Electron device manufacturing method, a pattern forming...

Details Electron device manufacturing method, a pattern forming... Electron device manufacturing method, a pattern forming...

2001-03-19

2003-11-25

Huff, Mark F. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

C430S022000, C430S030000

Reexamination Certificate

active

06653052

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an electron device such as a semiconductor device, a superconductive device, a micro machine and an electronic device, a pattern forming method used for the method, a photomask used for these methods and its manufacturing method, particularly relates to technique effective to apply to exposure technology in a process for manufacturing a semiconductor integrated circuit.
2. Description of the Related Prior Arts
In manufacturing a semiconductor integrated circuit, for a method of printing a minute pattern on a semiconductor wafer, lithography is used. In lithography, a projection tool is mainly used, a pattern of a photomask installed in a projection tool is printed on a semiconductor wafer and a device pattern is formed.
A normal photomask is produced by processing light shielding materials such as chromium (Cr) formed on the flat surface of a transparent quartz substrate. That is, a light shielding film made of chromium or others is formed on the flat surface of a quartz substrate in a desired shape. For the processing of the light shielding film, for example, after an electron beam sensitive resist is applied on the light shielding film, a desired pattern is written on the electron beam sensitive resist by an electron beam writer, next, a resist pattern in a desired shape is formed by development, afterward, dry etching or wet etching is applied using the resist pattern as a mask and the light shielding film is processed. Afterward, after the resist is removed, cleaning and others are performed and a light shielding pattern in a desired shape is formed on the transparent quartz substrate.
Recently, the integration of LSI has been accelerated, the enhancement of the operational speed has been demanded and the miniaturization of a circuit pattern has been demanded. This tendency particularly remarkably appears in a gate pattern that has a large effect upon the operational speed of a transistor. For a part of logic LSI products, a gate pattern of 0.1 &mgr;m is also already formed using a KrF excimer laser (wavelength: 248 nm) for exposure.
For a semiconductor memory, miniaturization is accelerated to reduce the cost and a dynamic random access memory (DRAM) according to a rule that half pitch is 0.18 &mgr;m is manufactured using a KrF excimer laser for exposure. DRAM according to a rule that half pitch is 0.13 &mgr;m using a KrF scanner is also developed.
It is owing to an exposure method called super resolution that by far smaller patterning than the wavelength of exposure is enabled. Super resolution effective to form a minute pattern is called phase shift lithography and is disclosed in Japanese published unexamined patent application No. Sho 58-173744 for example. The phase shift lithography is a method of forming structure called a phase shifter for alternately inverting the phase of exposure light in windows in which a part where exposure light is transmitted of a photomask, that is, a glass face is seen with a light shielding part between the windows and exposing using this photomask. As the phase of light transmitted in both transmitted parts is inverse, the amplitude of light may be zero in the light shielding part between the parts. In case the amplitude is zero, the intensity of light is also zero and the resolution is greatly enhanced.
For an example of the disclosure of another technique related to a mask, Japanese published unexamined patent applications No. Hei 9-211837 and No. Hei 5-289307 can be given.
For a phase shifter, there are a carved type that a part of a glass plate as a photomask is carved, a type that a transparent film having the thickness enough to invert the phase is formed on the base material of a photomask and a type that these two are mixed.
A carved type phase shift mask is produced as follows. As shown in (a) of
FIG. 2A
, a Cr film
202
made of light shielding material is deposited on the flat surface of mask base material (a quartz substrate)
201
by sputtering and an EB resist
203
is applied to it. A pattern for light shielding is written by EB (shown by an arrow
204
). The pattern is developed, a resist pattern
205
is formed ((b) of FIG.
2
A), the Cr film
202
is etched by dry etching or wet etching ((c) of FIG.
2
A), the resist is removed and a light shielding pattern
206
is formed ((d) of FIG.
2
A). Afterward, an EB resist
207
is applied and a pattern for forming a phase shifter is exposed (shown by an arrow
208
)((e) of FIG.
2
A). Development is performed, a resist pattern
209
is formed ((f) in
FIG. 2B
) and the quartz substrate is carved by desired depth by dry etching ((g) of FIG.
2
B). The resist is peeled, phase difference between both apertures
210
and
211
is inspected ((h) of FIG.
2
B), in case carved quantity for making phase difference does not reach a target value, an EB resist
212
is applied again, a shifter pattern is written
213
((i) in FIG.
2
B), development is performed, a shifter pattern
214
is formed ((j) in FIG.
2
B), the quartz substrate is etched again by dry etching ((k) in FIG.
2
C), the resist is peeled and phase difference is inspected ((
1
) in FIG.
2
C). Afterward, as shown in (m) of
FIG. 2C
, wet etching is performed, overhang structure
215
having the Cr film as an overhang is formed and a carved type phase shift mask is manufactured.
In the meantime, a transparent film formation type (hereinafter called an additive phase shifter type) phase shift mask is produced as follows. As shown in (a) of
FIG. 3A
, a Cr film
302
made of light shielding material is deposited on the flat surface of a mask substrate (a quartz substrate)
301
by sputtering and an EB resist
303
is applied on it. A pattern for light shielding is written by EB (
304
). Development is performed, a resist pattern
305
is formed ((b) of FIG.
3
A), the Cr film is etched by dry etching or wet etching ((c) of FIG.
3
A), the resist is removed and a light shielding pattern
306
is formed ((d) of FIG.
3
A).
Afterward, a spin-on-glass (SOG) film is applied, heating processing and others are performed and a transparent shifter
307
is formed ((e) in FIG.
3
A). Afterward, an EB resist
308
is applied and a pattern for forming a phase shifter is exposed (
309
) ((f) in FIG.
3
B). Development is performed, a resist pattern
310
is formed ((g) in
FIG. 3B
) and a transparent shifter is etched by dry etching or wet etching ((h) in FIG.
3
B). The resist is peeled, phase difference between both apertures
311
and
312
is inspected and a phase shift mask is acquired ((i) in FIG.
3
B).
For light shielding material in both methods, the metallic Cr film is used and in addition, as the accuracy of the light shielding pattern is required, the metallic Cr film is formed on the flat surface of the quartz substrate by sputtering.
For the type of the phase shift mask, there are a shifter edge type that phase difference is given to the light shielding pattern
401
which can be regarded as an optically isolated pattern as shown in
FIG. 4
by optical path difference
402
on both sides of the light shielding material
401
and Levenson type that a phase shifter
502
is alternately arranged on a light shielding pattern
501
closely assembled like a line and space as shown in
FIG. 5
in an aperture. Reference numbers
403
and
503
in
FIGS. 4 and 5
both denote a glass substrate. In both cases, structure for inverting the phase of exposure light transmitted in the aperture on both sides of the aperture is also provided.
A problem in the printing characteristics of the carved type phase shift mask is that the quantity of transmitted light in an aperture
602
(hereinafter called a phase 0) in which a glass substrate
601
is not carved or is not carved so much as shown in (a) of FIG.
6
and in an aperture
603
(hereinafter called a phase &pgr;) in which the glass substrate is deep carved varies by light scattering on the side
605
of the glass substrate formed under the side wall
604
of Cr light

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