Author: Fred Chen

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Application-Specific Lithography: 20nm Flash, 3D XPoint, 3D NAND Bit Lines

Application-Specific Lithography: 20nm Flash, 3D XPoint, 3D NAND Bit Lines
by Fred Chen on 08-10-2020 at 6:00 am
Categories: Lithography

Application Specific Lithography SemiWiki

Nonvolatile memory capacity reached 64 Gb levels when NAND Flash half-pitch reached 20 nm [1]. Having reached 14 nm [2], NAND Flash half-pitch is no longer being reduced, now that it has entered the 3D era. However, recently, 3D XPoint has found applications within the Optane platform [3]. The lithography for patterning 20 nm half-pitch… Read More

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EUV faces Scylla and Charybdis

EUV faces Scylla and Charybdis
by Fred Chen on 08-03-2020 at 6:00 am
Categories: Lithography

EUV faces Scylla and Charybdis

It is now time for the EUV community to realize they are caught between the proverbial Scylla and Charybdis. In Greek mythology, the two monsters terrorized ships that were unlucky enough to pass between them. By avoiding one, you approached the other.

S for Scylla, or Stochastics

Scylla was a former beautiful nymph turned into

… Read More
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Application-Specific Lithography: a 28 nm Pitch DRAM Active Area

Application-Specific Lithography: a 28 nm Pitch DRAM Active Area
by Fred Chen on 07-19-2020 at 2:00 pm
Categories: Lithography
5 Comments

Application Specific Lithography 28 nm Pitch DRAM Active Area

In the recent DRAM jargon, “1X”, “1Y”, “1Z”, etc. have been used to express all the sub-20 nm process generations. It is almost possible now to match them to real numbers which are roughly the half-pitch of the DRAM active area, such as 1X=18, 1Y ~ 17, etc. At this rate, 14 nm is somewhere around

… Read More
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Application-Specific Lithography: The 5nm 6-Track Cell

Application-Specific Lithography: The 5nm 6-Track Cell
by Fred Chen on 07-05-2020 at 10:00 am
Categories: Lithography
1 Comment

Application Specific Lithography The 5nm 6 Track Cell

An update is now available here: Application-Specific Lithography: Patterning 5nm 5.5-Track Metal by DUV

The 5nm foundry (e.g., TSMC) node may see the introduction of 6-track cells (two double-width rails plus four minimum-width dense lines) with a minimum metal pitch in the neighborhood of 30 nm. IMEC had studied a representative… Read More

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The Stochastic Impact of Defocus in EUV Lithography

The Stochastic Impact of Defocus in EUV Lithography
by Fred Chen on 06-28-2020 at 6:00 am
Categories: Lithography
3 Comments

The Stochastic Impact of Defocus in EUV Lithography

The stochastic nature of imaging has received a great deal of attention in the area of EUV lithography. The density of EUV photons reaching the wafer is low enough [1] that the natural variation in the number of photons arriving at a given location can give rise to a relatively large standard deviation.

In recent studies [2,3], it … Read More

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Can Threshold Switches Replace Transistors in the Memory Cell?

Can Threshold Switches Replace Transistors in the Memory Cell?
by Fred Chen on 06-08-2020 at 6:00 am
Categories: Lithography
1 Comment

Threshold switch I V

The overwhelming majority of transistors produced in the world are used in memory cells, either as the memory itself (Flash, SRAM), or as the access device (DRAM). Yet, it is not necessary to have a transistor in every memory cell. In 2015, 3D XPoint, the first major product based on transistor-less memory cells, was announced [1].

… Read More
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Feature-Selective Etching in SAQP for Sub-20 nm Patterning

Feature-Selective Etching in SAQP for Sub-20 nm Patterning
by Fred Chen on 06-02-2020 at 10:00 am
Categories: FinFET, Lithography

Feature Selective Etching in SAQP for Sub 20 nm Patterning

Self-aligned quadruple patterning (SAQP) is the most widely available technology used for patterning feature pitches less than 38 nm, with a projected capability to reach 19 nm pitch. It is actually an integration of multiple process steps, already being used to pattern the fins of FinFETs [1] and 1X DRAM [2]. These steps, shown… Read More

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Contact Resistance: The Silent Device Scaling Barrier

Contact Resistance: The Silent Device Scaling Barrier
by Fred Chen on 05-24-2020 at 6:00 am
Categories: Lithography

Contact Resistance The Silent Device Scaling Barrier

Moore’s Law has been about device density, specifically transistor density, increasing every certain number of years. Although cost is the most easily grasped advantage, there are two other benefits: higher performance (speed) and reduced power. When these benefits are compromised, they can also pose a scaling limitation.

… Read More
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The Uncertain Phase Shifts of EUV Masks

The Uncertain Phase Shifts of EUV Masks
by Fred Chen on 05-13-2020 at 10:00 am
Categories: Lithography
1 Comment

The Uncertain Phase Shifts of EUV Masks

EUV (Extreme UltraViolet) lithography has received attention within the semiconductor industry since its development inception in 1997 with the formation of the EUV LLC [1], and more recently, since the 7nm node began, with limited use by Samsung and TSMC being touted as key advantages [2, 3]. As with any key critical technology,

… Read More
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MOSFET Gate Length Scaling Limit at Reduced Threshold Voltages

MOSFET Gate Length Scaling Limit at Reduced Threshold Voltages
by Fred Chen on 05-10-2020 at 6:00 am
Categories: Lithography

MOSFET Gate Length Scaling Limit at Reduced Threshold Voltages

As transistor dimensions shrink to follow Moore’s Law, the functionality of the gate used to switch on or off the current is actually being degraded by the short channel effect (SCE) [1-5]. Moreover, the simultaneous reduction of voltage aggravates the degradation, as will be discussed below.

A Practical Lower Limit of… Read More