CN115430665A - Matrix laser cleaning method for removing nano-scale particles from semiconductor - Google Patents

Abstract

A host laser cleaning method for removing nano-scale particles from a semiconductor, the processing method comprising the steps of: s1, vertically mounting a silicon wafer to be cleaned on a rack in a vacuum chamber, and cooling the rack; s2, after the frame reaches the required temperature, vertically blowing the airflow of the carbon dioxide on the surface of the silicon wafer, and condensing to form a solid film; s3, using an Nd-YAG laser as a cleaning laser; s4, controlling the thickness of the film by using a reflectometer, starting a laser to start cleaning, raising the temperature of the rack after the cleaning is finished, and purging the surface of the silicon wafer; and S5, cooling the rack by using liquid nitrogen, and repeating the operations in the step S2 and the step S4, wherein the solid film is thinned from the thickness, the thickness is reduced by 150nm each time, and the cleaning is finished when the thickness of the film is reduced to 50nm. According to the matrix laser cleaning method for removing the nano-scale particles from the semiconductor, carbon dioxide is used as a matrix, particles with different sizes on a silicon wafer are effectively cleaned under the action of laser, and the substrate can be prevented from being damaged while liquid is not used.

Description

Matrix laser cleaning method for removing nano-scale particles from semiconductor

Technical Field

The invention relates to the technical field of semiconductor cleaning, in particular to a matrix laser cleaning method for removing nano-scale particles from a semiconductor.

Background

The removal of nanoparticles from semiconductor and other fragile surfaces is of great interest for applications in the semiconductor industry and nanotechnology. Currently, the trend towards further miniaturization reduces the size of particles which can further create defects in electronic circuits or nanostructures. Conventional techniques such as megasonic techniques do not meet the cleaning requirements for small size particles. Laser cleaning is one possible alternative cleaning method to solve this problem, i.e. the sample to be cleaned is irradiated with short nanosecond-level laser pulses. The advantage of this technique is that it is cost effective and environmentally friendly, and it is a contactless cleaning method that can selectively treat a single area of a wafer or a photolithographic mask. To date, there are two main laser cleaning methods. The first method is Dry Laser Cleaning (DLC), where the surface to be cleaned is directly illuminated by the laser pulse without any pre-treatment or additional layers. However, the particle positions have small defects, which are generated by local ablation under the particles, and the damage-free particle removal cannot be realized; the second method is vapor laser cleaning (SLC) using water or a water/alcohol mixture applied to the sample prior to the laser pulse, the laser energy either being absorbed directly by the liquid or being transferred from the substrate by thermal conduction resulting in nucleation of bubbles followed by explosive evaporation of the liquid layer. However, liquids are undesirable in the semiconductor industry for various reasons, such as the risk of watermark formation or structural damage that may result from capillary forces. Furthermore, complete wetting of the substrate is an unavoidable prerequisite and a complicated drying step must be added after the cleaning process. To this end, we propose a method of laser cleaning of a substrate to remove nano-scale particles from the semiconductor.

Disclosure of Invention

The main object of the present invention is to provide a method for cleaning a substrate by laser, which can effectively solve the problems of the background art.

A host laser cleaning method for removing nano-scale particles from a semiconductor, the processing method comprising the steps of:

s1, vertically mounting a silicon wafer to be cleaned on a rack in a vacuum chamber, and cooling the rack;

s2, after the frame reaches the required temperature, vertically blowing the airflow of the carbon dioxide on the surface of the silicon wafer, and condensing to form a solid film;

s3, using an Nd-YAG laser as a cleaning laser;

s4, controlling the thickness of the film by using a reflectometer, starting a laser to start cleaning, raising the temperature of the rack after the cleaning is finished, and purging the surface of the silicon wafer;

and S5, cooling the rack by using liquid nitrogen, and repeating the operations in the step S2 and the step S4, wherein the solid film is reduced from thickness to thickness by 150nm each time until the thickness of the film is reduced to 50nm, thus completing cleaning.

Further, the step S1 includes:

(1) filling the vacuum chamber with carbon dioxide as a matrix material;

(2) the rack is cooled with liquid nitrogen at a temperature between 135 and 175K.

Further, the step S2 includes: the condensation rate is between 40 and 350 mL/s.

Further, the step S3 includes: the laser wavelength was 532nm and the full width at half maximum (FWHM) was 9ns.

Further, the step S4 includes:

(1) the thickness of the solid film is 650nm;

(2) the shelf temperature is increased to 185-225K;

(3) and blowing the surface of the silicon wafer by using carbon dioxide gas flow after the temperature is raised.

Further, the step S5 includes:

(1) cooling the stand to 135 to 175K;

(2) repeating the operation for 4 times, wherein the thickness of the solid film is 500nm, 350nm, 200nm and 50nm in sequence.

The invention provides a matrix laser cleaning method for removing nano-scale particles from a semiconductor, which is characterized in that a silicon wafer to be cleaned is vertically arranged on a frame in a vacuum chamber, the vacuum chamber is filled with carbon dioxide to be used as a matrix material, and the frame is cooled to 135K-175K by liquid nitrogen; blowing the airflow of the carbon dioxide on the surface of the silicon slice vertically, condensing to form a solid film, wherein the condensation rate is between 40 and 350 ML/s; the solid layer is transparent to the laser wavelength, and the laser energy can be fully coupled into the substrate film by thermal conduction, thereby avoiding damage to the substrate; YAG laser as cleaning laser with wavelength of 532nm and full width at half maximum (FWHM) of 9ns; controlling the thickness of the film to be 650nm by using a reflectometer, and starting a laser to start cleaning; the matrix sublimes and the solid portion leaves the surface in the form of a tentacle layer, rather than through the liquid phase, thereby avoiding the aforementioned problems of liquid use; raising the temperature of the frame to 185K to 225K, and blowing the surface of the silicon wafer by using carbon dioxide airflow after raising the temperature; and cooling the shelf to 135-175K by using liquid nitrogen, and repeating the operations in the step S2 and the step S4, wherein the solid film is thinned from the thickness, the thickness is reduced by 150nm each time, and the thickness is reduced to 50nm by 500nm, 350nm, 200nm and 50nm in sequence, and then the cleaning is finished. Through the solid films with different thicknesses, the effect of effectively removing particles with different sizes is achieved.

Drawings

FIG. 1 is a schematic flow chart of a laser cleaning method for removing nano-scale particles from a semiconductor according to the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained by combining the specific embodiments.

As shown in fig. 1, a matrix laser cleaning method for removing nano-scale particles from a semiconductor, the processing method comprises the following steps:

s1, vertically mounting a silicon wafer to be cleaned on a rack in a vacuum chamber, and cooling the rack;

s2, after the frame reaches the required temperature, vertically blowing the airflow of the carbon dioxide on the surface of the silicon wafer, and condensing to form a solid film;

s3, using an Nd-YAG laser as a cleaning laser;

s4, controlling the thickness of the film by using a reflectometer, starting a laser to start cleaning, raising the temperature of the rack after the cleaning is finished, and purging the surface of the silicon wafer;

and S5, cooling the rack by using liquid nitrogen, and repeating the operations in the step S2 and the step S4, wherein the solid film is reduced from thickness to thickness by 150nm each time until the thickness of the film is reduced to 50nm, thus completing cleaning.

According to the technical scheme provided by the invention, the step S1 comprises the following steps:

(1) filling the vacuum chamber with carbon dioxide as a matrix material;

(2) the rack is cooled with liquid nitrogen at a temperature between 135 and 175K.

According to the technical scheme provided by the invention, the step S2 comprises the following steps: the condensation rate is between 40 and 350 mL/s.

According to the technical scheme provided by the invention, the step S3 comprises the following steps: the laser wavelength was 532nm and the full width at half maximum (FWHM) was 9ns.

According to the technical scheme provided by the invention, the step S4 comprises the following steps:

(1) the thickness of the solid film is 650nm;

(2) the shelf temperature is increased to 185-225K;

(3) and blowing the surface of the silicon wafer by using carbon dioxide gas flow after the temperature is raised.

According to the technical scheme provided by the invention, the step S5 comprises the following steps:

(1) cooling the stand to 135 to 175K;

(2) repeating the operation for 4 times, wherein the thickness of the solid film is 500nm, 350nm, 200nm and 50nm in sequence.

The invention provides a matrix laser cleaning method for removing nano-scale particles from a semiconductor, which is characterized in that a worker vertically installs a silicon wafer to be cleaned on a frame, places the silicon wafer in a vacuum chamber, fills the vacuum chamber with carbon dioxide, and cools the frame to 135K to 175K by using liquid nitrogen; blowing the airflow of the carbon dioxide on the surface of the silicon slice vertically, condensing to form a solid film, wherein the condensation rate is between 40 and 350 ML/s; YAG laser as cleaning laser with wavelength of 532nm and full width at half maximum (FWHM) of 9ns; then, a worker controls the thickness of the film to be 650nm by using a reflectometer, and starts a laser to start cleaning; after the temperature is increased to 185K to 225K, blowing the surface of the silicon wafer by using carbon dioxide airflow after the temperature is increased; and cooling the frame to 135 to 175K by using liquid nitrogen, and repeating the operation in the step S2 and the operation in the step S4, wherein the thickness of the solid film is reduced by 150nm each time, and the thickness is reduced to 50nm by 500nm, 350nm, 200nm and 50nm in sequence, so that the cleaning can be completed, particles with different sizes can be effectively cleaned, and the substrate is prevented from being damaged when no liquid is used.

The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (6)

1. A method of laser cleaning a substrate to remove nano-scale particles from a semiconductor, comprising: the processing method comprises the following steps:

s1, vertically mounting a silicon wafer to be cleaned on a rack in a vacuum chamber, and cooling the rack;

s2, after the frame reaches the required temperature, vertically blowing the airflow of the carbon dioxide on the surface of the silicon wafer, and condensing to form a solid film;

s3, using an Nd-YAG laser as a cleaning laser;

s4, controlling the thickness of the film by using a reflectometer, starting a laser to start cleaning, raising the temperature of the rack after the cleaning is finished, and purging the surface of the silicon wafer;

and S5, cooling the rack by using liquid nitrogen, and repeating the operations in the step S2 and the step S4, wherein the solid film is thinned from the thickness, the thickness is reduced by 150nm each time, and the cleaning is finished when the thickness of the film is reduced to 50nm.

2. The method of claim 1, wherein the substrate is a semiconductor substrate, and the method comprises: the step S1 comprises the following steps:

(1) filling the vacuum chamber with carbon dioxide as a matrix material;

(2) the rack is cooled with liquid nitrogen at a temperature between 135 and 175K.

3. The method of claim 1, wherein the substrate is a semiconductor substrate, and the method comprises: the step S2 includes: the condensation rate is between 40 and 350 mL/s.

4. The method of claim 1, wherein the substrate is a semiconductor substrate, and the method comprises: the step S3 comprises the following steps: the laser wavelength was 532nm and the full width at half maximum (FWHM) was 9ns.

5. The method of claim 1, wherein the substrate is a semiconductor substrate, and the method comprises: the step S4 includes:

(1) the thickness of the solid film is 650nm;

(2) the shelf temperature is increased to 185-225K;

(3) and blowing the surface of the silicon wafer by using carbon dioxide gas flow after the temperature is raised.

6. The method of claim 1, wherein the substrate is a semiconductor substrate, and the method comprises: the step S5 comprises the following steps:

(1) cooling the stand to 135 to 175K;

(2) repeating the operation for 4 times, wherein the thickness of the solid film is 500nm, 350nm, 200nm and 50nm in sequence.

Images