Manufacturing method of triaxial magnetic sensor

Abstract

This invention provides a method for manufacturing a triaxial magnetic sensor. First, an interlayer dielectric layer and a barrier layer are etched to form a first trench with a first tilt angle. Then, an oxide layer is formed on the inner wall of the first trench and on the interlayer dielectric layer. Finally, a second trench with a second tilt angle is formed through a reverse etching process. In the Trench ET process, the barrier layer TiN is etched away. The Trench ET Back process addresses the etching morphology issue, controls oxide layer loss, and increases the trench window, achieving a balance between improved trench morphology, TiN etching, and oxide layer thickness control, thereby improving device reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to a method for manufacturing a triaxial magnetic sensor. Background Technology

[0002] Micro-Electro-Mechanical Systems (MEMS) are miniature devices or systems fabricated using microfabrication technology. They integrate micro-sensors, micro-components, micro-actuators, signal processing, and control circuits. The manufacturing process involves basic steps such as thin-film deposition, photolithography, epitaxy, oxidation, diffusion, implantation, sputtering, evaporation, etching, dicing, and packaging to create complex three-dimensional shapes. The dimensions are typically in the micrometer or nanometer range. Magnetic sensors are a type of MEMS device that converts various magnetic fields and their changes into electrical signals. Magnetic sensors include giant magnetoresistive sensors (GMRs) and anisotropic magnetoresistive sensors (AMRs). Taking an anisotropic magnetoresistive sensor as an example, a nickel-iron alloy layer serves as the magnetoresistive layer. When an external magnetic field is applied to the magnetoresistive layer, the magnetic domains rotate, causing a change in the layer's resistance. This change in resistance is reflected in the output voltage, thus detecting the applied magnetic field. In recent years, the development of anisotropic magnetoresistive sensor technology has progressed from single-axis magnetic sensors to dual-axis magnetic sensors to triaxial (3D) magnetic sensors. Among existing technologies, triaxial magnetic sensors are widely used because they can comprehensively detect magnetic signals in the X, Y, and Z directions of space.

[0003] In the manufacturing process of existing AMR triaxial magnetic sensors, the magnetoresistive materials of the X-axis and Y-axis are formed on a plane, while the magnetoresistive material of the Z-axis needs to be perpendicular to the plane formed by the X-axis and Y-axis. Therefore, to form the axial magnetoresistive layer, a trench perpendicular to the plane must first be formed so that the Z-axis magnetoresistive material can be formed on the sidewall of the trench and the top surface near the sidewall of the trench.

[0004] In the Trench ET and Trench ET Back processes of triaxial magnetic sensors, the first step involves excavating the trench, followed by depositing (DEP) an oxide layer (OX), and then etching back to form the desired profile with a specific bevel angle. However, during the etching process, ensuring the bottom metal barrier layer (TiN) is completely etched, maintaining the height of OX, and achieving the required trench profile presents a challenge. Current processes typically retain part of the metal barrier layer (TiN) in the first Trench ET step, while simultaneously etching both OX and TiN in the second step. This leads to the following problem: the trench sidewalls become too steep, such as... Figure 1A As shown, the morphology of the formed trench does not meet the requirements (profile unmatch), and in addition, the oxide layer loss is too much, resulting in the oxide layer thickness not meeting the requirements. Figure 1B As shown, some oxide residue will be generated on the inner wall of the trench during the etching process, such as... Figure 1C As shown. Therefore, a method for manufacturing triaxial magnetic sensors is needed to improve the balance between trench morphology, TiN etching, and oxide layer thickness. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing a triaxial magnetic sensor, which achieves a balance between improving trench morphology, TiN etching, and controlling oxide layer thickness, thereby improving the reliability of the device.

[0006] To achieve the above objectives, the present invention provides a method for manufacturing a triaxial magnetic sensor, comprising:

[0007] A substrate is provided on which a metal layer, a barrier layer and an interlayer dielectric layer are sequentially formed;

[0008] The interlayer dielectric layer and the barrier layer are etched to form a first trench with a first tilt angle;

[0009] An oxide layer is formed on the inner wall of the first trench and on the interlayer dielectric layer; and,

[0010] A back-engraving process is performed to form a second groove with a second tilt angle.

[0011] Optionally, the depth direction of both the first trench and the second trench is consistent with the thickness direction of the substrate, and the first tilt angle is greater than the second tilt angle.

[0012] Optionally, the first tilt angle is 65° to 80°, and the second tilt angle is 52° to 56°.

[0013] Optionally, the depth of the first trench is 2.9 μm to 4 μm.

[0014] Optionally, after performing a back-etching process to form the second trench, the thickness of the interlayer dielectric layer is greater than 2.8 μm.

[0015] Optionally, the metal layer is made of aluminum, and the barrier layer is made of titanium nitride.

[0016] Optionally, both the interlayer dielectric layer and the oxide layer are made of silicon oxide.

[0017] Optionally, a partial thickness of the metal layer can be etched using a reverse etching process.

[0018] Optionally, the first trench and the second trench are formed by dry etching.

[0019] Optionally, it may also include: forming a magnetoresistive layer on a sidewall surface of the second trench, a portion of the trench bottom surface in contact with a sidewall, and a portion of the second trench surrounding a sidewall top surface.

[0020] Optionally, the magnetoresistive layer is a stack of silicon nitride, nickel-iron alloy, and tantalum nitride layers.

[0021] In summary, the manufacturing method of the triaxial magnetic sensor provided by this invention involves first etching the interlayer dielectric layer and the barrier layer to form a first trench with a first tilt angle, then forming an oxide layer on the inner wall of the first trench and the interlayer dielectric layer, and finally forming a second trench with a second tilt angle through a back etching process. That is, this invention etches away the barrier layer TiN in the Trench ET process, and focuses on solving the etching morphology problem in the Trench ET Back process, controlling the loss of the oxide layer, and increasing the trench window, thus achieving a balance between improved trench morphology, TiN etching, and oxide layer thickness control, thereby improving the reliability of the device. Attached Figure Description

[0022] Figures 1A to 1C These are electron microscope images of the structures corresponding to the steps in the manufacturing process of a triaxial magnetic sensor.

[0023] Figure 2 This is a schematic flowchart of a method for manufacturing a triaxial magnetic sensor according to an embodiment of the present invention;

[0024] Figures 3A to 3D This is a schematic diagram of the structure formed in the corresponding steps of the manufacturing method of the triaxial magnetic sensor provided in the embodiment of the present invention;

[0025] Figures 4A to 4C These are electron microscope images of the corresponding structures in the manufacturing method of the triaxial magnetic sensor provided in this embodiment of the invention.

[0026] The reference numerals in the attached figures are explained as follows:

[0027] 100 - Substrate; 110 - First trench; 120 - Second trench;

[0028] 101-Metal layer; 102-Barrier layer; 103-Interlayer dielectric layer; 104-Photoresist layer; 105-Oxide layer. Detailed Implementation

[0029] To make the content of this invention clearer and easier to understand, the following description, in conjunction with the accompanying drawings, further illustrates the invention. Of course, this invention is not limited to this specific embodiment, and common substitutions well-known to those skilled in the art are also covered within the scope of protection of this invention.

[0030] Secondly, the present invention is described in detail using schematic diagrams. When describing the examples of the present invention in detail, for ease of explanation, the schematic diagrams are not enlarged to a certain extent according to the general proportions, and this should not be regarded as a limitation of the present invention.

[0031] For ease of description, some embodiments of the present invention may use spatially relative terms such as “above,” “below,” “top,” and “under” to describe the relationship between one element or component and another (or more) elements or components as shown in the accompanying drawings of the embodiments. It should be understood that, in addition to the orientations described in the drawings, the spatially relative terms are also intended to include different orientations of the device during use or operation. For example, if the device in the drawings is flipped, it is described as an element or component “below” or “under” other elements or components, and will subsequently be positioned “above” or “on” other elements or components. The terms “first,” “second,” etc., used below are used to distinguish between similar elements and are not necessarily used to describe a particular order or temporal sequence.

[0032] Figure 2 This is a schematic flowchart illustrating a method for manufacturing a triaxial magnetic sensor according to an embodiment of the present invention, as shown below. Figure 2 As shown, the manufacturing method of the triaxial magnetic sensor provided in this embodiment includes the following steps:

[0033] Step S01: Provide a substrate, on which a metal layer, a barrier layer and an interlayer dielectric layer are sequentially formed;

[0034] Step S02: Etch the interlayer dielectric layer and the barrier layer to form a first trench with a first tilt angle;

[0035] Step S03: An oxide layer is formed on the inner wall of the first trench and on the interlayer dielectric layer; and,

[0036] Step S04: Perform a back-etching process to form a second groove with a second tilt angle.

[0037] Figures 3A to 3D This is a schematic diagram illustrating the structural steps of a method for manufacturing a triaxial magnetic sensor according to an embodiment of the present invention. Please refer to... Figure 2 As shown, and in combination Figures 3A to 3D The present invention provides a detailed description of the manufacturing method of the triaxial magnetic sensor.

[0038] First, refer to Figure 3A As shown, in step S01, a substrate 100 is provided, on which a metal layer 101, a barrier layer 102 and an interlayer dielectric layer 103 are sequentially formed.

[0039] Specifically, a substrate 100 is provided, which can be single-crystal silicon (Si), single-crystal germanium (Ge), silicon-germanium (GeSi), or silicon carbide (SiC), or silicon-on-insulator (SOI) or germanium-on-insulator (GOI); or it can be other materials, such as gallium arsenide or other III-V compounds. In this embodiment, the substrate 100 is only used as an example of a silicon substrate, and this is only an example; the present invention is not limited thereto.

[0040] An interlayer dielectric layer 103 is formed on the substrate 100, and at least one metal layer is embedded in the interlayer dielectric layer 103. Exemplarily, the metal layer includes a first metal layer (M1), a second metal layer (M2), a third metal layer (M3), and a top metal layer (Mt), embedded from bottom to top. The number of metal layers embedded in the dielectric layer is not limited and can be set according to actual conditions. Several metal layers are electrically connected through plugs. The plug is a conductive layer filling a through-hole in the dielectric layer between two metal layers.

[0041] Furthermore, a gate and a gate oxide layer are formed between the substrate 100 and the metal layer. In order to better illustrate the inventive points of this embodiment, the description of the gate, the gate oxide layer and other metal layers between the substrate 100 and the top metal layer for forming metal interconnect structures is omitted in this embodiment.

[0042] Furthermore, the metal layer 101 can be made of one or a combination of at least two of aluminum, copper, titanium, nickel, aluminum nitride, titanium nitride, and nickel nitride, and can be formed by sputtering. The interlayer dielectric layer 103 can be made of silicon oxide, silicon oxynitride, TEOS, or a low-k dielectric, and can be formed by thermal oxidation growth or chemical vapor deposition. The interlayer dielectric layer 103 serves as an insulating barrier between the subsequently formed magnetic material layer and the substrate 100. The barrier layer 102 is formed, for example, by physical vapor deposition (PVD), and can be made of materials with good adhesion, such as tantalum, tantalum nitride, or titanium nitride, to prevent metal ions in the metal layer from diffusing into the dielectric layer. In this embodiment, the metal layer 101 is the top metal layer, the metal layer 101 is made of aluminum (Al), the barrier layer 102 is made of titanium nitride (TiN), and the interlayer dielectric layer 103 is made of silicon oxide (SiO2).

[0043] Next, refer to Figure 3A and Figure 3B As shown, step S02 is performed to etch the interlayer dielectric layer 103 and the barrier layer 102 to form a first trench 110 with a first tilt angle α.

[0044] The interlayer dielectric layer 103 and the barrier layer 102 are etched using a dry etching or wet etching process to form the first trench 110. The depth direction of the first trench 110 is consistent with the thickness direction of the substrate, and the first trench 110 is a trench that is wider at the top and narrower at the bottom. The first trench 110 has a first tilt angle α, which is 65° to 80°, for example, 70°, 75°, etc.

[0045] Specifically, the interlayer dielectric layer 103 and the barrier layer 102 are anisotropically etched to form trenches in the interlayer dielectric layer 103. Specifically, a hard mask such as silicon nitride is first grown, then a photoresist layer 104 is coated on the hard mask, and the photoresist layer 104 is patterned to form trench photolithography windows. Then, using the patterned photoresist layer as a mask, the hard mask layer and the interlayer dielectric layer 103 are etched to form a first trench 110 with a first tilt angle. The hard mask is then removed by wet etching, using a mixture of hydrofluoric acid and sulfuric acid. The depth of the first trench 110 is greater than the thickness of the interlayer dielectric layer 102, meaning the bottom of the first trench 110 is located on the upper surface of the metal layer 101. The depth of the first trench 110 is 2.9 μm to 4 μm, for example, 3 μm.

[0046] In this embodiment, during the first trench 110 etching (Trench ET), the barrier layer (TiN) 102 is etched away while maintaining the trench profile. This allows the second trench 120 etching (Trench ET Back), which is more critical for device performance, to focus solely on addressing the etching profile. Specifically, during the first trench 110 etching (Trench ET), enhanced lateral etching can create a trench profile with a certain tilt angle. This facilitates the formation of the target tilt angle for the ET Back and also increases the angle window.

[0047] Next, refer to Figure 3C As shown, in step S03, an oxide layer 104 is formed on the inner wall of the first trench 110 and on the interlayer dielectric layer 103. The oxide layer 104 is made of the same material as the interlayer dielectric layer 103, for example, both are silicon oxide layers, and are formed by plasma-enhanced chemical vapor deposition.

[0048] Next, refer to Figure 3D As shown, step S04 is performed to conduct a back etching process, forming a second trench 120 with a second tilt angle. The oxide layer 104 and part of the interlayer dielectric layer are dry-etched to form a second trench 120 with a different tilt angle based on the first trench 110. The second tilt angle β is smaller than the first tilt angle α, and the second tilt angle β is 52° to 56°, for example, 54°.

[0049] In the first trench 110 etching process (Trench ET), the barrier layer (TiN) 102 has already been etched away. The second trench 120 etching process (Trench ET Back) allows for better control of oxide layer (including interlayer dielectric layer) loss (OXloss), thereby increasing the trench window. In other words, the Trench ET Back process only needs to address the etching morphology. Specifically, the oxide layer 104 and part of the interlayer dielectric layer 103 are dry-etched. By controlling the etching process parameters, the trench tilt angle is adjusted to achieve the target tilt angle (Z-axis angle, 54°).

[0050] In this embodiment, after the second trench 120 is formed by the back-etching process, the thickness of the interlayer dielectric layer 103 is greater than 2.8 μm. Furthermore, in other embodiments of the present invention, when the trench tilt angle is satisfied, a portion of the metal layer 101 is etched during the back-etching process to form the second trench 120.

[0051] Figures 4A to 4C These are electron microscope (EM) images of the corresponding structures in the manufacturing process of the triaxial magnetic sensor provided in this embodiment. For example... Figure 4AAs shown, the trench fabricated by the method provided in this embodiment has a gentle sidewall slope, which meets the morphological requirements of the device trench. The oxide layer thickness is greater than 2.8 μm, which meets the requirements. Figure 4B As shown, no oxide residue was generated on the inner wall of the trench during the etching process, such as Figure 4C As shown in the figure, the manufacturing method of the triaxial magnetic sensor provided in this embodiment achieves a balance between improved trench morphology, TiN etching, and oxide layer thickness control, thereby improving the reliability of the device.

[0052] Furthermore, the manufacturing method of the triaxial magnetic sensor provided in this embodiment also includes forming a magnetoresistive layer, which is formed on the surface of one sidewall of the second trench, the bottom surface of the trench in contact with one sidewall, and the top surface around the second trench in contact with one sidewall. The magnetoresistive layer is a stack of silicon nitride layer, nickel-iron alloy layer and tantalum nitride layer.

[0053] In summary, the manufacturing method of the triaxial magnetic sensor provided by this invention involves first etching the interlayer dielectric layer and the barrier layer to form a first trench with a first tilt angle. Then, an oxide layer is formed on the inner wall of the first trench and the interlayer dielectric layer. Finally, a second trench with a second tilt angle is formed through a back etching process. This invention etches away the barrier layer TiN in the Trench ET process and focuses on solving the etching morphology problem in the Trench ET Back process, controlling oxide layer loss and increasing the trench window. This achieves a balance between improved trench morphology, TiN etching, and oxide layer thickness control, thereby improving device reliability.

[0054] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for manufacturing a triaxial magnetic sensor, characterized in that, include: A substrate is provided on which a metal layer, a barrier layer and an interlayer dielectric layer are sequentially formed; The interlayer dielectric layer and the barrier layer are etched to form a first trench with a first tilt angle; An oxide layer is formed on the inner wall of the first trench and on the interlayer dielectric layer; as well as, A back-etching process is performed to form a second trench with a second tilt angle. The depth directions of both the first trench and the second trench are consistent with the thickness direction of the substrate, and the first tilt angle is greater than the second tilt angle.

2. The manufacturing method of the triaxial magnetic sensor according to claim 1, characterized in that, The first tilt angle is 65° to 80°, and the second tilt angle is 52° to 56°.

3. The method for manufacturing a triaxial magnetic sensor according to claim 1, characterized in that, The depth of the first trench is 2.9 μm to 4 μm.

4. The method for manufacturing a triaxial magnetic sensor according to claim 3, characterized in that, After the second trench is formed by the back etching process, the thickness of the interlayer dielectric layer is greater than 2.8 μm.

5. The method for manufacturing a triaxial magnetic sensor according to claim 1, characterized in that, The metal layer is made of aluminum, and the barrier layer is made of titanium nitride.

6. The method for manufacturing a triaxial magnetic sensor according to claim 5, characterized in that, Both the interlayer dielectric layer and the oxide layer are made of silicon oxide.

7. The method for manufacturing a triaxial magnetic sensor according to claim 1, characterized in that, The etching process etches a portion of the metal layer.

8. The method for manufacturing a triaxial magnetic sensor according to claim 1, characterized in that, The first trench and the second trench are formed by dry etching.

9. The method for manufacturing a triaxial magnetic sensor according to claim 1, characterized in that, Also includes: A magnetoresistive layer is formed on one sidewall surface of the second trench, the bottom surface of the trench in contact with one sidewall, and the top surface around the second trench in contact with one sidewall.

10. The method for manufacturing a triaxial magnetic sensor according to claim 9, characterized in that, The magnetoresistive layer is a stack of silicon nitride, nickel-iron alloy, and tantalum nitride layers.

Images