ELSEVIER Diamond and Related Materials 6(1997)440-443 DIAMOND AND RELATED J TERIAL$ Diamond nucleation enhancement by hydrofluoric acid etching of silicon substrate S. Schelz a,,, C.F.M. Borges ", L. Martinu b, M. Moisan ~ Groupe de phj'sique des plasmas, UniversitOde MontrOal, C.P. 6128, Succursale Centre-ville, MontrOal, H3C 3J7, Qukbec, Canada b DEpartement de G~)nie physique, Ecole Polytechnique de Montreal, C.P. 6079, Succursale Centre-ville, MontrEal, H3C 3A 7, Quebec, Canada Abstract We have investigated the effect of silicon substrate pretreatment by hydrofluoric acid (HF) on diamond nucleation. Si (I00) substrates were pretreated by ultrasonic scratching with a diamond powder suspension in methanol followed by HF (50%) etching and subsequent water rinsing. The nucleation density (No) was found to be up to 30% higher compared to the unetched substrates, provided the rinsing time was short. Such a nucleation enhancement leads to an increased initial deposition rate and to a lower surface roughness of the deposited diamond films. We found that the Si surface termination by H and F atoms after HF etching is a thermodynamically favorable configuration to initiate the nucleation process. © 1997 Elsevier Science S.A. Keywords: Diamond nucleation; Hydrofluoric acid etching; Silicon substrate 1. introduction It is very desirable to enhance tliamond nucleation in order to increase the initial depositio:l rate and decrease the surface roughness o1" the deposit,':d diamond fihns. A reduced surface roughness in combination with good diamond film quality is a common reouirement for many applications. It is a well-known fact tizat the nucleation and growth process of CVD diamond are strongly affected by the substrate surface morphology and chemi- cal reactions, and that pretreatment of the substrate is required to enhance the diamond nuclealion. It is the aim of the present paper to demonstrate a nucleation enhancement by a combination of pretreat- ment by abrasive diamond powder in an ultrasonic bath and by the subsequent etching of the silicon substrate by hydrofluoric acid (HF). The Si surface termination by H and F atoms after HF etching is found to play an important role in the increase of diamond nucleation. 2. Experimental Diamond film deposition was performed in a micro- wave plasma-assisted chemical vapor deposition on Si * Corresponding author. 0925-9635/97/$17.00 © 1997 Elsevier ScienceS.A. All rights reserved. PH S0925-9635(96)00653.X (100) substrates in a non-conventional surface wave sustained discharge yielding a plasma of hemispherical shape in front of the substrate [1]. The system was operated at 2.45GHz with a microwave power of 1500 W. The substrate temperature, measured with an optical pyrometer, was set at 85OC; the total flow rate of hydrogen and 0.5% methane (H2/CH4-plasma) was kept constant at 100sccm, and the pressure set at 10 Torr. Silicon substrates were pretreated with a diamond powder suspension in methanol in an ultrasonic bath followed by HF (50vo!.%) etching. After the etching procedure, the silicon substrates were rinsed in deionized water (100 ml) for various periods of time, and then immediately introduced into the microwave plasma reac- tor. In a second series of experiments, the prescratched substrates were etched in H F at different concentrations (10-50vo1.%) without subsequent water rinsing. The substrate topography anti surface chemical reactions were examined by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) after pretreat- ment and also after a short (5 rain) HE/CH4-plasma exposure. Samples submitted for 30 rain to the diamond deposition conditions were investigated by scanning electron microscopy (SEM) to determine the nucleation density. These experiments were performed three times