WO1991010931A1 - Fabrication de guide d'ondes - Google Patents

Fabrication de guide d'ondes Download PDF

Info

Publication number
WO1991010931A1
WO1991010931A1 PCT/GB1991/000044 GB9100044W WO9110931A1 WO 1991010931 A1 WO1991010931 A1 WO 1991010931A1 GB 9100044 W GB9100044 W GB 9100044W WO 9110931 A1 WO9110931 A1 WO 9110931A1
Authority
WO
WIPO (PCT)
Prior art keywords
substrate
matrix
silicon
porous
subjecting
Prior art date
Application number
PCT/GB1991/000044
Other languages
English (en)
Inventor
Anthony David Welbourn
John Nicholas Shepherd
Original Assignee
British Telecommunications Public Limited Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Telecommunications Public Limited Company filed Critical British Telecommunications Public Limited Company
Publication of WO1991010931A1 publication Critical patent/WO1991010931A1/fr

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/13—Integrated optical circuits characterised by the manufacturing method

Definitions

  • This invention relates to a method of fabricating an optical waveguide, and in particular to a waveguide fabrication method involving double porous anodisation of silicon.
  • the core of the waveguide for example with erbium or neodymium
  • the waveguide to be used as an active optical component such as an amplifier or a laser.
  • this doping is difficult to achieve.
  • the aim of the invention is to provide an improved method of fabricating an optical waveguide and particularly a doped waveguide.
  • the present invention provides a method of fabricating an optical waveguide, the method comprising the steps of:- (i) forming a strip of doped silicon in a silicon substrate;
  • an oxide cladding layer is formed on top of the substrate, said oxide layer overlying said matrix. This results in a buried waveguide whose core is completely surrounded by oxide, thereby resulting in a more uniform optical mode.
  • oxide cladding layer other overlay materials could be used to change the properties of the waveguide, for example by plasma interaction with a metal.
  • each of the porous anodisation steps is carried out by placing the substrate in an electrochemical cell in an HF solution.
  • the strip of doped silicon is formed in the substrate by a boron diffusion step.
  • the boron diffusion is carried out through a mask formed photolithographically on the surface of the substrate.
  • the nitridation step is carried out by heating the substrate in an atmosphere of ammonia, the nitridation process comprising the steps of:-
  • the doped region surrounding said matrix is formed by a boron diffusion process.
  • the oxidation process is carried out by heating the substrate in ' dry oxygen, the oxidation process comprising the steps of:-
  • the oxide cladding layer is formed by a deposition technique such as chemical vapour deposition (CVD) or plasma enhanced chemical vapour deposition (PECVD).
  • CVD chemical vapour deposition
  • PECVD plasma enhanced chemical vapour deposition
  • FIG. 1 Figs, l to 4 are schematic longitudinal cross-sections which illustrate the basic process sequence of the fabrication method of the invention.
  • Fig. 1 shows an n-type silicon substrate 1.
  • An oxide layer is then formed on the substrate 1, the oxide layer being lj_m thick and being subjected to a photolithographic process to form a mask 2.
  • Boron is then diffused into the substrate 1 through the mask 2.
  • the boron diffusion process defines a strip 3 of p silicon which is capable of supporting a fine porous structure in a subsequent anodisation step.
  • the diffusion schedule can be carefully controlled to provide a precise depth (typically between 0.25 and 5um) for the strip 3 which is to constitute the core of the waveguide. This stage of the process is shown in Fig. 1.
  • the mask 2 is then stripped off using a buffered HF etchant.
  • the substrate 1 is then subjected to porous ' anodisation, that is to say it is placed in an electrochemical cell in an HF solution.
  • the HF attacks the p silicon to form a porous structure having a very large surface area.
  • the HF attacks the doped p silicon preferentially, so that the porous anodisation is substantially restricted to the strip 3.
  • the size and density of the pores in the strip 3 depend upon the current density flowing in the cell.
  • the current density is of the order of lOmA/cm , so that a subsequent nitridation step results in a substantially fully-dense, stress-free matrix.
  • the substrate 1 is subjected to a nitridation step, during which the porous structure of the strip 3 has its volume porousity substantially filled with silicon oxynitride.
  • a nitridation step during which the porous structure of the strip 3 has its volume porousity substantially filled with silicon oxynitride. This is accomplished by loading the substrate 1 into a furnace at a temperature of 200 * C, subjecting the substrate to a ramped annealing step (the rate of temperature increase during this ramped annealing step being 8 * C per minute) until the temperature reaches 725 * C, and holding the substrate at this temperature for 60 minutes. The entire heating process is carried out under 0.5bar of ammonia. This results in a substantially fully-dense (> 90%) silicon oxynitride matrix 3' which is substantially stress-free.
  • the depth of the p layer 4 can be accurately controlled, preferably to a . depth of between 4 and 5um below the base of the silicon oxynitride matrix 3' (i.e. an overall depth of about 5 to 10 m).
  • the substrate 1 is then subjected to a second porous anodisation step, in which the HF in the electrochemical cell preferentially attacks the p layer 4 to form a porous structure.
  • the region of the p layer below the matrix 3' is found to be deeper than the rest of the layer 4. This is believed to be caused by enhanced diffusion of boron through residual pores, or by stress in the matrix 3'.
  • boron in the matrix 3' could be snow-ploughed into the substrate 1 during the nitridation step. This stage of the process is shown in Fig. 2.
  • the porous p structure 4 is then converted to a silicon dioxide matrix 4*, which encapsulates the silicon oxynitride matrix 3', by an oxidation process.
  • This process starts with a 60 minute low temperature (350'C) anneal in dry oxygen, and finishes with a 10 minute anneal at 1150 * C in steam, a ramped anneal in steam taking place between the two other heating steps.
  • the rate of temperature increase during the ramped anneal step is 4 * C per minute. This stage of the process is shown in Fig. 3.
  • an oxide cladding layer 5 2 thick is deposited on the top of the substrate 1 ( and overlying the silicon oxynitride matrix 3' ) by low pressure chemical vapour deposition (LPCVD) or by plasma-enhanced chemical vapour deposition (PECVD). This stage of the process is shown in Fig. 4.
  • This cladding layer 5 completes the encapsulation of the oxynitride strip 3 by oxide layers.
  • silicon oxynitride has a slighter higher ref ctive index than silicon dioxide, the strip 3 forms the waveguiding core of a strip waveguide.
  • the oxide cladding layer 5 is optional, as a useful waveguide is produced at the Fig. 3 stage.
  • the layer 5 is preferable, however, as it results in a buried waveguide whose core (the matrix 3') is completely surrounded by oxide. This results in a waveguide which has a more uniform optical mode.
  • other cladding materials may be used to change the properties of the waveguide, for example by plasma interaction with a metal.
  • the waveguide is to be used as an active optical component (such as an amplifier or a laser) its core (the matrix 3' ) is doped with an optically-active material such as erbium or neodymium. This doping step is carried out after the first porous anodisation step and before the nitridation step.
  • a waveguide fabricated in this manner has the following useful properties, namely:-
  • the sidewalls of the waveguiding core are smooth, having been defined by the first boron diffusion profile;
  • the depth of the waveguiding core can be accurately controlled by careful control of the first boron diffusion;
  • the waveguiding core is easy to dope (for example with erbium), so the waveguide can be used an an active optical component such as an amplifier or a laser;
  • the waveguide has a planar upper surface, both before and after the formation of the oxide cladding layer, so that subsequent processing is facilitated whether or not this optional cladding layer is present. If the cladding layer 5 is present, subsequent processing can include the opening up of windows in the cladding layer to provide selective regions of active overlay (for example for making sensors).

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Integrated Circuits (AREA)

Abstract

Procédé de fabrication d'un guide d'ondes optique comprenant initialement la formation d'une bande (3) de silicone dopé sur un substrat de silicone (1). Le substrat (1) est ensuite soumis à une phase d'anodisation poreuse par laquelle la bande de silicone dopé (3) est transformée en structure poreuse. Le substrat (1) est ensuite nitruré, ce qui conduit à la transformation de la structure poreuse (3) en matrice d'oxynitrure de silicone de pleine densité (3'). Une zone de silicone dopé (4) est alors formée autour de la matrice d'oxynitrure de silicone (3'). Le substrat (1) est ensuite soumis à une seconde phase d'anodisation par laquelle la région dopée (4) est convertie en une structure poreuse (4'). Le substrat (1) est alors oxydé, ce qui conduit à la conversion de la structure poreuse (4') en matrice de dioxyde de silicone de pleine densité. Finalement, une couche d'oxyde peut être formée au-dessus du substrat (1).
PCT/GB1991/000044 1990-01-15 1991-01-14 Fabrication de guide d'ondes WO1991010931A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9000852.5 1990-01-15
GB909000852A GB9000852D0 (en) 1990-01-15 1990-01-15 Waveguide fabrication

Publications (1)

Publication Number Publication Date
WO1991010931A1 true WO1991010931A1 (fr) 1991-07-25

Family

ID=10669308

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1991/000044 WO1991010931A1 (fr) 1990-01-15 1991-01-14 Fabrication de guide d'ondes

Country Status (3)

Country Link
AU (1) AU7074691A (fr)
GB (1) GB9000852D0 (fr)
WO (1) WO1991010931A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2306694A (en) * 1995-10-17 1997-05-07 Northern Telecom Ltd Strip-loaded planar optical waveguide
GB2312524A (en) * 1996-04-24 1997-10-29 Northern Telecom Ltd Planar optical waveguide cladding by PECVD method
JPH1114848A (ja) * 1997-06-19 1999-01-22 Kyocera Corp 光導波路の製造方法
JPH1152175A (ja) * 1997-07-31 1999-02-26 Kyocera Corp 光集積回路基板及びその製造方法
DE19755416C1 (de) * 1997-12-12 1999-06-10 Bosch Gmbh Robert Verfahren zur Herstellung von Lichtwellenleitern
DE19803852A1 (de) * 1998-01-31 1999-08-12 Bosch Gmbh Robert Verfahren zur Herstellung beidseitig oxidierter Siliziumwafer
EP1610159A1 (fr) * 2003-03-31 2005-12-28 Hamamatsu Photonics K. K. Substrat de silicium et procede de formation de ce dernier

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01227104A (ja) * 1988-03-08 1989-09-11 Fujikura Ltd 光伝送路装置及びその製造方法

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01227104A (ja) * 1988-03-08 1989-09-11 Fujikura Ltd 光伝送路装置及びその製造方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Applied Optics, vol. 16, no. 12, December 1977, W. Stutius et al.: "Silicon nitride films on silicon for optical waveguides", pages 3218-3222 *
Applied Physics Letters, vol. 47, no. 4, August 1985 American Institut of Physics, New York (US) D.E. Zelmon et al.: "Low loss optical waveguides fabricated by thermal nitridation of oxidized silicon", pages 353-355 *
Patent Abstracts of Japan, vol. 13, no. 547, (P-971)(3895), 7 December 1989; & JP-A-1227104 (FUJIKURA LTD) 11 September 1989 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2306694A (en) * 1995-10-17 1997-05-07 Northern Telecom Ltd Strip-loaded planar optical waveguide
GB2312524A (en) * 1996-04-24 1997-10-29 Northern Telecom Ltd Planar optical waveguide cladding by PECVD method
JPH1114848A (ja) * 1997-06-19 1999-01-22 Kyocera Corp 光導波路の製造方法
JPH1152175A (ja) * 1997-07-31 1999-02-26 Kyocera Corp 光集積回路基板及びその製造方法
DE19755416C1 (de) * 1997-12-12 1999-06-10 Bosch Gmbh Robert Verfahren zur Herstellung von Lichtwellenleitern
DE19803852A1 (de) * 1998-01-31 1999-08-12 Bosch Gmbh Robert Verfahren zur Herstellung beidseitig oxidierter Siliziumwafer
DE19803852C2 (de) * 1998-01-31 2003-12-18 Bosch Gmbh Robert Verfahren zur Herstellung beidseitig oxidierter Siliziumwafer
EP1610159A1 (fr) * 2003-03-31 2005-12-28 Hamamatsu Photonics K. K. Substrat de silicium et procede de formation de ce dernier
EP1610159A4 (fr) * 2003-03-31 2008-06-04 Hamamatsu Photonics Kk Substrat de silicium et procede de formation de ce dernier

Also Published As

Publication number Publication date
AU7074691A (en) 1991-08-05
GB9000852D0 (en) 1990-03-14

Similar Documents

Publication Publication Date Title
US4002512A (en) Method of forming silicon dioxide
EP1576399B1 (fr) Procede de fabrication de guides d'ondes optiques
US6690871B2 (en) Graded index waveguide
JP2000039532A (ja) プレ―ナ型導波路構造体を製造する方法および導波路構造体
KR970013012A (ko) 반도체기판 및 그의 제작방법
EP0552218B1 (fr) Procede de fabrication des guides d'ondes et rainures en v a alignement automatique
US5035916A (en) Optical waveguide and method for its manufacture
WO1991010931A1 (fr) Fabrication de guide d'ondes
US7563628B2 (en) Fabrication of optical waveguide devices
JP5137278B2 (ja) 光学デバイスの製造方法
Syms et al. Reflow and burial of channel waveguides formed in sol-gel glass on Si substrates
US5719086A (en) Method for isolating elements of semiconductor device
EP0189795B1 (fr) Plage de matériau impénétrable pour l'oxygène sur un substrat semi-conducteur
US6735370B1 (en) Waveguide for an optical circuit and method of fabrication thereof
Nagata et al. Single-mode optical waveguide fabricated by oxidization of selectively doped titanium porous silicon
JP3245347B2 (ja) 光導波路装置の製造方法
JP3245368B2 (ja) 光導波路の製造方法
JP3245367B2 (ja) 光導波路の形成方法
US7756377B2 (en) Waveguide comprising a channel on an optical substrate
JPH11237516A (ja) 石英系ガラス導波路およびその製造方法
JP3454134B2 (ja) 導波路およびその製造方法
JPH07333452A (ja) 光導波路の製造方法
JPH01227104A (ja) 光伝送路装置及びその製造方法
WO1996041219A1 (fr) Procede de fabrication de fibres optiques integrees et unite optique a fibres optiques integrees
JPS63186423A (ja) 半導体装置の製造方法

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AU CA JP US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IT LU NL SE

NENP Non-entry into the national phase

Ref country code: CA