JPH04132239A - wafer chuck - Google Patents

Abstract

PURPOSE:To be able to quickly attach and detach a wafer by imprinting positive and negative pulse alternating voltage at different phases into multiple electrodes placed in an insulation body and to attach the wafer by the static electricity produced. CONSTITUTION:For the electrodes A1, A2, A3, B1, B2 and B3, 12 wedge-shaped electrode boards are placed in a circular format, the insulation body 11 is a silicon resin, and when the platform 12 is an etching system, these are set up as conductive electrodes. With this structure, a reverse alternating voltage is applied on electrodes with the same code number during the same phase, the pulse voltage is divided into 3 phases, and reverse voltage is applied with same phase on A1 and B1, A2 and B2, and A3 and B3, respectively. For the time intervals between T1 to T2 and T3 to T4, positive and negative voltage is applied in 3 phases while shifting other electrodes. The pulse alternating voltage applied has a voltage strength of 1KV, pulse width of 5sec, and a frequency of about 0.33Hz. If positive and negative voltages are continuously applied on any pair of A and b electrodes, the attachment strength is not lost and since the applied voltage reverses positive and negative polarity in a short time period, it is possible to remove the wafer quickly without any residual polarization.

Description

[Detailed Description of the Invention] [Summary] Regarding wafer chucks used for wafer transport in wafer processes and stages of wafer processing equipment, the purpose of this invention is to enable quick attachment and detachment of wafers. It is characterized in that an alternating voltage of positive and negative pulses is applied to a plurality of electrodes, and the wafer is attracted by electrostatic force induced by the alternating voltage.

It is characterized in that the alternating voltage is applied to a plurality of electrodes with a phase shift.

It is characterized in that the insulator is made of silicone resin or ceramics.

The electrode is characterized in that it consists of a wedge-shaped plate and has a circular shape as a whole.

[Industrial application field]

The present invention relates to an everchuck used for wafer transport in a wafer process or a stage of a wafer processing apparatus.

In the wafer process of semiconductor manufacturing, wafers are automatically transported, and in wafer processing equipment such as etching equipment and vapor phase growth equipment, wafers are adsorbed (chucked) on a stage. This paper concerns the improvement of wafer chucks.

[Prior Art and Problems to be Solved by the Invention] Conventionally, electrostatic adsorption type wafer chucks have been used extensively in wafer processes, and FIG. 4 shows a schematic cross-sectional view of a conventional wafer chuck. Symbol 1 is a DC power supply and 2 is a wafer chuck.

3 is a wafer, and wafer chuck 2 has A inside the insulator.
It has a structure in which two electrodes, the electrode and the B electrode (for example, two half-moon-shaped electrodes) are buried, and when positive and negative DC voltages (high voltage of about 1 to 1.5 KV) are applied to the picture electrodes as shown in the figure, The insulator causes dielectric polarization, and positive and negative charges are induced on the surface of the insulator, and the wafer is chaffed by the electrostatic force.

However, after chucking the wafer, there is a problem that it is difficult to peel off easily.
b) shows a diagram illustrating the problems of the conventional method. That is, as shown in FIG.
) Then, the insulator on the AI pole side to which a positive voltage is applied causes dielectric polarization and induces a positive charge on the surface of the wafer chuck 2 (insulator). Then, negative charges are induced in the wafer on the opposing surface, which causes the wafer to be attracted. At the same time, when a negative voltage is applied to the other Bt pole side, positive charges are induced on the opposing wafer surface due to the similar dielectric polarization, and the wafer is attracted. In this way, wafer chuck 2
A charge with the opposite polarity to the inner electrode is induced on the wafer surface,
The wafer is attracted by the Coulomb force (electrostatic force). This is the principle of electrostatic chuck, and a wafer chuck based on this method is an electrostatic chuck.

However, since the wafer is then peeled off from the wafer chuck after the processing is completed, when the DC power supply 1 is turned off, as shown in FIG. Therefore, there is a problem that the adsorption force of the wafer chuck does not disappear and the wafer 3 is not peeled off quickly. In particular, insulators such as silicone resin and alumina have a long residual polarization time, and if they are adsorbed for a long time or used continuously, charges will accumulate and the wafer will not easily peel off.

The following table shows the relationship between the adsorption time (minutes) of a wafer chuck using an insulator made of silicone resin and the desorption state, where O means good desorption, Δ means slightly difficult desorption, and × means difficult desorption. It shows.

The present invention solves these problems and proposes a wafer chuck that allows quick loading and unloading of wafers.

[Means to solve the problem]

The problem is as shown in the embodiment of FIG.
(e.g., a plurality of electrodes embedded in silicone resin, ceramics) (e.g., a plurality of circularly configured electric scraping plates) A, , A, , A3B, , Bt, B2 with positive and negative phases shifted. Pulse alternating voltage (13 is alternating voltage power supply)
This problem can be solved by using a wafer chuck that applies an alternating voltage and attracts the wafer by the electrostatic force induced by the alternating voltage.

As described above, the inability to quickly attach and detach wafers impedes automatic transportation and impedes improvement in the throughput of wafer processing equipment.

[For production]

That is, in the present invention, a pulsed alternating voltage is applied to a plurality of electrodes, and if necessary, the voltage is applied with a phase shift for each adjacent electrode. In this case, since the applied voltage is reversed in a short period of time, no dielectric polarization remains in the insulator, and therefore, the wafer can be removed immediately when the insulator is turned off.

〔Example〕

1(a) and 1(b) show main parts of a wafer chuck according to the present invention, and FIG. 1(a) is a plan view, FIG. 3) is a CC sectional view of FIG. Symbol 1 in the diagram
1 is an insulator made of silicone resin, 12 is an aluminum pedestal, 13 is an alternating voltage power source, A.

, As , B+ , Bz , and BI are electrodes (tungsten electrodes), and the number of electrodes is 12 in total, and model-shaped electrode plates are arranged in a circle. The insulator 11 is made of silicone resin, has a resistivity of about 101s to 10"/Ω1, and a thickness of 4.
The thickness should be approximately 00 μm. In addition to silicone resin, ceramics, quartz, polyimide, plastic, etc. may be used as the insulator, and the pedestal 12 serves as a conductive electrode in the case of an etching device.

With the configuration shown in Fig. 1, an alternating voltage of the same phase and a reverse voltage is applied to the electrodes with the same additional symbol, and a pulse voltage is generated, for example, as shown in the alternating voltage application time chart of Fig. 2. Shift to 3 phases, A.

and B+, At and Bz, and As and B are in phase and reverse voltages are applied to each other. That is, a positive voltage is applied to At and a negative voltage is applied to B from time 0 to T, and a negative voltage is applied to A1 and a positive voltage is applied to BI from time T2 to T3.
Then, at time T, ~T4, the other electrodes were shifted and positive and negative voltages were applied in three phases, the voltage intensity was IKV, and the pulse width was 5 se.
At c, a pulsed alternating voltage with a frequency of about 0.33 Hz is applied.

In this way, if the electrodes are made multipolar and the phase is shifted, and positive and negative voltages are constantly applied to any pair of A and B electrodes, the adsorption force will not disappear, and moreover, the applied voltage can be reversed in a short period of time. Because of this, no polarization remains and the wafer can be removed immediately. FIGS. 3(a) to 3(d) are diagrams showing the polarization state of the wafer chuck according to the present invention, illustrating the portions of the AI electrode and the 81 electrode, where 3 is the wafer and 10 is the wafer according to the present invention. This is such a wafer chuck. The figure (a) shows the state from time 0 to T, the figure (b) shows the state from time T to T2, and the figure (C) shows the state from time T2 to T3. The same figure (d
) is time T.

-T4 is shown in the figure, but since the voltages applied before and after are reversed in this way, the polarization disappears immediately, and no polarization remains when the voltage is turned off.

The following table shows the relationship between the adsorption time (minutes) and the desorption state of the wafer chuck according to the present invention, and it can be seen that the desorption is good (0) even over a long period of time.

The above embodiment was explained using an example in which 12 electrodes are arranged and shifted in phase, but the multiple electrodes are divided into two without shifting the phase, and positive and negative pulsed alternating voltages are applied alternately to adjacent electrodes. The same effect can be obtained.

Furthermore, when shifting the phase, the number of electrodes and the phase may be increased or decreased to some extent, regardless of the above embodiments.

〔Effect of the invention〕

As is clear from the above explanation, when the wafer chuck according to the present invention is used, the wafer can be quickly attached and detached, and the wafer process can be carried out smoothly and automatically, resulting in improved efficiency of the wafer process and high quality of semiconductor devices. This will greatly contribute to the

[Brief explanation of the drawing]

Figures 1 (a) and (b) are main parts of the wafer chuck according to the present invention, Figure 2 is an alternating voltage application time chart, and Figure 3 (a).
- (d) are diagrams showing the polarization state of the wafer chuck according to the present invention, Figure 4 is a schematic cross-sectional view of a conventional wafer chuck, and Figures 5 (a) and (b) are problems with the conventional wafer chuck. FIG. In the figure, 1 is a DC power supply, 2 is a wafer chuck, 3 is a wafer 10 is a wafer chuck according to the present invention, 11 is an insulator, 12 is a pedestal, 13 is an alternating voltage source, A. B. B. B. indicates an electrode.

Claims (4)

[Claims] (1) A wafer chuck characterized in that an alternating voltage of positive and negative pulses is applied to a plurality of electrodes buried in an insulator, and a wafer is attracted by electrostatic force induced by the alternating voltage. (2) The wafer chuck according to claim 1, wherein the alternating voltage is applied to a plurality of electrodes with a phase shift. (3) The wafer chuck according to claim 1, wherein the insulator is made of silicone resin or ceramics. (4) The wafer chuck according to claim (1), wherein the electrode is made of a wedge-shaped plate and has a circular shape as a whole.