Last week during the deposition step, Chris and I discovered that part of the Cu “power cup” (piece that is bonded to target to make thermal contact with sputter gun) had eroded and coated the inside of the target shield with copper. Later EDX and TEM characterization showed that there was indeed contamination in the…
Last week a set of four wafers was processed at four different RTP temperatures (1000, 950, 900, 850 C). Unfortunately, the yield across these wafers was low due to possible metal contamination in the film and etch issues. However, the TEMs still show a range of porosities and pore sizes across the different thermal treatments….
For the last two weeks, we have observed that membranes have been wrinkling post-oxide strip. After some investigation, it was determined that the cause of wrinkling was from a cracked SiO2 target in the sputter system. I also saw a suppression of pore formation in the wrinkled films as compared to an unwrinkled membrane. The…
There has been some experimentation recently on trying to form very large pores in thick membranes. We have found that a high temperature anneal (1000 C) along with a fast ramp rate (100 C/s) w/o the susceptor can create these large voids. It seems that the distribution widens as we push the cut-off up. The…
For the last three weeks, we have increased the substrate bias power from 25 W to 32 W (for both oxide and a-Si) to adress some film quality issues. I have found that it is “harder” to open pores in a film deposited at higher bias. Below are micrographs showing the difference in porosity for…
Inspired by JP’s work with the Veeco Wyko, I attempted to fit pressure-displacement curves with the equation for thin film deformation (Vlassak and Nix 1992) for two membrane geometries: 100um x 100um and 1000um x 1000um. The relationship between displacement and pressure is: P = pressure, d = displacement, C1 and C2 are geometric coefficients,…
After seeing a reduction of pore size at 750 C, I decided to run three different soak times at a fixed acetylene concentration of 1 LPM. As expected, the longer soak time resulted in more occlusion. It seems that the carbon growth is almost linear: 5 min treatment shrinks the pores by 5 nm and…
Last week I ran a series of membranes through the carbonization process at four different temperatures (600, 700, 750 and 800 C) at a fixed acetylene concentration (1 LPM). As expected, the growth of the carbon ring around our pores is temperature dependent. Note: image processing was done on 100 kx micrographs with the exception…
With the new heater installed in the AJA sputter tool, the production team decided to run a set of wafers at six different chamber temperatures to re-characterize membrane morphology, mechanical strength and overall quality of material. These films were all deposited with 25 W substrate bias and annealed at 1000 C in the RTP with…
Last week I reported that carbonization can shrink pores. This week I was able to completely occlude the pores with a change in the process recipe. Instead of cutting off the acetylene flow before the thermal treatment, I kept the gas on for the entire process. What resulted was a complete occlusion of the pores….