Patent Application
20050127299
The present invention relates to an apparatus for checking a deteriorated layer formed in the inside of a workpiece along a dividing line by applying a laser beam capable of passing through the workpiece along the dividing line formed on the workpiece.
In the production process of a semiconductor device, a plurality of areas are sectioned by dividing lines called “streets” arranged in a lattice pattern on the front surface of a substantially disk-like semiconductor wafer, and a circuit such as IC, LSI or the like is formed in each of the sectioned areas. Individual semiconductor chips are manufactured by cutting this semiconductor wafer along the dividing lines to divide it into the areas in which the circuits are formed. An optical device wafer comprising gallium nitride-based compound semiconductors formed on the front surface of a sapphire substrate is also cut along dividing lines to be divided into individual optical devices such as light emitting diodes or laser diodes, and these devices are widely used in electric equipment.
Cutting along the dividing lines of the above semiconductor wafer or optical device wafer is generally carried out by a cutting machine called “dicer”. This cutting machine comprises a chuck table for holding a workpiece such as a semiconductor wafer or optical device wafer, a cutting means for cutting the workpiece held on the chuck table, and a cutting-feed means for moving the chuck table and the cutting means relative to each other. The cutting means has a spindle unit which comprises a rotary spindle, a cutting blade mounted to the spindle and a drive mechanism for rotary-driving the rotary spindle. The cutting blade comprises a disk-like base and an annular cutting edge which is mounted to the side wall periphery portion of the base and formed as thick as about 20 μm by fixing diamond abrasive grains having a diameter of about 3 μm to the base by electroforming.
Since a sapphire substrate, silicon carbide substrate, etc. have high Mohs hardness, cutting with the above cutting blade is not always easy. Further, since the cutting blade has a thickness of about 20 μm, the dividing lines for sectioning devices must be as thick as about 50 μm. Therefore, in the case of a device measuring about 300 μm×300 μm, the area occupied by the dividing lines is large, thereby reducing productivity.
Meanwhile, as a means of dividing a plate-like workpiece such as a semiconductor wafer, a laser beam processing method for applying a pulse laser beam capable of passing through the workpiece with its focusing point set to the inside of the area to be divided is attempted and disclosed by JP-A 2003-88975, for example. In the dividing method using this laser beam processing technique, the workpiece is divided by applying a pulse laser beam of an infrared range capable of passing through the workpiece from one side of the workpiece with its focusing point set to the inside to continuously form deteriorated layers in the inside of the workpiece along the dividing lines and exerting external force along the dividing lines whose strength has been reduced by the formation of the deteriorated layers.
To divide the workpiece having deteriorated layers formed in the inside along the dividing lines without fail by applying a pulse laser beam, the deteriorated layers must be reliably formed at a predetermined position in the inside of the workpiece. However, when a pulse laser beam is applied without positioning the focusing point of the pulse laser beam to the predetermined position in the inside of the workpiece, the deteriorated layers cannot be formed at the predetermined position in the inside of the workpiece. Since the deteriorated layers formed in the inside of the workpiece cannot be checked from the outside, there is a problem that when external force is exerted to the workpiece having no deteriorated layers in the inside along the dividing lines, the workpiece may be broken.
It is an object of the present invention to provide an apparatus for reliably checking a laser processed deteriorated layer formed in the inside of a workpiece by applying a laser beam to the workpiece.
To attain the above object, according to the present invention, there is provided an apparatus for checking a deteriorated layer formed in the inside of a workpiece by applying a laser beam capable of passing through the workpiece to the workpiece, comprising:
Preferably, the apparatus comprises which comprises a scanning-feed means for moving the light application means, the light receiving means and the workpiece holding means in a predetermined scanning-feed direction relative to one another. Preferably, the light application means irradiates an infrared laser beam.
Since the apparatus for checking a laser processed deteriorated layer according to the present invention is constituted as described above, the deteriorated layer which is formed in the inside of the workpiece and cannot be checked from the outside can be checked without fail.
FIGS. 8(a) and 8(b) are diagrams for explaining laser processing for forming a deteriorated layer in the inside of the semiconductor wafer shown in
To form the deteriorated layer in the inside of the semiconductor wafer 10 along the dividing line 11, the semiconductor wafer 10 is placed on the chuck table 20 of a laser beam processing machine in such a manner that the back surface 10b faces up and suction-held on the chuck table 20 as shown in FIGS. 8(a) and 8(b). After the semiconductor wafer 10 is suction-held on the chuck table 20, the dividing line 11 is detected from the back surface 10b by an infrared aligning means (not shown), and the chuck table 20 is moved to a laser beam application range where the condenser 21 of laser beam application means for applying a laser beam is located, to bring one end (left end in
The laser processing conditions in the above laser processing are set as follows, for example.
After the laser processing is carried out along the dividing line 11 in the predetermined direction formed on the wafer 10 as described above, the chuck table 20 or the laser beam application means is indexing-fed a distance corresponding to the interval between the dividing lines 11 in the indexing-feed direction perpendicular to the sheet surface in FIGS. 8(a) and 8(b) to further carry out the above laser processing. After the above laser processing is carried out on all the dividing lines 11 formed in the predetermined direction, the chuck table 20 is turned at 90° to carry out the above laser processing along dividing lines formed in the direction perpendicular to the above predetermined direction subsequently, thereby making it possible to form deteriorated layers 110 in the inside of the semiconductor wafer 10 along all the dividing lines 11. When a low-dielectric insulating film (Low-k film) or test element group (Teg) is not formed on the top surface of the dividing lines 11 formed on the front surface 10a of the semiconductor wafer 10, a pulse laser beam may be applied to the workpiece from the front surface 10a side of the semiconductor wafer 10 to form the deteriorated layers 110.
The deteriorated layer 110 formed in the inside of the semiconductor wafer 10 along the dividing line 11 cannot be checked from the outside as described above. Therefore, it is necessary to check whether the deteriorated layer 110 is formed at the predetermined position in the inside of the semiconductor wafer 10 without fail. The apparatus for checking a laser processed deteriorated layer in the inside of the workpiece will be described hereinbelow with reference to
The above chuck table mechanism 3 comprises a pair of guide rails 31 and 31 that are mounted on the stationary base 2 and arranged parallel to each other in the direction indicated by the arrow X, a first sliding block 32 mounted on the guide rails 31 and 31 in such a manner that it can move in the direction indicated by the arrow X, a second sliding block 33 mounted on the first sliding block 32 in such a manner that it can move in the direction indicated by the arrow Y, a support table 35 supported on the second sliding block 33 by a cylindrical member 34, and a chuck table 36 as a workpiece holding means. This chuck table 36 is made of a porous material, and a semiconductor wafer as the workpiece is held on the chuck table 36 by a suction means that is not shown. The chuck table 36 is turned by a pulse motor (not shown) installed in the cylindrical member 34. An infrared aligning means (not shown) is arranged above the chuck table 36.
The above first sliding block 32 has, on its undersurface, a pair of to-be-guided grooves 321 and 321 to be fitted to the above pair of guide rails 31 and 31 and has, on its top surface, a pair of guide rails 322 and 322 formed parallel to each other in the direction indicated by the arrow Y. The first sliding block 32 constituted as described above can move in the direction indicated by the arrow X along the pair of guide rails 31 and 31 by fitting the to-be-guided grooves 321 and 321 to the pair of guide rails 31 and 31, respectively. The chuck table mechanism 3 in the illustrated embodiment comprises an indexing-feed means 37 for moving the first sliding block 32 along the pair of guide rails 31 and 31 in the indexing-feed direction indicated by the arrow X. The indexing feed means 37 has a male screw rod 371 arranged between the above pair of guide rails 31 and 31 and in parallel to them, and a drive source such as a pulse motor 372 for rotary-driving the male screw rod 371. The male screw rod 371 is, at its one end, rotatably supported onto a bearing block 373 fixed on the above stationary base 2 and is, at the other end, transmission-coupled to the output shaft of the above pulse motor 372 by a speed reducer that is not shown. The male screw rod 371 is screwed into a threaded through-hole formed in a female screw block (not shown) projecting from the undersurface of the center portion of the first sliding block 32. Therefore, by driving the male screw rod 371 in a normal direction or reverse direction with the pulse motor 372, the first sliding block 32 is moved along the guide rails 31 and 31 in the indexing-feed direction indicated by the arrow X.
The above second sliding block 33 has, on its undersurface, a pair of to-be-guided grooves 331 and 331 to be fitted to the pair of guide rails 322 and 322 on the top surface of the above first sliding block 32 and can move in the scanning-feed direction indicated by the arrow Y by fitting the to-be-guided grooves 331 and 331 to the pair of guide rails 322 and 322, respectively. The chuck table mechanism 3 in the illustrated embodiment comprises a scanning-feed means 38 for moving the second sliding block 33 in the scanning-feed direction indicated by the arrow Y along the pair of guide rails 322 and 322 on the first sliding block 32. The scanning-feed means 38 has a male screw rod 381 which is arranged between the above pair of guide rails 322 and 322 and in parallel to them, and a drive source such as a pulse motor 382 for rotary-driving the male screw rod 381. The male screw rod 381 is, as its one end, rotatably supported onto a bearing block 383 fixed on the top surface of the above first sliding block 32 and is, at the other end, transmission-coupled to the output shaft of the above pulse motor 382 by a speed reducer that is not shown. The male screw rod 381 is screwed into a threaded through-hole formed in a female screw block (not shown) projecting from the undersurface of the center portion of the second sliding block 33. Therefore, by driving the male screw rod 381 in a normal direction or reverse direction with the pulse motor 382, the second sliding block 33 is moved along the guide rails 322 and 322 in the scanning-feed direction indicated by the arrow Y.
The above light application means 4 and the above light receiving means 5 are opposed to each other along the pair of guide rails 31 and 31 of the above chuck table mechanism 3 with the above chuck table 36 interposed therebetween. That is, the light application means 4 and the light receiving means 5 are opposed to each other in the direction perpendicular to the scanning-feed direction indicated by the arrow Y.
The above light application means 4 is so constituted as to apply light capable of passing through the workpiece. Here, the light capable of passing through the workpiece will be described hereinbelow.
The above light receiving means 5 comprises an infrared image pick-up device (infrared CCD), and its light receiving surface is inclined to form the same angle θ as the angle θ at which an infrared laser beam is applied to the exposed surface (top surface) of the wafer 10 held on the chuck table 36 as shown in
The apparatus for checking a laser processed deteriorated layer in the illustrated embodiment is constituted above, and its function will be described hereinbelow with reference to
The semiconductor wafer 10 having deteriorated layers formed in the inside along the dividing lines 11 by laser processing as described above is placed on the chuck table 36 of the checking apparatus shown in
Thereafter, as shown in
In
While the present invention has been described as related to the embodiment shown in the accompanying drawings, it is to be understood that various changes and modifications may be made in the invention without departing from the spirit and scope thereof. For example, in the illustrated embodiment, the light receiving means 5 is inclined at the same angle θ as the angle θ at which an infrared layer beam is applied by the light application means 4. The light receiving means 5 may be arranged in the diffraction direction of the infrared laser beam so as to receive the diffracted infrared laser beam.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-417869 | Dec 2003 | JP | national |
