GB2330456A

GB2330456A - Gas ionizer using a pyro-electric member conected to a peltier member as the high voltage source

Info

Publication number: GB2330456A
Application number: GB9822323A
Authority: GB
Inventors: Thomas Sebald
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-10-14
Filing date: 1998-10-14
Publication date: 1999-04-21
Anticipated expiration: 2018-10-14
Also published as: FR2769758A1; JPH11195386A; IT1302653B1; KR19990037076A; GB9822323D0; DE19745316C2; FR2769758B1; GB2330456B; ITMI982192A1; DE19745316A1; CN1226128A; TW419876B

Abstract

An ion emitter with a high voltage generator, consisting of the combination of a Peltier heating and cooling member (1a, 1b, 1c) and a member with pyro-electric properties (2), as well as an electrode arrangement (ion emitter 3 and counter electrode 4). By varying the current intensity and/or current direction at the Peltier member, a temperature variation is produced which is transmitted to the pyro-electric member. Electric potential differences are thus produced on two opposite surfaces of the member. Suitable electrodes of non-insulating materials are connected to these surfaces. The ion emitter may further be embedded in a insulator. A possible use for this ion emitter is to ionize gases, in the production areas of micro-electronic components, so as to neutralize any build up of static charges on the surrounding surfaces.

Description

1 2330456 The invention relates to an apparatus for producing high voltage

for the ionisation of gases in the production, assembly and quality control of micro-structured components and assemblies, in particular in the production of wafers and micro-electronic components and assemblies.

In the production and handling of products of microstructure technology, electrostatic charges may lead to damage. On the one hand, at the time of an uncontrolled discharge, the structures are destroyed or damaged by electrical overloading (EOS). If the components are handled under clean room conditions, thus there is a danger from dust, on account of Coulomb energy, static charges may lead to increased, undesirable particle deposition. In particular, in semiconductor component production, fixed disc manufacture and flat panel display manufacture, but also in the case of optical coatings, as well as in lacquering works, electrostatic charges are undesirable.

In order to preclude their production, all objects in these production areas are as far as possible made from conducting material and are specifically earthed. However, frequently the use of the latter cannot be achieved everywhere. Thus, high chemical resistance is partly required, which can be achieved solely by polyfluorine synthetic materials, which have high electrical surface resistances, or insulators must be used and frequently also the products themselves are highly insulating. However, this necessarily involves the danger of charges.

In these areas, static charges can only be neutralised by the supply of charge carriers through the air. Air ionisers produce air-borne charge carriers in the form of ions. By applying high voltage to points, edges or wires, ionisers of this type produce a gas discharge. In these gas discharge areas (Townsend discharge), the air is present in an ionised form. According to the polarity of the high voltage, the correspondingly polar ions 2 are forced by the field forces out of the gas discharge area and move as free ions (nitrogen is predominantly positive and oxygen negative), driven by electric fields or the airflow, through the air.

These processes are sufficiently well known, described in literature and there are a series of Patents relating to the construction of such ionisers (European Patent 0 448 929 Al, DE 35 43 618 Al, DE 36 03 947 Al, DE 35 22 881 Cl, US Patent 4,477,263; PCT WO 96/02966; US Patent 4,872, 083; PCT WO 92/03863; US Patent 5,153,811; US Patents 4,542,434; 4,117, 332; 4,956,582; 4,809,127; 3,711,743; PCT WO 87/04873 inter alia).

Modern clean room technology is moving away from large, hall-like clean rooms in which the production area and the personnel area are marginally separated from each other, towards machines encapsulated in clean room technology and small production areas (SMIF technology, 300 mm wafer technology, mini-environments). The ionisers, which correspond to the state of the art, require transformers or so-called cascade connections for producing high voltage. These systems are spatially relatively large. Installing these systems in small clean spaces (minienvironments) is not possible or only with difficulty on account of the restricted conditions. If the voltage supply is integrated, a great deal of space is lost, if the voltage supply is installed outside the mini-environment, high voltage cables with the related risks or the necessary safety precautions must be laid.

There is thus a need for small or miniaturized ionisation systems with an integrated high voltage source.

In addition, pyro-electric energy converters are known inter alia from US 4,620,262, which makes it possible without the detour via mechanical movements, to convert thermal energy efficiently into electrical energy.

3 Furthermore it is a drawback that conventional ionisers cause electrical alternating or direct fields extending relatively far (some 10 centimetres), which due to influence in the objects to be neutralised, lead to undesirable potentials or charge displacements. There is thus a need for ionisers with the smallest possible leakage fields.

It is the object of the invention to eliminate the drawbacks of the known state of the art and to provide an apparatus f or producing high voltage for the ionisation of gases in the production, assembly and quality control of microstructured components and assemblies, in particular in the manufacture of waf ers and micro-electronic components and assemblies, which can be used directly in or on small or miniaturized ionisation systems with an integrated high voltage source and which produces only small leakage fields.

Claims

The object is achieved according to the invention by the characterising

features of the main Claim. Advantageous developments of the invention are described in the Sub-claims.

For the production of high voltage, the pyrolytic effect on crystals with the highest possible pyro-electric coefficient is utilised.

The invention will be described in detail hereafter with reference to one embodiment and illustrated in the drawings, in which:

Figure 1 shows the diagrammatic construction of an ionisation device, Figure 2 shows the ionisation device according to Figure 1 in a dielectric.

In Figure 1, an ionisation device is illustrated in simplified form.

4 The ionisation device allows the production of high potentials (up to 10, 000 volts) by the connection of a heating and cooling member on the basis of the Peltier effect, with a positively doped semiconductor 1A and a negatively doped semiconductor 1C with a conductor 1B, with a pyroelectric material 2 with a high pyro-electri city constant, for example lithium niobate (LiNb03), lithium tantalate (LiTaO,) or even polyfluorohydrocarbons.

The Peltier member cools or heats the pyro-electric material, which is polarised on its outer surfaces by internal charge displacement. If one earths one of the two polarised surfaces, then one obtains high electrical voltages on the other surface with temperature-dependent level and polarity. If this voltage is directed to an electrode system of points 3, edges or wires as the high voltage side and a ground counter- e 1 ectrode 4 located close thereby, then ions are produced at the high voltage electrode and, on account of the small geometric dimension between the high voltage electrode and the earthed counterelectrode, small, undesirable electrical interference fields, which do not extend very far into the room, are produced.

By varying the polarity at the supply voltage of the Peltier member 5, the pyro-electric crystal is respectively cooled or heated and consequently produces alternately positive and negative ions. Since the crystal is electrically an insulator and the two polarised surfaces can thus be considered as capacitors, due to the self-regulation in the immediate vicinity, disregarding the inner resistances, the same number of positive or negative ions are always produced. This self -regulation opposes the requirements of a balanced production of ions in order to avoid mono-polar room charges. The supply voltage for technically usable Peltier members is a few volts (0.2 volts 10 volts). The wiring connected thereto can be combined very well with the requirements of modern clean room technology.

With pyro-electric single crystals, preferably lithium tantalate, which has a size of 5 mm times 5 mm, times 0.5 mm, charge carriers can be produced adequately in order to achieve technically useful neutralisation times of the electrostatic charges (< 20 secs.). Thus, a complete ioniser with high voltage supply and electrode system can be installed in a volume of less than one cubic centimetre.

The small dimensions and low disturbance fields make the invention predestined for use in mini-environments.

In Figure 2, the complete ionisation unit according to Figure 1 is embedded in a dielectric 6. Thus, a unit which is easy to clean results, which can also be used in corrosive media, which is an advantage for some areas of semiconductor process technology.

To summarise the foregoing, the apparatus to be protected relates to a high voltage generator, consisting of the combination of a Peltier heating and cooling member and a member with pyroelectric properties as well as a corresponding electrode arrangement. By varying the current intensity and/or current direction at the Peltier member, a temperature variation is produced on one side of the member. This temperature variation is transmitted to the pyro-metrically connected pyro-electric member. Thus high potential differences result on two opposite surfaces of the member, depending on its crystalline structure. Electrodes of non- insulating material are located on these surfaces, which electrodes form the electric field resulting from the potential difference so that a corona discharge for ionisation results.

The apparatus may have a very small and compact construction, if manufacturing methods of thin-layer and microstructure technology are used.

6 Claims 1. Apparatus for producing ions in gases, consisting of ionemitter electrodes, counter-electrodes and a high voltage generator, characterised in that the high voltage is produced by the heating and cooling of a pyro-electric material.
2. Apparatus for producing ions in gases, consisting of ionemitter electrodes, counter-electrodes and a high voltage generator, characterised in that the electrodes are connected directly to the high voltage generator.
3. Apparatus for producing ions in gases according to Claims 1 and 2, characterised in that the heating and cooling of the pyro-electric material is carried out by a Peltier member.
4. Apparatus for producing ions in gases according to Claims 1 and 2, characterised in that the heating is carried out by an electrical heating resistance and the cooling by convection in gases or thermal conduction on solid-state bodies.
5. Apparatus for producing ions in gases according to Claim 3, characterised in that a cyclic heating and cooling takes place due to cyclic polarity reversal of the current through the Peltier member, due to which a simultaneous cyclic change of the emitter electrode polarity and thus also ion polarity takes place.
6. Apparatus for producing ions in gases according to Claims 1 to 5, characterised in that the emitter electrode is a point or edge.
7. Apparatus for producing ions in gases according to Claims 1 to 6, characterised in that the electrodes are largely embedded in a dielectric.
8. Apparatus for producing ions in gases according to Claims 7 1 to 7, characterised in that emitter electrodes having cyclic opposed polarity are used as the counter-electrodes.
9. Apparatus for producing ions in gases according to Claims 1 to 8, characterised in that Peltier members of opposed polarity are connected electrically in parallel or electrically in series.
10. Apparatus for producing ions in gases according to Claims 1 to 9, characterised in that the temperature change is varied for regulating the quantity of ions emitted.
11. Apparatus for producing ions in gases according to Claims 1 to 10, characterised in that the initial voltage of the counter-electrode is varied for regulating the quantity of ions emitted.