📘 BSIM4_ANALYZER_DC

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Automated DC Analysis Tool for BSIM4 MOSFET Models (Vg–Id / Vd–Id)

This tool was originally developed for semiconductor device engineering education,
but is also designed with future commercial MOSFET parameter analysis applications in mind.

The system currently supports 130nm CMOS (NMOS/PMOS).
The folder results/90nm/ is intentionally empty and reserved for future feature expansion.
Extending the current 130nm analysis flow to 90nm is straightforward.

📚 Features

✔ Automated analysis pipeline: BSIM4 MOS model × ngspice × Python
✔ DC characteristics for NMOS/PMOS (130nm): Vg–Id (VGID) / Vd–Id (VDID)
✔ Automatic extraction of key parameters: Vth, gmmax, Idlin, Idsat
✔ Auto-generated log/lin PNG plots
✔ Suitable for education, compact modeling research, and commercial analysis tools
✔ Easily extendable to 90nm using template duplication

📁 Directory Structure

BSIM4_ANALYZER_DC/
├── models/
│   ├── nmos130.sp
│   └── pmos130.sp
│
├── templates/
│   ├── template_vgid.cir
│   └── template_vdid.cir
│
├── run/
│   ├── run_vgid.py
│   └── run_vdid.py
│
├── plot/
│   ├── plot_vgid.py
│   └── plot_vdid.py
│
├── results/
│   ├── 130nm/
│   │   ├── vgid/
│   │   └── vdid/
│   └── 90nm/           # ← Reserved for future expansion
│
├── bsim4.out
└── README.md

🚀 Usage

■ Requirements

Python 3.10+
ngspice
Required Python packages:
```
numpy
matplotlib
pandas   (optional)
```

■ Running Simulations

● Vg–Id (VGID)

python run/run_vgid.py

● Vd–Id (VDID)

python run/run_vdid.py

■ Generating Plots

● Vg–Id

python plot/plot_vgid.py

● Vd–Id

python plot/plot_vdid.py

📊 Output Files (with extracted parameters)

The tool processes raw ngspice .dat files and automatically extracts
important DC parameters, saving them as CSV files.

■ VGID Parameter Extraction (Vg–Id)

Parameter	Description	Method
Vth (gmmax method)	Threshold voltage	Vg at gm maximum
gmmax	Maximum transconductance	max(dId/dVg)

CSV example:

device,corner,Vth_gmmax,gmmax
nmos,HT,0.478,0.00123
pmos,RT,-0.512,0.00101

■ VDID Parameter Extraction (Vd–Id)

Parameter	Description	Method
Idlin	Linear-region Id	Low-Vd current (e.g., 50 mV)
Idsat	Saturation-region Id	High-Vd current (≈ Vdd)

CSV example:

device,corner,Idlin,Idsat
nmos,LT,1.23e-5,2.88e-4
pmos,RT,-9.88e-6,-2.42e-4

📦 Output File Types

.csv — extracted parameters
.dat — raw ngspice numeric output
.png — plots (linear & log scale)
.cir — executed circuit input file
.log — ngspice log

Example:

130nm_nmos_vgid_HT.csv
130nm_nmos_vgid_log.png
130nm_pmos_vdid_LT.csv
130nm_pmos_vgid_lin.png

🧩 Parameter Extraction Algorithms

● Vth (gmmax method)

Load Id–Vg curve
Compute gm = dId/dVg
Identify Vg where gm is maximum → Vth
Record gmmax

● Idlin / Idsat

Idlin = Id at low Vd (linear region)
Idsat = Id at high Vd (saturation region)
(Vd conditions defined in template_vdid.cir)

🔧 90nm Node (Future Extension)

results/90nm/ is reserved for expansion.
To add 90nm support, simply:

Add 90nm models under models/
Duplicate cir templates and rename
Modify run scripts for the new node

The structure is intentionally built for future commercial scalability.

📈 Example Plots Generated by BSIM4_ANALYZER_DC

The following figures are automatically produced by the
BSIM4 DC Analyzer (Vg–Id / Vd–Id) for 130nm NMOS/PMOS devices.
They demonstrate the tool’s ability to generate device characteristics
across temperature corners (LT / RT / HT).

▶ NMOS — Vg–Id (VGID, Linear Region)

Shows the gate-voltage sweep (Id–Vg) under linear Vd bias for NMOS,
revealing threshold voltage and mobility temperature dependence.

▶ NMOS — Vd–Id (VDID)

Illustrates output characteristics (Id–Vd) at fixed Vgs,
showing linear-to-saturation transition.

▶ PMOS — Vg–Id (VGID, Linear Region)

The PMOS transfer curve, plotted with SPICE polarity,
showing temperature effects on |Vth| and hole mobility.

▶ PMOS — Vd–Id (VDID)

PMOS output characteristics (Id–Vd), SPICE-polarity plotted.
Useful for extracting Idlin/Idsat and channel-length modulation trends.

These plots serve as reference examples for BSIM4 parameter exploration,
educational MOSFET modeling exercises, and future integration into
commercial MOSFET analysis tools.

📄 Hybrid License

This repository adopts a Hybrid License model:

Item	License	Description
Source Code	MIT License	Free to use, modify, and redistribute
Documentation / Text Materials	CC BY 4.0	Attribution required
Figures / Plots / Generated Images	CC BY-NC 4.0	Non-commercial use only
External References	Original license applies	Cite properly

📌 To-Do / Future Development

Official support for 90nm
Additional extraction metrics (μeff, λ, ro, Vdsat, gm/Id, etc.)
Temperature sweep support
GUI edition (lecture / commercial use)
Multi-process comparison tool
BSIM parameter fitting engine

👤 Author

📌 Item	Details
Name	Shinichi Samizo
GitHub