JP3998223B2 - Position detection apparatus, exposure apparatus, and device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a position detecting apparatus, an exposure apparatus having the position detection device, and a device Manufacturing how by the exposure device.
[0002]
[Prior art]
In the semiconductor exposure process, with respect to the relative alignment between the wafer to be exposed and the reticle, that is, so-called alignment, an image signal obtained by imaging an alignment mark formed on the wafer and the reticle with an imaging means such as a CCD conventionally. A method of performing pattern matching processing with a template pattern prepared in advance is known. For example, there is a pattern matching detection method disclosed in Japanese Patent Laid-Open No. 62-232504. In this method, one screen of the image signal of the alignment mark obtained by imaging with an imaging means such as a television camera or a CCD is divided into small areas, a density histogram is created for each area, and binarized. The position coordinates of a specific image pattern in a two-dimensional binary image are detected by template matching processing using a template. If this method is used, even if the luminance change occurs on the alignment mark due to uneven illumination, etc., a binarized image can be obtained adaptively for each small area, and the position of the object can be accurately determined. It is possible to detect and measure. The pattern matching detection method disclosed in Japanese Patent Application Laid-Open No. 62-232504 proposed by the present applicant is very effective as a means for specifically detecting the position of a mark from image information.
[0003]
[Problems to be solved by the invention]
However, according to this prior art, the position of the mark may not be detected when the brightness of the alignment mark on the wafer differs due to the surface condition of the wafer, the aging of the illumination, or the like. Therefore, the operator needs to adjust various parameters such as “irradiation light amount to the mark” and “screen division size” to search for and set a parameter value that can detect the mark position. This operation is very time-consuming, and operator skill is required to find the optimum measurement parameters.
[0004]
SUMMARY OF THE INVENTION In view of such problems of the prior art, without requiring labor and skill of steering author, is to make it possible to set the values of parameters of the detection position.
[0005]
[Means for Solving the Problems]
Position detecting device of the present invention to achieve this object, comprising imaging means for obtaining image information of the mark, and a pattern matching unit for performing pattern matching processing with the image information and the template, the mark in the position detecting device detects the position, the pattern matching unit, related to each of a plurality of relative positions of the mark for the previous SL imaging means, the line pattern matching processing in accordance with each of a plurality of values of the parameters of the position detector -out group Dzu the correlation obtained I, you and sets the value of the parameter.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the present invention, when there are a plurality of types of measurement processing parameters for which parameter values are to be set, the pattern matching means changes the parameter values of the respective measurement processing parameters, and parameters that can be taken by the change Pattern matching is performed for all combinations of values, and the parameter values are set based on the results.
[0008]
More specifically, the pattern matching means obtains the degree of correlation when each parameter value is used by pattern matching performed while changing the parameter value, and sets the parameter value based on the result. For example, the parameter value having the highest degree of correlation can be set as the parameter value of the measurement processing parameter. Alternatively, it has means for displaying and selecting the correlation values in the case of using each parameter value and the parameter values arranged in order of the correlation values, and the parameter value selected thereby is the parameter value of the measurement processing parameter You may make it set as.
[0009]
Furthermore, in the present invention, an image pickup unit for obtaining image information of the position detection mark is provided, and the pattern matching unit performs pattern matching performed while changing the parameter value. By performing the image information at each position acquired at the position, the degree of correlation when each parameter value is used is measured for the image information at each position, and the parameter value is set based on the result. In this case, the pattern matching means obtains a detection rate when each parameter value is used from the measurement result of the image information at each position, and considers both the degree of correlation and the detection rate. Can be set. Alternatively, the pattern matching means performs the measurement on the image information at each position for all the parameter values that can be taken by the change for the first position, and the correlation degree in the measurement at the first position for the other positions. The detection speed can be shortened by performing only the high parameter value.
[0010]
Thus, the position detection apparatus of the present invention automatically determines and sets measurement processing parameters for wafer position detection at the time of pre-alignment, for example, by performing pattern matching while changing parameter values in advance. Using this set measurement processing parameter, position detection during actual pre-alignment can be performed.
[0011]
【Example】
[First embodiment]
FIG. 1 is a schematic block diagram of an exposure apparatus having a position detection apparatus according to the first embodiment of the present invention. In the figure, CU is a central processing unit (hereinafter referred to as CPU), MM is a main storage unit composed of a read-only memory and a random access memory, and HD is an external storage device such as a hard disk or MO. The main storage unit MM and the external storage device HD are collectively referred to as a storage device MD. WF is a wafer to be aligned, and an alignment mark WM is recorded on the surface thereof. WS is a wafer stage that holds a wafer WF and moves it in a plane as well as in the direction of rotation. WL is a wafer drive device, which can receive a drive control signal from the central processing unit CU and drive the wafer stage WS to a predetermined position. IL is an illumination device for alignment, and uses, for example, a halogen lamp. The central processing unit CU can adjust the light quantity and the like of the illumination device IL by transmitting a signal to the control device LC.
[0012]
OS is a CCD imaging device. The IP is a processor for image processing, and has an image processing function that converts an image signal input from the CCD image pickup device OS into a digital signal, and performs division of a digital image, binarization processing, and the like. Further, the image processor IP has a function of communicating with the central processing unit CU, and can perform image processing on the image signal input from the CCD imaging device OS and transmit the image information to the central processing unit CU. . CS is a display means such as a CRT or a liquid crystal display, and presents the calculation result of the central processing unit CU and an enlarged image of the mark WM taken by the CCD image pickup device OS to the operator. KB is an input means such as a keyboard, a mouse, and a touch panel.
[0013]
The wafer stage WS holds the wafer WF transferred by a wafer transfer means (not shown) and moves it within the field of view of the objective lens 82 (FIG. 8) of the CCD imaging device OS. The CCD image pickup device OS picks up an image of the alignment mark WM irradiated to the illumination device IL through the objective lens 82 with the CCD 83. The image processor IP AD-converts the image signal of the alignment mark WM input from the CCD image pickup device OS, and then uses the technique disclosed in Japanese Patent Laid-Open No. 62-232504 to obtain binary image information. Output. The central processing unit CU has a function of performing pattern matching using a template pattern stored in the storage device MD, and calculating a relative coordinate value between the template and the alignment mark WM and a correlation degree of matching. .
[0014]
Further, in the position detection device according to the present embodiment, the central processing unit CU reads a plurality of parameter values stored in the storage device MD, and transmits these values to the image processing processor IP and the control device LC for measurement processing. It shall be possible to adjust the parameters. The measurement processing parameters here are parameters used for image processing such as the amount of light applied to the alignment mark WM, binarization of a grayscale image, and region division of an image. When position detection by pattern matching is difficult due to changes in the surface state of the wafer and illumination light over time, the position detection rate can be changed by adjusting these measurement processing parameters through the control device LC and the image processing processor IP. . Conventionally, the operator has adjusted the measurement processing parameters, but these processing can be automated by performing the processing described below in the central processing unit CU.
[0015]
FIG. 2 is a process diagram of the position detection apparatus of this embodiment. Hereinafter, in the present embodiment, a processing flow of a method for automatically optimizing the value of the measurement processing parameter will be described with reference to FIG. First, in the automatic measurement process of step S21, the correlation degree of pattern matching is automatically measured and calculated for all combinations of values that can be taken by one or more parameters among the measurement processing parameters during alignment. FIG. 3 is a flowchart showing detailed processing of this step.
[0016]
In order to simplify the description, it is assumed in the present embodiment that two measurement processing parameters P and Q can be set. The parameter P is an integer in the range of Pmin ≦ P ≦ Pmax, and the parameter Q is an integer in the range of Qmin ≦ Q ≦ Qmax.
[0017]
In step S31 of FIG. 3, the value of parameter Q is initially set to Qmin, and in step S32, the value of parameter P is initially set to Pmin. Next, alignment measurement is performed in step S33. Specifically, the values of the parameters P and Q are transmitted from the central processing unit CU to the control unit LC and the image processing processor IP, and after reflecting the parameter values, the registration mark WM is imaged by the CCD imaging device OS. Then, the image information of the mark WM is taken into the central processing unit CU through the image processor IP, pattern matching is performed using the template pattern stored in the storage device MD, and the correlation degree of matching is calculated. Next, in step S34, the measurement correlation value M (P, Q) measured in step S33 is recorded in the storage device MD, and in step S35, the value of the parameter P is incremented by one. In step S36, it is determined whether or not the parameter P exceeds Pmax. If not, the process returns to step S33 to continue the measurement, and if it exceeds, the process proceeds to step S37. In step S37, the value of the parameter Q is increased by 1, and in step S38, it is determined whether or not Q exceeds Qmax. If not, the process returns to step S32 to continue the measurement, and if it exceeds, the measurement is terminated.
[0018]
By performing such processing, the degree of correlation M (P, Q) is measured for all possible values of the parameters P and Q. The relationship between the measured correlation degree and the parameters P and Q is recorded in the storage device MD in a format as shown in FIG.
[0019]
Next, in the parameter set ranking step in step S22 of FIG. 2, the rank is determined for the ease of mark detection in the parameter value combination (P, Q) based on the measured correlation degree M (P, Q). To do. Specifically, the table of FIG. 4A calculated in the previous process and stored in the storage device MD is placed higher in the parameter value combination having the larger correlation degree M (P, Q), and FIG. ) To perform rearrangement.
[0020]
Next, in the parameter set reflecting step in step S23 of FIG. 2, a specific parameter value combination is reflected to the position detection device as a measurement parameter value among the ranked parameter value combinations. In this parameter reflection step, the parameter combination ranked in the previous step and stored in the storage device MD is determined to be the highest combination of parameter values, and this parameter value is determined by the control device LC. And transmitted to the image processor IP and reflected as the values of the measurement processing parameters P and Q.
[0021]
By performing the above processing, the combination of the parameter values having the highest correlation degree of pattern matching is automatically calculated, and can be reflected in the image processing processor IP and the control device LC as the value of the measurement processing parameter.
[0022]
[Second Embodiment]
In the first embodiment, in the parameter reflection step (step S23) in FIG. 2, the parameter combination stored in the storage device MD that has the highest correlation is determined as the optimum parameter value combination. Although the measurement processing parameter values are reflected, the processing contents may be changed so that the operator can select a parameter combination.
[0023]
For example, all of the parameter value combinations ranked in the parameter set ranking step (step S22) or the upper parameter value combinations are presented to the operator by the display means CS (FIG. 1). The display content of the data at this time may be in a format as shown in FIG. The operator can select a desired parameter value combination from the parameter value combinations presented by the display means CS using the input means KB (FIG. 1).
[0024]
In the parameter reflection step (step S23), the central processing unit CU presents the ranked parameter value combinations to the operator on the display means CS, and inputs the parameter value combination selected by the operator from among them. Input from the means KB, the parameter value combination is transmitted to the control device LC and the image processing processor IP, and reflected as the values of the measurement processing parameters P and Q.
[0025]
By performing the above processing, the operator can know the measurement processing parameter value having a high detection rate, and can select a desired parameter value combination from among parameter value combinations having a high degree of correlation. Therefore, the parameter value can be set more flexibly than in the first embodiment.
[0026]
[Third embodiment]
In the automatic measurement process (step S21) of FIG. 2 in the first embodiment, if the XY coordinate position of the wafer is moved and measurement is performed for all parameter value combinations at a plurality of locations, a more reliable result can be obtained. it can.
[0027]
Normally, when performing pre-alignment by pattern matching, in order to increase the detection rate, the center position of the alignment mark WM is positioned near the center of the imaging surface 81 of the measurement CCD imaging device OS as shown in FIG. The XY coordinate position of the wafer stage WS is adjusted so as to move. In other words, if the parameter value combination can detect the alignment mark WM even if the center position of the alignment mark WM is slightly shifted from the center of the tube surface, the detection rate is higher. Therefore, in this embodiment, the XY coordinates of the wafer WF are moved so that the mark WM comes to a coordinate position shifted by a minute distance from the center of the imaging surface of the CCD imaging device OS, and pattern matching measurement is performed at a plurality of locations. The degree of correlation is calculated based on the position, and the detection rate is also calculated from information indicating whether or not the mark WM has been detected.
[0028]
Now, when the image of the wafer WF is picked up by the CCD image pickup device OS, it is assumed that the alignment mark WM on the wafer WF is aligned with the coordinate position of the center 501 of the image pickup surface 81 as shown in FIG. Let the X and Y coordinates of the wafer be (WX1, WY1). Further, the X and Y coordinates of the wafer when the alignment mark WM on the wafer is aligned with the coordinate positions 502 to 505 that are a minute distance from the tube center 501 are (WX2, WY2) to (WX5, WY5). In this embodiment, a case where measurement is performed at these five locations will be described.
[0029]
FIG. 6 shows the flow of processing in the automatic measurement process in this embodiment. First, in step S61, the measurement position coordinates (WX, WY) are initialized so that the coordinates of the alignment mark WM are at the tube center 501. In step S62, the mark WM is at (WX, WY). The wafer stage WS is moved. From the start of the parameter loop in the next step S63 to the confirmation of the end of the parameter loop in step S66, the same processing as in FIG. 2 of the first embodiment is performed. Next, in step S67, it is determined whether the measurement has been completed at all measurement positions. If the measurement has not been completed, the coordinate value of the next measurement position is substituted for the values of WX and WY in step S69. Then, the process returns to step S62. If the measurement is completed at all measurement positions, the process proceeds to step S68, and the detection rate is recorded.
[0030]
Here, the detection rate is a value indicating whether or not the position of the mark WM can be detected at which measurement position in the same parameter value combination. For example, as shown in FIG. 7, as a result of measurement at a plurality of measurement positions (WX1, WY1) to (WX5, WY5) in a parameter value combination in which the values of parameters P and Q are P1 and Q1, (WX1, WY1) ), (WX3, WY3), and (WX4, WY4), if the mark can be detected, the detection rate in the parameter value combination (P1, Q1) is 3/5.
[0031]
As shown in the table of FIG. 7, the detection rate and the average value of the correlation degrees obtained at a plurality of measurement positions are stored in the storage device MD, and the automatic measurement process is terminated. In the next parameter value ranking step, the parameter value combinations are ranked using the detection rate and the correlation degree average value as indices. According to this, it becomes possible to determine a more reliable parameter value combination than in the first embodiment.
[0032]
[Fourth embodiment]
In the third embodiment, pattern matching measurement is performed at a plurality of measurement positions, but this increases the number of measurements and increases the measurement time. Therefore, when pattern matching is performed for all parameter value combinations at the first measurement position (imaging surface center), the correlation value may be low at the subsequent measurement positions for parameter value combinations that have a relatively low correlation. Since the process is high, the process may be changed so that the subsequent measurement is not performed. In this way, for parameter value combinations that are difficult to detect, measurement at other measurement positions can be omitted, so that the measurement time can be shortened.
[0033]
[Fifth embodiment]
In the first to fourth embodiments, an optimum parameter value is determined in a wafer position detection apparatus that performs pattern matching between the alignment mark WM on the wafer and a template pattern stored in advance. However, even in the reticle position detection apparatus that performs pattern matching between the alignment mark on the reticle and the template pattern, an optimal parameter value can be determined using the same method. Further, the same parameter value determining means may be used for the position detection device that performs pattern matching between the density distribution pattern of the image obtained by imaging the alignment mark on the wafer or reticle with the CCD and the template pattern. Good results can be obtained.
[0034]
[Device manufacturing example]
Next, device manufacturing examples that can utilize the above-described exposure apparatus will be described. FIG. 9 shows a flow of manufacturing a microdevice (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.). In step 31 (circuit design), a device pattern is designed. In step 32 (mask production), a mask on which the designed pattern is formed is produced. On the other hand, in step 33 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 34 (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 35 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 34, and is a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including. In step 36 (inspection), inspections such as an operation check test and a durability test of the semiconductor device manufactured in step 35 are performed. Through these steps, the semiconductor device is completed and shipped (step 37).
[0035]
FIG. 10 shows a detailed flow of the wafer process. In step 41 (oxidation), the wafer surface is oxidized. In step 42 (CVD), an insulating film is formed on the wafer surface. In step 43 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 44 (ion implantation), ions are implanted into the wafer. In step 45 (resist process), a resist is applied to the wafer. In step 46 (exposure), the circuit pattern of the mask is arranged in a plurality of shot areas on the wafer and printed by exposure using the above-described exposure apparatus or exposure method. In step 47 (development), the exposed wafer is developed. In step 48 (etching), portions other than the developed resist image are removed. In step 49 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.
[0036]
According to this, a large-sized device that has been difficult to manufacture can be manufactured at low cost.
[0037]
【The invention's effect】
According to the present invention described above, without requiring labor and skill of steering author, it is possible to set the value of the parameter of the detected position.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an exposure apparatus having a position detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the flow of processing in the apparatus of FIG.
FIG. 3 is a flowchart showing a process flow of an automatic measurement process in the flowchart of FIG. 2;
4 is an explanatory diagram of a relationship between a parameter value combination and a correlation degree in the processing of FIG.
FIG. 5 is an explanatory diagram of relative positions of an imaging tube and alignment marks in a third embodiment of the present invention.
FIG. 6 is a flowchart showing a process flow of an automatic measurement process in the third embodiment of the present invention.
7 is an explanatory diagram of a relationship between a parameter value combination, a correlation degree, and a detection rate in the process of FIG.
8 is a diagram illustrating an imaging state of an alignment mark in the process of FIG.
FIG. 9 is a flowchart showing an example of device manufacture in which the apparatus or method of the present invention can be used.
FIG. 10 is a flowchart showing a detailed flow of the wafer process in FIG. 9;
[Explanation of symbols]
CS: display means, CU: central processing unit, HD: external storage device, IL: illumination device, IP: processor, IP: image processor, KB: input means, LC: control device, MD: storage device, MM: Main storage unit, OS: CCD imaging device, WF: wafer, WL: wafer drive device, WM: alignment mark, WS: wafer stage, 81: imaging surface, 82: lens, 83: CCD, 501: imaging surface Center, 502-505: coordinate position.

Claims (6)

Imaging means for obtaining image information of the mark, and a pattern matching unit for performing pattern matching processing with the image information and the template, the position detecting device detecting a position of the mark,
It said pattern matching means, prior SL related to each of a plurality of relative positions of the mark with respect to the imaging means, a plurality of values correlation based on the pattern matching obtained I line in accordance with the respective parameters of the position detector Dzu-out, you and sets the value of the parameter position detecting device. If the parameter is more, the pattern matching means, and wherein the plurality of types of lines Ukoto the combination thus the pattern matching process for all of the values for the parameters, sets the value of the plurality of kinds of parameters The position detection device according to claim 1. Said pattern matching means relates each of the plurality of values, obtains a detection rate showing how could the position detection in a number of relative positions of the plurality of relative position, based on said correlation and the detection rate, wherein position detecting device according to claim 1 or 2, characterized in that setting the value of the parameter. Said pattern matching means, said for the first relative position among the plurality of relative positions performs pattern matching processing in accordance with each of the plurality of values, in the first relative position of the plurality of values for the other relative position position detection device according to any one of claims 1 to 3, characterized in that intends row pattern matching processing only for the higher was the value degree of correlation in the pattern matching process. An exposure apparatus that exposes a substrate through an original pattern,
5. An exposure apparatus comprising the position detection device according to claim 1 , wherein the position detection device detects a position of a mark formed on the original plate or the substrate . The step of exposing the substrate through the pattern of the original plate by the exposure apparatus according to claim 5 ;
Developing the exposed substrate . A device manufacturing method comprising:

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