CN114260585A

CN114260585A - Frequency-locking single-pulse green-light ultrafast laser wafer marking method and system

Info

Publication number: CN114260585A
Application number: CN202210019722.6A
Authority: CN
Inventors: 不公告发明人
Original assignee: Beijing Yingke Technology Co ltd
Current assignee: Beijing Yingke Technology Co ltd
Priority date: 2022-01-10
Filing date: 2022-01-10
Publication date: 2022-04-01

Abstract

The invention provides a method and a system for marking a frequency-locked single-pulse green light ultrafast laser wafer, wherein the method comprises the following steps: 1) an ultrafast laser capable of emitting high-energy single pulses at a high repetition frequency and high in single pulse energy consistency is arranged; 2) locking the transmitting frequency to a fixed value; 3) the ultrafast laser is input to a galvanometer through a shaping light path and a light beam transmission light path and is focused on the surface of the wafer after passing through a field lens; 4) and marking is finished under the control of a software and hardware controller. The marking method provided by the invention realizes marking through the processing surface of the ultrafast laser vaporization material with high single pulse energy, almost no heat affected zone appears, the damage degree of the laser to the wafer is reduced to the minimum, but the marking result is precise, fine and firm, and a brand new effect is provided. The height of the deposit is greatly reduced, the surface roughness of the wafer is small, and the marking consistency and uniformity are good.

Description

Frequency-locking single-pulse green-light ultrafast laser wafer marking method and system

Technical Field

The invention relates to the technical field of semiconductor laser processing, in particular to a method and a system for marking a frequency-locked single-pulse green-light ultrafast laser wafer.

Background

The first step after the wafer is off-line is to mark the wafer surface by using a laser (laser) to mark the lot number of the wafer at 12 o' clock.

The lot number is actually composed of a plurality of small holes or a plurality of small grooves scribed on the surface of the wafer by laser. The laser may deposit by-products (silicon, Si) of the drilling or scribing process while drilling or scribing process, and the deposit is too high to scratch the wafer by the subsequent physical Chemical Polishing (CMP). And (3) finding the wafer slices with abnormal marking: the stack height can be up to 8000nm or more, and ideally should be less than 1000 nm.

Chinese patent 201910191734.5 provides a laser wafer marking device, which releases nitrogen gas cleaning gas in the first sealing chamber along the moving direction of marking before laser marking, cleans the residues on the wafer in advance, and discharges the residues by vacuum pumping; when carrying out laser and beat the mark, along the moving direction of beating the mark, release nitrogen gas clean gas in the sealed intracavity of second, clean the deposit, utilize the vacuum to bleed simultaneously and carry out the discharge of deposit. This prevents the wafer from being scratched or cut.

But the method is only an auxiliary means necessary in the industry, and what can really reduce the deposits is the quality of laser marking, the fineness and the firmness of the marking and the minimum damage to the material. The laser marking technology for wafers still needs to be improved.

Disclosure of Invention

In view of the above, in order to overcome the defects of the prior art, the invention provides a method and a system for frequency-locked single-pulse green-light ultrafast laser marking of a wafer, wherein the method reduces the damage degree of the laser to the wafer to the minimum, but the marking result is precise, fine and firm, and provides a brand new effect. The height of the deposit is greatly reduced, the roughness is small, and the consistency and the uniformity are good.

The invention provides a frequency-locking single-pulse green-light ultrafast laser wafer marking method, which comprises the following steps:

1) the method comprises the steps of arranging a green light ultrafast laser which can emit high-energy single pulses under high repetition frequency and has high single pulse energy consistency, wherein the high repetition frequency is 10KHz-500KHz, the high-energy single pulse energy is 20uJ-1000uJ, and the energy difference between the single pulses is less than or equal to +/-5%;

2) locking a certain value of the transmitting frequency between 10KHz and 500 KHz;

3) ultrafast laser emitted by the laser device is amplified in beam size through a shaping light path, is input to a galvanometer through a beam transmission light path, and is focused on the surface of a wafer workpiece on a positioning platform after passing through a field lens;

4) setting laser parameters and processing parameters under the control of a software and hardware controller; controlling the galvanometer, the laser emission and the movement of the laser beam X, Y, Z axis completes the laser marking of the wafer surface pattern.

Further, the laser is an all-solid-state picosecond laser.

Further, the single pulse is a single pulse photon peak wave, and the width of the single pulse is 1-10 ps.

Furthermore, the laser window has a light spot of 1-3mm and a divergence angle of 0.5-1.5 mrad.

Further, the shaping optical path is a beam expanding optical path with the magnification of 1-8 times.

Furthermore, the light beam transmission light path is composed of transmission light paths with the transmission distance of 10-1000 mm.

Further, the rotating speed of the galvanometer is 100-10000 r/s, the field lens is an F-theta field lens or a telecentric field lens, and the focal length is 30-600 mm.

Further, the laser wavelength is 532 +/-5 nm.

Further, the minimum resolution feature size for forming the micro-structure of the marking pattern is 0.5-15 um.

The invention also provides a marking system of the ultrafast laser wafer marking method, the system comprises an ultrafast laser, a shaping light path, a light beam transmission light path, a focusing lens, a marking head, a positioning platform and a controller,

the ultrafast laser can emit high-energy single pulses under high repetition frequency, the single pulse energy consistency is high, the high repetition frequency is 10KHz-500KHz, the high-energy single pulse energy is 20uJ-1000uJ, and the single pulse energy consistency is less than or equal to +/-5%; locking a certain value of the transmitting frequency between 10KHz and 500 KHz; setting the laser wavelength to 532 +/-5 nm;

the focusing lens comprises a scanning galvanometer for controlling the deflection of the laser beam and a field lens for focusing the laser beam;

a wafer sucker is arranged on the positioning platform;

the laser is connected with a computer controller provided with laser marking system software through a data line, the computer controller inputs controlled laser power, scanning speed and repetition frequency signals into the laser, receives pulse synchronous signals of the laser, and controls a light path, a focusing lens, a marking head and a positioning platform to finish marking of the wafer workpiece on the sucker.

The positioning platform is also provided with X, Y and a Z-axis driving mechanism;

the invention has the beneficial effects that:

1. the invention is based on the locking ultrafast laser wafer marking method with high repetition frequency, single pulse work, high single pulse energy and high single pulse energy consistency, the damage degree to the wafer is reduced to the minimum, but the marking result is precise, meticulous and firm, and a brand new effect is provided. The roughness of the surface of the wafer is less than 20nm-100nm, the height of the deposit is less than 20nm-100nm, and the consistency and the uniformity are good.

2. The method realizes marking by the ultrafast laser vaporization material processing surface with high single pulse energy, but not by the action of melting by heat, so that the method hardly has the phenomena of a heat affected zone, and the processing surface hardly has slag adhering, cracks, edge breakage and the like. The invention does not need auxiliary powder and other materials, the marking content is fine and clear, and the material strength is almost unchanged.

3. The high-energy single pulse output by the marking method is unique in time domain, the specific position point of the workpiece material processing surface is very accurate in marking, the workpiece material processing surface cannot drift in space, and the marking quality is very good.

4. The marking method has the advantages of short processing time, almost no missing points or marks and accurate time sequence matching.

5. Under the irradiation of the ultrafast laser equipment with high single pulse energy consistency, the consistency of the optical processing process is good, the surface of the wafer is clear and bright, repeated irradiation is not carried out, the material is hardly darkened, and the characteristic parameters of the material are hardly changed.

Description of the drawings:

FIG. 1 is a schematic diagram of the internal structure of a frequency-locked uniform-energy single-pulse green-light ultrafast laser wafer marking system of the present invention;

FIG. 2 is a schematic diagram of the external structure of the single-pulse green-light ultrafast laser wafer marking system with uniform frequency locking energy according to the present invention;

wherein: 1. an ultrafast laser; 2. an optical path; 2-1, shaping the light path; 2-2. light beam transmission optical path; 3. a galvanometer; 4, a field lens; 5. a wafer; 6. a sucker, 7, a controller, 8, a reflector; 9. a laser carrying case; 10. a vision system; 11. marking a head; 12. a manipulator mechanism; 13. a work table; 14. a position to be processed; 15. presetting a position after processing; 16. positioning the platform; 17. a gripper; 18, X, Y, Z drive device.

Fig. 3 is a photograph showing the effect of the ultrafast laser marking method of the present invention on the precise marking of the wafer surface.

Detailed Description

The method and system for frequency-locked uniform-energy single-pulse green ultrafast laser wafer marking according to the present invention will be further explained with reference to the drawings and the embodiments, but the present invention is not limited to the following embodiments.

1) the method comprises the steps of setting a green light ultrafast laser 1 which can emit high-energy single pulses under high repetition frequency and has high single pulse energy consistency, wherein the high repetition frequency is 10KHz-500KHz, the high-energy single pulse energy is 20uJ-1000uJ, and the energy difference between the single pulses is less than or equal to +/-5%;

3) ultrafast laser emitted by the laser device is amplified in beam size through a shaping light path 2-1, is input into a galvanometer 3 through a beam transmission light path 2-1, and is focused on the surface of a wafer workpiece 5 on a positioning platform 16 after passing through a field lens 4;

4) setting laser parameters and processing parameters under the control of the software and hardware controller 7; and controlling the galvanometer 3 and laser emission, and controlling the movement of the laser beam X, Y, Z axis to complete the laser marking of the wafer surface pattern. (see FIG. 1)

In step 1) of the present invention, preferably, the emission frequency of the laser is a certain value between 50KHz and 500KHz, and the single pulse energy emitted by the laser is 50 to 200uJ, and more preferably, the emission frequency of the laser is a certain value between 100KHz and 500KHz, and the single pulse energy emitted by the laser is 50 to 100 uJ.

As an embodiment of the invention, the transmission distance of the light beam transmission optical path 2-2 is 10-1000 mm; preferably 100-; more preferably 500 and 800 mm.

As another embodiment of the present invention, the shaping optical path 2-1 is a beam expanding optical path with a magnification of 1-8 times; preferably, the shaping optical path is a beam expanding optical path with the magnification of 2-6 times; more preferably, the shaped optical path is a beam-expanding optical path with a magnification of 5 times.

As a further embodiment of the invention, the rotating speed of the galvanometer is 100-; preferably, the rotating speed of the galvanometer is 400-; more preferably, the rotation speed of the galvanometer is 500-.

As a further embodiment of the invention, the field lens is an F-theta field lens or a telecentric field lens 4, having a focal length of 30 to 300 mm; preferably, the field lens is an F-theta field lens or a telecentric field lens, and the focal length is 100-300 mm; more preferably, the field lens is an F-theta field lens or a telecentric field lens, and the focal length is 150-250 mm.

Step 4) of the present invention comprises the steps of:

1. laser pulse synchronizing signals in the forms of laser emission parameters and levels are set, and the laser pulse synchronizing signals and the starting time T1 are sent to the software and hardware controller 7 to serve as processing reference time.

2. Debugging the laser beam: the light beam is transmitted to the vibrating mirror 3 through the light beam transmission 2-1, the optical gate, the shaping optical path 2-2 and the reflector 8; the optical gate is controlled by TTL level; the software and hardware controller 7 sends a signal to the shutter to control its switching and a start time T2.

3. Debugging a galvanometer: the software and hardware controller 7 sends a control signal in the form of 5V high-low level of the galvanometer 3 and the start time T3 to the galvanometer 3.

4. The laser beam is debugged and focused near the positioning platform 16 through the field lens 4, and works within the effective range of the field lens 4.

5. And fixing the target workpiece on the positioning platform. The position and the boundary of the positioning platform are precisely adjusted, and the moving path is calibrated. And adjusting laser to focus near the workpiece, acting on the workpiece to be marked, and waiting for processing.

6. The software and hardware controller 7 is controlled in a manual or automatic mode of input and output by a computer, a singlechip, an ARM or a mobile phone.

7. The content to be marked is decomposed by the software and hardware controller 7, pixels, diameters, filling density, wiring paths and graphs in a readable format are obtained, and the boundary range of the pixels, the diameters, the filling density, the wiring paths and the graphs is limited by the area boundary which is not larger than the laser marking machine.

8. According to the contents and sequence of the wafer marking patterns, laser synchronous signals are input to a software and hardware controller to serve as a time reference, coordinates of a calibration positioning platform serve as a space reference, and the software and hardware controller sequentially transmits control signals, the time reference, delay time and control signal time sequence to a galvanometer, an optical shutter and a marking head to perform overall time sequence calibration and preliminary sample marking.

9. And verifying the degree of coincidence with the preset effect according to the preliminary proofing effect, fine-tuning the process and parameters of each part if the difference exists, locking the parameters until the effect is optimal, and starting marking.

The invention also provides a marking system for realizing the ultrafast laser wafer marking method, the system comprises an ultrafast laser 1, a shaping light path 2-1, a light beam transmission light path 2-2, focusing

lenses

3 and 4, a marking head 11, a positioning platform 16 and a controller 7,

the focusing lens comprises a scanning galvanometer 3 for controlling the deflection of the laser beam and a field lens 4 for focusing the laser beam;

a wafer sucker 6 is arranged on the positioning platform 16;

the laser 1 is connected with a computer controller 7 provided with laser marking system software through a data line, the computer controller inputs controlled laser power, scanning speed and repetition frequency signals to the laser 1, receives pulse synchronous signals of the laser 1, and controls the optical path 2, the focusing

lenses

3 and 4, the marking head 11 and the positioning platform 16 to finish marking.

The positioning platform 16 is also provided with X, Y and a Z-axis drive mechanism 18.

The laser is arranged in the laser bearing box 9, and a vision system 10 is arranged beside the marking head 11.

The positioning platform 16 is arranged on the workbench 13, and the workbench 13 is also provided with a to-be-processed station 14 and a processed preset position 15. The position movement before and after the marking of the wafer is completed by the gripper 17 on the robot mechanism 12.

(see FIG. 2)

Example 1: precision marking method for batch number on surface of wafer

The laser 1 is connected with a computer controller 7 provided with laser marking system software through a data line, the computer controller inputs controlled laser power, scanning speed and repetition frequency signals into the laser, and the laser is an all-solid-state picosecond laser. The controller receives the pulse synchronization signal of the laser, and controls the optical path 2, the focusing

lenses

3 and 4, the marking head 11 and the positioning platform 16 to complete marking.

The locking transmitting frequency is 500 KHz; the single pulse energy is 20 uJ;

the single pulse is a single pulse photon peak wave, and the single pulse width is 10 ps.

The laser window spot was 2mm and the divergence angle was 1.0 mrad.

The shaping optical path is a beam expanding optical path with 5 times of magnification.

The light beam transmission light path is composed of transmission light paths with the transmission distance of 500 mm.

The rotating speed of the galvanometer is 500 r/s, the field lens is an F-theta field lens, and the focal length is 150 mm.

The laser wavelength is 532 +/-5 nm.

The minimum resolution feature size to form the marked pattern microstructure is 0.5 um.

Marking with the laser:

(1) importing an image to be marked into a computer;

(2) reading an image to be marked through laser marking system software installed on a computer, and setting laser output power, laser repetition frequency and galvanometer working frequency;

and turning on the laser, scanning by the laser motion control system according to an image signal output by the computer, and laser marking the high-energy laser beam on the working surface of the wafer.

The marking effect is shown in fig. 3.

Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.

Claims

1. A frequency-locking single-pulse green light ultrafast laser wafer marking method is characterized by comprising the following steps:

2. The ultrafast laser wafer marking method of claim 1, wherein the laser is an all-solid-state picosecond laser.

3. The ultrafast laser wafer marking method as claimed in claim 1, wherein the single pulse is a single pulse photon peak wave and the single pulse width is 1-10 ps.

4. The ultrafast laser wafer marking method as claimed in claim 1, wherein the laser window spot is 1-3mm and the divergence angle is 0.5-1.5 mrad.

5. The ultrafast laser wafer marking method as claimed in claim 1, wherein the shaping optical path is a beam expanding optical path with a magnification of 1-8 times.

6. The ultrafast laser wafer marking method as claimed in claim 1, wherein the beam transmission path is a transmission path with a transmission distance of 10-1000 mm.

7. The ultrafast laser wafer marking method as claimed in claim 1, wherein the galvanometer rotation speed is 100-10000 rpm/sec, the field lens is an F-theta field lens or a telecentric field lens, and the focal length is 30-600 mm.

8. The ultrafast laser wafer marking method as claimed in claim 1, wherein the laser wavelength is 532 ± 5 nm.

9. The ultrafast laser wafer marking method of claim 1, wherein a minimum resolution feature size of the micro-structures forming the marking pattern is 0.5-15 um.

10. The marking system for implementing the ultrafast laser wafer marking method of claim 1, wherein the system comprises an ultrafast laser, a shaping optical path and a beam transmission optical path, a focusing lens, a marking head, a positioning platform and a controller,

a wafer sucker is arranged on the positioning platform;