CN218016452U - Ultra-short pulse semiconductor wafer recessive cutting device - Google Patents

Abstract

The utility model relates to an ultra-short pulse semiconductor wafer recessive cutting device, wherein a light source part is arranged in front of a chirp pulse generating part and is used for sending pulse laser to the chirp pulse generating part; the chirp pulse generating part is arranged between the light source part and the dispersion modulation part and is used for widening the ultrashort pulse laser of the light source part and compensating a wide pulse generated by the widened pulse laser by the dispersion modulation part; the dispersion modulation part sets a focusing point in the semiconductor wafer through the focusing part, so that the dispersion at the focusing point is completely compensated; the wafer cutting platform is arranged below the focusing part and used for placing the semiconductor wafer, and the cutting position of the semiconductor wafer is changed by moving the wafer cutting platform; and the track observation and feedback part is used for observing the focal position, feeding back signals to be transmitted to the dispersion modulation part and the focusing part and adjusting the focal position and the size. The utility model discloses can stabilize the position of laser focus, reduce the focus that is brought by nonlinear effect and float, promote laser cutting's precision.

Description

Ultra-short pulse semiconductor wafer recessive cutting device

Technical Field

The utility model relates to a chip processing field, concretely relates to device is cut to ultrashort pulse semiconductor wafer is hidden.

Background

The core of the intelligent device is high-end manufacturing technologies such as a semiconductor chip, chip processing, hidden cutting, low-k slotting and the like. The wafer recessing is an essential process in chip processing. The size of the high-end chip is in the nanometer scale, so the requirement on the wafer recessive cutting process needs to be extremely accurate, and the nanosecond/picosecond light source is difficult to realize high-precision recessive cutting due to relatively strong heat effect.

And in contrast, the femtosecond laser has small heat effect and high cutting precision. Therefore, the high-end cutting of the semiconductor wafer can be realized by using the femtosecond laser. However, the femtosecond pulses have non-linear effect on the propagation path, which is not negligible due to high peak power during focusing. Nonlinear effects can cause spatial self-focusing of the laser pulses, which ultimately causes the focal point to move forward in the direction of the laser path during cutting. The spatial self-focusing effect is a typical nonlinear effect of the light field high-order process. The laser peak power reaches 100MW and then is a physical process which must be considered in the processing process. The spatial self-focusing degree is in direct proportion to the square of the light intensity, so that the disturbance of any laser output energy and the mechanical vibration of a cutting system are amplified by a nonlinear effect, and finally the uncertainty of the focusing position in the semiconductor wafer stealth cutting process is caused.

Various means are used to reduce the uncertainty in the process of recessing semiconductor wafers, such as reducing laser power, increasing laser pulse width, and focusing with a large Numerical Aperture (NA) focusing objective. However, the recessing of the semiconductor wafer usually requires a higher peak power to reach the damage threshold of a very semiconductor wafer (e.g., siC wafer), so the methods of decreasing the laser power and increasing the laser pulse width are not suitable for most semiconductor wafers with high damage threshold. Meanwhile, the thermal effect of the cutting process can be improved by improving the pulse width of the laser, and the cutting precision is greatly reduced. Focusing with a high Numerical Aperture (NA) focusing objective lens is used, although the nonlinear effects on the laser focusing path can be reduced. However, the focusing point of the high-NA objective lens is too small, so that the cutting track is too narrow, and the cutting efficiency of the semiconductor wafer is greatly influenced. Considering that the chip demand in China is continuously increased, but the technical development is still limited by foreign environments, the new enterprises in China gradually invest capital personnel to carry out independent research and development, and the precision of chip cutting processing is particularly important under the form. Therefore, there is a need for a semiconductor wafer dicing apparatus that reduces the nonlinear effect on the dicing path while ensuring constant peak power of the focus point.

Disclosure of Invention

The utility model aims at providing a reduce stealthy device of cutting of ultrashort pulse semiconductor wafer of cutting process in nonlinear effect, the device and method can stabilize the position of laser focus, reduce the focus that is brought by nonlinear effect and float, promote laser cutting's precision.

In order to achieve the above purpose, the technical scheme of the utility model is that: an ultra-short pulse semiconductor wafer recessive cutting device comprises a light source part, a chirp pulse generation part, a dispersion modulation part, a focusing part, a wafer cutting platform and a track observation and feedback part, wherein the light source part is arranged in front of the chirp pulse generation part and used for sending pulse laser to the chirp pulse generation part; the chirp pulse generating part is arranged between the light source part and the dispersion modulation part and is used for widening the ultrashort pulse laser of the light source part and compensating a wide pulse generated by the widened pulse laser by the dispersion modulation part; the dispersion modulation part sets a focusing point in the semiconductor wafer through the focusing part, so that the dispersion at the focusing point is completely compensated; the wafer cutting platform is arranged below the focusing part and used for placing a semiconductor wafer, and the cutting position of the semiconductor wafer is changed through movement; the track observing and feedback part is arranged above the semiconductor wafer and used for observing the focus position, and feeding back signals to the dispersion modulation part and the focusing part and adjusting the focus position and size.

Further, the light source of the light source unit is any one of a solid, a gas, and an optical fiber, and the width of the laser pulse output by the light source unit is 10fs to 10ps.

Further, the chirp pulse generating part adopts a traditional Martinez grating structure and is used for generating positive chirp, or adopts a pulse propagation medium with a certain length and is used for generating positive chirp when pulses are propagated through the medium; and a traditional Treacy grating structure is adopted for generating negative chirp, or a pulse propagation medium with a certain length is adopted for pulse propagation to generate negative chirp after passing through the medium.

Further, the dispersion modulation part is composed of a glass slide, a concave lens, two dichroic mirrors, two gratings, a linear motor and a Fresnel zone plate; after passing through a glass slide, the wide light beam is irradiated on two 45-degree reflecting dichroic mirrors, light spots are expanded through a concave lens, the expanded light spots are irradiated on a first grating, and the expanded light spots are reflected into a second grating on a linear motor and then enter a Fresnel zone plate.

Furthermore, the Fresnel zone plate and the grating are combined and manufactured on the same substrate, the first grating is fixed in position, the second grating is placed on the linear motor, the first grating and the second grating are the same kind of grating, and the distance between the first grating and the second grating is regulated and controlled by a feedback signal of the track observation and feedback part.

Further, the focusing part consists of a concave lens, a focusing objective lens, a linear motor and a dichroic mirror, and the compensated pulse light beams are focused onto the 45-degree reflecting dichroic mirror through the concave lens, reflected to the focusing objective lens and focused inside the semiconductor wafer.

Further, the focusing objective lens is placed on the linear motor, and the distance between the second focusing objective lens and the semiconductor wafer is regulated and controlled by a feedback signal of the track observation and feedback part.

Further, the wafer cutting platform consists of a marble beam, a marble platform, a theta-axis motor, an X-axis linear motor and a Y-axis linear motor.

Further, the track observing and feedback part consists of a position detection sensor and a microscope objective, and the position detection sensor transmits feedback signals of the track and the focus position observed by the microscope objective to the dispersion modulation part and the focusing part for controlling the light intensity and the focus position at the focus in the cutting process.

Furthermore, the ultra-short pulse semiconductor wafer recessing device is used for semiconductor wafer cutting, semiconductor wafer surface grooving, chip cutting and low-k chip grooving.

Compared with the prior art, the utility model following beneficial effect has:

1. the utility model provides a reduce the nonlinear effect on the cutting route, guarantee the unchangeable semiconductor wafer cutting means of focus peak power simultaneously. The ultrashort pulse light source is used as a cutting light source, the cutting precision can be guaranteed by the ultrashort pulse high peak power at a focus point, and the cutting process is free of the adverse conditions of burrs, blackening, edge breakage and the like. Meanwhile, the weak nonlinear effect (self-focusing effect) on the cutting path controls the translation of the focusing position along the laser path within 100 nm.

2. Higher cutting rate. Compared with the current mainstream high NA objective focusing and cutting, the focusing point diameter of the device is adjustable from 1 to 30 mu m. In the actual wafer recessing process, the width of the scribe line is usually 10-30 μm. Compared with the high-NA objective lens focusing cutting which needs scanning for multiple times, the device only needs to adjust the cutting lens group according to the width of the required cutting track in advance, so that the focus is matched with the width of the actually-required cutting track, and cutting can be realized only through single scanning.

3. Excellent self-adaptive ability. And observing the cutting track in the scanning process, adjusting the pre-chirp amount, capturing the amplified wafer cutting track on the microscope objective by the CCD, and automatically adjusting the position of a part on the linear motor to realize chirp compensation on a cutting path, so that the cutting path can adapt to cutting channels with various widths.

Drawings

Fig. 1 is a schematic structural diagram of an ultra-short pulse semiconductor wafer recessive cutting apparatus of the present invention;

fig. 2 is an actual optical path diagram of the ultra-short pulse semiconductor wafer recessive cutting apparatus of the present invention;

fig. 3 is an integrated drawing of the whole machine in the practical process of the utility model.

Detailed Description

The following description is made in detail with reference to the accompanying drawings and examples, but this example can not be used to limit the present invention, and all the similar methods and similar variations thereof adopted by the present invention should be included in the protection scope of the present invention.

As shown in fig. 1,2, the semiconductor wafer recessive cutting apparatus of the present invention includes a light source 100, a chirped pulse generator 200, a dispersion modulator 300, a focusing unit 400, a wafer dicing platform 500, a track observation and feedback unit 600, and the like.

The chirp generation unit 200 receives the light source from the light source unit 100, and then spreads the ultrashort pulses of the light source unit by adding a large amount of chirps, and the generated wide pulses are compensated by the dispersion modulation unit. The dispersion modulating section 300 sets a focusing point inside the wafer by the focusing section 400, and the dispersion at the focusing point is completely compensated. The semiconductor wafer is placed on the wafer dicing table 500, and the table is moved to change the dicing position of the semiconductor wafer. The track observing and feedback section 600 is provided on the semiconductor wafer for observing the focal position, and feeds back a signal to the dispersion modulating section 300 and the focusing section 400, thereby changing the focal position and size.

Preferably, the light source of the light source unit 100 may be a solid, gas, optical fiber, or other laser system, and the light source unit outputs a pulse laser with a pulse width of 10fs to 10ps.

Preferably, the chirped pulse generating part 200 can generate positive chirp through a conventional Martinez grating structure (or an equivalent structure), or can generate positive chirp by allowing a pulse to propagate through a medium with a certain length. The negative chirp can be generated by a traditional Treacy grating structure (or an equivalent structure thereof), and the negative chirp can also be generated by allowing a pulse to propagate through a medium with a certain length.

Preferably, the dispersion modulation section 300 is composed of a concave lens 301, a first grating 302, a second grating 303, a first linear motor 304, and a fresnel zone plate 305. The fresnel zone plate and grating combination can be fabricated on the same substrate. The dispersion modulation section ensures that the generated high-order dispersion is conjugate to the chirp pulse generation section, thereby ensuring that the high-order dispersion is compensated during propagation. The first grating 302 is fixed, the second grating 303 is placed on the first linear motor 304, the first grating 302 and the second grating 303 are the same grating, and the distance is regulated and controlled by a feedback signal from the track observation and feedback part 600.

Preferably, the focusing unit 400 is composed of a concave lens 401, a focusing objective lens 402, a second linear motor 403, and a third dichroic mirror 404, and focuses the pulse generated by the dispersion modulation unit 300 inside the wafer. The second focusing objective 402 is placed on the second linear motor 403, and the distance between the second focusing objective and the semiconductor wafer is controlled by the feedback signal from the track observing and feedback unit 600.

Preferably, the wafer cutting platform 500 is composed of a marble beam 501, a marble platform 502, a theta-axis motor 503, an X-axis linear motor 504, and a Y-axis linear motor 505. The marble beam 501 is rigidly connected to the wafer cutting platform 500, and is used for placing the light source unit 100; the marble platform 502 is used for placing a wafer to be processed; the theta axis motor 503 is arranged in the case and used for controlling the X axis linear motor 504 and the Y axis linear motor 505; x-axis linear motor 504 and Y-axis linear motor 505 may change the wafer position in the X and Y axis directions, respectively. The semiconductor wafer is placed on the wafer dicing table 500, and the dicing position can be changed by moving the table.

Preferably, the track observing and feedback part 600 is composed of a position detecting sensor 601 and a microscope objective 602, the position detecting sensor 601 observes the track and the focus position through the microscope objective 602, and transmits a feedback signal to the dispersion modulating part and the focusing part, so as to control the light intensity and the focus position at the focus during the cutting process.

Preferably, the method and the device for recessing the semiconductor wafer can be used for cutting the semiconductor wafer, and can also be used for slotting the surface of the semiconductor wafer, cutting chips and slotting low-k chips.

The utility model discloses an ultrashort pulse semiconductor wafer recessive method of nonlinear effect among the reduction cutting process through reducing the nonlinear effect on the cutting route, guarantees the unchangeable semiconductor wafer cutting device of focus point peak power simultaneously. The device is characterized in that a laser light source part generates ultrashort pulses, and the pulses pass through a dispersion compensation element related to a propagation path to compensate chirp in the cutting process. The pulse dispersion is compensated as completely as possible at the focus point, so that the pulse width is narrow at the focus point, the peak power is high, and the method can be used for cutting. In the laser propagation path, the pulse width is wide and the nonlinear effect is weak because of the existence of a certain chirp.

In this embodiment: the pulse is output from the light source unit 100, in practical process, the light source can be solid, gas, optical fiber and other laser system, the light source unit outputs pulse laser, the pulse width is 10fs-10ps. The ultra-short pulse of the light source section 100 is widened by the chirp generation section 200 by adding a large amount of chirp, and the generated wide pulse is compensated by the dispersion modulation section 300. The dispersion modulation unit sets a focus point inside the wafer by the focusing unit 400, and the dispersion at the focus point is completely compensated. The semiconductor wafer is placed on the wafer dicing table 500, and the table is moved to change the dicing position. The track observing and feedback section 600 observes the focal position, and the feedback signal is transmitted to the dispersion modulation section and the focusing section, thereby changing the focal position and size. Pulse dispersion is compensated as completely as possible at the focus point, so on the wafer at the focus point, the pulse width is narrow and the peak power is high. In contrast, in the laser propagation path, since there is a certain chirp, the pulse width is wide and the nonlinear effect is weak. Therefore, the device can stabilize the position of the laser focus and reduce focus floating caused by nonlinear effect, thereby improving the precision of laser cutting.

The ultrashort pulse semiconductor wafer recessing method for reducing the nonlinear effect in the cutting process of the embodiment reduces the nonlinear effect on the cutting path and simultaneously ensures that the peak power of the focus point is unchanged. The ultrashort pulse semiconductor wafer stealth cutting system is described below in conjunction with the design of the above-described apparatus in a laboratory.

Fig. 2 shows an example of the present invention, which is a preferred embodiment of the present invention, and an optical fiber + solid-state laser system is used to perform the stealth dicing of the semiconductor wafer. The light source section 100 outputs a pulse width of 300fs, a single pulse energy of 100 μ J, a repetition frequency of 300kHz, and a wavelength of 1030 nm. The pulse laser generates positive chirp through a Martinez grating structure (or an equivalent structure thereof) to widen the input ultrashort pulse. The expanded light beam passes through a glass slide 201, then strikes two 45-degree reflecting dichroic mirrors I, II 202 and 203, and then passes through a concave lens 301 to expand the light spots. The expanded light spot is projected on the first grating 302, reflected into the second grating 303 on the linear motor 304, and then passes through a fresnel zone plate 305. The dispersion modulation section 300 is used to provide negative dispersion to ensure that high-order dispersion during propagation is compensated. The first grating 302 is fixed, the second grating 303 is arranged on the first linear motor 304, the distance between the first grating and the second grating is adjusted through the first linear motor 304, and the first linear motor 304 is connected with the track observing and feedback part 600 and is adjusted and controlled by the track observing and feedback part 600. As shown in fig. 2, the compensated pulse is focused on a dichroic mirror three 404 with a 45 ° reflection through a concave lens 401, reflected to a focusing objective 402, and then focused inside a semiconductor wafer 700. The focus point is 1-30 μm adjustable. The focusing objective 402 is placed on the second linear motor 403, the second linear motor 403 is connected with the track observing and feedback part 600, and the distance between the focusing objective 402 and the semiconductor wafer 700 is regulated and controlled by a feedback signal from the track observing and feedback part 600.

The reflected light from the semiconductor wafer 700 is captured by the position detection sensor 601 through the microscope objective lens 602 to observe the dicing track in real time, thereby adjusting the position of the component on the linear motor.

Fig. 3 is an integrated drawing of the whole machine in the practical process of the utility model. In the actual process, a water cooling system is added through mechanical design, and a pneumatic device is used for removing the follow-up of cutting materials at the focusing lens in real time, so that splashed wafer fragments are prevented from falling on the focusing lens, and the uncertainty of energy and a facula mode in the actual cutting process is influenced. The whole system is integrated on a framework made of hollow steel pipes. Therefore, mechanical vibration is effectively prevented, and the uncertainty of the track scanned by the motor can be reduced to be below 500nm through the system integration in the experimental process.

In the practical process, the SiC wafer cutting trajectory is realized by the experimental device shown in fig. 3. The width of the cutting track is about 6.4 mu m. The uncertainty of the track is about 120nm when the length of 1mm is scanned. Due to the fact that the nonlinear effect of the laser on a focusing path is reduced in the cutting process, the scanning precision of the laser is superior to that of all semiconductor wafer stealth cutting devices sold in China at present.

Claims (9)

1. An ultra-short pulse semiconductor wafer recessing device is used for semiconductor wafer cutting, semiconductor wafer surface grooving, chip cutting and low-k chip grooving, and is characterized in that: the system comprises a light source part, a chirped pulse generating part, a dispersion modulation part, a focusing part, a wafer cutting platform and a track observing and feedback part, wherein the light source part is arranged in front of the chirped pulse generating part and is used for emitting pulse laser to the chirped pulse generating part; the chirp pulse generating part is arranged between the light source part and the dispersion modulation part and is used for widening the ultrashort pulse laser of the light source part and compensating a wide pulse generated by the widened pulse laser by the dispersion modulation part; the dispersion modulation part sets a focusing point in the semiconductor wafer through the focusing part, so that the dispersion at the focusing point is completely compensated; the wafer cutting platform is arranged below the focusing part and used for placing the semiconductor wafer, and the cutting position of the semiconductor wafer is changed by moving the wafer cutting platform; the track observing and feedback part is arranged above the semiconductor wafer and used for observing the focus position, and feeding back signals to the dispersion modulation part and the focusing part and adjusting the focus position and size.

2. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the light source of the light source part is any one of solid, gas and optical fiber, and the width of the laser pulse output by the light source part is 10fs-10ps.

3. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the chirp pulse generating part adopts a traditional Martinez grating structure and is used for generating positive chirp, or adopts a pulse propagation medium with a certain length and is used for generating positive chirp when pulses are propagated through the medium; and a traditional Treacy grating structure is adopted for generating negative chirp, or a pulse propagation medium with a certain length is adopted for generating negative chirp after pulse propagation passes through the medium.

4. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the dispersion modulation part consists of a glass slide, a concave lens, two dichroic mirrors, two gratings, a linear motor and a Fresnel zone plate; after passing through the glass slide, the wide light beams are incident on two 45-degree reflecting dichroic mirrors, then beam-expanded light spots are incident on the first grating and reversely enter the second grating on the linear motor and then enter the Fresnel zone plate through the concave lens.

5. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 4, wherein: the Fresnel zone plate and the grating are combined and manufactured on the same substrate, the first grating is fixed in position, the second grating is placed on the linear motor, the first grating and the second grating are the same kind of grating, and the distance between the first grating and the second grating is regulated and controlled by a feedback signal of the track observation and feedback part.

6. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the focusing part consists of a concave lens, a focusing objective lens, a linear motor and a dichroic mirror, and the compensated pulse light beams are focused onto the 45-degree reflecting dichroic mirror through the concave lens, reflected to the focusing objective lens and focused inside the semiconductor wafer.

7. The ultrashort pulse semiconductor wafer stealth device of claim 6, wherein: the focusing objective lens is placed on the linear motor, and the distance between the second focusing objective lens and the semiconductor wafer is regulated and controlled by a feedback signal of the track observation and feedback part.

8. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the wafer cutting platform consists of a marble beam, a marble platform, a theta axis motor, an X axis linear motor and a Y axis linear motor.

9. The ultrashort pulse semiconductor wafer stealth dicing apparatus of claim 1, wherein: the track observing and feedback part consists of a position detection sensor and a microscope objective, and the position detection sensor transmits feedback signals of the track and the focus position observed by the microscope objective to the dispersion modulation part and the focusing part for controlling the light intensity and the focus position at the focus in the cutting process.

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