GB2220006A - Plasma processing apparatus - Google Patents

Abstract

Apparatus for plasma processing e.g. coating or etching a semiconductor body sample (1) has a reaction chamber (1) for establishing a low pressure environment, supply means (2) for supplying processing gases into the reaction chamber (1), a support (3) within the reaction chamber (1) for receiving a sample (4) to be processed, and means (5) spaced-apart from the sample support for generating a plasma inducing discharge within the reaction chamber (1) having first and second electrodes disposed within the chamber (1) spaced-apart from the sample support (3), and insulated from one another and interleaved in a plane extending transversely of the direction of flow of processing gases from the supply means (2) for allowing processing gases to flow between the electrodes towards the sample support (3) to enable a plasma of constituents of the processing gases to be generated in the spaces between the first and second electrodes (6 and 7) upon application of an electric potential across the first and second electrodes. <IMAGE>

Description

DESCRIPTION PLASMA PROCESSING APPARATUS This invention relates to apparatus for plasma processing a semiconductor body sample, which apparatus comprises a reaction chamber for establishing a low pressure environment, supply means for supplying processing gases into the reaction chamber, a support within the reaction chamber for receiving a sample to be processed, and means spaced apart from the sample support for generating a plasma-inducing discharge within the reaction chamber.

The use of such apparatus where the plasma is generated remote from the sample to be processed has been proposed in, for example, US-A-4066037 and EP-A-63273 to avoid the sample being subject to the plasma and so to avoid, or at least reduce, damage by ion bombardment and also where the apparatus is to be used for, for example, etching, to avoid or at least reduce contamination of the sample. Where the apparatus is to be used for plasma enhanced chemical vapour deposition, then the generation of the plasma remotely of the sample should avoid or at least reduce gas phase reactions in the vicinity of the sample and so result in less hazy films.

In the plasma enhanced chemical vapour deposition apparatus described in US-A-4066037 the plasma is generated by applying an rf source to a coil wrapped around the reaction chamber. Whilst such an arrangement does generate the plasma remotely of the sample, the plasma may not be too well confined to the area of generation and may spread through the reaction chamber towards the sample. EP-A-63273 describes a plasma etching system in which the plasma is generated in a separate chamber or tube remote from the reaction chamber containing the sample by applying a low frequency AC source across the two spaced-apart electrodes to generate a discharge.The plasma thus produced has however to pass through a conduit before reaching the reaction chamber so that the shorter lived species within the plasma may decay before reaching the reaction chamber and contamination of the plasma in the conduit may occur.

It is an aim of the present invention to produce apparatus for plasma processing a semiconductor body sample which enables the plasma to be located precisely within the reaction chamber remote from the sample to be processed and which reduces the risk of ion bombardment or contamination of the sample.

According to the present invention apparatus for plasma processing a semiconductor body sample, which apparatus comprises a reaction chamber for establishing a low pressure environment, supply means for supplying processing gases into the reaction chamber, a support within the reaction chamber for receiving a sample to be processed, and means spaced-apart from the sample support for generating a plasma inducing discharge within the reaction chamber, is characterised in that the discharge generating means comprises first and second electrodes disposed within the chamber spaced-apart from the sample support, the first and second electrodes being insulated from one another and being interleaved in a plane extending transversely of the direction of flow of processing gases from the supply means for allowing processing gases to flow between the first and second electrodes towards the sample support to enable a plasma of constituents of the processing gases to be generated in the spaces between the first and second electrodes upon application of an electric potential across the first and second electrodes.

As used herein, the term low pressure means a pressure below normal atmospheric pressure, that is, below one atmosphere (about 9.8 x 103Pa) preferably in the range of from 0.05 Torr (6.65 Pa) to 1 Torr (1.33 x 102Pa), and the term processing gases includes gases for enabling deposition of a layer on or removal of a layer from the sample.

Thus apparatus embodying the present invention provides discharge generating means in the form of first and second interleaved electrodes which are positioned remote from the sample support so that processing gases to be supplied to process a sample mounted on the support can pass through the spaces between the first and second electrodes, where, upon application of a potential across the first and second electrodes, for example by using an rf (radio frequency) source, a plasma can be generated from constituents of the processing gases. Such discharge generating means enables a plasma to be generated remotely of the sample to be processed to reduce the problems of damage to the sample by, for example, ion bombardment or plasma damage by sputtering by, for example, constituents of the plasma.

Also, where the apparatus is to be used for plasma enhanced chemical vapour deposition, then gas phase reactions at the sample should be reduced and so better quality deposited films should result. Moreover, apparatus embodying the invention enables the plasma to be precisely located within the reaction chamber, in fact the plasma is usually confined to the interleaved first and second electrodes.

One of the first and second electrodes may completely surround the other and may be connected, in use of the apparatus, to earth or ground, that is to the same potential as the reaction chamber, so as to ensure that plasma generation cannot occur between the discharge generating means and the reaction chamber wall.

Moreover, the fact that the first and second electrodes are interleaved in a plane extending transversely of the direction in which the processing gases are arranged to flow from the supply means means that the electric field generated by the potential applied across the first and second electrodes is arranged to be transverse to the direction of flow of processing gases from the supply means so that any ions which could cause damage to the sample should be deflected in a direction transverse to the flow of processing gases and not towards the sample.

Depending upon the reaction chamber, the sample support, which may also comprise a heater for heating the sample to a processing temperature, may be disposed to support a sample with the major surfaces of the sample along or transverse to the direction of flow of processing gases from the supply means, so that in the latter case the surface on which the sample is to be supported is parallel to the plane in which the first and second electrodes are interleaved.

The first and second electrodes may have opposed major surfaces extending along the direction of flow of processing gases from the supply means. The dimensions of the first and second electrodes along the direction of flow of processing gases from the supply means need however only be sufficient to enable a plasma to be sustained between the first and second electrodes.

The interleaved first and second electrodes forming the discharge generating means provide a structure which may be relatively easily moved within the reaction chamber enabling the separation of the discharge generating means from the sample support and/or the supply means to be adjusted. Various species are present in a plasma and the different species normally have different lifetimes. Using apparatus embodying the invention, the separation of the discharge generating means and the sample support may be relatively easily adjusted enabling control or adjustment of the particular species reaching the sample and so enabling control or adjustment of the plasma processing which may, where plasma enhanced chemical vapour deposition is concerned, enable control or adjustment of the characteristics of the film or layer being deposited. To this end, means may be provided in the reaction chamber for adjusting the spacing of the discharge generating means and the sample support, for example, both the discharge generating means and the sample support may be movably mounted to a support rail provided in the reaction chamber.

The interleaved first and second electrodes may be formed in any convenient manner. For example, the first and second electrodes may comprise a series of parallel metal, for example stainless steel, plates having first and second ends with the first ends of alternate ones of the plates being connected by connecting means, for example copper strips, to form the first electrode and the second ends of the remaining plates being connected by connecting means to form the second electrode.

Using such an arrangement, the number of metal plates and spacing of the metal plates may be relatively easily adjusted allowing the area of the discharge generating means in the plane transverse to the direction of flow of processing gases to be altered as desired to increase or decrease the area of plasma provided in operation of the apparatus so that, for example, the area of plasma provided can be optimised to the desired position of the plasma within the processing chamber so as, for example, to provide a smaller area or block of plasma when the discharge generating means is closer to the supply means and a larger area or block of plasma when the discharge generating means is closer to the sample support.

It should be understood that not all the gases to be used during the processing need pass between the interleaved first and second electrodes and that, for example, only one or more of the processing gases to be used may be supplied via the discharge generating means so that a plasma of constituents of only the said one or more processing gases is generated.Thus, for example, where the apparatus is to be used for plasma enhanced chemical vapour deposition and, for example, the sample is a silicon semiconductor body onto which a layer of silicon is to be epitaxially grown, then the carrier gas, normally hydrogen, may be passed between the interleaved first and second electrodes to form the plasma and the silicon containing gas, for example silane, supplied directly to the sample, bypassing the discharge generating means which should discourage gas phase reactions in the region of the plasma and encourage reaction at the sample surface to facilitate deposition of a good, smooth layer.

In order that the invention may be more readily understood embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a simplified schematic part-cross-sectional view of apparatus in accordance with the invention for plasma processing a semiconductor body sample; Figure 2 is a plan view showing in detail the interleaved first and second electrodes of the plasma inducing discharge generating means of the apparatus in accordance with the invention shown in Figure 1.

It should be understood that the Figures are merely schematic and are not drawn to scale. In particular in the interests of clarity certain dimensions may have been exaggerated whilst other dimensions may have been reduced.

Referring now to Figures 1 and 2, the apparatus for plasma processing a semiconductor body sample comprises a reaction chamber 1 for establishing a low pressure environment, supply means 2 for supplying processing gases into the reaction chamber 1, a support 3 within the reaction chamber 1 for receiving a sample 4 to be processsd and means 5 spaced apart from the sample support 3 for generating a plasma inducing discharge within the reaction chamber 1.

In accordance with the invention, the discharge generating means 5 comprises first and second electrodes 6 and 7 disposed within the chamber 1 spaced-apart from the sample support 3, the first and second electrodes 6 and 7 being insulated from one another and being interleaved in a plane extending transversely of the direction of flow of processing gases from the supply means 2 for allowing processing gases to flow between the first and second electrodes 6 and 7 towards the sample support 3 to enable a plasma of constituents of the processing gases to be generated in the spaces 8 between the first and second electrodes 6 and 7 upon application of an electric potential across the first and second electrodes 6 and 7.

The reaction chamber 1 is formed, in this example, as a stainless steel chamber, however, as will be appreciated by those skilled in the art, other forms of reaction chamber, for example a glass tubular reaction chamber, could be used. A pump 10, typically a Rootes blower backed up by a rotary pump, is connected to an outlet la of the reaction chamber to enable a desired low pressure environment to be maintained within the reaction chamber 1. As shown in Figure 1 the reaction chamber 1 is provided with two inlet ports lb and lc via which supply means 2 for processing gases may enter the reaction chamber 1, although as shown in Figure 1, only one of the inlet ports lb is being used.It will, of course, be appreciated that the reaction chamber may have any desired number of ports and that two or even more of the ports may be used for enabling processing gases to enter the reaction chamber 1.

As shown in Figure 1, the supply means 2 comprises a single gas supply pipe 2a. However, dependent on the types and number of different processing gases to be used, the supply means 2 may comprise two or more separate gas supply pipes. A heating coil controlled by an appropriate thermocouple arrangement (not shown) may be provided around the gas supply pipe(s) so as to avoid condensation problems where, for instance, organometallic compounds are to be used.

A support rail 100 formed, for example, of stainless steel is mounted by appropriate conventional brackets (not shown in Figure 1) to the inside wall of the reaction chamber 1 to carry the sample support 3 and the discharge generating means 5. The sample support 3 and the discharge generating means are mounted to the support rail 100 so as to be electrically insulated from the support rail 100 and so as to be movable along the support rail 100. The support rail 100 may be a stainless steel strip fixed at a mid point to the reaction chamber. The strip has a longitudinally extending slot through which support rods 101 carrying the sample support 3 and discharge generating means 5 extend so that, as illustrated very schematically in Figure 1, enlarged heads or studs 102 of the support rods rest on the support rail 100. The support rods 101 may be fixed in place by any suitable releasable fastening means, for example, bolts and nuts (not shown in Figure 1) enabling the location and relative spacing of the sample support 3 and the discharge generating means 5 to be relatively simply adjusted as desired. The semiconductor body sample 4 to be processed is mounted to the sample support 3 by means of fixing clips (not shown) provided on the sample support 3. In this example, the sample support 3 contains a resistance heater for heating the sample 4 to a desired processing temperature. The sample support 3 may be a stainless steel plate having on the surface which does not support the sample a spiral groove which receives a resistance heater.Where the processing temperature is below about 420 degrees Celsius, the sample support 3 may be formed by two aluminium blocks with the resistance heater sandwiched between the blocks, so as to be insulated from one aluminium block by a block of quartz and from the other aluminium block by a felt pad.

Of course, alternative sample heating means, for example, such as external radiant heating means, could be used to heat the sample.

As will be appreciated by those skilled in the art, although not shown in Figure 1, connecting wires from the resistance heater carried by the sample support 3 will be led out of the reaction chamber via an appropriate port, for example the port lb in the arrangement shown in Figure 1, to enable connection of the heater to an external electrical supply.

Figure 2 is a plan view, looking in the direction of arrow B in Figure 1, of the discharge generating means 5. As will be appreciated from Figures 1 and 2, the first and second electrodes 6 and 7 of the discharge generating means 5 are interleaved in a plane extending perpendicularly of the plane of the paper and along the direction A shown in Figure 1 and the gas supply pipe 2a is bent through approximately 90 degrees so as to provide an outlet 20 for providing a flow of processing gases towards the discharge generating means 5 in a direction parallel to the arrow B in Figure 1. Thus, the first and second electrodes 6 and 7 are interleaved in a plane extending transversely, in this example perpendicularly, of the direction B of the flow of processing gases from the outlet 20.As will be appreciated from Figure 2, the second electrode 7 surrounds the first electrode 6 on three sides, however, as indicated in phantom lines in Figure 2, the second electrode 7 may completely surround the first electrode 6.

In the example shown in Figure 2, the first and second electrodes 6 and 7 are formed by a series, nine in the arrangement shown, of parallel flat metal (for example stainless steel) plates 11, having first and second ends lla and llb with the first ends lla of alternate metal plates 11 being connected by connecting means in the form of metal, for example copper, strips 12, to form the first electrode 6 and the second ends llb of the remaining plates being connected by similar connecting strips 12 to form the second electrode 7. As indicated above, the second electrode 7 may completely surround the first electrode 6 by, in this example, connecting a further strip 12' (shown in phantom lines in Figure 2) between the end metal plates 11 of the second electrode 7.

As shown in Figure 2, the metal plates 11 are spaced-apart and so insulated from one another by ceramic, for example, aluminium oxide, coupling rods 13, the ends of which have screw threaded metal sleeves 14 which carry nuts 15 which serve to secure the ends of the metal plates. Thus, in order to assemble the first and second electrodes each end lia, llb of a metal plate, together with where appropriate the end of a connecting strip 12, is sandwiched between two coupling rods 13 and the nuts on either side tightened to provide a compression coupling. The adjacent metal plates are sandwiched between the other ends of the two coupling rods and further coupling rods and this procedure is carried out for each end of each plate until the desired number of metal plates 11 interconnected by strips 12 has been connected together.In the arrangement shown nine metal plates 11 are used with four being connected to form the first electrode 6 and five to form the second electrode 7. This method of coupling and spacing-apart the metal plates 11 has the advantage that the number of plates used to form the first and second electrodes 6 and 7 may be decreased or increased as desired by simply removing or adding plates 11 and coupling rods 13. However, where such flexibility is not necessary, it may be possible to form the first and second electrodes 6 and 7 so that the plates 11 are permanently interconnected and/or so that each electrode is formed as an integral arrangement.

Electrically conductive wires 16 and 17 are connected to the first and second electrodes 6 and 7, respectively, by sandwiching the wires between appropriate coupling rods 13 to enable an electrical potential to be applied across the electrodes.

The dimensions and spacing of the plates 11 and the number of plates 11 used will depend on the operating conditions and may be optimised accordingly. For example, the overall area in the plane in which the first and second electrodes 6 and 7 are interleaved may be adjusted depending upon the relative separation of the discharge generating means 5, the supply means and the sample support 3. Thus, for example, a larger area for the discharge generating means 5 may be required when the discharge generating means 5 is close to the sample support 3 and a smaller area may be required when the discharge generating means 5 is close to the supply means 2. As indicated above, with the arrangement shown in Figure 2, this can easily be achieved by adding or removing plates 11.The separation or space between opposed faces of adjacent metal plates 11 may be chosen, dependent upon the conditions, for example, the pressure within the chamber and the characteristics of the potential, for example the frequency and power of a rf (radio frequency) supply, to obtain the optimum plasma. The depth of the plates 11 in the direction B should be sufficient to enable a plasma to be sustained between the plates 11, that is, to provide sufficient capacitive effect, but is not otherwise important.

To take an example, the metal plates 11 may have a depth in the direction of the arrow B of about 15 mm, a thickness of about 1 mm, a length of about 100 mm, and a separation of about 15 mm.

In operation of the apparatus for plasma enhanced chemical vapour deposition (PECVD) a pressure of from about 1 Torr (1.33 x 102Pa) to about 0.05 Torr (6.65 Pa) may be maintained within the reaction chamber 1 and the potential for producing the plasma may be provided by connecting the first electrode 6 (via the wire 16) to an rf (radio frequency) source of about 13.5 MHz (MegaHertz) providing an output power of about lOW (Watts) or greater with the wire 17, and therefore the second electrode 7, connected to earth. In addition to or in place of the rf source, a dc bias potential may be applied across the first and second electrodes 6 and 7.As the second electrode 7 surrounds the first electrode 6 on at least three and possibly four sides and in this example is connected in operation of the apparatus to earth, that is to the same potential as the reaction chamber, the second electrode 7 acts as a shield preventing generation of a plasma between the second or outer electrode 7 and the reaction chamber 1 wall so facilitating confinement of the plasma. The discharge generating means 5 in the form of the interleaved first and second electrodes 6 and 7 may be positionedabout, for example, 10 cm from the outlet 20 of the gas supply means 2 and from about 10 cm to 40 cm from the sample 4 on the support 3.

The apparatus described above may be used, for example, to deposit a layer of silicon dioxide on a monocrystalline silicon sample 4 as will be described below.

Thus initially a monocrystalline silicon sample 4 which may have a diameter of, for example, about 4 inches (about 10cm) and an arsenic concentration of, for example, about 2.4 x 1025 atoms m#3 may, if desired, be cleaned of surface contaminants and protective thick oxide using a wet chemical cleaning process.

The wet chemical cleaning process may consist simply of a hydrofluoric acid dip etch or may be a hydrogen peroxide cleaning process such as described in a paper entitled 'Cleaning solutions based on hydrogen peroxide for use in silicon semiconductor technology' by W. Kern and D.A. Puotinen published in the RCA Review June 1970 at pages 197 to 206. Such wet chemical cleaning results in a thin native oxide being present on the surface 7a.

After the wet chemical cleaning process, the sample 4 is mounted on the support 3 within the reaction chamber 1. The reaction chamber 1 is then, as is conventional in the art, purged with nitrogen and the pressure in the reaction chamber 1 reduced to the desired operating pressure, in this example 0.5 Torr (66.5 Pa) using the pump 10.

The sample 4 is then heated by the heater contained in the support 3 to the desired deposition temperature, in this example 350 degrees Celsius. The gas supply to the gas supply pipe(s) 2a is then switched so as to provide the appropriate processing gases, in this example silane and nitric oxide in a ratio of NO:S1H4 of 6:1, in an inert carrier gas such as helium or argon.

In this example, flow rates of 120 cc per min. (cubic centimetres per minute) and 20 cc per min. were used for the nitric oxide and silane, respectively, and an inert carrier gas flow rate of from about 100 to 150 cc per min. was used for the inert carrier gas.

As mentioned above, the different processing gases may be supplied via separate outlets 20. The rf power source is also switched on, in this example providing a power of about 20W at 13.56 MHz, to generate an electric discharge between the first and second electrodes 6 and 7 causing a plasma to be formed in the spaces between the first and second electrodes 6 and 7 from the constituents of the processing gases. Typically with this arrangement, silicon dioxide is deposited at a rate of at least 12 nm per minute onto the sample.

Of course, apparatus in accordance with the invention could be used for plasma enhanced chemical vapour deposition of other materials on the silicon sample 4 using the methods appropriate in conventional plasma enhanced chemical vapour deposition. For example, the apparatus could be used for depositing silicon nitride or silicon oxynitride or for the epitaxial growth of silicon from, for example, silane or Sic13 and hydrogen gas, although in the case of epitaxial growth it would normally be necessary to carry out further cleaning in the reaction chamber, for example heating in the hydrogen carrier gas, to remove the volatile native oxide left after wet chemical cleaning.

Apparatus embodying the invention may be used for other types of plasma enhanced chemical vapour deposition and the semiconductor body sample need not necessarily be a silicon body. Also, the apparatus may be used for plasma enhanced etching or ashing, for example for providing a fluorinecontaining plasma for etching of silicon oxide, although in such circumstances higher rf powers would probably be required.

It has been found that, using apparatus in accordance with the invention, the discharge generating means comprising the first and second interleaved electrodes results in a very uniform plasma which is well confined to the region of the interleaved electrodes, it being possible to optimise conditions so that the plasma is entirely confined by the electrodes. Thus, a very precisely defined area of plasma can be achieved. Furthermore, the discharge generating means can relatively simply be moved within the reaction chamber so that the separation or spacing of the plasma from the substrate can be adjusted which should enable control over the processing, especially where deposition is concerned as the deposition rate has been found to decrease with increasing separation of the sample and the plasma. Various species are formed in a plasma and different species have different lifetimes.Thus, using apparatus embodying the invention which enables the separation of the sample support 3 and discharge generating means 5 to be relatively easily adjusted, enables control or adjustment of the species reaching the sample which will affect the characteristics of the plasmaprocessing and should, for example, enable the characteristics of a layer or film being deposited by plasma enhanced chemical vapour deposition using the apparatus to be adjusted or controlled to provide a layer or film with the desired characteristics.Furthermore, as indicated above, the first and second electrodes are interleaved in a plane extending transversely of the flow of the processing gases and the potential across the electrodes is similarly tranverse to the flow of the processing gases so that ions generated in the plasma tend to be deflected towards the negative electrode and not towards the sample being processed which should assist in reducing damage which may otherwise be caused to the sample by ion bombardment.

Although in the arrangement described above, the processing gases are all passed through the interleaved electrodes 6 and 7, this need not necessarily be the case. Indeed, it may be advantageous where deposition is concerned for at least one of the active species to be supplied directly to the sample so as to avoid gas phase reactions which could result in bad or uneven, for example 'snowstorm', deposition.Thus for example in the case of epitaxial growth of silicon, it may be possible for the silicon-containing gas, for example silane, to bypass the discharge generating means, for example by supplying the siliconcontaining gas to an outlet located very close to the surface of the sample, that is upstream of the discharge generating means, or by providing a relatively small area discharge generating means to form a small area plasma localised to the outlet of the hydrogen carrier gas and using a separate outlet for the silicon-containing gas.

In the arrangements described above, a simple pipe outlet is provided for the supply means. However, the or each gas supply pipe may have a shower head or other similar type of diffuser to provide a relatively even wide area flow of processing gas.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art of plasma enhanced processing and which may be used instead of or in addition to features already described herein.

Although claims have been formulated in this application to particular combinations of features it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims (8)

1. Apparatus for plasma processing a semiconductor body sample, which apparatus comprises a reaction chamber for establishing a low pressure environment, supply means for supplying processing gases into the reaction chamber, a support within the reaction chamber for receiving a sample to be processed, and means spaced-apart from the sample support for generating a plasma-inducing discharge within the reaction chamber, characterised in that the discharge generating means comprises first and second electrodes disposed within the chamber spaced-apart from the sample support, the first and second electrodes being insulated from one another and being interleaved in a plane extending transversely of the direction of flow of processing gases from the supply means for allowing processing gases to flow between the first and second electrodes towards the sample support to enable a plasma of constituents of the processing gases to be generated in the spaces between the first and second electrodes upon application of an electric potential across the first and second electrodes.

2. Apparatus according to Claim 1, wherein the sample support is arranged within the reaction chamber so that the surface on which the sample is to be supported is parallel to the plane in which the first and second electrodes are interleaved.

3. Apparatus according to Claim 1 or 2, wherein the first and second electrodes have opposed major surfaces extending along the direction of flow of processing gases from the supply means.

4. Apparatus according to Claim 1, 2 or 3, wherein the first and second electrodes comprise a series of parallel metal plates having first and second ends with the first ends of alternate ones of the plates being connected by connecting means to form the first electrode and the second ends of the remaining plates being connected by connecting means to form the second electrode.

5. Apparatus according to Claim 4, wherein the metal plates are formed of stainless steel and the connecting means are formed of copper.

6. Apparatus according to any one of the preceding claims, wherein means are provided for adjusting the spacing of the discharge generating means and the sample support.

7. Apparatus for plasma processing a semiconductor body sample, substantially as hereinbefore described with reference to the accompanying drawings.

8. Any novel feature or combination of features disclosed herein.