High-pressure sensor with aluminum oxide layer

Abstract

Reduces long-term drift in the sensor measurement signal of high-voltage sensors. [Solution] The present invention relates to a high-voltage sensor (10) comprising a base (12), a diaphragm (18) that can deflect along the normal direction (16) within a void region (14) in response to ambient pressure, measuring means (24) provided above the diaphragm (18) in the normal direction (16) and each having at least one measuring means layer (26) for electrically capturing the deflection of the diaphragm, and an insulating layer (30) disposed on at least the diaphragm (18), wherein a homogeneous aluminum oxide layer (32) is disposed between at least the measuring means layer (26) and the insulating layer (30).

Description

【Technical Field】 【0001】 The present invention relates to a high-pressure sensor based on the preamble of claim 1. 【Background Art】 【0002】 DE102005027365A1 describes a high-pressure sensor comprising a steel substrate, a diaphragm, an insulating layer, and measuring means made of a piezoresistive material, for example a NiCrSi alloy. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 DE102005027365A1 【Summary of the Invention】 【0004】 According to the present invention, a high-pressure sensor having the features according to claim 1 is proposed. Thereby, the long-term drift of the sensor measurement signal of the high-pressure sensor can be reduced. The aluminum oxide layer can reduce the influence of the charges present distributed in the insulating layer on the measuring means layer and can homogenize the charge distribution at the interface of the measuring means layer. 【0005】 The charges can be generated by interface traps at the interface between the insulating layer and an adjacent layer and form energy levels within the bandgap. The interface traps can be generated by dangling bonds, contamination, or structural defects in the material of the insulating layer. These interface traps can capture or release charge carriers, thereby generating charges. 【0006】 The aluminum oxide layer can reduce interface traps, especially by reducing dangling bonds and defects. Thereby, it has been confirmed that the surface density of the interface traps decreases to 5.20×10 10 cm -2 eV -1 . Furthermore, thereby, the surface density of the leakage current is reduced to 5.06×10-9 A / cm 2 This can be reduced. Thermodynamic stability can also be increased, thereby reducing the probability or diffusion of chemical reactions at the interface. 【0007】 In the following, the upper and lower sides refer to the normal direction. High-pressure sensors can be adapted to capture ambient pressures above 10 bar. For example, ambient pressures above 100 bar or even above 1000 bar may be measurable. 【0008】 The diaphragm and / or substrate may be formed from a metal, particularly a special steel, or a ceramic. The empty region may have a bridge structure below the diaphragm in the normal direction. This bridge structure may allow the diaphragm to have a thickness that changes at least in the lateral direction perpendicular to the normal direction. The bridge structure can be created by a cylindrical empty region within the substrate, thereby enabling the diaphragm to be fabricated integrally from the substrate. 【0009】 The diaphragm can be manufactured in a rectangular, oval, or circular shape when viewed in a plane with the normal direction as its normal. The diaphragm can be manufactured integrally from the substrate. The measuring means may be spaced apart from each other. These measuring means may be electrically connected to each other within a Wheatstone bridge circuit. The measuring means may be positioned so as to overlap laterally with the diaphragm edge to which the diaphragm is bonded to the substrate. The measuring means may be electrically connected, in particular, by wire bonding or flip-chip bonding. 【0010】 The measuring means layer may be formed from a piezoresistive material and / or a piezoelectric material. The measuring means layer may produce a change in electrical resistance or voltage in response to the mechanical stress acting thereon. The insulating layer may also be applied to the substrate. The insulating layer may be applied directly to the diaphragm and / or the substrate. The insulating layer may be placed between the measuring means layer and the diaphragm. 【0011】 The aluminum oxide layer may have a substantially constant thickness (i.e., a target thickness, but subject to tolerances throughout manufacturing). The average thickness of the aluminum oxide layer may be greater than 5 nm, preferably greater than 20 nm, and / or less than 100 nm. The aluminum oxide layer may be placed directly on the insulating layer and / or directly below the measuring means, in particular the measuring means layer. The aluminum oxide layer may be applied only on the insulating layer, on the upper side of the substrate. The aluminum oxide layer may be applied directly on the substrate, on at least one surface of the substrate other than the upper side, e.g., the side and / or the underside. 【0012】 Above the measuring means in the normal direction, a protective layer may be provided, in particular, for electrical insulation and / or to protect the measuring means from environmental influences. In one preferred embodiment of the present invention, it is advantageous that the aluminum oxide layer is formed entirely from amorphous aluminum oxide. This allows the aluminum oxide layer to have a uniformly distributed charge. The aluminum oxide layer may have a disordered and irregular material structure. The aluminum oxide layer may have isotropic electrical properties. 【0013】 In one preferred embodiment of the present invention, it is advantageous that the aluminum oxide layer is applied by atomic layer deposition. Atomic layer deposition (ALD) is a thin-film coating method that can produce very thin, uniform, and consistent layers by depositing material precisely at the atomic level. 【0014】 In a preferred embodiment of the present invention, the insulating layer is intended to be formed from silicon oxide. The insulating layer may cover the entire upper surface of the substrate. Alternatively, or in addition to the above, the insulating layer may be formed from silicon nitride or a metal oxide. The insulating layer may be applied by chemical vapor deposition. The insulating layer may be applied by plasma chemical vapor deposition (PECVD). 【0015】 In a preferred embodiment of the present invention, it is contemplated that the aluminum oxide layer is disposed entirely between the measuring means and the surface of the insulating layer. Thereby, the aluminum oxide layer can form an overall interface at least under the measuring means. 【0016】 In a preferred embodiment of the present invention, it is contemplated that the aluminum oxide layer is applied above the insulating layer in the normal direction without interruption in the plane. In a specific embodiment of the present invention, it is advantageous if the aluminum oxide layer covers at least the entire upper side of the insulating layer. 【0017】 In an advantageous embodiment of the present invention, it is contemplated that the aluminum oxide layer is disposed on at least one side wall of the substrate. However, the aluminum oxide layer may be disposed only above the diaphragm and / or above the substrate. The aluminum oxide layer can be disposed on all side walls. The aluminum oxide layer can also be disposed under the substrate. The aluminum oxide layer can be applied directly onto the substrate at at least one of the side walls of the substrate and / or under the substrate. 【0018】 In a specific form of the present invention, it is advantageous if the aluminum oxide layer surrounds at least the main part of the outer covering of the substrate. The aluminum oxide layer can surround the entire outer covering of the substrate. 【0019】 In a specific embodiment of the present invention, it is advantageous if the measuring means layer is formed from a nickel-chromium-silicon alloy. The measuring means can have only the measuring means layer. Further advantages and advantageous forms of the present invention are apparent from the description of the figures and the drawings. 【0020】 The present invention will be described in detail below with reference to the drawings. 【Brief Description of the Drawings】 【0021】 [Figure 1] It is a cross-sectional view of a high-pressure sensor in a specific embodiment of the present invention. [Figure 2] A graph showing the time evolution of the sensor measurement signal of a high-pressure sensor in a further specific embodiment of the present invention. 【Embodiments for Carrying Out the Invention】 【0022】 FIG. 1 shows a cross-section of a high-pressure sensor in a specific embodiment of the present invention. The high-pressure sensor 10 includes, for example, a metal substrate 12 and a diaphragm 18 that can bend along the normal direction 16 within the empty region 14 of the substrate 12 in response to ambient pressure and is integrally formed within the substrate 12. The empty region 14 has a bridge structure 20 below the diaphragm 18 in the normal direction 16, and the diaphragm 18 has a diaphragm thickness 22 that varies in the lateral direction perpendicular to the normal direction 16 due to this bridge structure 20. 【0023】 Above the diaphragm 18 in the normal direction 16, a plurality of spaced-apart measuring means 24 are provided. In particular, each piezoresistive measuring means 24 includes a measuring means layer 26 for electrically capturing the deflection of the diaphragm. The measuring means layer 26 is formed, in particular, from a nickel-chromium-silicon alloy. The measuring means 24 are arranged, in particular, so as to overlap laterally with the diaphragm edge 28 where the diaphragm 18 is joined to the substrate 12. 【0024】 The high-pressure sensor 10 further includes an insulating layer 30 made of silicon oxide, in particular, disposed between the measuring means layer 26 and the diaphragm 18. This insulating layer 30 covers the entire upper side of the substrate 12 and is disposed directly on the substrate 12. 【0025】 Preferably, an amorphous and homogeneous aluminum oxide layer 32 is disposed at least between the measuring means layer 26 and the insulating layer 30. The aluminum oxide layer 32 can be applied, in particular, by atomic layer deposition and can have a substantially constant layer thickness 34, that is, aimed for but affected by manufacturing tolerances. 【0026】 The aluminum oxide layer 32 is positioned entirely between the measuring means 24 and the surface of the insulating layer 30, and is applied planarly and continuously above the insulating layer 30, particularly in the normal direction 16. This aluminum oxide layer 32 covers the entire upper side 36 of the insulating layer 30, and may even surround the entire outer covering 38 of the substrate 12, including the side walls 40 and lower side 42 of the substrate 12. 【0027】 Figure 2 shows the temporal progression of the sensor measurement signal of a high-voltage sensor in a further specific embodiment of the present invention. The temporal progression of multiple measured sensor measurement signals 44 of this high-voltage sensor is shown in comparison with multiple measured sensor measurement signals 46 of a high-voltage sensor based on the current technology. In this regard, it can be seen that the sensor measurement signal 44 has less drift than the sensor measurement signal 46 and is therefore more stable over time. [Explanation of Symbols] 【0028】 10 High-voltage sensors 12 Base 14 Free space 16 Normal Direction 18 diaphragm 20 Bridge structure 22 Diaphragm thickness 24 Measurement means 26 Measurement means layer 28 Diaphragm edge 30 Insulating layer 32. Aluminum Oxide Layer 34 layer thickness 36 Upper side 38 Cover of the substrate 12 40 side wall 42 Lower side Multiple measured sensor measurement signals from 44 high-voltage sensors 46 Multiple measured sensor signals of a high-voltage sensor based on current technology

Claims

[Claim 1] base (12), A diaphragm (18) that can deflect along the normal direction (16) within the empty region (14) in response to ambient pressure, A measuring means (24) provided above the diaphragm (18) in the normal direction (16), and having at least one measuring means layer (26) for electrically capturing the deflection of the diaphragm, At least an insulating layer (30) disposed on the diaphragm (18) In a high-voltage sensor (10) having, A high-voltage sensor (10) characterized in that a homogeneous aluminum oxide layer (32) is disposed at least between the measuring means layer (26) and the insulating layer (30). [Claim 2] The high-pressure sensor (10) according to claim 1, characterized in that the aluminum oxide layer (32) is formed entirely from amorphous aluminum oxide. [Claim 3] The high-pressure sensor (10) according to claim 1 or 2, characterized in that the aluminum oxide layer (32) is formed by atomic layer deposition. [Claim 4] The high-voltage sensor (10) according to any one of claims 1 to 3, characterized in that the insulating layer (30) is formed from silicon oxide. [Claim 5] The high-voltage sensor (10) according to any one of claims 1 to 4, characterized in that the aluminum oxide layer (32) is disposed entirely between the surface of the measuring means (24) and the insulating layer (30). [Claim 6] The high-voltage sensor (10) according to any one of claims 1 to 5, characterized in that the aluminum oxide layer (32) is applied planarly and without interruption above the insulating layer (30) in the normal direction (16). [Claim 7] The high-voltage sensor (10) according to any one of claims 1 to 6, characterized in that the aluminum oxide layer (32) covers at least the entire upper side (36) of the insulating layer (30). [Claim 8] The high-pressure sensor (10) according to any one of claims 1 to 7, characterized in that the aluminum oxide layer (32) is disposed on at least one side wall (40) of the substrate (12). [Claim 9] The high-pressure sensor (10) according to any one of claims 1 to 8, characterized in that the aluminum oxide layer (32) surrounds at least the main portion of the outer covering (38) of the substrate (12). [Claim 10] The high-pressure sensor (10) according to any one of claims 1 to 9, characterized in that the measuring means layer (26) is formed from a nickel-chromium-silicon alloy.

Images