KR20040059253A - Alignment Mark Key with Convex and Concave Parts - Google Patents

Abstract

PURPOSE: An alignment mark key is provided to reduce search error by enhancing the strength of an optical signal using a search key with convex or concave portions. CONSTITUTION: An alignment mark structure is used for alignment in an exposure process. The alignment mark structure includes a plurality of alignment mark keys(31). One alignment mark key as a search key includes a plurality of convex or concave portions(A). A flat portion(B) is between the convex or concave portions. The convex or concave portions are spaced apart from each other.

Description

Alignment Mark Key with Convex and Concave Parts}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices, and more particularly, to a structure of a search mark for increasing the intensity of a search signal of a search mark used for alignment in an exposure process of a semiconductor manufacturing process.

When manufacturing a semiconductor, the exposure process is usually repeated about 15 to 20 times, and each process requires a high degree of alignment and overlapping accuracy of the mask (reticle) and the wafer. Alignment and superposition precision is the performance that shows how accurately the circuit pattern can be projected when the circuit pattern of the next process is exposed to the existing circuit pattern of the wafer. In general, the alignment mark of the exposure apparatus and the precision of the wafer stage It is implemented using.

As a device for searching a wafer using an alignment mark in a stepper, the following two are mainly used.

Firstly, the Laser Step Alignment (LSA) device is a device that recognizes alignment marks engraved on a wafer. The He-Ne laser passes a projection lens to signal the first diffracted light from the light reflected from the alignment mark. Device to find the mark center.

Second, the FIA (Field Image Alignment) device receives an image signal reflected from a wafer by using broadband light, for example, a halogen lamp, and recognizes the alignment mark through comparison based on a reference index. It is an advantageous device.

Such an alignment mark search apparatus searches by using an alignment mark or a search mark engraved on a wafer.

1 shows the general structure of an alignment mark. As shown in Figure 1, the alignment mark of the conventional stepper is composed of a plurality of keys (11) formed on the mask with or without chrome (chrome), the shape of the key 11 is a concave shaped clear key ( Clear Key) or Convex Dark Key.

Fig. 2A shows a signal appearing when scanning an alignment mark. As shown in Fig. 2A, the alignment mark is searched by detecting the pattern of the signal reflected from each key 11 of the alignment mark. However, in the alignment mark structure in which the square patterns are arranged uniformly, when the normal search is performed, the search signal is clearly distinguished and the intensity is large as shown in FIG. 2A. If the pattern is arranged too close to the search mark, the noise signal of the surrounding pattern is also detected by the search apparatus, which relatively weakens the signal strength of the search mark as shown in FIG. 2B, making the search difficult. Such a problem causes the search accuracy to drop, causing a search error.

The present invention has been made to solve such a problem, and aims to reduce the search error of the alignment mark in the exposure process by increasing the intensity of the rotation signal reflected and detected by the search mark.

1 is a plan view of a general structure of an alignment mark;

Figure 2a is a signal appearing when scanning the normal alignment mark,

2b shows a signal of an alignment mark whose intensity is relatively reduced by a peripheral pattern, and

3 shows the structure of an alignment mark according to the present invention.

-Explanation of symbols for the main parts of the drawings-

11: conventional alignment mark key 31: improved alignment mark key

A: convex portion B: concave portion

In order to achieve this object, the present invention provides an alignment that can increase the intensity of the signal reflected from each key by forming a plurality of convex or concave portions in the shape of lattice or checkerboard on the convex or concave keys constituting the alignment mark. Provide the structure of the mark.

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

3 shows the structure of an alignment mark according to the present invention. As shown in Fig. 3, a plurality of irregularities are formed in one key 31 of the alignment mark in the form of a grid or a checkerboard. Here, the uneven portion may be a convex protrusion or a concave depression. In the case of a device for finding the mark center by signal processing the first diffracted light from the light reflected from the alignment mark, the narrower the gap between the concave portion and the convex portion, the greater the intensity of the first diffracted light. By using this principle, as shown in the enlarged view of FIG. 3, by forming a plurality of uneven portions in one mark key 31, the first diffraction light detected from the plurality of uneven portions formed inside the key 31 is superimposed. , The intensity of the entire signal of the first-order diffracted light obtained from one key 31 is increased.

The shape of the uneven portion is configured in the form of a checkerboard. And, one unevenness is composed of a rectangular convex portion (A) and a planar portion (B), so that one planar portion (B) is located between the convex portion (A) and the convex portion (A). In addition, the number of uneven parts contained in one mark key 31 is made as large as possible.

On the other hand, in the method of directly detecting the reflected signal, for example, the structure of increasing the vertical reflected light amount of the convex portion, which is a portion in which the convex mark key is formed, and reducing the amount of vertical reflected light of the planar portion forming the base surface can be selected. In this case, a large number of irregularities that scatter light incident on the plane portion is formed in the plane portion to relatively reduce the amount of detection light of the plane portion. In this case, however, the search error caused by an abnormal increase in the signal detected by the peripheral pattern cannot be effectively reduced. Therefore, in the apparatus using the reflected light, the method of reducing the search error needs to use a method of applying a substance that increases the amount of reflected light to the convex portion.

According to the alignment mark structure, the intensity of the signal reflected and detected by the search mark is increased, thereby reducing the alignment error of the alignment process of the exposure process in which a plurality of processes are performed.

Claims (5)

In the key structure of the alignment mark used to align in the exposure process of the semiconductor manufacturing process, Alignment mark key formed with irregularities, characterized in that it comprises a plurality of irregularities arranged in a grid form. According to claim 1, wherein the uneven portion Alignment mark key formed with irregularities, characterized in that the convex portion. According to claim 1, wherein the uneven portion Alignment mark key formed with irregularities, characterized in that the recess. According to claim 2 or 3, wherein the uneven portion Alignment mark key formed with irregularities, characterized in that arranged at regular intervals apart. The method of claim 4, wherein the uneven portion Alignment mark key formed with irregularities, characterized in that the rectangular parallelepiped shape.