Patent Description:
The described reactor structure can however be better understood, for example, by considering the <CIT>.

In chemical deposition methods, such as atomic layer deposition (ALD), plasma can be used to provide required additional energy for surface reactions. The use of a plasma source, however, may cause certain requirements or specific problems for the deposition reactor. One such problem is that reactive species in plasma have a limited lifetime. The documents <CIT> and <CIT> disclose a plasma system having a high frequency inductively coupled plasma jet source. The document <CIT> disclose a method and system to obtain a high power density plasma. The document <CIT> discloses a remote plasma generation apparatus. The document <CIT> discloses an apparatus and method for treating a substrate with an excited species removed from a plasma.

It is an object of certain embodiments of the invention to cope with the limited lifetime of plasma or at least to provide an alternative to existing technology.

According to a first example aspect of the invention there is provided a method according to claim <NUM>, comprising:.

In certain embodiments, the constriction is in the form of a straight channel. In certain embodiments, the constriction forms a straight channel having a non-changing diameter. In certain embodiments, the constriction forms a straight channel having a non-changing diameter over its length. In certain embodiments, the constriction forms a straight channel of a cylindrical shape. In certain embodiments, the constriction forms a straight channel having a length along which the channel diameter is constant. In the embodiments, the constriction is a tubular item or of a tubular form. In the embodiments, the constriction reduces a cross-sectional flow area of the in-feed line by at least <NUM> %.

In certain embodiments, the constricted cross-sectional flow area is <NUM> % of the cross-sectional flow area before the constriction, or less. In certain preferable embodiments, the constricted cross-sectional flow area is <NUM> % of the cross-sectional flow area before the constriction, or less. In certain preferable embodiments, the constricted cross-sectional flow area is <NUM> % of the cross-sectional flow area before the constriction, or less. In certain preferable embodiments, the constricted cross-sectional flow area is <NUM> % of the cross-sectional flow area before the constriction, or less. In certain preferable embodiments, the constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction. In certain preferable embodiments, the constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction. In certain preferable embodiments, the constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction.

The term "cross-sectional flow area before the constriction" herein means the cross-sectional flow area of the in-feed line (flow channel) immediately preceding the constriction (e.g., the cross-sectional flow area of the plasma source tube).

In certain preferred embodiments, the flow rate of plasma gas entering the plasma formation section is within the range from <NUM> sccm to <NUM> sccm, preferably from <NUM> sccm to <NUM> sccm.

In certain preferred embodiments, a plasma power within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> to <NUM> W, or from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W, yet more preferably from <NUM> W to <NUM> W is applied to the plasma formation section.

In certain preferred embodiments, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied.

In certain preferred embodiments in which the uniformity of a deposited thin film is to be optimized, the duration of a plasma pulse, i.e., duration of the plasma formation period is within the range from <NUM> seconds to <NUM> seconds, the flow rate of plasma gas is within the range from <NUM> sccm to <NUM> sccm, preferably from <NUM> sccm to <NUM> sccm, and optionally the plasma power is within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W. In certain preferred embodiments in which film quality in terms of low leakage current through the film is to be optimized, the duration of the plasma formation period is within the range from <NUM> seconds to <NUM> seconds, the flow rate of plasma gas is within the range from <NUM> sccm to <NUM> sccm, preferably from <NUM> sccm to <NUM> sccm, and optionally the plasma power is within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W.

In certain preferred embodiments, a purge period of a non-plasma precursor with a duration within the range from <NUM> second to <NUM> seconds, more preferably from <NUM> seconds to <NUM> seconds, is applied.

In certain preferred embodiments in which the uniformity of a deposited thin film is to be optimized, the duration of the purge period of a non-plasma precursor is within the range from <NUM> seconds to <NUM> seconds, the flow rate of plasma gas is within the range from <NUM> sccm to <NUM> sccm, preferably from <NUM> sccm to <NUM> sccm, and optionally the plasma power is within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, and optionally the plasma formation period has a duration within the range from <NUM> seconds to <NUM> seconds. In certain preferred embodiments in which film quality in terms of low leakage current through the film is to be optimized, the duration of the purge period of a non-plasma precursor is within the range from <NUM> seconds to <NUM> seconds, the flow rate of plasma gas is within the range from <NUM> sccm to <NUM> sccm, preferably from <NUM> sccm to <NUM> sccm, and optionally the plasma power is within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W, and optionally the plasma formation period has a duration within the range from <NUM> seconds to <NUM> seconds.

In certain preferred embodiments, the flow rate of plasma gas entering the plasma formation section is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W is applied to the plasma formation section, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> second to <NUM> seconds is applied.

In certain preferred embodiments, the flow rate of plasma gas entering the plasma formation section is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, is applied to the plasma formation section, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> seconds to <NUM> seconds is applied.

In certain preferred embodiments, the flow rate of plasma gas entering the plasma formation section is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W is applied to the plasma formation section, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> seconds to <NUM> seconds is applied.

In certain embodiments, plasma reactant gas is excited by RF (radio frequency) radiation. In certain embodiments, plasma reactant gas is excited by microwave radiation. In certain embodiments, the plasma reactant gas is fed into a plasma source tube without injecting. In certain embodiments, the plasma reactant gas optionally together with carrier and/or inert gas is fed into a plasma source tube without injecting the gas into the plasma source tube. Accordingly, the plasma reactant gas optionally together with carrier and/or inert gas is conducted into the plasma source tube along a (regular) pipeline (i.e., without special injection arrangements). The pipeline in certain embodiments comprises at least one valve (or plasma reactant pulsing valve).

In certain embodiments, the plasma in-feed line comprises a vertical plasma source tube comprising the plasma formation section. In certain embodiments, the plasma in-feed line goes along a vertical path through the plasma formation section and the constriction.

In certain embodiments, a jet nozzle inlet liner is provided to implement the constriction. In certain embodiments, the jet nozzle inlet liner is a tubular item. In certain embodiments, the inner diameter of the part is essentially smaller than the inner diameters of other parts of the gas introduction. It has been observed that gas velocity increases inside the part since its cross section is smaller than the plasma source tube and the reaction chamber. The increase may be based on, for example, a choked flow effect. It has also been observed that gas velocity is not only increased inside the inlet liner but also at a relatively long distance downstream the inlet liner, and even close to the deposition target. An obtained jet flow is minimizing the delivery time from plasma source to deposition target. The jet flow in certain embodiments is in contact with surrounding gas and thus a contact surface area with solid material is minimal. This further improves reactive species (or plasma species) delivery to the deposition target since the average lifetime of reactive species is getting longer.

In certain embodiments, the constriction is implemented by an inlet part. In certain embodiments, the inlet part comprises a tubular part with a smaller inner diameter than the in-feed line (or with a smaller inner diameter than the plasma source tube). In certain embodiments, the inlet part comprises a tubular part that is chemically inert. In certain embodiments, the inlet part comprises a tubular part that is electrically insulating. In certain embodiments, the inlet part comprises an outer part or tube housing an inner tube.

In certain embodiments, the method comprises providing the constriction as a converging nozzle arrangement or as a converging-diverging nozzle arrangement. In certain embodiments, the method comprises: surrounding the reaction chamber by a vacuum chamber. In certain embodiments, the method comprises: performing sequential self-saturating surface reactions on a substrate surface in the reaction chamber.

According to a second aspect of the invention there is provided a substrate processing apparatus according to claim <NUM>, comprising:.

In the embodiments, the constriction reduces a cross-sectional flow area of the in-feed line by at least <NUM> %.

In certain embodiments, the apparatus comprises a plasma source. In certain embodiments, the plasma source is positioned upstream of the constriction. In certain embodiments, the plasma source comprises a plasma source tube (a tube travelling across the plasma source). In certain embodiments, plasma species is generated within the plasma source tube. In certain embodiments, an inlet part providing the constriction and the plasma source tube are concentric parts.

In certain embodiments, the apparatus comprises the plasma in-feed line in between the plasma source and the deposition target to introduce plasma species into the reaction chamber for the deposition target.

In certain embodiments, the deposition target is positioned within the reaction chamber. In certain embodiments, the deposition target is a substrate. In certain embodiments, the deposition target is a batch of substrates. In certain embodiments, the substrate is a wafer. In certain embodiments, the substrates in the batch of substrates are vertically oriented.

In certain embodiments, an inlet part providing the constriction is positioned between the plasma source and the reaction chamber. In certain embodiments, the plasma source is a remote plasma source. In certain embodiments, the plasma source is positioned on the outside of the reaction chamber.

In certain embodiments, the plasma species comprises gaseous plasma. In certain embodiments, the plasma species comprises radicals. In certain embodiments, the plasma species comprises ions.

In certain embodiments, the inlet part is centrally positioned within the plasma in-feed line. In certain embodiments, the inlet part has a narrower inner diameter than the other parts / remaining parts in the plasma in-feed line. In certain embodiments, the plasma in-feed line has at its narrowest inner diameter within the inlet part. In certain embodiments, the inlet part provides for the narrowest channel width of the plasma in-feed line.

In certain embodiments, the inlet part is in the form of an inlet liner with a holder for the inlet liner. In certain embodiments, the inlet liner is a tubular item. In certain embodiments, the inlet liner is transparent to visible light. In certain embodiments, the inlet liner is chemically inert. In certain embodiments, the inlet liner (inner tube) is electrically insulating. In certain embodiments, inlet part comprises an inner tube surrounded by an outer tube or outer part. In certain embodiments, the inner tube and the outer tube are concentric parts. In certain embodiments, the inner tube and the outer tube have a ring-like cross-section. In certain embodiments, the inner tube and the outer tube are tightly fitted against each other. In certain embodiments, the outer part or outer tube forms a holder for the inner tube. In certain embodiments, the outer part or outer tube is electrically conductive. In certain embodiments, the outer part or outer tube is applied with an appropriate electric potential, such as system ground. In certain embodiments, the inlet part is attached in between pipe portions.

In certain embodiments, the inlet part is a removable part. In certain embodiments, the inner tube is a removable part. In certain embodiments, the inlet part provides the plasma in-feed line with a sudden constriction, or a stricture, to enhance gas velocity. In certain embodiments, the inlet part provides the plasma in-feed line with a stepwise narrowing of flow path. In certain embodiments, the inlet part is followed by an expansion space expanding towards the reaction chamber. In certain embodiments, the flow path from the plasma source to the reaction chamber undergoes a stepwise expansion (or widening) at an interface or in connection with an interface between the inlet part and the expansion space. In certain embodiments, the inlet part is a non-actuated part, for example, not a valve. In certain embodiments, the inlet part is a passive part (i.e., non-active part). In certain embodiments, the cross-sectional area of the plasma in-feed line (expansion space) immediately after (or downstream of) the inlet part is larger than the cross-sectional area of the plasma in-feed line (plasma source tube) immediately before (or upstream of) the inlet part.

In certain embodiments, the reaction chamber is surrounded by a vacuum chamber.

In certain embodiments, the apparatus is configured to perform sequential self-saturating surface reactions on a substrate surface in the reaction chamber. In certain embodiments, the apparatus is configured to apply plasma-assisted atomic layer deposition.

According to a further example aspect there is provided a method, comprising:.

According to a further example aspect there is provided a substrate processing apparatus, comprising:.

The above embodiments are used merely to explain selected aspects or steps that may be utilized in implementations of the present invention. It should be appreciated that corresponding embodiments apply to other example aspects as well. Any appropriate combinations of the embodiments may be formed The invention is defined by the claims.

In the following description, Atomic Layer Deposition (ALD) technology is used as an example.

The basics of an ALD growth mechanism are known to a skilled person. ALD is a special chemical deposition method based on sequential introduction of at least two reactive precursor species to at least one substrate. A basic ALD deposition cycle consists of four sequential steps: pulse A, purge A, pulse B and purge B. Pulse A consists of a first precursor vapor and pulse B of another precursor vapor. Inactive gas and a vacuum pump are typically used for purging gaseous reaction by-products and the residual reactant molecules from the reaction space during purge A and purge B. A deposition sequence comprises at least one deposition cycle. Deposition cycles are repeated until the deposition sequence has produced a thin film or coating of desired thickness. Deposition cycles can also be either simpler or more complex. For example, the cycles can include three or more reactant vapor pulses separated by purging steps, or certain purge steps can be omitted. Or, as for plasma-assisted ALD, for example PEALD (plasma-enhanced atomic layer deposition), discussed herein one or more of the deposition steps can be assisted by providing required additional energy for surface reactions through plasma in-feed, or one of the reactive precursors can be substituted by plasma energy, the latter leading to single precursor ALD processes. Accordingly, the pulse and purge sequence may be different depending on each particular case. The deposition cycles form a timed deposition sequence that is controlled by a logic unit or a microprocessor. Thin films grown by ALD are dense, pinhole free and have uniform thickness.

As for substrate processing steps, the at least one substrate is typically exposed to temporally separated precursor pulses in a reaction vessel (or chamber) to deposit material on the substrate surfaces by sequential self-saturating surface reactions. In the context of this application, the term ALD comprises all applicable ALD based techniques and any equivalent or closely related technologies, such as, for example the following ALD sub-types: MLD (Molecular Layer Deposition), plasma-assisted ALD, for example PEALD (Plasma Enhanced Atomic Layer Deposition) and photon-enhanced Atomic Layer Deposition (known also as flash enhanced ALD or photo-ALD).

However, the invention is not limited to ALD technology, but it can be exploited in a wide variety of substrate processing apparatuses, for example, in Chemical Vapor Deposition (CVD) reactors, or in etching reactors, such as in Atomic Layer Etching (ALE) reactors.

<FIG> shows an apparatus <NUM> in accordance with certain embodiments. The apparatus <NUM> is a substrate processing apparatus which may be, for example, a plasma-assisted ALD reactor. The apparatus comprises a reaction chamber <NUM> and an in-feed line (or in-feed arrangement) <NUM> to introduce plasma, for example gaseous plasma, for a deposition target <NUM> positioned in the reaction chamber <NUM>. The deposition target <NUM> may be a substrate (or wafer) or a batch of substrates.

The apparatus <NUM> further comprises an exhaust line <NUM> leading to a vacuum pump <NUM>. The reaction chamber <NUM> may be in the general form of a cylinder that is rounded at its bottom, or it may be adopted to any other substrate shape. The exhaust line <NUM> in certain embodiments is positioned in the rounded bottom of the reaction chamber <NUM>. The vacuum pump <NUM> provides a vacuum for the reaction chamber <NUM>. The apparatus in certain embodiments comprises an outer chamber, a vacuum chamber <NUM> around the reaction chamber <NUM>. Inactive shield gas may be fed into an intermediate space in between the vacuum chamber <NUM> and the reaction chamber <NUM>. The pressure within the intermediate space is kept, by pumping, on a higher level compared to prevailing pressure within the reaction chamber <NUM>. The same vacuum pump <NUM> or another pump may be used to arrange an outgoing flow (of inactive gas) from the intermediate space.

The plasma in-feed <NUM> into the reaction chamber <NUM> is arranged from a plasma source, or a remote plasma source. The in-feed occurs from the top side of the reaction chamber <NUM>. Plasma species travel from plasma source tube <NUM> in a downward direction. In certain embodiments, the plasma source tube <NUM> forms part of the in-feed line <NUM>. The in-feed line <NUM> comprises a constriction provided by an inlet part <NUM> that is configured to speed up gas velocity. In certain embodiments, the inlet part <NUM> is positioned downstream of the plasma source tube <NUM>. In certain embodiments, the inlet part <NUM> is a tubular part having a narrower inner diameter than the plasma source tube <NUM> preceding the inlet part <NUM>. In certain embodiments, the plasma source tube <NUM> forms part of the plasma source. In certain embodiments, there may be another pipe portion in between the plasma source tube <NUM> and the inlet part <NUM>.

When the plasma species enters the inlet part <NUM> its velocity increases. The delivery time to the deposition target <NUM> is respectively reduced.

The inlet part <NUM> may be formed of an outer part or tube <NUM> housing an inner tube <NUM> providing the constriction. The outer tube <NUM> may be made of metal, for example. An example material is aluminum or steel. It may be an electrically conductive part. The inner tube <NUM> may be chemically inert. In certain embodiments, the inner tube <NUM> is made of quartz. In certain embodiments, the inner tube <NUM> is made of sapphire. The inner tube <NUM> may be electrically insulating. The outer tube <NUM> may comprise an inwardly protruding shape in its bottom portion for the inner tube <NUM> to rest on. Further, the outer tube <NUM> may contain an outwardly protruding shape in its top portion for fixing the inlet part <NUM> in between pipe portions by fixing means <NUM> or similar. The inner tube <NUM> may be an inlet liner for the outer tube <NUM>. The inner tube <NUM> may form a jet nozzle inlet liner.

In certain embodiments, the inlet part <NUM> has an input opening for receiving the plasma species into inside of the inner tube <NUM> in a top portion of the inlet part <NUM>. The inner tube <NUM> provides a straight cylindrical channel for the plasma species to flow downwards until an output opening in a bottom portion of the inlet part <NUM> outputs the plasma species with the increased velocity from the inside of the inner tube <NUM> into inside of the reaction chamber <NUM> (however, in other embodiments, the inlet part <NUM> may alternatively output the plasma species into an intermediate part positioned in between the inlet part <NUM> and the reaction chamber <NUM> so that the plasma species enter the reaction chamber <NUM> only via the intermediate part).

In certain embodiments, as shown in <FIG>, upon outputting the plasma species into inside of the reaction chamber <NUM> the plasma species experiences a step-like (stepwise) enlargement of the flow path. Accordingly, in certain embodiments, the flow path after the enlargement is sideways limited by the cylindrical wall of the reaction chamber <NUM>.

<FIG> shows an apparatus <NUM> in accordance with certain embodiments. The apparatus <NUM> and its operation generally corresponds to that of apparatus <NUM>. Therefore, a reference is made to the preceding description. However, in the embodiment shown in <FIG>, further features relating to substrate loading and unloading is presented.

A deformable in-feed part <NUM> (as an intermediate part) is positioned in between the inlet part <NUM> and the deposition target <NUM>. The deformable in-feed part <NUM> has a closed configuration for substrate processing, for example, by plasma-assisted ALD and an open configuration for substrate loading. In the closed configuration, the in-feed part <NUM> may be in an extended shape, and in the open configuration in a contracted shape. The closed configuration is depicted in <FIG> and the open configuration in <FIG>.

The deformable in-feed part <NUM> comprises a set of nested sub-parts or ring-like members which are movable to fit within each other. In the embodiment shown in <FIG> and <FIG>, the number of sub-parts is two. The sub-parts <NUM> and <NUM> form a telescopic structure. In the example embodiment shown in <FIG> and <FIG>, the upper sub-part <NUM> is attached to a wall of the vacuum chamber <NUM>. The attachment may be in a top wall of the vacuum chamber <NUM> or in another appropriate point depending on the embodiment. In other embodiments, the upper sub-part may be attached to an outlet of the inlet part <NUM>. A gradually widening flow path from the inlet part <NUM> into inside of the reaction chamber <NUM> may in that way be provided instead of the step-like enlargement. In certain embodiments, such as shown in <FIG> and <FIG>, the lower sub part <NUM> either closes an interface between the lower sub part <NUM> and the reaction chamber <NUM> (or reaction chamber wall) as depicted in <FIG> or provides for a loading gap for substrate loading into the reaction chamber <NUM> as depicted in <FIG>.

As shown in <FIG>, a retractable shaft of an elevator <NUM> is attached to the deformable in-feed part <NUM> or in connection with it. The elevator <NUM> operates the deformable in-feed part <NUM>. A substrate <NUM> (or a batch of substrates) is loaded into the reaction chamber <NUM> via a loading port <NUM> by a loader <NUM> (an end effector, a loading robot or similar) through the loading gap formed by vertically deforming the in-feed part <NUM> into its open configuration.

The plasma species travels as a vertical flow from the plasma source through the plasma source tube <NUM> and through the inlet part <NUM> with an increased velocity to the output opening or outlet of the inlet part <NUM> and therefrom along the gradually widening flow path to the deposition target <NUM> (in the reaction chamber <NUM>).

In certain embodiments, a protective inert gas flow <NUM> is provided in a downward direction around the inlet part <NUM> (see <FIG>).

<FIG> shows the inlet part <NUM> in accordance with certain embodiments. The inlet part <NUM> comprises the outer tube <NUM> housing the inner tube or inlet liner <NUM>. The inlet part <NUM> optionally comprises an opening <NUM> radially extending through the whole outer tube <NUM> of at least one side (but not through the inner tube <NUM>) for viewing the plasma from a side direction. In certain embodiments, a pressure sensor <NUM> is positioned within the opening <NUM>.

<FIG> shows simulation results of gas velocity in an apparatus in accordance with certain embodiments. The apparatus is of the type shown in the preceding <FIG>, especially in <FIG>. Accordingly, the apparatus comprises the plasma source tube <NUM> followed by the inlet part (with the inner tube <NUM> shown) with an inner diameter that is narrower than the inner diameter of the tube <NUM>. The inlet part is followed by an expansion volume (part <NUM>, or similar) expanding towards the deposition target <NUM> in the reaction chamber <NUM>. For the purposes of simulation, the plasma source tube <NUM> had an inner diameter of <NUM>, and the inner tube <NUM> an inner diameter of <NUM>. It is observed that gas velocity is not only increased inside the part <NUM> but also at a relatively long distance downstream the part <NUM>, and even close to the deposition target <NUM>.

<FIG> show simulation results of gas velocity in apparatus in accordance with other embodiments. Each of the embodiments shown in <FIG> show a similar effect. The gas velocity is not only increased inside the part <NUM> (which acts as a constriction) but also further downstream the part <NUM>. The inner diameter of the plasma source tube <NUM> in the embodiments shown in <FIG> is <NUM>, and <NUM> in the embodiment shown in <FIG>. The inner diameter of the inner tube <NUM> is <NUM> in the embodiment shown <FIG>. In the embodiment shown <FIG> the inner tube <NUM> inner diameter is <NUM>. In the embodiment shown <FIG> the inner tube inner <NUM> diameter is <NUM>. In the embodiment shown <FIG> the inner tube <NUM> inner diameter is <NUM>. In the embodiment shown <FIG> the inner tube <NUM> inner diameter is <NUM>.

<FIG> shows certain dimensions of the apparatus shown in <FIG>. The inner diameter of the plasma source tube <NUM> is denoted by ∅D<NUM>, the inner diameter of the inner tube <NUM> by ∅D<NUM>, the length of the inner tube <NUM> by H<NUM>, the inner diameter of the expansion space <NUM> at the point of the stepwise enlargement by ∅D<NUM>, and the distance from the reaction chamber side end of the inner tube <NUM> to the deposition target (or wafer) <NUM> by H<NUM>.

The inner tube <NUM> acts as a constriction in the plasma in-feed line.

It has been observed by tests and/or simulations that the effect of speeding up gas velocity has been successful within a wide range of constriction channel diameters ∅D<NUM>. It was observed that the effect was surprisingly obtained also with a very slight narrowing of the flow channel (plasma in-feed line). In fact, when a channel diameter ∅D<NUM> immediately preceding the constriction <NUM> was <NUM> the effect was obtained already with the constriction channel diameter value ∅D<NUM> = <NUM>.

Furthermore, the effect was also obtained with a very large narrowing of the flow channel, i.e., with the constriction channel diameter value ∅D<NUM> = <NUM>.

Furthermore, surprisingly, the effect was even obtained with larger values of ∅D<NUM>, such as, ∅D<NUM> = <NUM>.

In certain preferred embodiments, the constriction <NUM> reduces cross-sectional flow area of the in-feed line <NUM> by at least <NUM> %. An <NUM> % reduction is practically obtained, for example, in embodiments in which ∅D<NUM> is <NUM> and ∅D<NUM> is <NUM>.

It has been observed that the effect of speeding up gas velocity was further enhanced when ∅D<NUM> was within the range from <NUM> to <NUM> when ∅D<NUM> was <NUM>. Accordingly, in certain more preferred embodiments, a constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction <NUM>.

It has been observed that the effect of speeding up gas velocity was yet further enhanced when ∅D<NUM> was around <NUM>. Accordingly, in certain yet more preferred embodiments, a constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction <NUM>.

However, the effect was also obtained when ∅D<NUM> was <NUM> and ∅D<NUM> was <NUM> - a case scenario in which the flow channel was narrowed by a total of <NUM> %.

In certain preferable embodiments, in which the plasma source tube <NUM> is generally large (i.e., closer to <NUM> rather than <NUM>) the constricted cross-sectional flow area may be <NUM>% of the cross-sectional flow area before the constriction <NUM>, or less. In certain preferable embodiments, the constricted cross-sectional flow area is within the range from <NUM> % to <NUM> % of the cross-sectional flow area before the constriction <NUM>.

In certain preferred embodiments, the constriction <NUM> is of a tubular form with a reduced inner diameter (the inner diameter is reduced compared to the inner diameter(s) of the remaining portion of the in-feed line). In certain preferred embodiments, as mentioned in the preceding, the constriction <NUM> has a channel diameter ∅D<NUM> within the range from <NUM> to <NUM>. In certain more preferred embodiments, the constriction <NUM> has a channel diameter ∅D<NUM> within the range of <NUM> - <NUM>. In certain embodiments, these values are particularly preferable when coating <NUM> inch / <NUM> wafers. Accordingly, in certain embodiments, the channel diameter ∅D<NUM> is within the range from <NUM> % to <NUM> %, or more preferably from <NUM> % to <NUM> %, of the diameter of a round substrate, such as wafer. Although the values are particularly preferable for <NUM> inch / <NUM> wafers, the values and principles presented herein are generally applicable also to other wafer sizes, for example, <NUM> inch / <NUM> wafers.

In certain more general embodiments, the constriction <NUM> and the plasma in-feed line <NUM> preceding the constriction <NUM> are of tubular form, and the constriction <NUM> has an inner diameter ∅D<NUM> within the range from <NUM> to <NUM>, more preferably from <NUM> to <NUM> and the plasma in-feed line <NUM> preceding the constriction <NUM> has an inner diameter ∅D<NUM> larger than the inner diameter ∅D<NUM> of the constriction <NUM>, and wherein ∅D<NUM> is selected from an inner diameter range from <NUM> to <NUM>. In certain preferred embodiments, the constriction <NUM> and the plasma in-feed line preceding the constriction are of tubular form, and the constriction <NUM> has an inner diameter ∅D<NUM> within the range from <NUM> to <NUM> and the plasma in-feed line preceding the constriction <NUM> has an inner diameter ∅D<NUM> larger than the inner diameter ∅D<NUM> of the constriction <NUM> and ∅D<NUM> is selected from an inner diameter range from <NUM> to <NUM>.

The preferable embodiments relating to the constricted cross-sectional flow area or diameters provide the effect of reduced travel time of plasma species from plasma source to deposition target (compared to solutions that lack the constriction).

It has been observed that many lengths (longitudinal dimension) H<NUM> of the constriction <NUM> may be used to obtain the mentioned effect of speeding up gas velocity. However, in general, the length should be large enough to speed up adequately, for example, at least greater than ∅D<NUM>, or more preferably at least two or three times the width ∅D<NUM>. However, the distance to the deposition target should not be unnecessarily lengthened by choosing a far too long length H<NUM>. In certain preferred embodiments, it has been observed that the length ranging from <NUM> to <NUM> is preferable. In more preferred embodiments, the length H<NUM> within the range from <NUM> to <NUM> has been used.

In certain embodiments, the cross-sectional area of the plasma in-feed line (expansion space <NUM>) immediately after (or downstream of) the constriction <NUM> is larger than the cross-sectional area of the plasma in-feed line (plasma source tube <NUM>) immediately before (or upstream of) the constriction. In certain embodiments, the expansion space <NUM> is of a tubular form or has a ring-like or round cross-section. The channel formed by the expansion space expands in width towards the deposition target <NUM>. In certain example embodiments, the width ∅D<NUM> is within the range from <NUM> to <NUM> and the width ∅D<NUM> greater than ∅D<NUM> and within the range from <NUM> to <NUM>, for example <NUM>.

In certain embodiments, the distance H<NUM> from the inner tube <NUM> to the deposition target (or wafer) <NUM> is at least <NUM> for lateral spreading of the plasma species. In certain more preferred embodiments, the distance H<NUM> is within the range from <NUM> to <NUM>.

<FIG> shows a process timing diagram in accordance with certain embodiments. A plasma-enhanced atomic layer deposition cycle is presented. The cycle begins at time instant t<NUM> by a precursor pulse. The precursor pulse ends at time instant t<NUM>. During this precursor pulse period, precursor vapor from a precursor source is fed into the reaction chamber to consume the reactive sites of the deposition target. Half a monolayer of material is deposited. The precursor vapor is fed via a route that does not go through the plasma source, i.e., the precursor vapor route to the reaction chamber is separate from the plasma source. The precursor vapor is typically vapor of a metal precursor or a semiconductor precursor. The adsorption method onto the deposition target is typically thermal ALD.

The precursor pulse period is followed by a precursor purge period. During this period, the in-feed line(s) of the precursor vapor is purged by a first inert gas, such as nitrogen N<NUM> (Inert gas <NUM>). The precursor purge period ends at time instant t<NUM>.

The precursor purge period is followed by a plasma pulse period. The plasma pulse period begins at time instant t<NUM> and ends at time instant t<NUM>. First, a feed of a plasma gas (plasma reactant, e.g., oxygen O<NUM>) through the plasma source is began. After a gas stabilization period extending to time instant t<NUM>, the power of the plasma source is switched "ON". During a plasma formation period beginning at time instant t<NUM>, the plasma reactant and second inert gas, such as argon Ar (Inert gas <NUM>) is fed through the plasma source along the plasma source tube. Plasma species are formed from the plasma reactant in a plasma formation section during a plasma formation period until the plasma power is switched "OFF" at time instant t<NUM>. The plasma species enter the reaction chamber to react on the surface of the deposition target by the adsorbed precursor. A thin film of a full monolayer is obtained. The adsorption method onto the deposition target is plasma-enhanced ALD.

After a short plasma deactivation period from time instant t<NUM> to t<NUM>, a plasma purge period starts at time instant t<NUM>. During the plasma deactivation period, both the plasma reactant and the second inert gas flow through the plasma source. However, plasma is not formed since the power of the plasma source is "OFF".

During the plasma purge period from time instant t<NUM> to t<NUM>, the plasma reactant in-feed through the plasma source is "OFF". The plasma source is purged by the second inert gas. The deposition cycle ends at time instant t<NUM>. The deposition cycle is repeated to obtain a desired film thickness.

In certain embodiments, the flow of both the first inert gas and the second inert gas is "ON" during the whole deposition cycle.

<FIG> shows another representation of the timing diagram. Nitrogen N<NUM> is used as the first inert gas, and argon Ar as the second inert gas. Oxygen containing gas, such as O<NUM>, is used as the plasma reactant to deposit an oxide. During the plasma formation period (from time instant t<NUM> to t<NUM>) the plasma power (radio frequency, RF, power in this embodiment) is "ON" to produce O* plasma. Depending on the used precursor, an oxide thin film is formed. For example, by using Bis(diethylamino)silane SiH<NUM>[N(CH<NUM>CH<NUM>)<NUM>]<NUM> as the precursor, a silicon oxide SiO<NUM> thin film is obtained.

Accordingly, in certain embodiments oxygen containing gas, such as O<NUM>, is used as the plasma reactant, and Si containing precursor is used as the other precursor to deposit SiO<NUM>. In other embodiments, oxygen containing gas, such as O<NUM>, is used as the plasma reactant, and an aluminum containing precursor is used as the other precursor to deposit Al<NUM>O<NUM>. An example of an aluminum containing precursor is TMA (Al(CH<NUM>)<NUM>). Further applicable oxide coatings are, e.g., TiO<NUM>, HfO<NUM>, Y<NUM>O<NUM>, Co<NUM>O<NUM>, Ta<NUM>O<NUM>, MgO<NUM>, ZrO<NUM>, La<NUM>O<NUM>. Furthermore, nitrogen containing gas, e.g., N<NUM>, NH<NUM> or N<NUM>/H<NUM> is used as the plasma reactant in other embodiments to deposit nitride thin films. Depending on the used other precursor, nitride thin films such as AlN, TiN, Si<NUM>N<NUM> are formed. In other embodiments, elemental Pt, Ir, or Ru is deposited. In these embodiments, inter alia, the plasma reactant does not function as a precursor but is merely used as a means to provide required missing reaction energy to deposit the desired thin film material.

<FIG> shows another representation of the apparatus <NUM> in accordance with certain embodiments. The plasma reactant and the second inert gas enter the plasma source tube <NUM> of the plasma source <NUM> as depicted by an arrow <NUM>. The plasma species are formed in a plasma forming section <NUM> of the plasma source <NUM>. The apparatus <NUM> comprises the widening expansion space <NUM> on top of the reaction chamber <NUM>. After having passed through the constriction <NUM>, the formed plasma species flow through the expansion space <NUM> downwards to the reaction chamber <NUM> to react on the surface of the deposition target (a wafer, or another substrate) <NUM>.

Similarly, the precursor (non-plasma precursor) and the first inert gas enter the reaction chamber <NUM> as depicted by an arrow <NUM> via an in-feed part <NUM>. In certain embodiments, the in-feed of the precursor into the reaction chamber <NUM> is from a side or from sides of the reaction chamber <NUM> whilst the flow direction of the plasma species to the reaction chamber is from the top of the reaction chamber. The in-feed part <NUM> may be an inlet positioned in a side wall of the reaction chamber <NUM>. An intermediate space between the wall of the reaction chamber <NUM> and the wall of the outer chamber <NUM> is denoted by reference numeral <NUM>.

The first and/or second inert gases may act as a carrier gas for the corresponding precursor or reactant.

The operation of the apparatus is controlled by a control system <NUM>.

<FIG> further demonstrate the operation of the apparatus <NUM> in accordance with certain embodiments.

<FIG> shows gas flow configurations during (i) precursor pulse period. The (non-plasma) precursor and first inert gas (here: N<NUM>) flow via the in-feed part <NUM> into the reaction chamber <NUM> towards the deposition target <NUM>. The second inert gas (here: Ar) flows via the (unpowered) plasma source <NUM> towards the deposition target <NUM>.

<FIG> shows gas flow configurations during (ii) precursor purge period. The first inert gas (here: N<NUM>) flows via the in-feed part <NUM> into the reaction chamber <NUM>. The second inert gas (here: Ar) flows via the (unpowered) plasma source <NUM> towards the deposition target <NUM>.

<FIG> shows gas flow configurations during (iii) plasma pulse, i.e., plasma formation period. The first inert gas (here: N<NUM>) flows via the in-feed part <NUM> into the reaction chamber <NUM>. The plasma reactant and second inert gas (here: Ar) flow into the plasma source <NUM> for excitation by RF radiation. Plasma species produced from the plasma reactant gas and the second inert gas flow from the plasma source <NUM> to the reaction chamber <NUM>.

<FIG> shows gas flow configurations during (iv) plasma purge period. The first inert gas (here: N<NUM>) flows via the in-feed part <NUM> into the reaction chamber <NUM>. The second inert gas (here: Ar) flows via the (unpowered) plasma source <NUM> towards the deposition target <NUM>.

<FIG> shows a block diagram of the control system <NUM> in accordance with certain example embodiments. The control system <NUM> comprises at least one processor <NUM> to control the operation of the apparatus <NUM>. The control system further comprises at least one memory <NUM> comprising a computer program or software <NUM>. The software <NUM> includes instructions or a program code to be executed by the at least one processor <NUM> to control the apparatus <NUM>. The software <NUM> may typically comprise an operating system and different applications.

The at least one memory <NUM> may form part of the apparatus <NUM> or it may comprise an attachable module. The control system <NUM> further comprises at least one communication unit <NUM>. The communication unit <NUM> provides for an interface for internal communication of the apparatus <NUM>. In certain example embodiments, the control unit <NUM> uses the communication unit <NUM> to send instructions or commands to and to receive data from different parts of the apparatus <NUM>, for example, measuring and control devices, valves, pumps, and heaters, as the case may be.

The control system <NUM> may further comprise a user interface <NUM> to co-operate with a user, for example, to receive input such as process parameters from the user.

As to the operation of the apparatus <NUM>, the control system <NUM> controls e.g. the process timings of the apparatus, controls the opening and closing of valves, controls substrate loading and unloading, sets flow rates, sets plasma power, and controls pressures and temperatures in different parts of the apparatus <NUM>.

In certain preferred embodiments, the flow rate of plasma gas entering the plasma formation section <NUM> is within the range from <NUM> sccm to <NUM> sccm, more preferably from <NUM> sccm to <NUM> sccm. It has been observed that greater flow rate contributes to both to the quality of the deposited thin film in terms of low leakage current as well as low non-uniformity of the film. Further, it has been observed that the greater flow rate together with using the constriction <NUM> provides very good results in terms of low leakage current and low non-uniformity of the film.

In certain preferred embodiments, a plasma power within the range from10 W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W, or from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W, yet more preferably from <NUM> W to <NUM> W is applied to the plasma formation section <NUM>. It has been observed that greater plasma power contributes to the quality of the deposited thin film in terms of low leakage current (through higher plasma density). However, a moderate plasma power, i.e., from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W did provide good results in terms of non-uniformity of the film. Further, it has been observed that the greater plasma power together with using the constriction <NUM> provides very good results in terms of low leakage current, also if combined with the flow rate of the plasma gas within the range from <NUM> sccm to <NUM> sccm. Further, it has been observed that the moderate plasma power together with using the constriction <NUM> provides very good results in terms of low non-uniformity, also if combined with the flow rate of the plasma gas within the range from <NUM> sccm to <NUM> sccm.

In certain example embodiments, the plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied. However, in certain other embodiments, the plasma formation period may be longer or much longer.

In certain preferred embodiments, the plasma formation period is within the range from <NUM> seconds to <NUM> seconds. The plasma formation period within this range has been observed to contribute to low non-uniformity of the deposited thin film. In certain preferred embodiments, the plasma formation period is within the range from <NUM> seconds to <NUM> seconds. The plasma formation period within this range has been observed to contribute to low leakage current of the film.

Further, it has been observed that with the plasma formation period ranging from <NUM> seconds to <NUM> seconds together with using the constriction <NUM>, also if combined with the flow rate of the plasma gas within the range from <NUM> sccm to <NUM> sccm, and also optionally combined with the plasma power ranging from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, particularly low values of non-uniformity were obtained. Further, it has been observed that with the plasma formation period ranging from <NUM> seconds to <NUM> seconds together with using the constriction <NUM>, also if combined with the flow rate of the plasma gas within the range from <NUM> sccm to <NUM> sccm, and also optionally combined with the plasma power ranging from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W, particularly low leakage current values were obtained.

In certain preferred embodiments, a purge period of a non-plasma precursor with a duration within the range from <NUM> second to <NUM> seconds, preferably from <NUM> seconds to <NUM> seconds, is applied. It has been observed that the non-plasma precursor purge period ranging from <NUM> seconds to <NUM> seconds contributes to both to the quality of the deposited thin film in terms of low leakage current as well as low non-uniformity of the film. Further, it has been observed that the non-plasma precursor purge period ranging from <NUM> seconds to <NUM> seconds together with using the constriction <NUM>, optionally with using the flow rate of the plasma gas within the range from <NUM> sccm to <NUM> sccm, provides very good results in terms of low leakage current and low non-uniformity of the film.

In certain preferred embodiments, the constriction <NUM> is used together with the following set of process parameters: the flow rate of plasma gas entering the plasma formation section <NUM> is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W is applied to the plasma formation section <NUM>, a plasma formation period (plasma pulse) with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> second to <NUM> seconds is applied. The combination may be used to obtain low values of non-uniformity of the deposited thin film and/or low values of leakage current through the film.

In certain preferred embodiments, the constriction <NUM> is used together with the following set of process parameters: the flow rate of plasma gas entering the plasma formation section <NUM> is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, is applied to the plasma formation section <NUM>, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> seconds to <NUM> seconds is applied. The combination may be used to obtain particularly low values of non-uniformity of the deposited thin film.

In certain preferred embodiments, the constriction <NUM> is used together with the following set of process parameters: the flow rate of plasma gas entering the plasma formation section <NUM> is within the range from <NUM> sccm to <NUM> sccm, a plasma power within the range from <NUM> W to <NUM> W, preferably from <NUM> W to <NUM> W, more preferably from <NUM> W to <NUM> W is applied to the plasma formation section <NUM>, a plasma formation period with a duration within the range from <NUM> seconds to <NUM> seconds is applied, and a purge period of a non-plasma precursor with a duration within the range from <NUM> seconds to <NUM> seconds is applied. The combination may be used to obtain particularly low values of leakage current through the deposited thin film.

<FIG> shows a schematic drawing of an apparatus in accordance with certain further embodiments. In these embodiments, the inlet part <NUM> (see <FIG> in the preceding) is implemented by a converging nozzle arrangement <NUM>. In an embodiment as shown in <FIG>, the plasma reactant (or formed plasma species) enters a nozzle part <NUM>' (as depicted by arrow <NUM>). The nozzle part <NUM>' may be otherwise similar to the inner tube or inlet liner <NUM> described in the preceding but, instead of a flow channel with an unchanging geometry and diameter, the nozzle part <NUM>' provides a converging channel. As an example, the nozzle part <NUM>' may contain an upside-down placed truncated cone <NUM>' that forms a converging flow channel therein. The gas velocity accelerates within the converging channel provided by the nozzle part <NUM>'. At the reaction chamber end of the nozzle part <NUM>', the flow channel comprises a stepwise widening of the flow channel (flow path). At this point the plasma species is released with an increased velocity towards the deposition target <NUM> (in the reaction chamber <NUM>) as depicted by arrows <NUM>. The in-feed of non-plasma precursor(s) into the reaction chamber <NUM> is arranged via another route (i.e., a route not passing through the converging nozzle arrangement <NUM>). In certain embodiments, the in-feed of non-plasma precursor(s) is arranged (downstream of the converging nozzle arrangement <NUM>) from a side or from sides of the reaction chamber <NUM> whilst the flow direction of the plasma species to the reaction chamber is from the top of the reaction chamber.

<FIG> shows a schematic drawing of an apparatus in accordance with certain further embodiments. In these embodiments, instead of the converging nozzle arrangement <NUM>, the apparatus comprises a converging-diverging nozzle arrangement <NUM>. In an embodiment as shown in <FIG>, the plasma reactant (or formed plasma species) enters a nozzle part <NUM>" (as depicted by arrow <NUM>). The nozzle part <NUM>" may be otherwise similar to the nozzle part <NUM>' but, instead of a mere converging channel provided by part <NUM>', the nozzle part <NUM>" provides a converging channel followed by a diverging (expanding, in volume) channel. In certain embodiments, the converging and diverging channel parts comprise an interface therebetween which provides a stepwise widening of the flow channel (flow path). The stepwise widening is to prevent plasma recombination by collisions to the flow channel side wall(s). As an example, the nozzle part <NUM>" may contain an upside-down placed truncated cone that forms a converging flow channel, and followed by another truncated cone <NUM>' that forms a diverging (expanding) flow channel therein. The gas velocity accelerates within the converging channel provided by the nozzle part <NUM>". At the interface between the converging and diverging channels, the plasma species is released with an increased velocity towards the deposition target <NUM> (positioned within the reaction chamber <NUM>) as depicted by arrows <NUM>. The in-feed of non-plasma precursor(s) into the reaction chamber <NUM> is arranged via another route (i.e., a route not passing through the converging-diverging nozzle arrangement <NUM>). In certain embodiments, the in-feed of non-plasma precursor(s) is arranged (downstream of the converging-diverging nozzle arrangement <NUM>) from a side or from sides of the reaction chamber <NUM> whilst the flow direction of the plasma species to the reaction chamber is from the top of the reaction chamber. With the converging-diverging nozzle arrangement <NUM> even a supersonic gas jet is possible.

The presented converging nozzle feature and converging-diverging nozzle feature presented in the embodiments shown in <FIG> are applicable in all other presented embodiments. Similarly, features of the other embodiments are applicable in the embodiments shown in <FIG>.

Without limiting the scope and interpretation of the patent claims, certain technical effects of one or more of the example embodiments disclosed herein are listed in the following. A technical effect is providing improved reaction species delivery to the deposition target. A further technical effect is forming a chemically resistant barrier layer between metal parts and reactive plasma species. A further technical effect is providing thin films with attractive properties, such as low non-uniformity, and low leakage current.

The foregoing description has provided by way of non-limiting examples of particular implementations and embodiments of the invention a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented above, but that it can be implemented in other embodiments using equivalent means without deviating from the characteristics of the invention.

Claim 1:
A method, comprising:
introducing plasma species via a plasma in-feed line (<NUM>) into a reaction chamber (<NUM>) for a deposition target (<NUM>) in a substrate processing apparatus (<NUM>), wherein the plasma in-feed line (<NUM>) goes via a plasma formation section (<NUM>), the method being characterized in that it comprises: speeding up velocity of plasma species within the plasma in-feed line (<NUM>) and downstream from the plasma in-feed line (<NUM>) by a constriction (<NUM>) of a tubular form providing a straight cylindrical channel downstream of the plasma formation section (<NUM>), wherein the constriction (<NUM>) within the plasma in-feed line (<NUM>) reduces a cross-sectional flow area of the plasma in-feed line (<NUM>) by at least <NUM> %.