阅读说明：本技术 一种碳化硅功率器件及其制备方法 (Silicon carbide power device and preparation method thereof ) 是由 黄兴 陈欣璐 于 2021-09-03 设计创作，主要内容包括：本发明提供了一种碳化硅功率器件及其制备方法,涉及碳化硅功率器件领域,在第二导电类型注入基区、第一导电类型注入源区注入之前先制作耐1600℃以上高温的栅氧层和多晶SiC或AlN栅极,并将栅氧层和栅极作为上述离子注入的掩蔽层,再进行离子退火,既节省了现有光刻工序中用来形成第二导电类型注入基区和第一导电类型注入源区的光刻板,缩短了碳化硅器件的制备周期,也相应节省了形成第二导电类型注入基区的和第一导电类型注入源区的蚀刻步骤,减少由于蚀刻精度导致的器件沟道不均匀问题,最终提升了碳化硅功率器件良率,降低了相应的制造成本。(The invention provides a silicon carbide power device and a preparation method thereof, and relates to the field of silicon carbide power devices.A gate oxide layer and a polycrystalline SiC or AlN grid which can resist the high temperature of more than 1600 ℃ are firstly manufactured before a second conductive type injection base region and a first conductive type injection source region are injected, the gate oxide layer and the grid are used as masking layers for ion injection, and then ion annealing is carried out, so that a photoetching plate for forming the second conductive type injection base region and the first conductive type injection source region in the existing photoetching process is saved, the preparation period of the silicon carbide device is shortened, the etching steps for forming the second conductive type injection base region and the first conductive type injection source region are correspondingly saved, the problem of uneven device channels caused by etching precision is reduced, the yield of the silicon carbide power device is finally improved, and the corresponding manufacturing cost is reduced.)

1. A preparation method of a silicon carbide power device is characterized by comprising the following steps:

providing a silicon carbide semiconductor substrate, wherein the silicon carbide semiconductor substrate comprises a first conductive type semiconductor substrate and a first conductive type silicon carbide epitaxial layer positioned on the surface of the first conductive type semiconductor substrate; forming a first masking material layer on the surface of the epitaxial layer; carrying out a first photoetching procedure to form a first masking layer with an injection window; performing first ion implantation on the implantation window to form a second conductive type re-implantation body region;

stripping the first masking layer; forming a gate oxide material layer and a gate material layer on the surface of the gate oxide material layer, wherein the gate oxide material layer resists the high temperature of more than 1600 ℃, and the gate material layer is a polycrystalline SiC layer or an AlN layer; carrying out a second photoetching procedure on the gate oxide material layer and the gate material layer to form a gate structure, wherein the gate structure comprises a gate oxide layer positioned on the surface of the epitaxial layer and a gate positioned on the gate oxide layer;

forming a second conductive type injection base region by performing second ion injection by taking the grid structure as a second masking layer, wherein the second ion injection is inclined ion injection;

forming a first conductive type implantation source region by performing third ion implantation by taking the gate structure as a second masking layer, wherein the third ion implantation is inclined ion implantation or vertical ion implantation;

forming carbon films on the surfaces of the grid structure and the silicon carbide epitaxial layer, then carrying out ion annealing, and removing the carbon films after the ion annealing;

respectively forming a gate-source inter-electrode medium, a source electrode and a drain electrode.

2. The method of claim 1A preparation method of a silicon carbide power device is characterized in that a grid material layer with a polycrystalline SiC layer or an AlN layer formed on the surface of a grid oxide material layer specifically comprises the following steps: adding SiH₄、C₃H₈Forming a polycrystalline SiC layer by chemical vapor deposition; or mixing AlCl₃、NH₃The AlN layer was formed by chemical vapor deposition.

3. The method according to claim 1, wherein performing a second photolithography etching process on the gate oxide material layer and the gate material layer to form the gate structure specifically comprises: spin-coating a uniform photoresist film on the surface of a gate material layer of a silicon carbide semiconductor substrate; putting the silicon carbide semiconductor substrate into a photoetching machine and exposing under a grid structure photoetching plate; developing the silicon carbide semiconductor substrate subjected to exposure; etching the gate oxide material layer and the gate material layer; and removing the photoresist film by using acetone, methanol and deionized water in sequence, and finally forming a gate structure on the surface of the epitaxial layer of the silicon carbide semiconductor substrate.

4. The method of claim 1, wherein the gate oxide material layer is Al₂O₃A layer or a High-K material layer.

5. The method of claim 1, wherein the deposition process for forming the gate oxide material layer is atomic layer deposition.

6. The method according to claim 1, wherein the angle of the tilted ion implantation is 0 to 90 degrees.

7. The method of claim 1, wherein the carbon film is formed on the gate structure and the surface of the silicon carbide epitaxial layer by a high temperature carbonization photoresist or magnetron sputtering method.

8. The method of claim 1, wherein the ion annealing is performed at 1600 ℃ to 1800 ℃.

9. The method of claim 1, wherein the removing the carbon film after the ion annealing is performed by O₂The method for cleaning the plasma is realized.

10. A silicon carbide power device produced by the method for producing a silicon carbide power device according to any one of claims 1 to 9.

Technical Field

The invention relates to the field of silicon carbide power devices, in particular to a silicon carbide power device and a preparation method thereof.

Background

Silicon carbide is the fastest-developing wide bandgap power semiconductor material, and power devices manufactured by using the silicon carbide material have higher breakdown voltage and faster switching speed than devices manufactured by using the silicon material. However, the existing silicon carbide power device has a complex manufacturing process and a long manufacturing period, and the application of the silicon carbide power device is greatly limited.

Referring to fig. 1 to 5, corresponding to steps one to five of the manufacturing process of the silicon carbide power device in the prior art, respectively.

In the first step: after cleaning the silicon carbide semiconductor substrate, SiO is deposited on the surface of the epitaxial layer₂The layer is subjected to corresponding first photoetching procedure under a first photoetching plate to generate a first masking layer, and then the first masking layer is subjected to ion implantation to form a second conductive type re-implantation body region;

in the second step: stripping the first masking layer and depositing SiO on the surface of the epitaxial layer₂The layer is subjected to a corresponding second photoetching procedure under a second photoetching plate to generate a second masking layer, and then the second masking layer is subjected to ion implantation to form a second conductive type implantation base region;

in step three: stripping the second masking layer and depositing SiO on the surface of the epitaxial layer₂The layer is subjected to a corresponding third photoetching procedure under a third photoetching plate to generate a third masking layer, and then the third masking layer is subjected to ion implantation to form a first conductive type implantation source region;

in step four: stripping the third masking layer, carrying out ion annealing at the temperature above 1600 ℃ and depositing SiO on the surface of the epitaxial layer after annealing₂The layer and the polycrystalline silicon layer are subjected to a corresponding fourth photoetching procedure under a fourth photoetching plate to generate a grid electrode;

in the fifth step: depositing an inter-electrode isolation dielectric layer on the surface of the epitaxial layer, and performing a fifth photoetching procedure on the inter-electrode isolation dielectric layer to form a gate-source inter-electrode dielectric and a source region; a source electrode is formed in the source region, and a drain electrode is formed on the back surface of the substrate.

In summary, in the existing manufacturing process of the silicon carbide power device, at least five layers of photolithography boards are required, and 3 times of etching is required to be performed on the ion-implanted masking layer, so that the problems that the related manufacturing process is complicated, the accuracy requirement in the photolithography etching process is greatly increased, the yield of the device is affected, the manufacturing period of the device is long due to the complicated related manufacturing process, and the manufacturing cost of the silicon carbide power device is indirectly increased are caused.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the silicon carbide power device and the preparation method thereof, which greatly reduce the process complexity and the silicon carbide flow chip period, thereby indirectly reducing the manufacturing cost of the silicon carbide power device.

In order to achieve the above object, an embodiment of the present invention provides a method for manufacturing a silicon carbide power device, including: providing a silicon carbide semiconductor substrate, wherein the silicon carbide semiconductor substrate comprises a first conductive type semiconductor substrate and a first conductive type silicon carbide epitaxial layer positioned on the surface of the first conductive type semiconductor substrate; forming a first masking material layer on the surface of the epitaxial layer; carrying out a first photoetching procedure to form a first masking layer with an injection window; performing first ion implantation on the implantation window to form a second conductive type re-implantation body region; stripping the first masking layer; forming a gate oxide material layer and a gate material layer on the surface of the gate oxide material layer, wherein the gate oxide material layer resists the high temperature of more than 1600 ℃, and the gate material layer is a polycrystalline SiC layer or an AlN layer; carrying out a second photoetching procedure on the gate oxide material layer and the gate material layer to form a gate structure, wherein the gate structure comprises a gate oxide layer positioned on the surface of the epitaxial layer and a gate positioned on the gate oxide layer; forming a second conductive type injection base region by performing second ion injection by taking the grid structure as a second masking layer, wherein the second ion injection is inclined ion injection; forming a first conductive type implantation source region by performing third ion implantation by taking the gate structure as a second masking layer, wherein the third ion implantation is inclined ion implantation or vertical ion implantation; sputtering the gate structure and the surface of the silicon carbide epitaxial layer to form a carbon film, then carrying out ion annealing, and removing the carbon film after the ion annealing; respectively forming a gate-source inter-electrode medium, a source electrode and a drain electrode.

Optionally, the step of forming a gate material layer of the polycrystalline SiC layer or the AlN layer on the surface of the gate oxide material layer specifically includes: adding SiH₄、C₃H₈Forming a polycrystalline SiC layer by chemical vapor deposition; or mixing AlCl₃、NH₃The AlN layer was formed by chemical vapor deposition.

Optionally, performing a second photolithography and etching process on the gate oxide material layer and the gate material layer to form a gate structure specifically includes: spin-coating a uniform photoresist film on the surface of a gate material layer of a silicon carbide semiconductor substrate; putting the silicon carbide semiconductor substrate into a photoetching machine and exposing under a grid structure photoetching plate; developing the silicon carbide semiconductor substrate subjected to exposure; etching the developed gate oxide material layer and the developed gate material layer; and removing the photoresist film by using acetone, methanol and deionized water in sequence, and finally forming a gate structure on the surface of the epitaxial layer of the silicon carbide semiconductor substrate.

Optionally, the gate oxide material layer is Al₂O₃A layer or a High-K material layer.

Optionally, a deposition process for forming the gate oxide material layer is atomic layer deposition.

Optionally, the angle of the tilted ion implantation is 0 to 90 degrees.

Optionally, a carbon film is formed on the gate structure and the surface of the silicon carbide epitaxial layer, and the carbon film is formed by a high-temperature carbonization photoresist or a magnetron sputtering method.

Optionally, the ion annealing is performed at 1600 ℃ to 1800 ℃.

Optionally, removing the carbon film after the ion annealing is performed by O₂The method for cleaning the plasma is realized.

The embodiment of the invention also provides a silicon carbide power device, which is prepared by the preparation method of the silicon carbide power device.

In conclusion, the beneficial effects of the invention are as follows:

the embodiment of the invention provides a silicon carbide power device and a preparation method thereof, wherein a gate oxide layer and a grid electrode are firstly manufactured before a second conductive type injection base region and a first conductive type injection source region are injected, the gate oxide layer and the grid electrode are used as masking layers for the ion injection, and then the ion annealing is carried out, so that a photoetching plate for forming the second conductive type injection base region and the first conductive type injection source region in the conventional photoetching process is saved, the preparation period of the silicon carbide power device is shortened, the etching steps for forming the second conductive type injection base region and the first conductive type injection source region are correspondingly saved, the problem of uneven device channels caused by etching precision is reduced, the problem that the quality of an epitaxial layer is rough and uneven after the ion annealing is solved, and the carrier mobility in the device is influenced by the deterioration of the growth quality of the gate oxide is solved, finally, the yield of the silicon carbide power device is improved, and the corresponding manufacturing cost is reduced.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 to 5 are schematic flow structure diagrams illustrating a method for manufacturing a silicon carbide power device in the prior art;

fig. 6 to 11 are schematic flow-structure diagrams illustrating a method for manufacturing a silicon carbide power device according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail below with reference to specific examples in order to facilitate understanding by those skilled in the art.

The embodiment of the invention firstly provides a preparation method of a silicon carbide power device.

Referring to fig. 6, a silicon carbide semiconductor substrate is provided, which includes a first conductivity type semiconductor substrate 101 and a first conductivity type silicon carbide epitaxial layer 102 on a surface of the first conductivity type semiconductor substrate 101; forming a first masking material layer on the surface of the epitaxial layer; carrying out a first photoetching procedure to form a first masking layer with an injection window; a first ion implantation is performed to the implantation window to form a second conductive type re-implantation body region 103.

In the embodiment of the present invention, the first conductivity type semiconductor substrate 101 is a first conductivity type silicon carbide substrate.

In the embodiment of the invention, the first masking material layer is SiO₂Layer, in other embodiments, mayOther material layers are deposited on the surface of the epitaxial layer 102 as a first masking material layer as needed.

In this embodiment, the first conductivity type semiconductor substrate and the first conductivity type silicon carbide epitaxial layer are doped P-type, and the first ion implantation of the second conductivity type heavily-implanted body region is doped N-type.

In an embodiment of the present invention, the performing the first photolithography etching process to form the first masking layer having the implantation window specifically includes: spin-coating a uniform photoresist film on the surface of the first masking material layer; putting the silicon carbide semiconductor substrate into a photoetching machine and exposing under a re-injection body region photoetching plate; developing the photoresist film after exposure; etching the first masking material layer by taking the developed photoresist film as a mask; and removing the photoresist film by using acetone, methanol and deionized water in sequence, and finally forming a first masking layer with an injection window on the surface of the silicon carbide epitaxial layer 102.

Stripping the first masking layer; the first masking layer is removed by chemical stripping, and after the first masking layer is stripped, the silicon carbide semiconductor substrate needs to be cleaned, so that the surface of the silicon carbide epitaxial layer 102 is removed, and corresponding impurities are mixed due to possible contamination. In the related Cleaning step, the silicon carbide semiconductor substrate may be sequentially cleaned with acetone, methanol, and deionized water in an ultrasonic environment, and finally dried by blowing with nitrogen, or other Cleaning methods such as RCA Cleaning may be adopted, and thus, the details are not repeated herein.

Referring to fig. 7, a gate structure is formed on the surface of the silicon carbide epitaxial layer.

The step of forming the gate structure comprises: firstly, forming a gate oxide material layer on the surface of an epitaxial layer 102; forming a gate material layer on the surface of the gate oxide material layer; spin-coating a uniform photoresist film on the surface of the gate material layer; putting the silicon carbide semiconductor substrate into a photoetching machine and exposing under a grid structure photoetching plate; developing the photoresist film after exposureShadow; etching the gate oxide material layer and the gate material layer by taking the developed photoresist film as a mask; sequentially removing the photoresist film by using acetone, methanol and deionized water, and finally forming a gate structure on the surface of the epitaxial layer 102 of the silicon carbide semiconductor substrate, wherein the gate structure comprises a gate oxide layer 106 positioned on the surface of the epitaxial layer 102 and a gate 107 positioned on the gate oxide layer; wherein the gate oxide material layer is Al₂O₃The gate electrode comprises a layer or a High-K material layer, wherein the gate electrode material layer is a polycrystalline SiC layer or an AlN layer.

In other embodiments, a gate oxide material layer may be deposited on the surface of the epitaxial layer, and then subjected to a photolithography etching process under a photolithography mask corresponding to the gate oxide layer to form a gate oxide layer, and then a polycrystalline SiC layer may be grown on the surface of the gate oxide layer, and then subjected to a photolithography etching process under a photolithography mask corresponding to the gate electrode to form the gate electrode.

In the embodiment of the invention, trimethyl aluminum (TMA) can be grown by about 20nm at the temperature of 200-300 ℃ and in a deionized water environment through an Atomic Layer Deposition (ALD) process, then annealing is carried out at the temperature of 900-1100 ℃, and finally, 1600-DEG C high-temperature resistant Al is formed on the surface of the epitaxial layer 102 of the silicon carbide semiconductor substrate₂O₃And (3) a layer.

In other embodiments, a High temperature High-K material layer formed of HFO may be used as the gate oxide material layer₂And ZrO₂For representation, the High-K material with the melting point above 1600 ℃ is not described in detail.

The polycrystalline SiC layer can be formed by magnetron sputtering, Plasma Enhanced Chemical Vapor Deposition (PECVD), Atmospheric Pressure Chemical Vapor Deposition (APCVD) and the like on the surface of the gate oxide material layer, in the embodiment of the invention, SiH is added₄、C₃H₈Forming a polycrystalline SiC layer by chemical vapor deposition APCVD at a temperature of 1500 ℃ or higher.

In the embodiment of the invention, AlCl is added₃、NH₃APCVD on Al at temperatures above 600 deg.C by chemical vapor deposition₂O₃An AlN layer is formed on the surface of the layer.

Referring to fig. 8, a second conductive type implanted base region 104 is formed by performing a second ion implantation using the gate structure as a second masking layer.

The specific steps of forming the second conductivity type implanted base region 104 include: after the corresponding necessary cleaning step is completed, second ion implantation is performed by taking the gate structure as a second masking layer, so that a second conductive type implantation base region 104 is formed in the epitaxial layer 102, oblique ion implantation is adopted for the second ion implantation, the included angle of the oblique ion implantation is 0-90 degrees, and after the oblique ion implantation, an arc-shaped implantation appearance is formed at the end, close to the second masking layer, of the upper surface of the second conductive type implantation base region 104.

The embodiment of the invention adopts the inclined ion implantation method to define the channel, can define a shorter channel by using wider photoetching precision compared with the prior art, and is easier to reduce the on-resistance Rdson of the silicon carbide power device.

In this embodiment, the second ion implantation of the second conductive type implantation base region adopts N-type doping, and in other embodiments, the second ion implantation of the second conductive type implantation base region also adopts P-type doping.

Referring to fig. 9, a first conductive type implantation source region 105 is formed by performing a third ion implantation using the gate structure as a second masking layer.

The specific steps of forming the first conductive type implantation source region 105 include: and performing third ion implantation by using the gate structure as a second masking layer, so as to form a first conductivity type implantation source region 105 inside the second conductivity type implantation base region 104, wherein the third ion implantation may adopt oblique ion implantation or vertical ion implantation.

In this embodiment, the third ion implantation of the first conductive type implantation source region 105 adopts P-type doping, and in other embodiments, the third ion implantation of the first conductive type implantation source region 105 can also adopt N-type doping.

Compared with the prior art, the method for preparing the silicon carbide power device in the embodiment of the invention uses the gate oxide layer and the gate to form the gate structure as the second masking layer for ion implantation, saves a photoetching plate for forming the second conductive type implantation base region and the first conductive type implantation source region in the photoetching process, shortens the preparation period, and correspondingly saves the etching steps for forming the second conductive type implantation base region and the first conductive type implantation source region, thereby reducing the problem of uneven device channels caused by etching precision.

After the first conductive type implantation source region 105 is formed in the second conductive type implantation base region 104, annealing is required to be performed on the corresponding ion implantation region generated by the ion implantation to repair implantation damage after the ion implantation.

In the prior art, the ion annealing temperature of the silicon carbide device needs to be more than 1600 ℃, and SiO is used₂The melting point of the formed gate oxide layer is between 1600 ℃ and 1700 ℃, and if ion annealing is carried out after the gate and the gate oxide layer of the silicon carbide power device are formed, the original characteristics of the gate and the gate oxide layer can be damaged, so in the prior art, ion implantation is carried out firstly to form a corresponding ion implantation area, then ion annealing is carried out, and finally the gate oxide layer and the gate are formed.

In the embodiment of the invention, the carbon film protective layer is formed on the surface of the grid structure and the silicon carbide epitaxial layer to protect the grid and the grid oxide layer, and the polycrystalline SiC or AlN with higher temperature resistance is adopted as the grid, so that the grid and the grid oxide layer of the silicon carbide power device in the embodiment of the invention can still keep the original characteristics after ion annealing.

In addition, the preparation method of the silicon carbide power device provided by the embodiment of the invention also adopts the Al which is more resistant to high temperature₂O₃The gate oxide layer is made of a layer or a High-K material layer with High temperature resistance, so that the original characteristics of the gate and the gate oxide layer can be still maintained after ion annealing.

In the embodiment of the invention, a carbon film is formed on the surfaces of the grid structure and the silicon carbide epitaxial layer by a high-temperature carbonization photoresist or magnetron sputtering method; then carrying out ion annealing at 1600-1800 ℃; ion annealed and then passed through O₂The carbon film is removed by plasma cleaning.

In the prior art of firstly carrying out ion annealing and then carrying out gate structure preparation, after the ion annealing, the silicon carbide is heated and carbon is separated out, so that step clusters appear on the surface of a wafer, the surface appearance of the wafer is deteriorated, the subsequent gate oxide growth quality is further deteriorated, and the carrier mobility in a device is influenced. According to the preparation method of the silicon carbide power device, the grid electrode structure is formed on the surface of the epitaxial layer, and then annealing is carried out, so that the problem that the quality of the grid oxide layer of the silicon carbide power device is influenced due to the fact that the surface of the epitaxial layer is rough due to carbon precipitation after ion annealing is solved.

Referring to fig. 10, after performing ion annealing and necessary cleaning steps, a gate-source inter-dielectric layer covering the gate electrode is formed on the surface of the gate electrode, an inter-electrode isolation dielectric layer is first deposited, and a third photolithography etching process is performed on the inter-electrode isolation dielectric layer to form a gate-source inter-dielectric and a source region.

Referring to fig. 11, after forming a gate-source dielectric and a source region, ohmic contact metals are deposited on the back surface of the first conductive type semiconductor substrate and the source region, respectively, and ohmic contact annealing is performed, AlCu metal is deposited on the source region to form a source electrode, and Ti/Ni/Ag metal is deposited on the back surface of the first conductive type semiconductor substrate to form a drain electrode.

In the embodiment, the metal ohmic contacts on the front surface and the back surface are formed simultaneously, in other embodiments, the metal ohmic contact on the front surface and the AlCu source electrode can be formed firstly, after the wafer is thinned, the ohmic contact metal deposition is carried out on the back surface, and laser annealing is used. The embodiment of the invention also provides a silicon carbide power device prepared by the preparation method of the silicon carbide power device.

Referring to fig. 11, the silicon carbide power device includes: a silicon carbide semiconductor base including the first conductivity type semiconductor substrate 101 and a silicon carbide epitaxial layer 102 on a first surface of the substrate;

a drain electrode positioned on the other surface of the first conductive type semiconductor substrate, a gate structure positioned on the surface of the epitaxial layer and a gate-source dielectric covering the gate structure, wherein the gate structure comprises a gate oxide layer 106 positioned on the surface of the epitaxial layer 102 and a gate 107 positioned on the surface of the gate oxide layer 106; the gate oxide layer 106 is made of Al2O3 or High-temperature-resistant High-K, and the gate 107 is made of polycrystalline SiC or AlN;

an ion implantation region located on the surface of the silicon carbide epitaxial layer 102 and extending into the epitaxial layer 102, wherein the ion implantation region includes a second conductive type implantation base region 104, a second conductive type re-implantation body region 103 and a first conductive type implantation source region 105, the second conductive type implantation base region 104 is located at two sides of the gate structure, the first conductive type implantation source region 105 is located above the surface of the second conductive type implantation base region 104 and close to the gate structure, and the second conductive type re-implantation body region 103 is located above the surface of the second conductive type implantation base region 104 and far away from the gate structure;

and a source electrode located on the surface of the ion implantation region.

In the silicon carbide power device provided in the embodiment of the present invention, the first conductivity type is P-type doping, and the second conductivity type is N-type doping, that is, the first conductivity type implantation source region is a P-type implantation base region, the second conductivity type implantation base region is an N-type implantation base region, and the second conductivity type implantation source region is an N-type implantation source region.

In other embodiments, the first conductive type may also be N-type doped, and the second conductive type may also be P-type doped.

In a silicon carbide power device of an embodiment of the present invention, the first conductivity type semiconductor substrate 101 is a first conductivity type silicon carbide substrate.

Due to the fact that the silicon carbide power device adopts the inclined ion implantation, the second conductive type implantation base region 104 forms an arc-shaped implantation shape on the upper surface close to the end of the second masking layer.

Specifically, the silicon carbide power device in the embodiment of the present invention is a silicon carbide power MOSFET device, and in other embodiments, the silicon carbide power device may also be a silicon carbide IGBT device.

Finally, it is to be noted that any modifications or equivalent substitutions of some or all of the features may be made by means of the structure of the device according to the invention and the technical solutions of the examples described, without departing from the corresponding technical solutions of the invention, and the obtained essence falls within the scope of the structure of the device according to the invention and the claims of the embodiments described.