Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-07-09
2001-02-27
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S734000, C438S073000, C430S312000
Reexamination Certificate
active
06194312
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device manufacturing method and, more particularly, to a semiconductor device manufacturing method in which the uniformity of patterning in the photolithography process (to be referred to as a PR process hereinafter) is improved and a semiconductor device fabricated by this method.
The prior art will be described with reference to
FIGS. 6A and 6B
,
FIGS. 7A and 7B
, and
FIGS. 8A
to
8
D. As the prior art, a bolometer type infrared sensor described in Japanese Patent Laid-Open No. 80105794, in which bolometer type thermoelectric conversion elements are regularly formed, will be described, and a PR process for forming a bolometer will be particularly described. This prior art can be applied to a general semiconductor device in which required patterns are regularly formed in a predetermined region.
FIG. 6A
shows the arrangement of a two-dimensional bolometer type infrared sensor. An infrared sensor
50
is constituted by a light-receiving portion
51
, a horizontal scanner portion
52
, a vertical scanner portion
53
, and a signal output portion
54
.
The light-receiving portion
51
is constituted by a large number of pixels
55
two-dimensionally regularly arranged in a matrix. The vertical scanner portion
53
sequentially selects pixel rows at a horizontal scanning time period so as to read all the pixel rows arranged in the light-receiving portion
51
in the vertical direction within a predetermined vertical scanning time. The horizontal scanner portion
52
selects pixel columns so as to sequentially read signals from the respective pixels
55
arranged in the horizontal direction in the respective pixel rows selected by the vertical scanner portion
53
within a predetermined horizontal scanning time.
The signal output portion
54
outputs the pixels
55
selected by the horizontal scanner portion
52
and vertical scanner portion
53
. When the output terminal of the signal output portion
54
is connected to a unit that detects the resistance of the pixels
55
, a change in resistance of the pixels
55
is detected, thereby detecting the two-dimensional information on the incident infrared ray. Reference numeral
59
denotes an outer peripheral portion where the horizontal scanner portion
52
, the vertical scanner portion
53
, and the signal output portion
54
are arranged.
FIG. 6B
shows the pixel portion of the sensor shown in FIG.
6
A. In each pixel
55
, the temperature in the pixel
55
changes in accordance with the incident infrared ray, and the resistance of a bolometer
56
having a width al changes in accordance with this temperature change. This change in resistance is output from the corresponding pixel
55
to the outside as the signal through a pixel selection switch element (not shown) and interconnections
57
and
58
formed in the underlying substrate of the bolometer
56
.
In the bolometer type infrared sensor having the above arrangement, the uniformity of the respective pixels
55
is significant. Accordingly, the resistance of the respective pixels
55
arranged two-dimensionally regularly, i.e., the uniformity of the resistance of the bolometers
56
, is significant. To realize this uniformity, the interconnection width of the bolometers
56
in the light-receiving portion
51
must be uniformed.
FIG. 7A
shows a photomask which is used in the conventional PR process for forming a bolometer and entirely covers the sensor. In this case, the photomask is used for the manufacture of the sensor shown in FIG.
6
A.
FIG. 7B
shows a photomask portion shown in
FIG. 7A
which corresponds to one pixel portion.
Referring to
FIG. 7A
, a region
62
of a photomask
61
corresponds to the light-receiving portion
51
. A region
63
of the photomask
61
is the surrounding region of the region
62
, and corresponds to the outer peripheral portion
59
. In the region
62
, bolometer patterns
65
used in formation of the bolometers
56
of the light-receiving portion
51
are formed each with the predetermined width al to correspond to each pixel
55
, as shown in FIG.
7
B. Since the region
63
does not correspond to the light-receiving portion
51
, it is made of a transparent material so that no patterns by the bolometer material layer are formed.
FIGS. 8A
to
8
D show a manufacturing method of forming the bolometers of the light-receiving portion.
FIGS. 8A
to
8
D schematically show a section taken along the line A-A′ of FIG.
6
A and illustrate a case wherein the bolometers are formed by using the photomask
61
of FIG.
7
A.
As shown in
FIG. 8A
, a bolometer material layer
202
serving as the material of the bolometers is deposited on an underlying substrate
201
. As shown in
FIG. 8B
, a photoresist
203
is uniformly applied onto the bolometer material layer
202
.
Subsequently, bolometer patterns
56
each shown in
FIG. 7B
is exposed within the light-receiving portion
51
(region
62
) by using the photomask
61
of
FIG. 7A
, and is developed, to form bolometer patterns in the photoresist
203
, as shown in FIG.
8
C. At this time, on the outer peripheral portion
59
(region
63
), the photoresist
203
is completely removed.
Using the photoresist
203
formed with the bolometer patterns as the mask, etching, e.g., plasma etching, is performed for the bolometer material layer
202
to form bolometers
206
. At this time, on the outer peripheral portion
59
(region
63
), the bolometer material layer
202
is completely etched and removed. Then, as shown in
FIG. 8D
, the photoresist
203
on the bolometers
206
is removed.
A bolometer
206
b
formed near the boundary of the light-receiving portion
51
is weakly developed and etched during the process of
FIG. 8C
to FIG.
8
D. Accordingly, the bolometer
206
b
has a width a2 larger than the bolometer width al as the designed value on the photomask
61
, and the pattern uniformity is degraded. The phenomenon wherein development and etching become weak near the boundary of the light-receiving portion
51
is called “microloading effect”.
The “microloading effect” occurs when a wide region (region), e.g., the outer peripheral portion
59
(region
63
), is removed around a region (pattern region), e.g., the light-receiving portion
51
(region
62
), where regular patterns are formed, during formation of the bolometers. More specifically, in order to develop a photoresist or to etch a bolometer material layer over a wide region, larger amounts of developing agent, etching gas, and the like are used in the non-pattern region than in the pattern region. Accordingly, development and etching become relatively weak near the boundary of the non-pattern region, and a predetermined amount of development or etching is not performed. As a result, the width of the formed pattern becomes larger than the designed value of the photomask, and the pattern uniformity is degraded.
In
FIG. 8D
, only one bolometer
206
b
is wider than the predetermined width al. In fact, however, the width of the bolometers
206
gradually increases from the predetermined width al as it is closer to the boundary. In contrast to this, at a place remote from the boundary by a distance equal to or larger than a value to be described later, the width of the bolometers
206
is a predetermined value al, which is uniform.
As described above, since the width of the bolometer
206
of the pixel
55
located near the boundary between the light-receiving portion
51
and the outer peripheral portion
59
becomes larger than the predetermined value, the resistance of the bolometer
206
is decreased, and the uniformity of the resistance of the bolometers
206
in the light-receiving portion
51
is degraded.
In order to improve this pattern non-uniformity occurring near the boundary of the light-receiving portion
51
, for example, Japanese Patent Laid-Open No. 63-17528 describes a method of forming regular dummy patterns also on the outer peripheral portion
59
of a predetermined region (pattern region) where regular patterns are formed.
Abbott Barbara Elizabeth
Fourson George
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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