Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Reexamination Certificate
2001-11-08
2004-07-27
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
C438S150000, C438S151000, C438S166000, C438S168000, C438S187000, C438S198000, C438S308000, C438S378000, C438S482000, C438S487000, C438S488000, C438S942000
Reexamination Certificate
active
06767804
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to sequential lateral solidification(SLS).
One method of SLS, which may be referred to as the “2-shot process,” has been investigated for use in high-throughput processes. In this process, small beamlets, or a small beamlet, are projected onto regions of a silicon film overlying another substrate to induce melting and solidification(also referred to as “crystallization”) of large-grained polycrystalline silicon material. This may be referred to as a first shot. The small beamlets are then advanced and the process repeated such that the melted and solidified regions of this second shot overlap the regions of the first shot.
This process may be accomplished by using a single array of beamlets and making two or more passes over a given region of silicon film and microtranslating the array between passes. The process may also be accomplished by using multiple arrays of beamlets that are staggered with respect to each other and scanning the entire pattern in a across the silicon film. A single beamlet may also be used to iteratively stitch together crystallized regions, although this offers poor throughput.
The material produced using the above described process has severe directionality effects. The material has a plurality of narrow rectangular crystal grains oriented with the long axis perpendicular to the beamlet length.
As these directional effects are generally undesirable, a 2+2 process may be used to reduce, or eliminate, these directional effects. This may be accomplished by following up a first 2-shot process with a second 2-shot process carried out in a direction orthogonal to the first. This has been carried out by crystallizing silicon with an initial 2-shot process, rotating the sample being crystallized by 90 degrees, and then carrying out the second 2-shot process.
The need to rotate the sample by 90 degrees decreases throughput of the system, and adds complexity to the stage system for carrying out the SLS process.
SUMMARY OF THE INVENTION
Accordingly, a mask design is provided which enables a 2+2 process to be accomplished without the need to rotate the mask or the substrate relative to each other. This reduces the complexity of stages or mask mounts, and improves the angular alignment of the multiple 2-shot processes. The mask comprises a first set of two arrays of beamlets oriented substantially parallel to each other, and a second set two arrays of beamlets oriented at an angle, for example 90 degrees, relative the first set of two arrays.
The first set of two arrays is arranged so that a second array of beamlets is offset relative to a first array of beamlets, such that when the mask is transitioned the second array of beamlets will fill the gap between the first array of beamlets and slightly overlap the first array of beamlets.
A method of using the mask to accomplish a 2N processing is also provided.
REFERENCES:
patent: 6117752 (2000-09-01), Suzuki
patent: 6177301 (2001-01-01), Jung
patent: 6235614 (2001-05-01), Yang
patent: 6274888 (2001-08-01), Suzuki et al.
patent: 6326286 (2001-12-01), Park et al.
Article entitled, “Phase Transformation Mechanisms involved in Excimer Laser crystallization of Amorphous Silicon Films”, by Im et al., published in Appl. Phys. Lett. 63 (14), Oct. 4, 1993, pp 1969-1971.
Article entitled, “Sequential Lateral Solidification of Thin Silicon Films on SiO2”, by Sposili et al., published in Appl. Phys. Lett. 69 (19) Nov. 4, 1996, pp 2864-2866.
Article entitled, “Controlled Super-Lateral Growth of Si Films for Microstructural Manipulation and Optimization”, by Im et al., published in Phys. Stat. Sol. (a) 166, 603 (1998), pp 603-617.
Article entitled, “Crystalline Si Films for Integrated Active-Matrix Liquid-Crystal Displays”, by Im et al., published in MRS Bulletin/Mar. 1996, pp 39-48.
Article entitled, “Low-Temperature Single-Crystal Si TFT's Fabricated on Si Films Processed via Sequential Lateral Solidification”, by Crowder et al., published in IEEE Electron Device Letters, vol. 19, No. 8, Aug. 1998, pp 306-308.
Article entitled, “Single-Crystal Si Films for Thin-Film Transistor Devices”, by Im et al., published in Appl. Phys. Lett. 70 (25), Jun. 23, 1997, pp 34343436.
Isaac Stanetta
Niebling John F.
Rabdau Matthew D.
Ripma David C.
Sharp Laboratories of America Inc.
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