JPS6239539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dividing a transparent plate-like body, such as sapphire, by laser irradiation.

In the dicing process, in which semiconductor elements are formed on a wafer such as sapphire, the chips are divided into small rectangular chips. A method is used in which a laser beam is focused and irradiated to form a linear groove, and the material is divided along the groove.

However, as the size of the sapphire wafer increases, the thickness of the wafer also increases, making it difficult to divide using conventional methods, creating difficulties in the production process. In other words, the scribing method using a diamond point has the disadvantage that it will cause scratches if the wafer is thick and will not break along the line even if the wafer is bent after drawing the line, whereas the laser scribing method uses a CO ₂ laser to create the element pattern on the wafer. When irradiated, the sapphire absorbs the CO ₂ laser's 10.6 μm wavelength light and forms the groove efficiently, but the large laser spot size increases the groove width, which reduces the degree of device integration. This leads to a decrease in productivity.

On the other hand, when a YAG laser beam with a wavelength of 1.06 μm, which has a shorter wavelength than a CO ₂ laser, is focused and irradiated,
YAG laser light has low absorption rate on sapphire substrates, so processing efficiency is poor and it is difficult to form deep grooves. However, it is possible to form narrow grooves on the surface. In other words, with a CO ₂ laser, it is possible to process wide and deep grooves, but it is difficult to process narrow grooves. YAG lasers can process narrow and shallow grooves, but it is difficult to process grooves that are sufficient for dividing, and problems have arisen in that it is particularly difficult to divide wafers with a thickness of 0.5 mm or more.

This invention was made in view of the above-mentioned circumstances, and its purpose is to irradiate the surface of a plate-shaped body with a short-wavelength Q-switch pulse laser, and irradiate the back side with a long-wavelength laser to form a plate-shaped body. The present invention aims to provide a method for dividing a plate-shaped body, which can improve yield by dividing the body.

The present invention will be explained below based on an embodiment shown in the drawings. 1 and 2 show a first embodiment of the present invention, which is an apparatus for carrying out a method of dividing a semiconductor wafer c having semiconductor elements b formed on a sapphire substrate a as a plate-shaped body. 1
is a YAG laser oscillator as a continuously pumped short-wavelength Q-switched pulse laser, and a beam shutter 2 and a dichroic mirror 3 are provided in the output optical path of the YAG laser oscillator. The dichroic mirror 3 refracts the laser beam 4, and the condensing lens 5 irradiates the semiconductor wafer c. In this case, the semiconductor wafer c is covered with a plastic film d that protects the semiconductor element b.
etc. are coated. Further, a TV monitor camera 7 for pattern observation is installed above the dichroic mirror 3 via a field lens 6. A reflected beam 8 irradiated by an illumination device (not shown) illuminating the surface of the semiconductor wafer c can be aligned through a field lens 6 with a TV monitor camera 7 for pattern observation.

On the other hand, the semiconductor wafer c is placed on a mounting table 9, which is supported by a Y-direction drive table 10, which is supported by an X-direction drive table 11. And these table 1
0 and 11 are predetermined programs on the pedestal 12 so that movement in the X and Y directions is controlled by the control unit 13. Further, a CO ₂ laser beam condensing lens 14 is provided in parallel with the YAG laser condensing lens 5, and this includes a CO ₂ laser oscillator 15.
The laser beam 16 is incident and focused through a beam shutter 17 and a reflecting mirror 18, which control ON/OFF control.

Next, a method of dividing the semiconductor wafer c using the apparatus configured as described above will be explained. First, as shown in FIG.
Along the line (scribe line) between the patterns formed on the semiconductor element b formed on the surface of
The semiconductor wafer c is positioned so as to be irradiated with the YAG laser beam 4 while being observed by a TV monitor camera 7 for pattern observation, and thin and shallow grooves e, e are formed on the surface of the semiconductor wafer c. In this case, the focal spot of the YAG laser beam can be formed to a diameter of 15 μm to 30 μm, and the distance between semiconductor elements b and b is usually 100 μm.
It is possible to form grooves e, which are sufficiently narrow compared to those formed with a width of about 100 mm. Moreover, the plastic film d covering the semiconductor wafer c at this time can prevent substances scattered when irradiated with the laser beam from the sapphire substrate a from adhering to the semiconductor elements b and damaging them.

Next, as shown in FIG.
is turned upside down and placed on the mounting table 9 with the back side of the sapphire substrate a facing up. In this state, align the Y-direction drive table 10 and the X-direction drive table 11 again so that they move in accordance with the grooves e and e that have already been formed, and then move the X-direction drive table 11 to the right in the figure. . Then, as shown in FIG. 2, the spot forming position 19 of the CO ₂ laser beam 16 is controlled by the control unit 13 so as to irradiate the back surface facing the grooves e, which have already been formed, thereby forming the grooves. In this case, even if the spot size of the CO ₂ laser beam 16 is large, no semiconductor element b is formed on the back surface, so even if a wide groove is formed to the middle of the semiconductor wafer, it will not damage the semiconductor element b on the front surface. .

In this way, after forming grooves e...,... corresponding to the front and back surfaces of the semiconductor wafer c, when bending force is applied to the semiconductor wafer c along the grooves e..., the bending force is applied to the semiconductor wafer c along the grooves e,... The semiconductor element b is divided into a plurality of parts along the grooves e.

In this case, since the semiconductor element b is formed on the surface of the sapphire substrate a, it is not affected even if a wide groove is formed on the back surface by the CO ₂ laser, and the narrow groove e is formed on the front surface by the YAG laser. ... is formed, and the semiconductor elements b can be integrated at high density. Furthermore, even if the sapphire substrate a is large and thick, it can be easily divided by deepening the grooves formed on its back surface.

In the above embodiment, the grooves are first processed using the YAG laser, and then the grooves are processed using the CO ₂ laser, but this order may be reversed. Also,
After forming thin grooves on the surface using a YAG laser,
Beam irradiation with a CO ₂ laser may be a pulsed beam or a continuous beam.

FIG. 3 shows a second embodiment of the present invention, in which a YAG laser oscillator 1 is installed on the front side of a semiconductor wafer c, and a CO ₂ laser oscillator 15 is installed on the back side. That is, the semiconductor wafer c is held in an upright position by a holder 20, this holder 20 is supported on an
It was supported by

With this configuration, after the groove processing by the YAG laser oscillator 1, the semiconductor wafer c
Grooving can be performed using the CO ₂ laser oscillator 15 without turning over the substrate, improving work efficiency. In addition, in this case, from the front side of the semiconductor wafer c,
Of course, YAG laser oscillation and CO ₂ laser oscillation from the back side may be performed simultaneously.

In FIG. 3, the same components as those in FIG. 1 are designated by the same numbers and their explanations will be omitted.

As explained above, this invention irradiates the front surface of a plate-shaped body with a short-wavelength Q-switch pulse laser, and irradiates the back surface with a long-wavelength laser to form corresponding grooves on the front and back surfaces. Since the plate-like body is divided by using the present invention, the plate-like body can be divided accurately and easily, and is suitable for dividing semiconductor wafers, for example, and has the effect that the yield of devices can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the first embodiment of the present invention, FIG. 2 is a schematic diagram showing the same during CO ₂ laser processing, and FIG. 3 is a schematic diagram showing the second embodiment of the invention. Configuration diagram. 1...YAG laser oscillator (short wavelength Q-switch pulse laser), 15... _CO2 laser oscillator (long wavelength laser), c...semiconductor wafer (plate-shaped body).

Claims (1)

[Claims] 1. A step of irradiating the surface of a plate-shaped body with a short-wavelength Q-switch pulse laser to form a shallow groove with a narrow width;
Similarly, a method for dividing a plate-shaped body comprises the steps of irradiating the back surface of the plate-shaped body with a long-wavelength laser and dividing the plate-shaped body along the short-wavelength Q-switch pulse laser irradiation line. 2 The surface of the plate-shaped body is a wafer surface on which semiconductor elements are formed on a sapphire substrate, and the short wavelength Q-switch pulse laser is a YAG laser, and the long wavelength laser is a CO ₂
2. The method for dividing a plate-shaped body according to claim 1, wherein the method comprises using a laser.