JP2005189729A - Photomask and method for monitoring focus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask having a focus monitoring pattern to easily obtain a best focus position, and to provide a method for monitoring a focus. <P>SOLUTION: The photomask comprises a mask substrate, a device pattern arranged on the mask substrate, and one or more focus monitoring patterns arranged in a different position from the device pattern on the mask pattern, wherein the focus monitoring pattern has a sawtooth pattern comprising nearly triangular patterns continuously arranged without a space in one direction in a plan view. The focus monitoring pattern comprises a sawtooth pattern formed on at least one side of a rectangular pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photomask used for manufacturing a semiconductor device and a focus monitor method suitable for setting a focus condition of an exposure apparatus.

  In recent years, with the increase in the degree of integration of semiconductor devices, the dimensions of individual elements have been reduced, and the widths of wirings and gates constituting each element have also been reduced.

  The photolithography technology that supports this miniaturization includes a process of applying a resist composition to the surface of a substrate to be processed to form a resist film, and exposing a predetermined resist pattern by irradiating light with a resist pattern latent image Forming, forming a desired resist pattern by developing it, and processing the substrate to be processed using the resist pattern as a mask A process is included.

  In order to manufacture a semiconductor device having a fine design rule using such a photolithography technique, it is necessary to form a fine resist pattern. In order to make the resist pattern finer, it is necessary to improve the exposure resolution when forming the resist pattern latent image. Here, the exposure resolution is expressed by the process factor (kl), the exposure wavelength (λ), and the numerical aperture (NA) of the optical system (formula (1)).

        Exposure resolution = kl × (λ / NA) (1)

  As can be seen from equation (1), in order to reduce the exposure resolution, the development of a process capable of reducing the process factor (kl), the shortening of the exposure wavelength (λ), or the aperture of the optical system of the exposure apparatus. It is necessary to improve the number (NA). However, when the numerical aperture of the optical system is increased, there is a problem that the exposure resolution can be reduced while the depth of focus is lowered. For example, the depth of focus in a fine pattern corresponding to a design rule of 100 nm or less is about 0.35 μm, and it is expected that the depth of focus will be further reduced in the future with the progress of miniaturization.

  For the above problems, measures such as increasing the accuracy of the exposure apparatus, improving the exposure apparatus management technology, adopting a high-resolution resist, and improving the flatness of the silicon substrate or the thin film formed on the silicon substrate have been conventionally used. Has been taken. Among these, the method using a high-resolution resist is characterized in that the change in the resist line width caused by the change in the focus position of the exposure apparatus is small.

For example, when the focus position is shifted to the plus side, the line width at the bottom of the resist is formed as desired, but the film thickness t ₁ of the resist pattern 21 formed on the base film 20 is a desired value. It becomes thinner than t (FIG. 13A). Therefore, when the base film is etched using the resist pattern 21 as a mask, there is a problem that the base film 20 is etched even in a region that must be protected by the resist. Further, when the impurity is implanted into the semiconductor substrate (not shown) using the resist pattern 21 as a mask, there is a problem that the impurity penetrates the resist due to the thin film thickness of the resist.

When the focus position is shifted to the minus side, the line width w ₁ at the top of the resist pattern 22 is formed with a desired dimension (w), but the line width w ₂ at the bottom of the resist pattern 22 is desired. As a result, the resist pattern 22 has a reverse taper shape (FIG. 13B). As a result, there is a problem that the resist pattern 22 is liable to be inclined or fallen. This problem will be described in detail below.

  In general, a wet development method using a liquid developer is used for developing the resist film after exposure. For example, the resist film is immersed in a developer and a resist pattern is formed by utilizing the difference in solubility between the exposed film and the unexposed film. Subsequently, the developing solution and the resist dissolved in the developing solution are washed away with a rinse solution. Thereafter, a drying process is performed to remove the rinse liquid.

  Here, in a resist pattern with a reverse taper cross-section, when the rinse liquid is dried, the capillary force acts due to the pressure difference between the rinse liquid accumulated between the resist patterns and the air, so that the pattern is inclined. easy. In addition, when this inclination is significant, there may occur a pattern collapse that causes adjacent patterns to lean against each other. When such pattern inclination or collapse occurs, it becomes impossible to form a desired pattern on the substrate to be processed, resulting in a decrease in product yield or reliability. In addition, when a part of the fallen pattern is lost, it becomes a dust source, which causes a further decrease in yield.

  On the other hand, conventionally, the management of exposure conditions has been performed by measuring the line width of a line-and-space pattern or the line width of a predetermined simulated circuit pattern. However, when a high-resolution resist corresponding to the case where the depth of focus is shallow is used, it is difficult to manage the focus by the line width as described above. Furthermore, since the resist line width generally varies depending on the exposure amount and the focus, there is a problem that it is impossible to determine whether the cause of the variation is the exposure amount or the focus.

On the other hand, there is a method using SMP (Self Measurement Program) as a method for managing the focus of the exposure apparatus. This is a method for obtaining the best focus position by measuring the dimension s of the wedge-shaped focus monitor pattern, as shown in FIGS. In other words, when the focus position of the exposure apparatus is the best focus position, the focus monitor pattern is exposed with the largest dimension (FIG. 14A). However, when the focus position deviates from the best focus position to the plus side (FIG. 14B) or the minus side (FIG. 14C), the dimension s of the focus monitor pattern decreases. Accordingly, as shown in FIG. 15, plots the size s of the exposed focus monitoring pattern to the focus position x, by obtaining the point where the dimension s is maximized, is possible to calculate the best focus position x ₀ it can.

  However, even in the above SMP method, the size of the focus monitor pattern varies not only with the focus but also with the amount of exposure, so it cannot be specified whether the cause of the variation is the focus or the amount of exposure. For this reason, even if the focus position is appropriate, the exposure amount is not appropriate and the dimensions fluctuate, resulting in a problem that the best focus position cannot be obtained. In addition, when a wedge-shaped focus monitor pattern is arranged in an actual device, defocusing occurs in the outer peripheral area of the silicon substrate, thereby causing the pattern to be tilted or tilted, or dust to be generated due to a missing pattern. There was also a problem.

  FIG. 16A is a plan view of a wedge-shaped resist pattern in which pattern collapse has occurred, and FIG. 16B is a cross-sectional view thereof. In the example shown in the figure, the cross-sectional shape of the resist pattern 23 is inversely tapered due to defocusing. By having such a shape, the contact area between the resist pattern 23 and the base film 24 becomes very small in the wedge-shaped portion, so that the pattern tends to fall down.

  Conventionally, a method for arranging an auxiliary pattern on a wedge-shaped pattern (see, for example, Patent Document 1) has been proposed. However, according to this method, although the fall of the pattern is improved, the problem of the dimensional change of the pattern due to the exposure amount cannot be solved. A method using a left / right (vertical) asymmetric pattern as a focus monitor pattern has also been proposed (see, for example, Patent Document 2), but this method reduces the accuracy of edge roughness in a wedge-shaped pattern. There was a problem. Furthermore, a method using two focus monitor patterns (for example, see Patent Document 3) through which exposure light having different phases passes has been proposed. However, in this method, since the structure of the mask is complicated, the cost is reduced. There was a problem that caused an increase.

JP 10-319598 A JP-A-11-102061 JP 2001-189264 A

  The present invention has been made in view of the above-described problems. That is, an object of the present invention is to provide a photomask having a focus monitor pattern that can easily obtain the best focus position.

  It is another object of the present invention to provide a focus monitoring method that can easily obtain the best focus position.

  Other objects and advantages of the present invention will become apparent from the following description.

  The photomask of the present invention comprises a mask substrate, a device pattern disposed on the mask substrate, and one or more focus monitor patterns disposed at positions different from the device pattern on the mask substrate. The focus monitor pattern has a sawtooth pattern in which substantially triangular shapes are continuously arranged in the same direction with no gap when viewed in a plane.

  In the present invention, the focus monitor pattern may be a sawtooth pattern provided on at least one side of a rectangular pattern. Furthermore, the focus monitor pattern can be formed by providing a sawtooth pattern on each of two opposing sides of a rectangular pattern.

  In the present invention, the substantially triangular shape is preferably a substantially isosceles triangle having an apex angle of 45 degrees or less.

  The focus monitoring method according to the present invention includes a distance between a peak and a valley formed by a substantially triangular sawtooth portion and a best focus of an exposure apparatus for a focus monitor pattern transferred onto a resist film using the photomask of the present invention. The process of obtaining focus curve data indicating the relationship with the deviation from the position, the process of forming a device pattern on the resist film using the photomask of the present invention, and the process of forming the device pattern are transferred onto the resist film. For the focus monitor pattern, a step of measuring a distance L between peaks and valleys formed by a substantially triangular sawtooth portion, and a deviation amount D from the best focus position of the exposure apparatus from the measured distance L and focus curve data And determining the focus position of the exposure apparatus based on the obtained shift amount D. It is characterized in that a step of adjusting the focus position.

  In the present invention, as described above, the focus monitor pattern has a sawtooth pattern in which substantially triangles are continuously arranged in the same direction with no gap when viewed in a plane, so that the best focus position of the exposure apparatus can be easily detected. It becomes possible to do.

  Further, according to the present invention, the exposure apparatus is configured to measure the distance L between the peaks and valleys formed by the substantially triangular sawtooth portion of the focus monitor pattern transferred onto the resist film and compare it with the focus curve data. Since the deviation amount D from the best focus position can be obtained, the focus monitor of the exposure apparatus can be easily performed.

  As a result of earnest research, the inventor has obtained a mask substrate, a device pattern disposed on the mask substrate, and one or more focus monitor patterns disposed at positions different from the device pattern on the mask substrate. It is found that the best focus position can be easily obtained by using a photomask which is a sawtooth pattern in which the focus monitor pattern is a sawtooth pattern in which substantially triangles are continuously arranged in the same direction with no gap when viewed in plan. It was. Here, the substantially triangular shape is preferably a substantially isosceles triangle having an apex angle of 45 degrees or less. In addition, it is assumed that the substantially triangular shape includes a shape close to a trapezoid in which a vertex of the triangle is missing.

  In the following, the focus monitoring method according to the present invention will be described by taking the case of using a positive resist as an example.

FIG. 1A is a plan view of a focus monitor pattern exposed at the best focus position. In this case, the distance L ₁ of the peaks and valleys formed by a substantially triangular saw-tooth shaped portion becomes longest. On the other hand, FIG. 1B is a plan view of a focus monitor pattern exposed by shifting from the best focus position to the minus side. In this case, the peak pattern disappears due to defocusing. In addition, the valley is formed shallower due to insufficient exposure. Therefore, the distance L ₂ of the peaks and valleys becomes shorter than the distance L _1. Further, FIG. 1C is a plan view of the focus monitor pattern exposed by shifting from the best focus position to the plus side. In this case, as a result of the resist being exposed by the wraparound of light, the peak pattern disappears. On the other hand, as a result of the resolution being lowered due to defocusing, the valley is formed shallow. Therefore, also in this case, the distance L ₃ between the mountain and the valley is shorter than the distance L ₁ .

FIG. 2 shows a change in the distance L between the peaks and valleys of the sawtooth pattern portion according to the focus position x of the exposure apparatus. In the best focus position x _0, the contrast of light becomes the maximum, the distance between the peak and the trough L also becomes maximum. On the other hand, when the focus position x is shifted from the best focus position x ₀ to the plus side or the minus side, the distance L of the mountains and valleys is reduced. Then, as the amount of deviation from the best focus position x ₀ is increased, the distance L of the mountain and the valley is gradually decreases. Therefore, it is possible to determine whether or not the focus position is appropriate by measuring the distance L between the peaks and valleys of the sawtooth pattern portion.

  Next, the relationship between the exposure amount and the distance between the peaks and valleys of the sawtooth pattern portion will be described with reference to FIG.

  FIG. 3A is a plan view of the focus monitor pattern when the exposure amount is smaller than the appropriate value. Here, in the case of a positive resist, the irradiated portion becomes soluble in the developer by irradiating a predetermined amount of light, so that a resist pattern consisting of an unirradiated portion is obtained after development. However, when the amount of exposure is small, a sufficient amount of exposure energy for solubilization in the developer is not given, so it is compared with a pattern formed with an appropriate amount of exposure (the solid line pattern in the figure). Thus, the pattern is formed as a pattern (dotted line pattern in the figure) in which the tip of the peak extends and the tip of the valley recedes. That is, in FIG. 3A, the peak end 1 moves in the left direction of the figure (the direction of the arrow; the same applies hereinafter) relative to the peak end 1 ′ at the appropriate exposure amount. Similarly, the end portion 2 of the valley also moves to the left in the figure with respect to the end portion 2 'of the valley at the appropriate exposure amount. Since the movement amounts of the peaks and valleys are almost the same, even if the exposure amount is less than the appropriate value, there is no substantial change in the distances L and L ′ between the peaks and valleys as a result. Become.

  On the other hand, FIG. 3B is a plan view of the focus monitor pattern when the exposure amount is larger than the appropriate value. As the amount of exposure increases, the portion that becomes soluble in the developer increases due to the wraparound of light, so compared to the pattern formed with the appropriate amount of exposure (dotted line pattern in the figure), the tip of the mountain recedes, It is formed as a pattern in which the tip of the valley extends (a solid line pattern in the figure). That is, in FIG. 3B, the crest end 3 moves to the right in the figure relative to the crest end 3 'at the appropriate exposure amount. Similarly, the end portion 4 of the valley moves to the right in the figure from the end portion 4 'of the valley at the appropriate exposure amount. Since the movement amounts of the peaks and valleys are almost the same, even when the exposure amount is increased, the substantial changes in the distances L and L ″ between the peaks and valleys are the same as in the case of FIG. Will not be seen.

  As described above, the peak-to-valley distance in the sawtooth-shaped pattern portion varies as the focus position changes, but is not easily affected by the change in exposure amount. Therefore, the best focus position can be detected by measuring the distance between the peaks and valleys. Further, since it can be determined whether or not the change in the resist line width is caused by the shift of the focus position, information useful for analyzing defects occurring in the manufacturing process of the semiconductor device can be obtained.

  In the present invention, a sawtooth pattern in which substantially triangles are continuously arranged in the same direction with no gaps is provided on at least one side of a rectangle as viewed in a plane, and this is used as a focus monitor pattern. For example, even when the cross-sectional shape of the resist pattern becomes a reverse taper due to the shift of the focus position to the minus side, it is possible to prevent the resist pattern from being tilted or tilted. This will be described in detail below.

FIG. 4 is a plan view of the focus monitor pattern transferred to the resist 5 according to the present invention. In the figure, if the cross-sectional shape of the pattern becomes inversely tapered, the pattern portion P ₁ of the sawtooth, the contact area between the resist 5 and the base film 6 becomes small. On the other hand, a rectangular pattern portion P ₂ which is connected to the pattern portion P ₁ of the sawtooth shape is compared to the pattern portion P ₁ of the sawtooth-shaped, has a large contact area originally against the base film 6. Therefore, even if the cross-sectional shape becomes inversely tapered, the contact area between the base film 6 in the rectangular pattern portion P ₂ remains still large. Therefore, there is no possibility that the inclination or collapse occurs in a rectangular pattern portion P _2. Furthermore, this since the rectangular pattern portion P ₂ supports the pattern portion P ₁ of the sawtooth, the pattern portion even if the contact area of the P ₁ becomes small this part of the sawtooth (P ₁₎ tilt and collapse occurs Can be prevented. Therefore, no pattern loss occurs, and the generation of dust due to the resist 5 can be suppressed. In FIG. 4, the base film 6 may be an appropriate inorganic or organic film used in the manufacturing process of a semiconductor device such as an insulating film. Further, the base film 6 may be a semiconductor substrate such as a silicon substrate.

FIG. 5 is an example of a plan view of the focus monitor pattern according to the present embodiment. In the figure, a focus monitor pattern 7 pattern P ₄ sawtooth shape one side of the square pattern P ₃ has a structure articulated. The pattern P ₄ of the sawtooth shape has a pattern 8 of a plurality of isosceles triangle are arranged adjacent without a gap to one another structure. Here, the length l ₁ of one side of the square pattern P ₃ can be set to 2 μm, for example. The pattern P ₄ of the sawtooth may be pattern 8 of 10 isosceles triangle is formed so as to be adjacent without a gap. In the figure, each isosceles triangle pattern 8 is arranged such that these peaks and valleys are alternately and continuously connected. Then, the pattern 8 of the isosceles triangle, the length _{l 2} between vertices may be a 0.2μm example, the height _{l 3} may be a 2.5μm example.

FIG. 6 is another example of a plan view of the focus monitor pattern according to the present embodiment. In the figure, the focus monitor pattern 9 has a structure in which sawtooth-shaped patterns P ₆ and P ₇ are connected to two opposing sides of a rectangular pattern P ₅ . The sawtooth patterns P ₆ and P ₇ each have a structure in which a plurality of isosceles triangular patterns 10 and 11 are arranged adjacent to each other without a gap. In other words, the isosceles triangular patterns 10 and 11 are arranged such that these peaks and valleys are alternately and continuously connected.

In FIG. 6, for the rectangular pattern P ₅ , the short side length l ₄ can be set to 1 μm, for example, and the long side length l ₅ can be set to 2 μm, for example. The pattern P ₆ of the sawtooth shape can be formed adjacent the pattern 10 of 10 of an isosceles triangle. For each isosceles triangle pattern 10, the length l ₆ between the vertices can be set to 0.2 μm, for example, and the height l ₇ can be set to 2.5 μm, for example. It can be the same for the pattern P ₇ sawtooth shape.

  The examples of FIGS. 5 and 6 are suitable when the resist pattern to be formed is a so-called remaining pattern. On the other hand, when a blank pattern such as a contact hole pattern is formed in the resist, the exposure amount is usually twice to three times as much as when a remaining pattern is formed. For this reason, the portion that becomes soluble in the developer becomes larger due to the wraparound of light, so that the pattern cuts at the valleys become shallow, and the adjacent isosceles triangles are connected at the valleys. Therefore, it is preferable to shorten the length of the short side of the rectangle at the design stage.

For example, as shown in FIG. 7, the short side length l ₈ of the rectangular pattern P ₈ is set to 0.1 μm, for example. For the sawtooth patterns P ₉ and P ₁₀ , the length l ₉ between the vertices of the isosceles triangle patterns 12 and 13 is set to 0.4 μm, for example, and the height l _{10 is set} to 2.5 μm, for example.

  The dimensions of the sawtooth portion and the rectangular portion constituting the focus monitor pattern are not limited to the examples shown in FIGS. It is preferable to adjust the dimensions appropriately according to the design rules of the semiconductor device, the type and thickness of the resist. In the examples of FIGS. 5 to 7, a sawtooth pattern in which isosceles triangles are continuously arranged in the same direction without a gap is used, but the present invention is not limited to this. For example, a sawtooth pattern may be obtained by continuously arranging trapezoidal patterns lacking the vertices of an isosceles triangle in the same direction without gaps.

  The shape of the focus monitor pattern in FIGS. 6 and 7 is more complicated than the shape of the focus monitor pattern in FIG. However, according to the focus monitor pattern of FIGS. 6 and 7, the dimensional change of the sawtooth pattern portion due to the change of the focus position can be monitored in an amount twice as large as the focus monitor pattern of FIG. Therefore, it becomes possible to perform focus monitoring with higher accuracy.

  Next, the focus monitoring method according to the present invention will be described.

  FIG. 8 shows a state in which the distance between peaks and valleys in a sawtooth pattern portion is measured using a side length SEM (Scanning Electron Microscope). In addition, the pattern of a figure is a focus monitor pattern transcribe | transferred to the resist film using the photomask concerning this invention.

In FIG. 8, the part surrounded by a dotted line is a side area. The length measurement is performed by further dividing the length measurement area in the figure into a plurality of parts. For example, the number of scanning lines added is 16, and 32 side length points p are provided. Then, for each measuring point p, sequentially side length dimension W of the saw-tooth shape of the pattern portion P ₈ to the end of the pattern portion P ₉ of rectangular shape. Difference between the maximum value W _max and a minimum value W _min of the resulting dimension W is the distance L between peaks and valleys in the pattern portion P ₈ of the sawtooth.

  The distance L between the peaks and valleys obtained by the side length using the side length SEM varies depending on the focus position. That is, the distance L between the peaks and valleys shows the maximum value at the best focus position, and gradually decreases as the position shifts from the best focus position to the plus side or the minus side. Therefore, it is possible to determine whether or not the focus position of the exposure apparatus is appropriate by extending the distance L between the peaks and valleys. Here, in the present invention, a sawtooth-shaped pattern in which substantially triangles are continuously arranged in the same direction with no gap when viewed in a plane is used as the focus monitor pattern. For this reason, it is possible to increase the number of substantially triangles included in one side area compared to the case where approximately triangles are arranged at a predetermined interval. Therefore, since the number of side length points that can be measured by one operation can be increased, it is possible to improve measurement accuracy and shorten measurement time.

  9 and 10 show an example in which the distance between the peaks and valleys in the sawtooth pattern portion is measured using an optical microscope. Note that the patterns in these figures are focus monitor patterns transferred to the resist film using the photomask according to the present invention, as in FIG.

As shown in FIG. 9A, when the resist pattern is observed in a bright field, the edge portion 12 of the pattern appears darker than the other portions 13 due to light scattering. Therefore, by performing image processing on this, the distance between the peaks and valleys in the sawtooth pattern portion can be measured. In brief, the portion that appears dark when exposed at the best focus position becomes longer, while the portion that appears dark when exposed by shifting from the best focus position to the plus side or the minus side becomes shorter. Therefore, the focus monitor can be performed by obtaining the dark portion width w ₁ in FIG. 9B. In FIG. 9B, the horizontal axis represents the coordinate X on the resist, and the vertical axis represents the scattered light intensity I.

On the other hand, as shown in FIG. 10A, when the resist pattern is observed in a dark field, the edge portion 14 of the pattern appears brighter than the other portions 15 due to light scattering. Therefore, as in the case of FIG. 9, the distance between the peaks and valleys in the sawtooth pattern portion can be measured by image processing. Briefly, the portion that appears bright when exposed at the best focus position becomes longer, while the portion that appears bright when exposed by shifting from the best focus position to the plus side or the minus side becomes shorter. Accordingly, the focus monitor can be performed by obtaining the width w ₂ of the bright portion in FIG. In FIG. 10B, the horizontal axis represents the coordinate X on the resist, and the vertical axis represents the scattered light intensity I.

  FIG. 11 is a focus showing the relationship between the distance between the crest and trough in the sawtooth portion of the focus monitor pattern transferred onto the semiconductor substrate using the photomask of the present invention and the deviation from the best focus position of the exposure apparatus. It is an example of curve data. The solid line in the figure shows the change in the distance between the peaks and valleys in the sawtooth pattern portion with respect to the focus position. For comparison, the dotted line also shows how the line width of the conventional line and space pattern changes with respect to the focus position. In the figure, the horizontal axis represents the focus position x of the exposure apparatus, and the vertical axis represents the distance between the peaks and valleys (or the line width of the line and space pattern) L.

  In the figure, a region A is a focus allowable region in consideration of a predetermined margin from the best focus position. If the focus position is within this region, a resist pattern having a good shape can be obtained. On the other hand, the regions B and B ′ are line width tolerance regions obtained by considering the margin in the design value of the line width. Here, the region B is a line width allowable region obtained from the variation of the sawtooth pattern, and the region B ′ is a line width allowable region obtained from the variation of the line and space pattern.

  As can be seen from FIG. 11, the line width change of the conventional line-and-space pattern includes a region C that is out of the focus allowable region A although it is within the line width allowable region B. Specifically, the region C is a region in which the focus is shifted to the plus side from the best focus position, and the line width at the bottom of the resist is formed according to a desired dimension, but the film thickness of the resist is desired. It is a region formed thinner than the value of. In such a case, if the base film is etched using the resist pattern as a mask, a situation occurs in which the base film is etched even in a portion that should originally be protected by the resist. Further, when the impurity is implanted into the semiconductor substrate using the resist pattern as a mask, a situation may occur in which the impurity penetrates the resist.

  On the other hand, the dimensional change in the sawtooth pattern portion in the present invention is more sensitive to the focus position than the conventional example. By setting the line width allowable area B within the focus allowable area A, it becomes possible to perform strict focus monitoring.

  Specifically, first, a device pattern is formed on the resist film using the photomask according to the present invention. At this time, the focus monitor pattern is transferred onto the resist film together with the device pattern. Next, the distance L between the peaks and valleys in the sawtooth portion of the transferred focus monitor pattern is measured. Then, a deviation amount D from the best focus position of the exposure apparatus is obtained from the measured distance L and the focus curve data. Focus monitoring can be performed by adjusting the focus position of the exposure apparatus to the best focus position based on the obtained shift amount D.

  FIG. 12 is an example of a schematic plan view of the photomask of the present invention. This photomask is used, for example, when an ArF (argon fluoride) excimer laser (wavelength: 193 nm) corresponding to the design rule of 90 nm is used as an exposure light source. As shown in the figure, when four device patterns 17 corresponding to the semiconductor device are arranged on the mask substrate 16, the focus monitor pattern 18 is located at a position different from the device pattern 17, for example, each corner portion of the photomask. Place in the middle part. Then, using the method as described above, the distance between the peaks and valleys formed by the substantially triangular sawtooth portion of the focus monitor pattern 18 transferred onto the resist film is measured. As a result, the focus monitor can be performed, so that the leveling failure of the exposure apparatus due to the influence of the image plane inclination of the exposure apparatus and the deviation of the arrangement density of the actual circuit pattern can be easily inspected.

  In the present invention, the number of device patterns provided on the photomask is not limited to the example of FIG. 12, and can be set as appropriate according to the manufacturing process of the semiconductor device. Also, the number of focus monitor patterns is not limited to the example of FIG. 12, and is preferably set as appropriate according to the number of device patterns.

  As described above, according to the present invention, the best focus position can be easily obtained by using a sawtooth-shaped pattern in which substantially triangular shapes are continuously arranged in the same direction without any gaps as a focus monitor pattern. It becomes possible. As a result, a good resist pattern can be formed even when the depth of focus is shallow, so that the reliability and yield of the semiconductor device can be improved.

It is a top view of the focus monitor pattern in this Embodiment, (a) is when exposed at the best focus position, (b) is exposed when shifted from the best focus position to the minus side, (c) is the best This is a case where exposure is performed with a shift from the focus position to the plus side. In the present embodiment, the relationship between the focus position x and the distance L between the peaks and valleys of the sawtooth-shaped portion is shown. It is a top view of the focus monitor pattern in this Embodiment, (a) is a case where an exposure amount is smaller than an appropriate value, (b) is a case where an exposure amount is larger than an appropriate value. It is an example of the top view of the focus monitor pattern of this invention transferred to the resist. It is an example of the top view of the focus monitor pattern of this invention. It is an example of the top view of the focus monitor pattern of this invention. It is an example of the top view of the focus monitor pattern of this invention. In this Embodiment, it is explanatory drawing of the measuring method of the distance of the peak and valley in a sawtooth shape part. In this Embodiment, it is explanatory drawing of the measuring method of the distance of the peak and valley in a sawtooth shape part. In this Embodiment, it is explanatory drawing of the measuring method of the distance of the peak and valley in a sawtooth shape part. In the present embodiment, the relationship between the focus position x and the distance L between the peaks and valleys of the sawtooth-shaped portion is shown. It is an example of the plane schematic diagram of the photomask of the present invention. (A) is a sectional view of the resist pattern when the focus position is shifted to the plus side, and (b) is a sectional view of the resist pattern when the focus position is shifted to the minus side. FIG. 6 is a plan view of a conventional focus monitor pattern, where (a) is an exposure at the best focus position, (b) is an exposure shifted from the best focus position to the plus side, and (c) is an exposure from the best focus position. This is a case where the exposure is shifted to the minus side. It is explanatory drawing of the calculation method of the conventional best focus position. It is explanatory drawing of the conventional resist pattern collapse, (a) is a top view of a resist pattern, (b) is sectional drawing of a resist pattern.

Explanation of symbols

1, 3 Edges of peaks 2, 4 Ends of valleys 5 Resist 6, 20, 24 Base film 7, 9 Focus monitor pattern 21, 22, 23 Resist pattern

Claims (5)

A mask substrate;
A device pattern disposed on the mask substrate;
One or more focus monitor patterns arranged at positions different from the device pattern on the mask substrate,
The photomask, wherein the focus monitor pattern has a sawtooth pattern in which substantially triangles are continuously arranged in the same direction without a gap when viewed in a plan view.   The photomask according to claim 1, wherein the focus monitor pattern is provided with the sawtooth pattern on at least one side of a rectangular pattern.   3. The photomask according to claim 2, wherein the focus monitor pattern is provided with the sawtooth pattern on each of two opposing sides of the rectangular pattern.   The photomask according to claim 1, wherein the substantially triangular shape is a substantially isosceles triangle having an apex angle of 45 degrees or less. 5. The focus monitor pattern transferred onto the resist film using the photomask according to claim 1, the distance between peaks and valleys formed by substantially triangular sawtooth portions, and the best exposure apparatus Obtaining focus curve data indicating the relationship with the deviation from the focus position;
Forming a device pattern on a resist film using the photomask;
Measuring a distance L between peaks and valleys formed by a substantially triangular sawtooth portion of the focus monitor pattern transferred onto the resist film by the step of forming the device pattern;
Obtaining a deviation amount D from the best focus position of the exposure apparatus from the measured distance L and the focus curve data;
And a step of adjusting a focus position of the exposure apparatus to a best focus position based on the shift amount D.

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