JPH07120697B2 - Positioning device - Google Patents

Description

The present invention relates to a pattern position / dimension measuring device and an exposure device on a semiconductor wafer, a mask, a reticle, etc., and particularly to a pattern dimension measuring device and a pattern position measuring device. , Wafer and mask exposure apparatus.

[Conventional technology]

Conventionally, this type of device irradiates a laser beam or the like from above a material (wafer, reticle, mask, etc.) as shown in FIG. The position and dimension of the pattern are determined by detecting the light scattered (or diffracted) from the detector.

[Problems to be solved by the invention]

In the conventional position determining method described above, as shown in FIG.
If there is pattern asymmetry caused by passing through processes such as resist coating at the time of semiconductor manufacturing and film deposition by the CVD method, the sputtering method, etc., as shown in 16 and 17 of FIG. The intensity of scattered (or diffracted) light at the edge portion is different. Therefore, in particular, when detecting the center of scattered (or diffracted) light at two edges as the pattern center, 16
Since the combined waveforms of 17 and 17 are asymmetrical as shown in 18, there is a drawback that when the threshold is determined as shown in FIG. 4, it shifts from position C to position C by Δx. .

[Means for solving problems]

The even-order harmonic removal type high-precision positioning device of the present invention is an electrical even-order harmonic removal circuit or a mathematical even-order harmonic removal calculation program for removing even-order harmonics from a pattern signal detected by a detector. Or both of them.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is an example of a block diagram when the second harmonic is removed by using an electric filter. In this case, it is assumed that the scattered (or diffracted) light from the pattern edge can be repeatedly obtained by scanning the same place many times by the laser. The scattered (or diffracted) light that has entered the detector 5 is amplified to a certain level by the preamplifier 6 with AGC. From the amplified signal, the fundamental wave (f) extraction circuit 8 extracts the fundamental wave (f) having the largest amplitude, and the digitization circuit 9 digitizes the fundamental wave (f). This doubles the frequency (2f) through the double frequency generation circuit of 10, and converts it into the DC voltage corresponding to the frequency by the F / V converter of 11. Then, B, E, and F of 7 become the operation of CUT at the double frequency, and when the output detected by the synchronous detection circuit of 12 becomes the voltage below the value set by the comparator of 13, the analog SW of 14 turns on and the Second in the signal processing circuit
That is, a signal without harmonics is sent.

Next, the reason why the waveform becomes symmetrical when the second harmonic is removed will be described with reference to the drawings. First, 19 fundamental waves are 4V _PP , 2
It is assumed that the second harmonic of 0 is 2V _PP and the third harmonic of 21 is 1V _PP mixed, as shown in FIG. The horizontal axis in this case is time (coordinates), but when the waveforms are viewed with an oscilloscope or the like, the waveforms are synthesized and it looks like 22 in FIG.
This corresponds to the state where the right peak of the composite waveform shown by 8 in FIG. 4 is further lowered. FIG. 7 shows the result obtained by Fourier-transforming this signal into the frequency domain with a spectrum analyzer or the like. 7th
From the figure, if the second harmonic is cut by B, E, F (band elimination filter) having the characteristics of FIG.
As shown in the figure, only the third high frequency exists in addition to the fundamental wave. If this is shown in Fig. 5, it becomes Fig. 10,
If the waveform is viewed with an oscilloscope, it will be as shown by the thick solid line in Fig. 11 and it can be confirmed that it is symmetrical.

If the signal waveform is bilaterally symmetric, the shift of Δx shown in FIG. 4 is eliminated, and the positioning and the like can be performed accurately.

Further, in FIG. 1, the frequency of the second harmonic follows the pattern to some extent even if the width of the pattern changes, but if the frequency of the second harmonic is constant by simple positioning, the alternate long and short dash line The range of can be omitted.

Second Embodiment A second method for carrying out the present invention is a method of mathematically removing even harmonics. If a computer or signal processor is used, fast Fourier transform (FFT) can be performed by utilizing the periodicity of trigonometric functions. However, if this is used, the input waveform is once captured in a short sampling time, and the fast Fourier transform is performed. After cutting the signal of, the waveforms shown in FIG. 11 can be obtained by performing the inverse conversion again and synthesizing the waveforms. In this embodiment, therefore, it is only necessary to add the digital sampling circuit of the signal to the computer or the single processor, and there is an advantage that the hardware is simple.

〔The invention's effect〕

As described above, the present invention makes the detection signal waveform symmetrical by removing the even harmonics from the detection signal, and therefore, as shown in FIG. 12, at what slice level (threshold level) is processed. However, the detection position does not change, and Δx shown in FIG. 4 does not occur. Further, as shown in FIG. 12, since the detection position does not shift even at a high slice level, a noise amount of about a medium slice level may exist, and it also has an effect of noise resistance.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment circuit of the present invention, FIG. 2 is a laser irradiation and detection unit of FIG. 1, FIG. 3 is an enlarged view (asymmetric) of a pattern edge portion of 2 of FIG. 2, and FIG. Signal waveforms obtained by scanning the pattern of FIG. 4, FIG. 5 is a mixed diagram of the fundamental wave and second and third harmonics, FIG. 6 is the synthesized waveform and fundamental wave of FIG. 5, and FIG. Fig. 5 (Fig. 6) Spectral decomposition diagram of the signal waveform, Fig. 8 is the frequency characteristic of the second (even) harmonic elimination filter, Fig. 9 is the spectrum diagram after elimination of the second harmonic, Fig. 10 Is the mixed wave diagram of the spectrum diagram of FIG. 9, FIG. 11 is the composite waveform and fundamental wave of FIG. 10, and FIG.
It shows the effect of the slice level on the composite waveform in Fig. 11. 1 ... laser beam, 1 '... scattered or diffracted light, 2 ...
… Measured pattern or positioning pattern, 3 …… Document, 4
...... Scan type laser beam generator, 5 ...... Detector for detecting scattered or diffracted light, 6 ...... AGC (Auto Gain Contr
ol) preamplifier, 7 ... Voltage tuning type B, E, F (Band Elim
ination filter), 8 ... Fundamental wave extraction circuit, 9 ... Waveform shaping (digitization) circuit, 10 ... Second harmonic generation circuit, 11 ... Frequency / voltage (F / V) converter, 12 ... Synchronous detector, 13 …… Comparator, 14 …… Analog switch,
15 ...... Conventional signal processing circuit, 16 ...... Signal output of scattered (or diffracted) light from the left edge, 17 ...... Signal output of scattered (or diffracted) light from the right edge, 18 ...... Two Composite signal waveform of scattered (or diffracted) light, 19 ...
(4V _PP ), 20 …… Second harmonic (2V _PP ), 21 …… Third harmonic (1V _PP ), 22 …… Composite waveform of the three waves in Fig. 5, 2
3 …… Composite waveform of the two waves in Fig. 10.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G05D 3/12 W H01L 21/027 21/68 F

Claims (1)

[Claims] 1. In position and size measurement and positioning of a pattern engraved on a semiconductor manufacturing wafer, mask, reticle, etc., signal waves are made line-symmetrical by removing high frequencies of a detection signal to perform measurement and positioning. Positioning device characterized by the above.