Device and Method for Stopping an Etching Process

• US 20090124089A1
• Filed: 11/09/2007
• Published: 05/14/2009
• Est. Priority Date: 11/09/2007
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Brencher, Lothar
• Granted Patent: US 8,404,597 B2
• Time in Patent Office: Days
• US Class Current: 438/740
• CPC Class Codes: H01L 21/3083 characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H01L 21/76804 by forming tapered via holes
• CPC Class Codes: H01L 21/76832 Multiple layers
• CPC Class Codes: H01L 21/76877 Filling of holes, grooves or trenches, e.g. vias, with conductive material

Abstract

A method for etching a layer assembly, the layer assembly including an intermediate layer sandwiched between an etch layer and a stop layer, the method including a step of etching the etch layer using a first etchant and a step of etching the intermediate layer using a second etchant. The first etchant includes a first etch selectivity of at least 5:1 with respect to the etch layer and the intermediate layer. The second etchant includes a second etch selectivity of at least 5:1 with respect to the intermediate layer and the stop layer. The first etchant being different from the second etchant.

Claims

1. A method for etching a layer assembly comprising an intermediate layer sandwiched between an etch layer and a stop layer, the method comprising:

etching the etch layer using a first etchant, the first etchant comprising a first etch selectivity with respect to the etch layer and the intermediate layer; and

etching the intermediate layer using a second etchant, the second etchant comprising a second etch selectivity with respect to the intermediate layer and the stop layer, wherein the second etchant is different from the first etchant.

2. The method of claim 1, wherein the first etch selectivity comprises a ratio of at least 5:

1 and wherein the second etch selectivity comprises a ratio of at least 5;

1.

3. The method of claim 1, wherein the stop layer comprises a stop layer thickness and the step of etching the intermediate layer is performed such that the stop layer is opened to a depth, the depth comprising less than 50% of the stop layer thickness.

4. The method of claim 1, further comprising performing an the oxygen flash to remove polymers within an etching area.

5. The method of claim 1, further comprising defining an etch region by a resist mask, wherein the etch region is chosen such that outside the etch region the stop layer comprises a direct contact to the etch layer.

6. The method of claim 1, wherein etching the etch layer comprises etching the etch layer such that a part of the stop layer is exposed.

7. The method of claim 1, wherein etching the etch layer comprises etching with a fluorocarbon.

8. The method of claim 1, wherein etching the intermediate layer comprises etching with fluoro-methane.

9. A method for manufacturing a semiconductor device, the method comprising:

forming a stop layer;

forming an intermediate layer over the stop layer, the intermediate layer having an intermediate layer thickness;

forming an etch layer over the intermediate layer, the etch layer having an etch layer thickness; and

performing a first etching step with an etch selectivity,

wherein a ratio of the etch layer thickness to the intermediate layer thickness is at most 3 times the etch selectivity of the first etching step.

10. The method of claim 9, wherein forming the etch layer comprises forming the etch layer such that the etch layer thickness varies more than 10% around a mean value.

11. The method of claim 10, wherein forming the intermediate layer comprises forming the intermediate layer such that the intermediate layer thickness exceeds the ratio of the etch layer thickness to the etch selectivity.

12. A device for stopping an etching process, the etching process comprising a first etching step with a first etch selectivity and a second etching step with a second etch selectivity, comprising:

an etch layer comprising a first material and an etch layer thickness;

an intermediate layer comprising a second material and an intermediate layer thickness; and

a stop layer comprising a third material,

wherein the intermediate layer thickness is such that a ratio of the etch layer thickness to the intermediate layer thickness is at most 3 times the first etch selectivity of the first etching step,

wherein the first and second material are such that the first etching step comprises the first etch selectivity with respect to the first and second material and the first etch selectivity comprises at least a ratio of 5;

1, and

wherein the second and third material are such that the second etching step comprises the second etch selectivity with respect to the second and third material and the second etch selectivity comprise at least a ratio of 5;

1.

13. The device of claim 12, wherein the third material comprises a conducting material.

14. The device of claim 12, wherein the etch layer comprises an oxide layer and the stop layer comprises a metal layer, and wherein the oxide layer and the metal layer are integrated in a metal-oxide-semiconductor (MOS) structure.

15. The device of claim 12, wherein the second material comprises a dielectric material.

16. The device of claim 12, wherein the etch layer comprises non-uniformities with respect to the etch layer thickness or with respect to impurities within the first material.

17. The device of claim 12, wherein a stop layer thickness comprises a value within a range between 20 nm and 60 nm or within a range between 35 nm and 45 nm.

18. The device of claim 12, wherein the intermediate layer thickness is within a range of 10 nm to 50 nm or in a range of 20 nm to 30 nm.

19. The device of claim 12, wherein the stop layer and the etch layer extend into a further region, the stop layer and the etch layer comprising a direct contact in the further region.

20. An apparatus for stopping an etching process, the apparatus comprising:

a first means for stopping a first etching step of an etch layer using a first etchant, the first means comprising an intermediate layer; and

a second means for stopping a second etching step of the intermediate layer using a second etchant, the second means comprising a stop layer,

wherein the first etchant differs from the second etchant, and wherein the intermediate layer being sandwiched by the etch layer and the stop layer.