JPH0752749B2 - Wafer holding mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] When a semiconductor wafer is subjected to processing such as ion implantation and sputtering under vacuum or reduced pressure conditions, a gas is introduced between the back surface side of the wafer and a temperature-controlled stage. Cooling efficiency is improved. According to the present invention, a porous ceramic plate is attached to the stage side facing the wafer through a gas chamber for introducing a heat-conductive gas to effectively release heat from the wafer side to the stage side. Was improved.

[Industrial application field]

The present invention relates to improvement in heat conduction of a wafer holding mechanism in a semiconductor manufacturing apparatus, particularly when used under reduced pressure conditions.

In a semiconductor wafer process, processes such as sputter deposition, etching, and ion implantation are performed under vacuum or reduced pressure.

In these processes, the whole surface of a wafer with a large area can be quickly
In order to perform uniform processing, it is desirable to quickly remove the heat generated on the wafer surface in the process.

In a conventional mechanical wafer holding mechanism, even if the periphery of the wafer is fixed to a flat stage with a clamp,
Microscopically, the contact area is extremely small, and the wafer surface is separated from the stage due to local heating of the wafer, resulting in extremely poor heat conduction.

Therefore, the stage surface is not flat but has a convex curved structure to improve contact, a coating material with good thermal conductivity is sandwiched between the wafer and the stage, or a narrow gap between the wafer backside and the stage is used. A method of providing a gas chamber and utilizing heat conduction of gas has been proposed.

These methods are reported in the following published patents.

JP-A-58-132937 JP-A-58-213434 JP-A-58-213440 JP-A-58-213441 JP-A-58-32410 The present invention is particularly applicable to the case of cooling a wafer by utilizing heat conduction of gas. It is intended to improve heat conduction.

[Conventional technology]

A conventional wafer holding method utilizing heat conduction of gas will be described with reference to a cross-sectional view of FIG. 2 by taking a magnetron sputtering deposition apparatus as an example.

In the drawing, reference numeral 1 denotes a vacuum container having an exhaust hole 11 and a gas introduction hole 12 such as argon.

A target 3 made of a vapor deposition material is provided with a magnet 4 and an anode 5 in the case of a magnetron sputtering apparatus.

Reference numeral 2 denotes a wafer to be a substrate to be vapor-deposited, and the wafer is held by a stage 8 composed of an electrostatic attraction mechanism 6 and a heat sink 7. An inflow pipe 13 and a discharge pipe 14 for introducing cooling water are connected to the sheet sink to keep the heat sink at a low temperature during the processing period.

The electrostatic adsorption mechanism 6 is made of alumina, which is an insulator,
Electrodes 9 _a and 9 _b to which positive and negative voltages are applied are embedded inside.

A gas chamber 10 having a narrow gap of 50 μm or less is provided between the electrostatic adsorption mechanism 6 and the wafer 2 to serve as a cooling gas.
Gas such as He is introduced through the gas introduction pipe 15.

In the drawing, a high frequency power source applied between the target 3 and the stage, a power source of the electrostatic attraction mechanism, etc. are omitted.

[Problems to be solved by the invention]

When vapor deposition is performed using the sputtering apparatus shown in FIG. 2, atoms of the target material sputtered by argon ions are deposited on the wafer to form a thin film. At that time, the wafer is heated by collision energy. To do.

The amount of heat generated by the wafer is the amount of He introduced in the gas chamber.
The gas is transmitted to the stage 8 and removed.

However, since the portion of the stage facing the gas chamber 10 is the dense alumina surface of the electrostatic adsorption mechanism 8, the heat conduction from the He gas to the alumina surface is not necessarily good.

In order to shorten the processing time and increase the throughput of the equipment, a structure with good heat conduction from He gas to the stage is required.

[Means for solving problems]

The above problems can be solved by the wafer holding mechanism of the present invention, which is formed by surface-bonding the porous ceramic plate to the stage facing the gas chamber.

That is, as a wafer holding mechanism, a stage provided with an electrostatic adsorption mechanism on a cooling function section, a porous ceramic plate attached to the surface of the stage, and surrounding the porous ceramic plate, A protrusion for supporting the wafer,
A space formed by the porous ceramic plate, the protrusion, and a wafer placed on the protrusion and having a gas chamber into which a heat conductive gas is introduced is provided.

When the stage is composed of an electrostatic attraction mechanism and a heat sink, the porous ceramic plate is structured to be surface-bonded to the electrostatic attraction mechanism.

[Action]

For example, He gas, which is a heat-conducting medium, freely flows into and out of the porous ceramic plate, so that heat exchange from the wafer side to the porous ceramic plate by the gas is effectively improved.

Therefore, the heat conduction from the porous ceramic plate to the cooling function section via the electrostatic adsorption mechanism is greatly improved, and the heat generated on the wafer side can be efficiently released.

〔Example〕

An embodiment according to the present invention will be described in detail with reference to the drawings. Descriptions of the same symbols as those used in the section of the related art will be omitted.

The sectional view of FIG. 1 shows only the wafer holding mechanism. Portions not directly related to the present invention are omitted.

The main point of the present invention is that the porous alumina plate 16 which is the porous ceramic plate in FIG. 1 is surface-bonded to the electrostatic attraction mechanism 6.

The back surface of the wafer 2 and the porous alumina plate 16 are opposed to each other with a gap of about 50 μm interposed therebetween, and the gas chamber 10 is formed by a ring 17 provided so as to surround the periphery of the porous alumina plate 16 at the peripheral portion of the wafer. The He gas introduced into the gas chamber is configured so as not to leak into the vacuum container.

Multiple protrusions on the dense alumina surface of the electrostatic adsorption mechanism
18 is provided, and the protrusion maintains the gap size of the gas chamber by supporting the back surface of the wafer through a hole opened in the porous alumina plate.

Using the wafer holding mechanism having the above structure, introducing He gas into the gas chamber at about 3 Torr and measuring the thermal conductivity, the result was 0.03 W / cm ° C when the porous alumina plate was not provided. , 0.06W / cm ℃.

RIE (reactive ion etching) using CF ₄ + CHF ₃ gas
In the conventional structure, the resist film was burnt at an RF power of 4 W / cm ² , but in the structure of the present invention, etching was possible up to 8 W / cm ² without any abnormality.

When the SiO ₂ and PSG films were etched, the etching rate of the SiO ₂ film was greatly improved from the conventional 5000 Å / min to 10000 Å / min, and the PSG film was improved from 1 μm / min to 2.5 μm / min.

In the above-mentioned embodiment, the wafer is held by the electrostatic chucking mechanism as the wafer holding mechanism, but the use of the porous alumina plate is also effective when the mechanical clamp is used without using the electrostatic chucking mechanism. is there.

〔The invention's effect〕

As described above, when the wafer holding mechanism of the present invention is used to perform processing in a reduced pressure atmosphere such as sputtering, etching, and ion implantation, the temperature rise of the wafer is significantly suppressed, which contributes to speeding up the processing.

[Brief description of drawings]

FIG. 1 is a sectional view showing a wafer holding mechanism according to the present invention, and FIG. 2 is a sectional view showing a conventional magnetron sputtering apparatus. In the drawings, 1 is a vacuum container, 2 is a wafer, 3 is a target, 4 is a magnet, 5 is an anode, 6 is an electrostatic attraction mechanism, 7 is a heat sink, 8 is a stage, 9a and 9b are electrodes of the electrostatic attraction mechanism, 10 is a gas chamber, 11 is an exhaust hole, 12 is a gas introduction hole, 13 is a cooling water inflow pipe, 14 is a cooling water discharge pipe, 15 is a gas introduction pipe, 16 is a porous alumina plate, 17 is a ring, 18 Indicates a protrusion, and, respectively.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/31 H02N 13/00 D 8525-5H

Claims (2)

[Claims] 1. A stage having an electrostatic adsorption mechanism provided on a cooling function part, a porous ceramic plate attached to the surface of the stage, and surrounding the porous ceramic plate to support a wafer. Projections for the porous ceramic plate,
A wafer holding mechanism, comprising a space formed by the protrusion and a wafer placed on the protrusion and having a gas chamber into which a thermally conductive gas is introduced. 2. The stage comprises a cooling function section composed of a water-cooled heat sink and an electrostatic adsorption mechanism for adsorbing a wafer, and the porous ceramic plate is structured to be surface-adhered to the electrostatic adsorption mechanism. The wafer holding mechanism according to claim (1).