Polysilicon Resistor With Differently Doped Sub-Layers
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Solution Overview
Problem
In integrated circuits employing high-k metal gate technology, the use of metal layers for both gate electrodes and resistors limits the achievable sheet resistance of polysilicon resistors, leading to increased manufacturing costs and reduced yield due to the need for additional photolithography processes and masks.
Innovation Solution
A semiconductor structure with a polysilicon layer featuring differently doped sub-layers, where a sub-layer at the bottom is oppositely doped to the rest, and fluorine is implanted to moderate dopant diffusion, creating a layered structure that avoids the limitations imposed by metal layers, allowing for higher sheet resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If metal layers are used for both gate electrodes and resistors in high-k metal gate technology, then manufacturing process is simplified, but sheet resistance of polysilicon resistors is limited and cannot exceed certain values
Solution Approach 1:
The polysilicon layer is segmented into multiple sub-layers with different doping concentrations. The first sub-layer has a first doping concentration while the second sub-layer has a second doping concentration that is different from the first, allowing independent optimization of electrical properties for each sub-layer to achieve high sheet resistance without additional photolithography steps
Solution Approach 2:
Different regions of the polysilicon layer are given different local properties through selective doping. The varying doping concentrations in different sub-layers create local electrical property differences that enable high sheet resistance values while maintaining process simplicity
2Manufacturing precision
If additional photolithography processes and masks are introduced to achieve higher sheet resistance, then sheet resistance control is improved, but manufacturing complexity and costs increase
Solution Approach 1:
The polysilicon layer serves multiple functions: it acts as both the gate electrode material and the resistor material. By controlling doping concentrations in different sub-layers, the same layer structure achieves both high sheet resistance for resistors and appropriate electrical properties for gate electrodes, eliminating the need for separate processing steps
Solution Approach 2:
The doping concentration parameter is varied within the polysilicon layer to achieve different electrical properties. By changing the doping concentration from the first value in the first sub-layer to the second value in the second sub-layer, high sheet resistance is achieved without introducing additional process steps or masks
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 resistors with sheet resistances exceeding 800 ohm per square, improving performance while reducing manufacturing complexity and costs by eliminating the need for additional photolithography steps.
Implementation Method 1
Ions of fluorine are implanted into the second material layer. Ions of a first dopant are implanted into the second material layer. Ions of a second dopant are implanted into a second sub-layer of the second material layer.
Implementation Method 2
After the implantation of the ions of fluorine, the ions of the first dopant and the ions of the second dopant, an annealing process activating the first and the second dopant is performed.
Implementation Method 3
The second material layer includes a first sub-layer and a second sub-layer provided over the first sub-layer, wherein the first sub-layer and the second sub-layer are differently doped. This approach enables resistors with sheet resistances exceeding 800 ohm per square.
Data Source
AI summary
A semiconductor structure includes a substrate and a resistor provided over the substrate. The resistor includes a first material layer, a second material layer, a first contact structure and a second contact structure. The first material layer includes at least one of a metal and a metal compound. The second material layer includes a semiconductor material. The second material layer is provided over the first material layer and includes a first sub-layer and a second sub-layer. The second sub-layer is provided over the first sub-layer. The first sub-layer and the second sub-layer are differently doped. Each of the first contact structure and the second contact structure provides an electrical connection to the second sub-layer of the second material layer.