A table opening etching method for type II superlattice infrared detector

Abstract

The invention provides a table opening etching method for a type II superlattice infrared detector, belonging to the technical field of infrared detector table etching; the invention solves the problems of low etching rate, unclean etching, long etching time and the like in the existing type II superlattice infrared detector preparation process in table opening etching; the technical scheme adopted is: before depositing an inorganic mask layer, photoresist is coated on the opening position, and an opening structure is formed in the inorganic mask layer in advance by combining dry etching and cleaning and de-gumming for a relatively short time in the early stage, so that dry etching is not required in the table hole in the subsequent process, thereby avoiding a series of problems caused by a relatively low etching rate in the hole or a relatively long etching time caused by a thick inorganic mask layer; the invention is applied to the preparation of type II superlattice infrared detectors.

Description

Technical Field

[0001] The invention provides a table opening etching method for a type II superlattice infrared detector, belonging to the technical field of infrared detector table etching. Background Art

[0002] Superlattice infrared detector is a photovoltaic infrared detector based on superlattice semiconductor material. Superlattice is a multilayer film composed of two materials with good lattice matching, with thin layers ranging from a few nanometers to tens of nanometers grown alternately and maintaining strict periodicity. In fact, it is a specific form of layered fine composite material. Photovoltaic infrared detector is a device prepared based on the photovoltaic effect of the material. Type II superlattice material InAs / GaSb has the advantages of easy adjustment of energy band gap, flexible structure selection, large effective mass of electrons, and high material uniformity. It can well meet the requirements of high resolution, high sensitivity, multi-color detection and large-scale array of the new generation of infrared detectors, thus becoming an excellent detector material.

[0003] However, in the current preparation process of type II superlattice infrared detectors, there are major problems in the table pattern hole etching step: ① Due to the table hole structure, the dry etching rate in the hole is low, so it takes a long time to etch, and there is also the problem of the inorganic mask layer in the hole not being etched cleanly, which leads to the circuit being non-conductive and unable to perform subsequent tests; ② Due to the table inorganic mask layer SiO2 or SiN x It is relatively thick (thickness ≥ 1um), and it takes a long time to etch the opening, which will cause the photoresist in the remaining area outside the mesa hole to be unable to maintain its original shape, and then cause the mesa mask layer under the photoresist to be missing, which is not conducive to the normal progress of subsequent processes. Summary of the invention

[0004] In order to solve the problems of low etching rate, unclean etching and long etching time in table top hole etching in the existing type II superlattice infrared detector preparation process, the present invention proposes a table top hole etching method for a type II superlattice infrared detector.

[0005] The technical solution adopted by the present invention is: a table opening etching method for a type II superlattice infrared detector, comprising the following steps:

[0006] Step 1, the first opening photolithography: depositing a layer of photoresist on the epitaxial layer of the infrared detector, and then performing the first opening photolithography to form a patterned photoresist;

[0007] Step 2, mask layer deposition: depositing an inorganic mask layer on the entire surface of the epitaxial layer, at which point a small amount of deposit will be formed above the patterned photoresist;

[0008] Step 3, second hole opening photolithography: developing at a position outside the patterned photoresist to obtain a developed patterned photoresist;

[0009] Step 4, second hole etching & cleaning and degumming: Based on the previous step of photolithography, the deposits are removed by etching; after the etching is completed, the patterned photoresist and the developed patterned photoresist are removed together to form a patterned inorganic mask layer;

[0010] Step 5, mesa photolithography: forming a mesa patterned photoresist on the patterned inorganic mask layer by photolithography;

[0011] Step 6, mask layer etching: forming a mesa pattern on the patterned inorganic mask layer by etching, and cleaning to remove the mesa patterned photoresist after the etching is completed;

[0012] Step 7, mesa etching: etching the epitaxial layer to form a patterned epitaxial layer under the patterned inorganic mask layer;

[0013] Step 8, third hole photolithography & passivation layer deposition: fill the holes of the inorganic mask layer with photoresist; then deposit the inorganic passivation layer on the entire surface;

[0014] Step 9, the fourth hole photolithography: apply photoresist to the remaining positions outside the mesa hole;

[0015] Step 10, the fourth hole etching: etching the inorganic passivation layer in the area inside the mesa hole to expose the filling photoresist in the hole;

[0016] Step 11, cleaning and degumming: remove the filling photoresist and the coating photoresist by cleaning.

[0017] The thickness of the patterned photoresist is consistent with the thickness of the inorganic mask layer.

[0018] The etching process in step 4, step 6 and step 10 adopts dry etching or wet etching.

[0019] In step 7, the epitaxial layer is etched using an ICP etching process.

[0020] The material of the inorganic mask layer is SiO2 or SiN x .

[0021] In step 8, an inorganic passivation layer is deposited on the entire surface by chemical vapor deposition or atomic layer deposition.

[0022] In step 2, an inorganic mask layer is deposited on the entire surface by chemical vapor deposition, so that the inorganic mask layer covers the entire epitaxial layer.

[0023] The thickness of the filling photoresist in step 8 is consistent with the thickness of the inorganic mask layer.

[0024] The thickness of the inorganic mask layer is ≥1um, and the thickness of the inorganic passivation layer is ≤200nm.

[0025] The epitaxial layer adopts type II superlattice material.

[0026] The beneficial effects of the present invention compared with the prior art are as follows: before depositing the inorganic mask layer, the present invention applies photoresist at the opening position, and forms an opening structure in advance inside the inorganic mask layer by combining dry etching and cleaning and degumming for a relatively short time in the early stage. Subsequently, only a thin inorganic passivation layer needs to be etched for the opening, thereby greatly shortening the time required for the opening etching, avoiding the problem of incomplete etching of the inorganic mask layer due to the slow etching rate in the hole, and avoiding the problem that the photoresist in the remaining area outside the mesa hole cannot maintain its original shape due to a long etching time, thereby causing the mesa inorganic mask layer under the photoresist to be missing, which is not conducive to the normal progress of the subsequent process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings:

[0028] Figure 1 This is the schematic diagram after step 1 is completed;

[0029] Figure 2 This is the schematic diagram after step 2 is completed;

[0030] Figure 3 This is the schematic diagram after step 3 is completed;

[0031] Figure 4 This is the schematic diagram after step 4 is completed;

[0032] Figure 5 This is the schematic diagram after step 5 is completed;

[0033] Figure 6 This is the schematic diagram after step 6 is completed;

[0034] Figure 7 This is the schematic diagram after step 7 is completed;

[0035] Figure 8 This is the schematic diagram after step 8 is completed;

[0036] Fig. 9 This is a schematic diagram after step 9 is completed;

[0037] Fig.10 This is a schematic diagram after step 10 is completed;

[0038] Fig.11 This is a schematic diagram after step 11 is completed;

[0039] In the figure: 1 is an epitaxial layer, 2 is a patterned photoresist, 21 is a developed patterned photoresist, 22 is a mesa patterned photoresist, 23 is a filling photoresist, 24 is a coating photoresist, 3 is an inorganic mask layer, 31 is a deposit, and 4 is an inorganic passivation layer. DETAILED DESCRIPTION

[0040] like Figures 1 to 11 As shown, the present invention provides a table opening etching method for a type II superlattice infrared detector, wherein a photoresist is coated on the opening position before depositing the inorganic mask layer 3, and an opening structure is formed in advance inside the inorganic mask layer 3 by combining a relatively short period of dry etching and cleaning and de-gumming. In the subsequent process, there is no need to perform dry etching on the table hole, thereby avoiding a series of problems caused by a low etching rate in the hole or a long etching time due to a thick inorganic mask layer 3.

[0041] The specific implementation steps of the present invention are as follows:

[0042] Step 1, the first hole opening photolithography: a layer of photoresist is deposited on the epitaxial layer 1 of the infrared detector, and then the first hole opening photolithography is performed, the purpose of which is to develop in the center area of ​​the table (the table opening position of the normal process) to form a patterned photoresist 2, and the finished effect is as follows Figure 1 As shown;

[0043] Step 2, mask layer deposition: deposit an inorganic mask layer 3 on the epitaxial layer 1, and the entire epitaxial layer 1 can be covered by chemical vapor deposition. The main material of the inorganic mask layer 3 is SiO2 or SiN x The thickness of the inorganic mask layer 3 is consistent with the thickness of the patterned photoresist 2. Since the deposition method is full-surface deposition, a small amount of sediment 31 will be formed on the patterned photoresist 2. The deposition is completed as shown in FIG. Figure 2 As shown;

[0044] Step 3, second hole opening photolithography: developing at the position outside the patterned photoresist 2 to obtain the developed patterned photoresist 21, and the effect after the development is as follows: Figure 3 As shown;

[0045] Step 4, second hole etching & cleaning and degumming: Based on the previous step of photolithography, dry or wet etching is performed to remove the deposit 31; after the etching is completed, cleaning and degumming are performed. At this time, the top of the photoresist is exposed, so the patterned photoresist 2 and the developed patterned photoresist 21 can be removed together. After the degumming is completed, the effect is as follows: Figure 4 As shown, a patterned inorganic mask layer 3 is formed at this time;

[0046] Step 5, mesa photolithography: a mesa patterned photoresist 22 is formed on the patterned inorganic mask layer 3 by photolithography, and the effect is as follows: Figure 5 As shown;

[0047] Step 6, mask layer etching: a mesa pattern is formed on the patterned inorganic mask layer 3 by dry or wet etching, and after the etching is completed, the mesa patterned photoresist 22 is removed by cleaning. The effect of removing the photoresist is as follows: Figure 6 As shown;

[0048] Step 7, mesa etching: The epitaxial layer 1 is etched by an inductively coupled plasma (ICP) etching process to form a patterned epitaxial layer 1 below the patterned inorganic mask layer 3. After the etching is completed, the effect is as follows: Figure 7 As shown;

[0049] Step 8, third hole photolithography & passivation layer deposition: fill the holes of the inorganic mask layer 3 with photoresist 23 to flatten the table surface for subsequent etching; deposit the inorganic passivation layer 4 on the entire surface by chemical vapor deposition or atomic layer deposition, and the effect is as follows: Figure 8 As shown;

[0050] Step 9, the fourth hole photolithography: the photoresist 24 is applied to the remaining positions outside the mesa hole. The effect after coating is as follows Fig. 9 As shown;

[0051] Step 10, the fourth hole etching: dry or wet etching is performed on the area inside the mesa hole. Since the photoresist 23 is filled in the hole of the inorganic mask layer 3 in advance, the inorganic passivation layer 4 in the hole is raised, and the etching rate is less affected. In addition, since the inorganic passivation layer 4 is thin (thickness ≈ 200nm), much smaller than the inorganic mask layer 3 (thickness ≥ 1um), the required etching time is short, which will not affect the photoresist and thus have an adverse effect on the subsequent process. After the etching is completed, the effect is as follows: Fig.10 As shown;

[0052] Step 11, cleaning and degumming: The filling photoresist 23 and the coating photoresist 24 are removed by cleaning. The degumming effect is as follows: Fig.11 As shown; the subsequent process is no different from the normal process, so it will not be described in detail.

[0053] Different from the traditional process, after the table etching is completed, the hole etching is performed. The traditional process needs to etch the inorganic mask layer 3 (thickness ≥ 1um) + inorganic passivation layer 4 (thickness ≈ 200nm) in one step, and because the etching rate in the hole is relatively low, the etching time required for the overall hole etching is relatively long, which has an adverse effect on the photoresist, causing the table inorganic mask layer 3 to be missing, affecting the subsequent process; in addition, the low etching rate in the hole will also cause the inorganic mask layer 3 in the hole to be not etched cleanly, affecting the subsequent normal test. The present invention adopts a new hole etching process, which completes the hole etching of the inorganic mask layer 3 by etching + cleaning and degumming before the table photolithography, and only the inorganic passivation layer 4 needs to be etched later, thereby shortening the time required for the hole etching.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for etching a table opening of a type II superlattice infrared detector, characterized in that: The following steps are involved: Step 1, first hole-opening photolithography: depositing a layer of photoresist on the epitaxial layer (1) of the infrared detector, and then performing the first hole-opening photolithography to form a patterned photoresist (2); Step 2, mask layer deposition: depositing an inorganic mask layer (3) on the entire surface of the epitaxial layer (1), and a small amount of sediment (31) is formed on the patterned photoresist (2); Step 3, second hole opening photolithography: developing at a position outside the patterned photoresist (2) to obtain a developed patterned photoresist (21); Step 4, second hole etching & cleaning and degumming: based on the previous photolithography step, the deposit (31) is removed by etching; after the etching is completed, cleaning is performed to remove the patterned photoresist (2) and the developed patterned photoresist (21) together to form a patterned inorganic mask layer (3); Step 5, mesa photolithography: forming a mesa patterned photoresist (22) on the patterned inorganic mask layer (3) and above the holes of the inorganic mask layer (3) by photolithography; Step 6, mask layer etching: forming a mesa pattern on the patterned inorganic mask layer (3) by etching, and after the etching is completed, cleaning to remove the mesa patterned photoresist (22); Step 7, mesa etching: etching the epitaxial layer (1) to form a patterned epitaxial layer (1) below the patterned inorganic mask layer (3); Step 8, third hole photolithography & passivation layer deposition: fill the holes of the inorganic mask layer (3) with photoresist (23); then deposit the inorganic passivation layer (4) on the entire surface; Step 9, fourth hole opening photolithography: coating the remaining positions outside the mesa hole with photoresist (24); Step 10, the fourth hole etching: etching the inorganic passivation layer (4) in the area inside the mesa hole, so that the filling photoresist (23) in the hole is exposed; Step 11: Cleaning and degumming: removing the filling photoresist (23) and the coating photoresist (24) by cleaning.

2. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: The thickness of the patterned photoresist (2) is consistent with the thickness of the inorganic mask layer (3).

3. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: The etching process in step 4, step 6 and step 10 adopts dry etching or wet etching.

4. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: In step 7, the epitaxial layer (1) is etched using an ICP etching process.

5. The method for etching a table opening of a type II superlattice infrared detector according to claim 2, characterized in that: The material of the inorganic mask layer (3) is SiO2 or SiN x .

6. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: In step 8, an inorganic passivation layer (4) is deposited on the entire surface by chemical vapor deposition or atomic layer deposition.

7. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: In step 2, an inorganic mask layer (3) is deposited on the entire surface by chemical vapor deposition, so that the inorganic mask layer (3) covers the entire epitaxial layer (1).

8. The method for etching a table opening of a type II superlattice infrared detector according to claim 6, characterized in that: The thickness of the filling photoresist (23) in step 8 is consistent with the thickness of the inorganic mask layer (3).

9. The method for etching a table opening of a type II superlattice infrared detector according to claim 1, characterized in that: The thickness of the inorganic mask layer (3) is ≥1 um, and the thickness of the inorganic passivation layer (4) is ≤200 nm.

10. A method for etching a table opening of a type II superlattice infrared detector according to any one of claims 1 to 9, characterized in that: The epitaxial layer (1) adopts type II superlattice material.

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