CN116252400A

CN116252400A - Silicon wafer cutting process

Info

Publication number: CN116252400A
Application number: CN202310167323.9A
Authority: CN
Inventors: 张波; 赵彩霞; 赵军龙; 杨飞飞; 梁玲; 杨旭彪
Original assignee: Shanxi Luan Solar Energy Technology Co Ltd
Current assignee: Shanxi Luan Solar Energy Technology Co Ltd
Priority date: 2023-02-27
Filing date: 2023-02-27
Publication date: 2023-06-13

Abstract

The invention relates to the technical field of silicon wafer cutting, in particular to a silicon wafer cutting process, silicon blocks are cut by diamond wires to form silicon wafers, the silicon blocks are cut into the silicon wafers by the diamond wires in cutting fluid, the cutting fluid is water peroxide or isopropanol solution containing dioxygen, and the concentration of dioxygen ions in the cutting fluid is 0.05 mol/L-0.8 mol/L. 1. According to the invention, the silicon wafer is cut in the cutting liquid, the cutting liquid can take away heat generated in the cutting process, and compared with spraying the cutting liquid, the silicon wafer is less prone to generating local high temperature, and warping is avoided; 2. the cutting fluid contains dioxygen ions, so that free silicon on a cutting surface can be oxidized to form silicon dioxide, and further silicon atoms are combined by hydroxyl ions to form new covalent bonds, thereby ensuring the stability of cutting.

Description

Silicon wafer cutting process

Technical Field

The invention relates to the technical field of silicon wafer cutting, in particular to the field of large-size silicon wafer cutting.

Background

Silicon is the most commonly used semiconductor material, and when molten elemental silicon solidifies, the silicon atoms are arranged in a diamond lattice to form nuclei, which grow into crystal grains with the same crystal face orientation, forming monocrystalline silicon.

The monocrystalline silicon material is manufactured by quartz sand-metallurgical grade silicon-purifying and refining-depositing polycrystalline silicon ingot-monocrystalline silicon-silicon wafer cutting. The monocrystalline silicon material is mainly used as a semiconductor material and utilizes solar energy to generate electricity, supply heat and the like.

Crystal pulling is generally performed from polycrystalline silicon to single crystal silicon, and means that silicon atoms of molten elemental silicon are arranged in a diamond lattice to form a plurality of crystal nuclei when solidified, and if the crystal nuclei grow into crystal grains having the same crystal face orientation, the crystal grains are combined in parallel to crystallize into single crystal silicon. The single crystal silicon crystallized as a whole is a columnar silicon ingot, and therefore it is necessary to divide the columnar silicon ingot into a plurality of pieces and then cut the pieces into pieces. The cutting process refers to the process of cutting the segmented massive silicon ingot into slices.

In the prior art, a diamond wire is generally adopted to cut a massive silicon ingot into slices, the diamond wire makes reciprocating linear motion, the silicon block slowly sinks, and then the silicon block is cut into slices by the diamond wire, and in the cutting process, the cutting liquid needs to be continuously sprayed. The main problems in the cutting process are 1, uneven thickness and uneven crystal face of the cut silicon wafer, 2, deeper damaged layer of the cut silicon wafer, 3, fragments of the cut silicon wafer, 4, bending degree and warping degree of the cut silicon wafer, etc.

When diamond wires are used for cutting into pieces, various problems are caused mainly because 1, silicon materials are hard and brittle, 2, the temperature difference is obvious due to the fact that more heat is generated in the cutting process, and 3, the diamond wires have elasticity and vibrate to cause jumper wires and the like.

Glass containing silica as a main component can be cut into any shape in water without generating fragments, because the inside of the glass is a special structure formed by connecting a plurality of small silica polyhedron structures in series. Wherein each polyhedron consists of 4 peripheral oxygen atoms and silicon atoms positioned in the middle, and the 4 oxygen atoms and the silicon atoms are connected by a silicon-oxygen covalent bond. When the glass is put into water, a part of water molecules penetrate into the network structure inside the glass, so that the stable structure is destroyed, the original structure is destroyed, and the glass is weakened, namely, the silicon-oxygen covalent bond playing a role of connection is weakened, so that the glass is easily sheared. In addition, silicon atoms are attracted by hydroxyl groups in water molecules to form new covalent bonds, so that the glass can be ensured not to be broken in a large area.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: and the problems of fragments, tilted wafers, uneven thickness and uneven crystal faces generated during cutting of the silicon wafer are solved.

Those skilled in the art know that if the cutting speed is slow enough, the probability of generating fragments, fins, uneven thickness and uneven crystal faces is reduced, but too slow cutting speed in the process production not only affects the production efficiency, but also causes waste in time span, which is not preferable from the aspect of the process production. The inventor researches on deep problems of fragments, fins, uneven thickness and uneven crystal faces generated during cutting of a silicon wafer, and discovers that local temperature unevenness is caused mainly during rapid cutting, and meanwhile, due to uneven internal stress of the silicon wafer, diamond wire jump vibration further causes the problems.

The technical scheme adopted by the invention is as follows: a silicon wafer cutting process is characterized in that silicon blocks are cut by diamond wires to form silicon wafers, the silicon blocks are cut into the silicon wafers by the diamond wires in cutting fluid, the cutting fluid is water peroxide or isopropanol solution containing dioxygen, and the concentration of dioxygen ions in the cutting fluid is 0.05 mol/L-0.8 mol/L.

The silicon block is pressed down to the diamond wire to be cut by the diamond wire, the thickness of a diamond particle plating layer on the diamond wire is 3-5um, the linear speed of the diamond wire is 1300-1500m/min during cutting, the average cutting speed of a workpiece is 15-30mm/min, the tension of the diamond wire is 11-20N, and the temperature of cutting fluid is 20-30 ℃.

The cutting fluid also contains 0.1-0.5% of dispersant polyacrylate by mass percent.

The silicon blocks are arranged on the crystal support after being wrapped by the resin layer, in the cutting process, the silicon wafer is firstly cut by the resin layer and then cut by the silicon blocks, the outer side of the resin layer wrapping the silicon blocks is provided with a plurality of guide grooves which are in parallel structure, the distance between every two adjacent guide grooves is equal to the thickness of the silicon wafer to be cut, the width of each guide groove is equal to the diameter of the diamond wire, and the depth of each guide groove is 1-2mm.

The diamond wires are arranged in parallel on the same horizontal plane, and the movement directions of the adjacent diamond wires are opposite in the cutting process.

The beneficial effects of the invention are as follows: 1. according to the invention, the silicon wafer is cut in the cutting liquid, the cutting liquid can take away heat generated in the cutting process, and compared with spraying the cutting liquid, the silicon wafer is less prone to generating local high temperature, and warping is avoided; 2. the cutting fluid contains dioxygen ions, free silicon on the cutting surface can be oxidized to form silicon dioxide, and then silicon atoms are combined by hydroxyl ions to form new covalent bonds, so that the stability of cutting is ensured, meanwhile, the dispersant polyacrylate alcohol in the cutting fluid can enable the silicon atoms generated by cutting to be rapidly dispersed, and stress accumulation on the cutting surface is avoided, so that the cutting surface is not only smooth, but also the silicon wafer is not easy to break and warp; 3. in the cutting process, the cutting surface is soaked in the cutting liquid, the cutting liquid can buffer the vibration of the diamond wire, so that the problem of uneven silicon wafers is solved, meanwhile, the cutting liquid provides buoyancy and buffering for the silicon wafers, and the fragmentation of the silicon wafers can be reduced; 4. the outside of the resin layer of the package silicon block is provided with a guide groove, and the guide groove guides the diamond wire, so that uneven cutting of the silicon wafer is avoided, and the vibration of the diamond wire is reduced. 5. The wedge-shaped line below the diamond wire can provide support between two cutting surfaces, so that resistance generated during cutting of the diamond wire can be reduced, meanwhile, the silicon wafer is damped, the silicon wafer is prevented from being cracked, and the cutting efficiency of the diamond wire is improved.

Drawings

FIG. 1 is a schematic diagram of the structure of the present invention;

FIG. 2 is a schematic three-view of a silicon block to be cut;

FIG. 3 is a schematic view of the A-A structure of FIG. 2;

wherein, 1, a first diamond wire wheel, 2, a second diamond wire wheel, 3, a guide wheel, 4, a silicon block, 5, a resin layer, 6, a guide groove, 7, a silicon single crystal wrapped by the resin layer, 8, and a wedge wire.

Description of the embodiments

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples. The following examples are illustrative of the invention but are not intended to limit the scope of the invention.

As shown in fig. 1-3, in a silicon wafer cutting process, a silicon wafer is formed by cutting a silicon block by a diamond wire, and the silicon block is cut into a silicon wafer by the diamond wire in a cutting liquid, wherein the cutting liquid is water peroxide or a solution of isopropanol containing dioxygen. In one embodiment, the cutting fluid is an aqueous hydrogen peroxide solution and the concentration of dioxygen ions in the cutting fluid is 0.05 mole/liter. In one embodiment, the cutting fluid is a solution of dioxygen-containing isopropyl alcohol, the concentration of dioxygen ions in the cutting fluid is 0.8 mole/liter, and in one embodiment, the cutting fluid is a solution of dioxygen-containing isopropyl alcohol, the concentration of dioxygen ions in the cutting fluid is 0.5 mole/liter. In the invention, the peroxide is not required to completely oxidize the cut surface of the silicon wafer after cutting, and the purpose is to oxidize the free silicon generated at the cutting point, thereby damaging the bonding stability among the silicon atoms at the cutting point.

In one embodiment, the difference in cutting is not large when the pressing speed of the silicon block is 15mm/min, 25mm/min and 30mm/min, and the flatness of the cut surface starts to be poor when the pressing speed of the silicon block is 50 mm/min.

In one embodiment, the take-up reel is first fed with 3.8km diamond wire as the work piece begins to process. In the cutting process, the cutting tension of the diamond wire is 14N, the linear speed of the diamond wire is 1300m/min, and the feeding cutting speed is 15mm/min; the main cutting speed is 25mm/min; the cutting speed of the cutter is 15mm/min, the temperature of the cutting fluid is 20+/-1 ℃, the whole silicon block 4 wrapped with the resin layer 5 moves towards the diamond wire under the drive of the cutting machine frame in the cutting process, the diamond wire firstly walks from the head end to the tail end of the main roller in a reciprocating cutting mode in the cutting process, after the diamond wire cuts into the workpiece for 120mm, the diamond wire walks from the tail end to the head end of the main roller in a reciprocating cutting mode, and each reciprocating process diamond wire spirally walks in a groove of the main roller.

The cutting fluid also contains 0.2 percent of dispersant polyacrylate by mass. The dispersant polyacrylate can enable silicon atoms generated by cutting to be rapidly dispersed, and stress accumulation on a cutting surface is avoided, so that the cutting surface is not only smooth, but also is not easy to break and warp a silicon wafer.

The silicon blocks are arranged on the crystal support after being wrapped by the resin layer, in the cutting process, the silicon blocks are cut after the silicon chips are firstly cut by the resin layer, guide grooves are arranged on the outer side of the resin layer wrapping the silicon blocks, a plurality of guide grooves are formed in parallel, the distance between every two adjacent guide grooves is equal to the thickness of the silicon chips to be cut, the width of each guide groove is equal to the diameter of a diamond wire (if a wedge wire is adopted, the diameter of the diamond wire is equal to the diameter of the narrow end of the wedge wire), and the depth of each guide groove is 2mm. In one embodiment, the resin is an epoxy resin. The guide groove guides the diamond wire, so that uneven cutting of the silicon wafer is avoided, and vibration of the diamond wire is reduced. In one embodiment d1=2 mm and d2=1 cm. In one embodiment, the resin is a resin plate, ABS resin.

Claims

1. A silicon wafer cutting process for cutting silicon blocks by diamond wires to form silicon wafers is characterized in that: the silicon block is cut into silicon chips by diamond wires in a cutting fluid, wherein the cutting fluid is water peroxide or isopropanol solution containing dioxygen, and the concentration of dioxygen ions in the cutting fluid is 0.05 mol/L-0.8 mol/L.

2. A silicon wafer dicing process according to claim 1, wherein: the silicon block is pressed down to the diamond wire to be cut by the diamond wire, the thickness of a diamond particle plating layer on the diamond wire is 3-5um, the linear speed of the diamond wire is 1300-1500m/min during cutting, the average cutting speed of a workpiece is 15-30mm/min, the tension of the diamond wire is 11-20N, and the temperature of cutting fluid is 20-30 ℃.

3. A silicon wafer dicing process according to claim 1, wherein: the cutting fluid also contains 0.1-0.5% of dispersant polyacrylate by mass percent.

4. A silicon wafer dicing process according to claim 1, wherein: the silicon blocks are arranged on the crystal support after being wrapped by the resin layer, in the cutting process, the silicon wafer is firstly cut by the resin layer and then cut by the silicon blocks, the outer side of the resin layer wrapping the silicon blocks is provided with a plurality of guide grooves which are in parallel structure, the distance between every two adjacent guide grooves is equal to the thickness of the silicon wafer to be cut, the width of each guide groove is equal to the diameter of the diamond wire, and the depth of each guide groove is 1-2mm.

5. A silicon wafer dicing process according to claim 1, wherein: the diamond wires are arranged in parallel on the same horizontal plane, and the movement directions of the adjacent diamond wires are opposite in the cutting process.