JP2750554B2 - Vacuum suction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample holding device such as a pattern transfer device, a drawing device, various process manufacturing devices and an inspection length measuring device in LSI manufacturing, and more particularly to a vacuum suction device thereof.

[0002]

2. Description of the Related Art In recent LSI manufacturing, a fine circuit pattern on the order of submicrons is required as semiconductor devices become more highly integrated. For a pattern size of 0.2 μm or less, pattern transfer by X-ray exposure has been regarded as promising, instead of the optical transfer technique. In the X-ray exposure, an original image of a circuit pattern of a mask is projected onto a wafer in a one-to-one manner, and the circuit pattern is transferred. For this reason, the original dimensions of the mask must be the same as those of the semiconductor element circuit pattern, and the mask is required to have high-precision positional accuracy and dimensional accuracy of the circuit pattern.

The mask has a structure in which a membrane having an original image of a circuit pattern is formed substantially at the center of a Si wafer. The membrane has an area of several tens of mm x several tens
mm and a thickness of 1 μm to 2 μm. In order to evaluate the manufacturing accuracy and pattern transfer accuracy of the mask, when measuring the position and dimensional accuracy of the circuit pattern of the mask with an optical interference measuring machine, the mask is a flat surface correction device conventionally used in LSI manufacturing equipment. It was held in a vacuum suction device of a mold. FIG. 9 is a plan view of a vacuum suction device used in this length measuring device.
FIG. 10 shows a cross-sectional view thereof.

In a conventional vacuum suction apparatus, a wafer 2 (FIG. 9), which is an adsorbate, is adsorbed on an adsorber plate 1 in order to correct the adsorbate to a flat surface.
In FIG. 10 and FIG. 10, since the mask 200 is held, the central portion is missing. Here, the mask 200 is replaced with a wafer 2 having a uniform thickness.) Rings are arranged concentrically on the suction plate 1,
The protrusions 3 and the grooves 4 are formed alternately. The upper surface of the projection 3 becomes the suction surface 5. An evacuation hole 6 is formed in the bottom of the groove 4. An exhaust passage 7 is provided inside the suction plate 1. An exhaust hole 6 of each groove 4 communicates with an exhaust port 8 on the lower surface or side surface of the suction plate 1 via an exhaust passage 7. In this example, the exhaust port 8 is the lower surface of the suction surface 1. The exhaust port 8 is connected to a vacuum pump by an exhaust pipe. Here, the vacuum pump and the exhaust pipe are not shown.

When the vacuum pump is operated with the wafer 2 placed on the suction surface 5 on the suction plate 1, the groove 4 is evacuated. The wafer 2 is pressed against the suction surface 5 by a vacuum suction force, and is sucked on the suction plate 1 to correct the flat surface of the wafer 2.
The plane of the wafer 2 sucked on the suction plate 1 depends on the plane accuracy of the suction surface 5. If there are irregularities or steps on the suction surface 5, the wafer 2 will be sucked so as to follow the unevenness or steps on the suction surface 5. On the surface of the wafer 2, a change in shape corresponding to the irregularities and steps of the suction surface 5 appears. For this reason, in order to make the plane of the wafer 2 a highly accurate planar shape, the suction surface 5 having a highly accurate plane is required.
Must be adsorbed.

On the other hand, the wafer 2 has warpage, bending, and uneven thickness, and the flatness differs from one wafer to another. By adsorbing the wafer 2 on the suction surface 5 having a highly accurate flat surface, the planar accuracy of the wafer 2 having a unique flatness can be improved. At this time, since the wafer 2 is forcibly deformed so as to follow the suction surface 5, it is difficult to improve the planar accuracy by sucking the suction surface 5 manufactured with high precision. Will occur.

[0007] The mask 200 using the vacuum suction apparatus described above.
Is held, a portion of the Si wafer around the membrane 202 is vacuum-adsorbed on the adsorption surface 5 using the above-mentioned adsorption plate 1. Since the Si wafer is adsorbed so as to follow the adsorption surface 5, it is deformed by flattening. Since the membrane 202 is extremely thin, distortion occurs in the membrane 202 due to deformation of the Si wafer. As a result, there is a problem that an error occurs in the position and size of the circuit pattern due to the distortion of the membrane 202, and an accurate value cannot be obtained.

[0008]

As described above, the mask 2
Then, the position and size of the circuit pattern No. 00 are measured and the mask 200
When such a suction plate 1 is used to evaluate the accuracy of the above, there is a disadvantage that the distortion caused by the sample holding causes a position variation or a dimensional change of the circuit pattern, and the circuit pattern on the mask 200 cannot be measured accurately. . In particular, in a circuit pattern of a submicron order, distortion due to adsorption has been an important problem that cannot be ignored. Also, the mask 200
Since the reliability of the position and dimension measurement results of the circuit pattern cannot be obtained, there is a problem that it is difficult to compare the accuracy of the transfer pattern, which requires high-precision position and dimensional accuracy, with the original image 201.

In view of the above, the present invention has been made to solve such a problem, and an object of the present invention is to provide a vacuum suction device capable of holding an adsorbed material such as a wafer without deforming it. Is to do.

[0010]

To achieve the above object, according to an aspect of the vacuum suction device of the present invention, a vacuum suction port on a substrate surface
3 is provided a vacuum fixing portion, each of these vacuum fixing portion, and the minute annular portion in which the vacuum suction port is opened, this small with
The central part is fixed to the upper surface of the annular part and the vacuum suction port
Has a corresponding opening, larger than the outer diameter of the micro-annular part
An elastically deformable seed-like thin-film vacuum sealing member, and each of the vacuum-fixed portions is surrounded by the base surface.
And a pedestal that is higher than the upper surface of the minute annular portion . Further, in the vacuum suction device according to claim 2 of the present invention, the vacuum sealing member is particularly made of polyimide.

[0011]

According to the present invention, the adsorbate such as a wafer can be held at three points by supporting the minute tip of each vacuum fixing portion.
The adsorbate can be held without being deformed. In addition, since a vacuum sealing member such as a polyimide film is provided on the peripheral surface of the suction port of each vacuum fixing portion holding the adsorbate, that is, on the upper surface of the minute annular portion where the vacuum suction port opens.
The suction force increases due to the vacuum sealing action. Furthermore, on
The surface is higher than the base surface and the upper surface of the minute annular portion.
Lower pedestal around the vacuum fixing part,
When the device is not adsorbing the adsorbate,
The hanging vacuum sealing member was supported.
Accordingly, during vacuum suction, air flows through the gap between the adsorbed material and the vacuum sealing member, so that the pressure in this gap decreases, and the vacuum sealing member elastically deforms due to atmospheric pressure and directly contacts the adsorbed material. Thus, the adsorbate is sucked and held, so that a restraining force against a lateral force is generated, and the hold of the adsorbate such as a wafer can be strengthened. In other words, the base provided around the vacuum fixing portion, so that floating facilitate vacuum sealing member during vacuum suction.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a plan view of a suction device according to an embodiment of the present invention, and FIG. In these figures, three thin circular rings 11 having minute openings for vacuum suction are provided on a flat plate 10 serving as a base of the suction device. The ring 11 having three minute suction ports is arranged at the position of the vertex of an equilateral triangle that fits within the outer dimensions of the wafer 20 to be held. The height of the three rings 11 having the minute suction ports is the same, and is slightly higher than the surface of the flat plate 10 of the base. The ring 11 having three minute suction ports in the present embodiment is not limited to the position of the apex of the equilateral triangle, and may be freely arranged. The shape of the suction port may be an ellipse other than a circle or a rectangle.

The edge 12 of the ring 11 having such a minute suction port serves as a suction surface. An edge 12 of the ring 11 is provided with a vacuum sealing member, polyimide, which is larger than the outer shape of the ring 11.
A film 13 is attached. The polyimide film 13 is firmly fixed to the edge 12 of the ring 11 so that there is no peeling off or uneven bonding. In this embodiment, polyimide vacuum sealing member
The vacuum sealing member is a polyimide film 13
Not limited to this, any material may be used as long as it is extremely thin, soft and elastic with respect to the adsorbed material. Since the minute holes inside the ring 11 having the minute suction ports become the evacuation holes 14 for evacuation, they are not closed by the polyimide film 13.

An exhaust path 15 is formed inside the base plate 10 to communicate with the exhaust hole 14, and the base plate 10 is provided with an exhaust port 16. The position of the exhaust port 16 is determined by the apparatus configuration, and may be provided on the side surface or the lower surface of the flat plate 10. Here, it is provided on the lower surface of the flat plate 10. The exhaust port 16 is connected to a vacuum pump via an exhaust pipe. Here, the exhaust pipe and the vacuum pump are not shown.

The wafer 20 is placed on the ring 11 having three minute suction ports to which the polyimide film 13 is attached. At this time,
The wafer 20 is supported by only three points of each ring 11. Wafer 2
When the “0” is placed on the three rings 11, the side surface of the wafer 20 is brought into contact with the positioning pins 40 on the flat plate 10 in order to place the wafer 20 at a fixed position. In this example, the positioning pins 4
Reference numeral 0 denotes two wafers at the position of the orientation flat of the wafer 20 and one wafer at a position that regulates a direction parallel to the orientation flat. Positioning pin 4
0 indicates the number of wafers 20 if the wafer 20 can be held at a certain position,
There is no restriction on the arrangement position. In this example, the height of the positioning pins 40 is set so as not to protrude from the upper surface of the wafer.
It goes without saying that the positioning pin 40 may have a height within an allowable range in view of the device configuration.

On the other hand, a pedestal 50 which is lower than the height of the ring 11 and higher than the surface of the flat plate 10 is provided around the ring 11 having the minute suction port. Wafer 20 is coated with polyimide film 13
When placed on the ring 11 having a micro suction port with
The polyimide film 13 enters between the wafer 20 and the pedestal 50, and a gap is provided for free movement. The pedestal 50 is poly
It is made larger than the outer shape of the imide film 13. Pedestal 50 supporting the polyimide film 13 when not adsorbed to the wafer 20, suppress the sag of the polyimide film 13. At the time of vacuum suction, the polyimide film 13 is made to easily float.

Here, the apparatus can be constructed such that the ring 11 is slightly higher than the surface of the flat plate 10 and the polyimide film 13 can be easily lifted during vacuum suction.
If the protective film 13 can be protected from damage, the pedestal 50 need not be provided. When a vacuum pump (not shown) is operated to evacuate the wafer, the wafer 20 is vacuum-sucked to the edge 12 of the ring 11 having a minute suction port.

The principle of adsorption of the polyimide film 13 is as follows. As shown in the partial cross-sectional enlarged views of FIGS. 3 and 4, with the wafer 20 placed on the ring 11 having three minute suction ports, the vacuum pump is operated to pass the exhaust pipe 16 through the exhaust pipe. When the air is exhausted, air is sucked from the exhaust port 16 and the air flows through the gap between the back surface of the wafer 20 and the polyimide film 13 attached to the edge 12 of the ring 11 having the minute suction port. Decrease, polyimide film 13
Is elastically deformed by being pressed from below by the atmospheric pressure, and is attracted to the back surface of the wafer 20. For this reason, the inside of the polyimide film 13, that is, the inside of the ring 11 having the minute suction port is evacuated, and the wafer 20 is pressed against the edge 12 of the ring 11 having the minute suction port by the atmospheric pressure.

On the other hand, when removing the wafer 20, the evacuation is stopped and the evacuation hole 14 is set to the atmospheric pressure. As a result, the Porii
Since the mid film 13 automatically returns elastically, the wafer can be easily removed. Since the diameter of the exhaust hole 14 is small,
The degree of vacuum is low and the force for sucking the wafer is weak. However, the suction force increases due to the vacuum sealing action of the polyimide film 13 around the exhaust hole 14.

Furthermore, the lateral restraining force is generated by the adsorption of the polyimide film 13, and the lateral holding of the wafer 20 is strengthened. In holding the wafer 20, the wafer 20
Is supported only by the ring 11 having three minute suction ports. The ring 11 having the minute suction port has a small thickness, and the area of the edge 12 serving as a suction surface is small. Therefore, wafer 2
The contact area with 0 is small. In addition, since the vacuum suction force is weak, the wafer 20 is not deformed by the vacuum suction in the ring 11 having the minute suction port. A ring 11 with a minute suction port
Nothing is in contact with the wafer 20 other than the polyimide film 13. Therefore, the only factor that deforms the wafer 20 is the weight of the wafer 20 itself.

The edge 12 of the ring 11 having a minute suction port
Is small and the area is small, so that the probability of dust remaining on the edge 12 is small. On the other hand, as shown in FIG. 5, polyimide
Since the polyimide film 13 is soft, the dust 30 staying on the dry film 13 is wrapped in the polyimide film 13 at the time of adsorption and does not deform the wafer 20. in this way,
Since the influence of the dust 30 on the surface shape of the wafer 20 can be reduced, a stable and highly accurate flat surface can be obtained.

FIGS. 6 and 7 show the results of measuring the flatness of a 4-inch wafer before and after vacuum suction with an interferometer using the suction apparatus of this embodiment. 6 shows the state before vacuum suction, and FIG. 7 shows the state after vacuum suction. Before and after vacuum suction, the wafer 20
No change is observed in the pattern of interference fringes on the surface. This indicates that the wafer 20 is not deformed by the vacuum suction. As a result, even when the suction device of this embodiment is applied to a mask used for X-ray exposure, it is possible to hold a very thin membrane having an original image of a circuit pattern of a semiconductor element without giving a distortion. For this reason, accurate measurement of the position and dimensions of the original image of the circuit pattern on the membrane can be performed.

Next, the adsorption apparatus of this embodiment is mounted on a table of a sample moving mechanism of a light wave interferometer (Nikon: Laser XY-31), and the position of the pattern transferred onto the wafer 20 is determined. The reproducibility was measured. In the measurement, the positions of 25 cross marks arranged two-dimensionally at a pitch of 6 mm on a 4-inch wafer were measured. The measurement was repeated 20 times. FIG. 8 shows the result of the measurement. The reproducibility of the pattern position is ± 0.012 μm at 3σ in the X direction and 3 in the Y direction.
A highly accurate value of ± 0.010 μm was obtained for σ. The wafer 20 does not move even if the table moves in the two-dimensional direction during the measurement, and is reliably held by the suction device. Therefore, accurate and stable position and dimension measurement of the circuit pattern of the semiconductor element can be performed.

[0024] Thus, small suction opening of the ring 11, i.e., the diameter of the exhaust hole 14 is very small, the degree of vacuum is low, the force for sucking the wafer 20 is weak, polyimide around the exhaust hole 14 By providing the film 13, (i)
The suction force is increased by the vacuum sealing action of the polyimide film 13, and (ii) the holding force of the lateral force is generated by the suction of the polyimide film 13, so that the holding of the wafer 20 can be strengthened. The above measurement results show that the polyimide film 13 is working effectively.

From the above results, in the suction apparatus of this embodiment, the wafer 20 is not deformed by the vacuum suction. That is, it is possible to hold the wafer without deforming it while keeping the planarity of the wafer in its natural state, that is, in the state of the processed surface. Further, the wafer 20 is securely held without causing a position change or falling off from the suction device due to an inertial force at the time of acceleration / deceleration or constant speed movement accompanying the table movement of the sample moving mechanism. In particular, the effect of reinforcing the polyimide film 13 that covers the low vacuum suction force due to the minute-diameter exhaust hole 14 is remarkable.

[0026]

As described above, the vacuum suction device of the present invention deforms the suction object by supporting the suction object such as a wafer on the microscopic tips of the three vacuum fixing parts at three points under vacuum. It can be held without doing so. In addition, since a vacuum sealing member such as a polyimide film is provided on the peripheral surface of the suction port of each vacuum fixing portion for holding the adsorbed material, the suction force is increased by the vacuum sealing action, and the suction force increases the lateral direction. Therefore, the holding force of the adsorbate such as a wafer can be strengthened. Furthermore, the upper surface is
A pedestal that is higher than the body surface and lower than the upper surface of the minute annular portion
Is provided around the vacuum fixing part, so that
When the attachment device is not adsorbing the adsorbate,
Supports the vacuum sealing member hanging from the vacuum suction
Sometimes the vacuum sealing member comes up easily.
You.

Further, vacuum such as a ring having a minute suction port
Since the fixed part supports the adsorbate such as wafer,
The structure is simple and the device configuration can be simplified.
You.

[Brief description of the drawings]

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

FIG. 2A is a partial cross-sectional view showing a cross section taken along the line XY of FIG. 1, and FIG. 2B is an enlarged view of a portion A in FIG.

FIG. 3 is an enlarged partial cross-sectional view illustrating the principle of adsorption of a polyimide film according to the present embodiment.

FIG. 4 is an enlarged partial cross-sectional view illustrating the principle of adsorption of a polyimide film according to the present embodiment.

FIG. 5 is an enlarged view of a partial cross section for explaining the effect of the polyimide film of the present embodiment.

FIG. 6 is a diagram of interference fringes on the wafer surface showing the flatness before vacuum suction, which is an experimental result using the suction device of the present embodiment.

FIG. 7 is a diagram of interference fringes on the wafer surface showing the flatness after vacuum suction, which is an experimental result using the suction device of the present embodiment.

FIG. 8 is a diagram showing a result of measuring the reproducibility of a pattern position by attaching the adsorption device of the present example to a sample moving mechanism of a light wave interferometer.

FIG. 9 is a plan view of a conventional vacuum suction device.

FIG. 10 is a sectional view of a conventional vacuum suction device.

[Explanation of symbols]

Reference Signs List 10 flat plate 11 ring with minute suction port (vacuum fixing part) 12 edge of ring with minute suction port 13 polyimide film (vacuum sealing member) 14 exhaust hole 15 exhaust path 16 exhaust port 20 wafer 30 dust 40 Positioning pin 50 Base

 ──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-64-5572 (JP, A) JP-A-60-64926 (JP, U) JP-A-3-21843 (JP, U) JP-A 62- 118443 (JP, U) Hikaru Hei 1-176924 (JP, U) Hikaru Hei 2-271518 (JP, U)

Claims (2)

(57) [Claims] The present invention relates to three vacuum cleaners having vacuum suction ports on the surface of a substrate.
An empty fixing portion is provided, and each of these vacuum fixing portions has a minute annular portion in which the vacuum suction port is opened, and a central portion fixed to the upper surface of the minute annular portion and the vacuum portion.
It has an opening corresponding to the suction port and has an outer diameter of the minute annular portion.
Ri is constituted by a vacuum sealing member greater elastically deformable sheet-like thin film, wherein the higher than the substrate surface and before around each vacuum fixing portion
Vacuum suction device which is characterized that you provided the serial lower than the upper surface of the minute circular portion pedestal. 2. The vacuum suction device according to claim 1, wherein said vacuum sealing member is made of polyimide .