Articles you may be interested inThermal anneal activation of near-surface deep level defects in electron cyclotron resonance hydrogen plasmaexposed silicon J. Vac. Sci. Technol. B 15, 226 (1997); 10.1116/1.589269 Damage and contamination in lowtemperature electron cyclotron resonance plasma etching Damage formed by electron cyclotron resonance plasma etching on a gallium arsenide surface Damage and contamination produced after electron cyclotron resonance (ECR) etching of Si using CF 4 gas has been studied using electrical characterization, Rutherford backscattering spectroscopy (RBS), secondary ion mass spectroscopy (SIMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and etch pit density measurement techniques. Due to the sman dc self-bias voltage generated across the pla..<;ma sheath, ECR etching is expected to produce low damage and contamination levels. RBS measurements show that ECR etching does indeed produce less structural damage than that produced by conventional reactive ion etching (RIE). It is found that the damage and contamination levels from an ECR etching process are actually reduced by the addition of radio frequency (rO power to the wafer. The metallic impurity levels are shown to be greatly reduced by covering the stainless steel wall of the ECR source near the resonance region with an anodized Al liner. The plasma density in the resonance region of the reactor during ECR processes is much higher than that during RIE processes. Therefore, the ECR processes produce heavy metal contamination, which is mainly from the portion of the stainless steel wall of the reactor in contact with the plasma. Schottky diodes fabricated on the etched samples exhibit high leakage currents implying some damage and/or impurities are present in the near-surface region. Relationships that exist among the generation current of the metal-oxide-silicon (MOS) capacitors, the etch pit density and the metallic impurity level were studied. Some wafers were exposed to an Ar ECR/RIE plasma to compare the effects of pure physical sputtering and ion-assisted chemical etching, as when CF" was used. A possible explanation for the observed behavior is given.
Surface modifications of silicon induced by electron cyclotron resonance (ECR) etching with CF4 is studied using x-ray photoemission spectroscopy and Raman scattering techniques. It is shown that a silicon sample etched by ECR exhibits a thinner surface residual layer compared to those exposed to reactive ion etching (RIE) or hybrid ECR/RIE. Evidence of plasma-induced structural disorder in the silicon surface was only observed in the RIE-etched sample.
A comparative study of vacuum ultraviolet radiation damage has been carried out in an electron cyclotron resonance (ECR) and reactive ion etching (RIE) hybrid chamber. The damage was measured by changes in the density of interface states, the midgap capacitance–voltage shifts, and from photo I–V gate voltage shifts in metal–oxide semiconductor (MOS) capacitors before and after plasma exposure. The results suggest that the damage found in the samples exposed to either ECR or RIE plasmas appears in the form of neutral electron traps in the bulk of the SiO2 film and ‘‘slow’’ interface states. The positive charge found in the exposed samples results from the filling and emptying of these slow interface states and not from trapped holes. Electron trap densities are found to be in the low to mid 1012 cm−2 range for all plasma-exposed samples. Even after a standard post-metalization anneal (PMA), the density of electron traps is only reduced by approximately a factor of 2 and appears relatively independent of the type of the plasma exposure. The density of the slow interface states is found to be in the high 1011 cm−2 range and in the low 1010 cm−2 range, for the ECR plasma samples, before and after the PMA, respectively. The RIE exposed slow state density was initially ≂2×1012 cm−2 and reduced to 2×1111 cm−2 after the PMA, an order of magnitude higher than that of the ECR-plasma exposed samples.
Articles you may be interested inElectron cyclotron resonance plasma reactor for SiO2 etching: Process diagnostics, endpoint detection, and surface characterization An electron cyclotron resonance (ECR) etching reactor has been studied for its potential utility in plasma processing of thin films and semiconductor substrates. An ASTeX ECR source was installed on a conventional reactive ion etching reactor. Etch rates, etch uniformities, selectivities, etch profiles and dc bias voltages were measured as a function of many equipment and process parameters. Both the etch rates and the etch uniformity exhibited a strong dependence on the magnetic field strength and field profile at the wafer. The addition of a third electromagnet at the wafer for plasma collimation provided the greatest enhancement to the etching characteristics. Etch rates ofSi for radio-frequency (rf)-biased ECR were on the order of 1 ,urn/min. The dc bias voltages in the ECR case were less than 100 V. SiO l films were etched anisotropically with good selectivity to photoresist. The etch rate of Si0 2 was found to increase monotonically with bombardment energy from a threshold of 36 e V in agreement with a sputtering model, suggesting that the reaction occurs via ion-induced chemical processes. Anisotropic profiles were observed for Si using pure SF 6 in low pressure rf-biased ECR conditions. Clean vertical profiles were etched at high rates in polyimide using pure O 2 with very high selectivity to a Si 3 N4 mask and the underlying Si substrate. 2356J.
Si and SiO2 films have been etched using CF4 and H2 mixtures in a hollow cathode etching (HCE) reactor. We have measured etch rates and characterized the Si surfaces after HCE by x‐ray photoemission spectroscopy (XPS). Addition of H2 to CF4 did not significantly enhance the etch rate ratio of SiO2 to Si. The fluorocarbon film, which is responsible for the achievement of SiO2/normalSi etch selectivity in reactive ion etching (RIE) reactors (1), has not been observed by XPS for Si surfaces etched in our HCE reactor at high RF power levels. This result is similar to that found in magnetron ion etching (MIE) at high power (2). C‒C and C‒H groups were the predominant species detected on Si surfaces etched in the HCE reactor; only small amounts of CFx were present. Low fluorination of the carbonaceous film is believed to be due to high dissociation rates of the parent molecules in both the HCE and the MIE reactors. The low fluorination of the carbonaceous deposits on SiO2 surfaces results in low etch rates for SiO2 . When both carbon and fluorine arrive at the surface as in RIE, the oxygen in the SiO2 can form volatiles by reactions with carbon, while the Si can be removed by F atoms. When mostly carbon is deposited on the surface, as in HCE and MIE, the Si in the SiO2 is removed at a relatively slower rate. The thicknesses of the deposits on the Si surface were found to be smaller for the HCE reactor than for RIE reactor at high H2 percentages. Slow deposition of carbonaceous species on Si can account for the relatively high Si etch rates. The high Si etch rates and the effect of low fluorination of the carbonaceous deposits on SiO2 for CF4/H2 can account for the low etch rate ratios of SiOtrue2_ to Si in the HCE reactor.
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