Ethical Guidelines

University of Illinois trained engineers are the best and most highly sought in the world. Our graduates are superbly trained, highly competent, and creative. This, however, is not enough. Our engineers must also be trusted to conduct themselves according to the highest ethical standards. All teams must address ethical considerations in their projects. This requirement has two parts.

First, there is a stringent Code of Ethics published by professional societies, such as IEEE and ACM. The power of these Codes of Ethics is to provide guidance to engineers in decision making and to lend the weight of the collective community of engineers to individuals taking a stand on ethical issues. Thus the Code of Ethics both limits the professional engineer and empowers the professional engineer to stand firm on fundamental ethical bedrock. All teams must read the IEEE code and ACM code and comment on any sections of the code that bear directly on the project.

Second, we expect our students to have personal standards of conduct consistent with the IEEE and ACM Codes of Ethics, but also beyond it. That is, there are areas of ethics not addressed by these Codes that the engineer may consider in taking on projects or jobs or making other professional decisions. These are personal standards and choices. In the context of the class, there are no right or wrong answers here. Our students simply need to demonstrate that they are thinking deeply about their own decisions and the consequences of those decisions. We encourage our students to consider the wider impact of their projects and address any concerns raised by potential uses of the project. Students should ask themselves, "Would I be comfortable having my name widely attached to this project? Do I want to live in a society where this product is available or widely used? Would I be proud of a career dominated by the decision making demonstrated here?" Remember that UIUC engineers have a long history of inventions that really has changed the world.

If the students feel that these Codes of Ethics does not directly bear on their project and that there are no other reasonable concerns, they should not invent issues where there are none. Students will still be expected to be familiar with the IEEE Code of Ethics and ACM Code of Ethics.

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)

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