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17 February 2016

RASIRC's water-free anhydrous hydrogen peroxide demonstrates five-fold increase in hydroxyl density

In the white paper 'Anhydrous Hydrogen Peroxide Gas Delivery for Atomic Layer Deposition', RASIRC Inc of San Diego, CA, USA (whose products purify and deliver ultra-pure liquids and gases) has released research results showing that anhydrous hydrogen peroxide gas enables a five-fold increase in surface hydroxyl density compared to water in studies involving ALD nucleation on silicon germanium (SiGe) substrates.

Hydroxyl density is an important factor in minimizing interfacial defects, increasing uniformity and improving next-generation semiconductor device performance, says RASIRC. BRUTE Peroxide provides a stable, reliable flow of anhydrous hydrogen peroxide for atomic layer deposition (ALD) and atomic layer etch (ALE), adds the firm, whose products generate specialty gases from liquid sources.

Next-generation devices are moving from silicon to silicon germanium channels, says RASIRC. It is critical to form stable uniform oxides without Si or Ge dangling bonds on the interface grown by ALD at low temperatures. "Research proves conclusively that the presence of water in some ALD and ALE processes negatively affects interfacial layer uniformity, leading to higher defect density, slower initiation, and degraded performance," says president & founder Jeffrey Spiegelman. "Tests of BRUTE hydrogen peroxide confirm that removing the water during processing with dry H2O2 enabled a three-fold improvement in hydroxyl density compared to 30% H2O2 and water source," he adds.

New market requirements

Semiconductor devices driven by Moore's law are continuously becoming faster, smaller and more power efficient. Integration of new materials makes this possible, but requires new process steps for high-k dielectrics in gate stacks and finFET devices, says RASIRC. High aspect ratios limit the use of traditional oxidants. Plasma processing requires a line of sight, which is often not available. Ozone can burn and damage delicate surfaces. Water is sluggish. Anhydrous hydrogen peroxide provides an alternative for functionalizing the surface with a dense layer of hydroxyl groups prior to deposition, says the firm.

"As thermal budgets are reduced, water fails to chemically react at the interface and physically adsorbs on the surface, blocking active binding sites," says Spiegelman. "Without the interference of water, anhydrous hydrogen peroxide can chemically react at the interface layer, reducing the number of cycles needed to begin ALD growth at the surface," he adds. "Until now a safe method for storage, transport and delivery of anhydrous hydrogen peroxide has not been available. BRUTE Peroxide changes all that."

Research summary

Studies show that hydrogen peroxide is well suited for surface functionalization, because it is highly susceptible to splitting into two hydroxyl radicals on contact with surfaces. In contrast, water splits into one hydroxyl group and one hydrogen site on Ge surfaces, and may desorb, leading to vacant dangling bonds. Ozone is also problematic, where bridging metal-oxides and surface damage are typical.

Tests with SiGe(110) surfaces contrast the relative effectiveness of water, H2O/H2O2 solution and anhydrous hydrogen peroxide. The results show that hydroxyl density increases as the proportion of water decreases. Hydroxyl density with anhydrous hydrogen peroxide is five-fold that for water and three times more dense than for 30% H2O2/ H2O solution, concludes RASIRC.

Tags: RASIRC SiGe

Visit: www.rasirc.com/lp/resources/paper-RASIRC-BRUTE-Peroxide.pdf

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