JPS5942193A - Laser scribing method - Google Patents

Abstract

PURPOSE:To divide the respective elements of a semiconductor substrate, by irradiating the YAG laser which is outputted by a pulse excited ultrasonic Q switch and is condensed to the surface of the substrate opposite to the surface formed with a p-n junction layer thereby performing removal and generating cleavage with one time of irradiation. CONSTITUTION:The pulsed electric power from a main power source 13 is controlled by a switching circuit 11, by which the light emission of a flash lamp 6 is controlled and a YAG rod 5 is excited at repetitive periods. At this same instant, output energy is changed by an ultrasonic Q switch 9 and is irradiated to a semiconductor substrate 18 from the surface opposite to the surface formed with the p-n junction layer 22 of said substrate after the energy is condensed with a condenser lens 17. Worked holes 26 are successively superposed at the depth larger than half the thickness and are formed like a groove on the substrate 18 on a stand 21 on the incident side of the laser light L, whereby cleavage parts are formed from the bottoms of the holes 26 toward the surface in contact with the stand 21. The stand 21 on an X-Y table 19 is moved and controlled by a driving device 20 for the table 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention j] The present invention relates to a laser scribing method for dividing a semiconductor substrate.

[Technical background of the invention and its problems]

The so-called scribing process for dividing each element formed on a semiconductor substrate includes a method using laser light irradiation in addition to a mechanical method using a diamond blade. Although laser scribing has the advantage of not causing chipping unlike mechanical cutting, it does have an impact on semiconductor devices.

Whether it is done mechanically or with a laser, the splitting process is generally done in two steps: one is not cut completely in the swiping process, but the part is scribed halfway, and the next splitting process is done in the blaking process. If the entire process is cut with the intention of completing the process in one step, there is a problem in that the element is directly affected by heat. In the case of the above laser method, a pulse output carbon dioxide laser, a continuous excitation Q-switch Nd; YAG laser, etc. are used. The former laser has poor absorption into semiconductor materials;
The latter type of laser had a problem with the output power. [Object of the Invention] The present invention aims to absorb the semiconductor substrate and generate force on the table surface and the substrate, and to irradiate the semiconductor substrate once without directly exerting a thermal effect on the elements. This provides a scribing method for dividing a substrate.

[Summary of the invention]

Using a focused YAG laser output by a pulse-excited ultrasonic Q-switch, the layer containing the PN layer on the PN bonding layer formation side of the semiconductor substrate is removed along the scribe line to a depth at which an interosseous action occurs. This is done in succession.

[Embodiments of the invention]

The overall configuration mainly consisting of an apparatus for carrying out the present invention will be explained with reference to FIG. -The above configuration is the laser agitation section (
J), power supply unit (2) and emitted -3, -h laser beam (
It can be divided into three major elements: processing part (3) by L). The laser oscillation unit (1) is a general solid-state laser oscillation unit, in which an elliptical condenser mirror (4) housed in an insulating frame (not shown) includes a Nd; Furano sea lamps (6) are provided and are constantly water-cooled during oscillation. (7) is a high-reflection mirror, and (8) is an outgoing mirror, which are both J-length mirrors provided on the extension axis of the Nd;YAG rod (5). High reflective tax (7) and Nd;
YAG port, C (5) (!: Ultrasonic θ switch (
9) is provided. (1 (ll) (d) This is the active part of the switch. Also, the power supply part (2) supplies the DC current charged to the lamp (6) to the switching circuit (1).
1) and the main power supply u31 supplied via the inductance 11, and the stabilizing resistor U<31 connected in parallel with the main power supply u31 supplied through the inductance 11 to discharge the direct current for the simmer discharge to drive the 7-point filter lamp (6) wX. The auxiliary power supply u51 is supplied via the auxiliary power supply u51. On the other hand, the processing part (3) is exposed to laser light (L
) at right angles, a condensing lens surface disposed on the path of the reflected laser beam, and a semiconductor substrate, which is a broken workpiece, at the condensing position of the condensing lamp 117). It consists of an XY table (19) placed so as to be placed thereon and a 1vg moving device for the XY table equipped with a control mechanism.

Note that the semiconductor substrate (1,83 XY table (in particular, the mount t2, which is not connected to the device)) is placed on the semiconductor substrate (
The area around the I mark is visible and is sunken. In addition,
One surface of the semiconductor substrate in contact with the pedestal (I) is a surface on which a PN junction layer (2) is formed.

In the above configuration, by controlling the pulse power from the main mold #, u3) by the switching circuit (1υ), the light emission of the flannel lamp (6) is controlled by the secondary side I L Nd ;
'1'A() Rod (5) raises Jtin with a pulse width l and a repetition period of 1'o.

In this case, at the same time, high-frequency power 10 = 200 Ki (in the range of z (JN-OFF) is applied to the ultrasonic Q switch (9).
'Repeat around NJ i+te. This repeat ON/0
At the upper F frequency (, p), a train of short pulses (23) with a short pulse width as shown in (bl) is repeated rapidly during the time difference.
At Hz, the pulse width is 50 x at 20 μsec intervals.
A laser output waveform train (24...) with a narrow pulse width of about 10-Qsec (50+1 seconds) and a high peak output is oscillated as a group of 50 pulses. Pulse train of 10,000 beak output is 100 to 2 per second
00 times originator 200 times Kono-tsu (7) Pulse W '47
When a silicon wafer with a thickness of 5 mm is focused and irradiated, one pulse reaches a depth of 9.4 #l×4. If we change the width of this group of pulse trains, the output voltage of the pulse group will change even if the main type i (13 DC voltage is constant)
Since the machining depth changes proportionally, the machining depth, that is, the scribing depth, can be controlled. By irradiating such a group of pulses along the scribe line, a continuous row of holes or lines can be created. can be formed. In this case, ,
t(7) This shows that one scale can be formed in the darkness, and about 50 pulses with short pulse widths will be incident on the middle section of one hole as described above. Therefore, when machining a hole, four
At a high repetition rate with a small value, the average output energy during the pulse is more than 100 times that of a conventional CWQ switch laser (i.e., if the total pulse energy of one group is IJ and the duration χ = 1 ms, the average output energy is about 1 kW). , conventional C
WQ switch scriber has an average output of 10W)
This ability to irradiate can cause a powerful explosion inside the liquid hole during processing, and the explosion can be especially powerful since it is the output of a Q-switch pulse train. Therefore, even if the molten semiconductor material is released from the inside of the hole to the outside and the depth of the hole does not reach the full thickness, a strong shock wave will be generated from the tip of the hole in the unprocessed table 11TI. is given, and a hole can be created in a crystalline semiconductor material during hole machining.

The above will be specifically explained in FIG. 3 fa) and +b. The shape of the semiconductor substrate α peak is rectangular, and the laser beam (C1) is focused and irradiated along the processing scanning line (C) on the outer periphery of the semiconductor substrate. On the incident side of the machined holes (20...) are formed in a groove-like part by overlapping one after another at a depth of more than half the thickness.When forming the machined holes (26-),
An interosseous part (27) is formed from the bottom of the pear table 121) toward the 7th turn, and a cutting line is formed along the processing scanning line (2).

〔Effect of the invention〕

As described above, the hole is drilled to a depth that creates a gap between the bones that reaches one side due to the shock waves generated when drilling the hole, and the laser beam irradiation is scanned so that the holes overlap each other.
As a result, it has become possible to perform complete cutting in one step or with a weak braking force, without requiring the conventional operation of applying a strong force to the wafer for braking. Moreover, since the laser irradiation only reaches about half the thickness, there is no fear of direct thermal influence on the PN bonding layer, which is the surface in contact with the pedestal surface.

Furthermore, even in thick semiconductor substrates, deep grooves can be formed by changing the -Cruz excitation width and output intensity. Even in this case, the average excitation power can be restricted to a predetermined power that is less than Nd; the YAG rod will break due to thermal stress. It can be made wider. Therefore, it is possible to perform element division even on thick substrates. In addition, compared to conventional scribing using a laser beam, there is less re-solidified material remaining in the scribing groove, so for example, when machining the area along the periphery of the workpiece as shown in Figure 3(a), the frame width This has the effect that the bonding area can be used more widely and effectively.

[Brief explanation of drawings]

Figure 1 shows the configuration of an apparatus for explaining the present invention.
Fig. 3fa) is a plan view showing an example of processing phototaxis in the present invention.
This is required in the analytical surface diagram shown along line A-A in a).

Claims (1)

[Claims] In a laser scribing method in which a laser beam is focused and irradiated from the surface opposite to the surface on which the PN junction layer is formed of a semiconductor substrate, the laser beam is repeatedly outputted by a pulse-excited ultrasonic Q-switch and the focused YA
A laser scribing method comprising: using a G laser beam to remove the layer including the PN junction layer on the PN junction layer formation side to a depth that causes a 9YJ opening action;