JPH0737792A - Leveling method - Google Patents

Abstract

PURPOSE:To provide a highly precision leveling method wherein even a periphery of a chip is considered in any chip size. CONSTITUTION:This leveling method is provided with a detection system 3 for sensing a height in an area near four corners according to a size 1A of a chip to be exposed and adjusts a chip surface to make each diagonal height the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leveling method for exposing by a lithographic technique for manufacturing a semiconductor.

[0002]

2. Description of the Related Art In recent years, with the progress of miniaturization and the increase in chip size, the accuracy of the leveling function for adjusting the wafer surface to be parallel to the lens surface has become very important. The leveling function is installed in any stepper device.

An example of the leveling method actually used at present will be described below with reference to the drawings.

FIG. 4A shows an outline of a conventional leveling device. In FIG. 4A, 1 is a wafer to be exposed. 1A is a chip size for exposure. Two
Is a stage that is movable and can be moved to level the tip. Reference numeral 5 is an optical fiber, and 6 is a sensor for detecting the light emitted from the optical fiber 5.

The operation of the leveling device constructed as above will be described below.

First, before exposing the resist-coated wafer 1, the wafer 1 is irradiated with light rays obliquely laterally. The light radiated at this time is reflected on the resist or the substrate and strikes the sensor 6 that senses the amount of light. At this time, the most reflected light hits the sensor 6 when the wafer 1 becomes horizontal. The stage 2 is driven while irradiating light, the position with the largest light amount is recognized as the horizontal plane, and the leveling is performed.

[0007]

However, in the above structure, the leveling is mainly adjusted only near the tip center, so that when the tip size becomes large or becomes slender, the inclination cannot be completely corrected in the peripheral portion. There was a problem that there was a case where there was no. In order to solve this, a method of measuring the heights of the four sides of the chip using four sets of height detection systems 3 as shown in FIG.
-185318. However, this method also shows that if the surface is misaligned at the corner of the chip as shown in 1X,
The tilt cannot be corrected, which causes a focus shift.

In view of the above problems, the present invention provides a highly accurate leveling method that takes into consideration the periphery of the chip regardless of the chip size.

[0009]

In order to solve the above-mentioned problems, the leveling method of the present invention uses a height detection system which is movable or a stage is moved to move the stage so that the chip is in the vicinity of four corners (four corners or four corners) of any chip size. It has a configuration that measures the height of the scribe rain near the corner and adjusts the wafer surface horizontally with respect to the lens surface based on the result.

[0010]

According to the present invention, with the above-described structure, the leveling can be performed with emphasis on the four corners of the chip. As a result, the focus shift at the corner of the chip, which occurs in the conventional leveling, is eliminated. In general, the performance of the lens is worse at the periphery than at the center (more likely to be affected by aberration), and in that sense, the focus margin is small. The leveling error also increases as the distance from the center increases. In this sense as well, it is the farthest from the center of the chip.
The safest leveling method is to detect the height at the corner and correct the leveling.

[0011]

(Embodiment 1) A leveling method according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a configuration diagram of a leveling method according to an embodiment of the present invention.

In FIG. 1, 1 is a wafer, 1A is a chip size, 2 is a stage capable of adjusting plane movement and leveling, and 3 is a height detecting sensor.

FIG. 2 is a flow chart for explaining the operation in the embodiment. The operation of the leveling device will be described below with reference to FIGS.

First, in step 1, a chip 1A of 4
The height of the corner is measured by moving the stage 2 in parallel. The stage 2 moves in parallel so that the height detection sensor 3 can measure the height at the upper left of the chip 1A. After detecting the height of the upper left of the chip, the stage 2 moves so that the height of the upper right can be detected, and the lower right and lower left are measured by the same procedure.

Thereafter, in step 2, the stage 2 is returned to the exposure position, and the stages are driven so that the diagonal heights thereof are the same (horizontal), and the leveling is corrected. At this time, the average of the heights of the two corrected diagonal lines is set as the focus reference plane. As a result, the leveling and the autofocus function can be performed at the same time, and the throughput can be improved.

Then, in step 2, exposure is performed. After the exposure, the height detection sensor 3 is moved to the upper left of the next chip.

As described above, according to this embodiment, the stage is moved to the position of the detection system according to the chip size and the leveling is adjusted by measuring the four corners. In this system, the height detection system is adjusted. Since it is fixed, its structure can be simplified.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram of a leveling method showing a second embodiment of the present invention. In the figure, 11 is a wafer, 11A is a chip size to be exposed, 11B is a scriberain, 12 is a stage, and 13A to D are detection systems for detecting the height. The above is the same as the configuration of FIG. It is something. The difference from FIG. 1 is that the drive devices 14A to 14D of the detection systems 13A to 13D are provided.

The operation of the leveling device having the above structure will be described below. First, when the chip size to be exposed is determined, the drive devices 14A to 14D of the detection system are moved so that the heights of the scribe rains near the four corners of the chip can be detected. After the stage 12 moves to the exposure position, the scribe rain 11B near the four corners of the chip
The height of each of the four detection systems 13A to 13D simultaneously measures 4
Leveling is corrected by the measurement result of the set. At this time, the focus position of the tip can also be calculated from the measurement result, so that leveling adjustment and focus position measurement can be realized at the same time.

As described above, by providing four sets of movable height detection systems 13, four heights can be measured at the same time.
The time to move the stage can be omitted, and excellent throughput can be realized.

Although the height detection system 3 is fixed in the first embodiment, it may be movable. Further, the height detection systems 3 and 13 in the first and second embodiments are located right above the measuring point, but when the height cannot be detected from directly above because of the lens system, the measurement is performed obliquely. Good. In the first embodiment, the height of the scriberain was measured close to the four corners of the chip 1A, and in the second embodiment, the height of the scriberain was measured close to the four corners of the chip 11A. You may measure the height of the scribe rain) near the corner or the four corners.

[0023]

As described above, according to the present invention, by providing the height detection system that moves according to the chip size (or the stage can move), the height of a chip of any size in the vicinity of the four corners can be determined. The detection enables high-precision leveling.

[Brief description of drawings]

FIG. 1 is a perspective view of a leveling device according to a first embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation in the embodiment.

FIG. 3 is a perspective view of a leveling device according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a conventional leveling device.

[Explanation of symbols]

 1, 11 Wafer 1A, 11A Chip size exposed on wafer 11B Wafer scribe rain 2, 12 Levelable wafer stage 3, 13 Height detection system 14 Detection system driver 5 Optical fiber 6 Optical sensor

Claims (4)

[Claims] 1. A detection system for sensing the heights near the four corners according to the size of the chip to be exposed, and the heights of the diagonals are made equal based on the measurement results of the heights near the four corners. A leveling method characterized in that the tip surface is adjusted. 2. A leveling method, wherein an average of diagonal heights is averaged simultaneously with the adjustment of the chip surface, and the average value is recognized as a focus reference plane. 3. A set of detection systems for sensing the height is provided, and the heights near the four corners are sequentially measured while the detection system is moving or the stage is moving, depending on the size of the chip to be exposed. The leveling method according to claim 1, wherein the chip surface is adjusted horizontally with respect to the lens surface. 4. A movable type having four sets of detection systems for detecting height, which moves so as to be able to detect heights near four corners of a chip in accordance with the size of a chip to be exposed, and at the same time, the four corners can be detected. The leveling method according to claim 1, wherein the height of the chip is detected and the chip surface is adjusted horizontally with respect to the lens surface.