In this age of technology, Moore’s law has become a standard in characterizing the growth of society. Defined by the co-founder of Intel Gordon Moore in 1965, Moore’s law is an observation that over the span of computing hardware, the number of transistors doubles approximately every two years. The more accurate estimation often quoted as ‘18 months’ is due to Intel executive David House, who incorporated transistors becoming faster in his calculations a few years after Moore. Numerous other capabilities of electronic devices are strongly linked to the transistor trend: memory capacity, processing speed, pixel per size, etc (Brock). The following qualities are also improving at an approximately exponential rate and have given birth to other laws such as Koomey’s Law. It is significant as the cost of computing power and cost of data have decreased significantly over time.
Although initially derived as an observation, Moore’s remarkably accurate prediction is now used in the semiconductor industry to guide research and development targets and other long term planning; leading it to be labeled as the driving force of technological and social change of the 20th and 21st century. It propels semiconductor manufacturers to focus enormous resources in aiming for the specified increase in processing power under the assumption other competitors will actually attain it (Brock). This friendly competition has become harder and harder due to ‘Moore’s second law’; as the cost of computer power falls for consumers, the cost for producers to fulfil Moore’s law increases (research and development, manufacturing, test cost) for each generation of chips. Rising manufacturing costs is an important consideration to the sustainability of Moore’s law in the upcoming future. The idea that Moore’s law will continue indefinitely contradicts modern physics, which postulates there is an absolute limit in the scope that engineering and science in general can achieve. Companies will continue to push Moore’s law until it becomes a negative return and not a practical business practice. As this slowly happens, the linear growth of transistors per unit area will become an exponential approaching its carrier capacity. Moore himself admits this is inevitable in an interview in 2005: “It can't continue forever. The nature of exponentials is that you push them out and eventually disaster happens”. Sources in the semiconductor industry estimates Moore’s law will continue until 2015 to 2020, after which transistor density doubles only every three years. However, in 2010, an update to the International Technology Roadmap for Semiconductors has the growth declining starting in 2013. This observation can already be confirmed in 2018 with the plateauing of transistors per die in microprocessors released by Intel.
Understanding the reasons behind the decline and possible solutions is more complicated than most people assume. There are a variety of variables that need to be considered to fully understand the problem. However, in 2005, Moore defines the overall thematic behind the downturn: “In terms of size [of transistors] you can see that we're approaching the size of atoms which is a fundamental barrier, but it'll be two or three generations before we get that far—but that's as far out as we've ever been able to see”. The ability to physically produce circuits at a nanoscopic level is a major barrier in which companies have to overcome due to the limits of machinery and tools. In the beginning, lasers were widely used to etch circuits on silicon wafers. However, lasers are limited to a wavelength of 180 to 400 nanometer, the fundamental restriction in which light can be transmitted. In response, deep ultraviolet (DUV) lithography has become the new standard in microprocessor production. This method uses photo resistant solution to restrict the full wavelength of light being printed on the wafer. This method has already started becoming obsolete with the ever growing need of transistors to become smaller. ASML, a lightsource company, has been in the forefront in the research and development. ASML is able to produce wavelengths at a much lower wavelength through their creation of extreme ultraviolet light (EUV) lithography. EUV light is produced by targeting tin droplets with a high powered laser. The result is a plasma light source with a wavelength of 13.5 nanometers. Although currently still under development, EUV lithography is expected to be a major factor in the continuation of Moore’s law in 2020. It requires major funding to reach production level that ASML is currently working on getting. Furthermore, due to their monopoly and trade secrets, ASML’s employee workforce is another limiting factor as no other companies are able to efficiently compete.
Another variable to consider is the restraints of how microprocessors are currently designed. One of the biggest physical limitation present is the ability of CMOS transistors to store information(on or off, 1 or 0). Parameters such as channel length, gate insulator thickness, distance of interconnects, and other circuit parameters are not limited by how small they can be produced by humans. Rather, it is the basic fundamentals of current on an atomic level, specifically electrons, and the required distance needed for electrons to stay insulated in order to properly store data. The force of repulsion stated in Coulomb’s law and other laws of physics cannot be changed but rather accommodated for to a certain extent. As a result, the method in which data is stored transistors must either be modified or completely redesigned. A possible solution currently being researched is high electron mobility transistors (HEMT). Based on gallium nitride, HEMT allows electrons to move freely within one billionth of a meter (Phys). This allows the CMOS transistors to be replaced with a smaller transistors, allowing for an increase in transistors per density. However, due to the different chemical properties, HEMT have unknown frequency, voltage, and behavioral responses. Few companies are currently willing or have the resources to research the implications of HEMT.
Lastly, thermodynamics constraints have become a focal point as the power supply needed has increased with the number of transistors per area. A change in the state of a transistor releases heat to the surroundings. The amount of power one can supply to the chip is dependent on two factors: how much in a rise of temperature the chip can handle (typically around 400 Kelvin) and how quickly can the heat be dissipated from the chip. These two factors are closely linked to the material in which the chip is made of. Although silicon has been enormously crucial in its availability and material properties, silicon is close to its carrying capacity in the number of transistors it can effectively hold. This creates the problem of an alternative material in which wafers can be created from with no natural element suitable to replace it. The research and development of creating a material is a endeavour no engineering firm is currently willing to take. Power consumption is also limited by chip architecture, interconnects, and electrical parasites (Kumar). Combined with the previous point, current chip clock speeds have saturated to 3 GHz. The development of optical interconnects would theoretically still be limited by thermodynamics described above.
Parallel computation has recently become crucial in optimizing the gains described in Moore’s law. In order to manage power dissipation more effectively, multi-core chip design have become more popular with software being written in multi-thread processing. Most multithreaded development have overhead and will not see a linear increase in processing speeds by increasing the number of processors (Brock). Another possible solution being discussed is quantum computing, which revolves around the idea of superposition and entanglement. Instead of two definite states (1 or 0) used in transistors, quantum computation uses quantum bits, known as qubits. Each qubit can be in superpositions of states, allowing for more data to be stored rather than two. Furthermore, qubits theoretically require less physical space than transistors, allowing for more to be stored in a given density. However, quantum physics and computations are still in its infancy stage and will require many decades for it to even become possible.
Unless drastic measures are taken, the lack of companies willing to fund research and development in alternative chip production will result in the further stagnation in Moore’s law already seen. When Moore’s law becomes no longer a sustainable business adventure, the economic implications for technology companies will be huge. The inability for semiconductor manufacturers to rely on steady growth will lead to many engineering professions to lose relevance within the very near future.
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