Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
1999-04-15
2001-08-28
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S324000
Reexamination Certificate
active
06280908
ABSTRACT:
FIELD OF THE INVENTION
The present invention provides a method of decreasing the etch rate of a patterned resist on a substrate by treating the patterned resist with an atmosphere comprising molecules of a hardening agent. By incorporating the molecules of the hardening agent into the resist after exposure and development, but prior to substrate etching, the resist structure or pattern remains unchanged. Extensive optimization of resolution and resist contrast is thereby decoupled from the etching process leading to a more efficient development of new materials for lithography.
BACKGROUND OF THE INVENTION
In the field of semiconductor manufacturing, lithography is generally employed to provide a pattern to a substrate layer. Specifically, an imageable resist is applied to the substrate needing patterning, the imageable resist is then patterned through exposure and development, and the pattern is transferred to the underlying substrate by etching with a plasma of various reactive ion species, e.g. CF
4
.
Since the etch rate of most imageable resist films is greater than that of the underlying substrate layer, the imageable resist etches laterally at a much faster rate than the underlying substrate layer. This lateral etching of the imageable resist severely distorts the pattern formed in the substrate layer and prevents the formation of a desired, small feature sized pattern (100 nm or less) on the substrate layer.
Numerous attempts to overcome this problem have been developed and are now in use. One solution to this problem is to change the imageable resist's resistance to oxygen plasma by using a silylation technique. In accordance with prior art silylation techniques, the imageable resist is silylated before the film is patterned. Such silylating techniques are disclosed, for example, in M. Bottcher, et al. “Surface Imaging by Silylation for Low Voltage Electron-beam Lithography”, J. Vac. Sci. Technol. B12, 3473 (1994); C. Pierrat, et al. “PRIME Process for Deep UV and E-beam Lithography”, Microelectronic Engineering, Vol. 11, 507 (1990); and M. Irmscher, et al. “Comparative Evaluation of Chemically Amplified Resists for Electron-beam Top Surface Imaging Use”, J. Vac. Sci. Technol. B12, 3925 (1994).
Despite being successful in altering the etch rate of the imageable resist, this prior art method requires that changes be made in the resist chemistry and thus the exposure and development process. Such changes are not desirable since they introduce additional materials not typically employed in lithography.
Alternative solutions to this problem are even more complex involving, for example, resist films made from multiple layers of various polymers. The use of multi-polymer film layers is disclosed, for example, in M. A. McCord, et al., “Electron Beam Lithography”, Chapter 2 of Handbook of Microlithography, Micromachining and Microfabrication, Vol. 1: Microlithography, P. Rai-Choudhury, ed., SPIE Optical Engineering Press, Bellingham, Wash. (1997). Alternatively, resist polymers can be modified to include alicyclic compounds. These compounds increase etch resistance, but they also change the exposure and development properties of the film (R. D. Allen, et al., “Deep-UV Resist Technology”, Chapter 4, ibid.).
There is thus a need for developing a new and improved lithography method which can change the etch resistance of the imageable resist without altering any of the resist chemistry. There is also a need for developing a method which could shift the photolithography industry away from complex and expensive multilayer techniques, and perhaps streamline microelectronic fabrication research by decoupling etching properties from exposure properties.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a method of changing the etch resistance of an imageable resist so that the resist etches slower than any untreated resist layer.
A further object of the present invention is to provide a method of changing the etch rate of an imageable resist in such a fashion that the chemistry of the resist is unaltered and thus no changes in the exposure/development steps are needed.
A still further object of the present invention is to provide a method of improving the etch resistance of the imageable resist so that a reliable pattern having a substantially small feature size can be transferred to the underlying substrate layer.
These and other objects and advantages can be achieved in the present invention by treating a patterned layer of an imageable resist with an atmosphere containing a hardening agent, e.g. metalloid-containing compound, after the patterning step, but prior to etching. Specifically, the method of the present invention comprises the steps of:
(a) applying a layer of an imageable resist to a substrate layer;
(b) patterning the layer of imageable resist by removing selective areas thereof; and
(c) treating the patterned imageable resist with an atmosphere comprising molecules of a hardening agent so as to obtain a hardened resist surface that etches at a slower rate than the untreated resist.
After conducting step (c), the pattern is formed in the substrate layer by conventional etching such as reactive ion etching (RIE) and, thereafter the resist can be removed using conventional stripping techniques.
REFERENCES:
patent: 5756255 (1998-05-01), Sato
patent: 6063543 (2000-05-01), Hien
M. Bottcher, et al., “Surface Imaging by Silylation for Low Voltage Electron-Beam Lithography,” J. Vac. Sci. Technol. B vol. 12, No. 6, pp. 3473-3477 (1994).
M. Irmscher, et al. “Comparative Evaluation of Chemically Amplified Resists for Electron-Beam Top Surface Imaging Use,” J. Vac. Sci. Technol. B, vol. 12, No. 6, pp. 3925-3929 (1994).
M.A. McCord, “Chapter 2 Electron Beam Lithography,” Handbook of Microlithography, Micromachining and Microfabrication vol. 1: Microlithography, P. Rai-Choudhury, ed. SPIE Optical Engineering Press, Bellinham WA (1997).
Aviram Ari
Rooks Michael Joseph
August Casey P.
Duda Kathleen
International Business Machines - Corporation
Scully Scott Murphy & Presser
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