JPH04323849A - Vacuum chuck for wafer - Google Patents

Abstract

PURPOSE:To make a contact area with a wafer minimal when the amount of wafer distortion is made constant in chucking. CONSTITUTION:When the amount of a wafer distortion is made constant in chucking, the supporting area of one supporting extrusion is maximized by arranging a number of supporting extrusions 4 which support a wafer so that the adjacent three are staggered to form a regular triangle.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum chuck for wafers used for measuring, transporting, processing, etc. wafers of silicon, alumina, quartz, and other materials.

0002

2. Description of the Related Art Conventionally, as this type of vacuum chuck for wafers, those shown in FIGS. 5 and 6 are known.

The former vacuum chuck for wafers has a recess 12 at the bottom surrounded by a peripheral wall 11 on which the wafer is placed.
A central disc-shaped support protrusion 13 that supports the wafer at the same height as the peripheral wall 11 and a ring-shaped support protrusion 14 that is concentric with the central disc-shaped support protrusion 13 are provided, and an exhaust port (Fig. (not shown), and the latter vacuum chuck for wafers is equipped with a disk-shaped vacuum chuck that supports the wafer at the same height as the peripheral wall 21 at the bottom of the recess 22 surrounded by the peripheral wall 21 on which the wafer is placed. A large number of support protrusions 23 are connected to adjacent 4
The recesses 22 are arranged in a lattice pattern, and are provided with exhaust ports 24 for exhausting the air inside the recesses 22.

0004

[Problems to be Solved by the Invention] Here, it is considered desirable that a vacuum chuck for wafers satisfy the following conditions.

1) The wafer can be chucked while maintaining its flatness or with the amount of wafer strain being minimized.

2) The contact area with the wafer should be small in order to suppress wafer contamination by the chuck material.

However, none of the conventional vacuum chucks for wafers described above can be said to be optimal for satisfying the above conditions 1) and 2) at the same time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a vacuum chuck for a wafer that can minimize the area of contact with the wafer when the amount of strain on the wafer during chucking is kept constant.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the vacuum chuck for wafers of the present invention supports a wafer at the same height as the peripheral wall at the bottom of a recess surrounded by a peripheral wall on which the wafer is placed. In the vacuum chuck for wafers, the plurality of support protrusions are provided with a large number of support protrusions and an exhaust port for discharging the air in the recessed part.

0010

[Operation] In the above means, when the strain of the wafer during chucking is kept constant, the support area of one support protrusion is maximized.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a wafer vacuum chuck according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a peripheral wall erected around the upper surface of a disc-shaped chuck body 2, on which a wafer (not shown) is placed. At the bottom of the recess 3 surrounded by the peripheral wall 1, there are a number of disc-shaped or cylindrical support protrusions 4 that support the wafer at the same height as the peripheral wall 1.
They are arranged in a staggered pattern forming an equilateral triangle. Furthermore, an exhaust port 5 is provided at the bottom of the recess 3 to exhaust air from the recess 3 that is closed when the wafer is placed.

When a wafer is chucked using the vacuum chuck for wafers having the above configuration, a uniformly distributed load is applied to the wafer, and as shown in the vacuum chuck shown in FIG. By exhausting the air in the recess 9 through the exhaust port 8, the wafer W placed on the support projection 7 is clearly moved to the middle C between the support projections 7 (the one farthest from the support projection), assuming that the distance between the support projections 7 is 2a. ) is greatly distorted, resulting in the maximum amount of distortion τ.

Next, the area of the wafer supported by the 4,231 support protrusions of the present invention and the conventional vacuum chuck shown in FIG. 6 will be considered.

[0016] In order to equalize the amount of strain on the wafer when chucked by both vacuum chucks, the distance a from the farthest point from the support protrusion (position of maximum strain) to the center of the support protrusion is made equal. and the areas of the support protrusions are made equal.

First, in the vacuum chuck of the present invention,
As shown in FIG. 3, one regular hexagonal support area ET is allocated to each support protrusion 4, and its area ST
is expressed by the following formula.

[0018]

[Equation 1] On the other hand, in the conventional vacuum chuck shown in FIG. 6, as shown in FIG. 4, one square support area ES is allocated to each support protrusion 23, and the area SS is calculated by the following equation. expressed.

SS = 2a2 Therefore, it can be seen from ST > SS that the vacuum chuck of the present invention can provide a wider support area per support protrusion. Therefore, if a vacuum chuck has the same chucking area and can obtain the same level of flatness (if the wafer strain is the same), the number of support protrusions will be reduced to 77% (2/2.598) of the conventional one. This makes it possible to reduce the total contact area of the support projections that come into contact with the wafer.

As a result of calculating the amount of strain on the wafer by computer simulation using the finite element method, it was found that the vacuum chuck of the present invention is more advantageous when the number of support protrusions is the same.

[0021] Furthermore, in the above-mentioned embodiments, the case where the support protrusion is in the shape of a disc or a cylinder has been explained, but the support protrusion is not limited thereto, and may be in the shape of a square plate, a prism, or other shapes. Good too.

[0022]

As described above, according to the present invention, when the strain of the wafer during chucking is kept constant, the support area of one support protrusion is maximized, so that the wafer can be Minimize the contact area with the

[Brief explanation of drawings]

FIG. 1 is a plan view of a wafer vacuum chuck according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the state of a wafer chucked in a vacuum chuck.

FIG. 3 is an explanatory diagram of a support area by one support protrusion of the vacuum chuck according to the present invention.

FIG. 4 is an explanatory diagram of a support area by one support protrusion of a conventional vacuum chuck.

FIG. 5 is a perspective view of a conventional vacuum chuck.

FIG. 6 is a perspective view of another conventional vacuum chuck.

[Explanation of symbols]

1 Peripheral wall 3 Recessed part 4 Support protrusion 5　Exhaust port

Claims (1)

[Claims] Claim 1: A device for wafers, in which a number of support protrusions for supporting the wafer at the same height as the surrounding wall and an exhaust port for exhausting air in the recess are provided at the bottom of the recess surrounded by a peripheral wall on which the wafer is placed. A vacuum chuck for a wafer, characterized in that the plurality of support protrusions are arranged in a staggered manner, with three adjacent support protrusions forming an equilateral triangle.