DE102008022476B3 - Method for mechanical treatment of disk, involves allocating disk separated by wire saw from work piece having sawing edge to their extent - Google Patents

Abstract

The method involves allocating disk (11) separated by a wire saw from a work piece having a sawing edge to their extent. The disk is fixed on a window pane retainer, which is shifted in rotation. The mechanical treatment of the disk provided at the rotary window pane retainer is carried.

Description

The The invention relates to a method for processing a disk, suitable for removing the putty of discs after their separation from a workpiece by means of a wire saw.

Especially the method is suitable for use in the production of Semiconductor, z. For example, silicon wafers. The first steps in the Production of silicon wafers are usually as follows: pulling a cylindrical single crystal of a silicon melt Inoculation with a seed crystal, cylindrical grinding of the grown single crystal, saw up of the monocrystalline rod in slices.

Be wire saws used a variety of silicon wafers or even Solar wafers and other crystal wafers in one go from one Separate crystal, so find application in the production of products for the chip industry, for the photovoltaic industry, but also in the production of discs from crystals of any kind, z. B. Materials such as III-V Hall, Gallium nitride or silicon carbide or ceramics. Basically wire sawing always preferred when in length production process chains because of economical reasons It is advantageous to remove all slices in a single operation Separate workpiece and then be able to process an entire batch.

In the US 5,771,876 is the principle of operation of such a wire saw described.

such wire saws have a wire gate made of a saw wire that around two or more wire guide rollers is wound. The saw wire can be covered with a cutting surface. When using wire saws with Saw wire without firmly bound cutting grain is cutting grain in the form of a suspension ("Slurry") during the Abtrennvorganges supplied. During the separation process, the workpiece penetrates the wire gate, in the the saw wire arranged in the form of parallel adjacent wire sections is. The penetration of the wire gate is provided with a feed device causes the workpiece leads against the wire gate or the wire gate against the workpiece.

At the Separating silicon wafers from a crystal is common in that the crystal with a saw bar connected to the saw wire at the end of the procedure. The saw bar is for example a graphite strip (carbon strip), which is on the peripheral surface of the Crystal is glued or aufgekittet. The workpiece with the Saw bar is then aufkittet on a carrier body.

Usually becomes the saw pad on a silicon rod by hand applied. Depending on the length, Diameter, circumferential feature must have a corresponding saw pad selected be applied and on a defined surface.

Out DE 10335063 It is known to spray the bonding surface of the rods to be bonded with a release layer. The drying of the layer is accelerated by means of UV lamps. An adhesive, for. As a resin and hardener are mixed in a certain weight ratio in an automatic mixing and dosing in the correct ratio and applied by the robot on rod and adapter. Preferably, a water-soluble adhesive (releasable without chemicals) is used. Likewise, a water-soluble release agent can be applied before the application of the adhesive.

The resulting silicon wafers remain after separation as the Teeth of a Comb on the saw bar fixed and can so out of the wire saw be taken.

Later will the remaining saw bar detached from the silicon wafers. This happens z. B. manually by the respective personnel or is chemically replaced.

Out DE 10335062 It is known that the removal of the saw pad after the application of the water-soluble putty or the release layer takes place in an ultrasonic trough, preferably mechanically supported in or over the trough. A plunger for pushing off the coal can be positioned parallel to the edge of the disc. The carbon rails are transported with a conveyor belt in an easy to empty container.

Out US 6 074 442 A It is known to separate a saw pad by a mechanical processing of a wafer.

To Separating the silicon wafers from the crystal, removing the carbon ledges usually done mechanical processing steps aimed at the silicon wafer to give a form, which in particular by a profiled Edge and planparallel opposite sides are characterized. Forming processing steps therefore include besides edge rounding especially the lapping and grinding the sides of the silicon wafer.

DE 44 00 221 A1 discloses an apparatus for carrying out a method of producing chamfered silicon wafers. Between the steps "detachment of the saw pad" and "edge rounding" are a cleaning step on a cleaning section and a transport step with provided a conveyor belt.

at the common ones Procedures are the discs so after application of the adhesive by chemical Substances or by water, by weight or application an additional one Force separated from the putty strip. This creates undefined Detachment forces and in the worst case damages on the wafer.

The The object of the invention was to provide such undefined detachment forces and any damage to avoid.

The Task is solved by the method according to claim 1.

starting point is one by means of a wire saw zersägtes Workpiece. The discs form a so-called sawing comb and stick to the saw bar.

The Slices are subsequently isolated, d. H. the discs are broken out of the saw comb.

there remains a saw rest as well as previously on the lateral surface of the workpiece Stick applied glue to the individual panes.

Subsequently, will the disc with saw bar, z. Residual carbon bar, centered on a vacuum chuck, fixed and rotated.

Of the Remainder of the adhering carbon bar is then z. B. by saw wire, Water jet, laser beam, by means of a grinding wheel or another separated suitable separation process.

in the same operation also takes silicon material removal to the Wafer on a specific, desired To grind diameter and profile the edge.

The inventive method has the advantage that the removal of the lattice strip, removing the The residual carbon strip and the edge rounding of the wafer in one operation is realized.

in the Contrary to the prior art, a defined detachment force acts at the wafer edge. damage are avoided.

It It is known that the edge of the silicon wafer before the edge-rounding step extremely sensitive is. In particular, the removal of the carbon bar has been in this Context as extremely critical proved. This problem does not occur in the process according to the invention.

One Another advantage is that only a single centering of the wafer for several subsequent processing steps is necessary, which facilitates the handling and also leads to significant time savings.

Finally - too advantageous - comes that Method of separating the saw bar without the use of chemicals (for example, formic acid in the prior art).

One Edge profile generating processing step is therefore required because the edge in the unprocessed state is particularly susceptible to breakage is and the silicon wafer already by slight pressure and / or temperature loads damaged in the edge area can be. The untreated edge of a single crystal separated silicon wafer has a comparatively rough and uneven Surface. It often breaks down under mechanical stress and is a source disturbing Particle. It is therefore common to smooth the edge and give her a specific profile.

This is done by a material-removing machining of the edge of the silicon wafer with a corresponding processing tool. A suitable device is for example in DE 195 35 616 A1 disclosed.

Usually When edge-rounding, the silicon wafer is rotating on one side Chuck fixes and gets the edge against a turning one as well working surface delivered to a machining tool. Such a device is suitable, the edge of the silicon wafer with a machining tool to edit. For the machining tools used These are mostly grinding wheels attached to a spindle are fixed and have profiled peripheral surfaces that serve as work surfaces for Processing the edge of the silicon wafer serve. The material abrasive grain is usually stuck on the work surfaces bound and usually has a coarse grain on.

At the Edge rounding of silicon wafers with Notch is an additional Grinding spindle (Notchspindel) with a grinding pin (Profilnotchstift) required. Since the profile of Profilnotchstiftes usually identical with the profile of the profile grinding wheel is in the frame this invention not closer on the specifications of the Profilnotchstiftes. If certain specifications of the profile grinding wheel are mentioned, should this in the context of the invention also for the Profilnotchstifte used be valid.

According to the prior art, it is customary, the silicon wafers with a symmetrical to the median plane of the disc profile with similar Fa cetten on the front of the pane and the back of the pane or with an asymmetric edge profile with different facet widths on the front and back. The edge of the silicon wafer is given a profile which is geometrically similar to a target profile. A suitable method for this is, for example, in DE 101 31 246 C2 described.

example

Semiconductor rod, grown by means of CZ (Czochralski) - or FZ (floatzone) method is lifted into a putty device. The rod usually becomes on its lateral surface held on rollers and fixed. Part of the bar mantle will be over his whole length provided with an adhesive. On this glue is a coal bar cemented. The prepared rod is then in a wire saw sawed into slices. As sawdust is z. B. steel with brass or zinc coating used. When Cutting means is a silicon carbide / glycol suspension usual.

To the sawing the disks are broken out and put into a cassette (Horde) placed in a cleaning cart. There are the discs with demineralized Water cleaned. Subsequently a robot picks up a single disc from the cassette and places it on a conveyor belt, the disc on a centering sets. The centering chuck usually includes Centering pins and one made of transparent plastic Supporting surface. The disk is centered and oriented on the centering chuck (Pre-alignment). Subsequently, will the disc is lifted by means of a gripper on a Schleifchuck. This Schleifchuck usually includes pressure pins and so-called notch centering, which a fine correction of centering / orientation (alignment) enable. Then the disc is sucked by the Schleifchuck and the grinding process starts.

there the residual carbon strip and the glue are removed. In addition, will the disc in the same operation with a rounded edge Mistake.

figure

1 schematically shows a suitable for carrying out the method according to the invention construction.

1 shows disc 11 with residual coal 12 on transfer chuck 51 with centering pins 6 , There is the oriented incoming disk 11 centered. Then slice becomes 11 to vacuum chuck 52 transported. Then the disc starts 11 to slowly rotate and the still sticking residual carbon or glue 12 initially z. B. by using saw wire, water jet, laser or by means of another suitable separation device (shown schematically by 4 ) from the disc 11 separated. When you rotate through a grinding wheel 32 the remaining carbon and adhesive residues 12 removed and disc 11 ground to a defined diameter. Subsequently, with further rotation of the disc 11 the disc edge by means of a second grinding wheel 31 profiled (rounding of the edge).

Claims (5)

Method for the mechanical processing of a Disc comprising the following steps: a) provide a by means of a wire saw from a workpiece severed disc comprising a saw pad in its peripheral area; b) Fixing the disc on a disc holder, which sets in rotation can be; c) Mechanical machining on the rotating disk holder located disc, including removing the saw pad and rounding the edge of the disc by supplying rotating grinding wheels in one step. Method according to claim 1, characterized in that that removing the saw pad without any use of corrosive Chemicals takes place. Method according to claim 1 or 2, characterized that before the mechanical processing according to c) a part of the saw bar is separated mechanically or by means of a jet of water. Method according to one of claims 1 to 3, characterized that it is the workpiece around a semiconductor rod and at the disk around a semiconductor wafer, preferably a silicon wafer is. Method according to claim 4, characterized in that that the disc comprises an orientation notch and before the mechanical Machining according to c) centered and being oriented.