Polysilicon Resistor Doping for Stable Ultra-High Sheet Resistance
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Solution Overview
Problem
Polysilicon resistors with ultra-high sheet resistance (UHRES) face challenges in maintaining a low matching coefficient and resistance drift due to the inverse relationship between resistance and matching coefficient, with boron-doped resistors experiencing dopant diffusion issues.
Innovation Solution
Implanting polysilicon resistors with nitrogen and carbon dopants, along with phosphorus or arsenic, to improve resistance and matching coefficient, and using dilution doping for varying dopant levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If p-type boron-doped resistors are used to achieve low matching coefficient, then the matching coefficient is relatively low, but the resistance drifts over time due to diffusion of the boron
Solution Approach 1:
The patent converts the potential harm of dopant diffusion into a benefit by using nitrogen and carbon dopants that have lower diffusivity than boron. These dopants, when combined with phosphorus or arsenic, create a stable doped polysilicon structure that maintains low matching coefficient while preventing resistance drift, thus converting the limitation of conventional dopants into an advantage
Solution Approach 2:
The patent changes the chemical composition parameters by replacing boron with nitrogen and carbon dopants. This parameter change fundamentally alters the diffusion characteristics of the polysilicon resistor, achieving both low matching coefficient and high resistance stability over time, eliminating the drift issue associated with boron-doped resistors
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
Achieves stable resistors with low drift, low temperature coefficient, and improved matching coefficient, with sheet resistance exceeding 5 kΩ/□, addressing the limitations of boron-doped resistors.
Implementation Method 1
The UHRES resistor is implanted with phosphorus or arsenic and also with nitrogen and carbon
Implementation Method 2
The polysilicon resistor body contains an N-type dopant and carbon and nitrogen dopants
Data Source
AI summary
An integrated circuit includes a dielectric isolation structure formed at a surface of a semiconductor substrate and a polysilicon resistor body formed on the dielectric isolation structure. The polysilicon resistor body includes an N-type dopant having an N-type dopant concentration, nitrogen having a nitrogen concentration, and carbon having a carbon concentration. The sheet resistance of the resistor body is greater than 5 kΩ/square.