Etching method

• US 20030077909A1
• Filed: 10/23/2002
• Published: 04/24/2003
• Est. Priority Date: 10/24/2001
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Jiwari, Nobuhiro
• Granted Patent: US 6,939,806 B2
• Time in Patent Office: Days
• US Class Current: 438/710
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H01L 21/76814 post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors
• CPC Class Codes: H01L 21/76897 Formation of self-aligned vias or contact plugs, i.e. involving a lithographically uncritical step self-aligned silicidation on field effect transistors H01L29/665

Abstract

The etching method of the present invention for forming a hole having a high aspect ratio in a silicon oxide film formed on a substrate via a silicon nitride film includes the step of performing etching using an etching gas composed of a mixture of Ar gas, O₂ gas, C₅F₈ gas and CH₂F₂ gas.

Claims

1. An etching method for forming a hole having a high aspect ratio in a silicon oxide film formed on a substrate via a silicon nitride film, the method comprising the step of:

performing etching using an etching gas composed of a mixture of Ar gas, O₂ gas, C₅F₈ gas and CH₂F₂ gas.

2. The method of claim 1, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the etching gas is 20% or more.

3. The method of claim 1, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the etching gas is 50% or more.

4. The method of claim 1, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the etching gas is in the range of 50% to 70%.

5. An etching method for forming a hole having a high aspect ratio in a laminated film formed on a substrate via a silicon nitride film, the laminated film including a lower layer composed of an impurity-containing silicon oxide film and an upper layer composed of a substantially impurity-free silicon oxide film, the method comprising the steps of:

performing first-stage etching for the upper layer using a first etching gas composed of a mixture of Ar gas, O₂ gas and C₅F₈ gas in a relatively large mixing ratio of the O₂ gas to the fluorocarbon gas; and

performing second-stage etching for the lower layer using a second etching gas composed of a mixture of Ar gas, O₂ gas, C₅F₈ gas and CH₂F₂ gas in a relatively small mixing ratio of the O₂ gas to the fluorocarbon gas.

6. The method of claim 5, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the second etching gas is 20% or more.

7. The method of claim 5, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the second etching gas is 50% or more.

8. The method of claim 5, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the second etching gas is in the range of 50% to 70%.

9. An etching method for forming a second hole having a high aspect ratio in a laminated film formed on a silicon nitride film defining a first hole formed on a substrate, the laminated film including a lower layer composed of an impurity-containing silicon oxide film and an upper layer composed of a substantially impurity-free silicon oxide film, the second hole being made integral with the first hole, the method comprising the steps of

performing first-stage dry etching for the upper layer using a first etching gas composed of a mixture of Ar gas, O₂ gas and C₅F₈ gas in a relatively large mixing ratio of the O₂ gas to the fluorocarbon gas;

performing second-stage dry etching for the lower layer using a second etching gas composed of a mixture of Ar gas, O₂ gas, C₅F₈ gas and CH₂F₂ gas in a relatively small mixing ratio of the O₂ gas to the fluorocarbon gas; and

removing a residue of the lower layer in the first hole by wet etching.

10. The method of claim 9, wherein the ratio of the flow rate of the CH₂F₂ gas to the total flow rate of the C₅F₈ gas and the CH₂F₂ gas in the second etching gas is in the range of 20% to 70%.

11. The method of claim 9, wherein the lower layer is a BPSG film containing 3.7 wt % of boron and 7.0 wt % of phosphorus.