Charge Transfer Structure: Dark Current <1 nA/cm² at 25°C

Component Specifications

Definition

The Charge Transfer Structure is an integrated semiconductor component within CCD (Charge-Coupled Device) detector arrays that facilitates the controlled movement of photogenerated charge packets through a series of potential wells created by clocked electrode gates. This structure consists of polysilicon electrodes deposited on an insulating oxide layer above a silicon substrate, arranged in overlapping patterns to create transfer channels. During operation, precisely timed voltage sequences applied to these electrodes create moving potential minima that transport electrons from pixel to pixel toward the output amplifier, enabling the sequential readout of image information with minimal charge loss or distortion.

Working Principle

The Charge Transfer Structure operates on the principle of charge-coupled device technology, where photogenerated electrons are temporarily stored in potential wells beneath electrodes. By applying phased voltage pulses to adjacent electrodes in a precise sequence, the potential wells are modulated to create a directional gradient that pushes charge packets along the semiconductor surface. This bucket-brigade transfer mechanism moves electrons through the array with high efficiency (typically >99.99% per transfer) while maintaining spatial and charge integrity through careful control of electrode geometry, doping profiles, and clocking waveforms.

Materials

Primary materials include: P-type silicon substrate (resistivity 10-100 Ω·cm), thermally grown silicon dioxide gate insulator (thickness 100-150 nm), doped polysilicon electrodes (phosphorus or arsenic doped, thickness 300-500 nm), silicon nitride passivation layer, aluminum or copper interconnects. Advanced versions may incorporate buried channel designs with additional n-type epitaxial layers.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Dark Current	<1 nA/cm² at 25°C
Charge Capacity	100,000-1,000,000 electrons per pixel
Clock Frequency	1-50 MHz
Electrode Pitch	5-20 μm
Number Of Phases	2, 3, or 4 phase designs
Operating Voltage	5-15 V clock pulses
Transfer Efficiency	>99.99% per transfer
Operating Temperature	-50°C to +80°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 12232, ISO 15739, DIN 19040, DIN 58141

Parent Products

This component is used in the following industrial products

CCD Detector Array

A photosensitive electronic component that converts light signals into electrical signals for detection and measurement in optical spectrometers.

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Engineering Analysis

Risks & Mitigation

Charge transfer inefficiency accumulation
Clock feedthrough interference
Electromigration in electrodes
Radiation-induced damage
Thermal stress cracking

FMEA Triads

Trigger: Interface state trapping at Si-SiO₂ boundary
Failure: Progressive charge transfer inefficiency leading to image smearing
Mitigation: Optimized thermal oxidation processes, hydrogen annealing, and buried channel designs

Trigger: Electromigration in polysilicon electrodes under high current density
Failure: Increased electrode resistance and eventual open circuit
Mitigation: Current density limits in design, barrier layers, and redundant electrode structures

Trigger: Clock feedthrough from rapid voltage transitions
Failure:
Mitigation: Balanced clock drivers, shielded routing, and correlated double sampling circuits

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Electrode alignment ±0.25 μm, oxide thickness ±5%, doping concentration ±10%

Test Method

Electro-optical testing with calibrated light sources, charge transfer efficiency measurement using fat-zero technique, dark current characterization, modulation transfer function analysis

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Charge Transfer Structure

Manufacturer profiles associated with Charge Transfer Structure.

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Frequently Asked Questions

What is the main function of the Charge Transfer Structure in CCD arrays?

The primary function is to transport photogenerated electrons from individual pixels to the output amplifier with minimal loss or distortion, enabling the sequential readout of image information while maintaining spatial and charge integrity.

How does the Charge Transfer Structure achieve high transfer efficiency?

High transfer efficiency (>99.99%) is achieved through optimized electrode geometry, precise doping profiles, carefully controlled oxide thickness, and sophisticated clocking waveforms that minimize charge trapping at interfaces and ensure complete charge packet movement between potential wells.

What are the common failure modes of Charge Transfer Structures?

Common failures include charge transfer inefficiency due to interface states, dark current increase from contamination, electrode breakdown from voltage spikes, and clock feedthrough interference. These are mitigated through cleanroom manufacturing, proper passivation, and robust drive circuitry design.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Charge Transfer Structure