Search

JP-2026074621-A - Semiconductor equipment

JP2026074621AJP 2026074621 AJP2026074621 AJP 2026074621AJP-2026074621-A

Abstract

[Problem] To improve the trade-off between reverse breakdown voltage and current in semiconductor devices. [Solution] The semiconductor device 10 includes a channel layer 14, an electron supply layer 16, a first cap layer 18 provided in a first region W1 and a second region W2 on the electron supply layer 16 and made of an n-type nitride semiconductor with a larger band gap than the channel layer 14, a second cap layer 20 provided on the first cap layer 18 and made of an n-type nitride semiconductor with a smaller band gap than the first cap layer 18, a first ohmic electrode 22 provided on the second cap layer 20 in the first region W1, a second ohmic electrode 24 provided on the second cap layer 20 in the second region W2, and a Schottky electrode 26 provided in a recess 36 carved out from the upper surface of the electron supply layer 16 at a position between the first region W1 and the second region W2, and at a position away from the first region W1 and the second region W2, respectively. [Selection Diagram] Figure 1

Inventors

  • 安藤 裕二
  • ▲高▼橋 英匡
  • 分島 彰男

Assignees

  • 国立大学法人東海国立大学機構
  • 国立大学法人 熊本大学

Dates

Publication Date
20260507
Application Date
20241021

Claims (12)

  1. A channel layer made of nitride semiconductor, An electron supply layer provided on the channel layer and composed of a nitride semiconductor with a band gap larger than that of the channel layer, A first cap layer is provided in the first and second regions on the electron supply layer and is made of an n-type nitride semiconductor with a band gap larger than that of the channel layer, A second cap layer is provided on the first cap layer and is made of an n-type nitride semiconductor having a smaller band gap than the first cap layer, A first ohmic electrode provided on the second cap layer within the first region, A second ohmic electrode provided on the second cap layer within the second region, A semiconductor device comprising: a Schottky electrode provided in a recess carved out from the upper surface of the electron supply layer, at a position between the first region and the second region, and at a position away from each of the first region and the second region.
  2. The semiconductor device according to claim 1, wherein the n-type doping concentration of the first cap layer is higher than the n-type doping concentration of the second cap layer.
  3. The semiconductor device according to claim 1, wherein the thickness of the first cap layer is 5 nm or more and 10 nm or less.
  4. The semiconductor device according to claim 1, wherein the product of the n-type dope concentration of the first cap layer and the thickness of the first cap layer is 5 × 10¹² / cm² or more and 5 × 10¹³ / cm² or less.
  5. The semiconductor device according to claim 1, wherein the thickness of the second cap layer is 30 nm or more and 100 nm or less.
  6. The semiconductor device according to claim 1, wherein the product of the n-type dope concentration of the second cap layer and the thickness of the second cap layer is 6 × 10¹² / cm² or more and 2 × 10¹⁴ / cm² or less.
  7. The semiconductor device according to any one of claims 1 to 6, wherein the thickness between the channel layer and the recess in the electron supply layer is 1.5 nm or more and 14 nm or less.
  8. The semiconductor device according to claim 7, wherein the thickness between the channel layer and the upper surface of the electron supply layer is 5 nm or more and 100 nm or less.
  9. The semiconductor device according to any one of claims 1 to 6, wherein the distance from the recess to the first cap layer within the first region is 0.1 μm or more and 10 μm or less.
  10. The semiconductor device according to any one of claims 1 to 6, further comprising an insulating layer that covers the upper surface of the electron supply layer and the side surfaces of the first cap layer and the second cap layer.
  11. The semiconductor device is a field-effect transistor, wherein the first ohmic electrode is the drain, the second ohmic electrode is the source, and the Schottky electrode is the gate, according to any one of claims 1 to 6.
  12. The semiconductor device according to any one of claims 1 to 6, wherein the semiconductor device is a diode, the first ohmic electrode is a cathode, and the second ohmic electrode, which is short-circuited with the Schottky electrode, is an anode.

Description

This disclosure relates to a semiconductor device including a nitride semiconductor. High electron-mobility transistors (HEMTs), which use nitride semiconductors such as gallium nitride (GaN), are known as field-effect transistors capable of processing microwave signals. By connecting the gate electrode of a HEMT to one of its ohmic electrodes, it can be operated as a rectifier diode, also known as a gated anode diode (GAD). HEMTs used as rectifier diodes require normally-off operation. To achieve normally-off operation in a HEMT, the thickness of the electron supply layer located directly beneath the gate electrode must be reduced. Japanese Patent Publication No. 2022-129202 This is a schematic cross-sectional view showing the structure of a semiconductor device according to an embodiment.This graph shows the current-voltage characteristics of the semiconductor device according to the embodiment.This graph shows the conduction band energy and carrier concentration of the semiconductor device according to the example.This graph shows the current-voltage characteristics of the semiconductor device in the comparative example.This graph shows the conduction band energy and carrier concentration of the semiconductor device in the comparative example.This diagram schematically shows the manufacturing process of a semiconductor device according to an embodiment.This diagram schematically shows the manufacturing process of a semiconductor device according to an embodiment.This diagram schematically shows the manufacturing process of a semiconductor device according to an embodiment.This diagram schematically shows the manufacturing process of a semiconductor device according to an embodiment.This diagram schematically shows the manufacturing process of a semiconductor device according to an embodiment.This is a schematic cross-sectional view showing the structure of a semiconductor device according to a modified example.This diagram schematically shows the manufacturing process of a semiconductor device according to a modified example.This diagram schematically shows the manufacturing process of a semiconductor device according to a modified example.This diagram schematically shows the manufacturing process of a semiconductor device according to a modified example. The embodiments for implementing this disclosure will be described in detail below, with reference to the drawings. In this description, identical elements will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Figure 1 is a schematic diagram showing the structure of a semiconductor device 10 according to an embodiment. The semiconductor device 10 comprises a substrate 12, a channel layer 14, an electron supply layer 16, a first cap layer 18, a second cap layer 20, a first ohmic electrode 22, a second ohmic electrode 24, a Schottky electrode 26, and an insulating layer 28. The semiconductor device 10 is, for example, a field-effect transistor (FET), and more specifically, a high-electron-mobility transistor (HEMT). In this case, the first ohmic electrode 22 corresponds to the drain of the HEMT, the second ohmic electrode 24 corresponds to the source of the HEMT, and the Schottky electrode 26 corresponds to the gate of the HEMT. The semiconductor device 10 is, for example, a rectifier diode based on a HEMT. In this case, the first ohmic electrode 22 corresponds to the cathode, and the second ohmic electrode 24 corresponds to the anode, and is short-circuited with the Schottky electrode 26. Such a semiconductor device 10 is also called a gated anode diode (GAD) because the anode is connected to the gate of the HEMT. The semiconductor device 10 is a so-called gallium nitride (GaN) semiconductor element, and a GaN-based nitride semiconductor is used for the channel layer 14, electron supply layer 16, first cap layer 18, and second cap layer 20. Here, a GaN-based nitride semiconductor is a compound represented by Al x Ga y In 1-x-y N (0 ≤ x < 1, 0 < y ≤ 1, 0 < x + y ≤ 1), and is a compound that contains at least GaN. A two-dimensional electron gas (2DEG) 30 is generated near the interface between the channel layer 14 and the electron supply layer 16. The semiconductor device 10 controls the concentration of the 2DEG 30 by a control voltage applied to the Schottky electrode 26, thereby controlling the current flowing from the second ohmic electrode 24 to the first ohmic electrode 22. The semiconductor device 10 is configured to operate normally-off. The semiconductor device 10 is configured such that the current flowing from the second ohmic electrode 24 to the first ohmic electrode 22 is interrupted when the control voltage Vg is 0V. The substrate 12 is made of a material suitable for the crystal growth of nitride semiconductors, and is composed of silicon carbide (SiC), sapphire ( Al₂O₃ ), silicon (Si), or gallium nitride (GaN). In one embodiment, the substrate 12 is a semi-insulating SiC substrate. The ch