JP3382389B2 - Position shift detecting method and position shift detecting apparatus using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position shift detecting method and a position shift detecting apparatus using the same, and for example, in an exposure apparatus for manufacturing a semiconductor element, a first object such as two or more types of masks (reticles) is provided. When the formed fine electronic circuit patterns are sequentially exposed and transferred onto a second object such as a wafer for each mask (reticle), an alignment device that performs relative alignment between the mask and the wafer, and each mask ( It is suitable for a measuring device or the like that measures the overlay accuracy of the printed pattern on the wafer after the pattern on the reticle) is printed on the wafer.

In addition to the above, the present invention is suitable for measuring the line width of a diffraction grating as a printing pattern for measuring the relative alignment accuracy between a mask and a wafer, and a line width measuring method and line width measuring method. It relates to the device.

[0003]

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing a semiconductor device, when a pattern on a mask surface is projected and exposed on a wafer surface, a relative positional deviation between the mask and the wafer is detected. . There have been proposed various misalignment detection methods for detecting misalignment between the mask and the wafer at this time.

Of these, a diffraction grating is used as a pattern,
For example, Japanese Patent Application Laid-Open No. 2-90006 proposes a method for detecting the positional deviation of the diffraction grating from the phase difference between the two beat signals obtained by heterodyne interfering the diffracted lights from the two diffraction gratings. ing.

FIG. 19 is a schematic diagram of a positional deviation detecting device in an exposure apparatus for manufacturing a semiconductor element shown in the publication.

In FIG. 19, the laser light from the two-wavelength orthogonal polarization laser light source 140 is separated by the polarization beam splitter 142 via the mirror 141 into light of two wavelengths of a horizontal component and a vertical component. Then, the beams become elliptical beams 146 and 150 via the optical systems such as the mirror 143, the cylindrical lenses 144 and 149, and the objective lens 145, respectively, and the diffraction grating 14 formed on the wafer 147 on the xy stage 151.
It is incident on 8.

The diffraction grating 148, as shown in FIG.
It is composed of three sets of diffraction gratings 112, 113 and 114. Then, the heterodyne interference combined diffracted lights 153 to 155 are obtained in the respective three directions of the z direction. These synthetic diffracted lights 153-155 are split into two directions by the half mirror 156, and one of them is observed by the eyepiece 170.
The other is a prism mirror (157, 158, 15
9), a condenser lens (160, 161, 162), and a polarizing plate (163, 164, 165) through the photodetector 1
It is incident on 66 to 168. And the photodetector 166-
Optical heterodyne interference beat signals HY1 to HY3 at 168
Is obtained and is input to the signal processing unit 169. Then, from the change in the phase difference between the three signals HY1 to HY, the wafer 1
The amount of positional deviation between the first and second exposure patterns on the 47th surface is detected.

FIG. 20 is an explanatory view showing the diffraction grating on the wafer at this time. As shown in the figure, the diffraction gratings 112 and 113 are printed by the Nth exposure, and then the diffraction grating 114 is baked by the (N + 1) th exposure. The rotation component from the reference of the optical system is detected using the diffracted light from the diffraction grating 112 and the diffraction grating 113, and the actual positional deviation amount between the diffraction gratings is obtained from the diffracted light generated from the diffraction grating 113 and the diffraction grating 114. There is.

Further, a length measuring SEM (electron microscope), a laser microscope or the like has been conventionally used for measuring the line width of a printing pattern (diffraction grating) formed on a wafer surface.

[0010]

In the positional deviation detecting device shown in FIG. 19, when the shapes or materials of the diffraction grating 113 and the diffraction grating 114, which are the positional deviation detection marks, are changed, two positional deviation detection signals are generated. There is a problem that the phase difference of the beat signal (optical heterodyne interference beat signal) changes. At this time, it is conceivable that each semiconductor element manufacturing process has an offset value, but this method causes an error that cannot be removed as an offset because the phase difference signal is sensitive to the shape of the diffraction grating, and as a result, measurement The deterioration of reproducibility was a problem.

The inventor has found that the cause of the change in the phase of the beat signal depending on the material or shape of the diffraction grating is that "the amount of phase change when diffracted by the diffraction grating is different between P-polarized light and S-polarized light,
The value changes depending on the material and shape of the diffraction grating. "

Next, this will be described with reference to FIGS. 21 (A) and 21 (B). In FIGS. 21A and 21B, 11
0 and 111 are incident lights, 113 and 114 are diffraction gratings, 11
Reference numerals 5 and 116 are diffracted lights.

Now, two light beams of P-polarized light frequency f1 and S-polarized light of frequency f2 enter into diffraction grating 113 and diffraction grating 114, respectively, and diffracted light 115 and 116 from diffraction gratings 113 and 114, respectively. Φxa + φa and φxb + φb are added to the phases of the heterodyne beat signal when they are combined and interfered with each other.

Here, φxa and φxb are diffraction gratings 1, respectively.
13 and 114 are phase changes due to displacement from the optical system reference position, and φa and φb are phase changes determined by the materials and shapes of the diffraction gratings 113 and 114, respectively (the phase of P-polarized light and the phase of S-polarized light). This is a term that does not depend on the position change of the diffraction grating. At this time, the phase difference Δφ between the two beat signals can be written as follows.

Δφ = (φxa−φxb) + (φa−φb) = φΔx + (φa−φb) (1) where φΔx is the x direction of the diffraction grating 113 and the diffraction grating 114. Is the amount of phase change associated with the amount of relative displacement of the.

As shown in equation (1), the desired phase change φ
In addition to Δx, the detection error (φa-φb) is added,
With respect to the phase changes φa and φb, (φa −φb) was changed depending on the material and shape of the two diffraction gratings, leading to deterioration of reproducibility.

Further, the length measuring SEM is expensive in measuring the line width of the printed pattern, and in the case of the resist pattern in the measurement, it is necessary to deposit a conductive film (for example, gold) in advance in order to prevent charge-up. It takes time and labor, and nondestructive measurement is difficult. On the other hand, there is a problem that a laser microscope cannot obtain sufficient measurement accuracy.

The present invention takes advantage of the above, and by providing a measuring means or a correcting means for canceling the phase change caused by the change of the material or shape of the diffraction grating, the positional deviation is caused by the change of the material or shape of the diffraction grating. It is an object of the present invention to provide a positional deviation detection method capable of detecting a positional deviation with high accuracy without being affected by a semiconductor element manufacturing process, thereby preventing a detection error and a detection device using the same.

In addition, according to the present invention, the amount of phase change when diffracted by a diffraction grating is different for light having different polarization directions, and the fact that the amount depends on the material and shape of the diffraction grating makes it possible to use different polarization directions. An object of the present invention is to provide a line width measuring method and a line width measuring device for measuring the shape (particularly the line width) of a diffraction grating by measuring the phase difference between the diffracted lights of two light fluxes.

[0020]

Displacement detection method of the SUMMARY OF] of claim 1 invention (1-1) in the diffraction grating, the polarization direction is perpendicular irradiated with two different light beams having frequencies from each other results from the diffraction grating When a plurality of diffracted lights of different orders are combined and heterodyne interference is performed to obtain a plurality of beat signals, and a phase shift of the plurality of beat signals is used to detect a positional deviation of the diffraction grating from a predetermined position, the diffraction Light of p-polarization with frequency f1 is incident on the grating.
Of the + n-order diffracted light and s-polarized light at frequency f2
The -nth order diffracted light generated when light is incident is synthesized and
The first beat signal is generated by interfering with Telodyne, and the frequency is
-nth-order diffraction that occurs when p-polarized light is incident on f1
It does not occur when s-polarized light with light and frequency f2 is incident
+ N-th order diffracted light is combined to cause heterodyne interference and
Generate a beat signal and calculate the phase difference between the first and second beat signals.
Based on the properties of the diffraction grating,
Correct the phase error of the 2-beat signal to detect the positional deviation
It is characterized in that there.

[0021]

(1-2) Two light beams whose polarization directions are orthogonal to each other and have different frequencies are made incident on the first diffraction grating and the second diffraction grating,
Two diffracted lights of different orders generated from the first diffraction grating are combined to cause heterodyne interference to generate a first beat signal, and two diffracted lights of different orders generated from the second diffraction grating are combined to form a heterodyne. A first phase difference detecting step of generating a second beat signal by causing interference and detecting a phase difference between the first and second beat signals;
When a beat signal is made incident on a diffraction grating and at this time, two diffracted lights having different orders generated from the first and second diffraction gratings are combined and heterodyne interference is made to obtain a beat signal, between beat signals based on the properties of the diffraction grating And a second phase difference detecting step of detecting a phase difference between the third and fourth beat signals for correcting the phase error of the first phase difference detection. It is characterized in that a relative positional shift between the first and second diffraction gratings is detected by utilizing the phase difference obtained in the step and the second phase difference detecting step.

In particular, (1-2-1) in the second phase difference detecting step, in the first phase difference detecting step,
The substrate on which the second diffraction grating is formed is rotated by 180 degrees, the two diffracted lights generated from the first diffraction grating are combined to cause heterodyne interference, and the third beat signal is generated.
The two diffracted lights generated from the diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal, and the phase difference between the third and fourth beat signals is detected.

(1-2-2) In the second phase difference detecting step, the polarization direction of the light incident on the first and second diffraction gratings is rotated by 90 degrees in the first phase difference detecting step, and the first phase difference detecting step is performed.
The two diffracted lights generated from the diffraction grating are combined and heterodyne interfered to generate a third beat signal, and the two diffracted lights generated from the second diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal, Detecting the phase difference between the third and fourth beat signals.

(1-2-3) In the second phase difference detecting step, the two light beams for irradiating the first and second diffraction gratings are exchanged with each other in the first phase difference detecting step, and at this time, the first phase difference detecting step is performed. The two diffracted lights generated from the diffraction grating are combined to cause heterodyne interference to generate a third beat signal, and the second beat signal is generated.
The two diffracted lights generated from the diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal, and the phase difference between the third and fourth beat signals is detected.

(1-2-4) In the second phase difference detecting step, the two light beams are generated from the same direction as the direction in which the first and second diffraction gratings are irradiated with the two light beams in the first phase difference detecting step. Irradiation, two diffracted lights generated from the first diffraction grating are combined to generate a heterodyne interference to generate a third beat signal, and two diffracted lights generated from the second diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal. It is characterized in that a signal is generated and the phase difference between the third and fourth beat signals is detected.

(1-2-5) In the first phase difference detecting step, + n of p-polarized light whose frequency is f1 from the first diffraction grating is detected.
The second diffracted light and the s-polarized -nth-order diffracted light at the frequency f2 are combined to generate heterodyne interference, and the first beat signal is generated.
The + nth-order diffracted light of the p-polarized light having the frequency f1 and the -nth-order diffracted light of the s-polarized light having the frequency f2 and the -nth-order diffracted light from the diffraction grating are combined to generate the second beat signal, and the second beat signal is generated. The phase difference between the two beat signals is detected, and the second
In the phase difference detecting step, the + nth-order diffracted light of the p-polarized light having the frequency f2 and the −n of the s-polarized light having the frequency f1 are emitted from the first diffraction grating.
The 3rd beat signal is generated by combining the 2nd-order diffracted lights and causing heterodyne interference, and the + n-order diffracted light of the p-polarized light having the frequency f2 and the -n of the s-polarized light having the frequency f1 from the second diffraction grating are generated.
The second diffracted light is combined to cause heterodyne interference to generate a fourth beat signal, and the phase difference between the third and fourth beat signals is detected.

The position shift detecting device of the present invention is (2-1) the two light beams from the light source means for generating two light beams whose polarization directions are orthogonal to each other and whose frequencies are different from each other,
The light is made incident on the diffraction grating through illumination means that regulates the polarization, incident angle, etc., the diffracted light from the diffraction grating is combined by the combining means to form beat interference light, and the beat interference light is photoelectrically detected by the photoelectric detection means. The first beat signal is detected and the second light beam is similarly formed by passing the second light flux through an optical path different from the optical path of the light based on the first beat signal. The phase difference is detected by a phase difference meter, the phase error of the beat signal based on the property of the diffraction grating is detected by the phase error detection means, and the arithmetic unit calculates the phase difference of the diffraction grating based on the phase difference and the phase error. The feature is that the positional deviation from the predetermined position is obtained.

(2-2) The polarization directions are orthogonal to each other, and
The two light fluxes from the light source means for generating two light fluxes having different frequencies are made incident on the diffraction grating through the illumination means for controlling the frequency, the polarization, the incident angle, etc., and the frequency generated from the diffraction grating is f1 and the p polarization is + n. The first diffracted light is combined with the s-polarized -nth-order diffracted light having the frequency f2 by the synthesizing means to form the first beat signal, and the frequency generated from the diffraction grating is f1 and the p-polarized -nth-order diffracted light is the frequency f2. The s-polarized + n-th order diffracted light is combined by a combining means to form a second beat signal, the phase difference between the first and second beat signals is obtained by a phase difference meter, and the signal from the phase difference meter is calculated. It is characterized in that the displacement of the diffraction grating from a predetermined position is obtained by utilizing the diffraction grating. Particularly in the configuration (2-1) or the configuration (2-2), (2-2-1) the light source means is a dual-frequency orthogonal polarization laser.
Alternatively, the light source is a photoacoustic optical element .

The line width measuring method of the present invention comprises: (3-1) Two polarization directions are orthogonal to each other and different in frequency .
The luminous flux is made incident on the diffraction grating, the diffracted lights of the same order generated from the diffraction grating are combined and heterodyne interfered to obtain a measurement beat signal, the two luminous fluxes are combined and heterodyne interfered to obtain a reference beat signal, The grating line width forming the diffraction grating is measured by utilizing the phase difference between the measured beat signal and the reference beat signal.

The line width measuring apparatus of the present invention comprises (4-1) light source means for generating two light beams having different polarization directions and different frequencies, and a part of the two light beams is divided to form a reference beat signal. Reference beat forming means, and 2
Illuminating means for irradiating a diffraction grating with a light flux, measurement beat signal forming means for forming a measurement beat signal by heterodyne interference between diffracted lights of the same order from the diffraction grating, the reference beat signal and the measurement beat signal. And a calculator for calculating the grating line width forming the diffraction grating using the phase difference.

[0032]

Embodiment 1 FIG. 1 is a schematic view of the essential portions of Embodiment 1 of the present invention. This embodiment shows a case where the present invention is applied to an overlay accuracy measuring apparatus for measuring overlay accuracy of two layers of patterns in a semiconductor element manufacturing process.

2 is an expanded view of the optical path of FIG. 1, and FIGS. 3 and 4 are enlarged explanatory views of a part of FIG. FIG. 17 is a flowchart of the measurement sequence of this embodiment.

In the figure, reference numeral 1 denotes a dual frequency orthogonal polarization laser as a light source (light source means), which oscillates, for example, p-polarized light of frequency f1 and s-polarized light of frequency f2. The collimator lens 2 collimates the light flux from the light source 1 into parallel light. 3 is a polarization beam splitter, 4a and 4b are mirrors respectively, and 15a is a wafer 16 in the nth semiconductor exposure process.
Diffraction grating pattern formed above, 15b is (n + 1)
It is the diffraction grating pattern formed on the wafer 16 in the exposure process of the first time.

The collimator lens 2, the polarization beam splitter 3, the mirrors 4a and 4b, etc. constitute one element of the illumination means.

Reference numeral 5 is a mirror, 6 is a lens, 7 is a Glan-Thompson prism, and 8 is an edge mirror, which separates and reflects light in two directions. 9a and 9b are lenses, 10a and 1
0b is a sensor respectively. Reference numeral 11 denotes a phase difference meter, which calculates the phase difference between the signals from the sensors 10a and 10b. Reference numeral 12 is a storage device, 13 is a computing unit, 14 is a stage control system, and 17 is a rotary stage on which a wafer 16 is mounted. Reference numeral 18 denotes a y stage, and 19 denotes an x stage, which are movable in the y direction and the x direction, respectively.

The mirror 5, the lens 6, the Glan-Thompson prism 7, etc. constitute one element of the combining means.

Next, the operation of this embodiment will be described.

The p-polarized light 20 of frequency f1 emitted from the dual-frequency orthogonal polarization laser 1 passes through the collimator lens 2 and the polarization beam splitter 3. After that, the light is deflected by the mirror 4a to irradiate the diffraction gratings 15a and 15b on the wafer 16. At this time, + from the diffraction gratings 15a and 15b
The mirror 4a is set so that the first-order diffracted light is diffracted perpendicularly to the wafer 16.

On the other hand, the s-polarized light 21 of the frequency f2 emitted from the dual-frequency orthogonal polarization laser 1 passes through the collimator lens 2, is reflected by the polarization beam splitter 3, and is then deflected by the mirror 4b so as to be reflected by the diffraction gratings 15a and 15b. Irradiate.
At this time, the mirror 4b is set so that the −1st order diffracted light from the diffraction gratings 15a and 15b is diffracted perpendicularly to the wafer 16.

The incident beam is narrowed down by the collimator lens 2, and the two diffraction gratings 1 are formed on the wafer 16.
The spots are slightly larger than 5a and 15b (spot 23 in FIG. 4).

Here, after splitting into light 20 and 21 of two frequencies by the polarization beam splitter 3, the diffraction grating 15a,
They are recombined on 15b and follow the same optical path. This combined diffracted light is deflected by the mirror 5 and the lens 6
As described above, the light enters the Glan-Thompson prism 7 and the deflection directions thereof are aligned to cause heterodyne interference.

As shown in FIG. 2, the edge mirror 8 is installed at a position conjugate with the wafer 16 and the lens 6.
That is, as shown in FIG. 3, images 15a 'and 15b' of the diffraction grating 15a and the diffraction grating 15b are visible on the edge mirror 8. Thus, the synthetic heterodyne interference light from the diffraction grating 15a and the synthetic heterodyne interference light from the diffraction grating 15b are separated into two by transmitting one through the edge mirror 8 and reflecting the other.

Diffraction grating 15a reflected by the edge mirror 8
The diffracted light from is passed through the lens 9a and photoelectrically converted by the sensor 10a. As a result, the first beat signal is obtained.
The diffracted light from the diffraction grating 15b that has passed through the edge mirror 8 passes through the lens 9b and is photoelectrically converted by the sensor 10b. As a result, the second beat signal is obtained.

As shown in FIG. 2, the lenses 9a and 9b are arranged so that the wafer 16 and the edge mirror 8 and the sensors 10a and 10b are in a conjugate position, and the imaging magnification by the lenses 6 and 9a (9b) is the sensor. 10a (10
It is set so that the image of the diffraction grating is included in the light receiving surface of b). The phase difference meter 11 detects the phase difference DT1 of the two heterodyne beat signals obtained by the sensors 10a and 10b and stores them in the temporary storage device 12 (first phase difference detection step).

After that, the rotary stage 17 is rotated by 180 degrees, the x stage 19 and the y stage 18 are driven, the diffraction gratings 15a and 15b are aligned at the beam spot positions, and the third and fourth stages are performed in the same manner as described above. After obtaining the beat signal, the phase difference DT2 of the third and fourth beat signals is measured and sent to the temporary storage device 12 (second phase difference detecting step).

Then, the calculator 13 obtains the relative positional deviation between the diffraction grating 15a and the diffraction grating 15b from the phase difference DT1 and the phase difference DT2. Hereinafter, the phase of the diffracted light or the phase of the beat signal will be described with reference to FIGS.

In FIG. 4A, the complex amplitude display u1a of the + 1st order diffracted light 20a generated from the diffraction grating 15a of the p-polarized light 20 at the frequency f1 (angular frequency: w1) can be written as follows.

U1a = u0exp {w1 · t + φxa + φap} (2) where u0 is the amplitude of the light 20 and φxa is the diffraction grating 15a.
Is a phase change associated with the amount xa of displacement of the optical system from the reference line 24 in the x direction, and can be written as φxa = 2πxa / p, where p is the pitch of the diffraction grating 15a. Further, φap is the amount of phase change that p-polarized light receives due to diffraction, which is determined by the material and shape of the diffraction grating 15a, so-called property.

On the other hand, at frequency f2 (angular frequency: w2), s
The complex amplitude display u2a of the minus first-order diffracted light 21a generated from the diffraction grating 15a of the polarized light 21 can be written as follows.

U2a = u0exp {w2 · t−φxa + φas} (3) In addition, φas is a phase change amount that s-polarized light receives by diffraction, which is determined by the material and shape of the diffraction grating 15a. is there.

Further, at frequency f1 (angular frequency: w1), p
+ 1st order diffracted light 20 from the diffraction grating 15b of the polarized light 20
The complex amplitude representation u1b of b can be written as:

U1b = u0exp {w1.t + φxb + φbp} (4) where u0 is the amplitude of the light 20 and φxb is the diffraction grating 15b.
Is a phase change associated with the amount xb of displacement of the optical system from the reference line 24 in the x direction, and can be written as φxb = 2πxb / p, where p is the pitch of the diffraction grating 15b. Further, φbp is a phase change amount that p-polarized light determined by the material and shape of the diffraction grating 15a undergoes by diffraction.

On the other hand, at frequency f2 (angular frequency: w2), s
The complex amplitude display u2b of the minus first-order diffracted light 21b generated from the diffraction grating 15b of the polarized light 21 can be written as follows.

U2b = u0exp {w2 · t−φxb + φbs} (5) In addition, φbs is a phase change amount that s-polarized light receives by diffraction, which is determined by the material and shape of the diffraction grating 15b. is there.

At this time, the AC component Ia of the beat signal (first beat signal) obtained by the sensor 10a by causing the diffracted light 20a and the diffracted light 21a to heterodyne interfere with each other is as follows with I0 as the amplitude.

Ia = I0cos {(w1−w2) t + 2φxa + (φap−φas)} (6) Further, the beat signal (the first signal) obtained by the sensor 10b by causing the diffracted light 20b and the diffracted light 21b to interfere heterodyne. The AC component Ib of the 2-beat signal is as follows.

Ib = I0cos {(w1−w2) t + 2φxb + (φbp−φbs)} (7) The phase difference Δφ1 between the first and second beat signals expressed by the equations (6) and (7) is Δφ1 = 2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx + {(φap−φas) − (φbp−φbs)} ・ ・ ・ ・ ・ ・ ・ ・ (8) where , ΦΔx is the x of the diffraction grating 15a and the diffraction grating 15b.
The phase change associated with the relative positional deviation amount Δx in the direction is φΔx = 4πΔx / p (9).

On the other hand, the interference beat signal (third beat signal) Ia 'obtained by the sensor 10b of the diffracted lights 20a and 21a when the wafer 16 is rotated 180 degrees (FIG. 4B) is
Assuming that the displacement amount of the diffraction grating 15a in the x direction from the reference line 24 of the optical system is xa ', the following can be written.

Ia ′ = I0cos {(w1−w2) t + 2φxa ′ + (φap−φas)} (10) When the wafer 16 is rotated 180 degrees (FIG. 4B) The interference beat signal (fourth beat signal) Ib ′ obtained by the sensor 10a of the diffracted lights 20b and 21b is the diffraction grating 15
The deviation amount of the b in the x direction from the reference line 24 of the optical system is xb '
Then, we can write as follows.

Ib ′ = I0cos {(w1−w2) t + 2φxb ′ + (φbp−φbs)} (11) Here, the third and third equations (11) to (12) are used. Taking the phase difference Δφ2 of the 4-beat signal, Δφ2 = 2 (φxb'−φxa ')-{(φap−φas) − (φbp−φbs)} = 2φΔx − {(φap−φas) − (φbp−φbs) } (12) The phase difference Δ represented by the equations (8) and (12) in the computing unit 13
When the sum Δφ of φ1 and Δφ2 is taken, the error term ({} term) caused by the shape and material of the diffraction grating is canceled, and Δφ = Δφ1 + Δφ2 = 4φΔx = 8πΔx / p (13) ).

Therefore, the relative positional deviation amount Δx of the diffraction gratings 15a and 15b, that is, the positional deviation between the circuit pattern printed in the nth exposure and the circuit pattern printed in the (n + 1) th exposure is calculated by the following equation. You can

Δx = Δφ · P / (8π) (14) The error caused by the rotation component of the mark with respect to the detection optical system is, for example, the amount of deviation at the same time when the diffraction grating 15a is printed. If a reference mark composed of two diffraction gratings without a mark is printed on the wafer and the phase difference signal from the mark is detected before and after the wafer is rotated 180 degrees,
By using this value as a correction value, the offset value of the optical system and the error caused by the rotation component can be removed.

Further, in the present embodiment, the case of only the x direction is shown, but in the y direction as well, a diffraction grating for detecting the y direction deviation is similarly burnt in, and another set of optical elements for detecting the y direction deviation is set. Set up the system or set the rotary stage as shown in Figure 1.
From the state, the phase difference is detected by rotating 90 degrees, and then the phase difference is detected by rotating 180 degrees from the two signals.
The positional deviation amount Δy in the direction can be measured.

FIG. 5 is a schematic view of the essential portions of Embodiment 2 of the present invention, and FIG. 6 is an enlarged explanatory view of a portion of FIG. This embodiment is shown in FIG.
The third embodiment is different from the first embodiment in that the polarization converter 26a (26b) is arranged between the polarization beam splitter 3 and the mirror 4a (4b), and the other points are the same.

In FIG. 5, p-polarized light 20 having a frequency f1 emitted from the dual frequency orthogonal polarization laser 1 passes through the collimator lens 2 and the polarization beam splitter 3.
After that, the light is deflected by the mirror 4a through the polarization converter 26a, and the diffraction gratings 15a and 15b on the wafer 16 are irradiated with the light. At this time, the mirror 4a is arranged so that the + 1st order diffracted light generated from the diffraction gratings 15a and 15b is diffracted perpendicularly to the wafer 16.
Is set.

On the other hand, the s-polarized light 21 having the frequency f2 emitted from the dual-frequency orthogonal polarization laser 1 passes through the collimator lens 2, is reflected by the polarization beam splitter 3, and then is passed through the polarization converter 26b and is deflected by the mirror 4b. , The diffraction gratings 15a and 15b are irradiated. At this time, the diffraction grating 15
The mirror 4a is set so that the −1st order diffracted light generated from a and 15b is diffracted perpendicularly to the wafer 16. The polarization converters 26a and 26b can be switched on and off by a switching device (not shown). In the on state, the p-polarized light incident on the polarization converter 26a has a polarization direction of 9
It is changed by 0 degrees and emitted as s-polarized light.

Further, the s-polarized light that has entered the polarization conversion unit 26b has its polarization direction changed by 90 degrees and is emitted as p-polarized light. On the other hand, in the off state, the polarization direction remains unchanged. The polarization conversion unit can be configured using, for example, a wave plate.

The measuring method in this embodiment will be described below with reference to FIGS. 6 (A) and 6 (B).

Both the polarization converters 26a and 26b are turned off.
In the state, the + 1st order diffracted light 20a generated from the diffraction grating 15a of the p-polarized light 20 at the frequency f1 (angular frequency: w1)
The complex amplitude display u1a of can be written as follows.

U1a = u0exp {w1.t + φxa + φap} (15) where u0 is the amplitude of the light 20 and φxa is the diffraction grating 15a.
Is a phase change associated with the amount xa of displacement of the optical system from the reference line 24 in the x direction, and can be written as φxa = 2πxa / p, where p is the pitch of the diffraction grating 15a. Further, φap is a phase change amount which the p-polarized light determined by the material and shape of the diffraction grating 15a receives by diffraction.

On the other hand, at frequency f2 (angular frequency: w2), s
The complex amplitude display u2a of the minus first-order diffracted light 21a generated from the diffraction grating 15a of the polarized light 21 can be written as follows.

U2a = u0exp {w2 · t−φxa + φas} (16) Further, φas is a phase change amount that the s-polarized light 21 receives by diffraction, which is determined by the material and shape of the diffraction grating 15a. is there.

Further, at frequency f1 (angular frequency: w1), p
The complex amplitude display u1b of the + 1st order diffracted light 20b generated from the diffraction grating 15b of the polarized light 20 can be written as follows.

U1b = u0exp {w1.t + φxb + φbp} (17) where u0 is the amplitude of the light 20 and φxb is the diffraction grating 15b.
Is a phase change associated with the amount xb of displacement of the optical system from the reference line 24 in the x direction, and can be written as φxb = 2πxb / p, where p is the pitch of the diffraction grating 15b. Further, φbp is a phase change amount which the p-polarized light determined by the material and shape of the diffraction grating 15b receives by diffraction.

On the other hand, at frequency f2 (angular frequency: w2), s
The complex amplitude display u2b of the minus first-order diffracted light 21b generated from the diffraction grating 15b of the polarized light 21 can be written as follows.

U2b = u0exp {w2 · t−φxb + φbs} (18) Further, φbs is a phase change amount that s-polarized light receives by diffraction, which is determined by the material and shape of the diffraction grating 15b. .

At this time, the AC component Ia of the beat signal (first beat signal) obtained by the sensor 10a by causing the diffracted light 20a and the diffracted light 21a to heterodyne-interact is as follows with I0 as the amplitude.

Ia = I0cos {(w1−w2) t + 2φxa + (φap−φas)} (19) Also, the beat signal obtained by the sensor 10b by heterodyne interference between the diffracted light 20b and the diffracted light 21b. The AC component Ib of the (second beat signal) is as follows.

Ib = I0cos {(w1−w2) t + 2φxb + (φbp−φbs)} (20) The phase difference Δφ1 between the first and second beat signals represented by the equations (19) and (20). Is Δφ1 = 2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx + {(φap−φas) − (φbp−φbs)} (21) where , ΦΔx is the x of the diffraction grating 15a and the diffraction grating 15b.
The phase change associated with the relative positional deviation amount Δx in the direction is φΔx = 4πΔx / p (22)

On the other hand, both the polarization conversion units 26a and 26b are
Sensor 1 for diffracted light 20a, 21a in n state
0b interference beat signal (third beat signal) Ia
'Is x from the reference line 24 of the optical system of the diffraction grating 15a.
If the amount of deviation in the direction is xa ', then the following can be written.

Ia ′ = I0cos {(w1−w2) t + 2φxa ′ + (φas−φap)} (23) Further, the interference beat signal Ib ′ (first number) obtained by the sensor 10a for the diffracted lights 20b and 21b 4 beat signal) is the deviation amount of the diffraction grating 15b from the reference line 24 of the optical system in the x direction.
If b'is written, then Ib '= I0cos {(w1-w2) t + 2φxb' + (φbs-φbp)} (24) Here, from equation (23) to equation (24) If the phase difference Δφ2 of the third and fourth beat signals is taken, Δφ2 = 2 (φxa '−φxb')-{(φap-φas)-(φbp-φbs)} = 2φΔx-{(φap-φas)-( φbp−φbs)} (25) When the sum Δφ of the phase differences Δφ1 and Δφ2 represented by the equations (21) and (25) is calculated by the calculator 13, depending on the shape and material of the diffraction grating, The generated error term ({} term) is canceled out, and Δφ = Δφ1 + Δφ2 = 4φΔx = 8πΔx / p (26)

Therefore, the relative positional deviation amount Dx of the diffraction gratings 15a and 15b, that is, the positional deviation between the circuit pattern printed in the nth exposure and the circuit pattern printed in the (n + 1) th exposure is calculated by the following equation. You can

Δx = Δφ · P / (8π) (27) The error caused by the rotation component of the mark with respect to the detection optical system is, for example, the amount of deviation at the same time when the diffraction grating 15a is printed. If a reference mark composed of two diffractive gratings without a mark is printed on the wafer and detected, the value can be used as a correction value to eliminate the error caused by the offset value and the rotation component of the optical system.

In this embodiment, the case of only the x direction is shown, but in the y direction as well, a diffraction grating for detecting the y direction shift is similarly burnt in, and another set of optical elements for detecting the y direction shift is set. Set up the system or rotate the stage as shown in Figure 5.
From the state, the phase difference is detected by rotating 90 degrees, and then the phase difference is detected by rotating 180 degrees from the two signals.
The positional deviation amount Δy in the direction can be measured.

FIG. 7 is a schematic view of the essential portions of Embodiment 3 of the present invention, and FIG. 8 is an enlarged explanatory view of a portion of FIG. This embodiment is shown in FIG.
2 is different from that of the first embodiment in that after the light emitted from the dual-frequency orthogonal polarization laser 1 passes through the collimator lens 2, the plane of incidence on the polarization beam splitter 3 is switched using the deflection mirror 32. The other configurations are the same.

That is, as shown in FIGS. 8A and 8B, the p-polarized light 20 having the frequency f1 from the left side and the s-polarized light 21 having the frequency f2 from the right side are diffracted by the diffraction gratings 15a and 15b.
When irradiating to the
0, the case of irradiating the light 41 of the frequency f1 with p polarization from the right side is switched to two ways.

The measuring method of this embodiment will be described below with reference to FIG.
A description will be given using (A) and (B).

When the light is not reflected by the deflecting mirror 32, it is the same as the signal before rotating the wafer by 180 degrees in the first embodiment, and therefore it is the same as the expression (8) and the first and second beat signals The phase difference Δφ1 is Δφ1 = 2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx + {(φap−φas) − (φbp−φbs)} (28) Diffracted light 4 when reflected by the mirror 32 and incident on the polarization beam splitter 3 via the mirrors 33 and 34
The interference beat signal (third beat signal) Ia 'obtained by the sensors 10a of 0a and 41a can be written as follows, where xa' is the shift amount of the diffraction grating 15a from the reference line 24 of the optical system.

Ia ′ = I0cos {(w1−w2) t−2φxa ′ + (φap−φas)} (29) Further, the interference beat signal (the fourth beat) obtained by the sensor 10b of the diffracted lights 40b and 41b. Signal) Ib 'is the amount of deviation of the diffraction grating 15b from the reference line 24 of the optical system in the x direction by x.
Let b'be written as follows: Ib '= I0cos {(w1-w2) t-2φxb' + (φbp-φbs)} (30) Here, from equation (29) to equation (30) When the phase difference Δφ2 of the third and fourth beat signals is taken, Δφ2 = -2 (φxa '-φxb') + {(φap-φas)-(φbp-φbs)} = -2φΔx + {(φap-φas)- (Φbp−φbs)} (31) When the difference Δφ between the phase differences Δφ1 and Δφ2 represented by the equations (28) and (31) is calculated by the computing unit 13, it is caused by the shape and material of the diffraction grating. The error term ({} term) is canceled out, and Δφ = Δφ1−Δφ2 = 4φΔx = 8πΔx / p (32)

Therefore, the relative positional deviation amount Δx of the diffraction gratings 15a and 15b, that is, the positional deviation between the circuit pattern printed in the nth exposure and the circuit pattern printed in the (n + 1) th exposure is calculated by the following equation. You can

Δx = Δφ · P / (8π) ... (33) FIG. 9 is a schematic view of the essential portions of Embodiment 4 of the present invention, FIGS.
FIG. 10 is an enlarged explanatory diagram of a part of FIG. 9. In this embodiment, as compared with the first embodiment of FIG. 1, after the light emitted from the dual-frequency orthogonal polarization laser 1 passes through the collimator lens 2, the light is split into two by the beam splitter 35 and is made incident on the respective polarization optical elements 38. ing. This polarization optical element 38, as shown in FIG.
A transmitting portion 38a, a polarizing plate 38b that transmits p-polarized light,
Light-shielding portion 38c and polarizing plate 38d that transmits s-polarized light
Except that the actuator 37 is slid to change the incident position on the polarization optical element 38 in two ways, and the other configurations are the same.

In this embodiment, as shown in FIGS. 11 (A) and 11 (B), the p-polarized light 20 having the frequency f1 and the s-polarized light 21 having the frequency f2 from the right are diffracted by the diffraction gratings 15a, 1a.
5b is irradiated, and the left side is p-polarized light 20 of frequency f1 and the left side is s-polarized light 39 of frequency f2.

The measurement method of this embodiment will be described below with reference to FIG.
And FIG. 11 will be described.

The state of incidence on the polarization optical element 38 is shown in FIG.
In the case of (A), since it is the same as the signal before rotating the wafer 180 degrees in the first embodiment, it becomes the same as the expression (8), and the phase difference Δφ1 of the first and second beat signals is Δφ1 = 2. (Φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx + {(φap−φas) − (φbp−φbs)} (34) On the other hand, the polarization optical element 38 is slid. The interference beat signal (third beat signal) I obtained by the sensor 10a of the diffracted lights 20a and 39a in the incident state of FIG.
The term a'does not include the term of the phase change due to the displacement of the diffraction grating 15a and can be written as follows.

Ia '= I0cos {(w1−w2) t + (φap−φas)} (35) Further, the interference beat signal (fourth beat signal) obtained by the sensor 10b of the diffracted lights 20b and 39b. Ib 'does not include the term of the phase change due to the displacement of the diffraction grating 15b and can be written as Ib' = I0cos {(w1-w2) t + (φbp-φbs)} (36) Here, when the phase difference Δφ2 of the third and fourth beat signals of the equations (35) to (36) is taken, Δφ2 = {(φap−φas) − (φbp−φbs)} ... (37) When the difference Δφ between the phase differences Δφ1 and Δφ2 represented by the equations (34) and (37) is calculated by the computing unit 13, the term of error (term of {}) caused by the shape and material of the diffraction grating Is canceled and Δφ = Δφ1−Δφ2 = 2 · φΔx = 4π · Δx / p ... (38)

Therefore, the relative positional deviation amount Δx of the diffraction gratings 15a and 15b, that is, the positional deviation between the circuit pattern printed in the nth exposure and the circuit pattern printed in the (n + 1) th exposure is calculated by the following equation. You can

Δx = Δφ · P / (4π) (39) FIG. 12 is a schematic view of the essential portions of Embodiment 5 of the present invention. In Examples 1 to 4, the method of correcting the error caused by the material and shape of the diffraction grating by changing the optical system and using the measured values twice respectively was shown. On the other hand, the present embodiment aims at improving the throughput by providing an optical system for error correction in advance and detecting two signals at the same time.

FIG. 18 is a flow chart of the measurement sequence of this embodiment.

In FIG. 12, a dual-frequency orthogonal polarization laser 1
The light emitted from is deflected by the mirror 5 via the collimator lens 47 so as to be vertically incident on the wafer 16. The diffracted light from the diffraction gratings 15a and 15b is deflected by the mirror 4a (4b) via the lens 48 (49) and enters the polarization beam splitter 51. This polarization beam splitter 51 produces a pair of + 1-order diffracted light of p-polarized light of frequency f1 and -1st-order diffracted light of s-polarized light of frequency f2 generated from the diffraction gratings 15a and 15b;
The p-polarized light generated from a and 15b is divided into a light flux pair of the −1st-order diffracted light of frequency f1 and the s-polarized light of + 1st-order diffracted light of frequency f2.

On the other hand, the former luminous flux pair is separated into the diffracted light from the diffraction grating 15a and the diffraction grating 15b by the edge mirror 8 via the Glan-Thompson prism 7, and is photoelectrically detected by the sensors 10c and 10d, respectively, and the positional deviation beat signals are detected. (First and second beat signals) Ia and Ib.

Further, a half mirror 50 is provided between the wafer 16 and the polarization beam splitter 5, and a part of the diffracted light passes through the Glan-Thompson prism 7 and the edge mirror 8.
After being separated into the diffracted light from the diffraction grating 15a and the diffraction grating 15b by means of photoelectric detection by the sensors 10a and 10b, corrected beat signals (third and fourth beat signals) Ira, I
rb is obtained.

Correcting phase difference Δ obtained by the phase difference meter 11a
φ2 (Ira-Irb) is the same as the equation (37) and can be expressed as follows.

Δφ2 = {(φap−φas) + (φbp−φbs)} (40) Further, the phase difference Δφ1 between the first and second beat signals detected by the phase difference meter 11b. (Ia−Ib) is Δφ1 = 2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx + {(φap−φas) − (φbp−φbs)} ... (41) ).

Here, in the arithmetic unit 13, equations (41), (4
If the difference Δφ between the phase differences Δφ1 and Δφ2 expressed by the equation (0) is taken, the term of error ({} caused by the shape and material of the diffraction grating is
Is canceled out, and Δφ = Δφ1−Δφ2 = 2 · φΔx = 4πΔx / p (42)

Therefore, the relative positional deviation amount Δx of the diffraction gratings 15a and 15b, that is, the positional deviation between the circuit pattern printed in the nth exposure and the circuit pattern printed in the (n + 1) th exposure is calculated by the following equation. You can

Δx = Δφ · P / (4π) (43) FIG. 13 is a schematic view of the essential portions of Embodiment 6 of the present invention. This embodiment shows a case where the exposure apparatus for manufacturing a semiconductor element is applied to a positioning apparatus for positioning a wafer with respect to the apparatus main body.

In FIG. 13, a dual-frequency orthogonal polarization laser 1
The light emitted from is deflected by the mirror 5 via the collimator lens 47 so as to be vertically incident on the wafer 16. Diffracted light from the diffraction grating 15, which is an alignment mark on the wafer 16, is deflected by the mirror 4a (4b) via the lens 48 (49) and enters the polarization beam splitter 51. This polarization beam splitter 51 produces a pair of + 1st-order diffracted light of p-polarized light of frequency f1 and -1st-order diffracted light of s-polarized light of frequency f2 and p-polarized light of frequency f1 generated by the diffraction grating. 2 in the luminous flux pair of the + 1st-order diffracted light and the s-polarized light and the + 1st-order diffracted light of frequency f2
The former luminous flux pair becomes a positional deviation beat signal (first beat signal) Ia at the sensor 10a via the Glan-Thompson prism 7 and the lens 55.

On the other hand, the latter light flux pair becomes a positional deviation beat signal (second beat signal) Ib at the sensor 10b via the Glan-Thompson prism 7 and the lens 60.

At this time, the phase difference Δφ (Ia −Ib) between the first and second beat signals detected by the phase difference meter 11 is Δφ = {φx + (φp −φs)} − {− φx + (φp −φs )} = 2φx (44)

Here, φx is the amount of phase change associated with the amount x of displacement of the alignment mark (diffraction grating) of the wafer from the reference line of the optical system, and φx = 4πx / p, where φp and φs
Is the amount of phase change that does not depend on the positional deviation received when the p-polarized light and the s-polarized light are diffracted by the diffraction grating 15.

The positional shift amount x of the diffraction grating 15, that is, the wafer 16 with respect to the exposure device can be calculated by the following equation by the calculator 13.

X = Δφ · P / (4π) (45) Thereafter, the stage is driven by the detected position shift amount x.

FIG. 14 is a schematic view of the essential portions of Embodiment 7 of the present invention.
FIG. 15 is an enlarged explanatory diagram of a part of FIG. This embodiment shows a case where it is applied to an alignment device section of an X-ray semiconductor exposure apparatus.

FIG. 15 shows a diffraction grating 15a which is an alignment mark on the mask 65 and the wafer 16 in this embodiment.
The relationship between the diffraction grating 15b serving as the upper alignment mark, the incident light spot 23, and the diffraction direction is shown. There is a gap of 10 to 30 μm in the z direction between the mask 65 and the wafer 16, and the diffraction gratings 15a and 15b. Are slightly offset in the y direction and do not overlap.

In FIG. 14, a dual-frequency orthogonal polarization laser 1
The light emitted from is deflected by the mirror 5 via the collimator lens 47 so as to be vertically incident on the wafer 16. Diffraction grating 15a on mask 65 and wafer 1
The diffracted light generated from the diffraction grating 15b on
It is deflected by the mirror 4a (4b) via (49) and enters the polarization beam splitter 51.

By this polarization beam splitter 51, the p-polarized light from the diffraction gratings 15a and 15b becomes +
A pair of -1st-order diffracted light of the 1st-order diffracted light and s-polarized light of frequency f2, and a -1st-order diffracted light of p-polarized light of frequency f1 and + 1st-order diffracted light of s-polarized light of frequency f2 from diffraction gratings 15a and 15b The former light flux pair is divided into two, and is separated into the diffracted light from the diffraction grating 15a and the diffraction grating 15b by the edge mirror 8 via the Glan-Thompson prism 7 and then the lens 6
2a (62b) through the sensor 10a (sensor 10
Photoelectrically detected in b), the positional shift beat signals (first and second beat signals) Ia1 and Ib1 are obtained.

The latter luminous flux pair is the Glan-Thompson prism 7
Through the edge mirror 8 through the diffraction grating 15a and the diffraction grating 15
After being separated into the diffracted light from b, the lens 62c (62
position detection beat signal (third and fourth beat signals) I which is photoelectrically detected by the sensor 10c (sensor 15d) via d)
It becomes a2 and Ib2.

The phase difference Δφ1 (Ia1-Ib1) of the first and second beat signals obtained by the phase difference meter 11a can be expressed as follows.

Δφ1 = 2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = 2φΔx {(φap−φas) − (φbp−φbs)} ... (46) Also, The phase difference Δφ2 (Ia2-Ib2) of the third and fourth beat signals detected by the phase difference meter 11b is Δφ2 = -2 (φxa−φxb) + {(φap−φas) − (φbp−φbs)} = − 2φΔx + {(φap−φas) − (φbp−φbs)} (47)

Here, φxa and φxb are phase changes associated with the deviation amounts xa and xb of the diffraction grating 15a on the mask 65 and the diffraction grating 15b on the wafer 16 from the reference of the optical system, respectively, and φxa = 4πxa / p , Φxb = 4πx
b / p. Further, φap and φas are phase changes received when the p-polarized light and the s-polarized light are diffracted by the diffraction grating 15a, and the values change when the mask is replaced in the exposure process. φbp and φbs are phase changes received when p-polarized light and s-polarized light are diffracted by the diffraction grating 15b, and their values change when the shape and material of the diffraction grating 15b are changed in the exposure process.

When the difference Δφ between the phase differences Δφ1 and Δφ2 represented by the equations (46) and (47) is calculated by the computing unit 13, the error term ({} term) caused by the shape and material of the diffraction grating becomes It is canceled and Δφ = Δφ1−Δφ2 = 2φΔx = 4πΔx / p (48)

Therefore, the relative displacement amount Δx of the diffraction gratings 15a and 15b and the relative displacement of the wafer with respect to the mask can be obtained by the following equations.

Δx = Δφ · p / (4π) (49) Driving the mask or wafer (or both) with a dedicated control system 63 or 14 so that Δx becomes zero. This enables highly accurate alignment.

In each of the embodiments of the present invention, the same-magnification exposure apparatus in which the mask and the wafer are close to each other has been described, but it is of course applicable to reduction projection exposure.

FIG. 16 is a schematic view of a part of the eighth embodiment of the present invention. In Examples 1 to 7, an example using a dual-frequency orthogonal polarization Zeeman laser was shown as a light source, but in Examples 1 to 7, a light source using a photoacoustic optical element as shown in FIG. 16 may be used.

In FIG. 16, the light emitted from the single frequency laser 71 is incident on the polarization beam splitter 72a and is divided into two by the polarization direction. The transmitted light is frequency-modulated by the photoacoustic optical element 73a to become light L1 having a frequency f1, while the reflected light is frequency f by the photoacoustic optical element 73b.
2 light L2 is modulated. The Rukoto forming If this after polarization beam splitter 72b, to obtain the light of frequency f2 in light and s-polarized light of the frequency f1 in the p-polarized light traveling in the same optical path.

FIG. 22 is a schematic view of the essential portions of Embodiment 9 of the present invention. In this embodiment, each element (97, 9) for detecting the line width information of the diffraction grating is added to the positional deviation detecting device of the fourth embodiment shown in FIG.
8, 9c, 10c, 99) is added, and the function as a line width measuring device is also used. 22, the same elements as those shown in FIG. 9 are designated by the same reference numerals. FIG. 9 shows the positional deviation detection in this embodiment.
This is the same as described in the fourth embodiment.

Next, a method for measuring the line width of the diffraction grating 15 will be described. In this embodiment, when measuring the line width, the polarization optical element 38 is slid to move the beam splitter 3
Only the light passing through 5 transmits the transmitting portion 38a of the polarization optical element 38.
(See FIG. 10B).

In this embodiment, the light emitted from the dual-frequency orthogonal polarization laser 1 (p-polarized light of frequency f1 and s-polarized light of frequency f2) is split by the beam splitter 97 into reflected light and transmitted light. Of these, the reflected light is the Glan-Thompson prism 9
The polarization direction is aligned at 8 and the lens 9c causes the sensor 10c.
Is focused on. Glan Thomson prism 98, lens 9
c constitutes an element of the reference beat forming means. At this time, the sensor 10c obtains an interference beat signal (reference beat signal) IC as described later.

On the other hand, the light transmitted through the beam splitter 97 is divided into two by the beam splitter 35 via the collimator lens 2 and enters the polarization optical element 38. The light reflected by the beam splitter 35 is shielded by the light blocking portion 3 of the polarization optical element 38.
It is shielded by 8c. Then, only the light transmitted through the beam splitter 35 enters the diffraction grating 15. At this time, the p-polarized light 20 of frequency f1 and the s-polarized light 39 of frequency f2 are incident on the diffraction grating 15.

Of the diffracted lights of the same order diffracted by the diffraction grating 15, for example, p-polarized first-order diffracted light 20c of frequency f1
The first-order diffracted light 39c of frequency f2 in the s-polarized light and the s-polarized light is reflected by the mirror 5, passes through the lens 6, the Glan-Thompson prism 7, and the edge mirror 8 in this order, and the sensor 9b passes through the lens 9b.
It is focused on. The mirror 5, the lens 6, the Glan-Thompson prism 7, the lens 9b and the like constitute one element of the measurement beat signal forming means. At this time, the sensor 10b obtains an interference beat signal (measurement beat signal) Ib of the diffracted lights 20c and 39c.

Here, the interference beat signal Ib obtained by the sensor 10b does not include the term of the phase change due to the displacement of the diffraction grating 15, and can be written as follows. Ib = IOexp {(w1-w2) t + ([phi]-[phi] s)}, where [phi] p and [phi] s are the amounts of phase change during diffraction that differ depending on the material and shape of the diffraction grating 15 for p-polarized light and s-polarized light, respectively.・ (50)

On the other hand, the reference beat signal Ic obtained by the sensor 10c can be written as follows: Ic = IOexp {(w1-w2) t} (51) Here, from the equation (35), (36) When the phase difference Δφ in the equation is taken, Δφ = φp−φs (52)

The phase changes φp and φs depend on the material and shape of the diffraction grating 15. Now, the material is constant (for example, a resist pattern on silicon) and the pattern thickness is constant (the resist pattern is spin-coated in nm order). The phase difference φp and φs depends on the line width of each grating of the diffraction grating 15.

In this embodiment, the reference beat signal Ic from the sensor 10c is selected by the selection means 99 and input to the phase difference meter 11. The interference beat signal Ib from the sensor 10b is input to the phase difference meter 11. And phase difference meter 1
The phase difference Δφ of the equation (52) is obtained in 1 and the line width of each grating of the diffraction grating 15 is obtained from this.

FIG. 23 is an explanatory view showing a wafer for which optimum exposure conditions of the optical stepper are set. This figure is for finding the exposure condition for obtaining a desired line width by changing the exposure amount and focus position of the stepper for each shot and printing a line and base or the like. It is usually necessary to find optimum exposure conditions when starting a new semiconductor process or periodically because of stepper aging.

A diffraction grating having a resist thickness of 1 μm and a design line and base of 1 μm was printed on the wafer while changing the exposure amount and focus. The line widths of the diffraction gratings of the shot A and the shot B were measured with a laser microscope and found to be 0.99 μm and 0.81 μm. When the same wafer was measured by the line width measuring apparatus of the present invention shown in FIG. 22, the phase difference Δφ was 0.838 radians and 0.524 radians.

FIG. 24 shows the experimental result of the relationship between the line width and the phase difference Δφ in this example. The signal stability is completely unaffected by air fluctuations because the beam optical path is completely common path, and depends on the stability of the phase difference meter.
It was 62 radians. This value is 3.
This corresponds to 5 nm and has a resolution of the order of several nm. In the present embodiment, when obtaining the absolute line width, it may be configured in advance by using a length measuring SEM or the like.

[0140]

As described above, according to the present invention, by providing the measuring means or the correcting means for canceling the phase change caused by the change of the material or the shape of the diffraction grating, the position for the change of the material or the shape of the diffraction grating can be obtained. It is possible to achieve a positional deviation detection method and a detection apparatus using the positional deviation detection method that can detect the positional deviation with high accuracy without being affected by the semiconductor element manufacturing process.

Further, by measuring the phase difference between diffracted lights of the same order of two light fluxes having different polarization directions, it is possible to achieve a line width measuring method and a line width measuring device which are inexpensive, easy to handle and highly accurate.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram in which the optical path of FIG. 1 is expanded.

FIG. 3 is an enlarged explanatory view of a part of FIG.

FIG. 4 is an enlarged explanatory view of a part of FIG.

FIG. 5 is a schematic view of the essential portions of Embodiment 2 of the present invention.

FIG. 6 is an enlarged explanatory view of a part of FIG.

FIG. 7 is a schematic view of the essential portions of Embodiment 3 of the present invention.

FIG. 8 is an enlarged explanatory diagram of a part of FIG.

FIG. 9 is a schematic view of the essential portions of Embodiment 4 of the present invention.

FIG. 10 is an enlarged explanatory view of a part of FIG.

FIG. 11 is an enlarged explanatory view of a part of FIG.

FIG. 12 is a schematic view of the essential portions of Embodiment 5 of the present invention.

FIG. 13 is a schematic view of the essential portions of Embodiment 6 of the present invention.

FIG. 14 is a schematic view of the essential portions of Embodiment 7 of the present invention.

FIG. 15 is an enlarged explanatory diagram of a part of FIG.

FIG. 16 is a schematic view of a portion of Example 8 of the present invention.

FIG. 17 is a flowchart of the first embodiment of the present invention.

FIG. 18 is a flowchart of Embodiment 5 of the present invention.

FIG. 19 is a schematic view of a main part of a conventional positional deviation detecting device.

20 is an enlarged explanatory view of a part of FIG.

FIG. 21 is an enlarged explanatory view of a part of FIG.

FIG. 22 is a schematic view of the essential portions of Embodiment 9 of the present invention.

FIG. 23 is an explanatory diagram on the wafer surface of FIG. 22.

FIG. 24 is an explanatory diagram showing the relationship between the line width of the diffraction grating and the phase difference.

[Explanation of symbols]

1: Dual frequency orthogonal laser 2, 6, 9a, 9b: Lens 3: Polarization beam splitter 4a, 4b, 5: Mirror 7: Gran Thomson prism 8: Edge mirror 10a, 10b: Sensor 11: Phase difference meter 12: Storage device 13: arithmetic unit 14: Stage control device 15a, 15b: Diffraction grating 16: Wafer 17: Rotating stage 18: y stage 19: x stage 26a, 26b: Polarization converter 32: Deflection mirror 38: Polarizing optical element 50: Half mirror 51: Polarizing beam splitter 65: Mask 97: Beam splitter 98: Gran Thomson prism 99: Signal switching control unit 9c: Lens 10c: Sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 21/30 531J (56) References JP-A-5-203411 (JP, A) JP-A-5-87529 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 G01D 5/26-5/38 G03F 9/00-9/02 H01L 21/027

Claims (12)

(57) [Claims] To 1. A diffraction grating is irradiated with two different light beams having frequencies orthogonal polarization direction, a plurality of diffracted light from each other different orders resulting from diffraction grating synthesized by heterodyne interference to obtain a plurality of beat signals, When detecting a displacement of the diffraction grating from a predetermined position by using the phase difference of the plurality of beat signals , p-polarized light having a frequency of f1 enters the diffraction grating.
+ N-order diffracted light generated when reflected and frequency f2
The n-th order diffracted light that occurs when light is incident is synthesized.
To generate the first beat signal by
-N order that occurs when p-polarized light with a number of f1 is incident
When diffracted light and s-polarized light with frequency f2 are incident
The generated + n-th order diffracted light is combined to cause heterodyne interference and
2 beat signals are generated, and the phases of the first and second beat signals are generated.
The difference based on the property of the diffraction grating is obtained by obtaining the difference.
1, Correct the phase error of the 2nd beat signal and detect the position shift
A method for detecting a positional shift, which is characterized in that 2. A heterodyne structure in which two light beams having polarization directions orthogonal to each other and having different frequencies are incident on a first diffraction grating and a second diffraction grating, and two diffracted lights having different orders generated from the first diffraction grating are combined. Generate the first beat signal by interfering,
A first phase difference detecting step of generating two second beat signals by combining two diffracted lights of different orders generated from the second diffraction grating to cause heterodyne interference, and detecting a phase difference between the first and second beat signals. Then, the two light fluxes are made incident on the first and second diffraction gratings, and at this time, two diffracted lights of different orders generated from the first and second diffraction gratings are combined and heterodyne interference is obtained to obtain a beat signal. At this time, the second phase difference detection for generating the third and fourth beat signals for correcting the phase error between the beat signals based on the property of the diffraction grating and detecting the phase difference between the third and fourth beat signals And a relative position shift between the first and second diffraction gratings is detected by using the phase difference obtained in the first phase difference detecting step and the second phase difference detecting step. The positional deviation detection method. 3. In the second phase difference detecting step, the substrate on which the first and second diffraction gratings are formed is rotated by 180 degrees in the first phase difference detecting step, and is generated from the first diffraction grating. The two diffracted lights are combined to cause heterodyne interference to generate a third beat signal, and the two diffracted lights generated from the second diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal to generate the third beat signal. 3. The positional deviation detecting method according to claim 2, wherein the phase difference between the 4-beat signals is detected. 4. In the second phase difference detecting step, the polarization direction of the light incident on the first and second diffraction gratings is rotated by 90 degrees in the first phase difference detecting step, and the light generated by the first diffraction grating is changed by 90 degrees. The three diffracted lights are combined to cause the heterodyne interference to generate the third beat signal, and the two diffracted lights generated from the second diffraction grating are combined to cause the heterodyne interference to generate the fourth beat signal to generate the third beat signal. 3. The positional deviation detecting method according to claim 2, wherein the phase difference between the beat signals is detected. 5. In the second phase difference detecting step, the two light fluxes irradiating the first and second diffraction gratings are exchanged with each other in the first phase difference detecting step, and at this time, two light beams generated from the first diffraction grating are exchanged. The three diffracted lights are combined to cause the heterodyne interference to generate the third beat signal, and the two diffracted lights generated from the second diffraction grating are combined to cause the heterodyne interference to generate the fourth beat signal to generate the third beat signal. 3. The positional deviation detecting method according to claim 2, wherein the phase difference between the 4-beat signals is detected. The method according to claim 6 wherein said second phase difference detection step is irradiated with the first of the two light beams in the first phase difference detection step, the two light beams from the same direction of irradiation of the second diffraction grating, said The two diffracted lights generated from the one diffraction grating are combined to cause the heterodyne interference to generate the third beat signal, and the second beat signal is generated.
3. The position shift according to claim 2, wherein the two diffracted lights generated from the diffraction grating are combined to cause heterodyne interference to generate a fourth beat signal, and the phase difference between the third and fourth beat signals is detected. Detection method. 7. The first phase difference detecting step combines + nth-order diffracted light of p-polarized light having a frequency of f1 and −nth-order diffracted light of s-polarized light having a frequency f2 and heterodyne interference in the first phase difference detecting step. A 1-beat signal is generated, and the + nth-order diffracted light of the p-polarized light having the frequency f1 and the −n-order diffracted light of the s-polarized light having the frequency f2 and the −nth-order diffracted light from the second diffraction grating are combined to cause the heterodyne interference and the second beat signal Is generated and the phase difference between the first and second beat signals is detected. In the second phase difference detecting step, the + nth order diffracted light of the frequency f2 from the first diffraction grating and the p-polarized light and the frequency f1 are detected. , The s-polarized -nth-order diffracted light is combined to cause the heterodyne interference to generate the third beat signal,
The + nth-order diffracted light of the p-polarized light having the frequency f2 and the −nth-order diffracted light of the s-polarized light having the frequency f1 and the −nth-order diffracted light from the second diffraction grating are combined to generate the fourth beat signal by heterodyne interference.
3. The position shift detecting method according to claim 2, wherein the phase difference between the third and fourth beat signals is detected. 8. The polarization directions are orthogonal to each other and the frequency is
The two light fluxes from the light source means for generating two different light fluxes are made incident on the diffraction grating through the illumination means that regulates the frequency, polarization, incident angle, etc., and the diffracted light from the diffraction grating is combined by the combining means to form a beat. The interference light is formed, and the beat interference light is photoelectrically detected by photoelectric detection means to form a first beat signal.
The light flux an optical path and through to form a second beat signal in the same manner that is different from the optical path of the light based on the first beat signal, first, the phase difference of the second beat signal detected by the phase difference meter, The phase error of the beat signal based on the property of the diffraction grating is detected by the phase error detecting means, and the arithmetic operation unit obtains the displacement of the diffraction grating from the predetermined position based on the phase difference and the phase error. A positional deviation detection device characterized by the above. 9. The polarization directions are orthogonal to each other and the frequency is
The two light fluxes from the light source means for generating two different light fluxes are made incident on the diffraction grating through the illumination means for controlling the frequency, the polarization, the incident angle, etc., and the p-polarized + n-order diffracted light having the frequency f1 generated from the diffraction grating. And the s-polarized -nth-order diffracted light at the frequency f2 is combined by the synthesizing means to form the first beat signal, and the frequency generated from the diffraction grating is f1 and the p-polarized -nth-order diffracted light is at the frequency f2. The polarized + nth order diffracted light is combined by the combining means to form the second beat signal, the phase difference between the first and second beat signals is obtained by the phase difference meter, and the signal from the phase difference meter is used. A positional deviation detecting device, characterized in that the positional deviation of the diffraction grating from a predetermined position is obtained. 10. The light source means is a dual frequency orthogonal polarization laser.
Or a light source using a photoacoustic optical element,
The positional deviation detection device according to claim 8 or 9. 11. A measuring beat signal is obtained by causing two light beams, whose polarization directions are orthogonal to each other and having different frequencies , to enter a diffraction grating, and combining diffracted lights of the same order generated from the diffraction grating to cause heterodyne interference to obtain a measurement beat signal. A reference beat signal is obtained by combining light fluxes and causing heterodyne interference, and a grating line width forming the diffraction grating is measured by using a phase difference between the measurement beat signal and the reference beat signal. Characteristic line width measurement method. 12. The polarization directions are different from each other and the frequency is
Light source means for generating two different light fluxes, reference beat forming means for dividing a part of the two light fluxes to form a reference beat signal, illuminating means for irradiating the two light fluxes on a diffraction grating, and the same light source from the diffraction grating. A measurement beat signal forming unit that forms a measurement beat signal by heterodyne interfering diffracted light of orders, a phase difference meter that measures a phase difference between the reference beat signal and the measurement beat signal, and the phase difference is used And a calculator for calculating the line width of the grating forming the diffraction grating.