SiC MOSFET Ohmic Contacts With Thermal Budget Sequencing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing manufacturing processes for silicon carbide (SiC) MOSFET devices face challenges in optimizing thermal budgets, leading to high-temperature steps that are harmful for certain gate dielectrics and result in disordered interfaces and instability, affecting channel mobility and threshold voltage stability.
Innovation Solution
The method involves forming ohmic contacts prior to the gate terminal, using metal silicides covered with high-melting metal layers, and optimizing the thermal budget distribution to accommodate materials incompatible with high process temperatures, allowing for the use of high-K and hydrogen-rich materials by performing the silicide formation before gate dielectric processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-temperature thermal oxidation and annealing processes are used to form SiO2 gate dielectric on SiC, then the gate dielectric can be formed with ease of manufacture, but the thermal budget causes disordered interface regions and high interface state density that degrade channel mobility and threshold voltage stability
Solution Approach 1:
The patent applies preliminary action by forming the gate dielectric layer before creating the source and drain ohmic contacts. This sequence allows the gate dielectric to be formed under optimized conditions without subsequent high-temperature processing that would create disordered interface regions. The gate dielectric is formed at lower temperatures to avoid interface degradation, then ohmic contacts are formed afterward through selective removal and metallization processes.
2Adaptability or versatility
If high-k dielectric materials are used to increase threshold voltage, then the Vth value can be adjusted effectively, but the materials suffer from crystallization phenomena and degradation at the thermal budgets required for forming silicide contacts in SiC devices
Solution Approach 1:
The patent resolves this contradiction by performing the preliminary action of forming high-k dielectric layers before any high-temperature silicide contact formation. The gate dielectric stack including high-k materials is deposited and processed at lower temperatures first, establishing a stable interface before subsequent ohmic contact formation. This sequencing prevents the high-k materials from experiencing crystallization and degradation that would occur if they were exposed to high temperatures during silicide formation.
Solution Approach 2:
The patent applies parameter changes by modifying the processing temperature parameters throughout the manufacturing sequence. Lower temperatures are used for gate dielectric formation and intermediate processing steps, while higher temperatures are reserved only for final ohmic contact formation after the gate dielectric is already in place. This dynamic temperature parameter management allows high-k materials to maintain their dielectric properties while still achieving the necessary thermal processing for functional contacts.
3Manufacturing precision
If post-oxidation annealing in nitrogen-rich environments is performed to reduce interface state density, then the channel mobility can be improved, but the process requires high temperatures and long annealing times that increase the thermal budget and cause interfacial reoxidation
Solution Approach 1:
The patent eliminates the need for post-oxidation annealing by performing the preliminary action of forming the gate dielectric before any high-temperature processing. The gate dielectric is deposited and processed at lower temperatures under optimized conditions that directly achieve low interface state density without requiring subsequent high-temperature annealing in nitrogen-rich environments. This preliminary formation approach inherently creates a high-quality interface without the time and thermal budget costs of extended annealing processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the use of materials that would otherwise degrade at high temperatures, improving channel mobility and threshold voltage stability while reducing thermal budgets, thus enhancing the performance and robustness of SiC MOSFET devices.
Implementation Method 1
forming ohmic contacts by silicizing a metal, to form silicides
Implementation Method 2
High-temperature steps are involved in this process
Implementation Method 3
High-k insulators (known as 'high-k' materials) may be used in particular to increase the Vth value in on-state in SiC MOSFETs
Implementation Method 4
Silicon oxide (SiO2) is commonly used in commercial SiC MOSFETs as a gate dielectric, owing to the ease of manufacturing by thermal oxidation of SiC
Implementation Method 5
a post-oxidation annealing (POA) or post-deposition annealing (PDA) step is typically performed in environments rich in nitrogen (N2O, NO)
Data Source
Figure 1~2A
Figure 2B~2C
Figure 2D~2E
AI summary
Method of manufacturing an electronic device (20), comprising forming an ohmic contact (59; 61) at an implanted region (26; 55) of a semiconductor body (48). Forming the ohmic contact provides for performing a high-temperature thermal process for allowing a reaction between a metal material and the material of the semiconductor body, for forming a silicide of the metal material. The step of forming the ohmic contact is performed prior to a step of forming one or more electrical structures (52, 56) which include materials that may be damaged by the high temperature of the thermal process of forming the silicide.