JPH06112103A - Exposure apparatus and exposure method - Google Patents

Abstract

(57) [Summary] [Objective] The overlay accuracy is improved by reducing the amount of displacement due to lens distortion between the exposure apparatuses. A peripheral exposure device 9 for forming a mark peculiar to each exposure device at a predetermined position on the peripheral edge of the wafer 2, and a sensor unit 17 for image-recognizing the shape of the mark formed by this peripheral exposure device. The image processing unit 10 for identifying each exposure device by the image information recognized by the sensor unit 17, the memory unit 11b to which the distortion data of each exposure device is input in advance, and the image processing unit 10 are identified. A calculation unit 11a for comparing the distortion data with the distortion data of the exposure device that is currently performing exposure, and an exposure device that is currently performing exposure based on the information obtained by this calculation unit 11a A pressure control means 13 for controlling the pressure applied to the projection lens 5 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in an optical lithography process in an LSI manufacturing process and an exposure method using the exposure apparatus, and in particular, it is possible to improve overlay accuracy between the exposure apparatuses. And an exposure method using the exposure apparatus.

[0002]

2. Description of the Related Art Conventionally, an apparatus called a stepper has been known as an exposure apparatus used for semiconductor manufacturing.
This stepper reduces the pattern image formed on the reticle by the projection lens and sequentially exposes each shot area on one wafer while moving the wafer stepwise under the projection lens. Various improvements have been made to this stepper in order to improve the alignment accuracy. An example of a conventional method for improving the alignment accuracy is disclosed in Japanese Patent Laid-Open No. 61-44429. Hereinafter, with reference to FIG.
The alignment method disclosed in Japanese Patent No. 29 will be described.

FIG. 5 is a flow chart schematically showing an exposure sequence of the conventional enhancement global alignment (EGA) method disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-44429. Referring to FIG. 5, first, the wafer is pre-aligned using the orientation flat of the wafer (step S10). After that, the rotation of the wafer is corrected using the wafer global alignment (WGA) mark formed in each shot area (step S11).

Then, the wafer stage is moved based on the design value of the chip arrangement, and the laser step alignment (LSA) optical system is used to set the LSA of the printing pattern for a plurality of shot areas set for error detection.
Detect the alignment mark position. At the same time, the position of the wafer stage is detected by the laser interferometer.
Then, based on these detected values, an overlay error between the printing pattern on the wafer and the pattern image of the reticle is detected (step S12).

Next, a deviation from the actual position coordinate of each shot (position coordinate of the printing pattern) is obtained from the overlay error in each shot and the above-mentioned position coordinate of the wafer stage. Then, the average value of the deviations is calculated as a correction value (error parameter) (step S13). From this error parameter and the design value, a chip array map that has undergone rotation, orthogonality, baseline, and scaling correction is created (step S14).

Then, according to this chip arrangement map,
The wafer stage is positioned by the step-and-repeat method (step S15). Then, each shot is exposed (step S16). As described above, there are four correction values (error parameters) in the above cases: baseline correction, rotation correction, orthogonality correction, and scaling correction. By using these four correction values, it becomes possible to obtain a more accurately superimposed pattern.

[0007]

However, in the above-mentioned alignment method, when detecting the deviation of the alignment mark, the deviation due to the lens distortion is not taken into consideration. Therefore, there are problems as described below.

FIG. 4 is a schematic diagram showing how the exposed pattern deviates from the ideal grid due to lens distortion. With reference to FIG. 4, the actually exposed exposure pattern 21 is displaced from the ideal grating 20 by a predetermined amount due to lens distortion, as shown in FIG. In this case, the exposed position A ′ is displaced from the ideal position A by ΔX. Since such a deviation from the ideal position can exist in each exposure apparatus, when exposure is performed through a plurality of exposure apparatuses, the deviation of the exposure image from the ideal position as the exposure apparatus passes. It can be said that the amount will increase. As a result, there has been a problem that the overlay margin due to exposure between the exposure devices is significantly reduced.

The present invention has been made to solve the above problems, and an object thereof is to improve overlay accuracy by reducing an error due to distortion such as lens distortion between exposure apparatuses. To do.

[0010]

An exposure apparatus according to the present invention is a peripheral exposure apparatus for forming a mark peculiar to each exposure apparatus at a predetermined position on a peripheral portion of a wafer, and a mark formed by the peripheral exposure apparatus. A sensor unit for recognizing the shape of the image, an image processing unit for identifying each exposure device by the image information recognized by the sensor unit, and a memory unit in which distortion data of each exposure device is input in advance, Comparison means for comparing the distortion data of the first exposure device and the distortion data of the second exposure device identified by the image processing part, and the projection lens of the second exposure device based on the information obtained by the comparison means. And a pressure control means for controlling the pressure applied to.

According to the exposure method of the present invention, first, the first peripheral exposure apparatus forms a first mark peculiar to the first exposure apparatus at a predetermined position on the wafer. Then, the sensor unit recognizes the shape of the first mark formed by the first peripheral exposure apparatus, and at the same time, forms the second mark unique to the second exposure apparatus at a predetermined position on the wafer by the second peripheral exposure apparatus. To do. Then, each exposure apparatus is identified based on the information recognized by the sensor section by the image processing section, the distortion data of the first exposure apparatus identified by this image processing section is taken out from the memory section, and the second data is extracted by the comparing means. Compare with the distortion data of the exposure device. Then, based on the information obtained by the comparison means, the pressure control means controls the pressure applied to the projection lens of the second exposure apparatus.

[0012]

According to the exposure apparatus and the exposure method according to the present invention, it is possible to form a mark peculiar to each exposure apparatus at a predetermined position on the peripheral portion of the wafer. Thereby, each exposure apparatus can be specified by identifying the mark. Since the distortion data of each exposure device is input to the memory unit of the exposure device in advance, it is possible to appropriately obtain the distortion data generated by the specified exposure device. This makes it possible to compare the distortion data of the first exposure apparatus with the distortion data of the second exposure apparatus that is currently performing exposure.

Then, by comparing the distortion data of the first exposure apparatus and the distortion data of the second exposure apparatus by the comparison means, the deviation amount between them can be calculated. By controlling the pressure applied to the projection lens of the second exposure device in consideration of this displacement amount, it is possible to significantly reduce the displacement amount between the distortion data of the first exposure device and the distortion data of the second exposure device. Becomes As a result, the displacement due to distortion between the exposure devices can be significantly reduced,
As a result, it is possible to improve the alignment accuracy between the exposure apparatuses.

[0014]

EXAMPLE An example based on the present invention will be described below.
This will be described with reference to FIGS. FIG. 1 is a block diagram showing a schematic configuration of an exposure apparatus in an embodiment based on the present invention. With reference to FIG. 1, an exposure apparatus according to the present invention includes a wafer stage 1 on which a wafer 12 is placed and which performs a step-and-repeat operation, and a projection lens 5 provided on the wafer stage 1 at a predetermined distance. Projection lens 5
A reticle 4 installed on the reticle 4 with a predetermined space therebetween, and an illumination for printing an actual element pattern image on the reticle 4 onto a wafer 2 mounted on a wafer stage 1 via a projection lens 5. The system 3, the mirror 8 provided on the projection lens 5 at a predetermined distance, the mark detection optical system 7 for reading the position of the alignment mark of the existing baking pattern of the wafer 2 via the mirror 8, and the processing system 11 The wafer stage driving device 12, the image processing device 10, the peripheral exposure unit 9, and the pressure control unit 13 are provided.

The peripheral exposure section 9 is provided with a peripheral exposure device 9a and a sensor section 9b. This peripheral exposure device 9a
Thus, a resist image having a shape peculiar to the exposure apparatus is exposed on the wafer 2. As a result, a mark peculiar to the exposure apparatus is formed at a predetermined position on the peripheral portion of the wafer 2. Thereby, each exposure apparatus can be specified by identifying the mark.

Now, with reference to FIG. 2, a description will be given of which part of the wafer 2 the mark is formed by the peripheral exposure device 9a. FIG. 2 shows the wafer 2.
Shot area 15 and resist removal area 14 in
3A and 3B are explanatory diagrams schematically showing a peripheral exposure area 16.
Referring to FIG. 2, orientation flat portion 2a is formed on a predetermined portion of wafer 2. Then, a resist-removed region 14 in which the resist is removed in a strip shape from the peripheral portion of the wafer 2 by a distance of, for example, 2 to 3 mm is formed.

A shot area 15 exists at a predetermined distance from the resist removal area 14. Each shot will be performed in this shot area 15. In the present invention, the area between the resist removal area 14 and the shot area 15 (peripheral exposure area 16)
In addition, the peripheral exposure device 9a described above forms a mark unique to each exposure device. As a method of forming the mark, the mark is formed in the peripheral exposure region 16 by shifting the wafer 2 during exposure for forming the resist removal region 14, for example.

The peripheral exposure section 9 also has the sensor section 9b as described above. The sensor portion 9b has a function of recognizing a position from the orientation flat portion 2a of the wafer 2 where the mark is printed.

On the other hand, the sensor section 17 is connected to the image processing apparatus 10 as shown in FIG. 1, and the image processing apparatus 10 is connected to the processing system 11. The sensor unit 17 performs image recognition of the shape of the mark formed by the peripheral exposure device. Then, the image information captured by the sensor unit 17 is sent to the image processing apparatus 10. The image processing apparatus 10 identifies which exposure apparatus has performed the exposure. Then, the identified information is sent to the processing system 11.

On the other hand, in the processing system 11, the memory section 11b is provided.
And a calculation unit 11a are provided. Data of lens distortion of each exposure apparatus is stored in the memory section 11b in advance. The calculation unit 11a has a function as a comparison unit that appropriately retrieves the information stored in the memory unit 11b and compares the information. As a result, the calculation unit 11a can calculate the deviation amount of the distortion data between the exposure apparatuses.

Further, the processing system 11 is further connected to a wafer stage driving device 12 and a pressure control means 13. As a result, it becomes possible to move the wafer stage according to a command from the processing system 11. The processing system 11 also makes it possible to control the pressure in the room where the projection lens 5 is provided. As a result, the pressure control means 13 is operated according to the amount of deviation of the distortion data.
Makes it possible to control the pressure exerted on the projection lens.

Next, the exposure method according to the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a flow chart schematically showing the exposure method according to the present invention. Figure 3
First, exposure is performed using the first reduction projection exposure apparatus having a lens distortion as shown in FIG. 4 (step S1). At the same time, the sensor unit 9b in the peripheral exposure apparatus 9 detects a predetermined position in the wafer 2 which is set in advance. Then, the peripheral exposure unit 9a exposes a mark peculiar to the first exposure apparatus to the portion (step S2).

Next, the wafer 2 having a desired pattern is exposed by using another second reduction projection exposure apparatus. At that time, the sensor unit 17 and the image processing apparatus 10 read a mark peculiar to the first exposure apparatus (step S3).
This identifies which exposure apparatus was used to perform the exposure. The identified information is transmitted to the memory unit 11b (step S4). Then, the distortion data of the first exposure apparatus is taken out from the memory section 11b.

Then, the fetched distortion data is compared with the distortion data of the second exposure apparatus which is currently performing exposure. This is performed by the arithmetic unit 11a in the processing system 11. By comparing in this way, the amount of deviation between the two can be detected (step S5). Thereby, the distortion data is captured.

Then, the pressure control means 13 adjusts the atmospheric pressure in the lens chamber in which the projection lens 5 is installed so as to eliminate this displacement amount. As a result, the distortion of the lens can be adjusted, and the amount of deviation between the distortion data can be significantly reduced. As a result, it is possible to improve the overlay accuracy between the exposure apparatuses.

After performing the alignment processing based on the lens distortion data in this way, the same alignment method as in the conventional example is performed. In the above embodiment, the alignment was performed using the lens distortion data, but the present invention can be used for all information related to the exposure apparatus other than the lens distortion data.

[0027]

As described above, according to the present invention, it is possible to significantly reduce the amount of displacement due to distortion such as lens distortion between exposure apparatuses. As a result, it becomes possible to improve the alignment accuracy between the exposure apparatuses in each stage as compared with the conventional example, and as a result, it is also possible to improve the wafer yield.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an exposure apparatus in an embodiment based on the present invention.

FIG. 2 is a diagram showing a region where peripheral exposure is performed according to the present invention.

FIG. 3 is a flow chart schematically showing an exposure method according to the present invention.

FIG. 4 is a schematic diagram showing a shift between an ideal lattice pattern and a pattern including lens distortion after exposure.

FIG. 5 is a flowchart schematically showing a conventional exposure method.

[Explanation of symbols]

 5 Projection Lens 9 Peripheral Exposure Device 9a Peripheral Exposure Unit 9b Sensor Unit 10 Image Processing Device 11 Processing System 11a Computing Unit 11b Memory Unit 13 Pressure Control Means 17 Sensor Unit

Claims (2)

[Claims] 1. A peripheral exposure device for forming a mark peculiar to each exposure device at a predetermined position on a peripheral portion of a wafer, a sensor part for recognizing an image of a shape of the mark formed by the peripheral exposure device, An image processing unit for identifying each exposure device based on the image information recognized by the sensor unit, a memory unit in which distortion data of each exposure device is input in advance, and a first exposure device identified by the image processing unit. Comparing means for comparing the distortion data of the second exposure apparatus with the distortion data of the second exposure apparatus, and the second means based on the information obtained by the comparing means.
An exposure apparatus comprising: a pressure control unit for controlling the pressure applied to the projection lens of the exposure apparatus. 2. A step of forming a first mark peculiar to the first exposure apparatus at a predetermined position on the wafer by the first edge exposure apparatus, and a first mark formed by the first edge exposure apparatus by the sensor unit. The step of recognizing the shape of the mark; the step of forming a second mark peculiar to the second exposure apparatus at a predetermined position on the wafer by the second peripheral exposure apparatus; the information recognized by the sensor section by the image processing section. Identifying each exposure device based on the above, and extracting the distortion data of the first exposure device identified by the image processing unit from the memory unit and comparing it with the distortion data of the second exposure device by the comparison means. Controlling the pressure applied to the projection lens of the second exposure apparatus by the pressure control means based on the information obtained by the comparison means; An exposure method comprising.