JPS6146021A - Alignment mark - Google Patents

Abstract

PURPOSE:To do precisely alignment without resulting in erroneous detection even if there are foreign matters or defects near the alignment mark, by formig the mark such that two or more pairs of lines with intervals set at a given length are extended in plane directions perpendicular to each other. CONSTITUTION:For a predetermined mark 10, electron beams are scanned as shown by B1. When a foreign matter 20 is detected during scanning, it is easily determined that that is erroneous detectin or that may be erroneous detection because of three peaks detected. On scanning B2, the foreign matter 20 may be mistakenly detected because of two peaks. The mark 10, however, has intervals set at a given length between the line pair 10a and 10a and the line pair 10b and 10b respectively, so it can be determined that is erroneous detection by detecting an interval distance between the mark 10 and the foreign matter 20. Therefore, if the detection is done whole changing scanning positions, the detection by such a scanning B3 will be done necessarily, so that the mark can be precisely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to the shape of an alignment mark, and particularly to a mark shape suitable for electronic drawing alignment.

[Background technology]

The manufacturing process of semiconductor devices is carried out by forming various patterns of diffusion layers and thin films on the main surface of a semiconductor wafer. In this case, if the mutual plane positions of the patterns are misaligned, the fineness and characteristics of the device may deteriorate. It is difficult to obtain the circuit. For this reason, in this type of manufacturing, an alignment mark is formed on a part of the wafer in the preceding pattern formation process, and this mark is detected in the subsequent process and used as a reference for the subsequent process. ) A method of forming a pattern has been adopted.

By the way, when performing alignment using this mark, in conventional photolithography technology, a method is used in which a mark formed in a preceding step and a mark on a photomask used in a subsequent step are used to match the two. Therefore, even if some foreign matter or defects occur on the surface of the wafer, alignment is unlikely to be hindered.

However, in the FF11EB direct writing method, which has been put into practical use with the recent miniaturization of patterns, in which pattern exposure is performed by directly projecting an electron beam onto the wafer surface,
A method of directly detecting the marks formed in the preceding process has to be used, which poses a problem in that errors in mark detection are likely to occur due to the presence of foreign objects or defects.

That is, as shown in FIG. 5, the conventional alignment mark 1 is composed of a cross-shaped single line, and the EB line is scanned in a minute range in a direction orthogonal to each of these lines to detect changes in reflectance, etc. The mark is detected by Therefore, as shown in the figure, if there is a foreign object or defect 2 near the mark, this reflectance change will also be detected, and scanning as shown in the figure (AI) will detect two places. However, in the scanning shown in the figure (A2), even if defect 2 is detected instead of mark 10, it is not clear that it is an erroneous detection, and incorrect position data is detected. The image is captured as is, resulting in incorrect (misaligned) EB drawing.

Examples of detailed explanations of electron beam drawing technology include the November 1981 issue of Electronic Materials published by Kogyo Kenkyukai,
Published November 10, 1981, P.

There are 110 to P and 116.

[Purpose of the invention]

An object of the present invention is to provide a shape of an alignment mark that does not cause a detection error even if the conventional method described above is used as is when detecting the alignment mark.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by making the shape of the alignment mark such that at least two pairs of lines spaced at a predetermined distance extend in a plane direction orthogonal to each other, false detection can be avoided even if foreign objects or defects are present in the vicinity. Alignment can be performed accurately and with high precision without causing problems.

[Embodiment 1] FIG. 1 shows a planar shape of an alignment mark of the present invention, and FIG. 2 shows a cross-sectional state when detecting the mark position. That is, in this example, A and E for patterning 6 wirings are used.
B drawing is illustrated, and mark 10 is p as shown in Figure 2.
It is formed of t-silicide 17. In the figure, a SiN film 13, a polysilicon film 14, and a glabellar film 15 such as PSG are formed on a SiO□ film 12 on a silicon substrate 11, and a mark-shaped groove 16 is formed in this glabellar film 15.
Ru. In this groove 16, PT silicide 1;
The mark 10 is formed by filling the bottom of the mark.

Note that this pt silicide 17 is formed at the same time as the contacts in the element portion. An A2 wiring film 18 is formed on the PT silicide 17, and an electron beam resist film 19 is formed on the PT silicide 17 for patterning this AA wiring film 18 by phosphorography technology.

The mark 10, as shown in FIG.
b and 10b, which extend in a cross shape that intersects in the X and Y directions of the plane, and are formed roughly in the shape of an I-shape.

Therefore, according to this mark 10, if the EB line E is projected onto the surface of the wafer 11 from above and scanned as shown in FIG.
Since the reflectance of BiE is higher than that of other parts, it can be taken in as a mark detection signal, and the mark position can be detected by obtaining this signal in the plane X direction and Y direction. However, if a foreign object 20 is present near the mark (PT silicide 17) as shown in the figure, the reflectance at this location will also be increased, which may easily cause confusion in detection.

However, as shown in FIG. 1, in this example, the mark 101
'ltt, TE BiE illustrated (Bt), CB2)
Even if a foreign object 20 is detected during the scanning, there is a risk of false detection or false detection in the case shown in (B,) because there are three peak values. It can be determined that In addition, in the case of (B,) shown in the figure, there are two peak values, so it is easy to misdetect, but the mark 10
Since the distance between the line pairs 10a and 10a and 10b and 10b is set to the required value, the mark 10 and the foreign object 20
By detecting the interval between the two, this is determined to be an erroneous detection. Therefore, if detection is performed while changing the scanning position, detection as shown in (B) is always performed, and accurate mark detection can be achieved.

[Embodiment 2] FIGS. 3 and 4 show another embodiment. In this example, the second
It is applied to the patterning process of A2 wiring, and alignment marks are formed using Sio as an interlayer film and the step difference in the film. That is, a first AliJI 23 is patterned on the SiO2 film 22 on the silicon substrate 21, and then a 5i02 film 24 is formed as a glabellar film, and this SiO2 film 2
A mark 30 is formed by engraving a step 27 on the surface of the wafer. This etching is performed on the first A-g not shown.
Needless to say, this is formed at the same time as the contact to the wiring 23. A second AA wiring film 25 is formed on the 5i02 film 24, and an electron beam resist film 26 serving as a mask is formed thereon by EB writing.

As shown in FIG. 3, the mark 30 has a planar shape formed by two pairs of lines 30a and 30a at a required interval.

30b and 30b extend perpendicularly to each other in the planes X and Y directions, forming a ``CL'' shape as a whole.

Therefore, according to this mark 30, if the EB ray E is projected onto the surface of the wafer 21 from above and scanned as shown in 5 in FIG. Since the rate is higher than that of other parts, it can be taken in as a mark detection signal, and the mark position can be detected by obtaining these signals in the X and Y directions of the plane. However, if a defect 31 in the 5iOz film 24 occurs in the vicinity of the mark (etched part of the Stow film 24), the first A4 wiring 23 appears at this part and the reflectance increases, which tends to confuse the detection.

However, in this example as well as in the previous example, even if a defect 31 occurs near the mark 30 as shown in FIG. 3, the line pair 30a and 30a of the mark 30.

Since the line spacing between 30b and 30b is a required value, it can be easily determined that this is an erroneous detection in the scans shown in (CI), (C2), and (cs). In the end, only accurate mark position detection can be performed by scanning as shown in the figure (C4).

〔effect〕

(1) The planar shape of the alignment mark is such that at least two pairs of lines with the required spacing extend in mutually orthogonal directions, so even if there are foreign objects or defects in the vicinity of the mark, By detecting the characteristic line spacing of the marks, it is possible to reliably determine erroneous detection due to foreign objects or defects, and it is possible to reliably prevent erroneous mark position detection.

(2) Since the alignment mark has at least two pairs of lines extending at the required interval in the direction orthogonal to the plane, it is possible to judge erroneous detection in either the X direction or the Y direction of the plane. Planar position can be detected accurately and with high precision.

Although the invention made by the present inventor has been specifically explained above based on examples, the present invention is not limited to the above-mentioned examples (although it is possible to make various changes without departing from the gist of the invention). For example, the mark may have three or more line pairs, or may have a configuration in which two line pairs are arranged in two sets.Furthermore, the film material constituting the mark may vary depending on the processing process. Various types are available depending on the difference.

[Application field]

The above explanation has mainly been about the application of the invention made by the present inventor to the phosphorography technology that uses the EB direct writing method on semiconductor wafers, which is the field of application that formed the background of the invention, but the invention is not limited thereto. Instead, it uses light and Xi and can be applied to wafer position detection in lithography technology as well as other wafer processing.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an alignment mark according to an embodiment of the present invention, Fig. 2 is a cross-sectional view thereof, Fig. 3 is a plan view of another embodiment of the present invention, and Fig. 4 is a cross-sectional view thereof. , FIG. 5 is a plan view of the conventional mark. lO...Mark, 10a, 10b...Line pair, 11.
...Silicon substrate, 17...PT silicide, 18.
...AA wiring film, 20...Foreign matter, 21...Silicon substrate, 23...First AA wiring, 25...Second AA wiring, 27...Step, 30-...-f-ri, 30a, 3
0b... Line pair, B'1-a IC1-4... EB line scanning. Agent Patent Attorney Akira Takahashi Laughter 1 Figure ′ Figure 2

Claims (1)

[Scope of Claims] 1. An alignment mark that is formed on the surface of a semiconductor wafer in a preceding pattern forming process, and whose position is detected in a subsequent process to form a pattern in this process. An alignment mark characterized in that the planar shape of the mark is configured such that at least two pairs of lines spaced apart from each other extend in mutually orthogonal plane directions. 2. The alignment mark according to claim 1, which is formed by intersecting two pairs of lines in a cross shape to form a square shape. 3. Claims 1 or 2 constituted as a mark whose position can be detected by scanning the EB line in a direction orthogonal to each of the two line pairs and detecting the mark position based on a change in the reflected signal. alignment mark.