JPS60170936A - Automatic positioning inspection device - Google Patents

Abstract

PURPOSE:To enable to perform an inspection in a highly accurate manner by a method wherein, when positioning accuracy is detected using a vernier pattern, a laser beam is made to irradiate in a scanning manner on the surface whereon a pattern is superposed, the signal coming from the edge of the pattern is selected by the difference in intensity of the reflected light of said laser beam, and the amount of positional deviation is found by making a calculation. CONSTITUTION:The semiconductor wafer 4 having a vernier pattern on the surface is placed on a stage 5, and a lser beam is made to irradiate on the vernier pattern through the intermediary of a lense 3. Then, the light reflected from the edge of the pattern is detected by a lser detector 6, and this output is amplified by an amplifier 7. Said detector 6 and the amplifier 7 are built in an instrumental part 9, and the output coming from the instrumental part 9 is sent to the CPU containing a memory 11 and arithmetic operational parts. Subsequently, the result of the above operation is added to an interface 14 through the intermediary of an input-output control part 13, it is led back to the instrumental part 9, and the data of the input-output control part 13 is indicated on a indicating part 15. Through these procedures, the minimum value of the amount of deviation of pattern can be read out.

Description

DETAILED DESCRIPTION OF THE INVENTION lal Technical Field of the Invention The present invention relates to an automatic alignment inspection device, and more particularly to an inspection device that detects alignment accuracy using a vernier pattern.

fbl Prior Art and Problems As is well known, when manufacturing semiconductor devices such as ICs, pattern edges are repeatedly formed on a semiconductor wafer using a photo process.

In addition, pattern inspection is performed after pattern formation, and as ICs have recently become smaller and more dense, check inspection after the pattern edge process is particularly important for maintaining quality. Furthermore, pattern alignment inspection of a photomask as a medium to be transferred onto a wafer is equally important and indispensable.

In such pattern overlay inspection, alignment inspection using a vernier pattern has become widely used.
Widely used as a quantitative test.

However, since the conventional vernier pattern inspection is a visual inspection method in which the inspector visually reads the amount of deviation of the vernier, there are individual differences in the inspection and the accuracy is not necessarily high. On the other hand, other pattern inspections, such as pattern presence and dust adhesion inspections, have already been automated, which not only speeds up processing but also reduces inspection errors.

Therefore, from the viewpoint of reliability, it is desirable to automate the alignment inspection using the vernier pattern to process it at high speed, and to eliminate the individual differences caused by visual inspection, which have been a problem in the past.

tc+ OBJECTS OF THE INVENTION From this perspective, the present invention provides an automatic alignment inspection device using a vernier pattern.

fdl Structure of the Invention The object of the invention is to perform scanning by irradiating a surface on which the vernier patterns are overlapped with a laser beam, and to detect the intensity difference of the anti-RJ light in an alignment inspection method for detecting alignment accuracy using a vernier pattern. This can be achieved by an automatic alignment inspection device that selects a signal from a pattern edge and calculates the position of the signal to determine the amount of positional deviation.

(el　Embodiments of the invention An embodiment will be described in detail below with reference to one drawing.

FIG. 1 (al and (bl) show a front view and a cross-sectional view of a vernier pattern, and 1 is a rare pattern.

2 is the preferred pattern. Such a pattern is
Both are provided on a semiconductor wafer (sample to be inspected), and for example, if the ``female pattern'' is the first convex pattern that has already been etched, then the ``male pattern'' 2
is a second resist film formed thereon in the next step.
It is a convex pattern.

On the other hand, errors in a vernier pattern consisting of two convex patterns already formed on a wafer may be detected.

FIG. 2 shows a schematic diagram of the detection section according to the present invention.

In the present invention, the structure shown in FIG. 1 (al,
(Scanning is performed by irradiating a vernier pattern such as BL with a laser beam 1 through a lens 3 as shown in FIG. When the beam is scanned in this way and comes into contact with the pattern edge, the beam light is scattered and falls on the laser detector 6.
- The light is strongly incident. Therefore, the signal intensity is amplified through the amplifier 7 and binarized using a threshold value, so that only the signal from the pattern edge can be output.

FIG. 2 (bl shows an example of a pattern and its output signal, and if the scanning time between output signals a and b is X,
The pattern width is obtained by multiplying the scanning speed of the laser beam by X. Thus, when a vernier pattern such as shown in Fig. 1 (al, (bl) is scanned, an output signal such as FC+ shown in Fig. 1 is IMed, and the result is a combination of the "Ozu pattern", 2 and the "Nezumi pattern" l. You can understand the positional relationship.

The third page shows a schematic configuration diagram of the alignment inspection apparatus according to the present invention, in which the above-mentioned laser detector 6 and amplifier 7 are included in the measurement section 9. The measuring section 9 extracts the intensity of the laser beam as a signal, converts it into a binary value, and stores the output signal data in the memo January 1 of the data processing section (CPU) 10. The signal data is processed by the calculation unit 12, and the deviation amount is output from the human output control unit 13.The human output control unit 13 also controls the measurement unit 10 through the interface 14, and also controls input/output. The unit 13 is attached with a display device 15 for displaying test results.

The arithmetic processing in the arithmetic unit 12 will be explained by a specific example with reference to FIG. The five patterns shown in Figure 1 (al, (bl) are each 0.4 μIn pattern.

0.2μm pattern, 0 pattern, -0.2μm pattern, -0.4μm pattern, “Ozu pattern 2
An operation is performed to express the positional relationship within the pattern 1 by the absolute value of the difference between the output signals.

In Fig. 1, the width of the left side ゛1 and the male pattern 2 is P, and the width of the right ``female pattern'' ■ and 2 male patterns is Q. As shown in the figure, for the 0.4 pm pattern, lp, 'q, lO, for the 2 μm Bakun, for the IP2Q210 μm pattern, 1 Pa
For Q3 l -0,2p m pattern, 1P4Q41-0.48
In the m pattern, when 1PsQsl is calculated and graphed, a solid curve 48 shown in FIG. 4 is obtained. That is, in the related positions shown in FIG. 1, since the slope of the tangent line in the 0 μm pattern is 0, the amount of deviation in the example shown in this figure is 0. If a dotted curve ■ is obtained, -0
, 2 μm pattern, the slope of the tangent line is 0, so the amount of deviation is -0.2 μm.

The curve shown in FIG. 4 obtained in this way can be displayed as a graph on a CRT, recording paper, etc. Incidentally, such a curve is expressed by the formula d (Flx, -x, 1) - 〇where, d: differential operator F: curve function, and a numerical value can be obtained by solving this formula.

(This eliminates individual differences between inspectors and allows a constant and accurate amount of deviation to be determined, improving alignment accuracy and speeding up inspection processing, allowing inspection results to be obtained quickly.

(fl) Effects of the Invention As is clear from the above embodiments, the present invention improves the accuracy of alignment inspection and significantly contributes to improving the quality of semiconductor devices.

[Brief explanation of the drawing]

Figure 1 (al, (b), (cl) is a front view and cross-sectional view of the bar two pattern, Figure 1cI is a signal diagram according to the present invention obtained from it, Figure 2 [a) is a diagram according to the present invention. A schematic diagram of the detection unit of such an inspection device, FIG. 2 (bl is a diagram of the relationship between patterns and output signals, FIG. 3 is a schematic diagram of the configuration of the inspection device according to the present invention, and FIG. 4 is an output chart of 9) In the figure, 1 is the female pattern, 2 is the ozu pattern,
3 is a lens, 4 is a semiconductor wafer, 5 is a stage, 6 is a laser detector, 7 is an amplifier, 9 is a measurement section, 10 is a data processing section (CPU), and 11 is a memory. 12 is an arithmetic unit, 13 is an input/output control unit, 14 is an interface, and 15 is a display device. Figure 1 2VA Figure 3 0.4μm O, 2μm Opm -0, 2μm-0,
4μ "n bar ° - two major putters" reading

Claims (1)

[Claims] In an alignment inspection method that detects alignment accuracy using a vernier pattern, the surface on which the vernier patterns are superimposed is irradiated with laser beam light and scanned, and signals from pattern edges are selected based on the intensity difference of the reflected light. , an automatic alignment inspection device characterized in that the position of the signal is calculated and the amount of positional deviation is determined.