X-ray or gamma ray systems or devices – Specific application – Lithography
Reexamination Certificate
1999-06-18
2001-02-20
Bruce, David V. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Lithography
C378S034000, C430S005000
Reexamination Certificate
active
06192100
ABSTRACT:
FIELD OF INVENTION
The invention relates to pattern replication using x-rays and in particular to an X-ray mask mounting device called a pellicle, which serves to provide a spacing function and to protect the x-ray mask from contamination in semiconductor manufacturing.
BACKGROUND OF THE INVENTION AND RELATION TO THE PRIOR ART
The manufacturing of semiconductor integrated circuit devices is dependent upon the accurate replication of generated patterns onto the surface of a device substrate. This is usually accomplished by the production of a computer generated pattern into a chromium layer on a quartz substrate, and the pattern is then transferred via optical lithography. The replication operation is effected using a variety of processes; such as subtractive, for example etching; additive, for example deposition; and, by using such material modification techniques as oxidation, and ion implantation. Heretofore in the art, optical lithography, which is a projection printing technique has been employed in the replication process. In optical lithography the mask is located some distance from the wafer to be exposed and a four or five times reduction between the mask image and the wafer image can be involved, which simplifies both the lithography and mask production and in turn provides tolerance of defects.
As the art is progressing, the desire for greater density, is making the use of X-ray replication directly on the wafer very attractive. The considerations in using X-ray replication however are quite formidable. The X-ray technique involves proximity replication so that the X-ray mask images are made the same size as the final images on the wafer. Because of the one-to-one relationship of the image on an X-ray mask and the image formed on the wafer, any position errors in building the X-ray mask are replicated one for one onto the wafer. Thus, the position accuracy requirements for the fabrication of X-ray masks are very difficult to achieve and, as a result, X-ray masks are expensive to fabricate. In use, particles unavoidably settle on masks, but the ability, previously available in optical lithography, of keeping settled particles outside of the depth of focus window in the replication so that the particle is highly de-focused and does not print, is no longer available in the X-ray proximity replication. In some situations a particle that settled on a mask can absorb X-ray photons and must be removed. A major source of a settling particle problem comes from the effect of the X-ray energy on the resist material that form the desired patterns. When the x-ray resist is irradiated, organic material is released from the resist Because X-ray lithography is a proximity printing process, this material will travel the short distance between the mask and the wafer and then land on the x-ray mask. In particular, this material is prone to bonding to the x-ray mask absorber pattern. In a short time, this organic material begins to attenuate the x-rays resulting in longer exposure times, dimensional control problems, and pattern defects. This accumulation of contamination would ordinarily necessitate cleaning of the x-ray mask. However, due to the expense and fragility of the x-ray masks, and the risk involved with cleaning them, this is not considered to be a reasonable solution.
It is therefore important to protect the relatively delicate and not easily cleaned X-ray masks from contaminants and mechanical damage due to scratches and the like without introducing mechanical stresses that may affect the placement accuracy.
There has been some activity in the art directed to this problem in U.S. Pat. No. 5,793,836 in which a protective structure is described which provides a membrane that would lie between the mask and the wafer to assist in protecting the mask from contamination.
As progress with membranes advances a need is being encountered for less fragile and easier to mount structures.
SUMMARY OF THE INVENTION
In the invention a pellicle mounting structural principle is provided whereby a membrane for protection of an X-ray mask is interchangeably positioned with proper spacing between the X-ray mask and the resist on the wafer in which the pattern produced by the X-ray exposure is to be formed. The mounting principle employs a combined, membrane and rigidity and spacer member, together with a means for selectably separable retention to the supporting structural portion of the mask. The principle accommodates membrane materials that may not be flexible and provides an ability to remove the membrane for cleaning or replacement and to do it with ease in reestablishing the spacing with respect to the mask The means for the selectably separable retention to the supporting structural portion of the mask involves the use of springs and elastomers, securing to the sides of the supporting structural mask ring and the bonding of the spacer member directly to the mask
REFERENCES:
patent: 4131363 (1978-12-01), Shea et al.
patent: 4198263 (1980-04-01), Matsuda
patent: 4539070 (1985-09-01), Jarocinski et al.
patent: 4548883 (1985-10-01), Wagner
patent: 4606803 (1986-08-01), Lüthje et al.
patent: 4608326 (1986-08-01), Neukermans
patent: 4971851 (1990-11-01), Neukermans et al.
patent: 5663016 (1997-09-01), Hong
patent: 5675403 (1997-10-01), Cerrina et al.
patent: 5793836 (1998-08-01), Maldonado et al.
patent: 5809103 (1998-09-01), Smith et al.
patent: 5958631 (1999-09-01), Acosta et al.
patent: 6101237 (2000-08-01), Miyachi et al.
patent: 63-72119 (1988-04-01), None
patent: 64-13551 (1989-01-01), None
Acosta Raul Edmundo
Cordes Michael James
Cordes Steven Alan
Bruce David V.
Hobden Pamela R.
International Business Machines - Corporation
Morris Daniel P.
Riddles Alvin J.
LandOfFree
X-ray mask pellicles and their attachment in semiconductor... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with X-ray mask pellicles and their attachment in semiconductor..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray mask pellicles and their attachment in semiconductor... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611602