Dry etching utilizing showered electron beam assisted etching

Two kinds of ion beam etching techniques, Ar gas ion beam etching (IBE) and oxygen gas reactive ion beam etching (RIBE), were used for adhesion enhancement of the PI/Cu and Cu/PI interface, respectively.Ar gas IBE on Cu followed by deposition of PI film on the modified Cu surface can double the adhesion strength of spin-coated PI on Cu compared with unmodified Cu. The adhesion enhancement is due to increasing the surface contact area of the rough Cu surface to PI. However, a corrosion reaction happens at the polyamic acid (PAA) and Cu interface, resulting in the dissolution of Cu into the PI film and Cu oxide layer growth during curing of PI film. A Cr layer between Cu and spin-coated polyamic acid(PAA) is necessary to keep the Cu from dissolving in PAA and diffusing into PI. Ar IBE modification on Cu followed by deposition of a thin Cr layer on the modified Cu surface is recommended to enhance the adhesion strength of spin-coated PI on Cr.O2 RIBE on PI followed by evaporation of Cu on a modified PI increases the peel strength of Cu/PI by more than 25 times. The maximum peel strength of Cu on the PI modified by O2 RIBE is almost 70 grams/mm. The increase of adhesion is due to the mechanical interlocking of a unique structure of modified PI - a grass-like structure. This structure occurs because of the inhomogeniety of PI film - the presence of ordered and disordered phases in a PI film. In addition, the Cu/PI interface exhibits stability with thermal cycling and humidity, because the adhesion enhancement is mostly due to a mechanical effect and not a chemical effect. The diffusion of Cu into PI at various temperatures is not significant. Typically, Cu atoms can diffuse up to 300 at 400 °C in 1 hour. Another advantage of O2 RIBE on PI is the capability of enhancing the adhesion of the second PI layer on a first PI layer.These technologies allow the precise control of the adhesion strength of the PI/Cr/Cu and Cu/PI interfaces by independent variation of the beam energies, ion doses and angle of beam incidence. Also the ion source is easily installed in the same vacuum chamber for Cr and Cu evaporation. This provides low cost and simple operation.

Argon and reactive ion beam etching for SAW devices

Reactive Ion Beam Etching (RIBE) has been found to be an extremely useful technique for fabricating highly anisotropic ferroelectric device structures, particularly nonvolatile random access (NVRAM) memory devices, which are difficult to etch by other dry etching methods. The application of ion beam equipment to this field has been limited in the past by the use of standard Kaufman type ion sources, which have very short cathode lifetimes when operated with the reactive gases which are used to attain enhanced selectivity. This problem is solved by using the RF inductively coupled ion source described here. Etch results on ferroelectric PZT and Pt electrodes are presented for the RF source and compared with results for a Kaufman filament ion source. It is shown that RF RIBE with fluorocarbon gases provides higher etch selectivity for the ferroelectric (up to about 4:1 PZT/Pt) combined with relatively high etch rates (650 A/min for PZT at 500 eV). A complete practical ion beam process for patterning ferroelectric device structures is then described, incorporating the ferroelectric RIBE step. Highly anisotropic etched features are shown.

Dry etching and overgrowth process techniques have been developed for the fabrication of InGaN inner stripe laser diodes. The dry etch damage at the etched surface and the overgrown interface was estimated using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). As a result, the etch damage at the overgrown interface was shown to be repaired during the overgrowth. Groove stripes formed on the GaN layer by reactive ion beam etching (RIBE) were overgrown by GaN using metalorganic chemical vapor deposition (MOCVD). The morphology of the overgrown surface was observed by scanning electron microscopy (SEM). The grooves of widths less than 10 µm were buried completely at 1100°C and smooth, flat surfaces were obtained. We have fabricated the InGaN inner stripe (IS) lasers and reported on the first pulsed lasing operation of InGaN inner stripe lasers, fabricated by dry etching and overgrowth techniques.

By using a newly developed electron beam excited plasma (EBEP) system, etching characteristics of GaAs and Si in an ion energy range of 5 to 100 eV were investigated. Anisotropic etching profiles with high aspect ratios were obtained by both Ar ion beam etching (IBE) and Cl2 reactive ion beam etching (RIBE). Etching rates of 1.2 μm/min for GaAs and 0.5 μm/min for Si were demonstrated for the first time by Cl2 RIBE at ultralow ion acceleration voltage of 5 V. Selective ratios of etching rates for Si/SiO2 and GaAs/SiO2 are ∼33 and 80, respectively. Electrical and optical measurements on the etched samples indicated that damage degree introduced by the low-energy ions is negligible. Therefore, the EBEP system cannot only provide high etching rate because of its high ion current but also realize damageless ion etching due to its low ion energy.

Various drying etching techniques are briefly reviewed and application of some of these techniques for the fabrication of small structures in electronic and metallic materials are discussed. Experimental results from reactive ion etching, reactive ion beam etching, and chemically assisted ion beam etching will be shown for a number of substrate/etch mask systems at dimensions well below 1 μm linewidths.

A number of current and future optoelectronic components require the creation of waveguides in LiNbO3. In order to accomplish this, trenches between one and ten microns deep must be patterned into the LiNbO3 substrate. We have demonstrated the formation of near-vertical, smooth-walled trenches up to ten microns deep using Ar ion beam etching (IBE) and Ar/CHF3 reactive ion beam etching (RIBE) processes. Both Ar IBE and Ar/CHF3 RIBE processes can achieve etching rates of up to 100 nm/minute. Our patented RIBE process [K. E. Williams, et al. U.S. Patent No. 6,238,582 (29 May 2001)] has the additional advantage of providing up to a 5:1 selectivity for etching the LiNbO3 over a photoresist mask. The collimated beam available with IBE and RIBE allows control over feature profiles and redeposition removal. Using a combination of RIBE and a multiangle process, the sidewall angle and smoothness of the mask have been transferred into LiNbO3 substrates to depths between one and ten microns. This depth range can be expanded in either direction if an appropriate mask can be fabricated.

ABSTRACTDry etching characteristics of GaN using reactive ion beam etching (RIBE) were studied. Etching profile, etching rate and etching selectivity to a photoresist (PR) mask were investigated as a function of various etching parameters. Characteristics of chemically assisted reactive ion beam etching (CARIBE) and RIBE were compared at varied mixtures of CH4 and Cl2. A highly anisotropie etching profile with a smooth surface was obtained for tilted RIBE with Ch at room temperature. Etching selectivity to a PR was dramatically improved in RIBE and CARIBE when a volume fraction of CH4 to the mixture of CH4 and Ch was larger than 0.83.

Reactive ion beam etch (RIBE) is one of the most important dry etching techniques for microfabrication of semiconductor devices such as microsized vertical-cavity surface-emitting lasers (VCSELs) which have a side-etched shape near the bottom of mesas We think the side-etch is caused due to the temperature rise by ion irradiation. In this paper, the measurement of surface temperature by using a radiation thermometer is carried out, in-situ during RIBE. We propose a multistep RIBE to improve etching profiles in order to alleviate the temperature rise. In this experiment, we used a high-vacuum RIBE system which has an electron cyclotron resonance-type ion source.

We have developed a series of block co-polymerized polyimides for KrF lithography and EB lithography. Block co-polymerization is a synthesis method to control molecular structures. We have developed solvent soluble polyimides in powdered form. We can use these polyimides for dielectric materials in devices, and also can use as a dry etching mask in semiconductor processes. Here we report the details of dry etching properties for the block co-polymerized polyimides by reactive-ion-etching (RIE) using fluoride and chloride gases, typically used for Si etching and GaAs etching, respectively. Etching rates for EB exposed polyimide, photosensitive polyimide, novolac standard photoresist and Si at the condition of 80 W RF power and 60 sccm SF₆ gas flow, were measured as < 1 nm/min, 1.7 nm/min, 34 nm/min and 31 nm/min, respectively. We also checked the etching rate for EB exposed polyimide, photosensitive polyimide, novolac standard photoresist and GaAs at the condition of 50 W RF power and 3 sccm Cl₂ gas flow in the inductive coupled plasma (ICP) RIE, were measured as < 1 nm/min, 50 nm/min, 120 nm/min and 500 nm/min, respectively. Dry etching selectivity of EB exposed polyimide to Si is more than 31, and dry etching selectivity to GaAs is more than 500. These values are much higher compared to novolac standard photoresist. The high resolution EB exposed polyimide is promising for nano-patterning as stable dry etching mask. RIE resistance for polyimide photoresist is 20 times more than novolac standard photoresist for SF₆ etching gas, and more than twice for Cl₂ etching gas.

The excellent anisotropy of the reactive Ion BeM eTCHING(RIBE) process, its fairly high etch rate and the perfectly smooth etched surface have made it a desirable tool for III-V eletronic and optoeletronic device fabrication. The properties of a microwave excited ion source have been examined, the influence of the various parameters and the etch affect of various gases in Chemical Assisted Ion Beam Etching(CAIBE) have been studied. Application to the fabrication of lasers have demostrated that the initial reluctance to accept such a process for semiconductor device etching was not justified.

Very smooth InGaAsP/InP surfaces and sidewalls were obtained by using the enhanced sputtering effect of Ar addition to Cl2 etching gas in RIBE. The substrate temperature was raised to 180°C in order to remove involatile chlorides and impurities. Moreover, a vertical sidewall with no lateral etching under the mask was realized at the same time. This enables submicron dry etching for heterostructure devices.

We measured the chlorine plasma characteristics in reactive ion beam etching (RIBE) and chemically assisted ion beam etching (CAIBE) process. In the CAIBE process, the energy peak of Cl+ ionized by Ar+ appears in the energy range of 50–70 eV and this Cl+ energy peak increases with an increase of Ar+ energy. We observed that the excited state Cl2 density in CAIBE is lower than that in RIBE as measured by appearance mass spectrometry (AMS).

Ion incidence angle-dependent pattern formation on AZ® 4562 photoresist by reactive ion beam etching

Reactive ion beam etching (RIBE) offers intrinsic interest as an etch technique and its comparatively low operating pressure (10-4 torr in the bombardment chamber) allows the application of ion beam based surface analytical techniques to monitor the surface during etching. We report here on the RIBE of tungsten with a reactive ion beam generated from a carbon tetrafluoride (CF4)/argon (Ar) gas mixture.