Active solid-state devices (e.g. – transistors – solid-state diode – Test or calibration structure
Reexamination Certificate
2001-06-26
2003-05-06
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Test or calibration structure
C257S202000, C257S204000, C257S206000, C257S208000, C257S210000, C257S211000, C257S276000
Reexamination Certificate
active
06559476
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to method, structure, and layout for measuring bridge induced by amendment of mask layout.
2. Description of the Prior Art
Because pattern transferring process usually could not completely transfer pattern of mask into photoresist, and because consumption is not unavoidable during developing process and etching process. Practical patterns in and on substrate usually are different to patterns of mask, and following defects are unavoidable: end rounding, end shorting, corned rounding, critical dimension offset, and bridging phenomena.
Thus, in order to cancel previous defects in practical semiconductor fabrication, mask layout amendment, such as optical proximity correction (OPC), usually is performed after layout pattern is formed and before layout pattern is transferred. Moreover, because pattern of substrate usually is shorter/thinner than pattern of mask or is deformed, mask layout amendment usually widens/lengthens real required patterns of mask or adds auxiliary pattern(s) in neighborhood of real required patterns, to cancel the difference between substrate pattern and mask pattern, to let substrate pattern is equal to real required pattern of mask before mask layout pattern is performed. Furthermore, because mask pattern at least includes numerous elements in practical semiconductor fabrication, mask layout amendment almost is performed by computer in accordance with predetermined rule(s) and predetermined parameter(s). Hence, although both rule(s) and parameter(s) could be adjusted by the operator(s), but operator(s) could amend individual element whenever rule(s) and parameter(s) are determined.
Significantly, because critical dimension of semiconductor devices is continuously decreased and density of semiconductor devices is continuously increased, bridge (bridging phenomena) induced by amendment of neighboring patterns also is continuously increased. Refers to
FIG. 1A
,
FIG. 1B
,
FIG. 1C
, and
FIG. 1D
, which show relation between real required pattern
10
and amended pattern
11
, where
FIG. 1B
is the case no bridge happens and
FIG. 1D
is the case bridge happens. Reasonably, because bridge is the side effect during real required pattern
10
is changed into amend pattern
11
, appearance of bridge usually could not be eliminated during sequentially pattern transferring process and etching process. An then, undesired bridge usually appears in and on substrate, such as bridge between gate pattern (for forming gate) and neighboring contact pattern (for forming contact) or bridge between gate pattern of one transistor pattern and gate pattern of neighboring transistor pattern, and induces disadvantages such as abnormal short.
Therefore, how to certify no undesired bridge is induced by amendment of mask layout pattern is an indispensable part of mask layout amendment. For well-known technology, because distance between neighboring transistor is obviously larger than distance between gate and contacts of one transistor, also because gate of each transistor is obviously separated from gates of other transistors for popular layout, only bridge between gate and contacts which locates besides this gate is measured, refers to
FIG. 2A
,
FIG. 2B
, and FIG.
2
C.
Initially,
FIG. 2A
shows the transistor which should be formed. Layout of the transistor at least includes gate
21
and contacts
22
, which locate beside gate
21
and on device area
20
of mask. To check whether such transistor layout could be properly formed without bridge, pattern similar to
FIG. 2A
is formed on mask as
FIG. 2B
shows, approximated gate pattern
23
and some approximated contact patterns
24
are formed on amended device area
205
of mask. Herein, configuration of both approximated gate pattern
23
and approximated contact patterns
24
is essentially similar to the configuration of both gate
21
and contacts
22
, but the scale and relative distance could be different. Next, pattern shown in
FIG. 2B
is amended, such as optical proximity correction, and then amended pattern is transferred into substrate
25
to form gate
26
and some contacts
27
, as
FIG. 2C
shows. Herein, to emphasize how to measure bridge, only the case that some bridge occurs for closing gate
26
and contact
27
is shows. Afterward, electrically couples contacts
27
with a terminal, and then applies an electric signal on gate and measure whether this electrical signal appears on this terminal. Indisputably, electrical signal appears on terminal indicates that at least one contact
27
bridge with gate
26
, and then it is necessary to amended approximated gate pattern
23
and approximated contact patterns
24
of FIG.
2
B. Of course, it also could be viewed as this transistor layout could not be formed by current mask layout amendment or current mask layout amendment must be improved.
Surely, amendment of
FIG. 2B
not only requires message(s) about whether bridge is happened but also requires message(s) about what distance between gate
21
and contact
22
could prevent occurrence of bridge. Thus, as
FIG. 2D
shows, the popular solution is to form a mask layout pattern which connects several stimulated gate patterns
29
by one conductor line pattern
28
. Herein, each stimulated gate pattern
29
is briefly similar to, or even equal to, other stimulated gate patterns
29
, and each stimulated gate pattern
29
corresponds to several stimulated contact patterns
295
which are located beside it. Moreover, the distance between one stimulated gate pattern
29
and corresponding stimulated contact patterns
295
is different from the distance between each other stimulated gate pattern
29
and corresponding stimulated contact patterns. Clearly, after mask layout amendment and pattern transferring process, gates
26
and contacts
27
are formed on substrate
295
and are corresponding to stimulated gate patterns
29
and stimulated contact patterns
295
. In this way, by measuring which gate
26
has bridge(s) with corresponding contact(s)
27
and which gate
26
has no bridge with corresponding contact
27
, it is clear which stimulated gate pattern
29
and corresponding stimulated contact pattern
295
could to indicate both gate
21
and contacts
22
on mask, and could be ensure correctly pattern transfer without bridge.
However, owing to density of semiconductor devices is continuously increased and layout of semiconductor devices also is continuously evolved, not only distance between neighboring transistors approaches to the distance between gate and contacts of same transistor, but also gate of each semiconductor devices is close to gates of other semiconductor devices, such as static random access memory. Thus, conventional technology which only measures bridge between gate and contacts of same transistor could not handle all possible bridge. For example, while pattern to be formed is similar to
FIG. 2A
but gate
21
is longer than
FIG. 2A
, as
FIG. 2E
shows, it is possible that terminal of gate
26
is widen or is like a hammerheads, which usually called as endcap phenomena, although no bridge is happened. Obviously, whenever two neighboring transistors are so close to let they can not be separated during mask layout amendment, it is possible that gate of one transistor has bridge with gate of neighboring transistor, as
FIG. 2F
shows. Of course,
FIG. 2F
only shows one possible bridge, it also could be bridge between gate of one transistor and contact(s) of neighboring transistor, and also could be bridge between contact(s) of one transistor and contact(s) of neighboring contact(s).
As a summary, conventional technology only could measure bridge induced by both deformation of gate and deformation of contact(s) of same transistor during mask layout amendment, bit could not handle bridge induced by other reasons. Therefore, it is desired to amend conventional technology to correctly handle all possible bridge and to ensure accuracy of mask layout.
SUMMARY OF THE INVENTION
According to previous de
Flynn Nathan J.
Sefer Ahmed N.
United Microelectronics Corp.
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