JP-2026075080-A - Etching method

Abstract

[Problem] In one embodiment, to provide an etching method that can suppress the reduction in etching rate due to the native oxide film on the molybdenum surface. [Solution] In one embodiment, the present disclosure relates to an etching method for etching a layer to be etched containing molybdenum, comprising the following steps 1 and 2. Step 1: A pretreatment solution, which is an aqueous solution containing an acid or alkali and does not contain an oxidizing agent selected from the group consisting of sulfuric acid, nitric acid, and hydrogen peroxide, is brought into contact with the layer to be etched containing molybdenum. Step 2: An etching solution containing phosphoric acid and nitric acid is brought into contact with the layer to be etched after Step 1. [Selected Figure] None

Inventors

• 前田 尚也
• 内田 洋平

Assignees

• 花王株式会社

Dates

Publication Date

20260507

Application Date

20251020

Priority Date

20241021

Claims (7)

1. An etching method for etching a layer to be etched containing molybdenum, An etching method comprising the following steps 1 and 2. Step 1: A pretreatment solution, which is an aqueous solution containing an acid or alkali and does not contain an oxidizing agent selected from the group consisting of sulfuric acid, nitric acid, and hydrogen peroxide, is brought into contact with the layer to be etched, which contains molybdenum. Step 2: An etching solution containing phosphoric acid and nitric acid is brought into contact with the layer to be etched after Step 1.
2. The etching method according to claim 1, wherein the pretreatment solution is an aqueous solution containing at least one selected from hydrofluoric acid, ammonia, and a quaternary ammonium salt.
3. The etching method according to claim 2, wherein the quaternary ammonium salt is at least one selected from tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline.
4. The etching method according to claim 1, wherein the pH of the pretreatment solution used in step 1 is 3 or less, or 9 or more.
5. The etching method according to claim 1, wherein the etching solution used in step 2 further comprises at least one nitrogen-containing compound selected from polyallylamine, polyalkyleneimine, polyalkylene polyamine, and alicyclic amine.
6. The etching method according to claim 1, wherein the etching solution used in step 2 further contains an organic acid.
7. The etching method according to claim 1, wherein the etching rate in step 2 is 10% or more faster than the etching rate when the layer to be etched is etched without contact with the pretreatment solution.

Description

This disclosure relates to an etching method for etching a molybdenum-containing layer. In the manufacturing process of semiconductor devices, for example, a step is performed to etch a layer containing at least one metal such as tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, rhodium, copper, nickel, cobalt, titanium, aluminum, and iridium, or its nitride or oxide, by etching it into a predetermined pattern shape. In recent years, the semiconductor field has seen increasing integration, leading to a demand for more complex and miniaturized wiring. This has resulted in growing demands for pattern processing technologies and etching solutions, and various etching methods and solutions have been proposed (Patent Documents 1-2). For example, Patent Document 1 proposes a substrate processing method in which a molybdenum film is oxidized using a method different from conventional methods, and the oxidized portion of the molybdenum film is removed from the substrate while leaving the unoxidized portion of the molybdenum film on the substrate. Patent Document 2 proposes an etching solution for etching a laminated film of an aluminum-based metal film and a molybdenum-based metal film formed on an insulating film substrate, the etching solution containing a specific sulfonic acid compound, phosphoric acid, and nitric acid. Japanese Patent Publication No. 2024-18603Japanese Patent Publication No. 2007-191773 The timing of wafer etching at semiconductor wafer manufacturers varies; sometimes it's immediately after film deposition, sometimes several days later, and sometimes a month later. As a result, the thickness and uniformity of the native oxide film on the molybdenum metal surface differ from day to day. If the surface roughness and etching rate after etching vary depending on the state of the molybdenum metal surface, stable production of semiconductor wafers becomes difficult. As a result of diligent research by the present inventors, it has been found that by pre-treating the molybdenum-containing layer to be etched with an aqueous solution containing an acid or alkali before etching it with a mixed acid aqueous solution containing nitric acid and phosphoric acid, the decrease in etching rate due to the state of the molybdenum-containing layer to be etched (particularly the native oxide film of molybdenum) can be suppressed, and molybdenum can be etched well. Furthermore, the issue of differing surface roughness and etching rate after etching depending on the state of the molybdenum metal surface is a problem specific to etching using a mixed acid etching solution containing nitric acid and phosphoric acid. When using an acid/alkali etching solution with peracids or peroxides such as hydrogen peroxide as the oxidizing agent, the etching solution can dissolve MoO3 , and therefore the above-mentioned problem does not occur. In one embodiment, this disclosure relates to an etching method for etching a molybdenum-containing layer to be etched, comprising the following steps 1 and 2 (hereinafter also referred to as "the etching method of this disclosure"). Step 1: A pretreatment solution, which is an aqueous solution containing an acid or alkali and does not contain an oxidizing agent selected from the group consisting of sulfuric acid, nitric acid, and hydrogen peroxide, is brought into contact with the layer to be etched, which contains molybdenum. Step 2: An etching solution containing phosphoric acid and nitric acid is brought into contact with the layer to be etched after Step 1. According to this disclosure, in one embodiment, an etching method can be provided that can suppress the reduction in etching rate due to the native oxide film on the molybdenum surface. The etching method of this disclosure is used in one or more embodiments to etch a layer containing molybdenum. The etching method of this disclosure can be used in one or more embodiments to etch a molybdenum-containing metal in the manufacturing process of electronic devices, particularly semiconductor wafers. Accordingly, this disclosure relates in one embodiment to a method for manufacturing a semiconductor wafer, which includes the etching method of this disclosure. The etching method of this disclosure can be suitably used in the fabrication of semiconductor wafers in one or more embodiments. This enables uniform etching of the layer to be etched, thereby improving productivity and yield. The etching method of this disclosure can be used in one or more embodiments to etch electrodes containing molybdenum in the manufacturing process of electronic devices, particularly semiconductor memories such as non-volatile memories including 3D-NAND flash memory. Accordingly, this disclosure relates in one embodiment to a method for manufacturing a semiconductor memory, which includes the etching method of this disclosure. The etching method of this disclosure can be suitably used in one or more embodiments to produce