JPS62159441A - Alignment mark - Google Patents

Abstract

PURPOSE:To efficiently perform accurate alignment by forming alignment marks of a plurality of marks formed stepwisely different in sizes and formed at positioners to be aligned in a superposing manner. CONSTITUTION:An alignment mark 1 is composed of a plurality of marks 3, 4, 5, 6 formed stepwisely different in sizes and formed at positioners to be aligned in a superposing manner. When aligning a wafer 2, the wafer 2 is placed on a sample base. The magnification of a scan type electron microscope is set to 100 times to detect a first mark 3. Then, the microscope is set to 1,000 times to detect a second mark 4, and adjusted to become a center of a visual field. Then, it is set to 5,000 times to detect a third mark 5, and adjusted to become the center of the visual field. Further, it is set to 10,000 times to detect a fourth mark 6, and adjusted to become the center of the visual field. Thus, an accurate alignment is efficiently performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to alignment marks used for highly accurate alignment of silicon wafers in LSI manufacturing processes.

[Technical background of the invention and its problems]

Generally, in the manufacturing process of semiconductor integrated circuits.

Requires wafer alignment. In particular, very LSI
In electron beam direct writing on wafers,
Unlike mask drawing, high-precision alignment between patterns in each layer is essential. That is, even if the first layer pattern is drawn at the reference position, the positional deviation from the reference position occurs after the wafer processing step and the wafer for drawing the second layer pattern is set on the sample stage. Therefore, the second layer pattern is drawn while correcting the first position, angle, and amplitude. At this time, the alignment n degrees is required to be 1/1o to 1/14 of the minimum line width of the pattern. therefore.

In VLSI, 0.1 to 0.2. am (D precision, 1 so is required, 7. To achieve -r precision, 1 is usually performed by scanning the alignment mark formed on the wafer with an electron beam.This alignment The mark is
engineering, chips and CVD (Chemical Vapo)
It must be possible to obtain a sufficient position determination signal even after wafer processing steps such as ur deposition. Therefore.

Alignment marks were formed on the wafer using silicon steps, silicon oxide steps, V-shaped grooves, metal, and the like.

However, since conventional alignment marks are extremely small, they can only be detected with the low magnification of a scanning electron microscope, which is one reason for a decrease in work efficiency.

On the other hand, if the alignment mark is made large enough to be detected at low magnification, it will move out of the observation field of view, creating the hassle of searching for an even smaller alignment mark specially placed elsewhere.

In the end, it reduced work efficiency.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

It is an object of the present invention to provide an alignment mark that efficiently performs highly accurate alignment in the same case.

[Summary of the invention]

The alignment mark is composed of a plurality of marks that differ in size stepwise and are formed on the object to be aligned in a superimposed manner.

[Embodiments of the invention]

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the alignment mark (1) of this embodiment. This alignment mark (1) is formed on one main surface of the wafer (2) shown in FIG.

A first mark (3) in the shape of a cross that can be easily detected at a low magnification (for example, 100 times) using a scanning electron microscope.

For example, it is formed on the right shoulder of this first mark (3) and has a magnification of 1
A second mark (4) in the shape of a cross that can be easily detected at a magnification of about 1,000 times, and a second mark (4) as shown in FIG.
) is formed in the center of the triangular shape and can be easily detected with a trowel of about 5000 times, for example.As shown in FIG. and a fourth mark (6) in the shape of a cross that can be detected about 10,000 times more easily.

However, these first. Second. Third. 4th mark (3)
, (4), (5), and (6) are formed by steps carved on the main surface of Quano 1 (2) by etching. Two such alignment marks (1) are usually formed for each wafer (2). Further, one alignment mark (1) is formed for each chip (force) of Ueno (2).

Therefore, when aligning the wafer (2) using the alignment marks of this embodiment, the wafer (1) is
, placed on a sample stage that is movable in the Y direction.

Next, increase the magnification of the scanning electron microscope to 100x.

One of the pair of alignment marks (1), (1) provided on each wafer (2)
) is detected. Next, the second mark (1) provided close to the first mark (1) is detected at a magnification of 1,000 times and adjusted so that it is located in the center of the field of view. Next, the third mark (5) provided at the center of the second mark (1) is detected at a magnification of 5,000 times and adjusted so that it is located at the center of the field of view. moreover.

The fourth mark (6) provided at the center of the third mark (5) is detected at a magnification of 10,000 times and adjusted so that it is located at the center of the field of view. In this way, once the coordinate position of this fourth mark (6) is determined, the present box is moved to the other alignment mark (6).
Repeat the same operation for 1). next.

Alignment mark (1) provided for each chip...
Among them, the chip that performs the required processing (alignment marks provided corresponding to the force are detected in the same procedure, and the coordinate positions of the three fourth marks (6)... determined by the above detection) 1 position correction processing is performed based on 1, and drawing is performed using, for example, an electron beam. Note that the above marks (33, (4),
The detections in (5) and (6) are automatically performed by image processing such as pattern matching.

In this way, the alignment marks (1) of this embodiment are formed in four overlapping first and second positions so as to fall into almost the same visual field. Second. Third. 4th mark (3>, (4), (
5).

(6), so each mark (3), (4), (5), (6
) to the center of the field of view, highly accurate positioning can be performed efficiently. Especially from low magnification to high magnification.

Since the position can be confirmed at the same location, the trouble of moving the sample stage and searching for marks is eliminated, increasing the efficiency of positioning. Furthermore, large and small marks (3>, (4), (5), (6
) are grouped together at - location, space can be saved on the wafer (2) surface.

Note that in the above embodiment, one alignment mark (1) consists of four marks (3>, (4), (5), (6)
It consists of

As long as there are a plurality of them and they are in the same viewing area, the number may be set as appropriate as necessary. Also, regarding the shape of the mark, as long as it is compatible with automatic pattern recognition,
It is not limited to shape. Further, although the step in the above embodiment is a silicon step on a silicon wafer, the mark may be formed by using silicon oxide, a V-shaped groove, a metal step, or the like. Further, in the above embodiment, the alignment mark 1 is detected by a scanning electron microscope, but it can also be applied to alignment using a normal optical microscope. in this case.

The alignment mark may be a resist film, a paint film, or the like.

〔Effect of the invention〕

The alignment mark of the present invention is composed of a plurality of overlapping marks of different sizes so that they fit into the same visual field, so by increasing the magnification step by step from low to high magnification, , highly accurate alignment can be performed efficiently.

[Brief explanation of drawings]

FIG. 1 is a plan view of an alignment mark according to an embodiment of the present invention;
Figure 2 is a plan view of the wafer on which the alignment marks shown in Figure 221 are formed, Figure 3 is an enlarged view of Figure M1 within the dashed circle, f
Figure gA is an enlarged view within the broken line circle in Figure 3. (1)...Alignment mark, (2)...Wafer (
object to be aligned). (3)...First mark (rough alignment mark). (4)...Second mark (mark for precise positioning). (5)...Third mark (fl# fine alignment mark)
. (6)...Fourth mark (mark for precise positioning). Agent Patent Attorney Nori Chika Yudo Kikuo Takehana

Claims (3)

[Claims] (1) A rough alignment mark formed on the object to be aligned and having a size determined by a microscope for roughly positioning the object to be aligned, and the first mark. Coarse alignment is performed by the coarse alignment mark, which is formed on the object to be aligned at approximately the same position as the coarse alignment mark and has a size that can be discriminated at a magnification higher than the magnification of the microscope to be discriminated. An alignment mark comprising a precision alignment mark for precisely aligning an object to be aligned. (2) The alignment mark according to claim 1, wherein the precise alignment mark is formed inside the rough alignment mark. (3) The alignment mark according to claim 1, wherein the precision alignment mark is made up of a plurality of marks that are superimposed with different sizes in stages.