AlN Single Crystal - Wet Etching

AlN Single Crystal - Wet Etching

Material Name: AlN
Recipe No.: 10349
Primary Chemical Element in Material: Al
Sample Type: Single crystal
Uses: Etching
Etchant Name: None
Etching Method: Wet etching
Etchant (Electrolyte) Composition: The AlN single crystal samples used in the experiment were grown by a physical vapor transport (PVT) method in our laboratory. High purity AlN powder was first sintered at about 2000 C for 30-40 h to remove the high concentration of oxygen in the raw material. Then the sintered AlN material was placed in a tungsten crucible for the PVT single crystal growth using a tungsten mesh heater furnace manufactured by Suzhou Advanced Rare Metal Co, Ltd. The details of the PVT growth can be found in Ref. An AlN crystal boule with a diameter of about 40 mm was obtained after a growth at 2200 C for 40 h. A lot of AlN single crystal grains with nat- ural smooth hexagonal surfaces are formed in the boule. The surface can be identified as the (0001) Al face of the AlN single crystal by referring to the reported results in Ref. It is used directly as a sample for the wet etching since the (0001) Al surface can give clear and reliable results of the etching pit dislocation density. Sample wafers with a size of 5 x 10 x 0.6 mm3 were sliced from the boule and polished on both sides for the XRD and infrared absorption measurement. Prior to etching, the sample wafer was ultrasonic cleaned in acetone for 5 min, washed with alcohol and deionized wa- ter, and dried. Then the wafer was dipped into molten NaOH. KOH contained in a silver crucible for 3 min. The temperature of the molten NaOH.KOH was 300-400 C. After a continual etching of about 20 min, clear, regular hexagonal etch pits were observed on the (0001) Al face. The etch pits of the sample were examined and counted by using an Olympus X40 optical microscope. XRD and the infrared absorption were measured by using a Bede D/max-RB X-ray diffractometer (Japan, Rigaku, D/max-RB) and FTIR-120.
Procedure (Condition): No data
Note: The defects and the lattice perfection of an AlN (0001) single crystal grown by the physical vapor trans- port (PVT) method were investigated by wet etching, X-ray diffraction (XRD), and infrared absorption, respectively. A regular hexagonal etch pit density (EPD) of about 4000 cm(-2) is observed on the (0001) Al surface of an AlN single crystal. The EPD exhibits a line array along the slip direction of the wurtzite structure, indicating a quite large thermal stress born by the crystal in the growth process.
Reference: Li Weiwei, et al., Wet etching and infrared absorption of AlN bulk single crystals, Journal of Semiconductors, Vol. 30, No. 7, 2009, pp. 073002-1 - 073002-4.