Spin-on Polymer Research Articles

Estimation of the dielectric properties of low-k materials using optical spectroscopy

The dielectric function spectra of low dielectric constant (low-k) materials have been determined using spectroscopic ellipsometry, near-normal incidence spectroscopic reflectometry, and Fourier transform infrared transmission spectrometry over a wide spectral range from 0.03 to 5.4 eV (230 nm to 40.5 μm wavelength region). The electronic and ionic contributions to the overall static dielectric constant were determined for representative materials used in the semiconductor industry for interlayer dielectrics: (1) FLARE—organic spin-on polymer, (2) HOSP—spin-on hybrid organic-siloxane polymer from the Honeywell Electronic Materials Company, and (3) SiLK—organic dielectric resin from the Dow Chemical Company. The main contributions to the static dielectric constant of the low-k materials studied were found to be the electronic and ionic absorptions.

Characterization of organic low-dielectric-constant materials using optical spectroscopy

The dielectric function spectra of low dielectric constant (low-k) materials have been determined using high-precision four-zone null spectroscopic ellipsometry, near-normal incidence reflection spectrometry and Fourier transform infrared transmission spectroscopy. The optical functions over a wide spectral range from 0.03 to 5.4 eV (230 nm to 40.5 microm wavelength region) have been evaluated for representative low-k materials used in the semiconductor industry for interlayer dielectrics: (1) FLARE -- organic spin-on polymer, and (2) HOSP -- spin-on hybrid organic-siloxane polymer from the Honeywell Electronic Materials Company.

Silicon layer transfer using wafer bonding and debonding

Two experiments were performed that demonstrate an extension of the ion-cut layer transfer technique where a polymer is used for planarization and bonding. In the first experiment hydrogen-implanted silicon wafers were deposited with two to four microns low-temperature plasma-enhanced tetraethoxysilane (TEOS). The wafers were then bonded to a second wafer, which had been coated with a spin-on polymer. The bonded pairs were heated to the ion-cut temperature resulting in the transfer of a 400 nm layer silicon. The polymer enabled the bonding of an unprocessed silicon wafer to the as-deposited TEOS with a microsurface roughness larger than 10 nm, while the TEOS provided sufficient stiffness for ion cut. In the second experiment, an intermediate transfer wafer was patterned and vias were etched through the wafer using a 25% tetramethylammonium hydroxide (TMAH) solution and nitride as masking material. The nitride was then stripped using dilute hydrofluoric acid (HF). The transfer wafer was then bonded to an oxidized (100 nm) hydrogen-implanted silicon wafer. After ion-cut annealing a silicon-on-insulator (SOI) wafer was produced on the transfer wafer. The thin silicon layer of the SOI structure was then bonded to a third wafer using a spin-on polymer as the bonding material. The sacrificial oxide layer was then etched away in HF, freeing the thin silicon from the transfer wafer. The result produced a thin silicon-on-polymer structure bonded to the third wafer. These results demonstrate the feasibility of transferring a silicon layer from a wafer to a second intermediate “transfer” or “universal” reusable substrate. The second transfer step allows the thin silicon layer to be subsequently bonded to a potential third device wafer followed by debonding of the transfer wafer creating stacked three-dimensional structures.

Processing, Properties, and CMP Characteristics of a Spin-on Polymer: HSQ

AbstractThe structures and properties of the HSQ film during the cage/network transformation were studied by curing at 300°C for 1 hour. The experimental results show that the ratio of the network/cage structure of the cured HSQ film increases from 0.21 to 0.39 by curing. The porosity of the cured film increases from 10.0% to 12.3 %, while the refractive index decreases from 1.413 to 1.376 during curing. These results suggest that the dependence of the structure and properties of the HSQ film by curing. The CMP characteristics of HSQ were studied by using different kinds of slurries and surfactant. The CMP results of polishing HSQ suggest that the hardness and charge status of the abrasive, the interaction of the surfactant with the abrasive and film surface significantly affect the polishing results.

SiLK dielectric planarization by chemical mechanical polishing

As the feature size of integrated circuits is driven to smaller dimensions the importance of the inter- and intralayer isolator capacitance in future metallization schemes becomes more pronounced. Organic polymers with low dielectric constants are one class of material choice for the replacement of SiO 2. However, their successful integration into functional circuits requires new fabrication procedures. The embedded dielectric scheme offers an evolutionary path for their successful integration into a subtractive etched, aluminum-based integrated circuit. This scheme can effectively lower the total capacitance while minimally changing the rest of the metallization fabrication process. However, the non-conformal deposition of spin-on polymers requires an effective planarization process. Therefore, this paper focuses on the planarization capability of a chemical mechanical polishing process (CMP) using SiLK resin as the interlayer dielectric material. The experimental results demonstrate the high planarization capability of the CMP process using a commercially available slurry. The post-CMP degree of planarization is greater than 95% for all feature dimensions and this planarity can be achieved rapidly. SiLK dielectric coatings are therefore considered as a promising candidate to replace SiO 2 in existing Al/W-based technologies.

A Pretreatment Technique to Improvement the Ashing Resistance of Low K Spin-On-Polymer (SOP)

AbstractThe oxygen plasma via resists strip process cause significant damage to organic SOP, thus limiting its inter-level dielectric application. A simple treatment technology using reactive ion is proposed to reform the SOP surface. The reactive ion modification of the SOP can improve the resistance towards oxygen plasma. This is owing to the carbon atom absence in the SOP's surface area. The measurements of Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), stress, thickness variation, Scanning Electron Microscope (SEM) cross-sectional view for gap filling and dielectric constant show that SOP with reactive ion treatment (RIT) has better quality for non-etch-back process than SOP without RIT.

The effects of interlayer dielectric deposition and processing on the reliability of n-channel transistors

We report on the effects of interlayer dielectric (ILD) deposition and processing on metal–oxide–silicon field-effect transistor's (MOSFET's) Fowler–Nordheim (FN) stress reliability. The ILD materials examined are plasma-enhanced chemical vapor deposited (PECVD) fluorinated silicon oxide (FSO), PECVD tetra-ethyl- ortho-silicate (TEOS), and spin-on polymer. We used n-MOSFETs with 0.35 μm channel lengths and 90-Å-thick gate oxides as our test vehicles and transistor reliability was assessed using transistor parameter, charge-to-breakdown, and charge pumping measurements. We found out that deposition and processing of the polymer ILD have the least damaging effects on transistor's reliability, whereas deposition and processing of the FSO ILD cause the highest device degradation. We also examined the synergy between damage from ILD deposition and processing and damage from plasma etching by measuring a special test module containing transistors with charging antennae that are sensitive to gate-definition plasma etching. We observed that damage from plasma etching dominates over damage from polymer and TEOS ILD deposition and processing as indicated by the direct correlation between FN reliability and the antenna ratio. However, this was observed not to be the case for damage from FSO ILD deposition and processing which was observed to be as effective as plasma etching damage and to give rise to a “reverse antenna” effect; i.e., the smaller the antenna the less reliable the MOSFET. This is attributed to an interaction which involves plasma charging, fluorine diffusion and defect passivation by fluorine.

Electron Beam Processing for Spin-on Polymers and its Applications to Back-End-of-Line (BEOL) Integration

ABSTRACTThe versatility of e-beam processing provides the capability of tailoring the properties of spin-on polymers. Using different e-beam processing schemes, one can obtain a variety of films such as a homogeneous film with modified properties from the original, a film with variable properties as a function of depth, or a film having two distinct layers. In this paper, we demonstrated how to utilize this advantage of e-beam process to facilitate integration of spin-on polymers in the back-end-of-line manufacturing.

Organic and Inorganic Spin-On Polymers for Low-Dielectric-Constant Applications

Low-dielectric-constant materials (k < 3.0) have the advantage of facilitating manufacture of higher performance integrated-circuit (IC) devices with minimal increases in chip size. The reduced capacitance given by these materials permits shrinkage of spacing between metal lines to below 0.25 μm and the ability to decrease the number of levels of metal in a device. The technologies being considered for low-k applications are chemical vapor deposition (CVD) or spin-on of polymeric materials. For both types of processes, there are methods and materials capable of giving k < 3.0 dielectric stacks. This article will focus on the spin-on approach and discuss the properties of both organic and inorganic spin-on polymers.While CVD SiO2 has been the mainstay of the industry, spin-on materials are appropriate for many dielectric applications. Polyimides have applications as electrical insulators, and traditional spin-on silicates or siloxanes (k > 3.0) have served as planarizing dielectrics during the last 15 years. The newer spin-on polymers have greatly enhanced mechanical, thermal, and chemical properties, exhibiting lower dielectric constants than the traditional materials.

Low K Sog Etchback and Teos Oxide Capping

AbstractSOG etchback was studied using Applied Materials' 200mm MxP+ etch chamber on Allied Signal's SOG (spin-on-glass) T11 and low κ SOP (spin-on-polymer) 418 together with liner films of PE-oxide and oxynitride for IMD (inter-metal dielectric) planarization. Excellent chamber performance and wide process window were demonstrated. Etch selectivities between various SOG and liner films are tunable in a wide range allowing optimization of IMD planarization.

Laser direct writing of channel waveguides using spin-on polymers

A focused argon-ion laser beam (λ=350 nm) is used to fabricate optical channel waveguides on oxidized silicon wafers using a commerically available spin-on polymer. The polymerization process is photon induced, thus allowing the reaction to occur in a room-temperature ambient. This allows the fabrication of waveguides on a variety of substrates including those with low melting points. The losses in these waveguides are typically less then 1 dB/cm, making them applicable to a variety of optical interconnect problems. In particular, we demonstrate their use in the fabrication of an optical power tap.