[0002]

2. Description of the Related Art Integrated circuits such as LSIs and VLSIs are manufactured by repeating lithography steps such as exposure, development and etching. As for the minimum processing size required for such lithography, there is a tendency that higher precision is required with higher performance and higher integration of semiconductor integrated circuits. For example, DRA which is a typical LSI is used.
Taking a minimum design size of M as an example, a 16 Mbit DRAM
Is 0.5 μm, 0.35 μm for 64 Mbit DRAM,
0.25 μm with 256 Mbit DRAM, 1 Gbit D
RAMs are required to be further miniaturized to 0.18 μm, and a photomask called a high-resolution and high-precision reticle is required to satisfy these manufacturing requirements.

Various exposure techniques have been proposed to cope with the processing of these fine patterns. For example, in the phase shift method, by providing a phase shifter layer that inverts the phase of light by 180 ° on a photomask,
It is receiving attention as a technique for improving the depth of focus. There are various types of phase shift masks. Among them, Levenson type phase shift masks have a greater phase shift effect and improve the resolution of resist more than halftone type masks already in practical use. Can be.

An example of a conventional method for manufacturing a photomask and a phase shift mask having a light-shielding pattern of chrome or the like will be described below with reference to the drawings. First, as shown in FIG. 5A, a metal thin film layer 12 of chromium or the like is formed on an optically polished substrate 11, and an ionizing radiation resist such as chloromethylated polystyrene is uniformly applied by a spin coating method or the like. Apply, heat dry treatment, thickness 0.1-0.2μm
The resist layer 13 is formed to a degree. The heating and drying treatment varies depending on the type of resist and the equipment to be used, but the temperature is 80 to 180 ° C. and the time is 20 to 6 in the case of an oven.
0 minutes, about 1 to 30 minutes in the case of a hot plate.

Next, as shown in FIG. 1B, a pattern is drawn on the resist layer 13 by ionizing radiation 14 using an electron beam exposure apparatus or the like according to a conventional method, and an organic solvent such as ethyl cellosolve or ester is used as a main component. After developing with a developing solution, rinse with alcohol or the like to form a resist pattern 15 as shown in FIG.

Subsequently, if necessary, a heating process and a descum process are performed to remove unnecessary resist such as residues and scum remaining on the edge portion of the resist pattern 15 and the like, and FIG. As shown in FIG.
The metal thin film layer 12 exposed from the opening is dry-etched by the etching gas plasma 16 to form a light-shielding metal thin film pattern 17. The metal thin film layer may be etched by wet etching instead of dry etching.

[0007] Thereafter, as shown in FIG. 1E, the resist pattern 15 is ashed and removed by oxygen plasma 18, and a light shielding pattern 17 is formed by a metal thin film layer as shown in FIG. Complete the mask. Note that this step can be performed by solvent stripping instead of the incineration treatment using oxygen plasma.

Next, in order to manufacture a phase shift mask,
The photomask having the light-shielding pattern 17 formed through the steps shown in FIGS. 5A to 5F is inspected, corrected if necessary, washed, and then, as shown in FIG. Next, a phase shifter layer 19 is formed on the light shielding pattern 17. Next, as shown in FIG. 3H, the ionizing radiation resist layer 2 is formed on the phase shifter layer 19 in the same manner as described above.
0, and the resist layer 2 is formed as shown in FIG.
For 0, drawing is performed by performing alignment with the light-shielding pattern 17 using an electron beam exposure apparatus or the like. Thereafter, development and rinsing are performed to obtain a predetermined resist pattern 22 as shown in FIG.

Next, if necessary, a heat treatment and a descum treatment are performed, and then the phase shifter layer 1 exposed from the opening of the resist pattern 22 as shown in FIG.
9 is dry-etched with an etching gas plasma 23 to form a phase shifter pattern 24. The formation of the phase shifter pattern 24 may be performed by wet etching instead of dry etching by the etching gas plasma 23.

Next, the remaining resist is ashed and removed by oxygen plasma 25 as shown in FIG.

Through the above steps, a phase shift mask on the phase shifter as shown in FIG. 1 (m) is completed.

As shown in FIG. 6A, a phase shift mask of a phase shifter lower type is first formed on an alumina layer 3 serving as an etching stopper layer on a quartz substrate 34.
5 is formed. Next, as shown in FIG. 3B, a transparent film 36 made of SiO ₂ is formed on the film 35. Next, as shown in FIG. 3C, a chromium film 37 serving as a light-shielding film is formed on the transparent film 36. Next, as shown in FIG. 3D, an ionizing radiation resist layer 38 such as chloromethylated polystyrene is formed on the chromium film 37, and a predetermined pattern is drawn by ionizing radiation 39 such as an electron beam exposure apparatus. After development and rinsing, a resist pattern 38 is formed as shown in FIG. Next, as shown in FIG. 3F, wet etching of the chrome layer 37 is performed using the resist pattern 38 as a mask. As an etching solution, a ceric ammonium nitrate solution is used. Next, as shown in FIG.
To remove the resist to obtain a chrome mask as shown in FIG.

Next, as shown in FIG. 1I, an ionizing radiation resist layer 41 such as chloromethylated polystyrene is formed on the transparent film 35 on which the chromium pattern 37 is formed.
Alignment is performed on the resist layer 41 in accordance with a conventional method, and a predetermined pattern is drawn by ionizing radiation 42 such as an electron beam exposure apparatus, developed and rinsed to form a resist pattern 41 as shown in FIG. .

Next, after performing a heat treatment and a descum treatment as required, the transparent film 36 exposed from the opening of the resist pattern 41 is dried by an etching gas plasma 43 as shown in FIG. By etching, a phase shifter pattern 36 is formed. As an etching gas, CF ₄ , C ₂ F ₆ , CHF ₃ , CHF ₃ +
O ₂ and a mixed gas thereof are used.

Next, the remaining resist is ashed and removed by oxygen plasma 44 as shown in FIG. Through the steps described above, the phase shifter 36 as shown in FIG. 3 (m) is completed, and a phase shift mask of the type under the phase shifter is obtained.

[0016]

Since both photomasks and phase shift masks having such a light-shielding pattern are required to have ultra-high accuracy, they are manufactured by a direct exposure process using a current electron beam drawing apparatus or laser drawing apparatus. However, since the pattern is fine, a fatal defect often occurs, and the yield of a practical photomask is not improved. Further, since the pattern data is enormous, if the photomask becomes defective, it takes several tens of hours for redrawing, and there is a problem that profit cannot be obtained at all.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to produce an ultra-high-precision photomask by dividing and enlarging it and reducing and synthesizing it to shorten the photomask. It is an object of the present invention to provide a method for manufacturing at a high yield in a long time.

[0018]

According to the present invention, a photomask pattern is divided into a plurality of portions, and a divided photomask (reticle) is formed by enlarging each of the divided patterns at a predetermined magnification, for example, 4 to 5 times. Then, after pattern-synthesizing the divided photomasks at the inverse of the magnification on the original mask substrate and simultaneously synthesizing the patterns, developing and etching to produce a desired reticle, a phase shift mask or the like is used. This is a method for manufacturing a photomask.

That is, according to the present invention, in a mask pattern in which data is too large to collectively draw a pattern and in which a defect is liable to occur, the mask pattern is divided to shorten each drawing time, and It is characterized by facilitating pattern production by producing a five-fold enlarged pattern.

In this method, it is necessary to produce a plurality of divided photomasks for producing a single reticle and to project the reduced photomasks in a reduced size to combine them into one pattern. Considering the current situation of drawing and redrawing each time a defect appears, it is much more efficient to first create a mask with low difficulty and synthesize it using the reduced projection exposure method with established technology. Things.

The manufacturing method according to the present invention includes manufacturing not only ordinary photomasks but also phase shift masks of halftone type, Levenso type, edge light shielding type, rim type, etc., X-ray masks, ionizing radiation projection masks, Of course, it can be used for an EUV mask or the like.

Hereinafter, the method of manufacturing a photomask according to the present invention will be described in detail. First, as shown in FIG. 1, the layout pattern of a desired ultra-high-precision
Split more than split. In Figure 1, 4 is a photomask 1 having a layout pattern 2 ₁ to 2 ₄ chips, and a 5 dividing each layout pattern 2 ₁ to 2 ₄ to A-E.

Subsequently, for each of the patterns A to E, based on a reduction magnification of a reduction projection device to be used later,
For example, a mask 4 to 5 times the original reticle pattern is manufactured. FIG. 2 illustrates a divided photomask 3A in which a divided pattern 5A corresponding to the divided region A in FIG. 1 is formed, and FIG. 3 illustrates a divided photomask 3C in which a divided pattern 5C corresponding to the divided region C in FIG. 1 is formed. I do.

As a method for manufacturing these divided photomasks 3A to 3E, a normal photomask manufacturing method may be adopted (for example, steps (a) to (f) in FIG. 4). That is,
An ionizing radiation resist is applied, and a divided photomask pattern is drawn by an electron beam or laser on a baked chrome substrate for photomask production, developed and rinsed with a desired developing solution, and then heated and baked and, if necessary, discarded. Perform processing. After the treatment, the exposed chromium film is etched by a wet or dry etching method, and the remaining resist is stripped and washed. After sufficient cleaning, the pattern is inspected and possibly corrected to obtain a divided photomask consisting of, for example, a five-fold photomask pattern.

Subsequently, these five-fold patterns 5A to 5E
As shown in FIG. 4, using a divided photomask 3A to 3E made of I do. At this time, the projection magnification is the reciprocal of the magnification of the divided photomasks 3A to 3E, that is, 1/5 in the above example.

As the stepper 4 for performing such reduced projection exposure and pattern synthesis, an i-line stepper, a KrF or ArF excimer laser stepper, or a Kr
An F or ArF excimer laser scan stepper or the like can be used.

The exposed substrate is developed and rinsed with a desired developer, and then heated and baked. After the treatment, the exposed chromium film is etched by a wet or dry etching method, and the remaining resist is stripped and washed. After sufficient cleaning, the pattern is inspected and, if necessary, modified to obtain the desired high precision photomask.

According to the present invention as described above, the number of redraws of an ultra-high precision reticle can be reduced, and the process margin can be greatly improved. Therefore, it is possible to easily and stably and efficiently manufacture a defect-free high-precision mask. Further, in the case of a repeat order, a desired reticle can be manufactured in a short time.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a photomask according to the present invention will be described below. EXAMPLE The CPU photomask data of the 0.25 μm design rule was divided into six parts, and a four-fold mask of a desired five-fold reticle was produced for each pattern. The actual design rule of this mask is 5 μm
Therefore, a defect-free mask could be manufactured efficiently and in a short time by the conventional mask manufacturing technology using the electron beam lithography system MEBESIII. The six masks thus manufactured were exposed on a photoresist-coated original reticle substrate by a scan stepper. The exposed substrate was developed and rinsed with a desired developing solution, and then heated and baked. After the treatment, the exposed chromium film was etched by a dry etching method, and the remaining resist was peeled off and washed. After sufficient cleaning, the pattern was inspected, and some defects were corrected to obtain a desired high-precision photomask.

[Comparative Example] A photomask for CPU having a design rule of 0.25 μm was mounted on a high-precision electron beam lithography system
Exposure was performed for about 25 hours on a chromium substrate coated with an electron beam resist using ES4500. The exposed substrate was developed and rinsed with a desired developer, and then heated and baked. After the treatment, the exposed chromium film was etched by a wet method, and the remaining resist was peeled off and washed. After sufficient cleaning, the pattern was inspected and some defects were corrected to obtain a desired high precision reticle.

A mask manufactured by the conventional method of the comparative example;
As a result of comparison with the mask manufactured using the method of the present invention in the above embodiment, the time required for drawing is abnormally long in the conventional method, and defects and accuracy deterioration due to drawing errors and changes over time are likely to occur. Despite the use of the device, the yield is very poor, whereas the method of the present invention
Because it is an enlarged mask, a defect-free mask can be easily manufactured with a standard drawing apparatus, and the reticle is manufactured using the transfer method established in the semiconductor manufacturing process. Can be produced.

[0032]

As is apparent from the above description, according to the photomask manufacturing method of the present invention, the number of redraws of the ultra-high precision reticle can be reduced, and the process margin can be greatly improved. . Therefore, it is possible to easily and stably and efficiently manufacture a defect-free high-precision mask. Further, in the case of a repeat order, a desired reticle can be manufactured in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a state in which a photomask pattern is divided into a plurality according to the present invention.

FIG. 2 is a diagram illustrating one divided photomask obtained by enlarging a divided photomask pattern.

FIG. 3 is a view showing another divided photomask obtained by enlarging a divided photomask pattern.

FIG. 4 is a schematic diagram for explaining a step of reducing and transferring a divided photomask to an original photomask substrate.

FIG. 5 is a view for explaining a conventional example of a method for producing a photomask composed of a light-shielding pattern and a phase shift mask of a type placed on a phase shifter.

FIG. 6 is a view for explaining a conventional example of a method of manufacturing a phase shift mask of a phase shifter lower type.

[Explanation of symbols]

A-E ... divided region 1 ... photomask ₂₁ to ₂₄ ... layout pattern 3A to 3E ... split split photomask 4 ... stepper 5A-E ... divided patterns 6 ... chrome photomask substrate coated with photoresist

Claims (5)

[Claims] 1. A photomask pattern is divided into a plurality of patterns,
A divided photomask is produced by enlarging each of the divided patterns to a predetermined magnification, and then the pattern synthesis is performed simultaneously with the reduced projection of the divided photomask on the original mask substrate at a magnification inverse to that magnification. After developing,
A method for manufacturing a photomask, wherein a desired reticle is manufactured by etching. 2. The method according to claim 1, wherein the divided photomask or the reticle is a phase shift mask. 3. The method according to claim 1, wherein said pattern synthesis is performed by an i-line stepper. 4. The method according to claim 1, wherein said pattern synthesis is performed using KrF or ArF.
The method according to claim 1, wherein the method is performed using an excimer laser stepper. 5. The method according to claim 1, wherein the pattern synthesis is performed using KrF or ArF.
2. The method for manufacturing a photomask according to claim 1, wherein the method is performed using an excimer laser scan stepper.