Colloidal silica growth inhibitor and associated method and system

Patent metadata

Field	Value
Publication number	US-10325779-B2
Application number	US-201715467939-A
Country	US
Kind code	B2
Filing date	Mar 23, 2017
Priority date	Mar 30, 2016
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

A technique to inhibit the growth of colloidal silica deposits on surfaces treated in phosphoric acid is described. In one embodiment, the disclosed techniques include the use of a colloidal silica growth inhibitor as an additive to a phosphoric acid solution utilized for a silicon nitride etch. In some embodiments, the additive may have chemistry that may contain strong anionic groups. A method and apparatus is provided that monitors the silica concentration and/or the colloidal silica growth inhibitor concentration in the phosphoric acid solution during processing and adjusts the amount of those components as needed. Techniques are provided for a method and apparatus to control the additive concentration to be used as well as the silica concentration in the phosphoric acid solution. The techniques described herein provide a high selectivity etch of silicon nitride towards silicon dioxide without the growth of colloidal silica deposits on the exposed surfaces.

First claim

What is claimed is:

1. A method for wet etching of structures on a microelectronic substrate, comprising:
loading the microelectronic substrate into a wet chemical processing system, the microelectronic substrate having a first structure of silicon nitride and a second structure of silicon oxide, each having an exposed surface;
dispensing onto the substrate a wet etching solution,
wherein the wet etching solution comprises:
water,
phosphoric acid,
sulfuric acid, and
a colloidal silica growth inhibitor;

etching the first structure on the microelectronic substrate selectively over the second structure on the microelectronic substrate without creating a growth of colloidal silica deposits on the exposed surfaces of the first structure or second structure on the substrate; and
monitoring etch selectivity during the etching and adjusting the wet etching solution to maintain the selectivity,
wherein adjusting the wet etching solution comprises adjusting the concentration of the colloidal silica growth inhibitor, a flow rate of the colloidal silica growth inhibitor, a temperature of the colloidal silica growth inhibitor, the concentration of the water, a flow rate of the water, a temperature of the water, the concentration of the phosphoric acid, a flow rate of the phosphoric acid, a temperature of the phosphoric acid, the concentration of sulfuric acid, a flow rate of the sulfuric acid, a temperature of the sulfuric acid, a flow rate ratio of the phosphoric acid to the colloidal silica growth inhibitor, and a concentration of silica added to the wet etching solution.

2. The method of claim 1 , wherein the colloidal silica growth inhibitor contains at least one —COOH group, or at least one —PO3H2 group, or both.

3. The method of claim 1 , wherein the colloidal silica growth inhibitor is a polycarboxylate.

4. The method of claim 1 , wherein the colloidal silica growth inhibitor comprises at least one compound selected from citric acid, acetic acid, oxalic acid, malic acid, 2-phosphonobutane-1,2,4-tricarboxylate (PBTC), diethylenetriaminepentaacetate (DETPA), ethylenediamine-tetracarboxylate (EDTA), 1,2,3,4-butanetetracarboxylate (BTC), amino acids, L-histidine, L-phenylalanine, ammonium bifluoride, and/or ammonium fluoride.

5. The method of claim 1 , wherein adjusting the concentration of the colloidal silica growth inhibitor in the wet etching solution comprises adding more of the colloidal silica growth inhibitor to adjust its concentration in the wet etching solution.

6. The method of claim 1 , wherein monitoring etch selectivity during the etching and adjusting the wet etching solution to maintain the selectivity comprises monitoring the concentration of colloidal silica and the concentration of the colloidal silica growth inhibitor during the etching and increasing the concentration of the colloidal silica growth inhibitor as the concentration of colloidal silica increases.

7. A method for wet etching of structures on a microelectronic substrate, comprising:
loading the microelectronic substrate into a wet chemical processing system, the microelectronic substrate having a first structure of silicon nitride and a second structure of silicon oxide, each having an exposed surface;
selecting a target etch rate and a target etch selectivity for etching the first structure of silicon nitride relative to the second structure of silicon oxide;
dispensing onto the substrate a wet etching solution comprising water, phosphoric acid, and a colloidal silica growth inhibitor;
selectively etching the first structure over the second structure, wherein a colloidal silica concentration in the wet etching solution increases as the first structure of silicon nitride is etched, and wherein the colloidal silica growth inhibitor reacts with the colloidal silica to cause it to remain in solution without depositing on the exposed surfaces; and
while selectively etching the first structure, monitoring the concentrations of the colloidal silica growth inhibitor, water, phosphoric acid and colloidal silica in the wet etching solution and adjusting the wet etching solution by adjusting the concentration of one or more of the colloidal silica growth inhibitor, water, or silica to maintain a concentration profile for the wet etching solution that achieves the target etch rate and the target etch selectivity until the first structure is removed without depositing the colloidal silica on the exposed surfaces.

8. The method of claim 7 , wherein the adjusting includes adding more of the colloidal silica growth inhibitor to increase its concentration as the colloidal silica concentration increases to cause the increased colloidal silica concentration to remain in solution.

9. The method of claim 7 , wherein adjusting the wet etching solution further comprises adjusting one or more of a flow rate of the colloidal silica growth inhibitor, a temperature of the colloidal silica growth inhibitor, a flow rate of the water, a temperature of the water, a flow rate of the silica, a temperature of the silica, the concentration of the phosphoric acid, a flow rate of the phosphoric acid, a temperature of the phosphoric acid, and a flow rate ratio of the phosphoric acid to the colloidal silica growth inhibitor.

10. The method of claim 7 , wherein the colloidal silica growth inhibitor contains at least one —COOH group, or at least one —PO3H2 group, or both.

11. The method of claim 7 , wherein the colloidal silica growth inhibitor is a polycarboxylate.

12. The method of claim 7 , wherein the colloidal silica growth inhibitor comprises at least one compound selected from citric acid, acetic acid, oxalic acid, malic acid, 2-phosphonobutane-1,2,4-tricarboxylate (PBTC), diethylenetriaminepentaacetate (DETPA), ethylenediamine-tetracarboxylate (EDTA), 1,2,3,4-butanetetracarboxylate (BTC), amino acids, L-histidine, L-phenylalanine, ammonium bifluoride, and/or ammonium fluoride.

13. A method for wet etching of structures on a microelectronic substrate, comprising:
loading the microelectronic substrate into a wet chemical processing system, the microelectronic substrate having a first structure of silicon nitride and a second structure of silicon oxide, each having an exposed surface;
using a wet etching solution, selectively etching the first structure of silicon nitride over the second structure of silicon oxide for a time duration until the first structure is removed, wherein the wet etching solution comprises water, phosphoric acid, and a concentration of a colloidal silica growth inhibitor that is increased during the time duration from an initial concentration to a final, higher concentration to inhibit growth of colloidal silica deposits on the exposed surfaces of the first and second structures; and
monitoring etch selectivity during the etching and adjusting the wet etching solution to maintain the selectivity,
wherein adjusting the wet etching solution comprises adjusting a flow rate of the colloidal silica growth inhibitor, a temperature of the colloidal silica growth inhibitor, the concentration of the water, a flow rate of the water, a temperature of the water, the concentration of the phosphoric acid, a flow rate of the phosphoric acid, a temperature of the phosphoric acid, a flow rate ratio of the phosphoric acid to the colloidal silica growth inhibitor, and a concentration of silica added to the wet etching solution.

14. The method of claim 13 , wherein the colloidal silica growth inhibitor contains at least one —COOH group, or at least one —PO3H2 group, or both.

15. The method of claim 13 , wherein the colloidal silica growth inhibitor is a polycarboxy

Assignees

• Tokyo Electron Ltd

Inventors

• Rotondaro Antonio L P
• Printz Wallace P

Classifications

• H10P74/20

  characterised by the properties tested or measured, e.g. structural or electrical properties · CPC title

• H10P72/0422

  for wet etching · CPC title

• H10P72/0604

  Process monitoring, e.g. flow or thickness monitoring · CPC title

• H10P72/0424

  using mainly spraying means, e.g. nozzles · CPC title

• H10P50/283 Primary

  by chemical means · CPC title