JPS5844738A - Scribing method for sapphire substrate - Google Patents

Abstract

PURPOSE:To prevent a fine crack at the periphery of a groove having 110- 200mum of depth formed on a sapphire substrate by scanning a laser condensed beam to the forward seam direction of the substrate and forming the groove. CONSTITUTION:A spot of a CW exciting Q switch YAG laser is repeatedly emitted to a sapphire substrate to form a groove. Then, a crack is produced at the periphery of a groove when the scanning speed is constant, and the characteristics of the depth of the groove are designated by a curve (a) in the reverse seam direction scanning and by a curve (b) at the forward seam direction scanning. On the contrary, no crack is formed with the depth less than 110mum, and the cracks are abruptly increased when deeper than 200mum in the forward seam direction. Accordingly, the laser condensed beam is scanned in the forward seam direction of the substrate to form grooves of approx. 110-200mum in depth in a lattice shape. Then, when the substrate is bent along the grooves, no crack is produced at the periphery of the groove, thereby improving the yield and the reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a method for forming a sapphire substrate by scribing #It-7 on a sapphire substrate for SOS (silicon on sapphire).
The present invention relates to a method for scribing an iris substrate.

An SOS semiconductor device in which a Si film is formed on a sapphire substrate and a semiconductor element is formed thereon has been put into practical use.

This semiconductor device has 1. 7. After forming a semiconductor element 2 on the upper surface of the laser substrate 1, a focused laser beam is irradiated along the f-xvt scribing lines 3 and 4 to form scribing grooves 5 and 6.
, and then the sapphire substrate 1 is bent and divided along the scribing grooves 5 and 6. In this case, as shown in FIG. 2, a laser oscillator such as a CO□ laser oscillator or a YAG laser oscillator is used as the oscillator 1 that emits a focused laser beam, and the laser beam L1 oscillated from this oscillator 1 is 8, the light is focused by a condensing lens 9, and is converted into a laser condensed beam L3.
The light is focused on the At this time, the sapphire substrate is placed on the IFiXY table 10 and scanned along the scribing @3.4.

However, the conventional method as described above has several problems. That is, the sapphire substrate 1 is coated with CO having a wavelength of 10.6 μm, which has a high light absorption rate.

When scribing a sapphire substrate 1 with a laser, the minimum size that can be focused on the surface of the sapphire substrate 1 by a condensing lens is about 100 μm, and the scribing line 3.4
When scanning along, the scribing width between the semiconductor elements 2 is usually formed to be less than 100 μm, so the processing width increases from the scribing width and damages the semiconductor element 2t. Therefore, the scribing width is 100 μm or less. Considering the feeding accuracy of the horizontal XY table 10 and the scribing width that takes into account the alignment error between the laser pitch and the scribing width, a scribing width of 200 μm or more is required. On the other hand, in YAG laser scribing, the laser substrate 1 has a low YAG laser absorption rate and poor processing efficiency; Tonize can focus light to a diameter of about 25 μm.

Therefore, scribing can be performed at a low scriber speed. However, if the depth of the scribing is shallow, even if the 7-layer substrate 1 is broken off, it will not be able to be separated from the scribing lines 1 and 4, resulting in cracks occurring in the semiconductor element 2 and fine cracks around the grooves 5 and 6. Rack occurs in the direction of expansion of the sapphire, causing damage to the inside of the semiconductor element 2, and if the sapphire is split by bending, the reliability of the semiconductor element 2 will be reduced even if the sapphire can be split along the scribing line 3.4. In this way, when scribing the sapphire substrate 1 with the #1 CO2 laser, the laser spot size is too large and when using the YAG laser, fine crevices and burrs occur around the scribing *i*g. The space required for scribing has become a major obstacle in improving the degree of integration of semiconductor devices.

According to the inventor's experiments, CW excitation Q on a sapphire substrate
Switch YAG laser fr20~40#mφ condenser 4
Focus the light on the target, and repeat the frequency of 10 to 20 kHz.
When a scribing groove is formed on a sapphire substrate by scanning at a scanning speed of several volts, fine curvature and scratches are observed around the groove. The results shown in FIG. 3 were obtained by changing the scanning direction of the laser condensing lens with respect to the Ayer substrate. In other words, curves a and b are obtained by scanning the sapphire substrate with the focused laser beam along the scribing line, and keeping the scanning speed constant. It turns out that it becomes like b, 7(,a
When the depth exceeds 110 μm, the occurrence of cracks and cracks increases rapidly), and when the depth is less than that, there is no occurrence. ・b is when scanning in the opposite direction to a, and when a scribing groove is formed deeper than 200 μm, It can be seen that the occurrence of cracks increases rapidly. In addition, a sapphire substrate with a diameter of φ4' and a thickness of 500 to 600 μm is normally used, and it was found that it could be easily divided after forming scribing grooves to a depth of 110 to 200 μm on this sapphire substrate. At a depth of 7 telIOμm or less, cracks and scratches occur less as shown in a, but the yield on semiconductor devices cannot be divided well by bending.On the other hand, when the scribing depth is 110μm or more, bending and separation are However, as shown in Figure 3, the fist was divided faithfully along the scribing groove and the yield was good.
If the depth of the scribing groove is 10 meters or more, microcracks and cracks may occur around the scribing line, which will reduce the yield of semiconductor devices.

This invention was made in view of the above-mentioned circumstances, and its purpose is to form scribing grooves by scanning a laser focused beam in the grain direction of a gold sapphire substrate, thereby increasing the yield of semiconductor devices. ), the present invention aims to provide a sapphire substrate scribing method that can improve reliability.

The present invention will be described below based on embodiments shown in the drawings. FIG. 4 shows embodiment #11 of this invention.
Reference numeral 21 denotes an XY wheel, which can be moved in the X and Y directions by a drive control device & (not shown).

A sapphire substrate 23 having a semiconductor element 22 on its surface is placed on this XY table 21, and this sapphire substrate 2S has scribing lines 24... and 25... in the X direction and the Y direction. is formed. In this state, using an emitted Q-noise laser, 20
The scribing line 24 of the sapphire substrate 21 is irradiated with a focused laser beam focused on a focused spot of ~40 μmφ, and the XY table 21 is driven to complete the sapphire substrate 2Jt.
- When scanning once in the normal direction (direction of arrow A) along the scribing line 24, a scribing groove 21 with a depth of 110 to 200 tam is formed along the scribing line 24 of the sapphire substrate 23. In this way, the focused laser beam was scanned along the scribing lines 24, and by moving the sapphire substrate 13f in the Y direction using the XY table 21, the scribing lines 24 were scanned.
The scribing grooves 27 can be formed along the sapphire substrate 23, and the scribing grooves xtr, xr are formed in the sapphire substrate 23. Next, this? 7 Remove the sapphire substrate J from the table 21, and scribe grooves formed on the sapphire substrate 23.
o It is divided into squares by folding along JF.

FIG. 5 shows a second embodiment of the present invention, in which the first scribing process and the second scribing process are performed.
Step scribing was performed. First, in the first scribing step, as shown in FIG. In the second scribing step, as shown in (B), the laser focused beam 28t-scans the scribing groove 26 obtained in the first scribing step to form a scribing groove SO with a depth of 110 to 200 μm. In this case, in the first scribing step, the sapphire substrate JJt is scanned forward in the opposite grain direction with respect to the laser focused beam 28, and in the second scribing step, the sapphire substrate JJt is scanned in the opposite direction. The sapphire substrate 23 is scanned back and forth in the grain direction. That is, by scanning the sapphire substrate 23t1 back and forth, the depth 11 is the same as in the first embodiment.
A scribing groove 30f of 0 to 200 μm can be formed.

Therefore, as shown in FIG.
1 placed on the XY table 2) as shown by the solid arrow,
Scribing grooves parallel to the X direction can be formed in the sapphire substrate 23 by repeating one reciprocating movement of forward scanning from the start point A to the turning point and then backward scanning. Next, move the X-Y table 21 to Y
By reciprocating in the Y direction, scribing grooves parallel to the Y direction can be formed.

In the second embodiment, in the first scribing step, the focus of the laser beam 28 is set on the surface of the sapphire substrate 230, and in the scribing step @2, the focus is obtained in the first scribing step. By moving to the inner bottom surface of the scribed groove 26, the processing speed can be improved. Furthermore, by moving the focal point in this way, it is possible to prevent processing from occurring from the back surface of the sapphire substrate 23 during the WJl scribing process, and during the second scribing process, the scribing groove 26 obtained during the first scribing process can be Since the sapphire substrate 23 is exposed on the light scattering surface, it is possible to prevent blurring from occurring on the back surface or inside of the sapphire substrate 23 even if the focal point is moved from the surface to the inside by about 50 μm.

As described above, the present invention is to scan a focused laser beam in the grain direction of a sapphire substrate to form a scribing groove tube with a depth of 110 to 200 fim on a sapphire substrate. Therefore, it is possible to prevent the occurrence of microcracks, burrs, etc. around the scribing grooves, thereby preventing damage to the semiconductor element and improving the yield in the bending and dividing process.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a semiconductor device, Fig. W42 is a schematic configuration diagram showing a conventional scribing method, Fig. 3 is Fig. 27 showing experimental results, and Fig. 4 shows a first embodiment of the present invention. 5(4) and 5(B) are sectional views showing a second embodiment of the present invention, and FIG. 6 is a plan view for explaining the entire operation. 23... Fire board, xg, zr... scribing groove. Applicant's agent Patent attorney Takehiko Suzue $49 21 Figure 6 of spear 1 Figure 5 of spear (A)

Claims (1)

[Claims] In the method of forming scribing grooves by irradiating the surface of a sapphire substrate with a focused laser beam tube, the focused laser beam is scanned in the grain direction of the seven-layer substrate to scribe the seven-layer substrate to a depth of 110 to 200 μm. A method of scribing a sapphire substrate by forming grooves with t% mold.