JP2008053413A - Focal deviation measuring method, and focal alignment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire focal displacement by utilizing relation between the displacement from the optimal exposure position of the surface position of a base substrate and the difference in the top length of a resist pattern and the bottom length. <P>SOLUTION: In the case that a refractive index and thickness of the resist in the same exposure conditions are equal, an expression of relations between a difference ΔL and a displacement ΔF are obtained beforehand. The focal displacement is acquired for every exposure shot by substituting the difference ΔL between the top length Lt of the resist pattern for measuring and the bottom length Lb into the above relational expression. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defocus measurement method for determining a position of a substrate surface in a direction perpendicular to a surface of a semiconductor wafer when a resist layer formed on the semiconductor wafer is exposed in a photolithography process, and its focus The present invention relates to a focus alignment method for performing focus alignment using a focus shift amount obtained by a shift measurement method.

  In manufacturing a semiconductor device, a predetermined patterning is generally performed on a semiconductor wafer by a photolithography process and an etching process. With the recent miniaturization of semiconductor devices, the resist pattern formed on a semiconductor wafer by a photolithography process is also being miniaturized.

  In order to form a resist pattern, projection exposure of a mask pattern is performed on the resist layer formed on the surface of the semiconductor wafer from a direction perpendicular to the surface of the semiconductor wafer. As a factor that affects the quality of the resist pattern formed on the semiconductor wafer, there is a shift in the position of the semiconductor wafer surface with respect to the optimum exposure position of the semiconductor wafer surface in a direction perpendicular to the semiconductor wafer surface (for example, Patent Documents). 1 or 2).

  Here, the optimum exposure position is a position determined by the focal position of the reduction projection lens of the exposure apparatus, the refractive index and the thickness of the resist applied to the substrate surface, and the semiconductor wafer surface coincides with the optimum exposure position. Sometimes it is in focus.

  The semiconductor wafer is placed on the wafer stage of the exposure apparatus and exposed. At this time, there may be a case where a focus shift occurs in each region exposed at a time due to the tilt of the wafer stage, the surface unevenness, or the semiconductor wafer surface unevenness.

  Therefore, for each exposure shot, in order to align the position of the semiconductor wafer surface with the optimum exposure position, a measurement pattern in which a plurality of sub-patterns having a width equal to or smaller than the resolution limit of the exposure apparatus are arranged in parallel and separated from each other. A defocus measurement method using a change in the length of a resist pattern for measurement with respect to a change in the position of the semiconductor wafer surface has been proposed (for example, see Patent Document 1).

Further, a method has been proposed in which the upper and lower limits of the position of the semiconductor wafer surface are obtained from the relationship between the edge dimension of the cross section of the resist pattern and the position of the surface (for example, see Patent Document 2).
JP 2004-55575 A JP 2003-338443 A

  In the method disclosed in Patent Document 1 described above, if the amount of deviation from the optimum exposure position on the surface of the semiconductor wafer, that is, the amount of focus deviation is 0.4 μm or more, the amount of deviation can be obtained sufficiently. However, at present, the number of processes requiring an allowable range of about 0.1 μm as the amount of defocus is increasing. When the deviation amount is 0.4 μm or less, the change in the length of the measurement resist pattern with respect to the change in the surface position in the direction perpendicular to the substrate surface is small, and the linearity is poor. It is difficult to obtain the amount of deviation with the required accuracy by the defocus measurement method. Further, while the allowable range of the focus shift amount is about 0.1 μm, the shift amount can be measured with sufficient accuracy when the shift amount is 0.4 μm or more. Therefore, it is difficult to form a resist pattern for measuring a deviation amount and a resist pattern for forming a circuit pattern in the same process using one mask.

  Therefore, the inventor according to this application has conducted intensive research and uses a photomask having a measurement mask pattern composed of a plurality of measurement submask patterns similar to the measurement pattern disclosed in Patent Document 1. When the photolithography process is performed, the difference ΔL between the bottom length Lb and the top length Lt of the integral continuous measurement resist pattern to which the measurement mask pattern is transferred is linear with respect to the focus shift amount ΔF. Found to change. As a result, a relational expression between the difference ΔL between the top length Lt and the bottom length Lb of the measurement resist pattern and the deviation amount ΔF in the case where the refractive index and thickness of the resist under the same exposure conditions are equal is obtained in advance. Thereafter, by substituting the difference ΔL obtained by the measurement into the above-described relational expression, it is possible to acquire the defocus amount for each exposure shot.

  The present invention has been made in view of the above-described problems, and an object of the present invention is the relationship between the difference ΔL between the top length Lt and the bottom length Lb of the measurement resist pattern and the focus shift amount ΔF. Is used to provide a defocus measurement method for obtaining the defocus amount ΔF from the measured difference ΔL, and a focus alignment method using this defocus measurement method.

  In order to achieve the above-described object, the defocus measurement method of the present invention includes the following steps.

  First, a measurement mask pattern composed of a plurality of elongated rectangular quadrilateral measurement submask patterns arranged in parallel and with an arrangement period shorter than the resolution limit of the exposure apparatus, and a central region of the rectangular quadrilateral A first photomask having a pair of measurement mask patterns provided in a position in the longitudinal direction of the measurement submask pattern at a position sandwiching the measurement mask is prepared. Next, after a resist is applied on the base substrate to form a first resist layer, the entire first resist layer is perpendicular to the surface of the base substrate for each exposure shot using the first photomask. The exposure is performed by changing the substrate exposure position, which is a position in a different direction. Next, the exposed first resist layer is developed to obtain a pair of continuous measurement resist patterns in which the space between the measurement submask patterns corresponding to the measurement mask pattern is embedded. Next, the maximum separation distance between the outermost walls of the pair of measurement resist patterns measured in the direction corresponding to the longitudinal direction of the measurement submask pattern is defined as the bottom length Lb, and the minimum separation distance is defined as the top length. When the length Lt is set, the reference exposure position in focus is determined from the bottom length Lb and the substrate exposure position. Next, a relational expression is obtained between the difference ΔL (= Lb−Lt) between the bottom length Lb and the top length Lt and the shift amount ΔF of the substrate exposure position from the reference exposure position. Next, after applying a resist on the base substrate to form the second resist layer, the second resist layer having the same form as the first photomask is used, and the entire second resist layer is referenced to the substrate exposure position. Exposure is performed with the exposure position fixed. Next, the exposed second resist layer is developed to obtain a measurement resist pattern. Next, using the above-described relational expression, a focus shift amount ΔF is obtained for each exposure shot from the difference ΔL between the bottom length Lb and the top length Lt of the measurement resist pattern.

  According to the defocus measurement method of the present invention, a plurality of right-sided quadrilateral measurement sub-mask patterns arranged in parallel and with an arrangement period shorter than the resolution limit of the exposure apparatus as the measurement mask pattern provided in the photomask The thing which consists of is used. For this reason, the difference ΔL between the top length Lt and the bottom length Lb of the measurement resist pattern to which the measurement mask pattern is transferred is the amount of deviation from the optimum exposure position of the surface position of the base substrate, that is, the amount of focus deviation ΔF. Changes linearly with a large inclination. Therefore, even when the deviation amount ΔF is small, the deviation amount ΔF can be obtained including whether the deviation amount is in the vertical direction.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the shape, size, and arrangement relationship of each component are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, the composition (material) and numerical conditions of each component are merely preferred examples. Therefore, the present invention is not limited to the following embodiment. In addition, although there is a part which is hatched in the plan view, it is for emphasizing and showing the constituent elements, and does not show a cross section.

(Photomask)
With reference to FIG. 1, a photomask used in the defocus measurement method and the focus alignment method will be described. FIG. 1 is a diagram for explaining a photomask used in the present invention. FIG. 1A is a schematic enlarged plan view of a photomask, and FIG. 1B is a view showing a cross section cut along the line AA in FIG.

  The photomask 100 includes a transparent substrate 210 such as quartz glass, and a light shielding film 240 and a mask pattern 260 provided on the transparent substrate 210. A region parallel to the substrate surface of the photomask 100 is divided into a light shielding region 110 and a pattern region 120 defined by the light shielding region 110. A light shielding film 240 is formed on the transparent substrate 210 in the light shielding region 110. A mask pattern 260 is formed on the transparent substrate 210 in the pattern region 120. In this configuration example, the pattern region 120 has a rectangular shape. Here, the right-angled quadrilateral shape indicates either a square shape or a rectangular shape.

  The light shielding film 240 and the mask pattern 260 are obtained by depositing, for example, chromium on the transparent substrate 210 to form a light shielding film, and then patterning the light shielding film.

  In the center of the pattern area 120, a right-angled quadrilateral central area 140 is set. A measurement area 130 is set around the central area 140 corresponding to each side of the central area 140. One measurement mask pattern 250 is formed in each measurement region 130. In the central region 140, a circuit mask pattern 230 corresponding to the circuit pattern formed on the semiconductor wafer is formed using a light shielding film.

  The measurement mask pattern 250 includes a plurality of elongated rectangular quadrilateral measurement submask patterns 220. The measurement submask patterns 220 are arranged in parallel and at equal intervals. The measurement submask patterns 220 are provided such that their longitudinal directions are perpendicular to the sides of the central region 140. In addition, the measurement submask pattern 220 is arranged with its ends aligned in a direction parallel to the sides of the opposing central region 140. The arrangement period of these measurement submask patterns 220 is shorter than the resolution limit of the exposure apparatus.

  After applying a resist on a semiconductor wafer to form a resist layer and then performing exposure and development using the above-described photomask, the mask pattern of the photomask is transferred to the resist to form a resist pattern.

  With reference to FIG. 2, the measurement resist pattern formed corresponding to the measurement submask pattern 220 will be described. FIG. 2 is a diagram for mainly explaining the measurement resist pattern. FIG. 2A is a schematic enlarged plan view of a resist pattern including a measurement resist pattern and a circuit resist pattern. FIGS. 2B and 2C are respectively B in FIG. 2A. It is a figure which shows the cut end of the cross section along the -B line and CC line.

  The resist pattern 320 formed on the base substrate 310 is composed of a circuit resist pattern 300 corresponding to the central circuit mask pattern and a peripheral measurement resist pattern 330.

  Here, the measurement submask patterns 220 provided in the photomask 100 described with reference to FIG. 1 are arranged with an arrangement period shorter than the resolution limit of the exposure apparatus. For this reason, the measurement submask pattern 220 is not resolved when the mask pattern is transferred to the resist layer. Therefore, even if the resist layer is developed, the resist layer is not separated into individual resist patterns corresponding to the individual measurement submask patterns 220 on a one-to-one basis. Therefore, each of the measurement mask patterns 250 is formed as one integral continuous measurement resist pattern 330 in which the space between the measurement submask patterns 220 is embedded. For example, when a KrF excimer stepper with a wavelength of 248 nm is used as the exposure apparatus, the measurement submask pattern width is 0.1 μm, the interval is 0.1 μm, and the length is 4 μm. To do.

  The measurement resist pattern 330 is formed as a trapezoidal pattern with inclined side walls. Therefore, the bottom surface and the top surface of the resist pattern 330 are similar, but the area of the bottom surface is larger than the area of the top surface. Therefore, the maximum separation distance between the outermost walls of the two measurement resist patterns 330 facing each other across the circuit resist pattern 300 is Lb, and the minimum separation distance is Lt. Here, the outermost wall indicates the side wall of the surface (330b) opposite to the facing surface (330a) for each of the two opposing measurement resist patterns 330.

  The maximum separation distance Lb is the bottom length of the measurement resist pattern 330, that is, the length of the lower surface of the semiconductor wafer, and the minimum separation distance Lt is the top length of the measurement resist pattern 330, that is, It is the length of the upper surface facing the lower surface. These lengths are lengths along the direction corresponding to the long direction of the measurement submask pattern. The defocus is measured using these lengths Lt and Lb. Here, the bottom length Lb and the top length Lt are described as being measured using a portion of the resist pattern sandwiching the circuit resist pattern 300, that is, using a pair of measurement resist patterns. A resist pattern for measurement may be used. In this case, the maximum width measured in the direction corresponding to the longitudinal direction of the measurement submask pattern is the bottom length Lb ′, and the minimum width is the top length Lt ′.

  Note that in a pattern with a width narrower than the resolution limit of the exposure apparatus, the change in the length of the tip due to defocusing, that is, the change in the length in the direction corresponding to the longitudinal direction of the measurement submask pattern is large. The measurement of the length Lb (Lb ′) and the top length Lt (Lt ′) is preferably performed in a direction corresponding to the longitudinal direction of the measurement submask pattern having a large change.

  Further, since the projection lens of the exposure apparatus has an aberration that causes a difference in focal position in the horizontal direction and the vertical direction (X direction and Y direction in FIG. 1), the photomask has two sets in the X direction and the Y direction. The measurement mask pattern may be provided (see FIG. 1A). Note that, as a configuration including a set of measurement mask patterns as a photomask, measurement may be performed for each of the X direction and the Y direction.

(Defocus measurement method)
The defocus measurement method will be described with reference to FIGS. Note that the photomask and the resist pattern may be referred to FIGS. FIG. 3 is a schematic diagram showing a state in which exposure is performed using an exposure apparatus.

  According to the method for measuring defocus of the present invention, the difference ΔL between the top length Lt and the bottom length Lb of the resist pattern for measurement when the refractive index and the thickness of the resist under the same exposure conditions are equal in advance. By obtaining a relational expression of the deviation amount ΔF and then substituting the difference ΔL obtained by the measurement into this relational expression, the focal deviation amount can be acquired for each exposure shot. Details will be described below.

  In the following description, the top length Lt and the bottom length Lb may be collectively referred to as a resist length L.

  The process of obtaining the relational expression between the resist length L and the shift amount ΔF includes the following steps (hereinafter, steps are represented by S) 10 to S40.

  In step S10, first, a resist is applied to the base substrate 310 to form the first resist layer 340, and then the base substrate is provided with the first resist layer 340 on a wafer stage (not shown) of the exposure apparatus. 310 is fixed. Here, a semiconductor substrate or a substrate including a layer patterned by photolithography and etching on the semiconductor substrate can be used as the base substrate. In the following description, this substrate may be referred to as a semiconductor wafer. Further, the first photomask 100a on which the measurement mask pattern is formed is fixed on a reticle stage (not shown) of the exposure apparatus. As the first photomask, the photomask described with reference to FIG. 1 can be used.

  The first photomask 100a is projected onto the first resist layer 340 by the reduction projection lens 400, and exposure is performed. This exposure is performed on the entire region of the first resist layer 340 on the base substrate 310 while shifting the wafer stage by the region exposed by one exposure in the horizontal direction. At this time, the substrate exposure position Fm is changed for each exposure shot. The substrate exposure position Fm is a position in the direction (Z direction) perpendicular to the surface of the base substrate 310, and depends on the focal position of the reduction projection lens of the exposure apparatus, the refractive index and the thickness of the resist. Determined. In the step S10, it is assumed that the surface of the base substrate is a virtually flat surface without unevenness. The substrate exposure position Fm is determined by, for example, the distance between the reticle stage and the wafer stage and the average thickness of the base substrate. The position where the substrate exposure position Fm matches the optimal exposure position is referred to as a reference exposure position F0.

  In S20, the exposed first resist layer 340 is developed to obtain the first resist pattern, and then the resist length of the bottom length Lb and the top length Lt of the measurement resist pattern included in the first resist pattern is obtained. Measure L. The measurement resist pattern included in the first resist pattern may be referred to as a measurement first resist pattern.

  When the photomask described with reference to FIG. 1 is used as the first photomask 100a, the resist pattern described with reference to FIG. 2 is obtained as the first resist pattern. The measurement of the resist length L is performed by using a measurement apparatus including an optical microscope, for example, an overlay measurement apparatus generally used for overlay measurement of a base substrate and a layer formed on the base substrate in manufacturing a semiconductor device. It can be carried out.

  In S30, the reference deviation position ΔF and the resist length L are plotted on the orthogonal coordinate plane to obtain the reference exposure position. FIG. 4 is a characteristic diagram showing the relationship between the defocus amount ΔF (unit: μm) obtained by plotting and the resist length L (unit: μm). In FIG. 4, the horizontal axis indicates the shift amount ΔF, and the vertical axis indicates the resist length L. In FIG. 4, the curve I indicates the bottom length Lb, and the curve II indicates the top length Lt. Here, the bottom length Lb is maximum when the substrate exposure position Fm coincides with the reference exposure position F0, and the shift amount ΔF at this time is set to zero. Further, when the substrate exposure position Fm is shifted upward from the reference exposure position F0, that is, closer to the reduction projection lens 400 (see FIG. 3), the shift amount ΔF is set to a positive value, and the reference exposure position F0. In contrast, the shift amount ΔF is set to a negative value when it is shifted downward. As shown by curves I and II in FIG. 4, the substrate exposure position Fm at which the top length Lt is maximum is different from the substrate exposure position at which the bottom length Lb is maximum, that is, the reference exposure position F0.

  In S40, the deviation amount ΔF of the substrate exposure position Fm from the reference exposure position F0 and the resist length difference ΔL (= Lb−Lt) are plotted on the orthogonal coordinate plane, and the deviation amount ΔF and the resist length difference ΔL are plotted. Get a relationship. FIG. 5 is a characteristic curve diagram showing the relationship between the focus shift amount ΔF and the resist length difference ΔL. In FIG. 5, the horizontal axis indicates the deviation amount ΔF (unit: μm), and the vertical axis indicates the resist length difference ΔL (unit: μm).

  According to the result shown in FIG. 5, as indicated by the curve III, the difference ΔL shows a monotonous increase that rises to the right near the deviation amount ΔF of 0, that is, near the reference exposure position F0. In particular, in the range of −0.4 μm to +0.6 μm, the difference ΔL with respect to the shift amount ΔF can be linearly approximated within an error range of about 15%. That is, the difference ΔL with respect to the deviation amount ΔF is approximated by the following equation (1), where the slope is A and the intercept is B.

ΔL = A × ΔF + B (1)
It should be noted that the shape of this graph hardly changes when the same exposure apparatus is used as long as the resist material, the shape of the resist pattern, the structure of the underlying substrate, the exposure intensity, and the exposure time are the same. In FIG. 5, the straight line of the equation (1) is indicated by a dotted line IV.

  After obtaining a relational expression between the resist length difference ΔL and the deviation amount ΔF of the substrate exposure position Fm from the reference exposure position F0, this relational expression is used for each exposure shot in the following steps S50 to S70. From the resist length L, a deviation amount ΔF, which is a magnitude of defocus, is obtained.

  In step S50, as in step S10, first, a resist is applied on the base substrate to form a second resist layer, and then the base substrate including the second resist layer is fixed to the wafer stage of the exposure apparatus. . A second photomask having a measurement mask pattern having the same form as the first photomask is fixed to the reticle stage of the exposure apparatus.

  Next, the entire region of the second resist layer on the base substrate is exposed while shifting the wafer stage in the horizontal direction by the region exposed at a time. At this time, the substrate exposure position is fixed at the reference exposure position F0 obtained in the step S30, for example. Thereafter, the second resist layer is developed to obtain a second resist pattern including a measurement resist pattern. The measurement resist pattern included in the second resist pattern may be referred to as a measurement second resist pattern.

  At this time, even if the substrate exposure position Fm coincides with the reference exposure position F0 due to the tilt of the wafer stage or the unevenness of the base substrate or the wafer stage, the surface of the base substrate deviates from the optimum exposure position for each exposure shot. That is, the focus may not be achieved. In this case, the resist length L of the second resist pattern for measurement is also different for each exposure shot.

  In S60, the bottom length Lb and the top length Lt of the second resist pattern for measurement are measured.

  In S70, the amount of focus shift ΔF on the surface of the base substrate is obtained for each exposure shot from the difference ΔL between the measured bottom length Lb and top length Lt using equation (1).

  According to this defocus measurement method, by using a measurement mask pattern having a plurality of measurement submask patterns arranged in parallel and with an arrangement period equal to or less than the resolution limit of the exposure apparatus, This utilizes the fact that the difference ΔL between the top length Lt and the bottom length Lb changes linearly with respect to the focal shift amount ΔF, and the change is large. Therefore, even when the focus shift amount is small, the focus shift amount can be accurately obtained including whether the surface of the base substrate is shifted in the vertical direction from the optimum exposure position.

  When the conditions of the exposure apparatus and the resist are the same, once the above equation (1) is obtained, the steps S50 to S70 can be repeated for a plurality of base substrates using the equation (1). it can.

  In this defocus measurement method, the first photomask used for obtaining the relational expression between the resist length difference ΔL and the deviation amount ΔF and the second photomask used for obtaining the deviation amount ΔF from the difference ΔL are: It is sufficient if the measurement resist patterns having the same shape and size are provided, and the first photomask and the second photomask may be the same photomask.

  Further, an average shift amount obtained by averaging the shift amounts ΔF obtained by a plurality of exposure shots can be obtained as the focus shift amount.

  Here, the amount of defocus obtained by the above-described defocus measurement method is the sum of the amount due to the semiconductor wafer and the amount due to the exposure apparatus. For this reason, it is impossible to distinguish whether the amount of defocus obtained by the defocus measurement method of the present invention is caused by the exposure apparatus or the semiconductor wafer by only one operation. Therefore, in order to obtain the amount of defocus due to the exposure apparatus, it is necessary to perform an average operation by performing a plurality of operations on different semiconductor wafers.

(Focus alignment method)
The focus alignment method includes steps S10 to S80. Since the steps up to S70 are the same as the above-described defocus measurement method, description thereof is omitted. In the focus alignment method, focus alignment is performed based on the focus shift amount ΔF obtained in steps S10 to S70.

  In S80, the entire resist layer newly applied on the base substrate is displaced from the reference exposure position F0 by a deviation amount ΔF for each exposure shot using a third photomask having a circuit mask pattern. Exposure and development. For example, as a result of defocus measurement, it is assumed that the difference in resist length L in a certain exposure shot is ΔLm, and the shift amount at this time is ΔFm. When performing exposure of this exposure shot, exposure is performed by shifting the substrate exposure position by ΔFm from the reference exposure position F0.

  According to this focus alignment method, alignment can be easily performed using the deviation amount ΔF accurately obtained for each exposure shot.

  Here, in the step S80, an example is shown in which exposure is performed by shifting the substrate exposure position Fm from the reference exposure position F0 by the shift amount ΔF for each exposure shot, but the present invention is not limited to this. An average deviation amount obtained by averaging deviation amounts ΔF obtained by a plurality of exposure shots is obtained, the substrate exposure position is fixed at a position shifted from the reference exposure position by the average deviation amount, and the entire resist layer is exposed. Also good.

  The first photomask used in the step of obtaining the relational expression between the deviation amount ΔF and the difference ΔL in S10 to S40, and the second photomask used in the step of obtaining the deviation amount ΔF from the resist length L in S50 to S70. In either case, it is necessary to provide a measurement mask pattern. Further, the third photomask used in step S80 needs to have a circuit mask pattern.

  Therefore, if the first photomask is configured to include both the measurement mask pattern and the circuit mask pattern, the defocus measurement and the focus alignment are performed using the common photomask, here the first photomask. be able to. At this time, if the defocus amount ΔF obtained in step S70 satisfies the required standard, etching using the second resist pattern as a mask is performed without performing step S80. The substrate can be patterned. That is, defocus measurement and circuit pattern formation can be performed in the same process using the same substrate.

  When the conditions of the exposure apparatus and resist are the same, once the above equation (1) is obtained in the step S40, the steps S50 to S80 are performed on the plurality of base substrates using the equation (1). Can be repeated.

It is a figure for demonstrating a photomask. It is a figure for demonstrating a resist pattern. It is a schematic diagram which shows the state which is performing the exposure state using exposure apparatus. FIG. 6 is a characteristic diagram showing a relationship between a focus shift amount and a resist length. FIG. 6 is a characteristic diagram showing a relationship between a focus shift amount and a difference in resist length.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Photomask 100a 1st photomask 110 Light-shielding area 120 Pattern area 130 Measurement area 140 Central area 210 Transparent substrate 220 Submask pattern for measurement 230 Circuit mask pattern 240 Light-shielding film 250 Measurement mask pattern 260 Mask pattern 300 Circuit resist Pattern 310 Base substrate 320 Resist pattern 330 Measurement resist pattern 340 First resist layer 400 Reduction projection lens

Claims (13)

Measurement mask patterns each consisting of a plurality of elongated rectangular quadrilateral measurement submask patterns arranged in parallel and with an arrangement period shorter than the resolution limit of the exposure apparatus, and sandwiching a rectangular quadrilateral central region Preparing a first photomask having a pair of measurement mask patterns provided at positions spaced apart in the longitudinal direction of the measurement submask pattern;
Applying a resist on the base substrate to form a first resist layer;
Using the first photomask, exposing the entire first resist layer for each exposure shot by changing the substrate exposure position of the surface of the base substrate in a direction perpendicular to the surface;
The exposed first resist layer is developed to obtain a pair of first continuous measurement resist patterns corresponding to the measurement mask pattern, each embedded between the measurement submask patterns. Process,
The maximum separation distance between the outermost walls of the pair of measurement first resist patterns measured in the direction corresponding to the longitudinal direction of the measurement submask pattern is a bottom length Lb, and the minimum separation distance is a top. Determining a reference exposure position in focus from the bottom length Lb and the substrate exposure position when the length Lt is set;
Obtaining a relational expression between a difference ΔL (= Lb−Lt) between the bottom length Lb and the top length Lt and a shift amount ΔF of the substrate exposure position from the reference exposure position;
Applying a resist on the underlying substrate to form a second resist layer;
Using the second photomask having the same form as the first photomask, exposing the entire second resist layer with the substrate exposure position fixed at the reference exposure position;
Developing the exposed second resist layer to obtain a pair of measurement-specific second resist patterns, respectively;
And a step of obtaining a deviation amount ΔF for each exposure shot from the difference ΔL between the bottom length Lb and the top length Lt of the pair of second resist patterns for measurement using the relational expression. Defocus measurement method. Preparing a first photomask having a measurement mask pattern comprising a plurality of elongated rectangular quadrilateral measurement submask patterns arranged in parallel and with an arrangement period shorter than the resolution limit of the exposure apparatus;
Applying a resist on the base substrate to form a first resist layer;
Using the first photomask, exposing the entire first resist layer for each exposure shot by changing the substrate exposure position of the surface of the base substrate in a direction perpendicular to the surface;
Developing the exposed first resist layer to obtain a first continuous measurement resist pattern corresponding to the measurement mask pattern and embedded between the measurement submask patterns;
When the maximum width of the first resist pattern for measurement measured in the direction corresponding to the longitudinal direction of the measurement submask pattern is the bottom length Lb and the minimum width is the top length Lt, the bottom length Determining a reference exposure position in focus from Lb and the substrate exposure position;
Obtaining a relational expression between a difference ΔL (= Lb−Lt) between the bottom length Lb and the top length Lt and a shift amount ΔF of the substrate exposure position from the reference exposure position;
Applying a resist on the underlying substrate to form a second resist layer;
Using the second photomask having the same form as the first photomask, exposing the entire second resist layer with the substrate exposure position fixed at the reference exposure position;
Developing the exposed second resist layer to obtain an integrated continuous measurement second resist pattern;
A step of obtaining a shift amount ΔF for each exposure shot from the difference ΔL between the bottom length Lb and the top length Lt of the second resist pattern for measurement using the relational expression. Measuring method. The defocus measurement method according to claim 1 or 2, wherein the first photomask is used instead of the second photomask. 3. The defocus measurement method according to claim 1, wherein a photomask on which a circuit mask pattern is formed is prepared as the second photomask. 4. The defocus measurement method according to claim 3, wherein a photomask on which a circuit mask pattern is formed is prepared as the first photomask. In obtaining the relational expression,
Using the difference ΔL between the top length Lt and the bottom length Lb when the deviation amount ΔF is in the range of −0.4 μm to +0.6 μm, the relation is expressed as a linear straight line with an inclination of A and an intercept of B. The approximated following (1) Formula is obtained, The defocus measuring method as described in any one of Claims 1-5 characterized by the above-mentioned.
ΔF = A × ΔL + B (1) The focus shift measurement according to any one of claims 1 to 6, wherein after obtaining the shift amount ΔF for each exposure shot, the shift amount ΔF for each exposure shot is averaged to obtain an average shift amount. Method. After performing the step of obtaining the shift amount ΔF for each exposure shot by the defocus measurement method according to any one of claims 1 to 6,
Using a third photomask having a circuit mask pattern, the entire resist layer newly applied on the base substrate is exposed for each exposure shot, and the substrate exposure position is shifted from the reference exposure position for each exposure shot. A focus alignment method, wherein exposure is performed with a focus adjusted by displacing by an amount ΔF. After performing the step of obtaining the shift amount ΔF for each exposure shot by the defocus measurement method according to claim 5,
Using the first photomask, the entire resist layer newly applied on the base substrate is displaced for each exposure shot, and the substrate exposure position is displaced from the reference exposure position by the shift amount ΔF obtained for each exposure shot. Thus, the focus alignment method is characterized in that exposure is performed with the focus adjusted. In obtaining the relational expression,
Using the difference ΔL between the top length Lt and the bottom length Lb when the deviation amount ΔF is in the range of −0.4 μm to +0.6 μm, the relation is expressed as a linear straight line with an inclination of A and an intercept of B. 10. The focus alignment method according to claim 9, wherein the following expression (1) is obtained.
ΔF = A × ΔL + B (1) After obtaining the shift amount ΔF for each exposure shot by the defocus measurement method according to claim 1,
Averaging the amount of deviation ΔF for each exposure shot to obtain an average amount of deviation;
Using a third photomask having a circuit mask pattern, the entire resist layer newly applied on the underlying substrate is exposed at a position where the substrate exposure position is changed by an average deviation amount from the reference exposure position. A focus alignment method comprising: a step. After obtaining the shift amount ΔF for each exposure shot by the defocus measurement method according to claim 5,
Averaging the amount of deviation ΔF for each exposure shot to obtain an average amount of deviation;
Using the first photomask, the entire resist layer newly applied on the base substrate is exposed at a position where the substrate exposure position is changed by the average deviation amount from the reference exposure position. Focus focusing method. In obtaining the relational expression,
Using the difference ΔL between the top length Lt and the bottom length Lb when the deviation amount ΔF is in the range of −0.4 μm to +0.6 μm, the relation is expressed as a linear straight line with an inclination of A and an intercept of B. 13. The focus alignment method according to claim 12, wherein the following expression (1) is obtained.
F = A × ΔL + B (1)

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