JPS596555A - Wafer attraction fixed base - Google Patents

Abstract

PURPOSE:To remarkably reduce the probability that warp generates on a wafer, even when foreign matters are deposited on the back surface of a wafer or the top surface of an attraction base, with the difficulty of receiving the influence by the foreign matters. CONSTITUTION:The top surface of an attraction base 5 is finished to an accurate flat, and thus a reference flat 6 is formed, then said attraction base 5 is magnetized. The attraction base 5 is formed into a circle of slightly smaller diameter than the diameter of the wafer 3, and a projection of the height H is formed by fitting a rise rim 7 in the outer periphery thereof. Many steel balls 8 of the diameter H are formed and arranged on the reference flat 6 which is the top surface of the attraction base 5, and then spread all over inside the rise rim 7. When the wafer 3 is mounted on the attraction base 5, and a connection hole 10 is connected to a vacuum source P, the wafer 3 is attracted in vacuum toward the steel balls 8 and the rise rim 7. Thereat, even when the foreign matter 11 is deposited on the back surface (lower surface) of the wafer 3, the probability that the foreign matter 11 contained in the clearance surrounded by the steel balls each other and the wafer and deposited on the back surface of the wafer 3 has influences on the wafer 3 and thus generates warp is remarkably low.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wafer suction and fixing table used in a projection exposure type pattern printing apparatus or the like.

In the above-mentioned pattern printing apparatus, it is necessary to hold the wafer surface so that it is positioned within the focal depth range of the projection optical system. ) is used.

Reference numeral 1 denotes a suction table base, on the top of which a suction surface with good flatness is formed, and a large number of suction holes 2 are provided on this suction surface so that it can communicate with a vacuum source P.

When the wafer 5 is placed on the suction table base 1 and the suction hole 2 is communicated with the vacuum source P, the sea urchin/X5 is placed on the suction table base 10.
It is adsorbed and held on the top surface.

However, if foreign matter 4 such as dust or resist from the previous process is attached to the back surface of the wafer 3 (lower surface in the figure), or if foreign matter 4 is attached to the top surface of the suction table base 1,
The wafer 5 is affected by the foreign matter, and the portion above the foreign matter is warped so as to convex upward.

Generally, the depth of focus of a projection optical system is extremely shallow.

For example, since it is about ±5 μm, the above-mentioned warpage tends to cause the problem that the surface of the wafer 5 deviates from the depth of focus range and the resolution deteriorates.

The present invention was made in view of the above circumstances, and is not easily affected by foreign matter, and even if foreign matter is attached to the back surface of the wafer or the top surface of the suction table base, the probability of warping of the wafer is significantly reduced (, It is an object of the present invention to provide a wafer suction and fixing table capable of easily cleaning and removing foreign substances.

In order to achieve the above objects, the present invention uses a ferromagnetic material to form a suction table base having a reference plane, and a rim-shaped protrusion having a constant height around the reference plane. A plurality of balls made of magnetic material are arranged on the reference plane, the diameter of the balls is made equal to the height of the rim-like protrusion, and the gap between the plurality of balls is filled with a vacuum source. It is characterized by being configured so that it can be communicated with.

Next, an embodiment of the present invention will be described with reference to FIGS. 5 and 4. FIG. 3 is a plan view of the device of the present invention, which corresponds to FIG. 1 of the conventional device, and FIG. 4 is a vertical cross-sectional view of the wafer 3 being sucked and held by the device of the present invention, and corresponds to FIG. 2 of the conventional device. This is a diagram.

In the present invention, the suction table base 5 is constructed of a stone pot made of ferromagnetic material and has a reference plane, and the reference plane 6 is formed by finishing the top surface to an accurate plane.

The suction table base 5 is magnetized.

The present invention provides a rim having a constant height around the reference plane. In this embodiment, the suction table base 5 is formed into a circular shape with a diameter slightly smaller than the diameter of the wafer 3, and a raised rim 7 is fitted around the outer circumference to form a protrusion having a height H.

In the present invention, a plurality of magnetic spheres are placed on a reference plane, and the diameter of the spheres is made equal to the height of the rim. In this embodiment, a large number of steel balls 8 with a diameter H are formed to form a suction table base 5.
They are lined up on the reference plane 6 which is the top surface of 0, and spread all over the inside of the rising rim 7. A large number of steel balls 8 are attracted to the reference plane by the magnetic force of the suction base made of permanent magnetic steel.

The present invention is constructed so that a vacuum can be communicated to the gap between the steel balls. In this embodiment, a plurality of pores 9 are bored in the reference plane 6, and the vacuum source P is communicated with the vacuum source P through the communication hole 1o.

This embodiment is configured as described above.

When a wafer 3 is placed on the suction table base 5, the wafer 3 contacts the rising rim 7 and a number of steel balls 8 and is supported at a number of support points. When the communication hole 10 is connected to the vacuum source P in this state, the vacuum source P is communicated with the gaps between the many steel balls 8, and the wafer 5 is vacuum-adsorbed toward the steel balls 8 and the rising rim 7. At this time, even if a foreign object 11 is attached to the back surface (lower surface in the figure) of the wafer 5, the probability that the foreign object 11 will be caught between the wafer 3 and the steel ball 8 is very small, and in most cases, the steel ball It fits in the gap between Comrade 8 and Ueno 13. Therefore, the probability that the foreign matter 11 attached to the back surface of the wafer 3 will affect the wafer 6 and cause it to warp is much smaller than in the conventional apparatus. For the same reason, even if the foreign material 12 adheres to the top surface of the suction table base 50, the probability that it will affect the wafer 5 and cause it to warp is much smaller than in the conventional device. Even if foreign matter adheres to the steel balls 8, the probability that the wafer 3 will warp is very small.

In the wafer suction and fixing table according to the present invention.

Since the wafer 3 is suctioned and fixed via the rising rim 7 and the steel balls 8 without directly contacting the reference plane of the suction table base 50, the contact area is smaller than that of the conventional device (FIGS. 1 and 2) K.
It's quite small compared to that.

Therefore, it is appropriate that the degree of vacuum used for vacuum suction be lower than that in conventional devices.

In the device of this embodiment, the suction table base 5 or the steel ball 8
In order to remove foreign matter such as dust attached to the suction table base 5, the steel ball 8 is attracted to the steel ball 8 by a magnet (not shown, for example, an appropriate electromagnet) having a stronger magnetic force than the suction table base 5, and the steel ball 8 is separated from the suction table base 5. , the steel ball 8 and the suction table base 5 are each disassembled into individual units and cleaned. Steel ball 8 after cleaning
When the steel ball 8 is returned to the cleaned suction table base 5, the steel ball 8 is attracted to the suction table base 5 with a force and restored to its original state, so that a wafer can be vacuum suctioned (FIGS. 5 and 4).

As explained above, one aspect of the present invention is to form a suction table base having a reference plane from a ferromagnetic material, provide a rim having a constant height H around the reference plane, and Place a plurality of magnetic spheres with a diameter of H on the.

If the structure is configured so that a vacuum can be communicated between the plurality of magnetic spheres, it will be difficult to be affected by foreign matter (even if foreign matter is attached to the back surface of the wafer or the top surface of the suction table base, the wafer will not be affected). It has excellent practical effects in that the probability of warping is much lower and foreign matter can be easily cleaned and removed.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a conventional wafer suction and fixing table. 2 is a vertical sectional view of the same, FIG. 5 is a plan view of an embodiment of the present invention, and FIG. 4 is a vertical sectional view of the same. 111. Suction stand base, 200. Suction hole, 5-0. wafer. 4... Foreign object, 5... Suction table base, 6... Reference plane. 7... Rising rim, 8... Steel ball, 9... Pore,
10...Communication hole, 11.12...Foreign object. T 1 Illustration 7- 已

Claims (1)

[Claims] A suction table base having a reference plane is formed from a ferromagnetic material, a rim having a certain height is provided around the reference plane, and a plurality of magnetic spheres are placed on the reference plane. The wafer suction and fixing table is characterized in that the diameter of the sphere is made equal to the height of the rim, and the vacuum is communicated between the plurality of spheres.