A novel method for preparing a second-class superlattice infrared detector

Abstract

The invention provides a method for preparing a novel type II superlattice infrared detector, belonging to the field of infrared detectors; it solves the problem that the inorganic film layer of the current type II superlattice infrared detector usually contains large stress and is prone to cracks; it comprises the following steps: depositing an inorganic mask layer on an epitaxial layer; coating a photoresist on the inorganic mask layer, and developing to form a patterned photoresist; etching the inorganic mask layer to form a through-hole structure; forming a table patterned photoresist on the inorganic mask layer of the through-hole structure; forming a table pattern on the inorganic mask layer of the through-hole structure; etching the epitaxial layer, and forming a patterned epitaxial layer below the inorganic mask layer of the through-hole structure; depositing an inorganic passivation layer; performing photolithography or etching to open a hole on the table, and etching the inorganic mask layer and the inorganic passivation layer of the through-hole structure; the invention is used for preparing an infrared detector.

Description

Technical Field

[0001] The invention provides a method for preparing a novel second-type superlattice infrared detector, belonging to the technical field of infrared detectors. Background Art

[0002] Superlattice infrared detector is a photovoltaic infrared detector based on superlattice semiconductor materials. 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 alternately grown 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. The concept of InAs / GaSb type II superlattice (T2SL) was proposed in the 1970s and is one of the preferred materials for infrared detectors, especially for long-wave, very long-wave and multi-color infrared detection. When the valence band of one material is lower than the valence band of the other material, that is, when the energy bands of the two materials are staggered, a type II structure is formed. InAs / GaSb is a type II superlattice, which is formed by the alternating growth of InAs and GaSb for several periods to form a one-dimensional periodic structure. The conduction band and valence band of InAs and GaSb are completely staggered, where InAs is an electron potential well and GaSb is a hole potential well, and electrons and holes are confined in the two materials respectively. InAs / GaSb type II superlattice belongs to direct bandgap materials. The delocalization of electron wave functions in the superlattice can achieve normal incidence absorption without adding an additional grating. Therefore, compared with quantum well or quantum dot infrared detectors, InAs / GaSb type II superlattice detectors have simpler structures and higher quantum efficiency. InAs / GaSb type II superlattice infrared detectors have the following advantages. First, the energy band is adjustable (0-0.8eV), and the detection band of its infrared detector ranges from 1μm to 30μm, covering the three "atmospheric windows" bands of 1-3μm, 3-5μm and 8-14μm; low Auger recombination rate; and large effective mass. Type II superlattice materials are usually grown by molecular beam epitaxy (MBE), and the material uniformity is high. By using lattice-matched and commercially available GaSb substrates, large-area, uniform type II superlattice materials can be grown, making it easy to prepare large-array infrared detectors. Based on the above advantages, type II superlattice has unique advantages in the preparation of long-wave and very long-wave infrared detectors, and is therefore the preferred material for the preparation of a new generation of infrared detectors.

[0003] However, the hard mask and passivation layer of the current type II superlattice infrared detector are both inorganic layers SiO 2 or SiN x , the inorganic film layer usually contains large stress and is prone to cracks, which in turn leads to a significant increase in the risk of splitting in subsequent processes. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention proposes a novel method for preparing a type II superlattice infrared detector. By designing the inorganic film layer as a through-hole structure, the internal stress of the inorganic mask layer and the inorganic passivation layer can be released, thereby greatly reducing the risk of subsequent process cracking caused by film layer cracking due to excessive film layer stress.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a novel type II superlattice infrared detector, comprising the following steps:

[0006] S1: Mask layer deposition: depositing an inorganic mask layer on the epitaxial layer of the infrared detector;

[0007] S2: Mask layer lithography: coating photoresist on the inorganic mask layer and developing it at specific positions to form a patterned photoresist;

[0008] S3: Mask layer through hole etching: etching is performed on the inorganic mask layer to form a through hole structure, and after the etching is completed, cleaning is performed to remove the photoresist;

[0009] S4: mesa lithography: forming a mesa patterned photoresist on the inorganic mask layer of the through-hole structure;

[0010] S5: mask layer mesa etching: forming a mesa pattern on the inorganic mask layer of the through-hole structure, and cleaning and removing the photoresist after the etching is completed;

[0011] S6: epitaxial layer mesa etching: etching the epitaxial layer to form a patterned epitaxial layer below the inorganic mask layer of the through-hole structure;

[0012] S7: passivation layer deposition: depositing an inorganic passivation layer;

[0013] S8: Passivation opening: perform photolithography or etching opening on the table, etch the inorganic mask layer and inorganic passivation layer of the through-hole structure, and ensure that the number of through-holes outside the table of the inorganic mask layer is ≥1;

[0014] Then, indium pillars are prepared and interconnected to obtain a second type of superlattice infrared detector.

[0015] Further, the step of forming the passivation opening in step S8 can be replaced by the following steps:

[0016] S9: performing etching on the inorganic passivation layer deposited in step S7, and etching an opening on the mesa of the inorganic passivation layer;

[0017] S10: After the etching is completed, continue to cover the second inorganic passivation layer to form a pore structure in the inorganic passivation layer.

[0018] Furthermore, before the preparation of the indium pillar in step S8, the method further includes step S11: filling the through-hole structure of the inorganic mask layer with liquid organic material or a material with high tensile strength, and then solidifying it.

[0019] Furthermore, the method further comprises step S12: filling the through-hole structure of the inorganic mask layer or the pore structure of the inorganic passivation layer or the through-hole structure of the inorganic mask layer and the pore structure of the inorganic passivation layer with liquid organic material or a material with high tensile strength, and then curing the liquid organic material.

[0020] Furthermore, the etching depth in step S3 is ≥ 1 / 2 of the thickness of the mask layer, and the etching depth is < the thickness of the mask layer.

[0021] Furthermore, the epitaxial layer uses two types of superlattice materials;

[0022] The inorganic mask layer and inorganic passivation layer are both made of SiO 2 or SiN x Material.

[0023] Furthermore, in step S1, the inorganic mask layer covers the entire epitaxial layer by chemical vapor deposition.

[0024] Furthermore, in steps S3 and S5, dry or wet etching is used to form the through-hole structure of the inorganic mask layer and the mesa pattern of the inorganic mask layer.

[0025] Furthermore, in step S7, an inorganic passivation layer is deposited on the entire surface by chemical vapor deposition or atomic layer deposition.

[0026] Furthermore, in step S6, ICP is used to etch the epitaxial layer.

[0027] The beneficial effects of the present invention compared to the prior art are as follows: the present invention effectively releases the internal stress of the inorganic mask layer through a special inorganic mask layer through-hole structure without affecting subsequent processes, and at the same time, the stress of the inorganic passivation layer can also be released through the through-hole structure, thereby greatly reducing the risk of subsequent process cracking caused by film layer cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] Figure 1 A schematic diagram showing that the deposition of the mask layer in step S1 is completed;

[0030] Figure 2 This is a schematic diagram of the completion of the mask layer photolithography in step S2;

[0031] Figure 3 It is a schematic diagram of etching a through hole on the mask layer after removing the resist in step S3;

[0032] Figure 4 It is a schematic diagram after the mesa is photoetched on the through hole of the mask layer in step S4;

[0033] Figure 5 This is a schematic diagram of the mask layer after etching and stripping in step S5;

[0034] Figure 6 This is a schematic diagram of the table after etching in step S6;

[0035] Figure 7 is a schematic diagram after the passivation layer is deposited in step S7;

[0036] Figure 8 This is a schematic diagram of the step S8 after the passivation hole is opened;

[0037] Fig. 9 This is a schematic diagram of the process after passivation in step S9 of Example 2 is transformed into deposition etching and opening;

[0038] Fig.10 This is a schematic diagram of the second embodiment after step S10 of covering the second layer of inorganic passivation;

[0039] Fig.11 This is a schematic diagram of the step S11 of the third embodiment after the through hole of the inorganic mask layer is filled with liquid organic material;

[0040] Fig.12 This is a schematic diagram of the fourth embodiment after step S12 of filling the through holes of the inorganic mask layer and the pore structure of the inorganic passivation layer with liquid organic material;

[0041] In the figure: 1 is an epitaxial layer, 2 is an inorganic mask layer, 3 is a photoresist, 4 is a mesa patterning photoresist, 5 is an inorganic passivation layer, and 6 is a liquid organic material. DETAILED DESCRIPTION

[0042] like Figures 1 to 12 As shown, the present invention provides a novel method for preparing a second type of superlattice infrared detector, for SiO 2 or SiN x The inorganic mask layer 2 of the material is structurally designed. By etching multiple regular through-hole structures inside the inorganic mask layer 2, the through-holes are distributed below the table positions, and there is no through-hole design at the isolation groove positions between the table tops. This can effectively release the internal stress of the inorganic mask layer 2 and reduce the risk of cracking.

[0043] The present invention will be further described below based on specific embodiments.

[0044] Embodiment 1

[0045] The present invention provides a novel method for preparing a second type of superlattice infrared detector, comprising the following steps:

[0046] S1: Mask layer deposition: Deposit an inorganic mask layer 2 on the epitaxial layer 1 of the infrared detector. The entire epitaxial layer 1 can be covered by chemical vapor deposition. The main material of the inorganic mask layer 2 is SiO 2 or SiN x , the deposition effect is as follows Figure 1 As shown;

[0047] S2: Mask layer photolithography: Coat photoresist 3 on the inorganic mask layer 2, and develop it at a specific position to form a patterned photoresist 3. The effect is as follows: Figure 2 As shown;

[0048] S3: Mask layer through hole etching: dry or wet etching is used to form an inorganic mask layer 2 of a through hole structure, the etching depth is ≥ 1 / 2 of the mask layer thickness, and the etching depth is less than the mask layer thickness. After the etching is completed, the photoresist 3 is cleaned and removed. The effect of the de-bonding is as follows: Figure 3 As shown;

[0049] S4: Terrain photolithography: Terrain patterned photoresist 4 is formed on the inorganic mask layer 2 of the through-hole structure by photolithography. At this time, the through-hole is directly below the terrace. The effect is as follows: Figure 4 As shown;

[0050] S5: Mask layer mesa etching: A mesa pattern is formed on the inorganic mask layer 2 of the through-hole structure by dry or wet etching. After the etching is completed, the photoresist 3 is removed by cleaning. The effect of removing the photoresist is as follows: Figure 5 As shown;

[0051] S6: Etching of epitaxial layer mesa: The epitaxial layer 1 is etched by ICP to form a patterned epitaxial layer 1 under the inorganic mask layer 2 of the through-hole structure. After the etching is completed, the effect is as follows Figure 6 As shown;

[0052] S7: Deposition of passivation layer: Deposition of inorganic passivation layer 5 on the entire surface by chemical vapor deposition or atomic layer deposition, and the effect is as follows Figure 7 As shown;

[0053] S8: Passivation hole opening: Perform photolithography or etching hole opening on the table, and etch the inorganic mask layer 2 and inorganic passivation layer 5 of the through-hole structure to ensure that the number of through-holes outside the table of the inorganic mask layer 2 is ≥ 1. After the hole etching is completed, the effect is as follows: Figure 8 As shown; the subsequent process is no different from the normal process, so it will not be described in detail.

[0054] Embodiment 2

[0055] The process of steps S1-S7 of this embodiment is completely consistent with that of the first embodiment. The difference is that in this embodiment, on the basis of the inorganic mask layer 2 of the through-hole structure, the inorganic passivation layer 5 is designed to be a pore stress release structure, which also achieves the stress release effect. The specific implementation steps are as follows:

[0056] S9: First deposit an inorganic passivation layer 5, and then etch to achieve Fig. 9 Effect, an opening is etched in the inorganic passivation layer 5 on the mesa;

[0057] S10: After the etching is completed, the second inorganic passivation layer 5 is continued to be covered, and finally the inorganic passivation layer 5 of the pore stress release structure is as follows Fig.10 As shown, a pore structure is provided in the middle of the inorganic passivation layer 5 , and the stress of the inorganic passivation layer 5 is released through the pore structure.

[0058] Embodiment 3

[0059] The process of steps S1 to S8 of this embodiment is completely consistent with that of the first embodiment, except that the through hole of the inorganic mask layer 2 formed in step S8 of this embodiment is filled with liquid organic material 6 or other filling materials with high tensile strength. The specific implementation steps are as follows:

[0060] S11: filling the through-hole structure of the inorganic mask layer 2 with liquid organic material 6, and after curing, the effect of relieving stress can also be achieved. The effect after the through-hole structure is filled is as follows: Fig.11 shown.

[0061] Embodiment 4

[0062] The steps of obtaining the pore structure of the inorganic passivation layer 5 in this embodiment are completely consistent with those in the second embodiment. The difference is that the pore structure of the inorganic passivation layer 5 and / or the through-hole structure of the inorganic mask layer 2 formed in step S10 in this embodiment are filled with liquid organic material 6 or other filling materials with high tensile strength. The specific implementation steps are as follows:

[0063] S12: Filling the through-hole structure of the inorganic mask layer 2, or the pore structure of the inorganic passivation layer 5, or the through-hole structure of the inorganic mask layer 2 and the pore structure of the inorganic passivation layer 5 with liquid organic material 6, after curing, can also achieve the effect of relieving stress. The effect after the through-hole structure and the pore structure are fully filled on the basis of the second embodiment is as follows: Fig.12 shown.

[0064] In addition, the inside of the through-hole structure of the inorganic mask layer 2 may be filled separately, and the inside of the pore structure of the inorganic passivation layer 5 may be filled separately, but the separate filling is not illustrated.

[0065] The present invention designs an inorganic mask layer 2 that can release stress to have a through-hole structure, which is different from the traditional inorganic mask layer 2 and can effectively release the internal stress of the inorganic film layer 2; it also designs an inorganic passivation layer 5 that can release stress to have a pore structure, which is different from the traditional inorganic passivation layer 5 and can effectively release the internal stress of the inorganic film layer 5, thereby improving the integrity of the chip in subsequent processes.

[0066] 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 preparing a novel type II superlattice infrared detector, characterized in that: The following steps are involved: S1: Mask layer deposition: depositing an inorganic mask layer on the epitaxial layer of the infrared detector; S2: Mask layer lithography: coating photoresist on the inorganic mask layer and developing it at specific positions to form a patterned photoresist; S3: Mask layer through hole etching: etching is performed on the inorganic mask layer to form a through hole structure, and after the etching is completed, cleaning is performed to remove the photoresist; S4: mesa lithography: forming a mesa patterned photoresist on the inorganic mask layer of the through-hole structure, and the through-hole is directly below the mesa; S5: mask layer mesa etching: forming a mesa pattern on the inorganic mask layer of the through-hole structure, and cleaning and removing the photoresist after the etching is completed; S6: epitaxial layer mesa etching: etching the epitaxial layer to form a patterned epitaxial layer below the inorganic mask layer of the through-hole structure; S7: passivation layer deposition: depositing an inorganic passivation layer; S8: Passivation opening: perform photolithography or etching opening on the table, etch the inorganic mask layer and inorganic passivation layer of the through-hole structure, and ensure that the number of through-holes outside the table of the inorganic mask layer is ≥1; Then, indium pillars are prepared and interconnected to obtain a second type of superlattice infrared detector.

2. The method for preparing a novel type II superlattice infrared detector according to claim 1, characterized in that: The step of forming the passivation opening in step S8 can be replaced by the following steps: S9: performing etching on the inorganic passivation layer deposited in step S7, and etching an opening on the mesa of the inorganic passivation layer; S10: After the etching is completed, continue to cover the second inorganic passivation layer to form a pore structure in the inorganic passivation layer.

3. The method for preparing a novel type II superlattice infrared detector according to claim 1, characterized in that: Before the indium pillar preparation in step S8, the method further includes step S11: filling the through-hole structure of the inorganic mask layer with liquid organic material, and then curing the liquid organic material.

4. The method for preparing a novel type II superlattice infrared detector according to claim 2, characterized in that: The method further comprises step S12: filling the through-hole structure of the inorganic mask layer or the pore structure of the inorganic passivation layer or the through-hole structure of the inorganic mask layer and the pore structure of the inorganic passivation layer with liquid organic material, and then curing the liquid organic material.

5. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: The etching depth in step S3 is ≥ 1 / 2 of the thickness of the mask layer, and the etching depth is < the thickness of the mask layer.

6. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: The epitaxial layer uses two types of superlattice materials; Inorganic mask layer and inorganic passivation layer are made of SiO2 or SiN x Material.

7. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: Step S1: using chemical vapor deposition to make the inorganic mask layer cover the entire epitaxial layer.

8. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: In steps S3 and S5, dry or wet etching is used to form the through-hole structure of the inorganic mask layer and the mesa pattern of the inorganic mask layer.

9. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: In step S7, an inorganic passivation layer is deposited on the entire surface by chemical vapor deposition or atomic layer deposition.

10. A method for preparing a novel type II superlattice infrared detector according to claim 3 or 4, characterized in that: In step S6, the epitaxial layer is etched by ICP.

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