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  Method and apparatus for removing material from a substrate surfaceThe Patent Description & Claims data below is from USPTO Patent Application 20060037700. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to methods and apparatus for removing material from a substrate surface and in particular to methods and apparatus for the cleaning or etching of surfaces of electronics components and components related to the manufacture thereof. However, as will be understood by the skilled addressee, the invention is not limited to such uses. BACKGROUND [0002] Failure of electronics circuits due to problems experienced during manufacture is common. While there may be several sources of problems, a typical problem is commonly attributed to the existence of material such as residual surface organic contaminants (e.g., dirt, finger prints, etc), or residual material from different manufacturing stages, such as solvent residue and epoxy bleed-outs. [0003] Integrated circuits (ICs) are manufactured in a multi-layered process of moulding and bonding of component parts. Bonding typically includes wire bonding, where two adjacent 1C components are bonded by fusing wires between mounting pads of the adjacent components. Problems can occur in the bonding process if the mounting pads are not clean, resulting in a non-integral or weak bond, and thus a defective 1C. [0004] One proposed solution for improving the wire bonding is cleaning the mounting pads prior to the bonding process. Two cleaning methods are known: capacitive cleaning using a radio frequency (RF) power source; and ion cleaning using an ion beam in an Ar/O.sub.2 environment at 1500 eV. RF cleaning is achieved by applying RF to an electrode in a vacuum chamber which also contains a component requiring surface cleaning. A source of Ar is introduced into the chamber and a plasma is formed. The plasma ions chemically react with the material on the surface of the component. There are several problems associated with RF cleaning. Firstly, it is only possible to control the power input to an RF cleaning system. Secondly, there are significant health and safety requirements associated with operating high powered RF equipment, as well as ensuring any RF leakage doesn't affect nearby people and equipment. Thirdly, RF generators require complex matching networks to allow greater flexibility in cleaning regimes. Different matching networks are required for different applications or different operating pressures. Both RF and ion cleaning may also damage the components being cleaned by voltage discharge or arc formation. [0005] Other problems may arise due to lack of cleanliness of parts related to the manufacture of an 1C. For example, moulds used during the moulding process may have residual epoxy films which eventually need to be cleaned from the mould. Current cleaning processes for moulds include the use of wire brushes or chemical baths. However wire bath cleaning damages the mould and shortens its lifecycle, and chemical baths are relatively slow. One proposed method for extending the mould life is to coat the mould surface with 3-10 .mu.m of CrN, or "hard chrome", to increase resistance, to damage from wire brush cleaning. While extending the life of the mould by increasing resistance to wear, such coatings have the disadvantage of reducing the accuracy of the intended mould dimensions. [0006] It is an object of at least one of the embodiments of the present invention to ameliorate or overcome at least one of the above problems associated with the prior art, or at least to provide a suitable alternative thereto. SUMMARY [0007] According to a first aspect of the present invention there is provided a method of removing material from a substrate surface comprising the steps of [0008] providing a plasma using a power source; and [0009] contacting the substrate surface with one or more of ions, atoms or free radicals of the plasma, [0010] wherein the power source is supplied as a variable voltage. [0011] According to a second aspect of the present invention there is provided a method of removing material from a substrate surface comprising the steps of: [0012] placing the substrate in an evacuatable chamber having an electrode therein; [0013] providing a variable voltage to the electrode to provide a plasma in the chamber between the electrode and the substrate; and [0014] contacting the substrate surface with one or more of ions, atoms or free radicals of the plasma to remove at least a portion of the material on the surface. [0015] Advantageously, by supplying the power source as a variable voltage, the problems of arcing are prevented, and therefore the substrate is not unnecessarily damaged. [0016] Preferably, the variable voltage is a pulsed voltage, and more preferably the voltage is pulsed in consecutive 3-30 kHz periods. By providing the voltage in a pulse, a plasma can be formed without providing an arc and without unnecessarily heating the environment in which the material removing method is provided. [0017] Preferably the variable voltage is pulsed from 0V to a voltage between -300V and -1000V, and more preferably from 0V to a voltage between -380V and -600V. Also preferably, the voltage is applied in a 3 to 20 .mu.s pulse. Preferably, the pulse is provided once per 3-30 kHz period. Alternatively, the pulse may be provided more than once per period. For example, a pair of 3 .mu.s pulses, 5 .mu.s apart, may be provided per 3-30 kHz period. [0018] Preferably there are two opposed electrodes, wherein the power source is supplied to one of the electrodes and the other electrode is floating, and wherein the substrate is on the floating electrode. Alternatively, the other electrode is grounded, or the other electrode is either grounded, floating or of generally equal potential to the one electrode, and the substrate is on the one electrode. [0019] Preferably, the plasma is provided in an O.sub.2 environment, and more preferably the plasma is provided in an O.sub.2/CF.sub.4 environment. [0020] Preferably the plasma is provided in a chamber evacuated to about 80 to 1500 mTorr. [0021] Alternatively two substrates are provided on respective electrodes. In another alternative arrangement there are a plurality of spaced electrodes, at least some of which respectively support a respective one of a plurality of said substrates. In another alternative arrangement, at least one of the electrodes supports at least two said substrates on one or both of its opposing sides. Continue reading... Full patent description for Method and apparatus for removing material from a substrate surface Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method and apparatus for removing material from a substrate surface patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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