Management system, apparatus, and method, exposure apparatus, and control method therefor Number:7,385,700 from the United States Patent and Trademark Office (PTO) owispatent An exposure apparatus performs AGA measurement by using a predetermined sample shot group formed on a wafer, and decides an alignment parameter. The exposure apparatus executes wafer alignment processing and exposure processing by using the alignment parameter. The exposure apparatus notifies a central processing unit of AGA measurement results and the alignment parameter. An overlay inspection apparatus measures an actual exposure position on the exposed wafer, and notifies the central processing unit of the measurement result. The central processing unit optimizes alignment processing on the basis of the AGA measurement results, alignment parameter, and actually measured exposure position.<H Management, apparatus, Management, syst, 7385700.html, Patent, pto, 7385700

Title: Management system, apparatus, and method, exposure apparatus, and control method therefor

Abstract: An exposure apparatus performs AGA measurement by using a predetermined sample shot group formed on a wafer, and decides an alignment parameter. The exposure apparatus executes wafer alignment processing and exposure processing by using the alignment parameter. The exposure apparatus notifies a central processing unit of AGA measurement results and the alignment parameter. An overlay inspection apparatus measures an actual exposure position on the exposed wafer, and notifies the central processing unit of the measurement result. The central processing unit optimizes alignment processing on the basis of the AGA measurement results, alignment parameter, and actually measured exposure position.

Patent Number: 7,385,700 Issued on 06/10/2008 to Matsumoto, et al.

Inventors: Matsumoto; Takahiro (Tochigi, JP), Ina; Hideki (Kanagawa, JP), Suzuki; Takehiko (Saitama, JP), Sentoku; Koichi (Tochigi, JP), Oishi; Satoru (Tochigi, JP)
Assignee: Canon Kabushiki Kaisha (Tokyo, JP)

Appl. No.: 11/218,538

Filed: September 6, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10423889	Apr., 2003	6992767

Foreign Application Priority Data


Apr 30, 2002 [JP]			2002-129325

Current U.S. Class: 356/401 ; 355/53; 355/55; 355/67; 356/400; 700/108

Field of Search: 356/399-401 355/53,55,67 700/28,29 250/548,492.2

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Primary Examiner: Lauchman; Layla G.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto

Parent Case Text

This application is a divisional application of U.S. patent application Ser. No. 10/423,889, filed Apr. 28, 2003 now U.S. Pat. No. 6,992,767.

Claims

What is claimed is:

1. A processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and a measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; a first calculation of calculating a measurement error of the measured position based on the first and second data with respect to each of the plurality of sampled areas; and a second calculation of calculating an offset to be used for the measured position as the condition of the alignment measurement based on a plurality of measurement errors obtained over a plurality of substrates through said first calculation step with respect to each of the plurality of sampled areas.

2. A method according to claim 1, wherein said first calculation step calculates the measurement error by adding the first and second data.

3. A method according to claim 1, wherein said second calculation step calculates the offset by averaging the plurality of measurement errors over the plurality of substrates.

4. A method of manufacturing a device, comprising steps of: exposing a substrate to light using an exposure apparatus of which a condition of an alignment measurement is obtained through a processing method as defined in claim 1; developing the exposed substrate; and processing the developed substrate to manufacture the device.

5. A processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; estimating an alignment error to be obtained with respect to each of a plurality of subsets of the plurality of sampled areas based on the first and second data; and selecting, as the condition of the alignment measurement, a subset to be used for the alignment measurement from the plurality of subsets based on a plurality of alignment errors estimated in said estimating step.

6. A method according to claim 5, wherein said estimating step calculates a coefficient for approximately obtaining the measured position of the alignment mark from a position designed for the alignment mark based on the first data with respect to each of the plurality of subsets, and estimates the alignment error based on the coefficient and the second data with respect to each of the plurality of subsets.

7. A method according to claim 5, wherein said selecting step calculates a standard deviation of the plurality of estimated alignment errors with respect to each of the plurality of subsets, and selects the subset to be used for the alignment measurement based on a plurality of calculated standard deviations.

8. A method of manufacturing a device, comprising steps of: exposing a substrate to light using an exposure apparatus of which a condition of an alignment measurement is obtained through a processing method as defined in claim 5; developing the exposed substrate; and processing the developed substrate to manufacture the device.

9. A processing apparatus for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said apparatus comprising: a storage configured to store first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of the alignment marks of a plurality of the sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus, and to store second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; and a processor configured to calculate a measurement error of the measured position based on the first and second data with respect to each of the plurality of sampled areas, and to calculate an offset to be used for the measured position as the condition of the alignment measurement based on a plurality of calculated measurement errors obtained over a plurality of substrates with respect to each of the plurality of sampled areas.

10. An apparatus according to claim 9, wherein said processor is configured to calculate the measurement error by adding the first and second data.

11. An apparatus according to claim 9, wherein said processor is configured to calculate the offset by averaging the plurality of measurement errors over the plurality of substrates.

12. A processing apparatus for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said apparatus comprising: a storage configured to store first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus, and to store second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; and a processor configured to estimate an alignment error to be obtained with respect to each of a plurality of subsets of the plurality of sampled areas based on the first and second data, and to select, as the condition of the alignment measurement, a subset to be used for the alignment measurement from the plurality of subsets based on the estimated alignment errors.

13. An apparatus according to claim 12, wherein said processor is configured to calculate a coefficient for approximately obtaining the measured position of the alignment mark from a position designed for the alignment mark based on the first data with respect to each of the plurality of subsets, and to estimate the alignment error based on the coefficient and the second data with respect to each of the plurality of subsets.

14. An apparatus according to claim 12, wherein said processor is configured to calculate a standard deviation of the estimated alignment errors with respect to each of the plurality of subsets, and to select the subset to be used for the alignment measurement based on the calculated standard deviations.

15. A program for causing a computer to execute a processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of the sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; a first calculation of calculating a measurement error of the measured position based on the first and second data with respect to each of the plurality of sampled areas; and a second calculation of calculating an offset to be used for the measured position as the condition of the alignment measurement based on a plurality of measurement errors obtained over a plurality of substrates through said first calculation step with respect to each of the plurality of sampled areas.

16. A program for causing a computer to execute a processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; estimating an alignment error to be obtained with respect to each of a plurality of subsets of the plurality of sampled areas based on the first and second data; and selecting, as the condition of the alignment measurement, a subset to be used for the alignment measurement from the plurality of subsets based on a plurality of alignment errors estimated in said estimating step.

17. A processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; and obtaining the condition of the alignment measurement based on the first and second data.

18. A method of manufacturing a device, comprising steps of: exposing a substrate to light using an exposure apparatus of which a condition of an alignment measurement is obtained through a processing method as defined in claim 17; developing the exposed substrate; and processing the developed substrate to manufacture the device.

19. A processing apparatus for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said apparatus comprising: a storage configured to store first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus, and to store second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; and a processor configured to obtain the condition of the alignment measurement based on the first and second data.

20. A program for causing a computer to execute a processing method for obtaining a condition of an alignment measurement by an exposure apparatus for exposing a substrate to light, said method comprising steps of: acquiring first data of a difference between a calculated position of an alignment mark of a sampled area on the substrate calculated based on a plurality of measured positions of a plurality of alignment marks of a plurality of sampled areas on the substrate and the measured position of the alignment mark with respect to each of the plurality of sampled areas, the difference being obtained by the exposure apparatus; acquiring second data of an overlay error of a pattern on the substrate with respect to each of the plurality of sampled areas, the pattern being formed by exposing the substrate to the light based on the calculated positions of the plurality of alignment marks by the exposure apparatus, the overlay error being obtained by an overlay inspection apparatus; and obtaining the condition of the alignment measurement based on the first and second data.

Description

FIELD OF THE INVENTION

The present invention relates to a management system and a management method for managing an exposure apparatus, particularly, to an exposure apparatus, which is applied to the management system, and, more particularly, to effective alignment in a semiconductor exposure apparatus.

BACKGROUND OF THE INVENTION

Circuit micropatterning and an increase in density require a projection exposure apparatus for manufacturing a semiconductor device to project a circuit pattern formed on a reticle surface onto a wafer surface at a higher resolving power. The circuit pattern projection resolving power depends on the NA (Numerical Aperture) of a projection optical system and the exposure wavelength. The resolving power is increased by increasing the NA of the projection optical system or shortening the exposure wavelength. As for the latter method, the exposure light source is shifting from g-line to i-line, and further from i-line to an excimer laser. With the excimer laser, exposure apparatuses having oscillation wavelengths of 248 nm and 193 nm are available.

At present, a VUV (Vacuum Ultra Violet) exposure system with a shorter oscillation wavelength of 157 nm and an EUV (Extreme Ultra Violet) exposure system with a wavelength of 13 nm are examined as candidates for next-generation exposure systems.

Along with circuit micropatterning, demands have also arisen for aligning at a high precision a reticle on which a circuit pattern is formed and a wafer onto which the circuit pattern is projected. The necessary precision is one-third the circuit line width. For example, the necessary precision in a current 180-nm design is one-third, i.e., 60 nm.

In this situation, the exposure pattern overlay precision must be increased, and an increase in alignment precision is indispensable. The alignment method includes die-by-die alignment and global alignment. In die-by-die alignment, misalignment of an alignment mark is measured for each chip or shot. The misalignment is reduced to an allowance, and then exposure is executed. In global alignment, not all shots on a wafer are measured, but misalignment of several shots is measured, and a shot layout error on the wafer from the wafer stage coordinate system of an exposure apparatus is calculated. After that, the wafer is positioned at the precision of the wafer stage in accordance with the calculation result, and exposure is executed. Of these alignment methods, die-by-die alignment requires a large number of measurement operations, which is disadvantageous to throughput. Hence, global alignment advantageous to throughput is generally employed.

Various device structures have been proposed and examined for commercial use. With the spread of personal computers, and the like, micropatterning has shifted from memories such as a DRAM to CPU chips. For further IT revolution, micropatterning will be further advanced by the development of MMIC (Millimeter-wave Monolithic Integrated Circuits), and the like, used in communication system devices called a home wireless LAN and Bluetooth.RTM., highway traffic systems (ITS: Intelligent Transport Systems) represented by a car radar using a frequency of 77 GHz, and wireless access systems (LMDS: Local Multipoint Distribution Service) using a frequency of 24 to 38 GHz.

There are also proposed various semiconductor device manufacturing processes. As a planarization technique which solves an insufficient depth of exposure apparatus, the W-CMP (Tungsten Chemical Mechanical Polishing) process has already been used. Instead, the Cu dual damascene process has received a great deal of attention.

Various semiconductor device structures and materials are used. For example, there are proposed a P-HEMT (Pseudomorphic High Electron Mobility Transistor) and M-HEMT (Metamorphe-HEMT), which are formed by combining compounds such as GaAs and InP, and an HBT (Heterojunction Bipolar Transistor) using SiGe, SiGeC, and the like.

Under the present circumstance of the semiconductor industry, many apparatus variables (=parameters) must be set in correspondence with each exposure method and each product in the use of a semiconductor manufacturing apparatus, such as an exposure apparatus. The number of parameters to be optimized is very large, and these parameters are not independent of each other, but are closely related to each other.

These parameter values have conventionally been decided by trial and error by the person in charge of introducing an apparatus of a device manufacturer. A long time is taken to decide optimal parameter values. If, e.g., a process error occurs after the parameter values are decided, the parameter values of the manufacturing apparatus must be changed again along with a corresponding change in the manufacturing process. Also, in this case, a long time is taken to set parameter values.

In the semiconductor device production, the time which can be taken until the start of volume production after the activation of a manufacturing apparatus is limited. The time which can be taken to decide a parameter value is also limited. In terms of CoO (Cost of Ownership), the operating time of the manufacturing apparatus must be prolonged. To change a parameter value which has already been decided, it must be quickly changed.

In this situation, it is very difficult to optimize parameter values for various semiconductor devices in a short time and manufacture various semiconductor devices with optimal parameter values. Even a manufacturing apparatus which can originally achieve a high yield can only exhibit a low yield because the apparatus is used without optimizing parameter values, resulting in a potential decrease in yield. Such a decrease in yield leads to a high manufacturing cost, a small shipping amount, and weak competitiveness.

Especially, in global alignment, which is generally adopted as the alignment method described above, only several shots (to be referred to as sample shots) on a wafer are measured. Measurement is greatly influenced by the stability of the alignment mark manufacturing process of the shots (for each wafer or each lot). The yield may decrease due to a low overlay precision depending on the lot. This disadvantage will become more conspicuous along with an increase in wafer diameter.

SUMMARY OF THE INVENTION

The present invention has been made to overcome the conventional drawbacks, and has as its object to optimize, during volume production, a specific parameter value used in global alignment of an exposure apparatus.

It is another object of the present invention to optimally control the alignment offset amount even when the alignment mark of a sample shot used for global alignment is abnormal and an alternative shot is used.

It is still another object of the present invention to allow selecting an optimal sample shot from all shots on a wafer.

According to the present invention, the foregoing object is attained by providing a management system which manages alignment processing of an exposure apparatus, the management system comprising:

measurement means for measuring a position of a mark position on a photosensitive substrate;

exposure processing means for calculating an alignment parameter on the basis of a measurement result of the measurement means, executing alignment processing by using the calculated alignment parameter, and exposing the photosensitive substrate;

an inspection apparatus which measures an exposure position on the photosensitive substrate exposed by the exposure processing means; and

optimization means for optimizing the alignment processing on the basis of the exposure position acquired by the inspection apparatus.

According to another aspect of the present invention, the foregoing object is attained by providing a management method of managing alignment processing of an exposure apparatus, the management method comprising:

a measurement step of measuring a position of a mark on a photosensitive substrate;

an exposure processing step of calculating an alignment parameter on the basis of a measurement result in the measurement step, executing alignment processing by using the calculated alignment parameter, and exposing the photosensitive substrate;

an inspection step of inspecting an exposure result in the exposure processing step; and

an optimization step of optimizing the alignment processing on the basis of an exposure position acquired in the inspection step.

In still another aspect of the present invention, the foregoing object is attained by providing a management apparatus which manages alignment processing of an exposure apparatus, the management apparatus comprising:

first acquisition means for acquiring a measurement result of a position of a mark on a photosensitive substrate by the exposure apparatus;

second acquisition means for acquiring an actual exposure position by an inspection apparatus which inspects an exposure result by the exposure apparatus; and

optimization means for optimizing the alignment processing in the exposure apparatus on the basis of the measurement result acquired by the first acquisition means and the exposure position acquired by the second acquisition means.

In still another aspect of the present invention, the foregoing object is attained by providing a management method of managing alignment processing of an exposure apparatus, the management method comprising:

a first acquisition step of acquiring a measurement result of a position of a mark on a photosensitive substrate by the exposure apparatus;

a second acquisition step of acquiring an actual exposure position by an inspection apparatus which inspects an exposure result by the exposure apparatus; and

an optimization step of optimizing the alignment processing in the exposure apparatus on the basis of the measurement result acquired in the first acquisition step and the exposure position acquired in the second acquisition step.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 is a view showing the schematic arrangement of a management system for a semiconductor exposure apparatus according to the first embodiment;

FIG. 2 is a flow chart showing a flow of the management system for the semiconductor exposure apparatus according to the first embodiment;

FIG. 3 is a view showing the schematic arrangement of the semiconductor exposure apparatus according to the first embodiment;

FIG. 4 is a view showing wafer shot information used in the first embodiment;

FIG. 5 is a view for explaining a global alignment parameter according to the present invention;

FIG. 6 is a view for explaining coordinate transformation in global alignment according to the present invention;

FIG. 7A is a view showing the flow chart of the exposure apparatus and data exchange between an overlay inspection apparatus and a central processing unit according to the first embodiment;

FIG. 7B is a flow chart for explaining processing of the central processing unit according to the first embodiment;

FIG. 7C is a view for explaining alignment offset optimization processing according to the first embodiment;

FIG. 8 is a graph showing a measurement example of the alignment measurement error for each sample shot;

FIG. 9 is a view showing wafer shot information used in the second embodiment;

FIG. 10A is a view showing the flow chart of a semiconductor exposure apparatus used in the second embodiment, and data exchange between an overlay inspection apparatus and a central processing unit;

FIG. 10B is a flow chart for explaining processing of the central processing unit according to the second embodiment;

FIG. 10C is a view for explaining alignment offset optimization processing according to the second embodiment;

FIG. 11 is a graph for explaining optimization of a sample shot group according to the second embodiment;

FIG. 12 is a graph for explaining optimization of a sample shot group according to the second embodiment;

FIG. 13 is a flow chart for explaining the flow of a device manufacturing process; and

FIG. 14 is a flow chart for explaining a wafer process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.

First Embodiment

A management system according to the first embodiment will be described. Note that OAP (Optimization for Alignment Parameter in volume production) to be described below is adopted in the second embodiment, is not particularly necessary in the first embodiment, but will be explained for descriptive convenience.

An alignment variable optimization system, which is implemented by an exposure management system according to the first embodiment, is applied to the alignment system of an exposure apparatus, and corresponds to a volume production apparatus, will be called OAP (Optimization for Alignment Parameter in volume production). Parameter values in this specification include parameters which represent numerical values, and setting parameters representing selected values, and setting parameters representing selected states such as selection of the sample shot layout and alignment method which are not numerical values. In addition to numerical values, variables also include apparatus variation elements such as a choice and general conditions which are not numerical values.

FIG. 1 is a view showing the schematic arrangement of an overall exposure management system according to the first embodiment. The exposure management system of the first embodiment includes a plurality of exposure apparatuses (in FIG. 1, exposure apparatuses 1 and 2), an overlay inspection apparatus 3, a central processing unit 4, and a database 5, which are connected by a LAN 6 (e.g., an in-house LAN). The central processing unit 4 collects various measurement values, and the like, from the semiconductor exposure apparatuses 1 and 2 and the overlay inspection apparatus 3, and saves them in the database 5. While the semiconductor exposure apparatuses 1 and 2 operate in volume production, the central processing unit 4 optimizes parameter values, and notifies the semiconductor exposure apparatuses 1 and 2 of them.

FIG. 2 is a flow chart showing the rough flow of OAP processing, which is realized by the exposure management system according to the first embodiment.

Assume that a wafer to be exposed is loaded into the exposure apparatus 1, and a corresponding reticle is set in the exposure apparatus (not shown in FIG. 2). After the wafer and reticle are set, global alignment called AGA (Advanced Global Alignment) is executed with a variable value (=parameter value) set for an exposure job (job concerning exposure). In AGA, a sample shot is observed to measure a wafer position at the precision of an X-Y stage equipped with a laser interferometer. Alignment measurement data (the misalignment amount of each shot and the misalignment amount of a wafer: a wafer magnification, rotation, shift, and the like) at this time are stored in the exposure apparatus (process 11). Data which are measured AGA are transferred to the central processing unit 4 which controls OAP (data transfer 18).

AGA measurement is also performed with a variable value other than the job variable value by the second stage correction driving based on stage driving information, obtaining alignment measurement data (process 12). The measurement data obtained in this process are also transferred as values to the central processing unit 4, which controls OAP, similar to the data obtained at the variable value set for the previous job (data transfer 18).

After all data are obtained in processes 11 and 12, the stage position is controlled on the basis of the AGA result with the parameter value set for the job, and the wafer is exposed (process 13).

The wafer exposed by the exposure apparatus is developed in a subsequent process. The developed wafer is supplied to the overlay inspection apparatus 3 in which the alignment result, i.e., pattern misalignment is measured (process 14). The measurement value obtained by the overlay inspection apparatus 3 is also transferred to the central processing unit 4 (data transfer 19).

The central processing unit 4, which controls OAP, stores in the database 5 the received AGA measurement results transferred from the exposure apparatus (process 15). The inspection result by the overlay inspection apparatus 3 is also transferred by data transfer 19 to the central processing unit 4, which controls OAP (data transfer 19). The inspection result is stored in the database in a form (to be described later), as shown in FIG. 7C, in correspondence with the AGA measurement values by the exposure apparatus that have already been stored in the database (process 15).

The correlation between the AGA measurement value and the measurement result from the overlay inspection apparatus 3 is checked for a designed wafer. Whether the parameter value (in this case, parameter value used for AGA) set for the current job is optimal is decided (process 16). More specifically, a predetermined evaluation value (e.g., a shift amount or a rotation amount) is compared with an evaluation value with the currently set parameter value to obtain a difference between two evaluation values. Then, whether a parameter value, which provides a desirable evaluation value having the difference larger than a given threshold exists, is decided. Note that the threshold is obtained by the empirical rule, or the like, in advance, and set in the central processing unit 4, which controls OAP. If a parameter which provides a desirable evaluation value exists, its optimal parameter value is reflected in the exposure apparatuses 1 and 2, and used as a new job setting parameter value so as to apply the optimal parameter value to a lot exposure of subsequent lots (process 17 and data transfer 20). If a parameter value whose evaluation value is better than that obtained with the currently set parameter value, but the difference between these evaluation values does not exceed the threshold, no set parameter value is changed. This is because the difference between these evaluation values falls within the error range, or the effect of changing a parameter value is weak, but a change in parameter value may have an adverse effect (e.g., a decrease in throughput due to the setting change time or degradation of another exposure condition).

By repeating the above processing, the parameter value is optimized and can be used for subsequent lots even upon process variations.

The use of the OAP system can eliminate any examination using a special wafer in a volume production site in order to set a parameter value, in addition to volume production. In other words, the alignment variable can be optimized during volume production, and the effective performance of the exposure apparatus can be improved without decreasing the productivity.

The above-described OAP system can be briefly expressed as follows. OAP in this embodiment is a feed forward system. That is, actual alignment signals at an AGA shot are acquired with an actual job variable and another variable. The alignment signals are compared with results by the overlay inspection apparatus, and an optimal alignment variable can be used for subsequent lots.

A case wherein an alignment offset is applied as an alignment variable whose value is decided/updated without using OAP will be explained in detail as the first embodiment.

FIG. 3 is a view schematically showing the semiconductor exposure apparatus according to the first embodiment. Note that portions, except important portions in the first embodiment, are not illustrated. The exposure apparatus 1 comprises a reduction projection optical system 11, which reduces and projects a circuit pattern drawn on a reticle 10, a wafer chuck 13, which holds a wafer 12 bearing an underlying pattern and an alignment mark formed in a preprocess, a wafer stage 14, which locates the wafer 12 to a predetermined position, an alignment detection optical system 15, which measures the position of the alignment mark on the wafer, an AGA shot information storage 16, which stores a shot subjected to global alignment (AGA), and an offset information storage 17 used in positioning the wafer 12.

FIG. 4 shows a shot layout of the wafer 12 used in the first embodiment. In FIG. 4, AGA is executed by measuring misalignment of alignment marks formed in the areas of four shots (to be referred to as AGA sample shots) A1, A2, A3, and A4. In FIG. 4, a total of eight shots B11 to B42 are alternative sample shots used when some of the AGA measurement values of sample shots A1 to A4 are abnormal (measurement error). The measurement error occurs when, e.g., an alignment mark formation error occurs due to a semiconductor process error, failing to obtain a predetermined signal level. Whether the measurement error occurs can be decided based on, e.g., a phenomenon that the measurement value greatly shifts in comparison with the remaining shots. The AGA shot information storage 16 in the exposure apparatus 1 holds information on AGA sample shots and alternative sample shots (position coordinates on a wafer).

Global alignment (AGA) will be explained. FIG. 5 shows a stage wherein the shot layout on the wafer shifts with respect to the x-y coordinate system of the wafer stage of the exposure apparatus 1. The wafer shift can be described by six parameters: an x shift Sx, a y shift Sy, a tilt .theta.x about the x-axis, a tilt .theta.y about the y-axis, an x magnification Bx, and a y magnification By. The magnifications Bx and By represent expansion and contraction of the wafer with respect to the wafer stage feed of the exposure apparatus. The wafer expands and contracts owing to film formation and etching in a semiconductor process.

Let A.sub.i (i is the measurement shot number) be the measurement value of each AGA sample shot:

##EQU00001##

Let D.sub.i be the alignment mark design position coordinates of the sample shot:

##EQU00002##

In AGA, the following linear coordinate transformation is conducted using, as correction amounts, the six correction parameters (Sx, Sy, .theta.x, .theta.y, Bx, and By) representing wafer misalignment:

'.theta..times..times..theta..times..times..times..times. ##EQU00003##

In equation (3), .theta.x.apprxeq.0, .theta.y.apprxeq.0, Bx.apprxeq.1, and By.apprxeq.1, and approximations such as cos.theta.=1, sin.theta.=.theta., .theta.x.times.Bx=.theta.x, and .theta.y.times.By=.theta.y are used for descriptive convenience.

FIG. 6 shows linear coordinate transformation in equation (3). An alignment mark on a wafer is located at a position W, and shifts from a design position M by A.sub.i. The misalignment (residual) between D'.sub.i (position M') obtained by coordinate transformation in equation (3) and the alignment mark W on the wafer is R.sub.i. R.sub.i=(D.sub.i+A.sub.i)-D'.sub.i. (4)

In AGA, the correction parameters are so adjusted as to minimize the residual R.sub.i at each sample shot by applying the least squares method. That is, the correction parameters (Sx, Sy, .theta.x, .theta.y, Bx, and By), which minimize the mean square sum of the residual R.sub.i, are calculated by:

.times..times..times..times..times..times..theta..times..times..theta..tim- es..times..times..delta..times..times..delta..times..times..delta..times..- times..delta..times..times..delta..times..times..delta..times..times..delt- a..times..times..delta..times..times..delta..times..times..delta..times..t- imes..delta..times..times..delta..times..times. ##EQU00004##

A measurement value (x.sub.i, y.sub.i) and an alignment mark design position (X.sub.i, Y.sub.i) at each sample shot are substituted into equations (5) and (6), obtaining the correction parameter values (Sx, Sy, .theta.x, .theta.y, Bx, and By). After AGA measurement, the misalignment is corrected using the values of the correction parameters (to be also referred to as AGA parameters) obtained in this way, positioning each shot. A pattern on a reticle is then transferred onto the wafer.

The processing sequences of the exposure apparatus and central processing unit 4, according to the first embodiment, will be described.

FIG. 7A is a flow chart for explaining the processing sequence of the exposure apparatus according to the first embodiment. The exposure apparatus receives, from the central processing unit 4, ID information of a wafer to be exposed by the exposure apparatus. The exposure apparatus sets the wafer ID (wafer identification number) used for offset update processing out of the ID information (step S11). A wafer subjected to offset update processing may be periodically automatically set by the central processing unit 4 or manually set by the operator. AGA conditions are set for AGA processing. At this time, the values of alignment parameters (e.g., sample shot information, alignment offset, and the like) used for AGA are set (step S12). A wafer with a wafer ID is loaded (step S13), and pre-alignment for aligning a wafer within the measurement range of subsequent AGA is performed (step S14).

AGA measurement is done at sample shots designated by sample shot information set in step S12. In the first embodiment, AGA measurement is executed at sample shots in group A (A1 to A4) (step S15).

Whether measurement of an alternative sample shot is necessary is decided on the basis of the measurement values in step S15 (e.g., when some measurement values are erroneous) (step S16). If YES in step S16, whether an (unused) alternative sample shot group remains is decided (step S17). If NO in step S17, error processing is done such that the operator is notified of a message to this effect (step S18). If YES in step S17, AGA measurement is executed at a usable alternative sample shot (in the first embodiment, a sample shot in group B) (step S19). This measurement value replaces a measurement value excluded from the sample shots, and then whether an alternative sample shot is necessary is decided again in step S16.

If NO in