JP-7855430-B2 - Method for processing wafers and apparatus for processing wafers

JP7855430B2JP 7855430 B2JP7855430 B2JP 7855430B2JP-7855430-B2

Inventors

水谷彬

Assignees

株式会社ディスコ

Dates

Publication Date: 20260508
Application Date: 20220711

Claims (7)

A method for processing wafers, A modified layer formation step involves positioning the focal point of a pulsed laser beam with a wavelength that is transparent to the wafer within the line to be divided and irradiating it, while simultaneously feeding the wafer through the process to continuously form a modified layer within the line to be divided, The process includes a splitting step of applying an external force to the splitting line on which the modified layer has been formed to split it, In the modified layer formation process, A focusing point setting step, which sets the focusing point to be located at a first depth and a second depth shallower than the first depth from the side on which the pulsed laser beam is irradiated, A step to calculate arrival time, in which the arrival time for the thermal shock wave to reach the second depth is determined by using the speed at which the thermal shock wave propagates when a modified layer is formed at the first depth as the denominator and the difference between the first depth and the second depth as the numerator, A total time calculation step involves adding the arrival time to the time when the thermal shock wave reaches the second depth and the modified layer is formed at the second depth, in order to obtain the total time. A pulse width setting step in which the pulse width of the pulsed laser beam is set to a time equal to or greater than the total time, A method for processing wafers including [a specific component].
In the light-gathering point setting step, The wafer processing method according to claim 1, wherein the first depth and the second depth are set such that the arrival time falls within the time it takes for the thermal shock wave to be generated, attenuated, and disappear.
The wafer processing method according to claim 2, wherein, when the propagation speed of the thermal shock wave in the wafer is 182 m/s, and the time until the thermal shock wave is generated, attenuated, and disappears is 110 ns, the focusing point is set such that the difference between the first depth and the second depth is 20 μm or less, and the pulse width is set to 200 to 500 ns in the pulse width setting step.
In the modified layer formation process, The wafer processing method according to claim 1, wherein the pulse energy is set to 2.5 to 7.5 μJ.
In the modified layer formation process, The wafer processing method according to claim 1, wherein the pitch of the focal point, which is determined by using the feed rate for processing as the numerator and the repetition frequency of the pulsed laser beam as the denominator, is set to 2.25 to 10.25 μm.
The wafer processing method according to any one of claims 3 to 5, wherein the wafer is a silicon wafer with a thickness of 100 μm or less.
A wafer processing apparatus, The system includes a holding means for holding a wafer, a laser beam irradiation means for irradiating the wafer held by the holding means with a pulsed laser beam, and a processing feed means for relative processing feed between the holding means and the laser beam irradiation means. The laser beam irradiation means comprises an oscillator that emits a pulsed laser beam of a wavelength that is penetrating to a wafer, a concentrator that focuses the pulsed laser beam emitted by the oscillator and holds it in the holding means to position a focal point inside the wafer, a focal point setting unit that sets the focal point to be positioned at a first depth and a second depth shallower than the first depth with respect to the wafer held in the holding means, and a control means. The control means is, An arrival time storage unit calculates and stores the arrival time of the thermal shock wave when it reaches the second depth, using the speed at which the thermal shock wave propagates when the modified layer is formed at the first depth as the denominator and the difference between the first depth and the second depth as the numerator. A total time storage unit stores the total time obtained by adding the arrival time to the time when the thermal shock wave reaches the second depth and a modified layer is formed at the second depth, A pulse width adjustment unit sets the pulse width of the pulsed laser beam to a time equal to or greater than the total time, Includes , The focusing point setting unit is a spatial light phase modulator or a mask for forming an elliptical beam, in a wafer processing apparatus.

Description

This invention relates to a wafer processing method and a wafer processing apparatus. A wafer, with multiple devices such as ICs and LSIs partitioned along planned division lines and formed on its surface, is then divided into individual device chips by a dicing machine and used in electrical equipment such as mobile phones and personal computers. Furthermore, a technique has been proposed in which the width of the planned division line can be narrowed and the wafer can be prevented from being contaminated with cutting debris by positioning the focal point of a pulsed laser beam with a wavelength that is transparent to the wafer within the planned division line and irradiating it, while simultaneously feeding the wafer through the process to continuously form a modified layer within the planned division line, and then applying an external force to divide the wafer into individual device chips (see, for example, Patent Document 1). Patent No. 3408805 This is an overall perspective view of the laser processing apparatus of this embodiment.Figure 1 is a schematic block diagram showing the optical system of the laser beam irradiation means to be mounted on the laser processing apparatus shown in Figure 1.Figure 1 is a perspective view of a wafer processed by the laser processing apparatus shown.This is a perspective view showing an embodiment of the modified layer formation process.This is a partially enlarged cross-sectional view showing the first and second focal points formed in the modified layer formation process shown in Figure 4.This is a partially enlarged cross-sectional view showing how the modified layer is formed during the modified layer formation process. The following describes in detail embodiments of the wafer processing method and wafer processing apparatus based on the present invention, with reference to the accompanying drawings. Figure 1 shows a laser processing apparatus 1, which is an example of a wafer processing apparatus according to the present invention. The laser processing apparatus 1 is a device that performs laser processing on a wafer 10, for example, made of silicon (Si), which is held via a protective tape T on an annular frame F held by a holding means 3. The laser processing apparatus 1 is disposed on a base 2 and includes at least a laser beam irradiation means 7 that irradiates the surface 10a of the wafer 10 with a pulsed laser beam LB. The laser processing apparatus 1 includes, in addition to the holding means 3 and laser beam irradiation means 7 described above, a processing feed means 4 for relative processing feed between the holding means 3 and the laser beam irradiation means 7. The processing feed means 4 includes an X-axis moving means 4a for moving the holding means 3 in the X-axis direction and a Y-axis moving means 4b for moving the holding means 3 in the Y-axis direction. Furthermore, the laser processing apparatus 1 includes a frame 5 consisting of a vertical wall portion 5a erected on the side of the X-axis moving means 4a and Y-axis moving means 4b on the base 2, and a horizontal wall portion 5b extending horizontally from the upper end of the vertical wall portion 5a, as well as a control means 100 for controlling each operating part. The holding means 3 includes a rectangular X-axis movable plate 31 mounted on a base 2 so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 32 mounted on the X-axis movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support column 33 fixed to the upper surface of the Y-axis movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support column 33. A chuck table 35 is provided on the cover plate 34, extending upward through an elongated hole formed on the cover plate 34. The chuck table 35 is configured to be rotatable by a rotational drive means (not shown) housed within the support column 33. A circular suction chuck 36 is provided on the upper surface of the chuck table 35, which is made of a porous material that allows for airflow and has an XY plane specified by the X and Y coordinates as its holding surface. The suction chuck 36 is connected to a suction means (not shown) via a flow path through the support column 33. Four clamps 37 are arranged at equal intervals around the suction chuck 36 to grip and secure the frame F when holding the wafer 10 on the chuck table 35. The X-axis moving mechanism 4a converts the rotational motion of the motor 42a into linear motion via the ball screw 42b and transmits it to the X-axis movable plate 31, moving the X-axis movable plate 31 along a pair of guide rails 2A, 2A arranged on the base 2 along the X-axis. The Y-axis moving mechanism 4b converts the rotational motion of the motor 44a into linear motion via the ball screw 44b and transmits it to the Y-axis movable plate 32, moving the Y-axis movable plate 32 along a pair of guide rails 31a, 31a arranged on the X-axis movable plate 31 along the Y-axis. The