JP2908516B2 - Vacuum suction type wafer holding device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum suction type wafer holding device used in a semiconductor manufacturing apparatus, which suctions and holds the back surface of a wafer by vacuum suction.

[Conventional technology]

In a semiconductor manufacturing apparatus, as a wafer holding device for transferring a mask pattern onto a wafer, a vacuum suction type wafer holding device that sucks and holds the back surface of the wafer by vacuum suction (for example, Japanese Patent Publication No. 1-14703). Is often used.

Generally, when a wafer holding device holds a wafer and the contact thermal resistance of the contact surface between the wafer holding device and the wafer is large, the exposure energy for transferring the mask pattern onto the wafer increases the exposure energy for holding the wafer from the wafer. Since the wafer does not escape to the apparatus, the wafer temperature rises and thermal deformation is caused, and the pattern transfer accuracy is deteriorated. In particular, in the case of a vacuum suction type wafer holding device, since gas does not exist in a space other than the contact surface between the wafer holding device and the wafer, the pattern transfer accuracy is significantly deteriorated due to the rise in the wafer temperature.

Further, even when the vacuum suction type wafer holding device is used in a proximity type exposure apparatus in which a mask and a wafer are arranged at a distance of several tens of microns and a mask pattern is transferred, if the contact thermal resistance is large, the wafer may be damaged. As the temperature rises, the temperature of the mask also rises and thermal distortion occurs in the mask, so that the pattern transfer accuracy deteriorates.

Therefore, the projections provided on the surface of the main structural member of the vacuum suction type wafer holding device which faces the wafer to be sucked (hereinafter referred to as "opposing surface") are provided to reduce the contact thermal resistance and to reduce the contact heat resistance. In order to ensure the flatness of the wafer, a surface that comes into contact with the wafer (hereinafter, referred to as a “contact surface”) is flat-finished, and the wafer has a high rigidity to prevent the wafer from being warped after suction. The material is used.

[Problems to be solved by the invention]

However, in the above conventional example, although the contact surface of the projection is flat-finished, the contact surface has minute irregularities and undulations, and the surface of the wafer has minute irregularities and undulations. Is present, the actual contact area when the back surface of the wafer is vacuum-sucked is much smaller than the apparent area, so that contact thermal resistance increases and deterioration of pattern transfer accuracy can be completely prevented. There is a problem that can not be.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vacuum suction wafer holding device capable of reducing contact thermal resistance and improving pattern transfer accuracy.

[Means for solving the problem]

The vacuum suction type wafer holding device of the present invention is a device for holding a wafer by vacuum suction, comprising a plurality of protrusions having the same height formed on the surface of the main structural member and a material having a rigidity smaller than that of the wafer. And a resilient member higher or equal to the protruding portion, and the resilient member is provided so as to surround each of the plurality of protruding portions.

The height of the protrusion is D [mm], the Young's modulus of the elastic member is E [Pa], and the pressure difference between the front surface and the back surface of the wafer is T [mm].
For [Toor], the difference between the height of the elastic member and the height D of the protrusion The height D + d [mm] of the elastic member may be set within the range described above. Further, an outer peripheral wall is provided on an outer periphery of the wafer holding surface of the main structural member, and an inner side surrounded by the outer peripheral wall is provided. Vacuum suction may be performed, and the protrusion and the elastic member may be separately arranged with good symmetry.

[Operation] In the vacuum suction type wafer holding device of the present invention, the wafer suctioned by vacuum is held in contact with the contact surface of the projection and the contact surface of the elastic member, but the elastic member is smaller than the wafer. Since it is made of a material having a rigidity, even if there are minute irregularities or undulations on the back surface of the wafer, the contact surface is deformed according to the irregularities or undulations, so that the contact thermal resistance on the contact surface can be reduced. it can.

When the height of the protrusion is D [mm], the Young's modulus of the elastic member is E [Pa], and the pressure difference between the front and back surfaces of the wafer is T [Torr], the height of the elastic member is D + d
[Mm] Is set within the range, the suction force applied to the wafer at the time of suction can be made one order of magnitude larger than the repulsive force of the elastic member applied to the wafer in proportion to the displacement amount. Is reliably brought into contact with the contact surface of the projection.

Example Next, an example of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are schematic structural views showing a first embodiment of a vacuum suction type wafer holding apparatus according to the present invention, and FIGS.
The figure is a schematic configuration diagram showing the relationship between the protrusion 2 and the elastic member 3 before and after wafer suction.

The vacuum suction type wafer holding device according to the present embodiment is made of a material having a high rigidity (for example, stainless steel, aluminum, ceramics, etc.) for correcting the warpage of the wafer 5 to be sucked (see FIG. 2). A main structural member 1 integrally provided with a wall 1a and a surface (opposing surface) of the main structural member 1 facing the wafer 5 are provided integrally with the main structural member 1 with good symmetry. Twelve protrusions 2 as a plurality of protrusions having pin shapes having the same height, elastic members 3 provided at equal heights surrounding each of the protrusions 2, and the main structural member 1. It has a vacuum suction hole 4 provided in the main structural member 1 for connecting a central portion of the facing surface and a vacuum source (not shown). Here, the elastic member 3
Is made of a material having a lower rigidity than the main structural member 1 and the wafer 5 (for example, synthetic rubber). In addition, as shown in FIG.
Is provided so that the height D + d [mm] is higher than the height D [mm] of the protrusion 2 by d [mm]. Further, in order to ensure the flatness of the wafer 5 after suction, the surface (contact surface) of the projection 2 and the elastic member 3 is finished to be flat.

Next, the suction operation of the wafer 5 in the vacuum suction type wafer holding device of the present embodiment will be described with reference to FIG.

Prior to the suction operation, the wafer 5 is transported by a known transport band (not shown) to a position where the wafer 5 and the contact surface of the elastic member 3 come into contact as shown in FIG. 2 (A).
Thereafter, the vacuum suction hole 4 is connected to a vacuum source (not shown) to start vacuum suction on the back surface of the wafer 5. At this time, assuming that the pressure of the space on the front surface side of the wafer 5 is T [Torr], the gas existing in the main structural member 1, the outer peripheral wall 1a of the main structural member 1 and the space surrounded by the wafer 5 is Since the pressure in the space is reduced to about 0 [Torr] by the vacuum generating source, a pressure difference T [Torr] is generated between the front surface and the back surface of the wafer 5. Therefore, the wafer 5 includes Suction force is applied.

On the other hand, when the wafer 5 is sucked toward the opposing surface of the main structural member 1 by the suction force, the elastic member 3 contracts by an amount corresponding to the displacement of the wafer 5, so that the repulsive force of the elastic member 3 is reduced. It is applied to the back surface of the wafer 5 in proportion to the amount of displacement. Therefore, the repulsive force F when the wafer 5 is displaced by a difference d [mm] between the height D + d [mm] of the elastic member 3 and the height D [mm] of the protrusion 2 is: When the Young's modulus of the elastic member 3 is E [Pa], Therefore, in order for the back surface of the wafer 5 to contact the contact surface of the protrusion 2 against the repulsive force F, the height difference d [mm] may satisfy the following expression. .

Here, in order to ensure that the back surface of the wafer 5 abuts against the contact surface of the protrusion 2, the maximum value of the height difference d [mm] is reduced by one digit, and the height difference d [Mm] may satisfy the following equation.

When the suction operation is completed as described above, the rear surface of the wafer 5 is held by vacuum suction while being in contact with the contact surfaces of the protrusion 2 and the elastic member 3. Here, the contact surface of the projection 2 has minute irregularities and undulations even though the contact surface is flat-finished, and the surface of the wafer 5 has minute irregularities and undulations. Although the contact thermal resistance of the contact surface cannot be made smaller than that of the conventional one, the elastic member 3 is made of a material having a rigidity smaller than that of the wafer 5, so that fine irregularities or Even if there is undulation, the contact surface is deformed according to the unevenness or undulation, so that the contact thermal resistance on the contact surface can be reduced.

In order to confirm this, the main structural member 1 is made of stainless steel and the elastic member 3 is made of silicon rubber, the height D of the main structural member 1 is 1 mm, and the height D of the elastic member 3 is D + d.
Was set to 1.05 [mm] (difference in height d = 0.05 [mm]), a vacuum suction type wafer holding device of this embodiment was prototyped, and the contact thermal resistance R ₁ after suctioning the wafer 5 was measured. R ₁ = ₁ × 10 ⁻³ [K · m ⁻² / W] In addition, a prototype having the conventional structure without the elastic member 3 was manufactured in the same manner, and the contact thermal resistance R ₂ was measured. As a result, R ₂ = 1 × 10 ⁻² [K · m ⁻² / W] Was.

Therefore, according to the present embodiment, the contact thermal resistance can be reduced to 1/10 as compared with the conventional one, so that the temperature rise of the wafer 5 can be suppressed to 1/10 and the pattern transfer accuracy can be improved. Was.

The shape of the protrusion 2 used in this embodiment is a cylindrical pin shape as shown in FIG. 1, but is not limited to this, and may be, for example, a prismatic pin shape.

In the above description, the protrusion and the elastic member are provided with good symmetry on the facing surface of the main structural member, but may be provided asymmetrically. However, since the wafer generally has a disk-like shape, it is possible to maintain the flatness of the wafer after suction with high accuracy by providing the elastic member with good symmetry.

Further, the protrusion is provided integrally with the main structural member, but may be separate.

[Effects of the Invention] The present invention is configured as described above, and has the following effects.

Each of the plurality of protrusions includes a plurality of protrusions having the same height formed on the surface of the main structural member, and an elastic member higher or equal to the protrusions made of a material having a rigidity smaller than that of the wafer. Since the elastic member is provided so as to surround the wafer, the elastic member that is held in contact with the vacuum-sucked wafer is made of a material having a rigidity smaller than that of the wafer. Even if there is minute unevenness or undulation, the contact surface is deformed in accordance with the unevenness or undulation, so that the contact thermal resistance on the contact surface can be reduced, and the effect of improving the pattern transfer accuracy can be achieved.

When the height of the protrusion is D [mm], the Young's modulus of the elastic member is E [Pa], and the pressure difference between the front surface and the back surface of the wafer is T [Torr], the height of the elastic member is D + d
[Mm] Is set within the range, the suction force applied to the wafer at the time of suction can be made one order of magnitude larger than the repulsive force of the elastic member applied to the wafer in proportion to the displacement amount. There is an effect that the back surface of can be reliably brought into contact with the contact surface of the projection.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a vacuum suction type wafer holding apparatus according to the present invention, in which (A) is a cross-sectional view cut along the height of a contact surface of a protrusion, and (B) is (B). FIG. 2A is a cross-sectional view taken along the line AA ′, and FIG. 2 is a schematic configuration diagram showing the relationship between the protrusion 2 and the elastic member 3 before and after wafer suction, and FIG. 2A shows the relationship before wafer suction. FIG. 3B is a diagram showing the relationship after the wafer is sucked, and FIG. 2B is a diagram showing the relationship after the wafer is sucked. 1,11: Main structural member, 1a, 11a: Outer peripheral wall, 2,12: Projection, 3,13: Elastic member, 4,14: Vacuum suction hole, 5: Wafer, D: Projection Part height, d ... Difference in height.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koji Marumo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-58-57736 (JP, A) −104726 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/68

Claims (3)

(57) [Claims] 1. An apparatus for holding a wafer by vacuum suction, comprising: a plurality of projections having the same height formed on a surface of a main structural member; and a projection formed of a material having a rigidity smaller than that of the wafer. A vacuum suction type wafer holding device, comprising a high or equal elastic member, wherein the elastic member is provided so as to surround each of the plurality of protrusions. 2. The height of the protrusion is D [mm], the Young's modulus of the elastic member is E [Pa], and the pressure difference between the front and back surfaces of the wafer is T [mm].
For [Toor], the difference between the height of the elastic member and the height D of the protrusion 2. The vacuum suction type wafer holding device according to claim 1, wherein the height D + d [mm] of the elastic member is set in the range of (1). 3. The vacuum suction type wafer holding device according to claim 1, wherein an outer peripheral wall is provided on an outer periphery of the wafer holding surface of the main structural member, and an inner portion surrounded by the outer peripheral wall is evacuated. apparatus.