SUBSTRATE TREATING APPARATUS AND SUBSTRATE TREATING METHOD

The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a chamber having a space for treating a substrate therein; a support unit for supporting the substrate within the chamber; and an insulation member having a space of a predetermined volume therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

A claim for priority under 35 U.S.C. § 119 is made to Korean Patent Application No. 10-2021-0087214 filed on Jul. 2, 2021, in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

Embodiments of the inventive concept described herein relate to a substrate treating apparatus and a substrate treating method, more specifically, a substrate treating apparatus and a substrate treating method capable of adjusting an impedance of a chamber at which a substrate is treated.

BACKGROUND

The semiconductor manufacturing process may include a process of treating a substrate using a plasma. For example, during the semiconductor manufacturing process, an etching process may remove a thin film on the substrate using the plasma.

An isolator may be positioned below an electrostatic chuck supporting the substrate. According to an embodiment, the isolator may be composed of an Al2O3having a value between a dielectric constant of 9.4 to 10.5. Once sintered, the isolator has its own dielectric constant. However, the dielectric constant varies according to a sintering method and a material, and also becomes a factor that limits a chamber TTTM. In addition, if the isolator once installed is not replaced, an impedance of the chamber is fixed, and it is difficult to match an impedance level required during the process.

SUMMARY

Embodiments of the inventive concept provide a substrate treating apparatus capable of adjusting an impedance of a chamber.

The technical objectives of the inventive concept are not limited to the above-mentioned ones, and the other unmentioned technical objects will become apparent to those skilled in the art from the following description.

The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a chamber having a space for treating a substrate therein; a support unit for supporting the substrate within the chamber; and an insulation member having a space of a predetermined volume therein.

In an embodiment, the space is empty.

In an embodiment, a fluid is provided in a predetermined volume at the space.

In an embodiment, the space is filled with a fluid.

In an embodiment, the substrate treating apparatus further includes an adjusting unit for adjusting an injection amount of a fluid injected into the space.

In an embodiment, the adjusting unit adjusts the injection amount of the fluid so an impedance of the chamber is adjusted.

In an embodiment, the adjusting unit is a chiller or a pump.

The inventive concept provides a substrate treating apparatus. The substrate treating apparatus includes a chamber having a space for treating a substrate therein; a support unit for supporting the substrate within the chamber, and including an electrostatic chuck for adsorbing the substrate using an electrostatic force; a gas supply unit for supplying a treating gas within the space; a plasma source for generating a plasma from the treating gas; and an insulation member positioned below the electrostatic chuck, and having a space of a predetermined volume therein.

In an embodiment, the space is empty.

In an embodiment, a fluid is provided in a predetermined volume at the space.

In an embodiment, the space is filled with a fluid.

In an embodiment, the substrate treating apparatus further includes an adjusting unit for adjusting an injection amount of a fluid injected to the space.

In an embodiment, the adjusting unit adjusts the injection amount of the fluid so an impedance of the chamber is adjusted.

In an embodiment, the adjusting unit is a chiller or a pump.

The inventive concept provides a substrate treating method using the substrate treating apparatus. The substrate treating method includes injecting a fluid to the space

In an embodiment, the substrate treating method of includes adjusting an impedance of the chamber by adjusting an injection amount of the fluid.

In an embodiment, an impedance adjusting of the chamber is simultaneously adjusted with a substrate treatment.

According to an embodiment of the inventive concept, an impedance of a chamber may be effectively controlled.

According to an embodiment of the inventive concept, a life of a chamber may be increased.

The effects of the inventive concept are not limited to the above-mentioned ones, and the other unmentioned effects will become apparent to those skilled in the art from the following description.

DETAILED DESCRIPTION

The inventive concept may be variously modified and may have various forms, and specific embodiments thereof will be illustrated in the drawings and described in detail. However, the embodiments according to the concept of the inventive concept are not intended to limit the specific disclosed forms, and it should be understood that the present inventive concept includes all transforms, equivalents, and replacements included in the spirit and technical scope of the inventive concept. In a description of the inventive concept, a detailed description of related known technologies may be omitted when it may make the essence of the inventive concept unclear.

FIG.1is an exemplary view illustrating a substrate treating apparatus according to an embodiment of the inventive concept.

FIG.1illustrates a substrate treating apparatus W using a capacitively coupled plasma (CCP) treating method. Referring toFIG.1, the substrate treating apparatus10treats the substrate W using a plasma. For example, the substrate treating apparatus10may perform an etching process on the substrate W. The substrate treating apparatus10may include a chamber620, a substrate support unit200, a shower head300, a gas supply unit400, an exhaust baffle500, and a plasma generation unit600.

The chamber620may provide a treating space in which a substrate treating process is performed. The chamber620may have a treating space therein and may be provided in a sealed shape. The chamber620may be made of a metal material. The chamber620may be made of an aluminum material. The chamber620may be grounded. An exhaust hole102may be formed on a bottom surface of the chamber620. The exhaust hole102may be connected to an exhaust line151. A reaction by-product generated during the process and a gas remaining in an inner space of the chamber may be discharged to an outside through the exhaust line151. An inside of the chamber620may be depressurized to a predetermined pressure by the exhaust process.

According to an embodiment, a liner130may be provided inside the chamber620. The liner130may have a cylindrical shape with an open top surface and an open bottom surface. The liner130may be provided to be in contact with an inner surface of the chamber620. The liner130may protect an inner wall of the chamber620to prevent the inner wall of the chamber620from being damaged by the arc discharge. In addition, it is possible to prevent impurities generated during the substrate treating process from being deposited on the inner wall of the chamber620. Selectively, the liner130may not be provided.

The substrate support unit200may be positioned inside the chamber620. The substrate support unit200may support the substrate W. The substrate support unit200may include an electrostatic chuck210that sucks the substrate W using an electrostatic force. Alternatively, the substrate support unit200may support the substrate W in various ways such as a mechanical clamping. Hereinafter, the substrate support unit200including the electrostatic chuck210will be described.

The substrate support unit200may include an electrostatic chuck210, a bottom cover250, and a plate270. The substrate support unit200may be positioned inside the chamber620to be upwardly spaced apart from a bottom surface of the chamber620.

The electrostatic chuck210may include a dielectric plate220, a body230, and a focus ring240. The electrostatic chuck210may support the substrate W. The dielectric plate220may be positioned at a top end of the electrostatic chuck210. The dielectric plate220may be provided as a disk-shaped dielectric substance. The substrate W may be disposed on a top surface of the dielectric plate220. The top surface of the dielectric plate220may have a radius smaller than that of the substrate W. Therefore, an edge region of the substrate W may be located outside the dielectric plate220.

The dielectric plate220may include a first electrode223, a heating unit225, and a first supply fluid channel221therein. The first supply fluid channel221may be provided from a top surface to a bottom surface of the dielectric plate210. A plurality of first supply fluid channel221are formed to be spaced apart from each other, and may be provided as a passage through which a heat transfer medium is supplied to a bottom surface of the substrate W.

The first electrode223may be electrically connected to a first power source223a. The first power source223amay include a DC power.

A switch223bmay be installed between the first electrode223and the first power source223a. The first electrode223may be electrically connected to the first power source223aby on/off of the switch223b. When the switch223bis turned on, a DC current may be applied to the first electrode223. An electrostatic force is applied between the first electrode223and the substrate W by a current applied to the first electrode223, and the substrate W may be sucked to the dielectric plate220by the electrostatic force.

The heating unit225may be located below the first electrode223. The heating unit225may be electrically connected to the second power source225a. The heating unit225may generate a heat by resisting a current applied from the second power source225a. A generated heat may be transferred to the substrate W through the dielectric plate220. The substrate W may be maintained at a predetermined temperature by the heat generated by the heating unit225. The heating unit225may include a spiral shape coil.

The first circulation fluid channel231may be provided as a channel through which the heat transfer medium circulates. The first circulation fluid channel231may be formed in a spiral shape inside the body230. Alternatively, the first circulation fluid channel231may be disposed such that ring-shaped channels having different radii have the same center. Each of the first circulation fluid channel231may communicate with each other. The first circulation fluid channel231may be formed at the same height.

The second fluid channel232may be provided as a channel through which a cooling fluid circulates. The second circulation fluid channel232may be formed in a spiral shape inside the body230. Alternatively, the second circulation fluid channel232may be disposed such that ring-shaped channels having different radii have the same center. Each of the second circulation fluid channel232may communicate with each other. The second circulation fluid channel232may have a cross-sectional area greater than that of the first circulation fluid channel231. The second circulation fluid channel232may be formed at the same height. The second circulation fluid channel232may be located below the first circulation fluid channel231.

The second supply fluid channel233may upwardly extend from the first circulation fluid channel231and may be provided to a top surface of the body230. The second supply fluid channel243may be provided in a number corresponding to the first supply fluid channel221, and may connect the first circulation fluid channel231to the first supply fluid channel221.

The first circulation fluid channel231may be connected to a heat transfer medium storage unit231athrough a heat transfer medium supply line231b. The heat transfer medium may be stored in the heat transfer medium storage unit231a. The heat transfer medium may include an inert gas. According to an embodiment, the heat transfer medium may include a helium He gas. The helium gas may be supplied to the first circulation fluid channel231through the supply line231b, and may be supplied to the bottom surface of the substrate W through the second supply fluid channel233and the first supply fluid channel221sequentially. The helium gas may serve as a medium through which a heat transferred from the plasma to the substrate W is transferred to the electrostatic chuck210.

The second circulation fluid channel232may be connected to a cooling fluid storage unit232athrough a cooling fluid supply line232c. The cooling fluid may be stored in the cooling fluid storage unit232a. A cooler232bmay be provided within the cooling fluid storage unit232a. The cooler232bmay cool the cooling fluid to a predetermined temperature. Alternatively, the cooler232bmay be installed at the cooling fluid supply line232c. The cooling fluid supplied to the second circulation fluid channel232through the cooling fluid supply line232cmay circulate along the second circulation fluid channel232to cool the body230. The body230may cool the dielectric plate220and the substrate W together to maintain the substrate W at a predetermined temperature.

The body230may include a metal plate. In an embodiment, all of the body230may be provided as a metal plate.

The focus ring240may be disposed in an edge region of the electrostatic chuck210. The focus ring240may have a ring shape and may be disposed along the circumference of the dielectric plate220. A top surface of the focus ring240may be positioned such that an outer portion240ais higher than an inner portion240b. The top surface inner portion240bof the focus ring240may be positioned at the same height as the top surface of the dielectric plate220. The inner portion240bof the top surface of the focus ring240may support the edge region of the substrate W positioned outside the dielectric plate220.

The outer portion240aof the focus ring240may be provided to surround the edge region of the substrate W. The focus ring240may control the electromagnetic field so that the plasma density is uniformly distributed in an entire region of the substrate W. Accordingly, the plasma is uniformly formed over the entire area of the substrate S, so that each area of the substrate W may be uniformly etched.

The bottom cover250may be located at a bottom end of the substrate support unit200. The bottom cover250may be positioned to be upwardly spaced apart from the bottom surface of the chamber620. The bottom cover250may have a space255having an open top surface formed therein.

An outer radius of the bottom cover250may have a same length as an outer radius of the body230. In an inner space255of the bottom cover250, a lift pin module (not shown) or the like for moving a returned substrate W from an external transfer member to the electrostatic chuck210may be positioned. The lift pin module (not shown) may be spaced apart from the bottom cover250by a predetermined distance. A bottom surface of the bottom cover250may be made of a metal material. In the inner space255of the bottom cover250, air may be provided. Since air has a dielectric constant lower than that of an insulator, it may serve to reduce the electromagnetic field inside the substrate support unit200.

The bottom cover250may have a connection member253. The connection member253may connect the outer surface of the bottom cover250to the inner wall of the chamber620. A plurality of connection members253may be provided at the outer surface of the bottom cover250at regular intervals. The connection member253may support the substrate support unit200inside the chamber620. In addition, the connection member253may be connected to the inner wall of the chamber620so that the bottom cover250is electrically grounded. A first power line223cconnected to the first power source223a, a second power line225cconnected to the second power source225a, and a heat transfer medium supply line231bconnected to the heat transfer medium storage unit231a, etc may be extended within the bottom cover250through the inner space255of the connecting line.

A plate270may be positioned between the electrostatic chuck210and the bottom cover250. The plate270may cover a top surface of the bottom cover250. The plate270may be provided with a cross-sectional area corresponding to the body230. The plate270may include an insulator. According to an embodiment, one or more plates270may be provided. The plate270may serve to increase an electrical distance between the body230and the bottom cover250. The plate270may be an insulation member. Referring theFIG.2, an embodiment of the plate270will be explained further.

The shower head300may be positioned in the chamber620above the substrate support unit. The shower head may be placed to face the substrate support unit.

The shower head300may include a gas dispersion plate310and a support unit330. The gas dispersion plate may be positioned spaced apart from a top surface to a bottom of the chamber620. A predetermined space may be formed between the gas dispersion plate310and the top surface of the chamber620. A thickness of the gas dispersion plate310may be provided in a predetermined plate form. A bottom surface of the gas dispersion plate310may have its surface anodic oxidation(anodizing) treated so an arc generation is prevented by a plasma. An end of the gas dispersion plate310may have a same form and a same cross-sectional area as that of the substrate support unit200. The gas dispersion plate310may have a plurality of injection holes311. The injection holes311may vertically penetrate the top surface and the bottom surface of the gas dispersion plate310. The gas dispersion plate may include a metal material.

The support unit330may support a side part of the gas dispersion plate310. The support plate310is connected to a top surface of the chamber620, and a bottom surface is connected to a side of the gas dispersion plate310. The support place may include a non-metal material.

The gas supply unit400may supply a process gas into the chamber620. The gas supply unit400may include a gas supply nozzle410, a gas supply line420, and a gas storage unit430. The gas supply nozzle410may be installed at a center of a top surface of the chamber620. A spray hole may be formed at a bottom surface of the gas supply nozzle410. The injection port may supply a process gas into the chamber620. The gas supply line420may connect the gas supply nozzle410and the gas storage unit430. The gas supply line420may supply the process gas stored in the gas storage unit430to the gas supply nozzle410. A valve421may be installed at the gas supply line420. The valve421may open and close the gas supply line420and control a flow rate of the process gas supplied through the gas supply line420.

An exhaust baffle500may be positioned between the inner wall of the chamber620and the substrate support unit200. The exhaust baffle500may be provided in an annular ring shape. A plurality of through holes511may be formed at the exhaust baffle500. The process gas provided in the chamber620may pass through the through holes511of the exhaust baffle500and may be exhausted through the exhaust hole102. A flow of the process gas may be controlled according to a shape of the exhaust baffle500and a shape of the through holes.

The plasma generation unit600may excite the process gas in the chamber620to a plasma state. According to an embodiment of the inventive concept, the plasma generation unit600may be configured in an inductively coupled plasma (ICP) type. In this case, as shown inFIG.1, the plasma generation unit600may include a high frequency power source610for supplying a high frequency power, a first coil621and a second coil622electrically connected to the high frequency power source to receive the high frequency power.

The plasma generation unit600described herein is described as an inductively coupled plasma (ICP) type, but is not limited thereto and may be formed as a capacitively coupled plasma (CCP) type.

When a CCP type plasma source is used, the chamber620may include a top electrode and a bottom electrode, that is, a body.

The top electrode and the bottom electrode may be disposed parallel to each other in an up/down direction with a treating space therebetween. Not only the bottom electrode but also the top electrode may receive an energy for generating the plasma by receiving an RF signal by an RF power source, and the number of RF signals applied to each electrode is not limited to one as shown. An electric field is formed in a space between both electrodes, and the process gas supplied to the space may be excited in the plasma state. A substrate treatment process is performed using this plasma.

Referring back toFIG.1, the first coil621and the second coil622may be disposed at positions facing the substrate W. For example, the first coil621and the second coil622may be installed on top of the chamber620. A diameter of the first coil621is smaller than a diameter of the second coil622, so it may be positioned at an inner part of a top of the chamber620and the second coil622may be positioned at on outer part of the top of the chamber620. The first coil621and the second coil622may receive a high frequency power from a high frequency power source610to induce a time-varying magnetic field to the chamber, and thus the process gas supplied to the chamber620may be excited to the plasma.

Hereinafter, a process of treating a substrate using a substrate treating apparatus described above will be described.

When the substrate W is placed on the substrate support unit200, a DC current may be applied from the first power source223ato the first electrode223. An electrostatic force may be applied between the first electrode223and the substrate W by the DC current applied to the first electrode223, and the substrate W may be adsorbed to an electrostatic chuck210by the electrostatic force.

When the substrate W is adsorbed to the electrostatic chuck210, a process gas may be supplied into the chamber620through a gas supply nozzle410. The process gas may be uniformly injected into an inner region of the chamber620through an injection hole311of the shower head300. A high frequency power generated from a high frequency power source may be applied to a plasma source, and thus the electromagnetic force may be generated in the chamber620. The electromagnetic force may excite the process gas between the substrate support unit200and the shower head300with a plasma. The plasma may be provided to the substrate W to treat the substrate W. The plasma may perform an etching process.

FIG.2is a cross-sectional view illustrating a substrate treating apparatus according to an embodiment of the inventive concept in more detail.

InFIG.2, a description of an overlapping portion with the substrate treating apparatus inFIG.1will be omitted. Referring toFIG.2, the substrate treating apparatus in accordance with an embodiment of the inventive concept may contain an insulation member270having a space with a predetermined volume therein. The space271having a predetermined volume may be a fluid channel through which a fluid may communicate. According to an embodiment, the insulation member270may be positioned below the electrostatic chuck. According to an embodiment, the insulation member270may be a plate. In the following description of the inventive concept, the insulation member270and an isolator are used interchangeably.

According to an embodiment, the space271of the insulation member270may be provided in an empty state. According to an embodiment, the space271of the insulation member270may be provided filled with a predetermined volume. According to an embodiment, the space271of the insulation member270may be completely filled with a fluid.

In accordance with an embodiment, the substrate treating apparatus in accordance with this invention may further include an adjusting unit272capable of adjusting an injection amount of a fluid filling the space271in the insulation member270. According to an embodiment, the adjusting unit272may be a chiller or a pump. According to an embodiment, the adjusting unit272may include both a chiller and a pump. The adjusting unit272may adjust an impedance by adjusting an amount of an air and a fluid and varying a ratio. The adjusting unit272may adjust the impedance of the chamber by adjusting the injection amount of the fluid. In this case, the fluid filling the space271may be a non-conducting liquid. According to an embodiment, the liquid injected into the space271may be an fc40. According to an embodiment, the liquid injected into the space271may be an fc3283. According to an embodiment, the fluid filling the space271may be provided as a liquid having a high insulation effect.

The adjusting unit272may change a state of a dielectric constant of the insulation member270by adjusting a fluid amount within the fluid channel. According to the inventive concept, a material composition within the fluid channel may be changed through a chiller or pump included in the adjusting unit272. Through this, the impedance of the isolator may be changed during a process, thereby benefiting the process.

Although not illustrated inFIG.2, in addition to the adjusting unit272capable of controlling the fluid, the substrate treating apparatus may further include a measuring unit (not illustrated) capable of measuring the impedance of the chamber. According to an embodiment, by measuring the impedance of the chamber in real-time, the measuring unit may control a fluid amount injected into the space271to have a desired impedance.

According to the inventive concept, a fluid channel is formed in a ceramic isolator that is, an insulation member270, provided in a bottom part of the electrostatic chuck for an efficient use of the electrostatic chuck, thereby forming the space271and controlling an amount of the fluid included in the space271, thereby changing the impedance of the entire chamber. According to an embodiment, the ceramic isolator may be an insulation member270. A impedance of the insulation member270may be changed by controlling the amount of fluid injected into the fluid channel.

FIG.3illustrates an embodiment of forming a space271according to an embodiment of the inventive concept.

Referring toFIG.3, an embodiment in which a fluid channel path pattern is formed on an insulation member270is disclosed. According to the inventive concept, by forming a fluid channel within an isolator and injecting a fluid or a gas into the fluid channel, a part of the isolator is made into an empty space271, that is, a state having a predetermined dielectric constant in a vacuum dielectric constant 0 state, and thus an impedance matching may be actively controlled for TTTM(Tool To Tool Matching) of chambers. In addition, a process can be effectively performed by adjusting a dielectric constant of the isolator in a process step that requires a certain level of an impedance change between processes. According to an embodiment, a form of a fluid channel pattern may be variously formed.

In the case of the conventional technology, an existing isolator has a fixed dielectric constant after a sintering is completed, and thus there is a problem in that the dielectric constant is different according to the sintering conditions and materials of the isolator. In the conventional case, there is also a problem in that the ER gradient varies depending on the impedance of the isolator. Here, ER means an etching rate.

When the space271is formed by forming a fluid channel in the isolator according to the inventive concept, an impedance change may be induced according to a degree of filling of the space271in the isolator.

FIG.4toFIG.5illustrate a process change according to a thickness of the space271of the insulation member270.

In more detail,FIG.4illustrates an ER change for each inner space271within the insulation member270.FIG.5illustrates changes a CD change and a bias change for each inner space271within the insulation member270. A CD means a critical dimension.

Referring toFIG.4, an ER in accordance with an experimental example of dielectric constants of an inner space271of each insulation member270divided into embodiments A, B, C, and D, respectively, is disclosed. According to an embodiment, B indicates a case where Al2O3 is 100%, and A and D indicate a case where AL2O3 is 80% and AIR is 20%. C represents a 20% increase in power in the case of B. Referring toFIG.4, it can be found that as the dielectric constant of the inner space271of the insulation member270decreases (AL2O3->AIR), the ER increases. In other words, in accordance with the inventive concept, it is possible to induce an impedance change by filling and emptying the inner space271of an isolator at a predetermined ratio by using the adjusting unit272, that is, a chiller or a pump.

FIG.5shows a Vrms value, an Irms value, and a CH change and a bias change for each inner space of the isolator, respectively. Referring toFIG.4andFIG.5, a bottom impedance change, an ER change, and a CD change occurs according to an amount of a material occupying the inner space271of the insulation member270, thereby making it possible to use the material according to a situation.

The effects according to the inventive concept may be as follows. From a viewpoint of a TTTM of the chamber, it may be advantageous for the TTTM of the chamber to use an isolator which is variable than an isolator having a fixed dielectric constant value. In addition, in terms of improving a production efficiency of a facility, the inner change of the chamber due to an etching of a peripheral ring of the substrate may be controlled through a fluid according to the inventive concept to enable a using of the facility for a longer time. In addition, in terms of an entry to a facility process, for high-level processes that require various impedances, such a development can lead to a performing of a process of multiple conditions in a facility at once, or a performing of a process done with more precision.

FIG.6illustrates a space271within an insulation member270according to various embodiments of the inventive concept.

Referring toFIG.6(a), a fluid channel is configured in the isolator, and a dielectric constant is adjusted by changing the inner space271of the isolator to a condition that fills a fluid in a vacuum, thereby changing an impedance of a chamber to efficiently perform a process.

InFIG.6, when a fluid having a higher dielectric constant than the isolator is used to control the isolator, electrical characteristics of the isolator become stronger and cause an impedance weakening, thereby reducing an ER level. and when a fluid having a lower dielectric constant than the isolator is used, the ER level of the isolator may be induced to be higher.

Although only an embodiment in which the fluid is filling, half filling, or not in the space271is disclosed inFIG.6(a)toFIG.6(c), the inventive concept is not limited thereto and the fluid may be adjusted to have various volumes in the space271.

FIG.7is a flowchart illustrating a substrate treating method according to an embodiment of the inventive concept.

In accordance with the inventive concept, a step of injecting a fluid into a space271in an insulation member270, and a step of adjusting an impedance of a chamber by adjusting an injection amount of the fluid may be included.

According to an embodiment, the impedance of the chamber may be adjusted simultaneously with a substrate treatment. That is, while treating a substrate, the impedance may be changed in real time while adjusting the injection amount of the fluid. The inventive concept may change the impedance of the chamber by controlling an amount of a material filling the inner space271of a bottom isolator of the chamber, thereby facilitating a TTTM between chambers and an entry to high-level processes.

The effects of the inventive concept are not limited to the above-mentioned effects, and the unmentioned effects can be clearly understood by those skilled in the art to which the inventive concept pertains from the specification and the accompanying drawings.

Although the preferred embodiment of the inventive concept has been illustrated and described until now, the inventive concept is not limited to the above-described specific embodiment, and it is noted that an ordinary person in the art, to which the inventive concept pertains, may be variously carry out the inventive concept without departing from the essence of the inventive concept claimed in the claims and the modifications should not be construed separately from the technical spirit or prospect of the inventive concept.