KR20020065080A - Method for Measuring Wafer Warpage - Google Patents

Abstract

PURPOSE: A method for measuring a warpage of a wafer is provided to measure a warpage of a local region of the wafer by inserting a measuring key into a shot of the wafer. CONSTITUTION: A warpage of a wafer is measured by using a stepper and an overlay measurer. A key for measuring the warpage of the wafer is prepared. The key is formed with the first and the second blocks. The first block is arrayed on a diagonal line. The first block is formed with a plurality of bar patterns which are formed in a predetermined interval to one direction. The second block and the diagonal line of the first block cross each other. The second block is formed by a plurality of bar patterns which are formed in the predetermined interval to a vertical direction of the first block. The key is inserted into a shot of the wafer. The variation of X-axis bar patterns and Y-axis bar patterns of the key is checked and monitored by using an overlay measurer.

Description

Method for Measuring Wafer Warpage

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor fabrication process, and more particularly to a wafer warpage that inserts a wafer warpage measurement key into a shot to allow measurement of wafer warpage to a local area within the wafer. Numerical value).

As the high integration of semiconductor devices reduces design rules (process constraints regarding minimum line width and minimum line spacing), the height of the film layer is further increased, resulting in wafer warpage due to stress differences.

Due to the wafer distortion, in the exposure process, alignment between the substrate and the mask is difficult, and even if the alignment is properly performed, the projection of the chip pattern may not be accurate. In addition, the wafer warpage phenomenon continues to be a defective factor in subsequent processes.

Until now, the measurement of wafer warpage has been performed by measuring the entire wafer warpage by measuring the stress in the wafer through a stress gauge. In this case, it was possible to measure the warpage of the entire wafer, but it was not easy to identify the warpage difference by site. In addition, even if warpage measurement per wafer site is possible outside the line, the wafer must be discarded after such a test, and thus, the wafer was not prevented in the actual process.

On the other hand, a stepper, which is an exposure apparatus used in a step and repeat process, is a device in which a stage moves in the X-Y direction and repeatedly moves to be aligned. The stepper is used to expose on a reticle (a mask in which a pattern region is defined so that a chip pattern can be patterned on a wafer) so that the alignment key on the reticle matches the alignment key on the wafer. The wafer is aligned by adjusting the stage automatically or manually. Since the steps of the step and repeat process are mechanically operated, alignment errors occur during repeated processes, and when the alignment errors exceed the allowable range, device defects occur.

At this time, an area exposed on the wafer when exposed once using the reticle is called a one shot.

In general, an alignment key includes a global key used for actual alignment, and an AGA key for leveling a wafer step.

This alignment key is generated in a scribe line in the wafer (the area where no chip is formed in the shot) so that the wafer is aligned without directly affecting chip yield.

However, the conventional wafer warpage measurement method as described above has the following problems.

First, monitoring on a specific site was not possible because only the stress gauge of the wafer was monitored on the inner line.

Second, warpage measurements on site-specific areas within the wafer on the outer line were possible, but after testing, the wafers had to be discarded, which was not effective in preventing wafer warping.

An object of the present invention is to provide a wafer warpage measuring method that enables wafer warpage measurement to a local region within a wafer by inserting a wafer measuring key into a shot.

1 is a plan view showing a key for measuring warpage of the present invention

2 is a plan view showing a shot distribution in a wafer;

3 is a plan view showing the distribution of the chip and warpage measurement keys for one shot;

FIG. 4 is a plan view showing the structure of the warpage measuring key interposed in the one shot of FIG. 3 and the positions on the X and Y axes.

Wafer warpage measurement method of the present invention for achieving the above object is a wafer warpage measurement method using a stepper and an overlay measuring device, the first block composed of a plurality of bar patterns having one direction and a constant interval diagonally Preparing a wafer warpage measuring key arranged so that a second block having a direction perpendicular to the first block and having a plurality of bar patterns having a predetermined interval intersects a diagonal of the first block; And inserting the wafer warpage measuring key into a shot of the wafer, and monitoring the wafer warpage measuring key by changing the size of the bar pattern of the X and Y axes of the wafer warpage measuring key. It is characterized by.

Hereinafter, a wafer warpage measuring method according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view showing a wafer warpage measurement key of the present invention.

As shown in Fig. 1, the warpage measuring key has a first block composed of three bar patterns having a width of 4 μm and a length of 20 μm (the size of the first block is 20 μm × 20 μm) positioned diagonally (upper left and lower right) ) And two second blocks formed by changing the horizontal and vertical sizes of the first block bar pattern so as to cross the diagonal lines.

2 is a plan view showing a shot distribution in a wafer.

3 is a plan view showing the distribution of the chip and the warpage key for one shot.

FIG. 4 is a plan view showing the structure of the warpage measuring key interposed in the one shot of FIG. 3 and the positions on the X and Y axes.

As described above, one shot refers to an exposed area in a wafer when exposed once in a step and repeat process.

As shown in FIG. 2, since the step and the repeat process are repeatedly performed, there are shots 22 on the wafer 21 corresponding to the number of exposures.

As shown in FIG. 3, one or a plurality of chip patterns 31 are transferred for each shot. Thus, the wafer warpage measuring key 33 is formed on an area where the chip pattern 31 is not formed in the shot. Insert An area where such a chip pattern is not formed is called a scribe line 32. In practice, the scribe line 32 is sawed, and an alignment key such as a global key or an AGA key exists. This is because a pattern is not formed on the scribe line 32 so that the chip yield is not affected. .

The warpage measuring key 33 is located in a scribe line 32 that exists per shot relative to the previous shot.

The width and length of the bar pattern and the gap between the bar patterns in the wafer warpage measurement key having the structure as shown in FIG. 4 are continuously monitored by comparing with the initial set values. Since the warpage measurement pattern is mapped to all shots, it is possible to know from which numerical value the wafer warpage occurs. In addition, since continuous monitoring, it is possible to know exactly on which process the warpage occurred by reading the point where the numerical change occurred.

The warpage measurement is performed by monitoring the size change of the bar pattern on the X-axis and the Y-axis using an overlay measuring instrument used in an existing process.

This check is made hourly, wafer warpage occurs and the unit process is corrected and prevented later.

The second embodiment of the present invention monitors the topology of a wafer by using a phenomenon in which a stepper is moved in the X and Y directions during the step & repeat process, and a pattern of the wafer is formed. It is a technique to do.

In the second embodiment of the present invention, an AGA key formed to grasp the step in the wafer is used.

Move the stepper along the X and Y axes, and read the AGA key. Warpage is identified by monitoring the in-wafer topology of the AGA key.

When the AGA key is read, the stepper reacts differently to the degree of warpage, that is, when the warpage is severe and weak. That is, the measurement display of the stepper is displayed differently according to the warpage intensity.

Using this AGA key, it is possible to determine a high and low warpage area between areas where actual warpage has occurred without a separate key insertion. However, the AGA key is information about the relative warpage intensity, not the exact warpage number. In order to know the exact numerical value of warpage, the wafer warpage measuring method of a semiconductor device using the warpage measuring key, which is the first embodiment of the present invention described above, is used.

The first embodiment of the present invention is required when detailed wafer warpage information is required, and the second embodiment of the present invention does not require additional processing, and only when information enough to know the difference between wafer sites is required. need.

Since the information on the actual warpage is necessary in order to prevent wafer warpage, even if the second embodiment of the present invention is taken, the desired purpose can be achieved.

The wafer warpage measuring method of the present invention as described above has the following effects.

First, in-line monitoring of the warpage of the wafer can be done in-line, allowing quick modification of the process after warpage before the wafer warpage occurs.

Second, it is possible to find a specific site where a warp of a specific area in the wafer occurs.

Third, by inserting a pattern in a wide scribe line (field area), the polishing process is reduced, which helps to prevent dishing phenomenon occurring in the metal during the CMP planarization process.

Fourth, accurate data on warpage can be obtained by applying numerical values to wafer warpage.

Fifth, the warpage phenomenon of the wafer can be measured without adding a wafer warpage key on the wafer by reading the AGA key present on the wafer.

Claims (4)

In the wafer warpage measuring method using a stepper and an overlay measuring instrument, A first block composed of a plurality of bar patterns having one direction and having a predetermined spacing is disposed diagonally, and a second block composed of a plurality of bar patterns having a direction perpendicular to the first block and having a predetermined interval is formed of the first block. Preparing a wafer warpage measuring key arranged to intersect the diagonal line; Inserting the wafer warpage measuring key into a shot of a wafer; And monitoring the size change of the bar pattern of the X-axis and Y-axis of the wafer warpage measuring key by using the overlay measuring device. The method of claim 1, wherein the wafer warpage measuring key is inserted into a scribe line existing per shot for every shot. The wafer warpage measurement according to claim 1, wherein the overlay measuring device continuously monitors the width, length and length of the bar pattern of the key for the wafer warpage measurement by comparing with the initial set value. Way. The method of claim 1, wherein the stepper monitors the topologies in the wafer by using a phenomenon in which wafer patterns are formed while moving in the X and Y directions of the stage.