Imaging

A look inside the Single Photon Avalanche Diode (SPAD) from STMicroelectronics in Apple iPhone 7, with FlightSense Time-of-Flight proximity sensor

STMicroelectronics Time of Flight Proximity Sensor in the Apple iPhone 7 Plus

Published: 22/03/2017
Product code: SP17326
Price: EUR 3 490
Applications: Consumer

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Introduction
Summary
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Today, time-of-flight (ToF) systems are among the most profitable and innovative imaging technologies. Every major consumer product manufacturer wants to integrate such devices to provide 3D imaging, proximity sensing, ambient light sensing, gesture recognition, and more. STMicroelectronics has been investigating this technology in depth, and now provides several smartphone manufacturers ToF ranging sensors. Apple’s iPhone 7 Plus goes further with a custom proximity sensor, the smallest FlightSenseTM device in STMicroelectronics ToF portfolio.

Located in the front of the phone, above the main speaker, the FlightSenseTM proximity sensor uses optical land-grid array (LGA) packaging. The custom Apple device measures 2.80 mm x 2.40 mm, half the size of the rest of STMicroelectronics’s portfolio.

This report analyzes the complete microsystem, from the illumination device, which is a Vertical-Cavity Surface-Emitting Laser (VCSEL), to the collector, which is based on STMicroelectronics’ Single Photon Avalanche Diode (SPAD). It includes a complete cost analysis and price estimation of the device based on a detailed description of the package, the ToF detector and the VCSEL.

It also features a complete technology comparison with every product in STMicroelectronics’ ToF portfolio since the first generation, including the VL53L0X and VL6180X, especially looking at the SPAD’s evolution.

Overview / Introduction

STMicroelectronics Company Profile and Time of Flight technology

Apple iPhone 7 Plus Teardown

Physical Analysis

Physical Analysis Methodology
Package
- View and dimensions
- Package opening and wire bonding process
- Package cross-section: adhesives, PCB, filters, FOV
VCSEL Die
- View and dimensions
- Wire bonding, cavity
- Cross-section
- Process characteristics
ASIC Die
- View, dimensions and marking
- Die overview: active area, SPAD technology
- Die delayering, main block IDs and process
- Cross-section: metal layers, SPADs
- Process characteristics

Physical Comparison with VL53L0X and VL6180X

Package, Functions, FOV, Optical Blocking Package, ASIC and VCSEL, SPADs

Manufacturing Process Flow

Overview
ASIC Front-End Process
VCSEL Front-End Process
ASIC Wafer Fabrication Unit
VCSEL Wafer Fabrication Unit
Packaging Process Flow
Final Assembly Unit

Cost Analysis

Cost Analysis Overview
Main Steps Used in the Economic Analysis
Yield Hypotheses
ASIC and VCSEL Die Cost
- Front-end cost
- Back-end: Tests and dicing
- Wafer and die cost
Component
- Front-end cost
- Back-end: Tests and dicing
- Wafer and die cost

Estimated Price Analysis