GB2426252A

GB2426252A - Atomic layer deposition apparatus

Info

Publication number: GB2426252A
Application number: GB0609791A
Authority: GB
Inventors: Nityalendra Singh; Philip Francis Burns
Original assignee: Oxford Instruments Plasma Technology Ltd
Current assignee: Oxford Instruments Plasma Technology Ltd
Priority date: 2005-05-17
Filing date: 2006-05-17
Publication date: 2006-11-22
Anticipated expiration: 2026-05-17
Also published as: GB0511059D0; GB0510051D0; GB0609791D0; GB2426252B

Abstract

An apparatus 1 for processing a target comprising an outer chamber 2 for containing a first environment and an inner chamber 3 positioned within the outer chamber. The inner chamber is arranged when in use to contain the target and a process environment for applying a process to the target. A control system is used to provide the outer chamber with the first environment and the inner chamber with the process environment. The outer chamber can be made of an aluminium alloy and the inner chamber from stainless steel. Heaters 16 and a fan 15 are present for heating and cooling the chambers. The control system may take the form of a gas delivery system comprising a number of nozzles. A method of processing a target within the chamber is also disclosed.

Description

Processing Apparatus and Method The present invention relates to a

processing apparatus for processing a target, together with a method of processing using the apparatus.

Background to the Invention

Various types of processing apparatus are known in order to implement processing treatments upon targets. Such targets typically comprise substrates to which one or more layers or films of material are desired to be applied. The semiconductor industry is a particularly important example where the accurate processing of semiconductor substrates by the deposition of material layers is essential to the fabrication of devices.

One method of depositing thin films is atomic layer deposition (ALD). ALD is a technique that utilizes a phenomenon known as chemisorption to deposit a single monolayer of reactive molecules on a substrate surface. In ALD, individual precursors are pulsed onto the surface of a substrate in a sequential manner, without mixing the precursors in the gas phase. Each individual precursor reacts with the surface to form an atomic layer in a way that only one layer can form at a time. The surface reaction occurs such that the reaction is complete, and permits no more than one layer at a time to be deposited.

There are many problems associated with ALD techniques that greatly affect the cost of operation. For example, the rate of deposition is typically slower than conventional bulk deposition techniques because ALD is a cyclical process. There is also a greater likelihood of contamination and premature/unwanted deposition due to the highly reactive precursor species used in the chemisorption process. Contamination and unwanted deposition causes substantial downtime to clean and prepare the ALD hardware. In addition to the above, ALD chemicals are typically extremely reactive and will lead to extensive undesired CVD side reactions if they coexist in the chamber even at trace levels ALD process chambers (often known as "reactors") generally suffer from "memory effects" and cleaning problems. The memory effects tend to reduce the efficiency of the ALD reactor. Such memory effects are caused by the tendency of chemicals to adsorb on the walls of the ALD reactor and consequentially release from the walls of the ALD reactor on a time scale that is dictated by the adsorption energy and the temperature of the walls. This phenomenon tends to increase the residence time of trace amounts of chemicals in the ALD reactor. As a result, memory effects tend to * 2 increase the purge-time required for removal of chemicals. Thus, a real need exists for an ALD apparatus that minimizes memory effects.

Films grow on all areas of conventional ALD apparatuses that are exposed to the chemicals. In particular, film growth occurs on exposed chamber walls, as well as on the substrate. Film growth on chamber walls deteriorates performance of the ALD apparatus to the extent that the growth of film produces an increased surface area on the walls of the ALD chamber. The propensity of films to grow on the chamber walls scales with the surface area of the chamber walls. Likewise, increased surface area further extends chamber memory effects. An increase in surface area may result from the growth of inferior porous film deposits. Film growth that results in porous deposits can extend the chamber memory by entrapments of chemical molecules inside the pores. Thus, it is essential to the practical functioning of an ALD apparatus that growth of films and deposits is kept to a minimum, and that any film growth that does occur is controlled to deposit high quality films that effectively cover the walls without an increase of surface area or the growth of porosity.

Thus, a genuine need exists for an ALD apparatus that minimizes film growth and provides for the control of any film growth that is allowed to occur Plasma cleaning has been found to be relatively ineffective in ALD systems as it can be only be applied to a small amount of deposits. In addition, in situ plasma cleans allow the realization of a very long time between maintenance/cleaning procedures and in most cases physical cleaning is needed to complement the plasma cleaning.

In general, ALD precursors can be classified into three categories: (a) gases (NH3, N2, H2, He, N20, C12, 03, ..); (b) low vapour pressure compounds < 0.5 Torr at ambient temperature; and (c) high vapour pressure compounds 5 to 40 Torr at ambient temperature. Low vapour pressure compounds are relatively easy to manage as their usage is limited between condensation temperatures and decomposition temperatures.

Most of the low vapour pressure compounds contain H, C or N which can be removed at relatively low temperatures (< 200 degrees Celsius). However, certain compounds contain reducing agents (e.g. Zn), adsorb inside the reaction chamber and can only be removed quickly via thermal means. This implies a high temperature (> 300 degrees Celsius) and in the case of Zn, a temperature of 450 degrees Celsius is needed. One common and relatively cheap precursor for ALD is H20, which is widely used as an oxygen source for the deposition of gate oxides. The complete removal of water from the reaction chamber requires chamber temperatures >200 degrees Celsius as residual water tends to favour gas phase deposition if it is not completely removed..

Therefore, in summary, there is a need for an ALD process having increased deposition rates, an ALD process that reduces the possibility of contamination and unwanted deposition, an ALD hardware that is capable of isolating precursor gases or reactive species prior to deposition, an ALD hardware capable of facilitating a faster rate of deposition, and an ALD hardware capable of reducing cleaning times.

Although many of the above problems have been discussed in terms of atomic layer deposition (ALD), one or more of these problems is also found in other analogous processing apparatus, such as various plasma processing reactors, chemical vapour deposition (CVD) reactors, and so on. There is therefore a need to provide improved apparatus, which can be used for not only ALD but for other processes.

Summary of the Invention

In accordance with a first aspect of the present invention, we provide apparatus for processing a target, the apparatus comprises:- an outer chamber for containing a first environment; an inner chamber positioned within the outer chamber and arranged when in use to contain the target and a process environment for applying a process to the target; and, a control system adapted to provide the outer chamber with the first environment and the inner chamber with the process environment.

We have realised that many of the problems mentioned above can be addressed by the provision of apparatus having an inner chamber within an outer chamber. The inner chamber is the chamber in which the desired process takes place, whereas the outer chamber provides various advantages. The outer chamber acts as an intermediate barrier or environment between the inner chamber and the external environment. It can provide a controlled environment for the pre-processing of process pre-cursors. It can also provide a controlled environment which reduces the constraints upon the material, gas seals and other parameters which would otherwise be required if the inner chamber were directly surrounded by the external environment.

The provision of the outer chamber and its associated first environment allows for the volume of the inner chamber to be minimised. This is extremely advantageous in the reduction of memory effects and other volume related factors.

The provision of such apparatus also allows more than one type of process to be performed within such a chamber, such processes including atomic layer deposition, chemical vapour deposition, and plasma enhanced versions of these. Therefore the chamber design is more versatile since it has advantages with many process types.

The first environment and process environments are each typically gaseous * 4 environments under the control of the control system. Preferably when in use, the control system maintains the pressure of the gas in the first environment of the outer chamber in excess of the gas pressure of the process environment. Each of these pressures is typically less than atmospheric pressure. The advantage of having the higher pressure in the outer chamber is that this reduces the undesirable leakage of precursors or process gases into the outer chamber. Such leakages affect the processes in question and may also causes problems for cleaning of the apparatus. The provision of the outer chamber itself also reduces the required performance or integrity of any seals within the inner chamber since the pressure differential and indeed any temperature differential between the interior and exterior of the inner chamber is reduced with respect to a conventional processing chamber.

The inner chamber is typically fabricated from a material having a higher melting point than that of the outer chamber and indeed each of these chambers is typically operated at an elevated temperature. The outer chamber may be elevated to temperatures of up to about 300 degrees Celsius and is typically formed from an aluminium alloy. In contrast, the inner chamber is typically formed from a higher melting point material such as stainless steel, nickel 201, inconel, hastelloy, NiCu, and other high temperature alloys. The inner chamber is therefore preferably formed from a corrosion resistant material.

Since the outer chamber is typically operated at an elevated temperature, it may further comprise cooling piping or ducts, these being either attached to or within the walls of the outer chamber and through which a cooling fluid is provided so as to cool the walls of the chamber. Heat transfer fluids may be used to regulate the temperature of the outer chamber. This provides for a first environment at a higher temperature than that of the walls themselves.

Although natural cooling can be used in order to cool the inner chamber (following the completion of a process) and indeed the outer chamber, preferably the outer chamber is provided with a fan so as to cool the inner chamber and accelerate its cooling. The fan is advantageous since an ability to ramp the apparatus from ambient to a processing temperature and back again at a high speed is beneficial for productivity.

Typically the inner chamber is formed from two or more separable parts so as to allow access to the inner chamber interior. One or more of such parts, or indeed the entire inner chamber, is preferably removable from the interior of the outer chamber such that it may be maintained, cleaned, or indeed replaced with a different inner chamber, for example, for the provision of different a process.

In some cases, the inner chamber comprises upper and lower parts in which the * 5 lower part acts as a holder for the target. The target is typically a substrate such as a semiconductor substrate. This lower part may therefore act as a susceptor. Preferably this also contains pin lifts for handling targets such as semiconductor wafers.

A typical volume for the interior of the inner chamber is about 0.2 litres.

Preferably, one or more parts of the inner chamber may be moveable or adjustable so as to provide a variable volume within the inner chamber. A typical volume range for atomic layer deposition is 0.2 to 1 litre. This may be achieved in a number of ways. On such method is to provide bellows formed from high temperature and corrosion resistant materials. Such bellows are typically formed from flat, edge-welded rings. The moveable part(s) of the inner chamber may be mounted to an inner surface of the outer chamber such as the outer chamber roof.

Typically each of the outer and inner chambers is heated using a heating device.

A common device may be used to heat each chamber, or the device itself may comprise dedicated sub-devices. Typically such a heating device comprises a high power (greater than 5 kVV) tubular heater formed from refractory materials such as silicon carbide. The device may also comprise radiant heaters such an infrared emitters or halogen lamps, or other forms of heater such as inductive heaters. The inner chamber may be heated by such heaters up to a temperature of about 1000 degrees Celsius. The outer chamber may also be heated from heat transfer from the inner chamber at high temperatures. This is somewhat dependent upon the desired process and the material from which the inner chamber is fabricated.

Where a radiant heater is used, the inner chamber may be anodised in order to improve the absorption of the radiant heat. Typically with the apparatus described and appropriate materials, the inner chamber can be heated from ambient temperature to about 600 degrees Celsius in about 30 minutes.

The control system is operative to provide the first and process environment within the respective chambers. Typically the control system comprises a gas delivery system. This is typically arranged to supply at least one gas to the outer chamber so as to form the first environment, It is also arranged to supply at least one gas to the inner chamber so as to form the processing environment. The gas delivery system may be a common system or dedicated sub-systems. In order to maintain the environment(s), the control system preferably further comprises a pumping system which is adapted to cooperate with the gas delivery system so as to pump out the inner and the outer chambers. Again, a common or separate sub-systems may be provided. Therefore, it will be appreciated that the gas delivery and pumping systems may be separate systems for the outer and inner chambers respectively, or they may be combined systems. * 6

The gas delivery system may use a conventional means such as a "shower head" to apply the process gases to the inner chamber, these gases being typically "precursors". The gas delivery system may also comprise one or more injectors, each injector opening into the inner chamber so as to allow the direct injection of process gases into the inner chamber. The choice is dependent upon the process in question and in particular upon the types of precursor chosen. Since the outer chamber is typically at an operational temperature between that of the inner chamber, and ambient temperature, this may be used to pre-heat precursors and prevent unwanted condensation, a precursor manifold within the outer chamber can be used for this purpose.

The gas delivery system may also comprise a flow uniformity nozzle, such a nozzle comprising: a housing; an inlet region of the housing, having a first width, for the receipt of a gas; an outlet region of the housing, having a second width of greater width than the first width, for outputting the gas; guide walls of the housing to contain the gas in an expansion region between the inlet and outlet regions; and one or more guide vanes positioned in the expansion region; wherein the guide walls and vanes are arranged to guide the gas through the expansion region such that, at the outlet region, the output gas flow is substantially uniform across the width of the outlet region.

Such a nozzle is preferably used to provide a laminar flow of gas across the surface of a target. It will be appreciated that such smooth, nonturbulent gas flow is particularly beneficial for certain processes such as ALD, CVD and plasma enhanced ALD and CVD. The gas in question therefore flows from an inlet region, which may comprise an inlet port or pipe. The walls of the housing are preferably tapered or curved in the direction of the gas flow within the expansion region between the inlet and outlet regions. The one or more vanes, similarly may have a planar or curved surfaces along the direction of gas flow, this direction being normal to the width dimension. The walls and each vane therefore typically fan out in the expansion region and can be thought of as taking the appearance of a "rake" when viewed from above. The height of the housing in each of the inlet, expansion and outlet regions is preferably much less than at least the width of the outlet region. The height to width ratio is typically in the range 0.01 to 0.02. The ratio of the distance between the inlet and outlet regions to that of the width of the outlet region is about 4 to 1 or less. * 7

It is beneficial to provide two such flow uniformity nozzles, one acting as an inlet and one as an outlet. These are typically provided upon opposed sides of a region containing the target within the inner chamber. The nozzles and walls can therefore be formed from the walls of the inner chamber. The nozzle on one side acts in the reverse manner to that on the other, so as to provide flow symmetry and therefore ensures the smooth laminar flow across the substrate. It should be noted that the arrangement in this case is typically involved with a target having a substantially planar surface and the direction of gas flow is in a manner which follows the plane of the surface. This is quite different to many known process apparatuses in which the process gases are typically provided in a direction normal to the surface of the substrate target.

The apparatus may further comprise an inlet manifold for the supply of one or more process gases to the inner chamber, for example on the entrance side of the flow uniformity nozzle, the manifold having an internal expansion volume shaped so as to allow the adiabatic expansion of the process gas prior to entry into the inner chamber.

Although such a manifold and nozzle(s) are described with reference to the inner chamber of the present invention, similarly the manifold and/or nozzle(s) may be used independently to provide advantage in conjunction with other reactor designs, including

prior art designs.

It is also envisaged that the inner chamber at least could be provided with a bias system so as to provide the walls of the inner chamber with an electrical bias. This might be used in a plasma process or in the control of ions involved in the process.

In accordance with a second aspect of the present invention, we provide a method of processing a target using apparatus according to the first aspect of the invention, the method comprises: positioning the target within the inner chamber; and operating the control system so as to provide the process environment within the inner chamber and the first environment within the outer chamber, wherein the position of the target within the process environment of the inner chamber causes the target to be processed.

Typically such as method further comprises heating each of the inner and outer chambers, the inner chamber being heated to a temperature in excess of that of the outer chamber, wherein such a temperature may be thought of as a process temperature. The method also further comprises supplying one or more gases to the outer chamber and supplying one or more process gases to the inner chamber, the gas pressure of the outer chamber being in excess of that of the inner chamber. The gas or gases supplied to the outer chamber may be a substantially inert gas. The method may * 8 also further comprise a step of cleaning the inner chamber at least, following the removal of the target at the end of the process. The cleaning may be implemented by operating the inner chamber at an elevated temperature.

The method may be used as part of at least one of a plasma process, chemical vapour deposition process, atomic layer deposition process, a nanodeposition process or a thermal annealing process.

Brief Description of Drawings

Examples of an apparatus and method according to the present invention is now described with reference to the accompanying drawings, in which:Figure us a block diagram of the basic components of apparatus according to

the examples;

Figure 2a shows inner and outer chambers, partly in section according to a first

example;

Figure 2b shows a second example; Figure 2c shows a gas delivery manifold according to the second example; Figure 3 shows the use of uniform gas flow nozzles; Figure 4 shows the path of the gas using such nozzles; and, Figure 5 is a flow diagram of a method of using the apparatus of the examples

Description of Preferred Examples

Figure 1 is a schematic representation of apparatus of a thin film deposition system according to a first example of the invention. The example apparatus is generally indicated at 1. This comprises an outer chamber 2 within which is positioned an inner chamber 3. A gas delivery module 4 provides gases to each of the chambers 2, 3. A pumping module 5 vents each of the chambers 2, 3 so as to extract the gases including any gases created as a result of processing within the inner chamber 3. A controller 6 controls the overall process in each of the chambers 2, 3 and the two modules 4, 5. The controller typically comprises a computer processor or dedicated electronics such as a Programmable Logic Controller (PLC). The controller 6, and the modules 4, 5, collectively act as a control system for the apparatus 1.

In general, the gas deliver module 4 comprises source gases, valves and piping, massflow controllers, and an inlet delivery manifold which can be in the form of a showerhead. In ALD, the source gases are vapours obtained from liquid precursors such as halides, organometalics, alkoxides, which are held in containers and delivered into chamber using bubblers or local vapourizers. The radical generating gases such as H2, N2, NH3, .., are delivered into the chamber using a remote plasma source such as an inductively coupled plasma source. Fast pulsing valves are used to deliver fast vapour pulses into the reaction chamber (inner chamber 3). The processing chamber 3 consists of a heated electrode on which a substrate is placed prior to receiving vapour pulses.

The pumping module consists of pumps and throttle valves to quickly remove precursors from the reaction chamber.

The first example of the apparatus I is shown in more detail in Figure 2a. This shows the chambers 2, 3, together with associated apparatus, partially in section. The inner chamber 3 is provided inside the outer chamber 2. It will be noted that the inner chamber 3 comprises two main separable parts, these being an upper part 3a and a lower part 3b. The inner chamber 3 takes a somewhat oblate form and is arranged to be able to accommodate a 200mm diameter circular substrate (or 200mm square sided substrate).

The outer chamber 2 contains an internal volume 7 which is filled in use by nitrogen gas, this being introduced into the volume 7 at one or more points through the walls of the outer chamber 2, for example at the position indicated by the arrow 8. The nitrogen is introduced by the gas delivery module 4 using a suitable conduit. The pumping module 5 removes the nitrogen from the volume 7 via an exhaust port 9 at the centre base of the apparatus as shown in Figure 2a.

In this case, the pumping module 5 comprises a separate vacuum pump for the pumping of the internal volume 7 of the outer chamber 2. The gas delivery module 4 and pumping module 5 are controlled by the controller 6 so as to create an environment of nitrogen in the internal volume when the apparatus is in use.

The walls of the outer chamber in this example contain one or more cooling channels in the outer parts of the walls. Water is caused to flow through these channels so as to cool the walls. In the present case the outer chamber 3 is formed from aluminum. The cooling using the water is controlled so as not to condense any process gases or otherwise to interfere with the heating system used in the apparatus (as described below).

The outer chamber 2 is also provided with a lid 10 which can be removed so as to allow access to the interior of the chamber. The outer chamber lid is provided with high temperature gas seals. A lift mechanism 11 is mounted to the lid of the chamber the lower part of the lift mechanism being mounted to the upper part 3a of the inner chamber 3. This lift mechanism 11, under the process of the controller, or indeed manually, can be used to vary the internal volume of the inner chamber 3 by altering the * 10 spatial separation between the inner parts 3a and 3b. Nevertheless a gas seal is maintained between parts 3a and 3b by the provision of bellows so as to allow contact between the opposed surfaces of the parts 3a and 3b, whilst also allowing the internal volume of the inner chamber to be altered in accordance with the wishes of the user of the apparatus. This is not shown in Figure 2a.

A fan 15 is also shown in Figure 2a, this also being mounted to the lid of the outer chamber 2. The fan 15 is also operable by the controller 6 so as to provide cooling of the inner chamber 3. The fan can therefore be used to cool down the inner chamber from a processing temperature to ambient temperature prior to the removal of the lid (and part or all of the inner chamber) from the apparatus. The fan may be used therefore in cooling the inner chamber prior to a cleaning or maintenance operation.

A slit valve is also formed in a side wall of the outer chamber 2, so as to provide access for an arm (not shown in Figure 2a) which is operable to deliver and retrieve a substrate (target) from a processing position within the lower part 3b of inner chamber 3.

Such a substrate may be a silicon wafer, quartz, glass, lI-VI material, Ill-V material, GaAs, plastics, and so on. The substrate can also be fed into a processing position on a carrier plate.

Turning now to the details of the inner chamber 3, this is made from a high temperature and corrosion resistant material which in the present case is stainless steel.

Each of the parts 3a and 3b of the present example is formed from stainless steel and is of approximately similar size such that the inner chamber 3 has a "clam shell" design. In this case each of the upper and lower parts 3a, 3b is removable and replaceable readily by another inner chamber 3. In the present case, the inner chamber can be heated to a temperature of about 1000 degrees Celsius.

The inner chamber in the present example is heated via internal radiant heaters illustrated at 16 in Figure 2a. These are attached to a support structure surrounding the exterior of the inner chamber. Such radiant heaters are provided for each of the upper and lower parts 3a, 3b. Infrared lamps are used to perform this function. This also may be achieved by the use of tubular heaters embedded in the walls of the inner chamber to provide more uniform heating. The infrared lamps 16 are placed close to the inner chamber surface so as to distribute the heat evenly within the inner chamber. A temperature sensor, such as a thermocouple may also be embedded in the lower part 3b so as to monitor the temperature of the chamber, and therefore indirectly, of the substrate target. This can be used in a feedback loop to control the power supplied to the heaters 16 so as to maintain or control the temperature of the substrate in accordance with the desired process. O 11

In this example the inner chamber can be heated to about 600 degrees Celsius in about 30 minutes using the heaters. This temperature may be maintained at about 600 degrees Celsius +1- 1 degrees Celsius for a period of about 24 hours in an envisaged process.

Since the inner chamber is heated externally by radiant heaters, the outer surface of the chamber is anodized so as to enhance the absorption of the radiant heat.

In this example, the inner chamber is held in place by vacuum fittings and flanges.

Vacuum flanges can be used to connect to the gas delivery module 4 and pumping module 5 in order to supply the precursors for example. Coaxial tubing and flanges can also be used for this. A precursor supply conduit is shown at 40, with a corresponding exhaust conduit being shown at 41 in Figure 2a.

Figure 3 shows details of the interior of the inner chamber.

In this case, a uniform gas flow system is provided using gas flow uniformity nozzles. Referring to Figure 3, a circular planar substrate is shown at 20 (with 21 showing an alternative optional square planarsubstrate). The inner chamber walls are shown at 25, these also forming the housing for the uniform gas flow nozzles upon either side of the substrate. An inlet nozzle is generally shown at 26 whereas an outlet nozzle is generally shown at 27. The inlet nozzle 26 is formed by the walls of the chamber 25, and an inlet region 28 representing the end of an input gas conduit for example, together withvanes3l.

In the present example of the inlet nozzle 26, an end waIl 29 contains the input port 28 for the inlet gas. Tapered waIls 30 of the inner chamber 3 diverge from the end wall 29 in an expansion region, these being connected to opposed parallel walls 25 of the inner chamber, upon either side of the substrate 20, 21. The vanes 31 take various forms according to their angle with respect to the end wall 29. However, these generally have a short end portion curving into an elongate, approximately linear section, the distal end of which is again curved in the opposite direction in a final short section, terminating in the outlet region. The vanes 31 and walls 30 therefore cause the gas to flow and expand smoothly and uniformly such that a uniform gas profile is provided across the substrate as a function of distance between the opposed walls 25 on either side of the substrate. An outlet port 32 is provided for the outlet nozzle 27, with similar tapered walls and vanes, these being symmetrical to those on the opposite side of the substrate.

Figure 4 shows the gas flow distribution as small arrows 35, and it can be seen that a laminar and smooth flow with a uniform distribution across the figure (in a direction vertically in Figure 4) is provided by the ports 26, 27. A smooth flow is therefore provided by the gas flow uniformity nozzles which produces parallel streamlines to S 12 develop laminar flow across the substrate. This provides complete surface overage of the substrate 20,21 as is particularly desirable for a process such as ALD. The outlet port 32 is connected to the pumping module 5, the pumping module and gas delivery module 4 thereby providing a process environment defined by the gas as shown in Figure 4 as heated by the heaters 16 to a processing temperature. It will be appreciated for ALD that the gas delivery module and pumping module are operable in use so as to provide different process gases in sequence in accordance with the ALD process.

The gaseous precursors are delivered via fast pulsing valves into the chamber as part of the gas delivery module. " inch pipes are used which terminate in a 1 inch tube feeding the nozzle 26. The arrangement of the nozzle as described earlier produces an improved gas flow velocity profile across the surface of the substrate. The vanes can be screwed down into the tapering part of the nozzle 26. The vanes can therefore be consumable and replaced after becoming coated by the process. The outlet part of the nozzle has dimensions 250 mm in width and 5 mm in height. The ratio of the length of the nozzle to the diameter is between 2 to I and 4 to 1 so as to provide uniform coverage across 200 mm substrates. The upper part 3a of the inner chamber can be thought of as a "blade" to proportion the precursor flow stream as required to provide uniform growth over the substrate.

Referring to Figure 3, it will be appreciated that the volume of the inner chamber 3 is rather smaller than in conventional apparatus. The volume is adjusted to provide a minimal volume, for example to 0.2 litres or less, for fast removal of precursor materials from the reaction region. This is achieved by using the lift mechanism 11. The moveable upper part of the chamber ideally maintains a fluid tight or low leakage seal when in a closed position. Any leakage into the outer chamber is prevented by differential pressure provided by the higher vacuum of the outer chamber 2. This allows even a metal-to-metal seal to be used which provides for high temperature operation.

Because of the small volume of the reaction zone in comparison with known systems, less gas (whether a deposition gas or a purge gas) is necessary to be used in the chamber. Therefore the throughput of the chamber is greater and waste is minimised due to the small amount of gas used which reduces the cost of the operation as a whole.

The upper part 3a is raised during substrate transfer and lowered after the substrate is position on the lower part 3b. Prior to processing, the upper 3a and lower 3b parts of the inner chamber 3 may be removed to enable pumping to base pressures of less than 10 to 10.6 Torr using turbo-molecular pumps (greater than 400 litres per second) with a backing pump, each of these forming part of the pumping module 5. The pumping module may comprise of a fast throttling valve, a gate valve, a turbomoleuclar * 13 pump, a heated foreline, foreline traps (this may be heated or cooled and are dependent on the precursors), a high capacity backing pump (a dry pump or a roots/rotary stack).

The possibility to pump both inner and outer chamber using the same pumping configuration is beneficial. Prior to processing, both the chambers may be prepared by pumping using turbo molecular pumps (>400 litres/sec) to achieve a base pressure of i0 to 106 Torr in the outer and inner chamber. A substrate is loaded into the inner chamber and the inner chamber parts 3a and 3b are then moved together to isolate the substrate from the outer chamber and to provide minimal volume for processing. At this stage, the inner chamber may be pumped separately or using the above mentioned pumping module 5. The turbo pump may be bypassed during processing and pumping is only performed using the backing pump. The outer chamber is pumped using a different pumping line similar to pumping module 5. The outer chamber is kept at a higher pressure by flowing a controlled flow of inert gas such as nitrogen or argon during processing.

In the present example, the lower part 3b of the inner chamber is the wafer support and also comprises a minimal volume pin-lift assembly 36 as shown in Figure 2a. This has a 3-pin design and is operated using a pneumatic control to raise and lower the substrate. Then the volume is pumped back into the inner chamber pumping line to eliminate wafer movement during processing.

Figure 2b shows an alternative apparatus 1 when viewed in partial crosssection.

In this case, the heaters 16 provided in the first example are replaced by tubular heaters 16'. The tubular heaters 16' are embedded in the walls of the inner chamber. One heater (>3.4kW) is embedded in the upper part 3a of the inner chamber and a second heater (also >3.4kVV) is embedded in the lower part 3b of the inner chamber. Note that for high temperature processing, for which the temperature is in excess of about 600 degrees Celsius, multizone heaters may be used.

In this second example, an inlet manifold 70 is provided in the form of a gas injection manifold. An inductively coupled plasma (ICP) source may be mounted to this injection manifold at its proximal end. The role of the manifold 70 is to avoid the mixing of precursor gases such as trimethyl aluminium TMA and H20 before the reaction (inner) chamber. This eliminates any chemical vapour deposition reactions, which are like to occur. The manifold also provides separate atomic layer deposition precursors to the inner chamber. A third advantage is that it allows control of the adiabatic expansion of precursor gases which minimizes particle formation, for example by condensation.

The apparatus in the second example, and particularly the manifold 70, is arranged such that the precursor delivery lines feed into an intermediate volume within * 14 the manifold prior to reaching the reaction phase with an inner chamber. The geometry of the manifold, in the form of an expanding channel, allows less of an adiabatic expansion of the gas flowing through it. This in turn helps control the temperature of the gas. As will be appreciated, a sudden adiabatic expansion of a gas flowing through the manifold would decrease the temperature of the gas and result in condensation of the gas, leading to particle formation. By reducing the adiabatic expansion of the gas, more heat may be transferred to or from the gas and thus, the temperature of the gas may be more easily controlled. The gradually expanding channel within the injector manifold 70 as a function of the gas flow direction, may comprise one or more tapered inner surfaces. These may be tapered straight surfaces, concave or convex surfaces, or combinations thereof. Such surfaces may also be provided in a series of sections having different surface geometries such as a portion tapered and a portion non-tapered.

Figure 2c shows the gas delivery manifold 70. One quarter to one inch gas lines 80 terminate into the manifold. The manifold is connected to the inlet nozzle 26 formed by the walls 25 of the inner chamber, an inlet region 28 representing the end of an input gas conduit for example, together with vanes 31. The manifold 70 may be integrated with the lower part 3b of the inner chamber.

On the outlet side of the inner chamber 3, it will be noted in Figure 2b that bellows 75 are provided so as to allow movement of the inner chamber with respect of the outer chamber wall, and yet nevertheless provide a gas seal.

The method of using the apparatus according to either example, is now briefly described in association with Figure 5. In Figure 5 at step 200, the inner chamber parts 3a and 3b are separated so as to allow the loading of a substrate. The inner chamber may be already heated to processing temperature at this step. During this time, the environment (at vacuum) in the outer chamber is maintained by the control system comprising the controller, gas delivery module 4 and pumping module 5. At step 201, a substrate is loaded using a loading arm into a position within the lower part of the inner chamber 3b. At step 202 the open inner chamber and outer chamber are pumped down to base pressure using pumping module 5. At step 203 the upper part of the chamber and lower part are brought together so as to close the inner chamber. At step 204, the inner chamber is flushed, heated and evacuated to a predetermined vacuum pressure.

At step 205, the desired process is performed upon the substrate by the provision of gaseous precursors from the gas delivery module 4 which react with the substrate.

Such precursor gases are provided sequentially, with optional intermediate flushing. At step 206, the processed substrate is removed with the arm. Steps 201 to 206 are repeated for processing other substrates until a predetermined critical thickness is * 15 reached at step 207. The critical thickness in an ALD process may vary from 10's of nanometers to 100 micrometers. At step 208 optional cleaning and/or maintenance operations are performed. Where appropriate, plasma cleaning at step 209, is performed using a halogen mixture comprising of chlorine, fluorine compounds. Plasma cleaning may be performed at process temperatures or lower temperatures using an intermediate cooling step 210. Step 210 may also involve cooling down of both the inner and outer chambers from process temperature to room temperature for maintenance using the integrated fan 15. At step 211, the inner chamber is removed for physical cleaning (grit blasting, ultrasonic cleaning,...) and replaced with another one to continue processing of substrates.

The invention described above therefore provides a number of distinct advantages over prior art apparatus and methods. It should be noted for example that the frequency of cleaning between the inner and outer chambers is of the ratio of about to I for a cleaning film thickness of 25 micrometres.

In summary therefore, the apparatus described provides a new design of processing chamber having a number of benefits and improvements, such as: 1) A "chamber within chamber" design; 2) The inner chamber is the processing chamber; 3) The inner chamber is a hot wall chamber, capable of operating up to 1000 degrees Celsius; 4) The inner chamber reaction volume is variable, a minimum reaction volume for processing of substrates is about 0.2 I; 5) The inner chamber is sealed from the outer chamber 6) The inner chamber is made from high temperature and corrosion resistant material; 7) The inner chamber is light weight and is easily removed from the outer chamber for maintenance and cleaning; 8) The inner chamber is capable of being cooled rapidly - from 600 degrees Celsius to 20 degrees Celsius in less than 30 minutes; 9) The outer chamber is the higher pressure chamber and is capable of operating up to about 300 degrees Celsius; 10) The gas delivery nozzle is in a horizontal arrangement and is designed with flow guides (walls and vanes) to split the gas flow evenly into laminar flow streamlines to distribute gas flow evenly on the substrate in the reaction volume of the inner chamber; and, 11) Multiple thin film processing can be carried out with this hardware including * 16 Atomic Layer Deposition, Chemical Vapour Deposition, Plasma enhanced ALD and Plasma enhanced CVD, Plasma enhanced reactive ion etching, inductively coupled plasma deposition and etching. * 17

Claims

1 Apparatus for processing a target, the apparatus comprising:- an outer chamber for containing a first environment; an inner chamber positioned within the outer chamber and arranged when in use to contain the target and a process environment for applying a process to the target; and, a control system adapted to provide the outer chamber with the first environment and the inner chamber with the process environment.

2. Apparatus according to claim 1, wherein first and process environments are gaseous environments and wherein control system is adapted to maintain the pressure of the gas in the first environment in excess of that of the process environment.

3. Apparatus according to any of the preceding claims wherein the inner chamber is fabricated from a material having a higher melting point than that of the outer chamber.

3. Apparatus according to any of the preceding claims, wherein the outer chamber is fabricated from an aluminium alloy.

4 Apparatus according to any of the preceding claims, wherein the outer chamber has walls comprising ducts through which a cooling fluid is passed when in use

5. Apparatus according to any of the preceding claims, wherein a fan is provided within the outer chamber for cooling the inner chamber.

6. Apparatus according to any of the preceding claims, wherein the inner chamber is fabricated from a high melting point and corrosion resistant material.

7. Apparatus according to any of the preceding claims, wherein the inner chamber is formed from two or more parts so as to allow access to the inner chamber interior.

8. Apparatus according to claim 7, wherein one or more of the parts of the inner chamber are removable from the outer chamber.

9. Apparatus according to claim 7 or claim 8, wherein the inner chamber comprises upper and lower parts and wherein the lower part acts as a holder for the target.

10. Apparatus according to any of the preceding claims wherein the apparatus comprises a heating device so as to heat at least the inner chamber.

11. Apparatus according to claim 10, wherein the heating device comprises a radiant heater and wherein the inner chamber is anodised to enhance the heating effect.

12 Apparatus according to any of the preceding claims, wherein the apparatus is adapted such that the inner chamber can be heated from ambient temperature to about 600 degrees Celsius in about 30 minutes. * 18

13. Apparatus according to any of claims 10 to 12, wherein the control system is adapted to heat the inner chamber to a temperature in excess of that of the outer chamber.

14. Apparatus according to any of the preceding claims, wherein the control system comprises a gas delivery system.

15. Apparatus according to claim 14, wherein the gas delivery system is arranged to supply at least one gas to the outer chamber so as to form the first environment.

16. Apparatus according to claim 14 or claim 15, wherein the gas delivery system is arranged to supply at least one gas to the inner chamber so as to form the processing environment.

17. Apparatus according to any of claims 14 to 16, wherein the control system further comprises a pumping system.

18. Apparatus according to claim 17, wherein the pumping system is adapted to cooperate with the gas delivery system so as to pump one or more gases from the outer chamber.

19. Apparatus according to claim 17 or claim 18, wherein the pumping system is adapted to cooperate with the gas delivery system so as to pump one or more gases from the inner chamber.

20. Apparatus according to any of claims 14 to 19, wherein the gas delivery system comprises one or more injectors, each injector opening into the inner chamber so as to allow direct injection of process gases into the inner chamber.

21 Apparatus according to any of claims 14 to 20, wherein the gas delivery system comprises a flow uniformity nozzle, the nozzle comprising: a housing; an inlet region of the housing having a first width for the receipt of a gas; an outlet region of the housing having a second width of greater width than the first width, for outputting the gas; guide walls of the housing to contain the gas in an expansion region between the inlet and outlet regions; and one or more guide vanes positioned in the expansion region; wherein the guide walls and vanes are arranged to guide the gas through the expansion region such that, at the outlet region, the output gas flow is substantially uniform across the width of the outlet region.

22. Apparatus according to claim 21, wherein the walls are tapered or curved in the direction of gas flow within the expansion region.

23 Apparatus according to claim 21 or claim 22, wherein the one or more vanes have planar or curved surfaces along the direction of gas flow normal to the width dimension.

24. Apparatus according to any of claims 21 to 23, wherein the walls and each vane fan out in the expansion region.

25. Apparatus according to any of claims 21 to 24, wherein the height of the housing in the inlet, expansion and outlet regions is much less than the width of the outlet region.

26 Apparatus according to claim 25, wherein the height to width ratio is in the range 0.01 to 0.02.

27. Apparatus according to any of claims 21 to 26, wherein the ratio of the distance between the inlet and outlet regions, to the width of the outlet region is 4:1 or less.

28. Apparatus according to any of the preceding claims, wherein two flow uniformity nozzles, each according to any of claims 21 to 27, are provided upon opposed sides of a region containing the target within the inner chamber, the nozzle on one side acting in a reverse manner to that on the other side such that one nozzle provides a uniform gas flow of one or more process gases across the target and the other receives the one or more gases and exhausts them from the inner chamber.

29. Apparatus according to any of the preceding claims, wherein the inner chamber has one or more moveable walls so as to provide a variable volume.

30. Apparatus according to any of the preceding claims, further comprising a bias system for applying an electrical bias to the inner chamber.

31. Apparatus according to any of the preceding claims, further comprising an inlet manifold for the supply of one or more process gases to the inner chamber, the manifold having an internal expansion volume shaped so as to allow the adiabatic expansion of the process gas prior to entry into the inner chamber.

32. A method of processing a target using apparatus according to any of the preceding claims, the method comprising:- positioning the target within the inner chamber; and operating the control system so as to provide the process environment within the inner chamber and the first environment within the outer chamber, wherein the position of the target within the process environment of the inner chamber causes the target to be processed.

33. A method according to claim 32, further comprising heating each of the inner and outer chambers, the inner chamber being heated to a temperature in excess of that of the outer chamber.

34. A method according to claim 32 or claim 33, further comprising supplying one or more gases to the outer chamber and supplying one ore more process gases to the S 20 inner chamber, the gas pressure of the outer chamber being in excess of that of the inner chamber.

A method according to claim 34, wherein the gas supplied to the outer chamber is a substantially inert gas.

36. A method accorchrig to any of claims 32 to 35, wherein the processing method is at least one of a plasma process, a chemical vapour deposition process, an atomic layer deposition process, a nanodeposition process or a thermal annealing process.