TDK-Chirp Ultrasonic Time of Flight Sensor

The Piezoelectric Micromachined Ultra-sonic Transducer (PMUT) Time of Flight (ToF) sensor market for consumer and automotive applications, which is still in its infancy, is expected to reach $22M in 2023 according to the “Ultrasound Sensing Technologies for Medical, Industrial, and Consumer Applications 2018” report from Yole Développement. The main applications are automotive in-cabin gesture recognition, localization for virtual reality (VR) headsets, home robotics, smart speakers, and drones.

TDK-Chirp has developed the first PMUT technology for proximity sensing. It is a radical technology shift in the ToF sensor world, thanks to the very small volume of the sensor, only 15mm3 it can be easily integrated in small systems like drones, mobile, smart home. These characteristics like the sun immunity, low consumption, large field of view and its low cost make it interesting for full applications today cover by more complex and expensive 3D optical ToFs.

The Piezoelectric Ultrasonic Transducer Die is manufactured by STMicroelectronics (STM). STM has developed AlN technology to add to their MEMS portfolio technology. But the AlN transducer is not the only specific MEMS process. The transducer is manufactured on thin membranes etched by micromachining another speciality of STM.

The secret of the first MEMS ultrasonic transducer is not only in the piezoelectric material. The design and the manufacturing of the silicon membrane is very important because the resonance frequency is fixed by the physical dimension, mass and stiffness of the membrane. All the structure of the silicon is designed to obtain the good frequency as shown the cross-section and disassembly pictures. Even technological solutions developed for BAW filters are reused for this component.

This report is focused on the analysis of the ultrasonic ToF. It includes an ultrasonic MEMS transducer developed by Chirp (owner TDK) and one ASIC IC with all the function to drive the generation of pulse, measure the echo, runs Chirp’s DSP algorithms and I2C communication.

Along with the complete ultrasonic ToF MEMS teardown, this report goes with cost analysis and price estimation for the system. It also includes a physical and technical comparison with Vesper VM1000 microphone piezoelectric. The comparison focuses on package integration, the MEMS die and the ASIC die.

COMPLETE TEARDOWN WITH

• Detailed photos
• Precise measurements
• Materials analysis
• Manufacturing process flow
• Supply chain evaluation
• Manufacturing cost analysis
• Estimated sales price

Overview/Introduction

• Executive Summary
• Reverse Costing Methodology

Company Profile

• TDK Chirp
• CH-101
• STMicroelectronics

Teardown Analysis

• Summary of the Physical Analysis
• Packaging
  • Package views
  • Package cross-section
  • Package patents
• Sensor Die
  • Sensor die view and dimensions, process, cross-section and process characteristics
• ASIC Die
  • ASIC die view and dimensions
  • ASIC delayering and main blocks
  • ASIC die process, cross-section and process characteristics
• TDK CH-101. vs Vesper VM1000

Manufacturing Process

• Sensor Die Front-End Process and Fabrication Unit
• ASIC Die Front-End Process and Fabrication Unit
• Final Test and Packaging Fabrication Unit
• Summary of the Main Parts

Cost Analysis

• Summary of the Cost Analysis
• Yield Explanations and Hypotheses
• Sensor Die
  • Sensor die front-end cost
  • Sensor die probe test, thinning and dicing
  • Sensor die wafer cost
  • Sensor die cost
• ASIC Component
  • ASIC die front-end cost
  • ASIC die probe test, thinning and dicing
  • ASIC component cost
• Complete Module
  • Assembled components cost
  • Summary of the assembly
  • Module component cost

Comparison Cost  

Selling Price