Definition
A manufacturing process that uses polysilicon MOS gates and self-aligned structures to improve device speed, dimensions, and interconnection capabilities.
What it is
The silicon-gate process uses polysilicon to form MOS gates and uses the gate as a self-alignment reference when forming the source and drain regions. Compared with the earlier metal-gate approach, it permits more compact channels and smaller parasitic effects.
Why it emerged and what problems it solved
MOS integrated circuits needed improvements in speed, density, and manufacturing consistency at the same time. Silicon gates are more stable during high-temperature processing, and self-aligned structures reduce alignment errors, allowing more devices to fit in the same area.
Why it matters and what it enabled
The silicon-gate process turned the device-level advantages of MOSFETs into a practical capability for high-density chips. It supported both the replacement of main memory by DRAM and early microprocessors such as the 4004, advancing integrated circuits from functional modules toward CPU-level integration.
Principles and impact
Problems solved
- Reduced parasitic capacitance and dimensional constraints caused by alignment errors between metal gates and channels.
- Allowed MOS devices with smaller geometries to be used in logic, memory, and processor chips.
Principles
- The polysilicon gate withstands subsequent high-temperature steps and also serves as the alignment reference for forming source and drain regions.
- The gate, oxide layer, and channel structure combine with the planar process to form repeated MOS cells.
Improvements
- Shortened channels and interconnects to increase switching speed.
- Supported higher-density MOS RAM, ROM, and logic circuits.
Significance
- Became a key process for MOS memory and microprocessors in the 1970s.
- Combined smaller lithographic patterns with device self-alignment to sustain growth in single-chip integration density.
History and applications
People
Federico Faggin、Tom Klein、Frank Wanlass
Organizations
Fairchild Semiconductor、Intel
Events
The silicon-gate MOS process entered practical use in 1968、Used in the design and manufacture of the Intel 4004 in 1971
Applications
MOS dynamic RAM、MOS read-only memory、Microprocessors and peripheral chips
Limitations
- Has demanding requirements for the process window, oxide quality, and contamination control.
- Increasing density introduces constraints on power consumption, leakage, and heat dissipation.
Upstream and downstream relations
Upstream
Sources: 1964: First Commercial MOS IC Introduced1970: MOS Dynamic RAM Competes with Magnetic Core Memory on Price
Downstream
Sources: 1971: Microprocessor Integrates CPU Function onto a Single Chip1970: MOS Dynamic RAM Competes with Magnetic Core Memory on Price