Lab Notebook

Video, Slides

Keeping a professional record of your design work is a requirement of the course. If maintained properly, lab notebooks serve as an official and legal record of the development of the intellectual property related to your project. It also serves as a way to document and track changes to your design, results of all tests performed, and the effort you have put into your project. A well-kept notebook will simplify writing of all required documentation for this course (design review, final paper, etc) as all of the information in those documents should already exist in your notebook. Finally, keeping a notebook is simply good engineering practice and likely will be required by future employers, so it is a good idea to get in the habit of maintaining one now.

The Book

Any notebook with permanent bindings designed for laboratory record keeping is acceptable. Notebooks should have pre-numbered pages and square grids on their pages. We will not accept normal spiral-bound notebooks, as these are not permissible in court since pages can be easily replaced. While most of you probably won't be taking your design to court, we want to teach you to get into the habit of keeping legally acceptable records. Some of you may decide you do want to patent your project, so it will be very beneficial to have given yourself the legal advantage from the start.

Electronic Notebook

Alternatively, lab notebooks may be kept digitally as Markdown documents in a Git repo on Github or Gitlab, as in the example below. See a complete example of a 445 Git repo here.

notebooks/
├── alex/
│   ├── README.md
│   └── an_image.png
├── pouya/
│   └── README.md
└── nick/
    ├── README.md
    └── another_image.png
	

Notebook entries:

Each complete entry should include:

  1. Date
  2. Brief statement of objectives for that session
  3. Record of what was done

The record will include equations, diagrams, and figures. These should be numbered for reference in the narrative portion of the book. Written entries and equations should appear on the right-hand page of each pair. Drawn figures, diagrams, and photocopies extracted from published sources should be placed on the left-hand side, which is graph-ruled. All separate documents should be permanently attached to the notebook. All hand-written entries must be made in pen.

Overall, the book should contain a record that is clear and complete, so that someone else can follow progress, understand problems, and understand decisions that were made in designing and executing the project.

What to include:

There is always something to record:

Suppose you are only "kicking around" design ideas for the project with someone, or scanning library sources. Your objective is what you're hoping to find. The record shows what you found or what you decided and why, even if it isn't final.

One of the most common errors is to fail to record these seemingly "unimportant" activities. Down the road, they may prove crucial in understanding when and where a particular idea came from.

Submission and Deadlines

Lab notebooks must be submitted at lab checkout on Reading Day. If you are unable to attend lab checkout, please make arrangements with your TA ahead of time.

Four Point Probe

Simon Danthinne, Ming-Yan Hsiao, Dorian Tricaud

Four Point Probe

Featured Project

# Four Point Probe

Team Members:

Simon Danthinne(simoned2)

Ming-Yan Hsiao(myhsiao2)

Dorian Tricaud (tricaud2)

# Problem:

In the manufacturing process of semiconductor wafers, numerous pieces of test equipment are essential to verify that each manufacturing step has been correctly executed. This requirement significantly raises the cost barrier for entering semiconductor manufacturing, making it challenging for students and hobbyists to gain practical experience. To address this issue, we propose developing an all-in-one four-point probe setup. This device will enable users to measure the surface resistivity of a wafer, a critical parameter that can provide insights into various properties of the wafer, such as its doping level. By offering a more accessible and cost-effective solution, we aim to lower the entry barriers and facilitate hands-on learning and experimentation in semiconductor manufacturing.

# Solution:

Our design will use an off-the-shelf four point probe head for the precision manufacturing tolerances which will be used for contact with the wafer. This wafer contact solution will then be connected to a current source precisely controlled by an IC as well as an ADC to measure the voltage. For user interface, we will have an array of buttons for user input as well as an LCD screen to provide measurement readout and parameter setup regarding wafer information. This will allow us to make better approximations for the wafer based on size and doping type.

# Solution Components:

## Subsystem 1: Measurement system

We will utilize a four-point probe head (HPS2523) with 2mm diameter gold tips to measure the sheet resistance of the silicon wafer. A DC voltage regulator (DIO6905CSH3) will be employed to force current through the two outer tips, while a 24-bit ADC (MCP3561RT-E/ST) will measure the voltage across the two inner tips, with expected measurements in the millivolt range and current operation lasting several milliseconds. Additionally, we plan to use an AC voltage regulator (TPS79633QDCQRQ1) to transiently sweep the outer tips to measure capacitances between them, which will help determine the dopants present. To accurately measure the low voltages, we will amplify the signal using an JFET op-amp (OPA140AIDGKR) to ensure it falls within the ADC’s specifications. Using these measurements, we can apply formulas with corrections for real-world factors to calculate the sheet resistance and other parameters of the wafer.

## Subsystem 2: User Input

To enable users to interact effectively with the measurement system, we will implement an array of buttons that offer various functions such as calibration, measurement setup, and measurement polling. This interface will let users configure the measurement system to ensure that the approximations are suitable for the specific properties of the wafer. The button interface will provide users with the ability to initiate calibration routines to ensure accuracy and reliability, and set up measurements by defining parameters like type, range, and size tailored to the wafer’s characteristics. Additionally, users can poll measurements to start, stop, and monitor ongoing measurements, allowing for real-time adjustments and data collection. The interface also allows users to make approximations regarding other wafer properties so the user can quickly find out more information on their wafer. This comprehensive button interface will make the measurement system user-friendly and adaptable, ensuring precise and efficient measurements tailored to the specific needs of each wafer.

## Subsystem 3: Display

To provide output to users, we will utilize a monochrome 2.4 inch 128x64 OLED LCD display driven over SPI from the MCU. This display will not only present data clearly but also serve as an interface for users to interact with the device. The monochrome LCD will be instrumental in displaying measurement results, system status, and other relevant information in a straightforward and easy-to-read format. Additionally, it will facilitate user interaction by providing visual feedback during calibration, measurement setup, and polling processes. This ensures that users can efficiently navigate and operate the device, making the overall experience intuitive and user-friendly.

# Criterion for Success:

A precise constant current can be run through the wafer for various samples

Measurement system can identify voltage (10mV range minimum) across wafer

Measurement data and calculations can be viewed on LCD

Button inputs allow us to navigate and setup measurement parameters

Total part cost per unit must be less than cheapest readily available four point probes (≤ 650 USD)

Project Videos