Electric Compact Direct Diaphragm Valves：ECV_®

2nd Monodzukuri Grand Award for Parts
Electric Compact Direct Diaphragm Valve：ECV_®
Recommendation

New Industry Creation Hatchery Center, Tohoku University
Future Information Industry Creation Department
Professor Tadahiro Ohmi

Aiming to create semiconductor manufacturing technology that can be perfectly reproduced with no fluctuations, I have proposed ultra clean technology with 3 principles; ① Completely clean process atmosphere, ② Complete control of non-contaminated surfaces, ③ Complete control of all semiconductor process parameters that influence the results. I have investigated the cause of fluctuations in all semiconductor processes and have developed with many companies; new materials, components, processing technology, surface treatment technology, construction technology, and monitor/control technology that is required for the creation of ultra high performance semiconductor production lines, such as ultra pure gas supply systems, ultra pure water supply systems, ultra pure liquid medicine supply systems, and ultra high performance manufacturing equipment, etc. Within these, I have developed an indispensable electric compact direct diaphragm valve (ECV_®) in collaboration with Fujikin Incorporated, a precision flow control equipment manufacturer. It is a gas supply system that supplies all kinds of compositions and concentrations of gases with precise control to the equipment.

The business of information appliances that support digital networking is about to become highly contested and they essentially require a low/variable production for a very wide range of products, which is where semiconductor integrated circuits come in with a strength of being good for small lot mass production. Manufacturing equipment that have the production capacity of sixty silicon wafers per hour, have the ability to produce forty thousand wafers per month with one machine. Currently, semiconductor manufacturing equipment only have the functionality to perform one type of function. By constructing a semiconductor production line with this kind of equipment, and running all equipment at full power, it would be required to process a minimum of twenty five thousand silicon wafers per month. The initial investment for 200 mm wafers would be 100 billion yen, and for 300 mm wafers it would be 200 billion yen, which is certainly a large scale investment that is required and it would be impossible to adjust to the production of semiconductor circuits for digital appliances. If one machine can perform multiple different processes continuously, even with a small production of one to two thousand silicon wafers per month, it would be possible to make a enough profit with all equipment running at full operation.

To convert the industry from a single lump investment type to a staged investment type for the semiconductor industry, our laboratory is putting in all our effort into developing and implementing microwave excitation with ultra low electron temperature and high density plasma equipment that can process multiple different processes continuously.

In order to realize equipment that processes multiple different processes continuously, it is necessary to have a gas supply system that can sequentially switch quickly between multiple different source gases. In manufacturing equipment that processes silicon wafers one by one with a sheet-fed system, the process is usually initiated and suspended by controlling the opening and closing of the endpoint valves. If we try to perform multiple different processes one after another with the same equipment, it is necessary to set the timing and concentration of multiple different gases for the different processes, which is then supplied to the surface of the silicon wafers.

To perform a process with perfect reproducibility, the multiple gases that are supplied to the surface must be supplied at the set timing and concentration without any malfunctions. A pneumatic valve, also known as an automatic valve, has a very airtight construction, and it's characteristic is that it can be easily controlled if the fluid pressure is less than 1 MPa. However, 90% of the response time is required to replenish and release the gas in the actuator of the pneumatic valve, which causes the opening and closing of the valve to be dozens of milliseconds slower. Moreover, the response time of the valve is different depending on the length of the instrumentation tube supplying the gas and the pressure it is supplied at, which is a problem. As a result, there is a time lag between the valve's operation sequence and the actual movement of the valve, which produces backflow and defects on the surface of a circuit board are caused by the fluctuation in the initial gas composition and pressure.

The ECV_® developed in collaboration with Fujikin opens and closes the space between the valve seat and the valve seat weight, by using the valve weight and vertical motion together with the force of the coil. This removes the operation time of replenishing and releasing the gas of a drive shaft in a pneumatic valve, which makes the time required to open and close the valve a few milliseconds, and this quick response time is its main characteristic. Also, by developing a magnetic body material with an iron/cobalt alloy or iron/nickel alloy, which have a saturation magnetic flux density of 2T (Tesla), the volume of the magnetic body material is considerably lower, which allowed us to make the flow control valve more compact.

The excitation current supplied to the coil is separated into the large initial electric current to drive and open the valve, and a small electric current to maintain the open state of the valve. This electric current generates the magnetic field for the aforementioned coil, and the magnetic body is quickly pulled towards the coil. With this separation, energy consumption for the drive component is kept low. By combining the ECV_® with the simultaneously developed flow controller which controls flow rate by gas pressure, it became possible to control the composition and pressure of the source gas inside the equipment with high precisionv from the beginning of the process, and is achieved by just opening and closing the ECV_® at the endpoint.

The ECV_® removes all worries such as backflow generated by the response time lag of the gas pressure, instrumentation tube length, and individual differences of the operators. Also, it is possible to constantly open and close the valve with a quick electric signal, and you can make a compact gas supply ssytem with high reliability.

Furthermore, ultra large scale integration (ULSI) of the functional components have been composed of monocrystalline materials or amorphous materials. However, in order to further improve functionality and performance, polycrystalline materials such as ferroelectric thin films and high dielectric constant thin films are being introduced to functional components, and we are now moving to silicon technology. Ferroelectric thin films and high dielectric constant thin films usually contain oxygen compounds with 3 or 4 elements, and if you want to show the full capabilities of ferroelectricity and high dieelectric constants in a film as thing as possible, it is necessary to have film formation technology that can completely control the element composition at the monoatomic layer level. With the current pneumatic valves that open and close by air pressure, it is absolutely impossible to completely form a film of the polycrystalline material at the monoatomic layer level.

By using the ECV_®, it has become possible to completely control the element composition of the film forming process at the monoatomic layer level with a feed-forward system.

In our research facility, we have fully adopted the ECV_® in our gas supply panel for manufacturing equipment. By combining welded fittings with no external leaks, highly reliable welding technology, and passive metal treatment technology, we have been able to supply high purity gas to the process chamber, just by opening and closing the endpoint valve at the required time. The ECV_® has already been fully installed in manufacturing plants for semiconductors and flat screen displays, and is contributing to the improvement of reliability, rate of operation, and productivity in the production line.

I am confident that the importance of the ECV_® will become bigger and bigger as we move to a new generation in the semiconductor and large display industries, and I recommend this technology for the 2nd Monodzukuri Grand Award for Parts.

January 20th, 2005

The Electric Compact Direct Diaphragm Valves (ECV_®) are mainly used as a valve to supply particular source gases for semiconductor manufacturing equipment. In general, due to the cleanliness specifications for the valve, the output power of the valve to close is different from that of solenoid valves and is very large.

Actuators in clean specification valves have mainly been air operated due to the superior thrust they generate, and although compact clean specification electric valves have not yet appeared on the market, solenoids made of special alloys are able to generate large thrust and compact electric valves have been developed alongside air operated valves. Its characteristic is that the valve is operated by electric and a quick response time is possible. Compared to general conventional air operated valves, it is possible to quickly open and close the valve with less delay, and the main features are:

• 1. The response time of ECV_® is approximately one tenth of air operated valves (response time of less than 5 msec).
• 2. By using a powerful solenoid made of special materials, the actuator is the same size as air operated valves.
• 3. The valve only needs electricity to be operated.
• 4. The clean specification direct diaphragm construction has a high durability of ten million uses.

Specifications of ECV_®

Construction of ECV_®

Semiconductors are manufactured by semiconductor manufacturing equipment by using all types of gases (corrosive gas, poisonous gas, etc) in the manufacturing process for thin film deposition and etching.

The equipment that supplies the gas is called a gas supply system, but a direct diaphragm valves of clean specification that control the flow of gas is used in the gas supply system.

With current general air operated type valves, the response time of the valve fluctuates depending on the operation pressure and operation pressure supply tube.

These occur with the above response time fluctuations:

• ① Gas switching defect due to deviation in valve operation timing.
• ② Flow rate overshoot.
• ③ Problems such as incorrect estimation of the arrival time of the gas to the process chamber may occur. In particular, Atomic Layer Deposition (ALD) is becoming more mainstream in the recent semiconductor manufacturing process, and the use of valves that open and close at a high speed is increasing. The ECV_® valve sufficiently satisfies these requirements.