CN102520591A - Negative photoresist-based diffuser photo-etching process - Google Patents

Abstract

The present invention relates to a kind of diffusion plate photolithography process method based on negative photoresist, the method comprises the following steps: first, coating photoresist on the surface of the substrate, then pre-baking, spin-coated with negative photoresist The substrate of the glue is pre-baked to remove the solvent of the negative photoresist; followed by exposure, the diffusion sheet is placed on the mask plate, and the negative photoresist is exposed to ultraviolet light by using the diffusion sheet and the mask plate as a mask; finally After post-baking and development, the negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure; the diffusion sheet and the mask plate are used as a mask to participate in the exposure of the photoresist . The invention has the advantages of wide application range, simple process, good process repeatability, no need to modify existing photolithography equipment, low cost, easy realization of mass production and the like.

Description

A Diffusion Sheet Photolithography Process Method Based on Negative Photoresist

technical field

The present invention relates to a photolithography process method in the field of semiconductor technology, micro-electromechanical system (MEMS) field and integrated optics field, in particular to a diffusion sheet photolithography process method based on negative photoresist, more precisely, a simultaneous A negative-tone photoresist lithography process that uses a diffuser and a mask as a lithography mask.

Background technique

Photolithography plays a pivotal role in the fabrication of integrated optoelectronic devices. The photolithography process usually refers to the precise copying of the pattern of the photolithographic mask onto the photoresist coated with the surface of the material to be etched by photocopying. Lithography plays a pivotal role in the manufacturing process of integrated optical devices, MEMS and integrated circuit chips (IC). Lithography has been widely regarded as one of the key technologies for mass-manufacturing micro-nano structures and devices. The main way to fabricate micro-nano structures and devices.

At present, the conventional photolithography process is made by traditional microelectronic processing technology, which is used to prepare microstructure devices, waveguides, etc. These photolithography microstructures often have neat and clear corners, and their 3D surfaces are usually cuboid or polyhedron. The upper surface and lower surface graphics are consistent. However, with the development of integrated optical technology and the application of MEMS technology, it is necessary to make micro-devices with more complex shapes and structures, especially micro-structures or micro-devices (such as micro-lenses) with specific curved surface features, that is, the upper and lower surfaces of the micro-structure have Significantly different. The traditional photolithography process cannot prepare these special graphic microstructures. To meet this demand, some people have developed gray-scale photomask technology. Different degrees of cross-linking or dissolution under the action of ultraviolet light of different intensities can produce microstructures with curved surface characteristics. However, gray-scale photomask technology requires expensive, high-resolution gray-scale photomasks, which are complex to process and costly, and are not suitable for popularization and application. Although the curved surface microstructures based on the positive photoresist reflow technology can meet the requirements of micro-devices with complex shapes and structures within a certain range, due to the relatively low viscosity of the positive photoresist, its spin-coating thickness is often relatively large. Small, which limits the height of the microstructure that can be obtained, and the positive photoresist material itself is often easily eroded by acid, alkali or organic reagents, and is easily decomposed by photochemical reactions under ultraviolet light. The stability is poor, and the application range is limited. big limit. Therefore, it is necessary to find materials that are suitable for the fabrication of high aspect ratio structures and have stable physical and chemical properties to fabricate curved surface microstructures. Due to its excellent physical and chemical properties, compatibility with traditional microelectronics technology, and suitability for fabricating high aspect ratio structures, negative photoresist is the best candidate material for fabricating complex cross-sectional microstructures. However, since the cross-linked negative photoresist often has a high glass transition temperature, which is close to its carbonization and pyrolysis temperature, it is difficult to use the positive photoresist reflow method, that is, through the process of photolithography, development, and reflow, Make surface structures. Meanwhile, the reflow method can only manufacture a single structure of spherical crown section. In the production of complex three-dimensional structures, some people have proposed LIGA, laser ablation, laser holography and other photolithography methods. However, these methods often require expensive, high-resolution special exposure equipment, multiple film formation and overlaying are required in the process, and some processes require chemical mechanical polishing and dry etching. The process is complicated and it is difficult to ensure the accuracy of the structure size And the smooth surface of the structure is not conducive to the production of high-quality integrated optical devices and MEMS devices. Therefore, in response to the demand for three-dimensional structure fabrication, it is urgent to develop new, simple and low-cost process methods.

Diffusers have important applications in flat panel display, laser, LED lighting, imaging and other systems. The main function of the diffuser is to convert the incident light into diffuse or light with a certain spatial distribution. The incident parallel light is refracted and scattered in the diffuser to form a light field with specific energy distribution. Based on the different diffusion principles of incident light, it is mainly divided into two types: one is the doped particle type, and the other is the surface microstructure type. The former is currently widely used in flat panel displays, but its transmittance is low, the light field is uncontrollable, and due to the uneven doping, the light field is not uniform. The latter category includes ground glass types, holographic types, and microlens array types. The microlens array diffuser has high transmittance, and the diffusion angle, space and energy distribution of the light field can be adjusted by changing the shape and arrangement of the microlens array, which has great flexibility.

Contents of the invention

Technical problem: the purpose of the present invention is to overcome the deficiencies of the existing process methods, and propose a diffusion sheet photolithography process based on negative photoresist, which uses a diffusion sheet combined with a negative photoresist photolithography process, The diffuser is used to convert the light source from linear light to diffuse scattered light, and combined with the imaging characteristics of negative photoresist, a three-dimensional microstructure pattern that cannot be realized by traditional photolithography is prepared. The present invention can obtain arc-shaped, double-arc-shaped and other complex cross-sectional graphic structures by using single photolithography, has a wide range of applications, simple process, good process repeatability, no need to modify existing photolithography equipment, and low cost. Easy to achieve mass production and other advantages.

Technical solution: In order to solve the above-mentioned technical problems, the present invention provides a diffusion sheet photolithography process method based on negative photoresist, which includes the following steps:

First, a negative-tone photoresist is coated on the surface of the substrate,

Then pre-baking: pre-baking the substrate spin-coated with negative photoresist to remove the solvent of the negative photoresist;

Then exposure: the diffusion sheet is placed on the mask plate, and the negative photoresist is exposed to ultraviolet light by using the diffusion sheet and the mask plate as a mask;

Finally, post-baking and development: the negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure, that is, the order is arranged as substrate, negative photoresist, mask plate, diffuser, the incident wave enters from the diffuser;

The diffusion sheet and the mask plate are used as a mask to participate in the exposure of the photoresist.

The exposure includes any one of contact exposure, macro exposure or step projection exposure.

The incident wave is a single-wavelength laser produced by monochromatic light, the wavelength range of the single-wavelength laser is ultraviolet, visible or infrared band, the incident wave is light produced by light with spectral width, and the wavelength range of light is ultraviolet to infrared band .

The single-wavelength laser generated by the monochromatic light is the single-wavelength laser generated by the laser, and the light generated by the light with spectral width is the light generated by the high-pressure mercury lamp.

The type of the diffusion sheet is doped particle type or surface microstructure type or a combination of the two types, or the diffusion sheet is a group of diffusion sheets composed of multiple diffusion sheets.

The diffusion sheet is located on the mask plate, the diffusion sheet is in close contact with the mask plate or separated by a distance of several micrometers to tens of centimeters, and the diffusion sheet and the mask plate are made as a whole.

The substrate includes glass, silicon wafer, and polymer sheet.

Beneficial effect: the beneficial effect that the present invention has compared with existing technology is:

The diffusion sheet photolithography process method based on the negative photoresist proposed by the present invention can photoetch a special three-dimensional microstructure that cannot be prepared by a traditional photolithography process by using a single photolithography process. Compared with the positive photoresist, the negative photoresist used has the advantages of strong heat resistance and good stability. When the negative photoresist is fully exposed, the prepared pattern will be completely cross-linked and cured, no longer soluble in the developer, less affected by ultraviolet light, and the refractive index is stable. This method can be used to prepare various three-dimensional microstructure patterns. The photolithography process using diffusers can use different types of diffusers and negative photoresists to obtain various cross-sectional structures, and a specific cross-sectional shape can be obtained by one exposure. The preparation process is simple, and it is different from existing negative photoresists The resist lithography process is compatible, and the existing lithography equipment can not be modified, and mass production can be realized, which significantly reduces the device cost.

Description of drawings

FIG. 1 is a schematic diagram of a diffusion sheet photolithography method.

Figure 2a is a schematic diagram of negative photoresist lithography,

Figure 2b is a schematic diagram of the photolithography of a negative photoresist diffuser.

Figure 3a is a schematic diagram of lines after negative photoresist photolithography,

Figure 3b is a schematic diagram of the lines after photolithography of the negative photoresist,

Figure 3c is a schematic diagram of the lines after photolithography of the negative photoresist.

Figure 4a is a schematic diagram of lines after photolithography of a negative photoresist diffuser,

Figure 4b is a schematic diagram of the lines after photolithography of the negative photoresist diffusion sheet,

Figure 4c is a schematic diagram of the lines after photolithography of the negative photoresist diffusion sheet,

Figure 4d is a schematic diagram of the lines after photolithography of the negative photoresist diffusion sheet,

Figure 4e is a schematic diagram of the lines after photolithography of the negative photoresist diffusion sheet,

Figure 4f is a schematic diagram of the lines after photolithography of the negative photoresist diffusion sheet,

Fig. 4g is a schematic diagram of the lines after photolithography of the negative photoresist diffuser.

Fig. 5 is a schematic diagram of grooves after photolithography of the negative photoresist diffuser.

Fig. 6a is a schematic diagram of a photonic crystal structure unit after photolithography of a negative photoresist diffuser.

Fig. 6b is a schematic diagram of the photonic crystal structure unit after photolithography of the negative photoresist diffuser.

Fig. 7a is a schematic diagram of a photonic crystal after photolithography of a negative photoresist diffuser. the

Fig. 7b is a schematic diagram of the photonic crystal after photolithography of the negative photoresist diffuser. 

There are: substrate 1 , negative photoresist 2 , mask 3 , diffuser 4 , and incident wave 5 .

Detailed ways

The present invention will be described below with reference to the accompanying drawings.

The diffusion sheet photolithography process method based on the negative photoresist provided by the present invention comprises coating photoresist, pre-baking, exposure, post-baking, development, and the diffusion sheet and the mask plate are used as a mask to participate in the formation of the photoresist. Exposure, the structure from top to bottom includes: incident light, diffuser, mask, photoresist and substrate.

Referring back to Figure 1 - Figure 7b, the diffusion sheet photolithography process method based on negative photoresist, the method includes the following steps:

First, a photoresist is coated on the surface of the substrate,

Carry out prebaking then, the substrate that is spin-coated with negative photoresist is carried out prebaking, removes the solvent of negative photoresist;

Then exposure, the diffuser is placed on the mask, and the negative photoresist is exposed to ultraviolet rays using the diffuser and the mask as a mask

Finally, post-baking and development are carried out. The negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure;

The diffusion sheet and the mask plate are used as a mask to participate in the exposure of the photoresist.

The exposure includes any one of contact exposure, macro exposure or step projection exposure.

The incident wave 5 is a single-wavelength laser produced by monochromatic light. The wavelength range of the single-wavelength laser is ultraviolet, visible or infrared bands. The incident wave 5 is light produced by light with a spectral width. The wavelength range of the light is from ultraviolet to Infrared band.

The single-wavelength laser generated by the monochromatic light is the single-wavelength laser generated by the laser, and the light generated by the light with spectral width is the light generated by the high-pressure mercury lamp.

The type of the diffusion sheet 4 is doped particle type or surface microstructure type or a combination of the two types, or the diffusion sheet 4 is a group of diffusion sheets composed of multiple diffusion sheets.

The diffuser 4 is located on the mask 3 , and the diffuser 4 is in close contact with the mask 3 or separated by a distance of several micrometers to tens of centimeters, and the diffuser 4 and the mask 3 are made as a whole.

The substrate 1 includes glass, silicon wafer, polymer sheet or other materials coated with negative photoresist.

The diffusion film lithography process method based on negative photoresist comprises the following steps: first, coating negative photoresist on the surface of the substrate, and the substrate includes glass, silicon wafer or any other which can be coated with negative photoresist. The material of the photoresist, the thickness of the general photoresist is tens of nanometers to hundreds of microns; then, the substrate with the negative photoresist spin-coated is pre-baked to remove the solvent of the negative photoresist; then, The diffusion sheet is located on the mask plate, and the negative photoresist is exposed to ultraviolet rays by using the diffusion sheet and the mask plate as a mask. The diffusion sheet can be doped particle type, surface microstructure type or a combination of the two Type, the diffusion sheet group can be composed of multiple diffusion sheets, and the diffusion sheet is located on the mask plate. exposure, macro exposure and step projection exposure, the wavelength range of the incident wave includes ultraviolet, visible to infrared bands, can be monochromatic light such as single wavelength laser produced by lasers, or light with a certain spectral width such as Light generated by a high-pressure mercury lamp; finally, post-baking and development are carried out to obtain a specific cross-sectional structure, which is determined by the pattern size of the photolithography mask, exposure time and the type of negative photoresist.

Further, in the aforementioned negative photoresist-based diffusion sheet photolithography process, the mask can be fabricated as a whole by the diffusion sheet and the mask plate.

The principle of the diffuser photolithography process method based on negative photoresist proposed by the present invention is as follows: the parallel incident becomes uniform scattered light due to refraction and scattering in the diffuser, and forms divergent light in the negative photoresist. The light intensity distribution, the incident light is absorbed and weakened in the negative photoresist, and the exposure area is formed within the range of the exposure dose. The negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure.

A kind of diffusion sheet photolithography process method based on negative photoresist proposed by the present invention comprises the following steps from the technical point of view:

First, a negative photoresist 2 is coated on the surface of the substrate 1. The substrate includes glass, silicon wafer or any other material that can be coated with a negative photoresist 2. Generally, the thickness of the photoresist is several tens nanometers to hundreds of microns;

Then, the substrate 1 that is spin-coated with the negative photoresist 2 is pre-baked to remove the solvent in the negative photoresist 2; The membrane plate 3 is used as a mask to expose the negative photoresist 2 to ultraviolet light, and the diffusion sheet 4 can be of doped particle type, surface microstructure type or a combination of the two types, and can be composed of multiple diffusion sheets. group, the diffuser 4 is located on the mask 3, the diffuser 4 can be close to the mask 3 or separated by a distance of several microns to tens of centimeters, or made into a whole, the exposure includes contact Exposure, macro exposure and step projection exposure, the wavelength range of the incident wave 5 includes ultraviolet, visible to infrared bands, which can be monochromatic light such as single-wavelength laser produced by a laser, or light with a certain spectral width such as high voltage For the light generated by the mercury lamp, the parallel incident light becomes uniform scattered light due to refraction and scattering in the diffuser, forming a divergent light intensity distribution in the negative photoresist, and the incident light is in the negative photoresist. It is absorbed and weakened, and the range that meets the exposure dose forms an exposure area;

Finally, post-baking and development are carried out. The negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure. The cross-sectional structure is determined by the line size of the photolithography mask, exposure

Time and the type of negative photoresist are determined. Figure 4 shows the groove part of the negative photoresist obtained by photolithography of the diffuser.

The embodiments of the present invention will be described in detail below. This embodiment is based on the premise of the technical solution of the present invention

Carried out, provided detailed embodiment and specific operation process, but the protection scope of the present invention is not limited

in the following examples.

Example 1:

Fabrication of SU-8 Negative Photoresist Grooves on Monocrystalline Silicon Wafers

Firstly, SU-8 photoresist 2 is spin-coated on a single-side polished single-crystal silicon wafer substrate 1, then pre-baked on a hot plate, and cooled naturally to room temperature. Then place the diffuser 4 on the mask plate 3, use a photolithography machine to perform ultraviolet contact exposure, then pre-baked on a hot plate, and finally develop in the developer solution PMGEA to obtain the SU-8 negative photo The resist groove is shown in FIG. 5 , and part of its cross-sectional lines are shown in FIG. 4 .

Example 2:

Fabrication of NR9-3000PY negative photoresist photonic crystal on K9 optical glass

First, NR9-3000PY photoresist 2 was spin-coated on a K9 optical glass substrate 1, then pre-baked on a hot plate, and cooled to room temperature naturally. Then place the diffusion sheet 4 on the mask plate 3, use a photolithography machine to perform ultraviolet contact exposure, then pre-bake on a hot plate, and finally develop in the developer solution R6 to obtain the obtained NR9-3000PY negative photo The resist photonic crystal unit is shown in Figure 6, and its partial cross-section is shown in Figure 4. Due to the difference in the mask plate, negative photoresist columns and negative photoresist wells can be produced, and the photonic crystal is shown in Figure 7. Show. )

According to the graphic cross-section lines made in embodiment 1 and embodiment 2, the exposure process of the diffuser negative photoresist lithography proposed by the present invention is similar to the exposure process of the existing negative photoresist lithography in the exposure principle.

Compare, as shown in Figure 2:

In the existing negative photoresist exposure process, the mask plate 3 is divided into a light-transmitting area 7 and a non-light-transmitting area 8. After the parallel incident light 5 passes through the light-transmitting area 7, the negative light under the mask plate 3 Parallel photoresist 2

6. Form a rectangular exposure area 9, and form a non-exposed area in the negative photoresist under the non-light-transmitting area 8

Domain 10, due to the optical properties and photochemical reaction characteristics of the photoresist, the fully cross-linked negative photoresist in the exposed area 9 is retained during development, and the cross-section of the formed pattern is shown in Figure 3. The negative photoresist 2 The upper and lower surfaces of the upper and lower surfaces are the same or similar; in the diffusion sheet exposure process proposed by the present invention, the mask plate 3 is divided into a light-transmitting area 7 and a non-light-transmitting area 8, and the parallel incident light 5 first passes through the diffusion sheet 4 and passes through the diffusion sheet. Refraction and scattering in 4, after passing through the light-transmitting region 7, the light 6 with a certain angle is formed in the negative photoresist 2 under the mask plate 3, forming an exposure region 9 with a certain light intensity distribution, and the exposure region The morphology and size of the upper and lower surfaces of 9 are significantly different. A non-exposed region 10 is formed in the negative photoresist under the non-transparent region 8. Due to the optical characteristics and photochemical reaction characteristics of the photoresist, the exposed region 9 is fully exposed. The negative photoresist of the connection is retained in the development, and the partial cross-section of the formed pattern is as shown in Figure 4. The process method of the diffusion sheet negative photolithography proposed by the present invention is different from the existing negative photolithography process method. Compared with having a variety of cross-sectional shapes, the upper and lower surface topography can be the same or similar, or significantly different. According to the incident light 5 of different angles and wavelength ranges, different types of diffusers 4, different patterns of mask plates 3 and different types of negative photoresist 2 with different thicknesses, various photolithographic patterns can be freely combined and adjusted. 3D shape.

The above descriptions are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments, but all equivalent modifications or changes made by those of ordinary skill in the art according to the disclosure of the present invention should be included within the scope of protection described in the claims.

Claims (7)

1. a diffusion sheet photolithography process method based on negative photoresist, is characterized in that: the method comprises the steps: First, a negative photoresist (2) is coated on the surface of the substrate (1), Then pre-baking: pre-baking the substrate spin-coated with negative photoresist (2) to remove the solvent of the negative photoresist; Then exposure: the diffuser (4) is located on the mask (3), and the negative photoresist is exposed to ultraviolet light by using the diffuser and the mask as a mask; Finally, post-baking and development: the negative photoresist in the exposed area is cross-linked in the post-baking, insoluble in the developer, and has a specific cross-sectional structure, that is, the order is arranged as substrate (1), negative photoresist (2), mask plate (3), diffusion sheet (4), the incident wave (5) is injected from the diffusion sheet (4); The diffusion sheet and the mask plate are used as a mask to participate in the exposure of the photoresist. 2 . The photolithography process method of diffusion sheet based on negative photoresist according to claim 1 , wherein the exposure includes any one of contact exposure, macro exposure or step projection exposure. 3 . 3. The process method of diffuser sheet photolithography based on negative photoresist according to claim 1, characterized in that: the incident wave (5) is a single-wavelength laser generated by monochromatic light, and the wavelength of the single-wavelength laser The range is ultraviolet, visible or infrared band, the incident wave (5) is light generated by light with spectral width, and the wavelength range of light is ultraviolet to infrared band. 4. the diffusion sheet lithography process method based on negative photoresist according to claim 3, is characterized in that: the single-wavelength laser light that described monochromatic light produces is the single-wavelength laser light that laser device produces, and the light of spectral width is arranged The light produced is that produced by a high pressure mercury lamp. 5. The photolithography process method of diffusion sheet based on negative photoresist according to claim 1, characterized in that: the type of the diffusion sheet (4) is doped particle type or surface microstructure type or both The combined type, or diffuser (4), is a diffuser set consisting of multiple diffusers. 6. The photolithography process method of diffusion sheet based on negative photoresist according to claim 1, characterized in that: the diffusion sheet (4) is located on the mask plate (3), and the diffusion sheet (4) The diffusion sheet (4) and the mask plate (3) are integrally made in close contact with the mask plate (3) or at a distance of several micrometers to tens of centimeters. 7. The photolithography process method of diffusion sheet based on negative photoresist according to claim 1, characterized in that: the substrate (1) includes glass, silicon wafer, and polymer sheet.

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