Junction region between two waveguides and associated method of production

• US 10,451,802 B2
• Filed: 04/03/2019
• Issued: 10/22/2019
• Est. Priority Date: 06/30/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Baudot, Charles
• Primary Examiner(s): Bedtelyon, John
• Application Number:
  US16/374,214
• Publication Number:
  US 20190235166A1
• Time in Patent Office: Days
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12097 Ridge, rib or the like
• CPC Class Codes: G02B 2006/121 Channel; buried or the like
• CPC Class Codes: G02B 2006/12173 Masking
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/136 by etching

Abstract

A photonic integrated device includes a first waveguide and a second waveguide. The first and second waveguides are mutually coupled at a junction region which includes a bulge region. The bulge region is defined two successive etching operations using two distinct etch masks, where the first etching operation is a partial etch and the second etching operation is a complete etch.

Claims

1. A method for producing a photonic integrated device comprising a first waveguide and a second waveguide that are connected to one another by a junction region, the method comprising:

masking a first area of a semiconductor film on an insulator with a first mask;

performing a first etching operation on the semiconductor film wherein said first etching operation comprises etching partially through a thickness of the semiconductor film with the exception of a first area of the semiconductor film which is masked by the first mask;

masking a second area of the semiconductor film with a second mask, said second mask covering a portion of the first mask and covering a reduced thickness portion of the semiconductor film; and

performing a second etching operation on the semiconductor film wherein said second etching operation comprises etching completely through the semiconductor film to the insulator with the exception of the first area and the second area which are masked by the first and second masks;

wherein the first area defines a rib of the first waveguide, the junction region and a strip of the second waveguide, and wherein the second area defines a slab of the first waveguide having the reduced thickness.

2. The method of claim 1, wherein the second mask covering the second area of the semiconductor film extends on opposite sides of the portion of the first mask so that the slab of the first waveguide having the first reduced thickness extends on opposite sides of the rib of the first waveguide.

3. A method for producing a photonic integrated device comprising a first waveguide and a second waveguide that are connected to one another by a junction region, the method comprising:

masking a first area of a semiconductor film on an insulator with a first mask;

performing a first etching operation on the semiconductor film wherein said first etching operation comprises etching partially through a thickness of the semiconductor film with the exception of a first area of the semiconductor film which is masked by a first mask;

masking a second area of the semiconductor film with a second mask, said second mask covering a first portion of the first mask and covering a first reduced thickness portion of the semiconductor film;

performing a second etching operation on the semiconductor film wherein said second etching operation comprises etching partially through the semiconductor film with the exception of the first area and the second area which are masked by the first and second masks;

masking a third area of the semiconductor film with a third mask, said third mask covering a second portion of the first mask and covering a second reduced thickness portion of the semiconductor film;

performing a third etching operation on the semiconductor film wherein said third etching operation comprises etching completely through the semiconductor film to the insulator with the exception of the first area, the second area and the third area which are masked by the first, second and third masks;

wherein the first area defines a rib of the first waveguide, the junction region and a rib of the second waveguide, wherein the second area defines a slab of the first waveguide having the first reduced thickness, and wherein the third area defines a slab of the second waveguide having the second reduced thickness.

4. The method of claim 3, wherein the second mask covering the second area of the semiconductor film extends on opposite sides of the portion of the first mask so that the slab of the first waveguide having the first reduced thickness extends on opposite sides of the rib of the first waveguide.

5. The method of claim 3, wherein the third mask covering the third area of the semiconductor film extends on opposite sides of the portion of the first mask so that the slab of the second waveguide having the second reduced thickness extends on opposite sides of the rib of the second waveguide.

6. A method for producing a photonic integrated device from a semiconductor film on an insulator, wherein said semiconductor film comprises a first lateral area, a second lateral area, a central area, a first intermediate area that is located between the first lateral area and the central area and a second intermediate area that is located between the second lateral area and the central area, the method comprising:

applying a first mask over the semiconductor film, wherein said first mask comprises a first portion located over the first lateral area, a second portion located over the second lateral area, a central portion of constant width located over the central area, a first intermediate portion located over the first intermediate area and a second intermediate portion located over the second intermediate area, wherein a width of the first and second intermediate portions gradually widens in order to meet the constant width of the central portion;

performing a first etching operation on the semiconductor film wherein said first etching operation comprises etching partially through a thickness of the semiconductor film with the exception of areas which are masked by the first mask;

applying a second mask over the semiconductor film, wherein said second mask comprises a rectangular portion of constant width over the first lateral area and a third intermediate portion having a narrowing width over the first intermediate area and at least a part of the central area; and

performing a second etching operation on the semiconductor film wherein said second etching operation comprises etching completely through the semiconductor film to the insulator with the exception of areas which are masked by the first and second masks;

wherein the first portion of the first mask defines a rib of the first waveguide, the first intermediate portion, central portion and second intermediate portion define a junction region, the second portion of the first mask defines a strip of the second waveguide, and wherein the rectangular portion and third intermediate portion of the second mask defines a slab of the first waveguide having a reduced thickness.

7. The method according to claim 6, further comprising positioning the second mask so as to leave a margin of greater than thirty-five nanometers between an end of the third intermediate portion and edges of the central portion of the first mask which define the constant width.