TWI618261B - Etching agent and etching method for? manufacturing a pyramidal structure - Google Patents

Abstract

An etchant and an etching method for fabricating a pyramid structure, wherein an etchant having a surface tension of less than 40 dyn/ is obtained by mixing a first alkaline solution with a low-volatile anionic surfactant for accelerating dissociation of the first alkaline solution. Cm, when the etchant treats the surface of the crucible, the crucible surface has a pyramid structure, and the top end of the pyramid structure has an arc shape for achieving the technical effect of improving the step coverage of the semiconductor layer covering the pyramid structure when manufacturing the solar cell.

Description

Etchant and etching method for manufacturing pyramid structure

The present invention relates to an etchant and an etching method, particularly an etchant and an etching method for fabricating a pyramid structure.

In recent years, due to the high international energy prices and the growing concern about climate warming, green energy has set off an industrial revolution in many advanced countries. In the current situation of climate change and environmental awareness, the world is not only focused on improving energy efficiency and actively promoting energy conservation policies, but also is committed to developing renewable energy technologies, mainly because of the clean energy and zero pollution. The characteristics of self-production can be used for sustainable use. Among them, solar energy is the most valued and widely used, which in turn drives the maturity of solar power generation technology.

In general, in order to improve the photoelectric conversion efficiency of a heterojunction bismuth-based solar cell, an anisotropic etching process is generally performed on the surface of the ruthenium substrate by using an etchant, so that the surface of the ruthenium substrate has a pyramid structure to reduce The reflectivity increases the photocurrent. The conventional etchant is prepared by mixing sodium hydroxide and isopropyl alcohol (IPA), and performing an anisotropic etching treatment on the surface of the ruthenium substrate to produce a sharply undulating pyramid-shaped surface on the surface of the ruthenium substrate. . However, the angle of the conventional pyramid structure is too small, which easily affects the step coverage of the subsequent semiconductor layer, resulting in uneven thickness of the semiconductor layer and even causing a short circuit of the solar cell.

In addition, the IPA used in the conventional etchant is a high volatile organic compound (VOC), which is liable to cause the etching process to be unstable and cause damage to the environment.

In summary, it can be known that the anisotropic etching process using a conventional etchant has long been a pyramid structure which is prone to sharp undulations, thereby affecting the problem of the step coverage of the subsequent semiconductor layer, and is conventionally used by an etchant. The IPA is liable to cause the etching process to be unstable and cause damage to the environment. Therefore, it is necessary to propose an improved technical means to solve this problem.

The invention discloses an etchant and an etching method for fabricating a pyramid structure.

First, the present invention discloses an etchant for fabricating a pyramid structure for treating a crucible surface such that the crucible surface has a pyramid structure, and the top end of the pyramid structure exhibits an arc shape. The etchant for fabricating the pyramid structure comprises: a first alkaline solution and a low volatility anionic surfactant. Wherein, the first alkaline solution is used to etch the surface of the crucible; the low-volatile anionic surfactant is used to accelerate the dissociation of the first alkaline solution. Wherein, the surface tension of the etchant is less than 40 dyn/cm.

In addition, the present invention discloses an etching method for fabricating a pyramid structure, the steps comprising: mixing a first alkaline solution with a low-volatile anionic surfactant to form an etchant, wherein the low-volatile anionic surfactant is used to accelerate dissociation The first alkaline solution, the surface tension of the etchant is less than 40 dyn/cm; and the surface of the crucible is treated with an etchant so that the surface of the crucible has a pyramid structure, and the top end of the pyramid structure has an arc shape.

The system and method disclosed in the present invention are as above, and the difference from the prior art is that the present invention is a mixture of a first alkaline solution and a low-volatile anionic surfactant for accelerating dissociation of the first alkaline solution into an etchant, an etchant. The surface tension is less than 40 dyn/cm, so that when the etchant treats the surface of the crucible, the crucible surface has a pyramid structure, and the top end of the pyramid structure has an arc shape.

Through the above technical means, the present invention can improve the technical effect of the step coverage of the semiconductor layer covering the pyramid structure when manufacturing the solar cell.

The embodiments of the present invention will be described in detail below with reference to the drawings and embodiments, so that the application of the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.

The etching method for manufacturing the pyramid structure of the present invention will be further described below with reference to the drawings. Please refer to "FIG. 1", which is a flow chart of a method for manufacturing a pyramid structure etching method according to the present invention. The steps include: mixing An alkaline solution and a low volatility anionic surfactant are used as an etchant, wherein the low volatility anionic surfactant is used to accelerate the dissociation of the first alkaline solution, and the surface tension of the etchant is less than 40 dyn/cm (step 210) And treating the crucible surface with an etchant such that the crucible surface has a pyramidal structure and the top end of the pyramidal structure assumes an arc shape (step 220).

Wherein, the first alkaline solution may be selected from the group consisting of sodium hydroxide and potassium hydroxide, and the first alkaline solution may have a concentration by weight of 3% to 10%; a low volatility anionic interface The active agent can be various fluorine surfactants, and the low volatile anionic surfactant can be 0.5% to 1.5% by weight; the volume ratio of the first alkaline solution to the low volatile anionic surfactant can be Between seven and fifty-two to achieve a pyramid structure with a uniform particle size. Wherein, the volume ratio of the first alkaline solution to the low volatility anionic surfactant is the quotient of the volume of the first alkaline solution divided by the volume of the low volatility anionic surfactant.

In step 220, the temperature of the etchant treatment surface may range from 65 ° C to 95 ° C and the time range may be between 15 seconds and 60 minutes, and the temperature and time may be adjusted according to actual needs. The radius of curvature of the top end of the pyramid structure may be greater than 10 micrometers (μm), and the surface of the crucible having a pyramid structure may have a reflectance to visible light of less than 15%.

Wherein, when the first alkaline solution is sodium hydroxide or potassium hydroxide, the etchant treatment of the surface of the crucible is mainly carried out by bonding the hydroxide ions in the etchant to the suspension bonds of the deuterium atoms on the surface of the crucible. Etching, that is, the rate of dissociation of hydroxide ions determines the etch rate, and different types of polar base charges affect the dissociation rate of hydroxide ions, and even hinder the bond between the hydroxide ions and the helium atoms. . Therefore, in step 210, the first alkaline solution and the low-volatile anionic surfactant are mixed such that the anion in the low-volatile anionic surfactant absorbs with the cation in the first alkaline solution, thereby promoting hydrogen The dissociation rate of oxygen ions, which in turn increases the etch rate. In addition, due to the low volatility of the low volatility anionic surfactant, the above etchant is stable in the process of treating the ruthenium surface and does not cause harm to the environment.

In summary, through the above steps 210 and 220, the step coverage of the semiconductor layer covering the pyramid structure can be improved, and the process stability can be improved.

In addition, since the germanium substrate for fabricating the solar cell is formed by cutting the germanium column, the germanium substrate which has just been cut may cause the original ordered crystal lattice of the surface to be destroyed due to the cutting process, thereby causing the solar cell to be destroyed. The transmission of electrons and holes causes serious adverse effects. Therefore, it is necessary to perform cleaning and planarization etching before performing the above step 210. Therefore, before the step 210, the etching method for manufacturing the pyramid structure may further include: treating the surface of the crucible with a second alkaline solution to planarize the surface of the crucible, wherein the concentration of the second alkaline solution is 10% to 15% by weight. % (step 230). The second alkaline solution may be, but not limited to, sodium hydroxide or potassium hydroxide.

The contents of the present invention will be further described below in conjunction with the embodiments:

Example:

First, a germanium single crystal is grown by a CZ method, and a germanium wafer is produced from the germanium single crystal, wherein the germanium wafer is an N-type Si (100) germanium wafer having a resistivity of 1 Ωcm to 5 Ωcm and a thickness of 200 μm.

Next, the tantalum surface of the tantalum wafer is treated with a high concentration of potassium hydroxide (ie, a second alkaline solution) to planarize it (ie, step 230). Wherein, the concentration of potassium hydroxide is 10% by weight, and the temperature of the surface of the crucible of the potassium hydroxide (ie, the second alkaline solution) is 75 ° C and the time is 40 minutes.

Thereafter, the ruthenium wafer subjected to the second alkaline solution is subjected to the processing of step 220, wherein the etchant may be first prepared before step 220 is performed (ie, step 210). It should be noted that step 210 and step 230 are not provided. The execution of the time sequence before and after the relationship may be performed simultaneously or separately, but steps 210 and 230 are performed before step 220.

In this embodiment, the low volatility anionic surfactant can use 3MTM NovecTM fluorosurfactant, which has excellent solubility, easy mixing, low metal content and the ability to repeat continuous filtration, and is added to 3M. The TM NovecTM fluorosurfactant allows the surface tension of the etchant to be 19 dyn/cm, so that when step 220 is performed, bubbles generated during the etching reaction are less likely to remain on the surface of the crucible and the etching efficiency is lowered.

In this embodiment, the first alkaline solution of the etchant can be mixed with 3% by weight of potassium hydroxide and 1% by weight of 3MTM NovecTM fluorosurfactant, oxidizing The volume ratio of potassium to 3MTM NovecTM fluorosurfactant is twenty. The temperature at which step 220 is performed is 80 ° C and the time is 5 minutes.

Next, measuring the surface of the crucible after performing step 220, please refer to "2A" and "2B", and "2A" is an embodiment of the crucible surface obtained by applying the etching method for manufacturing a pyramid structure of the present invention. SEM electron micrograph, "2B" is an enlarged view of the pyramid structure of "2A". It can be seen from "Fig. 2A" and "Fig. 2B" that each pyramid structure has a size of about 1 μm to 3 μm, and the top end of each pyramid structure has an arc shape and the radius of curvature of the tip end is larger than 10 μm. Next, please refer to "3" and "3" is the relationship between the reflectance of different wavelengths of light on the surface of "2A". As can be seen from "Fig. 3", the reflectivity of the crucible surface having a pyramid structure to visible light is about 11.3%.

In summary, it can be seen that the difference between the present invention and the prior art is that the surface of the etchant is formed by mixing the first alkaline solution with a low-volatile anionic surfactant for accelerating dissociation of the first alkaline solution. The tension is less than 40 dyn/cm, so that when the etchant treats the surface of the crucible, the crucible surface has a pyramid structure, and the top end of the pyramid structure has an arc shape, thereby solving the problems of the prior art by using a technical means, thereby achieving the manufacture of solar energy. The technical effect of improving the step coverage of the semiconductor layer covering the pyramid structure when the battery is used.

While the present invention has been described above in the foregoing embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of patent protection shall be subject to the definition of the scope of the patent application attached to this specification.

Step 210 ‧ ‧ mixing the first alkaline solution with the low volatility anionic surfactant into an etchant, wherein the low volatility anionic surfactant is used to accelerate the dissociation of the first alkaline solution, and the surface tension of the etchant is less than 40 dyn/cm
Step 220‧‧‧ Treat the surface of the crucible with an etchant so that the crucible surface has a pyramidal structure, and the top end of the pyramidal structure has an arc shape. Step 230‧‧‧ Treat the crucible surface with a second alkaline solution to planarize the crucible surface Wherein the second alkaline solution has a concentration by weight of 10% to 15%

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the method of etching a pyramid structure of the present invention. Fig. 2A is a SEM electron micrograph of an embodiment of a crucible surface obtained by applying the etching method for fabricating a pyramid structure of the present invention. Figure 2B is an enlarged view of the pyramid structure of Figure 2A. Fig. 3 is a graph showing the relationship between the reflectance of light rays of different wavelengths after the surface of Fig. 2A.

Claims (15)

An etchant for fabricating a pyramid structure for treating a crucible surface such that the crucible surface has a pyramid structure, and the top end of the pyramid structure has an arc shape, and the etchant for fabricating the pyramid structure comprises: a first alkaline a solution for etching the surface of the crucible; and a low-volatile anionic surfactant for accelerating dissociation of the first alkaline solution; wherein the etchant has a surface tension of less than 40 dyn/cm. An etchant for fabricating a pyramid structure according to the first aspect of the invention, wherein the first alkaline solution is selected from the group consisting of sodium hydroxide and potassium hydroxide. An etchant for fabricating a pyramid structure according to claim 1, wherein the first alkaline solution has a concentration by weight of 3% to 10%, and the low volatile anionic surfactant has a concentration of 0.5 by weight. % to 1.5%. An etchant for fabricating a pyramid structure according to claim 3, wherein a volume ratio of the first alkaline solution to the low volatility anionic surfactant is between seven and fifty-two. An etchant for fabricating a pyramid structure according to claim 1, wherein the low volatility anionic surfactant is a various fluorosurfactant. A method for etching a pyramid structure, the method comprising: mixing a first alkaline solution with a low-volatile anionic surfactant to form an etchant, wherein the low-volatile anionic surfactant is used to accelerate dissociation of the first An alkaline solution having a surface tension of less than 40 dyn/cm; and treating the surface with the etchant such that the surface of the crucible has a pyramid structure, and the top end of the pyramid structure has an arc shape. The etching method of the pyramid structure according to claim 6 of the patent application, wherein the etchant treats the surface of the crucible at a temperature ranging from 65 ° C to 95 ° C. The etching method of the pyramid structure according to claim 6 of the patent application, wherein the etchant treats the surface of the crucible for a time ranging from 15 seconds to 60 minutes. The etching method of the pyramid structure according to claim 6, wherein the first alkaline solution is selected from the group consisting of sodium hydroxide and potassium hydroxide. According to the etching method of the pyramid structure of claim 6, wherein the first alkaline solution has a concentration by weight of 3% to 10%, and the concentration of the low-volatile anionic surfactant is 0.5% by weight. To 1.5%. The etching method of the pyramid structure according to claim 10, wherein the volume ratio of the first alkaline solution to the low-volatile anionic surfactant is between seven and fifty-two. The etching method of the pyramid structure according to claim 6 of the patent application, wherein the low volatility anionic surfactant is various fluorosurfactants. According to the etching method of the pyramid structure of claim 6, in the step of treating the surface of the crucible with the etchant, the method further comprises: treating the surface of the crucible with a second alkaline solution to planarize the surface of the crucible, Wherein, the second alkaline solution has a concentration by weight of 10% to 15%. An etching method of a pyramid structure according to claim 6 wherein the radius of curvature of the tip end of the pyramid structure is greater than 10 micrometers (μm). The etching method of the pyramid structure according to claim 6 of the patent application, wherein the surface of the crucible having the pyramid structure has a reflectance to visible light of less than 15%.