KR20010028305A - Method for revising registration - Google Patents

Abstract

PURPOSE: A method of compensating registration is to change tone of photoresist to exactly compensate the registration between an over-ray key and a substantial pattern on a mask. CONSTITUTION: A layer(102) to be etched is formed on a semiconductor substrate(100). The first photoresist pattern for exposing a desired area of the layer is formed on the layer using the first tone of photoresist. The layer is etched using the first photoresist pattern to transfer the pattern on the substrate. The first photoresist pattern is removed, and then the second photoresist pattern for exposing a desired area of the patterned layer is formed on a resultant structure using the second tone of photoresist(106). The patterned layer is etched using the second photoresist pattern to form a registration-estimating pattern, which is overlapped, with each pattern on the substrate. The second photoresist pattern is removed. The first tone is a positive tone, and the second tone is a negative tone.

Description

Positioning correction method {Method for revising registration}

The present invention relates to a registration correction method, and more particularly to a method for correcting the registration of the mask by changing the photoresist tone.

Fabrication of integrated circuits requires implanting impurities into small regions of the silicon substrate and interconnecting the regions to form circuit components. Patterns defining these areas are formed by a photographic process. Pattern tools commonly used in photographic processes are reticles and masks. A reticle is a tool that contains a pattern image that is step-repeated to expose the entire substrate, and a mask is a pattern tool that has patterns that can be transferred across the wafer in a single exposure. Reticles are used in two applications: to print a pattern image onto a mask and to print a pattern image directly onto a wafer from a step-repeat aligner (stepper). Among various methods for transferring circuit pattern data to a wafer, at present, a method of performing pattern generation using an electron-beam on a 10X or 5X reticle or 1X mask is mainly used.

As the semiconductor devices have been highly integrated, the circuit pattern has become smaller in size, and thus, in order to match the target size when drawing the circuit pattern on the mask or the reticle, the direction of the electron beam is minimized. If the spot size of the beam is reduced in half, the time for electron-beam writing is increased by four times. In addition, since the spot size must be different according to the pattern size, when the circuit pattern is drawn on the mask, the origin of the electron beam apparatus is first found, and then the circuit pattern is drawn on the mask to be moved to the position to be drawn again. Therefore, in this process, a manufacturing error of the mask is generated by the stage accuracy of the electron beam apparatus.

Typically, fabrication errors in masks or reticles are intended to check this by drawing a registration key on the mask itself. However, due to the difference in time between drawing the alignment key and the cell pattern or alignment key, changing the spot size during electron-beam recording, and the difference in the smashing unit according to the amount of circuit pattern data to be drawn, etc. When the origin of the beam equipment moves, an error occurs. Accordingly, when a mask misalignment occurs, the conventional method using a misalignment key cannot grasp the misalignment of the actual pattern in the cell.

1 is a flow chart of a conventional photographic process.

Referring to FIG. 1, first, a photoresist is spin coated on the wafer. Subsequently, in the exposure apparatus, the coordinate value of the alignment key formed by the photolithography process with the previous step is read using the diffraction phenomenon by the short wavelength laser or the difference in the intensity using the broadband white light. After the correction value is calculated and aligned, the photoresist layer is selectively exposed by irradiation with light such as ultraviolet rays, electron beams, or X-rays.

Subsequently, after the photoresist layer is patterned through a developing process, the overlay state of the previous layer is inspected using an overlay key in a separate overlay measuring apparatus. In this case, the alignment key used in the exposure facility and the overlay key used in the overlay facility have different patterns.

Subsequently, the overlay inspection result is read, and when the overlap measurement is spec-in, a subsequent process such as an etching process is performed. When the measurement value is spec-out, a correction value for misalignment is calculated. After that, the exposure and development processes are performed again.

2 is a layout diagram of a conventional reticle.

Referring to FIG. 2, auxiliary patterns such as an alignment key of an exposure apparatus or an overlay key of an overlay apparatus are formed in a scribe line region that separates the chip from the chip so as not to affect a circuit operation. According to the conventional alignment method, the alignment key in the alignment key area is used to perform alignment at the exposure equipment, and then read the overlay key at the overlay equipment to check the overlap between the critical pattern in the cell and the previous layer. .

At this time, in order to accurately check the overlap state between the main pattern in the cell and the previous layer, the position of the alignment key, the overlay key, and the main pattern in the cell must match the design value, and at least the position of the overlay key and the main pattern in the cell. Must match. However, according to the conventional method of drawing the alignment key outside the mask or the reticle, the alignment of the alignment key or the overlay key of the alignment key region can be grasped, but the alignment of the main pattern in the cell cannot be grasped.

In addition, when the circuit pattern is recorded on the mask or the reticle, the error of the circuit pattern recorded from the center of the mask to the outside is amplified by an error in the origin of the electron beam apparatus. Position matching error occurs. Thus, if the key patterns in the cell do not match the alignment key region as designed, the overlay measurement for the previous layer of the key pattern in the cell becomes meaningless.

An object of the present invention is to provide a position registration correction method that can accurately correct the position registration between the overlay key and the actual pattern on the mask by changing the photoresist tone.

1 is a flow chart of a conventional photographic process.

2 is a layout diagram of a conventional reticle.

3A to 7B are cross-sectional views and plan views illustrating a method of forming a position registration evaluation pattern according to the present invention.

8A to 9B are plan views illustrating a method of correcting position registration for a real pattern in a cell.

10 to 12 are plan views illustrating positioning evaluation patterns for various alignment keys.

<Description of the code | symbol about the principal part of drawing>

10 mask 100 semiconductor substrate

102 etching target layer 104 positive photoresist

106: negative photoresist

108, 202, 302, 402: Position matching evaluation pattern

200: LSA key 300: FIA key

400: WFA key

In order to achieve the above object, the present invention comprises the steps of forming an etched layer on top of the semiconductor substrate; Forming a first photoresist pattern on the etched layer to expose a predetermined region of the etched layer using a photoresist of a first tone; Etching the etched layer using the first photoresist pattern to transfer patterns onto the substrate; Removing the first photoresist pattern and forming a second photoresist pattern on the resultant to expose a predetermined region of the patterned etched layer using a second tone photoresist; Forming alignment evaluation patterns overlapping the respective patterns on the substrate by etching the patterned etched layer using the second photoresist pattern; And it provides a position matching correction method comprising the step of removing the second photoresist pattern.

Preferably, the first tone is a positive tone and the second tone is a negative tone.

Preferably, in the step of forming the second photoresist pattern, the second tone photoresist is overexposed.

According to the present invention, positional evaluation patterns overlapping each of the patterns on the substrate are formed using photoresists of different tones. Since the alignment evaluation patterns are formed on both the seal pattern in the cell and the various alignment keys in the alignment key region, the position alignment correction patterns are corrected by measuring the overlap degree of the seal pattern in the cell and the overlap degree of the alignment keys. can do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3A to 7B are cross-sectional views and plan views illustrating a method of forming a position registration evaluation pattern according to the present invention, wherein each "a" diagram shows a cross section of a manufacturing process step and each "b" diagram shows a plane.

Referring to FIGS. 3A and 3B, an etched layer 102 is formed by depositing an oxide film on the semiconductor substrate 100. After applying the positive photoresist having the property of removing the exposed portion on the upper portion of the etched layer 102, the predetermined area of the etched layer 102 by exposing and developing the positive photoresist using the mask 10 or the reticle A first photoresist pattern 104 is formed to expose 105. For example, the first photoresist pattern 104 defines a seal pattern of the cell region and various alignment key patterns of the alignment key region.

4A and 4B, the etched layer 102 is patterned using the first photoresist pattern 104 as an etching mask. As a result, the seal patterns are transferred to the cell region on the substrate 100, and various alignment keys such as an alignment key or an overlay key are transferred to the alignment region.

Subsequently, the first photoresist pattern 104 is removed by an ashing and stripping process.

Referring to FIG. 5A, a photoresist having a tone opposite to that of the photoresist used in the process of FIG. 2A, that is, a negative photoresist 106, is applied to the patterned result of the etched layer 102. The negative photoresist 106 has a property that the unexposed portions are removed.

6A and 6B, the second photoresist pattern 106 is formed by exposing and developing the negative photoresist using the mask 10. In this case, the mask 10 uses the same mask as that used in the process of FIG. 2A. Since the photoresist corresponding to the portion where the light shielding pattern is formed in the mask 10 is removed because the negative photoresist is used, The second photoresist pattern 106 is formed in a reverse phase of the first photoresist pattern 104.

At this time, the area (b) of the second photoresist pattern 106 is formed to be wider than the area (“a” of FIG. 2A) where the etched layer 102 is removed by the first photoresist pattern 104. When the etching target layer 102 is etched in the process, the alignment evaluation patterns overlapping the seal patterns in the cell and various alignment keys of the alignment key region may be formed. Therefore, the exposure amount is increased in the exposure step for forming the second photoresist pattern 106 so that the negative photoresist is overexposed.

Referring to FIGS. 7A and 7B, the etched layer 102 patterned with a seal pattern and various alignment keys in a cell is etched using the second photoresist pattern 106 as an etch mask. As a result, overlapping evaluation pattern patterns 108 are formed for each of the seal pattern and the alignment key (or overlay key) in the cell.

Subsequently, the second photoresist pattern 106 is removed by an ashing and stripping process.

In the conventional method, only the alignment of the various alignment keys of the alignment key region is evaluated using the alignment keys drawn on the mask or the reticle itself. Therefore, if the actual pattern in the cell does not match the alignment key region according to the design value, Overlay metrology becomes meaningless. In addition, even if the alignment of the alignment key is corrected, it may not be confirmed whether or not a match is made to the actual pattern in the cell.

In contrast, in the present invention, instead of drawing the alignment key in the mask or the reticle, the alignment evaluation patterns overlapping each of the seal pattern in the cell and the alignment key or the overlay key of the alignment key area are formed, and from this position evaluation evaluation pattern, By measuring the degree of overlap for each pattern it is possible to identify and correct the position registration of the mask.

Preferably, the formation of the alignment evaluation pattern is performed during a preventive maintenance (PM) cycle of the equipment, and a position alignment evaluation pattern is formed on a separate wafer on which an oxide film is deposited to correct the position alignment of the mask. do.

8A to 9B are plan views illustrating a method of correcting position registration for a real pattern in a cell.

8A and 8B, after forming the position matching evaluation pattern 108 for the actual pattern in the cell, the overlap values of the X-axis are measured for the left pattern and the right pattern, respectively. The average of the left overlap value and the right overlap value ( ) Is the position registration correction value.

For example, when the overlap value (x _L ) of the left pattern is 183 nm and the overlap value (x _R ) of the right pattern is 277 nm, the position registration correction value is Becomes Here, the minus sign indicates that the actual pattern in the cell is shifted to the left.

9A and 9B, the Y-axis overlap values of the position registration evaluation pattern 108 for the actual pattern in the cell are measured for the upper pattern and the lower pattern, respectively. Average of the upper and lower overlap values ( ) Is the position registration correction value. For example, if the actual pattern in the cell is rotated by 90 °, the left overlap value of the position registration evaluation pattern 108 becomes the overlap value of the upper pattern, and the right overlap value becomes the overlap value of the lower pattern. The axis overlap value can be obtained.

For example, when the overlap value y _T of the upper pattern is 255 nm and the overlap value y _B of the right pattern is 193 nm, the position registration correction value is Becomes Here, the (+) sign indicates that the actual pattern in the cell is biased upward.

10 to 12 are plan views illustrating positioning evaluation patterns for various alignment keys.

FIG. 10 is a plan view of a Nikon laser scan alignment (LSA) key, in which X-axis overlap values and Y-axis overlap values of the position registration evaluation pattern 202 overlapped with respect to the LSA key 200 are shown. Each measurement corrects the positional alignment of the mask with respect to the LSA key 200.

FIG. 11 is a plan view of Nikon's field image alignment (FIA) key, which measures the X-axis overlap value of the position registration evaluation pattern 302 overlapping the FIA key 300, and measures the FIA key 300. FIG. Correct the position registration of the mask.

FIG. 12 is a plan view of a wafer fine alignment (WFA) key manufactured by Microscan (MS) Inc., and measures the X-axis overlap value of the position registration evaluation pattern 402 overlapped with respect to the WFA key 400. Correct the position registration of the mask with respect to 400.

As described above, according to the present invention, after forming the position registration evaluation pattern overlapping with respect to the various alignment keys of the seal pattern and the alignment area in the cell, the overlap values of the position registration evaluation patterns for the seal pattern and the various alignment keys are obtained. Each measurement is made to correct the position registration of the mask. In addition, since the amount of misalignment of the alignment keys with respect to the actual pattern in the cell can be obtained, yield can be improved by minimizing the misalignment of the mask to secure a margin of the photolithography process.

In the above-described embodiment of the present invention, a method of correcting the mask alignment by obtaining an error amount of an alignment key relative to a real pattern in a cell using the same mask or the same reticle in the same exposure apparatus has been described. However, the positive photoresist and the negative photoresist are described. It is also possible to correct the positional alignment between the equipments by exposing different equipments to each other.

In addition, the alignment between the reticles can be corrected by exposing the positive photoresist and the negative photoresist with different reticles in the same exposure apparatus.

As described above, according to the position matching correction method of the present invention, position matching evaluation patterns overlapping each of the patterns on the substrate are formed by using photoresists of different tones. Since the alignment evaluation patterns are formed for both the seal pattern in the cell and the various alignment keys in the alignment key area, the position alignment of the mask is measured by measuring the overlap degree for the seal pattern in the cell and the overlap degree for the various alignment keys. You can correct it.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

Claims (3)

Forming an etched layer on top of the semiconductor substrate; Forming a first photoresist pattern on the etched layer to expose a predetermined region of the etched layer using a photoresist of a first tone; Transferring the patterns onto the substrate by etching the etched layer using the first photoresist pattern; Removing the first photoresist pattern and forming a second photoresist pattern on the resultant to expose a predetermined region of the patterned etched layer using a second tone photoresist; Forming an alignment evaluation pattern overlapping each of the patterns on the substrate by etching the patterned etched layer using the second photoresist pattern; And And removing the second photoresist pattern. 2. The method of claim 1, wherein the first tone is a positive tone and the second tone is a negative tone. The method of claim 1, wherein in the forming of the second photoresist pattern, the photoresist of the second tone is overexposed.