Methods for protecting the bottom of trenches using photoresist partial filling process in wet etching
By using a photoresist partial filling process to protect the bottom of the trench, the problem of damage to the bottom of deep trenches caused by wet etching is solved, and a low-cost, low-difficulty etching process is achieved, simplifying the process steps.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG XINYUENENG SEMICON CO LTD
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-26
AI Technical Summary
Existing wet etching processes can easily damage the bottom of deep trenches during the removal of residual oxide film, affecting subsequent process steps and increasing technical difficulty.
A partial photoresist filling process is used to prepare trench structures on the wafer surface through plasma etching and spin coating. The photoresist on the upper surface of the oxide layer is removed by photolithography and development, leaving the photoresist in the trench area in a partially filled state to protect the bottom of the trench from damage.
It effectively reduces the difficulty of the etching process, reduces etching costs and time, simplifies the process, protects the bottom of the deep trench, and avoids losses.
Smart Images
Figure CN122094413A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, particularly to the field of semiconductor etching technology, and specifically to a method for protecting the bottom of trenches using a photoresist partial filling process in wet etching. Background Technology
[0002] In semiconductor manufacturing, thin diodes, transistors, and other integrated circuits often utilize deep trenches to achieve a certain depth of isolation. Current deep trench fabrication generally involves the following steps: 1. Spin coating photoresist onto the wafer surface; 2. Transferring the photoresist layer pattern to the substrate using processes such as plasma etching; 3. Removing residual photoresist using methods such as plasma ashing; 4. Fabricating the deep trench structure using a hard mask layer as a mask and plasma etching; 5. Removing the upper residual oxide layer using wet etching. In step 5, the wet etching process, while removing the upper residual oxide film, also causes some damage to the bottom of the deep trench, including chemical etching. This damage alters the roughness, smoothness, and material properties of the deep trench bottom, and also affects subsequent process steps.
[0003] To reduce damage to the oxide at the bottom of deep trenches during wet etching to remove residual oxides from the upper layer, the current approach mainly involves improving the wet etching process conditions, using different wet solvent ratios, and increasing the selectivity of the oxide to the silicon matrix, thereby minimizing damage to the bottom of deep trenches. However, it is impossible to completely eliminate this damage.
[0004] Therefore, in this technical field, there is a need for a deep trench manufacturing process that protects the bottom of the deep trench during the wet removal of oxide layer residue, avoids the loss of the bottom trench, and reduces the technical difficulty of the process. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for protecting the bottom of trenches using a photoresist partial filling process in wet etching. This invention is applicable to the process of wet removal of oxide layer residues, protecting the bottom of deep trenches, avoiding the loss of bottom trenches, and reducing the technical difficulty of the process.
[0006] To achieve the above objectives, the first technical solution adopted by the present invention is: a method for protecting the bottom of a trench using a photoresist partial filling process in wet etching, comprising: preparing a trench structure in a predetermined area on the wafer surface by plasma etching; covering the trench and the entire wafer surface with photoresist using a spin coating process; performing exposure and development on the entire surface of the wafer covered with photoresist using a photolithography machine without using a photomask, removing the photoresist on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench structure by exposure and development, so that the remaining photoresist in the trench area is in a partially filled state; removing the exposed oxide layer on the wafer surface, while protecting the bottom of the trench from damage during the removal of the oxide layer by the remaining photoresist in the trench area.
[0007] Optionally, the step of using a photolithography machine without using a photomask to expose and develop the entire surface of the wafer to remove the photoresist on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench, so that the photoresist in the trench region is partially filled, further includes: controlling the depth of photoresist removal by controlling a specific exposure time so that the photoresist in the trench is retained.
[0008] Optionally, it also includes: using an organic solvent to dissolve the photoresist, removing the photoresist on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench, so that the photoresist in the trench region is in a partially filled state.
[0009] Optionally, the step of using an organic solvent to dissolve the photoresist, removing the photoresist on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench, so that the photoresist in the trench region is partially filled, further includes: controlling the depth of dissolving the photoresist by controlling the time, so that the photoresist in the trench is retained.
[0010] Optionally, it also includes: using a wet etching process to remove the exposed oxide layer on the wafer surface while protecting the bottom of the trench from damage.
[0011] Optionally, it also includes: using plasma etching to remove the exposed oxide layer on the wafer surface while protecting the bottom of the trench from damage.
[0012] Optionally, it also includes: removing any remaining filler photoresist within the trench.
[0013] Optionally, removing the remaining photoresist in the trench further includes: removing the remaining photoresist in the trench using a wet etching process.
[0014] Optionally, the removal of the remaining photoresist in the trench further includes: removing the remaining photoresist in the trench using a plasma ashing process.
[0015] Optionally, the step of using spin coating to cover the trench and the entire wafer surface with photoresist further includes: using a coating device to fill the trench with photoresist, so that the trench is filled with photoresist and a certain thickness of photoresist is formed on the entire wafer surface.
[0016] This invention utilizes plasma etching to fabricate trench structures in predetermined areas on a wafer surface, achieving a certain depth of isolation through deep trenches. A spin-coating process is then used to cover the trenches and the entire wafer surface with photoresist. A photolithography machine is then used without a photomask to expose and develop the entire wafer surface, removing some of the photoresist from the upper oxide layer and the upper trench area, leaving the trench area partially filled with photoresist. This process, employing photolithography without a photomask, allows the photoresist to fill only the protective deep holes, opening the areas to be etched, thus reducing the difficulty of the etching process and protecting the bottom of the trenches. This removes the exposed oxide layer on the wafer surface while protecting the bottom of the trenches from damage. During the wet removal of residual oxide film, the bottom of the deep trenches is protected, preventing damage to the bottom trenches and reducing the technical difficulty of the process.
[0017] This invention is applicable to both plasma etching and wet etching, effectively reducing the difficulty of etching processes, etching costs and time, achieving low cost and simple process. It is a novel method for eliminating damage at the bottom of deep trenches by filling deep trenches with photoresist suitable for wet etching. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the first process of the method for protecting the bottom of the trench using a photoresist partial filling process in wet etching according to the present invention; Figure 2 This is a schematic diagram of the second process of the method for protecting the bottom of the trench using a photoresist partial filling process in the wet etching of the present invention; Figure 3 This is a schematic diagram of the third process of the method for protecting the bottom of the trench using photoresist partial filling in wet etching according to the present invention; Figure 4 This is a schematic diagram of the fourth process of the wet etching method of the present invention, which utilizes photoresist partial filling technology to protect the bottom of the trench.
[0019] Figure reference numerals: 1. Photoresist; 2. Oxide layer; 3. Silicon-based material. Detailed Implementation
[0020] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.
[0021] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.
[0022] In semiconductor manufacturing, integrated circuits such as diodes and transistors often utilize deep trenches to achieve a certain depth of isolation. Wet etching processes, while removing residual oxide films from the upper layer, can cause damage to the bottom of the deep trenches through processes such as chemical etching. This damage alters the roughness, smoothness, and material properties of the trench bottom, and can also affect subsequent process steps. To reduce damage to the oxide at the bottom of the deep trenches during wet etching to remove residual oxide films, current methods primarily focus on improving wet etching process conditions, using different wet solvent ratios, and increasing the selectivity of the oxide to the silicon matrix. This minimizes damage to the bottom of the deep trenches, but it is impossible to completely eliminate it.
[0023] In this field, photoresist is often used to directly cover the trenches. However, the disadvantage of this method is that the area to be removed is also protected by the photoresist. There are two methods for removing the oxide layer: In plasma etching: the traditional method requires photoresist to be etched first before the surface oxide layer can be etched, which is costly and time-consuming. In wet etching: because the traditional method directly covers the entire wafer surface, the wet solvent and photoresist are isolated and cannot effectively contact the oxide layer to react, resulting in etching not being possible. Therefore, the traditional method is not applicable in wet etching.
[0024] Photoresist, also known as photosensitive material, is a photosensitive material used in industrial processes. Its core components are resin, photosensitizer, and solvent. It forms a patterned coating layer through exposure and development in photolithography. There are two types: positive and negative. In positive photoresist, the exposed portion dissolves in the developer, while in negative photoresist, the exposed portion forms a dissolution-resistant structure. It is mainly used in semiconductor manufacturing and LED electrode processing. Positive photoresist dominates advanced processes due to its resolution advantage, while negative photoresist is used in metal evaporation processes.
[0025] This invention provides a method for protecting the bottom of trenches in wet etching using a photoresist partial filling process, specifically as follows: Figures 1-4As shown, the process includes: fabricating trench structures on a predetermined area of the wafer surface using a plasma etching process; covering the trenches and the entire wafer surface with photoresist 1 using a spin-coating process; performing exposure and development on the entire wafer surface using a photolithography machine without using a photomask, removing some of the photoresist on the upper surface of the wafer oxide layer 2 and in the upper region of the trenches, so that the photoresist 1 in the trench area is partially filled; and removing the exposed oxide layer on the surface of the silicon-based material 3, while protecting the bottom of the trench from damage. Through the above process, by using a photolithography machine without using a photomask and only exposing the area, the photoresist only fills the protective deep holes, opening the area to be etched, thereby reducing the difficulty of the etching process and protecting the bottom of the trench.
[0026] In one specific embodiment of this application, in plasma etching, one less layer of photoresist can be etched, avoiding the problem of having to remove the surface photoresist before removing the surface oxide layer, thus reducing etching costs and production time, and simplifying the etching process. Plasma etching utilizes plasma generated by a high-frequency power supply or uses reactive gases. Active particles in the plasma, such as ions and free radicals, bombard the surface of the material to be etched, producing a physical sputtering effect, and simultaneously reacting chemically with the material to form volatile products, thereby achieving etching.
[0027] In one specific embodiment of this application, in wet etching, the wet etching solution can react directly with the surface oxide layer without contacting the bottom of the trench, achieving the effect of effectively removing the surface oxide layer while protecting the bottom of the trench. Wet etching utilizes a chemical solution, such as an etching solution, to react chemically with the material to be etched, causing the material to dissolve.
[0028] In one specific embodiment of this application, a photolithography machine is used to expose and develop the entire surface of the wafer without using a photomask, removing the photoresist 1 on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench, so that the photoresist in the trench region is in a partially filled state. The method also includes controlling the depth of photoresist removal by controlling a specific exposure time, so that the photoresist in the trench is retained.
[0029] In one specific embodiment of this application, the method further includes: dissolving the photoresist 1 using an organic solvent to remove some of the photoresist from the upper surface of the wafer oxide layer 2 and the upper region of the trench, so that the photoresist in the trench region is partially filled. The principle of the organic solvent is to use highly polar solvents such as acetone, NMP, and ethyl lactate to swell and dissolve the photoresist molecular chains. Advantages: low cost, simple equipment; can be used in batch processing with spray or immersion modes.
[0030] In one specific embodiment of this application, an organic solvent is used to dissolve the photoresist 1, removing some of the photoresist from the upper surface of the wafer oxide layer 2 and the upper region of the trench, resulting in a partially filled photoresist area in the trench. The method further includes controlling the depth of photoresist dissolution by controlling the time, thus retaining the photoresist within the trench. The exposure time of a lithography machine refers to the length of time the lithography machine exposes the wafer; it is a key parameter in the lithography process. The selection of the exposure time depends on the photosensitive characteristics of the photoresist and the complexity of the desired pattern. Generally, more complex patterns require longer exposure times to ensure the clarity and accuracy of the circuit pattern. By adjusting the exposure time, pattern distortion caused by proximity effects can also be compensated for, and with precise lithography equipment, accurate control from 0.1 to 999.9 seconds can be achieved.
[0031] In one specific embodiment of this application, the method further includes: using a wet etching process to remove the exposed oxide layer on the wafer surface while protecting the bottom of the trench from damage. In wet etching, the wet etching solution can react directly with the surface oxide layer without contacting the bottom of the trench, achieving the effect of effectively removing the surface oxide layer while protecting the bottom of the trench.
[0032] In one specific embodiment of this application, the method further includes: removing the exposed oxide layer on the wafer surface using plasma etching while protecting the bottom of the trench from damage. In plasma etching, one less layer of photoresist can be etched, avoiding the problem of having to remove the surface photoresist before removing the surface oxide layer, thus reducing etching costs and production time, and simplifying the etching process.
[0033] This invention is applicable to both plasma etching and wet etching, effectively reducing the difficulty of etching processes, etching costs and time, achieving low cost and simple process. It is a novel method for eliminating damage at the bottom of deep trenches by filling deep trenches with photoresist suitable for wet etching.
[0034] In one specific embodiment of this application, the method further includes: removing the remaining filler photoresist within the trench.
[0035] In this embodiment, removing the remaining photoresist in the trench further includes: removing the remaining photoresist in the trench using a wet etching process. Wet etching is a semiconductor manufacturing technology that achieves selective removal by reacting a chemical solution with the material, and it has isotropic characteristics. This method uses solutions such as hydrofluoric acid and phosphoric acid to etch materials such as silicon oxide and silicon nitride. The equipment includes three main categories: cleaning, brushing, and etching, and it has the advantages of low cost and high throughput.
[0036] In this embodiment, removing the remaining photoresist within the trench further includes: removing the remaining photoresist within the trench using a plasma ashing process. The plasma ashing operation mode involves introducing an O2 / N2 mixed gas into a low-pressure chamber to generate inductively coupled plasma, which uses active particles to bombard and carbonize and volatilize the photoresist. The etching rate and selectivity can be adjusted by selecting the oxygen ratio. Key parameters: RF power density is controlled at 5-15 W / cm². 2 Within this range, the pressure is maintained at 50-200 mTorr to ensure anisotropic etching characteristics. Applicable scenarios: removal of residual adhesive in three-dimensional structural devices and trenches with high aspect ratio.
[0037] In one specific embodiment of this application, the photoresist is used to cover the trench and the entire wafer surface using a spin coating process, and the process further includes: using a coating device to fill the trench with photoresist so that the trench is filled with photoresist and a certain thickness of photoresist is formed on the entire wafer surface.
[0038] This invention utilizes plasma etching to fabricate trench structures in predetermined areas on a wafer surface, achieving a certain depth of isolation through deep trenches. A spin-coating process is then used to cover the trenches and the entire wafer surface with photoresist. A photolithography machine is then used without a photomask to expose and develop the entire wafer surface, removing some of the photoresist from the upper oxide layer and the upper trench area, leaving the trench area partially filled with photoresist. This process, employing photolithography without a photomask, allows the photoresist to fill only the protective deep holes, opening the areas to be etched, thus reducing the difficulty of the etching process and protecting the bottom of the trenches. This removes the exposed oxide layer on the wafer surface while protecting the bottom of the trenches from damage. During the wet removal of residual oxide film, the bottom of the deep trenches is protected, preventing damage to the bottom trenches and reducing the technical difficulty of the process.
[0039] This invention is applicable to both plasma etching and wet etching, effectively reducing the difficulty of etching processes, etching costs and time, achieving low cost and simple process. It is a novel method for eliminating damage at the bottom of deep trenches by filling deep trenches with photoresist suitable for wet etching.
[0040] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method for protecting the bottom of trenches using a photoresist partial filling process in wet etching, characterized in that, include: Trench structures are fabricated in a predetermined area on the wafer surface using a plasma etching process. The photoresist is applied to cover the entire trench structure and the entire wafer surface using a spin coating process. Using a lithography machine without a photomask, the entire surface of the wafer covered with photoresist is exposed and developed. The photoresist on the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench structure are removed by exposure and development, so that the remaining photoresist in the trench area is partially filled. The exposed oxide layer on the wafer surface is removed, while the bottom of the trench is protected from damage by the remaining photoresist in the trench area during the oxide layer removal process.
2. The method for protecting the bottom of trenches using a photoresist partial filling process in wet etching according to claim 1, characterized in that, The process of using a photolithography machine without a photomask to expose and develop the entire surface of the wafer covered with photoresist, removing some of the photoresist from the upper surface of the wafer's oxide layer and the upper region of the trench structure, so that the remaining photoresist in the trench region is partially filled, includes: By controlling the specific exposure time of the lithography machine, the depth of photoresist removal can be controlled, thus preserving the photoresist portion within the trench.
3. The method for protecting the bottom of trenches using a photoresist partial filling process in wet etching according to claim 1, characterized in that, The method of using a photolithography machine without using a photomask to expose and develop the entire surface of the wafer covered with photoresist, removing some of the photoresist from the upper surface of the wafer oxide layer and the upper region of the trench structure through exposure and development, so that the remaining photoresist in the trench region is partially filled, also includes: Organic solvents are used to dissolve the photoresist, removing some of the photoresist from the upper surface of the wafer oxide layer and the upper region of the trench, so that the photoresist in the trench region is partially filled.
4. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 3, characterized in that, The step of using an organic solvent to dissolve the photoresist, removing the photoresist from the upper surface of the wafer oxide layer and part of the photoresist in the upper region of the trench, so that the photoresist in the trench region is partially filled, further includes: The depth of photoresist dissolution is controlled by adjusting the time, thus preserving a portion of the photoresist within the trench.
5. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 1, characterized in that, The process of removing the exposed oxide layer on the wafer surface, while simultaneously protecting the bottom of the trench from damage through residual photoresist in the trench region during oxide layer removal, includes: Wet etching is used to remove the exposed oxide layer on the wafer surface, while the remaining photoresist in the trench area protects the bottom of the trench from damage.
6. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 1, characterized in that, Removing the exposed oxide layer from the wafer surface, while protecting the bottom of the trench from damage during the oxide layer removal process using residual photoresist in the trench region, includes: Plasma etching is used to remove the exposed oxide layer on the wafer surface, while the remaining photoresist in the trench area protects the bottom of the trench from damage.
7. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 1, characterized in that, Also includes: Remove any remaining photoresist filling the trench.
8. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 7, characterized in that, The removal of remaining photoresist within the trench also includes: The remaining photoresist in the trenches is removed using a wet etching process.
9. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 7, characterized in that, The removal of remaining photoresist within the trench also includes: The remaining photoresist in the trench is removed using a plasma ashing process.
10. The method for protecting the bottom of trenches in wet etching using a photoresist partial filling process according to claim 1, characterized in that, The process of using spin coating to cover the photoresist in the trenches and the entire wafer surface also includes: The photoresist is filled into the trench using a coating device, so that the trench is filled with photoresist and a certain thickness of photoresist is formed on the entire wafer surface.