GB2180262A

GB2180262A - Forming substances by reactive sputtering

Info

Publication number: GB2180262A
Application number: GB08522056A
Authority: GB
Inventors: Christopher John Howard Wort; Stuart Philip Speakman
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1985-09-05
Filing date: 1985-09-05
Publication date: 1987-03-25
Anticipated expiration: 2005-09-05
Also published as: GB8522056D0; GB2180262B

Abstract

A target material 4 (Ti) is sputtered with a plasma 6 comprising an inert gas, such as argon, thereby to deposit the first species (Ti) on the substrate 1. A beam 8 of the second species (N2) is produced from a reactive gas by means of a Fast Atom Beam gun 9, or an ion gun, which is directed towards the substrate 1 thereby to form a substance (TiN) including the first and second species on the substrate 1. <IMAGE>

Description

SPECIFICATION Methods for forming substances This invention relates to methods offorming substances,and in particularto methods offorming substances on substrates by reactive sputtering.

A previously proposed method forming substances on substrates by reactive sputtering includes cleaning the substrate and a target comprising a component of the substance to be sputtered onto the substrate. After the cleaning has been carried out, a plasmaorargon isformed betweenthetargetand the substrate. The plasma sputters some ofthe target and the substrate. The plasma sputters some of the target material onto the substrate, the remaining component ofthe substance to be formed being obtained from a reactive gas. In this method, the reactive gas is fed into the argon plasma and becomes dispersed throughoutthe argon plasma. The reactive gas becomes ionised and multicomponentgases (for example methane) become "cracked" by virtue of the argon plasma energy.

Such a method has the disadvantage that the reac- tive gas is not selectively positioned within any particular region ofthe argon plasma and this can result in the reactive gas contaminating the target. Further, si nce the extent of ion isation or "cracking " ofthe reactive gas depends on the amount of energy in the argon plasma,the relative deposition rates of the components ofthe substance to be formed are affected and so itis difficultto control the stoichiometry of the substance being formed on the substrate.

The present invention is directed to a method of improving control of the stiochiometry ofthe substance being formed on the substrate.

According to the present invention there is provided a method offorming a substance a first and a second species on a substrate, the method comprising sputtering a target material with a plasma comprising an inert gas thereby to depositthefirst species on the substrate, producing from a reactive gas, by means of a FastAtom Beam gun or ion gun,a beam ofthe second species, and directing the beam ofthe second species into a region ofthe plasma therebyto depositthe second species on the substrate, whereby the substance comprising the first and the second species is formed on the substrate.

The beam ofthe second species is preferably directed into a region ofthe plasma,which region is in the vicinity of the substrate. Alternatively, the beam of the second species may be directed to the substrate.

Thefirstspecies and/orthe second species may comprise a pluralityofelementsorcompounds(and/ or ions thereof), a predetermined ionic species may be selectively directed from the beam of reactive gas by means of a magneticfield.

Methods offorming a substance on a substrate which embody the present invention are advantageous in thatthey improve control of the deposition rate of the first and the second species. Further, a relative deposition rates of a plurality of elements or compounds (and/orionsthereof) contained in the second species can be more easily controlled.

Such methods therefore provide improved stiochi ometric control of the substance formed on the substrate. In addition, such methods improve surface mixing ofthe constituents of the substance to be formed and improve the deposition of substances which comprise constituents having widely differing ionisation energies, for example, titanium nitride.

The invention will now be further described byway of example, with reference to the accompanying drawings in which like reference numerals designate likeelements,and in which: Figure Shows an arrangementforcleaning a substrate and a target; Figure2 shows an alternative arrangement for cleaning the substrate andthetarget, and; Figure3shows an arrangementforforming a substance on the substrate according to a method embodying the present invention.

In Figure 1 ,there is shown an arrangement for cleaning a substrate and a target, the arrangement being located within a vacuum chamber (not shown).

The arrangement comprises a substrate 1 on which a substance, such as titanium nitride, is to be formed.

The substrate 1 is mounted on an electrically powered heater (not shown), and powerfor the heater is supplied via a vacuum feed-through 2. The substrate 1 may be partiallysurrounded by a shield (not shown) which is electrically connected to earth in orderthatthe deposition may be confined to the substrate 1.

At an end of the vacuum chamber remote from the substrate 1, there is provided a radio frequency (or possibly magnetron) electrode 3, which may be water cooled, on which is disposed a target 4 of a substance, for example,titanium which isto be dep osited on the substrate 1. Atarget shield and anode ring 5 is provided around partofthetarget4andthe electrode 3 in orderto define an area oftarget4which is to be eroded.

Before the substance is formed on the substrate 1, the target 4 and the substrate 1 are cleaned in orderto remove surface contaimination. A plasma of an inert gas for example, an argon plasma 6 is struck between the target 4 and a removable shutter 7 which is at ground potential. The argon plasma 6 is derived from an argon gas inlet (not shown) between the electrode 3 and the target shield and anode ring 5, and is blown overthe surface of the target 4which helps to remove surface contamination from the target 4. The argon plasma 6 which is substantially confined between the removable shutter 7 and the target shield and anode ring 5 causesthe surface contamination to move from the target4 to the removable shutter 7.

The substrate 1 is cleaned by being exposed to a beam 8 (which may also be ofargon) derived from a FastAtom Beam (FAB) gun 9 or ion gun. In a case where the beam 8 comprises a charged (ionic) species, the orientation ofthe beam 8 can be changed by means of a magnetic field formed between a pair of magnetic deflection plates 10, and by varying the angle 0 and position h ofthe FEB gun 9.

Figure 2 shows an alternative arrangement in which the FAB gun 9 has a different location from that ofthe FAB gun 9 in Figure 1, and the substrate 1 is moved so that it can be exposed to the beam 8.

After cleaning the target 4 and the substrate 1, the substance is formed on the substrate 1. An example of a suitable arrangementforforming the substance on the substrate 1 is shown in Figure 3. In this arrangement, the FAB gun 9 is positioned in a similarloca tion to that shown in Figure 2 except that the sub strate 1 is positioned to face the target 4. lfthesubst- ance to be deposited is titanium nitride, the target 4 is formed oftitanium and is sputtered to form a first species oftitanium bya plasma 11 of inertgas,for example, argon. The plasma 11 is introduced into the region between the substrate 1 and target 4 in a sim ilar mannerto that described abovewith reference to Figures 1 and 2.The plasma 11 sputters target 4to cause titanium atoms and ions to become deposited on the substrate 1.

The FAB gun 9 is arranged to provide a second species in the form of a beam 12 comprising a mixture of nitrogen atoms and ions. The beam 12 is directed into the argon plasma 11 in the vicinity ofthe substrate 1, and in consequence, some ofthe atoms and ions of nitrogen become deposited on the substrate 1.

By controlling the energy of the plasma beam 12, the direction of orientation ofthe FAB gun 9 (angle 0 ) and the distance of the beam 12 from the substrate 1, the rate of deposition of nigrogen relative to that of titanium can be controlled. Hence, the method described above provides stiochiometric control ofthe substanceformed on the substrate 1.

Although the method offorming a substance on the substrate 1 has been described with reference to forming titanium nitride, other substances may be deposited by the method, for example, metal alloys, mixturesorcompoundscomprising,forexample, oxygen, carbon, hydrogen, nitrogen, flourine or chlorine.

If the beam 12 produced bythe FAB gun 9 comprises unwanted ionic species, these can be deflected from the beam 12 before they reach the substrate 1 by means ofthe magnetic deflection plates 10.

Claims

1. A method for forming a substance comprising a first and a second species on a substrate, the method comprising sputtering a target material with a plasma comprising an inert gas thereby to deposit the first species on the substrate, producing from a reactive gas, by means of a FastAtom Beam gun or an ion gun, a beam ofthe second species, and direct ing the beam ofthe second species into a region of the plasma thereby to depositthe second species on the substrate, whereby the substance comprising the first and the second species is formed on the sub strate.

2. A method according to claim 1 wherein the beam ofthe second species is directed into a region ofthe plasma in the vicinity ofthe substrate.

3. A method according to claim 1 wherein the beam ofthe second species is directed at the sub strate.

4. A method according to anyone of claims 1 to 3 wherein the first species and/or the second species comprises a plurality of elements or compounds, and/or ions thereof.

5. A method according to claim 4 wherein, when a species is an ionic species, the ionic species is/are directed from the beam of reactive gas by means of a magnetic field.

6. A method according to any one of the preced ingclaimswhereintheinertgascomprisesargon.

7. A method substantially as herein before descri- bed with reference to the accompanying drawings.