Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
2000-06-16
2001-08-28
Lebentritt, Michael (Department: 2824)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C438S694000, C438S747000, C438S757000, C438S763000, C438S970000
Reexamination Certificate
active
06281130
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to manufacturing processes for fabricating semiconductor integrated circuit devices. More particularly, it relates to an improved method of applying a developer onto a semiconductor wafer substrate having a ultra-thin resist film coating thereon so as to minimize unexposed film thickness loss during development.
As is generally known to those in the semiconductor industries, there is a continuing trend of manufacturing semiconductor integrated circuits with higher and higher densities on a smaller chip area. As a consequence of this desire for large scale integration, this has led to a continued shrinking of the circuit dimensions and features of the devices so as to reduce manufacturing costs and to improve circuit functionality. The ability to reduce the size structures such as shorter gate lengths in field-effect transistors is driven by lithographic technology which is, in turn, dependent upon the wavelength of light used to expose the photoresist. Currently, optical steppers expose the photoresist using light having a wavelength of 248 nm is widely used in manufacturing, but a radiation having a wavelength of 193 nm is being experimented in research and development laboratories. Further, the next generation lithographic technologies will in all likelihood progress toward a radiation having a wavelength of 157 nm and even shorter wavelengths, such as those used in Extreme Ultra-Violet (EUV) lithography (≈13nm).
As the wavelength of the radiation decreases, such classic image exposure techniques cannot be used to satisfactorily generate the pattern linewidths in the photoresist of greater than 0.25 &mgr;m (2500 Å). This is due to the fact that the organic-based photoresist materials will become increasingly opaque to the radiation. In order to overcome this drawback, there has been developed in recent years the use of ultra-thin resist (UTR) coatings in order to maintain the desired characteristics of the masked photoresist structures (e.g., near vertical sidewalls for the resist profiles, maximum exposure/focus latitude). In the current state-of-the-art, integrated circuit manufacturers have been using in the resist process a resist coating having a standard photoresist thickness of more than 0.5 &mgr;m (5,000 Å) for 248 &mgr;m lithography and 0.4 &mgr;m (4,000 Å) for 193 &mgr;m lithography. Thus, a resist coating having an UTR thickness is considered to be resist films of less than 0.25 &mgr;m (2500 Å) in thickness.
However, the development of ultra-thin resist coating is not without any problems due to the fact of the inherent thinness of the resist coating. For positive photoresist, the unexposed areas of the resist coating are insoluble and the exposed areas thereof are dissolved away when the substrate is immersed in an alkaline developing solution so as to produce a positive relief pattern on the substrate. Unfortunately, some of the resist coating, which is not exposed, is typically also dissolved during the development process. This is referred to sometimes as the “unexposed film thickness loss” or UFTL.
The loss of resist coating during the development process typically does not create any problems for the standard photoresist thickness of more than 5,000 Å. For example, the loss of 150 Åfor the standard photoresist thickness amounts only to 3% of the total thickness. On the other hand, the loss of 150 Åfor the Ultra-Thin Resist (UTR) coating having a thickness of, for instance, 1500 Åwould be a serious problem since this would amount to 10% of the total thickness. Such a large percentage loss can adversely affect the subsequent etching processes in which the resist acts as a mask, where the selectivity between the resist and a device layer (film) to be etched is low.
Another problem encountered during the development process for UTR films is that they are more susceptible to critical dimension (CD) variations caused by the location of the developer nozzle. In particular, where a developing solution is dispensed onto the central portion of the substrate surface, the developing solution is then distributed on the substrate surface from the central position to the peripheral position by spinning. It is generally known that the impact point of the stream(s) of developing solution with the resist accelerates development locally. For the standard thickness photoresist coatings, this effect can be tolerated. However, for the UTR film coatings, they cannot be tolerated due to their inherent thinness.
Accordingly, there has arisen a need of providing a way of applying a developer onto a semiconductor wafer substrate having a ultra-thin resist film coating thereon so as to minimize unexposed film thickness loss during development. This is accomplished in the present invention by applying the developing liquid from a developer nozzle which is off-set from the central portion of the wafer substrate and by allowing the developing liquid to contact the wafer substrate for less than 10 seconds.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide an improved method of applying a developing liquid onto a semiconductor wafer substrate having a ultra-thin film thereon.
It is an object of the present invention to provide a method of applying a developing liquid onto a semiconductor wafer substrate having a ultra-thin film thereon so as to minimize unexposed film thickness loss during development.
It is another object of the present invention to provide a method of applying a developing liquid onto a semiconductor wafer substrate having a ultra-thin resist film thereon so as to minimize nozzle induced critical dimension variations in the films during development.
It is still another object of the present invention to provide a method of applying a developing liquid onto a semiconductor wafer substrate having a ultra-thin film thereon which includes applying the developing liquid from a developer nozzle which is off-set from the central position of the wafer substrate.
In a preferred embodiment of the present invention, there is provided a method of applying a developing liquid onto a semiconductor wafer substrate having a ultra-thin resist film thereon so as to minimize unexposed film thickness loss during development. The development liquid is applied onto the semiconductor wafer substrate having the ultra-thin film thereon while spinning the wafer substrate at a rotational speed of 100 to 1,500 r.p.m. for 0.5 to 5 seconds from a developer nozzle off-set from the central position of the wafer substrate. The developing liquid is applied continuously onto the wafer substrate while decreasing the rotational speed to less than 100 r.p.m. for 1 second. The developing liquid is allowed to contact the wafer substrate for less than 10 seconds. Then, the liquid developer is rinsed off, and the wafer substrate is spun dry.
REFERENCES:
patent: 5015177 (1991-05-01), Iwata
patent: 5164286 (1992-11-01), Blakeney et al.
patent: 5223377 (1993-06-01), Samarakone et al.
patent: 5328806 (1994-07-01), Toukhy
patent: 5667922 (1997-09-01), Martiska et al.
patent: 5897982 (1999-04-01), Shibata et al.
patent: 5962196 (1999-10-01), Das et al.
patent: 5976620 (1999-11-01), Sanada et al.
patent: 6051358 (2000-04-01), Zampini et al.
patent: 6090534 (2000-07-01), Costigan et al.
patent: 6132940 (2000-10-01), Mih et al.
Advanced Micro Devices , Inc.
Chin Davis
Lebentritt Michael
LandOfFree
Method for developing ultra-thin resist films 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 developing ultra-thin resist films, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for developing ultra-thin resist films will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2446030