CN112086342B - Technological method for effectively removing back sealing points on back surface of back sealing silicon wafer - Google Patents

Technological method for effectively removing back sealing points on back surface of back sealing silicon wafer Download PDF

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Publication number
CN112086342B
CN112086342B CN201910519243.9A CN201910519243A CN112086342B CN 112086342 B CN112086342 B CN 112086342B CN 201910519243 A CN201910519243 A CN 201910519243A CN 112086342 B CN112086342 B CN 112086342B
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cleaning
silicon wafer
back sealing
polishing
wax
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CN112086342A (en
Inventor
林霖
史训达
刘云霞
陈克强
杨少坤
周莹莹
李奇
李兰军
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Youyan Semiconductor Silicon Materials Co ltd
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Youyan Semiconductor Silicon Materials Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02013—Grinding, lapping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02016—Backside treatment

Abstract

The invention discloses a process method for effectively removing back sealing points on the back surface of a back sealing silicon wafer. The process method comprises the following steps: (1) Cleaning the back cover of the back sealing sheet by using a single-sided polishing machine, wherein the pressure provided by the polishing machine is 50-100 g/cm 2 The cleaning liquid is pure water, the flow is 4-20L/min, and the polishing time is 1-100 minutes; (2) Cleaning and spin-drying the back sealing sheet treated in the step (1), wherein the cleaning liquid is a mixed solution containing hydrogen peroxide and ammonia; (3) And (5) polishing the back sealing piece in a rough, medium and fine mode by using a wax patch. The invention can eliminate the influence of the back sealing point on the surface morphology of the polished silicon wafer, and reduce the probability of the Dimple defect in the subsequent CMP process, thereby improving the overall yield of the silicon substrate material in the manufacturing process.

Description

Technological method for effectively removing back sealing points on back surface of back sealing silicon wafer
Technical Field
The invention relates to a process method for effectively removing back sealing points on the back surface of a back sealing silicon wafer, and belongs to the technical field of semiconductor materials.
Background
Conventional single-sided Chemical Mechanical Polishing (CMP) methods for silicon substrate materials typically use a wax patch to attach a wafer to a very flat fixture and polish the wafer on a single-sided polisher. And only one layer of wax film with the thickness of 0.5-2 microns is arranged between the silicon wafer and the clamp, and the silicon wafer and the clamp are adhered to each other, so that tight connection between the silicon wafer and the clamp is ensured.
If hard particles are mixed between the silicon wafer and the clamp, and the diameter of the particles exceeds the thickness of the wax film, a stress point is formed at the position of the particles under the high pressure of the polishing machine, and after polishing is finished, a pit is formed at the position of the particles corresponding to the polished surface, so that the defect of a simple is formed. So that the local flatness of the silicon wafer is deteriorated, and the silicon substrate sheet with such defects cannot be accepted in the subsequent photolithography process.
In order to avoid the occurrence of the situation, each manufacturer usually cleans particles adsorbed on the surface of the silicon wafer by using an SC-1 ultrasonic mode or a soft brush brushing mode before the wax patch is arranged, and spin-dries the particles. However, the method is only suitable for removing particles which float to the surface of the silicon wafer in the air and are adsorbed by static electricity. Particles that are adsorbed by van der Waals and atomic forces appear to be unable to function.
For low resistivity heavily doped silicon substrate sheets, a polysilicon layer, or silicon dioxide layer, is typically back-sealed on the back side (the non-polished side) of the wafer using Chemical Vapor Deposition (CVD) methods prior to CMP for gettering purposes.
In the CVD process, the residual particles on the surface of the silicon wafer can be wrapped by the polysilicon layer or the silicon dioxide layer to form a micron-sized salient point which cannot be seen by naked eyes; the CVD process itself may also form dot-like aggregates on the wafer surface, also known as micron-sized bumps, which are collectively referred to as backset points. The acting force between the two back sealing points and the silicon wafer belongs to intermolecular acting force, and cannot be cleaned in the subsequent cleaning process. And after chemical mechanical polishing, a simple defect can be formed on the polished surface of the silicon wafer, so that the qualification rate of the CMP process is reduced.
Disclosure of Invention
The invention aims to provide a process method for effectively removing back sealing points on the back surface of a back sealing silicon wafer, so as to eliminate the influence of the back sealing points on the surface morphology of the polished silicon wafer, reduce the probability of the Dimple defect in the subsequent CMP process and further improve the overall yield of the silicon substrate material in the manufacturing process.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a process method for effectively removing back sealing points on the back surface of a back sealing silicon wafer comprises the following steps:
(1) Cleaning the back cover of the back sealing sheet by using a single-sided polishing machine, wherein the pressure provided by the polishing machine is 50-100 g/cm 2 The cleaning liquid is pure water, the flow is 4-20L/min, and the polishing time is 1-100 minutes;
(2) Cleaning and spin-drying the back sealing sheet treated in the step (1), wherein the cleaning liquid is a mixed solution containing hydrogen peroxide and ammonia;
(3) And (5) polishing the back sealing piece in a rough, medium and fine mode by using a wax patch.
In the step (1), the back cover of the back sealing sheet is cleaned by a single-sided polisher, and the silicon wafer and the clamp can be bonded by a wax-free mode or a wax-free mode. The polishing cloth used for cleaning treatment adopts polyurethane material, a non-woven fabric structure, and a surface fluff, and the hardness of the polishing cloth is 40-60 Aspe-C.
As one of the preferable schemes of the invention, the step (1) uses a single-sided polishing machine to clean the back cover of the back sealing piece, and the polishing machine provides a pressure intensity of 50-100 g/cm 2 . The polishing machine provides a pressure of less than 50g/cm 2 When the back surface of the back-sealed silicon wafer is polished, the back sealing point on the back surface of the back-sealed silicon wafer cannot be effectively removed, and the back sealing point remains on the back surface of the silicon wafer, and a simple defect is generated in the subsequent wax polishing process. The polishing machine provides a pressure higher than 100g/cm 2 When the back sealing point on the back of the back sealing silicon wafer can be peeled off by the polishing cloth under the action of mechanical motion, but because the pressure is too large, the peeled point-shaped particles can leave obvious scratch marks on the back sealing film of the back sealing silicon wafer under the drive of the polishing cloth and pure water. Such scratches are not acceptable for subsequent epitaxial processes. More preferably, the polishing machine provides a pressure of 70 to 90g/cm 2 The optimal result of the back sealing point removing effect and no obvious scratch can be obtained in the pressure range.
As one of the preferable schemes of the invention, the back sealing piece treated in the step (1) is cleaned and dried in the step (2), the cleaning needs two steps, the cleaning liquid is a mixed solution containing hydrogen peroxide and ammonia in the first step, wherein the mass percent of the hydrogen peroxide is 2% -10%, the mass percent of the ammonia is 1% -8%, the cleaning temperature is 50-80 ℃ and the cleaning time is 1-60 minutes, and then the back sealing piece is cleaned by deionized water. The purpose of this step of cleaning is to dissolve away the wax film attached to the surface of the silicon wafer. And secondly, the cleaning solution is a mixed solution containing hydrogen peroxide and ammonia, wherein the mass percent of the hydrogen peroxide is 1-5%, the mass percent of the ammonia is 0.2-3%, the cleaning temperature is 60-80 ℃, the cleaning time is 1-60 minutes, and the purpose is to remove residual particles on the surface of the silicon wafer in a mode of matching with ultrasound, and then the silicon wafer is cleaned by deionized water and then spin-dried. Wherein the frequency of the ultrasonic wave is 38-128 KHz.
As one of the preferable schemes of the invention, the back sealing piece is polished roughly, moderately and finely in the step (3) in a mode of a wax-containing patch, wherein the wax-containing patch is liquid wax, the wax content in the liquid wax is 10% -40%, and the solvent is isopropanol, so that the thickness of the wax film on the back of the final silicon wafer is ensured to be uniform.
The invention has the advantages that:
the back sealing point generated in the CVD process on the back surface of the back sealing piece is effectively removed, the probability of generating a simple defect in the subsequent CMP process is reduced, and the yield of the CMP process is improved, so that the overall yield of the silicon substrate material manufacturing process is improved.
Drawings
FIG. 1 is a process flow diagram for use with the present invention.
FIG. 2 is a chart showing the SBIR box in example 1.
Detailed Description
The invention is further described with reference to the drawings and examples, which are not meant to limit the scope of the invention.
As shown in fig. 1, the process flow of the present invention is shown. The process method for removing the back sealing point of the back surface of the back sealing silicon wafer comprises the following steps: and cleaning the back cover of the back sealing sheet by using a single-sided polishing machine, cleaning the surface of the silicon wafer, spin-drying, and polishing the back sealing sheet roughly, moderately and finely in a waxed patch mode.
Example 1
And (3) adhering the silicon wafer with the 6-inch back-sealed polycrystalline silicon on a clamp of a single-sided polishing machine in a wax patch mode, wherein the surface of the silicon wafer to be polished is used as a waxed surface and is contacted with the clamp. The liquid wax used was 30% wax and 70% isopropyl alcohol. The polishing cloth used for cleaning treatment adopts polyurethane material, a non-woven fabric structure, and a surface fluff, and has a hardness of 45 Aspe-C. When cleaning, the polishing machine provides a pressure of 70g/cm 2 The cleaning liquid is pure water, the flow rate is 10L/min, and the polishing time is 3 minutes.
In the cleaning process, the silicon wafer is immersed in a cleaning solution with hydrogen peroxide content of 8% and ammonia content of 4%, the temperature of the cleaning solution is 65 ℃, and the immersing time is 7 minutes. And (3) washing the cleaning liquid on the surface of the silicon wafer with deionized water after washing. And immersing the silicon wafer into a cleaning solution with hydrogen peroxide content of 4.5% and ammonia content of 2%, wherein the temperature of the cleaning solution is 70 ℃, and the immersing time is 5 minutes. And after washing, washing the cleaning liquid on the surface of the silicon wafer with deionized water again, and finally spin-drying the silicon wafer.
And bonding the silicon wafer on a clamp of the single-sided polishing machine in a wax patch mode, wherein the surface of the silicon wafer which is not required to be polished is used as a waxed surface and is contacted with the clamp. The liquid wax used was 25% wax and 75% isopropyl alcohol.
In the final single-sided coarse, medium and fine polishing procedures, coarse polishing adopts polishing cloth with the hardness of 80# Asker C, coarse polishing adopts polishing solution with colloidal silica suspended particles with the particle size of 80-90 nm, the polishing solution is diluted 15 times by deionized water, the flow rate of the polishing solution is 7L/min, medium polishing adopts polishing cloth with the hardness of 68Asker C, medium polishing adopts polishing solution with the particle size of 20-40 nm, the flow rate of the polishing solution is 5L/min, and fine polishing adopts polishing solution with the particle size of 5-8 nm, the flow rate of the polishing solution is 1.5L/min.
The method is used for processing 300 pieces of 6-inch back-sealed polycrystalline silicon wafers, ADE8300 is used for detecting the geometric shape of each piece of silicon wafer after processing is finished, and SBIR (Standard test IR) is used for measuring whether a diode defect exists or not. The SBIR (Site Back-side Ideal Range) refers to the difference between the maximum value and the minimum value of the height from the fixed surface, which is defined by evaluating each of the divided regions (Site, dividing the entire surface of the single wafer into each region with a certain size) with respect to the flatness, with the fixed surface to which the single wafer is adsorbed and fixed as a fixed reference.
FIG. 2 is SBIR contrast data of the batch of silicon wafers of example 1, after polishing with wax, which was identical to another batch of silicon wafers without backside treatment by the method of the invention, but with wax polishing process conditions. It can be seen that in the backside processed batch, no outlier of the SBIR data, i.e. the backside seal was completely pretreated, and no simple defect was observed after wax polishing.

Claims (4)

1. A process method for effectively removing back sealing points on the back surface of a back sealing silicon wafer is characterized by comprising the following steps:
(1) Bonding the back sealing silicon wafer on a clamp of a single-sided polishing machine in a wax patch mode, wherein one surface of the back sealing silicon wafer to be polished is used as a waxing surface and is contacted with the clamp, the back cover of the back sealing silicon wafer is cleaned by the single-sided polishing machine, the pressure provided by the polishing machine is 50-100 g/cm < 2 >, the cleaning liquid is pure water, the flow is 4-20L/min, and the polishing time is 1-100 minutes;
(2) Cleaning and spin-drying the back-sealed silicon wafer treated in the step (1), wherein the cleaning liquid is a mixed solution containing hydrogen peroxide and ammonia; the cleaning comprises two steps: firstly, the mass percentage of hydrogen peroxide in the cleaning liquid is 2% -10%, the mass percentage of ammonia is 1% -8%, the cleaning temperature is 50-80 ℃, the cleaning time is 1-60 minutes, and then deionized water is used for cleaning; secondly, the mass percentage of hydrogen peroxide in the cleaning liquid is 1% -5%, the mass percentage of ammonia is 0.2% -3%, the cleaning temperature is 60-80 ℃, the cleaning time is 1-60 minutes, and the cleaning is carried out by matching with an ultrasonic mode, and then deionized water is used for cleaning;
(3) And bonding the back sealing silicon wafer on a clamp of a single-sided polishing machine in a wax patch mode, wherein the surface of the back sealing silicon wafer which is not required to be polished is used as a waxing surface and is contacted with the clamp, and rough, medium and fine polishing is carried out on the back sealing silicon wafer.
2. The process according to claim 1, wherein the polishing cloth used for the cleaning treatment in the step (1) is made of polyurethane, and has a surface hardness of 40 to 60Aske-C.
3. A process according to claim 1, characterized in that the ultrasound is used at a frequency of 38-128 KHz.
4. The process according to claim 1, wherein in the step (3), the wax patch is a liquid wax, the wax content in the liquid wax is 10% -40%, and the solvent is isopropyl alcohol.
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CN113140446A (en) * 2021-04-02 2021-07-20 杭州中欣晶圆半导体股份有限公司 Method for improving pit defect of LTO back-sealed silicon wafer
CN116516458B (en) * 2023-06-09 2024-04-16 中电科先进材料技术创新有限公司 Preparation method of intrinsic gettering silicon wafer and intrinsic gettering silicon wafer

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