阅读说明：本技术 一种用于红外探测器小孔腐蚀的腐蚀液及方法 (Corrosive liquid and method for corrosion of infrared detector small hole ) 是由 黄立 李胜利 马占锋 高健飞 黄晟 罗学强 于 2021-06-22 设计创作，主要内容包括：本发明提供了一种用于红外探测器小孔腐蚀的腐蚀液,包括作为溶剂的水,以及溶于水中的溶质,所述溶质包括盐酸、醋酸和氯化锌。另外,本发明还提供了红外探测器小孔腐蚀方法,包括在衬底牺牲层上沉积硫化锌层,作为增透膜；在硫化锌层上沉积非晶硅层,作为红外透过层和硫化锌湿法腐蚀的硬掩模版；对非晶硅层进行光刻、干法刻蚀和去胶,得到释放孔前驱体；用上述腐蚀液对硫化锌层进行单片式湿法腐蚀,得到所需要的小孔。该发明以盐酸作为腐蚀剂,并在盐酸中引入水、醋酸和氯化锌分别作为稀释剂、缓冲剂和保护剂,有效避免了硫化锌湿法腐蚀过程中的浮胶现象,显著改善了硫化锌侧向钻蚀严重的问题,解决了微尺寸孔湿法腐蚀的难题。(The invention provides a corrosive liquid for corrosion of infrared detector pinholes, which comprises water as a solvent and solutes dissolved in the water, wherein the solutes comprise hydrochloric acid, acetic acid and zinc chloride. In addition, the invention also provides a pinhole corrosion method of the infrared detector, which comprises the steps of depositing a zinc sulfide layer on the substrate sacrificial layer to be used as an anti-reflection film; depositing an amorphous silicon layer on the zinc sulfide layer to be used as an infrared transmission layer and a hard mask plate for zinc sulfide wet corrosion; carrying out photoetching, dry etching and photoresist removal on the amorphous silicon layer to obtain a release hole precursor; and carrying out single-chip wet etching on the zinc sulfide layer by using the etching solution to obtain the required small holes. According to the invention, hydrochloric acid is used as a corrosive agent, and water, acetic acid and zinc chloride are respectively used as a diluent, a buffering agent and a protective agent in the hydrochloric acid, so that the floating phenomenon in the wet corrosion process of zinc sulfide is effectively avoided, the problem of serious lateral undercutting of zinc sulfide is remarkably improved, and the problem of wet corrosion of micro-size holes is solved.)

1. The corrosive liquid for corroding the small holes of the infrared detector is characterized by comprising water as a solvent and solutes dissolved in the water, wherein the solutes comprise hydrochloric acid, acetic acid and zinc chloride.

2. The corrosive liquid for infrared detector pinhole corrosion as claimed in claim 1, wherein the mass concentration of the hydrochloric acid is 36-38%, and the mass concentration of the acetic acid is not less than 99.8%.

3. The corrosive liquid for corroding pores of the infrared detector as claimed in claim 2, wherein the volume ratio of the hydrochloric acid, the water and the acetic acid is 5:4: 1-5: 5: 1.

4. The corrosive liquid for pinhole corrosion of an infrared detector as set forth in claim 1, wherein the concentration of said zinc chloride is 24.0-27.0 mol/L.

5. A pinhole corrosion method for an infrared detector is characterized by comprising the following steps:

s1, coating a substrate sacrificial layer on the substrate containing the device structure to be processed;

s2, depositing a zinc sulfide layer on the substrate sacrificial layer to serve as an antireflection film;

s3, depositing an amorphous silicon layer on the zinc sulfide layer to be used as a hard mask plate for corroding the infrared transmission layer and the zinc sulfide layer;

s4, carrying out photoetching, dry etching and photoresist removal on the amorphous silicon layer to obtain a release hole precursor;

s5, carrying out wet etching on the zinc sulfide layer by using the etching solution of any claim 1 to 4 to obtain the required small holes.

6. The pinhole etching method of claim 5 wherein the sacrificial substrate layer is a sacrificial polyimide layer with a thickness of 2.0-2.2 μm.

7. The pinhole etching method of claim 5 wherein said zinc sulfide layer has a thickness of 1.0 to 1.2 μm.

8. The pinhole etching method of an infrared detector as set forth in claim 5, wherein the thickness of said amorphous silicon layer is 100 to 150 nm.

9. The pinhole etching method of claim 5 wherein the diameter of the release hole precursor is 0.8 to 1.0 μm.

10. The method for etching a pinhole in an infrared detector according to claim 5, wherein the wet etching in step S5 is a monolithic wet etching, and the temperature of the etching solution is 30 ± 2 ℃.

Technical Field

The invention belongs to the technical field of infrared detector manufacturing, and particularly relates to a corrosive liquid and a method for corrosion of an infrared detector pore.

Background

The infrared detector works on the principle that a thermal signal generated by infrared radiation of a thermosensitive material is converted into an electric signal. The atmospheric environment is transparent to infrared rays of 3-5 microns and 8-14 microns, and the infrared detector manufactured by utilizing the two wave bands can clearly observe an object to be monitored at night or in weather such as rain, snow, sand, dust, heavy fog and the like.

The infrared detector belongs to MEMS devices, comprises a plurality of small holes and micro-bridges, and in order to enable the detector to exert the best performance and protect the micro-structures, the infrared detector must be packaged in a vacuum environment, and zinc sulfide is often required to be introduced to the packaging structure as an infrared antireflection film in the vacuum packaging process; the redundant zinc sulfide can be removed by hydrochloric acid wet etching. However, no matter the concentrated hydrochloric acid or the dilute hydrochloric acid is used, the glue floating phenomenon can occur in the wet corrosion process of the zinc sulfide, and the pattern structure is damaged; the severe lateral undercutting phenomenon is also generated due to the isotropic characteristic of wet etching, and the packaging effect is seriously affected when the characteristic line width is very small, so that the formula of the etching solution and the pinhole etching process need to be improved.

Disclosure of Invention

The invention aims to solve the problems that the existing infrared detector is easy to generate floating glue phenomenon due to small hole wet corrosion, damage a pattern structure and serious lateral underetching.

To this end, the invention provides an etchant for corrosion of infrared detector pinholes, which comprises water as a solvent, and solutes dissolved in the water, wherein the solutes comprise hydrochloric acid, acetic acid and zinc chloride.

Furthermore, the mass concentration of the hydrochloric acid is 36-38%, and the mass concentration of the acetic acid is not less than 99.8%.

Furthermore, the volume ratio of the hydrochloric acid to the water to the acetic acid is 5:4: 1-5: 5: 1.

Furthermore, the concentration of the zinc chloride is 24.0-27.0 mol/L.

In addition, the invention also provides a pinhole corrosion method of the infrared detector, which comprises the following steps:

s1, coating a substrate sacrificial layer on the substrate containing the device structure to be processed;

s2, depositing a zinc sulfide layer on the substrate sacrificial layer to serve as an antireflection film;

s3, depositing an amorphous silicon layer on the zinc sulfide layer to be used as a hard mask plate for corroding the infrared transmission layer and the zinc sulfide layer;

s4, carrying out photoetching, dry etching and photoresist removal on the amorphous silicon layer to obtain a release hole precursor;

and S5, performing wet etching on the zinc sulfide layer by using the etching solution to obtain the needed small holes.

Furthermore, the substrate sacrificial layer is a polyimide sacrificial layer, and the thickness of the polyimide sacrificial layer is 2.0-2.2 micrometers.

Furthermore, the thickness of the zinc sulfide layer is 1.0-1.2 μm.

Further, the thickness of the amorphous silicon layer is 100-150 nm.

Further, the diameter of the release hole precursor is 0.8-1.0 μm.

Furthermore, the wet etching in the step S5 adopts monolithic wet etching, and the temperature of the etching solution is 30 ± 2 ℃.

Compared with the prior art, the invention has the beneficial effects that:

(1) the corrosive liquid for corroding the small holes of the infrared detector, which is provided by the invention, takes hydrochloric acid as a corrosive agent, and introduces water, acetic acid and zinc chloride into the hydrochloric acid as a diluent, a buffering agent and a protective agent respectively, so that the problems of over-quick corrosion of zinc sulfide and serious lateral undercutting are effectively solved.

(2) According to the infrared detector pinhole corrosion method provided by the invention, the infrared transmission material amorphous silicon is introduced to serve as the zinc sulfide wet corrosion hard mask, so that infrared absorption is not influenced, and the phenomenon of floating glue in the wet corrosion process is effectively avoided.

(3) According to the infrared detector pinhole corrosion method provided by the invention, by optimizing the formula of the corrosion solution and combining a single-chip wet corrosion process, the cutting channel can be completely corroded, a good pinhole appearance can be obtained, and the corrosion factor F can reach 1.45.

The present invention will be described in further detail below with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic view of an infrared detector louver configuration;

FIG. 2 is a schematic diagram of a prior art zinc sulfide wet etching morphology;

FIG. 3 is a schematic diagram of a chemical reaction process for zinc sulfide corrosion using the corrosive liquid of the present invention;

FIG. 4 is a schematic view of a process for etching a pinhole in an infrared detector according to the present invention;

FIG. 5 is a diagram illustrating a structure of a product actually processed according to an embodiment of the present invention.

Description of reference numerals: 1. a substrate; 2. a device structure to be processed; 3. a substrate sacrificial layer; 4. a zinc sulfide layer; 5. an amorphous silicon layer; 6. releasing the pore precursor; 7. a small hole; 8. and a wet etching release hole.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

In order to solve the problems that the glue floating phenomenon occurs and the pattern structure is damaged in the existing zinc sulfide wet etching process, the embodiment adopts an infrared detector window structure as shown in fig. 1, and the infrared detector window structure mainly comprises a substrate sacrificial layer 3, a zinc sulfide layer 4, an amorphous silicon layer 5 and small holes 7; the zinc sulfide layer 4 is used as an anti-reflection film, the amorphous silicon layer 5 is used as an infrared transmission layer and a zinc sulfide corrosion hard mask, the small holes 7 are used for releasing the substrate sacrificial layer cleanly, and the infrared transmission material amorphous silicon is introduced to the zinc sulfide layer 4 and used as a zinc sulfide wet corrosion hard mask, so that infrared absorption is not influenced, and the floating glue phenomenon in the wet corrosion process is effectively avoided.

However, the adhesion of the zinc sulfide in contact with the substrate sacrificial layer 3 is lower than that of the zinc sulfide in contact with amorphous silicon, and after the zinc sulfide is subjected to wet etching by using traditional hydrochloric acid as an etching solution, wet etching release holes 8 with an inverted trapezoid structure are formed, as shown in fig. 2, which causes a serious problem of lateral underetching. In order to improve the phenomenon, the formula of the corrosive liquid needs to be optimized to reduce the etching rate of the zinc sulfide; through a large number of experiments, the corrosive liquid for corrosion of the infrared detector small hole provided by the embodiment is finally selected to comprise water as a solvent and solutes dissolved in the water, wherein the solutes comprise hydrochloric acid, acetic acid and zinc chloride.

Wherein, hydrochloric acid is used as a corrosive agent, acetic acid is used as a buffering agent, water plays a role in dilution, and zinc chloride is used as a protective agent; the reaction principle of using the corrosive liquid to carry out zinc sulfide wet etching is shown in fig. 3, a very thin solid-liquid reaction interface layer exists between a zinc sulfide interface and a corrosive liquid interface, and hydrochloric acid and zinc sulfide react to generate a large amount of hydrogen sulfide gas at the reaction interface layer, namely, the chemical equation 1: ZnS +2H⁺=H₂S↑+Zn²⁺The gas is attached to the surface of the zinc sulfide, so that the corrosion of hydrochloric acid on the zinc sulfide can be prevented. In addition, zinc chloride is a strong acid and weak base salt, and hydrolysis reaction occurs, i.e., chemical equation 2: 2H₂O+Zn²⁺=Zn(OH)₂↓+2H⁺. A large amount of zinc chloride is present in the interface layer, with the consumption of hydrochloric acid，H⁺The ion concentration is reduced, so that chemical equation 2 is promoted to move rightwards to generate insoluble zinc hydroxide, the zinc hydroxide is attached to the surface of zinc sulfide and has a protection effect on the zinc sulfide, and the corrosion process of hydrochloric acid on the zinc sulfide is slowed down to a certain extent; meanwhile, as shown in chemical equation 1, as the concentration of hydrochloric acid is gradually decreased as the reaction proceeds, the corrosion rate of the solution is also decreased, and acetic acid is used to provide H⁺And regulating the corrosion rate of the solution.

Preferably, the mass concentration of the hydrochloric acid is 36-38%, the mass concentration of the acetic acid is not less than 99.8%, the volume ratio of the hydrochloric acid to the water to the acetic acid is 5:4: 1-5: 5:1, the content of the hydrochloric acid is too high, the corrosion rate of zinc sulfide is too high, and the lateral undercutting of the small hole is serious; if the content of water and acetic acid is too high, the corrosion of zinc sulfide is slow, and the production efficiency is low. The concentration of the zinc chloride is 24.0-27.0 mol/L.

The technological process for processing the small hole of the infrared detector by using the corrosive liquid is shown in figure 4, and the specific process is as follows:

s1, coating a substrate sacrificial layer 3 on a substrate 1 containing a device structure 2 to be processed, wherein the thickness of the substrate sacrificial layer 3 is 2.0-2.2 mu m; the substrate sacrificial layer 3 is coated with glue and is subjected to photoetching to expose the substrate sacrificial layer 3 which does not need to be protected, the substrate sacrificial layer 3 which is not protected by the photoresist is removed through dry etching, and the glue is removed through wet cleaning to obtain the structure shown in fig. 4 (a); the substrate sacrificial layer 3 is a polyimide sacrificial layer, and the processes of gluing, photoetching, dry etching, wet cleaning and removing the glue and the like for the substrate sacrificial layer are all the prior art, and the specific operation process is not described herein again.

S2, depositing a zinc sulfide layer 4 as an antireflection film on the substrate sacrificial layer 3 having the structure shown in fig. 4 (a); through simulation, the thickness of the zinc sulfide layer 4 is 1.0-1.2 mu m, and the zinc sulfide layer 4 with the thickness range has good transmittance to infrared light of 8-12 mu m and can ensure good step coverage.

S3, depositing an amorphous silicon layer 5 on the zinc sulfide layer 4 as an ir-transparent layer and a hard mask for zinc sulfide etching, to obtain the structure shown in fig. 4 (b). Through simulation, when the thickness of the amorphous silicon layer 5 is less than 2.0 μm, the infrared transmittance of the amorphous silicon layer is equivalent to that of non-absorption silicon, and the amorphous silicon layer is not too thick as a hard mask, so that the thickness of the amorphous silicon layer 5 is preferably 100-150 nm.

S4, performing photolithography, dry etching and photoresist removal on the amorphous silicon layer 5 to obtain a release hole precursor 6, as shown in fig. 4 (c); the diameter of the release hole precursor 6 is 0.8-1.0 μm.

S5, the etching solution obtained in the above embodiment is used to perform single wafer wet etching on the structure obtained in step S4, so as to obtain the required pinhole 7. Wherein, the monolithic wet etching process is the prior art, and the specific operation process is not described herein again; during the etching process, the temperature of the etching solution is 30 +/-2 ℃.

Specifically, the wafer rotates at a high speed in the corrosion process, and zinc sulfide in the cutting path is quickly and cleanly corroded due to continuous washing of brand new acid liquor; the corrosive liquid in the release hole precursor 6 is slowly exchanged due to the existence of capillary phenomenon, and the zinc sulfide at the release hole precursor 6 is slowly corroded, so that the cutting channel can be completely corroded by optimizing the formula of the corrosive liquid and combining a single-chip wet etching process, and a good small hole shape can be obtained.

As shown in fig. 5, the product morphology structure diagram obtained by combining the etching solution formula of this embodiment with the single-wafer wet etching process is shown, where the etching solution formula is a formula in which the volume ratio of hydrochloric acid to water to acetic acid is 5:5:1, the concentration of zinc chloride is 25.0mol/L, the mass concentration of hydrochloric acid is 37%, and the mass concentration of acetic acid is 99.8%; meanwhile, in the single-chip wet etching process, the thickness of the zinc sulfide layer is 1.02 μm, after the etching is finished, the diameter of the release hole precursor 6 (shown in figure 5) is 0.98 μm through detection, and the diameter of the etched small hole is 2.38 μm, so that the lateral underetching amount of the zinc sulfide is 0.7 μm, and the corrosion factor of the small hole can reach 1.45 (the corrosion factor is the ratio of the corrosion depth to the lateral underetching depth, and generally the value is more than 1.0, so that the production can be realized), the problem of serious lateral underetching of the zinc sulfide in the existing small hole etching process is effectively solved, and the small hole shape with a large corrosion factor is obtained.

In conclusion, the corrosive liquid for corrosion of the infrared detector small hole provided by the invention takes hydrochloric acid as a corrosive agent, and water, acetic acid and zinc chloride are respectively taken as a diluent, a buffering agent and a protective agent in the hydrochloric acid, so that the problems of over-quick corrosion and severe lateral underetching of zinc sulfide are effectively solved.

The above examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention, which is intended to be covered by the claims and any design similar or equivalent to the scope of the invention.