DD292119A5 - DEVICE FOR ELIMINATING AND ELECTROSTATIC HOLDING OF WAFERS - Google Patents

Abstract

The invention relates to a device for planarizing and electrostatic holding of wafers for microstructuring and control, z. B. in electron beam lithography. The object of the invention is to provide an electrostatic holding device in which a remaining after switching off the operating voltage residual charge is rapidly reduced. According to the invention, the object is achieved by applying a layer of defined electrical conductivity to the dielectric layer. Fig. 1 {holding device, electrostatic; Electron beam lithography; Layer structure; Dielectric; Flaechenelektrode; leveling; wafer; Platen; Microstructuring}

Description

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Field of application of the invention

The invention relates to a device that is applicable to Eb.ien and holding wafers for processing and control, especially in Eloktronenstrahllithografie.

Characteristic of the known state of the art

In the technology it is in connection with the microstructuring and also mi! the control of structured semiconductor wafers usual to use electrostatic acting holding devices. The wafers, which are technically curved or with insufficient flatness for processing or control, are leveled and held with these devices due to electrostatic attraction.

In DD-WP 143131, e.g. such an electrostatic chuck table described. The clamping table itself acts like the line and the wafer like the other plate of a capacitor. The intervening dielectric consists of the oxide of the surface material of the clamping table.

An improved version is set out with the DD-WP 235977. Here, a groove is incorporated in the bearing surface of the clamping table, which can be connected via a channel and a switching valve alternately with a vacuum pump and a compressed gas source. The vacuum ensures that even discs that have deformations within acceptable limits are printed on the support surface. By subsequently filling the groove with gas (during electrostatic holding), the tempering of wafer and clamping table is optimized.

The disadvantage of both solutions is that the chosen for the purpose of low self-heating of the electrostatic clamping system large Isolatonswiderstand the dielectric caused by large residual charge after switching off the operating voltage, a persistent holding of the wafer. The duration of continued holding is often beyond the object change time of the handling system, whereby the automated process is disturbed.

Object of the invention

The aim of the invention is a device for leveling and electrostatic holding of wafers, which ensures a secure hold and rapid relaxation with a simple structure and allows optimal flow of the technological process.

Explanation of the essence of the invention

The invention has for its object to provide a device for planarizing and holding wafers, in which a remaining after switching off the operating voltage residual charge quickly degraded and the wafer is thereby released. According to the invention, this object is achieved by a device for planarizing and electrostatically holding wafers, consisting of a base plate with a surface electrode, a dielectric layer arranged above it and a DC voltage source which in the working phase of the device bears against one pole on the surface electrode and on the wafer in that a layer of defined electrical conductivity having a thickness of less than 1 μm and a surface ^resistance R _ob between 10 ^s and 10 ^l0 ohms is applied to the dielectric layer (measured by means of two ^blade-shaped electrodes of opposite sides of a square) Size form) that the

DC voltage source with a pole on the flat electrode and the NC contact of a switch and with the second pole at the closing contact of the switch is present and that the changeover contact with the wafer and the layer with a defined electrical conductivity is connected.

The layer with defined electrical conductivity should advantageously made of a wear-resistant metallic material

and the dielectric layer is made of silicon dioxide. For planarizing and holding a wafer, the DC voltage source, one pole of which is connected to the planar electrode, is connected to the second pole via the closing contact of the switch to the wafer and the layer with defined electrical conductivity. For fast release of the wafer, the changeover switch is actuated and the surface electrode is short-circuited via the normally closed contact with the wafer and the layer with defined electrical conductivity. The layer with defined electrical conductivity dissipates the electrical charge quickly and the forces of the forces disappear.

The main advantage of the proposed solution is that with a simple construction of the device ensures a secure hold while and a quick release after processing and an optimal flow of the technological process is possible.

embodiment The invention will be explained below with reference to an embodiment / The accompanying drawing shows in Fig. 1: the basic structure of the device according to the invention.

A base plate 1 is provided with a surface electrode 2, a dielectric layer 3 and a layer 4 having a surface resistance FU between 10 ^g and 10 ° ohm. The dielectric layer 3 consists of SiO ₂ , the layer 4 of platinum with a thickness of less than 1 pm. For the base plate 1, a thermally stable, electromagnetically interaction-free material is provided with a coefficient of expansion close to zero, z. As titanium-carbon fiber composite or glass ceramic. In the base plate 1 evacuation channels 6 are incorporated, which lead outwards to the front side of the base plate 1 and thus provide for a rapid evacuation of the air volume under a warped or curved wafer 5. A DC voltage source (not shown) is connected to a pole on the surface electrode 2 and the NC contact of a changeover switch 7 and with the second pole on the closing contact of the switch 7 at. The associated changeover contact is connected to the wafer 5 and the layer 4 via a highly conductive edge strip 8.

For flattening and holding a wafer 5, the DC voltage source is applied to the wafer 5 and the layer 4 via the make contact and the edge strip 8. To release the wafer 5, the changeover switch is actuated and thus the surface electrode 2 is short-circuited via the normally closed contact with the wafer 5 and the layer 4.

Claims (3)

1. Device for planarizing and electrostatically holding wafers, in particular for electron beam machining, comprising a base plate with a surface electrode, a dielectric layer arranged above and a DC voltage source, which abuts in the working phase of the device with one pole on the surface electrode and on the wafer, characterized in that on the dielectric layer (3) a layer (4) having a defined electrical conductivity is applied, which has a thickness of less than 1 μηη and a surface resistance R _ob between 10 ⁸ and 10 ¹⁰ ohms that the DC voltage source with a pole at the surface electrode (2) and at the NC contact of a changeover switch (7) and with the second pole at the closing contact of the changeover switch (7) is applied and that the changeover contact with the wafer (5) and the layer (4) is connected with a defined electrical conductivity. 2. Device for planarizing and electrostatic holding of wafers according to claim 1, characterized in that the layer (4) with a defined electrical conductivity consists of a wear-resistant metallic material. 3. Apparatus for planarizing and electrostatically holding wafers according to claim 1, characterized in that the dielectric layer consists of silicon dioxide.