JP4659473B2 - Photoresist pattern forming method, diffraction grating manufacturing method, and semiconductor device manufacturing method - Google Patents

Description

  The present invention relates to a method of forming a photoresist pattern on a substrate having a step. The present invention also relates to a diffraction grating manufacturing method and a semiconductor device manufacturing method using this method.

  When manufacturing an optical element or a semiconductor device used in the optical fiber communication technology, it may be necessary to form a photoresist pattern on a substrate having a step. Hereinafter, the background art will be described by taking as an example a method of manufacturing a diffraction grating used in optical fiber communication technology.

  In a wavelength division multiplexing optical fiber communication system, a diffraction grating combines a light with different wavelengths and then introduces the light into an optical fiber, or after demultiplexing light with multiple wavelengths superimposed for each wavelength. Used as a branching filter to be taken out from an optical fiber. The diffraction grating performs multiplexing and demultiplexing by utilizing the fact that the diffraction angle of light incident on the diffraction grating changes depending on the wavelength.

  One type of such a diffraction grating is a binary diffraction grating. A binary diffraction grating used for optical fiber communication is a stepped structure in which the height increases (decreases) by a predetermined value for each predetermined width on the surface of a silicon substrate or the like that is transparent to the light to propagate. I have it. When forming the stepped structure on the substrate, LSI manufacturing technology such as lithography technology is applied.

In manufacturing the binary diffraction grating on the silicon substrate, the following steps (I) to (IV) are repeated n (n is a positive integer) times while changing the shape and position of the mask shielding portion. As a result, a binary diffraction grating having a maximum number of 2 ⁿ stages can be obtained.
(I) a step of forming a photoresist film on the surface of the silicon substrate;
(II) a step of exposing the photoresist film using a mask having a desired shielding portion to form a photoresist pattern;
(III) a step of obtaining a substrate having a step by etching the substrate surface to a desired depth using the photoresist pattern as an etching protective film; and
(IV) removing the photoresist pattern;
By the way, when forming a photoresist pattern with respect to the board | substrate which has a level | step difference, the film thickness of the photoresist film formed differs in the upper level side plane of a level | step difference, and a lower level side plane. That is, the photoresist film formed on the upper side plane is thinner than the film thickness of the photoresist film formed on the lower side plane.

  Thus, if there is a difference in the film thickness of the photoresist film, a difference occurs in the photoresist transmission distance of the exposure light between the upper side plane and the lower side plane. Therefore, a difference occurs in the exposure amount of the photoresist film by the exposure light reflected by the substrate surface between the upper side plane and the lower side plane.

  It is also known that the width of the photoresist pattern is as designed when the predetermined best focus depth of exposure light coincides with the middle point in the thickness direction of the photoresist film. However, if the film thicknesses of the photoresist films are different, it is difficult to match the best focus depth of the exposure light with the middle point of the thickness of the photoresist film on at least one of the upper and lower planes.

  Due to these effects, the width of the photoresist pattern may deviate from the design value.

  If the width of the photoresist pattern is less than the design value (insufficient coating), the substrate area that should be protected by the photoresist pattern is etched in the next etching, so that the area near the stepped portion is etched. Groove defects may occur. On the contrary, when the width of the photoresist pattern is larger than the design value (excess coating), in the next etching, the substrate region to be originally etched is protected by the photoresist pattern, so that the step portion Protruding defects may occur in the vicinity.

  With respect to such a problem, according to the conventional method, the exposure is performed by shifting the position of the masking portion of the mask each time the steps (I) to (IV) are repeated. Thereby, the generation of protrusion defects is prevented by processing the inclined surface of the stepped portion processed (etched) in the previous process again in the subsequent process (see, for example, Patent Document 1).

Further, according to another conventional method, a stepped structure having a desired number of steps is formed on the substrate while leaving a groove-like defect or a protrusion-like defect. Then, by forming a film of the same material as the substrate on the formed stepped structure, a groove-like defect or a protrusion-like defect is buried (for example, see Patent Document 2).
JP 2002-169011 A (page 3, FIG. 1) JP 2000-199813 A (page 3, FIG. 1)

  By the way, although the technique disclosed in Patent Document 1 can prevent the protrusion defects generated in the manufacturing process, there is a problem that the generation of the groove defects cannot be prevented. (Refer to Patent Document 1, left end of the lowermost stage in FIG. 1 (d)). Moreover, although the technique disclosed in Patent Document 2 can obtain a stepped structure without groove-like defects and protrusion-like defects, a step of forming a film made of the same material as the substrate is added. There is a problem that the number increases.

  The present invention has been made in view of these problems, and provides a photoresist pattern forming method capable of preventing the occurrence of not only protrusion-like defects but also groove-like defects without adding a special process. The issue is to provide. It is another object of the present invention to provide a method for manufacturing a diffraction grating and a method for manufacturing a semiconductor device to which the method for forming a photoresist pattern of the present invention is applied.

  In order to solve the above-described problems, a first method for forming a photoresist pattern according to the present invention includes the following steps. That is, first, a substrate having a first main surface and a second main surface provided on the opposite side of the first main surface is prepared. And the 1st plane currently formed in the 1st main surface of this substrate, the 2nd plane where the distance of the 2nd main surface is larger than the 1st plane, and the end of the 1st and 2nd planes A photoresist pattern is formed in a structure having a connection surface for connecting the parts.

First, in a lithography process, an original photoresist pattern is formed on the first plane so as to be separated from the connection surface, and a design area and an original photo as an area to protect the first plane from etching performed after the heat flow process. An interval corresponding to the deformation speed in the heat flow process of the original photoresist pattern is formed between the left and right ends of the resist pattern . In a subsequent heat flow step, the original photoresist pattern is heated and deformed to form a deformed photoresist pattern that contacts the connection surface at a position lower than the second plane.

  In this manner, the original photoresist pattern is formed apart from the connection surface, and the original photoresist pattern is deformed by heating to form a deformed photoresist pattern. As a result, the deformed photoresist pattern can be reliably brought into contact with the connection surface on the first plane without exceeding the upper end portion of the connection surface.

  The second method for forming a photoresist pattern according to the present invention includes the following steps.

  That is, first, a substrate having a first main surface and a second main surface provided on the opposite side of the first main surface is prepared. And the 1st plane currently formed in the 1st main surface of this substrate, the 2nd plane where the distance of the 2nd main surface is larger than the 1st plane, and the end of the 1st and 2nd planes A photoresist pattern is formed in a structure having a connection surface for connecting the parts.

First, in the lithography process, the original photoresist pattern is formed on the second plane so as to be separated from the end of the second plane, and the second plane is protected as an area to be protected from etching performed after the heat flow process. An interval corresponding to the deformation rate in the heat flow process of the original photoresist pattern is formed between the design region and the left and right ends of the original photoresist pattern . In the subsequent heat flow step, the original photoresist pattern is heated and deformed to form a deformed photoresist pattern that contacts the end of the second plane at a position higher than the end of the second plane.

  As described above, the original photoresist pattern is formed on the second plane so as to be separated from the end of the second plane, and the original photoresist pattern is deformed by heating to form the deformed photoresist pattern. Thus, the deformed photoresist pattern can be reliably brought into contact with the end portion on the second plane. It should be noted that surface tension that acts to keep its own surface area to a minimum acts on the original photoresist pattern that reaches the end by deformation. As a result, the original photoresist pattern remains at the end portion of the second plane, so that the connection surface does not droop beyond the end portion.

  According to the first method for forming a photoresist pattern of the present invention, when forming a photoresist pattern on a structure having a first plane and an upward connecting surface connected to the end portion, first, the original photoresist is formed. The pattern is formed on the first plane so as to be separated from the connection surface. Then, by deforming the original photoresist pattern by heating, it is brought into contact with the connection surface at a position lower than the upper end portion of the connection surface, and a modified photoresist pattern in which the contact width with the first plane is a design value is formed. To do. This prevents insufficient coating of the photoresist pattern in the vicinity of the end portion of the first plane and excessive coating in the vicinity of the upper end portion of the connection surface (end portion on the first main surface side of the connection surface). A pattern is formed. Therefore, the next etching prevents not only the protrusion defects but also the groove defects, and a structure as designed can be obtained.

  In addition, since the first method for forming a photoresist pattern of the present invention is an improvement over an existing process, no new process is added.

  Further, according to the second method for forming a photoresist pattern of the present invention, when forming a photoresist pattern on a structure having a second plane and a downward connecting surface connected to an end thereof, first, the original pattern is formed. A photoresist pattern is formed on the second plane so as to be separated from the end of the second plane. Then, by deforming the original photoresist pattern by heating, it is brought into contact with the end portion at a position higher than the upper end portion of the connection surface, and a deformed photoresist pattern in which the contact width with the second plane becomes the design value is formed. To do. This prevents insufficient coating of the photoresist pattern in the vicinity of the end of the second plane and excessive coating of the photoresist pattern caused by the photoresist flowing down beyond the end of the second plane. A resist pattern is formed. Therefore, the next etching prevents not only the protrusion defects but also the groove defects, and a structure as designed can be obtained.

  In addition, since the second method for forming a photoresist pattern according to the present invention is an improvement of an existing process, no new process is added.

  An embodiment of the present invention will be described with reference to FIGS. Each figure is only a schematic illustration to the extent that the present invention can be understood with respect to the shape, size, and arrangement relationship of each component. In the following, preferred configuration examples of the present invention will be described. However, the composition (material), numerical conditions, and the like of each component are merely preferred examples. Therefore, the present invention is not limited to the following embodiments.

(Embodiment 1)
The first embodiment relates to a method for manufacturing a semiconductor device. The semiconductor device manufacturing method includes a photoresist pattern forming process and an etching process to which the first photoresist pattern forming method of the present invention is applied, as will be described below. Here, the photoresist pattern forming process includes a photoresist coating process, a lithography process, and a heat flow process.

  A preferred example of the method for manufacturing the semiconductor device of the first embodiment will be described with reference to FIGS. FIG. 1A is a diagram illustrating a cross-sectional cutout of a main part of a substrate prepared in the first embodiment. FIGS. 1B and 1C and FIGS. 2A and 2B are cross-sectional cuts of the structure obtained in the manufacturing process of the semiconductor device, and are process diagrams respectively showing. 3A to 3D are cross-sectional cuts of the structure obtained in each manufacturing process step for explaining the method of manufacturing the semiconductor device of the first embodiment. Among these drawings, FIGS. 1B to 2A relate to a photoresist pattern forming process. In FIG. 1B to FIG. 2B, reference numerals of the second main surface (12) of the substrate to be described later are omitted as appropriate.

  First, a substrate prepared in Embodiment 1 is described with reference to FIG. The substrate 14 has a first main surface 10 and a second main surface 12 provided on the opposite side of the first main surface 10. A structure 20 including a first plane (first surface) 16, a connection surface (third surface) 18, and a second plane (second surface) 19 is provided on the first main surface 10 side of the substrate 14. ing. The first plane 16 is provided in parallel to the first major surface 10. A connection surface 18 perpendicular to the first main surface 10 is connected to the end portion 16a of the first plane 16 and extends in a direction from the second main surface 12 toward the first main surface 10 (that is, an upward direction in the drawing). ing. The end (upper end) 18a of the connection surface 18 on the first main surface 10 side is parallel to the first main surface 10 and is higher than the first plane 16, that is, with the second main surface 12 and The second plane 19 having a distance greater than the first plane is connected.

  As the substrate 10, a silicon substrate is preferably used. Further, the height of the connection surface 18 is about 1 μm.

  The structure 20 provided on the first main surface 10 side can be formed by a known method. That is, a predetermined photoresist pattern is formed on the first main surface 10, and etching is performed from the first main surface 10 side using this photoresist pattern as an etching protective film, so that the first plane 16, the connection surface 18, and the first A structure 20 including two planes 19 is formed.

  In the photoresist coating process shown in FIG. 1B, a photoresist film 21 is formed on the entire first main surface 10. The film thickness of the photoresist film 21 on the second plane 19 is usually about 1 μm.

  That is, preferably, in the spin coater, the second main surface 12 is fixed to a rotating jig, and the photoresist solution is dropped onto the first main surface 10 while rotating the substrate 14 at a high speed. Then, unnecessary photoresist solution is removed by scattering by centrifugal force, and the photoresist solution is applied to the first main surface 10 with a uniform thickness. Subsequently, the substrate 14 on which the photoresist solution is uniformly applied is pre-baked at a temperature of about 90 ° C., thereby forming a photoresist film 21.

  Here, as the photoresist, a novolac resin, which is a positive photoresist exposed with i-line (wavelength: 365 nm), is preferably used.

  In the lithography process shown in FIG. 1C, the photoresist film 21 is exposed using a mask (not shown) having a shielding portion. Thus, the original photoresist pattern 22 is formed on the first plane 16 so as to be separated from the connection surface 18.

  That is, the substrate 14 on which the photoresist film 21 is formed is set in an exposure apparatus. Then, exposure is performed by irradiating with i-line from a light source through a mask having a shield part having a predetermined shape, thereby transferring the mask part shape of the mask onto the photoresist film 21. Thereafter, development is preferably performed with an aqueous solution of TMAH (tetramethyl ammonium hydroxide) or the like, and unnecessary portions of the photoresist film 21 are removed to form the original photoresist pattern 22. Here, preferably, the contact width W1 of the original photoresist pattern 22 with the first plane 16 is normally about 1 μm.

  In FIG. 1C, an area indicated by reference numeral 24 is a design area. The design area 24 is an area where the photoresist pattern should protect the first plane 16 from etching which will be described later. As can be seen from the figure, the size of the original photoresist pattern 22 in the width direction is smaller than the design region 24. The design area 24 has a width (hereinafter referred to as a design value) of W2. A relationship of W2> W1 is established between the design value W2 and the contact width W1 of the original photoresist pattern 22.

  According to the prior art, the mask shielding portion used in the exposure is set to have a width (hereinafter referred to as a conventional width) such that the width of the photoresist pattern becomes the design value W2, but in the first embodiment, For reasons that will be described later, the width of the shielding portion of the mask is intentionally made narrower than before so that the width of the original photoresist pattern 22 becomes W1 (W2> W1).

  The right end portion of the design region 24 exists on the right side of the right end portion of the original photoresist pattern 22 and coincides with the end portion 16 a of the first plane 16, that is, the connection surface 18. Further, the left end portion of the design region 24 is provided on the left side of the left end portion of the original photoresist pattern 22. In other words, the design region 24 is provided so that the size in the width direction is larger than the original photoresist pattern 22 and includes the original photoresist pattern 22.

  Further, the distance DR1 (hereinafter referred to as the right distance DR1) between the right end portion of the original photoresist pattern 22 and the right end portion of the design region 24 is larger than the position error (about 30 nm) that occurs during mask alignment during exposure. Value. As a result, even if a mask alignment error occurs during exposure, the original photoresist pattern 22 can be reliably separated from the connection surface 18. A distance DL1 between the left end portion of the original photoresist pattern 22 and the left end portion of the design region 24 (hereinafter referred to as a left side distance DL1) is approximately the same as the right side distance DR1, but is slightly larger (about 10 nm). Value.

  In this embodiment, the right distance DR1 is 40 nm. The left interval DL1 is 50 nm. The left-side interval and right-side interval DL1 and DR1 vary depending on the heating conditions in the heat flow process described later, but it is preferable that the original photoresist pattern 22 be deformed by heating in the heat flow process.

  In the heat flow step shown in FIG. 2A, the original photoresist pattern 22 is heated and deformed to contact the connection surface 18 at a position lower than the upper end portion 18a of the connection surface 18, and the first plane 16 A modified photoresist pattern 26 having a contact width with the design value W2 is formed.

  That is, preferably, the original photoresist pattern 22 is heated by a hot plate at a temperature of 130 ° C. for 1 minute. This heating also serves as a post-bake for evaporating moisture and photoresist solvent from the original photoresist pattern 22 after completion of exposure. However, heating is performed at a temperature higher than a general post-bake temperature (110 ° C.). By this heating, the original photoresist pattern 22 is deformed with flexibility (heat flow). That is, the original photoresist pattern 22 is heated to increase flexibility, and eventually it becomes difficult to support its own weight, and finally, the original photoresist pattern 22 is deformed so as to increase the contact area with the first plane 16.

  Thereby, the original photoresist pattern 22 is deformed so as to be crushed by its own weight. That is, as the amount of deformation increases toward the lower part where a larger load is applied, the height is reduced (thickness is reduced) and the cross-sectional shape is substantially trapezoidal. The left and right end portions of the contact surface with the first plane 16 are deformed toward the left and right end portions of the design area 24, respectively. The moving speeds of the left and right end portions of the original photoresist pattern 22 in this deformation are the same.

  As shown in FIG. 1C, since the right distance DR1 (40 nm) is narrower than the left distance DL1 (50 nm), the right end portion of the original photoresist pattern 22 is first the right end of the design region 24 in the process of deformation. To the connection surface 18. Then, while the original photoresist pattern 22 is blocked by the connection surface 18, the left end portion of the original photoresist pattern 22 is deformed until it reaches the left end portion of the design region 24. By terminating the heating at this stage, the width of the modified photoresist pattern 26 can be set to the design value W2. In other words, the deformed photoresist pattern 26 has the left end coincident with the left end of the design area 24 and the right end coincides with the right end of 24 in the design area by being dammed to the connection surface 18.

  Here, the heating conditions (heating temperature and heating time) are such that the deformed photoresist pattern 26 contacts the connection surface 18 at a position lower than the upper end portion 18a of the connection surface 18 (position lower than the second plane 19). In addition, it is preferable that the width of the modified photoresist pattern 26 is set to a design value W2.

  When the heating temperature is too high or the heating time is too long, the width of the deformed photoresist pattern 26 becomes larger than the design value W2, or the deformed photoresist pattern 26 exceeds the upper end portion 18a of the connection surface 18. The second plane 19 may be covered, which is not preferable.

  If the heating temperature is too low or the heating time is too short, the width of the modified photoresist pattern 26 is less than the design value W2, or a gap is left between the modified photoresist pattern 26 and the connection surface 18. This is not preferable because there are cases.

  In order to find a suitable heating condition, the movement speed (deformation speed) of the left and right end portions of the original photoresist pattern 22 when the film thickness, the heating temperature, and the heating time of the original photoresist pattern 22 are used as parameters are tested in advance. It is preferable to obtain by such as.

  The inventors used an i-line resist (novolak resin) as the original photoresist pattern 22 and changed the width W1 of the original photoresist pattern 22 from 0.7 to 1.2 μm in increments of 0.1 μm. Heating experiments were performed at various temperatures while changing the film thickness to 640 nm, 960 nm, 1080 nm, and 1200 nm, and investigation of suitable heating conditions was performed.

  According to this experiment, it was found that the heating temperature is preferably 120 to 160 ° C. when the heating time is fixed to 1 minute. When the heating temperature is less than 120 ° C., the original photoresist pattern 22 is not sufficiently deformed, which is not preferable. On the other hand, when the heating temperature is higher than 160 ° C., the original photoresist pattern 22 is deformed too much, the width of the original photoresist pattern 22 becomes larger than the design value W2, or the original photoresist pattern 22 is excessive. It is not preferable because the edge portion is rounded and the edge portion is rounded. In particular, the heating temperature is most preferably 130 ° C. When the heating temperature is 130 ° C., a practically sufficient deformation speed can be obtained regardless of the film thickness of the original photoresist pattern 22.

  In the etching step shown in FIG. 2B, etching is performed from the first main surface 10 side of the substrate 14 using the modified photoresist pattern 26 as an etching protective film.

Here, as the etching method, preferably, a reactive ion etching method that provides high etching anisotropy is used. The etching gas preferably contains CF ₄ .

  As a result, portions other than the design region 24 protected by the modified photoresist pattern 26 are etched by a predetermined thickness. Although not shown, a semiconductor device having a desired structure can be obtained by removing the deformed photoresist pattern 26 by ashing or the like after the etching process.

  In the first embodiment, the height of the connection surface 18 is about 1 μm, but the height of the connection surface 18 is not particularly limited.

  Further, the contact width W1 of the original photoresist pattern 22 with the first plane 16, that is, the width of the original photoresist pattern 22 is about 1 μm, but the contact width W1 is not particularly limited.

  Further, in the first embodiment, the case where the first and second planes 16 and 19 are parallel to the first main surface 10 of the substrate 14 has been illustrated. This is not intended to limit the present invention only when the first and second planes 16 and 19 are completely parallel to the first main surface 10, and is a range of errors that occur when the substrate 14 is processed. Of these, cases in which the parallelism between the first and second planes 16 and 19 and the first main surface 10 are shifted are also included in the technical scope of the present invention. Further, the first and second planes 16 and 19 are not limited to completely flat planes, but are curved or uneven within a range of errors that occur when the substrate 14 is processed. May be.

  Similarly, regarding the connection surface 18, even when the verticality between the connection surface 18 and the first main surface 10 is deviated within the range of errors that occur when processing the substrate 14, the technical scope of the present invention is also included. included. Further, the connection surface 18 is not limited to a completely flat surface, and may be curved or uneven within an error range that occurs when the substrate 14 is processed.

  As described above, in the semiconductor device manufacturing method according to the first embodiment, the first formation method of the photoresist pattern according to the present invention is applied, so that the step is formed near the step portion formed by the first plane 16 and the connection surface 18. Generation | occurrence | production of the protrusion-like defect and groove-like defect resulting from the insufficient coating | cover of the photoresist pattern to generate | occur | produce or an excess coating can be prevented.

  That is, when a photoresist pattern is formed on a substrate having a stepped portion for the reason described in the Background Art section, the coating is insufficient in the vicinity of the stepped portion (FIG. 3A) or excessively covered (FIG. 3B). )) May occur.

  Insufficient coverage means that the width of the photoresist pattern 104 that should originally cover up to the vertical surface 102 of the stepped portion 100 is insufficient, and the vertical surface 102 and the side surface of the photoresist pattern 104 are separated. . When the etching process is performed in a state of insufficient coating, a groove-like defect 110 is generated on the lower flat surface 106 of the stepped portion 100 as shown in FIG.

  Similarly, overcoating means that the width of the photoresist pattern 104 becomes too large and the photoresist pattern 104 covers up to the upper flat surface 108 of the stepped portion 100. When the etching process is performed in the over-covered state, as shown in FIG. 3D, a protruding defect 112 is generated on the upper flat surface 108 of the stepped portion 100.

  Thus, the first method for forming a photoresist pattern according to the present invention is applied to the method for manufacturing a semiconductor device of the first embodiment. According to the first method for forming a photoresist pattern of the present invention, the original photoresist pattern 22 is formed apart from the connection surface 18 in a lithography process. Then, in the heat flow step, the original photoresist pattern 22 is deformed by heating to form a deformed photoresist pattern 26. Due to this deformation, the deformed photoresist pattern 26 contacts the connection surface 18 without exceeding the upper end portion 18a of the connection surface 18, and the contact width with the first plane 16 becomes the design value W2. Thereby, insufficient coverage in the vicinity of the end portion 16a of the first plane 16 and excessive coverage in the vicinity of the upper end portion 18a of the vertical surface are prevented. Therefore, in the etching process, which is the next process when manufacturing the semiconductor device, the occurrence of protrusion-like defects and groove-like defects can be prevented, and a semiconductor device as designed can be obtained.

  In the first method of forming a photoresist pattern according to the present invention, (i) the width of the mask shielding portion is narrowed during exposure, and (ii) heat flow is performed also as post-baking, so that the design dimension is achieved. A modified photoresist pattern 26 is formed. These (i) and (ii) are both improved existing processes. Therefore, no new process is added to the method for forming a photoresist pattern of the present invention.

(Embodiment 2)
A preferred example of the method for manufacturing the semiconductor device of the second embodiment will be described with reference to FIG. The second embodiment relates to a method of manufacturing a semiconductor device to which the second method for forming a photoresist pattern of the present invention is applied. The original photoresist pattern 28 is formed on the second plane 19 in the first embodiment. Is. Therefore, in this column, the description will be focused on differences from the first embodiment.

  4A to 4D are cross-sectional cuts of the structure obtained in the manufacturing process stage of the semiconductor device, and are process diagrams showing each. In FIG. 4, the same reference numerals are given to structures common to FIGS.

  A photoresist film 21 is formed on the entire surface of the first main surface 10 by the photoresist coating process shown in FIG. The photoresist film 21 has a film thickness on the second plane 19 of about 1 μm. The specific procedure for forming the photoresist film 21 is the same as in the first embodiment.

  In the lithography process shown in FIG. 4B, by exposing the photoresist film 21 using a mask (not shown) having a shielding portion, the original photoresist pattern 28 is formed on the second plane 19 on the second plane 19. It forms so that it may space apart from the edge part 19a. Here, the contact width W3 of the original photoresist pattern 28 with the second plane 19 is about 1 μm. The specific procedure for forming the original photoresist pattern 28 is the same as in the first embodiment.

  In FIG. 4B, an area indicated by reference numeral 30 is a design area. As can be seen from the figure, the size of the original photoresist pattern 28 in the width direction is smaller than the design region 30. The design region 30 has a width (hereinafter referred to as a design value) of W4, and a relationship of W4> W3 exists between the contact width W3 of the original photoresist pattern 28 with the second plane 19 and the design value W4. Holds. Note that the term “design region” has the same meaning as in the first embodiment.

  The right end portion of the design region 30 exists on the right side of the right end portion of the original photoresist pattern 28. The left end portion of the design region 30 is provided on the left side of the left end portion of the original photoresist pattern 22 and coincides with the end portion 19 a of the second plane 19, that is, the connection surface 18. That is, the design region 30 is provided so as to include the original photoresist pattern 28.

  Further, the distance DL2 between the left end portion of the original photoresist pattern 28 and the left end portion of the design area 30 (hereinafter referred to as the left side distance DL2) is the mask alignment at the time of exposure for the same reason as described in the first embodiment. Is set to a value larger than the position error (about 30 nm) that occurs at this time, and is 35 nm here. Further, a distance DR2 between the right end portion of the original photoresist pattern 28 and the right end portion of the design region 30 (hereinafter referred to as a right side distance DR2) is the same size as the left side distance DL2, but is slightly larger (about 5 nm). The value is set to 40 nm in this case.

  Here, although the left and right distances DL2 and DR2 vary depending on the heating conditions in the heat flow process described later, it is preferable that the original photoresist pattern 28 be deformed by heating in the heat flow process.

  In the heat flow step shown in FIG. 4C, the original photoresist pattern 28 is heated and deformed. Accordingly, the contact surface 18 contacts the end portion 19a of the second plane 19 at a position higher than the upper end portion 18a of the connection surface 18 (position higher than the end portion 19a of the second plane 19), and the contact width with the second plane 19 A modified photoresist pattern 32 having a design value W4 is formed. The phrase “contacts the end portion 19a of the second plane 19 at a position higher than the upper end portion 18a of the connection surface 18” means that the deformed photoresist pattern 32 stays at the end portion 19a of the second plane 19 and the connection surface. It means that 18 will not hang down.

  Specifically, the heat flow process is performed by heating the original photoresist pattern 28 at a temperature of 130 ° C. for 1 minute. Thereby, the original photoresist pattern 28 is deformed so as to be crushed by its own weight. That is, as the amount of deformation increases toward the lower part where a larger load is applied, the height is reduced (thickness is reduced) and the cross-sectional shape is substantially trapezoidal. Then, the left and right end portions of the contact surface with the second plane 19 are deformed toward the left and right end portions of the design region 30, respectively. The moving speeds of the left and right end portions of the original photoresist pattern 28 in this deformation are the same.

  Here, since the left-side distance DL2 (35 nm) is narrower than the right-side distance DR2 (40 nm), the left end portion of the original photoresist pattern 28 is first left in the design region 30, that is, the second end in the process of deformation. The end 19a of the plane 19 is reached. The original photoresist pattern 28 reaching the end 19a is subjected to surface tension that works to keep its own surface area to a minimum. Due to this surface tension, the original photoresist pattern 28 stays at the end 19a and does not hang down the connection surface 18. In this manner, while the left end portion of the original photoresist pattern 28 remains at the end portion 19 a, the original photoresist pattern 28 is deformed until the right end portion reaches the right end portion of the design region 30. By terminating the heating at this stage, the width of the obtained modified photoresist pattern 32 can be set to the design value W4. That is, the left end portion of the modified photoresist pattern 32 stays at the end portion 19 a of the second plane 19, thereby matching the left end portion of the design region 30 and the right end portion thereof matching the right end portion of the design region 30. .

  Here, suitable conditions for heating (heating temperature and heating time) in the heat flow step are the same as those in the first embodiment.

  In the etching step shown in FIG. 4D, the same etching as in the first embodiment is performed from the first main surface 10 side of the substrate 14 using the modified photoresist pattern 32 as an etching protective film. Although not shown, a semiconductor device having a desired structure can be obtained by removing the modified photoresist pattern 32 by ashing or the like after the etching process.

  In the second embodiment, the contact width W3 of the original photoresist pattern 28 with the second plane 19 is not particularly limited.

  As described above, in the method of manufacturing the semiconductor device according to the second embodiment, by applying the second method for forming a photoresist pattern according to the present invention, in the vicinity of the step portion formed by the second plane 19 and the connection surface 18. Generation | occurrence | production of the protrusion-like defect and groove-like defect resulting from the insufficient coating | cover of the photoresist pattern to generate | occur | produce or an excess coating can be prevented. That is, in the lithography process, the original photoresist pattern 28 is formed so as to be separated from the end 19a of the second plane 19. Then, in the heat flow process, the original photoresist pattern 28 is deformed by heating to form a deformed photoresist pattern 32. Due to this deformation, the deformed photoresist pattern 32 comes into contact with the end portion 19a of the second plane 19 at a position higher than the upper end portion 18a of the connection surface 18, and the contact width with the second plane 19 is the design value W4. Become. Thereby, insufficient coverage in the vicinity of the end portion 19a of the second plane 19 and excessive coating beyond the upper end portion 18a of the connection surface 18 are prevented. Therefore, in the etching process, which is the next process when manufacturing the semiconductor device, the occurrence of protrusion-like defects and groove-like defects can be prevented, and a semiconductor device as designed can be obtained.

  In the second method for forming a photoresist pattern according to the present invention, (i) the width of the mask shielding portion is narrowed during exposure, and (ii) the heat flow is performed also as post-baking, so that the design dimension is achieved. A modified photoresist pattern 32 is formed. These (i) and (ii) are both improved existing processes. Therefore, no new process is added to the second method for forming a photoresist pattern of the present invention.

  In the heat flow process, the surface tension that acts to keep the surface area of the original photoresist pattern 28 that reaches the end 19a of the second plane 19 by deformation is exerted on the original photoresist pattern 28. Due to this surface tension, the original photoresist pattern 28 stays at the end portion 19a, so that the connection surface 18 does not drop over the end portion 19a.

(Embodiment 3)
In the third embodiment, a preferred example of a method for manufacturing a semiconductor device will be described. The semiconductor device manufacturing method of the third embodiment includes a photoresist pattern forming step and an etching step, as will be described below. Here, the photoresist pattern forming process further includes a photoresist coating process, a lithography process, and a heat flow process.

  In the third embodiment, the original photoresist pattern is simultaneously formed on both the first plane 16 and the second plane 19 in the first or second embodiment.

  A method of manufacturing the semiconductor device according to the third embodiment will be described with reference to FIGS. FIG. 5A is a diagram showing a cross-sectional cut showing a main part of a substrate prepared in the third embodiment. FIGS. 5B and 5C and FIGS. 6A and 6B are cross-sectional cuts of the structure obtained in the manufacturing process step of the semiconductor device, and are process diagrams respectively showing. Among these drawings, FIGS. 5B to 6A relate to a photoresist pattern forming process. In FIGS. 5B to 6B, reference numerals of the second main surface (12) of the substrate to be described later are omitted as appropriate.

  First, a substrate prepared in Embodiment 3 is described with reference to FIG. The substrate 34 has a first main surface 10 and a second main surface 12 provided on the opposite side of the first main surface 10.

  A structure 40 including a first plane 36 and a first inclined surface 38 and a structure 41 including a second plane 42 and a second inclined surface 44 are provided on the first main surface 10 side of the substrate 34. .

  In the structure 40, the first plane 36 is provided in parallel to the first major surface 10. A first inclined surface 38 perpendicular to the first main surface 10 extending in the direction from the second main surface 12 toward the first main surface 10 (that is, the upward direction in the figure) is connected to the end 36a of the first plane. ing. Here, the height of the first inclined surface 38 is about 1 μm.

  The first inclined surface 38 is connected to another plane (second plane 42) at the end portion (upper end portion) 38 a on the first main surface 10 side of the first inclined surface 38.

  In the structure 41, the second plane 42 is provided in parallel to the first major surface 10. A second inclined surface 44 perpendicular to the first main surface 10 extending in the direction from the first main surface 10 toward the second main surface 12 (that is, the downward direction in the figure) is connected to the end 42a of the second plane. ing. Here, the end portion 42 a of the second plane 42 coincides with the end portion (upper end portion) 44 a of the second inclined surface 44 on the first main surface 10 side. Here, the second plane 42 is formed to be higher by about 1 μm than the first plane 36.

  The second inclined surface 44 reaches the second main surface 12 of the substrate 34, or is on another plane (not shown) at the end (lower end) of the first inclined surface 44 on the second main surface 12 side. It is connected.

  Note that the positional relationship between the structure 40 and the structure 41 in FIG. 5A is convenient. That is, if the structure 40 and the structure 41 having a height higher than the structure 40 are provided on the first main surface 10 side, the positional relationship between the structure 40 and the structure 41 in the height direction or the horizontal direction is There is no particular limitation.

  As the substrate 34, a silicon substrate is preferably used.

  In the photoresist coating process shown in FIG. 5B, a photoresist film 48 is formed on the entire first main surface 10. The photoresist film 48 has a thickness of about 1 μm from the highest plane existing on the first main surface 10 side. The specific procedure for forming the photoresist film 48 is the same as in the first embodiment.

  In the lithography process shown in FIG. 5C, the photoresist film 48 is exposed using a mask (not shown) having a shielding portion. Accordingly, the first original photoresist pattern 50 is formed on the first plane 36 so as to be separated from the first inclined surface 38. At the same time, the second original photoresist pattern 52 is formed on the second plane 42 so as to be separated from the end 42 a of the second plane 42.

  Here, the contact width W5 of the first original photoresist pattern 50 with the first plane 36 and the contact width W6 of the second original photoresist pattern 52 with the second plane 42 are both about 1 μm. The specific procedure for forming the first and second original photoresist patterns 50 and 52 is the same as that of the first embodiment.

  In FIG. 5C, an area indicated by reference numeral 54 is a first design area. As can be seen from the figure, the size of the first original photoresist pattern 50 in the width direction is smaller than that of the first design region 54. The first design region 54 has a width (hereinafter referred to as a design value) of W7, and W7> W5 between the contact width W5 of the first original photoresist pattern 50 with the first plane 36 and the design value W7. The relationship holds.

  The right end portion of the first design region 54 exists on the right side of the right end portion of the first original photoresist pattern 50 and coincides with the end portion 36 a of the first plane 36, that is, the first inclined surface 38. . The left end portion of the first design region 54 is provided on the left side of the left end portion of the first original photoresist pattern 50. That is, the first design region 54 is provided so as to include the first original photoresist pattern 50.

  Further, the distance DR3 between the right end portion of the first original photoresist pattern 50 and the right end portion of the first design region 54 (hereinafter, referred to as the right side distance DR3) is exposed for the same reason as described in the first embodiment. The value is larger than the position error (about 30 nm) that occurs at the time of mask alignment, and is 40 nm here. A distance DL3 between the left end portion of the first original photoresist pattern 50 and the left end portion of the first design region 54 (hereinafter referred to as the left side distance DL3) is substantially the same as the right side distance DR3. It is set to a large value (about 10 nm), and here it is 50 nm.

  In FIG. 5C, an area indicated by reference numeral 56 is a second design area. As can be seen from the figure, the size of the second original photoresist pattern 52 in the width direction is smaller than that of the second design region 56. The second design region 56 has a width (hereinafter referred to as a design value) of W8, and the contact width W6 of the second original photoresist pattern 52 with the second plane 42 is between the design value W8 and W8. The relationship> W6 holds.

  The right end portion of the second design region 56 exists on the right side of the right end portion of the second original photoresist pattern 52 and coincides with the end portion 42 a of the second plane 42, that is, the second inclined surface 44. . The left end portion of the second design region 56 is provided on the left side of the left end portion of the second original photoresist pattern 52. That is, the second design region 56 is provided so as to include the second original photoresist pattern 52.

  Further, the distance DR4 between the right end portion of the second original photoresist pattern 52 and the right end portion of the second design region 56 (hereinafter referred to as the right interval DR4) is exposed for the same reason as described in the first embodiment. This value is larger than the position error (about 30 nm) that occurs during mask alignment at this time, and is 35 nm here. Further, a distance DL4 (hereinafter, referred to as a left-side distance DL4) between the left end portion of the second original photoresist pattern 52 and the left end portion of the second design region 56 is substantially the same as the right-side distance DR4. It is a large value (about 5 nm), and here it is 40 nm.

  Here, the term “design area” has the same meaning as in the first embodiment.

  Thus, by setting the right distance DR3 (40 nm) to a value larger than the position error (about 30 nm) that occurs during mask alignment during exposure, the first original photoresist pattern 50 and the first inclined surface 38 Can be reliably separated. For the same reason, since the right-side distance DR4 is set to 35 nm, the second original photoresist pattern 52 and the end portion 42a of the second plane 42 can be reliably separated.

  Here, when the right distances DR3 and DR4 are compared with each other, DR3> DR4 is satisfied, and when the left distances DL3 and DL4 are compared with each other, DL3> DL4 is satisfied. This is because the deformation speed of the first original photoresist pattern 50, that is, the moving speed of the left and right end portions is higher than that of the second original photoresist pattern 52 in the heat flow process described later. This is because the first original photoresist pattern 50 is thicker than the second original photoresist pattern 52, so that a larger load is applied per unit area on the contact surface with the first plane 36. Therefore, the first original photoresist pattern 50 is more easily deformed than the second original photoresist pattern 52.

  In the heat flow step shown in FIG. 6 (A), the first original photoresist pattern 50 is heated and deformed to be lower than the first main surface side end (upper end) 38a of the first inclined surface 38. Then, the first modified photoresist pattern 58 is formed, which is brought into contact with the first inclined surface 38 and whose contact width with the first plane 36 is the design value W7. At the same time, the second original photoresist pattern 52 is heated and deformed, so that the end 42a of the second plane 42 is positioned higher than the end (upper end) 44a of the second inclined surface 44 on the first main surface 10 side. And a second modified photoresist pattern 60 having a contact width with the second plane 42 of the design value W8 is formed.

  That is, the first and second original photoresist patterns 50 and 52 are heated at a temperature of 130 ° C. for 1 minute.

  Accordingly, the first original and second photoresist patterns 50 and 52 are deformed so as to be crushed by their own weight. That is, as the amount of deformation increases toward the lower part where a larger load is applied, the height is reduced (thickness is reduced) and the cross-sectional shape is substantially trapezoidal. The left and right end portions of the contact surface with the first and second planes 36 and 42 are deformed toward the left and right end portions of the first and second design regions 54 and 56, respectively.

  First original photoresist pattern 50 is subjected to the same deformation as described in the first embodiment. That is, the right end portion of the first original photoresist pattern 50 first reaches the right end portion of the first design region 54, that is, the first inclined surface 38. Then, while the first original photoresist pattern 50 is blocked by the first inclined surface 38, the left end portion of the first original photoresist pattern 50 is deformed to reach the left end portion of the first design region 54.

  Second original photoresist pattern 52 undergoes the same deformation as that described in the second embodiment. That is, the right end portion of the second original photoresist pattern 52 first reaches the right end portion of the second design region 56, that is, the end portion 42 a of the second plane 42. The second original photoresist pattern 52 that reaches the end 42 a does not hang down the second inclined surface 44 and remains at the end 42 a due to surface tension. While the right end portion of the second original photoresist pattern 52 remains at the end portion 42 a, the left end portion of the second original photoresist pattern 52 is deformed until it reaches the left end portion of the second design region 56.

  For the reasons described above, the deformation rate of the first original photoresist pattern 50 due to heating is faster than that of the second original photoresist pattern 52. By the way, there is a relationship DR3> DR4 between the right intervals DR3 and DR4, and there is a relationship DL3> DL4 between the left intervals DL3 and DL4. Therefore, the time required for the first original photoresist pattern 50 to be deformed until it covers the design area 54 is substantially equal to the time required for the second original photoresist pattern 52 to be deformed while the design area 56 is covered. .

  By completing the heating at this stage, the width of the first modified photoresist pattern 58 can be set to the design value W7, and the width of the second modified photoresist pattern 60 can be set to the design value W8. That is, the first modified photoresist pattern 58 that contacts the first inclined surface 38 and the second modified photoresist pattern 60 that contacts the end portion 42a of the second plane 42 are obtained.

  The preferred conditions for heating (heating temperature and heating time) in the heat flow step are the same as in the first embodiment.

  In the etching step shown in FIG. 6B, the same etching as in the first embodiment is performed from the first main surface 10 side of the substrate 34 using the first and second modified photoresist patterns 58 and 60 as an etching protective film. Although not shown, a semiconductor device having a desired structure can be obtained by removing the first and second modified photoresist patterns 58 and 60 by ashing after the etching process.

  In the third embodiment, the height of the first inclined surface 38 is about 1 μm, but the height of the first inclined surface 38 is not particularly limited.

  Further, the contact widths W5 and W6 of the first and second original photoresist patterns 50 and 52 with the first and second planes 36 and 42 are about 1 μm, but the contact widths W5 and W6 are not particularly limited.

  In the third embodiment, the case where the first and second planes 36 and 42 are parallel to the first main surface 10 of the substrate 34 has been exemplified. This is not intended to limit the present invention only when the first and second planes 36 and 42 are completely parallel to the first major surface 10, but the range of errors that occur when processing the substrate 34. Of these, cases in which the parallelism between the first and second planes 36 and 42 and the first major surface 10 are shifted are also included in the technical scope of the present invention. Furthermore, the first and second planes 36 and 42 are not limited to a completely flat plane, but are curved or uneven within a range of errors that occur when the substrate 34 is processed. May be.

  Similarly, with respect to the first and second inclined surfaces 38 and 44, the perpendicularity between the first and second inclined surfaces 38 and 44 and the first main surface 10 is within the range of errors generated when the substrate 34 is processed. The case where the deviation is also included in the technical scope of the present invention. Further, the first and second inclined surfaces 38 and 44 are not limited to a completely flat surface, but are curved within a range of errors generated when the substrate 34 is processed, or have irregularities. It may be.

  Thus, in the method for manufacturing a semiconductor device of the third embodiment, the third method for forming a photoresist pattern of the present invention is applied. As a result, the photoresist pattern is insufficiently covered or excessively covered near the step formed by the first plane 36 and the first inclined surface 38 or near the step formed by the second plane 42 and the second inclined surface 44. It is possible to prevent the occurrence of protrusion-like defects and groove-like defects derived from. In other words, in the lithography process, the first original photoresist pattern 50 is formed apart from the first inclined surface 38, and at the same time, the second original photoresist pattern 52 is formed separated from the end 42 a of the second plane 42. In the heat flow step, the first and second original photoresist patterns 50 and 52 are deformed by heating to form deformed photoresist patterns 58 and 60. Due to the deformation, the first modified photoresist pattern 58 contacts the first inclined surface 38 without exceeding the upper end portion 38a of the first inclined surface 38, and the contact width with the first plane 36 becomes the design value W7. . Further, due to the deformation, the second modified photoresist pattern 60 is in contact with the end portion 42a of the second plane 42 at a position higher than the upper end portion 44a of the second inclined surface 44, and the contact width with the second plane is designed. The value is W8. Thereby, insufficient coating and excessive coating are prevented. Accordingly, in the etching process, which is the next process when manufacturing the semiconductor device, the occurrence of protrusion-like defects and groove-like defects can be prevented, and a semiconductor device according to the design dimensions can be obtained.

  In the third method of forming a photoresist pattern according to the present invention, (i) the width of the mask shielding portion is narrowed at the time of exposure, and (ii) heat flow is performed also as post-baking, so that the design dimension is achieved. First and second modified photoresist patterns 58 and 60 are formed. These (i) and (ii) are both improved existing processes. Therefore, no new process is added to the third method for forming a photoresist pattern of the present invention.

(Embodiment 4)
In the fourth embodiment, a preferred example of a method for manufacturing a diffraction grating will be described. Here, a method for manufacturing a binary diffraction grating will be described in particular. The binary-type diffraction grating is a stepped structure in which two or more planes parallel to the first main surface of the substrate and having different heights are connected to each other by a vertical surface perpendicular to the first main surface of the substrate. It is what has. In other words, it can be said that the binary diffraction grating is a step-like structure formed on the substrate, the height of which varies by a predetermined value for each predetermined width.

As described below, the binary diffraction grating is manufactured by repeating a process unit including a plurality of processes one or more times. One process unit consists of the following three processes.
(1) A step of exposing a photoresist film formed on the first main surface side of the substrate using a mask having a shielding part to form a photoresist pattern (photoresist pattern forming step);
(2) Using the photoresist pattern as an etching protective film, a step of etching the substrate from the first main surface side (etching step), and
(3) Step of removing the photoresist pattern remaining on the first main surface side (ashing step)
Here, the photoresist pattern forming step further includes (1-1) a photoresist coating step, (1-2) a lithography step, and (1-3) a heat flow step.

  In the fourth embodiment, a case where a binary diffraction grating having a seven-step staircase structure is formed by repeating the process unit three times while changing the shape and position of the shielding part of the mask will be described as an example. I do.

  7 to 9 are drawings for explaining the method of manufacturing the diffraction grating of the fourth embodiment. 7 (A) to (C), FIGS. 8 (A) to (C), and FIGS. 9 (A) and 9 (B) are cross-sectional cuts of the structure obtained in the manufacturing process of the diffraction grating, respectively. It is process drawing. Here, FIGS. 7A and 7B are process diagrams showing a cross-sectional cut of the structure corresponding to the first process unit, and FIGS. 7C, 8A, and 8B are second views. FIG. 8C is a process diagram illustrating a cross-sectional cut of a structure corresponding to a process unit, and FIGS. 8C and 9A and 9B are process diagrams illustrating a cross-sectional cut of the structure corresponding to a third process unit. is there.

  First, a substrate used in Embodiment 4 is described with reference to FIG. The substrate 62 has a first main surface 64 and a second main surface 66 provided on the opposite side of the first main surface 64. Then, first to seventh regions, which are seven regions adjacent to each other, are set on the first main surface 64. In the following, the first region is the region a, the second region is the region b, the third region is the region c, the fourth region is the region d, the fifth region is the region e, and the sixth region is the region f. The seventh area is referred to as area g. The seven regions a to g have the same width W. One unit structure T is constituted by these seven regions a to g.

The unit structure T is repeated adjacent to the width direction on the first main surface 64. Here, the unit structure located on the left side of the unit structure T is represented as T _Ln, and the unit structure located on the right side of the unit structure T is represented as T _Rn (where n is a unit measured by the width of the unit structure T) Distance from structure T). Using this representation, the arrangement of the unit structures on the first main surface 64 is represented from the left side of the drawing as follows: T _Ln ,..., T _L1 , T, T _{R1 ,.} The sequence is repeated adjacent to the width direction. .., T _Ln ,..., T _L1 , T, T _R1 ,..., T _Ln,.

Here, paying attention to the unit structure T, the region g _L1 of the adjacent unit structure T _L1 is adjacent to the left side of the region a of the unit structure T. Further, the region a _R1 of the adjacent unit structure T _R1 is adjacent to the right side of the region g of the unit structure T.

  In the binary diffraction grating manufactured in the fourth embodiment, the width W is 1 μm. Further, the height difference h between two adjacent planes across one vertical plane is set to 0.2 μm.

Further, in the description that followed the steps of the method of manufacturing the diffraction grating to be described later, the periodic structure _{..., T Ln, ..., T} L1, T, T R1, ..., T Ln, ... focused on unit structure T Medium Description However, the same manufacturing process is performed for unit structures other than the unit structure T at the same time.

  Next, a method for manufacturing a diffraction grating will be described with reference to FIGS. 7 (A) to 9 (B).

(1) First Step Unit (1-1) Photoresist Pattern Formation Step The photoresist pattern formation step will be described with reference to FIG.

(1-1-1) Photoresist Application Step Similar to the procedure of “photoresist application step” described in the first embodiment, a photoresist film of about 1 μm is formed on the entire surface of the substrate 62 on the first main surface 64 side. Form.

(1-1-2) Lithography step Then, exposure and development are performed in the same manner as in the “lithography step” described in the first embodiment, using a mask having a shielding portion at a position corresponding to the regions e to g. I do. After the development, the substrate 62 is post-baked by heating at 110 ° C. for 1 minute. Thus, a photoresist pattern 68 that covers the regions e to g is formed.

  As the mask, a mask having a shielding portion having a width equal to the width 3W of the regions e to g is used.

(1-2) Etching Step Using the photoresist pattern 68 as an etching protective film, the regions a to d are etched by a depth of 3 h (0.6 μm). The specific etching procedure is the same as that described in the “etching step” in the first embodiment.

As a result, the first vertical surface 70 perpendicular to the first main surface 64 at the boundary between the regions d and e and having the upper end portion 70a is formed at the boundary between the region g and the region a _R1 of the adjacent unit structure _TR1 . A second vertical surface 72 that is perpendicular to the first main surface 64 and has an upper end 72a is formed.

(1-3) Ashing process An ashing process is demonstrated with reference to FIG.7 (B). The photoresist pattern 68 is removed by ashing using O ₂ plasma.

Thus, region a~d is lowered by a depth 3h, region d, has a first vertical surface 70 in e boundary, the second perpendicular to the boundary between the region a _R1 unit structure T _R1 and an adjacent region g A structure having a surface 72 is obtained.

(2) Second Process Unit In the first process unit, a photoresist pattern forming process was performed on a horizontal unit structure T having no stepped portion. Therefore, it was not necessary to give special consideration to the width of the mask shielding part and post-bake. However, in the process units after the second process unit, the photoresist pattern forming process is performed on the unit structure T having the stepped portion on the first main surface 64 side. Therefore, the photoresist pattern forming process after the second process unit is performed by heating the original photoresist pattern also as a lithography process in which exposure is performed with the width of the mask shielding portion narrower than the design value and post baking. The heat flow process to deform | transform will be included.

(2-1) Photoresist Pattern Formation Step (2-1-1) Photoresist Application Step In the same manner as the “photoresist application step” described in the first embodiment, the first main surface 64 side of the substrate 62 is provided. A photoresist film is formed on the entire surface. The thickness of the photoresist film at this time is about 1 μm on regions e to g having the highest height in the direction from the second main surface 66 toward the first main surface 64.

(2-1-2) Lithography Process The lithography process will be described with reference to FIG.

  Exposure similar to that described in the first embodiment is performed using a mask having a shielding portion at positions corresponding to the regions c and d and the regions f and g. Here, a mask having a shielding part slightly smaller than the width 2W of the regions c and d and slightly smaller than the width 2W of the regions f and g is used. After the exposure is completed, development is performed in the same manner as described in the first embodiment.

  In this way, the first original photoresist pattern 74 covering the regions c and d and the second original photoresist pattern 76 covering the regions f and g are formed.

  As described above, since the mask shielding portion width is smaller than the width 2W of the regions c and d, the width of the first original photoresist pattern 74 is smaller than the design value 2W. That is, the region a side end (left end) 74L of the first original photoresist pattern 74 is separated from the boundary between the regions b and c by the interval SL1, and the region g side end (right end) 74R is It is separated from the first vertical surface 70 by a distance SR1. Here, SR1 = 40 nm and SL1 = 50 nm.

For the same reason, the width of the second original photoresist pattern 76 is also smaller than the design value 2W. That is, the region a side end (left end) 76L of the second original photoresist pattern 76 is separated from the region e, f boundary by the interval SL2, and the region g side end (right end) 76R is the region It is separated from the boundary (second vertical surface 72) between g and the region a _R1 of the adjacent unit structure T _{R1 by} the interval SR2. Here, SL2 = 40 nm and SR2 = 35 nm.

  For the same reason as described in the first embodiment, SR1, SR2, SL1, and SL2 are set to values larger than the position error (about 30 nm) that occurs during mask alignment during exposure.

  Here, when the right intervals SR1 and SR2 are compared with each other, SR1> SR2, and when the left intervals SL1 and SL2 are compared with each other, SL1> SL2. The reason for this is that, as described in the third embodiment, the first original photoresist pattern 74 is thicker than the second original photoresist pattern 76, and the deformation rate in the heat flow process is (first original photoresist pattern 76). This is because the relationship of photoresist pattern 74> second original photoresist pattern 76) is established.

(2-1-3) Heat Flow Step A heat flow step will be described with reference to FIG.

  The first and second deformations are performed by deforming the first and second original photoresist patterns 74 and 76 by heating the substrate 62 in the same manner as the procedure of the “thermal flow step” described in the first embodiment. Photoresist patterns 78 and 80 are formed.

  The first original photoresist pattern 74 is deformed in the same manner as described in the first embodiment. As a result, the region a side end (left end) 78L contacts the boundary between the regions b and c, and the region g side end. A first modified photoresist pattern 78 in which the portion (right end portion) 78R contacts the first vertical surface 70 at a position lower than the upper end portion 70a of the first vertical surface 70 is obtained.

Further, the second original photoresist pattern 76 is deformed in the same manner as described in the second embodiment, whereby the region a side end (left end) 80L comes into contact with the boundary between the regions e and f and the region g A second modified photoresist pattern that is in contact with the boundary between the region g and the region a _R1 of the adjacent unit structure T _R1 at a position where the side end (right end) 80R is higher than the upper end 72a of the second vertical surface 72. 80 is obtained.

  In the heat flow process, the left and right end portions of the first original photoresist pattern 74 must move by deformation over a longer distance than the left and right end portions of the second original photoresist pattern 76 (SL1> SL2, SR1> SR2). . However, as described above, since the relationship of (first original photoresist pattern 74> second original photoresist pattern 76) is established in the deformation speed in the heat flow process, the first original photoresist pattern 74 is in the region c, The time required to cover d is approximately equal to the time required for the second original photoresist pattern 76 to cover the regions f and g.

(2-2) Etching Step Using the first and second modified photoresist patterns 78 and 80 as an etching protective film, the regions a, b, and e are etched by a depth of 2 h (0.4 μm). The specific etching procedure is the same as that described in the “etching step” in the first embodiment.

  Thereby, the third vertical surface 82 that is perpendicular to the first main surface 64 at the boundary between the regions b and c and has the upper end portion 82a is perpendicular to the first main surface 64 at the boundary between the regions e and f, and the upper end. A fourth vertical surface 84 having a portion 84a is formed.

(2-3) Ashing process An ashing process is demonstrated with reference to FIG. 8 (B). The first and second modified photoresist patterns 78 and 80 are removed by an ashing process using O ₂ plasma.

  Thus, the regions a and b are lowered by a depth of 5 h, the regions c and d are lowered by a depth of 3 h, the region e is lowered by a depth of 2 h, and the third vertical surface 82 is provided at the boundary of the regions b and c. And a structure having the fourth vertical surface 84 at the boundary between the regions e and f is obtained.

(3) Third process unit (3-1) Photoresist pattern forming process (3-1-1) Photoresist coating process The substrate 62 is formed in the same manner as the “photoresist coating process” described in the first embodiment. A photoresist film is formed on the entire surface on the first main surface 64 side. The thickness of the photoresist film at this time is about 1 μm on the regions f and g having the highest height in the direction from the second main surface 66 to the first main surface 64.

(3-1-2) Lithography Step A lithography step will be described with reference to FIG.

  Exposure similar to that described in Embodiment 1 is performed using a mask having a shielding portion at positions corresponding to the regions b, d, e, and g. Here, a mask having a shielding part that is slightly narrower than the width W of the regions b and g and slightly narrower than the width 2W of the regions d and e is used. After the exposure is completed, development is performed in the same manner as described in the first embodiment.

  In this manner, the third original photoresist pattern 86 covering the region b, the fourth original photoresist pattern 88 covering the regions d and e, and the fifth original photoresist pattern 90 covering the region g are formed.

  As described above, since the mask shielding portion width is slightly narrower than the width W of the region b, the width of the third original photoresist pattern 86 is smaller than the design value W. That is, the region a-side end (left end) 86L of the third original photoresist pattern 86 is separated from the boundary between the regions a and b by the distance SL3, and the region g-side end (right end) 86R is It is separated from the third vertical surface 82 by a distance SR3. Here, SR3 = 50 nm and SL3 = 65 nm.

  For the same reason, the width of the fourth original photoresist pattern 88 is also smaller than the design value 2W. That is, the region a side end (left end) 88L of the fourth original photoresist pattern 88 is separated from the region c, d boundary by the distance SL4, and the region g side end (right end) 88R is the first end. 4 apart from the vertical plane 84 by a distance SR4. Here, SR4 = 40 nm and SL4 = 50 nm.

For the same reason, the width of the fifth original photoresist pattern 90 is also smaller than the design value W. That is, the region a-side end (left end) 90L of the fifth original photoresist pattern 90 is separated from the region f, g boundary by the interval SL5, and the region g-side end (right end) 90R is the region It is separated from the boundary (second vertical plane 72) between g and the region a _R1 of the adjacent unit structure T _{R1 by} the interval SR5. Here, SL5 = 40 nm and SR5 = 35 nm.

  For the same reason as described in the first embodiment, SR3, SR4, SR5, SL3, SL4, and SL5 are set to values larger than the position error (about 30 nm) that occurs during mask alignment during exposure. .

  Here, when the right intervals SR3, SR4, and SR5 are compared, SR3> SR4> SR5, and when the left intervals SL3, SL4, and SL5 are compared, SL3> SL4> SL5. The reason for this is the same as that described in (2-1-2), and the third to fifth original photoresist patterns 86, 88, and 90 are caused by the difference in thickness. This is because the relationship of (the third original photoresist pattern 86> the fourth original photoresist pattern 88> the fifth original photoresist pattern 90) is established in the deformation rate in the heat flow process of the photoresist patterns 86, 88, 90.

(3-1-3) Heat Flow Step The heat flow step will be described with reference to FIG.

  The third to fifth original photoresist patterns 86, 88, and 90 are deformed by heating the substrate 62 in the same manner as in the “thermal flow step” described in the first embodiment, thereby deforming the third to fifth original photoresist patterns 86, 88, and 90. Five modified photoresist patterns 92, 94 and 96 are formed.

  The third original photoresist pattern 86 is deformed in the same manner as described in the first embodiment, so that the region a side end (left end) 92L contacts the boundary between the regions a and b and the region g side end. A third modified photoresist pattern 92 in which the portion (right end portion) 92R contacts the third vertical surface 82 at a position lower than the upper end portion 82a of the third vertical surface 82 is obtained.

  The fourth original photoresist pattern 88 is deformed in the same manner as described in the first embodiment, whereby the region a side end (left end) 94L contacts the boundary between the regions c and d and the region g side end. A fourth modified photoresist pattern 94 is obtained in which the portion (right end portion) 94R is in contact with the fourth vertical surface 84 at a position lower than the upper end portion 84a of the fourth vertical surface 84.

The fifth original photoresist pattern 90 is deformed in the same manner as described in the second embodiment, whereby the region a side end (left end) 96L contacts the boundary between the regions f and g and the region g side end. The fifth modified photoresist pattern 96 is in contact with the boundary between the region g and the region a _R1 of the adjacent unit structure T _R1 at a position where the portion (right end portion) 96R is higher than the upper end portion 72a of the second vertical surface 72. can get.

  In the heat flow process, the distances to which the left and right ends of the third to fifth original photoresist patterns 86, 88, 90 should move are shortened in this order (SR3> SR4> SR5, SL3> SL4> SL5). . However, as described above, since the relationship of (third original photoresist pattern 86> fourth original photoresist pattern 88> fifth original photoresist pattern 90) holds in the deformation speed in the heat flow process, the third original photoresist pattern 86 holds. The time required for the photoresist pattern 86 to cover the region b, the time required for the fourth original photoresist pattern 88 to cover the regions d and e, and the fifth original photoresist pattern 90 to cover the region g. The time required for this is approximately equal.

(3-2) Etching Step Using the third to fifth modified photoresist patterns 92, 94, and 96 as an etching protective film, the regions a, c, and f are etched by a depth h (0.2 μm). The specific etching procedure is the same as that described in the “etching step” in the first embodiment.

(3-3) Ashing step The ashing step will be described with reference to FIG. The third to fifth modified photoresist patterns 92, 94 and 96 are removed by ashing using O ₂ plasma.

  Thus, the region a is lowered by a depth 6h, the region b is lowered by a depth 5h, the region c is lowered by a depth 4h, the region d is lowered by a depth 3h, and the region e is reduced by a depth 2h. As a result, the region f is lowered by the depth h, and a structure in which the height of the region g does not change is formed. That is, from the region a to the region g, a binary diffraction grating composed of seven planes whose height increases by h is formed.

  In the fourth embodiment, the first to fourth vertical surfaces 70, 72, 82, and 84 are exemplified as being perpendicular to the first main surface 64. The present invention is not intended to limit the present invention only when the vertical surfaces 70, 72, 82, 84 are completely perpendicular to the first main surface 64, and within the range of errors that occur when processing the substrate 62, The case where the perpendicularity of the first to fourth vertical surfaces 70, 72, 82, 84 and the first main surface 64 is shifted is also included in the technical scope of the present invention.

  Further, a plane extending over the areas a to d (see FIG. 7B) formed in the first process unit, and a plane extending over the areas a and b and a plane extending over the area e formed in the second process unit. (See FIG. 8B) is parallel to the first main surface 64 within the range of the processing error of the substrate 62.

As described above, according to the fourth embodiment, the seven-stage binary diffraction grating is formed on the substrate through the first to third process units. In this case, the first and second original photoresist patterns 74 and 76 are formed in the lithography step (2-1-2). Subsequently, in the heat flow step of the step (2-1-3), the first and second original photoresist patterns 74 and 76 are deformed by heating, whereby the first and second deformed photoresist patterns 78 as designed. , 80. This prevents the photoresist pattern from being insufficiently covered or excessively covered at the step portions near the regions d and e and the step portions near the regions g and a _R1 . Therefore, it is possible to prevent the occurrence of protrusion-like defects and groove-like defects in the etching process of step (2-2).

Further, in the lithography step of step (3-1-2), third to fifth original photoresist patterns 86, 88, 90 are formed. Subsequently, in the heat flow step of step (3-1-3), the third to fifth original photoresist patterns 86, 88, and 90 are deformed by heating to thereby change the third to fifth deformed photoresists as designed. Patterns 92, 94 and 96 are obtained. Thus, the stepped portion in the vicinity of region b, c, area e, the step portion and the region g in the vicinity of f, the stepped portion in the vicinity of a _R1, insufficient coverage or excessive coating of the photoresist pattern is prevented. Therefore, it is possible to prevent the occurrence of protrusion-like defects and groove-like defects in the binary diffraction grating in the etching step of step (3-2). Thereby, the binary type diffraction grating which does not have a protrusion-like defect and a groove-like defect can be manufactured over the entire seven steps.

  In the photoresist pattern forming step, the width of the mask shielding portion is narrowed at the time of exposure, and heat flow is performed also as post-baking, so that the first to fifth modified photoresist patterns 78, 80, 92, 94, 96 are formed. That is, the photoresist pattern forming process is an improvement over the existing process. Therefore, no new process is added to the diffraction grating manufacturing method of the present invention.

FIG. 6 is a diagram (part 1) for explaining the method for manufacturing the semiconductor device of the first embodiment; FIG. 6 is a second diagram illustrating the method for manufacturing the semiconductor device according to the first embodiment; FIG. 3 is a diagram (No. 3) for explaining the method of manufacturing the semiconductor device of the first embodiment; FIG. 10 is a diagram for explaining the method for manufacturing the semiconductor device of the second embodiment. FIG. 10 is a diagram (part 1) for explaining a method of manufacturing a semiconductor device according to a third embodiment; FIG. 10 is a diagram (part 2) for explaining the method of manufacturing the semiconductor device of the third embodiment; FIG. 10 is a diagram (No. 1) for describing a method of manufacturing the diffraction grating of the fourth embodiment. FIG. 10 is a (second) diagram for explaining the manufacturing method of the diffraction grating of the fourth embodiment. FIG. 13 is a (third) diagram for explaining the manufacturing method of the diffraction grating of the fourth embodiment.

Explanation of symbols

10, 64 First main surface 12, 66 Second main surface 14, 34, 62 Substrate 16 First plane 19 Second plane 18 Connection surface 20, 40, 41 Structure 21, 48 Photoresist film 22, 28 Original photoresist pattern 24, 30 Design area 26, 32 Modified photoresist pattern 36 First plane 38 First inclined surface 42 Second plane 44 Second inclined surface 50, 74 First original photoresist pattern 52, 76 Second original photoresist pattern 54 1 design area 56 2nd design area 58, 78 1st modified photoresist pattern 60, 80 2nd modified photoresist pattern 68 photoresist pattern 70 1st vertical surface 72 2nd vertical surface 82 3rd vertical surface 84 4th vertical surface 86 Third original photoresist pattern 88 Fourth original photoresist pattern 90 Fifth original photoresist pattern 92 Third modified photoresist pattern 94 Fourth modified photoresist pattern 96 Fifth modified photoresist pattern 100 Stepped portion 104 Photoresist pattern 102 Vertical surface 106 Lower side plane 108 Upper side plane 110 Groove defect 112 Projection defects 16a, 19a, 36a 42a End portions 18a, 38a, 44a, 70a, 72a, 82a, 84a Upper end portions 74L, 76L, 78L, 80L, 86L, 88L, 90L, 92L, 94L, 96L Left end portions 74R, 76R, 78R, 80R, 86R, 88R, 90R, 92R, 94R, 96R Right end W Width W1, W3, W5, W6 Contact width W2, W4, W7, W8 Design value DR1, DR2, DR3, DR4 Right spacing DL1, DL2, DL3, DL4 Left spacing a -G 1st area-7th area T, T _Rn , T _Ln unit structure Height difference SR1 to SR5, SL1 to SL5 spacing

Claims (13)

In a substrate having a first main surface and a second main surface provided on the opposite side of the first main surface,
The second plane having a distance between the first plane formed on the first major plane and the second major plane is larger than the first plane, and the ends of the first and second planes are connected to each other. In forming a photoresist pattern in a structure having a connection surface,
An original photoresist pattern is formed on the first plane so as to be separated from the connection surface, and a design area as an area to protect the first plane from etching performed after a heat flow process and the original photoresist Lithography process for forming an interval according to the deformation speed in the heat flow process of the original photoresist pattern between the left and right ends of the pattern ,
By deforming by heating the original photoresist pattern, and the thermal flow process of forming a deformation photoresist pattern in contact with the connection surface at a position lower than the second plane,
A method for forming a photoresist pattern comprising the steps of:   2. The photoresist pattern according to claim 1, wherein in the heat flow step, the original photoresist pattern is deformed so that a contact width of the deformed photoresist pattern with the first plane becomes a design value. 3. Forming method. In a substrate having a first main surface and a second main surface provided on the opposite side of the first main surface,
The second plane having a distance between the first plane formed on the first major plane and the second major plane is larger than the first plane, and the ends of the first and second planes are connected to each other. In forming a photoresist pattern in a structure having a connection surface,
An original photoresist pattern is formed on the second plane so as to be separated from an end of the second plane, and a design area as an area to protect the second plane from etching performed after the heat flow step; A lithography step of forming an interval according to a deformation speed in the heat flow step of the original photoresist pattern between the left and right end portions of the original photoresist pattern ;
By deforming by heating the original photoresist pattern, and the thermal flow process of forming a deformation photoresist pattern in contact with the end portion of the second plane at a position higher than the end portion of the second plane ,
A method for forming a photoresist pattern comprising the steps of:   4. The photoresist pattern according to claim 3, wherein in the heat flow step, the original photoresist pattern is deformed so that a contact width of the deformed photoresist pattern with the second plane becomes a design value. Forming method.   The first and second planes are parallel to the first main surface, and the connection surface is perpendicular to the first main surface. Of forming a photoresist pattern. In the substrate having the first main surface and the second main surface provided on the opposite side of the first main surface,
A structure comprising a first plane and a first inclined surface extending in a direction from the second main surface connected to an end of the first plane toward the first main surface; and
A structure comprising a second plane and a second inclined surface extending in a direction from the first main surface connected to an end of the second plane toward the second main surface;
In simultaneously forming a photoresist pattern on the first plane and the second plane of the first main surface on which is formed,
A first original photoresist pattern is formed on the first plane so as to be separated from the first inclined surface, and a design region as a region to protect the first plane from etching performed after a heat flow step; An interval corresponding to the deformation speed of the first original photoresist pattern in the heat flow step is formed between the left and right end portions of the first original photoresist pattern , and the second original photoresist pattern is connected to the first original photoresist pattern. A design region as a region to be protected from etching performed after a heat flow process and the second original photoresist pattern, and formed on two planes so as to be separated from the end portion of the second plane; of between right and left ends, a lithography step of forming a gap corresponding to the deformation rate in the thermal flow process of the second original photoresist pattern ,
By heating the substrate, the first original photoresist pattern and the second original resist pattern are simultaneously deformed to form a first modified photoresist pattern and a second modified photoresist pattern, respectively.
The first modified photoresist pattern is brought into contact with the first inclined surface at a position lower than a first main surface side end of the first inclined surface; and
The second modified photoresist pattern is brought into contact with the end portion of the second plane at a position higher than the end portion on the first main surface side of the second inclined surface.
The heat flow step;
A method for forming a photoresist pattern comprising the steps of:   7. The photoresist pattern according to claim 6, wherein the first and second planes are parallel to the first main surface, and the first and second inclined surfaces are perpendicular to the first main surface. Forming method. The second main surface, and
A second surface provided on the opposite side of the second main surface and having a first distance from the second main surface, and the second main surface is a second longer than the first distance. A first main surface having a second surface having a distance of 3 and a third surface located between the first surface and the second surface;
Preparing a substrate comprising:
An original resist pattern is formed on the first surface so as to be separated from the third surface, and a design region as a region to protect the first surface from etching performed after the heat flow step and the original Forming an interval according to the deformation speed in the heat flow step of the original photoresist pattern between the left and right ends of the photoresist pattern ;
By deforming by heating the original photoresist pattern, and the thermal flow process of forming a deformation photoresist pattern in contact with the third surface,
A method for forming a photoresist pattern comprising the steps of: The second main surface, and
A second surface provided on the opposite side of the second main surface and having a first distance from the second main surface, and the second main surface is a second longer than the first distance. A first main surface having a second surface having a distance of 3 and a third surface located between the first surface and the second surface;
Preparing a substrate comprising:
A design region as a region where an original resist pattern is formed on the second surface so as to be separated from an end of the second surface, and the second surface is to be protected from etching performed after the heat flow step Forming an interval according to the deformation rate in the heat flow step of the original photoresist pattern between the left and right ends of the original photoresist pattern ;
A heat flow step of forming a modified photoresist pattern in contact with an end of the second surface by heating and deforming the original photoresist pattern; and
A method for forming a photoresist pattern comprising the steps of: Preparing a substrate having a first main surface and a second main surface provided on the opposite side of the first main surface;
(1) exposing a photoresist film formed on the first main surface side of the substrate using a mask having a shielding part to form a photoresist pattern;
(2) using the photoresist pattern as an etching protective film, etching the substrate from the first main surface side;
(3) removing the photoresist pattern;
Including one or more process units consisting of
By changing the shape and position of the shielding portion of the mask for each process unit, two or more planes that are parallel to the first main surface and have different heights are formed on the first main surface at respective end portions. In manufacturing a diffraction grating having a stepped structure connected by a vertical plane perpendicular to
In the step (1) in the second and subsequent process units, the following first and second photoresist pattern forming methods are both implemented, or any one of them.
(A) One of the two or more planes that is connected to an end of the plane and is perpendicular to the first major surface extending in a direction from the second major surface toward the first major surface. In the case of forming a photoresist pattern on the plane having a structure having the structure, an original photoresist pattern is formed on the plane so as to be separated from the vertical plane, and the plane is protected from etching performed after a heat flow process. A lithography process for forming an interval according to a deformation speed in the heat flow process of the original photoresist pattern between a design area as a power area and left and right ends of the original photoresist pattern; and the original photoresist pattern By heating and deforming, the vertical surface is brought into contact with the vertical surface at a position lower than the first main surface side end portion, and The first photoresist pattern forming method comprising the said heat flow process tactile width to form a modified photoresist pattern serving as a design value and,
(B) One of the two or more planes, which is connected to an end of the plane and is perpendicular to the first main surface extending in a direction from the first main surface toward the second main surface. In the case of forming a photoresist pattern on the plane having a structure having the structure, an original photoresist pattern is formed on the plane so as to be separated from an end portion of the plane, and the plane is removed from etching performed after a heat flow step. A lithography process for forming an interval according to a deformation speed in the thermal flow process of the original photoresist pattern between a design area as an area to be protected and left and right ends of the original photoresist pattern; By heating and deforming the resist pattern, the vertical pattern is brought into contact with the end at a position higher than the first main surface side end, and the flat surface The second photoresist pattern forming method comprising the said heat flow process contact width to form a modified photoresist pattern serving as a design value 3. When manufacturing a semiconductor device using the method for forming a photoresist pattern according to claim 1 or 2, the method further comprises an etching step of performing etching using the modified photoresist pattern as an etching protective film after the heat flow step. A method for manufacturing a semiconductor device. When manufacturing a semiconductor device using the method for forming a photoresist pattern according to claim 3 or 4, the method further comprises an etching step of performing etching using the modified photoresist pattern as an etching protective film after the heat flow step. A method for manufacturing a semiconductor device. When manufacturing a semiconductor device using the method for forming a photoresist pattern according to claim 6, an etching process for performing etching using the first and second photoresist patterns as an etching protective film is provided after the heat flow process. A method of manufacturing a semiconductor device.

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