JP2006049363A - Stencil mask and stencil mask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stencil mask, along with stencil mask blanks, capable of easily determining an etching condition. <P>SOLUTION: A difference between a maximum value and a minimum value of two-dimensional aspect ratio 2DAR, where 2DAR=ä(ARx<SP>2</SP>+ARy<SP>2</SP>)/2}<SP>1/2</SP>, in a plurality of membrane divisions, is 1.5 or less. Here, ARx is aspect ratio (=Tz/Lx) of thickness Tz of a substrate which is dug by etching in Z-axis direction against length Lx in X-axis direction of the opening to be a membrane division: ARy is aspect ratio (=Tz/Ly) of thickness Tz of substrate dug by etching in Z-axis direction against length Ly in Y-direction of the opening to be a membrane division: and thickness of substrate Tz corresponds to the height of a support frame or beam. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a stencil mask and a stencil mask blank used for manufacturing a semiconductor device.

  With the miniaturization of semiconductor devices, it is becoming difficult to form fine patterns by lithography using ultraviolet light. Therefore, lithography techniques using X-rays, electron beams, ion beams and the like have been proposed and researched and developed.

  Conventionally proposed electron beam transfer lithography includes PREVAIL (projection exposure with variable axis immersion lenses), SCALPEL (scattering with angular limitation in projection electron-beam lithography) and LEEPL (low energy electron-beam proximity projection lithography). Is mentioned.

  A high energy electron beam having an acceleration voltage of about 100 kV is used for PREVAIL and SCALPEL. In the case of PREVAIL and SCALPEL, the electron beam that has passed through a part of the mask is imaged on the resist by a 4 × reduction projection system, and the pattern is transferred. On the other hand, a low energy electron beam having an acceleration voltage of about 2 kV is used for LEEPL. In the case of LEEPL, when an electron beam passes through a hole provided in a mask, a pattern is transferred onto the resist at an equal magnification.

  A stencil mask membrane used for LEEPL has a large number of holes corresponding to the pattern, and an electron beam is incident on the resist film on the silicon wafer through these holes. A support frame (frame) is provided around the membrane to compensate for the mechanical strength of the stencil mask, and a number of beams are provided in the membrane to increase the rigidity of the membrane itself. These beams are intended to improve the rigidity of the membrane, and are arranged so as to form complementary patterns in order to connect patterns by multiple exposure.

For example, Patent Document 1 describes a stencil mask 1M in which a membrane 3M is divided into four complementary pattern sections I to IV by beam strip segments 6a, 6b, 6c, and 6d as shown in FIG. When this is used for multiple exposure, the mask 1M is stepped relative to the silicon wafer in the order of complementary pattern sections I → II → III → IV, and a donut-shaped pattern or the like that cannot be formed by a single exposure. Form on resist.
JP 2003-59819 A

  However, in the conventional stencil mask 1M, since the membrane division region 5M1 having a small opening area exists in the center portion of the membrane, it is very difficult to determine the etching conditions at the time of beam formation. That is, in the membrane division region 5M1 having a small opening area, the mutual space between the beams is narrow, and the etching rate is smaller than in the other membrane division regions 5M2 to 5M6 (regions where the mutual space between the beams is wide). At present, the entire etching conditions must be determined in accordance with the etching rate of the region 5M1.

  However, if the entire etching time is determined in accordance with the small opening region 5M1 penetrating last, the etching stopper layer of the large opening region 5M5, 5M6 penetrating first may end up without enduring. is there. Thus, it is very difficult to determine the optimum etching conditions, which is a big problem to be solved in the manufacturing process.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a stencil mask and a stencil mask blank that can easily determine etching conditions.

  The stencil mask of the present invention includes a membrane in which holes through which charged particle beams pass are patterned, a support frame that supports the periphery of the membrane, and the support frame so as not to overlap the charged particle beam passage holes in a planar view. And includes a plurality of beams supporting the membrane, a skirt around the connecting portion of the beam and the membrane in a planar view, and the beam, and dividing the membrane into a plurality of membrane division regions And a beam strip that divides the membrane into four complementary pattern sections in the first to fourth quadrants along the orthogonal X-axis and Y-axis, Extends along the X axis and is included in the complementary pattern section of the first quadrant, and includes the complementary pattern section of the first quadrant and the complementary pattern section of the fourth quadrant. A first X-axis beam strip segment extending along the X-axis, included in the complementary pattern section of the third quadrant, and the complementary pattern section of the second quadrant and the complementary pattern section of the third quadrant A second X-axis beam strip segment that divides and extends along the Y-axis, and is included in the complementary pattern section of the first quadrant, and includes the complementary pattern section of the first quadrant and the complementary pattern section of the second quadrant A first Y-axis beam strip segment that divides, and extends along the Y-axis, and is included in the complementary pattern section of the third quadrant; the complementary pattern section of the third quadrant and the complementary pattern section of the fourth quadrant; And the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR given by the following formula is less than 1.5. To be formed as Stencil mask to be characterized.

2DAR = {(ARx ² + ARy ² ) / 2} ^1/2
However, ARx: the aspect ratio (= Tz / Lx) of the thickness Tz of the substrate that can be etched in the Z-axis direction with respect to the length Lx in the X-axis direction of the opening to be the membrane division region, and ARy: the membrane division region The aspect ratio (= Tz / Ly) of the thickness Tz of the substrate that can be etched in the Z-axis direction with respect to the length Ly of the opening Y-axis, the thickness Tz of the substrate: equivalent to the height of the support frame or the beam.

  The stencil mask blanks of the present invention includes a membrane, a support frame that supports the periphery of the membrane, a plurality of beams that are provided inside the support frame in a planar field of view and support the membrane, and the beams in a planar field of view. The membrane includes a skirt around the connecting portion with the membrane and the beam, and divides the membrane into a plurality of membrane division regions, and the membrane has four first rectangular shapes along the X axis and the Y axis perpendicular to each other. Stencil mask blanks comprising beam bands divided into complementary pattern sections in the fourth quadrant, wherein the beam bands extend along the X axis and are included in the complementary pattern sections in the first quadrant A first X-axis beam strip segment separating the complementary pattern section in the first quadrant and the complementary pattern section in the fourth quadrant, extending along the X-axis, A second X-axis beam strip segment that is included in the complementary pattern section of the third quadrant and separates the complementary pattern section of the second quadrant and the complementary pattern section of the third quadrant, and extends along the Y-axis, A first Y-axis beam strip segment that is included in the complementary pattern section of the first quadrant and separates the complementary pattern section of the first quadrant and the complementary pattern section of the second quadrant, and extends along the Y-axis, A plurality of membranes, comprising: a second Y-axis beam strip segment that is included in a complementary pattern section of the third quadrant and separates the complementary pattern section of the third quadrant and the complementary pattern section of the fourth quadrant; The stencil mask blank is characterized in that the divided area is formed such that the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR given by the following formula is less than 1.5.

2DAR = {(ARx ² + ARy ² ) / 2} ^1/2
However, ARx: the aspect ratio (= Tz / Lx) of the thickness Tz of the substrate that can be etched in the Z-axis direction with respect to the length Lx in the X-axis direction of the opening to be the membrane division region, and ARy: the membrane division region The aspect ratio (= Tz / Ly) of the thickness Tz of the substrate that can be etched in the Z-axis direction with respect to the length Ly of the opening Y-axis, the thickness Tz of the substrate: equivalent to the height of the support frame or the beam.

  In the above case, it is more preferable to further reduce the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR to less than 1.0 (see FIGS. 2 and 6). Further, it is more preferable that the two-dimensional aspect ratio 2DAR value of all the membrane division regions is less than 1.0 (see FIGS. 2 and 6). This not only eliminates the membrane segmentation area with a small opening size, but also eliminates the membrane segmentation area with a long and narrow opening, which increases the distance between the beam and the beam (or the support frame) and facilitates etching. is there.

  2 and 5 to 7 used in the description of the present invention and the conventional example, a grid-like auxiliary line is drawn in each divided region so that the two-dimensional aspect ratio 2DAR of the membrane divided region can be understood. It is out.

  In order to extend the distance between the support frame and the beam, it is preferable to provide a membrane division region having a dummy opening through which the charged particle beam does not pass in the peripheral portion of the membrane (see FIG. 6). This is because if the opening at the center portion of the membrane is expanded, an elongated opening may be formed between the peripheral edge and the support frame, and this can be eliminated by providing a dummy opening.

  In the present specification, the “dummy opening” refers to a non-pattern region that is formed at the periphery of the membrane as a part of one membrane division region, but does not have a charged particle beam passage hole for an actual transfer pattern. It is defined as a thing. For example, the hatched area indicated by the symbol DM in FIG. 6 corresponds to the dummy opening.

  In this specification, the “two-dimensional aspect ratio” is defined by 2DAR given by the following formula (1).

2DAR = {(ARx ² + ARy ² ) / 2} ^1/2 (1)
However, ARx in the above formula (1) is the aspect ratio (= Tz / Lx) of the thickness Tz of the substrate that can be etched by etching in the Z-axis direction with respect to the length Lx in the X-axis direction of the opening to be the membrane division region, ARy indicates the aspect ratio (= Tz / Ly) of the thickness Tz of the substrate that can be etched in the Z-axis direction with respect to the Y-axis direction length Ly of the opening to be the membrane division region. The substrate thickness Tz corresponds to the height of the support frame or beam.

  For example, since the standard thickness Tz of an 8-inch (200 mm) diameter wafer is 725 μm, the opening size of the reference membrane divided region is set to 1 mm × 1 mm (designed with a beam center pitch P = 1.25 mm). Sometimes ARx and ARy are each 0.725. When these are applied to the above equation (1) and calculated, the 2DAR value is 0.73 by rounding off the third decimal place. Further, when the two-dimensional aspect ratio is calculated for a membrane division region having an aperture size as small as 0.25 mm × 0.25 mm (quarter size), ARx and ARy are 2.9, respectively. Becomes 2.9.

  Since an internal stress is applied to the membrane forming layer, as described in Patent Document 1, if the opening size is increased, the amount of distortion of the membrane becomes excessive and cannot be used as a mask. For this reason, the maximum size of the reference opening is limited to about 2 mm × 2 mm, preferably about 1 mm × 1 mm, when single crystal silicon is used for the membrane. The maximum opening size is allowed up to about 2 mm × 2 mm. However, in order to provide a flat membrane without distortion even after opening, it is desirable to keep the size to 1 mm × 1 mm or less.

  In this specification, the term “complementary mask” means that a pattern that cannot be formed by a single exposure can be formed by a plurality of exposures (multiple exposure), so that at least two exposures are performed in any pattern formation scheduled area. It is defined as a stencil mask to which the segment division region (opening) of the membrane is assigned.

  Further, the “complementary pattern section” is defined as a section of a complementary mask that is sectioned corresponding to each exposure.

  In addition, the “beam strip segment” is defined as a beam strip section that separates adjacent complementary pattern sections from each other.

  In the complementary mask, two beam groups that belong to adjacent complementary pattern sections and face in the same direction are connected to mutually different positions with respect to the beam strip segments that divide both complementary pattern sections.

  Since the stencil mask and stencil mask blank of the present invention do not have a small opening membrane dividing region in the central portion of the membrane, the entire etching time can be shortened. For this reason, it is possible to effectively prevent overetching of the etching stopper layer that protects the support frame and the remaining portion to be the beam.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the stencil mask 1 </ b> A is formed using a silicon wafer 2. A central portion of the silicon wafer 2 is removed in a square shape, and a membrane 3A is formed in this portion. The thick silicon wafer 2 surrounding the membrane 3A is used as a support frame (frame) 9 for supporting the thin film membrane 3A (see FIG. 4G). Beams 4 are formed in a lattice pattern on the membrane 3A. The beam 4 is a remaining portion in which a plurality of openings are formed in the silicon wafer 2. The ends of all the beams 4 are connected to the frame 9 or the other beams 4, and there are no places where the beams 4 are interrupted.

  Hereinafter, a substantially square portion surrounded by the beam strip portion 6 of the membrane 3A will be referred to as membrane divided regions 5A1 to 5A6. As shown in FIG. 3, the beam strip portion 6 includes a beam 4 and a skirt portion 11 (skirt) 11 provided in parallel with the beam 4 with a minute width.

  Assuming that the center of the silicon wafer 2 in FIG. 1 is the origin and the membrane 3A in FIG. 2 is an XY plane, the membrane 3A is divided into four regions by the X axis and the Y axis. Hereinafter, these divided regions are referred to as complementary pattern sections I to IV. The membrane 3A does not need to be strictly square, and if the sections I to IV are a rectangle having two sides of the X axis and the Y axis or a polygonal shape close to it, the lengths of all the sides of the sections I to IV are complete. Does not have to match.

  The beam band portion 6 includes four beam band segment segments 6a to 6d, and divides the membrane 3A into four complementary pattern sections I to IV. The first X-axis beam strip segment 6d extends along the X-axis and is included in the first quadrant complementary pattern section I. The first quadrant complementary pattern section I and the fourth quadrant complementary pattern section IV. It is divided. The second X-axis beam strip segment 6b extends along the X-axis and is included in the complementary pattern section in the third quadrant, and includes a complementary pattern section II in the second quadrant and a complementary pattern section III in the third quadrant. It is divided. The first Y-axis beam strip segment 6a extends along the Y axis and is included in the complementary pattern section in the first quadrant, and includes a complementary pattern section I in the first quadrant and a complementary pattern section II in the second quadrant. It is divided. The second Y-axis beam strip segment 6c extends along the Y-axis and is included in the complementary pattern section in the third quadrant, and includes a complementary pattern section III in the third quadrant and a complementary pattern section IV in the fourth quadrant. It is divided.

  As shown in FIG. 2, the position of the first X-axis beam strip segment 6d and the second X-axis between the sections I and II adjacent in the X-axis direction or between the sections III and IV. It does not coincide with the position of the shaft beam strip segment 6b. The shift amount between both beam strip segments 6b and 6d is equal to the width of one beam. Similarly, between the section I and the section IV adjacent in the Y-axis direction, or between the section II and the section III, the position of the first Y-axis beam strip segment 6a and the second Y-axis beam strip It does not coincide with the position of the segment 6c. The shift amount between both beam strip segments 6a and 6c is equal to the width of one beam. The widths W1 and W2 of the beam strip portion 6 can be set to about 100 to 200 μm. In the complementary mask 1A, two beam groups facing in the same direction belonging to adjacent complementary pattern sections are connected to positions different from each other with respect to the beam band segment that divides both complementary pattern sections. For example, the beam group of the section I and the beam group of the section II are not on the same line, and are in contact with the beam band segment 6a that partitions the section I and the section II at a position shifted.

  In the mask 1A of the present embodiment, two membrane division regions 5A6 having an expanded size (1.5 mm × 1.5 mm) larger than the membrane division region 5A4 when the reference size is 1 mm × 1 mm are provided in the central portion of the membrane 3A. Provided. These two expanded membrane divided regions 5A6 are arranged point-symmetrically with respect to the center of the membrane in the sections II and IV. In section II and section IV, an expanded-size membrane partition area 5A6, a reference-size membrane partition area 5A4, and a smaller-sized (0.75 mm × 0.75 mm) membrane partition area 5A1 are arranged in a diagonal line. Yes.

  Further, in the section II and the section IV, a membrane division region 5A5 having a semi-expansion size (1.5 mm × 1.0 mm) is arranged adjacent to the expansion membrane division region 5A6 along the beam strips 6a and 6c. A semi-expanded size (1.0 mm × 1.25 mm) membrane division region 5A5 is arranged adjacent to the expansion membrane division region 5A6 along the beam strips 6b and 6d.

  Further, in the sections II and IV, the membrane division area 5A2 having a size smaller than the reference size (1.0 mm × 0.75 mm) and the membrane division area 5A3 having a size equivalent to the reference size (1.5 mm × 0.75 mm). And are provided.

  Note that only the membrane division region 5A4 of the reference size is provided in the sections I and III.

  In the mask 1A of the present embodiment, the two-dimensional aspect ratio 2DAR values of the membrane division regions 5A1, 5A2, 5A3, 5A4, 5A5, and 5B6 are 0.97, 0.86, 0.77, 0.73, 0,. 62, 0.48.

  FIG. 3 is an enlarged perspective view of one of the membrane dividing regions 5 and the surrounding beams 4 and beam bands 6. As shown in FIG. 3, the membrane 3 </ b> A (3 </ b> B, 3 </ b> C) is divided into a plurality of membrane division regions 5 by a beam strip portion 6 including a beam 4. The hole 8 corresponding to the pattern cannot be formed in the beam 4 but is formed in the membrane division region 5.

  A skirt 11 is provided between the membrane division region 5 and the beam 4 as a skirt for absorbing an error when forming the membrane division region. A portion where the beam 4 and the skirts 11 on both sides thereof are combined corresponds to the beam band portion 6. In principle, the hole 8 is formed in the membrane dividing region 5, but it may be formed so as to protrude from a part of the skirt 11 in some cases. The widths W1 and W2 of the beam strip 6 can be set to about 100 to 200 μm, for example.

  According to LEEPL, it is possible to slightly change the incident angle of the electron beam to the stencil mask 1A. The range of the incident angle of the electron beam is usually about 0 to 10 mrad. When the stencil mask 1A is formed using an 8-inch diameter wafer, the height of the beam 4 is 725 μm, which is the thickness of the 8-inch silicon wafer.

  Next, a method for manufacturing the stencil mask and the stencil mask blank of the present invention will be described with reference to FIG.

  The SOI wafer 21 as a base material has a silicon thin film as a membrane forming layer 3a on one surface of the silicon wafer 2 with a silicon oxide film 10 interposed therebetween. The membrane forming layer 3a is formed to a predetermined film thickness (for example, 500 nm) of 1 μm or less. In order to form holes with high accuracy by etching the membrane, it is generally necessary to keep the ratio of the membrane thickness to the hole diameter (aspect ratio) to 10 or less, preferably 5 or less. Therefore, in order to form, for example, a pattern hole having a line width of 90 nm in the stencil mask, the membrane thickness needs to be 1 μm or less. For the membrane forming layer 3a of the present embodiment, a silicon thin film doped with a predetermined amount of a predetermined dopant is used to control internal stress, but other silicon-based materials such as a silicon nitride film can also be used.

  First, as shown in FIG. 4A, a silicon oxide film having a predetermined thickness is formed on the back side of the SOI wafer 21 as a protective film 22 for dry etching. A resist is applied on the protective film 22 and baked. This resist film is exposed with the beam and frame pattern shown in FIG. 2 and developed to form a resist pattern 23. Using this resist pattern 23 as a mask, the protective film 22 is dry-etched as shown in FIG.

Next, the silicon substrate 2 is dry etched using the resist pattern 23 and the protective film 22 as a mask. This process is strong anisotropic etching using an etching gas such as SF ₆ or NF ₃ , and the side wall of the silicon substrate that has been shaved becomes nearly vertical as shown in FIG. Ratio beams 4 and frames 9 are formed. In this step, the silicon oxide film 10 functions as an etching stopper layer.

  For example, when an 8-inch wafer is used as the SOI wafer 21, the thickness of the silicon substrate 2 is 725 μm. Therefore, when the silicon substrate 2 is dry-etched using the resist pattern 23 as a mask without providing the protective film 22, the resist pattern 23 is consumed before the etching for the thickness of the silicon substrate 2 is completed. It becomes difficult to form the beam 4 and the frame 9 having a desired height and shape. Therefore, how to set the film thickness of the protective film 22 is important.

  Next, as shown in FIG. 4D, the silicon oxide film 10 is etched using the beam 4 and the frame 9 as a mask. For this etching, for example, wet etching using hydrofluoric acid as an etchant is used. In this step, the protective film 22 is also removed, and a desired stencil mask blank 30 is obtained.

  Next, the stencil mask blank 30 is held by a spin chuck of the coating apparatus so that the membrane forming layer 3a is on the upper surface, and a resist is applied on the membrane forming layer 3a, as shown in FIG. 4 (e). Then, a resist layer 24 having a predetermined thickness is formed.

  Next, as shown in FIG. 4F, a pattern 24 a for forming a hole is transferred to the resist layer 24. The patterning of the resist layer 24 can be performed by ordinary electron beam lithography.

Next, dry etching is performed on the membrane forming layer 3a using the resist layer 24 as a mask to form the stencil mask hole 8, and the membrane forming layer 3a corresponding to the back side of the beam 4 at a predetermined position is aligned. An alignment mark 25 is formed. By providing the alignment mark 25, it is possible to perform alignment with high accuracy over the entire thin film. For this dry etching, for example, SF ₆ or NF ₃ is used as an etching gas. Thereafter, the resist layer 24 is peeled off. In this way, a stencil mask 40 shown in FIG. 4G is obtained.

  An outline of how to use the stencil mask will be described.

  The stencil mask 1A is arranged so that the surface on the membrane 3A side is close to the wafer surface to which the pattern is transferred. When the stencil mask 1A is scanned with the electron beam from the frame 9 side, the electron beam is transmitted only through the hole 8, and the pattern is transferred to the resist on the wafer.

  When exposure is performed using the stencil mask 1A, first, the stencil mask 1A and the wafer to be processed are fixed, and the patterns of the sections I to IV are transferred. Next, the stencil mask 1A and the wafer are relatively moved, and different sections of the stencil mask 1A are arranged on the transferred patterns of the sections I to IV. Usually, it is easier to move the wafer to be processed while the stencil mask 1A is fixed.

  After the wafer to be processed is moved, the stencil mask 1A is scanned again with an electron beam. The above steps are repeated, and multiple multiple exposures are performed so that the patterns of the four sections I to IV (see FIG. 2) of the stencil mask 1A overlap. Thereby, the pattern existing in the beam 4 portion is also transferred complementarily to the resist.

  In the stencil mask 1A of the present embodiment, the two-dimensional aspect ratio 2DAR values of the membrane division regions 5A1, 5A2, 5A3, 5A4, 5A5, and 5B6 are 0.97, 0.86, 0.77, 0.73, 0, respectively. The difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is 0.49. As described above, since the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is reduced, the etching becomes easy and the entire etching time can be shortened.

(Second Embodiment)
Next, the mask of the second embodiment will be described with reference to FIG. In addition, description of the part which this embodiment overlaps with the said 1st Embodiment is abbreviate | omitted.

  In the stencil mask 1B of the second embodiment, in the section II and the section IV, the membrane division region 5B1 having an elongated size (0.75 mm × 0.25 mm) along the four beam bands 6a, 6b, 6c, and 6d An elongated size (1.0 mm × 0.25 mm) membrane division region 5B2 and an elongated size (1.5 mm × 0.25 mm) membrane division region 5B3 are provided. Further, in the peripheral portions of the sections II and IV, the membrane division region 5B4 having a size smaller than the reference size (0.75 mm × 0.75 mm) and a size slightly smaller than the reference size (1.0 mm × 0.75 mm). ) Membrane dividing region 5B5. Note that only the reference-size membrane division region 5B6 is provided in the division I and the division III.

  In the stencil mask 1B of the present embodiment, the two-dimensional aspect ratio 2DAR values of the membrane division regions 5B1, 5B2, 5B3, 5B4, 5B5, and 5B6 are 2.2, 2.1, 2.1, 0.97, 0, respectively. .86, 0.73. Accordingly, the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR in the mask 1B of the present embodiment is 1.47. As described above, since the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is reduced, the etching becomes easy and the entire etching time can be shortened.

(Third embodiment)
Next, the mask of the third embodiment will be described with reference to FIG. In addition, description of the part which this embodiment overlaps with the said 1st Embodiment is abbreviate | omitted.

  In the stencil mask 1C of the third embodiment, in the sections II and IV, the membrane having a size smaller than the reference size (0.75 mm × 0.75 mm) along the four beam strips 6a, 6b, 6c, and 6d. A divided region 5C1 and a membrane divided region 5C2 having a size (1.0 mm × 0.75 mm) slightly smaller than the reference size are provided. Also, in the peripheral portions of the sections II and IV, the membrane division region 5C1 having a size smaller than the reference size (0.75 mm × 0.75 mm) and a size slightly smaller than the reference size (1.0 mm × 0.75 mm). ) Membrane dividing region 5C2.

  The membrane division regions 5C1 and 5C2 at the peripheral portions of the sections II and IV include dummy openings DM indicated by hatching in the drawing. The electron beam at the time of exposure does not pass through these dummy openings DM. Note that only the reference-size membrane division region 5C3 is provided in the division I and the division III.

  In the stencil mask 1C of the present embodiment, the two-dimensional aspect ratio 2DAR values of the membrane division regions 5C1, 5C2, and 5C3 are 0.97, 0.86, and 0.73, respectively. Therefore, the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR in the mask 1C of this embodiment is 0.24. As described above, since the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is reduced, the etching becomes easy and the entire etching time can be shortened.

  Further, by providing the dummy opening DM, there is an advantage that a small opening or a long and narrow opening is not generated at the periphery of the membrane, and the etching conditions can be set more easily.

(Comparative example)
Next, a mask of a comparative example will be described with reference to FIG.
The stencil mask 1M of the comparative example has membrane division regions 5M1 each having an opening of the minimum size (0.25 mm × 0.25 mm) in the sections II and IV when the reference size is 1 mm × 1 mm. . Further, in the section II and the section IV, the membrane division region 5M2 having an elongated size (0.75 mm × 0.25 mm) and an elongated size (1.0 mm) are respectively provided along the four beam strips 6a, 6b, 6c, and 6d. × 0.25 mm) membrane dividing region 5M3. Note that only the membrane division region 5M6 having a reference size (1 mm × 1 mm) is provided in the sections I and III.

  The two-dimensional aspect ratio 2DAR values of the membrane division regions 5M1, 5M2, 5M3, 5M4, 5M5, and 5M6 are 2.9, 2.2, 2.1, 0.97, 0.86, and 0.73, respectively. Therefore, the difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR in the comparative example mask 1M is 2.17, which is considerably larger than the values in the first to third embodiments. Therefore, the etching of the portions belonging to the membrane divided regions 5M1, 5M2, and 5M3, particularly the etching of the membrane divided region 5M1, is slower than the other regions 5M4, 5M5, and 5M6, and the entire etching time is aligned with the membrane divided regions 5M1. When the length is increased, the etching stopper layer 10 in the other regions 5M4, 5M5, and 5M6 is consumed, and the membrane forming layer 3a is also over-etched. On the other hand, if the etching time is aligned in the membrane division regions 5M4, 5M5, and 5M6, the elongated membrane division regions 5M1, 5M2, and 5M3 are not sufficiently dug, and the membrane division region 5M1 is completely up to the end line. It was not possible to dig up, and the membrane division region could not be formed.

  The stencil mask of the present invention can be used for low-speed electron beam proximity transfer lithography (LEEEPL) and PREVAIL (projection exposure with variable axis immersion lenses). Moreover, the stencil mask blank of this invention can be utilized as a semi-finished product which can form a desired pattern hole in a membrane arbitrarily on the user side.

The top view which shows the stencil mask which concerns on embodiment of this invention. The top view which expands and shows the principal part of the stencil mask of FIG. The perspective view which expands and shows one unit of a membrane division | segmentation area | region, and the surrounding beam. (A)-(g) is process drawing which shows the manufacturing method of the stencil mask of this invention. The top view which expands and shows the principal part of the stencil mask which concerns on other embodiment of this invention. The top view which expands and shows the principal part of the stencil mask which concerns on other embodiment of this invention. The principal part enlarged plan view which shows the stencil mask of a comparative example.

Explanation of symbols

1A, 1B, 1C, 1M, 1N ... stencil mask,
2 ... Silicon substrate (silicon wafer),
3, 3A, 3B, 3C, 3M, 3N ... membrane,
3a ... Membrane forming layer (silicon-based thin film),
4… Beam,
5, 5A1 to 5A6, 5B1 to 5B6, 5C1 to 5C3, 5M1 to 5M6 ... membrane division region,
DM ... Dummy opening,
6 ... Beam band
6a ... 1st Y-axis beam strip segment,
6b second X-axis beam strip segment,
6c second Y-axis beam strip segment,
6d ... first X-axis beam strip segment,
8 ... charged particle beam passage hole (electron beam passage hole),
9: Support frame (frame),
10 ... Etching stopper layer (silicon oxide film),
11 ... Hem (skirt),
21 ... SOI wafer,
22 ... Protective film (silicon oxide film),
23, 24 ... resist film,
25 ... Alignment mark,
30 ... Stencil mask blanks,
40 ... stencil mask,
I: Complementary pattern section in the first quadrant,
II: Complementary pattern section in the second quadrant,
III ... Complementary pattern section in the third quadrant,
IV: Complementary pattern section in the fourth quadrant.

Claims (8)

A membrane in which holes through which charged particle beams pass are patterned, a support frame that supports the periphery of the membrane, and provided inside the support frame so as not to overlap the charged particle beam passage holes in a planar view, A plurality of beams supporting the membrane, and a skirt and a beam around a connection portion between the beam and the membrane in a planar view, and dividing the membrane into a plurality of membrane dividing regions, and orthogonal X-axis and A stencil mask comprising a beam strip that divides the membrane into four complementary pattern sections in the first to fourth quadrants in a rectangular shape along the Y-axis,
The beam strip is
A first X-axis beam strip segment extending along the X axis and included in the complementary pattern section of the first quadrant and separating the complementary pattern section of the first quadrant and the complementary pattern section of the fourth quadrant;
A second X-axis beam strip segment extending along the X-axis, included in the complementary pattern section of the third quadrant and separating the complementary pattern section of the second quadrant and the complementary pattern section of the third quadrant;
A first Y-axis beam strip segment extending along the Y axis and included in the complementary pattern section of the first quadrant and separating the complementary pattern section of the first quadrant and the complementary pattern section of the second quadrant;
A second Y-axis beam strip segment extending along the Y axis and included in the complementary pattern section of the third quadrant and separating the complementary pattern section of the third quadrant and the complementary pattern section of the fourth quadrant; Have
The stencil mask, wherein the plurality of membrane division regions are formed such that a difference between a maximum value and a minimum value of a two-dimensional aspect ratio 2DAR given by the following formula is less than 1.5.
2DAR = {(ARx ² + ARy ² ) / 2} ^1/2
However,
ARx: aspect ratio (= Tz / Lx) of the thickness Tz of the substrate that is etched by etching in the Z-axis direction with respect to the length Lx in the X-axis direction of the opening to be the membrane division region,
ARy: Aspect ratio (= Tz / Ly) of the thickness Tz of the substrate that can be etched by etching in the Z-axis direction with respect to the Y-axis direction length Ly of the opening to be the membrane division region,
Substrate thickness Tz: equivalent to the height of the support frame or the beam. The stencil mask according to claim 1, wherein a difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is less than 1.0. The stencil mask according to any one of claims 1 and 2, wherein the two-dimensional aspect ratio 2DAR value of all the membrane division regions is less than 1.0. 4. A membrane division region having a dummy opening through which a charged particle beam does not pass is provided at a peripheral edge portion of the membrane in order to expand a distance between the support frame and the beam. A stencil mask according to item. A membrane, a support frame that supports the periphery of the membrane, a plurality of beams that are provided inside the support frame in a planar view, and that support the membrane, and a periphery of a connection portion between the beams and the membrane in a planar view And the beam is divided into a plurality of membrane dividing regions, and the membrane is rectangularly shaped along four orthogonal X-axis and Y-axis, and four complementary pattern sections in the first to fourth quadrants. A stencil mask blank comprising:
The beam strip is
A first X-axis beam strip segment extending along the X axis and included in the complementary pattern section of the first quadrant and separating the complementary pattern section of the first quadrant and the complementary pattern section of the fourth quadrant;
A second X-axis beam strip segment extending along the X-axis, included in the complementary pattern section of the third quadrant and separating the complementary pattern section of the second quadrant and the complementary pattern section of the third quadrant;
A first Y-axis beam strip segment extending along the Y axis and included in the complementary pattern section of the first quadrant and separating the complementary pattern section of the first quadrant and the complementary pattern section of the second quadrant;
A second Y-axis beam strip segment extending along the Y axis and included in the complementary pattern section of the third quadrant and separating the complementary pattern section of the third quadrant and the complementary pattern section of the fourth quadrant; Have
The stencil mask blank is characterized in that the plurality of membrane division regions are formed so that a difference between a maximum value and a minimum value of a two-dimensional aspect ratio 2DAR given by the following formula is less than 1.5.
2DAR = {(ARx ² + ARy ² ) / 2} ^1/2
However,
ARx: aspect ratio (= Tz / Lx) of the thickness Tz of the substrate that is etched by etching in the Z-axis direction with respect to the length Lx in the X-axis direction of the opening to be the membrane division region,
ARy: Aspect ratio (= Tz / Ly) of the thickness Tz of the substrate that can be etched by etching in the Z-axis direction with respect to the Y-axis direction length Ly of the opening to be the membrane division region,
Substrate thickness Tz: equivalent to the height of the support frame or the beam. 6. The stencil mask blank according to claim 5, wherein a difference between the maximum value and the minimum value of the two-dimensional aspect ratio 2DAR is less than 1.0. The stencil mask blank according to any one of claims 5 and 6, wherein the two-dimensional aspect ratio 2DAR value of all the membrane division regions is less than 1.0. 8. A membrane division region having a dummy opening through which a charged particle beam does not pass is provided at a peripheral edge portion of the membrane in order to expand a distance between the support frame and the beam. Stencil mask blanks according to item.

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