JPH05136022A - Alignment method - Google Patents

Abstract

PURPOSE:To provide the title alignment method capable of processing wave- forms without making an alignment error when the detected wave-forms are notably different from one another in the X and Y directions during the photosteps in the semiconductor device manufacture. CONSTITUTION:When the detected wave-forms of alignment marks are notably different from one another in the X and Y directions during the various semiconductor manufacturing steps, the wave-form processing steps of the alignment marks in the X and Y directions are respectively and independently set up so that the alignment marks in the X and Y directions may be wave-form processed meeting the optimum requirements. Furthermore, even when the discrepancies between the detected wave-forms in the X and Y directions are not so conspicuous as to make an alignment error, the processing time can be notably cut down while particularly augmenting the alignment precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo process for manufacturing a semiconductor device, and more particularly to alignment.

[0002]

2. Description of the Related Art In recent years, design rules for manufacturing semiconductor devices have been progressively miniaturized year by year, and a process rule of 0.8 μm in a mass production stage and 0.5 μm in a trial production stage has been adopted. Along with this, it is naturally required that the alignment accuracy with the underlying pattern is high. Normally, 1/3 to 1/4 of the process rule is usually required for the alignment accuracy, and 0.3 for the 0.8 micron rule.
The micron and 0.5 micron rule requires an alignment accuracy of about 0.15 micron.

There are roughly two types of alignment sensor systems. One is a method of using a laser as a light source to detect the diffracted light by making the light beam of the laser incident on an alignment mark, and the other is to use a light source such as a halogen lamp as a light source having a width of about 200 nm as an alignment mark. Incident on the CCD and the alignment mark
There is a method of picking up an image using a camera or the like and detecting the position of the alignment mark using an image processing technique. In general, the former is called dark-field alignment and the latter is called bright-field alignment.

The type of alignment sensor is also classified according to the method of incidence of the light source on the alignment mark. One is the TTL method performed through the lens and the OFF AXIS that is incident and detected from outside the lens.

Next, the alignment method includes global alignment, D by D alignment, EGA and the like. The D by D alignment is an alignment method in which position measurement is performed for all effective chip points. EGA
Is a method of extracting some reference chips from all the effective chip points and performing linear correction on all the effective chips using the data of the reference chips. If the stage accuracy is dramatically improved, the D by D alignment is more accurate, but with the current stage accuracy, the EGA is higher in alignment accuracy if the number of reference chips is sufficiently large.

FIG. 2 is a schematic view showing a waveform processing method of a conventional bright field alignment sensor. Similar to the conventional technique, alignment marks 21 used for alignment are patterned on the semiconductor substrate.
A He-Ne laser scans 22 the alignment mark 21 from the side. The alignment mark 21
When the scanning line 22 of the He-Ne laser is incident on the edge of the diffracted light, diffracted light is generated, and the diffracted light senses the detection waveform as shown in FIG. 2 and complements the absolute position of the alignment mark 21. .. The position is supplemented also in the Y direction by the same method.

Next, FIG. 3 is a schematic diagram showing a waveform processing method of a conventional bright field alignment sensor. Similar to the conventional technique, alignment marks 31 used for alignment are patterned on the semiconductor substrate. The alignment mark 31 imaged by the CCD camera is finally recognized as a detection waveform as shown in FIG. Outside the alignment mark 31,
An outer index 32 and an inner index 33, which are installed on the optics of a bright field alignment sensor, are positioned, and the absolute position of the alignment mark 31 is measured using the index and the detection waveform. For example, when the alignment mark 31 does not have a slight deviation, the center of the alignment mark 31 is located at the intermediate position between the outer index 32 and the inner index 33. By setting the pitch of the alignment marks 31 in advance, similar measurement is performed not only for the central alignment mark but also for other alignment marks.

In any of the current alignment systems, position measurement is performed by the same alignment sequence in the X and Y directions.

[0009]

However, the prior art has the following problems.

In the prior art, when measuring the absolute position of the alignment mark, the diffracted light by the alignment mark and the image data of the CCD camera are processed with the same waveform processing parameters in the X and Y directions. Therefore, when the states of the alignment mark in the X direction and the alignment mark in the Y direction are significantly different, the waveform may not be processed in the optimum state in the X direction and the Y direction with the same waveform processing parameter. In the worst case, an alignment error may occur and alignment may not be possible. Various factors such as etching characteristics, underlayer spattering characteristics, and deposition characteristics may be considered as the difference in alignment mark state, but the process is becoming more complicated due to the progress of miniaturization. The likelihood of doing so is increasing.

Therefore, the present invention solves such a problem and an object thereof is to provide an alignment method capable of performing waveform processing without causing an alignment error even when the detected waveforms in the X direction and the Y direction are significantly different from each other. It is in the place of providing.

[0012]

In the photo process of semiconductor manufacturing, when aligning the underlying pattern and the pattern in the next step on a semiconductor substrate having the underlying pattern, the X-direction of the underlying pattern is adjusted. A parameter for waveform processing for detecting the absolute position of the alignment mark and the alignment mark in the Y direction of the underlying pattern is set independently, and the position of the alignment mark is detected by the X direction, the Y direction, and the independent sequence. Is characterized by.

[0013]

FIG. 1 is a diagram showing an outline of an alignment method according to an embodiment of the present invention. In FIG. 1, the wafer substrate shows an alignment mark after aluminum sputtering and a processing waveform when the wafer substrate is aligned.

Generally, in the wiring process of semiconductor manufacturing, especially in the photo process after aluminum sputtering, it is very difficult to obtain the alignment waveform. The reason is that aluminum is a reflective material and that aluminum grains are likely to be deposited because of high temperature during aluminum sputtering. In addition, the same thing may occur in the wiring process of middle reflection such as polysilicon.

In this embodiment, the alignment is performed using a bright field type alignment sensor which is relatively easy to align in the photo process of aluminum wiring. As shown in FIG. 1, the detected waveforms of the alignment mark 11 in the X direction and the alignment mark 12 in the Y direction are obviously different depending on the conditions of the aluminum sputter, the resist coating, and the base. When the difference between the detection waveform of the alignment mark 11 in the X direction and the detection waveform of the alignment mark 12 in the Y direction is relatively small, the alignment signal can be processed without error even by the conventional alignment method. As described above, when the detected waveform of the alignment mark 11 in the X direction and the detected waveform of the alignment mark 12 in the Y direction are significantly different, an error has occurred in the process of processing the alignment signal in the conventional alignment method. Therefore, in the present embodiment, the alignment mark 11 in the X direction has a waveform processing sequence in which the inside 13 of the edge of the detected waveform is recognized as the edge of the alignment mark 11, and conversely, the alignment mark 12 in the Y direction has the detected waveform. The waveform processing sequence was used in which the outside 14 of the edge was recognized as the edge of the alignment mark 12. As a result, the alignment process can be performed even if the detection waveform of the alignment mark 11 in the X direction and the detection waveform of the alignment mark 12 in the Y direction are significantly different as shown in FIG. Further, even when the difference in the detected waveform of the alignment mark is small, the time required to process the waveform signal is significantly shortened, and the alignment accuracy is significantly improved.

As described above, since the waveform processing sequence of the detection waveform in the X direction and the waveform processing sequence of the detection waveform in the Y direction can be set independently, the detection waveform of the alignment mark in the X direction and the detection waveform of the alignment mark in the Y direction can be set. Waveforms can be processed without alignment error even when the difference is large, and the processing time is significantly increased even when the difference in the detected waveform between the X-direction alignment mark and the Y-direction alignment mark is not so large that an alignment error occurs. This is effective in shortening the processing time.

Although one embodiment of the present invention has been described above, in addition to this, 1) the alignment method of the present invention is used for a dark field alignment sensor.

2) Set waveform processing parameters in the X or Y direction of a specific chip.

3) The alignment method of the present invention is used for alignment sensors other than those described in this specification.

Needless to say, the same effects as in this embodiment can be obtained with respect to the above.

[0021]

In the photo process of semiconductor manufacturing, when aligning the base pattern and the pattern of the next step on the semiconductor substrate having the base pattern, the X-direction alignment mark of the base pattern and the alignment mark The parameters of the waveform processing for detecting the absolute position of the alignment mark in the Y direction of the base pattern are set independently, and the position of the alignment mark is detected in the X direction, the Y direction, and the sequence independent of each other. Even if the detection waveform of the alignment mark and the detection waveform of the alignment mark in the Y direction are significantly different from each other, waveform processing can be performed without alignment error, and the detection waveforms of the alignment mark in the X direction and the alignment mark in the Y direction can be changed. Large processing time even if the difference is not enough to cause an alignment error There is an effect that is shortened, alignment accuracy is also remarkably improved in.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a dark-field alignment sensor.

FIG. 3 is a diagram showing an outline of a bright field alignment sensor.

[Explanation of symbols]

 11 ... Alignment mark in X direction 12 ... Alignment mark in Y direction 13 ... Waveform processing edge in X direction 14 ... Waveform processing edge in Y direction 21 ... Alignment mark 22 ... He- Ne laser scanning line 31 ... Alignment mark 32 ... Outside index 33 ... Inside index

Claims (1)

[Claims] 1. In the photo process of semiconductor manufacturing, when the base pattern and the pattern of the next process are aligned on the semiconductor substrate having the base pattern, the alignment mark in the X direction of the base pattern and the alignment mark The parameters of the waveform processing when detecting the absolute position of the alignment mark in the Y direction of the base pattern are set independently, and the X direction,
An alignment method, wherein the position of an alignment mark is detected by an independent sequence in the Y direction.