Despite the economic slowdown, the semiconductor industry is still the world's fastest-growing manufacturing industry. For BOC Edwards this offers the chance to expand the business much faster than more traditional industrial gases or vacuum markets alone could ever hope to achieve.
Here is a simple chemistry test: Which is the most abundant chemical element in the earth's crust, and the one at the very centre of BOC?
If the world 'oxygen' sprang to your lips, take a bow - you are absolutely right. It also occurs in water, and forms 21% of the atmosphere by volume.
Easy enough so far. Are you ready for another? This one is tougher: Which is the second most abundant element on earth?
Here is a clue: it forms 28% of the earth's crust. Still stuck? This substance is crucial to the The BOC Group's business, and BOC Edwards in particular. That last hint should help you. The answer is silicon.
How those chips are produced, and BOC Edwards' role in their manufacture, is a fascinating and complex story.
Today the industry represents a $200 billion global market and it is estimated that every new integrated circuit factory represents a $100 million opportunity for BOC Edwards. Silicon (symbol Si, atomic number 14) is a browny-black metalloid element found in sand and a wide range of silicate minerals.
It has a compact tetrahedral structure, similar to that of diamonds and is the raw material from which glass is made. Its properties fall between those of metals and insulators. In its pure state, silicon acts as an insulator. However, when 'doped' by adding small amounts of elements such as phosphorus, arsenic, or boron, it becomes a good conductor. This allows silicon to be manipulated to form junctions - the basis for creating transistors and the foundation for the entire field of modern microelectronics. So, where do microchips come from, and how does BOC Edwards fit in?
Wafer fabrication
Microchip production is a highly complicated sequence. The first stage is wafer fabrication: producing the wafer of silicon on which the integrated circuits will eventually be built. This stage consists of four basic steps.
Step one is to manufacture ultrapure silicon. This is typically produced from the reaction of trichlorosilane and hydrogen at 1000°C.
The resultant material has randomly arranged crystals and is known as polysilicon. The polysilicon is then melted at 1200°C before step two, crystal pulling.
In this, a single seed crystal is touched on to the surface of the molten polysilicon and slowly withdrawn. As the polysilicon cools it crystallises and each crystal takes on the same orientation as the seed.
The seed and melt are rotated in opposite directions throughout the crystal growing, producing ingots several feet long and up to 300 mm in diameter.
Step three is wafer slicing. The silicon ingot is ground to the required diameter before a diamond saw slices it into wafers about one fortieth of an inch thick.
One side of each wafer, the working surface, is then polished. The completed wafers are then cleaned in strong acids, rinsed in de-ionised water and dried in filtered nitrogen.
The final step in wafer production is usually epitaxy, which involves the controlled growth on to the wafer of a thin layer of silicon a few microns thick to create a pure layer with the appropriate properties.
After a final cleansing, the completed wafers are packaged and shipped to the chip makers.
Building the chip
As in the factory where wafers are produced, the first requirement for chip manufacture is absolute cleanliness.
Ideally, humans would be banned from fabrication plants (fabs) as they emit about 750,000 particles an hour, mostly dead skin cells.
A ban is impractical, so bunny suits - protective clothing - are worn to minimise contamination. The equipment, gases and chemicals that come into contact with the wafer also have to be of the highest purity.
The whole process involves hundreds of steps and can take many weeks to complete. It begins by cleaning the wafers, an operation that is repeated many times throughout the process. The first stage is to cover the wafer with a microscopic layer of glass-like silicon dioxide. This layer is etched and stencilled so that specific areas of the wafer can be treated. To do this, masks are created on chromium-plated glass and are used to make each layer of the integrated circuit.
Each pattern is transferred from the mask to the wafer using a photographic process. A light-sensitive material called photoresist is spread over the surface, which is then exposed to ultraviolet light through the mask.
The exposed photoresist is then dissolved away and the exposed areas are modified by a doping process known as ion implantation, whereby ions are injected into the upper layers of the wafer to create two distinct types of semiconducting regions, positive (for emitting) and negative (for collecting).
These back to back p-n junctions permit electric current to be switched on or off and can be connected to other semiconducting regions by metal wiring, creating an integrated circuit that can carry a complex set of signals.
Stage one is completed with a thorough cleansing and adding another microscopic layer of silicon dioxide.
The next mask is applied, and the process is repeated until all layers are in place and are selectively connected to each other to produce the desired integrated circuit.
As many as 25 pattern transfers and 500 process steps are involved.
Finally a protective glass layer is added and the chip-bearing wafer is complete. Now the wafer is attached to a frame and a saw cuts the individual chips, a process known as 'dicing'. Good chips are automatically removed from the frame, while sub-standard ones are left behind. Each component is then tested again in extremes of temperatures and electrically stressed beyond normal conditions.
Chips that pass this final test are marked and packaged for distribution, ending up inside many devices from mobile phones and computers to pet identity tags and musical mugs.
Where BOC Edwards fits in
BOC Edwards is a key global player in supporting the manufacture of computer chips, with unsurpassed expertise in electronic process materials, equipment and services.
There are some 80 major fabs worldwide and BOC Edwards has a presence in every one. Process materials include gases, such as hydrogen and helium, that have many applications. They include about 40 special gases used in applications such as chamber cleaning, doping, etching, ion implantation and purging.
The company supplies all these materials to stringent purity specifications, as well as a number of delivery options: bulk or cylinder, on-site generation and gas dispense cabinets.
Special gases such as silane, the material from which silicon is produced, tend to be toxic, corrosive or flammable (silane ignites spontaneously on contact with air) so safety is paramount and abatement of process by-products is a top priority.
Chemical distribution is another essential element in chip production. Recently BOC Edwards has expanded its capability in chemical handling equipment. Expertise includes blend and dispense systems for new processes involving large (300 mm diameter) wafers and ever-smaller chips featuring copper interconnects instead of traditional aluminium wiring.
With contamination an ever-present threat, monitoring and control systems are vital. The FabSense range of monitoring devices represents the first affordable answer to complete system-wide monitoring.
Without vacuum, chip manufacture would be impossible. Pumping is used to achieve a clean, reduced-pressure environment necessary for many process steps.
Ion implantation, for example, demands ultra-high vacuum to avoid the ions colliding with atmospheric molecules and being scattered.
Vacuum technology has always been at the heart of BOC Edwards' business. Dry pumps, now the industry standard, were first developed by the company and the product range, from on-tool 'proximity' pumps to ultra-high vacuum magnetically levitated turbo-molecular devices, is wide.
