Etching line width regulation and control method and micro-bolometer supporting leg structure preparation method
By establishing a three-dimensional prediction model and step-by-step etching process, the problem of unstable etching line width of the microbolometer support leg is solved, and the precise control of the etching line width is achieved, the stability and reliability of the etching process are improved, and the dimensional accuracy requirements of micro-nano devices are met.
Patent Information
- Application Number
- CN202510366665.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-07-11
AI Technical Summary
There is a lack of effective methods in the prior art to stably control the etch line width of the microbolometer support legs, resulting in degradation or failure of the detector performance, especially when the line width deviates from the set value during lithography and etching processes, reworking processes are prone to residual photoresist or structural damage.
By establishing a three-dimensional prediction model of ‘exposure energy-regulating time-line width’, and combining the step-by-step process of pre-etching and formal etching, an etching line width regulation method is constructed, which is divided into two stages: pre-etching and formal etching. Different etching gas ratios and process conditions are used to accurately regulate the final etching line width.
The precise control of the etch line width is achieved within the tolerance range of ±25nm, which improves the stability and reliability of the etching process, meets the strict requirements of micro-nano devices for dimensional accuracy, and avoids performance degradation caused by etch line width deviation.
Smart Images
Figure CN120296962A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor manufacturing technology, and particularly relates to an etching line width control method and a preparation method for the support leg structure of a microbolometer. Background Art
[0002] A microbolometer is an important infrared detection device, and its performance depends to a great extent on two key parameters, namely thermal conductance (G) and temperature coefficient of resistance (α). According to industry knowledge, the responsivity of a resistive microbolometer is proportional to the temperature coefficient of resistance α and inversely proportional to the thermal conductance G of the main heat loss mechanism. However, in an uncooled infrared resistive microbolometer, the value of the thermal conductance G can vary within several orders of magnitude, while the variation range of the temperature coefficient of resistance α is relatively small. Therefore, in the design process, the optimization of the thermal insulation device becomes a key link in improving the performance of the detector.
[0003] The thermal conductance G of a microbolometer can be calculated by the formula: G = 2∑ i g i h i W / L, where g i and h i represent the thermal conductivity and thickness of each film layer on the support leg respectively, W is the width of the support leg, and L is the length of the support leg. After the product design is completed, the length L of the support leg is not affected by the processing technology, and the film layer thickness h i is relatively stable. In contrast, the width W of the support leg is most significantly affected by the processing technology. Therefore, how to stably control the width of the support leg has become the core factor affecting the performance of the detector.
[0004] In the actual processing process, the stability of the support leg width mainly depends on the line width after lithography and the etching process. If the lithography line width exceeds the set value, the product needs to be reworked, and problems such as photoresist residue or structural damage are likely to occur during the rework process. In addition, if the line width after etching deviates from the target value, the performance of the detector will be significantly reduced. It can be seen that there is a lack of a method in the prior art that can effectively control the etching line width to ensure precise control of the support leg width, so as to meet the product design requirements. Summary of the Invention
[0005] In order to solve all or part of the above problems in the prior art, the present invention provides an etching line width control method and a preparation method for the support leg structure of a microbolometer. By establishing a three-dimensional prediction model of "exposure energy - regulation time - line width" and combining the step-by-step processes of pre-etching and formal etching, the present invention can timely correct the situation where the lithography line width or the etching line width deviates from the set value, so as to ensure that the final etching line width meets the product design requirements, and effectively avoid the decline or failure of product performance caused by the deviation of the etching line width.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] An etching line width control method, comprising the following steps:
[0008] Step 100, establishing a three-dimensional prediction model, including:
[0009] S101. Perform photolithography on the wafer with n different exposure energies E_i (i = 1, 2,... n) to form n groups of photolithography patterns, and measure the corresponding photolithography line widths CD_i of each group; perform a pre-etching process on each group of photolithography patterns and measure the corresponding pre-etching line widths CD'_i of each group;
[0010] S102. For each group of photolithography patterns after pre-etching, apply m different control times T_j (j = 1, 2,... m) to perform the formal etching process, and measure the corresponding etching line widths CD”_i of each group;
[0011] S103. Based on the mapping relationship between the exposure energy E_i, the control time T_j, the pre-etching line width CD'_i, and the etching line width CD”_i, construct a three-dimensional prediction model of "exposure energy-control time-line width";
[0012] Step 200, actual application, the etching process is divided into pre-etching and formal etching, including:
[0013] S201. Perform photolithography and pre-etching processes on the wafer to obtain the actual photolithography line width CD_x and the pre-etching line width CD'_x;
[0014] S202. According to the target etching line width CD_T required for the wafer, input the photolithography line width CD_x and the pre-etching line width CD'_x into the three-dimensional prediction model, and use the target etching line width CD_T as a constraint condition to output the corresponding etching time T_y;
[0015] S203. Perform formal etching according to the etching time T_y to obtain the final etching line width.
[0016] The line widths obtained in the above steps are all measured by a scanning electron microscope (CD-SEM) or a focused ion beam (FIB).
[0017] The present invention also provides a preparation method for the supporting leg structure of a microbolometer. Based on step 100 in the above-mentioned etching line width control method, according to the actual requirements for the preparation of the supporting legs of the microbolometer, data collection and simulation are carried out to establish a corresponding three-dimensional prediction model, and then the following process steps are executed:
[0018] S301. Sequentially form a sacrificial layer, a first dielectric layer, a conductive layer, and a second dielectric layer on the substrate surface;
[0019] S302. Coat a bottom anti-reflection coating and a photoresist layer on the surface of the second dielectric layer in sequence, and perform exposure and development processes on the photoresist layer to form a photoresist pattern;
[0020] S303. Perform photolithography on the bottom anti-reflection coating to form a patterned mask, and obtain the corresponding photolithography line width CD_x;
[0021] S304. Based on the patterned mask, perform a pre-etching process to etch the second dielectric layer and the conductive layer, and terminate at the surface of the first dielectric layer to obtain the corresponding pre-etching line width CD'_x;
[0022] S305. Input the photolithography line width CD_x and the pre-etching line width CD'_x into the three-dimensional prediction model, and use the target etching line width CD_T required for the support leg structure as a constraint condition to obtain the etching time T_y, and use it as a process condition to perform the formal etching process to etch the first dielectric layer and terminate at the surface of the sacrificial layer;
[0023] S306. Remove process residues to form a support leg structure.
[0024] The etching selectivity of the formal etching process for the photoresist is higher than that of the pre-etching process.
[0025] In step S304, the etching gas for the pre-etching process includes Cl2, CF4 and AR, and the etching gas ratio is AR:CL2:CF4 = 4:6:9 - 4:5:9.
[0026] In step S305, the etching gas for the formal etching process includes O2, CHF3 and AR, and the etching gas ratio is O2:CHF3:AR = 1:8:20 - 1:4:10.
[0027] The bottom anti-reflection coating is removed by a dry etching process, and the etching gas is CF4.
[0028] In step S305, by adjusting the etching time T_y of the formal etching process, the final etching line width is controlled within a tolerance range of ±25 nm.
[0029] In step S306, the target etching line width of the obtained support leg structure is between 200 - 300 nm.
[0030] The present invention has at least the following beneficial effects:
[0031] 1) By establishing a three-dimensional prediction model of "exposure energy - regulation time - line width", it is possible to accurately predict the corresponding regulation time according to the actual photolithography line width and pre-etching line width, combined with the target etching line width.
[0032] 2) Divide the etching process into two stages: pre-etching and formal etching. Ensure the stability and morphology quality of the initial structure through the pre-etching process, and then precisely control the line width through the formal etching process. This step-by-step strategy can effectively reduce the errors and unstable factors that may occur in a single etching step.
[0033] 3) Optimize the etching process through FIB characterization and error analysis. This data-based optimization method can effectively reduce the impact of process fluctuations on the etching results and improve the stability and reliability of the etching process.
[0034] 4) The present invention can precisely control the etching line width within a very small tolerance range of the target value (such as ±25 nm), meeting the strict requirements of micro-nano devices for dimensional accuracy. Description of the Drawings
[0035] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0036] Figure 1 It is a flowchart of a method for controlling the etching line width according to an embodiment of the present invention.
[0037] Figure 2 It is a schematic diagram of a three-dimensional prediction model in a method for controlling the etching line width according to an embodiment of the present invention.
[0038] Figure 3 It is a schematic process flow diagram of a method for preparing a microbolometer support leg structure according to an embodiment of the present invention.
[0039] Figure 4 It is a schematic diagram of the actual product effect processed by using a method for preparing a microbolometer support leg structure according to an embodiment of the present invention.
[0040] Reference numerals: 1, substrate; 2, sacrificial layer; 3, first dielectric layer; 4, conductive layer; 5, second dielectric layer; 6, bottom anti-reflection coating; 7, photoresist layer. Detailed Embodiments
[0041] The following will clearly and completely describe the technical solutions in the specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.
[0042] In the embodiments of the present invention, with reference toFigure 1 and Figure 2 As shown in Figure 2 , a method for controlling the etching line width is provided, including the following steps:
[0043] Step 100: Establish a three-dimensional prediction model, including:
[0044] S101. Perform photolithography on the wafer with n different exposure energies E_i (i = 1, 2,... n) to form n groups of photolithography patterns, and measure the corresponding photolithography line widths CD_i of each group; perform a pre-etching process on each group of photolithography patterns, and measure the corresponding pre-etching line widths CD'_i of each group;
[0045] S102. For each group of photolithography patterns after pre-etching, apply m different regulation times T_j (j = 1, 2,... m) to perform the formal etching process, and measure the corresponding etching line widths CD”_i of each group;
[0046] S103. Based on the mapping relationship of the exposure energy E_i, the regulation time T_j, the pre-etching line width CD'_i, and the etching line width CD”_i, construct a three-dimensional prediction model of "exposure energy - regulation time - line width";
[0047] Step 200, actual application, the etching process is divided into pre-etching and formal etching, including:
[0048] S201. Perform photolithography and pre-etching processes on the wafer in sequence to obtain the actual photolithography line width CD_x and the pre-etching line width CD'_x;
[0049] S202. According to the target etching line width CD_T required for the wafer, input the photolithography line width CD_x and the pre-etching line width CD'_x into the three-dimensional prediction model, and use the target etching line width CD_T as a constraint condition to output the corresponding etching time T_y;
[0050] S203. Perform formal etching according to the etching time T_y to obtain the final etching line width.
[0051] The line widths obtained in the above steps are all measured by a scanning electron microscope (CD-SEM) or a focused ion beam (FIB).
[0052] As Figure 2 shown, taking photolithography with the exposure energy E_3 as an example, the formed photolithography line width is CD_3. After the pre-etching process with the pre-etching time T_0, the pre-etching line width CD'_3 is obtained. At this time, if the formal etching time T_2 is applied, the final etching line width that meets the target value CD_T can be obtained.
[0053] In an actual production scenario, affected by the condition of the lithography machine itself, the situation of the wafer incoming materials, and environmental variables, the lithography line width may deviate from the calibrated value. Specifically, when the line width CD_3 after lithography increases to CD_2 due to process fluctuations, after being processed for the same pre-etching time T_0, the pre-etching line width correspondingly increases to CD'_2. To achieve the target line width CD_T, at this time, it is necessary to extend the formal etching time T_3 (T_3 > T_2) to obtain a compliant final etching line width (CD”_2 = CD_T); conversely, if the lithography line width CD_3 decreases to CD_4 due to process anomalies, the pre-etching line width after being processed for the pre-etching time T_0 decreases to CD'_4, then the formal etching time can be shortened to T_1 (T_1 < T_2) to achieve the target line width CD_T (CD”_4 = CD_T).
[0054] Similarly, when the pre-etching process is affected by changes in the equipment state and causes line width deviation: if the pre-etching line width CD'_3 abnormally increases to CD'_2, it is necessary to apply a longer formal etching time T_3 (T_3 > T_2) to compensate for the line width deviation; if the pre-etching line width CD'_3 abnormally decreases to CD'_4, then only a shortened formal etching time T_1 (T_1 < T_2) needs to be applied to complete the line width correction. This dual regulation mechanism is achieved through the non-linear mapping relationship of the three-dimensional prediction model, effectively improving the process tolerance.
[0055] The present invention also provides a preparation method for the support leg structure of a microbolometer, in combination with reference Figure 3 and Figure 4 As shown, based on step 100 in the above-described etching line width regulation method, data collection and simulation are carried out to establish a corresponding three-dimensional prediction model, and then the following process steps are executed:
[0056] S301. A sacrificial layer 2, a first dielectric layer 3, a conductive layer 4, and a second dielectric layer 5 are sequentially formed on the surface of the substrate 1;
[0057] S302. A bottom anti-reflection coating 6 and a photoresist layer 7 are sequentially coated on the surface of the second dielectric layer 5, and the photoresist layer 7 is subjected to exposure and development processing to form a photoresist pattern;
[0058] S303. The bottom anti-reflection coating 6 is subjected to lithography processing to form a patterned mask and obtain a corresponding lithography line width CD_x;
[0059] S304. Based on the patterned mask, a pre-etching process is carried out to etch the second dielectric layer 5 and the conductive layer 4 and terminate at the surface of the first dielectric layer 3 to obtain a corresponding pre-etching line width CD'_x;
[0060] S305. Input the lithography line width CD_x and the pre-etch line width CD'_x into the three-dimensional prediction model, and with the target etch line width CD_T required for the support leg structure as the constraint condition, obtain the etch time T_y, and use it as the process condition for the formal etching process to etch the first dielectric layer 3 and terminate at the surface of the sacrificial layer 2;
[0061] S306. Remove process residues to form the support leg structure.
[0062] This method calls step 100 in the aforementioned etch line width regulation method, establishes a corresponding three-dimensional prediction model according to the actual requirements of the preparation of the microbolometer support leg, and obtains the required regulation time T_y from the trained three-dimensional model to optimize and regulate the formal etching process.
[0063] In this embodiment, the sacrificial layer 2 is specifically a polyimide sacrificial layer, the first dielectric layer 3 is specifically a silicon nitride layer, the conductive layer 4 is specifically metal titanium, and the second dielectric layer 5 is specifically a silicon nitride layer. In the etching process, the etching selectivity of the formal etching process for photoresist is higher than that of the pre-etching process. The bottom anti-reflection coating 6 is a non-photosensitive material and remains on the surface of the second dielectric layer 5 after development, and it needs to be removed by dry etching subsequently, and the etching gas selected is CF4.
[0064] In step S304, the etching gas for the pre-etching process includes Cl2, CF4, and AR, and the ratio range of the etching gas is AR:CL2:CF4 = 4:6:9 - 4:5:9. This etching process can etch silicon nitride and metal titanium simultaneously, but the etching selectivity for photoresist is relatively poor. However, this process has a good etching morphology and less polymer residue is generated during the etching process.
[0065] In step S305, the etching gas for the formal etching process includes O2, CHF3, and AR, and the ratio range of the etching gas is O2:CHF3:AR = 1:8:20 - 1:4:10. The characteristic of this process is that it has a high selectivity for photoresist. However, its etching morphology is relatively poor, so it is not suitable for use alone. This step can effectively regulate the final line width.
[0066] In this embodiment, the target etch line width of the support leg structure is 200 - 300 nm. By precisely regulating the etch time of the formal etching process, the final etch line width can be controlled within a tolerance range of ±25 nm of the target value. Figure 4Shows the actual effect of the product processed by the method provided by the present invention. The target etched line width CD_T in the layout design of this product is 250 nm, and the lithography line width CD_i is 283 nm. After being processed by the preparation process of the present invention, the final etched line width measured by FIB (Focused Ion Beam) slicing is about 236 nm, which is within the actual requirement range of the product (250 nm ± 25 nm).
[0067] By establishing a three-dimensional prediction model of "exposure energy - regulation time - line width", the present invention can accurately predict the corresponding regulation time according to the actual lithography line width and pre-etch line width, combined with the target etched line width, so as to achieve precise control of the etched line width during the formal etching process. The etching process is divided into two stages: pre-etching and formal etching, and different etching gas ratios and process conditions are adopted. In the pre-etching stage, an etching gas ratio with good etching morphology and less polymer residue (Cl2, CF4, and AR, with the ratio range of AR:CL2:CF4 = 4:6:9 - 4:5:9) is used, which can ensure that the etched structure has good morphology. In the formal etching stage, an etching gas ratio with a high selectivity ratio for photoresist (O2, CHF3, and AR, with the ratio range of O2:CHF2:AR = 1:8:20 - 1:4:10) is used. Although its etching morphology is relatively poor, by precisely regulating the etching time, the final etched line width can be effectively regulated. This step-by-step etching process flow not only ensures the quality of the etching morphology but also realizes precise regulation of the etched line width, overcomes the problem that a single etching process is difficult to simultaneously meet the requirements of good etching morphology and precise line width control, and improves the overall performance and reliability of the etching process.
[0068] The present invention can accurately control the etched line width within a very small tolerance range of the target value (such as ±25 nm), meeting the strict requirements of micro-nano devices for dimensional accuracy. This has important technical value for the field of high-precision micro-nano processing (such as microbolometers, MEMS devices, etc.).
[0069] It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.
Claims
1. An etching line width control method, characterized in that It includes the following steps: Step 100: Establish a three-dimensional prediction model, including: S101. Perform photolithography on the wafer with n different exposure energies E_i (i = 1, 2,... n) to form n groups of photolithography patterns, and measure the corresponding photolithography line widths CD_i of each group; perform a pre-etching process on each group of photolithography patterns and measure the corresponding pre-etching line widths CD'_i of each group; S102. For each group of photolithography patterns after pre-etching, apply m different regulation times T_j (j = 1, 2,... m) respectively to perform the formal etching process, and measure the corresponding etched line widths CD”_i of each group; S103. Based on the mapping relationship among the exposure energy E_i, the regulation time T_j, the pre-etching line width CD'_i, and the etched line width CD”_i, construct a three-dimensional prediction model of "exposure energy-regulation time-line width"; Step 200, actual application. The etching process is divided into pre-etching and formal etching, including: S201. Perform photolithography and pre-etching processes on the wafer to obtain the actual photolithography line width CD_x and the pre-etching line width CD'_x; S202. According to the target etched line width CD_T required for the wafer, input the photolithography line width CD_x and the pre-etching line width CD'_x into the three-dimensional prediction model, and use the target etched line width CD_T as a constraint condition to output the corresponding etching time T_y; S203. Perform formal etching according to the etching time T_y to obtain the final etched line width.
2. The etching line width control method according to claim 1, wherein The line widths obtained in the above steps are all measured by a scanning electron microscope (CD-SEM) or a focused ion beam (FIB).
3. A preparation method of a support leg structure of a microbolometer, characterized in that, Based on Step 100 in the etched line width regulation method according to Claim 1 or 2, according to the actual requirements for the preparation of the microbolometer support legs, collect data and perform simulations, establish a corresponding three-dimensional prediction model, and then execute the following process steps: S301. Form a sacrificial layer, a first dielectric layer, a conductive layer, and a second dielectric layer on the substrate surface in sequence; S302. Coat a bottom anti-reflection coating and a photoresist layer on the surface of the second dielectric layer in sequence, and perform exposure and development processes on the photoresist layer to form a photoresist pattern; S303. Perform photolithography on the bottom anti-reflection coating to form a patterned mask and obtain the corresponding photolithography line width CD_x; S304. Based on the patterned mask, perform a pre-etching process to etch the second dielectric layer and the conductive layer and terminate at the surface of the first dielectric layer to obtain the corresponding pre-etching line width CD'_x; S305. Input the photolithography line width CD_x and the pre-etching line width CD'_x into the three-dimensional prediction model, and use the target etched line width CD_T required for the support leg structure as a constraint condition to obtain the etching time T_y, and use it as a process condition to perform the formal etching process to etch the first dielectric layer and terminate at the surface of the sacrificial layer; S306. Remove process residues to form a support leg structure.
4. The preparation method according to claim 3, characterized in that, The etching selectivity of the formal etching process for the photoresist is higher than that of the pre-etching process.
5. The preparation method according to claim 3, characterized in that, In step S304, the etching gas for the pre-etching process includes Cl2, CF4, and AR, and the etching gas ratio is AR:Cl2:CF4 = 4:6:9 - 4:5:
9.
6. The preparation method according to claim 3, characterized in that, In step S305, the etching gas for the formal etching process includes O2, CHF3, and AR, and the etching gas ratio is O2:CHF3:AR = 1:8:20 - 1:4:
10.
7. The preparation method according to claim 3, characterized in that, The bottom anti-reflection coating is removed by a dry etching process, and the etching gas used is CF4.
8. The preparation method according to claim 3, characterized in that, In step S305, by adjusting the etching time Ty of the formal etching process, the final etching line width is controlled within a tolerance range of ±25 nm.
9. The preparation method according to claim 3, characterized in that, In step S306, the target etching line width of the obtained support leg structure is between 200 - 300 nm.