JPS5916343A - Scribing method for sos wafer - Google Patents

Abstract

PURPOSE:To enable to scribe a SOS wafer of a large plate thickness at a high speed and without covering a protection film by a method wherein the process of forming the first scribing groove in the surface of the SOS wafer and the process of forming the second one in the back surface are provided. CONSTITUTION:In the first process, scribe scanning is performed as arrow marks on the surface of the SOS wafer 8 with a diamond point, resulting in the formation of the first scribing groove 9 in lattice form. In the second process, while detecting the first scribing groove 9 in the surface of the SOS wafer 8, the back surface of said SOS wafer 8 is so irradiated with CO2 laser by a laser scribing device that the laser runs along the first scribing groove 9, resulting in the formation of the second scribing groove 10. Thereafter, the division of the SOS wafer 8 is performed by a normal means. Even a SOS wafer of the plate thickness of approx. 600mum can be so scribed that the chip dimensional accuracy after division becomes better, and a protection film is unnecessitated at the time of scribing.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides an S
The present invention relates to a method for scribing an OS wafer.

[Technical background of the invention and its problems]

As is well known, the method for scribing SOS wafers is as follows:
Examples include a diamond scribing method, a laser scribing method, and a blade dicing method. Below, the features and drawbacks of these methods will be explained in order.

(Re-diamond scribing method: This method uses S
While transporting the OS wafer vacuum-chucked chill pull in the X direction at predetermined intervals, make cuts in the Y direction with a diamond point under a constant load;
This method involves making cuts in the direction and then applying a rubber roller to divide the pieces. However, although this method has advantages such as a fast scribing speed (approximately 80 tMl/5ec) and no need to use a protective film to protect the elements formed on the SOS surface, it is difficult to remove the scribe blind. When the angle and load are increased, thick cracks occur in the scribe line and no stress is applied in the depth direction, making it impossible to divide a thick SOS with a film thickness of 600 μm or more. It had a drawback.

(2) Laser scribing method: This method irradiates the surface of a 6SOS wafer with laser light, melts and evaporates the irradiated part to create a narrow groove, and then bends and divides the SOS wafer along the groove. The type of laser beam includes YAG laser, C02 laser, etc. However, in the scribing method using a YAG laser, firstly, the wavelength is as short as 1.06 μm, so the absorption efficiency for the tsphire substrate constituting the SOS wafer is poor, and the scribing speed cannot be increased.

Second, a protective film is required to protect the elements formed on the surface of the SOS wafer from melt spatter during scribing. Third
However, when the depth of the machined groove becomes large, cracks occur. On the other hand, the scribing method using a C02 laser has a long wavelength of 10.6 μm, which has the advantage of good absorption efficiency and the ability to increase the scribing speed. (3) Blade dicing method: In this method, an ultra-thin circular grindstone is rotated at high speed to cut grooves on the surface of the SOS wafer, and the SOS wafer is cut along the grooves.・This is a method of completely folding and bending and dividing. However, this method
Since the sapphire substrate of the wafer has a high hardness, a thick blade must be used, resulting in a disadvantage that the width of each cut groove is wide and the dicing speed is slow.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for scribing SOS wafers having a large thickness and which can be scribed at full speed without covering with a protective film.

[Summary of the invention]

The present invention is a scribing method for SOS wafers that utilizes the respective advantages of the diamond scribing method and the CO2 laser scribing method based on the fact that the sapphire substrate constituting the SOS wafer is transparent. In the present invention, as a first step, the surface of the SOS wafer is scribed with a diamond point to form a first scribe groove. The formation of this first scribe groove eliminates the drawback that when dividing an SOS wafer scribed from the back side, each chip and f are divided depending on the cleavage direction of the sapphire substrate, making it impossible to obtain sufficient accuracy. It is done for the purpose of The diamond point scribing conditions may be such that an SOS wafer having a thickness k (approximately 100 to 150 μm) obtained by subtracting the depth of the groove scribed by the FC02 laser from the thickness of the SOS wafer can be divided. Further, the load applied to the scribe point may be 100 g or less. As a second step, a C02 laser is applied to the back side of the SOS wafer.
A second scribe groove is formed by scribing along the scribe groove. The width of this second scribe groove is usually wide, but in the case of the back side, there is no restriction on the width since it does not directly affect the elements on the front side.

[Embodiments of the invention]

The present invention will be explained based on FIGS. 1 to 3.

For now, a laser scribing device used for scribing using a CO2 laser in the second step of the present invention will be explained with reference to FIG. 1 in the figure is a support stand. On this support base l, eleventh and second tables 21 and 22 are sequentially provided which are movable in the X direction and the Y direction, respectively.

In addition, 1. An I/Y/4' motor and a DC motor (not shown) are connected to the second tables 21+22, respectively.

On the second table 22, there is provided a vacuum chuck 3 capable of rotating in a 90 degree direction, which suctions and fixes the SOS material onto the top thereof. Furthermore, a laser oscillator 4 is provided above the table 21+22. Near this oscillator 4, there is an optical system (dotted line) for irradiating the SOS wafer on the vacuum chuck 3 with a laser beam from the oscillator 4.
5 is provided. This optical system 5 includes a Rade oscillator 4
It consists of a reflector 6 that changes the direction of the laser beam from the reflector 6 by 90 degrees, and a lens 7 that focuses the laser beam from the reflector 6 onto a predetermined position on the SOS wafer.

The first step of the present invention is to prepare a 600 μm thick S as shown in FIG.
A third diamond point is placed on the surface of the OS wafer 8.
Perform scripe scanning as shown by the arrow in the figure to a depth of 4~
A grid-like first scribe groove 9 of 5 μm is formed.

In the second step, while detecting the first scribe groove 9 on the surface of the SOS wafer 18, the back surface of the SOS wafer 8 is coated with CO2 using the laser scribe unit shown in FIG.
A laser is irradiated along the first scribe groove 9 to form a second scribe groove 10. Thereafter, the division of SOS Ueno-8 will be carried out by normal means.

According to the above-mentioned present invention r (according to the SOS wafer 8
A first scribe groove 9 is formed using a diamond point on the front side, and a high-output CO2 is formed on the back side.
□Since the second scribe groove 10 is formed using a laser, even SOS wafers 1 with a thickness of about 600 μm can be scribed with good chip size accuracy after division, and there are advantages such as no need for a protective film during scribing. has.

In addition, since the sapphire substrate constituting the SOS wafer 8 is transparent, when forming the second scribe groove 10, the first scribe groove 1/) on the surface of the SOS wafer 8 is detected while the sapphire substrate is transparent. The CO2 laser irradiation can be easily performed, and the SOS wafer 8 can be divided more reliably.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a method for scribing an SOS wafer, which is capable of scribing an SOS wafer having a thickness of approximately 600 μm at high speed and satisfactorily without covering the wafer with a protective film.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a laser scribing device that irradiates a CO2 laser onto an SOS wafer used in the present invention, Fig. 2 is a cross-sectional view of an SOS wafer on which first and second scribe grooves have been formed, and Fig. 3 is a FIG. 2 is an explanatory diagram showing scribe scanning of an SOS wafer. 8... SOS wafer, 9... First scribe groove,
10...Second scribe groove.

Claims (1)

[Claims] A step of forming a first scribe groove by scribing with a diamond point on the front surface of the SOS wafer, and a step of irradiating the back surface of the wafer with a C02 laser along the first scribe groove to form a second scribe groove. 1. A method for scribing SOS weno, comprising the step of forming.