I am trying to improve the SiNx deposition rate and film uniformity thorugh MW PECVD process. Previous research have reported the effects of deposition parameters such as plasma power, SiH4/NH3 gas ratio, total gas flow, substrate temperature etc., would effect the deposition rate and optical parameters of the SiNx thin film.
I was wondering what would be the effect of increasing the SiH4 gas sources towards the thin film deposition rate, refractive index or thin film thickness/uniformity? As shown in the attached sketch (not actual condition of equipment), is it possible that if I increase the SiH4 gas showers, at the same total gas flow and chamber pressure (controlled by exhaust valves), more SiH4 can be introduced into the chamber, improving the deposition rate?
My concern is the uniformity of SiNx thickness and RI within wafer.
Any ideas / comments regarding this setting is much appreciated.
Hi Reza;
In fact; all the film characteristics you work on are changing with the flow. For example the deposition rate increases with the increasing SiH4 flow. And also the uniformity is increases with the SiH4 flow. And if you increase the SiH4 flow, the n value also incereases. Also the stress of the film goes up with the SiH4 flow. May be you interest with the link.
http://www.nectec.or.th/nac2005/documents/20050329_MicroElectronics-01_Presentation.pdf
Regards.
Hi Osman,
Thank you for the link. I really appreciate it.
The data presented is in-line with the data that I have on hand. As of now, what was conducted on my side was adjusting the process parameters (SiH4 flow, control chamber pressure etc).
What I am trying to evaluate is the effect of changing the equipment set-up, specifically in this case, increasing the source of SiH4 gas into the chamber. For example, if currently there is only 3 gas showers that flows in SiH4 gas, I was wondering if I increase the gas showers to 6 units, so that the flow of SiH4 can be distributed more evenly across the same area. The gas flow would be the same.
My concern is that, with increased gas showers sources (source of SiH4 into the chambers);
1. Would the Si deposits on the quartz tube increase? This would definitely reduce the tube life.
2. Would the plasma density be similar? Or would the area of plasma increase when I increase the SiH4 source?
Or, would increasing the SiH4 sources have no significant effect on the electrical and optical properties of the SiNx film, since I am mintaining the gas flow and chamber pressure ?
Hi Reza;
Thank you for clarifying my mind. Actually I think that if you increase the number of the SiH4 showers, the amount of the SiH4 is constant. In this case you will get a more homogeneous ambient for the reaction. This would be good for the surface uniformity.
To be honest; I did not understand why do you think that the SiH4 showers increase the Si deposition of the quartz. Both cases have the same amount of SİH4. Even, if you do that, I think your quartz tube will be protected due to the reaction homogenity.
Best wishes.
Hi Osman,
Actually, I was looking for a new approach to improve the uniformity of SiNx layer on the Si wafers. Since the data from adjusting the deposition parameters are well documented, I was thinking of adjusting the hardware instead, hence the idea to increase gas showers. Some other ideas that I have is to maybe increase the size of the showers.
Thank you for your comments. I felt more assured to go on with the plan, since you do agree that increasing the gas showers would not be detrimental to the SiNx properties.
Thank you.
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