Method for making a photolithographic mask

Details Method for making a photolithographic mask Method for making a photolithographic mask

2000-03-14

2003-03-25

Huff, Mark F. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Radiation modifying product or process of making

Radiation mask

C430S323000, C430S296000, C430S394000, C378S035000

Reexamination Certificate

active

06537706

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for making masks used in photolithography for making semiconductors. In particular, the present invention relates to a method for making such a mask that is unaffected by substrate deformation.
BACKGROUND OF THE INVENTION
When making a photolithographic mask, absorption film
101
and photoresist layer
102
may be deposited on substrate
100
, as shown in
FIG. 1
a
. The stresses those layers apply to substrate
100
can deform it by bending it. That deformation could cause displacement errors that render the resulting mask unsuitable for generating sub 0.1 micron features.
FIGS. 1
b
-
1
e
illustrate how such deformation can produce unacceptable displacement errors. After film
101
and layer
102
are formed, an e-beam writing step is performed to define those portions of photoresist layer
102
that will be removed prior to etching absorption film
101
. That e-beam writing step is thus applied to a deformed substrate. The resulting structure is shown in
FIG. 1
b
. The photoresist is then developed, generating the structure shown in
FIG. 1
c
. Removing part of photoresist layer
102
releases some of the stress, causing substrate
100
to deform relative to its shape during the e-beam writing step. In essence, the substrate starts to “snap back” from the bent position it assumed during that step.
Next, absorption film
101
is etched (
FIG. 1
d
) and the remaining portions of photoresist layer
102
are removed (
FIG. 1
e
). These steps release additional stress, causing substrate
100
to further deform relative to its shape during the e-beam writing step. By applying the e-beam writing step to a bent substrate, which subsequently snaps back toward its initial shape (i.e., its shape prior to the deposition of film
101
and layer
102
), the resulting mask defines features that are displaced from where they had been prescribed by the e-beam writing step.
FIG. 2
provides a graphical representation for how this process can cause displacement errors. Depositing film
101
and layer
102
(steps
201
and
202
, respectively) applies stresses that cause in plane distortion
210
and
211
, respectively. After the e-beam writing step (step
203
), photoresist removal, absorption film etching, and photoresist stripping steps (steps
204
,
205
, and
206
, respectively) release stress, which causes substrate
100
to return toward its initial shape. This can cause features, demarcated by the e-beam writing step, to be displaced relative to features that the resulting mask defines.
Accordingly, there is a need for a method for making a photolithographic mask that reduces the deformation caused by depositing films on a substrate. The present invention provides such a method.


REFERENCES:
patent: 5291536 (1994-03-01), Itoh et al.
patent: 5553110 (1996-09-01), Sentoku et al.
patent: 5677090 (1997-10-01), Marumoto et al.
patent: 5773177 (1998-06-01), Ikeda et al.

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