Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
2001-04-30
2003-05-13
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S022000
Reexamination Certificate
active
06562525
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photo mask to be used for photolithography, and to a method of inspecting a pattern defect through use of the photo mask, and to a method of manufacturing a semiconductor device through use of the photo mask.
2. Description of the Background Art
Recently, demand has existed for an increase in the speed and capacity of a semiconductor device, and miniaturization of the device has also been pursued. Development of a system LSI formed from a combination of a semiconductor memory and a logic LSI has also been pursued in accordance with diversification of information processing.
So-called eDRAM (embedded DRAM) having DRAM and a logic LSI mixed therein is mentioned as one example of the system LSI. The eDRAM has the advantageous ability to process massive images at high speed.
FIG. 5
is a cross-sectional view for describing the structure of DRAM acting as a common semiconductor device. As shown in
FIG. 5
, reference numeral
101
designates a semiconductor substrate;
102
designates an element isolation region;
103
designates a gate insulation film;
104
designates a polysilicon film acting as a conductive film;
105
designates a tungsten silicide (WSi) film;
106
and
107
designate insulation films;
108
designates a side wall protective insulation film; and
109
and
115
designate poly-plugs which come into contact with a storage node. Reference numerals
110
,
111
,
113
,
116
,
117
,
120
and
122
designate nitride or oxide films, which serve as interlayer dielectric films. Reference numerals
112
and
121
designate metal interconnections;
118
designates a storage node of a lower electrode; and
119
designates an upper electrode.
The semiconductor device (DRAM) such as that shown in
FIG. 5
is manufactured by way of a plurality of manufacturing processes; that is, a film-growth process for forming a dielectric film and a conductive film; an etching process for forming a contact hole and a trench; a smoothing process using the CMP technique; and a photolithography process for forming a resist pattern.
Before and after each of the foregoing processes, a pattern defect inspection operation is performed for managing substances stuck to a product (product wafer). The pattern defect inspection operation is an inspection for specifying defective pattern attributable to extraneous matter, insufficient exposure, or etching failures, and is performed through use of an SEM (scanning electron microscope) or an optical microscope. Various types of inspection methods have been available in accordance with applications.
Next, a conventional photo mask to be used for photolithography processes will now be described.
FIG. 6
is a view for describing a conventional photo mask.
FIG. 7A
is a view for describing a conventional mask dimension inspection mark shown in FIG.
6
.
As shown in
FIGS. 6 and 7A
, reference numeral
10
designates a photo mask;
2
designates a product pattern;
13
designates a mask dimension inspection mark; and
4
designates a line pattern.
The photo mask
10
shown in
FIG. 6
is a reticle having drawn thereon a product pattern
2
and mask dimension inspection marks
13
provided on the periphery of the product pattern
2
.
The product pattern
2
is a circuit pattern of an actual product.
The mask dimension inspection marks
13
are for measuring the processing precision of a photo mask at the time of production of the photo mask. Patterns of the mask dimension inspection marks
13
are originally unnecessary during the photolithography process. Hence, the patterns of the marks
13
are irrelevant to operation of the semiconductor device.
As shown in
FIG. 7A
, each of the mask dimension inspection marks
13
includes a plurality of line patterns
4
which are equal in width to that of the product pattern
2
.
Next, a method of inspecting pattern defects (also called “defective patternes”) using the conventional photo mask
10
will be described.
FIG. 7B
is a cross-sectional view for describing a method of inspecting a pattern defect using a conventional photo mask.
As shown in
FIG. 7B
, a silicon nitride film
22
is formed to a thickness of about 500 angstroms on a semiconductor substrate
21
, by the LPCVD method. Next, a silicon oxide film
23
is formed on the silicon nitride film
22
to a thickness of about 8,000 angstroms by the LPCVD method. Further, a photoresist film (not shown) is formed on the silicon oxide film
23
.
Next, a wafer is exposed through use of a photo mask
10
shown in
FIG. 6
, thereby forming a resist pattern (not shown) on the silicon oxide film
23
. Further, the wafer is subjected to dry etching while the resist pattern is used as a mask, whereby opening sections
28
corresponding to the mask dimension inspection marks
13
shown in
FIG. 7A
are formed in the silicon oxide film
23
.
Subsequently, a barrier metal film
25
is formed from, for example, TIN or TaN, to a thickness of about 1,000 angstroms on the internal surface of each of the opening sections
28
and the silicon oxide film
23
. Next, a tungsten film
26
is formed on the barrier metal film
25
to a thickness of about 4,000 angstroms, by means of sputtering. Further, unnecessary portions of the tungsten film
26
and barrier metal film
25
are removed from the silicon oxide film
23
by means of the CMP technique, whereby a structure such as that shown in
FIG. 7B
is produced.
Next, a product pattern (not shown), of the patterns formed in the manner as mentioned above, is subjected to a pattern defect inspection through use of an SEM or optical microscope. If defective patterns are found, the positions (coordinates) of defective patterns are specified while the patterns corresponding the mask dimension inspection marks
13
are taken as the points of origin (coordinate standards).
As mentioned above, utilizing mask dimension inspection marks
13
as coordinate standards when the coordinates of a defective pattern are specified during pattern defect inspection is effective for accurate specification of coordinates of the defective patterns.
However, the mask dimension inspection marks
13
are miniaturized for their originally-intended purposes in association with miniaturization of a semiconductor device and the product pattern
2
.
Therefore, the mask dimension inspection marks
13
patterned onto a semiconductor substrate by use of the conventional photo mask
10
are difficult to find.
Particularly, since the mask dimension inspection marks
13
are miniaturized; namely, since the line patterns
4
are miniaturized, as shown in
FIG. 7A
, the opening sections
28
are completely embedded even when the tungsten film
26
is formed to a small extent, as shown in FIG.
7
B. Further, if the wafer is smoothed by means of CMP after the formation of tungsten film
26
, the surface of the wafer assumes a mirror state, thereby rendering the minute line patterns
4
much more difficult to find.
Therefore, at the time of pattern defect inspection, it is difficult to use the mask dimension inspection marks patterned onto the semiconductor substrate as coordinate standards. Hence, accurate specification of coordinates of a defective pattern cannot be carried out.
SUMMARY OF THE INVENTION
The present invention has been conceived to solve the previously-mentioned problems and a general object of the present invention is to provide a novel and useful photo mask to be used for photolithography, and is to provide a novel and useful method of inspecting a pattern defect, and is to provide a novel and useful method of manufacturing a semiconductor device.
A more specific object of the present invention is to perform inspecting operation of a pattern defect utilizing mask dimension inspection marks drawn on a photo mask.
The above object of the present invention is attained by a following photo mask to be used for photolithography, and by a following a method of inspecting a pattern defect, and by a following method of manufacturing a semiconductor device.
According t
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Rosasco S.
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