JPH06175351A - Method for peeling resist - Google Patents

Abstract

PURPOSE:To prevent resticking and to obviate the generation of a change in transmittance arising from the surface roughening of shifter layer and a change in scrubbing resistance by passing a substrate to be peeled under the flow of a peeling liquid having ultrasonic vibration. CONSTITUTION:The band-shaped liquid flow is first generated by using the heated resist peeling liquid. The liquid flow 1 having the ultrasonic vibration is generated by applying the prescribed ultrasonic vibration thereto by using a shower 4. A phase shift mask substrate 2 arranged horizontally on a transporting machine 3 is passed at a prescribed rate under this liquid flow. Sine the resist peels off by that the component molecules of the peeling liquid 1 having the ultrasonic vibration give the vibration to the resist and, there is no need for setting the peeling liquid at a high temp. Since the shifter layer is not affected, the change in the transmittance does no arise either. Since the resist is removed together with the liquid flow of the peeling liquid, the resticking to the substrate is prevented. Further, the damage on the shifter layer surface is decreased as compared with oxygen plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to resist stripping in a lithography process, and more particularly to resist stripping of a photomask used for manufacturing integrated circuits such as LSI and VLSI.

2. Description of the Related Art In semiconductor integrated circuits such as IC, LSI and VLSI, a resist is applied to a substrate to be processed such as a Si wafer and a desired pattern is exposed by a stepper or the like,
It is manufactured by repeating a so-called lithographic process of developing and etching. The photomasks used in such a series of processes tend to be required to have higher precision as the performance and integration of semiconductor integrated circuits become higher. The width of the device pattern is 1Mbit DRA
1.2 μm for M, 0.8 μm for 4 Mbit DRAM, 1
A 6 Mbit DRAM is required to be further miniaturized to 0.6 μm, and various exposure methods are being researched in order to meet such a demand. However, the DRA after this
In the case of an M-class device pattern, the resolution limit of the resist pattern in the conventional i-line stepper becomes the limit. For example, JP-A-58-173744 and JP-B-62-
A photomask of a new concept called a phase shift mask as disclosed in Japanese Patent No. 59296 has been proposed. Phase shift lithography using this phase shift mask is a technique that attempts to increase the resolution by manipulating the phase of light passing through the mask, and a shifter layer, which is a transmissive film for inverting the phase, is provided in the light transmissive portion. Form.

Here, an example of the manufacturing process of the phase shift mask will be briefly described with reference to the drawings. FIG. 4 is a cross-sectional view showing a manufacturing process of the phase shift mask, in which 11 is a substrate, 12 is a chrome pattern, 13 is a shifter layer, 14 is a resist layer, 15 is ionizing radiation, 16 is a resist pattern, and 17 is a resist pattern. Is an etching gas, 18 is a shifter pattern,
Reference numeral 19 represents oxygen plasma. First, as shown in FIG. 4A, a chromium pattern 12 is formed on an optically polished substrate 11 by a conventional method, and a shifter layer 13 is formed thereon as shown in FIG. 4B. Next, a resist layer 14 is formed on the shifter layer 13 as shown in FIG. 6C, and a predetermined pattern is drawn on the resist layer 14 by ionizing radiation 15 as shown in FIG. Then, a resist pattern 16 is formed as shown in FIG. Next, as shown in FIG.
A portion of the shifter layer 13 exposed from the opening of 6 is etched by an etching gas 17 to form a shifter pattern 18
To form. Next, the remaining resist is ashed and removed by oxygen plasma 19 as shown in FIG. Through the above steps, the phase shift mask having the shifter 18 as shown in FIG.

[0003]

However, in the process of manufacturing the conventional phase shift mask as described above, when the remaining resist is ashed and removed by oxygen plasma as shown in FIG. Since it is not visible, even the shifter layer formed in the lower layer of the resist is peeled off although it is on the surface. Further, as another method for removing the remaining resist, there is a method of immersing the mask in a dip tank containing a removing solution, but since the removal is difficult only by this, the temperature of the removing solution is set to 90 ° C to 120 ° C. There is also considered a method in which the temperature is raised or an ultrasonic wave generator is installed under the dip tank, and the component molecules of the stripping solution having ultrasonic vibrations vibrate the resist to strip it. However, when the temperature of the stripping solution is high, there is a problem that the shifter layer is affected and the transmittance changes. Further, even if ultrasonic vibration is used, the phase shift mask has a large step difference in the pattern as compared with a normal photomask, so that there is a problem that the resist that has been peeled once adheres to the concave portion again. For example, the film thickness of a normal mask is about 1000 Å, whereas the film thickness of a phase shift mask is about 5000 Å, and the depth of the concave portion of the pattern becomes deep. Further, when etching the shifter layer as shown in FIG. 4 (f), a resist having a dry etching resistance is used so that the resist sufficiently functions as a mask. In that case, the surface of the resist is hardened by etching. Therefore, it is difficult to remove the resist by the conventional method as described above.

[0004]

The present invention has been made to solve the above-mentioned problems, and is a method of stripping a resist by passing a substrate to be stripped under a stripping liquid flow having ultrasonic vibration. Is. Here, the position at which the substrate is passed may be horizontal or vertical. In addition, when the substrate to be peeled is loaded on a spinner and rotated to peel the resist under a flow of the peeling liquid having ultrasonic vibration, the peeled resist does not re-adhere and the peeling liquid can be easily removed. The peeling is quick. The present invention is effective when applied to a phase shift mask as described above, and as the stripping solution, a solution of DMSO (dimethyl sulfoxide), mixed acid (sulfuric acid, nitric acid), N-methylpyrrolidone, or the like is used. The temperature of the solution is heated to 40 ° C to 60 ° C, and the liquid amount is 5
It is preferably about 15 liters / min.

[0005]

In the present invention, since the component molecules of the stripping solution having ultrasonic vibrations are stripped by vibrating the resist,
It is not necessary to heat the stripping solution to a high temperature as in the conventional case. Therefore,
Since it does not affect the shifter layer, the transmittance does not change. Further, unlike the ultrasonic peeling method by dipping, the resist is removed together with the liquid flow of the peeling liquid, so that reattachment to the substrate can be prevented. Furthermore, it is possible to reduce damage to the surface of the shifter layer as compared with oxygen plasma.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 3 is a view showing a cross section of a phase shift mask substrate. In the figure, 6 is a substrate, 7 is a chrome pattern, 8 is a shifter pattern, and 9 is a resist pattern. First, a sifter layer is formed on a substrate having a chrome pattern formed thereon by spin coating, sputtering or the like, and a chemical amplification negative resist SAL-601 manufactured by Shipley Co. is spin coated on the sifter layer and prebaked at 120 ° C. for 30 minutes. Thus, a uniform film having a thickness of 600 nm was obtained. Next, acceleration voltage 10k
Pattern exposure was performed using a V electron beam exposure apparatus, and PEB (post-exposure bake: post-exposure bake) was performed at 120 ° C. after the exposure. Then, development is performed with a developer MF-321 manufactured by Shipley Co., which is an alkaline aqueous solution containing tetramethylammonium hydroxide as a main component,
Dry etching was performed using a shifter layer exposed through the opening of the obtained resist pattern to which a fluorine-based gas or oxygen was added. In this way, a phase shift mask as shown in FIG. 3 was produced, and thereafter, the resist was stripped by the following method.

FIG. 1 is a side view showing an embodiment of the peeling method of the present invention. First, using a resist stripping solution N-380ll manufactured by Nagase Electronics Co., which was heated to 60 ° C., a strip-shaped liquid flow was created from above. High Joe Sonic US manufactured by Kaijo
A shower 4 was used to apply ultrasonic vibrations at 950 MHz to create a liquid stream 1 having ultrasonic vibrations. Next, under this liquid flow, the phase shift mask substrate 2 horizontally arranged on the carrier 3 was passed at a carrier speed of 0.5 cm / sec and a liquid amount of 12 liter / min. The resist once removed from the substrate did not redeposit, and there was no damage to the pattern as compared with the conventional method.

Example 2 A phase shift mask as shown in FIG. 3 was prepared in the same manner as in Example 1, and the resist was stripped by the following method. FIG. 2 is a side view showing an embodiment of the peeling method of the present invention. First, a resist stripping solution N-38011 manufactured by Nagase Electronics Co., Ltd., which was heated to 60 ° C., was used to form a strip-shaped liquid stream from above. A high-megasonic US shower 4 manufactured by Kaijo Co., Ltd. was used to apply ultrasonic vibration of 950 MHz to form a liquid stream 1 having ultrasonic vibration. next,
The phase shift mask substrate 2 loaded on the spinner 5 under this liquid flow is rotated at a rotation speed of 50 rpm for a rotation time of 5 minutes and a liquid amount of 1
It was rotated at 2 liters / min. The resist once removed from the substrate did not reattach, and the stripping solution was easily removed.

Here, the phase shift mask has been described by taking the type in which the shifter layer is formed on the chrome pattern as an example, but the present invention can also be applied to other types of phase shift masks. Further, although it is more effective when used for a phase shift mask having a large pattern step, it can be applied to a photomask having only a chrome pattern and other substrates.

[0010]

As is clear from the above description, according to the resist stripping method of the present invention, the resist is removed together with the liquid flow of the stripping solution, so that re-adhesion can be prevented. Further, since the mask is not immersed in the stripping solution and the stripping solution does not need to be heated to a high temperature, changes in transmittance and scrub resistance due to the surface roughness of the shifter layer do not occur.

[Brief description of drawings]

FIG. 1 is a side view illustrating an embodiment of a resist stripping method of the present invention.

FIG. 2 is a side view illustrating an embodiment of the resist stripping method of the present invention.

FIG. 3 is a sectional view showing an embodiment of a phase shift mask substrate.

FIG. 4 is a cross-sectional view showing a manufacturing process of a conventional phase shift mask.

[Explanation of symbols]

 1 Liquid Flow with Ultrasonic Vibration 2 Phase Shift Mask Substrate 3 Carrier 4 US Shower Main Body 5 Spinner 6 Substrate 7 Chrome Pattern 8 Shifter Pattern 9 Resist Pattern 11 Substrate 12 Chrome Pattern 13 Shifter Layer 14 Resist Layer 15 Ionizing Radiation 16 Resist Pattern 17 Etching gas 18 Shifter pattern 19 Oxygen plasma

Claims (4)

[Claims] 1. A method of stripping a resist, which comprises passing a substrate to be stripped under a stripping liquid flow having ultrasonic vibrations. 2. The resist stripping method according to claim 1, wherein the substrate to be stripped is a phase shift mask. 3. A method of stripping a resist, comprising loading a substrate to be stripped on a spinner and rotating the substrate under a flow of a stripping liquid having ultrasonic vibrations. 4. The resist stripping method according to claim 3, wherein the substrate to be stripped is a phase shift mask.