Unravelling complex nanoelectronic devices A challenge-based learning assignment – part I: the teacher perspective

With the new academic year just started, this blogpost focuses on teaching, and describes the assignment we designed as part of a course on plasma processing. The inspiration for this assignment is that we all are accustomed to the marvels of modern smartphone communication and advanced computing technology, but most people are not aware of the decades of innovation behind these developments. By asking students to investigate the process flow employed for the fabrication of state-of-the-art nanoelectronic devices, they learn to handle open-ended tasks, and complexity in general. While we started with (earlier versions of) this assignment already in our curriculum 2015/2016, it nicely fits in the recent focus on challenge-based learning (CBL) within the field of education.^1,2

The course

As teachers from the Plasma & Materials Processing (PMP) research group, we teach every year the course Plasma Processing Science & Technology (PPST) as part of the MSc program Applied Physics at Eindhoven University of Technology (see course information below). The design of this course is based on two rather different objectives. First of all, the students should obtain knowledge on how plasmas can be used to process materials. In addition, we find it important that the students broaden their perspective, and learn about some of the technologies which were employed to fabricate the devices they use every day, such as laptops and smartphones. In a way, we hope to transfer some of our fascination for the complexity of these fabrication schemes to the students. While broadening their perspective, the main objective is that the students develop some important skills: (i) learning independently from available sources, (ii) being able to unravel complex procedures, and (iii) critical reading / interpretation of relevant literature.

Course information – Plasma Processing Science & Technology

Course code: 3MP170
Offered by: dept. Applied Physics, Plasma and Materials Processing group
Teachers: Ageeth Bol, Erwin Kessels, Harm Knoops, Adrie Mackus (responsible lecturer)
Credits: 5 ECTS
Quartile: 3
Description: Plasma processing has been an essential ingredient for scaling down electronics in the past decades, and it can be said that without plasma etching we wouldn’t have smartphones or any other handheld devices. With nanoelectronics reaching the atomic scale, new plasma processing techniques for etching and deposition of materials are needed, while related developments in photovoltaics also require the processing of interfacial layers with atomic scale accuracy. In this course, the state-of-the-art of nanofabrication of integrated circuits, microelectromechanical systems (MEMS) and solar cells is described, with a focus on the role of plasmas in the materials processing.

The assignment

To develop and assess the skills mentioned above, we designed a practical assignment in which the students unravel how specific nanodevices are fabricated, for example the processor or the NAND memory chip in the latest iPhone. The students are asked to identify the processing steps that are performed during the fabrication based on variety of information sources. Part of the motivation for this assignment is that the companies fabricating these devices often do not share the details of how it is done. In other words, it is not always clear which processes/technologies that are developed in the scientific community eventually end up in an actual device (see Figure 1). In the assignment, the students are asked to study a specific device architecture, and combine what they have learned in the lectures with information from different sources as illustrated in Figure 2: i.e., patent literature, websites with information on reverse engineering of devices (e.g., www.techinsights.com), and scientific literature. In that way, we ask the students to close the gap between academic research and industrial application (Figure 1).

Figure 1 – The gap between scientific research in academia and fabrication in the industry. This figure illustrates the “valley of death” that needs to be crossed for implementation of new technologies, but also the difference in culture regarding the sharing of information.

Figure 2 – Slide showing an overview of information sources available to the students.

State-of-the-art nanodevices

The devices the students studied in the past year varied from different process flows for fabrication of gate-all-around transistors to various memory architectures and future self-aligned fabrication schemes. Every year we select new topics to ensure that the students investigate state-of-the art technology. Figure 3 shows two examples of the collection of last year.

The consequence of choosing recent topics every year is that there is typically no correct or wrong answer to the question how a specific device can be made. Also for us as teachers, it often remains a big puzzle what the best fabrication approach could be. The focus in the assessment of the assignment is therefore more on the method the students employed to come to a comprehensive picture. Students who use creativity in combining information from different sources typically score best in the evaluation.

Figure 3 – Examples of process flows investigated: (a) the Saddle-FinFET in Micron Technology’s 1- DRAM by Mark Smits, and (b) TMSC’s embedded MRAM cell by Cindy Lam.

Open-ended character

The main challenge in this assignment is that it is extremely open-ended. When introducing the assignment, I explain that when starting a job after the MSc program in 1-2 years, they will mostly have to deal with this type of problems. In the real world, there is typically no answer model, or even a straightforward solution to a given task. It seems that sharing this future perspective helps to motivate the students to take up the challenge.

Because of open-ended character, it is however difficult for many students to find suitable sources of information and to sufficiently understand the device architecture to get started. To provide some guidance and to facilitate interactions with other students, we divide the class in groups of ~5 students who work on a similar topic (e.g., front or back-end-of-line). A PhD or postdoc from the PMP research group joins the group meetings to guide the discussions and give general advice on where to find the information. We make sure that there is some overlap in the topics the students in the group work on, such that they can also learn from each other in these discussions.

Peer review and feedback

The students write an individual report on their topic, and we ask to submit a first version of the report roughly two weeks before the final deadline. This first version is distributed to two other students from other groups for peer review. The peer review has basically two functions: the students obtain feedback from fellow students that helps to improve their report, but they can also obtain some inspiration for their own report by reading two other reports. At the same time, the students learn about the culture of peer review in scientific publication, illustrated in Figure 4. To this end we share the peer reviews and rebuttal letter of one of our own manuscripts as an example.

Towards the end of the course, we organize a session during which the groups share what they learned during the assignment by giving a short presentation. This presentation is not graded, but it can serve as a good moment to get some additional input from the teachers, supervisors and fellow students, before finishing the final version of the report. Although it is challenging to discuss all topics in detail within one morning session, hearing the variety of different topics after each other shows how fascinating nanoelectronic device fabrication is. One additional benefit of this way of flipping the classroom is that we as teachers also learn new things in the discussions with the students. Since students look at a problem with fresh perspective, they often find additional sources of information that we might have overlooked otherwise.

Figure 4 – The peer review procedure for scientific publication.

Towards life-long learning

The vision behind the design of the assignment is that nowadays it is very important to teach the student certain skills instead of merely focusing on knowledge transfer. In the PPST course, the students learn the state-of-the-art of plasma processing. However, since this is a field that will develop further in the coming decades, we also want to give them the tools for how to study and make use of the technologies that will be developed in the future.

Based on the interactions with the students when running this assignment in the past few years, it is clear that many students learn a lot from performing such an open-ended assignment. This will also be illustrated nicely in part II of this story, featuring the student perspective. I can see how CBL will become more and more important for preparing our students for the diverse careers of the future, and I am enthusiastic about the attention CBL is currently receiving at our university.^2,3 In a society in which many technologies change rapidly, it is not only important to have knowledge on specific current-day technologies and the underlying physical principles, but it is essential to be able to continuously acquire knowledge and information as part of lifelong learning.

References

(1) Nichols, Mark H., Cator, Karen (2009), Challenge Based Learning White Paper. Cupertino, California: Apple, Inc.

(2) https://innovationorigins.com/en/how-education-is-evolving-students-now-learn-through-challenge-based-learning/.

(3) Eindhoven University of Technology. (2018). TU/e strategy 2030. Drivers of change. https://www.tue.nl/en/our-university/about-the-university/tue-strategy-2030/.