A preparation method of a type-II superlattice infrared detector for optimizing mesa fabrication

Abstract

The present invention provides a method for fabricating a type-II superlattice infrared detector with optimized mesa fabrication, belonging to the technical field of infrared detector fabrication; the method includes the following steps: First, a buffer layer and a first ohmic contact layer are sequentially and uniformly grown above a substrate; an insulating definition layer is grown above the first ohmic contact layer; after the growth of the definition layer is completed, a Mask is adsorbed above the position of the definition layer, and the opening position of the Mask is the mesa range defined by the definition layer; corresponding film layers are sequentially grown as required; a passivation layer is grown; subsequently, passivation opening, gold electrodes, indium electrodes, and flip-chip interconnection are carried out according to conventional processes to obtain an infrared detector; the present invention can avoid mesa etching, thereby avoiding material damage caused by dry etching and wet etching, and further improving device performance.

Description

Technical Field

[0001] The invention provides a method for preparing a type II superlattice infrared detector with optimized table surface production, belonging to the technical field of infrared detector preparation. Background Art

[0002] For the mesa etching process, both dry etching and wet etching have their own advantages and disadvantages. Dry etching, currently the industry usually uses ICP dry etching technology to 2 For mesa etching of hard mask, inert gas Ar is used as carrier gas in ICP, and chlorine-based plasma is used as main etching gas, where Cl 2 The molecules collide with high-speed electrons and break down to produce Cl atoms, which diffuse to the surface of the material and react with the material to produce InCl x 、AsCl 3 、GaCl 3 and SbCl 3 Add CH to the etching gas 4 / H 2 , making the etching process stable and the surface of the etched material smoother. Dry etching has the advantages of isotropy, high uniformity, good controllability and high pattern transfer, but it will inevitably cause physical damage to the surface and sidewalls of the material. Wet etching, currently more commonly used is phosphoric acid / citric acid / hydrogen peroxide (H 3 PO 4 / C 6 H 8 O 7 / H 2 O 2 ) mixed solution is used to etch the superlattice material. The principle is that hydrogen peroxide is used as an oxidant to oxidize the material, phosphoric acid reacts with the oxide to form a complex, and citric acid dissolves these complexes to prevent them from adhering to the side wall of the material, thereby achieving the purpose of high-quality etching. However, wet etching inevitably causes drilling at the bottom of the mesa, and citric acid has obvious crystal orientation selectivity for InAs materials, and "collapse" will occur in InAs / InAsSb materials with a higher InAs component and long-wave InAs / GaSb materials. It can be seen that whether it is dry etching or wet etching, the device will be damaged to a greater or lesser extent, and the problem affecting mesa etching needs to be solved urgently. Summary of the invention

[0003] In order to overcome the deficiencies in the prior art, the present invention proposes a method for preparing a type II superlattice infrared detector with optimized table production, which can avoid table etching and thus avoid material damage caused by dry etching and wet etching, thereby improving device performance.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a type II superlattice infrared detector with optimized table production, comprising the following steps:

[0005] 1) First, a buffer layer and a first ohmic contact layer are uniformly grown in sequence on the substrate;

[0006] 2) growing an insulating definition layer above the first ohmic contact layer;

[0007] 3) After the definition layer is grown, a mask is adsorbed above the definition layer. The opening position of the mask is the table range defined by the definition layer.

[0008] 4) Grow corresponding film layers in sequence as needed;

[0009] 5) Growth of passivation layer;

[0010] 6) Subsequently, conventional processes are used to passivate holes, form gold electrodes, indium electrodes, and flip-chip interconnects to obtain an infrared detector.

[0011] After step 4) is completed, the mask is removed and the subsequent steps are performed. Since the function of the mask is to limit the subsequent epitaxial material film layer of the first ohmic contact layer, the mask can be removed after the epitaxial material film layer growth is completed.

[0012] The definition layer is made of organic insulating material.

[0013] The definition layer is used to determine the range of mesa growth. The definition layer is provided with openings, and the positions of the openings in the definition layer are the range of mesa growth.

[0014] The mask is also provided with openings, and the shape of the openings of the mask is consistent with the shape of the openings of the definition layer.

[0015] The mask is adsorbed on the definition layer through a magnet array.

[0016] The Mask uses a precision metal mask, which is generally made of Invar alloy (iron-nickel alloy) or other materials with low thermal expansion coefficient to ensure that it will not deform during the process.

[0017] The film layers grown sequentially in step 4) include an M-type barrier layer, an absorption region, a second ohmic contact layer and a cap layer.

[0018] The substrate adopts type II superlattice material.

[0019] The passivation layer is made of SiO 2 or Si 3 N 4 Material.

[0020] The beneficial effects of the present invention compared to the prior art are as follows: the present invention grows the mesa through the shape of the insulating definition layer and the Mask, and the width of the definition layer depends on the process capability. Compared with the width of the isolation groove between the current mesas, the width of the definition layer is obviously smaller, thereby increasing the effective mesa area that can absorb infrared wavelengths, improving the light response of the infrared detector, and improving the device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings:

[0022] Figure 1 This is a schematic diagram of the hierarchical structure of the present invention when it is prepared;

[0023] Figure 2 is a shape diagram of the Mask in Embodiment 1 of the present invention;

[0024] Figure 3 is a shape diagram of the Mask in Embodiment 2 of the present invention;

[0025] Figure 4 is a shape diagram of the Mask in Embodiment 3 of the present invention;

[0026] In the figure: 1 is a substrate, 2 is a buffer layer, 3 is a first ohmic contact layer, 4 is an M-type barrier layer, 5 is an absorption region, 6 is a second ohmic contact layer, 7 is a cap layer, 8 is a definition layer, and 9 is a mask. DETAILED DESCRIPTION

[0027] like Figures 1 to 4 As shown, the present invention provides a method for preparing a type II superlattice infrared detector with optimized table production, which is mainly to change and optimize the growth morphology of epitaxial materials. At present, the epitaxial material growth in the industry is an overall uniform growth, followed by table etching, hole opening, gold electrode growth, indium electrode growth, slicing, flip-chip interconnection, glue dispensing, and polishing. When the epitaxial material grows, the present invention forms a "definition layer" on the substrate 1 in advance, and when the epitaxial material grows, a mask plate 9, i.e., Mask, is used to determine the growth position of the epitaxial material, and directly grow to form a table to avoid etching.

[0028] According to the following Figure 1 The method of the present invention is described in detail, comprising the following steps:

[0029] 1) First, a buffer layer 2 and a first ohmic contact layer 3 (P-type, N-type, etc. as required) are uniformly grown in sequence on the substrate 1. Since the first ohmic contact layer 3 needs to be connected to the lower electrode, it is not necessary to isolate each mesa, so the first ohmic contact layer 3 is uniformly grown as a whole.

[0030] 2) A definition layer 8 is grown on top of the first ohmic contact layer 3. The definition layer 8 is made of an organic insulating material, such as a polyimide film layer, which can ensure electrical insulation between the mesas. The function of the definition layer 8 is to determine the range of mesa growth. The definition layer 8 is provided with openings. The shape of the openings on the definition layer 8 is the shape of the mesa, which can be determined as needed. For example, it can be a square, diamond, circle, or other required shapes. In addition, since the definition layer 8 is insulating, the width between the two openings on the definition layer 8 can be reduced as much as possible within the process allowable range, thereby increasing the mesa area, increasing the effective area of ​​infrared detection, and increasing the signal input.

[0031] 3) After the definition layer 8 is grown, a mask is adsorbed above the definition layer 8. For example, a magnet array can be used to adsorb the mask on the protrusion of the definition layer 8 by magnetic force. The adsorption method is not limited. The tighter the mask and the definition layer 8 are adsorbed, the better. The function of the mask is to limit the growth range of the epitaxial material. The mask uses a fine metal mask (FMM for short). The opening position of the mask is the table range defined by the definition layer 8. That is, the opening shape of the mask is consistent with the opening shape of the definition layer 8.

[0032] 4) Other required film layers such as M-type barrier layer 4, absorption region 5, second ohmic contact layer 6, cap layer 7 are sequentially grown in the openings of the Mask as needed. The film layers are not limited here and can be grown as needed. The Mask can be removed after the growth is completed, and the growth of the mesa is completed.

[0033] 5) Then grow a passivation layer. The material of the passivation layer is not limited, and optional materials include SiO 2 、Si 3 N 4 The thickness of the passivation layer is not limited.

[0034] 6) Subsequently, conventional processes in the industry are followed to carry out passivation opening, gold electrode, indium electrode, flip-chip interconnection and other processes.

[0035] Example 1

[0036] like Figure 2 As shown, the opening shape of the Mask is a square, and the square is the growth range of the epitaxial material, that is, the mesa formed subsequently.

[0037] Example 2

[0038] like Figure 3 As shown, the opening shape of the Mask is circular, and the circle is the growth range of the epitaxial material, that is, the mesa formed subsequently.

[0039] Example 3

[0040] like Figure 4 As shown, the opening shape of the Mask is a rhombus, and the rhombus is the growth range of the epitaxial material, that is, the mesa formed subsequently.

[0041] The preparation method of the present invention eliminates the table etching process, avoids the side wall leakage current caused by etching the table, thereby increasing the signal-to-noise ratio and improving the device performance.

[0042] 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 type II superlattice infrared detector with optimized table production, characterized in that: The following steps are involved: 1) First, a buffer layer and a first ohmic contact layer are uniformly grown in sequence on the substrate; 2) growing an insulating definition layer on the first ohmic contact layer; the definition layer is used to determine the range of mesa growth, the definition layer is provided with openings, and the positions of the openings in the definition layer are the range of mesa growth; 3) After the definition layer is grown, a mask is adsorbed above the definition layer. The opening position of the mask is the table range defined by the definition layer. 4) Grow an M-type barrier layer, an absorption region, a second ohmic contact layer and a cap layer in the opening of the Mask in sequence as needed; 5) Growth of passivation layer; 6) Subsequently, conventional processes are used to passivate holes, form gold electrodes, indium electrodes, and flip-chip interconnects to obtain an infrared detector.

2. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 1, characterized in that: After step 4), remove the mask and proceed to the next steps.

3. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 2, characterized in that: The definition layer is made of organic insulating material.

4. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 1, characterized in that: The mask is also provided with openings, and the shape of the openings of the mask is consistent with the shape of the openings of the definition layer.

5. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 4, characterized in that: The mask is adsorbed on the definition layer through a magnet array.

6. The method for preparing a type II superlattice infrared detector with optimized table production according to any one of claims 1 to 5, characterized in that: The Mask adopts a precision metal mask.

7. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 6, characterized in that: The substrate adopts type II superlattice material.

8. The method for preparing a type II superlattice infrared detector with optimized table production according to claim 7, characterized in that: The passivation layer is made of SiO2 or Si3N4 material.

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