摘要:

Most electron cyclotron resonance (ECR) sources available today are working with electromagnets. A new source, developed for etch applications, is supplied with permanent magnets. This leads to strong short‐range magnetic fields and the ECR condition is fulfilled on a ring near the chamber wall. Having the maximum electric field strength of the 2.45 GHz along this ring in the microwave radiator leads to efficient plasma production. The principle source characteristics are demonstrated with oxygen plasmas. At low pressure (some 10−4—some 10−3mbar) and moderate microwave power (100–500 W) the plasma burns as a ring plasma. Increasing pressure and/or microwave power over the above mentioned values leads to a ‘‘bulk’’‐type plasma. The change from ‘‘ring’’‐type to bulk‐type plasma occurs discontinuously and is connected (a) with a discontinuity in the run of the reflected power and (b) with a sudden change in the relative ion flux densities of different ionic fragments measured by mass spectrometry. Absolute ion densities up to 5×1010cm−3have been found by Langmuir probe measurements in a bulk plasma at a pressure of 1×10−3mbar. Anisotropic etching of polysilicon over SiO2was performed in the ring mode with pure Cl2as feed gas and applying a radio‐frequency (rf) extraction to the ECR plasma. Low damage etching was achieved due to the low direct‐current (dc)‐bias voltage of 150–200 V with very good anisotropy. The poly‐Si etchrate was 85 nm/min with a selectivity of 18:1 to SiO2and a uniformity of ±7.5% over 200 mm wafers.

ISSN:0734-211X    

DOI:10.1116/1.585614

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

To investigate the transition from the low density mode to the high density mode in an electron cyclotron resonance (ECR) discharge, a Langmuir probe and anEfield probe were used to measure ion density andEfield intensity as functions of axial position and power. The experiments were performed in argon at 0.13 Pa in a 7.9 cm diam cyclindrical source chamber propagating TE11mode 2.45 GHz microwave power. Low mode was characterized by a standing wave throughout the plasma chamber and minimal power absorption. High mode exhibited nearly complete power absorption and no standing wave past the ECR zone. A sliding short (ss) was used to determine if the position of anEfield null in the source chamber affected the transition between these two modes for various magnetic field configurations. The ss position had little effect on mode transition, relative power absorption or ion density when positioned downstream from a broad, large volume resonance zone (resonance near the mirror midplane). However, the plasma could not be ignited if the short was placed at or upstream from the large volume resonance zone.If the magnetic field was adjusted to yield a sharp, small volume resonance zone (resonance midway between the midplane and the throat), then positioning the ss to force anEfield null at the resonance zone would prevent plasma ignition, even at 800 W forward power. The ion density exhibited a hysteresis (i.e., a direct jump from no plasma to a plasma density observed at other sliding short positions for that same forward power, thereafter following the ion density versus forward power dependence observed at nearby ss positions) on power cycling when the sliding short was within ∼1 cm of the broad resonance zone or within ∼1 cm of forcing a null in the sharp resonance zone caes. The ion density versus power curve for the broad volume case exhibited a change in slope over the transition region (Pforward≊40 W) when the ion density at the resonance zone was ≊1×1011cm−3. For the narrow zone cases, a region of bistability (i.e., rapid plasma density fluctuations between low and high mode with little or no change in external input power) was observed for which the ion density fluctuated between a value near 5×1010cm−3in low mode and 5×1011cm−3in high mode. Similar transitions were observed in a 14.6 cm diam ECR source with a TM01mode, indicating that the effect is not solely dependent on the microwave field structure in the ECR chamber.

ISSN:0734-211X    

DOI:10.1116/1.585572

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A wide area windowless plasma disk excited by a soft vacuum electron beam provides a wide area uniform source of vacuum ultraviolet (VUV) photons as well as atomic radicals. Hydrogen and oxygen when excited by the soft vacuum electron beam, emit strong atomic resonance radiation at 121.6 and 130 nm, respectively; in fact up to 8% of the total applied discharge power is emitted as VUV photons. The spatial uniformity of the atomic VUV resonance radiation approaches 6% across a disk 19 cm in diameter. The density of atomic oxygen species generated in the plasma disk has also been experimentally determined using an established polymer film etch rate method as well as with a conventional silver thin film sensor. We employ the disk plasma in a windowless configuration to achieve lower temperature chemical vapor deposition (CVD) than conventional thermal CVD. The VUV photon flux as well as the radical and excited atomic gas species emitted from the lamp can assist dissociation of feedstock reactant gases as well as assist heterogeneous surface reactions and increase surface mobility of absorbed species allowing for lower temperature CVD. Thin films of an aluminum nitride and hydrogenated amorphous silicon have been deposited at temperature between 100–400 °C. The deposited films show improvement over other plasma and photo‐assisted CVD processes in the film quality achieved, the area covered, the substrate temperature required, and the maximum deposition rates that are possible.Insitugeneration of arsine (AH3) and unsaturated arsenic hydrides AsHx(x≤2) have also been achieved by placing elemental arsenic in an environment rich in atomic hydrogen created from the disk–plasma source.

ISSN:0734-211X    

DOI:10.1116/1.585573

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Thin gate oxides used in metal‐oxide‐semiconductor devices are susceptible to mobile ion contamination introduced at critical patterning levels during photoresist stripping. Trace amounts of heavy, alkali metal ions such as sodium (Na+) and potassium (K+) that are found in even the best photoresists are very difficult to oxidize and do not form volatile products that can be easily removed in a typical O2plasma. These ionic, heavy metals and their byproducts can be driven into critical underlying layers by self‐induced bias potentials and positive ion bombardment within an O2plasma environment. To examine this potential problem, a series of commercially available photoresist ashing systems were selected to study the influence of process‐induced mobile ion contamination on sensitive underlying devices. The systems tested included a ‘‘downstream’’ rf plasma asher, a ‘‘downstream’’ microwave plasma system, and a nonplasma ozone ashing system. In this study, photoresist stripping rates and mobile ion (Ni) contamination levels were measured under various processing conditions for 125‐, 150‐, and 200‐mm wafer substrates. Ashing rate measurements are detailed for the ozone ashing system and activation energies are calculated for ozone only and with the addition of nitrous oxide radical products to the ashing gas stream. Measured mobile ion contamination shows a strong temperature dependence for the ‘‘downstream’’ plasma ashing systems tested while the nonplasma, ozone ashing system showed no temperature dependence to process temperatures exceeding 300 °C and it was equal to the wet‐chemical controls.

ISSN:0734-211X    

DOI:10.1116/1.585574

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Characteristics are reported for a resist stripping process downstream of an oxygen plasma to which water vapor is added. The effects of additive water vapor are an increase in atomic oxygen concentration in the plasma, a decrease in activation energy of ashing reaction, and protection of semiconductor devices from the sodium contamination from the resist. The atomic oxygen concentration was approximately doubled by mixing 10% H2O into the oxygen plasma. The activation energy of the ashing reaction to the resist made from novolak resin decreased from about 0.5 to 0.39 eV by the addition of water vapor of more than 1%. The activation energy of hydrogen abstraction from hydrocarbon molecules by an OH radical was lower than that by a ground state oxygen atom [O(3P)], which was the dominant ashing species in the oxygen plasma downstream, and that by an atomic hydrogen was higher than that by the ground state oxygen atom. Moreover, the activation energy in the downstream ashing of the oxygen plasma added to which was 1% water vapor was lower than that of the oxygen plasma to which 3% hydrogen was added, even though the relative concentration of atomic hydrogen in each plasma was equal. Therefore the decrease in the activation energy was probably due to the OH radical generated in the plasma and the downstream. Sodium atoms in the resist were blocked from entering into the semiconductor devices in the stripping process by use of the O2+H2O plasma downstream. Thus sodium was not removed and remained on the wafer surface after resist stripping. Also, by adding N2or CF4to the O2+H2O plasma, we can increase the ashing rate without losing the above characteristics.

ISSN:0734-211X    

DOI:10.1116/1.585575

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Experimental observations concerning the formation of a high‐density plasma in an inductively coupled radio frequency (11.4 MHz) discharge in argon are described. These observations are complemented by probe measurements that provide a quantitative description of plasma properties over an useful range of vapor pressure, 0.02–0.2 Torr, and rf power, 50–400 W. It is shown that a dense plasma of the order of 1012cm−3can be easily formed, having the configuration of a luminous plasmoid embedded in a low‐density, 1010cm−3, diffuse plasma.

ISSN:0734-211X    

DOI:10.1116/1.585576

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We report comparison of etch damage between reactive ion and magnetron plasma etch environments and propose a qualitative model. Gate oxide damage is controlled by both plasma current and voltage and under some conditions can be worse for magnetron etching, especially in the case of very thin gate oxide. Moderate magnetron voltages (<50 V) may still be high enough (given the increased plasma density) to charge polysilicon gates causing degradation. Further reduction of voltage (and hence current) through modification of geometry and chemistry can reduce this damage to gate oxide and the gate edge diode for magnetron etching, producing results superior to reactive ion etching.

ISSN:0734-211X    

DOI:10.1116/1.585577

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

Damage to thin gate oxides from etching of polysilicon gates was studied using gate oxide breakdown histograms and time‐dependent dielectric breakdown measurements. The effect of various polysilicon etch parameters was investigated in a radio frequency (rf) triode etcher. Increasing rf power caused a substantial increase in damage. Reducing bias at constant power also resulted in an increase in damage, indicating that ion energy is not the only cause of damage. Area, isolation edge, and source/drain edge contributions to gate oxide defect densities were calculated as a function of rf power during polysilicon etch. As rf power was increased, the area contribution increased the most, indicating that gate oxide damage from polysilicon etching is not an edge phenomenon but a surface phenomenon. The effect of gate oxide thickness was investigated. Damage increased significantly as gate oxide thickness was reduced. Finally, the rf triode etcher was compared with a microwave electron cyclotron resonance (ECR) etcher. The ECR etcher caused fewer damaged capacitors, but some modifications to the triode etch process (such as lower rf power or pure chlorine chemistry) produced fewer damaged capacitors than the ECR.

ISSN:0734-211X    

DOI:10.1116/1.585578

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A multichamber single‐wafer chemical vapor deposition reactor has been designed and built for ultrahigh vacuum, low temperature, selective silicon epitaxy. The reactor is equipped withinsitumonitors for study and control of both predeposition wafer cleaning and epitaxial growth process. A detailed description of the system and its preliminary performance are reported. An argon or helium plasma excited by electron cyclotron resonance (ECR) has been used for predeposition wafer cleaning. Results of the ECR plasma characterization by a Langmuir probe are presented. Furthermore, structural quality of the wafers subjected to plasma cleaning were evaluated by Rutherford backscattering spectroscopy and scanning electron microscopy. Results showed that a damage free substrate can potentially be achieved at a wafer temperature of 500 °C.

ISSN:0734-211X    

DOI:10.1116/1.585579

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A microwave electron cyclotron resonance ion source has been developed and studied for use in a reactive ion‐beam system. The system has been tested and fully characterized for thin film etching. The CF4reactive ion beam etching of W and Mo, have been investigated as a microfabrication technique for integrated semiconductor devices of submicron geometry. The etching rate has been characterized as a function of ion energy, ion‐beam current density, and angle of beam incidence. It has been found that the etching rate increase linearly with current density and pressure. The rate also increases with ion energy, but the rate of increase drops as the ion energy increases. The maximum etching occurs at a beam angle of 35°.

ISSN:0734-211X    

DOI:10.1116/1.585580

出版商:American Vacuum Society    

年代:1991

数据来源: AIP