Damage-free plasma-enhanced CVD passivation of AlGaN/GaN high electron mobility transistors

A passivated high-electron mobility transistor (HEMT) device, comprising:

• an AlGaN/GaN heterostructure having an AlGaN layer disposed on an upper surface of a GaN layer;
• a first thin HF SiN layer deposited by high-frequency plasma-enhanced chemical vapor deposition (HF PECVD) on the upper surface of the AlGaN layer, the first thin HF SiN layer being annealed to density the first thin HF SiN layer and improve its performance as a barrier to plasma damage on the upper surface of the AlGaN layer;
• a gate formed directly on a first area of an upper surface of the annealed first thin HF SiN layer;
• a second thin HF SiN layer deposited by HF PECVD directly on the upper surface of the annealed first thin HF SiN layer and along the sides of the gate;
• and
• a thick HF/LF SiN layer deposited by high-frequency/low-frequency plasma-enhanced chemical vapor deposition (HF/LF PECVD) directly on an upper surface of the second thin HF SiN layer;
• the annealed first thin HF SiN layer, the second thin HF SiN layer, and the thick HF/LF SiN layer comprising tri-layer SiN passivation on the upper surface of the AlGaN layer of the HEMT device;
• wherein the HF PECVD deposition of the first and second thin HF SiN layers prevents plasma damage to the upper surface of the AlGaN layer from nitrogen ions during the deposition of the first and second thin HF SiN layers;
• and
• wherein the first and second thin HF SiN layers prevent damage to the upper surface of the AlGaN layer during a low-frequency plasma deposition cycle of the thick HF/LF SiN layer deposition.

A method for forming a passivated AlGaN/GaN high electron mobility transistor (HEMT) device, comprising:

• depositing an AlGaN barrier layer on an upper surface of a GaN channel/buffer layer;
• forming a gate on an upper surface of the AlGaN barrier layer;
• depositing a thin HF SiN layer by means of high-frequency plasma-enhanced chemical vapor deposition (HF PECVD) directly on the upper surface of the AlGaN barrier layer and along the sides of the gate;
• annealing the thin HF SiN layer to density the thin HF SiN layer and improve its performance as a barrier to plasma damage on the upper surface of the AlGaN barrier layer;
• and
• depositing a thick HF/LF SiN layer by means of high-frequency/low-frequency plasma-enhanced chemical vapor deposition (HF/LF PECVD) on the annealed thin HF SiN layer;
• the annealed thin HF SiN layer and the thick HF/LF SiN layer comprising bi-layer SiN passivation on the upper surface of the AlGaN barrier layer of the HEMT device;
• wherein the HF PECVD deposition of the thin HF SiN layer prevents plasma damage to the upper surface of the AlGaN barrier layer from nitrogen ions during the deposition of the thin HF SiN layer;
• and
• wherein the annealed thin HF SiN layer prevents damage to the upper surface of the AlGaN barrier layer during a low-frequency plasma deposition cycle of the thick HF/LF SiN layer deposition.

A method for forming a passivated AlGaN/GaN high electron mobility transistor (HEMT) device, comprising:

• depositing an AlGaN barrier layer on an upper surface of a GaN channel/buffer layer;
• depositing a first thin HF SiN layer directly on an upper surface of the AlGaN barrier layer by means of high-frequency plasma-enhanced chemical vapor deposition (HF PECVD);
• annealing the first thin HF SiN layer to densify the first thin HF SiN layer and improve its performance as a barrier to plasma damage on the upper surface of the AlGaN barrier layer;
• forming a gate directly on a first area of an upper surface of the annealed first thin HF SiN layer;
• depositing a second thin HF SiN layer by means of high-frequency plasma-enhanced deposition (HF/LF PECVD) directly on a second area of the upper surface of the annealed first thin HF SiN layer and on the sides of the gate;
• and
• depositing a thick HF/LF SiN layer by means of high frequency/low-frequency plasma-enhanced chemical vapor deposition (HF/LF PECVD) directly on an upper surface of the second thin HF SiN layer;
• the first and second thin HF SiN layers and the thick HF/LF SiN layer comprising tri-layer SiN passivation on the upper surface of the AlGaN barrier layer of the HEMT device;
• wherein the HF PECVD deposition of the first and second thin HF SiN layers prevents plasma damage to the upper surface of the AlGaN barrier layer from nitrogen ions during the deposition of the first and second thin HF SiN layers;
• and
• wherein the first and second thin HF SiN layers prevent damage to the upper surface of the AlGaN barrier layer during a low-frequency plasma deposition cycle of the thick HF/LF SiN layer deposition.