DE2050651C3 - Method for operating an electron beam generating device having an electron-emitting cathode and an auxiliary electrode for beam shaping for the evaporation and / or processing of materials under an ultra-high vacuum and device for carrying out the method - Google Patents

Description

The present invention relates to a method of operating an electron-emitting device Cathode and an auxiliary electrode for beam shaping having electron beam generating device for evaporation and / or processing of materials under ultra-high vacuum and a Execution to carry out this procedure.

Numerous different electron beam devices for vaporizing or processing under high vacuum conditions have been described in the literature. All have an electron-emitting cathode during operation and additionally at least one auxiliary electrode for beam shaping. Many modern technologies require an ever better vacuum, e.g. B. It is important for the vapor deposition of thin-film electronic circuits that the vapor-deposited substances are not contaminated by components of the residual gas atmosphere in the vapor deposition system. This means that in many cases a high vacuum of about 10 ~ ^e t is no longer sufficient and the process must therefore be carried out in the so-called ultra-high vacuum range at significantly lower pressures.

It is known that it is advantageous for creating an ultra-high vacuum in a recipient Possibility of all parts of the system to be exposed to the vacuum at 300 to 450 ° C for several hours Pickling out with constant pumping out of the desorbed gases and later on during pumping

ίο to cool ultra-high vacuum. Radiation ovens are often used for this purpose used in the form of hoods, which are placed over the recipient of the vacuum system can be. Working with such bake-out devices is tedious and time-consuming.

Up to now, devices for evaporation or processing of materials have been degassed often? .also carried out in such a way that by radiant heating from the heated hot cathode the surrounding parts to a little higher

»O Temperatures than 450 ° C were heated. on The mentioned auxiliary electrode could also do this for several hours at the mentioned temperature be degassed. Then when pumping to ultra-high vacuum and during operation, it was

»5 then chilled. According to the known state of the art So all measures have been taken, which - as far as the degassing of the auxiliary electrodes is concerned - could contribute to the improvement of the vacuum achievable in the system.

Unexpectedly, however, it has been shown that in recipients in which an electron beam device was operated, despite the thorough degassing described, the ultra-high vacuum during operations could not be maintained.

Even the application of the high voltage - even before the evaporation or processing of the material began - could lead to a gas outbreak and increase a previously laboriously achieved vacuum from 10 ~ ⁹ to 10 "* Torr so difficult, although the heating for the purpose of degassing was carried out according to the known regulations, could not be seen.

The object of the invention is the evaporation or processing of substances under ultra-high vacuum, thus still to enable at a better vacuum than 10 "Torr.

The object is achieved in that the auxiliary electrode before performing the Evaporation or processing is placed on a positive potential with respect to the cathode, whereby they are heated by electron bombardment from the cathode to a temperature above 600 "C and degassed in the process is that the released gases are pumped out and then the auxiliary electrode on the for Beam shaping required potential switched and the vapor deposition and / or processing of the material is carried out after further pumping to ultra-high vacuum.

By using this simple measure, it is now possible to vaporize or process materials by means of electron beams at pressures of 10 ~ ^fi Torr and below, provided of course that the vacuum system used is suitable for this, ie is sufficiently tight and has pumps which they are able to bring to this vacuum before

the electron beam device started up

So that such an advance could be achieved is very surprising because, according to other experiences with the degassing of vacuum components, especially when it was a question of thin electrode sheets, several hours of heating at a maximum of 450 ° C was completely sufficient. A longer ⁸ bakeout or one at a higher temperature did not bring about any significant improvement. The fact that the invention nevertheless achieved such success can probably be explained by the fact that when electron beam guns are used for vapor deposition or processing of materials, positive ions are still formed even in a high vacuum and the auxiliary electrode is bombarded with these ions so intensely that it is heated to a much higher temperature than the usual degassing temperature. Presumably, further gases are then given off during Betneb, which prevents the maintenance of an ultra-high vacuum. As already mentioned, it was previously believed that one could suppress further gas emission during operation by cooling the auxiliary electrode, but apparently even the most intense heat dissipation from the auxiliary electrode is not enough to prevent the heating of at least the parts of the surface directly exposed to the ion bombardment and that The gas released as a result was sufficient to sensitively limit the quality of the vacuum. In contrast ^ / * W_vtoan temk £ has as result that one lfselektrode to the cooling of the H may even completely without this simplification of the assembly is additionally achieved VerbiHigung, but above all a wesenthche increase operational safety.

It is recommended to electron bombard the auxiliary electrode before evaporation or processing to be carried out until it has heated up to a temperature which is considerably higher than the the maximum temperature of the auxiliary electrode occurring during evaporation or processing.

In most cases of application of the invention, the auxiliary electrode should for the purpose of complete discharge -ur.g to be heated to at least 1000 ° C.

The device for carrying out the invention is characterized in that a circuit with changeover switch is provided around the auxiliary electrode optionally to a positive potential in relation to the cathode or to that for beam shaping the potential required for evaporation or processing. . .

Below is an embodiment of a Elchen facility described in more detail on the basis of the drawing.

Fig. 1 shows the structure of an evaporation gel L a? Device for evaporation medium.

^H ? S? SJS

the exit of
IodeS

Auxiliary elec-

picks up the return line. The high _{i <± well-} known way? through the converter

a ring beam

^^^ Z ^ tm ^ TSc Electric Isoxo the Mo ^ flanged st mtl ^ ^^ ^

with * beze «ctoetj» _(electrical conduction

? «K ^^ g" _ £ _the wall of the Auidampfanende connection with the "^ _{mise] sk} .

age) ^ listening to d «" ^ _q , ^^

i _S Trodes a negative bpaim * _{lAtaodt be} Jolt glegt w. £ uur _{d E} i _Ektro to nen

* ^ ÄS and in the crucible cool _over high-

Cathode acts as an anode. S becomes the heating wire on the material in the crucible, if U ₀ the chip _K & _{thode and} anode and /

. ₅ ^^^ S ^^ tO ^ circuit of the In / « ^s ™ S _erun f _the crucible, 4 the ring ^ ² ^ 'f ^ auxiliary electrode. The hot cathode ka hode ^ and 5 the nm high voltage

is supplied by the secondary _{heating current}

^ ΕΓ ™ ^ «line 11 to f ^^ ßenden high voltage source. _{Electric current} measuring instruments emitted during operation

1 ^^^^^ Γ High voltage is ^read from «ub * ^wa "; ^^ ϊ; .. "^ 14. D'.e ^ K switch J connected,

there

gj ^^ Kί switch

SeS encourages you to do so optionally via the

the ent it ermogl, ^ _{planning laundri} during the comparison

40

.otentia to

the ^about f J
the part of

Jf "S ^ nn or via the to an opposite ^ ^^

^1üeses

20th

while
stung; in
The ^

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It is

against ^

^this _{resistance 18} flow-

with the cathode be _ßinstrument

i. wU.Sd of the via the HiIN resistor 18 flowing portion ^ sod through the instr, The electrical conduction given to the auxiliary electrode

_{Bake out} the auxiliary ^ ^ ^^ ^ _desired

is reached, which, as mentioned, should lie, which the help ^^^^, _ibetr i _eb t accepts. _7weckm äßi _e (as in the embodiment ™ eckmaöig iV ™ _evaporation fen and / or electron beam ώ

? S? SJS; associated electrical circuit, eo In F i g. 1 means 1 the wall of a vacuum evaporation system in which the copper crucible 2, which is provided with a trough for receiving the material to be evaporated and carried by the cooling water and drainage 3 ^P , is arranged. To the generation

serving hollow ring-shaped with a slitter each »

G
while

lying on the ground

_{or his} bearer ^^ ^

The invention is therefore the most important factor

sa S ^ ₈ C _on ^ «*

tension can be placed.

1 sheet of drawings

Claims (5)

Patent claims: 1. A method for operating an electron-emitting cathode and an auxiliary electrode for beam shaping having electron beam generating device for evaporation and / or processing of materials under ultra-high vacuum, characterized in that the auxiliary electrode is placed on a positive potential relative to the cathode before the evaporation or processing is carried out is heated by electron bombardment from the cathode to a temperature above 600 ⁰ C and is degassed so that the released gases are pumped out, and then the auxiliary electrode is switched to the potential required for beam shaping and the vapor deposition and / or processing of the material after further pumping is carried out on ultra-high vacuum. 2. The method according to claim 1, characterized in that that the electron bombardment of the auxiliary electrode before evaporation or processing is carried out until it has heated to a temperature which is above the during the evaporation or processing occurring maximum temperature of the auxiliary electrode. 3. The method according to claim 1, characterized in that the electron bombardment of the Auxiliary electrode is carried out before evaporation or processing until it is heated to at least 1000 ° C. 4. Device for carrying out the method according to claim 1, characterized in that that a circuit with changeover switch is provided to the auxiliary electrode optionally on one opposite positive potential of the cathode or that for beam formation during evaporation to lay the necessary potential for processing. 5. Device for performing the method according to claim 4, characterized by the Design of the circuit in such a way that the auxiliary electrode is optionally at ground potential or negative High voltage can be placed.