JP2000058427A - Position detecting method and device, and manufacture of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an alignment operation of high accuracy to be carried out without being affected by uneven application of resist by a method wherein a rugged pattern of high symmetry is preferentially selected out of rugged patterns, and position data as to the rugged patterns are detected resting on a picture image obtained by picking up the rugged pattern. SOLUTION: The position (center position) of a mark is detected through an optical system. At this point, the mark which is judged excellent in symmetry resting on its cross sectional shape is preferentially selected out of marks (S4), and the picture image of the selected alignment mark of high symmetry is picked up by an image sensing means provided in a detection system, and position data on the alignment mark are detected resting on the picture image picked up by the image sensing means (S5). A circuit pattern on a reticule and a wafer are aligned with each other through the detected position data as to the alignment mark (S6), and a circuit pattern is transferred onto the wafer by exposure (S7). After an exposure operation that is carried out for all shots is finished, the wafer is taken out from a movable stage (S8), and processing is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting method and a position detecting device capable of measuring the position of an object to be measured with high accuracy and aligning the object to be measured to a predetermined position, and using the same. The present invention relates to a method of manufacturing a semiconductor device, and particularly to an apparatus for manufacturing a semiconductor element, in which a projection lens system sequentially projects and exposes an image of a circuit pattern on a reticle surface to each pattern area on a wafer and applies the circuit pattern to each pattern area on the wafer. This is suitable for a projection exposure apparatus called a stepper for manufacturing a semiconductor element, which is used for manufacturing a plurality of semiconductor devices by transferring the same.

[0002]

2. Description of the Related Art Conventionally, in a projection exposure apparatus for manufacturing a semiconductor device called a stepper, a circuit pattern on a reticle is sequentially reduced and projected onto each pattern area on a wafer by a reduction type projection optical system. The image of the circuit pattern is transferred to each pattern area. For this reason, in the stepper, it is necessary to precisely align each pattern area on the wafer with respect to the reticle and to perform projection exposure.

For this purpose, an alignment optical system for detecting a plurality of positioning step patterns (alignment marks) formed on a wafer by a stepper to obtain position information of the plurality of positioning step patterns (alignment marks) is provided. .

Conventionally, an alignment method using this type of alignment optical system has been disclosed in Japanese Patent Laid-Open No. Hei 5-13304.
TTL alignment method is disclosed in JP-A-64-8
No. 9327 discloses an off-axis alignment method. The TTL alignment method is a method of directly observing the alignment between the reticle and the wafer for each shot via a projection lens, and the off-axis alignment method is alignment using a microscope arranged at a position different from the exposure position of the wafer. The information is detected and the wafer is sent to the exposure position to perform the alignment.

FIG. 5 is a schematic diagram showing an example of a conventional semiconductor exposure apparatus and an off-axis alignment detection system. This semiconductor exposure apparatus converts a circuit pattern on a reticle 24 placed at a predetermined position on a reduction projection lens 22 into a wafer placed on a movable stage 26 below the reduction projection lens 22 by an exposure illumination system 23. The circuit pattern is projected onto each pattern area on the wafer 25 sequentially, and an image of the circuit pattern is transferred to each pattern area on the wafer 25. The alignment detection system 21 is arranged near the reduction projection lens 22, and is configured to detect the positions of a plurality of alignment marks arranged in a scribe line (not shown) on the wafer 25.

Then, the position of the wafer 25 with respect to the reticle 24 is accurately detected based on the position information of each alignment mark obtained through the alignment detection system 21, whereby each pattern area of the wafer 25 with respect to the reticle 24 is accurately detected. It is configured to be aligned.

The alignment mark is formed of a concave or convex step pattern, and is illuminated by alignment illumination light with a resist applied thereon.

The image of the illuminated alignment mark is converted to CC
The center position of the alignment mark is determined by capturing an image using a photoelectric conversion element such as a D camera and performing pattern matching on the obtained detection signal to determine the center of gravity.

Although alignment marks are formed at a plurality of locations on the wafer, the alignment of the entire wafer with respect to the reticle is performed only once before exposure for the purpose of improving throughput and position detection accuracy. After that, the so-called global alignment method, in which mechanical positioning is performed by a step-and-repeat method in accordance with a design value of a shot arrangement on a wafer, is predominant. In the global alignment method, the position of all the marks on the wafer is not detected, but the signals of only a few representative marks are detected to align the wafer.

[0010]

However, in the above-described conventional alignment method using only an optical system, the influence of the process on the alignment accuracy is not completely eliminated, and the detection signal of the alignment mark depends on the resist film thickness. Lens effect and multiple interference. As a countermeasure for this, a wider band of illumination light has been considered. However, although this has a certain effect in reducing the multiple interference, it has not been possible to completely suppress the lens effect. Here, the lens effect of the resist covering the alignment mark will be described with reference to FIG. The alignment mater has a cross-sectional shape in which a resist is (in general) asymmetrically coated on an alignment target having a predetermined step formed symmetrically or asymmetrically. Part of the light illuminated on the resist surface is refracted by the inclined resist surface, is reflected by the base surface at a predetermined angle, and is again affected by refraction when emitted from the resist surface. Due to these two refraction effects, the optical paths of the light beams emitted from the left and right mark edges are asymmetrically modulated, which is one of the major causes of the alignment error. For example, if the resist film thickness distribution in the vicinity of the alignment mark is symmetric, the detection signal is symmetrical as shown in FIG. 7; however, a spin coating method or the like mainly used in the current resist coating process is used. The cross-sectional shape of the resist surface is generally asymmetric, and some of the cross-sections are close to symmetric and others are not. In such a case, in the conventional alignment method in which an image near the center of the alignment mark is mechanically detected, the detection signal is often left-right asymmetric as shown in FIG. 8, and the symmetry of the waveform is utilized by utilizing the symmetry of the waveform. In the alignment method for obtaining the center position, the detection accuracy and the alignment accuracy have been reduced.

Accordingly, an object of the present invention is to provide an alignment method and apparatus capable of realizing high-precision alignment without being affected by unevenness in resist application in order to solve the above-mentioned problems of the prior art. It is assumed that.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a method and apparatus for detecting a position according to the present invention are directed to a method of forming a concave portion or a concave portion formed on a substrate in a predetermined shape. When detecting the position information of a plurality of step patterns formed of convex portions, each of the step patterns is illuminated, an image of the illuminated step pattern is captured, and the symmetry of the surface shape of the captured step pattern is measured. A step pattern with good symmetry is preferentially selected from the step patterns, and the selected step pattern is illuminated, and position information of the step pattern is detected based on an image obtained by imaging.

Here, a specific step pattern is selected by:
From the waveform of a detection signal of a concave portion or a convex portion in a predetermined axial direction parallel to the substrate surface obtained by imaging, the cross-sectional shape of the substrate in this axial direction is measured, and the center of gravity of the cross-sectional shape is determined by, for example, a template matching method or The measured cross-sectional shape is inverted left and right and detected by autocorrelation, and a step pattern with a small amount of left and right steps (good symmetry) with respect to the center of gravity can be selected. It is preferable to use an atomic force microscope for measuring the symmetry of the surface shape, but a confocal microscope may be used.

A device manufacturing method according to the present invention is a method for manufacturing a device by exposing a device pattern on a reticle and transferring the pattern onto a wafer. The method includes the steps of: The position information is detected, and the position of the wafer and the reticle is aligned based on the detected position information of the alignment mark.

Based on the above configuration, even if the cross-sectional shape of the resist surface in the vicinity of the alignment mark in the wafer surface is asymmetric, and some of the cross-sectional portions are nearly symmetric and others are not, the surface shape can be measured. A mark having good symmetry is selected from among the surface shapes of the step pattern portion obtained, and the position information of the step pattern based on the image of the step pattern illuminated by the illumination mechanism at the mark detected by the imaging means. , The detection signal becomes close to left-right symmetric, and even in the alignment method for obtaining the center position of the alignment mark using the symmetry of the waveform, the detection accuracy and the alignment accuracy do not decrease. .

If an atomic force microscope is used to measure the surface shape, it can be easily added to a conventional alignment apparatus, and the surface shape of the resist can be formed at high speed and with high accuracy. There is an effect that the measurement can be performed without giving an adverse effect.

[0017]

(First Embodiment) Next, a first embodiment of the present invention will be described with reference to FIG. The position detecting method and apparatus according to the present embodiment is configured such that a circuit pattern on a reticle 4 placed at a predetermined position on a reduction projection lens 2 is moved by an exposure illumination system 3 onto a movable stage 6 below the reduction projection lens 2. The circuit pattern is sequentially projected on each pattern area on the wafer 5 placed on the wafer 5, and the image of the circuit pattern is transferred to each pattern area on the wafer 5. The alignment detection system 1 includes a mechanism for illuminating an alignment mark formed on the wafer 5 and a CCD or the like for picking up an image of the illuminated alignment mark. It is configured to detect the positions of a plurality of alignment marks arranged in a line (not shown). The alignment mark is formed of a concave or convex step pattern, and is illuminated by alignment illumination light in a state where a resist is applied thereon.

The image of the illuminated alignment mark is converted to CC
The center position of the alignment mark is obtained by capturing an image with a D camera and pattern-matching the obtained detection signal to obtain the center of gravity.

Although the alignment marks are formed at a plurality of positions for each shot on the wafer,
To improve throughput and position detection accuracy, align the entire wafer with the reticle only once before exposure, and then mechanically position the wafer using the step-and-repeat method according to the design value of the shot array on the wafer. That is, a so-called global alignment method is adopted.

In this embodiment, the atomic force microscope 8 for measuring the surface shape of the wafer 5 is provided with the reduction projection lens 2.
It is arranged in the vicinity, and is configured to detect the surface shape of the alignment mark portion formed on the wafer 5 on the moving stage 6 whose position is controlled by the interferometer 7.

Next, a method for positioning an alignment mark in this embodiment will be described. As shown in the flow chart of FIG. 2, when the wafer 5 is mounted on the moving stage 6 whose position is controlled by the interferometer 7 (step S1), each shot as shown in FIG. Is detected (step S2). The detected signal is an image processing center of gravity is obtained, step amount d _1, d ₂ at the position of the left and right such as the distance to the center of gravity, ... From the symmetry of the respective marks are determined (step S3). As a method of obtaining the center of gravity, a generally known method of performing template matching on a surface shape detection waveform, a method of inverting a detection signal to the left and right, and obtaining an autocorrelation may be used. When the detection of the cross-sectional shape of the mark of the set shot is completed, the stage 6 is driven, and the position (center position) of the mark by the optical system 1 is detected. At this time, a mark with good symmetry obtained from the cross-sectional shape is preferentially selected (step S4), and an image of the selected alignment mark with good symmetry is also taken by the imaging means of the detection system 1. At this time, the position information of the alignment mark is detected (step S5). Then, the circuit pattern on the reticle 4 is aligned with the wafer 5 based on the detected position information of the alignment mark (step S).
6) The circuit pattern is transferred onto the wafer 5 by exposure (step S7). When the exposure for all shots is completed, the wafer 5 is taken out of the moving stage 6 (Step S8), and the process is terminated.

Next, a method of position detection by the optical system 1 will be described. Light emitted from an alignment illumination system using non-exposure light such as a He or Ne laser as a light source illuminates a mark formed on a wafer 5 placed on a stage 6 that can be driven in xyz directions. The reflected light or the scattered light from the mark again passes through the alignment optical system 1 to form an image of the mark on a CCD camera. The signal detected by the CCD camera is subjected to image processing to detect the position of the mark, and the stage 6 is driven from the detected value to align the position of the wafer 5.

Based on the above configuration, even when the cross-sectional shape of the resist surface in the vicinity of the alignment mark is asymmetric, and some of the cross-sections are close to symmetric and others are not, both of the alignment mark portions obtained by the surface shape measuring mechanism can be used. An alignment mark having good symmetry is selected from among the surface shapes, and position information of the alignment mark is detected based on an image of the alignment mark illuminated by the illumination mechanism in the alignment mark detected by the imaging unit. By doing so, the detection signal becomes nearly symmetrical, and even in the alignment method that uses the symmetry of the waveform of the detection signal to determine the center position of the alignment mark, the detection accuracy may decrease, and the alignment accuracy may decrease. There is no.

When an atomic force microscope is used for the surface shape measuring mechanism, it can be easily added to a conventional alignment device, the surface shape of the resist can be measured at high speed and with high accuracy, and the subsequent process can be performed on the resist surface. This has the effect of not having any adverse effect.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. As in the first embodiment, the position detecting method and apparatus according to the present embodiment uses the exposure illumination system 13 to convert the circuit pattern on the reticle 14 located at a predetermined position on the reduction projection lens 12 Wafer 1 placed on lower movable stage 16
5 is sequentially reduced and projected onto each pattern area on the wafer 5.
It is configured to transfer the image of the circuit pattern to each of the upper pattern areas. The alignment detection system 11 includes a first
The configuration is the same as that of the embodiment, and includes a mechanism for illuminating the alignment mark formed on the wafer 15, a CCD for capturing an image of the illuminated alignment mark, and the like. It is configured to detect the positions of a plurality of alignment marks arranged in an upper scribe line (not shown). Also, the alignment mark on the wafer 15 and the method of detecting and positioning the alignment mark are the same as in the first embodiment.
Uses an alignment method. Further, in this embodiment, an atomic force microscope 18 for detecting the surface shape of the wafer 15 and a surface shape detection system 10 having a moving stage 19 whose position is controlled by an interferometer or the like are provided with the reduction projection lens 12. It is installed outside of an exposure apparatus provided with a reduction projection system including an alignment detection system 11 and the like.

Next, a description will be given of a method of positioning an alignment mark in this embodiment. In this embodiment, in the alignment flow shown in FIG. 2, the detection of the mark cross-sectional shape (step S2) and the calculation of the mark symmetry (step S3) are performed in advance by the surface shape detection system 10, and the alignment for each wafer is performed. The information is temporarily recorded as mark information on a recording medium such as a memory / floppy disk. As in the first embodiment, the method of calculating the symmetry of the mark is such that the sectional shape of the uneven alignment mark for each shot as shown in FIG. 3 is detected by the atomic force microscope 18 and the detected signal is subjected to image processing. The center of gravity is obtained, and the step amounts d ₁ , d ₂ ,.
・ Symmetry of each mark is required. Similar to the first embodiment, the method of finding the center of gravity may be a template matching method of a generally known surface shape detection waveform, or a method of inverting the detection signal to the left and right to obtain by autocorrelation. When the exposure is performed by the exposure apparatus, the wafer 15 is moved by the moving stage 1 whose position is controlled by the interferometer 17.
6, the mark having good symmetry obtained from the cross-sectional shape is preferentially selected based on the alignment mark information of each wafer recorded by the recording medium (Step S).
4) The position information of the alignment mark is detected based on the image of the selected alignment mark having good symmetry detected by the imaging means of the detection system 1 (step S5). The method of position detection by the optical system 11 is the same as in the first embodiment.

Based on the above configuration, even if the cross-sectional shape of the resist surface in the vicinity of the alignment mark is asymmetric, and some of the cross-sections are close to symmetric and others are not, both of the alignment marks obtained by the surface shape measuring mechanism can be used. An alignment mark having good symmetry is selected from among the surface shapes, and position information of the alignment mark is detected based on an image of the alignment mark illuminated by the illumination mechanism in the alignment mark detected by the imaging unit. By doing so, the detection signal becomes nearly symmetrical, and even in the alignment method that uses the symmetry of the waveform of the detection signal to determine the center position of the alignment mark, the detection accuracy may decrease, and the alignment accuracy may decrease. There is no.

When an atomic force microscope is used for the surface shape measuring mechanism, the surface shape of the resist can be measured at high speed and with high accuracy, and the resist surface is not affected so as not to hinder the subsequent process. This has the effect. Also,
Since the surface shape detection system is provided outside the exposure apparatus and the alignment mark shape information of each wafer is recorded once, it is not necessary to detect the surface shape of each wafer at the time of exposure alignment by the exposure apparatus, and the exposure throughput Is not reduced.

Although the first and second embodiments of the present invention have been described above, the application of the present invention is not limited to a semiconductor manufacturing apparatus, but is typically based on a plurality of microstructures of the same shape covered with a thin transparent film. The present invention can be applied to a method and an apparatus for observing a typical fine structure and positioning using a plurality of positioning marks. It goes without saying that the present invention can be modified in various ways within the scope of techniques known to those skilled in the art.

(Third Embodiment) Next, a method of producing a device by controlling an exposure apparatus by using job parameters edited and linked in the above-described steps will be described. FIG. 9 shows a flow of manufacturing micro devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, micromachines, etc.). In step S11 (circuit design), the circuit of the semiconductor device is designed. Step S
At 12 (mask fabrication), a mask having a designed pattern is fabricated. Step S13 (wafer manufacturing)
Then, a wafer is manufactured using a material such as silicon or glass. Step S14 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step S15 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer manufactured in step S14.
Bonding), a packaging step (chip encapsulation), and the like. In step S16 (inspection), an operation check test of the semiconductor device manufactured in step S15 is performed.
Perform inspections such as a durability test. Through these steps, a semiconductor device is completed and shipped (step S17).

FIG. 10 shows a detailed flow of the wafer process. In step S21 (oxidation), the surface of the wafer is oxidized. In step S22 (CVD), an insulating film is formed on the wafer surface. In step S23 (electrode formation), electrodes are formed on the wafer by vapor deposition. Step S2
In step 4 (ion implantation), ions are implanted into the wafer. In step S25 (resist processing), a photosensitive agent is applied to the wafer. In step S26 (exposure), the circuit pattern of the mask is printed onto the wafer by exposure using an exposure apparatus having means for confirming the suitability of the above-described exposure. Step S2
In step 7 (development), the exposed wafer is developed. Step S
In step 28 (etching), portions other than the developed resist image are removed. In step S29 (resist stripping), unnecessary resist after etching is removed. By repeating these steps S21 to S29, multiple circuit patterns are formed on the wafer.

In this embodiment, in each of the above-described repetitive processes, in alignment at the time of exposure, the detection error of the alignment mark due to the influence of the resist is reduced, so that high-precision exposure becomes possible. A highly integrated device can be manufactured at low cost.

[0033]

As described above, by applying the position detecting method and apparatus of the present invention to semiconductor exposure,
Since the refraction effect of the observation illumination light on the resist surface can be reduced, errors due to the asymmetry of the resist and the alignment pattern are reduced, and as a result, there is an effect that highly accurate alignment can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing an alignment method of the present invention.

FIG. 3 is a surface shape waveform diagram of an alignment mark coated with a resist, which is taken by an atomic force microscope.

FIG. 4 is a schematic view showing a second embodiment of the present invention.

FIG. 5 is a schematic view showing a conventional example.

FIG. 6 is an explanatory diagram of a resist refraction effect.

FIG. 7 is a cross-sectional view of an alignment mark on which a resist is symmetrically applied and a detection signal waveform diagram thereof.

FIG. 8 is a cross-sectional view of an alignment mark on which a resist is applied asymmetrically and a detection signal waveform diagram thereof.

FIG. 9 is a flowchart showing a manufacturing process of a micro device.

FIG. 10 is a detailed flowchart of the wafer process of FIG. 9;

[Explanation of symbols]

1,11,21: Alignment detection system, 2,12,2
2: reduction exposure lens, 3, 13, 23: exposure illumination system,
4, 14, 24: reticle, 5, 15, 25: wafer,
6, 16, 26: stage, 7, 17, 27: interferometer,
8, 18: atomic force microscope, 10: surface shape detection system, 1
9: Stage.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Ina 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Minoru Yoshii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Co., Ltd. F-term (reference) 5F046 EA12 EA13 EB01 FA10 FB18

Claims (7)

[Claims] 1. A method for detecting position information of a plurality of step patterns formed of a concave portion or a convex portion formed in a predetermined shape on a substrate, wherein each of the step patterns is illuminated, and an image of the illuminated step pattern is formed. Imaging, measuring the symmetry of the surface shape of the captured step pattern, the step of preferentially selecting the step pattern with good symmetry from the plurality of step patterns, illuminating the selected step pattern, and imaging Detecting the position information of the step pattern on the basis of the image obtained by the method. 2. The method according to claim 1, wherein the step of selecting the step pattern includes a cross-sectional shape of the substrate in the axial direction from a waveform of a detection signal of the concave portion or the convex portion in a predetermined axial direction parallel to the substrate surface obtained by imaging. 2. The position detecting method according to claim 1, further comprising: measuring a center of gravity of the cross-sectional shape by a template matching method, and selecting a step pattern having a small left and right step amount with respect to the center of gravity. 3. The step of selecting the step pattern includes a step of selecting a cross-sectional shape of the substrate in the axial direction from a waveform of a detection signal of the concave portion or the convex portion in a predetermined axis direction parallel to the substrate surface obtained by imaging. 2. The method according to claim 1, further comprising: measuring the cross-sectional shape, inverting the measured cross-sectional shape from side to side, detecting a center of gravity of the cross-sectional shape by autocorrelation, and selecting a step pattern having a small amount of left and right steps relative to the center of gravity. Position detection method. 4. The position detecting method according to claim 1, wherein an atomic force microscope is used for measuring the symmetry of the surface shape. 5. The position detecting method according to claim 1, wherein a confocal microscope is used for measuring the symmetry of the surface shape. 6. An apparatus for detecting position information of a plurality of step patterns formed of concave portions or convex portions provided in a predetermined shape on a substrate, illuminating each of the step patterns, and capturing an image of the illuminated step pattern. Then, measure the symmetry of the surface shape of the captured step pattern, means to preferentially select the step pattern with good symmetry from the plurality of step patterns, and illuminate the selected step pattern, image and Means for detecting position information of the step pattern based on the obtained image. 7. A method for manufacturing a device by exposing a device pattern on a reticle and transferring it to a wafer, the method comprising:
7. A method for detecting position information of an alignment mark formed on the wafer by using the position detection device according to claim 6, and performing position adjustment between the wafer and the reticle based on the detected position information of the alignment mark. Device manufacturing method.