CN110497546A - Method and equipment for free-bonded composite abrasive multi-wire cutting silicon wafer - Google Patents

Abstract

A method and equipment for multi-wire cutting of silicon wafers with free-fixed composite abrasives, belonging to the technical field of semiconductor material processing, which solves the problems existing in silicon crystal slicing. The method for multi-wire cutting of silicon wafers with free-fixed composite abrasives includes the use of fixed abrasives The method of multi-wire cutting saws the silicon ingot, and sprays the abrasive liquid containing suspended diamond abrasive grains to the cutting area at the same time; The liquid is brought into the slit of the silicon crystal ingot to form free abrasive grains and consolidated abrasive grains to work together to saw the silicon crystal ingot, and cut the silicon crystal ingot into several pieces in one process; free-consolidated The composite abrasive multi-wire cutting equipment for silicon wafers includes free abrasive multi-wire cutting equipment, and diamond abrasive grains are consolidated on the surface of all wires of the free abrasive multi-wire cutting equipment; the invention is used for cutting silicon wafers.

Description

Method and equipment for free-bonded composite abrasive multi-wire cutting silicon wafer

technical field

The invention belongs to the technical field of semiconductor material processing, and in particular relates to a method and equipment for multi-wire cutting of silicon wafers with free-solidified composite abrasives.

Background technique

Silicon-based semiconductor processing technology is a key technical condition for the development of high-tech industries such as integrated circuits, electronic information, and solar photovoltaics. Silicon crystal slicing is the front-end process of the semiconductor processing industry chain, and its processing capacity directly determines the performance and quality of subsequent processes and end products. In order to continuously improve the performance and economic benefits of end products, silicon crystal slicing processing technology is required to develop in the direction of large diameter, small thickness, high quality, high production capacity, high efficiency and low consumption. In the processing of silicon crystals with a diameter of 300mm and above, and slice kerfs of 120μm and below, the free abrasive multi-wire cutting technology and the diamond-bonded abrasive multi-wire cutting technology are currently widely used.

The free abrasive multi-wire cutting technology uses multiple parallel wires to apply sawing power, and the abrasive particles suspended in the abrasive liquid are used as sawing tools to slice silicon crystal ingots.

The diamond-bonded abrasive multi-wire cutting technology uses multiple parallel wires with diamond or silicon carbide abrasive grains on the surface to directly saw the silicon crystal ingot, and at the same time use the cooling liquid to cool it.

For the free abrasive multi-wire cutting technology, because the abrasive particles are suspended in the abrasive liquid, the effective cutting contact interface is very small, resulting in long cutting time and relatively low cutting efficiency; Affected by factors such as density and viscosity, the surface roughness of silicon wafers cut by free abrasives is large; the size deviation of silicon wafers cut with a finer diameter 120 μm saw wire is often higher than that of saw wires with a diameter of 140 μm; free abrasives are cut in a brittle mode For silicon ingots, the surface of the processed silicon crystal slices has isotropic morphology; and affected by the elastodynamic effect of the grinding fluid, the grinding degree of the slit entrance, middle and slit exit is uneven, resulting in different positions of the silicon crystal slices. First, the surface shape errors such as warpage, curvature and TTV of silicon wafers vary greatly; these problems limit the application and development of free abrasive wire saw cutting.

For the fixed abrasive multi-wire cutting technology, the abrasive grains are in direct rigid contact with the silicon ingot, although the cutting efficiency increases, and as the wire wear increases, it shows a better plastic removal effect and less surface cracks, but the surface cracks Deeper, the average fracture strength of the wafer is lower, and the life of the saw wire is shortened; in addition, the bonded abrasive cuts the silicon wafer in a brittle-plastic mixed mode, and the surface of the silicon crystal slice tends to have obvious parallel and uneven cut marks; The elastic modulus of silicon wafers sawn by fixed abrasives is stronger in the direction parallel to the line marks, and weaker in the direction perpendicular to the line marks; Accepted high breakage rate; the critical fracture performance of silicon crystal slices cut by fixed abrasives along the vertical cutting grain direction is 57% of that of silicon crystal slices cut by free abrasives, and the specific reasons for the extreme fragility of silicon crystal slices cut by fixed abrasives are still unclear; Due to these essential disadvantages, the fixed abrasive multi-wire cutting technology cannot completely replace the free abrasive wire sawing process.

Generally speaking, the silicon wafer multi-wire cutting technology has been developing in the direction of increasing the size of the processed workpiece, thinning the slice, and improving the quality of the silicon wafer. The main goals for the silicon wafer industry are to improve the surface quality of silicon wafers by reducing total thickness variation and surface defects, and to increase productivity by reducing wafer thickness. The larger the silicon ingot, the thinner the kerf, the longer and deeper the thin kerf between the saw wire and the silicon ingot, the more uneven the grinding fluid will be and even cut off, which will seriously affect the full play of the grinding fluid. The development needs of the semiconductor silicon wafer industry have increasingly brought greater difficulty to manufacturing technology. The diameter of silicon wafers has gradually increased and the thickness has continued to decrease. The current processing methods cannot meet the development requirements of silicon wafers.

Contents of the invention

The purpose of the present invention is in order to solve the above-mentioned problem that silicon crystal slicing exists, a kind of method and equipment of free-solidified composite abrasive multi-wire cutting silicon wafer are provided, and its technical scheme is as follows:

A method for free-solidified composite abrasive multi-wire cutting of silicon wafers, which includes sawing silicon ingots by using a fixed abrasive multi-wire cutting method, and spraying abrasive fluid containing suspended diamond abrasive grains to the cutting area; The metal wire with diamond abrasive grains brings the abrasive liquid containing suspended diamond abrasive grains into the slit of the silicon crystal ingot during the wire walking process, forming free abrasive grains and consolidated abrasive grains to work together to saw the silicon crystal ingot Cutting, cutting the silicon ingot into several pieces in one process.

The free-bonded composite abrasive multi-wire cutting equipment for silicon wafers includes free abrasive multi-wire cutting equipment, and diamond abrasive grains are consolidated on the surface of all wires of the free abrasive multi-wire cutting equipment.

The beneficial effects of the present invention are: the present invention integrates the advantages of free-consolidated abrasive grinding and makes up for their respective deficiencies; Abrasive grains exhibit a certain movement law; silicon crystal ingots have the properties of brittle materials, and free abrasive grains and consolidated abrasive grains perform double friction coupling grinding on silicon crystal ingots to increase the contact area between diamond abrasive grains and silicon crystal ingots , to enhance the macroscopic effective cutting performance; during the processing, the difference in the contact form of the free and consolidated diamond abrasive grains to the silicon crystal ingot leads to the difference in the way and number of impacts with the silicon crystal ingot. Reducing the depth of cut is the key method to improve the processing of plastic domain and reduce the processing of brittle domain, so as to improve the processing quality of brittle materials. The sum and cycle of internal energy storage and release are responsible for the depth of cut of silicon crystal materials ground by diamond abrasive grains. Consolidated abrasive grains exert uniform and single direction on the silicon crystal ingot, and the utilization rate of grinding is higher. The fluid performance of the viscous abrasive fluid reduces the parallel cutting cracks of the consolidated abrasive grains on the silicon crystal ingot, and enhances the microscopic plastic cutting performance. And increase wire breakage protection, so that it is easier to effectively cut; the coupling cutting effect of the two kinds of abrasive grains is complementary, the distribution density of abrasive grains is more uniform, and the saw wire increases the material removal rate and improves the cutting ability. Reduce the brittle cutting of silicon crystal ingots by free abrasive particles, increase the plastic cutting of silicon crystal ingots by consolidated abrasive particles, reduce wafer surface cracks, significantly improve processing accuracy, better surface quality, and reduce the breakage rate of silicon wafers;

Compared with the existing processing method, the present invention has the advantages of more uniform distribution of abrasive grains than traditional free abrasive silicon slice processing, effectively reducing the situation of high abrasive grain density at the entrance of the slit, serious friction, and uneven processing of silicon wafer materials at various positions ; Compared with the traditional bonded abrasive silicon slice processing, the contact area between the saw wire and the bonding material between the workpiece and the abrasive is increased. Due to the action of the viscous abrasive liquid, the contact pressure of the saw wire will be reduced, preventing damage and increasing the life of the saw wire; due to the significant improvement in processing accuracy, the processing capacity is increased, and silicon wafers with a diameter of more than 300 mm and a thickness of less than 120 μm can be cut; Through the matching and setting of grinding parameters, the controllability of the cutting system is obtained, which is the basic guarantee for the stable processing of the silicon wafer cutting system.

Specifically, the free abrasive grains in the slurry and the abrasive grains consolidated on the saw wire have separate and coupled effects on the silicon crystal, such as impact, damage, pressing, rolling and cutting. The trajectory of free abrasive particles is more orderly, which increases the effective cutting force and improves the material cutting effect. Therefore, through the action of the abrasive liquid, the microscopic processing components in the plastic domain are increased in the brittle and plastic mixed cutting of the silicon crystal by the consolidated abrasive grains.

Silicon wafer crack damage is closely related to surface quality in the slicing process of crystalline silicon materials. The form and distribution of subsurface cracks at the bottom of the slit and the side of the slit are different, and the surface damage degrees of the two silicon wafers are different. The distribution of subsurface damage cracks at the bottom of the cutting groove is dense, while the distribution of subsurface cracks on the side of the cutting seam is very small. The diamond abrasive grains on the wire saw squeeze and slide the silicon crystal, removing the crystal in a brittle way. In actual cutting, the material removal thickness at the bottom of the kerf is the highest, and the material removal thickness at the kerf boundary is extremely small, and material removal in the brittle domain can be transformed into material removal in the plastic domain. The bottom of the kerf is a crack generated by the brittle removal of material, and most of the material on the side of the kerf is removed by plastic material. There are also some cracks with large transverse length remaining on the side of the cutting slit, coupled with the micro-vibration inside the cutting system, resulting in secondary removal of the crystal side, forming new cracks on the surface of the slit, and expanding the original cracks, reducing the slit side The proportion of plastic domain material removal. The fluid behavior of the slurry reduces the micro cutting lines on the surface of the silicon wafer along the direction perpendicular to the cutting direction caused by the consolidated abrasive particles. In the cutting of silicon wafers with fixed abrasives, the abrasive grains on the side of the saw wire make the crystalline silicon form parallel stripes and periodically distributed cutting lines of different depths. Low breaking strength. The abrasive slurry forms a protective effect on this phenomenon, and reduces cracks on the surface of the silicon wafer through the substitution of free abrasives.

Silicon wafer free-bonded composite abrasive multi-wire cutting technology belongs to composite processing, which can effectively reduce macro cutting force and cutting load. In the method, the line mark, peeling, damaged layer and residual stress on the surface of the silicon chip are improved. By improving the composition of the cutting fluid, the role of the tool carrier during the cutting process is improved. Further optimize the process parameters to obtain the best working range to improve the quality of silicon wafer processing, improve processing capacity and product quality, and reduce costs.

Description of drawings:

Fig. 1 is a schematic diagram of the principle of the present invention.

Detailed ways:

Referring to Fig. 1, the method for free-solidified composite abrasive multi-wire cutting of silicon wafers, which includes sawing silicon crystal ingot 3 by adopting the method of fixed abrasive multi-wire cutting, and spraying the abrasive liquid 2 containing suspended diamond abrasive grains at the same time to the cutting area; the metal wire 1 with solid diamond abrasive grains on the surface brings the abrasive liquid 2 containing suspended diamond abrasive grains into the slit of the silicon crystal ingot 3 during the wire-feeding process, forming a joint of free abrasive grains and consolidated abrasive grains. function, the silicon crystal ingot 3 is jointly sawed, and the silicon crystal ingot 3 is cut into several pieces in one process.

The equipment for free-solidified composite abrasive multi-wire cutting of silicon wafers includes free abrasive multi-wire cutting equipment, and diamond abrasive grains are consolidated on the surface of all metal wires 1 of the free abrasive multi-wire cutting equipment.

A method for multi-wire cutting of silicon wafers with free-bonded composite abrasives, the diameter of the steel wire used is between 50 and 250 μm; the average particle size of the diamond abrasive grains consolidated on the steel wire is between 5 and 30 μm; The distance between the diamond abrasive grains on the surface is about twice its average grain size, which is adjusted by the parameters of plating or welding; limited by the material removal speed on the slice surface and the cutting amount caused by the size of the abrasive grains themselves, the saw wire The wire-feeding speed is about 20m/s; the grinding liquid 2 containing suspended diamond abrasive grains used is a mixture of diamond abrasive grains with an average particle diameter of 5 to 30 μm and polyethylene glycol liquid at a mass ratio of 20% to 30%. Concentration ratio mixing, stirring environment temperature is greater than 20 ℃, less than 40 ℃, stirring for 1 to 2 hours, within 5 minutes after the stirring is stopped, the slurry has no stratification phenomenon, forming a homogeneous mixed liquid, which is a diamond abrasive grain of viscous polyethylene glycol suspension.

Claims (3)

1. The method for free-solidified composite abrasive multi-wire cutting silicon wafers is characterized in that it comprises the method of adopting fixed abrasive multi-wire cutting to saw silicon crystal ingots (3), and at the same time, the grinding material containing suspended diamond abrasive grains Liquid (2) is sprayed onto the cutting area. 2. the method for free-solidified composite abrasive multi-wire cutting silicon wafers as claimed in claim 1 is characterized in that the diameter of the steel wire used is between 50 and 250 μm; the average grain size of the diamond abrasive grains consolidated on the steel wire The diameter is between 5 and 30 μm; the distance between the diamond abrasive particles consolidated on the steel wire is twice the average particle size; the wire speed of the saw wire is 20m/s; the abrasive liquid containing suspended diamond abrasive particles used (2) It is to mix diamond abrasive grains with an average particle diameter of 5 to 30 μm and polyethylene glycol liquid in a concentration ratio of 20% to 30% by mass, and the stirring environment temperature is greater than 20°C and less than 40°C, stirring for 1 made in 2 hours. 3. The equipment for free-solidified composite abrasive multi-wire cutting silicon wafers, which includes free abrasive multi-wire cutting equipment, is characterized in that diamond abrasive grains are consolidated on the surface of all wires (1) of the free abrasive multi-wire cutting equipment.