Metal Gate Transistor Fabrication with Protected Polysilicon Resistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for fabricating metal gate transistors and polysilicon resistors face issues such as high resistance of polysilicon gates leading to lower performance, depletion effects, and the deterioration of polysilicon resistor performance during the transition to metal gates.
Innovation Solution
An integrated method is developed to fabricate metal gate transistors and polysilicon resistors where a salicide block photo mask is used to protect the high resistance structure of the polysilicon resistor, allowing the metal layer to fill only the necessary openings while maintaining the resistance of the resistor at a sufficient value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polysilicon material is used to fabricate gate electrodes, then heat resistance is improved, but device performance deteriorates due to high resistance
Solution Approach 1:
The gate electrode structure is segmented into multiple layers: a polysilicon layer providing heat resistance and a metal layer providing low resistance for high performance. This segmentation allows each material to contribute its advantageous properties without the drawbacks of using either material alone.
Solution Approach 2:
The gate electrode is formed as a composite structure combining polysilicon and metal materials. The polysilicon layer serves as a foundation providing thermal stability, while the metal layer overlaying it provides excellent electrical conductivity, creating a composite material system that exhibits both heat resistance and low resistance simultaneously.
2Ease of manufacture
If polysilicon gate is used, then fabrication process is simplified, but depletion effect occurs reducing driving ability
Solution Approach 1:
The gate structure is divided into a polysilicon base layer and a metal overlay layer. The polysilicon layer maintains the simple fabrication process benefits, while the metal layer specifically addresses the depletion effect by providing superior electrical characteristics and reducing gate resistance.
Solution Approach 2:
A composite gate structure is formed where the polysilicon layer provides fabrication simplicity and the metal layer compensates for depletion effects. This composite approach allows the device to benefit from both the ease of polysilicon processing and the superior electrical performance of metal gates.
3Ease of manufacture
If metal layer fills the region where high resistance structure was located, then metal gate fabrication is completed, but polysilicon resistor performance deteriorates
Solution Approach 1:
The metal layer is selectively deposited only in the transistor region where the dummy gate is located, while the resistor region maintains its polysilicon high resistance structure. This local differentiation allows the transistor to achieve metal gate performance while the resistor retains its intended high resistance characteristics.
Solution Approach 2:
The substrate is segmented into distinct transistor and resistor regions with different material compositions. The transistor region receives the metal layer overlay on polysilicon, while the resistor region maintains pure polysilicon structure, allowing each component to be optimized for its specific function.
Data Source
AI summary
An integrated method includes fabricating a metal gate transistor and a polysilicon resistor structure. A photoresistor layer is defined by an SAB photo mask and covers a part of a high resistance structure of the polysilicon resistor. When the dummy gate of the transistor is etched, the part of the high resistance structure is protected by the patterned photoresistor layer. The polysilicon resistor is formed simultaneously with the transistor. Furthermore, the polysilicon resistor still has sufficient resistance and includes two metal structures for electrical connection.