Schottky Diode Leakage Current Control via Depletion Barrier
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Solution Overview
Problem
Schottky diodes in CMOS processes face issues with reverse bias leakage currents and breakdown voltages due to image force barrier lowering, which existing solutions attempt to address by increasing device size and complexity.
Innovation Solution
Incorporating a leakage current control (LCC) region with a buried semiconductor layer and epitaxial layers to create a depletion region that surrounds the Schottky barrier, reducing reverse bias leakage by forming a current barrier through carefully designed doping and depth of the LCC regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional Schottky diode structure is used, then low forward turn-on voltage and fast switching characteristics are achieved, but reverse bias leakage current increases and breakdown voltage decreases
Solution Approach 1:
The invention divides the semiconductor substrate into distinct functional regions: a lightly-doped drift region and a separately-formed LCC region with different doping concentrations. This segmentation allows each region to perform its specific function - the drift region maintains fast switching characteristics while the LCC region controls leakage current, resolving the contradiction between speed and harmful leakage effects.
Solution Approach 2:
The invention applies local quality by creating a region with non-uniform doping concentration where the LCC region has a higher doping concentration than the drift region. This local variation in doping quality enables the LCC region to form an extended depletion layer that specifically targets and reduces reverse bias leakage current without affecting the overall fast switching performance of the diode.
2Object-generated harmful factors
If additional structures are added to reduce leakage current, then reverse bias leakage current decreases, but device size and fabrication complexity increase
Solution Approach 1:
The invention merges the LCC region formation into the existing CMOS fabrication process sequence, forming the LCC region through a dedicated implant step that integrates with standard process flows. This combining approach reduces fabrication complexity compared to adding entirely separate structures, while still achieving effective leakage current reduction through the specialized doping profile.
3Object-generated harmful factors
If LCC region with higher doping concentration is formed, then reverse bias leakage current is reduced through extended depletion layer, but forward voltage drop may increase
Solution Approach 1:
The invention applies local quality by creating a region with non-uniform doping concentration where the LCC region has a higher doping concentration than the drift region. This local variation in doping quality enables the LCC region to form an extended depletion layer that specifically targets and reduces reverse bias leakage current without affecting the overall fast switching performance of the diode.
Solution Approach 2:
The invention changes the doping concentration parameter locally within the LCC region to be higher than the drift region, creating a controlled transition zone. This parameter change enables the formation of an extended depletion layer that reduces leakage current while the overall device geometry and doping profile are optimized to maintain acceptable forward voltage characteristics.
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 configuration effectively reduces reverse bias leakage current by creating a depletion region that prevents current from traversing the active area, maintaining low forward bias voltage and fast switching characteristics without increasing device size or complexity.
Implementation Method 1
LCC regions form a current barrier that prevents carriers from flowing between the drift region and the substrate
Implementation Method 2
A Schottky diode fabricated in a CMOS process often employs a silicide overlying n-doped or p-doped silicon as the diode's Schottky barrier junction
Data Source
AI summary
A Schottky diode includes a device structure having a central portion and a plurality of fingers. Distal portions of the fingers overlie leakage current control (LCC) regions. An LCC region is relatively narrow and deep, terminating in proximity to a buried layer of like polarity. Under reverse bias, depletion regions forming in an active region lying between the buried layer and the LCC regions occupy the entire extent of the active region and thereby provide a carrier depleted wall. An analogous depletion region occurs in the active region residing between any pair of adjacent fingers. If the fingers include latitudinal oriented fingers and longitudinal oriented fingers, depletion region blockades in three different orthogonal orientations may occur. The formation of the LCC regions may include the use of a high dose, low energy phosphorous implant using an LCC implant mask and the isolation structures as an additional hard mask.