CN100468013C - Phase-shift photomask and method for improving printability of on-wafer structures - Google Patents

Abstract

A phase shift photomask and method for improving printability of a structure on a wafer are disclosed. The method includes providing a photomask including a zero degree PSW formed on a top surface of a substrate and a 180 degree PSW formed in a first region of the substrate. An orthogonal PSW that facilitates projection of an increased intensity of radiant energy through a second region of the substrate during a lithography process is formed in the second region between the zero degree PSW and the 180 degree PSW.

Description

Phase-shift photomask and method for improving printability of on-wafer structures

related application

This application claims "PHASE SHIFTPHOTOMASK AND METHOD FOR IMPROVING PRINTABILITY OFA STRUCTURE ON A WAFER"), U.S. Provisional Patent Application Serial No. 60/520,809.

This application also claims "PHASESHIFT PHOTOMASK AND METHOD FOR IMPROVING PRINTABILITY OF A STRUCTURE ON", filed April 30, 2004 by Kent Nakagawa, entitled "PHASESHIFT PHOTOMASK AND METHOD FOR IMPROVING PRINTABILITY OF A STRUCTURE ON A WAFER"), U.S. Provisional Patent Application Serial No. 60/566,733.

technical field

The present invention relates generally to photolithographic methods and, more particularly, to phase shift photomasks and methods for improving the printability of structures on wafers.

Background technique

As device manufacturers are producing devices that are shrinking in size, so are the demands placed on the photomasks used in the fabrication of these devices. A photomask (also referred to as a reticle or mask) generally consists of a substrate on which a pattern layer is formed. The absorber layer contains a pattern representing an image, and this pattern can be transferred to a wafer in a photolithography system. As the feature size of devices decreases, the corresponding patterns on the photomask also become smaller and more complex. Therefore, mask quality becomes one of the most important factors in forming a stable and reliable manufacturing process.

In addition to using sub-wavelength line structures, some applications require the use of near-wavelength structures. Traditionally, alternate aperture phase shift masks (AAPSM) can be used to fabricate subwavelength line structures. AAPSMs typically include etched regions of the substrate that provide destructive interference that enables lines to be printed on the wafer at wavelengths smaller than the wavelength of light used in the lithography system. However, near-wavelength structures are usually formed using binary photomasks. In some applications (such as high-capacity hard disk drives), the photomask contains sub-wavelength AAPSM regions adjacent to or directly adjacent to near-wavelength regions. At the junction of the near-wavelength structure and the sub-wavelength structure, the curvature of the feature edge may be exaggerated due to the transition between the sub-wavelength AAPSM region and the near-wavelength AAPSM region.

Existing techniques for reducing feature edge curvature include optical proximity correction (OPC) or geometrically modifying etched or non-etched regions of the substrate. However, these techniques have little effect on reducing the curvature of feature edges. Another technique to correct for feature edge curvature involves increasing the amount of light at the point where the near-wavelength structure meets the sub-wavelength line structure by using an intensity-attenuating light-transmitting material. However, this technique affects the phase-shift properties of etched and non-etched regions, which degrades the quality of subwavelength line structures.

Contents of the invention

In accordance with the teachings of the present invention, those disadvantages and problems associated with printing structures onto wafers are largely reduced or eliminated. In a particular embodiment, an orthogonal phase shift window (PSW) formed between the 0 degree PSW and the 180 degree PSW of the substrate provides increased intensity during the photolithographic process.

According to one embodiment of the present invention, a method of improving the printability of a structure on a wafer includes providing a photomask having a 0 degree PSW formed on an upper surface of a substrate and a 180 degree PSW formed in one area. An orthogonal PSW is formed in the second region between the aforementioned 0 degree PSW and the 180 degree PSW, which may facilitate projecting radiant energy of increased intensity through the second region during a photolithography process.

According to another embodiment of the present invention, a method for improving the printability of a structure on a wafer includes forming a pattern layer on at least a portion of a substrate, and forming a 0-degree PSW in the pattern layer, The upper surface of the sheet is exposed. A 180-degree PSW is formed in the first exposed region of the substrate, and an orthogonal PSW is formed in the second region between the above-mentioned 0-degree PSW and the 180-degree PSW. The second region projects radiant energy of increased intensity.

According to another embodiment of the present invention, a photomask for improving the printability of structures on a wafer includes a 0 degree PSW formed on a top surface of a substrate. The 180-degree PSW is formed by the first channel in the substrate, and the orthogonal PSW is formed by the second channel between the 0-degree PSW and the 180-degree PSW. The second region projects radiant energy of increased intensity.

According to another embodiment of the present invention, a photomask for improving the printability of a structure on a wafer includes a pattern layer formed on at least a portion of a substrate, and a pattern layer formed in the pattern layer, the substrate The upper surface of the exposed 0 degree PSW. A 180 degree PSW is formed by the first trench in the substrate such that the 0 degree PSW and the 180 degree PSW together form at least one edge in the subwavelength feature. Near-wavelength features are formed in the patterned layer adjacent to the sub-wavelength features. An orthogonal PSW is formed by a second channel in the substrate between the 0 degree PSW and the 180 degree PSW, wherein the second channel extends into a portion of the subwavelength feature and a portion of the near wavelength feature. During a photolithography process, the orthogonal PSW may facilitate projecting radiant energy of increased intensity through said second region.

Important technical advantages of several specific embodiments of the present invention include an orthogonal PSW that can facilitate fabrication of both near-wavelength and sub-wavelength features with a single photomask. The orthogonal PSW is used to enhance the intensity of radiant energy projected onto the wafer surface in the region corresponding to the orthogonal PSW. This increased strength provides a desirable curvature at the junction of the near-wavelength structure and the sub-wavelength structure, and may eliminate the need for separate photomasks to form the two structures. Furthermore, the orthogonal PSW allows imaging of the aforementioned structures with a single exposure.

Another technical advantage of several specific embodiments of the present invention includes an orthogonal PSW that eliminates the sharp curvature that can occur when imaging near-wavelength features adjacent to sub-wavelength features on the surface of a wafer . To correct the curvature at the junction of near-wavelength and sub-wavelength structures imaged on the wafer, the amount of light projected through the photomask onto the wafer at the aforementioned intersection regions should be increased. The orthogonal PSW is designed so that it is approximately orthogonal to the 0 degree PSW and the 180 degree PSW that form at least a portion of the sub-wavelength features on the photomask. The orthogonal PSW is used to enhance the light intensity at the junction of the above structures. At the same time, because the orthogonal PSW does not affect the phase shift characteristics of the 0-degree PSW and the 180-degree PSW, it does not make the printing of sub-wavelength structures or near The setup of the angled portion of the wavelength structure is distorted.

In each embodiment of the present invention, it may have all the above-mentioned technical advantages, have some of them, or have none of these advantages. From the following drawings, descriptions and claims, those skilled in the art can clearly understand other technical advantages of the present invention.

Description of drawings

Embodiments of the present invention and their advantages will be more fully and thoroughly understood by reading the following description in conjunction with the accompanying drawings, in which like reference numerals indicate like features, wherein:

Figure 1 shows a cross-sectional view of a photomask assembly taught by the present invention;

Figure 2 illustrates an exemplary embodiment of a photomask taught by the present invention;

Figure 3 shows a cross-sectional view of another exemplary embodiment of a photomask taught by the present invention;

Figure 4 shows an illustration of a manufacturability simulation implemented with a quadrature phase shift window (PSW) taught by the present invention;

Figure 5 shows an illustration of a manufacturability simulation achieved with an orthogonal PSW taught by the present invention at an exposure wavelength;

Figure 6 shows an illustrative graph of a manufacturability simulation achieved with an orthogonal PSW taught by the present invention at another exposure wavelength.

Detailed ways

Preferred embodiments of the present invention and their advantages are best understood by referring to FIGS. 1 through 6 , wherein like reference numerals are used to identify like and corresponding parts throughout the drawings.

FIG. 1 shows a cross-sectional view of an exemplary photomask assembly 10 . Photomask assembly 10 includes pellicle assembly 14 mounted on photomask 12 . The phase shift window (PSW) 24 of substrate 16, pattern layer 18, 0 degree, orthogonal PSW26 and 180 degree PSW28 forms photomask 12, and photomask 12 is called reticle or mask again, and it can have Various sizes and shapes (including but not limited to round, rectangular and square). The photomask 12 can also be any photomask including, but not limited to, a one-time master mask, a five-inch reticle, a six-inch reticle, a nine-inch reticle, or any other reticle that can be used to pattern a circuit A reticle of the appropriate size is projected onto a semiconductor wafer with an image of it. The photomask 12 can also be a binary mask, a phase shift mask (PSM) (such as an alternating aperture phase shift mask, also known as a Levenson-type mask), an optical proximity correction (OPC) mask, or any other Types of masks suitable for use in lithographic systems.

The photomask 12 includes a patterned layer 18 formed on an upper surface 17 of a substrate 16 which, when exposed to electromagnetic energy in a photolithography system, projects a pattern onto a semiconductor wafer (not expressly shown). )on the surface. Substrate 16 may be made of a transparent material such as quartz, artificial quartz, fused silica, magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), or any other suitable material, wherein these materials At least seventy-five percent (75%) of incident light having a wavelength between about 10 nanometers (nm) and about 450 nm is transmitted. In another embodiment, substrate 16 may be made of a reflective material, such as silicon, or any other suitable material that reflects more than about fifty percent (50%) of the wavelengths Incident light between about 10 nm and about 450 nm.

The pattern layer 18 can be made of such as chromium, chromium nitride, metal-oxygen-carbon-nitride (such as MOCN, wherein M can be made of chromium, cobalt, iron, zinc, molybdenum, niobium, tantalum, titanium, tungsten, aluminum, magnesium and silicon), or may be made of any other electromagnetic energy absorbing wavelengths in the ultraviolet (UV), deep ultraviolet (DUV), vacuum ultraviolet (VUV), extreme ultraviolet (EUV) range made of suitable materials. In another embodiment, the pattern layer 18 may be made of a partially transmissive material such as molybdenum silicide, which has about one percent (1%) to about Thirty percent (30%) transmittance.

 AF或旭硝子制造的

)之类的材料制成，或是对波长处于UV、DUV、EUV和/或VUV范围内的电磁辐射透明的另一种合适的表膜。可以用诸如离心铸造的传统技术来准备表膜22。Frame 20 and pellicle 22 may form pellicle assembly 14 . Frame 20 is typically made of anodized aluminum, however, it may also be made of stainless steel, plastic, or other suitable material that will not degrade or outgas when exposed to electromagnetic energy within a photolithographic system. The membrane 22 can be made of nitrocellulose, cellulose acetate, amorphous fluoropolymers (such as those manufactured by EI du Pontde Nemours)

Made by AF or Asahi Glass

), or another suitable film that is transparent to electromagnetic radiation with wavelengths in the UV, DUV, EUV and/or VUV range. The skin 22 may be prepared by conventional techniques such as centrifugal casting.

Surface film 22 protects photomask 12 from contaminants such as dust particles by ensuring that contaminants are kept a specified distance away from photomask 12 . This is especially important in lithography systems. During a photolithographic process, photomask assembly 10 is exposed to electromagnetic energy generated by a radiant energy source within a photolithographic system. The electromagnetic energy may include light of various wavelengths, such as light having a wavelength approximately between the 1 line and the G line of a mercury arc lamp, or DUV, VUV, or EUV light. The pellicle 22 is designed to pass most of the electromagnetic energy during exposure. Contaminants collected on the pellicle 22 are likely to be out of focus at the surface of the wafer being processed, therefore, the exposed image on the wafer should be sharp. The use of a pellicle 22 formed in accordance with the teachings of the present invention is satisfactory with all types of electromagnetic energy, and these electromagnetic energies are not limited to light waves as described herein.

Photomask 12 can be formed from a photomask blank using standard photolithography processes. In a photolithography process, a mask pattern file including data of the pattern layer 18 may be generated from a mask layout file. In one embodiment, the mask layout file described above includes polygons representing transistors and electrical connections of the integrated circuit. When an integrated circuit is fabricated on a semiconductor wafer, the polygons in the mask layout file also represent the different layers of the integrated circuit. For example, transistors may be formed on a semiconductor wafer having a diffusion layer and a polysilicon layer. Accordingly, the mask layout file may include one or more polygons drawn on the diffusion layer and one or more polygons drawn on the polysilicon layer. The polygons for each layer can be converted into a mask pattern file representing one layer of the integrated circuit. Each mask pattern file can be used to generate a mask for a particular layer. In some embodiments, the mask pattern file may include multiple layers of the integrated circuit such that features from the multiple layers may be imaged on the surface of the semiconductor wafer with the photomask.

Desired features can be imaged in the photoresist layer of the photomask blank using a laser, electron beam, or X-ray lithography system. In one embodiment, the laser lithography system uses an argon ion laser that emits light at a wavelength of approximately 364 nanometers (nm). In another embodiment, the laser lithography system uses a laser that emits light at a wavelength of about 150 nm to about 300 nm. Photomask 12 can be manufactured by following steps: develop and etch the exposed area of photoresist layer and form pattern; Etch each part that is not covered by photoresist on pattern layer 18; Remove undeveloped photoresist to form pattern on substrate 16 to form a pattern layer 18 .

In the illustrated embodiment, photomask 12 also includes a 0 degree PSW 24, an orthogonal PSW 26, and a 180 degree PSW 28. Orthogonal PSW 26 and 180 degree PSW 28 may be trenches formed in substrate 16. The combination of the 0 degree PSW 24 and the 180 degree PSW 28 can provide a phase shift of about 180 degrees such that when the photomask assembly 10 is used in a lithography system, the radiant energy passing through the 180 degree PSW 28 is the same as that passing through the 0 degree PSW 24 The radiated energy is about 180 degrees out of phase. The 180 degree phase shift between the 0 degree PSW 24 and the 180 degree PSW 28 produces destructive interference which creates dark or opaque regions in the photoresist layer formed on the wafer. The dark regions correspond to portions of the photoresist layer that were not exposed to radiant energy such that the photoresist is not removed from the dark regions during the development process.

The quadrature PSW 26 may be simultaneously orthogonal to the 0 degree PSW 24 and the 180 degree PSW 28 such that it does not contribute to or negatively interact with the phase shift produced by the 0 degree PSW 24 and the 180 degree PSW 28. In the illustrated embodiment, the quadrature PSW 26 is approximately half as deep as the 180 degree PSW 28 such that its phase shift relative to the 0 degree PSW 24 and the 180 degree PSW 28 is approximately 90 degrees. In another embodiment, the orthogonal PSW 26 is approximately fifty percent (50%) deeper than the 180 degree PSW 28 such that its phase shift relative to the 0 degree PSW 24 is approximately 270 degrees relative to The phase shift for a 180 degree window 28 is about 90 degrees. The 0-degree PSW 24 can be formed by etching the pattern layer 18 to expose the upper surface 17 of the substrate 16, and the orthogonal PSW 26 and the 180-degree PSW 28 can be formed by etching the substrate 16 to form a channel, wherein the above-mentioned channel The depth is adapted to produce a desired phase shift at one or more exposure wavelengths.

During the photolithography process, the orthogonal PSW 26 can increase the intensity of radiant energy projected onto the area of the wafer corresponding to the area where the orthogonal PSW 26 is located. This increased strength can result in the desired cornering effect without compromising the 180 degree phase shift required to produce the desired linewidth. In one embodiment, the orthogonal PSW 26 may be formed in the same photomask fabrication process as the 0 degree PSW 24 and the 180 degree PSW 28. In another embodiment, the orthogonal PSW 26 can be formed on the substrate 16 in a separate manufacturing process, such that the photomask 12 initially includes a 0 degree PSW 24 and a 180 degree PSW 28, and then changes to include an orthogonal PSW 26 .

In one embodiment, an orthogonal PSW 26 may be formed in the photomask 12 for imaging the read/write head structure of a hard disk drive. In other embodiments, orthogonal PSW 26 may be used in any design that would benefit from having a substantially exact corner connection between two structures where one structure (such as a sub wavelength structure) has a width much smaller than the exposure wavelength of the lithography system, while the width of another structure (such as a near-wavelength structure) is greater than or equal to the exposure wavelength of the lithography system. This type of design can be used to form integrated circuits with specific performance, spacing or timing requirements.

Figure 2 shows a cross-sectional view of an exemplary embodiment of a photomask including orthogonal PSWs. In the illustrated embodiment, photomask 30 includes substrate 16, patterned layers 18a and 18b (collectively referred to as patterned layer 18) formed on upper surface 17, 0 degree PSWs 24a and 24b (collectively referred to as 0 degree PSW 24), Orthogonal PSWs 26a and 26b (collectively referred to as orthogonal PSWs 26) and 180 degree PSWs 28a and 28b (collectively referred to as 180 degree PSWs 28).

As shown, the 0 degree PSW 24a can be formed by etching the patterned layer 18a to expose the upper surface 17 of the substrate 16. Orthogonal PSW 26a may be formed by etching substrate 16 to form a trench in substrate 16 whose depth is within the range of a photolithographic system when photomask 30 is used to project an image onto the wafer surface. A phase shift of about 90 degrees relative to 0 degrees PSW 24a is produced at the exposure wavelength of . In another embodiment, the trenches form a depth of orthogonal PSW 26a that produces a phase shift of about 270 degrees relative to 0 degree PSW 24a at the exposure wavelength. Orthogonal PSW 26a may be adjacent to 0 degree PSW 24a, and patterned layer 18a may separate these windows.

The 180 degree PSW 28a can be formed by etching the substrate 16 to form a channel in the substrate 16, wherein the depth of the channel produces a phase angle of about 180 degrees relative to the 0 degree PSW 24a at the exposure wavelength of the lithography system. shift. The 180 degree PSW 28a can be adjacent to the orthogonal PSW 26a, and the patterned layer 18a can separate the two layers. The 0 degree PSW 24a and the 180 degree PSW 28a can be used together to form subwavelength features, which can be imaged as subwavelength structures on the wafer surface during the photolithography process. As mentioned above, with reference to FIG. 1, the function of the orthogonal PSW 26 is, by increasing the intensity of the radiant energy projected on the wafer in the region corresponding to the window, at the junction of the sub-wavelength line structure and the near-wavelength structure. produce the desired curvature.

Photomask 30 may also include 0 degree PSW 24b, orthogonal PSW 26b, and 180 degree PSW 28b. As shown, 180 degree PSW 28b may be formed in substrate 16 at a location directly adjacent to orthogonal PSW 26b. Additionally, an orthogonal PSW 26b may be formed directly adjacent to a 0 degree PSW 24b. In other embodiments, patterned layer 18b may separate at least one of 0 degree PSW 24b, orthogonal PSW 26b, and 180 degree PSW 28b. Although the photomask 30 is shown in the figure to include a specific pattern employing a 0 degree PSW 24, an orthogonal PSW 26, and a 180 degree PSW 28, it is also possible to set the orthogonal PSW between the 0 degree PSW and the 180 degree PSW. form any pattern. In addition, photomask 30 may be similar in size, shape and type to photomask 12 shown in FIG. 1 .

FIG. 3 shows a cross-sectional view of another exemplary embodiment of a photomask including orthogonal PSWs. In the illustrated embodiment, photomask 40 includes substrate 16, 0 degree PSWs 32a, 32b, and 32c (collectively referred to as 0 degree PSWs 32), orthogonal PSWs 34a, 34b, and 34c (collectively referred to as orthogonal PSWs 34) and 180 degree PSW 36a and 36b (collectively referred to as 180 degree PSW 36). In the illustrated embodiment, photomask 40 is a chrome-free photomask used in chrome-free phase lithography (CPL). Photomask 40 may include absorber layer 38 formed on portions of the upper surface of substrate 16 outside the mask area to prevent transfer of multiple images to the surface. The material used to form the absorption layer 38 may be similar to the material used to form the pattern layer 18 shown in FIG. 1 . In another embodiment, the upper surface of the substrate 16 may not include any absorbent layer material.

The 0 degree PSW 32 can be formed by exposing a layer of photoresist (not clearly shown), developing the photoresist to form a pattern, and etching the absorber layer 38 to expose the upper surface 17 of the substrate 16. Another layer of photoresist (not explicitly shown) may be formed over the 0 degree PSW 32 and any remaining absorber layer 38. In one embodiment, a pattern comprising orthogonal PSWs 24 and 180 degree PSWs 36 is formed in the photoresist by exposing the photoresist and developing the photoresist to expose the upper surface 17 of the substrate 16. The exposed areas of the substrate 16 are etched, forming channels in the substrate 16 whose depths produce relative The phase shift of the PSW 32 at 0 degrees is approximately 90 degrees. The 180 degree PSW 36 may be formed by depositing a layer of photoresist (not clearly shown) over the 0 degree PSW 32, the channels formed by the first etch process, and any remaining absorber layer 38. The photoresist is exposed and developed to reveal the portions of the trench corresponding to the 180 degree PSW 36. The exposed portion of the trench is then further etched to form a trench whose depth produces a phase shift of approximately 180 degrees relative to 0 degree PSW 32 at one or more exposure wavelengths.

In other embodiments, it may be formed by depositing a layer of photoresist (not explicitly shown) over the 0 degree PSW 32, the trenches formed by the first and second etch steps, and any remaining absorber layer 38. Quadrature PSW 34. The photoresist can be exposed and developed to reveal portions of the aforementioned trenches corresponding to the orthogonal PSW 34. The exposed portion of the trench is then further etched to form a trench whose depth produces a phase shift of approximately 270 degrees relative to 0 degree PSW 32 at one or more exposure wavelengths.

Orthogonal PSW 34 and 180 degree PSW 36 may also be formed in separate steps. For example, the orthogonal PSW 34 may be formed by depositing a layer of photoresist over the exposed portion of the substrate 16 and any remaining absorber layer 38 and exposing only the regions of the photoresist corresponding to the orthogonal PSW 34. . These exposed areas can then be etched to form a channel whose depth produces a phase shift of approximately 90 degrees relative to 0 degree PSW 32 at one or more exposure wavelengths. Then, by depositing a layer of photoresist on each exposed portion of the substrate 16 (for example, including each channel forming the orthogonal PSW 34) and exposing only the part of the photoresist corresponding to the 180-degree PSW 36 Area to form 180 degree PSW 36. The photoresist can be developed to expose the upper surface of the substrate 16, and the substrate 16 can then be etched to form a trench having a depth that yields an angle of about 180 degrees at one or more exposure wavelengths. phase shift.

As shown, 0 degree PSW 32a may be directly adjacent to orthogonal PSW 34a, and 180 degree PSW 36 may be separated from orthogonal PSW 34 by a small portion of unetched substrate. As mentioned above with reference to FIG. 1 , the orthogonal PSW 34 can be used to increase the intensity of radiant energy projected onto the wafer surface (not expressly shown) in the region corresponding to the window. This increased strength creates a desired curvature at the junction of the sub-wavelength line structures and the near-wavelength line structures on the wafer.

Photomask 40 also includes 0 degree PSWs 32b and 32c, orthogonal PSWs 34b and 34c, and 180 degree PSW 36b. As shown, 180 degree PSW 36b may be formed in substrate 16 at a location directly adjacent to orthogonal PSWs 34b and 34c. Additionally, orthogonal PSW 34b may be formed directly adjacent to 0 degree PSW 32b, and orthogonal PSW 34c may be formed directly adjacent to 0 degree PSW 32c. In other embodiments, any desired pattern may be formed by forming orthogonal PSWs between 0 degree PSW and 180 degree PSW. Photomask 40 is similar in size, shape and type to photomask 12 shown in FIG. 1 .

FIG. 4 shows an illustration of a manufacturability simulation performed with an exemplary embodiment of an orthogonal PSW. In the simulation results, line 50 represents the edge of a 0-degree PSW formed on the photomask, and line 52 represents the edge of a 180-degree PSW formed on the photomask. The elongated regions between lines 50, 52 represent subwavelength features 54, which are formed on the photomask described above and can be imaged on the surface of the wafer to form subwavelength structures. In one embodiment, the subwavelength features 54 are approximately 100 nanometers wide. In another embodiment, the width of the sub-wavelength features 54 may be less than the exposure wavelength of the photolithography system. The wide triangular region between lines 56 and 58 represent near-wavelength features 60, which are formed on the photomask described above and can be imaged on the surface of the wafer to form near-wavelength structures.

Rectangle 62 represents an orthogonal PSW formed in the substrate of the photomask. In one embodiment, the orthogonal PSW is about 200 nanometers long and about 100 nanometers wide. In another embodiment, the width of the orthogonal PSW is approximately equal to the width of the subwavelength feature 54 . In another embodiment, the orthogonal PSW may be a square with side lengths approximately equal to the width of the sub-wavelength features 54 . In other embodiments, the width of the orthogonal PSW may be greater or less than the width of the sub-wavelength features 54 . In the illustrated embodiment, the orthogonal PSW may be symmetrically disposed between the near-wavelength feature 60 and the sub-wavelength feature 54 . In other embodiments, the orthogonal PSW may be arranged such that a substantial portion thereof extends into the near-wavelength feature 60 or the sub-wavelength feature 54 .

Lines 64 and 66 illustrate how near-wavelength structures corresponding to near-wavelength features and sub-wavelength structures corresponding to sub-wavelength features are imaged on the wafer surface without the use of orthogonal PSW. As shown, the curve representing the junction between sub-wavelength feature 54 and near-wavelength feature 60 is distorted such that it makes an angle with the horizontal that is greater than the target angle specified for the junction between the features. Lines 68 and 70 show how near-wavelength and sub-wavelength line structures are imaged on the wafer surface after using orthogonal PSW. As shown, the angle to the horizontal is reduced and the structures imaged on the wafer more accurately represent the desired structures. In one embodiment, orthogonal PSWs may be used to print near-wavelength structures at angles from about 0 degrees to about 90 degrees from the horizontal.

FIG. 5 shows an explanatory diagram of a simulation using an orthogonal PSW with an exposure wavelength of 248 nm. As shown, lines 72 and 74 represent the near-wavelength and sub-wavelength line structures printed on the wafer without the use of an orthogonal PSW (eg, rectangle 62) with an exposure wavelength of 248 nm. Lines 76 and 78 show how the near-wavelength and sub-wavelength line structures are imaged on the wafer surface using orthogonal PSW. As shown, when an orthogonal PSW is included in the photomask, the angle between lines 76 and 78 and the horizontal is reduced so that the curvature of the image on the wafer is closer to the desired curvature (e.g., from This can be seen from the interception of lines 50 and 56 and the interception of lines 52 and 58 in the figure).

Figure 6 shows an explanatory diagram of a simulation using an orthogonal PSW with an exposure wavelength of 193 nm. As shown, lines 80 and 82 represent the near-wavelength and sub-wavelength line structures printed on the wafer without the use of an orthogonal PSW with an exposure wavelength of 193 nm. Lines 84 and 86 illustrate how the near-wavelength and sub-wavelength line structures are imaged on the surface of the wafer using the orthogonal PSW described above. As shown, the enhanced radiant energy creates a sharper transition between near-wavelength structures and sub-wavelength structures in regions of the wafer's surface corresponding to orthogonal PSWs (eg, rectangle 62).

Although the present invention has been described in terms of specific preferred embodiments, various changes and modifications to those embodiments will become apparent to those skilled in the art, and such changes and modifications fall within the present invention as defined in the appended claims. In the range.

Claims (32)

1. A method of improving the printability of structures on a wafer, comprising: A photomask comprising a substrate is provided, the photomask further comprising: a 0 degree phase shift window PSW formed on the upper surface of the substrate; and a 180 degree PSW formed in the first region of the substrate, the 0 degree PSW and the 180 degree PSW cooperate to form sub-wavelength features; etching a second region of the substrate to form a substantially orthogonal PSW between the 0 degree PSW and the 180 degree PSW, the substantially orthogonal PSW being configured to pass through the second region during a photolithographic process projecting radiant energy of increased intensity; and A near-wavelength feature adjacent to the sub-wavelength feature is located on the photomask. 2. The method of claim 1, further comprising the near-wavelength feature making an angle between about 0 degrees and about 90 degrees from the horizontal. 3. The method of claim 1, further comprising extending the substantially orthogonal PSW into a portion of the near-wavelength feature and a portion of the sub-wavelength feature. 4. The method of claim 1, further comprising: The near-wavelength features are configured to facilitate projecting near-wavelength structures onto a wafer during a photolithography process; The subwavelength features are configured to facilitate projecting subwavelength structures onto a wafer during a photolithography process; and The substantially orthogonal PSW is configured to create a sharper transition between the near-wavelength structure and the sub-wavelength structure. 5. The method of claim 1, further comprising: forming the substantially orthogonal PSW from a first trench in the substrate having a first depth that establishes a phase shift of about 90 degrees relative to the 0 degree PSW; and The 180 degree PSW is formed by a second trench in the substrate, the second trench having a second depth approximately twice the first depth. 6. The method of claim 1, further comprising: forming the 180 degree PSW from a first trench in the substrate, the first trench having a first depth; and The substantially orthogonal PSW is formed by a second trench in the substrate having a second depth approximately fifty percent greater than the first depth such that the substantially orthogonal The PSW establishes a phase shift of approximately 270 degrees relative to the 0 degree PSW. 7. The method of claim 1, further comprising attaching a pellicle assembly to the substrate. 8. The method of claim 1, further comprising: The photomask includes a patterned layer formed on at least a portion of the upper surface of the substrate; and The 0 degree PSW exposing the upper surface of the substrate is formed in the pattern layer. 9. The method of claim 1, further comprising using the substantially orthogonal PSW in a photolithography process to fabricate a read head or a write head of a hard disk drive. 10. A method of improving the printability of structures on a wafer, comprising: forming a patterned layer on at least a portion of the substrate; forming a 0-degree phase shift window PSW exposing the upper surface of the substrate in the pattern layer; forming a 180 degree PSW in a first exposed region of the substrate, the 0 degree PSW and the 180 degree PSW cooperating to form at least one edge of a subwavelength feature; A 90-degree PSW between the 0-degree PSW and the 180-degree PSW is formed in the second exposed region of the substrate, and the 90-degree PSW is configured to pass through the second exposed region during a photolithography process. projecting radiant energy of increased intensity; and A near-wavelength feature is formed on the photomask adjacent to at least one edge of the sub-wavelength feature. 11. The method of claim 10, further comprising the near-wavelength feature making an angle between about 0 degrees and about 90 degrees from the horizontal. 12. The method of claim 10, further comprising extending the 90 degree PSW into a portion of the near-wavelength feature and a portion of the sub-wavelength feature. 13. The method of claim 10, further comprising: The near-wavelength features are configured to facilitate projecting near-wavelength structures onto a wafer during a photolithography process; The subwavelength features are configured to facilitate projecting subwavelength structures onto a wafer during a photolithography process; and The 90 degree PSW is configured to create a sharper transition between the near-wavelength structure and the sub-wavelength structure. 14. The method of claim 10, further comprising: forming the 90 degree PSW from a first trench in the substrate, the first trench having a first depth; and The 180 degree PSW is formed by a second trench in the substrate, the second trench having a second depth approximately twice the first depth. 15. The method of claim 10, further comprising attaching a pellicle assembly to the substrate. 16. The method of claim 10, further comprising using the 90 degree PSW in a photolithography process to fabricate a read head or a write head of a hard disk drive. 17. A photomask for improving the printability of structures on a wafer, comprising: A 0-degree phase shift window PSW formed on the upper surface of the substrate; a 180 degree PSW formed by a first channel in said substrate, said 0 degree PSW and said 180 degree PSW cooperate to form a sub-wavelength feature; a substantially orthogonal PSW between the 0 degree PSW and the 180 degree PSW formed by the second trench in the substrate, the substantially orthogonal PSW being configured to pass through the said substantially orthogonal PSW projects radiant energy of increased intensity; and A near-wavelength feature adjacent to the sub-wavelength feature. 18. The photomask of claim 17, further comprising said near wavelength features having an angle between about 0 degrees and about 90 degrees from horizontal. 19. The photomask of claim 17, further comprising the substantially orthogonal PSW extending into a portion of the near-wavelength features and a portion of the sub-wavelength features. 20. The photomask of claim 17, further comprising: the near-wavelength feature configured to facilitate projecting near-wavelength structures onto a wafer during a photolithography process; the subwavelength features configured to facilitate projection of subwavelength structures onto a wafer during a photolithography process; and The substantially orthogonal PSW is configured to create a sharper transition between the near-wavelength structure and the sub-wavelength structure. 21. The photomask of claim 17, further comprising: said first channel having a first depth; and The second channel has a second depth, the second depth being about half the first depth, such that the substantially orthogonal PSW establishes a phase shift of about 90 degrees relative to the 0 degree PSW. 22. The photomask of claim 17, further comprising: said first channel having a first depth; and said second trench having a second depth about fifty percent deeper than said first depth such that said substantially orthogonal PSW establishes about 270 degrees relative to said 0 degree PSW phase shift. 23. The photomask of claim 17, wherein the substantially orthogonal PSW comprises a square. 24. The photomask of claim 17, wherein the substantially orthogonal PSW comprises a rectangle. 25. The photomask of claim 17, further comprising a pellicle assembly attached to the substrate. 26. The photomask of claim 17, further comprising: a patterned layer formed on at least a portion of the upper surface of the substrate; and The 0-degree PSW formed in the pattern layer exposing the upper surface of the substrate. 27. The photomask of claim 17, further configured to facilitate fabrication of read or write heads for hard disk drives in a photolithographic process. 28. The photomask of claim 17, wherein the photomask is a chrome-free photomask. 29. A photomask for improving the printability of structures on a wafer, comprising: a patterned layer formed on at least a portion of the substrate; A 0-degree phase shift window PSW formed in the pattern layer and exposing the upper surface of the substrate; a 180 degree PSW formed by a first channel in said substrate, said 0 degree PSW and said 180 degree PSW cooperate to form a sub-wavelength feature; near-wavelength features formed in the patterned layer adjacent to the sub-wavelength features; and a 90 degree PSW formed by a second channel in the substrate between the 0 degree PSW and the 180 degree PSW, the 90 degree PSW extending into a portion of the near wavelength feature and the As part of the subwavelength feature, the 90 degree PSW is configured to facilitate projecting increased intensity radiant energy through the 90 degree PSW during a photolithography process. 30. The photomask of claim 29, further comprising a pellicle assembly attached to the substrate. 31. The photomask of claim 29, further comprising: said first channel having a first depth; and The second channel has a second depth that is about half the first depth. 32. The photomask of claim 29, further comprising: the near-wavelength feature configured to facilitate projecting near-wavelength structures onto a wafer during a photolithography process; the subwavelength features configured to facilitate projection of subwavelength structures onto a wafer during a photolithography process; and The 90 degree PSW configured to create a sharper transition between the near-wavelength structure and the sub-wavelength structure.

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