HEADING 84.56 - MACHINE-TOOLS FOR WORKING ANY MATERIAL BY REMOVAL OF MATERIAL BY LASER OR OTHER LIGHT OR PHOTON BEAM ULTRA SONIC ELECTRO-DISCHARGE ELECTRO-CHEMICAL ELECTRON BEAM IONIC-BEAM OR PLASMA ARC PROCESSES (+) .

46 COMMODITIES

8456.10 - Operated by laser or other light or photon beam processes

8456.20 - Operated by ultrasonic processes

8456.30 - Operated by electro-discharge processes

- Other :

8456.91 - - For dry-etching patterns on semiconductor materials

8456.99 - - Other

The machine-tools of this heading are machines used for the shaping or surface- working of any material. They must meet three essential requirements :

(i) They must work by removing material;

(ii) They must carry out operations of the kind performed by machine-tools equipped with conventional tools;

(iii)They must use one of the following seven processes : laser or other light or photon beam ultrasonic electro-discharge electro-chemical electron beam ionic-beam or plasma arc.

(A) MACHINE-TOOLS FOR WORKING BY LASER OR OTHER LIGHT OR PHOTON BEAM PROCESSES

Laser-beam machining (photonic machining) consists of bombarding a target with photons. This group covers in particular machines for drilling (metals semiconductor crystals rubies for watches etc.) machines for cutting metals or other hard materials and machines for engraving (figures letters lines etc.) on various highly resistant materials.

(B) MACHINE-TOOLS FOR WORKING BY ULTRASONIC PROCESSES

Ultrasonic machine-tools consist of a punch subjected to ultrasonic vibrations and an abrasive in suspension in a liquid. These machines may incorporate an abrasive recycling system.

This group includes machine-tools which are used in particular :

(1) For cutting semiconductor chips and for cutting or drilling ceramic substrates for integrated circuits;

(2) For working diamond or metal carbide dies;

(3) For drilling or shaping minerals;

(4) For engraving glass;

(5) For milling broaching or polishing.

(C) MACHINE-TOOLS FOR WORKING BY ELECTRO-DISCHARGE PROCESSES

The principle of this type of machining is the removal of metal between two metallic electrodes (the workpiece and the tool) by sudden electrical discharges of very short duration at the rate of several hundred thousand cycles per second. This group covers for example high-frequency electric-spark cutting machines.

(D) MACHINE-TOOLS FOR WORKING BY ELECTRO-CHEMICAL PROCESSES

The principle of this type of machining is the removal of metal by electrolysis. The workpiece (anode) is a conductor of electricity as is the tool (cathode). Both are submerged in a selected electrolyte which makes cathodic deposition impossible and all that occurs is anodic dissolution. This group includes :

(1) Electrolytic polishing apparatus used for polishing specimens for microscopic or metallurgical examination.

(2) Electrolytic sharpeners for sharpening cutting tools cutting chip-breaker grooves or cutting metal carbide plates; these machines utilise a diamond wheel.

(3) Machines for deburring various kinds of gear-wheel by anodic dissolution.

(4) Machines for precision finishing flat surfaces etc.

(E) MACHINE-TOOLS FOR WORKING BY ELECTRON BEAM PROCESSES

Electron beam machining consists of bombarding the workpiece on a very small surface with electrons emitted by a cathode accelerated by an intense electrical field and focussed by a system of magnetic or electrostatic lenses.

(F) MACHINE-TOOLS FOR WORKING BY IONIC-BEAM PROCESSES

The beam of these machine-tools works by continuous action not by impulses as inthe case of the laser beam.

(G) MACHINE-TOOLS FOR WORKING BY PLASMA ARC PROCESSES

Plasma arc machining involves intense ionisation of a gas by means of an electric current produced by a magnetic impulse generator under high tension. It permits cutting plates at a very high speed and rough-cutting and machining coarse-feeding threads.

(H) MACHINE-TOOLS FOR DRY-ETCHING PATTERNS ON SEMICONDUCTOR MATERIALS

Machine-tools for dry-etching patterns on semiconductor materials form part of the process of semiconductor wafer manufacture. Some dry etchers use radio frequency (RF) energy with frequencies in the 100-450 kHz range. Other dry etchers use RF energy with frequencies at the 13.56 MHz level and still others use microwave frequencies at the 2.45 GHz level. The choice of frequency of the energy input can effect the ion energy of the resulting plasma. In some ases the ions of the plasmas have very little directed energy. In other cases the ions have large amounts of directed energy. The latter case may involve ion beams.

Terms used to describe specific forms of dry etching are " parallel plate plasma etching reactive ion etching magnetically enhanced ion beam etching ion beam etching and electron cyclotron resonant etching ". The different terms describe the various techniques used to create gaseous plasmas with different behaviour patterns.

PARTS AND ACCESSORIES

Subject to the general provisions regarding the classification of parts (see the General Explanatory Note to Section XVI) parts and accessories of the machine-tools of this heading are classified in heading 84.66.

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The heading also excludes : (a)Ultrasonic apparatus for cleaning (heading 84.79).

(b)Soldering brazing or welding machines and apparatus whether or not capable of cutting (heading 85.15).

(c)Testing machines (heading 90.24).

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Subheading Explanatory Note.

Subheading 8456.91

This subheading covers machine-tools for dry-etching patterns on semiconductor materials; thesemachine-tools are generally known as dry etchers. Dry etchers use several different methods for creating a gaseous plasma which removes thin film materials from semiconductor wafers. The dry- etching process is applied to the semiconductor wafer after a lithography process has been performed to produce the pattern to be etched. It is anisotropic in that ions impinge upon the wafer in parallel courses perpendicular to the plane of the wafer. Anisotropic etching allows the pattern to be replicated on the semiconductor wafer without undercutting the sides of the etched channels.

Dry etchers generally incorporate one or more reaction chambers pumps vacuum pumps radio- frequency or microwave generators gas-flow control equipment and process control equipment.

They may incorporate automatic wafer-loading mechanisms and their reaction chambers may be capable of simultaneously processing multiple semiconductor wafers.

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