JP3490797B2 - Pattern position measuring method and optical device 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 measuring method and an optical device using the same, and more particularly, it is applied to aligning a wafer and a mask in an exposure step which is one step of manufacturing a semiconductor integrated circuit device. And effective technology.

[0002]

2. Description of the Related Art In semiconductor integrated circuit devices, high integration and fine processing are being promoted, and accordingly, fine patterns are required.

In the process of manufacturing a semiconductor integrated circuit device,
For example, it is necessary to superimpose patterns of a plurality of layers, for example, dozens of layers, with their positions being accurately aligned with each other. If the pattern shifts between different layers, the reliability and yield of the semiconductor integrated circuit device are reduced.

Therefore, for example, an integrated circuit pattern formed on a mask such as a reticle or a photomask (in this specification, substrates on which a pattern such as the reticle or photomask is drawn is generically referred to as a mask) is used. In the exposure step of transferring onto a wafer such as a semiconductor wafer, the position of an integrated circuit pattern already formed on the wafer is measured, the pattern is aligned with the pattern on the mask, and then the exposure process is performed. ing.

The alignment is necessary not only in the exposure method using a mask, but also in the exposure method not using a mask such as a direct writing method using an electron beam or an ion beam. In addition, the position measurement of the pattern formed on the wafer is performed by measuring the positions of the integrated circuit patterns of two different layers in the overlay accuracy measuring device that inspects the alignment accuracy of the exposure device, and measuring their relative positions. The same is done in the method of obtaining.

As a study by the present inventor, in measuring the position of a pattern formed on a wafer, an optical image of the pattern detected by an image sensor or the like is converted into an image signal, and the image signal is disclosed in, for example, Japanese Patent Laid-Open No. 53-53. -69063 publication, the symmetry matching method and the template matching method described in "Image Analysis Handbook" (published in the first edition of 1991) published by The University of Tokyo Press. You can

These algorithms use the image signal f
At each position x on (x), an evaluation function F (x) indicating the centrality of the integrated circuit pattern on the wafer is obtained, and the position [x] having the extreme value is detected to determine the central position of the integrated circuit pattern. It is what you want. In the calculation formula of this evaluation function, as an example of the calculation formula of the evaluation function of the symmetry matching method,

[0008]

[Equation 1]

What is indicated by is known. this is,
This is a value obtained by integrating the squared value of the difference between the left and right signal values that are equidistant j from the virtual center position x with the folding width w on the left and right of the virtual center position x, and the signals are symmetrical at the center position of the integrated circuit pattern. , And the evaluation function F (x) is minimized.

As an example of the calculation formula of the evaluation function of the template matching method,

[0011]

[Equation 2]

The one indicated by is known. this is,
Center O of template data t (x) and image signal f
When the virtual center x of (x) is overlapped, the sum of squares of the difference between the function f (x) and the function t (x) is minimized in the left and right integration range w.

The calculation formula of the evaluation function used in the processing of the image signal is known to be modified in several kinds other than the above-mentioned one, but all of them are selected based on a single algorithm or some judgment condition. Has been used.

[0014]

However, the present inventor has found that the above-described pattern position measuring method has various problems as described below.

That is, a semiconductor integrated circuit pattern is formed by repeatedly stacking thin films such as a photoresist film or an insulating film on a wafer, and a positioning pattern as an alignment mark is also formed by a process such as etching. It has a structure in which thin films are stacked on the step pattern and has non-uniformity depending on the precision of processing.

Even if the alignment pattern has no nonuniformity, the photoresist film coated on the alignment pattern may have nonuniformity due to factors such as spin coating.

As a result, when a pattern having such a structure is optically detected, the image signal changes in a complicated manner due to the influence of light wave interference and the like, resulting in erroneous detection and measurement error.

For such a problem, it may be possible to take a measure to reduce the fluctuation by widening the detection wavelength and selecting a plurality of optical systems.

However, as the high integration of the semiconductor integrated circuit device further progresses in the future, the required alignment accuracy becomes higher, and the step difference on the wafer becomes higher. There is a demand for a technology capable of accommodating highly complex changes in

In response to such a request, using the symmetry matching method or the template matching method makes it difficult to reduce erroneous detection due to the local extreme value of the evaluation function, and the measurement due to the asymmetry of the pattern. It is difficult to adjust the parameters to reduce the value shift, and even if high-precision alignment is possible in a specific process, the alignment accuracy decreases when the process changes or the quality of the process changes. There is a problem of doing.

An object of the present invention is to provide a pattern position measuring method which can measure with high accuracy.

Another object of the present invention is to provide an optical device using a pattern position measuring method capable of highly accurate measurement.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0024]

The typical ones of the inventions disclosed in the present invention will be outlined below.

The pattern position measuring method according to the present invention is applied to a pattern formed on a wafer and a pattern formed on the mask, which are arranged on the wafer separated from each other on the wafer. A method for measuring the position of a pattern formed on a wafer when aligning a transferred image, wherein the position of the pattern is measured by processing an image signal of the image of the pattern formed on the wafer. At this time, by changing both the position in the actual waveform where the center position of the template is superposed and the parameter relating to the shape of the template, by obtaining the combination of the parameters in which the actual waveform and the template best match,
The position of the pattern on the wafer shall be detected and measured.

[0026]

According to the above-described pattern position measuring method of the present invention, when the pattern position is measured by processing the image signal of the image of the pattern formed on the wafer, the center position of the template is superposed. The position of the pattern on the wafer is detected and measured by determining the combination of the parameters that best match the actual waveform and the template while changing both the position in the waveform and the parameter relating to the shape of the template.

Therefore, when the image signal of the image of the pattern formed on the wafer is processed to measure the position of the pattern, a parameter indicating the virtual center of the actual waveform, that is, the position of the center of the template data on the actual waveform. By simultaneously changing the parameters relating to the shape of the template, the combination of the parameters that best matches the actual waveform is obtained, and the virtual center of the actual waveform at that time is set as the center position of the pattern formed on the wafer.

As a result, since the virtual center of the actual waveform is calculated while changing the shape of the template so as to best match the change of the waveform, the position of the image of the pattern on the wafer does not depend on the change of the waveform. It can be measured with high accuracy.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and a duplicate description will be omitted.

(Embodiment 1) FIG. 1 is a schematic configuration diagram showing an exposure apparatus having a pattern position measuring method which is an embodiment of the present invention. The pattern position measuring method of the present invention and an optical device using the same will be specifically described with reference to FIG.

In FIG. 1, reference numeral 1 denotes a mask having an integrated circuit pattern for manufacturing a semiconductor integrated circuit device, for example.
2 is, for example, a semiconductor wafer or an SOI (Silico) which is a starting material for manufacturing a semiconductor integrated circuit device.
wafer, such as a wafer.

Reference numeral 3 denotes a projection exposure system, and the projection exposure system 3 is
An image of the integrated circuit pattern formed on the mask 1 is formed on the wafer 2 by the mercury lamp 4, the reflecting mirror 4a, the condenser lens 5, and the reduction lens 6, and the wafer 2 is spin-coated by a spin coating method or the like. The applied photoresist film can be exposed to transfer the pattern.

Reference numeral 20 denotes a mask position detection system. The mask position detection system 20 is composed of an optical component 7, an optical component 8, a light source 9 and a detector 10, and can measure the position of the mask 1.

Reference numeral 11 denotes a wafer position detection system. The wafer position detection system 11 is composed of a mirror 12, a half mirror 13, a light source 14 and a detector 15. The illumination light of the light source 14 is irradiated onto the wafer 2 to reflect it. By guiding the light to the detector 15, an image of the pattern formed on the wafer 2 can be formed and converted into an image signal.

Reference numeral 16 denotes a position measurement calculation system. The position measurement calculation system 16 is a detector 15 in the wafer position detection system 11.
Thus, the position of the pattern converted into the image signal can be measured.

Reference numeral 18 denotes a control system, and the control system 18 is XY
The stage 17 and the wafer position detection system 11 can be controlled, and the XY stage 17 is moved to measure the position of the alignment pattern using, for example, alignment marks at a plurality of positions on the wafer 2, and the mask 1 is measured. The coordinate calculation for superimposing the projected image of the pattern on the pattern on the wafer 2 can be performed.

Further, the control system 17 can control the signal for transferring the projected image of the pattern on the mask 1 onto the wafer 2 by moving the XY stage 17 to the coordinates obtained by the method described above.

2A and 2B are views showing a positioning pattern 21 using, for example, an alignment mark formed on the wafer 2. FIG. 2A is a plan view and FIG. 2B is a sectional view.
2B, the photoresist film 22 is formed on the step portion of the alignment pattern 21 formed in the etching process.
Is applied.

FIG. 3 is a waveform diagram showing the image signal of the alignment pattern 21 converted by the wafer position detection system 11, and the alternate long and short dash line shows the center of the pattern. The image signal is deformed due to scattering at the step portion, difference in reflectance between the underlying portion and the pattern portion, and modulation at the end portion due to change in shape and film thickness of the step portion, and its waveform largely changes depending on the process.

FIG. 4 is a diagram showing an evaluation function showing the centrality of the pattern obtained from the image signal shown in FIG. 3, and shows false detections and measurement errors that occur when a single algorithm is used. Explaining. As shown in FIG. 4, there is a local minimum value 19 having a level close to the local minimum value indicating the center of the pattern. Further, the position of the minimum value is shifted from the true position at the center of the pattern due to the asymmetry of the image signal. Reference numeral 19a indicates the distance being shifted.

The pattern position measuring method of this embodiment is such that when the image signal of the image of the pattern formed on the wafer 2 in the above-mentioned exposure apparatus is processed to measure the position of the pattern, the virtual center of the actual waveform is measured. That is, by simultaneously changing the parameter indicating the position of centering template data described later on the actual waveform and the parameter relating to the shape of the template, the combination of the parameters that best matches the actual waveform is obtained, and the virtual waveform of the actual waveform at that time is obtained. The center is the center position of the pattern formed on the wafer 2.

FIG. 5 is a diagram showing a template used in the pattern position measuring method of this embodiment. In FIG. 5, p1 indicates the pattern width, p2 indicates the edge portion scattering, and p3 indicates the pattern portion reflection intensity, and p1, p2 and p
3 is a parameter that defines the shape of the template of this embodiment.

Further, in the pattern position measuring method of the present embodiment, the shape of the template is changed while searching the pattern position center during the processing operation of the template matching.

Even in the same process, since the scattering of the edge portion and the reflection intensity of the pattern portion are changed as shown in the three examples in FIG. By deforming the template, the minimum value indicating the center position can be kept small regardless of the shape of the actual waveform, and it is possible to prevent erroneous detection because there is no reversal with the local minimum. Further, by changing the shape of the template as well, the convergence of the multi-parameter optimization calculation is improved, so that the pattern position can be detected with high accuracy.

The method of simultaneously optimizing the virtual center of the actual waveform and the shape parameter of the template is as follows.

The function corresponding to the waveform of the template is T
(X, p1, p2, p3), and the function corresponding to the detected actual waveform is R (x).

Also, the evaluation function E is

[0048]

[Equation 3]

It is assumed that

In the pattern position measuring method of the present embodiment, the evaluation function E is not only the virtual center c of the actual waveform but also the function of the parameters p1, p2, p3 relating to the shape of the template. Is different from.

The parameters c, p1, p2, p are set so as to simultaneously satisfy the equations (4), (5), (6) and (7).
If 3 is determined, the shape of the template having the smallest difference from the actual waveform and the most likely position in the actual waveform obtained when using the template can be obtained at the same time.

[0052]

[Equation 4]

[0053]

[Equation 5]

[0054]

[Equation 6]

[0055]

[Equation 7]

As an optimization method of the evaluation function using a plurality of parameters necessary for the above-mentioned calculation processing, for example, C
It is possible to use the Gauss-Newton method described in “Waveform Data Processing for Scientific Measurement” (written by Shigeo Minami, 1986) published by Q Publishing.

When the position measurement of the pattern is always performed with high accuracy, the above-mentioned arithmetic processing using the template shown in FIG. 5 may be carried out for each detection of the pattern center position. Even a detection signal from the alignment pattern in the same process, the same lot, and the same wafer can be detected by the state of the underlying film such as the thickness of the photoresist film or a minute fluctuation in the thickness of the photoresist film. Since the actual waveform changes, the pattern center position can be detected with high accuracy every time by optimizing the shape of the template for each waveform, so that the position of the pattern can be measured with high accuracy.

When it is desired to detect the pattern center position at high speed, the above-mentioned arithmetic processing using the template shown in FIG. 5 is performed only once at the time of setting the condition of the pattern position detecting system. The parameter relating to the shape of the template obtained at that time may be used as it is in the subsequent detection of the pattern center position.

That is, the pattern center position detection from the second time onward may be determined by a fixed template. In this case, the parameters to be determined at the second and subsequent pattern position detections are reduced only to the virtual center of the actual waveform and the amount of calculation is reduced, so that the pattern center position detection time can be shortened.

Further, the frequency at which the pattern center position detection for simultaneously determining the parameters relating to the shape of the template is performed is set not only when the conditions of the pattern position detection system are set, but also at the beginning of each process, the beginning of each lot or the beginning of each wafer. By doing so, it is possible to finely respond to the shape of the actual waveform that gradually changes even in the same process. By properly setting the frequency of such pattern center position detection, the detection time can be shortened without degrading the accuracy of pattern center position detection.

In the above-described pattern position measuring method of this embodiment, when the image signal of the image of the pattern formed on the wafer 2 is processed to measure the pattern position, the center position of the template is superposed. The position of the pattern on the wafer 2 is detected and measured by determining the combination of the parameters that best match the actual waveform and the template while changing both the position in the waveform and the parameter relating to the shape of the template. .

Therefore, when the image signal of the image of the pattern formed on the wafer 2 is processed to measure the position of the pattern, the virtual center of the actual waveform, that is, the position of the center of the template data on the actual waveform is shown. By simultaneously changing the parameters and the parameters relating to the shape of the template, a combination of parameters that best matches the actual waveform is obtained, and the virtual center of the actual waveform at that time is set to the wafer 2
This is the center position of the pattern formed above.

As a result, since the virtual center of the actual waveform is calculated while changing the shape of the template so as to best match the change in the waveform, the position of the image of the pattern on the wafer 2 does not depend on the change in the waveform. It can be measured with high accuracy.

In the conventional template matching method, if an appropriately selected template is used,
Since a relatively macroscopic feature can be captured, the extreme value of the evaluation function corresponding to the center position of the pattern can be kept sharp and the variation in detection can be reduced. However, if the template is fixed, there is a problem that the sharpness of the extreme value of the evaluation function indicating the center of the pattern decreases due to the change of the waveform, and the dispersion of the measured values increases.

On the other hand, according to the pattern position measuring method of the present embodiment, the shape of the template is changed in accordance with the change of the waveform, so that the convergence of the parameter optimization calculation is maintained and the variation of the measured value is kept. Can be kept small.

Further, in the pattern position measuring method of the present embodiment, a template having left and right independent shape-related parameters is used as a template so that a left-right asymmetric shape can be expressed.

As a result, the virtual center of the actual waveform can be obtained while optimizing the shape of the template independently on the right and left sides, so that the position of the pattern on the wafer 2 can be measured with high accuracy even from an asymmetrical waveform. can do.

In the conventional symmetry matching method, if the symmetry with respect to the center of the pattern is maintained even if the shape of the waveform is largely changed, the extreme value corresponding to the center of the pattern appears sharply and the accuracy is high. It is possible to measure
If the asymmetry of the change in the waveform becomes strong, the peripheral extreme value and the extreme value at the center of the pattern become close to each other, so that there is a problem that erroneous detection easily occurs. Further, even if there is no erroneous detection, the extreme value corresponding to the center of the pattern shifts, and as a result, the measured value also shifts.

On the other hand, according to the pattern position measuring method of the present embodiment, the shape of the template can be changed left and right independently so as to maintain the degree of coincidence even for an asymmetrical waveform, so that the extreme value The level can be kept small and shifts can be prevented.

Further, in the pattern position measuring method of the present embodiment, the calculation process for simultaneously determining the parameters relating to the virtual center of the actual waveform and the template shape is carried out every time the position of the alignment pattern formed on the wafer 2 is detected. It is possible to optimize by using the virtual center of the actual waveform as a parameter by substituting the result obtained earlier for the parameter relating to the shape of the template.

As a result, the parameters relating to the shape of the template obtained at the time of the first detection of the pattern position on the wafer 2 can be fixed thereafter, and the optimization calculation can be performed using only the virtual center of the actual waveform as a parameter. The time required for detecting the position of the pattern on the wafer 2 can be shortened while maintaining accuracy.

Further, in the optical apparatus such as the exposure apparatus using the pattern position measuring method of the present embodiment, the pattern position can be measured with high accuracy, so that the pattern formed on the mask 1 is The alignment with the pattern formed on the wafer 2 can be performed with high accuracy.

As a result, the pattern formed on the mask 1 and the pattern formed on the wafer 2 can be aligned with high accuracy in the exposure step in the manufacturing process of the semiconductor integrated circuit device. It is possible to manufacture a semiconductor integrated circuit device having fine processing and a high degree of integration with a high manufacturing yield.

(Embodiment 2) FIG. 7 is a diagram showing a template used in a pattern position measuring method according to another embodiment of the present invention.

In the first embodiment described above, as shown in FIG. 2, the photoresist film 2 on the alignment pattern 21 is formed.
In the shape of No. 2, the photoresist film 22 is applied by a spin coating method such as spin, and the photoresist film 22 is applied from one direction with respect to the alignment pattern 21.
Since the photoresist forming the photoresist flows in, the shape of the photoresist film 22 is often different between the right and left of the alignment pattern 21 as shown in FIG.

The waveform obtained from the image signal of the image of the alignment pattern 21 has a bilaterally asymmetrical shape, as shown in FIG.

Therefore, in order to correspond to these actual waveforms, the template of which an example is shown in FIG. 7 is used. In FIG. 7, p1r is the right pattern width, p1s is the left pattern width, p2r is the right edge scattering, p2s is the left edge scattering, and p3 is the pattern reflection intensity, p1
r, p1s, p2r, p2s and p3 are parameters defining the shape of the template of this embodiment.

If the parameters relating to the shape of the template shown in FIG. 7 and the virtual center of the actual waveform are simultaneously optimized by the above method, the pattern position center is searched while deforming the template so as to best overlap the asymmetric actual waveform. Therefore, it is possible to suppress the shift of the detection result from the true position, which occurs when using the bilaterally symmetric template, so that the pattern position can be detected with high accuracy.

When the position measurement of the pattern is always performed with high accuracy, the above-mentioned arithmetic processing using the template shown in FIG. 7 may be carried out for each detection of the pattern center position. Even a detection signal from the alignment pattern in the same process, the same lot, and the same wafer can be detected by the state of the underlying film such as the thickness of the photoresist film or a minute fluctuation in the thickness of the photoresist film. Since the actual waveform changes, the pattern center position can be detected with high accuracy every time by optimizing the shape of the template for each waveform, so that the position of the pattern can be measured with high accuracy.

Further, like the template of this embodiment,
The detection of the pattern center position can be made highly accurate also by increasing the parameters relating to the shape of the template. As the number of parameters of the template is increased, the change of the actual waveform can be more flexibly dealt with and the degree of coincidence can be increased.

(Embodiment 3) FIG. 10 is a schematic block diagram showing an overlay accuracy measuring apparatus having a pattern position measuring method which is another embodiment of the present invention.

The overlay accuracy measuring apparatus having the pattern position measuring method of this embodiment is an apparatus for measuring the pattern positions of two layers on a wafer and measuring the relative error between the pattern positions of the two layers. Thus, for example, it can be used for quality inspection of overlay accuracy of the exposure apparatus of the first embodiment described above.

In FIG. 10, the illumination light from the light source 23 includes the condenser lens 24, the half mirror 25, and the objective lens 2.
The wafer 2 is irradiated with the laser beam 6 through.

The reflected light reflected on the surface of the wafer 2 is magnified by the objective lens 26 and the relay lens 27 and guided to the detector 28, and the image of the pattern formed on the wafer 2 is converted into an image signal.

This image signal is processed by the image processing unit 29, and the relative error in the pattern position between the two layers is calculated. The control unit 30 moves the XY stage 31 and measures the relative error in the pattern position between the two layers at a plurality of points on the wafer 2. The distribution of the relative error of the pattern position measured in this way is statistically processed and converted into an error factor such as a reduction error of the pattern transferred by the reduction projection exposure apparatus, and used for accuracy control of the apparatus.

11A and 11B are views showing an example of the overlay accuracy measuring pattern formed on the wafer 2. FIG. 11A is a plan view and FIG. 11B is a sectional view.

The center Ca of the reference layer pattern 32 already formed on the wafer 2 and the center Cb of the newly transferred matching layer pattern are measured, and the relative error is Δx = Cb−.
Calculate as Ca.

FIG. 11C is a diagram showing an example of the measured image signal of the above-mentioned pattern. The image signal of the reference layer pattern 32 shown by a solid line frame and the image signal of the matching layer pattern 33 shown by a broken line frame. For each of the above, an evaluation function indicating the centrality of the pattern is obtained, the extreme value thereof is detected, and the center of each pattern is measured.

It is obvious that the method described in the first and second embodiments can be applied to the step of obtaining the evaluation function.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments,
It goes without saying that various changes can be made without departing from the spirit of the invention.

For example, the present invention can be applied to various optical devices such as a direct drawing device using an electron beam or the like and a device for measuring overlay accuracy of patterns.

[0092]

The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.
It is as follows.

(1) In the pattern position measuring method of the present invention, when measuring the position of the pattern by processing the image signal of the image of the pattern formed on the wafer, the actual waveform for superimposing the center position of the template The position of the pattern on the wafer is detected and measured by determining the combination of the parameters that best match the actual waveform and the template while changing both the internal position and the parameter relating to the shape of the template.

Therefore, when the image signal of the image of the pattern formed on the wafer is processed to measure the position of the pattern, a parameter indicating the virtual center of the actual waveform, that is, the position where the center of the template data is placed on the actual waveform. By simultaneously changing the parameters relating to the shape of the template, the combination of the parameters that best matches the actual waveform is obtained, and the virtual center of the actual waveform at that time is set as the center position of the pattern formed on the wafer.

As a result, the virtual center of the actual waveform is calculated while changing the shape of the template so as to best match the change of the waveform, so that the position of the pattern image on the wafer does not depend on the change of the waveform. It can be measured with high accuracy.

In the conventional template matching method, if an appropriately selected template is used,
Since a relatively macroscopic feature can be captured, the extreme value of the evaluation function corresponding to the center position of the pattern can be kept sharp and the variation in detection can be reduced. However, if the template is fixed, there is a problem that the sharpness of the extreme value of the evaluation function indicating the center of the pattern decreases due to the change of the waveform, and the dispersion of the measured values increases.

On the other hand, according to the pattern position measuring method of the present invention, the shape of the template is changed according to the change of the waveform, so that the convergence of the parameter optimization calculation is maintained and the variation of the measured values is reduced. Can be kept.

(2) In the pattern position measuring method of the present invention, a template having left and right independent shape-related parameters is used as a template so that a left-right asymmetric shape can be expressed.

As a result, the virtual center of the actual waveform can be obtained while optimizing the shape of the template independently on the right and left sides, and thus the position of the pattern on the wafer can be measured with high accuracy even from the asymmetrical waveform. be able to.

In the conventional symmetry matching method, if the symmetry with respect to the center of the pattern is maintained even if the shape of the waveform is largely changed, the extreme value corresponding to the center of the pattern appears sharply and the accuracy is high. It is possible to measure
If the asymmetry of the change in the waveform becomes strong, the peripheral extreme value and the extreme value at the center of the pattern become close to each other, so that there is a problem that false detection is likely to occur. Further, even if there is no erroneous detection, the extreme value corresponding to the center of the pattern shifts, and as a result, the measured value also shifts.

On the other hand, according to the pattern position measuring method of the present invention, the shape of the template can be independently changed to the left and right so as to maintain the degree of coincidence even with an asymmetrical waveform. Can be kept small,
Moreover, shifting can be prevented.

(3) In the pattern position measuring method of the present invention, the calculation process for simultaneously determining the parameters relating to the virtual center of the actual waveform and the shape of the template is performed every time the position of the alignment pattern formed on the wafer is detected. Instead, the template shape parameters can be used by substituting the results obtained earlier, and only the virtual center of the actual waveform can be used as a parameter for optimization.

As a result, the parameters relating to the shape of the template obtained at the time of the first detection of the pattern position on the wafer can be fixed thereafter, and the optimization calculation can be performed using only the virtual center of the actual waveform as a parameter. The time required to detect the position of the pattern on the wafer can be shortened while maintaining accuracy.

(4) In the optical device such as the exposure device using the pattern position measuring method of the present invention, the position of the pattern can be measured with high accuracy, so that the pattern formed on the mask and the wafer. The alignment with the pattern formed on the substrate can be performed with high accuracy.

As a result, in the exposure process in the manufacturing process of the semiconductor integrated circuit device, the pattern formed on the mask and the pattern formed on the wafer can be aligned with high accuracy, which results in high manufacturing. It is possible to manufacture a semiconductor integrated circuit device having a fine processing and a high degree of integration with a high yield.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an exposure apparatus having a pattern position measuring method according to an embodiment of the present invention.

2A and 2B are diagrams showing an alignment pattern formed on a wafer, wherein FIG. 2A is a plan view and FIG. 2B is a sectional view.

FIG. 3 is a waveform diagram showing an image signal of the alignment pattern converted by the wafer position detection system.

FIG. 4 is a diagram showing an evaluation function showing the centrality of a pattern obtained from the image signal shown in FIG.

FIG. 5 is a diagram showing a template used in a pattern position measuring method according to an embodiment of the present invention.

FIG. 6 is a diagram showing a detected waveform obtained from an image signal of an image of a positioning pattern on a wafer. (A)-(c) is a figure which shows the example of each detected waveform.

FIG. 7 is a diagram showing a template used in a pattern position measuring method according to another embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating the occurrence of coating unevenness in a photoresist film.

9 is a diagram showing a detected waveform obtained from an image signal of the image of the alignment pattern on the wafer shown in FIG. (A)
And (b) are diagrams showing examples of detected waveforms.

FIG. 10 is a schematic configuration diagram showing an overlay accuracy measuring device having a pattern position measuring method according to another embodiment of the present invention.

11A and 11B are diagrams showing a pattern for overlay accuracy measurement formed on a wafer, FIG. 11A is a plan view, FIG. 11B is a sectional view, and FIG. 11C is a diagram showing image signals.

[Explanation of symbols] 1 mask 2 wafers 3 Projection exposure system 4 Mercury lamp 4a reflector 5 Condensing lens 6 reduction lens 7 Optical parts 8 optical components 9 light sources 10 detectors 11 Wafer position detection system 12 mirror 13 Half mirror 14 Light source 15 detectors 16 Position measurement calculation system 17 XY stage 18 Control system 19 local minimum 19a Shifting distance 20 Mask position detection system 21 Positioning pattern 22 Photoresist film 23 Light source 24 Condenser lens 25 half mirror 26 Objective Lens 27 relay lens 28 detectors 29 Image processing unit 30 control unit 31 XY stage 32 reference layer pattern 33 Layering pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keizo Kuroiwa 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Inside the Semiconductor Business Division, Hitachi, Ltd. (72) Shinji Kuniyoshi 5 Suimizumoto-cho, Kodaira-shi, Tokyo Hitachi Co., Ltd. Semiconductor Business Division, Hitachi, Ltd. (72) Inventor, Maojima, Central 5-201-1, Kamimizuhonmachi, Kodaira-shi, Tokyo, Hitachi, Ltd., Semiconductor Business Division (56) Reference: JP-A-5-335212 (JP, A) JP-A-4-32219 (JP, A) JP-A-6-151274 (JP, A) JP-A-6-258045 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) G03F 9/00 H01L 21/027

Claims (5)

(57) [Claims] 1. A pattern formed on a wafer that is arranged at a distance from a mask on which a pattern is formed, and an image transferred on the wafer of the pattern formed on the mask are located. A method for measuring the position of a pattern formed on the wafer when performing alignment, wherein when measuring the position of the pattern by processing the image signal of the image of the pattern formed on the wafer, The position of the pattern on the wafer is determined by obtaining the combination of the parameters that best matches the actual waveform and the template while changing both the position in the actual waveform where the center position is superimposed and the parameter related to the shape of the template. A pattern position measuring method characterized by detecting and measuring. 2. The pattern position measuring method according to claim 1, wherein the shape of the template has a bilaterally asymmetrical shape. 3. The pattern position measuring method according to claim 1 or 2, wherein a parameter related to the shape of the template determined by obtaining a combination of the parameters in which the actual waveform and the template best match each other, A pattern position measuring method characterized by being used during position detection calculation. 4. An optical device, wherein the pattern position measuring method according to claim 1, 2, or 3 is used in an optical device. 5. The optical device according to claim 4, wherein the optical device irradiates the projection exposure system for projecting an image of a pattern formed on a mask onto a wafer with illumination light from a light source onto the wafer. A wafer position detection system that converts the image of the pattern formed on the wafer into an image signal by detecting the reflected light, and the position of the pattern on the wafer by processing the image signal An optical apparatus, which is an exposure apparatus having a position measurement calculation system for