Light Receiving Element Dual Recessed Pad Structure

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Solution Overview

Problem

The existing light receiving elements with thick semiconductor substrates face challenges in forming pad openings, leading to poor connections between electrode pads and bonding wires due to etching residues and reaction products, which can cause corrosion and signal transmission errors.

Innovation Solution

The light receiving element incorporates a dual recessed portion structure on the semiconductor substrate, with a first recessed portion on the back side and a second recessed portion on the front side, designed to prevent the deposition of reaction products and ensure a clean surface for the electrode pad, thereby enhancing the connection reliability between the electrode pad and the bonding wire.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the semiconductor substrate thickness is increased to improve sensitivity for infrared light detection, then the photoelectric conversion sensitivity is improved, but the pad opening formation becomes difficult and etching residues occur

Engineering Contradiction:

Improvelight detection sensitivityVSAvoidpad opening formation quality

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The pad opening formation process is segmented into two distinct stages: first forming a through-hole from the back surface to expose the electrode pad, then forming a recessed portion from the front surface to reach the electrode pad surface. This segmentation allows each stage to be optimized independently, solving the problem of etching residues in thick substrates while maintaining sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The through-hole is formed preliminarily from the back surface before forming the final recessed portion from the front surface. This preliminary action creates a pathway that facilitates complete etching and prevents reaction product deposition, ensuring a clean electrode pad surface for reliable bonding wire connection.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a deep pad opening is formed to reach the electrode pad in thick substrates, then electrical connection is achieved, but reaction products are deposited and corrode the electrode pad

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidreaction product deposition and corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of forming the pad opening only from the front surface (conventional method), the invention inverts the approach by first forming a through-hole from the back surface, then forming the recessed portion from the front surface. This inverted sequence allows reaction products to be discharged through the back opening, preventing deposition and corrosion of the electrode pad while ensuring reliable electrical connection.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of operation

If wire bonding is performed through a deep pad opening, then external electrical connection is achieved, but poor connection occurs due to etching residues

Engineering Contradiction:

Improvewire bonding capabilityVSAvoidbonding connection quality

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The through-hole is formed preliminarily from the back surface to completely remove etching residues and reaction products before wire bonding is performed. This preliminary cleaning action ensures the electrode pad surface is free from contaminants, enabling reliable wire bonding connection while maintaining ease of operation.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The dual recessed portion structure effectively prevents the deposition of reaction products, reducing the likelihood of corrosion and ensuring a reliable electrical connection between the electrode pad and the bonding wire, thus improving the sensitivity and durability of the light receiving element.

Implementation Method 1

a photoelectric conversion unit that is disposed in the semiconductor substrate and performs photoelectric conversion on incident light

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20230178579A1Light receiving element and electronic device

Publication Date: 2023.06.08 SONY SEMICON SOLUTIONS CORP

AI summary

To prevent the occurrence of poor connection between an electrode pad and a bonding wire.A light receiving element includes a wiring region, an electrode pad, a first recessed portion, and a second recessed portion. The wiring region is disposed next to the front side of a semiconductor substrate, the wiring region including a wiring layer for transmitting a signal and an insulating layer for insulating the wiring layer, the wiring layer being connected to a photoelectric conversion unit that is disposed in the semiconductor substrate and performs photoelectric conversion on incident light. The electrode pad is disposed in the wiring region and is connected to the wiring layer so as to be connected to the outside. The first recessed portion is formed on the back side of the semiconductor substrate and has the bottom near the front side of the semiconductor substrate and near the electrode pad. The second recessed portion is formed at the bottom of the first recessed portion and has the bottom formed on a surface of the electrode pad.