US-12622040-B2 - Diode with contact structure including an improved barrier region and related manufacturing process

US12622040B2US 12622040 B2US12622040 B2US 12622040B2US-12622040-B2

Abstract

The present disclosure is directed to a diode with a semiconductor body of silicon including a cathode region, which has a first conductivity type and is delimited by a front surface; and an anode region, which has a second conductivity type and extends into the cathode region from the front surface. The diode further includes a barrier region of cobalt disilicide, arranged on the anode region; and a metallization region of aluminum or of an aluminum alloy, arranged on the barrier region. The barrier region contacts the anode region.

Inventors

Ettore CHIACCHIO
Ignazio BERTUGLIA

Assignees

STMICROELECTRONICS S.R.L.

Dates

Publication Date: 20260505
Application Date: 20230104
Priority Date: 20220110

Claims (13)

1 . A diode comprising: a semiconductor body; a cathode region in the semiconductor body and delimited by a front surface of the semiconductor body, the cathode region having a first conductivity type; an anode region in the semiconductor body and extending into the cathode region from the front surface, the anode region having a second conductivity type, the anode region including an inner portion and a peripheral portion; a field oxide region on the semiconductor body and on the peripheral portion of the anode region; a front dielectric region on the field oxide region; a first opening in the field oxide region and the front dielectric region, the first opening overlying the inner portion of the anode region; a barrier region including cobalt disilicide, the barrier region extending in the first opening, in direct contact with the inner portion of the anode region; and a metallization region including aluminum, arranged on the barrier region.
2 . The diode according to claim 1 , wherein the semiconductor body includes silicon, the second conductivity type is a P-type conductivity, and the anode region has a peak doping level between 1*10 14 cm −3 and 1*10 16 cm −3 .
3 . The diode according to claim 1 , wherein the metallization region extends on the front dielectric region and in the first opening.
4 . The diode according to claim 1 , wherein the semiconductor body includes an enriched anode region having the second conductivity type, and the enriched anode region extends into the inner portion of the anode region, and has a doping level higher than a doping level of the anode region.
5 . The diode according to claim 1 , wherein the barrier region extends on the inner portion and on the peripheral portion of the anode region, the front dielectric region is on a portion of the barrier region that is on the peripheral portion of the anode region, and the metallization region extends on the front dielectric region and on the portion of the barrier region that is on the inner portion of the anode region.
6 . The diode according to claim 1 , wherein the anode region includes an enriched anode region extending into the inner portion, the enriched anode region has a doping level that is greater than a doping level of the inner portion and the peripheral portion, and the barrier region extends inside the first opening, on the enriched anode region.
7 . A device, comprising: a semiconductor substrate; a cathode region in the semiconductor substrate; an anode region in the cathode region; a barrier region on the anode region; a first dielectric layer on the semiconductor substrate, the first dielectric layer having a first opening overlying the barrier region; a second dielectric layer on the first dielectric layer, the second dielectric layer having a second opening overlying the first opening; a first metallization structure on a first side of the semiconductor substrate; and a second metallization structure on a second side, opposite to the first side, of the semiconductor substrate, on the second dielectric layer, and in the second opening, the second metallization structure including aluminum.
8 . The device of claim 7 , wherein a portion of the second dielectric layer is spaced from the anode region by a portion of the barrier region.
9 . The device of claim 7 , further comprising: an enriched anode region in the anode region and underlying the barrier region.
10 . A diode comprising: a semiconductor body; a cathode region in the semiconductor body and delimited by a front surface of the semiconductor body, the cathode region having a first conductivity type; an anode region in the semiconductor body and extending into the cathode region from the front surface, the anode region having a second conductivity type, the anode region including an inner portion, a peripheral portion, and an enriched anode region extending into the inner portion, the enriched anode region having a doping level that is greater than a doping level of the inner portion and the peripheral portion; a field oxide region on the peripheral portion; a front dielectric region on the field oxide region; and a first opening in the field oxide region and the front dielectric region, and overlying the enriched anode region, and a barrier region including cobalt disilicide, extending inside the first opening, on the enriched anode region; and a metallization region including aluminum, arranged on the barrier region.
11 . The diode according to claim 10 , wherein the semiconductor body includes silicon, the second conductivity type is a P-type conductivity, and the anode region has a peak doping level between 1*10 14 cm −3 and 1*10 16 cm −3 .
12 . The diode according to claim 10 , wherein the metallization region extends on the front dielectric region and in the first opening.
13 . The diode according to claim 10 , wherein the barrier region extends on the inner portion and on the peripheral portion of the anode region, the front dielectric region is on a portion of the barrier region that is on the peripheral portion of the anode region, and the metallization region extends on the front dielectric region and on the portion of the barrier region that is on the inner portion of the anode region.

Description

BACKGROUND Technical Field The present disclosure relates to a diode with a contact structure including an improved barrier region and to the related manufacturing process. Description of the Related Art As is known, in the field of semiconductor device manufacturing, the coupling between a semiconductor device and the outside world is made possible by contact structures that include metal regions (also known as metallizations), which are often formed by aluminum and are arranged in contact with the underlying semiconductor material (in particular, silicon). Since aluminum tends to diffuse into silicon (a phenomenon also known as “interdiffusion”), with consequent diffusion in underneath doped regions and shortening with the deeper doped areas of the silicon, appropriate precautions should be taken to prevent this from happening. For example, it is known that the aforementioned problem is overcome by adding a certain amount of silicon (for example, with a concentration typically comprised in the range 0.8-2%) in the aluminum region, to reduce the solubility of aluminum in the underlying semiconductor material; however, the material thus formed is characterized by high resistivity and has a relatively complicated manufacturing flow. For this reason, solutions have been proposed over time that provide for the use of one or more barrier layers formed by metal materials other than aluminum, such as titanium and related alloys, which guarantee the formation of good contacts on the semiconductor material and have a reduced solubility compared to aluminum. The barrier layers are interposed between the semiconductor material and the aluminum region. In general, metal-semiconductor junctions based on one or more layers of titanium and/or related alloys prove to be satisfactory for contacting N-type or P-type semiconductor regions, provided that the doping is sufficiently high (approximately, higher than 1*1016 cm−3); conversely, the junction exhibits a non-ohmic, i.e., rectifying, behavior. The aforementioned rectifying behavior is particularly evident in case of so-called low efficiency injection anode diode, which are characterized by the presence of an anode region with P-type doping and low doping level (for example, with peak comprised between 1*1014 cm−3 and 1*1016 cm−3). In this case, the anode region has a reduced doping to increase the switching speed of the diode, although this involves an increase in the voltage drop in conduction regime, i.e., an increase in the so-called forward voltage, with the same current flowing through the diode. A partial solution to the aforementioned problem of rectifying contacts in case of P-type semiconductive regions with low doping level is to adopt a barrier layer formed by platinum silicide, so as to benefit from the fact that platinum silicide has a lower Schottky barrier potential height than silicon with P-type doping. Unfortunately, however, platinum silicide has a negative forward voltage drop temperature coefficient at high current levels; this causes, in high power applications with multiple diodes connected in parallel, an irreversible imbalance effect, wherein the diode having the lowest voltage drop at the ends thereof draws the largest part of the load current, up to reaching the thermal runaway condition and the consequent destruction of the electronic component. Furthermore, this imbalance effect becomes even more critical as the junction temperature increases, since the average lifetime of the minority carriers induced by platinum has a positive temperature coefficient which contributes to further lower the voltage drop of diodes in conduction. US 2017/0186847 A1 discloses a diode according to the preamble of claim 1. The paper “Impact of Elevated Source Drain Architecture on ESD Protection Devices for a 90 nm CMOS Technology Node”, of Thijs S. et al., ELECTRICAL OVERSTRESS/ELECTROSTATIC DISCHARGE SYMPOSIUM, 2003, EOS/ESD '03, IEEE, Piscataway, NY, USA, 21 Sep. 2003, pp. 1-8, discloses a diode with a metallization of copper arranged on a barrier region. BRIEF SUMMARY Various embodiments of the present disclosure provide a diode that at least partially overcomes the drawbacks of the prior art, and methods of fabricating the same. The diode includes a semiconductor body having a cathode region, which has a first conductivity type and is delimited by a front surface; and an anode region, which has a second conductivity type and extends into the cathode region from the front surface. The diode further includes a barrier region of cobalt disilicide, arranged on the anode region; and a metallization region of aluminum or of an aluminum alloy, arranged on the barrier region. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS For a better understanding of the present disclosure, embodiments thereof are now described, purely by way of non-limiting example and with reference to the attached drawings, wherein: FIGS. 1, 2, 24, 25, and 26 schematically show cross-se