CN113967872A

CN113967872A - Laser-assisted polishing method for monocrystalline silicon wafer

Info

Publication number: CN113967872A
Application number: CN202111083488.5A
Authority: CN
Inventors: 管迎春; 李欣欣; 崔智铨
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2021-09-16
Filing date: 2021-09-16
Publication date: 2022-01-25

Abstract

The invention discloses a laser-assisted polishing method for a monocrystalline silicon wafer, and belongs to the technical field of laser-assisted processing. The ultra-fast laser is used for carrying out cross scanning treatment on the monocrystalline silicon mechanical grinding piece, so that the surface roughness of the monocrystalline silicon grinding piece is reduced, meanwhile, the efficiency of the irradiated silicon wafer in chemical mechanical polishing is greatly improved, and the material removal rate can reach 3.39 times that of an untreated silicon wafer. The method is applied to the planarization processing of the silicon wafer, so that the production cost can be effectively reduced, and the production efficiency is improved.

Description

Laser-assisted polishing method for monocrystalline silicon wafer

Technical Field

The invention belongs to the technical field of laser-assisted processing, and particularly relates to a laser-assisted polishing method for monocrystalline silicon wafers.

Background

The silicon material has excellent performances of unidirectional conductivity, heat sensitivity, photoelectric property, doping property and the like, can grow into large-size high-purity crystals, has rich reserves and low price, and thus becomes the most important semiconductor base material with the most wide global application. The development of Integrated Circuits (ICs) is not independent of the base material silicon wafers, and more than 90% of the ICs worldwide are silicon wafers.

The development of the information technology industry and the integrated circuit industry place ever-increasing demands on the manufacture of semiconductor materials, which are required to have higher surface quality (e.g., low surface roughness, warpage, flatness, no surface/sub-surface damage) as the chip area is continuously reduced and the integration is rapidly increased. At present, the surface treatment of semiconductor materials mainly comprises two major steps of mechanical grinding and chemical mechanical polishing. The mechanical grinding process can remove cutting saw marks generated in the previous process, reduce warping degree and surface roughness, but the grinding process can generate new surface/subsurface damage. The damage generated during the grinding process can be removed by Chemical Mechanical Polishing (CMP), which combines mechanical friction with chemical corrosion to obtain a high quality polished surface, however, the CMP process is time consuming and affects the wafer production efficiency due to the low material removal rate of CMP, and the wafer manufacturing cost is also increased.

Therefore, developing a method capable of improving the chemical mechanical polishing efficiency of a silicon wafer and improving the material removal rate in the CMP process is a problem to be solved in the field of semiconductor manufacturing.

Disclosure of Invention

The invention aims to provide a laser-assisted polishing method for a monocrystalline silicon wafer, which can be applied to the surface planarization processing process of the monocrystalline silicon wafer and improve the production efficiency of the monocrystalline silicon wafer with high surface quality.

In order to achieve the above object, a laser-assisted polishing method for a single crystal silicon wafer of the present invention is characterized by comprising the steps of:

step (1), providing a monocrystalline silicon wafer subjected to mechanical grinding;

scanning the monocrystalline silicon wafer in the step (1) by using ultrafast laser processing equipment;

step (3), putting the monocrystalline silicon wafer subjected to laser treatment into absolute ethyl alcohol, ultrasonically cleaning and drying;

and (4) carrying out chemical mechanical polishing on the wafer.

The laser parameters set in the laser scanning process in the step (2) are as follows: the laser wavelength is 355nm-1070nm, the laser pulse width is 50fs-500ps, the laser power is 5W-50W, and the laser pulse frequency is 1kHz-1 MHz;

and (3) performing laser scanning on the wafer by using a galvanometer in the step (2), wherein the scanning mode is vertical cross scanning.

And (3) scanning the surface of the wafer by using a vibrating mirror in the step (2) at a certain speed, wherein the scanning speed is 100-3000 mm/s, the scanning interval is 10-200 mu m, and the scanning frequency is 10-30 times.

The invention has the advantages that:

(1) the laser processing adopted by the method is non-contact processing, has no auxiliary material loss, and does not generate secondary damage to the processing material;

(2) the method can effectively improve the material removal rate in the silicon wafer polishing process, shorten the polishing time, greatly improve the production efficiency, improve the yield of the silicon polished wafer and reduce the production cost;

(3) the method reduces the use and discharge of polishing slurry harmful to the environment by shortening the processing time of the chemical mechanical polishing process, thereby reducing the pollution of the silicon wafer processing process to the environment.

Description of the drawings:

FIG. 1 shows a comparison of the material removal efficiency of a CMP process for a laser treated silicon abrasive sheet and an untreated silicon abrasive sheet using the present method;

FIG. 2 is a microscope photograph showing the surface of a laser cross-irradiated silicon abrasive sheet prepared using the present method;

figure 3 is a microscope image of the surface of an untreated silicon abrasive sheet.

The specific implementation mode is as follows:

the embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Example 1:

(1): a silicon single crystal polished wafer manufactured by Tebavance company is taken, is placed in absolute alcohol for ultrasonic cleaning for 10 minutes and is dried.

(2): and (3) placing the polished and cleaned sample on a workbench of a picosecond laser processing system (with the wavelength of 1030nm), setting the laser power to be 9W, the frequency to be 200KHz, the scanning speed to be 500mm/s, the scanning interval to be 30mm and the scanning times to be 5 times, setting the scanning path to be cross scanning, starting the laser processing system to start processing, and obtaining the laser processing silicon wafer with reduced roughness.

(3): and putting the monocrystalline silicon wafer subjected to laser treatment into absolute ethyl alcohol, ultrasonically cleaning for 10 minutes, and drying.

(4): and placing the laser-treated silicon wafer and the untreated mechanical grinding wafer in the same polishing disk for chemical mechanical polishing, and recording the surface quality and the material removal efficiency of the silicon wafer every 20 minutes.

As shown in fig. 1, the results show that the material removal rate of the laser-treated silicon wafer is 3.39 times that of the untreated mechanical abrasive wafer, which greatly improves the processing efficiency.

Example 2:

(1): a monocrystalline silicon grinding sheet produced by the Shunsheng electronic technology company is taken, is placed in absolute alcohol for ultrasonic cleaning for 10 minutes and is dried.

(2): placing the polished and cleaned sample on a workbench of a femtosecond laser processing system (wavelength of 515nm), setting the laser power to be 10W, the frequency to be 100KHz, the scanning speed to be 800mm/s, the scanning interval to be 20mm, scanning times to be 10 times, setting the scanning path to be cross scanning, starting the laser processing system to start processing, and obtaining the laser processing silicon wafer with reduced roughness.

The result shows that the material removal rate of the laser-treated silicon wafer is 1.87 times that of an untreated mechanical grinding wafer, and the processing efficiency is greatly improved.

The technical means according to the aspect of the present invention is not limited to the technical means described above, and includes any combination of the above technical features. The scope of the invention is defined by the appended claims.

Claims

1. A laser assisted polishing method for single crystal silicon wafers, characterized by comprising the steps of:

and (4) carrying out chemical mechanical polishing on the wafer.

2. The laser-assisted polishing method for single crystal silicon wafers as claimed in claim 1, wherein the laser parameters set in step (2) are: the laser wavelength is 355nm-1070nm, the laser pulse width is 50fs-500ps, the laser power is 5W-50W, and the laser pulse frequency is 1kHz-1 MHz.

3. The laser-assisted polishing method for the monocrystalline silicon wafer according to claim 1, wherein the step (2) is performed by scanning the wafer with laser by using a galvanometer, and the scanning mode is vertical cross scanning.

4. The laser-assisted polishing method for the monocrystalline silicon wafer according to claim 1, wherein in the step (2), the laser is scanned on the surface of the wafer at a certain speed by using the oscillating mirror for scanning, the scanning speed is 100mm/s-3000mm/s, the scanning interval is 10 μm-200 μm, and the scanning times are 10-30 times.