Project Wafer

ELET 4154 Microelectronics

Project Wafer Log Book

Dale Salmon March 17, 2015 – May 1, 2015

ELET 4154 Microelectronics

Dale Salmon Hunt Project Wafer Log Book Microelectronics

Week 1 Summary (3/17/2015) This week was scheduled to consist of a four point probe test and measurements. Due to time constraints these steps were not completed by us, but by Professor Hunt.

Week 2 Summary (3/24/2015)

This week Greg and I performed the step etch on Control Wafer 1. This step requires you to lower the wafer ¼ in every 45 seconds. After this we DI rinsed and spun dry the control wafer, and then handed it off to the next group. The etch was examined and the colors were matched to their respected Angstrom values and the following graph was produced from the data.

This week for our personal project wafers we were instructed to perform the lithography step and then the HF etch and Piranha and RCA clean afterwards. Our wafer was placed in the machine used to apply the photoresist and the vacuum was turned on to keep our wafer in place. The amount of photoresist applied was about the size of a half dollar. The machine was started up which spun the wafer to apply the photoresist for the required time. After that we soft baked our wafers for about a minute and a half at roughly 125°C. Following that was exposing our wafer to the developed image for the required time. Next was developing our image on the wafer, this step was a little tricky because there was a lot of mixed results among the class concerning development time. In my case, after observing the wafer under a microscope, it was clear that I needed to develop for a longer amount of time. I repeated the developing and observing stage a few times until it was done correctly. After that I was ready to hard bake and perform the HF oxide etch. Our wafers went into the HF solution for approximately 15 minutes and then after that we DI rinsed and spun dry them. Again we observed the wafer under the microscope and then performed the Piranha and RCA clean steps. Once complete with that, we observed the wafer under a microscope one last time and recorded images, as seen below. After the laboratory Professor Hunt put our wafers in the furnace for the Boron Diffusion.



Greg and I, for the control wafer, were instructed to perform the oxide etch which consisted of placing the wafer in the HF for the required time until all the oxide was removed.

This week for the project wafer consisted of only an HF dip to etch all of the oxide and then an RCA clean. Our wafers were placed face down in the HF for about 20 minutes. The best way to tell they were done etching was to observe how the HF acted on the wafer (whether it was hydrophilic or hydrophobic). Once the wafer was done etching we performed a DI rinse and then, as mentioned previously, the RCA clean.

Week 4 Summary (4/14/2015) This week for the lab project the second layer of oxide was developed and etched. The process started with coating the wafer with photoresist and soft baking. Then the wafer was ready to be lined up, exposed, and developed. This took a lot of time because of lining up the second layer with the first. The crosses were not visible on the mask and after a couple of unsuccessful tries, Professor Hunt decided to try something new. A new mask was made with only the corner windows opened up. These were developed and then stripped and photoresist was re-applied. After this coating of photoresist and the open windows, the crosses were able to be seen much clearer. The wafer was then developed and placed in the HF for 13 minutes to etch the oxide. After this the photoresist was stripped and a Piranha clean and RCA clean were done, then images were taken. This image shows the smallest capacitor on my die and the background layer is seen and the second layer appears to line up well.


This week we followed a similar procedure as last week for the lab project. The third layer of oxide was developed and etched. The process started with coating the wafer with photoresist and soft baking. Then the wafer was ready to be lined up, exposed, and developed. This took a lot of time because of lining up the third layer with the second. The crosses were not visible on the mask initially but after a few unsuccessful tries the layers lined up acceptably. The layers are still not perfect but in the acceptable area. The wafer was then hard baked and placed in the HF for 13 minutes to etch the oxide. After this the photoresist was stripped and a Piranha clean and RCA clean were done, then images were taken. The images below show the smallest resistor and the smallest transistor on my die showing the previous layers behind them. Photos were taken before and after etching.


Week 6 Summary (4/28/2015) This week was the last week for actually making anything. The final layer (aluminum) was coated by Professor Hunt before the week began. The first step was photoresist followed by a soft bake. The wafer was then lined up with the new mask and the crosses could actually be seen quite well this time. After a short time of lining up the wafer was exposed to the light. After this the wafer was placed in the developer solution for a quick 10 second dip until you could see the line clear up. The wafer was observed under a microscope and was given the okay to etch. The wafer was then hard baked for 5 minutes and then placed in the aluminum etch solution. This was a quick process and after the etch had removed all excess aluminum it was rinsed and spun dry. Photos were taken to show this point. After the etch was finished, the wafer was covered in acetone and the photoresist was removed. Photos were taken after this step to document the final product.


Results Summary (5/1/2015)

After a sinter was performed by Professor Hunt the wafer was ready for testing. All components tested were on die I7 (resistors) and J8 (transistors) which are my designed components. Tests were done under a microscope with LabVIEW and Excel. Results can be seen below. Resistors:


Serpentine Resistors:


Capacitors:


Transistors:

Die J8 Transistor T1



Project Wafer

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