JPH04294518A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To adjust the exposed area of wafers to the optimum focusing state as a whole. CONSTITUTION:At the time of exposing wafers respectively containing a plurality of chips, the heights of a plurality of focus measuring points 1-4 and 5-8 are measured by arranging the wafers against an exposing device after deciding the focus measuring points 1-4 and 5-8 containing three points which do not exist on the same straight line and the heights of the focus measuring points are adjusted so that the heights can become nearly the same by tilting the wafers on the basis of the measured results. The focus measuring points 1-4 are decided in the scribe areas 10 of the wafers. In addition, the points 5-8 are decided in the peripheral areas 9b excluding element areas 9a in chips 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for adjusting the focus of an exposed surface of a wafer.

[0002]In addition to the large chip size of recent ICs,
In order to form extremely fine patterns on a wafer, it is necessary to accurately measure the flatness of the wafer during pattern exposure and to adjust focus based on the flatness measurement.

0003

[Prior Art] In exposure equipment, mainly steppers,
In order to perform accurate pattern transfer, the flatness of the exposed area on the wafer is measured prior to exposure.

FIG. 2 is a diagram for explaining focus measurement, and shows a state in which a wafer is placed in an exposure apparatus, with reference numeral 11 an inspection light, 12 a wafer, 13 a chuck, and 14
is a stage, 15 is a light source, 16 is a light receiving sensor, 1
7 represents a reticle, 18 represents a lens system, and 19 represents a mirror.

The stage 14 can move forward and backward, left and right, and up and down with the wafer 12 mounted thereon, and the chuck 13 can rotate around two axes while the wafer 12 is mounted thereon.

Conventionally, the wafer 12 is placed in an exposure apparatus, and
A plurality of focus measurement points are provided in the element region of the wafer 12 or a region including the element region, a laser beam is irradiated to the focus measurement point, the reflected light is received by a light receiving sensor, and the flatness is determined from the intensity distribution and position. . That is, the wafer 12 is moved up and down to find the height position (the height of the plane including the focus measurement point and perpendicular to the optical axis of the lens system 18) where the amount of light received is the greatest.

As another method, a light beam is applied over almost the entire exposed area, and the height position is determined based on the averaged information. However, the element area that has gone through various processes has unevenness and the height varies depending on the location, making it difficult to measure the exact height position of the exposure area, and exposure may exceed the depth of focus of the exposure equipment. If this happens, accurate pattern transfer may not be possible, resulting in defects.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a method for adjusting the focus of an exposure surface so as to accurately transfer a pattern and obtain the best image.

[0009]

[Means for Solving the Problems] FIG. 1 is a diagram showing focus measurement locations according to the present invention. The above problem was solved by setting multiple focus measurement points 1 to 4 and 5 to 8, including three points that are not on the same straight line, in an area of the same height excluding the element area when exposing a wafer containing multiple chips. , the wafer is placed in an exposure device, the heights of the plurality of focus measurement points 1 to 4 and 5 to 8 are measured, and the wafer is tilted based on the measurement results, and the heights of the plurality of focus measurement points 1 to 4 are measured. This problem is solved by a method of manufacturing a semiconductor device in which the heights of 4, 5 to 8 are adjusted to be approximately equal.

[0010] Furthermore, the plurality of focus measurement points 1 to
4 is solved by a method of manufacturing a semiconductor device in the scribe area 10 of a wafer. Further, the plurality of focus measurement points 5 to 8 are solved by the method of manufacturing a semiconductor device located in the peripheral region 9b of the chip 9 excluding the element region 9a.

[0011]

[Operation] In the present invention, the focus measurement point is set in an area having the same height excluding the element area. Although the element area becomes uneven after going through various processes, the scribe area 10 between the chips 9 is flat and has the same height, and the peripheral area 9b within the chip 9 excluding the element area 9a is also uneven. have almost the same height. Therefore, if a focus measurement point is provided in such an area, height measurement can be performed accurately.

The wafer 12 is placed on the chuck 13 of the exposure device.
Although the exposure surface is not necessarily perpendicular to the optical axis of the exposure optical system when the The inclination of the exposure surface can be determined from this, and the inclination can be corrected to make the exposure surface perpendicular to the optical axis of the exposure optical system.

[0013]

Embodiment FIG. 1 is a diagram showing focus measurement locations. The chip 9 is, for example, 10 mm square and has an element area 9a and a peripheral area 9b around the element area 9a. The peripheral region 9b has a width of, for example, 100 μm, and is a region where a pad is formed.

[0014] The width between each chip 9 is, for example, 200 μm.
There are m scribe areas 10. In Figure 1, 1 to 4
are focus measurement points in the scribe area, and 5 to 8 are focus measurement points in the peripheral area of the chip.

The wafer 12 as described above is placed on the chuck 13 of an exposure apparatus as shown in FIG. 2, and the focus measurement points 1 to 4 in the scribe area 10 are measured. Focus measurement points 1 to 4 are defined in the scribe area 10 around the chip 9 to be exposed.

The inspection light 11 may be a laser beam or a light including a broad wavelength band. Alternatively, a lens system may be used to focus the light on the measurement location. The stage 14 is driven back and forth and left and right to bring the focus measurement point 1 under the optical axis of the lens system 18. Next, the height of the focus measurement point 1 is measured by driving the stage 14 up and down. Similarly,
Measure the heights of focus measurement points 2, 3, and 4.

Next, focus measurement points 1 to 1 are measured.
Based on the height value of 4, the chuck 13 is rotated and adjusted so that the heights of focus measurement points 1 to 4 are approximately equal. In this state, the chip area 9 is exposed for pattern transfer. Even if there are irregularities in the element region 9a, they are within the depth of focus, allowing accurate pattern transfer.

Similarly, exposure for pattern transfer of adjacent chip areas is performed one after another. In this way, the entire surface of the wafer is exposed for pattern transfer. Instead of setting focus measurement points 1 to 4 in the scribe area 10, the chip 9
The focus measurement points 5 to 8 may be defined in the peripheral region 9b excluding the element region 9a. Since the peripheral area 9b has good flatness where the pads are to be formed, accurate pattern transfer is possible in this case as well.

In the conventional method, a focus measurement point is provided in the element area, and the exposure area may not fall within the depth of focus, but according to the method of the present invention, good focus can be achieved over the entire exposure area at any time. Obtainable.

[0020] Note that focus measurement points 1 to 4, 5 to 8
When measuring the height position, it is also possible to measure the height position without moving the stage 14 up and down. Furthermore, height measurement is possible even if the focus measurement point is not under the optical axis.

[0021]

[Effect of the invention] As explained above, according to the present invention,
The focus of the exposure surface can be adjusted to obtain the best focus for accurately transferring a pattern to a wafer chip.

The present invention is effective in forming fine patterns with high dimensional accuracy, and contributes to higher density of semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a diagram showing focus measurement locations.

FIG. 2 is a diagram for explaining focus measurement.

[Explanation of symbols]

1 to 4 are focus measurement points, focus measurement points 5 to 8 in the scribe area are focus measurement points, focus measurement point 9 in the peripheral area of the chip is the chip 9a, element area 9b of the chip is the peripheral area 10 of the chip. The scribe area 11 is the inspection light 12, the wafer 13, the chuck 14, the stage 15, the light source 16, the light receiving sensor 17, the reticle 18, the lens system 19, and the mirror.

Claims (3)

[Claims] Claim 1: When exposing a wafer containing a plurality of chips, a plurality of focus measurement points (one
-4, 5-8), place the wafer in an exposure device, and measure the plurality of focus measurement points (1-4, 5-8).
The wafer is tilted based on the measurement result, and the focus measurement points (1 to 4, 5
~8) A method for manufacturing a semiconductor device, comprising adjusting the heights of items 1 to 8) to be approximately equal. 2. The plurality of focus measurement points (1 to 1)
4. The method of manufacturing a semiconductor device according to claim 1, wherein the step 4) is in a scribe area (10) of the wafer. 3. The plurality of focus measurement points (5 to 5)
2. The method of manufacturing a semiconductor device according to claim 1, wherein the area 8) is located in a peripheral region (9b) of the chip (9) excluding the element region (9a).