US-12628373-B2 - Semiconductor device having a field termination structure and a charge balance structure, and method of producing the semiconductor device

US12628373B2US 12628373 B2US12628373 B2US 12628373B2US-12628373-B2

Abstract

A semiconductor device includes: a semiconductor substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the semiconductor substrate; a field termination structure in the termination region and including a continuous region of a first conductivity type and a plurality of rings of the first conductivity type in the continuous region and having a higher average doping concentration than the continuous region; and a charge balance structure in the active device region and including interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type. The charge balance structure extends into the termination region below the field termination structure such that at least an outermost one of the columns of the first conductivity type is connected to the continuous region of the field termination structure.

Inventors

Michael Hell
Rudolf Elpelt
Frank Hille
Caspar Leendertz
Armin Willmeroth

Assignees

INFINEON TECHNOLOGIES AG

Dates

Publication Date: 20260512
Application Date: 20221213

Claims (20)

1 . A semiconductor device, comprising: a semiconductor substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the semiconductor substrate; a field termination structure in the termination region and comprising a continuous region of a first conductivity type and a plurality of rings of the first conductivity type in the continuous region and having a higher average doping concentration than the continuous region; and a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, wherein the charge balance structure extends into the termination region below the field termination structure such that at least an outermost one of the columns of the first conductivity type is connected to the continuous region of the field termination structure, wherein a first subset of the plurality of rings of the first conductivity type is positioned between the active device region and a second subset of the plurality of rings of the first conductivity type, wherein the second subset of the plurality of rings of the first conductivity type is positioned between the first subset of the plurality of rings of the first conductivity type and the edge of the semiconductor substrate, wherein the charge balance structure extends into the termination region below the first subset of the plurality of rings of the first conductivity type but not below the second subset of the plurality of rings of the first conductivity type.
2 . The semiconductor device of claim 1 , wherein the interleaved columns of the charge balance structure disposed below the first subset of the plurality of rings of the first conductivity type in the termination region have the same spacing and the same vertical and horizontal dimensions as the interleaved columns of the charge balance structure disposed in the active device region.
3 . The semiconductor device of claim 1 , wherein at least some of the columns of the first conductivity type of the charge balance structure disposed below the first subset of the plurality of rings of the first conductivity type in the termination region have a different width and/or depth as the columns of the first conductivity type of the charge balance structure disposed in the active device region.
4 . The semiconductor device of claim 1 , wherein for a first rectilinear part of the termination region, the interleaved columns of the charge balance structure run parallel to the rings of the field termination structure, wherein for a second rectilinear part of the termination region, the interleaved columns of the charge balance structure run transverse to the rings of the field termination structure, and a corner part of the termination region connects the first and second rectilinear parts.
5 . The semiconductor device of claim 1 , wherein the charge balance structure extends to an outer edge of the field termination structure.
6 . The semiconductor device of claim 1 , wherein the continuous region and the plurality of rings of the first conductivity type terminate at a same depth in the semiconductor substrate.
7 . The semiconductor device of claim 1 , wherein the continuous region extends deeper into the semiconductor substrate than the plurality of rings of the first conductivity type.
8 . The semiconductor device of claim 7 , wherein the field termination structure comprises a plurality of rings of the second conductivity type in the continuous region and interleaved with the plurality of rings of the first conductivity type.
9 . The semiconductor device of claim 7 , wherein the continuous region connects each column of the first conductivity type in the termination region to the plurality of rings of the first conductivity type.
10 . The semiconductor device of claim 1 , wherein a width and/or an average doping concentration of the plurality of rings of the first conductivity type decreases in a horizontal direction heading towards the edge of the semiconductor substrate.
11 . The semiconductor device of claim 1 , wherein an average doping concentration of the plurality of rings of the first conductivity type is greater than an average doping concentration of the columns of the first conductivity type.
12 . The semiconductor device of claim 1 , wherein a plurality of the columns of the first conductivity type are disposed below the field termination structure and electrically connected to the plurality of the rings of the first conductivity type.
13 . The semiconductor device of claim 12 , wherein a depth of the plurality of the columns of the first conductivity type disposed below the field termination structure decreases in a horizontal direction heading towards the edge of the semiconductor substrate.
14 . The semiconductor device of claim 12 , wherein a width and/or an average doping concentration of the plurality of the columns of the first conductivity type disposed below the field termination structure decreases in a horizontal direction heading towards the edge of the semiconductor substrate.
15 . The semiconductor device of claim 1 , wherein the semiconductor substrate is a SiC substrate.
16 . The semiconductor device of claim 1 , further comprising a transition region of the first conductivity type between the active device region and the termination region, wherein the transition region has a higher average doping concentration than both the continuous region of the field termination structure and the columns of the first conductivity type, wherein the charge balance structure extends below the transition region and into the termination region, and wherein the columns of the first conductivity type disposed below the transition region are connected to the transition region.
17 . The semiconductor device of claim 1 , wherein the columns of the first and/or second conductivity type in the active device region have a different doping profile than each column of the same conductivity type disposed below the field termination structure.
18 . The semiconductor device of claim 1 , wherein an upper part of the columns of the first conductivity type are doped more heavily than an adjacent upper part of the columns of the second conductivity type, and wherein a lower part of the columns of the first conductivity type are doped more lightly than an adjacent lower part of the columns of the second conductivity type.
19 . A semiconductor device, comprising: a SiC substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the SiC substrate; a junction termination extension of a first conductivity type in the termination region; and a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, wherein the charge balance structure extends into the termination region below the junction termination extension, wherein a depth of the interleaved columns of the charge balance structure disposed below the junction termination extension decreases in a horizontal direction heading towards the edge of the SiC substrate.
20 . A semiconductor device, comprising: a semiconductor substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the semiconductor substrate; a field termination structure in the termination region and comprising a continuous region of a first conductivity type and a plurality of rings of the first conductivity type in the continuous region and having a higher average doping concentration than the continuous region; and a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, wherein the charge balance structure extends into the termination region below the field termination structure such that at least an outermost one of the columns of the first conductivity type is connected to the continuous region of the field termination structure, wherein the continuous region extends deeper into the semiconductor substrate than the plurality of rings of the first conductivity type, wherein the field termination structure comprises a plurality of rings of the second conductivity type in the continuous region and interleaved with the plurality of rings of the first conductivity type.

Description

BACKGROUND SiC (silicon carbide) power devices require a suitable edge termination to ensure break down stability. The design of the edge termination is especially challenging for superjunction devices which are based on the idea of charge balancing in the device drift region. Typical superjunction edge termination designs require dimensioning or doping of the superjunction pillars to be different in the cell field where the active device cells reside compared to the termination region which separates the cell field from the chip (die) edge. Such designs locate the breakthrough in the cell field. The manufacturing of this kind of design is especially challenging for SiC devices which requires additional masks and precise mask alignment, or even masks with smaller openings for the termination region. In terms of cost-performance, very high-energy implantations may be used to manufacture SiC superjunction pillars. Accordingly, masks with small openings require very high thickness or even the use of metal as the masking material. Such masks would be extremely expensive and give rise to higher minimal mask openings and higher process variation than typical oxide or even photoresist masks. Therefore, such designs are costly, require careful adjustment for different voltage classes, and suffer from process variations. Other SiC superjunction edge termination solutions require a complicated processing step involving SiC back etch and regrowth. Thus, there is a need for an improved edge termination design for SiC superjunction devices. SUMMARY According to an embodiment of a semiconductor device, the semiconductor device comprises: a semiconductor substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the semiconductor substrate; a field termination structure in the termination region and comprising a continuous region of a first conductivity type and a plurality of rings of the first conductivity type in the continuous region and having a higher average doping concentration than the continuous region; and a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, wherein the charge balance structure extends into the termination region below the field termination structure such that at least an outermost one of the columns of the first conductivity type is connected to the continuous region of the field termination structure. According to an embodiment of a method of producing a semiconductor device, the method comprises: forming a plurality of device cells in an active device region of a semiconductor substrate, the semiconductor substrate also having a termination region between the active device region and an edge of the semiconductor substrate; forming a field termination structure in the termination region and comprising a continuous region of a first conductivity type and a plurality of rings of the first conductivity type in the continuous region and having a higher average doping concentration than the continuous region; and forming a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, the charge balance structure extending into the termination region below the field termination structure such that at least an outermost one of the columns of the first conductivity type is connected to the continuous region of the field termination structure. According to another embodiment of a semiconductor device, the semiconductor device comprises: a SiC substrate having an active device region that includes a plurality of device cells and a termination region between the active device region and an edge of the SiC substrate; a junction termination extension of a first conductivity type in the termination region; and a charge balance structure in the active device region and comprising interleaved columns of the first conductivity type and of a second conductivity type opposite the first conductivity type, wherein the charge balance structure extends into the termination region below the junction termination extension, wherein a depth of the interleaved columns of the charge balance structure disposed below the junction termination extension decreases in a horizontal direction heading towards the edge of the SiC substrate. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE FIGURES The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. The features of the various illustrated embodiments can be combined unless they exclude each