Characterization of low permittivity (low-k) polymeric dielectric films for low temperature device integration

Abstract

Spin-coated low-k dielectrics are now widely used in integrated circuit processing due to their low permittivity and planarization properties. Another area of potential application is in large area digital imaging using amorphous silicon (a-Si:H) technology where low-k dielectrics enable new integration schemes for thin film transistors (TFT) and sensors. In this work, the properties of spin-coated, polymeric, low-k dielectric materials, BCB (benzocyclobutene) and HSQ (hydrogen silsesquioxane), are studied after treating them with low temperature anneals. Fourier transform infrared spectroscopy (FTIR), high frequency capacitance–voltage, topographic planarization, and wafer deflection stress measurements have been used to characterize the films so as to correlate with processing conditions. Lower k values are obtained for lower process temperatures and are correlated by capacitance and FTIR measurements. Annealing in the presence of O2 appears to increase the permittivity. The BCB films yield low stress and good (>90%) planarization and are suitable as interlevel dielectrics in the vertical integration of a-Si TFT and sensor arrays.

Low Dielectric Constant Materials

“…290 Contrary to these observations, other reports indicate a continuous increase in density and refractive index/ dielectric constant. 291,292 Although reasons for these inconsistencies are not clear, a possible explanation may be differences in the levels of trace oxygen during the initial film cure, leading to more oxide-like structures.…”

Synthesis and characterization of low-k films for large area imaging applications

“…The lowering of k at high T cure may by indicative of an increased porosity in the film. It should also be noted here that in inorganic dielectric films such as hydrogen silsesquioxane (HSQ) the k value was found to increase with T cure [6,9]. …”

“…The principal techniques used to deposit such materials are chemical vapour deposition and spin-coating [3]. In addition to the application in ICs, low-k materials can also be used as inter-level dielectrics in pixelated a-Si:H TFT arrays for imaging and display applications [4][5][6]. For this purpose, we synthesized an organic liquid polymer using methyltriethoxysilane [7] as the base material.…”

Low-Temperature Front-Side BEOL Technology with Circuit Level Multiline Thru-Reflect-Line Kit for III-V MOSFETs on Silicon

“…This can be attributed to Debye-type dielectric relaxation centered at frequencies far above the measurement range, dominating over the total loss at high frequencies. One possible explanation is the low BCB curing temperature which can result in the polymerization rate less than 100% [10]. Additionally, groundplane opening beneath probe pads could cause complex behavior in attenuation.…”