Self-aligned methods based on low-temperature selective epitaxial growth for fabricating silicon carbide devices

A method of making a silicon carbide p-n junction diode comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one SiC mesa comprising a bottom SiC layer of the first conductivity type disposed on the SiC substrate or drift region and a top SiC emitter layer of a second conductivity type disposed on the bottom SiC layer, and at least one contact disposed at least on the top SiC emitter layer and on the SiC substrate, the method comprising:

• optionally forming a drift region on the SiC substrate;
• forming at least one SEG mask on the SiC substrate or the drift region wherein the SEG mask has window openings exposing the surface of the SiC substrate or the drift region;
• forming by selective epitaxial growth a bottom SiC layer of the first conductivity type in the SEG mask window openings and disposed on the SiC substrate or the drift region;
• forming by selective epitaxial growth a top SiC emitter layer of the second conductivity type in the SEG mask window openings and disposed on the bottom SiC layer;
• and
• forming at least one contact on at least the top SiC emitter layer and the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide diode comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one SiC emitter mesa formed by selective epitaxial growth, optionally a plurality of mesa edge termination regions, and at least one ohmic contact disposed on at least the emitter mesa and on the SiC substrate, the method comprising:

• optionally forming a drift region disposed on the SiC substrate;
• forming at least one SEG mask having at least one window opening and disposed on the SiC substrate or drift region, wherein the window opening exposes the surface of the SiC substrate or drift region;
• optionally removing to a selected depth a portion of the SiC substrate or drift region in the window opening, thereby forming at least one trench in the exposed surface of the SiC substrate or drift region;
• forming by selective epitaxial growth at least one SiC emitter mesa in at least one of the SEG mask window openings and disposed on the SiC substrate or drift region;
• optionally forming by selective epitaxial growth simultaneously with the formation of the SiC emitter mesa a plurality of mesa edge termination regions in at least one other SEG mask window opening and disposed on the SiC substrate or drift region;
• and
• forming at least one ohmic contact on at least the emitter mesa and the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide diode comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one Schottky contact layer, a plurality of mesa edge termination regions, and at least one ohmic contact disposed on at least the SiC substrate, the method comprising:

• optionally forming a drift region disposed on the SiC substrate;
• forming at least one SEG mask having a plurality of window openings and disposed on the SiC substrate or drift region, wherein at least one window opening of the plurality of window openings exposes a first portion of the surface of the SiC substrate or drift region;
• optionally removing to a selected depth a portion of the SiC substrate or drift region in the at least one window opening of the plurality of window openings, thereby forming at least one trench in the exposed first portion of the surface of the SiC substrate or drift region;
• forming by selective epitaxial growth a plurality of mesa edge termination regions in the plurality of SEG mask window openings and disposed on the SiC substrate or drift region;
• removing the SEG mask, thereby exposing a second portion of the surface of the SiC substrate or drift region;
• forming the at least one Schottky contact layer on the exposed second portion of the surface of the SiC substrate or drift region, wherein the Schottky contact layer is in contact with two adjacent mesa edge termination regions;
• and
• forming ohmic contacts on at least the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide diode, comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one SiC emitter mesa comprising at least a first layer and a second layer of different doping levels formed by selective epitaxial growth, optionally a plurality of mesa edge termination regions formed by selective epitaxial growth having the same conductivity type as one of the first layer or second layer of different doping levels of the SiC emitter mesa, and ohmic contacts disposed at least on the emitter mesa and on the SiC substrate, the method comprising:

• optionally forming a drift region on the SiC substrate;
• forming a first SEG mask having a plurality of window openings and disposed on the SiC substrate or drift region, wherein the plurality of the window openings exposes the surface of the SiC substrate or drift region;
• optionally removing to a selected depth a portion of the SiC substrate or drift region in at least one window opening of the plurality of window openings in the first SEG mask, thereby forming at least one trench in the exposed surface of the SiC substrate or drift region;
• forming a second SEG mask disposed on the first SEG mask, wherein the second SEG mask covers the exposed surface of the SiC substrate or drift region in a first group of the plurality of window openings and does not cover the exposed surface of the SiC substrate or drift region in a second group of the plurality of window openings;
• forming by selective epitaxial growth on the exposed surface of the SiC substrate or drift region in the second group of the plurality of window openings a first layer of the SiC emitter mesa having a selected doping level;
• removing at least a portion of the second SEG mask covering the surface of the SiC substrate or drift region in the first group of the plurality of window openings;
• forming by selective epitaxial growth a second layer of the SiC emitter mesa having doping different from the doping of the first layer of the SiC emitter mesa and disposed on the first layer of the SiC emitter mesa in the second group of the plurality of window openings, and simultaneously forming at least one mesa edge termination region having doping different from the doping of the first layer of the SiC emitter mesa and disposed on the surface of the SiC substrate or drift region in the first group of the plurality of window openings;
• and
• forming at least one ohmic contact on at least the SiC emitter mesa and the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide diode, comprising a SiC substrate of a first conductivity type, optionally a drift region of the first conductivity type disposed on the SiC substrate, a plurality of SiC emitter mesas of a second conductivity type formed by selective epitaxial growth, optionally a plurality of mesa edge termination regions of the second conductivity type formed by selective epitaxial growth, at least one Schottky contact layer disposed on the SiC substrate or drift region, and at least one ohmic contact disposed on at least the plurality of emitter mesas and on the SiC substrate, the method comprising:

• optionally forming a drift region of a first conductivity type disposed on the SiC substrate;
• forming a SEG mask having a plurality of window openings and disposed on the SiC substrate or drift region, wherein the plurality of window openings exposes the surface of the SiC substrate or drift region;
• optionally removing to a selected depth a portion of the SiC substrate or drift region in at least one window opening of the plurality of window openings of the SEG mask, thereby forming at least one trench in the exposed surface of the SiC substrate or drift region;
• forming by selective epitaxial growth a plurality of SiC emitter mesas in a first group of the plurality of the SEG mask window openings and disposed on the SiC substrate or drift region and optionally forming a plurality of mesa edge termination regions in a second group of the plurality of SEG mask window openings and disposed on the SiC substrate or drift region;
• forming at least one ohmic contact on at least one emitter mesa of the plurality of SiC emitter mesas;
• removing the SEG mask;
• forming at least one Schottky contact layer on the SiC substrate or drift region between at least two of the plurality of SiC emitter mesas;
• and
• forming at least one ohmic contact on at least the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide transistor, comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one SiC channel mesa having a portion thereof of the first conductivity type, at least one SiC gate region having a portion thereof of a second conductivity type, optionally a SiC gate-contact region of the second conductivity type, and at least one contact disposed at least on the SiC channel mesa and on the SiC substrate and disposed on the SiC gate-contact region or on the SiC gate region, the method comprising:

• optionally forming a drift region of a first conductivity type on the SiC substrate;
• forming at least one SiC channel mesa having at least a top surface and sidewalls and having at least a portion thereof of the first conductivity type and disposed on the SiC substrate or drift region and having at least one gate-SEG mask disposed on the top surface of the SiC channel mesa;
• and
• forming by selective epitaxial growth at least one SiC gate region having a portion thereof of the second conductivity type and disposed on the SiC substrate or drift region and on the sidewalls of the SiC channel mesa, wherein the at least one gate-SEG mask is used to prohibit epitaxial growth on the top surface of the SiC channel mesa;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.

A method of making a silicon carbide bipolar junction transistor, comprising a SiC substrate of a first conductivity type, optionally a SiC drift region of the first conductivity type disposed on the SiC substrate, at least one SiC intrinsic base region of a second conductivity type, at least one SiC emitter mesa of the first conductivity type, at least one SiC base-contact region of the second conductivity type, optionally a plurality of SiC mesa edge termination regions, and a plurality of contacts disposed at least on the SiC emitter mesa, on the SiC base-contact region, and on the SiC substrate, the method comprising:

• optionally forming a drift region of a first conductivity type on the substrate layer;
• forming at least one intrinsic base region of a second conductivity type disposed on the SiC substrate or drift region;
• forming at least one emitter mesa having vertical sidewalls of the first conductivity type disposed on the intrinsic base region;
• forming a base-contact-region-SEG mask covering at least one selected portion of the SiC emitter mesa;
• forming by selective epitaxial growth at least one base-contact region of the second conductivity type, wherein the base-contact-region-SEG mask is used as the mask for selective epitaxial growth and the base-contact region is in contact with at least one selected portion of the intrinsic base region;
• and
• forming a plurality of contacts on at least the SiC emitter mesa, on the SiC base-contact region, and on the SiC substrate;
• wherein the selective epitaxial growth is by selective epitaxial growth conducted at temperatures sufficiently low to prevent mask degradation during growth.