Patent Description:
The present application relates to isolators providing galvanic isolation between circuits.

Isolators provide electrical isolation between circuits which communicate with each other. In some situations, circuits which communicate with each other operate at different voltages, for instance one at a relatively high voltage and the other at a relatively low voltage. In some situations, the circuits may or may not operate at different voltages than each other, but are referenced to different electrical ground potentials. Isolators can be used to electrically isolate circuits in either of these situations.

<CIT> describes a method for fabricating a circuitry component including two mutual induced coils.

<CIT> describes an isolation system including a first and second capacitive plate, an enhanced isolation layer, a first bonding wire and an isolation trench.

According to an aspect of the present application, micro-isolators exhibiting enhanced isolation breakdown voltage are described. The micro-isolators may include an electrically floating ring surrounding one of the isolator elements of the micro-isolator. The isolator elements may be capacitor plates or coils. The electrically floating ring surrounding one of the isolator elements may reduce the electric field at the outer edge of the isolator element, thereby enhancing the isolation breakdown voltage. A micro-isolator according to the present invention is defined in appended claim <NUM>.

Various aspects and embodiments of the application will be described with reference to the following figures. Items appearing in multiple figures are indicated by the same reference number in all the figures in which they appear.

According to an aspect of the present application, an isolator element is positioned within an electrically floating conductive ring, with a non-linear dielectric material between them. In some embodiments, the isolator element is a coil, and in other embodiments it is a capacitor plate. In some embodiments, the isolator element and electrically floating conductive ring are both encapsulated by a dielectric material, which in some embodiments may be the same non-linear dielectric material between the isolator element and the electrically floating conductive ring. In some embodiments, the isolator element is encapsulated by the non-linear dielectric material while the electrically floating conductive ring is not. In some embodiments, the isolator element is encapsulated by a dielectric material differing from the non-linear dielectric material between the isolator element and the electrically floating conductive ring. According to some embodiments, multiple electrically floating conductive rings may surround the isolator element. They may be the same height as the isolator element or a different height. In some embodiments, an isolator comprising two isolator elements includes one or more electrically floating conductive rings around each of the isolator elements.

The aspects and embodiments described above, as well as additional aspects and embodiments, are described further below. These aspects and/or embodiments may be used individually, all together, or in any combination of two or more, as the application is not limited in this respect.

<FIG> illustrates a cross-sectional view of a micro-isolator having two isolator elements with a floating conductive ring around one. The micro-isolator <NUM> comprises a substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM>.

The first isolator element 104a and second isolator element 104b are coils in this non-limiting example. The micro-isolator <NUM> may therefore work as an inductive micro-isolator, and may be a transformer. The first isolator element 104a and second isolator element 104b may be made of a metal, such as gold, aluminum, or copper. In some embodiments, the first isolator element 104a and second isolator element <NUM> are made of different materials. For example, isolator element 104a may be made of gold and isolator element 104b may be made of aluminum. In some embodiments, they may be made of the same material, such as being made of the same metal.

The floating conductive ring <NUM> may be made of a metal. In some embodiments, the floating conductive ring <NUM> may be made of the same metal as the first isolator element 104a. For example, they may be patterned from the same metal layer, although not all embodiments are limited in this respect. The first isolator element 104a and the floating ring <NUM> may be made of gold. The first isolator element 104a and floating conductive ring <NUM> have a height H. In this non-limiting embodiment, they have the same height, although alternatives are possible, with an example described further below. Electrical contact may be made to first isolator element 104a at its ends, as can be seen in <FIG>.

<FIG> is a top view of the micro-isolator <NUM> taken along the line 1B-1B of <FIG>. As shown, the floating conductive ring <NUM> surrounds the first isolator element 104a. The floating conductive ring is concentrically outside the first isolator element 104a. Electrical contact to the first isolator element 104a is made at pad <NUM> and end <NUM> (which may be a separate pad). The first isolator element 104a may pass over or under the floating conductive ring <NUM> near the end <NUM> to avoid being in electrical contact. In an alternative embodiment, floating conductive ring <NUM> may include a break or gap near the end <NUM> through which the first isolator element 104a passes. In some embodiments, the first isolator element 104a may be configured to receive a high voltage, such as greater than <NUM> Volts, greater than <NUM> Volts, greater than <NUM> Volts, between <NUM> V and <NUM> kV, or any range or values within those ranges.

The first isolator element 104a and floating conductive ring <NUM> may have any suitable shapes. In the non-limiting example of <FIG>, they are circular. Alternative shapes are possible, however, as the various aspects described herein are not limited to a particular shape of isolator element or the floating conductive ring.

Returning to <FIG>, the dielectric layer <NUM> may be any suitable dielectric for isolating the first isolator element 104a from the second isolator element 104b. In some embodiments, the dielectric layer <NUM> comprises a polymer. For example, it may be polyimide. In some embodiments, the dielectric layer may comprise multiple layers. For example, the dielectric layer <NUM> may comprise two or more layers of polyimide, or a layer of polyimide and a layer of a second type of dielectric.

The first isolator element 104a and the floating conductive ring <NUM> are separated in-plane by a gap g. The gap g may have any suitable distance. The floating conductive ring <NUM> serves to reduce the electric field buildup at the outer edge of the first isolator element 104a, and may perform a grading function of smoothing the voltage between the first isolator element 104a and surrounding structures. As a result, the breakdown voltage of the micro-isolator <NUM> is increased compared to if the floating conductive ring <NUM> was omitted. The value of g may be selected to provide a desired level of electric field reduction. If g is too great, the floating conductive ring <NUM> may not meaningfully reduce the electric field at the outermost edge of the first isolator element 104a. If g is too small, electrical breakdown may occur between the first isolator element 104a and the floating conductive ring <NUM>. In some embodiments, g may be in a range from <NUM> microns to <NUM> microns, including any value within that range. Other values are also possible.

The gap g is filled with the non-linear dielectric <NUM>. The non-linear dielectric <NUM> may be a relatively conductive insulator to aid the electric field grading function of the floating conductive ring <NUM>. In some embodiments, the non-linear dielectric <NUM> is stoichiometric silicon nitride (SiN<NUM>) or non-stochiometric silicon nitride (SiNx, with x not equal to <NUM>). Alternatives include silicon oxynitride (SiONx), doped amorphous silicon (a-Si:H), doped amorphous carbon (a-C:H), silicon carbide (SiC), and zinc oxide (ZnO). When doped materials are used, any suitable doping may be employed to provide a level of conductivity resulting in a desired level of electric field grading. In some embodiments, the non-linear dielectric <NUM> may be a high-k ferroelectric materials like baryum titanate (BaTiO<NUM>) strontium titanate (SrTiO<NUM>), titanate dioxide (TiO<NUM>), hafnium dioxide (HfO<NUM>), zirconium dioxide (ZrO<NUM>) or alumina (Al<NUM>O<NUM>), as they may exhibit similar electric field grading behavior. It should be noted that including a floating conductive ring in an isolator, without a non-linear dielectric between the first isolator element and the floating conductive ring, can decrease the electric breakdown voltage of the isolator, rather than decreasing it. Thus, the combination of a floating conductive ring with a conductive non-linear dielectric material between the isolator element and the floating conductive ring may provide the desired increase in electric breakdown voltage.

The dielectric layer <NUM> may be a passivation layer. In some embodiments, the dielectric layer <NUM> is polyimide. In some embodiments, the dielectric layer <NUM> is an oxide. Alternative materials are possible for the dielectric layer <NUM>.

A non-limiting example of an implementation of the micro-isolator <NUM> is now provided. The substrate <NUM> may be formed of silicon or a dielectric (such as glass). The first isolator element 104a may be formed of gold. The second isolator element 104b may be formed of aluminum. The floating conductive ring <NUM> may be formed of gold. Alternative isolator elements 104a and 104b as well as the floating conductive ring <NUM> may be formed of copper. The dielectric layer <NUM> may be formed of polyimide and may be between <NUM> microns and <NUM> microns thick. The non-linear dielectric <NUM> may be formed of silicon nitride. The dielectric layer <NUM> may be formed of oxide. The height H may be <NUM> microns and the gap g may be <NUM> micron. Other materials and dimensions may be used in other embodiments. Also, it should be appreciated that some embodiments of a micro-isolator as described herein include one or more of the elements formed of the specific materials just described, but that one or more of the elements may be formed of different materials.

It should be appreciated from <FIG> and <FIG> that in some embodiments a micro-isolator with enhanced isolation breakdown voltage is provided. The micro-isolator may comprise a first isolator element in a first plane, a second isolator element in a second plane, a first dielectric material, comprising a polymer such as polyimide, disposed between the first and second isolator elements, and an electrically floating conductive ring disposed in the first plane and surrounding the first isolator element. The first and second isolator elements may be separated in a vertical dimension (the up and down direction of <FIG>), and the first isolator element and floating conductive ring may be separated in a second dimension (the left-right direction in <FIG>).

<FIG> illustrates an alternative micro-isolator according to a non-limiting embodiment. The micro-isolator <NUM> differs from the micro-isolator <NUM> in that the micro-isolator <NUM> is a capacitive micro-isolator, having capacitor plates as the isolator elements. Specifically, the micro-isolator <NUM> comprises substrate <NUM>, first isolator element 204a, second isolator element 204b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM>. Substrate <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, dielectric layer <NUM>, gap g, and height H were previously described in connection with <FIG>, and thus are not described in detail again here.

The first isolator element 204a and second isolator element 204b are capacitor plates. They may be formed of any suitable materials, such as the materials described previously in connection with first isolator element 104a and second isolator element 104b, respectively. The isolator elements 204a and 204b may have any suitable shapes. In some embodiments, they are circular, in other embodiments rectangular or square, and in still other embodiments may have different shapes. The floating conductive ring <NUM> may surround the first isolator element 204a. In some embodiments, the floating conductive ring <NUM> has the same shape as the first isolator element 204a, for example being a circle, a square, or other suitable shape. The floating conductive ring <NUM> may be made of any of the materials described previously in connection with floating conductive ring <NUM>.

<FIG> illustrates a cross-sectional view of an alternative micro-isolator comprising multiple floating conductive rings, according to a non-limiting embodiment of the present application. The micro-isolator <NUM> comprises substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive rings 306a, 306b. 306n, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM>. The substrate <NUM>, first isolator element 104a, second isolator element 104b, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM> have been described previously herein in connection with <FIG> and <FIG>, and therefore are not described again in detail here.

The floating conductive rings 306a, 306b. 306n may be any suitable floating conductive rings. Each of them may be substantially the same as the floating conductive ring <NUM> described previously in connection with <FIG> and <FIG>, in terms of material and sizing. The floating conductive rings 306a, 306b. 306n have different radii (in the xy-plane), with floating conductive ring 306a having a shorter radius than floating conductive ring 306b, which in turn has a shorter radius than floating conductive ring 306n. The floating conductive rings 306a. 306b may be concentrically positioned with respect to each other.

Any suitable number n of floating conductive rings may be provided. In the embodiment of <FIG>, between two and ten floating conductive rings may be provided. However, other numbers are possible.

The floating conductive rings 306a. 306n may be the same in terms of material, spacing, height, and width in some embodiments. However, in those embodiments in which multiple floating conductive rings are provided, one or more of those variables may be varied among the floating conductive rings. For example, in some embodiments, two or more of the floating conductive rings 306a. 306n may differ in height (in the z-direction in this figure). For example, some of the floating conductive rings may have the height H described previously, while others may have a shorter height, such as is described further below in connection with <FIG>. Any suitable gaps may be provided between the floating conductive rings, as shown. The gap g1 is between the outermost edge of the first isolator element 104a and the floating conductive ring 306a. The gap g2 is between the floating conductive ring 306a and the floating conductive ring 306b. In some embodiments, the gaps increase in size the further from the first isolator element 104a they are. That is, the gap sizing may increase moving away from the first isolator element 104a. Increasing the gap size may increase the resistance between the floating conductive rings, which may facilitate electric field grading. The floating conductive rings may have widths w. In some embodiments, they have a uniform width. In other embodiments, the widths may be varied among the floating conductive rings 306a.

<FIG> illustrates a cross-sectional view of an alternative micro-isolator in which the floating conductive ring is not encapsulated by the same non-linear dielectric material encapsulating the isolator element 104a, according to an alternative embodiment. The micro-isolator <NUM> includes many of the same components previously described in connection with <FIG> and <FIG>. However, in contrast to the micro-isolator <NUM> of <FIG>, the micro-isolator <NUM> is configured such that the non-linear dielectric <NUM> does not encapsulate the floating conductive ring <NUM>. Such a configuration may be used for any suitable purpose. In some embodiments, manufacturing of the micro-isolator may be eased by forming the floating conductive ring <NUM> without being encapsulated by the non-linear dielectric <NUM>. Other benefits may also be realized.

<FIG> illustrates a cross-sectional view of an alternative micro-isolator in which the non-linear dielectric material filling the gap between the isolator element and the floating conductive ring is a different material than that encapsulating the isolator element, according to a non-limiting embodiment of the present application. The micro-isolator <NUM> comprises substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, dielectric layer <NUM>, and non-linear dielectric <NUM>. The substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM> have been described previously herein in connection with <FIG> and <FIG>, and therefore are not described again in detail here.

In the micro-isolator <NUM> the non-linear dielectric <NUM> does not entirely fill the space between the first isolator element 104a and the floating conductive ring <NUM>. The non-linear dielectric <NUM> encapsulates the first isolator element 104a and floating conductive ring <NUM> in this non-limiting example, however a second non-linear dielectric <NUM> is included between the first isolator element 104a and the floating conductive ring <NUM>. The non-linear dielectric <NUM> may be any suitable non-linear dielectric. In some embodiments the non-linear dielectric <NUM> and the non-linear dielectric <NUM> may exhibit similar properties. In some embodiments, the non-linear dielectric <NUM> and the non-linear dielectric <NUM> may exhibit differing non-linear properties. For example, one may be more strongly non-linear than the other in response to an electric field. One may be more conductive than the other.

<FIG> illustrates a cross-sectional view of an alternative micro-isolator in which the floating conductive ring surrounding the isolator element has a different height than the isolator element. The micro-isolator <NUM> comprises substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM>. The substrate <NUM>, first isolator element 104a, second isolator element 104b, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM> have been described previously herein in connection with <FIG> and <FIG>, and therefore are not described again in detail here.

The floating conductive ring <NUM> differs from the floating conductive ring <NUM> of <FIG> in that its height differs from that of the first isolator element 104a. The floating conductive ring <NUM> has a height Hr, which differs from the height H of the first isolator element 104a. The height Hr may be selected to simplify fabrication. Filling the gap between the first isolator element 104a and the floating conductive ring may be difficult in practice depending on the height H of the first isolator element 104a. Making the height Hr less than H may facilitate filling the gap with the non-linear dielectric <NUM>. The height Hr may be less than <NUM>% of the height H, for example being between <NUM>% and <NUM>% of the height H, between <NUM>% and <NUM>% of the height H, less than <NUM>% the height H, or less than <NUM>% the height H, including any value within those ranges. As a non-limiting example, H may be <NUM> microns and Hr may be less than <NUM> micron, for example being on the order of <NUM> nanometers. In some alternative embodiments, Hr may be greater than H.

<FIG> illustrates a top view of a micro-isolator having a serpentine isolator element surrounded by a plurality of floating conductive rings, according to a non-limiting embodiment of the present application. The illustrated serpentine isolator element <NUM> may be formed of any of the materials described previously herein in connection with first and second isolator elements 104a and 104b. The floating conductive rings <NUM> are oval or race-track shaped, and may be formed of any of the materials described previously herein in connection with floating conductive ring <NUM>. The number of floating conductive rings <NUM> is not limiting. In this non-limiting example, ten floating conductive rings <NUM> are included. The floating conductive rings <NUM> each surround the serpentine isolator element <NUM>. The floating conductive rings <NUM> are concentrically positioned with respect to each other.

<FIG> illustrates a top view of a micro-isolator having a segmented floating conductive ring surrounding an isolator element, according to a non-limiting embodiment of the present application. The illustrated micro-isolator comprises isolator element 104a and segmented floating conductive ring <NUM>. The isolator element 104a was described previously in connection with <FIG> and <FIG>, and thus is not described in detail again here. The segmented floating conductive ring <NUM> surrounds the isolator element 104a. The segmented floating conductive ring <NUM> comprises a plurality of segments <NUM> separated by gaps gr. The number of segments <NUM> and the distance of the gaps gr may be selected to provide a desired level of electric field grading.

While <FIG> illustrates an example of a segmented floating conductive ring, a further alternative is a ring formed by a plurality of metallic inclusions. That is, in some embodiments, a ring of dielectric material with metallic inclusions may be used as a floating conductive ring. The amount and size of the metallic inclusions may be selected to provide a desired level of electric field grading.

<FIG> illustrates a cross-sectional view of a micro-isolator having floating conductive rings surrounding both the top and bottom isolator elements, according to a non-limiting embodiment of the present application. The micro-isolator <NUM> comprises substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, dielectric layer <NUM>, and floating conductive ring <NUM>. The substrate <NUM>, first isolator element 104a, second isolator element 104b, floating conductive ring <NUM>, dielectric layer <NUM>, non-linear dielectric <NUM>, and dielectric layer <NUM> have been described previously herein in connection with <FIG> and <FIG>, and therefore are not described again in detail here.

The floating conductive ring <NUM> surrounds the isolator element 104b. The floating conductive ring <NUM> may be substantially the same as the floating conductive ring <NUM>. In some embodiments, however, the floating conductive ring <NUM> may be formed of the same material as the isolator element 104b. Thus, in some embodiments, the floating conductive rings <NUM> and <NUM> are made of different materials.

<FIG> shows that the micro-isolator <NUM> may include electrical access to the second isolator element 104b by way of a pad <NUM> and electrical interconnect structure <NUM>. In this manner, a center of the second isolator element 104b may be electrically contacted even though the pad <NUM> is in the same plane as the second isolator element 104b.

The micro-isolator <NUM> also includes an encapsulant <NUM>. The encapsulant <NUM> may be a resin or any other suitable material.

While <FIG> illustrates a micro-isolator having a floating conductive ring surrounding a top isolator element, and <FIG> illustrates an embodiment with floating conductive rings surrounding top and bottom isolator elements, an alternative embodiment of a micro-isolator includes a floating conductive ring surrounding a bottom isolator element only. In general, it may be desirable to have a floating conductive ring surrounding the isolator element that receives a high voltage. In some embodiments, that may be a top isolator element, and in some embodiments it may be a bottom isolator element. Thus, floating conductive rings of the types described herein may be positioned around top or bottom isolator elements, or both. In some embodiments, a micro-isolator includes two or more isolator elements, with a floating conductive ring surrounding one or more of them.

An isolator of the types described herein may be deployed in various settings to galvanically isolate one portion of an electric circuit from another. One such setting is in industrial applications. In some embodiments, an isolator may isolate a motor driver from other portions of an electric system. The motor driver may operate at voltages equal to or greater than 600V in some embodiments (e.g., up to <NUM>. 5kV or more), and may comprise an inverter to convert a DC signal to an AC signal. In some embodiments, the motor driver may comprise one or more insulated gate bipolar transistors (IGBT), and may drive an electric motor according to a three-phase configuration.

Another such setting is in photovoltaic systems. In some embodiments, an isolator may be installed in a photovoltaic system to isolate a photovoltaic panel and/or an inverter from other parts of the system. In some embodiments, an isolator may be installed between a photovoltaic panel and an inverter.

Another such setting is in electric vehicles. In some embodiments, an isolator of the types described herein may be used to isolate any suitable part of an electric vehicle, such as a battery or a motor driver, from other parts of the vehicle.

<FIG> is a block diagram illustrating an example of a system comprising an isolator of the types described herein. System <NUM> may comprise isolator <NUM>, low-voltage device <NUM>, and high-voltage device <NUM>. In some embodiments, low-voltage device <NUM> may comprise a device operating at less than 500V. In some embodiments, high-voltage device <NUM> may comprise a device operating at 500V or higher.

Isolator <NUM> may be implemented using micro-isolator <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> and may be disposed between the low-voltage device and the high-voltage device. By isolating the two devices from one another, a user may be able to physically contact the low-voltage device without being electrically shocked or harmed. Low-voltage device <NUM> may comprise a user interface unit, such as a computer or other types of terminals, and/or a communication interface, such as a cable, an antenna or an electronic transceiver. High-voltage device <NUM> may comprise a motor driver, an inverter, a battery, a photovoltaic panel, or any other suitable device operating at 500V or higher. In the embodiments in which high-voltage device <NUM> comprises a motor driver, high-voltage device <NUM> may be connected to an electric motor <NUM>.

It should be appreciated from the description of <FIG> and the types of micro-isolators described herein that some embodiments of the present application provide an isolated system, comprising: a first device configured to operate in a first voltage domain; a second device configured to operate in a second voltage domain; and an isolator coupled between the first device and second device and comprising an electrically floating ring surrounding a first isolator element of a pair of vertically separated isolator elements.

The electrically floating ring may be a first electrically floating ring, and the isolated system may further comprise a second electrically floating ring surrounding a second isolator element of the pair of vertically separated isolator elements. In some embodiments, one or both-when multiple floating conductive rings are provided-are segmented rings. The electrically floating conductive ring may be shorter than the isolator element it surrounds, in some embodiments. In any such embodiments, a non-linear dielectric material may encapsulate the isolator element that is surrounded by a floating conductive ring.

Aspects of the present application may provide one or more benefits, some of which have been previously described. Now described are some non-limiting examples of such benefits. It should be appreciated that not all aspects and embodiments necessarily provide all of the benefits now described. Further, it should be appreciated that aspects of the present application may provide additional benefits to those now described.

Aspects of the present application provide an isolator capable of withstanding voltages exceeding 300V (e.g., 1kV, <NUM>. 5kV, 2kV, <NUM>. 5kV, 3kV, and <NUM>. 5kV) while limiting the probability of electric breakdown. As a result of such a reduction in the probability of electric breakdown, the lifetime of the isolator may be extended.

Claim 1:
A micro-isolator (<NUM>) with enhanced isolation breakdown voltage, comprising:
a first isolator element (104a) in a first plane, wherein the first isolator element comprises a first coil or a first plate;
a second isolator element (104b) in a second plane, wherein the second isolator element comprises a second coil or second plate;
a first dielectric material (<NUM>), comprising a polymer, disposed between the first and second isolator elements;
a first electrically floating ring (306a) disposed in the first plane and surrounding the first isolator element (104a); and
a second electrically floating ring (306b) concentric with the first electrically floating ring (306a);
wherein the first electrically floating ring (306a) and the second electrically floating ring (306b) differ in one or more of height, width, or material.