JP4665679B2 - Photomask, distortion detection apparatus thereof, and method of manufacturing semiconductor integrated circuit - Google Patents

Description

  The present invention relates to a photomask, a distortion detection device thereof, and a method for manufacturing a semiconductor integrated circuit.

  In a manufacturing process for forming a circuit pattern of a semiconductor integrated circuit such as an IC or LSI, first, a reticle or photo on which a circuit pattern is formed by performing drawing or transfer exposure processing on a mask blank for a photomask. A mask (hereinafter referred to as a photomask) is manufactured. Next, the circuit pattern is transferred to the resist layer formed on the wafer of the semiconductor integrated circuit substrate by the exposure apparatus using the photomask to form a circuit pattern.

  A method for manufacturing a photomask will be described. First, a light shielding film is formed on one side of a transparent substrate made of quartz glass or the like. The formation of the light shielding film is a method of forming a multilayer film of metal or metal oxide by a sputtering film forming method. Next, the transparent substrate is fixed on a stage of a resist coating apparatus, a resist solution is dropped on the surface, the stage is rotated at a high speed, the resist solution is dispersed and applied to a uniform thickness, and then heated to perform reticle or Manufacture mask blanks for photomasks. Next, a resist pattern of a circuit pattern is formed using a drawing apparatus. Mask blanks are placed on the stage of the drawing apparatus, transported to the drawing chamber, and the mask blanks are fixed by a predetermined method. In the drawing apparatus, a resist pattern is manufactured by exposing a resist to an electron beam using a drawing procedure manual (job file) describing drawing conditions and procedures edited in advance and design data of a drawing data file. Next, the resist pattern is developed. Next, the light shielding film is etched using the resist pattern as a mask, and then the resist pattern is peeled off to complete the manufacture of the reticle or photomask on which the circuit pattern is formed.

  In the formation of the resist pattern by the electron beam exposure, the mask blank distortion causes a problem that the position accuracy of the design data is lowered or the dimensional accuracy of the circuit pattern width is lowered.

  A method for manufacturing a semiconductor integrated circuit will be described. As an example of a manufacturing process for forming a circuit pattern of a semiconductor integrated circuit, a circuit pattern of a photomask is formed with a size 4 to 10 times larger than an actual size, and then a circuit pattern of a wafer is exposed by reduced projection. The circuit pattern of the photomask is formed with a size reduced to 1/4 to 1/10 by the method.

  In the formation of the circuit pattern of the semiconductor integrated circuit, the distortion of the photomask is slightly different from the surface of the photomask on which the circuit pattern is formed and the wafer surface of the transfer substrate. This is not accurately transferred to the resist on the wafer, causing a problem of deforming the shape of the resist pattern on the wafer. The distance between the slightly different photomask surface and the wafer surface of the substrate to be transferred is caused by the amount of distortion of the photomask, and the focus shifts when the circuit pattern of the wafer is exposed.

  In recent years, as the integration and miniaturization of circuits in semiconductor integrated circuits have progressed, circuit patterns have become more complex and miniaturized, and the shape of the circuit is required to have high accuracy. Problems that adversely affect the transfer to the wafer and affect the shape of the circuit pattern after the transfer to the wafer tend to increase.

Therefore, a method for detecting the degree of distortion of the photomask is required, and it is necessary to verify the influence of the distortion.

  However, at present, a measuring apparatus and a measuring method for detecting and verifying photomask distortion are not clearly defined, and there is no appropriate confirmation method.

  FIG. 3 is a partially enlarged side sectional view for explaining the distortion of a conventional photomask. The mask blank is formed by forming a light shielding film made of metal or metal oxide on one side of a transparent substrate made of quartz glass or the like, and forming a resist layer on the light shielding film. A photomask is completed by forming a pattern by etching. In the photomask manufacturing specification, the flatness of the transparent substrate alone or the flatness of the mask blank, that is, the upper limit of the distortion amount is defined. However, after the pattern formation, the area ratio between the glass exposed surface and the light shielding film surface becomes irregular, and the flatness of the photomask slightly changes and the flatness deteriorates. That is, there is a problem that the amount of distortion increases. On the other hand, in the photomask manufacturing process, at the time of processing, after the mask blanks are placed on the stage, a method of fixing the mask blanks on the stage by a predetermined method is adopted, and a method of processing in a fixed state is used. It is common. In this case, after the stage is released, there is a problem that the accuracy of the pattern deteriorates, for example, the shape thereof changes or the position accuracy of the pattern changes. On the other hand, in the manufacturing process of a semiconductor integrated circuit, when a photomask with unstable flatness is used at the time of processing, there is a problem of circuit pattern accuracy deterioration due to fixation to the stage or due to instability of the photomask itself. is there.

  3a to 3c are partially enlarged side sectional views for explaining the distortion of a conventional photomask. FIG. 3 is a side sectional view showing a state in which the photomask 1 is placed on the stage 11. At the time of processing in the apparatus, the photomask is fixed by a predetermined method, the back surface of the photomask is forcibly brought into close contact with the stage surface, and used in a state approximating normal flatness.

  In FIG. 3a, the flatness of the photomask 1 is normal, and there is no variation between placement on the stage and fixation on the stage, and the circuit pattern accuracy is also normal.

  In FIG. 3b, the flatness of the photomask 1 is abnormal, the center part has an upwardly curved distortion, and there is a change between placement on the stage and fixation on the stage, and the accuracy of the circuit pattern is also There is an abnormal problem. On the other hand, there is a similar problem when both ends have a distortion that curves upward.

  In FIG. 3c, the flatness of the photomask 1 is abnormal, it has a distortion that curves upward only on one side, there is a change between placing on the stage and fixing on the stage, and the accuracy of the circuit pattern is also There is an abnormal problem. 3B to 3C described above, there is a problem that the height of the surface of the photomask becomes non-uniform, and the variation in the height of the surface increases as the amount of distortion of the photomask increases. The variation in the height of the surface has a problem of causing a fluctuation in the focal position when optical processing is performed.

  In FIGS. 3b to 3c described above, the flatness is corrected in the normal direction when fixed on the stage, but the flatness is corrected as the degree of deterioration of the flatness on the stage is increased. It becomes difficult. For this reason, it is necessary to limit the degree of flatness degradation in the mounting according to the required accuracy, and there is a problem of standardizing the method.

  For this reason, a photomask having a large amount of distortion has a problem of affecting the transfer to the wafer and greatly deteriorating the yield of the wafer due to the accuracy degradation of the formed circuit pattern (see Patent Document 1). .

The known literature is described below.
Japanese Patent Laid-Open No. 10-209008

  An object of the present invention is to provide a photomask that is simply detected by detecting the distortion of the photomask itself, and to provide a distortion detection device for detecting and verifying the distortion of the photomask. An object of the present invention is to provide a method of manufacturing a semiconductor integrated circuit using a photomask that detects distortion and is verified.

  In the invention according to claim 1 of the present invention, a wiring circuit pattern made of a light-shielding film is arranged and formed in a transfer effective region partitioned and formed in the central portion of the transparent substrate on one side of the transparent substrate, and the auxiliary outside the transfer effective region. A photomask in which an auxiliary pattern made of a light-shielding film is arranged and formed in a pattern arrangement area, wherein a plurality of auxiliary patterns having the same shape for distortion measurement are arranged and formed in the auxiliary pattern arrangement area.

  The invention according to claim 2 of the present invention is the photomask according to claim 1, wherein the distortion measuring pattern is a pattern whose shape can be easily visually recognized.

  The invention according to claim 3 of the present invention is the photomask according to claim 1 or 2, wherein the shape of the distortion measurement pattern is a rhombus or a star.

  The invention according to claim 4 of the present invention is the photomask according to any one of claims 1 to 3, wherein the distortion measurement patterns are arranged and formed at at least four corners of the auxiliary pattern arrangement region. .

  The invention according to claim 5 of the present invention is characterized in that the distortion measurement patterns are arranged and formed in the same direction of the auxiliary pattern arrangement region. It is.

  The invention according to claim 6 of the present invention is a photomask distortion detecting apparatus for detecting a distortion amount of a photomask using the photomask according to any one of claims 1 to 5, wherein the photomask is a photomask. A stage for driving in the XY and θ directions on which the pattern forming surface is mounted on the upper surface, a light source for illuminating the photomask so as to face the surface of the photomask at a position above the stage, A first imaging unit that is disposed at a position and captures light reflected on the photomask as an image and a second imager that is disposed at a position below the stage and captures light transmitted through the photomask as an image. And a distortion detection apparatus including the imaging unit.

  The invention according to claim 7 of the present invention is characterized in that the distortion detection apparatus includes a monitor image display unit that displays an image captured by the first imaging unit or the second imaging unit. Item 7. The distortion detection device according to Item 6.

  The invention according to claim 8 of the present invention is characterized in that the strain detection device includes a temperature / humidity adjustment unit and has a function of maintaining the entire device at an arbitrary temperature and humidity. A distortion detection apparatus according to item 1.

The invention according to claim 9 of the present invention is a method for manufacturing a semiconductor integrated circuit in which a mask pattern is transferred and formed on a semiconductor integrated circuit substrate through a photomask, and the substrate on which a resist layer and a processed layer are formed. And a manufacturing process of transferring a pattern for a semiconductor integrated circuit by irradiating the resist layer with exposure light through the photomask according to any one of claims 1 to 5. A method for manufacturing an integrated circuit.

  If the distortion detection device of the present invention is used, in a photomask with zero distortion, the distortion measurement pattern image arranged in the auxiliary pattern arrangement region of the photomask is a non-deformable shape and a normal rhombus Captured in the image part. On the other hand, in a photomask having a distortion amount, an image of the distortion measurement pattern arranged in the auxiliary pattern arrangement region of the photomask is captured in the image portion as an abnormal shape, for example, an elliptical shape, with a deformed shape.

  If the strain detection apparatus of the present invention is used, in a photomask having a strain amount, the size of the rhombus shape of the strain measurement pattern changes, and for example, it is captured in the imaging unit as a rhombus image with a diagonal line length reduced.

  If the distortion detection apparatus of the present invention is used, an image of a distortion measurement pattern is taken into the imaging unit by transmitted light or reflected light, so that the state of the distortion amount can be visually observed to verify pass / fail judgment. Further, it becomes possible to measure the amount of distortion using the captured transmitted light image and reflected light image, and more accurate measurement can be performed.

  When the monitor image display unit of the distortion detection device of the present invention is used, when measuring the amount of distortion using the captured transmitted light image, reflected light image, or transmitted light image and reflected light image, on the monitor screen. This makes it possible to measure the amount of distortion with a more accurate measurement.

  According to the photomask of the present invention, the presence or absence of distortion of the photomask itself can be easily known from the amount of change in the shape and dimensions of the distortion measurement pattern.

  According to the photomask distortion detection device of the present invention, it is possible to convert the image data into a digital image, and the amount of change in the shape and dimensions of the distortion measurement pattern can be determined from the image data. The presence or absence of distortion of itself can be easily determined.

  According to the method for manufacturing a semiconductor integrated circuit according to the present invention, a photomask having no distortion is discriminated from image data, and the semiconductor integrated circuit is manufactured by using the photomask having no distortion. Since the semiconductor integrated circuit having the shape can be manufactured, the quality can be improved and the manufacturing yield can be improved.

  A photomask of the present invention, a distortion detection device thereof, and a method of manufacturing a semiconductor integrated circuit will be described below based on an embodiment.

  FIGS. 1A to 1C are plan views for explaining the shape of the distortion measurement pattern according to the present invention and the arrangement position thereof.

FIG. 1A is a plan view of a photomask 1 in which circuit patterns and auxiliary patterns are arranged on one side of a transparent substrate. A transfer effective area 9 is defined in the center of the transparent substrate, and an auxiliary pattern arrangement area 2 is defined in the outer periphery. In the transfer effective area 9, a wiring circuit pattern is mainly disposed, and only the wiring circuit pattern is an area for transferring onto a semiconductor integrated circuit substrate, for example, a wafer. In the auxiliary pattern arrangement region 2, auxiliary patterns such as alignment patterns and quality control patterns are mainly arranged. The auxiliary patterns are not transferred onto the wafer, but only when a photomask or a semiconductor integrated circuit is manufactured. This is an area to utilize. In the photomask, a wiring circuit pattern made of a light shielding film is arranged and formed in the transfer effective area 9, and an auxiliary pattern made of a light shielding film is arranged and formed in the auxiliary pattern arrangement area 2 outside the transfer effective area. Yes. In the photomask of the present invention, a plurality of auxiliary patterns of the distortion measurement pattern 3 are arranged in the auxiliary pattern arrangement area 2 outside the effective transfer area, for example, four at the four corners. Arrangement of the distortion measurement patterns should be optimized by selecting an arbitrary number and arrangement position.

  FIG. 1B shows the shape of one embodiment of the strain measurement pattern of the present invention, which is the shape of the strain measurement pattern 3 formed on the photomask, and the diagonal length of the long side is W. The rhombus with the diagonal length of the short side is H. The strain measurement pattern 3 formed on the photomask is defined as upward (or downward) with the diagonal length (W) of the long side set to the left and right and the diagonal length (H) of the short side set up and down, It is necessary to arrange all the distortion measurement patterns in that direction. That is, it is a photomask that arranges and forms all distortion measurement patterns in the same direction of the auxiliary pattern arrangement region.

  FIG. 1C is an image of reflected light obtained by visually observing the distortion measuring pattern 3 of the present invention shown in FIG. 1A using an apparatus, that is, an image capturing the reflected light as an image. In this case, for example, when there is no distortion in the photomask, the edge position of the image of the reflected light image processed and the design data position of the distortion measurement pattern 3 are compared and collated so that both positions are completely The long side diagonal length (W) and the short side diagonal length (H) are the same. In addition, when the photomask is distorted, the edge position of the captured image and the design data position of the distortion measurement pattern 3 are shifted according to the distortion amount, resulting in a position mismatch, and the long side Each of the diagonal length (W) and the diagonal length (H) of the short side is mismatched in length, and the difference increases in proportion to the amount of distortion.

  FIGS. 2A and 2B are schematic diagrams for explaining the strain detection apparatus of the present invention.

  FIG. 2A shows the strain detection apparatus 10. The strain detection apparatus 10 of the present invention includes a stage 11 that is driven in the XY and θ directions, on which the pattern forming surface of the photomask 1 of the present invention is placed. The stage 11 has a function of placing the photomask 1 with the pattern forming surface as an upper surface, and a function of driving in parallel in the X-axis direction and the Y-axis direction, and rotating the photomask 1 in the θ direction. ing. The stage 11 has a function of adjusting by using a rotational drive in order to finely adjust the inclination of the coordinate axis (for example, the inclination of the X axis) of the coordinate system of the strain detection apparatus 10 and the coordinate system of the photomask 1 placed thereon. ing. Further, the stage 11 is driven in parallel in the X-axis direction or the Y-axis direction to a position immediately below or directly above the first or second imaging unit in order to observe the distortion measurement pattern 3 on the photomask 1. It has a function to do.

  The strain detection apparatus 10 includes a light source 12 for irradiating illumination light at a position above the stage 11 so as to face the surface of the photomask 1. The light source 12 is an optimal illumination environment, for example, parallel illumination light, and has a function of changing the illuminance.

  The strain detection device 10 is disposed at a position above the stage 11, is disposed at a position below the stage 11, and a first imaging unit 13 that captures light reflected on the photomask 1 as an image, And a second imaging unit 14 that captures, as an image, light that is irradiated to and transmitted through the photomask 1. Each of the first and second imaging units 13 and 14 includes a CCD camera or an image sensor device, and has a function of capturing analog information such as imaging information such as photographs and printed materials, and conversion processing from the analog image to a digital image. The image feature extraction software has a processing function. That is, conversion into a digital image by image pattern recognition in which the change in density is binarized and processed.

  The distortion detection apparatus 10 includes an image display unit 15 for a monitor image that displays a digitized image captured by the first imaging unit 13 or the second imaging unit 14. The image display unit 15 can easily display various monitor images. For example, the image display unit 15 can superimpose and display the distortion measurement patterns 3 at the four corners of the photomask 1 shown in FIG. is there. As another method, there is a method in which one image of the distortion measurement pattern 3 and the design data are superimposed and displayed, and the amount of change in the shape is visually recognized. In the distortion detection apparatus 10 of the present invention, the digitized image data is processed in a predetermined processing procedure, and the result is compared with the determination criteria stored in the database, so that the verification can be appropriately performed by a clear method.

  The strain detection apparatus 10 includes a temperature / humidity adjustment unit 16 having a function of maintaining the entire apparatus at an arbitrary temperature and humidity. Since the temperature / humidity adjusting unit 16 is used, it is adjusted to a constant temperature / humidity during the inspection, and for example, the amount of distortion of the photomask at the same temperature / humidity as that of the wafer during manufacture of the semiconductor integrated circuit can be detected.

  The strain detection apparatus 10 is a strain detection system for detecting the amount of strain of a photomask having a strain measurement pattern according to the present invention, which complicates the shape of the strain measurement pattern or binary changes in density. By changing the processing means such as making the divided area into a finer area when it has been changed, it is possible to verify the quality of the distortion amount of the photomask to a finer level.

  FIG. 2B is a cross-sectional side view for explaining a change in the shape of the distortion measurement pattern depending on the presence or absence of distortion of the photomask. In addition, the reference figure in a broken-line frame is the distortion measurement patterns 30 and 33 imaged by the distortion detector. The distortion measurement pattern 30 in the reference diagram is a normal distortion measurement pattern in which there is no distortion of the photomask, that is, there is no change in shape. The distortion measurement pattern 33 is an abnormal distortion measurement pattern having a photomask distortion, that is, a shape change. The upper part of FIG. 2B is the position 23 of the imaging unit, and the lower part of the figure is the position 21 of the photomask surface. The height of the position 23 of the image pickup unit and the position 21 of the photomask surface is adjusted at the center of the figure without distortion, and the height is the position of the focal point. Next, on the left in the figure, the focal position is directly above the photomask surface, and on the right in the figure, the focal position is directly below the photomask surface, and both are out of focus. In the reference diagram, the captured image is visually recognized. In the center of the drawing, the distortion measurement pattern has a normal shape. On the left and right of the drawing, the distortion measurement pattern has an abnormal shape.

  In the distortion detection apparatus 10 of the present invention, the amount of distortion of the photomask is converted into the amount of change in the distance between the position 23 of the imaging unit and the position 21 of the photomask surface, and the amount of change in the distance is converted into the degree of blurring of the visual image. The blurring of the visually recognized image was converted into digital data by feature extraction using image recognition, for example, line figure extraction or edge extraction, and differentiated by comparison and collation of the digital image. The differentiated data was compared with the magnitude of photomask distortion to construct a database.

A detection procedure by the distortion detection apparatus 10 of the present invention will be described. The stage 11 on which the photomask of the present invention is placed and the image capturing of the first imaging unit 13 will be described. First, the stage is moved from the reference height position of the photomask to the center position of the first imaging unit 13. Next, the focal position is adjusted to the photomask surface at this position. Next, the stage is moved until the distortion measurement pattern to be photographed reaches the center position of the first imaging unit 13. Next, the distortion measurement pattern is photographed. Next, the stage is moved again until the reference position of the photomask reaches the center position of the first imaging unit 13 again. Next, the focal position is adjusted to the photomask surface at this position. Next, the stage is moved until the next pattern for distortion measurement to be photographed reaches the center position of the first imaging unit 13. The distortion measurement pattern is photographed. Thereafter, the process is repeated until the corresponding distortion measurement pattern is shot. That is, the detection procedure includes moving the stage to the reference height position / focusing the photomask surface / moving the stage to the distortion measurement pattern / photographing the distortion measurement pattern / moving the stage to the second reference height position / The focus position is adjusted to the surface of the second photomask, the stage is moved to the second distortion measurement pattern, and the distortion measurement pattern is photographed. The stage is moved by registering the coordinate position in advance and automatically moving according to the procedure. Further, automatic movement may be used in combination with a method of automatically recognizing a distortion measurement pattern.

  In the manufacture of a semiconductor integrated circuit in which a mask pattern is transferred and formed on a semiconductor integrated circuit substrate via a photomask, the method for manufacturing a semiconductor integrated circuit according to the present invention, that is, the strain detection pattern having the strain measurement pattern according to the present invention is provided. This is a manufacturing process in which a pattern for a semiconductor integrated circuit is transferred by irradiating an exposure light to a resist to be processed using a photomask in which the amount of distortion used is verified.

(A)-(c) is a top view explaining the shape of the pattern for distortion measurement of this invention, and its arrangement position. (A)-(b) is the schematic explaining the distortion detection apparatus of this invention. (A)-(c) is a partial expanded sectional side view explaining the distortion of the conventional photomask.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photomask 2 ... Auxiliary pattern arrangement | positioning area | region 3 ... Pattern for distortion measurement 9 (formed on a photomask) ... Transfer effective area 10 ... Distortion detection apparatus 11 ... Drive stage 12 ... (Illumination) Light source 13 ... First imaging part 14 ... second imaging unit 15 ... (monitor) image display unit 16 ... temperature / humidity adjustment unit 21 ... photomask surface position 23 ... imaging unit position 30 ... normal distortion measurement pattern 33 (taken by the distortion detection device) ... Abnormal distortion measurement pattern (imaged by distortion detector)

Claims (9)

  A wiring circuit pattern made of a light shielding film is arranged and formed in a transfer effective area partitioned and formed in the central part of the transparent substrate on one side of the transparent substrate, and an auxiliary pattern made of a light shielding film is arranged in an auxiliary pattern arrangement area outside the transfer effective area. A photomask comprising a plurality of auxiliary patterns of distortion measurement patterns having the same shape arranged in an auxiliary pattern arrangement region in the arranged photomask.   2. The photomask according to claim 1, wherein the distortion measuring pattern is a pattern in which a change in shape can be easily visually recognized.   3. The photomask according to claim 1, wherein the distortion measurement pattern has a rhombus shape or a star shape.   4. The photomask according to claim 1, wherein the distortion measurement patterns are arranged and formed at at least four corners of the auxiliary pattern arrangement region.   5. The photomask according to claim 1, wherein the distortion measurement patterns are arranged and formed in the same direction of the auxiliary pattern arrangement region.   6. A photomask distortion detecting apparatus for detecting a distortion amount of a photomask using the photomask according to claim 1, wherein the pattern forming surface of the photomask is placed on an upper surface. And a stage that is driven in the θ direction, a light source for illuminating the surface of the photomask so as to face the surface of the photomask at a position above the stage, arranged at a position above the stage, and irradiated to the photomask A first imaging unit that captures reflected light as an image, and a second imaging unit that is arranged at a position below the stage and captures light that is irradiated to and transmitted through a photomask as an image, Strain detector.   The distortion detection apparatus according to claim 6, wherein the distortion detection apparatus includes a monitor image display unit that displays an image captured by the first imaging unit or the second imaging unit.   The distortion detection apparatus according to claim 6, wherein the distortion detection apparatus includes a temperature and humidity adjustment unit and has a function of maintaining the entire apparatus at an arbitrary temperature and humidity.   6. A method of manufacturing a semiconductor integrated circuit in which a mask pattern is transferred and formed on a semiconductor integrated circuit substrate through a photomask, wherein the substrate is provided with a resist layer and a layer to be processed on the surface thereof. A manufacturing method of a semiconductor integrated circuit, comprising: a manufacturing process of transferring a pattern for a semiconductor integrated circuit by irradiating the resist layer with exposure light through the photomask according to claim 1.

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