Contact exposure method

Abstract

To prevent the peeling of a photoresist and the damage of a mask circuit pattern at the time of contact exposure.SOLUTION: The surfaces of a photoresist and a mask pattern are protected with a cellulose film which is made of very thin, long and tough cellulose fibers and is transparent to exposure light and are subjected to contact exposure.

Description

[0001] The present invention relates to a contact exposure method for forming a pattern on a workpiece. [Background technology]

[0002] Contact exposure is the exposure method that was first implemented to form a high density pattern on a workpiece using inexpensive equipment. [Prior art documents]

[0003] [Patent Document 1] JPH0883749A Japan [Non-Patent Document 1] Journal of the Japan Institute of Electronics Packaging Vol. 19 No. 41216227 Current status and prospects of printable device packaging technology Development of paper devices using cellulose nanofibers, by Masaya Nogi [Non-patent document 2] Development of Immersion Lithography - NEC Summary of the Invention [Problem to be solved by the invention]

[0004] The contact exposure method can expose high-density patterns using inexpensive equipment, but as described in Patent Document 1, it can cause peeling of the photoresist and damage to the mask pattern, making it difficult to transfer the pattern accurately, and the damage to the mask can cause a rise in running costs.

[0005] To achieve the above-mentioned objective, the method of the present invention covers the surfaces of the photoresist and mask pattern with cellulose nanofibers, which are long and strong and have good transmittance for ultraviolet rays with wavelengths of 400 to 800 nm, as described in Non-Patent Document 1, thereby preventing peeling of the photoresist and damage to the mask pattern caused by hard microparticles. [Effects of the Invention]

[0006] Coating the photoresist surface with thin, strong, and long cellulose nanofibers that are transparent to ultraviolet light reduces the risk of the brittle photoresist peeling off.

[0007] Similarly, coating the surface of a photomask pattern with cellulose nanofiber prevents particles other than cellulose nanofiber from becoming trapped in the pattern grooves, making it difficult to transfer the pattern.

[0008] Furthermore, even when hard particles exist between the photoresist and the photomask pattern, the cellulose nanofibers act as cushions, reducing damage to the photomask pattern.

[0009] Cellulose nanofiber itself has very little ultraviolet absorption in the 400 to 800 nm range of ultraviolet light used in exposure light sources, so fine particles made of cellulose nanofiber rarely interfere with pattern transfer. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the contact exposure method of the present invention will now be described.

[0011] A cellulose nanofiber aqueous solution is applied to the photoresist surface and dried, and also to the photomask pattern surface and dried, forming a cellulose nanofiber film on the photoresist surface and the photomask pattern surface, which are then brought into close contact. Then, alignment is performed in this close contact state, and contact exposure is performed.

[0012] This allows for accurate alignment, but at the same time, fine particles made of cellulose nanofibers are generated, which may interfere with pattern transfer. However, as described in Non-Patent Document 1, the transmittance of ultraviolet light in the wavelength range of 400 to 800 nm used for exposure is extremely high, so fine particles made of cellulose nanofibers alone have almost no effect on pattern transfer.

[0013] More accurate alignment is possible by performing divided exposures and performing alignment for each exposure.

[0014] By carrying out the planarization process, it is no longer necessary to press the photomask against the photoresist with strong pressure. By suspending the photomask from all sides with graphene or graphite films, the photomask can be brought into contact with the photoresist with minimal, uniform pressure over the entire surface, which further reduces the generation of cellulose nanofiber particles and minimizes damage to the photoresist and mask pattern. At this time, step-and-repeat exposure can be performed, which is more accurate than alignment.

[0015] As described in Patent Document 1, since it is laborious to hold the workpiece in a vacuum chuck, by using an electronic chuck to remove warping from the workpiece, spraying the resist, and then applying an aqueous solution of cellulose nanofiber, it is possible to easily flatten the resist surface and improve exposure efficiency.

[0016] There is an example in which a cellulose solution is applied to the surface of a photoresist or mask pattern in a manner similar to that used to produce celluloid.

[0017] As described in Non-Patent Document 2, if an aqueous cellulose nanofiber solution is directly brought into contact with a photoresist for a long period of time, the photoresist and the aqueous cellulose nanofiber solution will be affected, potentially causing problems with pattern transfer. Therefore, there is an immersion exposure method in which the photoresist surface is treated to be water-repellent and an aqueous cellulose nanofiber solution is used.

[0018] At this time, the refractive index is about 1.5. The haze is almost 0, and a B51 nm light source of a XeF excimer laser can be used, enabling the finest pattern transfer. [Industrial Applicability]

[0019] The present invention can be used during exposure in semiconductor manufacturing.

Claims

1. A contact exposure method in which cellulose is placed between the photoresist and the mask for contact exposure.

2. 2. The contact exposure method according to claim 1, wherein a cellulose nanofiber film is formed on both or either one of the photoresist surface and the mask pattern surface, and then contact exposure is carried out.

3. 2. The contact exposure method according to claim 1, wherein the contact exposure is carried out with an aqueous solution of cellulose nanofibers interposed between the photoresist and the mask.