TWI559074B - Photomask - Google Patents

Description

Mask

The present invention relates to a photomask and a method of manufacturing the photomask.

In the traditional optical lithography technology, the ultraviolet (UV) exposure technology of the photomask to the photoresist layer can be mainly divided into two types: contact optical lithography and doubling lithography.

The reticle used in the contact optical lithography technology has a surface feature pattern size of 1:1 in proportion to the pattern actually reproduced on the substrate, and is exposed directly to the surface of the photoresist layer; and doubling lithography The reticle used has a surface feature pattern size that is actually multiplied by a number of patterns on the substrate, and the photoresist is exposed by way of projection by an optical system.

Wherein, in the contact optical lithography technology, the light-shielding pattern on the surface of the reticle is in contact with the photoresist layer on the substrate, and the light-shielding pattern is easily worn out to shorten the service life of the reticle. In addition, when the surface of the substrate coated with the photoresist layer is not very flat, the photomask and the photoresist layer may generate an indefinite gap and distance, which may cause scattering and diffraction of light, thereby causing dimensional errors of the exposure and causing The lateral exposure range of the shallow portion of the photoresist layer is enlarged, so that a high aspect ratio photoresist structure cannot be produced.

Therefore, it has become one of the subjects to provide a mask manufacturing method which is low in cost, fast in process speed, low in operating temperature, and easy to manufacture.

In view of the above problems, an object of the present invention is to provide a photomask and a method of manufacturing a photomask which are low in cost, fast in process speed, low in operating temperature, and easy to fabricate.

To achieve the above object, a method of manufacturing a photomask according to the present invention. The steps include: providing a substrate. A plurality of microstructures are formed on the substrate, wherein each of the microstructures is a tapered columnar structure or a tapered tapered structure. A liquid shading solution is provided. Spin coating on the substrate, The liquid shading solution is sprayed or cast to form a light shielding layer on the substrate. The light shielding layer is cured.

In an embodiment, the substrate is a flexible substrate.

In one embodiment, the material of the flexible substrate is urethane acrylate (PUA), polyvinyl alcohol (PVA), ultraviolet light curing resin, polydimethyl methoxide (PDMS), or a combination thereof.

In one embodiment, the material of the light shielding layer is carbon black photoresist, red photoresist or green photoresist.

In one embodiment, each of the microstructures protrudes from the substrate and is partially obscured by the light shielding layer.

The invention further provides a photomask comprising a flexible substrate and a light shielding layer. The flexible substrate has a plurality of microstructures on its surface. The light shielding layer is disposed on the surface of the substrate between the microstructures to form a first light shielding portion, and the light shielding layer disposed on the surface of the microstructures forms a second light shielding portion, and the light transmittance of the second light shielding portion is higher than the first light shielding portion . The light shielding layer is a single layer body.

In one embodiment, the material of the light shielding layer is carbon black photoresist, red photoresist or green photoresist.

In one embodiment, each of the microstructures is a tapered columnar structure or a tapered tapered structure.

In summary, the present invention forms a plurality of microstructures on a substrate, and the microstructures are tapered columns or tapered tapered structures, and then liquid shading by spin coating, atomization spraying or casting. The solution is formed on the substrate, and the manufacturing method is more cost-effective, faster in process speed, lower in operating temperature, and easier to manufacture than the conventional method in which the metal layer is used as the light-shielding material. The layer uniformity of the light shielding layer can be made better. In addition, by selecting a flexible substrate, the degree of adhesion between the photomask and the semiconductor substrate can be made higher, and the precision of exposure and development is better.

10‧‧‧Main mould

11‧‧‧Substrate

111‧‧‧glass back

11a‧‧‧Microstructure

12‧‧‧Lighting layer

12a‧‧‧First Shading Department

12b‧‧‧second shade

S1~S5‧‧‧ method steps

1 is a flow chart showing the manufacture of a photomask according to a preferred embodiment of the present invention.

2A-2D are schematic views showing the manufacture of a photomask according to a preferred embodiment of the present invention.

3A-3B are scanning electron microscopes for manufacturing a main mold of a preferred embodiment of the present invention. (SEM) observation chart.

3C is a scanning electron microscope (SEM) observation view of a substrate in accordance with a preferred embodiment of the present invention.

3D-3E are scanning electron microscope (SEM) observation views of a photomask according to a preferred embodiment of the present invention.

FIG. 3F is a graph showing the relationship between the thickness of the black photoresist and the optical density.

4 is a scanning electron microscope observation view of a patterned pattern produced using a photomask according to a preferred embodiment of the present invention.

5A-5B are scanning electron microscope (SEM) observation views of a photomask according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of fabricating a reticle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements and steps will be described with the same reference numerals.

It should be noted that the photomask of the present invention and the manufacturing method thereof can be applied to a yellow light lithography process of a semiconductor and an optoelectronic display, or to a yellow light lithography process when a patterned sapphire substrate is formed by a light emitting diode, but is not limited by the above application. . Further, the photomask of the present invention may be a contact type stereo reticle.

Please refer to FIG. 1 to FIG. 4 together. FIG. 1 is a flow chart of fabricating a photomask according to a preferred embodiment of the present invention. 2A-2D are schematic views showing the fabrication of a photomask according to a preferred embodiment of the present invention. 3A-3B are scanning electron microscope (SEM) observation views of a master mold in accordance with a preferred embodiment of the present invention. 3C is a scanning electron microscope (SEM) observation view of a substrate in accordance with a preferred embodiment of the present invention. 3D-3E are scanning electron microscope (SEM) observation views of a photomask according to a preferred embodiment of the present invention. FIG. 3F is a graph showing the relationship between the thickness of the photoresist of the carbon black and the optical density. 4 is a schematic view of a patterned light-shielding layer fabricated using a photomask of a preferred embodiment of the present invention.

The photomask of this embodiment includes a substrate 11 and a light shielding layer 12 (Fig. 2D). The surface of the substrate 11 has a plurality of microstructures 11a, and the microstructures 11a of the present embodiment protrude from the substrate 11, and the microstructures 11a are partially shielded by the light shielding layer 12 (instead, only a part of the microstructures 11a are exposed to the light shielding layer). 12). In this embodiment, the line width can be adjusted by adjusting the degree to which the microstructure 11a is shielded by the light shielding layer 12.

In addition, the microstructure 11a of the present embodiment is a tapered tapered structure, for example, a pyramid structure having a narrow width and a narrow width. However, in another embodiment, the microstructure 11a may also be a tapered column. The structure is not limited by the shape of the embodiment.

The microstructures 11a can be fabricated by chemical etching, plasma dry etching or mechanical processing, but are not limited by these methods.

The light shielding layer 12 is filled on the microstructures 11a and between the microstructures 11a and is a single layer. The light shielding layer 12 can cover the partial microstructures 11a to form a patterned light shielding layer.

The manufacturing process of the photomask of this embodiment will be described in detail below.

The mask manufacturing step of the embodiment includes at least providing the substrate 11 (step S1). The substrate 11 of the present embodiment is a flexible substrate made of urethane acrylate (PUA), polyvinyl alcohol (PVA), ultraviolet curing resin, polydimethyl methoxide (PDMS), and combinations thereof. Or other light-transmissive soft polymer materials. Among them, polydimethylsiloxane (PDMS) can be selected according to different requirements of h-PDMS, s-PDMS and UV-PDMS.

The advantage of using the flexible substrate in this embodiment is that even if the wafer size is increased and the unevenness of the wafer surface is enlarged at the same time, compared with the mask made by the conventional rigid substrate, The reticle made of the flexible substrate can be flexed to have a better fit to the surface of the wafer, so that the error caused by the unevenness of the wafer surface during the exposure and development process can be reduced. The wafer circuit also has better linewidth accuracy.

Next, a plurality of microstructures 11a are formed on the substrate 11, wherein each of the microstructures is a tapered columnar structure or a tapered tapered structure (step S2). The microstructure 11a on the substrate 11 can be copied from the main mold 10 through the substrate 11 by casting, or can be processed on the surface of the substrate after being formed by machining or chemical etching. In the present embodiment, the substrate 11 is produced by copying from the main mold 10 as an example.

2A-2B, 3A-3B, firstly, the present embodiment uses tantalum nitride as the material of the main mold 10, and uses a semiconductor lithography technique to form a plurality of concave tapered tapered structures on the surface of the tantalum nitride. The main mold 10 is formed (Fig. 2A, Fig. 3A). Specifically, a circular hole-shaped recess having a diameter of 2 μm was formed on the surface of the tantalum nitride, and an array of recessed holes spaced apart from each other by 10 μm was formed. Then, it was etched by a potassium hydroxide solution (KOH, 45 wt%, 65 ° C) for 5 minutes through a mash processing technique in a microelectromechanical process, and then etched with hydrofluoric acid (HF). The main mold 10 formed under the foregoing conditions was observed under a scanning electron microscope (SEM), and the results are shown in Fig. 3A. The embodiment The plurality of recessed tapered tapered structures formed on the main mold 10 are spaced apart from each other by 10 μm, the bottom is 2 μm wide, and the depth is about 1.4 μm.

Next, a substrate (for example, PDMS) is filled in a casting manner on the surface of the main mold 10 (Fig. 2B), and heated to solidify the substrate to form the substrate 11. In this embodiment, the glass backing plate 111 may be covered on the substrate, and the substrate is cured by heating at 40 to 100 ° C to form the substrate 11. Finally, the fully cured substrate 11 is peeled off from the mold 10 to form a PDMS transparent substrate 11 having a microstructure 11a having a tapered tapered structure as shown in Fig. 2C. In an experimental example of the present embodiment, the substrate may be cured by heating at 40 ° C to 100 ° C to form the substrate 11 . Further, the tapered tapered structure array formed under the above conditions was observed by scanning electron microscope (SEM) at a magnification of 3000 times, and as shown in FIG. 3C, the size of each microstructure was measured to be 10 μm, the bottom width was 2 μm, and the height was measured. About 1.3 μm.

Next, a liquid shading solution is provided (step S3), and the liquid shading solution is spin-coated, atomized sprayed or cast on the substrate 11, and the light shielding layer 12 is formed on the substrate 11 (step S4). However, this embodiment adopts a spin coating method, but in other embodiments, the light shielding material can also achieve a similar coating effect by means of atomizing spray and air knife scraping or casting. Moreover, the speed of the spin coating will be adjusted depending on the fluidity of the light shielding material, the surface roughness of the substrate 11, and the distribution or configuration of the microstructures 11a.

The liquid shading solution is a spin coating solution with high light blocking rate and can be attached to the surface of the stereo structure via heat curing or photocuring, for example, a carbon black photoresist, a red photoresist or a green photoresist or any A rotatable coated shading material that masks a specific wavelength. In addition, a surface treatment portion may be added before step S3 or step S4.

Next, the light shielding layer 12 is cured, and the light shielding layer 12 is a single layer body (step S5). The light shielding layer 12 is formed on the substrate 11 and serves as a light shielding. The curing method can be either thermal curing or photo curing, and the curing method will be adjusted according to different shading solutions. In this embodiment, the mask after curing the light shielding layer 12 is observed under a scanning electron microscope, as shown in FIGS. 3D to 3E.

As shown in FIGS. 2D, 3D and 3E, when the light-shielding material is spin-coated on the microstructure 11a, the surface of the light-shielding layer 12 is slightly recessed due to the surface tension of the edge of the microstructure 11a. Moreover, the embodiment can adjust the amount of the light shielding material or the speed of the spin coating so that the light shielding material is only filled between the microstructures 11a.

In addition, the shape and depth of the microstructure 11a will be adjusted with the transmittance of the light-shielding material itself. Please refer to FIG. 3F, taking a carbon black photoresist as a light-shielding material, and a carbon black photoresist for ultraviolet light. The optical density (OD) is about 3/μm, which means that the carbon black photoresist layer has a transmittance of about 0.001 for ultraviolet light per 1 μm thickness. As can be seen from FIG. 3F, when the thickness of the carbon black photoresist layer is 1.4 μm, the optical density is about 3.25, that is, the transmittance is about 0.06%; and when the thickness of the carbon black photoresist layer is 0.8 μm, the optical density is about 2, that is, The penetration rate is about 1%. In other words, when using a light-shielding material having the same optical density value, stacking a thicker light-shielding material will result in lower transmittance.

When the light-shielding material is filled and the tapered tapered structure is formed, the first light-shielding portion 12a and the second light-shielding portion 12b having different transmittances are formed, and the thickness of the second light-shielding portion 12b is greater than the first light-shielding portion. The thickness of the portion is such that the light transmittance of the first light transmitting portion 12a is higher than that of the second light blocking portion 12b. The first light blocking portion 12a and the second light blocking portion 12b are merely labeled for ease of understanding, and are not referred to as the first portion. The light shielding portion 12a and the second light shielding portion 12b are two independent members, and the first light shielding portion 12a and the second light shielding portion 12b are not limited to have uniform optical properties. Although the microstructure 11a of the embodiment is in the form of a tapered tapered structure, other embodiments may be provided with other lower width and narrower designs so as to fill the light shielding material of each of the microstructures 11a. The thickness is not uniform, so that the light shielding layer 12 having a plurality of different transmittances can be formed.

It should be noted that the reticle structure of the present embodiment will be subsequently applied to a semiconductor process. The semiconductor structure can be fabricated by attaching the photomask of the present embodiment to the light shielding layer on the semiconductor substrate, and after performing exposure and development, and removing the photomask. For example, FIG. 4 is a schematic diagram of a photomask combined with a precision displacement platform and a patterned pattern formed by a yellow light lithography process according to an embodiment of the present invention.

In addition, the user can control the thickness of the light shielding layer 12 by changing the rotation speed of the spin coating, thereby adjusting the line width of the product obtained after using the mask. For example, if the substrate 11 having the above-described microstructure 11a having a size of 10 μm, a bottom width of 2 μm, and a height of about 1.3 μm is used for spin coating at a number of revolutions of 1000 rpm, as shown in FIG. 3E, it will be formed to have a thickness of approximately A photomask of a 1 μm carbon black photoresist layer (ie, the light shielding layer 12 of the present embodiment). When the mask is used for the yellow lithography process and the metal lift-off process, a metal dot structure having a period of 10 μm and a diameter of about 400 nm can be produced. The same substrate 11 is used (the microstructure 11a has a size of 10 μm and a bottom width of 2 μm, The height is about 1.3 μm), but spin coating at a rotational speed of 5000 rpm, the thickness of the formed carbon black photoresist layer is about 350 nm, as shown in FIGS. 5A and 5B, at which time the upper half of the microstructure 11a is not carbonized. The black photoresist layer (ie, the light shielding layer 12) is covered. When the mask is used for the yellow lithography process and the metal lift-off process, a metal dot structure having a period of 10 μm and a diameter of about 750 nm (not shown) can be produced. In summary, since the liquid shading solution is a fluid, the higher the rotational speed of the spin coating, the less the liquid shading solution staying on the substrate 11; and the thinner the thickness of the finally formed shading layer 12, the microstructure 11a is not The larger the portion covered by the carbon black light-shielding layer, the larger the line width of the product obtained by using the photomask for the yellow light lithography process and the metal lift-off process.

In summary, the present invention forms a plurality of microstructures on a substrate, and the microstructures are tapered columns or tapered tapered structures, and then liquid shading by spin coating, atomization spraying or casting. The solution is formed on the substrate, and the manufacturing method is more cost-effective, faster in process speed, lower in operating temperature, and easier to manufacture than the conventional method in which the metal layer is used as the light-shielding material. The layer uniformity of the light shielding layer can be made better. In addition, by selecting a flexible substrate, the degree of adhesion between the photomask and the semiconductor substrate can be made higher, and the precision of exposure and development is better.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

S1~S5‧‧‧ method steps

Claims (3)

A reticle comprising: a flexible substrate having a plurality of microstructures on a surface thereof; and a light shielding layer disposed on the surface of the substrate between the microstructures and forming a first light shielding portion disposed on the microstructures The light shielding layer of the surface forms a second light shielding portion, wherein the light transmittance of the second light shielding portion is higher than the first light shielding portion, wherein the light shielding layer is a single layer body. The photomask of claim 1, wherein the material of the light shielding layer is carbon black photoresist, red photoresist or green photoresist. The reticle of claim 1 or 2, wherein each of the microstructures is a tapered columnar structure or a tapered tapered structure.