Digital CMOS Abbreviation M Alphabet Dictionary
Manchester Carry Chain
A highly efficient carry propagation mechanism frequently used in high-speed adders. It comprises a sequence of dynamic gates that implement generate-propagate logic. While it excels for small-bit additions due to minimal overhead, its delay increases quadratically with bit count, making it less suitable for large adders.
Mask Misalignment
A potential source of defects in semiconductor fabrication where different photomasks used for patterning layers are not correctly aligned relative to each other. Misalignment can result in transistors failing to form, leading to unintended shorts or opens in the circuit, or causing interconnections to fail. Various fabrication processes, design rules, and self-aligned techniques aim to reduce the risks of mask misalignment and its impact on chip yield.
Master Latch
The initial latch in a master-slave flip-flop configuration. The master latch stores data during the first phase of a clock cycle. Proper data settling in the master latch is crucial to prevent setup-time violations.
Mean Time Between Failures (MTBF)
A measure representing the average time interval between two consecutive failures in a system. It is the reciprocal of the failure rate. MTBF is a critical parameter for assessing the reliability of a system. In digital circuits, achieving a high MTBF is important, especially in synchronization circuits to minimize metastability issues.
Memory
An electronic circuit is used for storing data, which can be accessed either randomly or sequentially. Memories can be categorized as volatile (temporary storage) or nonvolatile (permanent storage) and read-only or read-write. They consist of dense storage cells that are addressed using data and address buses, with address decoders preventing bus contention.
Metal
A material characterized by a very small or negligible bandgap, resulting in abundant charge carriers and empty states. Metals exhibit exceptionally high electrical conductivity due to the overlap of valence and conduction bands.
Metal Mask
A photomask is used in semiconductor fabrication to define the patterns of metal wires on the chip. Multiple metal masks correspond to different metal layers in the technology. The number of available metal layers varies depending on the semiconductor process and technology generation, with more layers facilitating easier placement and routing.
Metallurgical Grade Silicon
Silicon has undergone mechanical and chemical purification processes, making it fairly pure but not suitable for use in semiconductor manufacturing. It finds applications in various industrial processes.
Metastability
A phenomenon that occurs when data is transferred between different clock domains in digital systems. Metastability leads to unpredictable behavior where data sampled by a different clock can result in setup-time violations, causing incorrect data output. It is a common challenge when crossing clock domains and can be mitigated through synchronization techniques.
Metastable Point
The logic threshold of an inverter, lies in the middle of its transition region. Although it is a stable point for the inverter bistable pair, any deviation from this point, no matter how small and in either direction, causes the pair to exit to one of the two stable regions. This characteristic of the threshold is why it is referred to as metastable.
Micrometer-Based Rules
Design rules specified in absolute micrometer (µm) measurements. These rules are typically specific to a particular semiconductor vendor and technology. They are lenient in terms of design constraints, enabling denser chip designs. However, designs adhering to micrometer-based rules may lack portability and scalability to different technologies.
Minority Carrier Injection
When a PN junction is forward-biased, it results in the injection of a significantly large number of minority charge carriers (either electrons or holes) into the regions on either side of the junction. This injection occurs primarily due to diffusion. Although these excess minority carriers quickly recombine, they maintain a steady-state flux, contributing to the substantial forward current in PN junctions.
Mobility
A physical constant representing the ease with which charge carriers (electrons or holes) can move or drift through a crystalline material. Mobility is influenced by crystal imperfections, particularly the concentration of dopants. In most cases, electrons exhibit higher mobility than holes, meaning they move more easily under the influence of an electric field.
Modified Booth Algorithm
An extension of the Booth algorithm used for binary multiplication. In the modified Booth algorithm, pairs of bits in the multiplier (operand) are first encoded before performing the multiplication. These bit pairs are non-overlapping, effectively reducing the number of summands by half and shifting them by two-bit positions relative to each other. While this raises the radix and may complicate the partial product unit, applying Booth encoding to the multiplier simplifies the logic.
Monocrystalline Silicon
Silicon consists of a single crystal domain, where all atoms are aligned throughout its volume. Monocrystalline silicon is typically produced by melting silicon and then allowing it to solidify. It possesses excellent electrical and mechanical properties and is widely used in semiconductor device fabrication.
Monostable Circuit
A circuit with a single stable output state can be maintained indefinitely until it is deliberately switched to the opposite (unstable) state. However, the circuit will naturally return to its stable state after a certain time, ensuring the stability of the primary output state.
MOS Capacitor (Metal-Oxide-Semiconductor Capacitor)
A type of capacitor formed by sandwiching a metal plate, typically heavily doped polysilicon, between a silicon dioxide (oxide) insulator and a semiconductor plate, often doped silicon. The MOS capacitor is notable for its vertical structure and is of particular interest in understanding the vertical arrangement within a MOSFET.
MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)
A symmetric transistor consisting of a vertical MOS capacitor structure combined with heavily doped source and drain regions. It operates by allowing the gate voltage to create or remove a conductive channel between the source and drain regions. MOSFETs pose challenges in design due to their capacitive loads but are easily scalable and offer high fan-out, making them dominant in Very Large Scale Integration (VLSI) circuits.
Multi-Port Memory
A memory with multiple independent ports, typically two or more. Each port is characterized by its own address bus, data-in bus, data-out bus, write-enable signal, and clock. Multi-port memories share a single memory core but have multiple separate address decoders. Special care is required to manage conflicts when two ports access the same address asynchronously or when one attempts to read while another writes.
Multilayer PCB (Printed Circuit Board)
A PCB is composed of multiple routing layers separated by insulating layers. Multilayer PCBs provide additional routing dimensions, simplifying the achievement of timing closure. Components are still mounted on the top and bottom layers of the board.
Multiplicand
In binary long multiplication, the multiplicand is the binary word that is multiplied by the multiplier. Each bit in the multiplier multiplies the entire multiplicand, resulting in summands that are as large as the multiplicand.
Multiplier (Operand)
In binary long multiplication, the multiplier, also referred to as the operand, is the binary word responsible for multiplying the multiplicand. Each bit in the multiplier affects the entire multiplicand, leading to as many summands as there are bits in the multiplier.
