Chalcogen Doped Field Stop Zone in Power Semiconductor Substrates
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Solution Overview
Problem
Conventional field stop zones in power semiconductor devices require high thermal budgets for deep penetration, which is not economical and incompatible with front-side superstructure devices, and existing starting materials like float zone silicon have limitations in radial resistance variations and oxygen impurities, making it challenging to achieve deep field stop zones for higher voltage applications.
Innovation Solution
The method involves applying stress to release self-interstitials in a semiconductor substrate, implanting chalcogen atoms, and annealing to form a field stop zone with chalcogen dopant atoms that extend to a depth of at least 50 μm, utilizing selenium or other chalcogens as double donors to enhance diffusion depths with a limited thermal budget, and adjusting the doping concentration for effective field stop zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional doping methods with high thermal budget are used to achieve deep field stop zones, then the penetration depth increases, but the thermal budget becomes too high and incompatible with front-side superstructure devices
Solution Approach 1:
The patent changes the doping substance from conventional pentavalent elements to chalcogen elements (S, Se, Te), which have higher diffusion constants. This parameter change allows achieving deeper penetration (50 μm or more) at lower temperatures (900-1000°C) without requiring high thermal budgets that would damage front-side devices
Solution Approach 2:
The patent replaces the thermal diffusion mechanism with ion implantation followed by low-temperature annealing. This substitution allows precise control of doping depth and concentration while minimizing thermal exposure, enabling deep field stop zones without high thermal budget
2Reliability
If float zone silicon is used as starting material to reduce oxygen impurities, then oxygen content decreases, but radial resistance variations increase and manufacturing cost increases
Solution Approach 1:
The patent changes the starting material from float zone silicon to neutron-transmutation-doped (NTD) silicon. This parameter change provides extremely uniform radial resistance (±1%) while maintaining low oxygen impurity levels, as the neutron transmutation process creates homogeneous doping throughout the crystal structure
Solution Approach 2:
The patent uses a composite approach by combining NTD silicon substrate with chalcogen doping. The NTD provides uniform base doping and low oxygen, while the chalcogen layer provides the field stop function with deep penetration at low thermal budget
3Length of stationary object
If chalcogen elements are used for field stop zones, then diffusion depth increases at moderate temperatures, but the depth is still insufficient for blocking voltages of 1200V and above
Solution Approach 1:
The patent applies ion implantation before annealing to pre-position chalcogen atoms at the desired depth. This preliminary action ensures that the doping profile achieves the required 50 μm or deeper penetration before the thermal annealing process activates the dopants, enabling sufficient depth for 1200V and above blocking voltages
Solution Approach 2:
The patent uses self-interstitials as an intermediary to enhance chalcogen diffusion. By creating a high concentration of self-interstitials through stress application or proton irradiation, the diffusion constant of chalcogen atoms is dramatically increased, enabling deeper penetration at lower temperatures and shorter times
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 allows for deeper field stop zones with improved dynamic characteristics and reduced radial resistance variations, enabling higher voltage blocking capabilities while maintaining a low thermal budget, thus addressing the limitations of conventional doping methods and starting materials.
Implementation Method 1
Chalcogen elements also have a higher diffusion constant than pentavalent elements, so that already at moderate process temperatures approximately between 900° C. and 1,000° C., penetration depths up to 30 μm can be realized
Implementation Method 2
applying stress at a side of the undoped semiconductor substrate to release self interstitials in the substrate
Implementation Method 3
implanting chalcogen atoms into the side of the substrate
Implementation Method 4
annealing the substrate to form a first semiconductor region containing the chalcogen atoms
Data Source
AI summary
A semiconductor substrate includes a first side and a second side opposite the first side. A semiconductor material extends between the first and second sides and is devoid of active device regions. The semiconductor material has a first region and a second region. The first region extends from the first side to a depth into the semiconductor material and includes chalcogen dopant atoms which provide a base doping concentration for the first region. The second region extends from the first region to the second side and is devoid of base doping. Further, a power semiconductor component is provided.