Method for manufacturing magnetic sensor
By using material layers of different etching rates in the manufacturing process of magnetic sensors to form an inclined surface, the complexity and sensitivity problems of existing magnetic flux steering devices are solved, and efficient detection of the Z magnetic field is achieved.
Patent Information
- Application Number
- CN202380077559.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-07
- Filing Date
- 2023-10-16
- Publication Date
- 2025-06-27
AI Technical Summary
Existing flux steering gears have complexity, incompatibility and external magnetic field influences in manufacturing and use, resulting in reduced sensitivity and increased signal noise.
By using two materials, the first, second and third layers with different etch rates, the second layer is etched isotropically at the open window of the third layer using an etching process, and the first layer is etched after the second layer is etched through to form at least one inclined surface for forming a magnetic sensing element on the surface.
Effectively generate inclined surfaces to achieve sensitive detection of Z magnetic field, avoid the disadvantages of magnetic flux steering, and improve the sensitivity and signal quality of magnetic sensors.
Smart Images
Figure CN120225893A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a magnetic sensor and a magnetic sensor. Background Art
[0002] A common method for sensing a Z magnetic field is to use a flux concentrator (Flussumlenkern). The flux concentrator is arranged such that the magnetic field from the Z direction is redirected so that a portion of the magnetic field falls as a field on a planar sensitive sensing element. Such a flux concentrator is typically composed of a soft magnetic material structure. The manufacture of such a flux concentrator is rather complex and only conditionally compatible with semiconductor processes. In addition, there is the drawback that a strong external magnetic field can change the magnetization of the flux concentrator in this way: the sensitivity of the entire system is affected and thus an offset is generated. Another drawback is that the flux concentrator contributes to signal noise and thus reduces the detection performance of the sensor. Summary of the Invention
[0003] The task underlying the present invention is to provide a solution that overcomes the above-mentioned drawbacks.
[0004] This task is solved by the corresponding subject matter of the independent claims. Advantageous configurations of the present invention are the subject matter of the respective dependent claims.
[0005] According to a first aspect, there is provided a method for manufacturing a magnetic sensor, comprising the following steps:
[0006] Arranging a first material having a first etching rate on a substrate to form a first layer on the substrate,
[0007] Arranging a second material having a second etching rate on the first layer to form a second layer on the first layer,
[0008] wherein the first etching rate is less than the second etching rate,
[0009] Arranging a third material on the second layer to form a third layer on the second layer, wherein the third etching rate is in particular less than the first and second etching rates and is resistant to etching for the etching medium used,
[0010] Structuring the third layer to produce a structure having at least one open window in the third layer,
[0011] Etching, in particular isotropically etching, the second layer through the at least one open window, whereby the third layer is undercut, and wherein the first layer is etched after the second layer has been etched through to produce at least one inclined surface in the etched first layer,
[0012] Forming a magnetic sensing element on at least one inclined surface of the first layer.
[0013] According to a second aspect, there is provided a magnetic sensor, comprising:
[0014] a substrate on which a first layer made of a first material is formed, wherein the first material has a first etching rate,
[0015] wherein a second layer made of a second material is partially formed on the first layer, wherein the second material has a second etching rate,
[0016] wherein the first etching rate is less than the second etching rate,
[0017] wherein the first layer has at least one inclined surface at least locally in an area not covered by the second layer, and a magnetic sensing element is formed on the inclined surface.
[0018] The present invention is based on and includes the recognition that the above task is thus solved: using two materials that have different etching rates in an etching medium. Through at least one open window in the third layer, the second layer is first etched by an isotropic etching process, wherein the third layer is undercut starting from the edge of the structure. After the second layer is etched through, the first layer is etched more slowly than the second layer, wherein the second layer acts as a laterally varying etching mask for the first layer. The etching of the second layer gradually exposes more and more of the surface of the first layer laterally, and the first layer has a slower etching rate both laterally and vertically than the varying etching mask formed by the etching of the second layer. Therefore, one or more inclined surfaces are generated in the etched first layer, and the slope or angle of these inclined surfaces relative to a perpendicular to the substrate surface can be adjusted and / or influenced by the selected etching rate ratio between the first etching rate and the second etching rate.
[0019] Therefore, the following technical advantages are effectively achieved: at least one inclined surface can be effectively generated or formed in the first layer. A magnetic sensing element is formed on the at least one inclined surface, such that the magnetic sensing element can measure or detect the Z component of the magnetic field corresponding to the angle without the need for a magnetic flux deflector.
[0020] The magnetic sensing element consists of a stack of thin layers and is in particular a magnetic sensing element in the plane, i.e., the magnetic sensing element is sensitive in particular to a magnetic field parallel to its surface, i.e., parallel to the (thin) layer (identified as X or Y).
[0021] Therefore, the disadvantages of the prior art described above can be overcome or avoided in an effective manner.
[0022] Therefore, the Z magnetic field can be sensed in an effective manner without the need for a magnetic flux deflector for this purpose.
[0023] Therefore, the magnetic sensor has an inherent sensitivity to the magnetic field in the Z direction.
[0024] The Z direction or the Z axis extends orthogonally to the main plane of the substrate / the substrate surface.
[0025] The substrate is, for example, a wafer, such as a Si wafer, i.e., a silicon wafer.
[0026] In one embodiment of the method, it is provided that the first material and / or the second material are each a dielectric.
[0027] Therefore, for example, the following technical advantages are achieved: materials that are particularly suitable in terms of their etching rate ratio are used. Thus, the etching process can be carried out effectively.
[0028] In one embodiment of the method, it is provided that the first material is arranged on the substrate such that the first layer has a first layer thickness, and wherein the second material is arranged on the first layer such that the second layer has a second layer thickness, where the second layer thickness can be implemented to be less than the first layer thickness.
[0029] Therefore, for example, the following technical advantages are achieved: the etching process can be carried out effectively. The first layer can be, for example, 10 - 30 times thicker than the second layer, which means that the first layer thickness can be, for example, 10 - 30 times larger compared to the second layer thickness. For example, the first layer thickness can be in the range of 1 or a few μm.
[0030] In one embodiment of the method, it is provided that the first layer and the second layer are composed of the same material, where the material of the first layer and the material of the second layer can have respectively different stoichiometric compositions and / or etching rates.
[0031] Therefore, for example, the following technical advantages are achieved: particularly suitable materials are used. In particular, the etching process can thus be controlled or influenced in an advantageous and effective manner, such that the previously mentioned angle can be effectively adjusted or influenced in this way.
[0032] In one embodiment of the method, it is provided that the first material and / or the second material can each include one or more of the following elements selected from the following group of materials: Si x O y , in particular SiO2, Si x N y , in particular Si3N4, silicon, in particular polysilicon.
[0033] Therefore, for example, the following technical advantages are achieved: particularly suitable materials can be used.
[0034] In non - stoichiometric Si x O yThe ratio of silicon to oxygen in [it] can be arbitrarily adjusted within a certain range. Therefore, the selectivity can also be precisely adjusted and thus the angle is also precisely adjusted.
[0035] In one embodiment of the method, it is provided that the third layer is removed after the inclined surface is generated and before the magnetic sensing element is formed on the inclined surface of the first layer.
[0036] This causes, for example, the following technical advantage: The magnetic sensing element can be effectively formed on the inclined surface.
[0037] In one embodiment of the method, it is provided that the third material is a lithographic material such that a lithographic layer is formed as the third layer, wherein the structuring of the third layer is carried out by means of a lithographic process.
[0038] In one embodiment of the method, the third material consists of a (particularly other) etch-resistant material, namely a so-called hard mask. The hard mask has a lower etch rate relative to the first and second layers and can itself be structured by means of a lithographic process.
[0039] This causes, for example, the technical advantage that the third layer can be effectively structured.
[0040] The hard mask itself is structured by means of a lithographic process, but it can be more etch-resistant than a photoresist mask, especially in the case of long etching times and / or aggressive etching media.
[0041] The lithographic material includes, for example, a photoresist, especially a negative resist or a positive resist.
[0042] For the concept of "photoresist", the concept of "resist" can also be used.
[0043] The explanations made in connection with the method apply analogously to the magnetic sensor, and vice versa. This means that the technical functionality and technical features of the magnetic sensor according to the second aspect are similarly derived from the corresponding technical functionality and technical features of the method according to the first aspect, and vice versa.
[0044] The magnetic sensor according to the second aspect is or is manufactured, for example, by means of the method according to the first aspect.
[0045] For example, the third material has a third etch rate that is less than the second etch rate. For example, the third material does not have an etch rate. The third material is, for example, etch-resistant to the etching medium used for the first and second layers.
[0046] The etch rate in the sense of this specification particularly relates to a defined etching medium for etching.
[0047] The magnetic sensing element is, for example, based on the AMR effect (anisotropic magnetoresistive effect), and / or based on the GMR effect ("giant magnetoresistance" effect or "giant magnetoresistance" effect), and / or based on the TMR effect ("tunnel magnetoresistance" effect or "magnetic tunnel resistance" effect).
[0048] The expression "at least one" means "one or more".
[0049] If the singular form is used for the magnetic sensing element, the plural form should always be included, and vice versa. The same applies to the inclined surface. This means, for example, that one or more inclined surfaces, in particular two or more inclined surfaces, can be formed in the first layer. This means, for example, that one or more magnetic sensing elements can be formed on the one or more inclined surfaces. This means, for example, that one or more magnetic sensing elements can be formed on each of the one or more inclined surfaces.
[0050] The inclined surface is, for example, a flat surface in the sense of this specification. The inclined surface has, for example, a flat section in the sense of this specification. The magnetic sensing element is formed, for example, on this flat surface or on this flat section.
[0051] By etching the first layer, a groove is produced, for example, in the first layer. This groove has, for example, at least one inclined sidewall and / or at least one inclined surface.
[0052] Etching is, in the sense of this specification, or includes, for example, wet etching. For example, an isotropic dry etching method can be used.
[0053] "The first layer of the magnetic sensor has at least locally an inclined surface in the region not covered by the second layer, on which the magnetic sensing element is formed" means, in other words, that the first layer has at least partially an inclined surface in the region not covered by the second layer, on which the magnetic sensing element is formed.
[0054] In one embodiment of this method, it is provided that the third material is another material resistant to the etching medium used, such that an etch-resistant layer is formed as the third layer, wherein the structuring of the third layer is carried out by means of a lithography process.
[0055] In one embodiment of the method, it is provided that the first material and the second material are formed from the same chemical elements. This means that the first material and the second material do not have different chemical elements.
[0056] In one embodiment of the method, it is provided that the first material and the second material have composition with respectively consistent stoichiometry, wherein the first material and the second material have at least one different chemical element. Description of the Drawings
[0057] The present invention will be explained in more detail below with the aid of preferred embodiments.
[0058] Shown here are:
[0059] Figure 1 : Flow chart of a method for manufacturing a magnetic sensor,
[0060] Figures 2 to 8 : At different time points in a method for manufacturing a magnetic sensor and
[0061] Figure 9 : A magnetic sensor.
[0062] The same reference signs are used below for the same features. Detailed Description of the Invention
[0063] Figure 1 A flow chart of a method for manufacturing a magnetic sensor is shown, including the following steps:
[0064] Lay 101 a first material having a first etching rate on a substrate to form a first layer on the substrate,
[0065] Lay 103 a second material having a second etching rate on the first layer to form a second layer on the first layer,
[0066] wherein the first etching rate is less than the second etching rate (for a defined etching medium),
[0067] Lay 105 a third material on the second layer to form a third layer on the second layer,
[0068] Structure 107 the third layer to produce a structure having at least one open window in the third layer, in which the material of the third layer is completely removed,
[0069] Etch 109, in particular isotropically etch, the second layer through the at least one open window (in the case of using a defined etching medium), whereby the third layer is undercut 111, wherein after the second layer has been etched through, etch 113 the first layer to at least locally, i.e. partially, produce at least one inclined surface in the etched first layer.
[0070] Form a magnetic sensing element 115 on the at least one inclined surface of the first layer.
[0071] For example, generate at least one magnetic sensing element on the at least one inclined surface of the first layer.
[0072] Figure 2 A wafer 201 is shown as an example of a substrate in the sense of this specification. The wafer 201 includes a structural layer 203, which may include a plurality of structures, such as conductor tracks, electrical contacts, and / or other electrical and / or mechanical functional elements.
[0073] Form a first layer 205 made of a first material on the wafer 201. Form a second layer 207 made of a second material on the first layer 205. The first material has a first etching rate. The second material has a second etching rate. The first etching rate is less than the second etching rate.
[0074] Form a photolithography layer 209 made of a photolithography material on the second layer 207. The photolithography layer 209 is an example of a third layer in the sense of this specification.
[0075] The first layer 205 has a first layer thickness greater than the second layer thickness of the second layer 207.
[0076] The photolithography layer 209 is, for example, a resist, i.e., a photoresist.
[0077] Figure 3 Shown in Figure 2 The arrangement shown, which consists of layers after structuring the photolithography layer 209 by means of a photolithography process. Through this structuring, the material of the photolithography layer 209 is completely removed in an area of the photolithography layer 209 and an open window 301 is formed in the photolithography layer 209. An etching process is performed through this window 301. Specifically, through this window 301, the second layer 207 is etched, whereby the photolithography layer 209 is undercut. After etching through the second layer 207, the first layer 205 is etched to produce two inclined surfaces in the etched first layer: a first inclined surface 303 and a second inclined surface 305. Based on the shape of the open window 301, other inclined surfaces may also be produced in the first layer 205 during the etching process. It should be noted that in an embodiment not shown, it may be provided that only one inclined surface is produced, i.e., the first or second surface 303, 305. In an embodiment not shown, more than two inclined surfaces may be produced.
[0078] By specifying a determined etching time, the depth of the groove produced by etching in the first layer 205 can be affected.
[0079] The recess has, for example, two inclined sidewalls: a first inclined surface 303 and a second inclined surface 305.
[0080] Figure 4 Shown at Figure 3 the end of the etching process of the arrangement of layers shown in. The etching can stop, for example, on a material with a very low etching rate or no etching rate. Currently, the etching process stops on the wafer 201, more precisely on the structural layer 203.
[0081] Figure 5 Shown at Figure 4 the end of the arrangement of layers shown in after removing the photolithography layer 209.
[0082] Figure 6 Shown at Figure 5 the end of the arrangement of layers shown in after removing the second layer 207. The removal includes, for example, a chemical-mechanical polishing or a selective etching process.
[0083] Figure 7 Shown similar to Figure 4 at a time point at the end of the etching process, wherein the difference is that, according to Figure 7 the second layer thickness of the second layer 207 is greater than the second layer thickness of the second layer 207 shown in Figure 4 . If such a higher layer thickness is used, a step with a steeper edge can additionally be produced after removing the photolithography layer 209, which is identified in Figure 8 by the ellipse with the reference mark 801. Residues of the second layer 207 remain on the first layer 205.
[0084] One advantage of the present invention is in particular that the angle produced is independent of the layer thickness of the second layer 207 (as long as the second layer is significantly thinner than the first layer 205). This improves the process control in an advantageous manner.
[0085] Figure 9 Shown during the use of Figure 8A magnetic sensor manufactured in the case of the layer arrangement shown. A first magnetic sensing element 903 is formed on the first inclined surface 301. A second magnetic sensing element 905 is formed on the second inclined surface 305. These two magnetic sensing elements 903, 905 are electrically contacted from below through a common conductive contact layer 907, namely the so-called bottom electrode. This bottom electrode does not have to be through. These two magnetic sensing elements 903, 905 have respectively one own conductive contact layer 909, 911 from above, namely the so-called top electrodes, for the electrical contact of the corresponding magnetic sensing elements 903, 905. It is also possible that the top electrodes are through and the bottom electrodes are led outwards. In an embodiment not shown, the individual magnetic sensing elements 903, 905 can be contacted differently. For example, they can be connected in series, in parallel or in a combination of the two connections in a suitable manner.
[0086] In addition, Figure 9 shows two arrows with reference numerals 913, 915, and these arrows show the orientation of the magnetic field to be detected.
[0087] In summary, an inclined structure: an inclined surface can be effectively generated by the solution described here. This method is especially based on generating one or more inclined surfaces by a wet chemical method that utilizes the different etching rates of silicon oxides with different silicon contents. On a silicon substrate that may optionally contain other structures, such as a silicon wafer, a thick silicon oxide layer (first layer) with a very small etching rate, such as a silicon-rich one, can be deposited, and then an optionally thin SiO2 layer (second layer) with a high etching rate and other, such as stoichiometric, material compositions can be deposited. Then, for example, a resist (third layer) is deposited and the desired structure (at least one open window) is generated in a subsequent lithography process. In a subsequent wet chemical etching process, the thin stoichiometric SiO2 layer is first etched isotropically in the at least one open window structure. As a result, the resist is undercut starting from the edge of the structure, and after etching through the thin stoichiometric SiO2 layer, the thick silicon-rich Si x O y layer is etched, where the thin stoichiometric SiO2 layer can be regarded as a laterally varying etching mask. Etching the thin layer gradually exposes more and more of the surface of the thick Si x O y layer, and this Si x O y layer has a slower isotropic etching rate / etching speed than the varying etching mask composed of the second layer 207 composed of stoichiometric SiO2. Here, in the thick Si x Oy A uniform etched angle is generated in the material, and the slope of this angle can be adjusted / influenced by the selected etching rate ratio between the rapidly etched SiO2 layer and the slowly etched Si x O y layer. Here, "thick" and "thin" mean that the first layer has a greater layer thickness than the second layer. The first layer has a first layer thickness and the second layer has a second layer thickness, where the first layer thickness is advantageously greater than the second layer thickness.
[0088] The inclined surface formed in this way serves as an inclined base for one or more magnetic sensing elements. The solution described here utilizes, for example, two dielectric layers etched at different rates.
[0089] The angle of the inclined surface, for example, relative to the main plane / surface of the wafer or relative to the perpendicular line with respect to the main plane / surface of the wafer, can thus be very well controlled, i.e., adjusted. This is particularly advantageous for serving as the base of a magnetic sensing element that should measure or sense the Z component of the magnetic field to be detected. This angle has a direct impact on the sensitivity of such a measurement. In addition, this angle is decisive for further processing, such as depositing magnetic materials or lithography on the inclined surface. The generation of the inclined surface can be very well controlled because the angle is determined almost solely by the etching rate ratio of the two dielectric layers used.
[0090] This selectivity is the quotient of the second etching rate and the first etching rate.
[0091] All types of reflow processes and / or isotropic etching processes used, for example, to fabricate flat lithography edges typically produce curved edges and thus do not produce a flat / plane surface with a constant angle. In contrast, the method described here shows a constant angle relative to the wafer surface, i.e., relative to the main plane of the wafer, on most sides (the sidewalls of the grooves). Therefore, a larger portion of the side is available for the sensing element and subsequent processes are significantly simplified.
[0092] At the same time, the transition from the side (inclined surface) to the flat bottom surface can, for example, have a gentle rounded corner depending on the etching rate and / or the materials used, which is also advantageous for subsequent processes.
[0093] Some reflow processes must be performed at high temperatures, which limits the use of ASIC circuits ("Application-Specific Integrated Circuit", i.e., anwendungsspezifische integrierte Schaltung, application-specific integrated circuit) on silicon substrates / silicon wafers. The method described here can be advantageously performed at low temperatures.
[0094] When an ion beam etching process is used to produce side surfaces, i.e., inclined surfaces, on the one hand, there is a problem of an increase in the surface roughness of the etched plane. The wet etching process exemplarily presented here naturally has a very low surface roughness. This is particularly important and advantageous for the base plane used for TMR sensing elements, since roughness in the order of magnitude of the tunnel barrier thickness (≤2 nm) can already cause an increase in sensor noise.
[0095] Another problem when using an ion beam etching process is the shadow effect and the resulting necessary spacing between the individual elements. The integration density can be significantly increased by means of the method described, which results in a cost reduction.
Claims
1. A method for manufacturing a magnetic sensor (901), comprising the following steps: Arranging (101) a first material having a first etching rate on a substrate (201) to form a first layer (205) on the substrate (201), Arranging (103) a second material having a second etching rate on the first layer (205) to form a second layer (207) on the first layer (205), Among them, The first etching rate is less than the second etching rate, Arranging (105) a third material on the second layer (207) to form a third layer (209) on the second layer (207), Structuring (107) the third layer (209) to produce a structure having at least one open window (301) in the third layer (209), Etching (109), in particular isotropically etching, the second layer (207) through the at least one open window (301), whereby the third layer (209) is undercut (111), wherein after the second layer (207) is etched through, the first layer (205) is etched (113) to produce at least one inclined surface (303, 305) in the etched first layer (205), Forming (115) magnetic sensing elements (903, 905) on the at least one inclined surface (303, 305) of the first layer (205).
2. The method according to claim 1, wherein The first material and / or the second material are each a dielectric.
3. The method according to claim 1 or 2, wherein The first material is arranged on the substrate (201) such that the first layer (205) has a first layer thickness, and wherein the second material is arranged on the first layer (205) such that the second layer (207) has a second layer thickness, wherein the second layer thickness is less than the first layer thickness.
4. The method according to any one of the preceding claims, wherein, The first material and the second material have respectively different stoichiometric compositions.
5. The method according to any one of the preceding claims, wherein The first material and the second material are formed of the same chemical elements.
6. The method according to any one of the preceding claims 1 to 3, wherein, The first material and the second material have respectively consistent stoichiometric compositions, wherein the first material and the second material have at least one different chemical element.
7. The method according to any one of the preceding claims, wherein The first material and / or the second material each comprise one or more of the following elements selected from the following group of materials: Si x O y , in particular SiO2, Si x N y , in particular Si3N4, silicon, in particular polycrystalline silicon.
8. The method according to any one of the preceding claims, wherein, The third layer (209) is removed after producing the inclined surfaces (303, 305) and before forming the magnetic sensing elements (903, 905) on the inclined surfaces (303, 305) of the first layer (205).
9. The method according to any one of the preceding claims, wherein, The third material is another material resistant to etching with respect to the etching medium used, such that a layer (209) resistant to etching is formed as the third layer (209), wherein the structuring of the third layer (209) is carried out by means of a lithography process.
10. A magnetic sensor (901), comprising: A substrate (201) on which a first layer (205) made of a first material is formed, wherein the first material has a first etching rate, wherein a second layer (207) made of a second material is partially formed on the first layer (205), wherein the second material has a second etching rate, Wherein, the first etching rate is less than the second etching rate. Wherein, the first layer (205) has at least one inclined surface (303, 305) at least locally in a region not covered by the second layer (207), and magnetic sensing elements (903, 905) are formed on the inclined surface.