Polysilicon Resistor Structure for DRAM Integration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current resistor structures in dynamic random access memory (DRAM) face integration issues when combining polysilicon resistors with metal-gate MOSFETs, leading to increased complexity and cost, and doped silicon resistors do not match the performance of polysilicon resistors.
Innovation Solution
A novel resistor structure is developed using a substrate with shallow trench isolation, featuring a winding polysilicon resistor portion and terminal portions that connect to a metal layer, fabricated using identical material layers and processes as memory devices, thereby integrating polysilicon resistors with improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon resistors are combined with metal-gate MOSFETs on a single IC chip, then electrical performance is improved, but fabrication process complexity increases
Solution Approach 1:
The patent makes the polysilicon layer serve dual functions: as the gate electrode material for metal-gate MOSFETs and as the resistor material. This multi-functionality allows both components to coexist on the same chip without requiring separate fabrication processes, thereby improving electrical performance while avoiding increased fabrication complexity
Solution Approach 2:
The invention merges the polysilicon resistor fabrication process with the metal-gate MOSFET fabrication process by using the same polysilicon deposition and patterning steps for both structures, eliminating the need for additional hard mask deposition and reducing overall process complexity
2Ease of manufacture
If doped silicon resistors are used in current DRAM, then integration with existing processes is achieved, but electrical performance deteriorates
Solution Approach 1:
The patent changes the material parameter from doped silicon to polysilicon, which fundamentally alters the electrical properties including resistivity, temperature coefficient, and parasitic capacitance. This material substitution maintains compatibility with existing DRAM fabrication processes while dramatically improving electrical performance
3Reliability
If additional hard mask deposition is performed to deposit polysilicon resistor, then polysilicon resistor fabrication is achieved, but manufacturing cost increases
Solution Approach 1:
The polysilicon layer is designed to serve multiple purposes: as the gate electrode for MOSFETs, as the resistor element, and as a pattern definition layer that eliminates the need for separate hard mask deposition. This multi-functionality achieves polysilicon resistor fabrication without additional manufacturing steps or costs
Solution Approach 2:
The polysilicon structure itself serves as the pattern definition and protection layer during fabrication, eliminating the need for external hard mask materials. The same polysilicon deposition and patterning processes that create the MOSFET gates automatically define the resistor geometry, making the system self-sufficient
Data Source
AI summary
A resistor for dynamic random access memory includes a substrate with a memory cell region and a peripheral region defined thereon, and a resistor formed on a shallow trench isolation of the substrate, wherein the resistor is provided with a winding portion and terminal portions at two ends of the winding portion. The winding portion is electrically connected with an overlying metal layer through contacts, and the terminal portion includes a polysilicon layer and a metal multilayer from the bottom up.