JPS587055B2 - Gap setting device in proximity aligner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gap setting device in a proximity aligner.

2. Description of the Related Art In manufacturing semiconductor devices, a pattern of a mask is transferred to a photosensitive agent coated on the surface of a semiconductor substrate (hereinafter referred to as a wafer).

Various methods are used for this transfer method, but the mask and wafer are supported in close proximity (for example, with a spacing of several μm), and ultraviolet rays, soft X-rays, or ions are emitted from above the mask. There is a so-called proximity method in which a beam or the like is irradiated.

The gap between the mask and Uenohachi (hereinafter referred to as gap) in this proximity method is very small, and it is very difficult to obtain a predetermined gap, and various methods have been devised.

For example, there is a device using a mechanical reference surface as shown in FIG.

This conventional device will be explained below. First, in Figure 1a,
A tool 1 having a step 1a corresponding to a predetermined gap is fixed to a mask table 2 by vacuum suction.

The wafer 3 is pressed against the tool 1 from below by a mechanism 5 for pushing up from below via a wafer chuck 4.

In this state, the mechanism 5 pushing up from the -F direction is clamped by a mechanism not shown.

Since the lower surface of this wafer chuck 4 is a spherical seat, even if the wafer 3 is wedge-shaped, the upper surface of the wafer 3 is attached to the tool 1.
can be placed in close contact with the surface of the

Next, in FIG. 1b, the vacuum between the mask table 2 and the tool 1 is cut off, the tool 1 is removed, and the mask 6 is vacuum-adsorbed onto the surface of the mask table 2 instead. You can get a gap tag of .

FIG. 2 is an example of another conventional apparatus, which uses three gap sensors to set the gap between the mask and the wafer.

In FIG. 2, a wafer 21 is held by a wafer chuck 22 by vacuum suction.

The wafer chuck 22 has three screws (23A in FIG.
23B (only two are shown).

The height and surface direction of the wafer chuck 22 can be adjusted by three motors (only two motors 24A and 24B are shown in the figure) connected to three screws.

The wafer chuck 22 is pulled downward by a tension spring 26 that is stretched between the wafer chuck 22 and the support base 25.

The mask 27 is fixed to the mask holder 28 by vacuum suction.

The mask holder 28 is fixed to the mask table 29 by vacuum suction.

The mask holder 28 has a gap sensor (30 in the figure).
Only two (A, 30B) appear in the mask 27
This allows the gap between the mask and wafer to be measured.

That is, by controlling the three motors while checking the values of the three gap sensors, the gap between the mask and the wafer can be adjusted to an arbitrary value.

When using the conventional device described above, the following problems need to be solved.

The problem is that the flatness of the wafer surface is not sufficiently good, and this problem is becoming worse with the recent trend of increasing the diameter of wafers.

If a conventional apparatus is used to perform transfer onto a wafer surface having such a problem, a difference in the gap will occur due to the difference in flatness, so the gap for the entire surface of the wafer will not be a correct value.

Therefore, the entire surface of the wafer cannot be transferred correctly.

A method to avoid this drawback is to divide the wafer into small areas where flatness can be obtained and repeat transfer for each area.

However, with respect to this method, the conventional apparatus described above has the following drawbacks.

That is, in the apparatus shown in FIG. 1, the mask must be removed and the tool set for each transfer, which is too time-consuming.

In addition, the wafer surface is likely to be scratched because the tool repeatedly contacts the wafer surface.

Further, in the apparatus shown in FIG. 2, gap sensors are arranged to surround the mask and gap measurement is performed outside the transfer portion of the wafer, so the gap setting accuracy is not sufficient.

Another drawback is that when transferring to the edge of the wafer, one or two of the gap sensors protrude outside the wafer, making it impossible to measure the gap.

It is an object of the present invention to provide a gap setting device which eliminates these drawbacks of conventional devices.

Hereinafter, the present invention will be explained using FIG. 3 and FIG. 4 showing each embodiment.

In FIG. 3 showing the first embodiment, a wafer 31 is held on the upper surface of a wafer holder 32 by vacuum suction.

The wafer holder 32 has a Z stage 33 and an XY stage 3.
4, and can be moved in the Z direction; X direction; and Y direction, respectively, according to instructions from the computer 35.

The Z stage and the XY stage are each controlled by a servo motor (not shown).

The mask 36 is held by a mask holder 37 by vacuum suction.

The mask holder 37 is held on the mask table 38 by vacuum suction.

One gap sensor 39 is built into the mask table 38.

The operation will be explained below.

First, the Z stage 33 is fixed at a fixed position.

The XY stage 34 is moved to scan the wafer 31 under the gap sensor 39, and the coordinates (x
, y) is measured and the value is stored in the computer 35.

Next, the XY stage 34 is moved under the mask 36 and the mask pattern is repeatedly transferred onto the photosensitive agent coated on the wafer 31 surface. The Z stage 33 is controlled according to the value of the height of the wafer with respect to the coordinates of each point, so that the gap between the transferred portion of the mask 36 and the wafer 31 is always constant.

By operating as described above, it is possible to perform transfer over the entire surface of the wafer with a constant gap.

In this embodiment, an example using one gap sensor has been described, but it is also possible to use a plurality of sensors in parallel in order to improve measurement efficiency.

FIG. 4 shows a second embodiment of the invention.

The difference between FIG. 3 and FIG. 3 is that the gap sensor is incorporated into the mask holder and is located to the right of the center of the transfer area of the mask by the width L of the transfer area.

Identical numbers refer to the same parts as those in FIG. The operation will be explained below.

First, the XY stage 34 is controlled to bring the portion of the wafer 31 to be transferred directly below one gap sensor 40 .

In this state, Z is determined by the measurement value of the gap sensor 40.
The stage 33 is controlled and the gap is set to a predetermined value.

Next, move the XY stage 34 to the left by L to remove the mask 3.
Transfer the first area according to step 6.

When the transfer of the first area is completed, the second area is located directly below the gap sensor 40, so the Z stage 33 is controlled again based on the measured value of the gap sensor 40.

Next, move the XY stage 34 to the left by L to remove the mask 3.
Transfer the second area according to step 6.

Thereafter, the entire area is transferred in the same manner repeatedly.

When the second embodiment is used, there is no need to store information about the wafer's 1,000-sided degree in the computer 35, so the capacity of the computer can be small.

According to the present invention as described above, the measuring means 39 and 40 scan the wafer and measure the height of each point on the wafer, the memory stage 35 stores the height value of each point on the wafer, Because the moving stages 33 and 34 are provided to move the wafer to the bottom of the mask and control the gap between the mask and the wafer according to the height of each point on the wafer stored in the storage means,
It is possible to set the gap between the mask and the wafer even at the periphery of the wafer, and the mask pattern can be correctly transferred over the entire surface of the wafer.

[Brief explanation of drawings]

FIG. 1 shows a first conventional gap setting device, a second conventional gap setting device,
The figure shows a second conventional example of a gap setting device. FIG. 3 shows a first embodiment of the present invention, and FIG. 4 shows a second embodiment. Explanation of symbols of main parts, 31... wafer, 32...
Wafer holder, 33...Z stage}...Movement means, 34...XY stage}...Movement means, 35...
・Calculator...Storage means, 36...Mask, 39,4
0...Gap sensor...Measuring means.

Claims (1)

[Scope of Claims] 1. Proximity technology in which a mask and a wafer are supported in close proximity and the mask pattern is transferred to a photosensitive agent coated on the wafer surface by irradiating ultraviolet rays, soft X-rays, etc. from above the mask. - In the aligner, a measuring means scans the wafer and measures the height of each point on the wafer, a storage means stores the height value of each point on the wafer, moves the wafer to below the mask, and measures the height of each point on the wafer. A gap setting device comprising a moving means for controlling the gap between the mask and the wafer according to the height value of each point on the wafer stored in the storage means. 2. The gap setting device according to claim 1, wherein the measuring means is at least one gap sensor 39 built into the mask table 38 that holds the mask holder by vacuum suction. . 3. The gap setting device according to claim 1, wherein the measuring means is one gap sensor 40 built into a mask holder 37 that holds a mask by vacuum suction. 4. In the gap setting device according to claim 1, the moving means includes a Z stage that moves the wafer in the Z direction according to instructions from the storage means, and an XY stage that moves the wafer in the X and Y directions. A gap setting device featuring: 5. In the gap setting device according to claim 3, the gap sensor 40 is mounted on the mask holder 37 such that the distance between the center of the transfer area of the mask 36 and the center of the sensor is equal to the transfer area L of the mask. A gap setting device characterized in that it is incorporated into.