JPS5924849A - Cleaning method of photomask - Google Patents

Abstract

PURPOSE:To clean a photomask to be used as an original plate in photolithography without damaging the metallic film for light shielding, by dipping the photomask in a bath of a sulfuric acid or the like while applying a voltage between the photomask and the counter electrode thereof. CONSTITUTION:A photomask 8 formed with a figured patternlike chromium film 12 on a glass substrate 10 provided with a light transmittable conductive film 11 is subjected to a cleaning treatment. More specifically, the above-mentioned photomask 8 (a symbol 9 is a clip) and a platinum plate 14 are dipped perpendicularly in the sulfuric acid 2 in a cleaning tank 1. The acid 2 is heated to about 90-120 deg.C with a heater 3 and foam 15 of ozone-contg. air is ejected through a blow pipe 5 and a blow-out port 6 into the acid 2 to generate a Caro's acid. On the other hand, about 1.5-2.5V DC voltage is applied between the plate 14 (cathode) and a chromium film 12 (anode) by a power source 13. Therefore, the film 12 is immobilized by the oxide film formed on the surface thereof and since it is insoluble, only the foreign matter such as photoresist sticking on the mask 8 is dissolved away in the Caro's acid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a photomask used as an original in Photoringraph f.

In general, this German photomask & co is durable and +1]! 8
In order to create a 111μ treetop film as above, a mask imitating a chrome 6 series light J was used. The chromium mask shown in C is made by depositing chromium M with a thickness of approximately 1.0 μm on a glass plate, and forming a pattern on the Oj film using phosphorography.

7/ROM has strong corrosion resistance, so use a mixture of chromic acid and sulfuric acid heated to 90° to 130°C as a cleaning solution. can be excluded.

However, if chromic acid is not properly treated as a waste liquid, it will cause serious damage and its use has become impossible.

Set and ζ-chromic acid-(IIit acid cleaning pickling method mask cleaning method, force ('J-strict (1hSOs)? 1! By bubbling ozone into sulfuric acid!
! ! Can be built.

If this acid is heated to 90 to 120° C. and the entire mask is immersed, organic matter and metals adhering to the mask can be oxidized and removed.

Even when chromium is immersed in an oxidizing agent such as oxidizing acid, an oxidized layer forms on the surface and becomes insoluble. However, if the density of this chromium oxide is poor, Utr
tv slowly m rIpt-r.

° Also, the presence of a reducing agent destroys the passivity of chromium.
This can cause chromium to dissolve rapidly.

If chromium does not dissolve and spring up, light will pass through it with a transmittance of a few percent to a few percent, making it useless as a mask.

Therefore, it is an object of the present invention to prevent the photoresist or other organic substances attached to the photomask from dissolving while preventing the metal film for continuous light such as the chromium film on the photomask from dissolving.
It is an object of the present invention to provide a photomask cleaning method capable of dissolving and removing foreign substances such as metal pieces.

Hereinafter, the present invention will be explained in detail according to an embodiment shown in the drawings.
Explain.

FIG. 1 is a sectional view showing an embodiment of an apparatus for carrying out the photomask cleaning method according to the present invention.

In this example, cleaning (11-1 is acid resistant, 11υj
A thermal container 1 contains sulfuric acid (basic acid) 2 as a cleaning acid. Further, in the cleaning tank 1, a heater 3 and a heater coil 4, which are inserted into the heat-resistant glass g or quartz tube, are provided to heat the sulfuric acid 2.

In addition, an ozone blowing pipe 5 is installed in the cleaning tank 1, and an ozone blowing pipe 5 for bubbling ozone in the acid 2 is installed. coil 4
A large number of ozone blow-off holes (i) are formed in the horizontal direction on the upper side (111). Deil 1
゜゜r11J6's own cutting saw 7'' - The photomask 8, which is a broken cleaning object, is immersed in sulfuric acid 2 in an upright position by holding the soil with clips 9 made of titanium or platinum.
ing. This photomask 81diJ2tZlt is shown in FIG.
1, and a chromium film 12 as a decorative film is formed thereon to form a chrome graphic pattern.

In other words, the chromium film 12 of the photomask 8 is isolated and has no conductivity as a whole.
In order to use the chromium film 12 as an anode, it is advantageous to provide the entire permeable conductive gland 11 under the chromium film 12, thereby making the entire ROM film 12 gold conductive.

The original transparent conductive film 11 is formed by depositing a Wl film of tin oxide and indium oxide on the glass substrate 10 by sputtering or the like.

This A mask 8 is connected to the anode 11111 of the power source 13.
n, the entire shape of the chromium film 12 is kept as an anode t'L
Ru.

On the other hand, as a counter electrode to this anode, a platinum plate 14 is immersed in sulfuric acid 2 for 6 tons and placed on the cathode side of the source 13 at an angle of 71°.

The first mask cleaning action according to this embodiment will be briefly explained.

As shown in FIG. 1, all the anodes of the photomask 8 were immersed in sulfur tf3/(Sulfur fill!) 2 VC with 13L of platinum plate 14 (il-containing persimmon), and the heater 3 and heater coil 4 with sulfuric acid 2, for example 1)
The air containing ozone is heated to 0°C to 120°C, and the ozone-rich air is discharged from the ozone blowing hole 6 of the ozone blower into the sulfuric acid 2. bubble 1
5. Created a meeting. -F: In the cleaning tank 1 at t″L,
Hydrolic acid (H2SO5) is extracted from sulfuric acid 2. This rhoacid has an extremely strong oxidizing effect.

On the other hand, between the MiJ H'r2 photomask 8 and the platinum plate 14, there is a tun υ as a cathode in the former case,
913 nits x vrct, tJ: 1.5-25 Cv
] in (At, Tli IIE k is applied. -
1:'n, the chromium film 12 with the floor 8n on the W pole has an oxide film on the surface, becomes passivated, and the chromium film 12 is exposed to the bath 1j. This did not occur, and the 12μ chromium film remained unbathed.

In this way, the photomask 8 is, for example, 10 to 3
If immersed in Karo's acid for 0 minutes, the photomask 8 will be free of any smeared photoresist, rubbish, or other materials, metal pieces, etc. J4 (i- Can be removed by dissolving.

In the past, the mask cleaning apparatus of this embodiment was used to clean foreign matter from a chrome mask, or to peel off resist that had become unsightly after etching during mask manufacturing.
Chromium IIQ Q) Welding, resist, and other 4
One machine object or a metal replica piece can be removed by melting.

In the above-mentioned embodiment, there is a method in which the chromium film on the mask 211 is used as an anode to prevent corrosion, and in the above-described method, the chromium film is used as a cathode to prevent corrosion, and the present invention also includes this method. In this cathodic protection method, the above-mentioned
Since the membrane may be reduced and dissolved in sulfuric acid, a permeable membrane that is difficult to dissolve even under reduced conditions must be used.
L cannot be.

The present invention can also be applied to cleaning photomasks in which the light-shielding film C' is replaced with a passivated film such as tantalum, tungsten, titanium, or other metal film.

In addition, as a cleaning acid, in addition to sulfuric acid reed or Karo acid,
A mixed solution of sulfuric acid and nitric acid, a mixed solution of sulfuric acid and hydrogen peroxide, etc. can be used.

As explained above, the present invention has the following features: 111 for photomask light-shielding gold 1jiBIH: Melting and shearing NN1ζ photoresist)-E or other M precipitates, metal pieces, etc. on the photomask without melting. Can be removed.

[Brief explanation of the drawing]

Fig. 11g is a cross-sectional view of an embodiment of an apparatus for carrying out the first mask cleaning method according to the present invention, and Fig. 2 is a cross-sectional view of an embodiment of a photomask used in the present invention. . 1...Cleaning 11.2...Sulfuric acid, 3...Heater, 4...Heater coil, 5...Ozone blowing TC18
...Photomask, 10...Glass substrate, 11...
・iY:; permeability conductive film, 12... chromium film, 13
...1 prisoner, 14...platinum plate. 1 substitute Patent attorney Usui 1) Toshiyuki I9', ゛・,
′: Koichi, NoV

Claims (1)

[Claims] 1. In a method for cleaning a photomask used as an original plate in photolithography, the surface of the photomask is cleaned of original material.
2. Provide a light-shielding metal film, and immerse this photomask in a cleaning acid in a cleaning tank, keeping the photomask at the anode or cathode with respect to the counter electrode. Applying paper pressure to both poles [7 times cleaning is the best time] 1st method for cleaning the mask. 2. As the cleaning acid, sulfur tt'ii* is Caro's acid, a mixture of sulfuric acid and nitric acid, 1M sulfuric acid and 1M (a mixture of hydrogen ablation is used). Range of M requirements 1st term Cleaning power of the Hd-mounted photomask lt: .