GaN Transistors for Space Applications: Design, Manufacturing, Testing, and Reliability

Gallium Nitride (GaN) transistors are revolutionizing the field of electronics, especially for space applications where reliability and performance are paramount. SAGaN aims to develop high voltage GaN transistors that can withstand the harsh conditions of space. The development of the transistor is carried out by the cooperation of SAGaN Consortium, formed by IMEC, DISCO, Semi Zabala, and Sener Aerospace. This blog post will explore the design, manufacturing, testing, and reliability of GaN transistors for space applications.

1. Cumulative Effects: Exposure to radiation environment degrades the electrical parameters of the transistor. The units are measured, then exposed to artificial radiation environments up to different dosage and re-measured to evaluate the impact of the environment.
2. Single Event Effects (SEE): Particles can interact with the transistor leading to a transitory modification of its state. During this transient period, the transistor can experience heavy currents that may destroy the device, or drastically alter its parameters. To test this, heavy ion particles are simulated using a cyclotron to test the components’ performance under different levels of radiation Energy.

The design process is led by Semi Zabala and begins with a pre-learning cycle using existing structures from the IMEC process. Devices undergo SEE heavy ion testing to establish a baseline resistance to radiation. Subsequent learning cycles focus on optimizing radiation performance and electrical parameters, with thorough failure analyses guiding design changes.

The manufacturing process starts with the growth and inspection of GaN-on-Si substrates. IMEC produces a set of wafers aligned with the design needs of the previous section. It also performs on-wafer measurements to ensure that the process is successful. This process is performed with several design variations. IMEC delivers wafers containing several transistors to DISCO.

The transistors need to be separated from each other as they are used as individual pieces. This process is performed by DISCO. Also, the wafers need to be thinned to improve its thermal characteristics. This is done in two steps:

1. Grinding: This process involves reducing the thickness of semiconductor wafers to prepare them for further processing.
2. Dicing: Wafers are diced into individual chips, which are then picked and placed packs for its delivery.

Packaging is critical for the performance and reliability of GaN transistors. Space applications demand either hermetic packages made from metal, ceramic, and glass to protect against moisture and harmful gases, or advanced plastic packages which are more cost effective.

Reliability testing for space applications follows stringent standards like the ESCC 5000, which defines requirements for the qualification, procurement, and delivery of semiconductor components. Key tests include:

• High Temperature Reverse Bias (HTRB) and High Temperature Gate Bias (HTGB): These tests stress the device under high temperature and bias conditions to detect early life failures.

SAGAN is guided by these standards to address the specificities of GaN HEMT transistors, ensuring they meet the rigorous demands of space applications.

The development of GaN transistors for space applications involves a meticulous process of design, manufacturing, testing, and qualification. By the expertise of consortium partners and leveraging advanced technologies, the SAGAN project aims to deliver high-reliability components capable of withstanding the harsh conditions of space. This endeavour not only advances the field of electronics but also paves the way for more robust and efficient space missions.