The New Vice Chancellor.

The new Vice Chancellor, Professor Alec Broers, was installed on Tuesday 1st October.

Alec Broers, formerly Master of Churchill College, Head of the Engineering Department and Professor of Electrical Engineering is the first Engineer to be appointed as Vice Chancellor of Cambridge University.

Of particular interest to us is the fact that he is also a Caius Engineer.

Biography

Alec entered Caius as an affiliated student in 1960, after taking his first degree at the University of Melbourne. In Cambridge he read the Electrical Sciences Tripos (EST), graduating in 1962. He continued as a research student, working initially on scanning electron microscopy and then on other aspects of electron beam lithography (the art of drawing extremely small patterns by the use of electron beams). After completing research for his Ph.D. he took a post at the IBM Research Laboratories at Yorktown Heights where he continued to work in the field of electron beam lithography. In 1977 he was given what he describes as `then the best job in the world' when he was made an IBM Fellow - one of 40 such individuals selected from the 30,000 engineers and scientists employed by IBM. As an IBM Fellow he was free, for the next five years, to pursue any research topic he wished, with the full backing of the resources of IBM. Following this, he moved to the IBM East Fishkill Laboratory where he was initially responsible for semiconductor processing technology and later became head of advanced development, responsible for developing the next generation of IBM bipolar semiconductor devices.

In 1984 he returned to Cambridge as Professor of Electrical Engineering, where he established a group to undertake research on microstructures, exploring the ultimate limits of devices whose sizes approach atomic dimensions. In 1990 he became Master of Churchill College and then in 1992 he agreed (somewhat reluctantly) to take on additionally the post of Head of the Engineering Department. Alec has always maintained his ties with Caius and, since his return from America, has regularly appeared at College events, such as the summer garden party and the celebration of Dr. Caius birthday just before the start of each Michaelmas term. His original association with Caius, like many events in life, was by chance rather than long term planning. He has always had a strong interest in music and high fidelity sound reproduction, and was a member of his school choir in his early days in Australia. His decision to come to Cambridge was influenced by the fact that, in those days, Britain was the world centre for high fidelity equipment manufacture and he also had ambitions to sing in a Cambridge College Choir. However, most Colleges tended to discourage a combination of choral activities and engineering, believing that this represented too great a work-load on students. Caius happened to be more tolerant and so, in 1960, Alec entered the College as a Choral Exhibitioner and Affiliated Student.

Research

Alec Broers' research activities in Cambridge and at IBM have formed a vital element in the amazing advances witnessed in microelectronics over the last few decades. During that short period, the world of electronics has undergone a dramatic upheaval that has revolutionised the way we live. This was the theme of a lecture given by Professor Broers on the 21^st March this year as part of the University's contribution to the National Science, Engineering and Technology Week - an annual celebration bringing the achievements and wonders of science to the public. A summary of his lecture ('Squid & Chips') by David Holburn follows:

Jack Kilby's notebook, and the integrated circuit he developed

Only forty years ago, electronics relied on the thermionic valve - a comparatively bulky device which consumed significant power. The beginning of the revolution is hailed by many as the discovery of the germanium bipolar transistor by Bardeen, Shockley and Brattain at Bell Laboratories in the USA. The recognition in 1954 that the use of silicon instead of germanium could produce better transistors, and the development of the much simpler field-effect transistor paved the way for the microelectronics revolution that was to follow. In 1958, Jack Kilby at Texas Instruments invented the monolithic integrated circuit, in which for the first time four transistors were integrated into a single substrate to form a complete amplifier.

This was man's first hesitant step into the era of microcircuit engineering. Although progress was at first slow, other manufacturers gradually followed suit; the development of the logic gate, the semiconductor memory and the microprocessor soon followed, and marked the dawn of the computer age.

Since then, the scale of integration achieved in microcircuits has risen in a meteoric way, and integrated circuits may now contain millions of transistors on a chip of silicon the size of a fingertip, and cost but a few pence. It has been estimated that in the brief history of microelectronics, in excess of 1016 transistors have been manufactured world-wide.

Placing millions of transistors in this way is intricate and exacting. To try and get some idea of the degree of complexity and the manufacturing challenges associated with a modern-day integrated circuit, we can think of it like this: if the circuit were magnified such that the individual transistors were of the size of office buildings, and the interconnections between them were of the size of the streets and avenues, then the entire circuit at this scale would stretch from London to San Francisco.

It is difficult to think of any other endeavour in the history of man that has been brought to such a state of refinement. Broers puts it like this: "If the motor car had undergone the same degree of development as the integrated circuit, the journey by car from Cambridge to London would nowadays take just a couple of seconds, using half a teaspoonful of petrol. There would be no need to find a parking meter at the other end, because the cost of buying a replacement car would be about 10p, a fraction of the parking fee!"

But what is the irresistible attraction of making devices progressively smaller? Apart from the obvious benefits, of offering more devices and hence greater functionality within a single package, there are a number of other important advantages that accrue from scaling integrated circuits to smaller dimensions. For example, if transistor dimensions are reduced by a factor k, the area occupied by each device is evidently reduced by k2. Analysis shows that the time taken for a signal to pass through the transistor falls, also by a factor k, and the power consumed by it is also reduced by k2. So smaller devices are faster, require less power, and cost less. These are the powerful incentives which drive chip manufacturers inexorably towards smaller and smaller devices.

To take a well-known example, the Intel Pentium processor in the PC (widely used in the office and the home) was originally manufactured using transistors with minimum dimensions of 0.8 m. Its clock speed was limited to 66 MHz. By reducing the minimum dimension to 0.6 m, the clock speed can be raised to 100 MHz, allowing the processor to carry out 50% more instructions per second. The latest Pentium Pro has minimum dimensions of 0.35 m, and can run at 200 MHz.

Unfortunately the enhanced performance brought about by scaling devices comes at considerable cost. Precision associated with chip manufacturing is measured in micrometres (and increasingly in fractions of micrometres). Maintaining this level of precision demands chip production environments that are thousands of times cleaner than today's cleanest surgical operating theatres. The manufacture of integrated circuits begins with a paper-thin wafer of single-crystal silicon the size of a dinner plate, and involves hundreds of separate procedures, all of which must be carried out correctly to produce working devices. However, there are certain easily identified steps which are repeated many times. These include deposition of insulating or conducting layers on to the wafer; implantation of dopant (impurity) atoms into the surface; and oxidation, in which silicon is converted to its oxide to form an insulator or dielectric.

Perhaps the most important process, however, is that of lithography, in which the patterns describing the shapes and sizes of the circuit elements are transferred to the surface of the wafer. This pattern transfer step is seen as one of the critical activities limiting the smallest dimension that can be achieved reliably, and it is the refinement of these lithographic techniques that has occupied Professor Broers for a significant part of his research career. Up to now, this has been often been accomplished by photographic reduction of patterns created with the help of a computer-aided design tool. But as the size of the features imaged becomes comparable to the wavelength of light, fidelity suffers, and the proportion of working devices declines. To remedy this problem, Professor Broers has pioneered the use of electron beams both to create and to inspect the microscopical geometries required in current manufacturing processes. The characteristic wavelength of an electron beam depends upon its energy, but may be a thousand fold less than that of visible light. Other methods which are coming to the fore involve the use of X-rays, generated using particle accelerators. These have the advantage of very short wavelength as well as the ability to expose patterns much more quickly than electron beam-based systems, but the equipment required to achieve this is tremendously expensive, its cost being counted in hundreds of millions of dollars.

Nonetheless, X-ray pattern transfer is now seen as being the only viable runner in a race which is leading to laboratory prototype devices with even higher densities of integration, greater speed and lower power consumption. Perhaps the most fascinating of these devices is the Coulomb Blockade, which depends for its operation on the properties of a single electron, and may possibly lead to the ultimate compact computer memory device. The challenge that faces Industry is how to make devices of this kind economically and in sufficient quantity. Some of the major contestants in this race are British companies who, through the excellence of their own efforts and continued collaboration with University researchers, are set to assume a leading role on the world microelectronics stage.

(An extended biography of Alec Broers will be found in the IEE Review, Vol 41 Number 5)