No abstract

Tri‐n‐Butyl‐Phosphane Silver(I) Complexes with Carboxylate‐, Tropolonate‐ or N‐Hydroxyphthalimide Building Blocks; Synthesis and their Use as Spin‐on Precursors Treatment of AgNO3 (1) with one equivalent of HX (2a, X = trop; 2b, X = phthal; trop = troponolate; phthal = N‐hydroxy‐phthalimide anion) in presence of NEt3 affords the silver(I) salts [AgX] (3a, X = trop; 3b, X = phthal) in quantitative yield. When instead of 2a and 2b oxalic acid (4a) or quadratic acid (1,2‐dihydroxycyclobutene‐3,4‐dione) (4b) are reacted with 1 under similar reaction conditions, then the corresponding disilver salts [Ag2E] (5a, E = ox; 5b, E = quad; ox = oxalate; quad = quadratic acid dianion) are accessible in excellent yield. The reaction of 3 and 5 with m equivalents of nBu3P (6) produces the phosphane silver(I) complexes (nBu3P)mAgX (m = 1: 7a, X = trop; 7b, X = phthal; m = 2: 8a, X = trop; 8b, X = phthal) and (nBu3P)mAg‐E‐Ag(PnBu3)m (m = 1: 9a, E = ox; 9b, E = quad; m = 2: 10a, E = ox; 10b, E = quad; m = 3: 11a, E = ox; 11b, E = quad), which can be isolated after appropriate work‐up as colourless (9–11), yellow (7a, 8a) or red‐purple (7b, 8b) species. The solid‐state structures of 7b and 9a are reported. Complex 7b exists of two (nBu3P)Ag(phthal) units in which the oxygen atoms of the N‐hydroxyphthalimide anions are μ‐bridging both silver atoms. The thus formed 4‐membered Ag2O2 cycle is planar and the silver atoms show the coordination number 3. Complex 9a exhibits a planar dinuclear structure with the anticipated oxalate building block in a μ‐1,2,3,4 bridging mode. As typical for 7b also for 9a a tricoordinated silver(I) ion is present, whereby the phosphanes act as neutral capping ligands. The thermal behaviour of selected species (7b, 8b, 9a, 10a, 11a and 11b) was studied by applying thermogravimetry. The decomposition of the latter complexes starts between 100–160 °C and is completed in the region of 350–400 °C. One – four decomposition steps are typical. The decomposition of 9a was studied in detail. Elimination of nBu3P occurs at first, while loss of CO2 from in‐situ generated [Ag2ox] gives elemental silver. For that reason, 9a was used as spin‐on precursor in the deposition of silver on TiN‐coated oxidized silicon wafers. REM studies showed that closed and homogeneous silver layers were formed. The resistivity was determined to 3.4 μΩcm.

Copper CVD has been investigated for a few years as a key process for copper metalization technology among others because of its capability for high step coverage and low process temperatures. Beside low resistivity a high film growth rate, along with strong adhesion of the Cu film to the underlayer are essential for practical use in fabrication line. This paper presents the effect of carrier gas and precursor composition on the characteristics of copper MOCVD using the Cu(hfac)TMVS precursor.Thin copper films were deposited by the MOCVD method in a coldwall LPCVD system using Cu(hfac)TMVS as precursor and argon or hydrogen as carrier gas. The experimental setup and procedure are described in detail elsewhere [I]. The films were deposited on different underlayers at 4" silicon wafers at wafer temperatures between 170°C and 250°C and a chamber pressure of 500 mTorr. Film properties were determined by four-point probe, surface profilometer, transmission and scanning electron microscope (TEM, SEM).The theoretical calculated deposition rate (limited only by the conversion efficiency of 50% for this process) of 240 n d m i n for the used conditions surpasses the experimental results (130 n d m i n ) clearly. One reason is the limitation of the experimental deposition rate by some more parameters like the reactor geometry and additional precursor consumption at the heater. A deposition rate improvement is possible by opening additional reaction pathways using additives like water [2] or the use of hydrogen as carrier gas [2, 31.Former investigations [ 11 showed a strong effect of a hydrogen pretreatment on the nucleation characteristics. In addition to these considerations the effect of hydrogen as carrier gas on the deposition characteristics was investigated. Without any other additives to the precursor only the known effect of the hydrogen on the nucleation behaviour was confirmed fig. 1).Under the deposition conditions mentioned above no sign of an additional reaction pathway was found, the deposition rate was the same for both Ar and H2 up to 220°C.Compared to the Cu deposition using inert carrier gas a significant influence on the Cu film properties was found depending on the substrate material. Using W as substrate material, in the nucleation phase different wetting angles were found. In the presence of H2 the wetting angle was > 90" causing not completely coherent nucleation layer. Also a higher film roughness was found caused by the isolated grains at the surface cfig. 2). As a result the film resistivity raises considerably to values > 3 p cm.These influences will be discussed for other substrate materials. MAM'97 -Materials for Avanced Metallization 25