DE4314152A1 - Appts. to eliminate tendency of wafer substrates to swing in semiconductor processing - comprising elastically deformable ring with its inner periphery lying next to source - Google Patents

Abstract

Appts. to eliminate the tendency of wafer substrates to swing in machines used to process semiconductor wafers and in which the wafers are processed individually and the substrate is movably stored relative to the source, is claimed. The novelty is that the appts. has an elastically deformable ring with its inner periphery lying next to the source. The ring has two concentrically lying circular disks of different dias., one of which is connected to a rubber-elastic compsn. ADVANTAGE - Process parameters do not have to be changed.

Description

The invention relates to a device for eliminating the Vibration tendency of the disc carrier in machines for a machining of the surfaces of semiconductor wafers, the disks are processed individually and the shit Bträger is movably mounted relative to the shaft.

It is known that thin semiconductor wafers made of silicon or gallium arsenide the basis for the manufacture vie ler, highly integrated electronic components. Disks of this type are made from rod-shaped single crystals sawn out. Depending on the semiconductor material and use the required disc diameter vary. For the manufacture of highly integrated memory chips Silicon-based become the largest, technically achievable Diameter used. As a rule, the sawn experienced Discs first a lapping or grinding treatment in order to Sawing causes damage to the crystal structure in the upper to eliminate area. Subsequent process steps serve especially the purpose, the geometry and the upper to perfect the surface quality of the panes. Here these include, for example, mechanical and chemomechanical polishing process in which the discs under the influence  a mechanically abrasive polishing agent and / or a harsh chemical to be polished.

The other explanations refer to machines with whose help lapped the surfaces of semiconductor wafers, be ground or polished on one side and in Single disc processing. Both with one-sided lapping, as well as with one-sided polishing, the discs are in usually sucked in on flat disc supports or glued. The disc support forms part of the factory piece holder with which the free disc surface against the rotating work surface, the lapping or polishing quarter is led. When grinding, the conditions are ver similar, only that instead of the workpiece holder Tool holder, in the place of the disc carrier of the Tool holder and in place of the work surface fixed semiconductor wafer kick. Although in the following the Simplicity because of only lapping and polishing machines will be, it goes without saying that with a ent speaking term choice the device according to the invention can also be used in grinding machines.

The workpiece holder guides during disc processing an oscillatory and a rotational movement. The for these movements responsible forces and the contact pressure with which the pane is guided against the work surface, are from a shaft reaching into the workpiece holder transfer. The connection of the disc carrier to the shaft is advantageously not completely rigid, son allowed, as already in the European Patentan message EP 2 84 343 A2 has been described, low hori zontal and tilting deflection movements of the disc carrier. This is achieved in that the shaft end piece with its face in a central recess in the disc carrier rests without being firmly connected to it. The  Space between the cylindrical border of the Aus take and the parallel outer surface of the Shaft end piece enables free play of the shaft end piece in the recess. The possibility of the usual, be movable disc carriers, low horizontal and Performing tilting compensatory movements is particularly important attributed this free play. The free play forms as it were the defined design area within the sen the disc carrier movably mounted relative to the shaft and within which movements are permitted.

The movably mounted disc carrier is for a freeze lapping or polishing result essential and necessary, because

• a) the frictional force that arises during disc processing attacks horizontally in the plane of the disc surface and the support of this frictional force with a certain Höhenver set on the shaft. The different amount of the An Grip points of this pair of forces generate a turning torque ment on the disc carrier. This setting torque would Principle of sloping the disc carrier and there with a "conical" formation of the machined Guide washer. For disc carriers facing the shaft are rigidly mounted, this disadvantageous effect is also detectable. A beginning inclination of the relative to Shaft movably mounted disc carrier, however, causes that the contact pressure is no longer concentric over the total surface of the shaft end face, but eccentrically over one Edge part of the wave end face is transferred with the Re result that the transferred contact pressure of the positioning movement counteracts exactly. The axis of rotation of the disc carrier could even take structural measures to counter the waves axis inclined. In this case, too, the axes  inclination by the mechanism described corri be greeded.
• b) it is avoided that possible bumps transfer the work surface to the surface of the pane will.
• c) minimal alignment differences of shaft axis and Worktop axis that are already balanced with different polishing cloth thicknesses or disc thicknesses can result, since the disks normally in a bo Gen-shaped movement around a pivot point with a horizontal Axis are delivered.

Nevertheless, the movably mounted disc carrier, be especially when lapping or polishing large disks with through knives of at least 150mm, also considerable problems. It self-excited friction vibrations occur, one The natural frequency of the machine or a part of the machine In unfavorable cases, the lapping or polishing process can even be canceled because the whole machine is like that begins to vibrate, for example, for editing prepared slices slip out of the hordes and get damaged will. Other consequences of this disorder are one with the Vibration-related noise pollution, an increased Machine load and, above all, one in uncontrolled deteriorating lapping or polishing result the machined disks.

The excitation of the vibrations by the moving shit Bearers can be avoided in part by giving way process parameters such as the speed of the work surface, the Composition of the lapping or polishing agent, the procurement the polishing cloth or the contact pressure the. However, such measures have the undesirable consequence  that the target disc quality is no longer, or only at the price of longer processing times per Disc can be reached.

The object of the invention was therefore to provide a direction to remove the vibration tendency of the shit Bearer specifying the occurrence of frictional vibrations and reliably avoids the harmful consequences.

The task is solved by a device for elimination the tendency of the disc carrier to vibrate in machines for one-sided processing of the surfaces of semiconductors slices, the slices being processed individually and the disc carrier is movably supported relative to the shaft, characterized by an elastically deformable guide ring, which is flush with the inner circumference of the shaft lies.

Surprisingly, the support of the shaft by the Guide ring according to the invention to prevent the Machine, especially when processing disks with Diameters of at least 150mm, to natural vibrations is excited.

The invention is explained in more detail below with reference to figures. Fig. 1 shows cross-sectional drawings of preferred embodiments of the guide ring. In Fig. 2 the cross section of a workpiece holder is shown, which is equipped with a guide ring. Of course, the drawings are only to be understood as an example and not as a limitation of the invention.

As shown in Fig. 1a, the guide ring 1 before preferably consists of two concentric, circular discs of different diameters. The space between the outer circular disc 2 and the inner circular disc 3 is filled out by a rubber-elastic mass 4 . The rubber-elastic mass keeps the two circular discs in a tight bond with each other. The outer edge of the guide ring forming the outer circular disc is provided with a plurality of holes 5 , preferably 2 to 6 with the same from each other. The inner diameter of the inner circular disc is adapted to the diameter of the shaft so that the guide ring is flush with the inner circumference given by the inner circular disc on the shaft. The circular disc thickness is advantageously 3 to 6 mm. Steel or metal alloys with steel-like properties are particularly suitable as materials for the circular disks, although hardened plastics can also be used. The rubber-elastic mass, for example a silicone rubber, rubber or synthetic rubber with a molecular structure made of carbon, preferably has a Shore A hardness of 25 to 60. Conveniently, the selected material should also have a high tensile strength so that the guide rings made from it can withstand the operating conditions for a particularly long time. Finally, good adhesion of the mass to the material from which the circular disks are made must be observed.

Due to the movement of the disk carrier during operation of the disk processing machine, the rubber-elastic mass in a guide ring according to the embodiment shown in FIG. 1a is mainly subjected to pressure and tension. In Figs. 1b and 1c are shown in cross-section drawings find the risk of embodiments in which the rubber-elastic composition undergoes mainly a thrust load (Fig. 1b) or a combined shear, compression and tensile stress (Fig. 1c). In contrast to the guide ring of the embodiment according to FIG. 1a already described, the inner circular disk 3 and the outer circular disk 2 partially overlap in the embodiments according to FIGS. 1b and 1c (in addition, the position of the guide ring in the disk carrier is indicated in FIGS. 1b and 1c) ). The thickness of the outer circular disc is reduced approximately from half of the disc radius towards the inner circumference in a jump or wedge shape. The resulting recess is advantageously filled with the rubber-elastic mass 4's so that, together with the inner circular disc resting thereon, an almost uniform thickness of the guide ring results. The rubber-elastic mass expediently holds the two circular disks in a tight bond with one another and forms with them the guide ring according to the invention.

If necessary, the guide ring can also be made in one piece and consist overall of a rubber-elastic mass or a plastic. Stable and lubricious plastics such as polyoxymethylene (POM) or polytetrafluoroethylene (PTFE) are preferably used. The elasticity of the one-piece guide ring is preferably matched by design measures. This can be done by drilling holes in the guide ring concentrically to the outer circumference or by the plastic of the guide ring being grooved in a region lying concentrically to the outer circumference. A preferred embodiment is shown in Fig. 1d. The entirely plastic de, one-piece guide ring 1 is in a concentric to the outer circumference area to a web S tapered ver, whereby the necessary elastic deformability of the guide ring is increased.

In a development of the embodiments shown at least the inner circumference flush against the shaft  of the guide ring with a plastic covering that an improved sliding ability against the shaft enables.

It has been found that with the guide ring of the design area within which the disc support is relative to The shaft is movably supported by the choice of rubber elastic mass is defined selectable. Without the leader ring is ahead due to the free play of the shaft end piece given and in particular can not be shortened. It was also found that within the chosen interpretation the guide ring has a larger amount Stability must be able to develop as the maximum frictional force is the ge during the processing of the effect reaches. Then the vibration tendency of the disc carrier effectively eliminated. Basically, therefore, is the leader ring in its design based on preliminary tests to be chosen so that with given process parameters as with for example lapping or polishing pressure and rotation speed working area, this condition is met.

The elements of the disk carrier essential for understanding the invention are, as shown in FIG. 2, a base plate 6 , a retaining ring 7 and an insert plate 8 . The A plate is conveniently shaped so that it has both a central recess for receiving the shaft 9 , and a recess on the surface that allows the inclusion of the guide ring 1 . The end of the shaft end piece rests in the central recess of the insert plate. The guide ring preferably forms an exchangeable part of the disk carrier. The supply or discharge of process fluids and the introduction of the vacuum for suction of the semiconductor wafer takes place via one or more risers 10 in the shaft. The O-ring 11 provides the necessary sealing against vacuum and process fluids.

According to the invention, the guide ring 1 lies flush with the inside of the shaft 9 . About the holes 5 in the Füh approximately ring and corresponding holes in the insert plate, the guide ring with the screws 12 is firmly screwed to the insert plate. It can therefore be replaced routinely or if it is worn out without any special effort. The exchange with a differently designed guide ring - for example with one whose elastically deformable mass has a different Shore hardness or one that is designed for thrust instead of pressure and tensile loading - is currently easy to carry out. The type of loading of the guide ring is not critical, so that in principle other fastening types known in the art can also be used.

The remaining components of the workpiece holder shown in FIG. 2 are known to the person skilled in the art. They also do not need to be described, because the invention would not be characterized in more detail thereby.

The guide ring according to the invention completely prevents that free play of the shaft in the disc carrier without the movable Storage of the disc carrier in its various functions to hinder. The tendency of the disc carrier to vibrate gene is successfully eliminated by the guide ring that even without changing the process parameters a damage leveling of the processing machine or parts of this is omitted. As already mentioned at the beginning, he is not for use in lapping and polishing machines NEN limited, but especially in grinding machines can be used.

Claims (4)

1. Device for eliminating the tendency to vibrate of the wafer carrier in machines for one-sided processing of the surfaces of semiconductor wafers, the wafers being machined individually and the wafer carrier being mounted so as to be movable relative to the shaft, characterized by an elastically deformable guide ring which, with its inner circumference, on the Shaft is flush. 2. Device according to claim 1, characterized in that the guide ring of two, concentric to each other circular disks of different diameters and one the two circular disks in a tight bond mutually holding rubber-elastic mass, formed becomes. 3. Device according to one of claims 1 or 2, characterized characterized in that the guide ring in the design rich within which the disc carrier relative to the The amount of the shaft is movably supported re resistance can develop as the maximum Frictional force is used during disc processing Effect. 4. Use of the device according to claims 1 to 3 in machines for one-sided processing of surfaces of individual semiconductor wafers, especially in lapping, Polishing and grinding machines.