JP2002043217A - Surface level detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out step measurement of a wafer, etc., under optimized conditions for obtaining correction information wherein a step of a wafer, etc., which is necessary during exposure, is corrected. SOLUTION: A plurality of parameters which are necessary for step measurement are defined in advance to a wafer whose surface condition shifts one after another passing through each process, and in steps S1 and S2, for example, it is judged whether step measurement is necessary or not to a set wafer by a parameter. In a step S4, the place of measurement shot for carrying out step measurement is judged. In a step S7, and a step S9, measurement shot is scanned and step measurement is carried out, thus obtaining correction information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface position detecting method for obtaining correction information for correcting a step on a target wafer in an exposure apparatus used for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In recent semiconductor devices, it is necessary to transfer a high-definition image in accordance with high integration. Therefore, especially when exposure is performed between steps, it is important to manage the image plane of the circuit pattern so as to match the exposure plane of the wafer. Since the surface of the wafer on which devices are actually being formed has a step due to the circuit pattern formed on the base, the distance to the wafer is determined by measuring the step in advance and using the step data obtained as a result of the measurement. The correction information is obtained and set based on the correction information.

A semiconductor device is formed on a wafer through a plurality of steps such as lamination and etching, and an exposure apparatus is used when performing exposure between the plurality of steps and transferring a circuit pattern image onto the wafer surface. . As for the capability of the exposure apparatus, it is possible to perform all exposures by repeatedly using one exposure apparatus.However, in a manufacturing factory where a mass production system is established, a plurality of exposure apparatuses are provided and the plurality of exposure apparatuses are arranged. Exposure of the same contents is performed in parallel using an apparatus, or exposure of different contents is performed for each exposure apparatus, thereby improving the manufacturing efficiency.

[0004]

However, in order to make the coupling surface of the image of the circuit pattern coincide with the exposure surface of the wafer, the step data of the wafer is measured. The method and conditions for measuring the level difference were not determined. For example, even when different exposures are performed by a plurality of exposure apparatuses, step measurement is performed under the same conditions. For this reason, there have been problems that it takes more time than necessary for measuring the level difference and that the measurement conditions are not optimized.

[0005] The invention according to claims 1 to 5 of the present application (hereinafter, referred to as
An object of the present invention is to solve the above-mentioned problem by setting parameters required for step measurement and managing step measurement for each exposure.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the first invention is directed to an object which is manufactured in a plurality of steps and whose surface state sequentially transitions through each of the steps. The following method is employed in a surface position detection method for obtaining correction information for correcting a step formed on the surface of a target object between necessary steps.

That is, parameters necessary for measuring the step data for obtaining the correction information are defined in advance, and the step data is measured based on the parameters.

According to a second aspect, in the surface position detecting method according to the first aspect, the parameters include an instruction to update the step data, a shot position on a target object for which the step data is measured, and an abnormal value. Processing rule in the case, the number of measurement shots required for measuring the level difference data, a determination value for determining whether or not the measurement of the level difference data was successful, and an allowable value for allowing an abnormality in the level difference , And the number of scans in the shot.

According to the first and second aspects of the present invention, the configuration as described above allows the measurement of the step data to be performed to obtain the correction information for correcting the step between the respective steps. Will be

According to a third aspect, in the surface position detecting methods of the first and second aspects, a plurality of devices for obtaining correction information for correcting a step formed on the surface of the target object between the necessary steps are provided. When used, these devices are connected to a host computer to form a system, and each device is operated based on the parameters under the control of the host computer.

By adopting such a configuration, when measuring the level difference data of the target object in each device, the measurement is performed by controlling the parameters. In the fourth invention, the third
In the surface position detecting method according to the invention, part or all of the information on the step of the target object obtained by each of the devices is provided to an arbitrary device outside the system via the host computer. .

By adopting such a configuration, information relating to a step can be used outside the system. According to a fifth aspect, in the surface position detecting method according to the third or fourth aspect, the host computer is connected to a network, and a part or all of the information on the step of the target object obtained by each device is provided. Is communicated to a remote place via the host computer and the network.

By adopting such a configuration, information on a step can be used even in a remote place.

[0014]

FIG. 1 is a flowchart of a surface position detecting method according to an embodiment of the present invention, and FIG.
1 is a configuration diagram of an exposure system that performs the surface position detection method of FIG.

This exposure system includes a plurality of exposure apparatuses 11
, 11-2,..., 11-n, and these exposure apparatuses 1
It comprises a host computer 12 for controlling 1-1 to 11-n. Each of the exposure devices 11-1 to 11-n includes:
The process is designed so that the exposure, which is performed several times during the plurality of steps, is shared with the wafer of the target object on which the semiconductor device is formed through the plurality of steps. Each of the exposure apparatuses 11-1 to 11-n includes an optical system (not shown) for performing exposure, a height measurement system (not shown) for measuring the height of each point on the wafer, and a not-shown system for controlling the position of the wafer. And a control system. When performing each exposure,
A step formed on the wafer surface is obtained in advance, a correction amount as correction information corresponding to the step is calculated, and exposure is performed by controlling the position of the wafer based on the correction amount.

The host computer 12 is an analysis means 2 comprising a wafer defect inspection device or a review station.
1 can provide information. Further, the host computer 12 transmits an L (not shown) through the line 22.
It is connected to an AN (Local Area Network) or the Internet and can communicate with remote locations.

FIG. 3 shows the details of steps S7 and S9 in FIG. 1, and FIG. 4 shows the details of step S28 in FIG. The operation of the surface position detection method of FIG. 1 and the system of FIG. 2 will be described with reference to FIGS.

In the host computer 12, parameters necessary for obtaining correction amount information are defined in advance. By designating the parameters, each of the exposure apparatuses 11-1 is defined.
11-n to measure step data. The parameters include a step data update instruction for indicating the timing of measuring the step data, a measurement shot position on the target object for measuring the step data, a processing rule when an abnormal value is output, and a step data. The number of measurement shots for each wafer required for the measurement, the determination value for determining whether or not the measurement of the level difference data was successful, the allowable value for allowing abnormalities in the level difference data, and the And the number of scans are defined.

Each of the exposure apparatuses 11-1 to 11-n is controlled by parameters provided from the host computer 12, and measures steps of the wafer by executing steps S1 to S14 in FIG. And an exposure based on the correction amount is performed.

First, in step S1, each of the exposure apparatuses 11-1 to 11-n performs the first (1st) exposure of a wafer as a set target object based on an instruction to update step data in parameters. Is determined. If it is not the first time (No), the process proceeds to the next step S2. At the stage of performing the first exposure, there is no harmful step on the wafer surface. Therefore, by performing the determination in step S1, unnecessary measurement of step data can be omitted. Further, even at the first exposure, the step data can be updated by setting.

In step S2, each of the exposure apparatuses 11-1 to 11-1
-N determines whether the set wafer is a wafer for which the measurement of the step data needs to be performed. That is, it is determined whether or not the step data needs to be updated. If the wafer needs step data update (YES), the process proceeds to step S3. As described above, by performing the determination in step S2, even when, for example, the same exposure is continuously performed on wafers of the same lot, the step data is measured and the step data is updated at a timing necessary for process management. Can be implemented. Further, even if the lot is different, the measurement can be omitted when it is not necessary to update the step data.

In step S3, each exposure apparatus 11-
1 to 11-n perform rough alignment based on the orientation flat of the set wafer. In step S4, the measurement shot for measuring the level difference data on the wafer is referred to as EGA (Enhanced Global) by referring to the measurement shot position of the parameter designated by the host computer 12.
Alignment) It is determined whether the shot matches. If they match (YES), one of the EGA shots is selected and fine alignment is performed in step S5. If they do not match (NO), fine alignment is performed on the shot specified by the parameter in step S6 based on the EGA mark.

After the alignment in step S5, steps S7 and S8 repeat the step measurement scan for the number of shots specified by the parameters. After the alignment in step S6, the steps S9 and S10 repeat the step measurement scan for the specified number of shots. The processing of step S7 and step S9 are the same processing, and are constituted by, for example, steps S21 to S28 in FIG.

First, in step S21, a stage (not shown) of the exposure apparatus is controlled to perform focusing at the center of the step measurement shot, and in step S22, a plurality of heights arranged in the X direction at the start position of the measurement shot including the approach region. Adjust the detection points of the measurement system. Step S23
In step (2), the measurement shot is scanned in the Y direction at each detection point, and data of steps for a plurality of rows are discretely acquired and read into a memory or the like (reading of focus sensor values).

In step S24, it is determined whether or not scanning for the number of times of averaging for the same shot of the parameter given from the host computer has been completed, and if not completed (NO), the process proceeds to step S22.
And scan again. If the scans for the number of times of averaging have been completed (YES), the process proceeds to step S
Proceed to 25.

In step S25, it is checked whether or not scanning has been performed on the step measurement shots for the number of measurement shots specified by the parameters to obtain step data. If scanning has not been performed for all the specified step measurement shots and necessary step data has not been obtained (NO), the process returns to step S21, and the steps up to step S24 are repeated. When scanning is performed for all designated step measurement shots in the wafer and necessary step data is obtained (Y
In ES), the process proceeds to step S26.

Step S26 is a process for determining whether or not the number of successful shots described later in the wafer is equal to or greater than the number specified by the parameter. If the number is not equal to or greater than the number specified (NO), the process proceeds to step S27. An error occurs in the step data update processing. If the number of successful shots is equal to or greater than the specified number (YES), a correction amount as correction information is calculated in step S28.

When calculating the level difference correction amount, in step S28a of FIG. 4, the data of the level difference of a plurality of rows of each measurement shot is read out for the number of times of measurement, and in step S28b, the data is converted into the intra-shot coordinate system and Averaging within. At this time, the displacement of the detection point in the scanning direction is interpolated by least squares approximation, spline or Fourier series, and the position in the step data is adjusted. In step S28c, for each measurement shot, grid-like data arranged at a specified pitch in the X and Y directions with reference to the shot center position is obtained. At this time, an interpolation function as needed is used.

In step S28d, an appropriate offset and weight are set for the data at the selected position in the grid data, and an approximate plane is calculated for each measurement shot. This approximate surface may be a flat surface or a curved surface. Then, the step data for each measurement shot is converted into difference data (offset data) from the approximate surface. However, step data that is more than a first threshold value specified by a parameter from the approximate surface is excluded from the approximate surface calculation target.

In step S28e, data (abnormal value data) separated from the approximate surface by a distance equal to or more than the second threshold value specified as a parameter is detected. Shots are obtained, and the level difference data of only the remaining successful shots is averaged to calculate a device level difference correction amount. Interpolation as needed is also performed at the time of averaging here. The abnormal value data detected at this time is transmitted to the host computer 12 in step S28f. The host computer 12 transmits the abnormal value data to an analysis means 21 including an external wafer defect inspection device or a review station. As described above, the correction amount is obtained.

When step S28 is completed, it is checked in step S8 and step S10 in FIG. 1 whether step S28 has been completed for all of the measurement shots. If the process of step S28 remains,
The process returns to step S5 or step S9. When the processing of step S28 has been completed for all the measurement shots, the processing proceeds to step S11.

In step S11, the exposure shot of the wafer is focused based on the correction amount of the device step data obtained so far. In this focusing, not only the height but also the inclination of the wafer is adjusted by a position control system. In step S13, exposure is performed. In addition,
If it is determined in step S2 that the step data is not updated, steps S3 to S10 are not performed, and in step S11, focusing is performed based on the measured device step data correction amount, and exposure in step S13 is performed. If it is determined in step S1 that the wafer has been exposed for the first time, focusing is performed in step S12, and exposure in step S13 is performed.

In step S14, it is determined whether or not all the exposures on the wafer have been completed. If the exposure has been completed, a series of processing ends. In the present embodiment as described above,
It has the following advantages.

(1) Six types of parameters required for measuring the level difference data are defined, and the exposure apparatus 1 is defined by the parameters.
Since the measurement of the step data in 1-1 to 11-n is controlled, the condition for each measurement of the step data can be managed, optimized measurement can be realized, and unnecessary measurement can be omitted.

(2) The exposure apparatuses 11-1 to 11-n are connected to the host computer 12, and parameters are defined in the host computer 12 to define each of the exposure apparatuses 11-1.
11-n, the reliability of the surface position detection method having the advantage (1) can be improved, and stable exposure can be realized.

(3) Since abnormal value data is transmitted from the host computer 12 to the analysis means 21 such as a wafer defect inspection apparatus or a review station, the abnormal value data can be used when analyzing a wafer as a defect, and This will help quality control over the entire manufacturing process.

(4) The host computer 12 is connected to the line 2
2 and the LAN or the Internet via the line 22, it is possible to share parameters for step measurement and exposure conditions with a remote management center or manufacturing factory. The present invention can be variously modified regardless of the above embodiment. For example, there are the following modifications.

Although the target object is a wafer forming a semiconductor device, a liquid crystal device performing similar exposure may be used as a target object. Although the example in which the plurality of exposure apparatuses 11-1 to 11-n perform exposure of different contents in the manufacture of the semiconductor device has been described, exposure of the same contents may be performed in parallel.

[0039]

As described above in detail, according to the first and second aspects of the present invention, parameters required for measuring step data for obtaining correction information are defined in advance, and the step difference is determined based on the parameters. Since data measurement is performed, even when, for example, the exposure of an object is shared by using a plurality of exposure apparatuses, the measurement conditions can be optimized and unnecessary measurement can be omitted. become.

According to the third invention, a plurality of devices for obtaining correction information are connected to the host computer, and the host computer controls these devices. Therefore, the same effect as in the first and second inventions. And its reliability is improved.

According to the fourth aspect, since information on the step of the target object is provided to the external device, the information can be reflected in the improvement of the overall quality control in manufacturing the target object. According to the fifth aspect, the host computer is connected to the network,
Since the information of the step is communicated to the remote place, the information of the step can be shared with the remote place.

[Brief description of the drawings]

FIG. 1 is a flowchart of a surface position detection method according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an exposure system.

FIG. 3 is a flowchart showing steps S7 and S9 in FIG. 1;

FIG. 4 is a flowchart showing a configuration example of step 28 in FIG. 3;

[Explanation of symbols]

10 Exposure system, 11-1 to 11-n Exposure apparatus
12 host computer, 21 analysis means, S1 to S
10, S21 to S28 ... processing steps of the surface position detection method.

Claims (5)

[Claims] 1. A correction method for correcting a step formed on a surface of a target object between required steps for a target object manufactured in a plurality of steps and whose surface state sequentially transitions through each of the steps. In a surface position detection method for obtaining information, a parameter required for measuring the step data to be performed to obtain the correction information is defined in advance, and the step data is measured based on the parameter. Position detection method. 2. The parameter includes an instruction to update the step data, a measurement shot position on a target object for measuring the step data, a processing rule when an abnormal value appears, and a measurement required for measuring the step data. The number of shots, a judgment value for judging whether or not the measurement of the step data was successful, an allowable value for allowing an abnormality in the step, and the number of scans in the shot were selected. The method according to claim 1, further comprising a parameter. 3. When a plurality of devices for obtaining correction information for correcting a step formed on the surface of the target object during the necessary steps are used, these devices are connected to a host computer to configure the system. The apparatus according to claim 1 or 2, wherein each device is operated based on the parameter under the control of the host computer.
The surface position detection method described. 4. The apparatus according to claim 3, wherein part or all of the information on the step of the target object obtained by each device is provided to an arbitrary device outside the system via the host computer. The surface position detection method described. 5. A method in which the host computer is connected to a network, and a part or all of information on a step of the target object obtained by each of the devices is communicated to a remote place via the host computer and the network. The surface position detection method according to claim 3 or 4, wherein: