Etching trenches in a substrate

• US 8,993,451 B2
• Filed: 04/15/2011
• Issued: 03/31/2015
• Est. Priority Date: 04/15/2011
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: McHugh, James F., Kundalgurki, Srivatsa G.
• Primary Examiner(s): OLSEN, ALLAN W
• Application Number:
  US13/088,106
• Publication Number:
  US 20120264307A1
• Time in Patent Office: 1,446 Days
• Field of Search: None
• 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 comprising a semiconductor material body having a principal surface;

forming a dielectric layer over the principal surface of the semiconductor material body;

producing at least one etch window in the dielectric layer;

introducing etch stabilizing ions into a portion of the semiconductor material body of the substrate proximate the principal surface and through the etch window in the dielectric layer, the etch stabilizing ions consisting essentially of fluorine ions implanted to a fluorine ion concentration greater than 5E18 ions per cm³; and

forming the one or more trenches by etching away at least part of the semiconductor material body of the substrate containing the etch stabilizing ions through the etch window in the dielectric layer, the one or more trenches each comprising a cavity or micro-cavity extending into, but not through the semiconductor material body of the substrate, and having a width between about 500 and 1200 micrometers.

2. The method of claim 1, wherein etching is carried out using tetra-methyl-ammonium hydroxide (TMAH).

3. The method of claim 2, further comprising after etching using TMAH, removing TMAH etching reaction products from the portion of the semiconductor material body of the substrate.

4. The method of claim 1, wherein the body of semiconductor material comprises silicon.

5. The method of claim 1, wherein introducing the etch stabilizing ions comprises implanting the portion of the semiconductor material body with fluorine ions at a fluorine dose in the range of about 1E14 per cm² to 1E16 per cm².

6. The method of claim 1, wherein introducing the etch stabilizing ions comprises implanting the portion of the semiconductor material body with fluorine ion at one or more energies in the range of about 5 KeV to 1MeV.

7. the method of claim 1, wherein introducing the etch stabilizing ions comprises implanting the portion of the semiconductor material body with fluorine ions at more than one energy.

8. 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 fluorine ions into a portion of the substrate comprising a semiconductor material and underlying the etch window such that the portion of the substrate comprising the semiconductor material has a fluorine ion concentration greater than 5E18 per cm³; and

forming the one or more trenches by etching at least part of the portion of the substrate comprising the semiconductor material, underlying the etch window, and containing the fluorine ions, the one or more trenches each comprising a cavity or micro-cavity having a width between about 100 and 2000 micrometers and a depth between about 2 and about 50 micrometers.

9. The method of claim 8, wherein the semiconductor material comprises silicon.

10. The method of claim 9, wherein the fluorine ions are introduced by ion implantation.

11. The method of claim 10, wherein the ion implantation is performed at an energy in the range of about 5 KeV to 1MeV.

12. The method of claim 11, wherein the ion implantation is provided at more than one energy to establish the concentration of implanted fluorine ions as a function of depth in the portion of the substrate comprising a semiconductor material.

13. The method of claim 9, wherein the step of forming one or more trenches comprises, etching the portion of the substrate comprising a semiconductor material and underlying the etch window using tetra-methyl-ammonium hydroxide (TMAH).

14. The method of claim 13, further comprising removing TMAH etching reaction products from the portion of the substrate comprising a semiconductor material and underlying the etch window.

15. The method of claim 8 wherein introducing the etch stabilizing ions comprises introducing etching stabilizing ions consisting essentially of fluorine ions into the portion of the semiconductor material body.

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

forming a dielectric layer over the principal surface of the silicon wafer;

producing an etch window in the dielectric layer;

implanting fluorine ions through the etch window and into a silicon-comprising portion of the silicon wafer proximate the principal surface; and

forming the trench by locally etching through the etch window the silicon-comprising portion of the silicon wafer containing the fluorine ions using tetra-methyl-ammonium hydroxide (TMAH), the trench comprising a cavity or micro-cavity extending into, but not through the silicon wafer;

wherein the etching step comprises at least two silicon etching steps separated by one or more cleaning steps.

17. The method of claim 16 wherein the etch window is produced to have a width and length generally corresponding to the desired width and length of the trench.