Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-08-10
2004-05-04
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S077000
Reexamination Certificate
active
06731373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for imprinting wafer-identifying information, and an exposure method and apparatus for imprinting wafer-identifying information, on wafers on which a plurality of thin-film devices are formed in a batch.
2. Description of the Related Art
Thin-film devices produced by thin-film fabrication technology include semiconductor devices and thin-film magnetic heads and the like. To produce such thin-film devices, a plurality of thin-film devices are formed in a batch on a wafer (substrate) using the thin-film fabrication technology or the like and thereafter this wafer is separated into individual thin-film devices.
Generally, for example, in order to control the fabrication process and to prevent the occurrence of defective devices, each of the aforementioned thin-film devices are provided with wafer-identifying information for identifying a wafer to which the thin-film device belongs and device location information for identifying the position of the thin-film device in the wafer. These pieces of information are imprinted on each wafer before the wafer is separated into individual thin-film devices. However, the step of imprinting the information may be performed before, during, or after the formation of the thin-film devices.
Conventionally, the following two methods have been typically adopted as methods for imprinting wafer-identifying information and device location information on wafers. The following explanations will be given assuming that a wafer is imprinted with, as wafer-identifying information, a wafer identification number that is different from one wafer to another, and, as device location information, a device location number that indicates a position of the thin-film device in a wafer.
According to the first method, device location numbers are imprinted using photolithography and wafer identification numbers are imprinted by laser marking. The first method is explained below with reference to the flowchart of FIG.
11
. According to the first method, initially, a predetermined base is coated with a resist to form a resist layer (step S
201
). Then, using a mask having a pattern of a device location number drawn thereon, this resist layer is exposed in a batch to light for forming a latent image of the device location number (step S
202
). After the exposure, the resist layer is developed to form a patterned resist layer (step S
203
). Thereafter, the patterned resist layer may be entirely left unremoved so as to express the device location number with this patterned resist layer. Alternatively, using the patterned resist layer as a mask, the base of the patterned resist layer may be etched by ion milling or the like to imprint the device location number thereon. Then, a wafer identification number is entered to a laser marking apparatus (step S
204
). Subsequently, using the laser marking apparatus, the wafer identification number is imprinted by means of a laser beam, that is, laser marking is performed (step S
205
).
The second method employs laser marking to imprint wafer identification numbers and device location numbers. Now, the second method will be explained below with reference to the flowchart of FIG.
12
. According to the second method, a wafer identification number is entered to a laser marking apparatus (step S
211
). Then, using the laser marking apparatus, a wafer identification number and a device location number are imprinted by means of a laser beam, that is, laser marking is performed (step S
212
). The device location number is generated in the laser marking apparatus by means of software, for example, so as to correspond to the thin-film device to be imprinted therewith.
The aforementioned first and second methods are described, for example, in Published Unexamined Japanese Patent Application (KOKAI) No. Hei 9-50606.
FIG. 13
is an explanatory view illustrating an exemplary configuration of the laser marking apparatus employed in the aforementioned first and second methods. The laser marking apparatus has an X-Y stage
302
, on which a wafer
301
is to be placed, capable of moving in X and Y directions that are orthogonal to each other. The apparatus further has an X-direction position controller
303
for controlling the position of the X-Y stage
302
in the X direction, and a Y-direction position controller
304
for controlling the position of the X-Y stage
302
in the Y direction. The laser marking apparatus further has a laser beam source
305
for emitting a laser beam, a lens
306
for condensing the laser beam emitted from the laser beam source
305
, and a mirror
307
for reflecting the laser beam condensed by the lens
306
to irradiate the wafer
301
on the X-Y stage
302
with the reflected laser beam. The laser marking apparatus further has a controller
308
for controlling the X-direction position controller
303
, the Y-direction position controller
304
, and the laser beam source
305
, and has a storage device
309
connected to the controller
308
. The storage device
309
stores the position in the wafer
301
to imprint information thereon, and the information to be imprinted on the wafer
301
, and provides the controller
308
with these pieces of information as appropriate.
In accordance with the information stored in the storage device
309
, the controller
308
of the laser marking apparatus shown in
FIG. 13
allows the wafer
301
to be irradiated with the laser beam emitted from the laser beam source
305
while controlling the X-direction position controller
303
and the Y-direction position controller
304
to vary the position of the X-Y stage
302
and the wafer
301
placed thereon. This makes it possible to imprint the wafer identification number and the device location number at the predetermined position on each thin-film device in the wafer
301
. Instead of varying the position of the X-Y stage
302
and the wafer
301
, the laser beam may be moved by moving mirror
307
, for example.
In both the first and second methods, at least wafer identification numbers are imprinted by laser marking, on the thin-film devices of a wafer one by one. Accordingly, there is a problem that much time is required for imprinting the information including the wafer identification number, and the time required for imprinting the information would increase as the number of thin-film devices on a wafer increases. In particular, in the case where the thin-film device is a thin-film magnetic head, the size of a wafer tends to increase while the thin-film device decreases in size. For this reason, it is conceivable that the number of thin-film devices in a wafer will become greater in the future and the time required for imprinting information such as wafer identification numbers per wafer will increase accordingly.
For example, suppose that information such as wafer identification number is imprinted by laser marking and that 0.5 seconds are required for imprinting on each thin-film device. In this case, for a 3-inch (76.2 mm) wafer having 4,000 thin-film devices formed thereon, 2,000 seconds (about 33 minutes) would be required for imprinting on each wafer. For a 6-inch (152.4 mm) wafer having 16,000 thin-film devices formed thereon, 8,000 seconds (about 2 hours and 13 minutes) would be required for imprinting on each wafer.
Device location numbers are not different among wafers having the same type of thin-film devices formed thereon. Accordingly, for such wafers, it is possible to imprint device location numbers through photolithography using a common mask on which the device location number is drawn, as in the first method. In the first method, the device location number is imprinted through photolithography, which saves the time required for laser marking. However, it requires an additional step of performing photolithography to imprint the device location number.
Published Unexamined Japanese Patent Application (KOKAI) No. Sho 62-20116 discloses a technique for imprinting device location numbers in a batch on all the devi
Adams Russell
Esplin D. Ben
TDK Corporation
LandOfFree
Method for imprinting a wafer with identifying information,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for imprinting a wafer with identifying information,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for imprinting a wafer with identifying information,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3266506