KR100576518B1 - Lithographic apparatus and exposing method in semiconductor devices using the same - Google Patents

Abstract

The present invention relates to an exposure apparatus and an exposure method of a semiconductor element using the same. More particularly, the exposure accuracy is increased by exposing only the overlay mark to form a latent image, measuring the overlapping accuracy, calculating the alignment error, and then correcting the alignment error to expose the overlapping accuracy. The present invention relates to an exposure apparatus capable of improving and achieving a uniform overlay and improving productivity, and an exposure method of a semiconductor device using the same.

An object of the present invention is an exposure apparatus having an optical system including a light source and at least one lens, a mirror, and a filter, and for projecting a pattern formed on a reticle by light transmitted through the optical system onto a substrate, the overlay mark on the substrate. And an overlay mark area exposure system for exposing a region to form a latent image and a latent image measuring system for measuring overlapping accuracy from the latent image.

Therefore, the exposure apparatus of the present invention and the exposure method of the semiconductor element using the same to expose only the overlay mark to form a latent image, measure the overlapping accuracy, calculate the alignment error, and then correct the alignment error to expose the exposure accuracy to improve all the substrate By correcting the overlay with respect to the uniform overlay can be achieved and has the effect of improving the productivity.

Latent images, overlays, overlay accuracy, exposure

Description

Lithographic apparatus and exposing method in semiconductor devices using the same}             

1 is a plan view and a cross-sectional view showing an overlay mark according to the prior art.

2 is a block diagram showing an embodiment of an exposure apparatus according to the present invention.

3 is a configuration diagram showing another embodiment of the exposure apparatus according to the present invention.

4 is a flowchart illustrating a method of exposing a semiconductor device according to the present invention.

5 is a plan view and a cross-sectional view showing an overlay mark according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method of a semiconductor device using the same, and more particularly, to expose only an overlay mark to form a latent image, to calculate an alignment error by measuring overlapping accuracy, and then to correct an alignment error. The present invention relates to an exposure apparatus capable of improving overlapping accuracy, achieving a uniform overlay, and improving productivity, and an exposure method of a semiconductor device using the same.

In recent years, with the rapid development of information media such as computers, semiconductor device manufacturing technology is also rapidly developing. The semiconductor device has been developed in the direction of improving the degree of integration, miniaturization, operating speed and the like. As a result, requirements for microfabrication techniques, such as lithography techniques for improved integration, are becoming more stringent.

Lithography technology is a photographic technology for transferring a pattern formed on a mask including a reticle to a substrate, and is a core technology that leads to miniaturization and high integration of semiconductor devices. In general, a lithography process involves a series of processes including applying photoresist, softbake, aligning and exposing, post exposure baking (PEB), and developing. Perform through.

Since the highly integrated semiconductor device has a complicated stacked structure which undergoes a plurality of lithography processes, accurate arrangement between the pattern of the upper layer and the pattern of the lower layer becomes an important factor in determining the characteristics and yield of the device. As such, the alignment between the exposure masks and the exposure apparatus and the substrate in each step for forming the laminated structure are made based on a mark of a specific shape.

The mark measures an overlay, which is an alignment key or alignment mark used for layer to layer alignment between different masks or between dies for one mask, and an overlay precision between patterns. There is an overlay accuracy measurement mark or overlay mark. Overlapping precision is an index indicating interlayer alignment between a previous step and a current step in a device having a stacked structure, and is influenced by errors in the process, errors in the mask itself, and system errors.

Stepper, a step-and-repeat exposure device that has been used since 1990s, exposes one shot and then moves the stage by one shot on the X and Y axes. In general, it has a mask size of about 5 to 6 inches and has a uniformity because it limits the shot area. The light passing through the projection lens of the stepper is reduced to 1/5 and is usually exposed to the substrate. to be. The stage is aligned automatically or manually based on the stepper alignment mark, and the stage is mechanically operated so that an alignment error occurs in a repetitive process. If the alignment error exceeds an allowable range, a defect occurs in the device. do.

The stepper alignment mark can obtain the displacement components of individual shots, but cannot obtain field components such as field magnification or shot rotation, and the field components can measure separate overlapping accuracy. Because of the use of equipment, yield and productivity are reduced due to the duplication of work, and when field component differences between boards occur, proper compensation of the entire lot is not possible, and these field component differences between boards are misaligned in the lithography process. There is a problem that a large amount of defects are connected to. The adjustment range of the overlapping accuracy according to the misalignment is in accordance with the design rule of the device, and usually within 20-30% of the design rule.

In an exposure process using a stepper, when a pattern formed on a reticle is reduced and projected onto a substrate, a problem occurs that the reduction ratio is different from a predetermined value, which is called a reduction ratio error.

BACKGROUND OF THE INVENTION Scanners have recently been used because of the advantage of improving the uniformity and realizing a large field that can cope with the increase in chip size by exposing using slits in the field. Typically, a mask size of about 6 inches and a quarter reduction exposure.

In the scanner type exposure apparatus, asymmetrical exposure occurs in which the magnifications of the X and Y axes are not constant. When trying to form a square pattern using a scanner device, the degree of asymmetry between the X and Y axes is referred to as biaxial symmetry error.

In addition, in the scanner type exposure apparatus, the reticle and the substrate move together, but the traveling direction of the substrate and the traveling direction of the reticle do not coincide, thereby forming an undesired parallelogram. This mismatch in the direction of travel between the reticle and the substrate is called directional error.

In order to minimize biaxial symmetry error and direction error that occur when the scanner and stepper are mixed, conventionally, the photoresist of the alignment mark area is exposed and developed on the stepper to form a photoresist pattern and the lower layer is etched to form the alignment mark. Then, the scanner is aligned based on the alignment mark, the overlapping accuracy is measured, and then the main exposure for pattern formation is performed by calculating and correcting the reduction ratio error, the biaxial symmetry error, and the direction error value.

The alignment mark and the overlay measurement mark are formed in a scribe lane, which is a portion where a chip is not formed in a semiconductor substrate, and a measurement method using a vernier alignment mark as a measuring method of misalignment using the alignment mark. It is measured and compensated by an inspection method and an automatic inspection method using a box in box or a box in bar alignment mark.

1 is a plan view and a cross-sectional view showing an overlay mark structure according to the prior art.

로 구해진다.As shown in FIG. 1, the conventional overlay mark is a vertical shift between the outer box 11 formed in the previous step and the inner box 13 formed in the current step, The rotation correction and orthogonal measurement are performed to generate an overlay correction value, and the generated correction value is an alignment correction value of the exposure apparatus and is reflected in the next exposure process. Here, the outer box 11 is formed of a pattern of the lower structure 10, and the inner box 13 is formed of a photoresist used for patterning the lower structure on the interlayer insulating layer 12. In one example, the distance (X, Y) between the outer box 11 and the inner box 13 is measured to determine the overlapping accuracy of the semiconductor structure depending on whether these distances are the same or not. In other words, the nesting precision

Obtained by

According to the above conventional technique, the overlapping precision is measured after the exposure process is completed. Therefore, in order to overlay correction, after the exposure process is completed, the overlapping precision is measured, the photoresist is removed through the developing process, the correction value is inserted, and the exposure process for semiconductor device pattern formation is performed again.

The overlapping precision measurement according to the prior art has the following problems. First, since the overlapping accuracy is measured after the exposure is completed, it takes a long time to proceed the exposure process again. Second, since the overlapping accuracy cannot be measured for all the substrates, the overlapping accuracy for the unmeasured substrates cannot be known. Third, since only the measured substrate is analyzed and the correction value is determined, the non-measured substrate cannot be accurately corrected.

In order to solve the above problems, Korean Patent Laid-Open Publication No. 2001-0061363 discloses a latent image by exposing an alignment key region in a stepper type exposure apparatus, and then aligns the scanner type exposure apparatus with respect to the latent image and the alignment key. A method of improving the overlapping degree in a semiconductor device manufacturing process using a stepper and an exposure apparatus of a scanner method for exposing an area to measure overlapping accuracy is disclosed.

However, the method of improving the superimposition degree as described above does not actually specify a device or method for forming a latent image, and there is a problem that it is difficult to apply when exposing only using a stepper or a scanner.

Accordingly, the present invention is to solve the problems of the prior art as described above, to improve the overlapping accuracy by exposing only the overlay mark to form a latent image, measuring the overlapping accuracy, calculating the alignment error, and then correcting the alignment error for the exposure. An object of the present invention is to provide an exposure apparatus capable of achieving a uniform overlay and improving productivity, and an exposure method of a semiconductor device using the same.

An object of the present invention is an exposure apparatus having an optical system including a light source and at least one lens, a mirror, and a filter, and for projecting a pattern formed on a reticle by light transmitted through the optical system onto a substrate, the overlay mark on the substrate. And an overlay mark area exposure system for exposing a region to form a latent image and a latent image measuring system for measuring overlapping accuracy from the latent image.

The object of the present invention is to apply a photoresist on a substrate, to expose an overlay mark area of the photoresist to form a latent image, to measure the overlapping accuracy using the latent image, from the measured overlapping precision It is also achieved by an exposure method of a semiconductor device, comprising the step of calculating the alignment error and performing exposure to form the semiconductor device pattern by correcting the alignment error.

Details of the above object and technical configuration of the present invention and the effects thereof according to the present invention will be more clearly understood by the following detailed description with reference to the drawings showing preferred embodiments of the present invention.

2 is a block diagram showing an embodiment of an exposure apparatus according to the present invention.

As shown in FIG. 2, the exposure apparatus of the present invention includes a light source 102, an illumination system 104, a condenser lens 106, an exposure area setting system 250, a projection lens 114, and a latent image measuring system 200. Although not shown in the drawing, the illumination system 104 includes a fly's eye lens, a light focusing sensor, a mirror, a filter, and a region of transmitted light to correspond to the area of the reticle for improving the uniformity of light. And a reticle blind and a collimator lens.

The exposure area setting system 250 includes light blocking means 252 for limiting an exposure area of light passing through the light source 102, the illumination system 104, and the condenser lens 106 and the reticle 108 to an overlay mark area. And a driving unit 254 that allows the light blocking means to be inserted into and removed from the light path of the exposure apparatus. In addition, the light blocking means 252 is configured to adjust the area blocking the light according to the device and the layer (layer) or to make a constant area through which light is transmitted, but the light blocking means 252 through the drive unit 254 The reciprocating motion may be performed to expose the overlay mark area sequentially. The overlay latent image mark is formed by exposing only the overlay mark area through the light blocking means 252.

Although not shown in the drawing, the exposure area setting system 250 includes an optical concentrator for focusing light, an optical fiber for exposing an overlay mark region with light collected by the optical concentrator, and an optical apparatus for exposing the optical concentrator and the optical fiber. It is possible to include a drive to enable insertion and removal on the optical path of the optical fiber to enable the reciprocating motion.

 The position of the exposure area setting system 250 may be not only before and after the reticle 108, but also before and after the projection lens 114.

The latent image measuring system 200 measures an overlay mark after exposing an overlay mark area, and measures the measurement light source 202, the beam splitter 204, the lens 206, the reflector 206, and the detector 210. It is possible to include. The measurement light source 202 uses light having a different wavelength from that of the exposure light source 102 and receives the reflected light from the detector 210 after irradiating light to an overlay latent image mark formed on the substrate W. To measure the overlapping accuracy. Exposure to form a semiconductor device pattern is performed by correcting an alignment error based on the measured overlapping accuracy.

3 is a configuration diagram showing another embodiment of the exposure apparatus according to the present invention.

As shown in FIG. 3, the exposure apparatus of the present invention includes a light source 102, an illumination system 104, a condenser lens 106, a projection lens 114, an overlay mark area exposure system 300, and a latent image measuring system 200. Although not shown in the drawing, the illumination system 104 includes a fly's eye lens, a light focusing sensor, a mirror, a filter, and a reticle blind so that the area of transmitted light corresponds to the area of the reticle. And a calibrator lens.

The overlay mark region exposure system 300 may include an overlay mark exposure light source 302, an overlay mark exposure illumination system 304, an optical fiber 306, and a driver 308 for setting light concentration and light path. The overlay mark area system 300 may be configured to move the optical fiber 306 using the driver 308 to adjust its exposure position and area according to a device and a layer. The overlay mark light source 302 may use a light source different from that of the light source 102 for exposing the semiconductor device pattern, but it is preferable to use the same light source. In this case, when exposing the overlay mark region, it is possible to further include an optical path adjusting system for transmitting light to the overlay mark region exposure system 300.

Although not shown in the figure, light blocking means may be used instead of the optical fiber 306. In this case, the shading means serves to block the light so that the light reaches only the overlay mark area, and is configured to be variable in area. In addition, the overlay mark illumination system 304 does not perform a light focusing function.

The latent image measuring system 200 measures an overlay mark after exposing an overlay mark area, and measures the measurement light source 202, the beam splitter 204, the lens 206, the reflector 206, and the detector 210. It is possible to include. The measurement light source 202 uses light having a different wavelength from that of the exposure light source 102 and receives the reflected light from the detector 210 after irradiating light to an overlay latent image mark formed on the substrate W. To measure the overlapping accuracy.

The exposure apparatus of the present invention is preferably a stepper or scanner and is not limited to the optical system configuration shown in FIGS. 2 and 3. That is, it is applicable regardless of the configuration difference of the optical system according to the type of exposure apparatus, and can be applied regardless of the configuration difference of the optical system according to the device maker.

4 is a flowchart illustrating a method of exposing a semiconductor device according to the present invention, and FIG. 5 is a plan view and a cross-sectional view illustrating an overlay mark according to the present invention.

Hereinafter, a process of performing exposure with the exposure apparatus of the present invention will be described with reference to FIGS. 4 and 5.

First, the semiconductor substrate is transferred to an exposure apparatus to apply a photoresist (S100). A predetermined lower structure 20 is formed on the semiconductor substrate (not shown), and an outer box 21 for overlay measurement formed by the lower structure 20 exists, and an interlayer insulating layer 22 is disposed thereon. do. The interlayer insulating film 22 is shown as an example and is not necessarily present.

Next, an overlay mark area of the photoresist is exposed to form a latent image (S101). By exposing an overlay mark area, the photoresist causes a reaction and the photoresist causes a thickness change or a phase change so that the exposed portion 30 and the unexposed portion 40 show a difference to form a latent image 23. Done.

로 구해진다.Next, the overlapping precision is measured using the latent image 23 (S102). Generates an overlay correction value by measuring the vertical and horizontal misalignment, rotation, and orthogonality between the outer box 21 formed in the previous step and the inner box 23 formed in the present step, and the generated correction value is an alignment correction value of the exposure apparatus. It is reflected in the next exposure process. In one example, the distances X 'and Y' between the outer box 21 and the inner box 23 are measured to determine the overlapping accuracy of the semiconductor structure depending on whether these distances are the same or not. In other words, the nesting precision

Obtained by

Next, an alignment error is calculated from the measured overlapping precision (S103). The alignment error includes biaxial symmetry error, reduction ratio error and direction error.

Finally, after the exposure is corrected to form the semiconductor device pattern by correcting the alignment error (S104), a subsequent process such as development is performed. Since the alignment error is corrected and exposed, the overlapping accuracy between the patterns can be greatly improved. Since the photoresist removing process is not necessary before the exposure to form the semiconductor device pattern, the process is simplified and overlay compensation is performed on all substrates. As a result, there is no variation in the overlapping accuracy between the substrates. In addition, the present invention is also applicable to the case where a stepper or scanner type exposure apparatus is used alone without being mixed.

Although the present invention has been shown and described with reference to preferred embodiments as described above, it is not limited to the above-described embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

Therefore, the exposure apparatus of the present invention and the exposure method of the semiconductor element using the same to expose only the overlay mark to form a latent image, measure the overlapping accuracy, calculate the alignment error, and then correct the alignment error to expose the exposure accuracy to improve all the substrate By correcting the overlay with respect to the uniform overlay can be achieved and has the effect of improving the productivity.

Claims (5)

An exposure apparatus comprising a light source and an optical system including at least one lens, a mirror, and a filter, and projecting a pattern formed on a reticle by light transmitted through the optical system on a substrate. An overlay mark region exposure system for exposing an overlay mark region on a substrate to form a latent image; And Latent image measuring system for measuring overlapping accuracy from the latent image Exposure apparatus comprising a. The method of claim 1, The overlay mark area exposure system A light source for exposing an overlay mark region; An illumination system for adjusting light emitted from the light source for exposing the overlay mark region; An optical fiber for exposing an overlay mark region with light passing through the illumination system; And Driving unit for driving the optical fiber Exposure apparatus comprising a. The method of claim 1, The overlay mark area exposure system A light source for exposing an overlay mark region; An illumination system for adjusting light emitted from the light source for exposing the overlay mark region; And Light blocking means to expose the light passing through the illumination system only in the overlay mark area Exposure apparatus comprising a. In the exposure method of a semiconductor element, Applying a photoresist on the substrate; Exposing an overlay mark region of the photoresist to form a latent image; Measuring overlapping accuracy using the latent image; Calculating an alignment error from the measured overlapping precision; And Performing exposure to form a semiconductor device pattern by correcting the alignment error Exposure method of a semiconductor device comprising a. The method of claim 4, wherein The latent image formation and latent image measurement are performed in the same exposure apparatus.

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