Ultramicroscopy 11 (1983)303-306 303 North-Holland Publishing Company SHORT NOTE A NOVEL SAMPLE PREPARATION TECHNIQUE FOR CROSS-SECTIONAL TEM INVESTIGATION OF INTEGRATED CIRCUITS J. VANHELLEMONT, H. BENDER, C. CLAEYS *, J. VAN LANDUYT, G. DECLERCK *, S. AMELINCKX and R. VAN OVERSTRAETEN * Unioersiteit Antwerpen, R UCA, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium Received 5 May 1983 1. Introduction With the ever increasing packing density of integrated circuits, the phenomena occurring at the edge of the different film structures gain more importance. In CMOS (Complementary Metal-Oxide-Semiconductor) processing, e.g., a "bird's beak" is formed at the edge of the nitride mask during isolation oxidation. Gate oxide thin- ning poses a serious problem with the trend to- wards thinner gate oxides. To describe these phenomena accurately one has to observe the structures in cross-section at high magnification. This aim cannot be reached by optical microscopy due to its low magnification and resolution or by scanning electron microscopy because of the low contrast between the con- stituent layers, Transmission electron microscopy is the ideal technique which allows high magnifica- tion with good (absorption) contrast. Here the problem is reduced to the preparation of suitable specimens. Several publications [1-4] are devoted to this problem. This note describes a preparation technique which allows one to obtain specimens both for classical and high resolution electron microscopy (HREM) more quickly and easily, so that cross-section investigation on a routine basis becomes possible. 2. Technical details of the preparation method A convenient way to study the configuration at the edge of film structures is to have a periodic structure consisting of parallel bands as used in memory circuits. In our study on local oxidation [5], a nitride pattern consisting of SiaN 4 bands parallel to the (110) direction is used as an oxida- tion mask. The width of the bands is 12 #m, the spacing between them is 10/tm and the structure has a total width of 2 ram. After local oxidation the wafer is covered with a LPCVD (Low Pressure Chemical Vapor Deposited) polysilicon layer of about 450 nm thickness to protect the surface during specimen preparation. * Katholieke Universiteit Leuven, ESAT, Kardinaal Mercier- laan 94, B-3030 Hevedee, Belgium. Fig. !. Optical micrograph of a wafer cut in strips with a thin-bladed diamond saw. The nitride pattern is clearly visible and is contained in the 2 mm strips. 0304-3991/83/0000-0000/$03.00 © 1983 North-Holland