Polysilicon Resistor Doping for High Sheet Resistance Stability
Find Innovative SolutionsGenerate Solutions
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 significant drift over time.
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 to vary dopant levels, reducing hydrogen diffusion and dopant mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the resistance of polysilicon resistors is increased to achieve ultra-high sheet resistance, then the sheet resistance value improves, but the matching coefficient deteriorates causing greater mismatch across wafers and lots
Solution Approach 1:
The patent changes the dopant type from boron to phosphorus or arsenic, and introduces additional dopants (nitrogen and carbon) to achieve ultra-high sheet resistance while maintaining low matching coefficient and reducing resistance drift. This parameter change in doping composition resolves the contradiction between high resistance and good matching.
Solution Approach 2:
The patent uses a composite doping approach by combining multiple dopants (phosphorus or arsenic with nitrogen and carbon) in the polysilicon resistor. This composite doping strategy achieves both ultra-high sheet resistance and improved matching coefficient, resolving the technical contradiction.
2Manufacturing precision
If p-type boron-doped resistors are used to achieve ultra-high sheet resistance, then the matching coefficient improves, but resistance drift increases over time due to boron diffusion
Solution Approach 1:
The patent changes the dopant type from boron to phosphorus or arsenic, which have lower diffusion rates. This parameter change in dopant selection maintains good matching coefficient while significantly reducing resistance drift over time, resolving the contradiction between matching precision and compositional stability.
Solution Approach 2:
The patent introduces nitrogen and carbon dopants that act as diffusion barriers, effectively 'trapping' the phosphorus or arsenic dopants in place. This approach uses additional dopant elements to prevent the movement of primary dopants, achieving long-term resistance stability.
3Stability of the object's composition
If nitrogen and carbon dopants are implanted to improve matching coefficient and reduce drift, then the stability and matching improve, but the manufacturing process complexity increases
Solution Approach 1:
The patent combines the implantation of multiple dopants (phosphorus or arsenic with nitrogen and carbon) into a unified doping process. By merging these dopant introductions, the patent achieves improved resistance stability and matching coefficient while managing process complexity through integration rather than separate sequential steps.
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 challenges of resistance stability and uniformity across wafers and lots.
Implementation Method 1
The UHRES resistor is implanted with phosphorus or arsenic
Implementation Method 2
polysilicon resistors—resistance and matching coefficient—tend to be inversely related
Implementation Method 3
The UHRES resistor is implanted with phosphorus or arsenic and also with nitrogen and carbon
Implementation Method 4
which improve the resistance and the matching coefficient
Implementation Method 5
The UHRES implantation process may also be provided to other polysilicon resistors, such as high sheet resistance (HSR) resistors, at the same time to improve the matching coefficient of the resistors
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.