Active solid-state devices (e.g. – transistors – solid-state diode – Alignment marks
Reexamination Certificate
2001-04-02
2002-06-04
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Alignment marks
C257S048000
Reexamination Certificate
active
06400038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alignment method for disposing an object to be inspected in position on a defect inspection apparatus in defect inspection of a semiconductor device such as a DRAM or a microcomputer, or a display device such as a TFT or a PDP. The invention also relates to a semiconductor device having a predetermined alignment mark.
2. Background of the Invention
The defect inspection is carried out halfway through a manufacturing process of the semiconductor device or the display device. The defect inspection apparatus requires accurate positioning of a testing chip that may be any part of a testing object, such as a semiconductor device, on a stage. Thus, an alignment mark for alignment is attached to the chip.
FIG. 28
is a plan view showing the component of a chip
200
on the testing object. A rectangular alignment mark
100
is attached to the chip. In order to ensure exact alignment motion on the chip
200
, an operator specifies a predetermined alignment point on the alignment mark
100
and teaches the coordinates of the alignment point and alignment mark image to the defect inspection apparatus.
FIG. 29
is a view of a teaching screen
300
. The alignment mark
100
is displayed thereon. For example, a point of intersection of sides
10
a
and
10
b
of the alignment mark
100
is specified as an alignment point AP
100
, and the image of the alignment mark
100
and the position of the specified alignment point AP
100
are taught to and stored in the defect inspection apparatus.
To locate the testing chip
200
in position in the defect inspection apparatus, the defect inspection apparatus searches the chip
200
located on the stage of the apparatus for the same figure as the taught alignment mark
100
, using image signal processing technique. Then, the alignment point AP
100
is decided on the basis of the discovered figure.
However, automatical searching of the alignment mark by the defect inspection apparatus is getting increasingly difficult due to, for example, an introduction of a CMP (Chemical Mechanical Polishing) method to a planalization technique for a wafer surface. When the automatical searching by the defect inspection apparatus fails, an operator searches for the alignment mark manually and locates the stage in position.
FIG. 30
is an illustration of the testing chip for the manual alignment operation. The operator search the chip
200
for the alignment mark
100
within a lens view field
400
of a lens of the defect inspection apparatus, while moving the chip
200
by driving the stage of the defect inspection apparatus. After discovering the alignment mark
100
, the operator decides the alignment point AP
100
from the discovered alignment mark
100
, following the procedure for designating the alignment point AP
100
. Then, the testing object which includes the chip
200
is moved by driving the stage of the defect inspection apparatus so that the specified alignment point AP
100
is superimposed on a center O of a target scope
50
displayed at the lens view field
400
. The target scope center O is the landmark of the apparatus detection point (coordination).
FIG. 31
shows that the alignment mark
100
has the indistinct threefold outline. This kind of phenomenon may occur in both cases where the alignment mark
100
is displayed on the teaching screen
300
so that the alignment point etc. is taught to the defect inspection apparatus, and where the alignment mark
100
is displayed at the lens view field
400
in inspection. Thus, aside from the case where one and the same operator conducts an inspection and teach the alignment point location to the defect inspection apparatus, when one operator conducts an inspection and another operator do the teaching, they may decide that a wrong position be the alignment point because of their differences of recognition of the figure outline. This prevents accurate alignment. Such a problem will arise, for example, when one operator teaches the alignment point AP
100
to the defect inspection apparatus while another operator decides an alignment point AP
101
in inspection. Further, when the point previously taught at the other process is taught as the alignment point, the same problem will arise because of differences of layers to be formed.
FIGS. 32
to
35
sequentially show the alignment method improving accuracy in alignment. With a coarse alignment mark
100
and a fine alignment mark
101
formed on a chip
201
, the testing chip is aligned on the basis of the coarse alignment mark
100
in the same way as described above (see FIG.
33
). The chip is then aligned on the basis of the fine alignment mark
101
after the lens set at the defect inspection apparatus is changed into a higher-powered one (see FIGS.
34
and
35
). However, since the coarse alignment mark
100
and the fine alignment mark
101
are separately formed, an area necessary to form the alignment mark is increased, and accordingly, an element forming area of the chip
201
is reduced.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to an alignment method comprising steps of: searching for an alignment mark of a testing object; recognizing first and second angles which are previously specified on the basis of the outline of a figure forming the alignment mark, from the discovered alignment mark; and deciding an intersection of a first bisector of the first angle and a second bisector of the second angle to be an alignment point.
Preferably, according to a second aspect of the present invention, in the alignment method according to the first aspect, each of the first and second angles is formed by specifying two line segments out of a plurality of line segments and crossing said line segments. The plurality of line segments form the outline.
Preferably, according to a third aspect of the present invention, in the alignment method according to the first aspect, a search for the alignment mark is conducted within a lens view field where a target scope having first and second axes is displayed. The first and second axes are arranged in parallel with the first and second bisectors, respectively.
Preferably, according to a fourth aspect of the present invention, in the alignment method according to the third aspect, the figure is a rhombus in shape, and adjacent two angles out of four angles of the rhombus are specified as the first and second angles.
Preferably, according to a fifth aspect of the present invention, in the alignment method according to the fourth aspect, obtaining an intersection of the first and second bisectors is equivalent to obtaining an intersection of two diagonals of the rhombus.
Preferably, according to a sixth aspect of the present invention, in the alignment method according to the third aspect, the alignment mark is a pattern formed on the testing object.
Preferably, according to a seventh aspect of the present invention, in the alignment method according to the sixth aspect, the pattern is a rectangle in shape, and two adjacent angles out of four angles of the rectangle are specified as the first and second angles.
Preferably, according to an eighth aspect of the present invention, in the alignment method according to the first aspect, the alignment mark includes a coarse alignment mark and a fine alignment mark. The alignment method comprises steps of: aligning the testing object on the basis of the coarse alignment mark, using a low-powered lens; and aligning the testing object on the basis of the fine alignment mark after changing the first low-powered lens into a high-powered lens. The fine alignment mark is formed in the coarse alignment mark.
Preferably, according to a ninth aspect of the present invention, in the alignment method according to the first aspect, the alignment mark consists of a plurality of figures.
Preferably, according to a tenth aspect of the present invention, in the alignment method according to the first aspect, the alignment mark is formed in a dicing line.
An eleventh
Miyazaki Yoko
Mugibayashi Toshiaki
Mitsubishi Denki & Kabushiki Kaisha
Nelms David
Nhu David
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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