Wet Etch Enhancement of HfO&lt;sub&gt;2&lt;/sub&gt; Films by Implant Processing

To facilitate selective removal of the gate dielectric toward the gate electrode, wet etch characteristics of HfSiO x and HfSiO x ͑N͒ in acidified HF solutions were determined as a function of several process parameters. Etch behavior of Hf-silicates was found to be little influenced by the various chemical vapor deposition processes. The top part ͑0-2 nm͒ of thick Hf-silicate layers etched similar to as-deposited thin layers ͑Ͻ2 nm͒, while the bulk part etched significantly more slowly. However, etch rates were strongly dependent on composition ͑lower for Hf-rich silicates͒. Also, the removal rate of HfSiO x ͑N͒ was mainly dependant on the amount of incorporated nitrogen and crystallization temperature. Thermally nitrided layers were easier to remove compared to plasma-nitrided layers. Postnitridation anneals at high temperature in nitrogen environment decreased the etch rate. After removal, Hf concentrations below 1 ϫ 10 11 atoms/cm 2 for most of the HfSiO x ͑N͒ layers under study were observed after a short ͑typically a few seconds͒ etch process in a single-wafer spin-cleaning tool.

Section: Resultsmentioning

confidence: 91%

mentioning

confidence: 99%

Wet Etch Characteristics of Hafnium Silicate Layers

Claes

Paraschiv

Dictus

et al. 2006

“…-Recently, wetetching of several high-k materials was done by using fluoride-based chemistry [15][16][17][18] and Schwalke et al adopted this procedure for Pr 2 O 3 etching. 19 We carried out several HF-based experiments on Pr 2 O 3 and Pr 2−x Ti x O 3 layers varying the concentration as well as the temperature of the etchant.…”

Section: Hf-based Etching Of Pr 2 O 3 and Prmentioning

confidence: 99%

“…Recently, combinations of reactive ion etching ͑RIE͒ and wet-etching processes have been extensively used to etch Zr-and Hf-based oxides. 13,[15][16][17][18] In the case of Pr 2 O 3 , we made attempts to use RIE etching but found that this process is unable to provide the needed selectivity to etch MOS structures.…”

mentioning

confidence: 99%

A CMOS Process-Compatible Wet-Etching Recipe for the High-k Gate Dielectrics Pr[sub 2]O[sub 3] and Pr[sub 2−x]Ti[sub x]O[sub 3]

Mane

Wenger

Schroeder

et al. 2005

The fabrication of complementary metal oxide semiconductor ͑CMOS͒ structures with praseodymium oxide ͑Pr 2 O 3 ͒ or titaniumdoped praseodymium oxide ͑Pr 2−x Ti x O 3 ͒ ͑0 ഛ x ഛ 1͒ layers as integrated high-k gate dielectrics requires the development of a process-compatible etching recipe. Different wet-etching processes in acid-based chemistry were evaluated and solutions of diluted sulfuric acid were identified as suitable etchants for Pr 2 O 3 and Pr 2−x Ti x O 3 layers on Si substrates. Metal-oxidesemiconductor stacks with poly-Si as the potential gate electrode were patterned with the help of tetramethyl ammonium hydroxide as the selective etchant attacking the poly-Si gate electrode material but not the underlying Pr-based high-k gate dielectric layers.In recent years, due to aggressive scaling down of complementary metal oxide semiconductor ͑CMOS͒ devices, the SiO 2 layer thickness in CMOS structures has reached physical limits which call for identifying alternative high-k dielectrics to replace SiO 2 as the gate oxide material. 1,2 According to the International Technology Roadmap for Semiconductors (ITRS 2003), alternative high-k gate oxide of thickness less than 1.5 nm equivalent oxide thickness ͑EOT͒ will be required for sub-100 nm metal oxide semiconductor field effect transistor ͑MOSFET͒ technology. 3 A variety of high-k materials have been extensively studied and some of them were suggested as possible alternatives to replace the SiO 2 gate dielectric. 1-8 High-k materials can also be used in metal-insulatormetal ͑MIM͒ structures for radio frequency ͑rf͒ devices. 6 Recently, rare earth sesquioxides like

“…In current CMOS process, dilute hydrofluoric acid ͑DHF͒ is widely used to remove the remaining gate dielectric after gate etching to open source and drain regions for the silicidation process 15 because it can selectively remove SiO 2 and SiO x N y without attacking the Si substrate and the polycrystalline Si gate. However, many researchers have found that the etch rates of HfO 2 and Hf x Si 1−x O 2 decrease sharply in HF solutions, especially when they have undergone intensive thermal treatment, [16][17][18][19][20][21][22] although Hf is dissoluble in aqueous HF. 23 This is very similar to the etching of Ta 2 O 5 in aqueous HF.…”

mentioning

confidence: 99%

Investigation of Wet Etching Properties and Annealing Effects of Hf-Based High-k Materials

Chen

Yoo

Chan

2006

Wet etching properties of Hf based high-k dielectrics of HfO 2 , ͑HfO 2 ͒ x ͑Al 2 O 3 ͒ 1−x , Hf oxynitride and Hf silicate were investigated, using various chemicals employed for the current CMOS device fabrication. Experimental results show that fluorides species such as F − , HF 2 − HF and H 2 F 2 are very effective for dissolving Hf and HfO 2 in acids. HfF 4 is highly soluble in HF with a solubility of ϳ1.48 mol/L, which is much higher than the calculated result, and its solubility increases with reduced pH value. Etching properties of those high-k dielectrics in HF and annealing effects on their microstructure were explored. It is observed that the etch rates of Hf and HfO 2 increase with increasing HF concentration and after HF etch, Hf and HfO 2 surfaces become F terminated. Although the mechanisms responsible for the change in HF etch rates after the Hf based high-k films have undergone annealing are dependent on their chemical property, it is universally observed that the formation of the crystalline phase of HfO 2 is the primary attributor to the reduced etch rates. The HF etching of Hf based high-k films occurs via weak points in the films, e.g., Hf-N, Al-O and Si-O bonds, as well as amorphous areas of HfO 2 .