ETCHING TRENCHES IN A SUBSTRATE

• US 20120264307A1
• Filed: 04/15/2011
• Published: 10/18/2012
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Kundalgurki, Srivatsa G., McHugh, James F.
• Granted Patent: US 8,993,451 B2
• Time in Patent Office: Days
• US Class Current: 438/705
• CPC Class Codes: B81C 1/00063 Trenches
• CPC Class Codes: B81C 1/00626 Processes for achieving a desired geometry not provided for in groups B81C1/00563 - B81C1/00619
• CPC Class Codes: B81C 2201/0136 by doping limited material regions
• CPC Class Codes: H01L 21/02057 Cleaning during device manufacture
• CPC Class Codes: H01L 21/26506 in group IV semiconductors
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: H01L 21/3083 characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane

Abstract

Etch stabilizing ions (37) are introduced, e.g., by ion implantation (34), into a portion (36) of a substrate (20) underlying an etch window (24) in a masking layer (22) covering the substrate (20), where a trench (26) is desired to be formed. When the portion (36) of the substrate (20) containing the etch stabilizing ions (37) is etched to form the trench (26), the etch stabilizing ions (37) are progressively released at the etch interface (28′) as etching proceeds, substantially preventing gas micro-bubbles or other reaction products at the etch interface (28′) from disrupting etching. Using this method (700), products containing trenches (26) are much more easily formed and such trenches (26) have much smoother interior surface (28).

Claims

1. A method for providing an electronic product containing one or more trenches, comprising:

providing a substrate having a principal surface;

introducing etch stabilizing ions into a portion of the substrate proximate the principal surface; and

forming the one or more trenches by etching away at least part of the portion of the substrate containing the etch stabilizing ions.

2. The method of claim 1, further comprising:

forming on the principal surface a mask layer resistant to etching of the substrate;

opening an etch window in the mask layer overlying the desired location of the one or more trenches; and

etching away the at least part of the portion of the substrate containing the etch stabilizing ions through the etch window.

3. The method of claim 2, wherein etching is carried out using tetra-methyl-ammonium hydroxide (TMAH).

4. The method of claim 3, further comprising after etching using TMAH, removing TMAH etching reaction products from the portion of the substrate.

5. The method of claim 1, wherein the substrate comprises silicon and the etch stabilizing ions comprise fluorine.

6. The method of claim 5, wherein the etch stabilizing ions are introduced by ion implantation.

7. The method of claim 6, wherein the ion implantation is provided at a fluorine dose in the range of about 1E14 per cm² to 1E16 per cm².

8. The method of claim 6, wherein the ion implantation is performed at one or more energies in the range of about 5 KeV to 1 MeV.

9. The method of claim 6, wherein the ion implantation is provided at more than one energy.

10. A method for etching one or more trenches in a substrate, comprising:

providing a substrate adapted to receive the one or more trenches therein;

forming on the substrate a mask layer resistant to etching of the substrate;

opening an etch window in the mask layer overlying the desired location of the one or more trenches;

introducing etch stabilizing ions into a portion of the substrate underlying the etch window; and

forming the one or more trenches by etching at least part of the portion of the substrate underlying the etch window containing the etch stabilizing ions.

11. The method of claim 10, wherein the substrate comprises silicon and the etch stabilizing ions comprise fluorine.

12. The method of claim 11, wherein the etch stabilizing ions are introduced by ion implantation.

13. The method of claim 12, wherein the ion implantation is provided to a doping concentration in the substrate greater than 5E18 per cm³.

14. The method of claim 13, wherein the ion implantation is performed at an energy in the range of about 5 KeV to 1 MeV.

15. The method of claim 14, wherein the ion implantation is provided at more than one energy to establish the concentration of implanted ions as a function of depth in the portion.

16. The method of claim 11, wherein the step of forming one or more trenches comprises, etching the portion of the substrate underlying the etch window using tetra-methyl-ammonium hydroxide (TMAH).

17. The method of claim 16, further comprising removing TMAH etching reaction products from the portion of the substrate underlying the etch window.

18. A method for forming a trench in a principle surface of a silicon wafer, comprising:

implanting fluorine ions in a portion of the silicon wafer proximate the principal surface; and

forming the trench by locally etching the portion of the silicon wafer containing the fluorine ions.

19. The method of claim 18, wherein the etching step comprises at least two silicon etching steps separated by one or more cleaning steps.

20. The method of claim 19, wherein the at least two silicon etching steps use a tetra-methyl-ammonium hydroxide (TMAH) etchant.