KR20000042445A - Leveling apparatus for wafer - Google Patents

Abstract

PURPOSE: A leveling apparatus for a wafer is provided to exactly measure a height and a tilt of the wafer and thereby to establish an optimum focus for an exposure process. CONSTITUTION: A leveling apparatus for measuring a height and a tilt of a wafer(W) placed on a wafer stage(WS) includes a leveling sensor having a P-branch and a Q-branch which are symmetric with respect to the wafer(W), first reflecting mirrors(M1,M2,M3,M4) disposed underneath the branches, detectors(D) symmetric with respect to the wafer(W), and second reflecting mirrors(M5,M6) underneath the detectors(D). The light emitted from the respective branches applies to the wafer(W) via the first reflecting mirrors(M1,M2,M3,M4), and then the light reflected from the wafer(W) reaches the detectors(D) via the second reflecting mirrors(M5,M6). In particular, the size of the leveling sensor is approximately 20 micrometer, and the respective branches are connected to respective actuator motors(AM). Therefore, the leveling sensor is capable of moving and thereby enables to cover a wider range of measurement.

Description

Leveling device for wafer height and tilt measurement

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 leveling device for measuring the height and inclination of a wafer, which can achieve a more accurate focus during an exposure process.

Focusing during wafer exposure involves measuring the height and tilt of the wafer surface using a leveling sensor in the exposure equipment, calculating the signal obtained therefrom, and focusing each die accordingly. The pattern is exposed.

Conventional leveling measurement methods consist of a rough measurement step that measures extensively and a fine measurement step that measures the height and inclination of the wafer surface in the range of ± 25 μm. In the fine measurement step, the height and inclination of the wafer are measured more accurately by comparing the difference between signals measured at four spots.

In the rough measurement step, either the P branch or the Q branch is used, so only the center height of the exposed filed is measured, making accurate height correction impossible. In the fine measurement step, both the P and Q branches are used for more precise Measurements are made, through which the height and inclination of the exposed field are calculated and corrected according to the measurement results. The role of the micro-measuring device is important to get an accurate focus set point.

1 is a schematic diagram of a leveling sensor of the prior art, wherein the leveling sensor LS comprises a P-branch forming a P1 spot, a P2 spot on a wafer, and a Q-branch forming a Q1 spot, a Q2 spot on a wafer. It is shown that the field size is 25 μm. Depending on the height of the wafer, sensor spot sensitivity is different.

However, the conventional leveling sensor configured as shown in FIG. 1 cannot move each branch so that the spot formation position cannot be adjusted on the wafer, thereby limiting the measurement range.

In other words, only 90% of each spot is checked when a die is detected. On the die formed at the wafer edge, all signals from four spots are not detected because of the limitation of the wafer stage's travel distance. There is a problem.

FIG. 2A is a schematic diagram illustrating a case where a leveling sensor is located inside the wafer W so that signals from all four spots P1, P2, Q1 and Q2 can be detected, and FIG. 2B is a leveling sensor at the wafer edge. Is a schematic diagram illustrating a case where the signal can be detected only from the Q2 spot where is located.

As the wafer edge does not detect all the signals from the four spots, an additional correction method is required, such as the need for a separate software.

In addition, as the process progresses, an error occurs between the compensation processing method through the software and the topology of the actual wafer due to the severe step generated on the wafer, thereby causing a focus failure. As a result, the defect in the pattern causes defects in the wafer edge die, which causes a decrease in yield. In addition, when applying a conventional micro system, it takes a separate signal processing time and there is a problem that the error occurs once.

The present invention devised to solve the above problems can more accurately measure the height and inclination of the wafer to set the optimum focus of exposure. The object is to provide a leveling device for wafer height and tilt measurement.

1 is a conventional leveling sensor,

2A and 2B are schematic diagrams for explaining measurement states using a conventional leveling device, respectively;

3A is a schematic diagram showing a leveling device according to an embodiment of the present invention;

3B is a schematic diagram showing a leveling sensor employed in the leveling device of the present invention;

3C is an enlarged view of a portion 'B' of FIG. 3A;

4A and 4B are schematic views showing a job file in the case of using a conventional leveling device and a leveling device according to the present invention, respectively.

* Explanation of reference numerals for the main parts of the drawings

P, Q: Branch P1, P2, Q1, Q2: Spot

W: wafer D: detector

M1, M2, M3, M4, M5, M6: Reflector L: Lens

WS: Wafer Stage S: Support

In order to achieve the above object, the present invention provides a leveling sensor having two branches for forming a spot on the wafer and detecting a signal for focus height and tilt of the wafer from the spot. (level sensor); And a power transfer device for moving the branch, and a leveling device for measuring wafer height and tilt.

The leveling device according to the present invention is characterized in that the size of a conventional leveling sensor is small and the spot can be moved from side to side by attaching a motor to the spot of each branch. Accordingly, the height and inclination of the wafer edge can be measured more accurately. That is, by focusing a pattern defocus phenomenon caused by weak leveling on the wafer edge die during wafer exposure using a movable leveling sensor, defects of the die formed on the wafer edge are reduced, thereby improving production yield.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail.

FIG. 3A is a schematic diagram showing a leveling device according to an embodiment of the present invention, FIG. 3B is a schematic diagram showing a leveling sensor employed in the leveling system of the present invention, and FIG. 3C is part 'B' of FIG. 3A. An enlarged view of.

As shown in Fig. 3A, the leveling device according to an embodiment of the present invention has two branches each detecting a signal about the focus height and the tilt of the wafer from two spots each having a motor mounted therefrom. A leveling sensor, reflectors M1, M2, M3, and M4 reflecting the light incident from the leveling sensor onto the surface of the wafer W, and detectors D detecting the light reflected from the surface of the wafer. Reflecting mirrors M5 and M6 are reflected. In FIG. 3A, reference numeral 'L' denotes a lens for reduced projection of a mask in a conventional exposure apparatus, and 'WS' denotes a wafer stage. 'S' stands for support.

As shown in FIG. 3B, a leveling sensor according to an embodiment of the present invention is a leveling sensor including a P-branch forming a P1 spot and a P2 spot on a wafer, and a Q-branch forming a Q1 spot and a Q2 spot ( The field size of LS) is 20 μm, and the height and inclination of the wafer can be more accurately measured by reducing the field size as compared with the conventional art. As shown in Fig. 3C, an actuator motor AM is mounted so that each branch moves.

4A and 4B are schematic diagrams showing a job file in the case of using the conventional leveling device and the leveling device according to the present invention, respectively. Is showing.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

The present invention made as described above can improve the hardware and software limitations of the conventional leveling sensor and reduce the focus and leveling defects generated during wafer exposure, thereby preventing reprocessing due to patterning defects and shortening wafer alignment time. In addition, it is possible to reduce the production cost by increasing the production yield per unit wafer by improving the edge die, which was weak due to the process progress and remained defective.

Claims (3)

A leveling device for measuring wafer height and tilt, A leveling sensor having two branches forming spots on the wafer and detecting signals from the spot for signals of focus height and inclination of the wafer; And Power train for moving the branch Leveling device for wafer height and tilt measurement comprising a. The method of claim 1, The leveling device, A reflector reflecting light from the leveling sensor onto a wafer surface; A detector for detecting light reflected from the wafer surface; And And a reflector for reflecting light reflected from the wafer surface to a detector. The method of claim 1, And the two branches each define two spots.