X-ray or gamma ray systems or devices – Specific application – Lithography
Reexamination Certificate
2000-08-09
2002-11-05
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Lithography
C378S034000
Reexamination Certificate
active
06477225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to contact lithographic masks having submicron features, and to a method for producing such masks. These tools are useful in the preparation of plating molds for fabricating metal microparts and are particularly useful for providing molds having lateral feature dimensions on the order of tenths to hundredths of microns while also having feature depth dimensions on the order of ten to hundred times those dimensions.
2. Description of Related Art
A variety of methods are presently known for making microparts. U.S. Pat. No. 5,256,360 to Li, teaches the use of a precisely controlled micro-electrode discharge machine (EDM) to make the micro-filter mold and suggests the use of laser-beam micro-machining, or electron-beam micro-machining, as suitable alternative processes. However, Li ('360), also teaches that molds made using conventional integrated circuits (IC) processing and lithographic processes in silicon tend to incorporate high internal strain, are prone to damage, are expensive to produce, and thus not economical to manufacture.
U.S. Pat. No. 5,501,893 to Laermer, et al. describes a lithographic technique for etching silicon, generally referred to as “anisotropic etching,” where it is possible to achieve deeply-extending trenches while simultaneously providing side walls which are as nearly parallel and vertical as desired. In order to achieve these geometries it is necessary to allow etching to progress only on the bottom of the etched trench in the silicon substrate and not on the walls of the trench. In particular, Laermer ('893) teaches a two stage process for alternately etching an exposed silicon surface in a reactive ion plasma followed by coating the etched surfaces with a thin polymerized layer, wherein the polymer coating serves to protect the wall surfaces of the trench from action of the plasma since these surfaces are not directly face the incoming flux of plasma ions. However, the polymer layer applied to the “floor” surface of the trench quickly breaks down in the presence of the ion bombardment since this surface directly faces the incoming ions. The polymer layer, therefore, forms a very effective etching “stop” on those edges or surfaces not directly in the path of the ion flux allowing for directional etching.
The process continues in this manner, alternating etching steps with coating steps, until the predetermined etching depth of the structures in the silicon substrate is reached.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a process for fabricating highly accurate, three dimensional x-ray masking tools.
It is another object to provide an x-ray mask comprising a silicon substrate having a foil-like metal pattern embedded into the thickness of the substrate.
Yet another object of the invention is to provide an x-ray mask having an embedded metal pattern whose thickness is sufficient to attenuate virtually all x-ray radiation having an energy at or below 10 KeV which strikes the pattern in a direction parallel to the metal thickness.
It is another object of the invention to provide an x-ray mask wherein the embedded pattern comprises a plurality of structural elements exhibiting features having lateral dimensions of much less than 1 micron.
Still another object of the invention is to provide an x-ray mask wherein the features include both the structural elements comprising the pattern, and the separation distances between those elements.
Yet another object of the invention is to provide an embedded pattern having features exhibiting a height-to-width aspect ratio of greater than about 30-to -1.
Another object of the invention is to provide a robust x-ray mask tool which is capable of withstanding repeated handling and very long exposure to high-dose x-ray radiation.
REFERENCES:
patent: 5751780 (1998-05-01), Fukuda et al.
patent: 5902706 (1999-05-01), Huh
patent: 6317480 (2001-11-01), Shoki et al.
Becker, E.W.; Ehrfeld, W.; Hagmann, P.; Maner, A.; Muenchmeyer, D.; “Fabrication of microstructures with high aspect ratios and great structural heights by synchrotron radiation lithography, galvanoforming, and plastic moulding (LIGA process),”Microelectronic Engineering, vol. 4 (1986) pp. 35-56 Published by Elsevier Scientific Publishers B.V.
Ehrfeld, W.; Glashauser, W.; Muenchmeyer, D.; Schelb, W.; “Mask making for synchrotron radiation light,”Microelectronic Engineering, vol. 5 (1986) pp. 463-470 Published by Elsevier Scientific Publishers B.V.
Ehrfeld, W.; Lehr, H.; “Deep x-ray lithography for the production of three-dimensional microstructures from metals, polymers, and ceramics,”Radiat. Phys. Chem., vol. 45 No. 3 (1995) pp. 349-365 Published by Pergamon Press, Elsevier Scientific Ltd.
Bhardwaj, J.K.; Ashraf, H.; “Advanced silicon etching using high density plasmas”Proceedings of SPIEvol. 2639 (1996) pp. 224-233 Published by SPIE—The International Society for Optical Engineering.
Ajmera, P.K.; Stadler, S.; Abdollahi, N.; “Development of a low-cost X-ray mask for high-aspect ratio MEM smart structures”Proceedings of SPIEvol. 3328 (1998) pp. 14-22 Published by SPIE—The International Society for Optical Engineering.
Shew, B.-Y.; Cheng, Y.; Shih, W.-P.; Lu, M.; Lee, W.H.; “High percision, low cost mask for deep x-ray lithography”Microsystems Technology, vol. 4 (1998) pp. 66-69 Published by Springer-Verlag.
Klein, J.; Guckel, D.P.; Siddons, D.J.; Johnson, E.D.; “X-ray masks for very deep X-rGy lithography”Microsystems Technology, vol. 4 (1998) pp. 70-73 Published by Springer-Verlag.
Sheu, J.T.; Chiang, S.; Su, S.; “Fabrication of intermediate mask for deep x-ray lithography”Microsystems Technology, vol. 4 (1998) pp. 74-76 Published by Springer-Verlag.
Chen, D.; Zhang, D.; Ding, G.; Zhao, X.; Zhang, J.; Yang, C.; Cai, B.; “DEM technique: A new three-dimensional micro fabrication technique for non-silicon materials”Proceedings of SPIEvol. 3680 No. 2 (1999) pp. 1099-1104 Published by SPIE—The International Society for Optical Engineering.
Harris, C.; Desta, Y.; Kelly, K.W.; Calderon, G.; “Inexpensive, quickly producable X-ray mask for LIGA”Microsystems Technology, vol. 5 (1999) pp. 189-195 Published by Springer-Verlag.
Coane, P.; Giasolli, R.; Ledger, S.; Lain, K.; Ling, Z.; Goettert, J.; “Fabrication of HARM structures by deep X-ray lithography using graphite mask technology”Microsystems Technology, vol. 6 (2000) pp. 94-98 Published by Springer-Verlag.
Morales Alfredo M.
Skala Dawn M.
Evans Timothy P.
Kim Robert H.
Sandia National Laboratories
Song Hoon K.
LandOfFree
X-ray mask and method for providing same 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 and method for providing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray mask and method for providing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2976282