Manufacturing method of magnetic sensor

Abstract

The present invention relates to a method for manufacturing a magnetic sensor, the method comprising the steps of: depositing a first material having a first etching rate on a substrate to form a first layer on the substrate; depositing a second material having a second etching rate on the first layer to form a second layer on the first layer, the first etching rate being smaller than the second etching rate; depositing a third material on the second layer to form a third layer on the second layer; patterning the third layer to generate a pattern having at least one opening window in the third layer; etching, in particular isotropically etching, the second layer through the at least one opening window, thereby undercutting the third layer; etching the first layer after through-etching the second layer to generate at least one slanted surface in the etched first layer; and forming a magnetic sensing element on the at least one slanted surface in the first layer.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a magnetic sensor and a magnetic sensor. [Background technology]

[0002] A common method for detecting Z-fields is to use magnetic flux deflectors. These are positioned to deflect the magnetic field from the Z direction, thereby allowing a portion of this field to reach the planar sensitive sensing element. These magnetic flux deflectors are usually constructed from structures made of soft magnetic materials. The fabrication of such magnetic flux deflectors is very complex, and their compatibility with semiconductor processes is limited. Another drawback is that strong external magnetic fields can alter the magnetization of the magnetic flux deflector, thereby affecting the sensitivity of the entire system and causing an offset. Another drawback is that the magnetic flux deflector contributes to signal noise, reducing the detection rate of the sensor. Summary of the Invention [Problem to be solved by the invention]

[0003] The problem underlying the present invention is to provide a concept that overcomes the above-mentioned drawbacks. [Means for solving the problem]

[0004] This problem is solved by the subject matter of the respective independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims. According to a first aspect, depositing a first material having a first etch rate on a substrate to form a first layer on the substrate; depositing a second material having a second etch rate on the first layer to form a second layer on the first layer, the second etch rate being less than the second etch rate; disposing a third material on the second layer to form a third layer on the second layer, the third material having an etching rate that is particularly smaller than the first and second etching rates and that is particularly etch-resistant to the etching medium used; patterning the third layer to generate a pattern in the third layer having at least one open window; etching, in particular isotropically etching, the second layer through at least one opening window, whereby the third layer is undercut, and after etching through the second layer, etching the first layer to create at least one inclined surface in the etched first layer; forming a magnetic sensing element on at least one oblique surface of the first layer; A method for manufacturing a magnetic sensor is provided, including:

[0005] According to a second aspect, A magnetic sensor is provided that includes a substrate having a first layer formed on the substrate, the first layer being made of a first material, the first material having a first etching rate, a second layer partially formed on the first layer, the second material having a second etching rate, the first etching rate being less than the second etching rate, and the first layer having at least one inclined surface having a magnetic sensing element formed thereon in at least a portion of an area not covered by the second layer.

[0006] The present invention is based on and incorporates the realization that the above-mentioned problems can be solved by using two materials with different etching rates in an etching medium. The second layer is first etched by an isotropic etching process through at least one opening window in the third layer, undercutting the third layer from the pattern edge. After the second layer is through-etched, the first layer is etched more slowly than the second layer, and the second layer acts as a laterally varying etching mask for the first layer. The etching of the second layer gradually exposes the surface of the first layer laterally, and the etching rate of this first layer is slower in both the horizontal and vertical directions than the varying etching mask formed by the etching of the second layer. This results in one or more sloped surfaces in the etched first layer, and the slope or angle of this slope relative to the solder, perpendicular or perpendicular to the substrate surface, can be adjusted and / or influenced by the selected etching ratio between the first and second etching rates.

[0007] This effectively provides a technical advantage in that the at least one tilted surface can be efficiently generated or formed in the first layer, and a magnetic sensing element is formed on the at least one tilted surface so that a Z component of a magnetic field corresponding to an angle can be measured or detected without the need for a magnetic flux deflector.

[0008] The magnetic sensing element is made up of a stack of thin layers and is in particular an in-plane magnetic sensing element, i.e. it is particularly sensitive to magnetic fields parallel to its surface, i.e. parallel to the (thin) layers (called X or Y).

[0009] Therefore, the above-mentioned drawbacks of the prior art can be overcome or avoided in an efficient manner. Therefore, the Z magnetic field can be sensed in an efficient manner without the need for a flux deflector.

[0010] Thus, the magnetic sensor is inherently sensitive to magnetic fields in the Z direction. The Z direction or Z axis is perpendicular to the main surface / substrate surface of the substrate. The substrate is, for example, a wafer, for example a Si wafer, ie a silicon wafer.

[0011] In one embodiment of the method, it is contemplated that the first material and / or the second material are each a dielectric. This provides the technical advantage that, for example, a material that is particularly suited in terms of etching rate is used, and therefore the etching process can be carried out efficiently.

[0012] In one embodiment of the method, a first material is disposed on the substrate such that the first layer has a first thickness, and a second material is disposed on the first layer such that the second layer has a second thickness, and the second thickness may be less than the first thickness.

[0013] This provides the technical advantage of, for example, allowing an etching process to be carried out efficiently. The first layer may be, for example, 10 to 30 times thicker than the second layer, i.e., the thickness of the first layer may be, for example, 10 to 30 times thicker than the second layer. For example, the thickness of the first layer may be in the range of 1 to several μm.

[0014] In one embodiment of the method, it is contemplated that the first layer and the second layer are composed of the same chemical elements, and the first layer material and the second layer material may have different stoichiometric compositions and / or etching rates.

[0015] This provides the technical advantage, for example, that particularly suitable materials can be used, and in particular that the etching process can be advantageously and efficiently controlled or influenced, and thus the aforementioned angle can be efficiently adjusted or influenced.

[0016] In one embodiment of the method, the first material and / or the second material is Si x O y , especially SiO2, Si x N yIt is contemplated that the material may comprise one or more element(s) selected from the group of materials: Si, in particular Si3N4, Si, in particular polycrystalline Si.

[0017] This offers the technical advantage that, for example, particularly suitable materials can be used. non-stoichiometric Si x O y The ratio of silicon to oxygen in the SiO 2 layer may be set arbitrarily within a certain range, thereby allowing the selectivity and therefore the angle to be precisely adjusted.

[0018] One embodiment of the method contemplates removing the third layer after the beveled surface is created and before the magnetic sensing element is formed on the beveled surface of the first layer. This provides the technical advantage that, for example, magnetic sensing elements can be efficiently formed on the inclined surface.

[0019] In one embodiment of the method, the third material is a photolithographic material, and therefore a photolithographic layer is formed as the third layer, and patterning of the third layer is intended to be performed by a photolithographic process.

[0020] In one embodiment of the method, the third material consists of (particularly another) etch-resistant material, a so-called hard mask, which has a lower etching rate than the first and second layers and which itself can be patterned using a photolithographic process.

[0021] This provides the technical advantage, for example, of allowing efficient patterning of the third layer. The hard mask itself is patterned by a photolithographic process, but can have a higher etch resistance than a photoresist mask, especially if the etching time is long and / or the etching medium is aggressive.

[0022] Photolithographic materials include, for example, photoresists, particularly negative and positive resists. The term "photoresist" can also be used as the term "resist."

[0023] The embodiments made in relation to the method apply analogously to the magnetic sensor and vice versa, i.e. the technical functionality and technical features of the magnetic sensor according to the second aspect result analogously from the corresponding technical functionality and technical features of the method according to the first aspect and vice versa.

[0024] The magnetic sensor according to the second aspect is, for example, manufactured by or was manufactured by the method according to the first aspect. For example, the third material may have a third etching rate that is less than the second etching rate, or may have no etching rate, or may be etch-resistant to the etching medium used for the first and second layers.

[0025] The etching rates in the ranges herein relate specifically to the particular etching medium used in the etching. The magnetic sensing element is based, for example, on the AMR effect ("anisotropic magnetoresistance effect") and / or the GMR effect ("giant magnetoresistance" effect or "giant magnetoresistance effect") and / or the TMR effect ("tunneling magnetoresistance effect" or "magnetic tunnel resistance effect").

[0026] The phrase "at least one" means "one or more." When the singular form is used for the magnetic sensing element, it should always be read in conjunction with the plural form, and vice versa. The same applies to the inclined surface. For example, one or more inclined surfaces, particularly two or more inclined surfaces, can be formed on the first layer. For example, one or more magnetic sensing elements can be formed on one or more inclined surfaces. This means, for example, that one or more magnetic sensing elements can be formed on one or more inclined surfaces.

[0027] An inclined surface within the scope of this specification is, for example, a planar surface. An inclined surface within the scope of this specification is, for example, a surface having a planar portion. A magnetic sensing element is formed on, for example, the planar surface or the planar portion.

[0028] Etching the first layer may, for example, result in a recess in the first layer, the recess having, for example, at least one sloping sidewall and / or a first sloping surface. Etching within the scope of this specification may be or include, for example, wet etching. For example, an isotropic dry etching process may be used.

[0029] The fact that the first layer of the magnetic sensor has an inclined surface in at least a portion of the area that is not covered by the second layer, and that a magnetic detection element is formed on that inclined surface, means, in other words, that the first layer has an inclined surface in at least a portion of the area that is not covered by the second layer, and that a magnetic detection element is formed on that inclined surface.

[0030] In one embodiment of the method, the third material is another material that is etch-resistant to the etching medium used, so that an etching-resistant layer is formed as the third layer, and patterning of the third layer is performed by a photolithography process.

[0031] In one embodiment of the method, it is contemplated that the first material and the second material are formed from the same chemical elements, meaning that the first material and the second material do not have different chemical elements.

[0032] In one embodiment of the method, it is contemplated that the first material and the second material each have the same stoichiometric composition, and the first material and the second material have at least one different chemical element. [Brief explanation of the drawings]

[0033] The present invention will now be described in more detail with reference to preferred embodiments. [Figure 1] 1 shows a flowchart of a method for manufacturing a magnetic sensor. [Figure 2] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 3] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 4] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 5] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 6] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 7] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 8] 1 illustrates various points in a method for manufacturing a magnetic sensor. [Figure 9] 1 shows a magnetic sensor. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, the same reference numerals may be used for the same features. Figure 1 shows depositing 101 a first material having a first etch rate on a substrate to form a first layer on the substrate; depositing 103 a second material having a second etching rate on the first layer to form a second layer on the first layer, the first etching rate being less than the second etching rate (for the particular etching medium); disposing 105 a third material on the second layer to form a third layer on the second layer; patterning 107 the third layer to generate a pattern in the third layer having at least one open window where the material of the third layer has been completely removed; etching 109, in particular isotropically etching (using a specific etching medium) the second layer through at least one opening window, whereby the third layer is undercut 111, and after etching through the second layer, etching 113 the first layer, in order to generate at least one inclined surface in the etched first layer, at least in some areas, i.e. partially; forming a magnetic sensing element on at least one oblique surface of the first layer; 1 shows a flowchart of a method for manufacturing a magnetic sensor, including:

[0035] For example, at least one magnetic sensing element is created on at least one tilted surface of the first layer. 2 shows a wafer 201 as an example of a substrate within the scope of this specification. The wafer 201 comprises a patterned layer 203 that can contain a number of patterns, such as conductor tracks, electrical contacts and / or further electrical and / or mechanical functional elements.

[0036] A first layer 205 made of a first material is formed on wafer 201. A second layer 207 made of a second material is formed on first layer 205. The first material has a first etch rate. The second material has a second etch rate. The first etch rate is less than the second etch rate.

[0037] A photolithography layer 209 made of a photolithography material is formed on the second layer 207. The photolithography layer 209 is an example of a third layer within the scope of this specification.

[0038] The first layer 205 has a first thickness that is greater than a second thickness of the second layer 207 . The photolithography layer 209 is, for example, a resist, ie, a photoresist. 3 illustrates the layer arrangement shown in FIG. 2 after the photolithography layer 209 has been patterned by a photolithography process. The patterning completely removes the material of the photolithography layer 209 in one area of ​​the photolithography layer 209, forming an opening window 301 in the photolithography layer 209. An etching process is performed through this window 301. Specifically, the second layer 207 is etched through the window 301, thereby undercutting the photolithography layer 209. After the second layer 207 is through-etched, the first layer is etched to create two sloped surfaces in the etched first layer, namely, a first sloped surface 303 and a second sloped surface 305. Based on the shape of the opening window 301, for example, additional sloped surfaces may be created in the first layer 205 during the etching process. It should be noted that in embodiments not shown, it may be contemplated that only one inclined surface is generated, i.e., the first inclined surface or the second inclined surface 303, 305. In embodiments not shown, two or more inclined surfaces may be generated.

[0039] By providing a particular etching time, the depth of the recesses etched into the first layer 205 can be influenced. The recess has, for example, two sloping side walls, namely a first sloping surface 303 and a second sloping surface 305 .

[0040] 4 shows the arrangement of layers shown in FIG. 3 at the end of the etching process. The etching can be stopped, for example, on a material with a very low or no etching rate. In this example, the etching process stops on wafer 201, or more precisely, on patterned layer 203.

[0041] FIG. 5 shows the arrangement of layers shown in FIG. 4 after removal of photolithographic layer 209. Figure 6 shows the layer arrangement shown in Figure 5 after removal of second layer 207. Removal may include, for example, chemical mechanical polishing or a selective etching process.

[0042] 7 shows the end point of the etching process similar to that of FIG. 4, with the difference that the second layer thickness of the second layer 207 according to FIG. 7 is greater than the second layer thickness of the second layer 207 shown in FIG. 4. If such a greater layer thickness is used, after removing the photolithographic layer 209, an additional step with a steeper edge results, which is shown in FIG. 8 by the oval labeled 801. Remnants of the second layer 207 remain on the first layer 205.

[0043] One advantage of this method is that the angle set is independent of the layer thickness of the second layer 207 (if it is significantly thinner than the first layer 205), which advantageously improves process control.

[0044] FIG. 9 illustrates a magnetic sensor fabricated using the layer arrangement shown in FIG. 8. 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. At the bottom, the two magnetic sensing elements 903, 905 are electrically connected by a common conductive contact layer 907, or so-called bottom electrode. The bottom electrode need not be continuous. At the top, the two magnetic sensing elements 903, 905 each have their own conductive contact layer 909, 911, or so-called top electrode, for electrically contacting the corresponding magnetic sensing element 903, 905. Similarly, the top electrode may be continuous, with the bottom electrode leading outward. In embodiments not shown, the individual magnetic sensing elements 903, 905 can be contacted in different ways. For example, they can be connected in a series circuit, a parallel circuit, or a combination thereof.

[0045] Furthermore, two arrows labeled 913 and 915 are shown in FIG. 9, which indicate the direction of the detected magnetic field. In summary, the concept described herein can be used to efficiently generate sloped patterns, i.e., sloped surfaces. This method is based on the creation of one or more sloped surfaces using a wet chemical method that utilizes the different etching rates of silicon oxides with different silicon contents. A thick SiO layer with a low etching rate, i.e., for example, silicon-rich, is deposited on a silicon substrate, e.g., a silicon wafer, which may optionally contain other patterns. This is followed by the optional deposition of a thin SiO layer with a high etching rate, e.g., a different, e.g., stoichiometric, material composition, e.g., a second layer. A resist (third layer), for example, is then deposited thereon, and a desired pattern (at least one opening window) is then created, e.g., by a lithography process. Then, in a wet chemical etching process, the thin stoichiometric SiO layer is first isotropically etched, e.g., in the at least one opening window pattern, so that the resist is undercut at the pattern edges. After the thin stoichiometric SiO layer is through-etched, a thick Si-rich Si layer is then deposited. x O y The thin stoichiometric SiO layer can be considered a laterally varying etch mask, with the layer being etched at a smaller / lower etch rate than the stoichiometric layer. Etching of this thin layer leaves a thicker Si layer, which has a slower isotropic etch rate / etch rate than the varying etch mask, consisting of the second layer 207 of stoichiometric SiO. x O y The surface of the layer is gradually exposed laterally. At this time, the Si x O y The etch angle of the material becomes uniform, with the slope being the rapidly etched SiO2 layer and the slowly etched Si x O y The thickness can be adjusted / affected by the selected etching rate between the layers. The terms "thick" and "thin" here mean that the thickness of the first layer is greater than the thickness of the second layer. Thus, the first layer has a first thickness, and the second layer has a second thickness, with the first thickness preferably being greater than the second thickness.

[0046] The tilted surface thus formed is used as a tilted base for one or more magnetic sensing elements.The concepts described herein use, for example, two dielectric layers that etch at different rates.

[0047] This allows for very precise control, i.e., adjustment, of the angle of the inclined surface relative to the wafer's main surface / surface or the angle of the inclined surface relative to the solder relative to the wafer's main surface / surface. This is particularly advantageous when used as the basis for magnetic sensing elements that measure or sense the Z component of the detected magnetic field. This angle has a direct impact on the sensitivity of such measurements. Furthermore, this angle is extremely important for subsequent processing, such as the deposition of magnetic materials on the inclined surface and lithography. This angle is determined almost exclusively by the etching rates of the two dielectric layers used, allowing for very good control over the creation of the inclined surface.

[0048] The selectivity is the quotient of the second etch rate and the first etch rate. For example, any reflow process and / or isotropic etching process that produces a flat photoresist edge typically produces a curved edge, not a flat surface with a constant angle. In contrast, the method described herein produces a constant angle relative to the wafer surface over the majority of the side surface (the sidewall of the recess). Therefore, most of the side surface can be used as a sensing element, greatly simplifying subsequent processes.

[0049] At the same time, the transition from the side (sloping surface) to the flat bottom surface may be gently rounded, depending for example on the etching rate and / or the material used, which is also advantageous for further processing.

[0050] Many reflow processes must be performed at high temperatures, limiting the use of ASIC ("Application-Specific Integrated Circuit") circuits on silicon substrates / wafers. The methods described herein can be advantageously performed at low temperatures.

[0051] When using an ion beam etching process to create side surfaces, i.e., inclined surfaces, there is a problem of increased roughness of the etched surface. The wet etching process presented here as an example naturally results in a very low surface roughness. This is particularly important and advantageous for the substrate surface of TMR sensing elements, since roughness of the same order of magnitude as the tunnel barrier thickness (2 nm or less) can already lead to increased sensor noise.

[0052] Another problem when using ion beam etching processes is the shadowing effect and the resulting distance required between individual elements. The method presented here allows for a significant increase in integration density, leading to cost savings.

Claims

1. disposing (101) a first material having a first etching rate on a substrate (201) to form a first layer (205) on the substrate (201); depositing (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), the first etching rate being less than the second etching rate; disposing (105) a third material on the second layer (207) to form a third layer (209) on the second layer (207); patterning (107) said third layer (209) to generate a pattern in said third layer (209) having at least one opening window (301); etching (109), in particular isotropically etching, the second layer (207) through the at least one opening window (301), whereby the third layer (209) is undercut (111), and after etching through the second layer (207), etching (113) the first layer (205) to generate at least one inclined surface (303, 305) in the etched first layer (205); forming (115) a magnetic sensing element (903, 905) on the at least one inclined surface (303, 305) of the first layer (205); A method for manufacturing a magnetic sensor (901), comprising:

2. The method of claim 1 , wherein the first material and / or the second material are each a dielectric.

3. the first material is disposed on the substrate (201) such that the first layer (205) has a first thickness; the second material is disposed on the first layer (205) such that the second layer (207) has a second layer thickness; the second layer thickness is smaller than the first layer thickness; The method according to claim 1 or 2.

4. The method of any one of claims 1 to 3, wherein the first material and the second material have different stoichiometric compositions.

5. The method according to any one of claims 1 to 4, wherein the first material and the second material are composed of the same chemical element.

6. the first material and the second material each have the same stoichiometric composition; the first material and the second material have at least one different chemical element; The method according to any one of claims 1 to 3.

7. The first material and / or the second material is Si ｘ O ｙ , especially SiO ２ , Si ｘ N ｙ , especially Si ３ N ４ 7. The method according to any one of claims 1 to 6, wherein the silicon dioxide comprises one or more elements selected from the group of materials: , Si, in particular polycrystalline Si.

8. 8. The method of claim 1, wherein the third layer (209) is removed after the inclined surfaces (303, 305) are created and before the magnetic sensing elements (903, 905) are formed on the inclined surfaces (303, 305) of the first layer (205).

9. The third material is another material that is etch-resistant to the etching medium used, so that an etching-resistant layer (209) is formed as the third layer (209); the patterning of said third layer (209) is carried out by a photolithography process; The method according to any one of claims 1 to 8.

10. A substrate (201), a first layer (205) of a first material formed on the substrate (201), the first material having a first etch rate; a second layer (207) made of a second material partially formed on the first layer (205), the second material having a second etching rate; the first etching rate is less than the second etching rate; The first layer (205) has at least one inclined surface (303, 305) on which a magnetic sensing element (903, 905) is formed in at least a portion of an area not covered by the second layer (207). Magnetic sensor (901).

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