Electrical device including capacitor with improved dielectric structure

Abstract

The invention relates to an electrical device including a capacitor having an improved dielectric structure and a method of manufacturing the same. In particular, the proposed electrical device (100) comprises: a capacitor comprising: a cathode (110), an anode (130) and a dielectric structure (120) between the cathode (110) and the anode (130), in which the dielectric structure (120) comprises a stack of dielectric layers (121 to 123), the stack of dielectric layers (121 to 123) comprising: a dielectric layer (121) in contact with the cathode (110), and one or more other dielectric layers (122, 123), and wherein the product of the dielectric strength # imgabs0 # and the dielectric constant # imgabs1 # of the dielectric layer (121) in contact with the cathode (110) is greater than the product of the dielectric strength # imgabs2 # and the dielectric constant # imgabs3 # of each of the one or more other dielectric layers (122, 123).

Description

Technical Field

[0001] The present invention relates to the field of electrical devices. More specifically, the present invention relates to an electrical device including a capacitor and a method for manufacturing the same. The present invention is particularly advantageous for realizing capacitors for high voltage applications, but such applications are given as illustrative examples only and do not limit the present invention. Background Art

[0002] The present invention is in the particular scope of, but is not limited to, three-dimensional (3D) capacitors for high voltage applications.

[0003] Capacitors with 3D capacitive structures have been developed to provide high energy storage density. Typically, such 3D capacitive structures are conformally formed on reliefs (e.g., holes, grooves, or pillars) and provide a large specific area for a given component size. However, capacitors with 3D structures cannot be directly transferred to high voltage applications (e.g., exceeding 900V or 1,200V) without considering the specific characteristics and limitations of these applications.

[0004] In particular, in order to withstand high voltages, 3D capacitor structures with significantly thicker dielectric structures (e.g., thicker than 500 nm, or even 1,000 nm) are used. It is also known to use multilayer dielectric structures for high voltage applications. This allows the properties of the dielectric structure to be adjusted, including its dielectric strength, mechanical stress, and adhesion to the capacitor electrodes. In order to increase the breakdown voltage and ensure reliable operation at high voltages, thick multilayer dielectric structures are used to achieve high dielectric strength.

[0005] However, using extremely thick dielectric structures induces significant mechanical stress within the capacitor structure. This mechanical stress can lead to cracks in the dielectric structure and, consequently, to a degradation of its electronic properties, including a decrease in dielectric strength and an increase in leakage current. This negatively impacts the capacitor's breakdown voltage and reliability.

[0006] Therefore, there is a need for electrical devices including capacitors having improved dielectric structures that can reliably withstand high voltages. Summary of the Invention

[0007] The present invention has been made in view of the above problems.

[0008] According to one aspect The present invention provides an electrical device including a capacitor, wherein the capacitor includes: a cathode capacitor electrode, an anode capacitor electrode, and a dielectric structure between the cathode capacitor electrode and the anode capacitor electrode.

[0009] wherein the dielectric structure comprises a stack of dielectric layers, the stack comprising: a dielectric layer in contact with the cathode capacitor electrode, and one or more other dielectric layers, and

[0010] wherein a product of a dielectric strength and a dielectric constant of a dielectric layer in contact with the cathode capacitor electrode is greater than a product of a dielectric strength and a dielectric constant of each of the one or more other dielectric layers.

[0011] The present invention relates to an electrical device comprising a polarized capacitor comprising a cathode and an anode. Polarized capacitors are intended for use with a specific polarity, wherein the cathode is the negatively charged electrode of the capacitor and the anode is the positively charged electrode of the capacitor. When a polarized capacitor is used with the proper polarity (negatively charged cathode, positively charged anode), the electrical performance of the capacitor, particularly its breakdown voltage, is enhanced (compared to using the capacitor with improper polarity).

[0012] In the following, the expression "dielectric strength of a dielectric layer" (also called dielectric stiffness) is used to refer to the maximum electric field E that a dielectric layer can withstand without experiencing electrical breakdown. crit The expression "dielectric constant of a dielectric layer" is also used to refer to the relative dielectric constant ε of a dielectric layer. r Or absolute dielectric constant. In this disclosure, for convenience, the relative dielectric constant ε is used r , but those skilled in the art will be able to substitute absolute permittivity values ​​for relative permittivity values ​​if necessary.

[0013] The present invention proposes to use a multilayer dielectric structure (a stack of said dielectric layers stacked in the direction anode-cathode) with the highest quality factor E crit ×ε r This allows the dielectric properties of the dielectric structure to be significantly improved for the following reasons (these reasons are further detailed below with reference to the accompanying drawings).

[0014] First, we consider a single dielectric layer. For a single layer, the Selbeherr model relates the effective breakdown of the layer to: (a) the electric field E applied to the layer 场 The leakage current (current density) of the driver ), and (b) the dielectric strength E of the layer crit According to the Selberherr model, when the ratio E crit / E 场 As increases, the dielectric layer achieves higher breakdown.

[0015] Second, we consider a dielectric structure with a stack of multiple dielectric layers. Using such a dielectric structure, it can be shown that the dielectric structure with the highest ratio Ecrit / E 场 The dielectric layer has the highest quality factor E crit ×ε r In other words, it has the highest quality factor E crit ×ε r The dielectric layer is the strongest layer of the dielectric structure (ie, the layer with the highest breakdown voltage).

[0016] Third, in polarized capacitors, the cathode appears to be the critical electrode. The direction of the electric field promotes the injection of electrons on the cathode side (electrons move to higher potentials). For this reason, placing the strongest dielectric layer of the dielectric structure in front of the cathode allows reducing electron free circulation.

[0017] From the above, it can be inferred that the prime factor E with the highest quality crit ×ε r Placing the dielectric layer in contact with the cathode improves the dielectric properties of the dielectric structure. Specifically, it reduces leakage current in the dielectric structure and increases its dielectric strength. This has been confirmed by the inventors' experimental results (described in detail below). As a result, a higher breakdown voltage and improved reliability of the capacitor are achieved.

[0018] For these reasons, the present invention provides an electrical device including a capacitor having an improved dielectric structure capable of reliably withstanding high voltages.

[0019] In a specific embodiment , at least one of the one or more other layers of the dielectric structure (ie, a dielectric layer of the dielectric structure not in contact with the cathode) comprises a non-stoichiometric silicon-rich silicon nitride.

[0020] This embodiment proposes to use non-stoichiometric silicon-rich silicon nitride to form the dielectric structure. This material is also called "low stress silicon nitride" and is labeled Si x N y , where x / y>3 / 4. The use of silicon-rich silicon nitride allows providing a dielectric structure with limited intrinsic mechanical stress. Therefore, an advantage of this embodiment is that it limits the mechanical stress within the capacitor structure, and any negative consequences associated with such stress.

[0021] In a specific embodiment , the dielectric layer in contact with the cathode capacitor electrode comprises stoichiometric silicon nitride (Si3N4),

[0022] At least one of the one or more other dielectric layers comprises a non-stoichiometric silicon-rich silicon nitride (Si x N y , where x / y>3 / 4) (i.e., the layer of the dielectric structure not in contact with the cathode), and

[0023] At least one of the one or more other dielectric layers comprises a layer comprising silicon oxide (SiO 2 ) (ie, another layer of the dielectric structure not in contact with the cathode).

[0024] The advantage of this embodiment is that it provides a dielectric structure with strong adhesion to the anode and limited intrinsic mechanical stress. The use of (thermally grown) silicon oxide SiO2 allows strong adhesion to the anode (e.g., silicon substrate including protruding walls). In addition, the non-stoichiometric silicon-rich silicon nitride Si x N y The use of (where x / y>3 / 4) allows limiting the mechanical stresses within the dielectric structure.

[0025] The advantage of this embodiment is that it provides a dielectric structure with strong dielectric strength and reduced leakage current. This is due to the stacking sequence of the different layers within the dielectric structure. The dielectric layer comprising stoichiometric silicon nitride (Si3N4) has the highest quality factor E crit ×ε r dielectric layer and is placed in contact with the cathode.

[0026] In a specific embodiment , the thickness of the dielectric layer comprising stoichiometric silicon nitride (Si3N4) is 20nm to 200nm,

[0027] Contains non-stoichiometric silicon-rich silicon nitride (Si x N y , wherein x / y>3 / 4) the thickness of the dielectric layer is 500nm to 1500nm, and

[0028] The thickness of the dielectric layer including silicon oxide (SiO 2 ) is 100 nm to 1000 nm.

[0029] The inventors have observed that the dielectric structure provided according to this embodiment is particularly advantageous. The materials and thicknesses used for the various dielectric layers allow providing a dielectric structure with strong adhesion to the anode, limited intrinsic mechanical stress and a high breakdown voltage.

[0030] In a specific embodiment , containing non-stoichiometric silicon-rich silicon nitride (Si x N y , where x / y>3 / 4) the intrinsic mechanical stress of the layer is 300 MPa to 600 MPa.

[0031] According to this embodiment, the lower stress silicon nitride Si x N y(where x / y>3 / 4) is used to form a dielectric structure for a capacitor. This allows for providing a thick dielectric structure while limiting its inherent mechanical stresses. In other words, it allows for providing a thick dielectric structure while avoiding degradation of the dielectric structure's electrical properties due to mechanical stress within the structure. Therefore, an advantage of this embodiment is that it provides a capacitor having a dielectric structure suitable for high voltage applications.

[0032] In a specific embodiment , the cathode capacitor electrode includes (or is formed of): a metal layer, a degenerate semiconductor layer, or a trap-rich layer (eg, a polysilicon layer).

[0033] According to this embodiment, the cathode is made of a metal layer, a degenerate semiconductor layer, or a trap-rich layer (e.g., a polysilicon layer). In other words, the cathode behaves like a metal. This allows the nonlinear effects associated with semiconductors to be eliminated. In particular, this prevents the occurrence of depletion mechanisms if the capacitor is used with reverse polarity (i.e., with inappropriate polarity).

[0034] In a specific embodiment , the anode capacitor electrode or the cathode capacitor electrode includes a conductive structure having concavities and convexities (eg, pores, holes, grooves, or pillars).

[0035] This embodiment proposes the use of three-dimensional capacitors. That is, capacitors whose capacitive structures are conformally formed on irregularities (e.g., holes, grooves, or pillars). The use of three-dimensional capacitors allows for a large specific area for a given component size. As a result, high capacitance density follows.

[0036] According to one embodiment, the anode (or corresponding cathode) includes a conductive structure formed using a semiconductor substrate having a groove. The dielectric structure extends conformally on the conductive structure, and the cathode (or corresponding anode) extends conformally on the dielectric structure. The use of a semiconductor substrate allows the use of a thick dielectric layer (for example, by using a wide groove). This provides a capacitor with a high energy storage density and a high breakdown voltage, which is particularly suitable for high voltage applications.

[0037] According to another example, the anode (or corresponding cathode) includes a conductive structure formed using an anodic aluminum oxide (AAO) substrate having holes covered by a conductive layer. The dielectric structure extends conformally on the conductive structure, and the cathode (or corresponding anode) extends conformally on the dielectric structure. The use of the AAO substrate with holes allows for high capacitance density. This provides a capacitor with high energy storage density, which is suitable for low voltage applications.

[0038] In a specific embodiment, the electrical device is configured to be used at an operating voltage measured between the anode capacitor electrode and the cathode capacitor electrode exceeding 900V or 1,200V, and preferably at an operating voltage of 1,200V to 1,500V.

[0039] For example, the proposed electrical device can be used as a decoupling or buffer capacitive element for power electronics.

[0040] In another specific embodiment , the electrical device is configured to be used at an operating voltage of 0.65V to 10V measured between the anode capacitor electrode and the cathode capacitor electrode.

[0041] According to another aspect The present invention also provides an electronic circuit comprising a voltage source and the proposed electrical device, wherein the anode capacitor electrode of the electrical device is connected to the positive output terminal of the voltage source, and the cathode capacitor electrode of the electrical device is connected to the negative output terminal of the voltage source.

[0042] According to another aspect , the present invention provides a method for manufacturing an electrical device, the method comprising:

[0043] A capacitor forming an electrical device, the capacitor comprising: a cathode capacitor electrode, an anode capacitor electrode, and a dielectric structure interposed between the cathode capacitor electrode and the anode capacitor electrode,

[0044] wherein the dielectric structure comprises a stack of dielectric layers, the stack comprising: a dielectric layer in contact with the cathode capacitor electrode, and one or more other dielectric layers, and

[0045] wherein a product of a dielectric strength and a dielectric constant of a dielectric layer in contact with the cathode capacitor electrode is greater than a product of a dielectric strength and a dielectric constant of each of the one or more other dielectric layers.

[0046] The proposed manufacturing method may be adapted to obtain any of the electrical devices defined in the present disclosure.Furthermore, it should be noted that embodiments of the proposed method for manufacturing an electrical device present the advantages described with respect to embodiments of the proposed electrical device.

[0047] In a specific embodiment , the proposed method comprises a preliminary step of selecting the dielectric layer in contact with the cathode capacitor electrode such that:

[0048] The product of the dielectric strength and the dielectric constant of the dielectric layer in contact with the cathode capacitor electrode is greater than the product of the dielectric strength and the dielectric constant of each of the one or more other dielectric layers.

[0049] In a specific embodiment, the proposed method includes, for each dielectric layer of the dielectric structure:

[0050] The product of the dielectric strength and the dielectric constant of the dielectric layer is obtained (determined, estimated, or calculated).

[0051] In a specific embodiment , the product of the dielectric strength and dielectric constant of each dielectric layer is obtained based on:

[0052] the properties of the material contained in the dielectric layer (e.g., the composition of the material, the type of material such as crystalline or polycrystalline), and

[0053] the thickness of the dielectric layer, and

[0054] It is preferably also based on the deposition technique used (or intended to be used) for the dielectric layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further features and advantages of the invention will become apparent from the following description of certain embodiments of the invention, given by way of illustration only and not limitation, with reference to the accompanying drawings, in which:

[0056] Figure 1 and Figure 2 a cross-sectional view showing an electrical device according to an embodiment of the present invention; and

[0057] Figure 3 and Figure 4 Shown are experimental results related to the present invention. DETAILED DESCRIPTION

[0058] The present invention provides electrical devices including capacitors having improved dielectric structures. More specifically, embodiments of the present invention seek to improve the dielectric properties of multilayer dielectric structures, particularly by reducing leakage current and increasing the dielectric strength of the dielectric structures.

[0059] The present invention pertains to a specific range of 3D capacitors for high voltage applications. The following description of the invention will relate to this specific range, which is given by way of illustrative example only and should not be construed as limiting the invention. The present invention can also be used in applications other than high voltage applications, and in capacitors other than 3D capacitors.

[0060] Figure 1 A cross-sectional view showing an electrical device according to an embodiment of the present invention is described below to explain the present invention.

[0061] Electrical device 100 A polarized capacitor is included, formed by a cathode capacitor electrode 110 (here, the top electrode) and an anode capacitor electrode 130 (here, the bottom electrode) separated by a dielectric structure 120 .

[0062] Bottom electrode 130 The conductive structure includes a concave-convex conductive structure, wherein the concave-convex conductive structure is formed by opposite walls 131 extending upward from a bottom surface BS of the conductive structure.

[0063] The conductive structure can be formed by etching a semiconductor substrate (eg, a doped silicon substrate). The conductive structure can also be formed by a 3D substrate covered by a conductive layer (eg, an anodic aluminum oxide substrate including holes).

[0064] The wall 131 can be in a (substantially) linear shape, a curved shape, or a (substantially) linear shape connected together by an angle. In a specific embodiment, the wall 131 forms one or more grooves, such as a plurality of separate adjacent grooves or a groove extending in a curved shape.

[0065] Dielectric structure 120 Conformally extends over the wall 131 of the bottom electrode 130 . Dielectric structure 120 A stack including a plurality of dielectric layers 121 to 122 (stacked one on another along a direction from the bottom electrode 130 to the top electrode 110 , ie, an anode-cathode direction).

[0066] Top electrode 110 At least one conductive layer (eg, a polysilicon layer) extending conformally over the dielectric structure 120 is included.

[0067] The top electrode 110 fills the recess (eg, trench) formed by the walls 131 . In other words, the top surface of the top electrode 110 is above the top surface of the dielectric structure 120 and above the top surface of the walls 131 .

[0068] The figure shows a polarized capacitor in which the top electrode is a cathode 110 and the bottom electrode is an anode 130. However, other embodiments of the invention are envisioned in which the bottom electrode is a cathode and the top electrode is an anode.

[0069] Embodiments of the present invention also relate to an electronic circuit comprising a voltage source and the proposed electrical device 100, wherein the anode 130 of the electrical device 100 is connected to the positive output terminal of the voltage source and the cathode 130 of the electrical device 100 is connected to the negative output terminal of the voltage source.

[0070] For example, the proposed electrical device 100 may be used as a decoupling or buffering capacitive element for power electronics in which the operating voltage exceeds 900V or 1,200V, and preferably is 1,200V to 1,500V.

[0071] For such applications, the capacitor of the electrical device 100 must be able to reliably withstand high voltages. Therefore, it is necessary to have a high breakdown voltage and high reliability. Meeting these requirements depends particularly on the dielectric properties of the dielectric structure 120 used in the capacitor.

[0072] This leads to the question of how to select and place the various layers of the dielectric structure 120 to improve its dielectric properties and meet these requirements. To answer this question, the inventors made the following developments and observations that support the present invention, namely points (1) to (4):

[0073] (1) Single dielectric layer: electric field, leakage current, and breakdown

[0074] First consider a single dielectric layer. For a single layer, the Selbeherr model relates the effective breakdown of a single layer to: (a) the electric field E applied to the layer 场 The leakage current of the driver (i.e., the current density in the following equation ), and (b) the dielectric strength E of the layer crit .

[0075] Further details about the model can be found in S. Selberherr, “On modeling MOS-devices”, Process and device modeling, North-Holland Publishing Co., NLD, pp. 265-299, 1986, and in W. Maes et al., “Impact ionization in silicon: A review and update”, in Solid-State Electronics, Vol. 33, No. 6, pp. 705-718, 1990.

[0076] The Selberherr model describes avalanche in the case of breakdown. In this model, the avalanche generation term of electrons is expressed as follows:

[0077]

[0078] in is the current density, q is the elementary charge, and α n is the electron ionization rate. The latter is defined by the following expression:

[0079]

[0080] In this equation, the coefficient T (temperature) and exponent γ n is a positive real number. Here, E critis the threshold electric field for activating the ionization mechanism. It varies depending on the material composition and its microstructure. In addition, E 场 is the effective electric field component experienced by the charges flowing in the dielectric, given by express.

[0081] From the above equation, we can see that the higher the E crit / E 场 The ratio results in a lower ionization rate α n , thus resulting in lower avalanche generation terms

[0082] Therefore, considering a single dielectric layer, it can be inferred that when the ratio E of the dielectric layer crit / E 场 As is increased, the dielectric layer achieves a higher breakdown field.

[0083] (2) Multilayer dielectric structure: electric field division between dielectric layers

[0084] Now consider a dielectric structure comprising a stack of multiple layers and investigate the electric field partitioning between the different layers of the dielectric structure.

[0085] For this purpose, an example is used in which the dielectric structure includes a SiO2 layer and a Si3N4 layer.

[0086] The electric field value in the SiO2 layer is set to Evaluate the electric field value in the Si3N4 layer using the dielectric constant ratio Table 1 in the Appendix summarizes the ε values ​​for thin dielectric layers of SiO2 and Si3N4 (and thin dielectric layers of other materials). r Based on the values ​​in Table 1, we get Finally obtained

[0087] Now, the E of each layer in the dielectric structure can be determined crit ×E 场 Ratio. Using the values ​​in Table 1, we get as well as

[0088] Therefore, we get In other words, and The margin between and Therefore, the Si3N4 layer will wear out faster than the SiO2 layer. This negatively affects the reliability and / or breakdown voltage of the considered dual-layer dielectric structure, and thus negatively affects the reliability and / or performance of the capacitor.

[0089] In fact, for most multilayer dielectric structures, the dielectric strength ratio does not match the dielectric constant ratio. As a result, one of the dielectric layers of the dielectric structure wears out faster than the other layers. This negatively impacts the reliability of the capacitor.

[0090] The dielectric constant ratio can be used The analysis shows that lead to This means that the SiO2 layer has the highest quality factor Therefore, it has the highest ratio The results are not limited to this particular example, but apply to any material (and / or its deposition method) and any number of layers in a dielectric structure.

[0091] Therefore, considering the multilayer dielectric structure, the one with the highest quality factor E crit ×ε r The dielectric layer also has the highest ratio E crit / E 场 dielectric layer.

[0092] By combining this result with the conclusion of point (1), it can be inferred that the one with the highest quality factor E crit ×ε r The dielectric layer is the layer with the highest breakdown in the dielectric structure.

[0093] It can then be concluded that the one with the highest quality factor E crit ×ε r The dielectric layer is the strongest dielectric layer in the multilayer dielectric structure.

[0094] (3) Polarized capacitors: key electrodes

[0095] Based on the above points, the next step is to determine where to place the strongest dielectric layer in the dielectric structure to improve the dielectric properties of the structure.

[0096] In polarized capacitors, the cathode appears to be the critical electrode (as confirmed by the inventors' experimental results detailed below). The direction of the electric field promotes electron injection on the cathode side (electrons move to higher potentials). Therefore, the strongest dielectric layer in the dielectric structure is placed in front of the cathode to reduce free electron circulation.

[0097] (4) The proposed solution will have the highest quality factor E crit ×ε r The dielectric layer is placed in contact with the cathode

[0098] According to the above points (1) to (3), it can be inferred that the highest quality factor E crit ×ε rPlacing the dielectric layer in contact with the cathode improves the dielectric properties of the dielectric structure. Specifically, it reduces leakage current in the dielectric structure and increases its dielectric strength. This has been confirmed by the inventors' experimental results (described in detail below). Consequently, a higher breakdown voltage and improved reliability of the capacitor result.

[0099] The above summarizes the principles of the present invention. These principles will now be explained by describing an exemplary embodiment of the present invention in the following figure.

[0100] Figure 2 A cross-sectional view of an electrical device according to an embodiment of the present invention is shown.

[0101] and Figure 1 compared to, Figure 2 The electrical device 100 includes a dielectric structure 120 having a stack of three dielectric layers 121 , 122 , 123 stacked on top of each other.

[0102] In contact with the top electrode 110 (here the cathode) First dielectric layer 121 The layer 121 comprises stoichiometric silicon nitride (Si3N4). The thickness of the layer 121 is 20 nm to 200 nm.

[0103] The second dielectric layer 122 comprises non-stoichiometric silicon-rich silicon nitride (Si x N y , where x / y>3 / 4). The thickness of this layer is 500 nm to 1500 nm. The mechanical stress of the second dielectric layer 122 is 300 MPa to 600 MPa. The use of this silicon-rich silicon nitride layer 122 (also known as low-stress silicon nitride) allows the provision of a dielectric structure 120 with limited intrinsic mechanical stress.

[0104] The third dielectric layer 123 The dielectric layer 123 conformally extends over (contacts) the bottom electrode 130 (here, the anode) and comprises silicon oxide (SiO2). The thickness of this layer is 100 nm to 1000 nm. The dielectric layer 123 can be formed using thermal oxidation of the conductive structure 110 (e.g., a silicon substrate). The use of the silicon oxide layer 123 allows for strong adhesion to the bottom electrode 130.

[0105] This embodiment is particularly advantageous because it provides a dielectric structure 120 with strong adhesion to the bottom electrode 130 (including the walls 131 ) and limited intrinsic mechanical stress.

[0106] It should also be emphasized that this embodiment also provides a dielectric structure 120 having strong dielectric strength and reduced leakage current. This is due to the stacking sequence of the different dielectric layers 121 to 123 within the dielectric structure 120.

[0107] Following the above principle, the stacking order of the dielectric layers 121 to 123 is such that the dielectric layer 121 in contact with the cathode 110 has the highest quality factor E of all the layers in the dielectric structure 120. crit ×ε r (Right now, and ).

[0108] Table 2 in the Appendix presents the E of thick dielectric layers of different materials. crit ×ε r Specifically, using the values ​​in this table, we get: Greater than and greater than

[0109] It should be noted that Always below Due to the reduced ratio of nitrogen (N) to silicon (Si), the non-stoichiometric silicon-rich silicon nitride layer (Si x N y ) has reduced mechanical stress and electrical properties compared to stoichiometric silicon nitride layers (Si3N4).

[0110] As described below, experimental results of the inventors confirm that the proposed dielectric structure 120 exhibits enhanced dielectric strength and reduced leakage current.

[0111] Figure 3 The figure shows the experimental results related to the present invention. The figure compares the dielectric properties of a double-layer dielectric structure (dashed line) and a triple-layer dielectric structure (solid line).

[0112] More precisely, the curves on this figure show the current density J in the dielectric structure as a function of the electric field E applied thereto (for double-layer and triple-layer dielectric structures).

[0113] The double-layer dielectric structure 120-A (dashed line) is composed of a silicon oxide (SiO2) layer and a non-stoichiometric silicon-rich silicon nitride (Si x N y The three-layer dielectric structure 120-B (solid line) also includes a stoichiometric silicon nitride (Si3N4) layer with a thickness of 50 nm. The Si3N4 layer has the highest quality factor E crit ×ε r and located between the cathode and Si x N y Between layers.

[0114] like Figure 3As shown in Figure 1, the introduction of a thin layer of silicon nitride in front of the cathode provides the following advantages. First, it reduces the current density within the dielectric structure at high electric field values ​​(as indicated by the vertical arrows in the figure). Second, it increases the dielectric strength of the dielectric structure by approximately 10% (as indicated by the horizontal arrows).

[0115] The proposed solution thus provides a dielectric structure with higher dielectric strength and reduced leakage current, ie with improved dielectric properties. It can be inferred that capacitors using such a dielectric structure exhibit increased breakdown voltage and improved reliability.

[0116] The experimental results shown in the figure below further confirm the advantages of the proposed solution.

[0117] Figure 4 The figure shows the experimental results related to the present invention. The figure compares the dielectric properties of a three-layer dielectric structure according to different polarities.

[0118] The curves on this figure show the current density J in a dielectric structure as a function of the electric field E applied thereto (for different polarities).

[0119] The three-layer dielectric structure 120 is composed of a silicon oxide (SiO2) layer, a non-stoichiometric silicon-rich silicon nitride (Si x N y ) layer and a stack of stoichiometric silicon nitride (Si3N4) layers. The Si3N4 layer exhibits the highest quality factor E crit ×ε r .

[0120] In the first polarity (labeled POS in the figure and shown by dashed lines), the Si3N4 layer is located in front of the anode, while in the second polarity (labeled NEG in the figure and shown by solid lines), the Si3N4 layer is located in front of the cathode.

[0121] If the Figure 4 As shown, it will have the highest quality factor E crit ×ε r Placing the layer in front of the cathode offers the following advantages. First, it significantly reduces the current density in the dielectric structure (as indicated by the vertical arrows in the figure). For electric field values ​​of 5 MV / m to 6 MV / m (corresponding to the electric field values ​​envisioned for applications), the current density is reduced by a factor of less than 100. Second, it also improves the dielectric strength of the dielectric structure (as indicated by the horizontal arrows in the figure).

[0122] The experimental results in this figure confirm that the cathode is the key electrode in polarized capacitors. They also show that the highest quality factor E crit ×ε r The layer placed in front of the cathode improves the dielectric properties of the dielectric structure.

[0123] Further variations: Although the present invention has been described above with reference to certain specific embodiments, it will be understood that the present invention is not limited to the particularities of these specific embodiments. Many variations, modifications and developments of the above embodiments are possible within the scope of the claims.

[0124] In particular, the present invention has been described with reference to capacitors having a 3D capacitive structure and intended for high voltage applications. However, other embodiments of the invention are contemplated, for example, embodiments in which the capacitor has a planar capacitive structure or is intended for applications other than high voltage applications.

[0125] It should be understood that references herein to directions and positions such as "top" and "bottom," "front" and "back" refer only to the directions that apply when the structures and components are oriented as shown in the drawings.

[0126] appendix

[0127] Table 1: Properties of various materials that can be used for dielectric structures considering thin films (thickness 1 nm to 20 nm, or 1 nm to 100 μm)

[0128]

[0129] Table 2: Properties of various materials that can be used for dielectric structures considering thick films (thickness greater than 500nm, or even 1000nm)

[0130]

[0131]

Claims

1. An electrical device (100) comprising a capacitor, the capacitor comprising: a cathode capacitor electrode (110), an anode capacitor electrode (130), and a dielectric structure (120) interposed between the cathode capacitor electrode (110) and the anode capacitor electrode (130), wherein the dielectric structure (120) comprises a stack of dielectric layers (121 to 123), the stack of dielectric layers (121 to 123) comprising: a dielectric layer (121) in contact with the cathode capacitor electrode (110), and one or more other dielectric layers (122, 123), and wherein the dielectric strength of the dielectric layer (121) in contact with the cathode capacitor electrode (110) is and dielectric constant The product of is greater than the dielectric strength of each of the one or more other dielectric layers (122, 123) and dielectric constant The product of .

2. The electrical device (100) of claim 1, wherein at least one of the one or more other layers (122, 123) of the dielectric structure (120) comprises a non-stoichiometric silicon-rich silicon nitride.

3. The electrical device (100) according to claim 2, wherein: The dielectric layer (121) in contact with the cathode capacitor electrode (110) comprises stoichiometric silicon nitride, At least one of the one or more other dielectric layers (122, 123) comprises a layer (122) comprising a non-stoichiometric silicon-rich silicon nitride, and At least one of the one or more other dielectric layers (122, 123) includes a layer (123) comprising silicon oxide.

4. The electrical device (100) according to claim 3, wherein: The dielectric layer (121) comprising stoichiometric silicon nitride has a thickness of 20 nm to 200 nm, The dielectric layer (122) comprising non-stoichiometric silicon-rich silicon nitride has a thickness of 500 nm to 1500 nm, and The thickness of the dielectric layer (123) containing silicon oxide is 100 nm to 1000 nm.

5. The electrical device (100) according to any one of claims 2 to 4, wherein the layer (122) comprising non-stoichiometric silicon-rich silicon nitride has an intrinsic mechanical stress of 300 MPa to 600 MPa.

6. The electrical device (100) according to any one of claims 1 to 5, wherein the cathode capacitor electrode (110) comprises a metal layer, a degenerate semiconductor layer, or a trap-rich layer.

7. The electrical device (100) according to any one of claims 1 to 6, wherein the anode capacitor electrode (130) or the cathode capacitor electrode (110) comprises a conductive structure having irregularities such as pores, holes, grooves or pillars.

8. The electrical device (100) according to any one of claims 1 to 7, wherein the electrical device (100) is configured to be used at an operating voltage measured between the anode capacitor electrode (130) and the cathode capacitor electrode (110) exceeding 900 V or 1200 V, and preferably at an operating voltage of 1200 V to 1500 V.

9. The electrical device (100) according to any one of claims 1 to 7, wherein the electrical device (100) is configured to be used at an operating voltage of 0.65V to 10V measured between the anode capacitor electrode (130) and the cathode capacitor electrode (110).

10. An electronic circuit comprising a voltage source and an electrical device (100) according to any one of claims 1 to 9, wherein an anode capacitor electrode (130) of the electrical device (100) is connected to a positive output terminal of the voltage source, and a cathode capacitor electrode (110) of the electrical device (100) is connected to a negative output terminal of the voltage source.

11. A method for manufacturing an electrical device (100), the method comprising: A capacitor is formed for the electrical device (100), the capacitor comprising: a cathode capacitor electrode (110), an anode capacitor electrode (130), and a dielectric structure (120) between the cathode capacitor electrode (110) and the anode capacitor electrode (130), wherein the dielectric structure (120) comprises a stack of dielectric layers (121 to 123), the stack of dielectric layers (121 to 123) comprising: a dielectric layer (121) in contact with the cathode capacitor electrode (110), and one or more other dielectric layers (122, 123), and wherein the dielectric strength of the dielectric layer (121) in contact with the cathode capacitor electrode (110) is and dielectric constant The product of is greater than the dielectric strength of each of the one or more other dielectric layers (122, 123) and dielectric constant The product of .

12. The method according to claim 11, comprising the preliminary step of selecting the dielectric layer (121) in contact with the cathode capacitor electrode (110) such that: The dielectric strength of the dielectric layer (121) in contact with the cathode capacitor electrode (110) and dielectric constant The product of is greater than the dielectric strength of each of the one or more other dielectric layers (122, 123) and dielectric constant The product of .

13. The method according to claim 12, comprising, for each dielectric layer (121 to 123) of the dielectric structure (120): The dielectric strength of the dielectric layers (121 to 123) is obtained ( to ) and dielectric constant ( to ) is the product of .

14. The method according to claim 13, wherein the dielectric strength ( to ) and dielectric constant ( to ) is obtained based on the following: the properties of the materials contained in the dielectric layers (121 to 123), and the thickness of the dielectric layers (121 to 123), and It is also preferably based on the deposition technique used for said dielectric layers (121 to 123).

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