US-12622193-B2 - Substrate processing method and substrate processing apparatus

Abstract

A technique enabling wet etching of a first silicon oxide film with high selectivity with respect to a metal film and a second silicon oxide film is provided. A substrate processing method of wet-etching a substrate having a stacked structure including a metal film, a first silicon oxide film, and a second silicon oxide film having a moisture content lower than that of the first silicon oxide film is provided. The substrate processing method includes performing an etching while increasing etching selectivity of the first silicon oxide film with respect to the second silicon oxide film and the metal film by supplying an etching liquid, which is prepared by diluting sulfuric acid, hydrogen peroxide and hydrofluoric acid in an anhydrous organic solvent, to the substrate such that the metal film, the first silicon oxide film, and the second silicon oxide film are simultaneously exposed to the etching liquid.

Inventors

• Koji KAGAWA

Assignees

• TOKYO ELECTRON LIMITED

Dates

Publication Date

20260505

Application Date

20220815

Priority Date

20210824

Claims (20)

1. 1 . A substrate processing method of wet-etching a substrate having a stacked structure including a metal film, a first silicon oxide film, and a second silicon oxide film having a moisture content lower than that of the first silicon oxide film, the substrate processing method comprising: performing an etching while increasing etching selectivity of the first silicon oxide film with respect to the second silicon oxide film and the metal film by supplying an etching liquid, which is prepared by diluting sulfuric acid, hydrogen peroxide and hydrofluoric acid in an anhydrous organic solvent, to the substrate such that the metal film, the first silicon oxide film, and the second silicon oxide film are simultaneously exposed to the etching liquid.
2. 2 . The substrate processing method of claim 1 , wherein the anhydrous organic solvent is acetic acid, isopropyl alcohol (IPA), ethylene glycol, glycerin, or acetone.
3. 3 . The substrate processing method of claim 1 , wherein the anhydrous organic solvent is acetic acid or ethylene glycol.
4. 4 . The substrate processing method of claim 1 , wherein the metal film is a tungsten film, the first silicon oxide film is boro-phospho silicate glass (BPSG), and the second silicon oxide film is tetraethoxy silane (TEOS).
5. 5 . The substrate processing method of claim 1 , wherein polymer attached to a surface of the stacked structure exposed to the etching liquid is removed all at once by the etching liquid.
6. 6 . The substrate processing method of claim 1 , wherein a temperature of the etching liquid is within a range from a room temperature to 80° C.
7. 7 . The substrate processing method of claim 1 , wherein the etching selectivity of the first silicon oxide film with respect to the second silicon oxide film is larger than 4.
8. 8 . The substrate processing method of claim 1 , wherein an etching rate of the metal film is less than 10 Å/min (angstrom per minute).
9. 9 . The substrate processing method of claim 1 , wherein the etching liquid contains 0.01 wt % to 15 wt % of sulfuric acid, 0.1 wt % to 10 wt % of hydrogen peroxide, and 0.005 wt % to 1 wt % of hydrofluoric acid, and a rest of the etching liquid is composed of the anhydrous organic solvent, and moisture contained in stock solutions of the sulfuric acid, the hydrofluoric acid, and the hydrogen peroxide.
10. 10 . The substrate processing method of claim 1 , wherein the etching liquid contains 1 wt % to 15 wt % of sulfuric acid, 0.2 wt % to 2 wt % of hydrogen peroxide, and 0.005 wt % to 0.5 wt % of hydrofluoric acid, and a rest of the etching liquid is composed of the anhydrous organic solvent, and moisture contained in stock solutions of the sulfuric acid, the hydrofluoric acid, and the hydrogen peroxide.
11. 11 . The substrate processing method of claim 1 , wherein the stacked structure as a target of the wet-etching includes the metal film made of tungsten as a lowest layer, the first silicon oxide film made of boro-phospho silicate glass (BPSG) formed on the metal film, and the second silicon oxide film made of tetraethoxy silane (TEOS) formed on the first silicon oxide film, and the stacked structure is provided with a trench extending continuously in a stacking direction from a top of the stacked structure to a surface of the metal film.
12. 12 . The substrate processing method of claim 11 , wherein the stacked structure includes a silicon nitride film between the metal film and the first silicon oxide film and between the first silicon oxide film and the second silicon oxide film.
13. 13 . The substrate processing method of claim 12 , wherein the stacked structure includes a silicon nitride film provided directly on the second silicon oxide film and a hard mask layer provided directly on the silicon nitride film, the stacked structure has the trench formed by performing dry etching with the hard mask layer as an etching mask, polymer generated by the dry etching is attached to an inner wall surface of the trench, and the polymer is removed by the etching liquid.
14. 14 . The substrate processing method of claim 13 , wherein the etching liquid contains 0.01 wt % to 15 wt % of sulfuric acid, 0.1 wt % to 10 wt % of hydrogen peroxide, and 0.005 wt % to 1 wt % of hydrofluoric acid, and a rest of the etching liquid is composed of the anhydrous organic solvent, and moisture contained in stock solutions of the sulfuric acid, the hydrofluoric acid, and the hydrogen peroxide.
15. 15 . The substrate processing method of claim 14 , wherein the anhydrous organic solvent is acetic acid, isopropyl alcohol (IPA), ethylene glycol, glycerin, or acetone.
16. 16 . The substrate processing method of claim 14 , wherein the anhydrous organic solvent is acetic acid or ethylene glycol.
17. 17 . The substrate processing method of claim 13 , wherein the etching liquid contains 1 wt % to 15 wt % of sulfuric acid, 0.2 wt % to 2 wt % of hydrogen peroxide, and 0.005 wt % to 0.5 wt % of hydrofluoric acid, and a rest of the etching liquid is composed of the anhydrous organic solvent, and moisture contained in stock solutions of the sulfuric acid, the hydrofluoric acid, and the hydrogen peroxide.
18. 18 . The substrate processing method of claim 17 , wherein the anhydrous organic solvent is acetic acid, isopropyl alcohol (IPA), ethylene glycol, glycerin, or acetone.
19. 19 . The substrate processing method of claim 17 , wherein the anhydrous organic solvent is acetic acid or ethylene glycol.
20. 20 . A substrate processing apparatus, comprising: a substrate holder configured to hold a substrate; an etching liquid supply configured to supply an etching liquid to the substrate held by the substrate holder; and a controller configured to perform a substrate processing method as claimed in claim 1 by controlling an operation of the substrate processing apparatus.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This Application is a U.S. national phase application under 35 U.S.C. § 371 of PCT Application No. PCT/JP2022/030867 filed on Aug. 15, 2022, which claims the benefit of Japanese Patent Application No. 2021-136507 filed on Aug. 24, 2021, the entire disclosures of which are incorporated herein by reference. TECHNICAL FIELD The various aspects and embodiments described herein pertain generally to a substrate processing method and a substrate processing apparatus. BACKGROUND A manufacturing process of a semiconductor device includes a wet etching process of selectively etching multiple types of films formed on a substrate. Patent Document 1 discloses a method of wet-etching a substrate, which includes a SiO2 thermal oxide film as a first insulating film and a SiN film (or a SiON film by a CVD method) as a second insulating film stacked on the first insulating film, by using a HF aqueous solution. In the disclosure of Patent Document 1, a HF concentration is increased to about 5% when it is required to increase etching selectivity of the SiO2 film with respect to the SiN film, whereas the HF concentration is lowered when non-selective etching is required. Patent Document 1: Japanese Patent No. 3,974,028 SUMMARY In an exemplary embodiment, there is provided a substrate processing method of wet-etching a substrate having a stacked structure including a metal film, a first silicon oxide film, and a second silicon oxide film having a moisture content lower than that of the first silicon oxide film. The substrate processing method includes performing an etching while increasing etching selectivity of the first silicon oxide film with respect to the second silicon oxide film and the metal film by supplying an etching liquid, which is prepared by diluting sulfuric acid, hydrogen peroxide and hydrofluoric acid in an anhydrous organic solvent, to the substrate such that the metal film, the first silicon oxide film, and the second silicon oxide film are simultaneously exposed to the etching liquid. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross sectional view illustrating an example of a stacked film structure to be selectively wet-etched according to an exemplary embodiment of a substrate processing method. FIG. 2 is a schematic cross sectional view of a stacked structure, showing an example of a target etching result in the exemplary embodiment. FIG. 3 is a schematic cross sectional view of a stacked structure, showing an example of an undesirable etching result. FIG. 4 is a schematic diagram illustrating an example substrate processing apparatus of performing a substrate processing method. FIG. 5 is a schematic diagram illustrating another example substrate processing apparatus of performing the substrate processing method. DETAILED DESCRIPTION FIG. 1 is a schematic cross sectional view showing a stacked structure as a target of a wet etching processing according to an exemplary embodiment of a substrate processing method of the present disclosure. In the present exemplary embodiment, the wet etching processing is performed as a part of a capacitor shape correcting processing. A wet etching process is performed as a subsequent process to a dry etching process. FIG. 1 illustrates a stacked structure as a target of wet etching. The stacked structure includes a tungsten film W, a silicon nitride (SiN) film, a boro-phospho silicate glass (BPSG) film as a first silicon oxide film, a silicon nitride (SiN) film, a tetraethoxy silane (TEOS) film as a second silicon oxide film, a silicon nitride (SiN) film, and a hard mask HM that are stacked in sequence from the bottom. This stacked structure is formed directly on a substrate (not shown) such as a silicon wafer, or is formed on the substrate with one or more other layers (films) interposed therebetween. FIG. 1 shows a state immediately after a hole is formed by dry-etching a layer (film) above the tungsten film W by using the hard mask HM as an etching mask. Polymer P generated during the dry etching is attached to a surface of a trench. In the wet etching according to the present exemplary embodiment, it is required to wet-etch the BPSG film from the state shown in FIG. 1, while suppressing etching of the W film and TEOS film, as illustrated in FIG. 2. It is not desirable that the TEOS film is deeply etched as schematically shown in FIG. 3. As a specific example, it is required to satisfy a condition of ‘etching rate of BPSG/etching rate of TEOS>4’ and a condition of ‘etching rate of W film <10 Å/min’. In addition, in the wet etching according to the present exemplary embodiment, it is also required to remove the polymer P generated in the previous dry etching process. Without being limited to the shown example, the polymer may adhere to a surface of an etching target object (a surface of the stacked structure (a top surface of the uppermost layer thereof) and an inner wall surface of a recess (hole or groove)). In order