Pattern Reinforcement

In order to increase processing speed and reduce the power consumption of electronic devices, the microelectronics industry continues to push for feature size reduction. However, at the resist thickness required to produce ultra-small feature sizes, when the pattern is etched into the silicon, the pattern usually begins to deteriorate, making it impossible to produce the required high aspect ratio (height-to-width ratio).

The anti-reflective coating reduces the reflectivity at the resist interface, thereby providing better linewidth control while minimizing the loss of resist performance. The reflectivity is reduced by attenuating the light passing through the anti-reflective coating or by matching the refractive index of the anti-reflective coating to the resist system at the exposure wavelength used.

Pattern Reinforcement Fig.1 The photolithography stack is fabricated on 300 mm diameter silicon wafers and is composed of three layers: spin-on-carbon, silicon-containing anti-reflective coating and 193 nm photolithography resist. (Girardot C, et al. 2014)

As a leader in semiconductor equipment manufacturing, Alfa Chemistry can provide customers with solutions for patterning enhanced materials that can improve process margins, defect control, and higher resolution patterning steps associated with semiconductor fabrication of advanced integrated circuits.

Our Solution

Anti-reflective coating is an important part of lithography. Alfa Chemistry offers two main types of anti-reflective coatings: top anti-reflective coating (TARC) and bottom anti-reflective coating (BARC).

	Benefits	Drawbacks
TARC only uses destructive interference to control the refractive index and thickness of resist and TARC to control reflectivity, which does not change the reflectivity of the substrate.	Simplified process	Need separate waste discharge
		Environmental hazards (may include perfluorooctane sulfonate and perfluorooctanoic acid or other perfluorocarbons)
		Difficult to control thickness
		Mixing can affect resist
BARC uses refractive index, thickness, and light absorption to control reflectivity. They effectively make the substrate non-reflective.	Larger processing window	Requires etch open step for dry BARCs
	Reflective notch and shape control
	Better reflection control and process stability
	Wet developable BARC has no etching openings
	Compatible with common resist waste discharge

TARC and BARC can be used in the same process, and BARC can provide better CD control and a wider process window. Please contact us to learn more about our products.

Pattern Reinforcement Fig.2 (a) Line and space pattern without a BARC, (b) line and space pattern with a BARC. (Lenhart J. L, et al. 2007)

References

Girardot C, et al. (2014). "Pulsed Transfer Etching of PS-PDMS Block Copolymers Self-Assembled in 193 nm Lithography Stacks." ACS Applied Materials & Interfaces. 6(18), 16276-16282.
Lenhart J. L, et al. (2007). "Understanding deviations in lithographic patterns near interfaces: Characterization of bottom anti-reflective coatings (BARC) and the BARC–resist interface." Applied Surface Science. 253(9), 4166-4175.

Pattern Reinforcement

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