A method for hard mask etching pattern and a preparation method of a refrigeration infrared detector

Abstract

The application provides a hard mask etching pattern method and a preparation method of a refrigeration infrared detector. The hard mask etching pattern method is completed through one-time photoetching process and twice or thrice etching process, a double-step etching pattern is formed at the same time, the generation of undercut phenomenon is reduced, the internal stress of the etching sidewall is relieved, the conductivity of the step region is improved, the filling defects generated when filling a substance on the step in the subsequent process are reduced, the yield of the device in the subsequent process is improved, and the performance of the device is improved. The hard mask layer in the second opening is etched by taking the patterned photoresist layer as a mask, so that a step-shaped hard mask layer is formed, and the fracture of the hard mask layer is reduced.

Description

Technical Field

[0001] This invention relates to the field of cooled infrared detector technology, and in particular to a method for etching patterns using a hard mask. Background Technology

[0002] In current first- to third-generation semiconductor manufacturing, ICP etching (Inductively Coupled Plasma) or RIE etching (Reactive Ion Etching) are essential process steps. During ICP or RIE etching, SiO2 is typically used as the hard film layer to obtain a good SiO2 profile.

[0003] In recent years, ICP etching or RIE etching, as common plasma dry etching methods, has achieved excellent etching results when etching materials such as silicon, silicon dioxide, and III-V compounds. Therefore, ICP etching or RIE etching is widely used in the fabrication processes of various optoelectronic devices. Currently, this technology has been used in the etching process of SiO2 hard masks for GaSb-based cooled infrared detectors. The etching end face of the SiO2 hard mask has good flatness, perpendicularity, suitable etching rate, and high selectivity.

[0004] However, during the etching process of SiO2 hard mask, undercutting is prone to occur, which affects the normal progress of subsequent processes and reduces the yield and performance of cooled infrared detectors. Summary of the Invention

[0005] The purpose of this invention is to provide a method for etching patterns with a hard mask and a method for fabricating a cooled infrared detector, thereby reducing the occurrence of undercutting phenomena, reducing their impact on subsequent processes, improving the yield of subsequent processes, and enhancing the performance of the device.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for etching patterns using a hard mask, comprising the following steps:

[0007] A substrate is provided, the substrate comprising a base and a conductive material layer formed on the base;

[0008] A hard mask layer and a patterned photoresist layer are sequentially formed on the substrate, the photoresist layer having a first opening;

[0009] Using the patterned photoresist layer as a mask, the hard mask layer at the first opening is etched, and the etching stops in the hard mask layer, resulting in a residual film layer on the hard mask layer at the first opening.

[0010] performing a cleaning process to remove the residue film layer, and the cleaning process expands the size of the first opening to form a second opening;

[0011] masking the patterned photoresist layer, etching the hard mask layer at the second opening, and exposing part of the conductive material layer at the second opening;

[0012] masking the patterned photoresist layer, further etching the hard mask layer at the second opening and the exposed conductive material layer, and etching to stop in the conductive material layer to form a patterned hard mask layer and a double-step conductive material layer, thereby forming a double-step substrate.

[0013] Optionally, performing a cleaning process to remove the residue film layer, and the cleaning process expands the size of the first opening to form a second opening comprises:

[0014] passing oxygen or oxygen plasma through the surface of the hard mask layer to remove the residue film layer on the surface of the hard mask layer, and the cleaning process expands the size of the first opening to form a second opening.

[0015] Further, the flow rate of the cleaning process passing oxygen or oxygen plasma is 10-50sccm, the control pressure is 5-50mT, the radio frequency power is 90-500W, and the process time is less than 10min.

[0016] Further, the flow rate of the cleaning process passing oxygen or oxygen plasma is 20-40sccm, the control pressure is 10-35mT, the radio frequency power is 100-500W, and the process time is less than 5min.

[0017] Further, the size of the second opening is larger than that of the first opening by 0.5-2μm.

[0018] Further, masking the patterned photoresist layer, etching the hard mask layer at the first opening, and etching to stop in the hard mask layer comprises:

[0019] masking the patterned photoresist layer, etching the hard mask layer at the first opening by a plasma dry etching process, and etching to stop in the hard mask layer.

[0020] Further, the etching gas of the plasma dry etching process comprises a mixed gas of SF6, CHF3 and Ar, wherein the gas flow of CHF3 is 20-80sccm, the gas flow of SF6 is less than 30sccm, the gas flow of Ar is less than 50sccm, the radio frequency power is 90-500W, the control pressure is 4-30mT, and the process time is 10-25min.

[0021] Further, the hard mask layer at the second opening is etched by a plasma dry etching process with the patterned photoresist layer as a mask, and part of the conductive material layer at the second opening is exposed.

[0022] Further, the etching gas of the plasma dry etching process comprises a mixed gas of CHF3 and Ar, wherein the gas flow of CHF3 is 60-80sccm, the gas flow of Ar is less than 30sccm, the radio frequency power is 90-500W, and the control pressure is 3-30mT.

[0023] In another aspect, the application provides a preparation method of a refrigeration infrared detector, which comprises the above-mentioned hard mask etching pattern method.

[0024] Compared with the prior art, the method for etching a pattern of a hard mask and the method for manufacturing a refrigeration infrared detector provided by the application comprise the following steps: providing a substrate, wherein the substrate comprises a base and a conductive material layer formed on the base; sequentially forming a hard mask layer and a patterned photoresist layer on the substrate, wherein the photoresist layer has a first opening; taking the patterned photoresist layer as a mask, etching the hard mask layer at the first opening and stopping etching in the hard mask layer, and a residual film layer appears on the hard mask layer at the first opening; performing a cleaning process to remove the residual film layer, and the cleaning process expands the size of the first opening to form a second opening; taking the patterned photoresist layer as a mask, etching the hard mask layer at the second opening and exposing part of the conductive material layer at the second opening; and taking the patterned photoresist layer as a mask, further etching the hard mask layer at the second opening and the exposed conductive material layer and stopping etching in the conductive material layer to form a patterned hard mask layer and a double-step conductive material layer, thereby forming a double-step substrate. The method for etching a pattern of a hard mask is completed by one photoetching process and two or three etching processes, and a double-step etching pattern is formed at the same time, the generation of undercut is reduced, the internal stress of the etching sidewall is relieved, the conductive capacity of the step area is improved, the filling defects generated when filling a substance on the step in the subsequent process are reduced, the yield of the device in the subsequent process and the performance of the device are improved, and the hard mask layer in the step shape is formed by taking the patterned photoresist layer as a mask and etching the hard mask layer at the second opening, and the hard mask layer in the step shape reduces the phenomenon of fracture of the hard mask layer. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figures la-lc It is a structural schematic diagram of each step of the method for manufacturing a refrigeration infrared detector;

[0026] Figure 2 It is a flowchart of the method for etching a pattern of a hard mask according to an embodiment of the application;

[0027] Figures 3a-3f It is a structural schematic diagram of each step of the method for etching a pattern of a hard mask according to an embodiment of the application.

[0028] BRIEF DESCRIPTION OF DRAWINGS:

[0029] Figures la-lc In the drawings:

[0030] 10 - superlattice substrate; 20 - SiO2 hard mask layer; 30 - photoresist layer; 40 - trench;

[0031] Figures 3a-3f In the drawings:

[0032] 100 - Substrate; 110 - Base; 120 - Conductive material layer; 200 - Hard mask layer; 300 - Photoresist layer; a - First opening; b - Second opening. Detailed Implementation

[0033] Current methods for fabricating cooled infrared detectors include the following steps:

[0034] like Figure la As shown, step S11: A superlattice substrate 10 is provided, on which a SiO2 hard mask layer 20 is formed.

[0035] like Figure lb As shown, step S12: A patterned photoresist layer 30 is formed on the hard mask layer 20. The patterned photoresist layer 30 has a pattern that is used to form a mesa.

[0036] like Figure lc As shown, in step S13: using the patterned photoresist layer 30 as a mask, the SiO2 hard mask layer 20 is etched in one step to transfer the pattern into the SiO2 hard mask layer 20 and expose the superlattice substrate 10. At this time, due to the patterning effect, SiO2 material residue remains in the etched area of ​​the SiO2 hard mask layer 20, resulting in a cutting phenomenon. Furthermore, the etched SiO2 hard mask layer 20 is prone to breakage.

[0037] Analysis revealed that during the etching of the SiO2 hard mask layer 20, an uneven fluorocarbon film forms on its surface. This film reduces the etching rate in some areas of the SiO2 hard mask layer 20. While most of the SiO2 hard mask layer 20 has been etched, the area covered by the film remains unetched, resulting in material residue in the etched areas and causing undercutting. This phenomenon affects the normal operation of subsequent processes, reduces their yield, and impacts device performance.

[0038] To address the aforementioned issues, this invention provides a method for hard mask etching patterns. The hard mask etching pattern is completed through a three-stage etching process. Using the patterned photoresist layer as a mask, the hard mask layer at the first opening is etched. After etching stops within the hard mask layer, a cleaning process is performed on the surface of the hard mask layer. This removes the fluorocarbon film from the surface of the hard mask layer, eliminating the influence of the fluorocarbon film on subsequent surface etching processes. This reduces the occurrence of undercutting phenomena, thereby minimizing their impact on subsequent processes, improving device yield, and enhancing device performance.

[0039] The method for hard mask etching pattern and the method for manufacturing a refrigeration infrared detector will be described in more detail below with reference to the accompanying drawings, in which the preferred embodiments of the present application are shown. It should be understood that those skilled in the art can modify the present application described herein while still achieving the advantageous effects of the present application. Therefore, the following description should be understood as a broad general knowledge to those skilled in the art, and not as a limitation on the present application.

[0040] For clarity, not all of the features of an actual implementation are described in this document. In the following description, numerous specific details are set forth to provide a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without such specific details. In other instances, well-known methods have not been described in detail in order to avoid obscuring the present application. It will be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions can be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which can vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but can nevertheless be a routine undertaking of design, fabrication, and manufacture for those skilled in the art having the benefit of this disclosure.

[0041] The present application is described in more detail in the following paragraphs with reference to the accompanying drawings. The advantages and features of the present application will become more apparent from the following description taken in conjunction with the accompanying drawings. It should be understood that the drawings are very simplified and are not drawn to scale, and are only used to facilitate, clarify and assist in the explanation of the embodiments of the present application.

[0042] Figure 2 A flow chart of a method for hard mask etching pattern according to an embodiment of the present application. As shown in Figure 2 the embodiment provides a method for hard mask etching pattern, for example, in a method for manufacturing a refrigeration infrared detector. The method for hard mask etching pattern comprises the following steps:

[0043] Step S21: providing a substrate, the substrate comprising a substrate and a conductive material layer formed on the substrate;

[0044] Step S22: sequentially forming a hard mask layer and a patterned photoresist layer on the substrate, the photoresist layer having a first opening;

[0045] Step S23: etching the hard mask layer at the first opening with the patterned photoresist layer as a mask, and stopping the etching in the hard mask layer, a residual film layer appearing on the hard mask layer at the first opening;

[0046] Step S24: performing a cleaning process to remove the residual film layer, while the cleaning process enlarges the size of the first opening to form a second opening;

[0047] Step S25: Using the patterned photoresist layer as a mask, etch the hard mask layer at the second opening and expose part of the conductive material layer at the second opening;

[0048] Step S26: Using the patterned photoresist layer as a mask, further etch the hard mask layer at the second opening and the exposed conductive material layer, and stop etching in the conductive material layer to form a patterned hard mask layer and a double-step conductive material layer, thereby forming a double-step substrate.

[0049] The following combination Figures 2-3f This section describes a method for etching patterns using a hard mask.

[0050] Figure 3a This is a schematic diagram of the substrate provided in this embodiment. Figure 3a As shown, step S1 is first performed, providing a substrate 100, which includes a base 110 and a conductive material layer 120 formed on the base 110. The base 110 may be a silicon base or a compound base.

[0051] In this embodiment, the substrate 110 is, for example, a compound substrate, and the conductive material layer 120 is, for example, a superlattice composite layer. A buffer layer (not shown) is also included between the substrate 110 and the conductive material layer 120. The materials of the compound substrate and the buffer layer are, for example, indium phosphide (InP), and the buffer layer can be a doped buffer layer or an undoped buffer layer. In other embodiments, the material of the compound substrate is, for example, gallium arsenide (GaAs), and the material of the buffer layer is, for example, gallium antimonide (GaSb). The superlattice composite layer includes a p-type superlattice structure layer and an n-type superlattice structure layer sequentially formed on the buffer layer.

[0052] Figure 3b This is a schematic diagram of the structure after the patterned photoresist layer is formed in this embodiment. For example... Figure 3b As shown, step S22 is then performed, in which a hard mask layer 200 and a patterned photoresist layer 300 are sequentially formed on the substrate 100, the photoresist layer 300 having a first opening a. The hard mask layer 200 is made of dielectric materials such as silicon dioxide and silicon nitride, and its thickness is 0.9 nm to 2.2 nm.

[0053] This step specifically includes the following steps:

[0054] First, the hard mask layer 200 is formed on the substrate 100 by a deposition process;

[0055] Next, a photoresist layer 300 is coated on the hard mask layer 200;

[0056] Next, the photoresist layer 300 is patterned by exposure, development and other processes to form a patterned photoresist layer 300. At this time, the patterned photoresist layer 300 has a first opening a for forming a groove in the substrate, which is a mesa with an L-shaped cross section in the height direction of the substrate 100, or a trench with a U-shaped cross section, or a hole with a U-shaped cross section, etc. In this embodiment, the groove is a mesa with an L-shaped cross section in the height direction of the substrate 100. It should be noted that, for the sake of convenience, this embodiment only includes one mesa with an L-shaped cross section in the height direction of the substrate.

[0057] Figure 3c The structure diagram for etching the first opening and stopping etching in the hard mask layer in this embodiment. As shown in Figure 3c Step S23 is then performed to etch the hard mask layer 200 at the first opening a using the patterned photoresist layer 300 as a mask, and to stop etching in the hard mask layer 200, with a residual film layer (not shown in the figure) appearing on the hard mask layer 200 at the first opening a. Specifically, the hard mask layer 200 at the first opening a is etched by a plasma dry etching process using the patterned photoresist layer 300 as a mask, and etching is stopped in the hard mask layer 200.

[0058] In this step, the etching gas of the plasma dry etching process includes a mixture of SF6, CHF3 and Ar, wherein the gas flow of CHF3 is 20-80 seem, preferably 65-75 seem; the gas flow of SF6 is less than 30 seem, preferably less than 10 seem; the gas flow of Ar is less than 50 seem, preferably less than 15 seem; the radio frequency power is 90-500 W, preferably 100-120 W; the control pressure is 4-30 mT (tons), preferably 15-25 mT. The thickness of the hard mask layer 200 after etching is greater than about 70% of the total thickness of the hard mask layer 200 before etching, and further, the thickness of the hard mask layer 200 after etching is greater than about 90% of the total thickness of the hard mask layer 200 before etching. The surface of the hard mask layer 200 at the first opening a is formed with a fluorocarbon film (i.e. a residual film layer) by this etching process, which is uneven on the surface of the hard mask layer 200 after etching, and which affects the normal progress of the etching process of the fluorocarbon hard mask layer 200.

[0059] Figure 3d The structure diagram after the cleaning process in this embodiment. As shown in Figure 3dAs shown, in order to remove the fluorocarbon film, step S24 is performed to execute a cleaning process to remove the residue film layer, and the cleaning process expands the size of the first opening a to form a second opening b.

[0060] The cleaning process is, for example, an oxygen removal process, that is, by introducing oxygen or oxygen plasma into the surface of the hard mask layer 200, the fluorocarbon film on the surface of the hard mask layer 200 is removed, so that the subsequent surface etching process of the hard mask layer 200 is not affected by the fluorocarbon film, reducing the occurrence of undercut phenomenon, thereby reducing its impact on subsequent processes, improving the yield of the device, and improving the performance of the device. During the cleaning process, due to the ashing effect of oxygen on the photoresist, part of the photoresist located at the first opening a is removed, expanding the size of the first opening a to form a second opening b, wherein the size of the second opening b is larger than the size of the first opening a by 0.5 μm to 2 μm. At this time, the exposed hard mask layer 200 is stepped.

[0061] In this step, the flow rate of oxygen or oxygen plasma introduced by the cleaning process is 10 sccm to 50 sccm, preferably, the flow rate of oxygen or oxygen plasma introduced by the cleaning process is 20 sccm to 40 sccm; the control pressure is 5 mT to 50 mT; preferably, the control pressure is 10 mT to 35 mT; the radio frequency power is 90 W to 500 W, preferably, the radio frequency power is 100 W to 500 W; the process time is less than 10 min, preferably, the process time is less than 5 min. The cleaning process expands the opening size at the first opening a to form a second opening b, at this time, part of the hard mask layer 200 not subjected to etching is exposed, so that the hard mask layer 200 exposed by the second opening b is stepped. The stepped hard mask layer 200 can greatly reduce the phenomenon of hard mask layer 200 breaking; compared with the subsequent process of forming a passivation layer on the surface of the substrate to form a double-stepped substrate, the steps are reduced, and only one photoresist is needed to complete the process requirement, which optimizes the process steps, reduces the waste of photoresist material, and greatly reduces the breaking phenomenon of the passivation layer.

[0062] Figure 3e The structure after further etching the hard mask layer at the second opening in this embodiment is shown in the figure. Figure 3e As shown, step S25 is then performed to etch the hard mask layer 200 at the second opening b using the patterned photoresist layer 300 as a mask, and to expose part of the conductive material layer 120 at the second opening b. Specifically, the hard mask layer 200 at the second opening b is etched by a plasma dry etching process, and part of the conductive material layer 120 at the second opening b is exposed.

[0063] In this step, the etching gas of the plasma dry etching process includes a mixed gas of CHF3and Ar, wherein the gas flow of CHF3is 60-80sccm, preferably, the gas flow of CHF3is 65-75sccm; the gas flow of Ar is less than 30sccm, preferably, the gas flow of Ar is less than 15sccm; the radio frequency power is 90-500W, preferably, the radio frequency power is 130-500W; the control pressure is 3-30mT, preferably, the control pressure is 3-25mT. After the etching of this step, most of the hard mask layer 200 in the second opening b (the hard mask layer 200 at the first opening a) has been etched completely, and the conductive material layer 120 is exposed, while the enlarged part of the first opening a has not been etched due to the thickness of the hard mask layer 200, at this time, the hard mask layer 200 at the second opening b is in a stepped shape, and the stepped hard mask layer 200 reduces the phenomenon of hard mask layer fracture.

[0064] Figure 3f The structure of the substrate after forming the double-step in this embodiment is shown in FIG. 6. As shown, step S26 is then performed to further etch the hard mask layer 200 at the second opening b and the exposed conductive material layer 120 with the patterned photoresist layer 300 as a mask, and the etching stops in the conductive material layer 120, so as to remove the remaining hard mask layer 200 at the second opening b, and form a patterned hard mask layer 200 and a double-step conductive material layer 120, thereby forming a double-step substrate 100’ to realize the manufacturing of a dual-color or multi-color refrigeration infrared detector. Figure 3f The double-step conductive material layer 120 can improve the conductivity of the step area and reduce the filling defects generated when filling the material on the step in the subsequent process, thereby improving the yield of the device in the subsequent process and the performance of the device.

[0065] In summary, the application provides a method for etching a hard mask pattern and a preparation method of a refrigeration infrared detector, the method comprising the following steps: providing a substrate, the substrate comprising a substrate and a conductive material layer formed on the substrate; sequentially forming a hard mask layer and a patterned photoresist layer on the substrate, the photoresist layer having a first opening; etching the hard mask layer at the first opening with the patterned photoresist layer as a mask, and stopping etching in the hard mask layer, a residual film layer appearing on the hard mask layer at the first opening; performing a cleaning process to remove the residual film layer, while the cleaning process enlarges the size of the first opening to form a second opening; etching the hard mask layer at the second opening with the patterned photoresist layer as a mask, and exposing part of the conductive material layer at the second opening; further etching the hard mask layer at the second opening and the exposed conductive material layer with the patterned photoresist layer as a mask, and stopping etching in the conductive material layer to form a patterned hard mask layer and a double-step conductive material layer, thereby forming a double-step substrate. The application completes hard mask etching pattern by one photoetching process and two or three etching processes, forms a double-step etching pattern, reduces the generation of undercut phenomenon, relieves the internal stress of the etching sidewall, improves the conductivity of the step area, reduces the filling defects generated when filling the material on the step in the subsequent process, improves the yield of the device in the subsequent process, and improves the performance of the device. By etching the hard mask layer at the second opening with the patterned photoresist layer as a mask, a step-shaped hard mask layer can be formed, which reduces the phenomenon of hard mask layer fracture.

[0066] In addition, it should be noted that, unless specifically described or indicated, the terms "first", "second", "third" in the description are only used to distinguish the components, elements, steps, etc. in the description, and are not used to represent the logical relationship or sequence relationship between the components, elements, steps, etc.

[0067] It can be understood that, although the application has been disclosed as above with preferred embodiments, the above embodiments are not intended to limit the application. For any person skilled in the art, many possible changes and modifications or equivalent embodiments of the technical solutions of the application can be made by using the disclosed technical contents without departing from the scope of the technical solutions of the application. Therefore, any simple modification, equivalent change and modification of the above embodiments made according to the technical essence of the application without departing from the content of the technical solutions of the application, all still belong to the scope of protection of the technical solutions of the application.

Claims

1. A method of hard mask etching a pattern, the method comprising: The method comprises the following steps: providing a substrate, the substrate comprising a substrate and a conductive material layer formed on the substrate; forming a hard mask layer and a patterned photoresist layer on the substrate in sequence, the photoresist layer having a first opening; masking with the patterned photoresist layer, etching the hard mask layer at the first opening by a plasma dry etching process and stopping etching in the hard mask layer, so that a residual film layer appears on the hard mask layer at the first opening; performing a cleaning process, removing the residual film layer on the surface of the hard mask layer by introducing oxygen or oxygen plasma into the surface of the hard mask layer, and expanding the size of the first opening by ashing to form a second opening; masking with the patterned photoresist layer, etching the hard mask layer at the second opening by a plasma dry etching process until part of the conductive material layer at the second opening is exposed, so that the hard mask layer at the second opening is in a stepped shape; masking with the patterned photoresist layer, further etching the hard mask layer at the second opening and the exposed conductive material layer, and stopping etching in the conductive material layer to form a patterned hard mask layer and a double-stepped conductive material layer, thereby forming a double-stepped substrate.

2. The method of claim 1, wherein, The flow rate of oxygen or oxygen plasma introduced in the cleaning process is 10sccm~50sccm, the control pressure is 5mT~50mT, the radio frequency power is 90W~500W, and the process time is less than 10min.

3. The method of claim 2, wherein, The flow rate of oxygen or oxygen plasma introduced in the cleaning process is 20sccm~40sccm, the control pressure is 10mT~35mT, the radio frequency power is 100W~500W, and the process time is less than 5min.

4. The method of claim 3, wherein, The size of the second opening is larger than that of the first opening by 0.5μm~2μm.

5. The method of claim 1, wherein, When etching the hard mask layer at the first opening by a plasma dry etching process, the etching gas of the plasma dry etching process comprises a mixed gas of SF6, CHF3 and Ar, wherein the gas flow rate of CHF3 is 20sccm~80sccm, the gas flow rate of SF6 is less than 30sccm, the gas flow rate of Ar is less than 50sccm, the radio frequency power is 90W~500W, and the control pressure is 4mT~30mT.

6. The method of claim 1, wherein, When etching the hard mask layer at the second opening by a plasma dry etching process, the etching gas of the plasma dry etching process comprises a mixed gas of CHF3 and Ar, wherein the gas flow rate of CHF3 is 60sccm~80sccm, the gas flow rate of Ar is less than 30sccm, the radio frequency power is 90W~500W, and the control pressure is 3mT~30mT.

7. A method for fabricating a cooled infrared detector, characterized in that, The method for etching a pattern of a hard mask comprises any one of claims 1~6.

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