半導体工学その2



## ■ 1.1 Analog IC Development Flow (Overall Process)

The development of analog ICs involves numerous stages of design, evaluation, and reviews, starting from specification planning to mass production. Even under an accelerated schedule, the entire process typically takes **6 to 10 months**. Each stage is governed by multiple **Design Reviews (DR)**. If any issue is identified, it may trigger a **step-back** to the previous phase for correction or rework.

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### ◉ Overall Development Steps

### 1. Specification Planning and Development Strategy

Based on customer requirements and market needs, the performance and functionality of the IC are defined.

Key considerations include:

* Operating speed, power consumption, absolute maximum ratings, voltage and temperature ranges, load drive capability.
* Package size, pin count, thermal resistance, cost, reliability, equipment constraints.

The optimal **process technology, package type**, and **circuit architecture** are selected to meet these requirements, and a **development specification document** is created.

Additionally, project timelines, personnel planning, cost estimation, and profitability analysis (i.e., ROI, market volume, product lifecycle) are carried out.

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### 2. Design Review I (DR-I)

Experts from product planning, design, manufacturing, and quality departments gather to evaluate the feasibility and completeness of the specifications and plans.

Once approved, the project proceeds to the design phase.

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### 3. Circuit Design

Designers carry out the topological design and transistor-level circuit implementation. Simulations such as SPICE are performed to verify circuit behavior.

Consideration is also given to ESD protection, safety regulations, and analog performance factors.

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### 4. Design Review II (DR-II)

The validity of the circuit architecture, simulation results, and design margins are evaluated and reviewed.

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### 5. Layout Design

The physical layout of the IC is created based on the schematic. Factors such as:

* Chip area, interconnect lengths, package constraints,
* Thermal distribution, noise immunity, and yield optimization
  are all taken into account.

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### 6. Design Review III (DR-III)

This stage checks for:

* Layout vs. schematic consistency (LVS),
* Design rule compliance (DRC),
* The impact of parasitic components.

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### 7. Photomask Fabrication

Using the finalized layout, photomasks are manufactured through:

* Electron beam lithography, resist development, etching,
* Defect inspection and correction, pellicle mounting.

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### 8. Wafer Process (Front-End)

Semiconductor manufacturing processes such as:

* Thin-film deposition, photolithography, doping, etching
  are repeated to build up the IC circuits on the silicon wafer.

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## ◉ Evaluation and Testing Phase

### 9. Preliminary Characterization

Before full packaging, performance is evaluated using:

* Bare wafer probing or
* Ceramic-packaged samples (engineering builds).

This allows early detection of design flaws and performance issues, enabling rapid feedback and design revisions.

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### 10. Probe Test (Wafer Probing)

Electrical tests are performed by contacting each chip on the wafer using probes.

This stage checks for pass/fail criteria, verifies fuse trimming if applicable, and sorts chips accordingly.

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### 11. Assembly (Packaging)

Includes the following sequential steps:

* Dicing, die bonding, wire bonding, molding, and marking.

Thermal resistance, package form factor, and pin layout are considered during this process.

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### 12. Design Review IV (DR-IV)

Verifies whether post-assembly performance remains within specification.

Design adjustments may be needed due to packaging-induced changes in electrical or thermal behavior.

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### 13. Final Electrical Characterization

Comprehensive performance verification is conducted on the fully assembled device.

Key analog characteristics such as linearity, noise, temperature dependence, and high-frequency response are evaluated.

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### 14. Final Test

Performed on a lot basis before shipment to confirm electrical functionality and compliance with specifications.

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### 15. Design Review V (DR-V)

A holistic product quality evaluation covering:

* Electrical performance, cost, delivery schedule, reliability, appearance, and packaging conformity.

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### 16. Reliability Testing

Includes:

* High-temperature operating life (HTOL),
* Thermal cycling,
* Solder heat resistance tests, etc.

The product must meet defined reliability targets to proceed.

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## ◉ ES (Engineering Sample) vs. CS (Commercial Sample)

* **Engineering Sample (ES)**:
  Meets functional and performance specifications but not yet guaranteed for reliability.
  Provided to customers for evaluation purposes.

* **Commercial Sample (CS)**:
  Fully qualified in terms of performance and reliability.
  Supplied for customer product integration and pre-production trials.

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### 17. Mass Production Transfer and Shipment

Once CS qualification is complete, the product is transferred to the mass production line. This includes:

* Standardizing manufacturing/testing procedures,
* Implementing quality assurance systems, and
* Preparing for full-scale shipment.

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