Description: In the last paper we learned about various micro-electro-mechanical systems (MEMS) sensors and sensing technologies that were of interest to you. The manufacturing process underlying many of the devices involved lithography to create patterns on the wafer which are used to guide downstream operations that are either additive or subtractive in nature. In this assignment, I’ve selected articles for you to read and reflect on that are related to lithography and also MEMS devices.
Details: Make sure to answer each of the questions, as this is on what I will be grading. I can’t give partial credit if you have not attempted a question. The assignment is heavily weighted toward your own work. There is a minor component (component #2) related to a MEMS patent that you may work on with another student if you so choose. The grading breakdown is as follows…
Component #1 (Photolithography) = 80 points
Component #2 (MEMS Patent) = 20 points
Total points = 100 points
Articles included in this assignment:
A roadmap for optical lithography. Rothschild, Optics and Photonics News. June 2010.
Lithography and other patterning techniques for future electronics. F. Pease and S. Y. Chou, Proceedings of the IEEE, Vol. 96, 2008.
High-aspect ratio photolithography for MEMS applications. Miyajima, Journal of MEMS, Vol. 4, 1995.
Basics of US Patents and the Patent System, G. Elliott, 2006.
Micromechanical elements and methods for their fabrication, US Patent #4,740,410, R. S. Muller et al., 26 April 1988.
COMPONENT #1: These papers discuss photolithography. They are slightly dated but provide an excellent background on technology that has been developed to continue to sustain Moore’s Law. We will discuss in class some more recent technology advances that have enabled more recent nodes.
I ask you specific questions for the first two and ask you to review the last one. The first two reinforce some of the concepts in class and also put these in context of industry targets/activities, the last ties everything to MEMS devices.
Paper #1. A roadmap for optical lithography. Read the paper and answer the following questions (15 points total).
What international forum manages lithography targets and requirements for the industry? From what regions of the world is this forum sponsored? What is the goal of this forum? What is a node? What node are we at currently and where are we headed over the next 10-15 years?
What is CDmin, why is it important, and what parameters affect its value? Over what range of values have these parameters changed over the past 20 years and what are the prospects for changing them further?
What is the highest resolution achieved with optical lithography in this paper and how was it done? Give an example of how we might reach the 23-nm node and how we may reach sub-23 nm node?
Paper #2. Lithography and other patterning techniques for future electronics. Read the paper and answer the following questions (25 points total).
Describe the driving forces behind improvements in lithography / patterning, touching upon the relation to the IC industry and scaling effects in particular.
Review the history of semiconductor IC patterning since the 1960s, touching upon printing techniques, optics, illumination sources and mask making techniques.
What determines lithographic resolution in proximity printing? What type of diffraction is important? Why is lowering wavelength difficult? What is the drawback of going to x-rays? What wavelength is the industry holding at now and what developments have enabled IC production at lower nodes?
What variant technology is the favorite to supplant optical lithography? Why is it better than the conventional variant? What are some of its characteristics?
Define mechanical patterning, chemical patterning and mixed patterning. What are the advantages and disadvantages of non-radiation-based patterning? Give an example of mechanical patterning and an example of chemical patterning. Very briefly describe each example.
Paper #3. High-aspect ratio photolithography for MEMS applications. Read the article and write a review that discusses the motivation behind the work, the experimental configuration/process, the primary observations, the fabricated devices, and the conclusions of the authors. This should be written as a concise summary and flow in paragraph form, not as individual/separate bullet items. (40 points total)
In the course of your review, be sure to have touched upon the following points.
With regard to the motivation behind the work… the authors demonstrate results of a specific technique developed to produce high aspect ratio features, what other options have been suggested and what are the respective problems.
With regard to the experiment, be sure to review the process that the authors used and identify the parameters that the authors adjusted in their experiment.
With regard to the observations (experimental results), be sure to review how the performance indicators changed with variation in the input parameters and also how these performance indicators were measured.
Finally, with regard to the devices they demonstrate their process with, be sure to mention how their experimental observations influenced the fabrication process for these devices.
COMPONENT #2. This component of the project is meant to expose you to patents, an important part of MEMS devices in real-world applications. The 1st article is a brief description of the patent and review process in the US. This is worthwhile for you in general and is a nice primer for reading the patent. The patent describes a multi-step fabrication process used to manufacture a MEMS device. Because patent language can get confusing, I’m giving you the option to work together with another student, which may be helpful toward understanding the document. If you choose to work with another student, turn in copies of the answers with each of your individual assignments and note with whom you worked.
Patent paper #1 – Basics of US Patents and the Patent System. Read the paper and answer the following questions. Be direct. (5 points total)
1) When was the US patent system created? In what document does it find its origins? How does it stimulate the economy and advance quality of life in the United States? What was the first US patent*?
2) Who is the primary gatekeeper in the US Patent system? What is the responsibility of this organization? What are the 3 basic steps in the process of examining a patent application?
3) Describe what makes subject matter eligible for patenting. Make sure to mention what section of the US code governs subject matter eligibility, what the 2 key elements are that determine eligibility, and what is the importance of utility to the actual subject matter to be patented.
4) What section of the US code governs novelty and what section governs obviousness? What considerations define the current test for obviousness? How does the way in which obviousness is determined have a significant influence on the overall effectiveness of the patent system?
5) What section of the US code details appropriate disclosure of inventions? What are the important elements of a patent specification? With regard to speculation, how is a patent specification different from a peer-reviewed journal publication?
*You can find the answer for this on uspto.gov or google.
Patent paper #2 – Review US Patent #4,740,410. Answer the following questions (15 points total).
Generally, what is this patent for? Is it for a product or process or both? What technological need does it address? What are the objects of this invention? What are the potential applications of this invention in the micromechanical field?
The patent claims identify several methods used to make various devices. The primary claims are listed as #’s 1, 16, 18, 23, 25, 27, 29, 31, and 40. The other (secondary) claims are derived from (and reference) these primary claims.
Of the primary claims, which is the most generic? Why is it the most powerful? Describe the steps involved in this primary claim and list products that might come from this generic method as they are mentioned in the respective secondary claims.
Starting on line 36 of column 4 and ending on line 57 of column 4 is a specific description of the fabrication of a particular component. Of the remaining primary claims, which one is described here (note that the materials are specified)? Which of the step(s) (a through i) in the primary claim refer to photolithography steps? What is the primary difference between claims 18 and 23? What is the primary difference between claims 23 and 27?