IMAGING Infrared

STMicroelectronics’ Time of Flight Proximity Sensor & Flood Illuminator in the Apple iPhone X

Published: 30/01/2018
Product code: SP18383
Price: EUR 3 490
Applications: Consumer

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Introduction
Summary
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A unique combination of STMicroelectronics’ latest proximity sensor, based on single-photon avalanche diode (SPAD) technology and a VCSEL illuminator, all in Apple’s most advanced handset.

Ahead of its competitors, Apple has begun using 3D sensing. For the iPhone’s 10th anniversary, Apple integrated this new function under the name “True Depth sensing”. The system features a near-infrared (NIR) camera, a dot projector, and a flood illuminator, along with a proximity sensor. All modules work together to form a high-end security solution: facial recognition. Since the Apple 7, STMicroelectronics has supplied Apple with a custom proximity sensor, one which represents the smallest FlightSenseTM device in its ToF portfolio. And with the Apple X, STMicroelectronics has gained significant market share by integrating several of its components (from the NIR camera to the 3D touch controller), including a new custom version of the proximity sensor featuring a flood illuminator.

Located in the front above the main speaker, the proximity sensor/flood illuminator is packaged using optical LGA. The device is unique to Apple. In the past, STMicroelectronics released a custom proximity sensor two times smaller (2.80 x 2.40 mm) than the devices in its portfolio, based on FlightSenseTM technology. This new version comes with a flood illuminator used in the True Depth system. The flood illuminator is an NIR VCSEL with a wide beam that illuminates the face and allows for nighttime user recognition with the NIR camera. The packaging is specially designed for the flood illuminator’s heat management.

In this report the complete microsystem is analyzed, from the two illumination devices (which are vertical-cavity surface-emitting lasers (VCSEL)) to the collector (based on the SPAD developed by STMicroelectronics). Moreover, a complete cost analysis and price estimate is presented for the device, based on a detailed description of the package, the ToF detector, the VCSEL, and the second VCSEL for flood illumination.

Also featured is a complete technology comparison with STMicroelectronics’ ToF portfolio since its first generation: the VL53L0X, the VL6180X, and the most recent custom proximity sensor in the Apple iPhone 8.

Overview / Introduction

STMicroelectronics – Company Profile & Time of Flight (ToF) Technology

Apple iPhone X Plus – Teardown

Physical Analysis

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

Physical Comparison with Apple’s iPhone 8, the VL53L0X, and the VL6180X

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

Manufacturing Process Flow

Overview
ASIC and VCSELs Front-End Process
ASIC and VCSELs Wafer Fabrication Unit
Packaging Process Flow

Cost Analysis

Cost Analysis Synthesis
Economic Analysis – Main Steps Used
Yield Hypotheses
ASIC & VCSEL Die Cost
- Front-end cost
- Back-end – tests and dicing
- Wafer and die cost
Component
- Packaging cost
- Packaging cost per process steps
- Component cost

Estimated Price Analysis