JPS649619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning a light exposure mask used in manufacturing semiconductor devices such as IC, LSI, VLSI, etc.

In the semiconductor device manufacturing process, the light exposure process has the greatest control over economic efficiency, and conventionally the occurrence of defects in the light exposure mask and the adhesion of foreign matter from the semiconductor substrate to the mask during the light exposure process have been studied. ing. In particular, the change in exposure technology from a contact exposure method to a projection exposure method or a reduction projection exposure method has eliminated the transfer of foreign matter from the semiconductor substrate to the mask, and has significantly reduced manufacturing time. However, since the light exposure method irradiates the mask with far-ultraviolet or ultraviolet rays, electrostatic charges may accumulate on the conductive layer or semiconductor layer of the required light-shielding pattern formed on one main surface of the transparent substrate of the mask. , floating dust is attracted to the front and back surfaces of the mask before and after use. This adsorbed dust can be removed from one or both sides (front and back) with a neutral detergent, pure water, jet scrub, etc. using a conventional mask cleaning machine.
However, with conventional equipment, it has been impossible to guarantee that less than 5% of the transferred pattern chips are free from dust. Furthermore, in reduction projection exposure equipment, there is a demand for a reticle/mask cleaning machine that eliminates defects of 3μ or larger and does not generate stains or dirt when the cleaning liquid dries. A mask cleaning technique that is responsive and has good workability was unknown.

SUMMARY OF THE INVENTION An object of the present invention is to provide a mask cleaning method that has excellent workability and reliably removes dust and the like adsorbed on the front and back surfaces of a mask.

Another object of the present invention is to provide a reticle mask cleaning method that can completely remove deposits of 3 microns or more from a reticle mask used in a reduction projection exposure apparatus.

According to the present invention, a transparent substrate made of glass or quartz, etc., is provided with a conductive layered chromium monoxide light-shielding pattern or a semiconductive light-shielding pattern made of germanium, iron oxide, etc. on one main surface of a transparent substrate such as glass or quartz. A method of cleaning a light exposure mask is realized. That is, in the first step of the light exposure mask of the present invention, the front and back surfaces of the substrate are immersed in a hydrophilic electrolytic solution such as aqueous ammonia, phosphoric acid, caustic soda, or sodium phosphate, so that the front and back surfaces of the mask become wet. Next, while supplying pure water as a rinsing liquid to the front and back surfaces of the mask, brush cleaning is performed using a rotating brush. After being mechanically cleaned with a brush, the mask is cleaned with an alcohol-based organic liquid, and the aqueous solution on the surface is replaced with the organic liquid. After this, the mask is steam-cleaned and dried with an organic gas such as alcohol vapor or Freon vapor.

The cleaning method of the present invention first brings a hydrophilic electrolyte into contact with the front and back surfaces of the mask to sufficiently wet the front and back surfaces of the mask, remove static electricity, and wash away adsorbed dust. Next, while this electrolyte is being washed away with a rinse solution, the brush is cleaned.
Mechanically clean sticky substances, stains, etc. Since the electrolytic solution is hydrophilic, the electrolytic solution remains on the front and back surfaces of the mask for the time required for brush cleaning, so that the cleaning effect can be maintained. The alcohol-based organic liquid replaces the aqueous solution on the front and back surfaces of the mask with an organic chemical, thereby preventing the aqueous solution from entering the next steam cleaning process. Steam cleaning with organic chemicals → drying has a fast drying speed and there are no droplets on the front and back surfaces of the mask, so it is possible to dry the surface cleanly without staining or staining.

The figure is a model diagram of a mask cleaning apparatus that implements an embodiment of the present invention. In this embodiment, a mask 11, 1 for manufacturing semiconductor devices is used, in which a light-shielding pattern of chromium oxide of a desired shape is coated on one surface of a transparent quartz substrate.
It has four cleaning tanks 20, 30, 40, and 50 for cleaning the cleaning tanks 2, 13, and 14 in the order of steps. Each cleaning tank is capable of simultaneously cleaning the front and back surfaces of the mask to be cleaned, and for this reason, the mask is held at its end with a suitable jig and is moved up and down within each cleaning tank.

In the first cleaning tank 20, the front and back surfaces of the mask 14 to be cleaned are cleaned by a pair of shower pipes 21 and 21' of 0.5% by weight ammonia water in the same electrolyte tank 20.
Wash with shower before and after soaking in step 2. Electrolyte tank 22
During the cleaning period, the ammonia water overflows and the dust floating on the surface flows out. mask 1
4 is the pipe 2 after being taken out from this tank 22.
The front and back surfaces are washed by the flow of ammonia water from 1 and 21' and sent to the next process.

In the second cleaning tank 30, the mask 13 is scrubbed with a pair of rotating brushes 32, 32' while its front and back surfaces are rinsed with pure water or dilute carbonated water sprayed from a pair of shower pipes 31, 31'.
When sent from this tank 30 to a tank 40 for the next process, it is shower washed through pipes 31, 31'.

The mask 12 sent to the third tank 40 is cleaned by passing between a pair of shower pipes 41 and 41', and is cleaned with isopropyl alcohol inside an overflow type cleaning tank 42.
From 41', it is shower washed with the same alcohol and sent to the tank 50 for the next process.

The mask 11 sent to the fourth tank 50 heats the Freon solution 51 stored at the bottom of the tank to 50 to 60°C with a submerged heater to form a Freon gas atmosphere layer in the tank. The front and back surfaces of the mask are steam-cleaned using Freon gas, and then taken out of the bath and quickly dried at room temperature.

As mentioned above, in this embodiment, the mask to be cleaned in the first step is immersed in a hydrophilic electrolytic solution to sufficiently wet the front and back surfaces, and after removing static electricity on the front and back surfaces, the dust is washed out with the electrolytic solution. . Next, in the second step, rinsing with electrolyte and scrubbing with a brush are performed simultaneously to mechanically remove sticky substances, deposits, etc. Furthermore, in the third step, alcohol washing is performed to replace the aqueous solution with an organic chemical, thereby preventing the aqueous solution from remaining in the steam drying by Freon, and preventing the generation of dirt and stains during the steam drying. Further, according to this embodiment, cleaning without contamination and dust can be carried out in a very rational manner in a short time, and the workability is excellent.

[Brief explanation of drawings]

The figure is a schematic sectional view for explaining a preferred embodiment of the invention. 11, 12, 13, 14...Mask, 20, 3
0, 40, 50...Cleaning tank for each process, 22...Hydrophilic electrolyte tank, 31, 31'...Shower pipe for rinsing, 42...Alcohol tank.

Claims (1)

[Claims] 1. A method for cleaning a mask for manufacturing a semiconductor device having a light-shielding pattern of a desired shape on one main surface of a transparent substrate, including a first step of wetting the front and back surfaces of the mask with a hydrophilic electrolyte; a second step of cleaning with a rotating brush while supplying a rinsing liquid to the front and back surfaces of the mask, a third step of contacting an alcohol-based organic liquid to the front and back surfaces of the mask, and then cleaning the front and back surfaces of the mask with an organic gas. and a fourth step of steam cleaning and drying.