 |
Description  |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the semiconductor art and more
particularly to a semiconductor device capable of easy wafer positioning
by recognizing a pattern fabricated or formed on a wafer using a
photoetching process, for instance.
2. Prior Art
FIG. 1 shows an outline of a semiconductor device wherein elements 20a and
20b having approximately the same area are fabricated on the same chip 20
to be cut out of a wafer 10.
Referring to FIG. 1, 30 denotes a region by which two or more elements
formed on one chip are sectionalized. This region will be referred to as
"a street". Dot-dash lines X.sub.1, X.sub.2 and Y.sub.1, Y.sub.2 denote
scribe lines along which a wafer and a chip 20 on which are fabricated
elements 20a and 20b having approximately the same area are cut out. 5
denotes a monitor pattern formed at a corner of each chip for pattern
recognition.
Although a region along which a wafer is cut out is usually called "a
street", it will be understood that the term will be limited to the
previously mentioned particular case according to this invention.
Now, pattern recognition consists of irradiation, for example, by a
scanning laser beam, upon a wafer on which a pattern is fabricated and
sensing the pattern by means of an image sensor such as a CCD (charge
coupled device) for recognition of the entire pattern of an element or X-
and Y-axis scribe lines for wafer positioning control. This is followed by
processes such as alignment, scribing, etc.
Pattern recognition takes place, as shown at 4 in FIG. 1, by irradiating a
scanning laser beam upon the region 4 bounded by dotted lines on the wafer
10.
In pattern recognition, for instance, the region 4 bounded by dotted lines
on the wafer is irradiated with a scanning laser beam and the individual
element patterns are discriminated from each other by only sensing X- and
Y-axis scribe lines, without sensing the overall patterns, in order to
shorten the processing time.
Scattered reflections take place from the regions of scribe lines Y.sub.1
and Y.sub.2 and the street 30 within the chip as shown in FIG. 2, when the
wafer is irradiated with a laser beam.
Since the intensity of light reflected from these regions is attenuated, an
output waveform as shown in FIG. 2 is obtained. However, there may arise a
possibility of erroneous recognition of the individual patterns, because
the scribe lines and the street have approximately the same reflection
factor.
This will result in an alignment process under conditions of erroneous
pattern recognition or in cutting out chips along X.sub.1 and X.sub.2
scribe lines (dot-dash line) and streets Ya and Yb (shown dotted) and at
times, chips may be cut out so as to break up some elements into
fragments.
There has been a problem of the occurrence of defects in the alignment
process caused by erratic pattern recognition in cases where the pattern
is relatively simple, i.e., that of a variable-capacitance diode.
A process of irradiation of a laser beam upon the entire patterns to
recognize monitor patterns in the individual patterns to solve such a
problem used to become a cause for inability of a high-speed wafer
processing, that is, productivity used to be greatly sacrificed.
In other words, such a process could not be recommended and there remained
room for improvements.
SUMMARY OF THE INVENTION
A principal object of this invention is to provide a semiconductor device
having a pattern configuration capable of pattern positioning by
recognizing only a part of the pattern.
A semiconductor device according to this invention has been contrived to
fulfill the above-mentioned object.
The invention relates to semiconductor devices such that at least two
elements having approximately the same area are formed within the same
chip. These two or more elements formed on the same chip are so disposed
as to be divided into so many sections by a pattern having a street (or
streets) which is unparallel to any scribe line along which a wafer is cut
out.
This results in ease with which individual patterns fabricated on a wafer
can be recognized.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 shows an example of a pattern for a conventional semiconductor
device;
FIG. 2 is an output waveform diagram when the semiconductor device of FIG.
1 is irradiated with a laser beam and its reflected light is detected;
FIG. 3 is a sketch of a pattern for an embodiment of a semiconductor device
according to this invention;
FIG. 4 is an output waveform diagram obtained when the semiconductor device
of FIG. 3 is irradiated with a laser beam and its reflected light is
detected;
FIG. 5 is a sketch of a pattern for another embodiment of a semiconductor
device according to this invention;
FIG. 6 is a sketch of a pattern for still another embodiment of a
semiconductor device according to this invention; and
FIG. 7 is a sketch of a pattern for a further embodiment of a semiconductor
device according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, some preferred embodiments of semiconductor devices according to this
invention will be described by reference to FIGS. 3 through 7.
A variable-capacitance diode, for instance, employs a semiconductor device
containing two or more elements arranged on one chip.
A description will now be made of a semiconductor device notably effective
for such a pattern.
FIG. 3 illustrates a part of an embodiment in which semiconductor devices,
each containing two elements on the same chip, are arranged in succession
on a wafer.
Referring to FIG. 3, 1 denotes a part of a wafer which has been subjected
to a process such as diffusion, 2 denotes a chip on which elements 2a and
2b having approximately the same area are formed; 3 denotes a street by
which elements formed on the same chip 2 are divided into two sections.
X.sub.1, X.sub.2, . . . and Y.sub.1,Y.sub.2. . . shown by the dot-dash
lines are scribe lines.
The street 3 in FIG. 3 diagonally divides the chip 2 into two sections. The
elements 2a and 2b divided by the street 3 have approximately the same
area.
When the region 4 bounded by dotted lines on the wafer 1 is irradiated with
a scanning laser beam, the scribe lines, or X- and Y-axis are detected and
wafer position is determined, followed by an alignment process.
FIG. 4 is an output waveform diagram obtained when the wafer of FIG. 3 is
irradiated with a laser beam and a reflected light from the wafer is
detected. The ordinate and the abscissa denote respectively the intensity
of a reflected light and the time axis.
A in FIG. 4 denotes an output corresponding to scattered reflections of a
laser beam from scribe line Y.sub.1, and B denotes those from street 3.
Pattern recognition is carried out from the waveform shown in FIG. 4.
A great deal of scattered reflections corresponding to the width of the
scribe line Y.sub.1 will occur with a resultant great attenuation of the
reflected light, when a laser beam of a constant width scans the region 4
at a constant speed and the position of the scribe line Y.sub.1.
In contrast, when a laser beam scans the position of the diagonal street 3,
the time interval during which the street 3 is scanned will become longer
than that during which the position of scribe line Y.sub.1 is scanned. In
addition, an attenuation of the reflected light in the latter case will be
lesser than that in the former case. By detecting a reflected light from
such a wafer, the scribe lines Y.sub.1, Y.sub.2, . . . and the street 3
can easily be discriminated from each other.
When the region 4 on the wafer is irradiated with a laser beam, the
position of Y-axis on the wafer 2 is detected. The wafer position is
detected by applying a similar method for the X-axis.
Pattern recognition thus takes place without scanning a laser beam over the
entire pattern surface of a chip on the wafer 2. Therefore, high-speed
positioning can be effected. Needless to say, positioning may be effected
by detecting the street 3.
FIG. 5 also illustrates a case where elements 2a and 2b having the same
area are sectionalized by the street 3 having an angle with respect to a
scribe line. As compared with a case of diagonally sectionalizing the
elements 2a and 2b as shown in FIG. 3, the street 3 in FIG. 5 forms lesser
acute angles than in FIG. 3 with respect to the X- and Y-axis. This is
effective in improvement of withstand voltage characteristics of the
elements.
FIG. 6 shows an embodiment of a chip 2 wherein four elements 2a, 2b, 2c,
and 2d having approximately the same area are formed. As illustrated, two
streets 3 are diagonally arranged to intersect at the center of the chip
2, dividing the chip surface into four equal parts. If the same diffusion
process is applied, the electrical characteristics of all four elements
will be the same.
Even with this embodiment, the scribe line X- and Y-axis and the streets 3
can be easily discriminated from each other by irradiating the region 4
with a laser beam and measuring the reflected light.
This embodiment is advantageous in that the four elements having the same
area can be formed with ease and that recognition of the individual
patterns is quite easy.
FIG. 7 is an embodiment of this invention wherein chip 2 is divided into
two elements by an S-shaped street 3. Any suitable wave-type street may be
used instead of the S-shaped street.
Even with such a pattern configuration, the scribe lines and the street 3
can be easily discriminated from each other and pattern recognition
becomes easy by detecting a reflected light of a laser beam from a part of
the pattern, because a reflected light from the scribe lines Y.sub.1,
Y.sub.2, . . . differs in the attenuation amount from that from the street
3.
Furthermore, with the embodiments illustrated in FIGS. 5 and 7, the acute
angle parts can be made much less in number than those in the embodiments
of FIGS. 3 and 6. Therefore, the electrical characteristics of each
element can be considerably improved.
A semiconductor device according to this invention is represented by a
variable-capacitance diode, for instance, formed by a comparatively simple
pattern.
However, a similar concept will be obviously applicable to the integrated
circuitry, provided there exists a boundary region which divides the area
of a chip into sections in the initial diffusion process or as mentioned
previously.
A semiconductor device according to this invention is one in which two or
more elements are formed on the same chip and one provided with a pattern
effective in wafer positioning in alignment.
With a semiconductor device having such a pattern, alignment positioning is
greatly facilitated by sensing only a part of the entire pattern, without
the need for sensing the entire pattern.
Furthermore, there is an advantage such that elements having the same area
can be easily formed on the same chip.
According to a pattern of a semiconductor device of this invention, pattern
recognition becomes feasible by irradiating a laser beam upon an extremely
narrow range.
Such a pattern recognition system can claim to be suitable for high speed,
and effective wafer processing as compared with pattern recognition by
scanning a laser beam over the entire pattern surface, because only a part
of the wafer needs to be irradiated.
* * * * *
|
|
 |
|
 |
Description |
|
