Plasma – an art rather than a science.
I recently came across an article that described the soul as a plasma, a transitional phase between matter and energy. The essay was accompanied by the beautiful pictures of plasma globes that have become so common. There was a stage in my life/career as a physicist that this would annoy me. Somebody deliberately ignoring the science and trying to twist the reality of what plasma is and making it into something that I know it is not. However, as I have grown older and maybe more wise, maybe not, I am more tolerant of different views of the world.
However it does raise one of my real concerns – plasma as a black art. Plasma is now widely used throughout industry and is gaining new applications on a daily basis, for example the plasma sabre – torch. Industry has avoided direct measurement and control of the plasma state. Many would argue that the common strategy used in industry could well be described as a “black box” strategy (I avoided the temptation to call it a “black art” strategy). This strategy has served industries like the semiconductor industry very well but a time will come when the capabilities of plasma processing will be limited by this strategy. A more scientific approach would be to measure the key plasma parameters and correlate these parameters with the process outcomes. Then, reproducing the plasma parameters would be sufficient to replicate the process outcomes. We could call this the “plasma parameter” strategy.
The plasma parameter strategy seems obvious and it would make plasma processing much easier to engineer and simplify process development and transfer. Why, then has it not blossomed? The key issues seems to me to be i) plasma wall/surface interactions mean that reproducing a specific set of plasma parameters is not so easy and ii) more importantly, measuring the exact plasma state is not straight forward.
I would be very grateful if you could comment on what you think is holding back the “plasma parameter” strategy.
To define a plasma state in terms of parameters means measuring plasma density and temperature, but also requires knowledge of non-equilibrium states. This is where it gets quite complex. Plasmas have chemistry, so we need to know the gas composition. Plasmas are also have highly non-equilibrium dynamics, at least most of the useful industrial plasma are cold plasma. Ions are accelerated in sheaths. Electrons are heated by RF fields and only weakly transfer their energy. So we do not have a concept such as temperature to classify a plasma state that consists of an huge range of particle velocities. So there is a need to measure the distribution functions of electrons and ions of every species before we can begin to classify a plasma state. This is not possible to do at the moment in a simple way that can be used by a plasma process engineer. So we stick with the black box strategy. Control the inputs to the plasma and hope the process results are stable enough to deploy in the field.
One of my remaining ambitions is to improve sensor technology so that science can start to measure and quantify the plasma state above a wafer or substrate in sufficient detail to be able to predict the process outcome. This technology will not happen overnight and I hope I am around long enough to see it happen. In the mean time I need to explore my plasma consciousness and open my soul to the flow of plasma energy.
“Let’s take a quick look at what we call plasma. While there is much that has been discovered about it and its varying forms, there is much we don’t know about plasma. Plasma is a fourth form of matter. It is highly unstable. The other three forms are solids, liquids, and gases. We see plasma manifest as fire, lightning, solar activity, et. al. It seems to me to be a transitional phase between matter and energy, a conduit, as it were, between the two. Plasma usually gives off some form of radiation as it flashes in and out of existence, usually heat and light. Yet there is plasma that exists at levels we cannot see or feel, just as there is an infinity of frequencies of energy we cannot sense with these physical bodies. Indeed, even the machines we build to detect these wavelengths are limited in their ability to do so.
So, one might ask, how is it that consciousness can be plasma? Well, if plasma can be considered a transitional phenomenon, we can take a look at its function when interfacing with the brain, an instrument we all carry around with us in our heads. Electrical impulses are stimulating the neurons which cause us to understand what’s going on in the world around us. Electric impulses flash through the material that is the brain and cause it to function. We use these same electrical impulses to control the actions of our body that interact with the physical world. In this way there is a constant flow of plasma inside our body which is converting matter to energy acting upon the inner workings of our bodies and through our bodies acting upon the universe outside of it.”