Copper etching solution for semiconductor and its application in spin-spray process

Abstract

The application provides a copper etching solution for semiconductor and application thereof in a rotary spraying process. The copper etching solution contains 1-3% of peroxide, 1-5% of phosphoric acid, 0.1-1% of a pH regulator, 0.5-1% of a corrosion inhibitor and 0.01-0.1% of an additive, and the balance is deionized water in percentage by mass. The corrosion inhibitor is a polyphenol compound, and the additive is a phosphate betaine. The pH regulator adjusts the pH of the solution to maintain an acidic environment, slows down the decomposition of the peroxide, enhances the stability of the peroxide, and the constant pH range can effectively control the dissolution rate of copper oxide and stabilize the etching rate of copper. The corrosion inhibitor inhibits the etching of Ti, so that the etching solution has a high selectivity ratio to the Ti adhesion layer. The introduction of the additive reduces the surface tension of the etching solution, so that the etching solution can be well applied to the rotary spraying process and good uniformity is obtained.

Description

Technical Field

[0001] This invention belongs to the field of wet etching technology for metal layers in semiconductor manufacturing, and specifically relates to a copper etching solution for semiconductors suitable for rotary spraying processes. Background Technology

[0002] In an era of rapid development of strategic emerging industries such as 5G communication, smart home appliances and industrial control, industrial IoT and medical electronics, the field of special process semiconductors for radio frequency front-end and MEMS sensors has achieved the transformation from Al process to copper process due to the advantages of copper metal, such as low resistance, high conductivity, small electromigration effect and low manufacturing cost.

[0003] When copper is used as the metal electrode layer, a Ti layer needs to be added underneath as a diffusion barrier and adhesion layer. This requires a high selectivity for the Ti layer during the etching of the copper metal layer. Many patent documents report formulations for copper etching, but these formulations are highly corrosive to the Ti barrier layer and insulating dielectric layers such as oxides due to their chlorine and fluorine content, or they contain sodium, potassium, and other metal salts, making them unsuitable for the high-quality manufacturing requirements of semiconductors. Furthermore, this etching technology is widely used in packaging, circuit boards, precision machining, and electronic component processing. The immersion process it mostly employs results in formulations that, due to their complex composition, high concentration, high cost, high viscosity, and tendency to foam, cannot be directly applied to rotary spray processes.

[0004] Therefore, there is a need to develop a low-concentration copper etchant suitable for semiconductor rotary spraying processes, which has a stable etching rate, a high selectivity for Ti layers, and good etching uniformity. Summary of the Invention

[0005] This invention provides a copper etching solution for semiconductors and its application in a rotary spray process. It has high selectivity for Ti layers and can be used in a rotary spray process to obtain good uniformity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a copper etching solution for semiconductors, which, by mass percentage, contains 1% to 3% peroxide, 1% to 5% phosphoric acid, 0.1% to 1% pH adjuster, 0.5% to 1% corrosion inhibitor and 0.01% to 0.1% additive, with the balance being deionized water; wherein the additive is phosphate betaine.

[0007] Furthermore, the peroxide is at least one of hydrogen peroxide, ethyl peroxybenzene, and 4,4′-peroxydibenzoic acid.

[0008] Furthermore, the pH adjuster is an alcohol amine or an amino acid.

[0009] Further, the pH adjuster is at least one of monoethanolamine, triethanolamine, 5-amino-1-pentanol, L-lysine, or DL-citrulline.

[0010] Furthermore, the corrosion inhibitor is at least one of tea polyphenols, ellagic acid, and rapeseed polyphenols.

[0011] Furthermore, the phosphate betaine is any one of dodecyl hydroxypropyl phosphate betaine, tetradecyl hydroxypropyl phosphate betaine, and hexadecyl hydroxypropyl phosphate betaine.

[0012] Furthermore, the pH of the copper etching solution is 1.6-2.0. Preferably, the pH is 1.7-1.9.

[0013] This invention also relates to a method for preparing the aforementioned copper etching solution for semiconductors, wherein each raw material component is taken according to the specified ratio, and deionized water, phosphoric acid, corrosion inhibitor, peroxide and additives are added in sequence. After each component is added, the mixture is stirred before adding the next component. Finally, a pH adjuster is added to adjust the pH to the required level.

[0014] The present invention also relates to the application of the aforementioned copper etching solution for semiconductors in a rotary spray process.

[0015] The present invention has the following beneficial effects:

[0016] The copper etching solution provided by this invention, suitable for semiconductor applications, uses peroxide as an oxidant and phosphoric acid as a solvent. A pH adjuster is added to control the pH of the solution, maintaining an acidic environment, slowing down the decomposition of peroxide, and enhancing its stability, thereby maintaining a stable etching rate. Simultaneously, a constant pH range effectively controls the dissolution rate of copper oxide, thus stabilizing the copper etching rate. The addition of a corrosion inhibitor suppresses the etching of Ti, maintaining a high selectivity of the etching solution for the Ti layer. Furthermore, the addition of phosphate betaine additive reduces the surface tension of the solution while avoiding defects such as foaming, resulting in excellent wettability on the copper metal surface. This accelerates the exchange rate between reactants and products at the copper interface with the solution, thereby improving the etching reaction rate and achieving good etching uniformity, making it well-suited for rotary spray processes.

[0017] The etching solution provided by this invention has a low content range of each component, which greatly reduces the production cost. When used in the semiconductor field, it can maintain a stable etching rate and good uniformity, while having a high selectivity for Ti films. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the test points on the Cu specimens in the examples and comparative examples. Detailed Implementation

[0019] The embodiments of the present invention will now be described in detail with reference to examples.

[0020] The copper etching solution for semiconductors of this invention is composed of the components listed in Table 1, with the remainder being deionized water. The preparation order is: deionized water, phosphoric acid, corrosion inhibitor, peroxide, additives, and finally, an organic alcohol amine or amino acid to adjust the pH of the solution. After each component is added, it is stirred thoroughly with a stirring rod before adding the next component, until the last component is added and then mixed thoroughly to obtain the copper etching solution for semiconductors. The content of each component is expressed as a mass percentage (%). pH refers to the pH of the etching solution.

[0021]

[0022]

[0023]

[0024] The prepared semiconductor copper etching solution was used to etch test pieces coated with Ti and Cu metal films on a silicon substrate at 25°C. The etching method was spin-jet etching, with the Cu metal film etched for 20 seconds and the Ti metal film etched for 10 minutes. The thickness of the metal films before and after etching was recorded using a four-point probe, and the etching rate of each metal layer was calculated. Three Cu test pieces and three Ti test pieces were etched consecutively, and the thickness of the copper sheet was measured. Figure 1 The etching rates at the nine points shown are presented, and the average etching rate and etching uniformity U% for each of the nine test points are calculated and recorded in Table 2. U% = (etching rate) MAX -Etching rate MIN ) / 2*Etching Rate 平均值 , where the etching rate MAX、 Etching rate MIN、 Etching rate 平均值 The values ​​represent the maximum, minimum, and average etching rates at the nine test points. The etching rate at the center point of three Ti wafers was measured, and the average etching rate of the three wafers was calculated and recorded in Table 2.

[0025] Table 2

[0026]

[0027]

[0028] As can be seen from the experimental results of the above embodiments, the copper etching solution for semiconductors provided by the present invention can maintain a stable etching rate and good uniformity under the rotary spray process, while having a high selectivity for Ti film layers.

[0029] The specific embodiments of the present invention have been described in detail above, but are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. The application of a semiconductor copper etching solution in a rotary spray process, characterized in that: The etching solution contains, by mass percentage, 1.25% hydrogen peroxide, 2.5% phosphoric acid, 0.65% corrosion inhibitor, and 0.05% additives, with a pH adjuster added to control the pH at 1.8, and the remainder being deionized water. The pH adjuster is monoethanolamine, triethanolamine, 5-amino-1-pentanol, or L-lysine; the corrosion inhibitor is one of tea polyphenols, ellagic acid, or rapeseed polyphenols; and the additive is dodecyl hydroxypropyl phosphate betaine or tetradecyl hydroxypropyl phosphate betaine.

2. The application according to claim 1, characterized in that: Take each raw material component according to the formula, and add deionized water, phosphoric acid, corrosion inhibitor, peroxide and additive in sequence. After each component is added, mix well before adding the next component. Finally, add pH adjuster to adjust to the required pH.

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