Development quality evaluation method of photoresist
By etching shallow grooves on the substrate and measuring the resistance of the ion implanted area, the problems of large errors and low test efficiency in the evaluation of photoresist development quality are solved, especially in the development quality evaluation of thick resist layers in CMOS image sensors, achieving more accurate and efficient testing.
Patent Information
- Application Number
- CN202511065387.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-30
- Publication Date
- 2025-09-12
AI Technical Summary
Existing technologies for evaluating photoresist development quality suffer from large errors, cumbersome operations, and low testing efficiency. In particular, the impact of STI structures is not fully considered in evaluating the development quality of thick resist layers used in CMOS image sensor manufacturing.
By etching different types of shallow trenches on the substrate to form a shallow trench isolation structure, and using the photoresist pattern as a mask for ion implantation, the resistance of the ion implantation area is measured to evaluate the development quality. Considering the influence of the STI structure, the four-probe method or multimeter is used for measurement.
The accuracy and test efficiency of photoresist development quality evaluation are improved, subjective reading errors are reduced, and costs are reduced. The method is suitable for photoresist development quality evaluation of thick photoresist layers.
Smart Images
Figure CN120630604A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of photoresists, and in particular relates to a method for evaluating the development quality of photoresists. Background Art
[0002] Photoresist, also known as photoresist, is used as a corrosion-resistant coating material during the photolithography process. Development removes unwanted photoresist and forms the pattern defined by the photomask. The remaining photoresist pattern serves as a mask in subsequent etching and ion implantation processes.
[0003] The manufacturing process for CMOS image sensors involves extensive ultra-high-energy ion implantation, requiring the application of thick photoresist layers exceeding 15,000 Å (1 Å = 0.1 nm). Compared to thinner photoresist layers, thicker layers are more prone to neck or foot phenomena, resulting in reduced photoresist development quality. However, the quality of photoresist pattern development significantly impacts the fidelity and stability of the CMOS process. Therefore, evaluation of photoresist development quality is essential before formal product production.
[0004] The existing technology evaluates the development quality by measuring the size of the photoresist pattern after the photoresist is developed. Corresponding size measurements must be performed for different photoresist patterns, which has the disadvantages of large errors, cumbersome operations, and low testing efficiency. Summary of the Invention
[0005] The development quality of photoresist is not only related to the properties of the photoresist itself, but also affected by the STI (Shallow Trench Isolation) structure on the substrate. The thicker the photoresist layer, the more obvious the impact of the STI structure on the development quality.
[0006] In order to more accurately evaluate the development quality of the photoresist, taking into account the influence of the STI structure, the present invention provides a method for evaluating the development quality of the photoresist, comprising the following steps:
[0007] Etching a shallow trench on the substrate and filling it to form a shallow trench isolation structure higher than the substrate surface;
[0008] Laying photoresist on the surface of the substrate and exposing and developing it to obtain a photoresist pattern;
[0009] performing ion implantation on the substrate using the photoresist pattern as a mask;
[0010] Measuring the resistance of the ion implantation area;
[0011] The development quality of the photoresist is evaluated based on the resistance of the ion implanted area.
[0012] The present invention not only takes into account the influence of the STI structure, but also evaluates the development quality based on the resistance of the ion implantation area. Compared with evaluating the development quality based on the size of the photoresist pattern, it can avoid subjective reading errors in size measurement and obtain more accurate measurement results. At the same time, the measurement operation is also simpler, thereby improving test efficiency.
[0013] Furthermore, different types of shallow grooves are etched on the same substrate.
[0014] It plays the role of simultaneously measuring the photoresist development quality under multiple STI structures, reducing substrate usage, lowering costs and improving test efficiency.
[0015] Furthermore, the following types of shallow grooves are included: annular shallow grooves, long point-shaped shallow grooves, corrugated shallow grooves and strip-shaped shallow grooves.
[0016] Although the shallow trench structures on the market have different shapes, the present invention summarizes and organizes these types of shallow trenches based on their positions relative to the isolated devices, which can basically cover all types of shallow trenches on the market. It has good versatility and no need to perform personalized etching for different shallow trench structures, thereby reducing costs and increasing efficiency.
[0017] Furthermore, the annular shallow grooves are arranged in a rectangular array on the substrate.
[0018] The isolated devices are generally arranged in a rectangular array on the substrate. After the annular shallow grooves are arranged in a rectangular array, the corresponding devices are surrounded by the shallow grooves.
[0019] Furthermore, the long point-shaped shallow grooves are arranged in a rectangular array on the substrate.
[0020] The isolated devices are generally arranged in a rectangular array on the substrate. After the long point-shaped shallow grooves are arranged into a rectangular array, the two ends of the corresponding device are isolated by the shallow grooves.
[0021] Furthermore, the wave-shaped shallow grooves are parallel to each other on the substrate.
[0022] The isolated devices are generally arranged in a rectangular array on the substrate, and the wave-shaped shallow grooves are arranged parallel to each other, corresponding to the situation where one side and both ends of the device are isolated by the shallow grooves.
[0023] Furthermore, the strip-shaped shallow grooves are parallel to each other on the substrate.
[0024] The isolated devices are generally arranged in a rectangular array on the substrate, and the strip-shaped shallow trenches are arranged parallel to each other, corresponding to the situation where one side of the device is isolated by the shallow trench.
[0025] Furthermore, when the substrate is a P-type substrate, the resistance of the ion implanted region is measured as an N-region; when the substrate is an N-type substrate, the resistance of the ion implanted region is measured as a P-region.
[0026] The minority carriers in the P-type substrate are electrons, and the minority carriers in the N-region are holes. After injecting phosphorus, arsenic, antimony and other ions, the N-region is formed. The photoresist pattern affects the ion injection amount in the ion injection area, and the ion injection amount affects the resistance of the ion injection area. Therefore, the resistance of the N-region is measured.
[0027] The minority carriers in the N-type substrate are holes, and the minority carriers in the P region are electrons. After injecting boron, aluminum, indium and other ions, the N region is formed. The photoresist pattern affects the ion injection amount in the ion injection area, and the ion injection amount affects the resistance of the ion injection area, so the resistance of the P region is measured.
[0028] Furthermore, when the resistance of the ion implantation region is within a threshold range, it is determined that the development quality is qualified.
[0029] After photoresist development, defects in the photoresist image include the "neck" phenomenon, which reduces the mask area, and the "foot" phenomenon, which increases the mask size. The "neck" phenomenon increases the ion implantation dose and reduces the resistance, while the "foot" phenomenon reduces the ion implantation dose and increases the resistance. Therefore, the development quality is considered acceptable when the resistance is within the threshold range.
[0030] Furthermore, the thickness of the photoresist is greater than or equal to 15000 Å.
[0031] The present invention is particularly suitable for evaluating the development quality of thick photoresist layers (15000 Å), such as thick photoresist layers in the manufacturing process of CMOS image sensors. Of course, the present invention is also applicable to non-thick photoresist layers. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0033] Figure 1 is a schematic diagram of the topographic defects of the photoresist image;
[0034] Figure 2 is a flow chart of a method for evaluating the development quality of a photoresist in an embodiment of the present invention;
[0035] Figure 3 Schematic diagram of the distribution of annular shallow grooves in a CMOS image sensor;
[0036] Figure 4 Schematic diagram of the distribution of long dot-shaped shallow grooves in a CMOS image sensor;
[0037] Figure 5 It is a schematic diagram of the distribution of waveform shallow grooves in CMOS image sensors;
[0038] Figure 6 This is a schematic diagram of the distribution of strip-shaped shallow grooves in a CMOS image sensor. DETAILED DESCRIPTION
[0039] In the manufacturing process of CMOS image sensors, there are a lot of ultra-high energy ion implantations, which require coating thick layers of more than 15000 Å (1 Å = 0.1 nm). Compared with thin layers, thick layers are more likely to have foot or neck phenomena. The foot and neck phenomena refer to Figure 1 As shown in areas A and B, this results in a decrease in the photoresist development quality. However, the quality of photoresist pattern development has a significant impact on the fidelity and stability of CMOS processes. Therefore, it is necessary to evaluate the photoresist development quality before formal product production.
[0040] The existing technology evaluates the development quality by measuring the size of the photoresist pattern after the photoresist is developed. Corresponding size measurements must be performed for different photoresist patterns, which has the disadvantages of large errors, cumbersome operations, and low testing efficiency.
[0041] The development quality of photoresist is not only related to the properties of the photoresist itself, but also affected by the STI (Shallow Trench Isolation) structure on the substrate. The thicker the photoresist layer, the more obvious the impact of the STI structure on the development quality.
[0042] In order to more accurately evaluate the development quality of the photoresist, taking into account the influence of the STI structure, some embodiments of the present invention provide a method for evaluating the development quality of the photoresist, referring to Figure 2 As shown, the following steps are included:
[0043] Etching a shallow trench on the substrate and filling it to form a shallow trench isolation structure higher than the substrate surface;
[0044] Laying photoresist on the surface of the substrate and exposing and developing it to obtain a photoresist pattern;
[0045] performing ion implantation on the substrate using the photoresist pattern as a mask;
[0046] The resistance of the ion implantation area can be measured by a probe method, such as a four-probe method, a two-probe method, or a multimeter.
[0047] The development quality of the photoresist is evaluated based on the resistance of the ion implanted area.
[0048] The present invention not only takes into account the influence of the STI structure, but also evaluates the development quality based on the resistance of the ion implantation area. Compared with evaluating the development quality based on the size of the photoresist pattern, it can avoid subjective reading errors in size measurement and obtain more accurate measurement results. At the same time, the measurement operation is also simpler, thereby improving test efficiency.
[0049] In some embodiments of the present invention, different types of shallow trenches are etched on the same substrate.
[0050] It plays the role of simultaneously measuring the photoresist development quality under multiple STI structures, reducing substrate usage, lowering costs and improving test efficiency.
[0051] In some embodiments of the present invention, the following types of shallow grooves are included: annular shallow grooves, long point-shaped shallow grooves, wave-shaped shallow grooves, and strip-shaped shallow grooves.
[0052] Although the shallow trench structures on the market have different shapes, the present invention summarizes and organizes these types of shallow trenches based on their positions relative to the isolated devices, which can basically cover all types of shallow trenches on the market. It has good versatility and no need to perform personalized etching for different shallow trench structures, thereby reducing costs and increasing efficiency.
[0053] In some embodiments of the present invention, the annular shallow grooves are arranged in a rectangular array on the substrate.
[0054] The isolated devices are generally arranged in a rectangular array on the substrate. After the annular shallow grooves are arranged in a rectangular array, the corresponding devices are surrounded by the shallow grooves.
[0055] In some embodiments of the present invention, the long dot-shaped shallow grooves are arranged in a rectangular array on the substrate.
[0056] The isolated devices are generally arranged in a rectangular array on the substrate. After the long point-shaped shallow grooves are arranged into a rectangular array, the two ends of the corresponding device are isolated by the shallow grooves.
[0057] In some embodiments of the present invention, the wave-shaped shallow grooves are parallel to each other on the substrate.
[0058] The isolated devices are generally arranged in a rectangular array on the substrate, and the wave-shaped shallow grooves are arranged parallel to each other, corresponding to the situation where one side and both ends of the device are isolated by the shallow grooves.
[0059] In some embodiments of the present invention, the strip-shaped shallow grooves are parallel to each other on the substrate.
[0060] The isolated devices are generally arranged in a rectangular array on the substrate, and the strip-shaped shallow trenches are arranged parallel to each other, corresponding to the situation where one side of the device is isolated by the shallow trench.
[0061] In some embodiments of the present invention, when the substrate is a P-type substrate, the resistance of the ion implanted region is measured as an N-region; when the substrate is an N-type substrate, the resistance of the ion implanted region is measured as a P-region.
[0062] The minority carriers in the P-type substrate are electrons, and the minority carriers in the N-region are holes. After injecting phosphorus, arsenic, antimony and other ions, the N-region is formed. The photoresist pattern affects the ion injection amount in the ion injection area, and the ion injection amount affects the resistance of the ion injection area. Therefore, the resistance of the N-region is measured.
[0063] The minority carriers in the N-type substrate are holes, and the minority carriers in the P region are electrons. After injecting boron, aluminum, indium and other ions, the N region is formed. The photoresist pattern affects the ion injection amount in the ion injection area, and the ion injection amount affects the resistance of the ion injection area, so the resistance of the P region is measured.
[0064] In some embodiments of the present invention, when the resistance of the ion implantation region is within a threshold range (determined in a pre-calibrated manner), it is determined that the development quality is qualified.
[0065] After photoresist development, defects in the photoresist image include the "neck" phenomenon, which reduces the mask area, and the "foot" phenomenon, which increases the mask size. The "neck" phenomenon increases the ion implantation dose and reduces the resistance, while the "foot" phenomenon reduces the ion implantation dose and increases the resistance. Therefore, the development quality is considered acceptable when the resistance is within the threshold range.
[0066] In some embodiments of the present invention, the thickness of the photoresist is greater than or equal to 15000 Å.
[0067] The present invention is particularly suitable for evaluating the development quality of thick photoresist layers (15000 Å), such as thick photoresist layers in the manufacturing process of CMOS image sensors. Of course, the present invention is also applicable to non-thick photoresist layers.
[0068] A CMOS image sensor includes photodiodes and transistors. Transistors are active devices. To avoid mutual interference between active devices, the active devices need to be isolated. The following describes different types of STI structures in CMOS image sensors.
[0069] refer to Figure 3 As shown in the figure, the red ring represents the annular shallow groove, which is arranged in a rectangular array on the substrate. The blue area within the annular shallow groove is the transistor layout area, and the green area represents the photodiode layout area. After ion implantation into the substrate using the photoresist pattern as a mask, corresponding devices can be formed in the corresponding areas, corresponding to the situation where the transistor device is surrounded by the shallow trench isolation structure.
[0070] refer to Figure 4As shown in the figure, the red blocks represent long dot-shaped shallow grooves, which are arranged in a rectangular array on the substrate. The blue area within the long dot-shaped shallow grooves is the transistor layout area, and the green area represents the photodiode layout area. After ion implantation into the substrate using the photoresist pattern as a mask, corresponding devices can be formed in the corresponding areas, corresponding to the situation where the two ends of the transistor device are isolated by the shallow trench isolation structure.
[0071] refer to Figure 5 As shown in the figure, the red ribbon represents the wavy shallow groove, which is parallel to each other on the substrate. The blue area in the wavy shallow groove is the transistor layout area, and the green area represents the photodiode layout area. After ion implantation into the substrate using the photoresist pattern as a mask, corresponding devices can be formed in the corresponding areas, corresponding to the situation where one side and both ends of the transistor device are isolated by the shallow groove.
[0072] refer to Figure 6 As shown in the figure, the red ribbon represents the strip-shaped shallow groove, which is parallel to each other on the substrate. The blue area on one side of the strip-shaped shallow groove is the transistor layout area, and the green area represents the photodiode layout area. After ion implantation into the substrate using the photoresist pattern as a mask, corresponding devices can be formed in the corresponding areas, corresponding to the situation where one side of the transistor device is isolated by the shallow groove.
[0073] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.
Claims
1. A method for evaluating the development quality of a photoresist, characterized in that: The following steps are involved: Etching a shallow trench on the substrate and filling it to form a shallow trench isolation structure higher than the substrate surface; Laying photoresist on the surface of the substrate and exposing and developing it to obtain a photoresist pattern; performing ion implantation on the substrate using the photoresist pattern as a mask; Measuring the resistance of the ion implantation area; The development quality of the photoresist is evaluated based on the resistance of the ion implanted area.
2. The method for evaluating the development quality of a photoresist according to claim 1, wherein: Different types of shallow trenches are etched on the same substrate.
3. The method for evaluating the development quality of a photoresist according to claim 2, wherein: The shallow grooves include the following types: annular shallow grooves, long point-shaped shallow grooves, corrugated shallow grooves and strip-shaped shallow grooves.
4. The method for evaluating the development quality of a photoresist according to claim 3, wherein: The annular shallow grooves are arranged in a rectangular array on the substrate.
5. The method for evaluating the development quality of a photoresist according to claim 3, wherein: The long point-shaped shallow grooves are arranged in a rectangular array on the substrate.
6. The method for evaluating the development quality of a photoresist according to claim 3, wherein: The wave-shaped shallow grooves are parallel to each other on the substrate.
7. The method for evaluating the development quality of a photoresist according to claim 3, wherein: The strip-shaped shallow grooves are parallel to each other on the substrate.
8. The method for evaluating the development quality of a photoresist according to claim 1, wherein: When the substrate is a P-type substrate, the resistance of the ion-implanted region is measured as an N-region; when the substrate is an N-type substrate, the resistance of the ion-implanted region is measured as a P-region.
9. The method for evaluating the development quality of a photoresist according to claim 1, wherein: When the resistance of the ion implantation region is within a threshold range, it is determined that the development quality is qualified.
10. The method for evaluating the development quality of a photoresist according to claim 1, wherein: The thickness of the photoresist is greater than or equal to 15000A.