CN221009962U

CN221009962U - Stator for electric actuator

Info

Publication number: CN221009962U
Application number: CN202321774086.4U
Authority: CN
Inventors: L·塞吉齐; F·韦尔切西; G·隆戈尼
Original assignee: STMicroelectronics SRL
Current assignee: STMicroelectronics SRL
Priority date: 2022-07-08
Filing date: 2023-07-07
Publication date: 2024-05-24
Anticipated expiration: 2033-07-07
Also published as: CN117375336A

Abstract

Embodiments of the present disclosure relate to stators for electric actuators. A stator for an electric actuator or motor, comprising: a solid body; a ferromagnetic core region between the semiconductor layers, electrically insulated from the semiconductor layers; a plurality of conductive vias passing through the solid body; a first plurality of conductive strips extending parallel to each other over the core; and a second plurality of conductive strips extending parallel to each other over the core and opposite the first plurality of conductive strips; wherein the first plurality of conductive strips, the plurality of conductive vias, and the second plurality of conductive strips form windings or coils of the stator.

Description

Stator for electric actuator

Technical Field

The present disclosure relates to a stator for an electric actuator.

Background

It is known that three-phase asynchronous motors are powered by a system of three-phase voltages (i.e. three voltages phase-shifted by 120 ° with respect to each other). Structurally, a three-phase motor consists of a fixed part (stator) carrying three windings, the axes of which are arranged 120 ° with respect to each other, and a moving part (rotor) arranged at the centre of the stator windings, carrying a circuit closed on itself. Alternatively, the stator may be envisaged as six windings phase shifted 60 ° with respect to each other. There is a gap of air or dielectric between the stator and the rotor to enable the rotor to rotate freely.

As previously described, the coils of the stator are powered by a three-phase voltage system that causes each coil to generate a variable magnetic field. In the region between the three coils, the magnetic field is the sum of the magnetic fields of the coils. Due to the mutual arrangement of the coils and the three-phase voltage system supplying the windings, the magnetic field generated is not fixed, but variable; the magnetic field rotates around the motor shaft at a preset frequency (equal to the current frequency).

Due to the magnetic flux concatenated with the rotor winding, an induced electromotive force is established, which is contrary to the reason why the induced electromotive force is generated.

Due to the miniaturization of components for developing micro robots or micro actuators, it is considered necessary to miniaturize components of three-phase motors. In particular, miniaturization of stator assemblies including coils is attempted.

Disclosure of utility model

One embodiment is a stator and electric actuator or motor designed to overcome the shortcomings of the prior art.

In view of the above, the present utility model aims to provide a miniaturized stator for an electric brake.

According to the present disclosure, a stator and an electric actuator are provided.

According to one or more aspects of the present disclosure, there is provided a stator for an electric actuator, including: a solid body including a semiconductor layer disposed between a first insulating layer and a second insulating layer; a ferromagnetic core region between the semiconductor layers, electrically insulated from the semiconductor layers; a plurality of conductive vias passing through the solid body; a first plurality of conductive strips on the first insulating layer, the first plurality of conductive strips extending parallel to each other at a position corresponding to and above the first side of the core region; a second plurality of conductive strips on the second insulating layer, the second plurality of conductive strips extending parallel to each other at a position corresponding to and above a second side of the core region, the second side being opposite the first side, wherein the first plurality of conductive strips, the plurality of conductive vias, and the second plurality of conductive strips are electrically connected together to form a coil wrapped around the core region; a first protective cap coupled to the second insulating layer and provided with a cavity for receiving the first plurality of conductive strips; a second protective cover coupled to the first insulating layer and provided to accommodate respective cavities of the second plurality of conductive strips; and a hole, alongside the coil, passing through at least one of the first protective cover and the second protective cover, and through the first solid body and the second solid body.

In one or more embodiments, the stator includes a number of coils equal to three or a multiple of three.

In one or more embodiments, the first protective cover has a protrusion inside the cavity.

In one embodiment, a stator for an electric actuator includes: a solid body including a semiconductor layer disposed between a first insulating layer and a second insulating layer; a ferromagnetic core region between the semiconductor layers, electrically insulated from the semiconductor layers; and a plurality of conductive vias passing through the solid body. The stator includes: a first plurality of conductive strips on the first insulating layer, the first plurality of conductive strips extending parallel to each other at a position corresponding to and above the first side of the core region; and a second plurality of conductive strips on the second insulating layer, the second plurality of conductive strips extending parallel to each other at a position corresponding to and above a second side opposite the first side of the core region. The first plurality of conductive strips, the plurality of conductive vias, and the second plurality of conductive strips are electrically connected together to form a coil wrapped around the core region. The stator includes a first protective cover coupled to the second insulating layer and provided with a cavity for accommodating the first plurality of conductive strips; a second protective cover coupled to the first insulating layer and provided to accommodate respective cavities of the second plurality of conductive strips; and a hole, alongside the coil, through at least one of the first protective cover and the second protective cover, and through the first and second solid bodies.

By using the embodiment according to the present disclosure, it is possible to solve at least a part of the foregoing problems and achieve the corresponding effects, such as miniaturization of a stator for an electric brake.

Drawings

For a better understanding of the present disclosure, preferred embodiments thereof will now be described, purely by way of non-limiting example, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a schematic representation of a stator in a top view according to one aspect of the present disclosure;

fig. 2 illustrates an enlarged detail of a coil of the stator in fig. 1 in a top view;

FIGS. 3A and 3B illustrate respective cross-sectional views of the coil of FIG. 2 along cross-sectional lines A-A and B-B, respectively;

Fig. 4A to 4I and 4L to 4S illustrate steps of manufacturing the stator of fig. 1 in a sectional view along a sectional line C-C of fig. 1;

Fig. 5A to 5D illustrate in cross-section steps of manufacturing a conductive path for forming a part of the coil of fig. 2;

FIG. 6 shows a stator according to an alternative embodiment of the stator of FIG. 4S in a cross-sectional view along section line C-C of FIG. 1;

fig. 7A and 7B illustrate partial steps of manufacturing the stator of fig. 1 in a cross-sectional view along section line C-C of fig. 1, according to another embodiment of the present disclosure;

fig. 8A to 8F illustrate in cross-section steps of manufacturing a conductive path for forming a portion of the coil of fig. 2 according to the alternative embodiment of fig. 5A to 5D;

Fig. 9A to 9C show in cross-section intermediate steps of forming an electrical connection path designed to provide a current signal to the coils of the stator of fig. 1; and

Fig. 10A and 10B show a three-phase asynchronous motor including a stator and a rotor according to the present disclosure in top view and cross-sectional view, respectively.

Detailed Description

In one embodiment, a method of manufacturing a stator for an electric actuator includes: a first body is provided that includes a first semiconductor layer, a first structural layer on a first side of the first semiconductor layer, and a second structural layer on a second side of the first semiconductor layer, the second structural layer being opposite the first side. The first and second structural layers are made of a material that is selectively removable relative to the material of the first semiconductor layer. The method includes forming a ferromagnetic core region on the first structural layer, covering the core region with a protective dielectric layer, and providing a second body including a second semiconductor layer on a third structural layer, wherein the third structural layer is made of a material that is selectively removable relative to a material of the second semiconductor layer. The method includes coupling a second semiconductor layer of a second body to the protective dielectric layer; a plurality of conductive vias are formed through the first and second semiconductor layers and through the first and third structural layers, and a first plurality of conductive strips are formed on the third structural layer at locations corresponding to and above the first side of the core region, the first plurality of conductive strips being parallel to each other and in electrical contact with the plurality of conductive vias. The method comprises the following steps: coupling a first protective cap at the third structural layer, the first protective cap having a cavity configured to receive the first plurality of conductive strips; and forming a second plurality of conductive strips on the second structural layer corresponding to and above a second side of the core region, the second side being opposite the first side, the second plurality of conductive strips being parallel to each other and in electrical contact with the plurality of conductive vias through conductive paths through the second structural layer. The method includes coupling a second protective cover to the second structural layer, the second protective cover having respective cavities designed to receive a second plurality of conductive strips; etching selective portions of the second protective cap extending laterally relative to the first and second plurality of conductive strips to form through openings through the second protective cap, and forming holes through the first and second structural bodies by removing selective portions of the first and second bodies that are aligned in direction with the through openings.

Fig. 1 is a schematic diagram of a stator 1 for a three-phase asynchronous motor according to one aspect of the present disclosure. The stator 1 of fig. 1 is obtained in a body 2 comprising a semiconductor material using MEMS technology. The stator 1 has coils or windings, the number of which is equal to 3 or a multiple of 3. In the example of fig. 1, there are six coils 3a, 3b, 3c and 3a ', 3b ', 3c '.

The windings 3a and 3a 'are electrically connected to a signal generator 4a (voltage or current generator), the signal generator 4a being configured such that the same current i _a flows in both windings 3a, 3 a'.

The windings 3b and 3b 'are electrically connected to a signal generator 4b (voltage or current generator), the signal generator 4b being configured such that the same current i _b flows in both windings 3b, 3 b'.

The windings 3c and 3c 'are electrically connected to a signal generator 4c (voltage or current generator), the signal generator 4c being configured such that the same current i _c flows in both windings 3c, 3 c'.

There is a conductive lead (indicated as a whole by reference numeral 5) for transmitting a current i _a-i_c to the windings 3a-3c, 3a '-3c'.

The windings 3a-3c are arranged along a circular path 6 defined through the body 2 and are separated from each other by the same angle of 60 °. Likewise, the windings 3a '-3c' are also arranged along the circular path 6 and are separated from each other by the same 60 ° angle. More specifically, windings 3a and 3a' are aligned along the diameter of circumference 6 and are therefore separated from each other by an angle of 180 ° along circumference 6. The same applies to other windings.

The circular path 6 defines a hole through the body 2 and may be a through opening or an opening closed on one side of the body 2. Windings 3a-3c and 3a '-3c' protrude (or at least partially overhang) at least partially from the opening of circular path 6. A rotor (not shown) of the three-phase asynchronous motor may be inserted into the opening of the circular path.

Fig. 2 shows an enlarged view of a coil (e.g., coil 3 a) in cartesian planes of mutually orthogonal axes X, Y, Z, where only some elements useful for understanding the present disclosure are presented. In particular, the coil 3a of fig. 2 has conductive strips 10 (for example made of metal, in particular gold), the conductive strips 10 extending on opposite sides of a core 8 made of ferromagnetic material, for example made of an alloy comprising nickel-iron (NiFe). The mutually coplanar conductive strips 10 (i.e. all the conductive strips above the core 8 and all the conductive strips respectively below the core 8) are parallel to each other and are physically separated and electrically insulated from each other (along the X-axis). The number of coplanar conductive strips 10 is chosen according to, for example, the desired properties, at the design and size stage of the final device to be produced; the greater the number of windings (i.e., conductive strips), the greater the force generated by the stator thus obtained. As a non-limiting example, the number of coplanar conductive strips 10 is between 2 and 100.

To produce the coil 3a, each conductive strip 10 extending above the core 8 is electrically coupled at a first end 10 'thereof to a conductive strip 10 extending below the core 8 and at a second end 10″ thereof opposite to the first end 10' to another conductive strip 10 extending below the core 8. In this context, the terms "above" and "below" refer to the direction of the axis Z.

To achieve the supply of current i _a to the coil 3a, two conductive strips 10 (in fig. 2, the first and last of the top series of coplanar leads) have respective ends coupled to respective conductive strips 10, while the other end is coupled to respective conductive leads 5a, 5b. The conductive lead 5a provides a current ia to the coil 3a at the input, while the conductive lead 5b draws a current leaving the coil 3 a. The conductive leads 5a and 5b are connected to opposite terminals (+ and-) of the voltage or current generator 4a, respectively. The same applies to the other coils 3b-3c, 3a '-3c'.

The electrical coupling between the conductive strips 10 extending in different planes (i.e. opposite the core 8) is obtained by means of conductive vias 14, the conductive vias 14 extending, for example, in a direction orthogonal to the plane in which the conductive strips 10 lie, in electrical contact with the conductive strips 10 above the core 8 and with the corresponding conductive strips 10 below the core 8.

Fig. 3A is a simplified cross-sectional view of the winding 3A of fig. 2 along the cross-sectional line A-A, and fig. 3B is a simplified cross-sectional view of the winding 3A of fig. 2 along the cross-sectional line B-B.

Referring to fig. 4A to 4I and fig. 4L to 4S, the following is a description of steps of a method of manufacturing the stator 1. Fig. 4A to 4I and 4L to 4S are represented in the same triaxial reference system X, Y, Z as fig. 2 and illustrate the section C-C of fig. 1 in a cross-sectional view.

Referring to fig. 4A, there is provided: an SOI (silicon on insulator) substrate 20 comprising a semiconductor material (e.g., silicon) substrate 22; an intermediate layer 23 of insulating material (e.g., silicon oxide) extending over the substrate 22; and a top layer 24 of semiconductor material (e.g., silicon) extending over the intermediate layer 23.

The step of oxidizing the top layer 24 is then performed to form a thin layer 25 of insulating material (e.g., silicon oxide). As an example, the thickness of the substrate 22 is in the range between 500 μm and 900 μm, the thickness of the intermediate layer 23 is in the range between 0.2 μm and 2 μm, the thickness of the top layer 24 is in the range between 0.2 μm and 100 μm, and the thickness of the layer 25 is in the range between 0.1 μm and 3.5 μm.

Then (fig. 4B), a core layer made of nickel-iron alloy (or some other compatible material) is formed, for example, by deposition, and then defined by photolithography (or by some other defining technique) to form the previously described core 8. One core 8 is formed for each winding 3a-3c, 3a '-3 c'. The shape and extension of the core 8 are defined in the design phase according to the desired properties of the stator 1. For example, the core 8 has a substantially rectangular shape, the long sides of which are dimensioned to extend, such as along X, through the extension of the windings of the respective coil; for example, for a coil with two windings, the core 8 may have an extension along X of about 20 μm; for a coil with 100 windings, the core 8 may have an extension of about 800 μm. The dimensions of the short sides of the core 8 are in the range between 20 μm and 500 μm, for example. The thickness of the core 8 along the Z-axis is for example between 0.01 μm and 3 μm.

Then (fig. 4C), an insulating layer 28 made of TEOS, for example, is formed on the layer 25 and the core 8; the TEOS layer 28 is then planarized to planarize its top surface, preferably without exposing the core 8.

Next (fig. 4D), a further deposition of an insulating layer 29 is performed, for example on the layer 28 and the core 8, the insulating layer 29 being made of, for example, the same material as the layer 28 (here TEOS). The thickness (measured along the core 8 along Z) of the layer 30 thus obtained (given by the sum of the layers 28 and 29) is for example between 0.2 μm and 5 μm. In this step, the conductive leads 5 shown as examples in fig. 9A to 9C and described with reference to the above figures may be formed.

Then (fig. 4E), the insulating layer 30 and the bottom layer 25 are selectively removed in the region where the central opening of the stator 1 for inserting the rotor is to be formed (as shown in the subsequent step). This forms a trench 32 having a circular shape and a diameter d _t (e.g., between 50 μm and 2000 μm). Trenches 32 pass directly through layers 30 and 25 exposing surface portions of semiconductor layer 24.

Then (fig. 4F), wafer-to-wafer bonding (bonding) is performed to couple another SOI wafer 35 over the insulating layer 30. The SOI wafer 35 includes: a substrate 36 made of a semiconductor material, such as silicon; an intermediate layer 37 made of an insulating material, such as silicon oxide, which extends over the substrate 36; and a top layer 38 made of a semiconductor material, such as silicon, which extends over the intermediate layer 37. Coupling with the insulating layer 30 is obtained at the top layer 38 of the SOI wafer 35. The trenches 32 are thus closed to form buried cavities (however, for simplicity, the same reference numeral 32 is used). The coupling is obtained by known fusion-bonding techniques.

Then (fig. 4G), the substrate 36 of the SOI wafer 35 (to this step, which has the function of handling the substrate) is completely removed, for example by grinding or CMP processes or some other suitable technique. The intermediate layer 37 is thereby exposed.

An arrangement for forming the conductive via 14, which is not visible in the cross-sections of fig. 4A to 4I and fig. 4L to 4G as described above, is now performed.

Reference will now be made to fig. 5A to 5D, which illustrate by way of example the manufacturing steps for forming the conductive vias 14. A case where only one through hole 14 is formed is shown; the present teachings are applicable to the case where all of the conductive vias 14 are formed simultaneously.

Referring to fig. 5A, in the region where the through hole 14 is to be formed, the intermediate layer 37 is selectively etched. For this reason, using mask etching, a mask is obtained by a photolithography technique to form a plurality of openings 41 (as described above, only one opening is shown in fig. 5A), and a surface portion of the semiconductor layer 38 is exposed through the plurality of openings 41.

Then (fig. 5B), etching is performed at the opening 41 a plurality of times (using an appropriate etching chemistry depending on the material to be removed) to sequentially remove the semiconductor layer 38, the insulating layer 30, the layer 25, and the semiconductor layer 24 exposed by means of the opening 41, thereby exposing a surface portion of the intermediate layer 23. The trench 43 is formed in this way.

For the formation of the trench 43, for example, the same mask (not shown) for forming the opening 41 is used. As an example, to remove silicon of layers 38 and 24, dry etching is performed using a plasma containing, for example, SF ₆, to remove TEOS of layer 30, dry etching is performed using a plasma containing, for example, CF ₄, and to remove silicon oxide of layers 37 and 25, dry etching is performed using a plasma containing, for example, CF ₄.

Then (fig. 5C), the step of passivating the inner side walls of the trenches 43 is performed, for example, by laying an insulating layer 46 of, for example, silicon oxide, having a thickness (measured along axis X) between 0.05 μm and 1 μm.

The formation of the via 14 is then completed (fig. 5D) by filling the trench 43 with a conductive material 48 (e.g., copper) via electrodeposition and planarization (these are RDL interconnects here). The conductive material 48 fills the trench 43 completely to a height (along Z) extending from the surface of the insulating layer 37. Passivation layer 46 electrically isolates conductive material 48 from semiconductor layers 24 and 38.

Reference is now made again to section C-C.

Fig. 4H shows a manufacturing step after the conductive via 14 is formed according to fig. 5A to 5D.

Referring to fig. 4H, insulating layer 37 is selectively etched to form openings 50 that are substantially aligned along Z with buried cavities 32. In plan view, in plane XY, opening 50 has a circular shape and a diameter d _t' equal to or greater than diameter d _t. Openings 50 and 32 are concentric.

Then (fig. 4I), a conductive strip 10 is formed at the first side of the core 8 (simultaneously for each winding 3a-3C and 3a '-3C'). The conductive strip 10 is formed over the insulating layer 37.

Gold can be formed (grown) using typical processes, in particular: depositing a seed layer; lithographically patterning the seed layer to define a predefined shape of the conductive strip 10 (i.e., a shape defined at the design stage); and electrochemical deposition of gold.

Each conductive strip has a thickness along Z of between 3 μm and 10 μm.

Then (fig. 4L), a cover 56 is coupled to the insulating layer 37. The cover 56 has a cavity 58 sized to fully receive the conductive strip 10 formed prior to this processing step. The coupling area of the cover to the layer 37 is thus located outside the area where the conductive strips 10 (the conductive strips of all windings 3a-3c, 3a '-3 c') are present. The coupling is obtained by known techniques of permanent coupling between two silicon wafers, wherein for example gold-gold metal bonding, bonding with glass fiber material, fusion bonding. The cap 56 is made of, for example, silicon and has a protective layer 59 at the cavity 58, the material of the protective layer 59 being selectively removable from the material of the cap 56 (e.g., silicon oxide in the case of a silicon cap 56). The protective layer 59 uniformly covers the walls of the cover 56 defining the cavity 58. Thus, after the coupling step of fig. 4L, protective layer 59 faces insulating layer 37 and conductive strip 10.

Referring to fig. 4M, a rotating step of the body 20 and the cover 56 is performed to perform a processing step at the substrate 22.

Next (fig. 4N), the substrate 22 is completely removed, for example, by a grinding or CMP step or some other suitable technique. The intermediate layer 23 is thereby exposed.

Then (fig. 4O), the insulating layer 23 is etched to remove a selective portion thereof, thereby forming an opening 61 concentric with the opening 50 and having the same size and shape.

In this processing step, selective etching of the insulating layer 23 is also performed at the conductive vias 14 formed in the step of fig. 5D to expose the conductive material 48 at the layer 23. This step is not illustrated in the figures.

Next (fig. 4P), a conductive tape 10 is formed on a side of each core 8 opposite to the side on which the conductive tape 10 has been previously formed. The conductive tape 10 formed in the step of fig. 4P extends over the insulating layer 23. The formation of the above-described conductive strip 10 is obtained according to the same process as previously described, which comprises: depositing a seed layer; lithographically patterning the seed layer to define a predefined shape of the conductive strip 10 (i.e., a shape defined at the design stage); and electrochemical deposition of gold.

The gold layer is over the layer 23 and extends within openings made in the region of the layer 23 corresponding to the conductive vias 14 so as to reach them and make electrical contact with them.

Then (fig. 4Q), the cover 62 is coupled to the insulating layer 23. The cover 62 has a cavity 64 of a size that fully contains the conductive strip 10 formed in step 10 of fig. 4P (symmetrically, the opening 64 of the cover 62 corresponds to the opening 58 of the cover 56). The coupling area of cover 62 with layer 23 thus also corresponds to the coupling area of cover 56 with layer 37 and is located outside the area where conductive strip 10 (the conductive strip of all windings 3a-3c, 3a '-3 c') is present. The coupling is obtained by known fusion bonding techniques. The cover 62 is made of, for example, silicon.

Next (fig. 4R), an etching mask 68 is formed on the cap 62; the mask 68 has an opening 69, and the opening 69 has the same shape (e.g., circular shape) as the openings 50 and 61 and has a size (diameter in this example) equal to or larger than the size (diameter) of the openings 50 and 61. Circular opening 69 is concentric with circular openings 50 and 61.

Then (fig. 4S), an etching step (e.g., a dry etch, using, for example, CF ₄ to remove oxide and SF ₆ to remove silicon) is performed at cap 62 to completely remove the portions exposed through openings 69 of mask 68. Etching is performed to completely remove the portion of semiconductor layer 38 exposed through opening 61 and then to remove the portion of semiconductor layer 24 exposed through cavity 32.

Since the etching chemistry is selective, etching does not proceed in a manner that removes portions of cap 56 as long as protective layer 59 acts as an etch stop layer.

The mask 68 may be removed or left to protect the cover 62.

According to one embodiment of the present disclosure, the manufacture of the stator 1 is thereby completed. The stator 1 of fig. 4S has an opening 70 for inserting a rotor of the non-penetrating type.

To form the through opening, it is conceivable to form a corresponding opening in the protective layer 59 of the cap 56 (obtained during formation of the protective layer 59), and to continue the etching of fig. 4S until the material of the cap 56 exposed through the opening in the protective layer 59 is completely removed.

In this case, the stator 1 of fig. 6 is obtained, in which the opening for inserting the rotor is of the through type.

According to another embodiment (as shown in fig. 7A), in order to strengthen the structure, in the case of a through-opening, the cover 56 may be shaped such that it has a protrusion 72 in the region of the cover 56, the protrusion 72 being aligned with the opening 50 after the coupling described in fig. 4L. In this case, the protective layer 59 is free of locations where the cover 56 must be selectively removed to create a through opening for the rotor. In other words, the protective layer 59 extends uniformly except for the portion of the protrusion 72 that is aligned with the opening 50 after coupling. When the cover 56 is coupled to the rest of the structure, the protrusion 72 rests (through the protective layer 59) on the intermediate layer 37, defines the opening 50 by the intermediate layer 37, and covers the opening 50 in a top view of the plane XY.

Referring to fig. 7B, etching of cap 62 and semiconductor layers 38 and 24 continues through the openings in protective layer 59 by removing the exposed portions of protrusions 72 until a through opening is formed completely through cap 56.

In use in an electric machine, the rotor may be fully inserted through the stator into the opening so formed.

In another embodiment (not shown), the etching of fig. 7B is performed not to form a through opening completely through the cap 56, but to form a non-through opening in the protrusion 72 that terminates within the cap 56. This embodiment, similar to the embodiment described with reference to fig. 4S, presents the advantage of a stronger structural support provided by the presence of the protrusions 72 compared to fig. 4S.

Fig. 8A to 8F show an embodiment of a part of the stator 1 as an alternative to what has been described above. In particular, fig. 8A to 8F relate to a possible further embodiment of forming the conductive via 14 in a manner alternative to that represented in fig. 5A to 5D. Fig. 8A to 8F illustrate a portion of the stator 1 during an intermediate manufacturing step, limited to the region in which the conductive via 14 is present. The present teachings are applicable to the manufacture of all conductive vias simultaneously and, more generally, to the manufacture of the remainder of the stator, wherein there is an interaction between the manufacture of the conductive vias 14 and the manufacture of the remainder of the stator 1.

Elements of the stator 1 that are common to the previously described embodiments are denoted by the same reference numerals and will not be described further.

Referring to fig. 8A, after SOI substrate 20 is provided and core 8 of the design requirements is formed as shown in fig. 4A, etching is performed on thin layer 25 and top layer 24 in the region of body 20 where via 14 is to be formed, as shown in fig. 4B. The opening 80 is thus formed, through which a surface portion of the intermediate layer 23 is exposed. The opening 80 has a shape selected between circular, elliptical, quadrangular or generally polygonal in plan view of the plane XY, with a diameter between 10 μm and 200 μm.

Then (fig. 8B), the step of forming the layer 30 is performed according to what has been described with reference to fig. 4C to 4D. Layer 30 also penetrates into the opening formed in the step of fig. 8A, covering the sidewalls and their bottoms (incomplete filling). In a manner not illustrated in the cross-sectional view of fig. 8B, an opening 32 is also formed according to the situation already described in fig. 4E.

Then (fig. 8C), SOI substrate 35 is coupled in a manner similar to that described with reference to fig. 4F. In the embodiment of fig. 8C, prior to the coupling step, SOI substrate 35 is processed to form (e.g., by photolithographic and etching techniques) openings 83 in top layer 38; the opening 83 has a shape and diameter corresponding to the shape and diameter of the opening 80. Next, a step of forming an electrically insulating protective layer 84 (e.g., a thermally grown or deposited silicon oxide layer) is performed on the top layer 38 and the inner walls and the bottom of the opening 83. Protective layer 84 is selectively etched to expose a surface portion of layer 38 in a region directly facing opening 35 after coupling of SOI wafers 20 and 35. Thus, as shown in fig. 4F, the top and lower regions of the cavity 32 are made of the same material (here silicon) to facilitate the subsequent etching step for opening the central passage into which the rotor is to be inserted.

Then (fig. 8D), the substrate 36 is removed as shown in fig. 4G, leaving the intermediate layer 37.

Referring to fig. 8E, a step of continuous etching is performed to open the trench 88 in which the conductive region of the via 14 will be formed later (fig. 8F). The trench 88 is formed by etching the intermediate layer 37 at the cavities 80, 83. Since in this embodiment layers 37 and 84 are both made of the same material (silicon oxide), a single etch is sufficient to locally remove layers 37 and 84. Etching is then performed by removing the layer 30 thus exposed through the opening 80, and likewise removing the intermediate layer 23. The etching chemistry used in the step of fig. 8E is, for example, CF ₄ or C ₄F₈, which removes all of the oxide layers considered.

The etching of the intermediate layer 23 may be omitted or may be performed only partially. In this case, layer 23 will in any case be removed to obtain a conductive path of the through hole 14, as has been described in the same step of fig. 4O.

The step of filling the trench 88 with a conductive material (e.g., copper) is then performed as described with reference to fig. 5D to form the conductive region 90 of the via 14.

The subsequent steps of manufacturing the stator 1 are then performed as described with reference to fig. 4H to 4S.

The variants of fig. 7A to 7B (as in other embodiments not shown but described) also apply to the embodiment of the stator 1 of fig. 8A to 8F.

The manufacture of the conductive leads 5 does not in itself form part of the present disclosure and these may be obtained in a known manner. For example, as shown in fig. 9A, the conductive leads 5 may be formed by removing selective regions of the layer 30 after the step of forming the layer 30, the thickness of the layer 30 being, for example, equal to or less than the thickness of the layer 29. This step defines the shape and extension of the path 91 of the lead 5.

Then (fig. 9B), a step of filling the path 91 formed in this intermediate step with a conductive material 92 (e.g., copper) is performed.

As shown in fig. 9C, a further step of deposition of a layer 94 (made of the same material as layer 29, for example TEOS) covers the conductive material 92, burying the conductive leads 5. The layers 28, 29 and 94 stacked on top of each other are in any case indicated as a whole by the reference numeral 30, in order to be simple and uniform in keeping with the above description, which is not altered by the presence of the conductive leads buried in the layer 30.

In order to obtain access to the conductive leads, it is sufficient to produce holes through the layer covering the conductive leads in a manner known per se in the area of the prearranged area for electrically accessing the conductive leads 5.

Fig. 10A is a schematic diagram of an XY plan top view of a portion of a three-phase asynchronous motor including a stator 1 according to the present disclosure and a rotor 100 inserted into a bore 7 of the stator 1.

Fig. 10B is a sectional view of a portion of the three-phase asynchronous motor of fig. 10A along section line X-X. Fig. 10B is merely an example based on fig. 7B. However, the teachings of fig. 10B apply with obvious adaptation to all embodiments described in accordance with the present disclosure.

The advantages provided by this disclosure are apparent from an examination of the features described and illustrated herein.

In particular, the stator described above is obtained in a miniaturized and economically advantageous manner according to the manufacturing steps available in the manufacturing context of semiconductor devices and systems.

Finally, it is apparent that modifications and variations can be made to the disclosure described and illustrated herein without departing from the scope of the disclosure.

For example, the formation of one, some or all of openings 32 (fig. 4E), 50 (fig. 4H) and 61 (fig. 4O) may be omitted, and the corresponding insulating layer removed during the step of fig. 4A. In this case it is advantageous to use etching chemistries that are different from each other for removing the silicon layers 24, 38 and for removing the silicon oxide/TEOS layers 23, 25, 30, 37. Also, it is advantageous to use an etch with a suitable directionality (along Z) to prevent removal of structural areas of the stator 1, which extend transversely with respect to the area where the holes 7 are to be formed.

In particular, the present disclosure has explicitly mentioned three-phase asynchronous motors; however, the present teachings are applicable to manufacturing stators for different types of motors or actuators, such as single-phase synchronous types, single-phase asynchronous types, three-phase synchronous types, and the like.

A method of manufacturing a stator (1) for an electric actuator may be summarized as comprising the steps of: providing a first body (20), the first body (20) comprising a first semiconductor layer (24), a first structural layer (25) and a second structural layer (23), the first structural layer (25) being on a first side of the first semiconductor layer (24), the second structural layer (23) being on a second side of the first semiconductor layer (24), the second side being opposite to the first side, wherein the first and second structural layers are made of a material that is selectively removable with respect to the material of the first semiconductor layer (24); forming a ferromagnetic core region (8) on the first structural layer (25); covering the core region (8) with a protective dielectric layer (30); -providing a second body (35) comprising a second semiconductor layer (38) on a third structural layer (37), wherein the third structural layer is made of a material that is selectively removable with respect to the material of the second semiconductor layer (38); coupling a second semiconductor layer (38) of the second body (35) to the protective dielectric layer (30); forming a plurality of conductive vias (15), the plurality of conductive vias (15) passing through the first and second semiconductor layers (24, 38) and through the first and third structural layers (25, 37); -forming a first plurality of conductive strips (10) on the third structural layer (37) in correspondence with and above the first side of the core region (8), the first plurality of conductive strips (10) being parallel to each other and in electrical contact with the plurality of conductive vias (15); coupling a first protective cover (56) at the third structural layer (37), the first protective cover (56) having a cavity (58) designed to house the first plurality of conductive strips (10); forming a second plurality of conductive strips (10) on the second structural layer (23) in a position corresponding to and above a second side of the core region (8), the second side being opposite the first side, the second plurality of conductive strips (10) being parallel to each other and in electrical contact with the plurality of conductive vias (15) through conductive paths (15) passing through the second structural layer (23); coupling a second protective cover (62) to the second structural layer (23), the second protective cover (62) having respective cavities (64) designed to receive a second plurality of conductive strips (10); etching selective portions of the second protective cap (62) extending laterally relative to the first and second plurality of conductive strips (10) to form through openings through the second protective cap (62); and forming a hole (70, 7) through the first and second structural bodies (20, 35) by removing selective portions of the first and second bodies (20, 35) aligned with the through opening in the direction (Z).

The steps of forming the first plurality of conductive strips (10), the plurality of conductive vias (15) and the second plurality of conductive strips (10) may include electrically coupling the first and second plurality of conductive strips (10) to the plurality of conductive vias (15) to form an electrical path that achieves a winding or coil around the core region (8).

The method may further comprise the steps of: at portions of the first structural layer (25), the second structural layer (23), the third structural layer (27), and the protective dielectric layer (30) where the holes (70, 7) are to be formed, removing selective portions of the first, second, and third structural layers (25, 23, 37) and selective portions of the protective dielectric layer (30), the step of continuing the etching may include removing the first and second semiconductor layers exposed through the first, second, and third structural layers (25, 23, 37) and through the protective dielectric layer (30).

The method may further comprise the steps of: selective portions of the first protective cap (56) are etched in alignment with the through openings and holes (70, 7) through the second protective cap (62) in the direction (Z).

The step of forming a plurality of conductive vias (15) may include: after the step of coupling the second semiconductor layer (38) to the protective dielectric layer (30), forming a respective plurality of trenches (43) through the first and second semiconductor layers (24, 38) and through the first and third semiconductor layers (25, 37); forming a respective plurality of insulating layers (46) within each trench (43) to cover the exposed portions of the first and second semiconductor layers (24, 38) within each trench (43); and filling each trench (43) with a conductive material.

The step of forming a plurality of conductive vias (15) may include, prior to the step of coupling the second semiconductor layer (38) to the protective dielectric layer (30), forming a respective plurality of first trenches (80) through the first semiconductor layer (24) and through the first structural layer (25) according to an arrangement pattern; uniformly covering the inner wall of each first trench (80) with a protective dielectric layer (30); forming a corresponding plurality of second trenches (83) through the second semiconductor layer (38) according to an arrangement pattern; and uniformly covering the inner wall of each second trench (83) with an insulating layer (84), wherein the step of coupling the second semiconductor layer (38) to the protective dielectric layer (30) may comprise aligning each first trench (80) with the corresponding second trench (83) in the (Z) direction, and the step of forming the plurality of conductive vias (15) may further comprise removing selective portions of the third structural layer (37) and the insulating layer (84) aligned perpendicular to each second trench (83) in the direction (Z), optionally completely or partially removing the second structural layer (23), and filling each first and second trench (80, 83) with a conductive material after the step of coupling the second semiconductor layer (38) to the protective dielectric layer (30).

The first protective cover (56) may have a protrusion (72) inside the cavity (58), the protrusion (72) extending in a direction (Z), the step of coupling the first protective cover (56) to the third structural layer (37) may include coupling the protrusion (72) to the third structural layer (37) laterally with respect to the first and second plurality of conductive strips (10), the method may further include the steps of: portions of the protrusions (72) exposed through the apertures (70, 7) are removed to form openings that are either partial or directly through the first protective cover (56).

The first, second and third structural layers may be made of an electrically insulating material.

The stator (1) for an electric actuator may be summarized as comprising: a solid body (20; 35) comprising a semiconductor layer (24, 38) arranged between a first insulating layer (23) and a second insulating layer (37); a ferromagnetic core region (8) electrically insulated from the semiconductor layers (24, 38) between the semiconductor layers (24, 38); a plurality of conductive vias (15) passing through the solid body (20; 35); a first plurality of conductive strips (10) on the first insulating layer (23), the first plurality of conductive strips (10) extending parallel to each other at a position corresponding to and above the first side of the core region (8); a second plurality of conductive strips (10) extending parallel to each other on a second insulating layer (37) in a position corresponding to and above a second side of the core region (8), the second side being opposite the first side, wherein the first plurality of conductive strips (10), the plurality of conductive vias (15) and the second plurality of conductive strips (10) are electrically connected together to form a coil wound around the core (8); a first protective cover (56) coupled to the second insulating layer (37) and provided with a cavity (58) for housing the first plurality of conductive strips (10); a second protective cover (62) coupled to the first insulating layer (23) and provided to house respective cavities (64) of the second plurality of conductive strips (10); and a hole (70, 7) alongside the coil, through at least one of the first protective cover and the second protective cover, and through the first solid body and the second solid body.

The stator may include a number of coils equal to three or a multiple of three.

An electric actuator or motor may be summarized as including a stator.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments and the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A stator for an electric actuator, comprising:

A solid body including a semiconductor layer disposed between a first insulating layer and a second insulating layer;

A ferromagnetic core region between the semiconductor layers, electrically insulated from the semiconductor layers;

a plurality of conductive vias through the solid body;

a first plurality of conductive strips on the first insulating layer, the first plurality of conductive strips extending parallel to each other at a position corresponding to and above a first side of the core region;

A second plurality of conductive strips on the second insulating layer, the second plurality of conductive strips extending parallel to each other at a position corresponding to and above a second side of the core region, the second side being opposite the first side, wherein the first plurality of conductive strips, the plurality of conductive vias, and the second plurality of conductive strips are electrically connected together to form a coil wrapped around the core region;

A first protective cap coupled to the second insulating layer and provided with a cavity for receiving the first plurality of conductive strips;

A second protective cover coupled to the first insulating layer and provided to accommodate respective cavities of the second plurality of conductive strips; and

And a hole, which is arranged side by side with the coil, passes through at least one of the first protective cover and the second protective cover, and passes through the first solid body and the second solid body.

2. The stator of claim 1, comprising a number of coils equal to three or a multiple of three.

3. The stator of claim 1, wherein the first protective cover has a protrusion inside the cavity.