Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
1998-10-21
2001-11-20
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C438S132000, C356S401000
Reexamination Certificate
active
06320242
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a semiconductor device which is provided with a positioning pattern for accurately cutting fuse elements formed on semiconductor chip surfaces by laser beam irradiation.
In analog semiconductor integrated circuit devices, there is known a laser trimming method for adjusting analog characteristics. For example, a description of such a method is made in Japanese Patent Laid open No. H5-13670. An integrated circuit is two-dimensionally patterned on a semiconductor wafer, and thereafter measurements are mad of various integrated circuit electric characteristics in a wafer state. Then fuse elements provided in interconnections are selected to adjust analog characteristics and cut by laser beam irradiation. The laser trimming method such as this can make adjustments of the integrated circuit analog characteristics into desired characteristics through selectively cutting the fuse elements. A positioning pattern is provided on a surface of the semiconductor wafer in order to irradiate a laser beam onto predetermined fuse elements. FIG.
3
(
a
) is a plan view of a conventional positioning pattern, FIG.
3
(
b
) is a sectional view of the conventional positioning pattern, and FIG.
3
(
c
) is a diagram showing a variation in the light reflection amount where the positioning pattern is scanned over by irradiating a light beam along a C-C′ line direction. The conventional positioning pattern comprising, as shown in FIG.
3
(
a
), a so-called theta mark
301
provided in a scribe line area
203
to perform comparatively rough positioning in a semiconductor wafer rotating direction, and an X-direction trimming mark
302
and Y-direction trimming mark
303
for accurately positioning one by one semiconductor integrated circuit chips
201
placed in repetition. The theta mark
301
is desirably in a featured form different from that of the pad area
202
in the semiconductor integrated circuit chip
201
such that automatic recognition can be made.
Although a &Ggr;-form was shown in the example in FIG.
3
(
a
), another form may be satisfactory provided that it is in a featured form and recognition is easy to perform.
As shown in FIG.
3
(
b
) the conventional positioning pattern is formed by a rectangular aluminum film
105
on a silicon-oxide first insulation film
102
provided on the silicon substrate
101
. If a light beam is scanned over along a direction of a line C-C′ in FIG.
3
(
a
), a light reflection pattern as shown in FIG.
3
(
c
) is obtained due to high reflectivity of the aluminum film
105
. High light reflection amount is exhibited on the aluminum film
105
, while the portion having no aluminum film
105
becomes low in light reflection amount. The position as a reference for trimming is grasped using a part where the light reflection amount varies between the high light reflection amount and the low light reflection amount. The positional relationship between the positioning pattern and the fuse element formed by a polysilicon film of the integrated circuit is determined during design. Accordingly, by irradiating a light beam onto the positioning pattern to detect a position where the light reflection amount varies, a coordinate of a desired fuse element is calculated. By irradiating laser to that site, the fuse elements can be selectively trimmed.
In the conventional laser trimming, however, the fuse elements and the positioning pattern are formed by different thin films, making possible to perform accurate positioning. Where a reference position is detected by a positioning pattern that is an aluminum pattern and then laser trimming is made on the polysilicon thin film as a fuse element, there occurs mis-alignment in laser irradiation area
32
with respect to the fuse element
31
as shown in
FIG. 14
due to mis-registration occurring in the semiconductor process between the aluminum pattern and the elements formed by a polysilicon thin film. The laser irradiation area
32
is in an energy distribution of a Gaussian distribution, and low in energy intensity at a laser irradiation end. Consequently, if there is a mis-registration between the polysilicon film patterning and the aluminum film patterning during the wafer process, there arises a problem that stable cutting of the fuse elements becomes impossible. Incidentally, reference numeral
33
denotes burning in the underlying layer, and
34
denotes a portion left uncut of a fuse.
Also, in the conventional method the laser trimming positioning patterns are often placed in the scribe line area between the semiconductor integrated circuit chips. The scribe line area is a cutting allowance used for scribing (cutting) the semiconductor wafer. If there exist many films in this area, the dicing cutter edge might be damaged during dicing process, raising a problem that dicing process throughput is lowered and in an extreme case the semiconductor integrated circuit chip is damaged due to improper dicing.
Therefore, it is an object of this invention to provide a semiconductor device in which the fuse elements for the semiconductor chips can be accurately positioned and trimmed. Furthermore, it is an object of the present invention to enhance the trimming positioning accuracy thereby enabling reduction in size of the fuse element areas and hence cost.
It is another object to provide a semiconductor device with which no trouble is encountered in the dicing process by reducing the laser trimming positioning pattern area occupied in the scribe line area or introducing the laser trimming positioning pattern in the semiconductor integrated circuit chip.
SUMMARY OF THE INVENTION
In order to solve the problems the present invention adopted the following means.
(1) There is provided, in a semiconductor device having semiconductor integrated circuits arranged two-dimensionally placed in repetition in a matrix form through scribe lines on a surface of a semiconductor wafer, fuses to be cut by laser trimming provided on the semiconductor integrated circuits, and a laser trimming positioning pattern provided on the surface of the semiconductor wafer, the semiconductor device being characterized in that the laser trimming positioning pattern is structured by a thin film the same as that forming the fuse.
(2) A semiconductor device as recited in (1) is provided, wherein the laser trimming positioning pattern is formed by high light reflectivity regions and a low light reflectivity region sandwiched by the high light reflectivity regions. Pr conversely, a semiconductor device as recited in (1) is provided, wherein the laser trimming positioning pattern is formed by low light reflectivity regions and a high light reflectivity region sandwiched by the low light reflectivity regions.
(3) A semiconductor device as recited (2) is provided, wherein the low light reflectivity region is of dotted or lattice or stripe pattern for causing light diffused reflection.
(4) A semiconductor device as recited in (2) is provided, wherein laser trimming fuse elements are formed by a polysilicon thin film.
(5) There is provided, in a semiconductor device having the semiconductor integrated circuits arranged two-dimensionally in repetition in a matrix form through the scribe lines on a surface of the semiconductor wafer, the fuses provided on the semiconductor integrated circuits, and a laser trimming positioning pattern provided on the surface of the semiconductor wafer, the semiconductor device being characterized by comprising the laser trimming positioning pattern is formed by the high light reflectivity region and the low light reflectivity region, the high light reflectivity region being formed by a high light reflectivity film formed on a flat underlying layer, and the low light reflectivity region being formed by the high light reflectivity film formed on a dotted or lattice or stripe formed light diffusely reflective pattern structured by a same thin film as the fuse.
(6) A semiconductor device as recited in (5) is provided, wherein the laser trimming positioning pattern is formed by t
Ando Noritoshi
Kojima Yoshikazu
Sugiura Kazunari
Takasu Hiroaki
Yazawaw Michiaki
Adams & Wilks
Chaudhuri Olik
Peralta Ginette
Seiko Instruments Inc.
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