Semiconductor device manufacturing: process – Chemical etching – Combined with coating step
Reexamination Certificate
1999-09-15
2001-05-22
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Combined with coating step
C438S695000, C438S696000, C438S697000, C438S700000, C438S745000, C438S712000
Reexamination Certificate
active
06235637
ABSTRACT:
BACKGROUND OF INVENTION
1) Field of the Invention
This invention relates generally to fabrication of a semiconductor device and more particularly to a method for laser marking a wafer without inducing flat edge particles.
2) Description of the Prior Art
Currently, semiconductor wafers are generally marked for identification and traceability. One approach to marking wafers is to cut a mark directly into the silicon layer of the wafer using laser scribing techniques. The mark is made by removing a volume of material from the silicon layer of the wafer. The removal of silicon material creates a silicon slag. As disclosed in an article by Chi-Shen Lo et al. titled “Integration Laser Marker for Flat Edge Particle Reduction”, laser marking has been identified as the root cause of reduced yields from what is commonly referred to as flat edge particles. Analysis of the contaminating particles has shown them to be silicon removed by the marking process. A need exists for a method of laser marking semiconductor wafers without inducing flat edge particles.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following patents.
U.S. Pat. No. 5,610,104 (Mitchell) shows a method for marking a mark on a silicon substrate. This patent teaches a method of laser marking a wafer by forming an insulating layer on the silicon surface, marking the insulating layer by laser scribing, then removing the silicon or oxidized silicon exposed by the laser scribing process using a wet etch process and removing the insulating layer.
U.S. Pat. No. 5,237,343 (Osada) shows a method for scribing ink jet heads.
U.S. Pat. No. 5,877,074 (Chang et al.) shows a method of laser marking a wafer.
U.S. Pat. No. 5,851,928 (Cripe et al.) discloses a method of isotropically etching a substrate.
U.S. Pat. No. 4,732,646 (Elsner et al.) recites a marking method comprising: forming holes in a masking layer, performing a high-energy ion implant, and etching into the substrate.
The article “Integration Laser Marker for Flat Edge Particle Reduction,” (Chi-Shen Lo et al.) SEMI, IC Seminar (1997) identifies laser marking as the root cause of the flat edge particle yield reduction, and recites a method of reducing flat edge particle defects by controlling mark position and beam energy.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for laser marking a semiconductor wafer without inducing flat edge particle yield reduction.
It is another object of the present invention to provide a robust and economical method for laser marking a semiconductor wafer without inducing flat edge particle yield reduction.
To accomplish the above objectives, the present invention provides a method for marking a semiconductor wafer without inducing flat edge particles, using a laser scribing technique. The process begins by providing a semiconductor wafer having a marking area with a silicon top layer. The semiconductor wafer is coated with a photoresist layer. A volume of the photoresist layer and a volume of silicon top layer are removed corresponding to the intended marking. Optionally, the marking pattern can be further etched into the silicon top layer by anisotropic etching, using the photoresist layer as an etching mask. In another option, the laser scribing process can be set to scribe the marking pattern in the photoresist layer without scribing the silicon top layer. The marking pattern can then be anisotropically etched into the silicon top layer, using the photoresist layer as an etching mask. Alternatively, the photoresist layer can be patterned to form an opening in the photoresist layer over a marking area, thereby exposing the silicon top layer. The silicon top layer is then marked using a laser scribing technique, and the photoresist layer prevents contamination of the device areas of the wafer by the resulting silicon slag.
The present invention provides considerable improvement over the prior art. A semiconductor wafer can be marked using a laser scribing technique without inducing flat edge particle defects. Particles generated by the laser scribing technique are trapped by the photoresist layer, and are subsequently removed with the photoresist layer.
The present invention provides several advantages over a process using an insulating layer to protect active areas from contamination by silicon slag. Photoresist is less expensive to form than an insulating layer. Without an insulating layer, high temperature processing and pre-cleaning are not required, reducing cycle time and cost. Also, since photoresist is softer and easier to remove than an insulating layer, the method of the present invention is more effective in removing silicon particles generated by the laser scribing process.
The present invention achieves these benefits in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
REFERENCES:
patent: 4732646 (1988-03-01), Elsner et al.
patent: 4765865 (1988-08-01), Gealer et al.
patent: 4877481 (1989-10-01), Fukuda et al.
patent: 5187601 (1993-02-01), Yamazaki et al.
patent: 5237343 (1993-08-01), Osada
patent: 5373137 (1994-12-01), McLaughlin
patent: 5610104 (1997-03-01), Mitchell
patent: 5733711 (1998-03-01), Juengling
patent: 5851928 (1998-12-01), Cripe et al.
patent: 5877064 (1999-03-01), Chang et al.
patent: 5956596 (1999-09-01), Jang et al.
patent: 6063695 (2000-05-01), Lin et al.
Chi-Shen Lo et al., “Integration Laser Marker for Flat Edge Particle Reduction”, SEMI, IC Seminar (1997), pp. 267-278.
Chen Sheng-Hsiung
Tsai Ming-Hsing
Ackerman Stephen B.
Perez-Ramos Vanessa
Saile George O.
Stoffel Willian J.
Taiwan Semiconductor Manufacturing Company
LandOfFree
Method for marking a wafer without inducing flat edge... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for marking a wafer without inducing flat edge..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for marking a wafer without inducing flat edge... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475680