JPS61276218A - Pattern for measurement of superposing error - Google Patents

Abstract

PURPOSE:To dissolve the deviation of the focal surface of a pattern observation device and to obtain a high-measurement precision vernier by a method wherein a pattern to be used for measuring the superposing error between the first and second patterns in the lithography process is formed so that the observation positions of the first and second patterns coincide with each other on the same plane in the focal depth of the pattern observation device using the vernier. CONSTITUTION:The depth of the pattern of a substrate 103 is adjusted and the pattern observation device is constituted so that the edges (e) of the pattern of the substrate and the edges (f) of a resist pattern 11 coincide with a focusing surface FF being conformed to the upper surface of the substrate using the vernier. Moreover, in consideration of the film thickness of films 104 to be formed on the substrate, the edges (e) of the pattern of the substrate and the edges (g) of a resist pattern 12 can be brought onto the focusing surface FF being conformed to the upper surface of the substrate. When such the vernier is used, the deviation between the images, which is generated when the focal point is made to shift, is not generated because there is not need to deviate the focal point. As a result, the reliability of the measured value is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a lithography process in the manufacturing process of semiconductor devices, and is particularly used for measuring pattern overlay errors.

[Technical background of the invention and its problems]

Conventionally, misalignment when overlapping masks during exposure in a phosphorography process has been measured using a vernier.

The means is to create a pattern of any shape and any pitch,
The method involves overlapping in two perpendicular directions, and measuring the overlapping error based on the degree of overlapping and the pitch, and is mainly performed visually by an observer. An example of a vernier and an example of error reading are shown in FIG. Vernier patterns 1010°101A, 101B..., Io shown by solid lines in the figure
ta and 101b=- are both formed at equal intervals on the substrate, and this interval is set to, for example, 0.1 μm. Also, vernier patterns 1020, 102A, 102B..., 102 of the mask used for 1 alignment
a, 102b, . . . are indicated by dots in the drawing.

By the way, as shown in FIG. 1, the vernier pattern of the substrate and the pattern of the mask match 101C and 102G. The parts surrounded by broken lines in the figures before and after these are enlarged and shown in Figure 7.
In other words, the mask misalignment shown in the figure is +3 μm since it is the third mask from 1010.

In addition, alignment error measurement using a minute line width measuring device has recently been carried out. As shown in Figure 8, this
``Measure the distance between both patterns in the j direction, X1 + X2y
Alternatively, as shown in FIG. 9, the reference lines X and Y are determined, and the distance between the lines and the parallel parts for each pattern is set a1 to a4. This is a method of measuring as shown in b□ to b4 and calculating the error.

The vernier for performing the mask alignment is usually formed in the structure shown in FIGS. 10 to 12. That is, when the pattern (a) in FIG. 10 is observed while focusing on the main surface 103a of the substrate 103, the bottom of the pattern becomes blurred as shown by the broken line as shown in FIG. 10(b). Next, as shown in FIG.
An i02 film, a polycrystalline silicon film, a molybdenum silicide film, etc. are deposited, and as shown in FIG. 12, a resist film is laminated and applied, and exposed and developed to form a resist pattern 105. Diagram (a) for each episode? (b
) is the same as the display in FIG. Next, in the case shown in FIG. 12, the pattern observed when the focal position during measurement is set to the concave portion of the film 104 is shown in FIG. has been done. Further, the output waveform of the contrast along the line A-A of the pattern in FIG. 3(a) is shown in FIG. 3(b). Similarly, FIG. 14 shows an observation pattern when the focus position is set on the concavity of the substrate pattern in FIG. 12(a), and FIG. FIG. 15 shows an observed pattern when the focus position is set on the upper surface of the resist pattern 105, and FIG. 16 shows the observed pattern in the same manner as above.

When reading the vernier, the focal plane is usually set between c"d, c"a, and a-b shown in Fig. 12, but depending on the pattern, the edge of the resist may be traced, or the edge on the substrate side may be located between the edges of the upper layer. There are problems such as blurring due to the film. Also, C
In reading with and d, the difference between the two focal plane positions (heights) is often large, and the edges of the pattern often cannot be clearly seen.

As described above, when reading the conventional overlay error measurement pattern (vernier), the following problems occur.

(1) Since the height of each vernier is different, the depth of focus is shallow at high magnification, so both verniers are not in focus at the same time.6 (2) Reading errors occur due to (1).

(3) When a measuring device or the like is used according to (1), there is a large variation in reproducibility.

[Purpose of the invention]

In view of the conventional problems, the present invention provides an overlay error measurement pattern that eliminates focal plane deviation and provides a vernier with high measurement accuracy.

[Summary of the invention]

The overlay error measurement pattern according to the present invention has at least one combination of a first pattern formed on a semiconductor substrate and a second pattern overlaid thereon, wherein the fR of the first pattern and the second pattern is It is characterized in that the detection positions are processed to be on the same plane within the depth of focus of the pattern a detection device.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5. In addition, in the description, parts that are the same as the conventional ones are indicated by the same reference numerals in the drawings, and the description thereof will be omitted.

FIG. 1a shows the edge e of the substrate pattern and the edge f of the resist pattern 11 by adjusting the depth of the pattern on the substrate 103.
The figure shows the case where the image is brought to the focus plane FF which is aligned with the top surface of the substrate.
Figure C shows a contrast output waveform along line A--A in the figure.

What is shown in FIG. 2 below is a focus plane F in which the edge e of the substrate pattern and the edge g of the resist pattern 12 are aligned with the top surface of the substrate, taking into account the thickness of the film 104 formed on the substrate.
Figures a, b, and Q are the same as those shown in Figure 1 above.

In the case shown in FIG. 3, a resist film 23 is applied on a substrate pattern film 104 (FIG. 3).

This is then developed or etched to form a resist film 33 having a thickness adjusted so that the top surface matches the top surface of the substrate (Fig. r), and a matching resist pattern 13 is formed on this. be. In this case, the resist film 33 whose thickness has been adjusted is not limited to a resist. Then, by bringing the edge e of the substrate pattern and the edge g of the resist pattern to the focus plane FF aligned with the top surface of the substrate, Figures a, b, and Q (same as in Figure 1 above)
is obtained.

Furthermore, the device shown in FIG. 4 has a feature in which vernier patterns are used in which the substrate patterns do not overlap, and the focus plane is set on the bottom surface of one pattern, and the other pattern is focused on the top surface of the film 114. . Then, the edge e of one pattern and the edge g of the resist pattern 14 formed on the film 114 of the other pattern are aligned on the same focus plane. The parts shown in each of figures a, b, and Q are the same as those shown in FIG. 1 above.

The one shown in FIG. 5 below uses a vernier pattern that does not overlap the substrate pattern, similar to the one shown and explained in FIG. The focus plane is the same as the edge g of 6. Also, the points shown in each of the figures at be a are the same as those in FIG. 1 above.

〔Effect of the invention〕

According to this invention, it is easier to read than conventional verniers,
It also has a number of notable advantages, such as low reading errors and excellent measurement reproducibility. In addition, examples of when using a measuring device are shown in contrast profiles in Figures 1 to 5 and Figure 1.
As shown in FIGS. 3 to 16, a profile with high contrast and strong resistance to noise caused by other edges and surface materials was obtained.

In particular, the embodiment described with reference to FIGS. 4 and 5 is effective against noise. This significantly improved the reproducibility of measured values. Furthermore, since the focus is not shifted, the image shift that occurs when the focus is moved does not occur, and the reliability of the measured values is improved.

[Brief explanation of the drawing]

Figures 1 to 5 relate to embodiments of the present invention, each time Figure a is a cross-sectional view of a part, Figure 3 is a pattern to be observed, Figure C is a contrast profile diagram, and Figures P to 3 in Figure 3. r is a cross-sectional view showing the state in the middle of forming what is shown in Figure a, Figure 6 is a vernier diagram for conventional visual overlay error measurement, and Figure 7 shows the part surrounded by the broken line in Figure 6. An enlarged view of the vernier, FIGS. 8 and 9 are plan views showing the conventional error measurement method, FIGS. 10 to 12 show the formation order of the conventional mating vernier, and each figure a is a cross-sectional view. The figure shows the observed pattern.
13 to 16 are observation patterns shown by changing the focus of the surface on which the vernier pattern is formed, and in each figure, figure a shows the pattern, and figure a shows the contrast profile. 11, 12.13. , 14.15---Resist pattern 103---One substrate 104, 114---Part

Claims (1)

[Claims] In an overlay error measurement pattern having at least one combination of a first pattern formed on a semiconductor substrate and a second pattern superimposed thereon, the observation positions of the first pattern and the second pattern are the focal point of the pattern observation device. A pattern for measuring overlay error characterized by being processed to be on the same plane within a depth.