Metal layer etching method applied to a three-axis magnetic sensor

Abstract

The present application discloses a metal layer etching method applied to a three-axis magnetic sensor, comprising: providing a substrate, the substrate including a three-dimensional region and a two-dimensional region, a magnetic sensor with a three-dimensional topography being formed in the three-dimensional region, a metal layer being formed on the three-dimensional region and the two-dimensional region, the metal layer sequentially including a first metal layer, a second metal layer and a third metal layer from bottom to top; covering a photoresist on the third metal layer to expose the third metal layer in a target region; performing a first etching to etch to a target depth in the second metal layer to form a first trench, and during the process of performing the first etching, making the first trench present a topography with an opening width greater than the bottom width by increasing the flow rate ratio of a passivation gas; performing a second etching, stopping the etching at the surface of the first metal layer to form a second trench, and during the process of performing the second etching, making the second trench present a topography with an opening width greater than the bottom width by increasing the flow rate ratio of the passivation gas.

Description

Technical Field

[0001] This application relates to the field of microelectronic manufacturing technology, and particularly to a metal layer etching method applied to a three-axis magnetic sensor. Background Art

[0002] Magnetic sensors are widely used in modern industrial and electronic products, and they measure physical parameters such as current, position, and direction by sensing the magnetic field intensity. Taking anisotropic magneto-resistance (AMR) as an example, when an external magnetic field is applied to the magneto-resistive layer, the resistance of the magneto-resistive layer changes, and the change in resistance is reflected as a change in the output voltage in the sensing system, thereby achieving the purpose of monitoring the external magnetic field.

[0003] In recent years, with the development of technology, magnetic sensors have evolved from single-axis magnetic sensors and biaxial magnetic sensors to three-axis magnetic sensors, which can detect magnetic field signals in three directions of the X-axis, Y-axis, and Z-axis in a three-dimensional space. Generally, a three-axis magnetic sensor includes a three-dimensional region and a two-dimensional region. The three-dimensional region is used to integrate magnetic sensors with three-dimensional topography (for example, it has an inclined magneto-resistive layer), and the two-dimensional region does not contain devices with three-dimensional topography. When etching the metal layers of the three-dimensional region and the two-dimensional region, due to the influence of depth, as Figure 1 shown, the three-dimensional region has an inclined and sloped topography, and the exposure energy is greater than that of the two-dimensional region. If the photoresist is opened due to excessive exposure energy on the slope, a "pitting" defect will be formed (as shown by the dotted line in Figure 1 ), thereby reducing the reliability and yield of the device. Summary of the Invention

[0004] This application provides a metal layer etching method applied to a three-axis magnetic sensor, which can solve the problem that pitting defects are easily formed in the metal layer etching of the three-axis magnetic sensor provided in the related art. The method includes:

[0005] Providing a substrate, the substrate includes a three-dimensional region and a two-dimensional region, a magnetic sensor with three-dimensional topography is formed in the three-dimensional region, a metal layer is formed on the three-dimensional region and the two-dimensional region, the substrate includes a silicon nitride layer, and the metal layer sequentially includes a first metal layer, a second metal layer, and a third metal layer from bottom to top;

[0006] Covering a photoresist on the third metal layer to expose the third metal layer in the target area;

[0007] Performing a first etching to etch to a target depth in the second metal layer to form a first trench. During the first etching process, by increasing the flow rate ratio of the passivation gas, the first trench is formed with a morphology where the opening width is greater than the bottom width;

[0008] Perform a second etching, stopping the etching at the surface of the first metal layer to form a second trench. During the process of performing the second etching, by increasing the flow rate ratio of the passivation gas, the second trench is formed with a morphology where the opening width is greater than the bottom width.

[0009] In some embodiments, the passivation gas includes at least one of trifluoromethane, difluoromethane, octafluorocyclobutane, fluoromethane, and nitrogen.

[0010] In some embodiments, the flow rate ratio of the passivation gas to the etching gas is 2:1 to 3:1.

[0011] In some embodiments, the magnetic sensor includes an AMR sensor.

[0012] In some embodiments, the AMR sensor includes a magnetoresistive layer that is inclined when viewed in cross-section.

[0013] In some embodiments, the magnetoresistive layer includes at least one of nickel-iron alloy, nickel-iron-chromium alloy, nickel-iron-rubidium alloy, or iron-nickel-cobalt alloy.

[0014] In some embodiments, the second metal layer includes an aluminum layer.

[0015] In some embodiments, the first metal layer includes a tantalum nitride layer.

[0016] In some embodiments, the second metal layer includes at least one metal multi-layer film.

[0017] In some embodiments, the metal multi-layer film includes a titanium nitride layer / titanium layer.

[0018] The technical solution of the present application has at least the following advantages:

[0019] During the etching process of the metal layer of the triaxial magnetic sensor, by increasing the flow rate ratio of the passivation gas, the etched trench has a morphology where the opening width is greater than the bottom width, thereby slowing down the longitudinal etching at the position where the three-dimensional region is covered by the photoresist, alleviating the pitting defect to a certain extent, and improving the yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1It is a transmission electron microscope (TEM) image of pitting defects generated by a three-axis magnetic sensor provided in the related art;

[0022] Figure 2 It is a flowchart of a metal layer etching method applied to a three-axis magnetic sensor provided by an exemplary embodiment of the present application;

[0023] Figures 3 to 5 It is an etching schematic diagram of a metal layer etching method applied to a three-axis magnetic sensor provided by an exemplary embodiment of the present application. Detailed implementation manners

[0024] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0025] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0027] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0028] Refer to Figure 2 , which shows a flowchart of a metal layer etching method applied to a three-axis magnetic sensor provided by an exemplary embodiment of the present application, as Figure 2As shown, the method includes:

[0029] Step S1: Provide a substrate, which includes a three-dimensional region and a two-dimensional region. A magnetic sensor with a three-dimensional topography is formed in the three-dimensional region, and a metal layer is formed on both the three-dimensional region and the two-dimensional region. The substrate sequentially includes a silicon substrate and a silicon nitride layer from bottom to top, and the metal layer sequentially includes a first metal layer, a second metal layer, and a third metal layer from bottom to top.

[0030] Among them, the three-axis magnetic sensor in the embodiments of the present application includes an AMR sensor. The AMR sensor includes a magnetoresistive layer that is inclined when viewed in cross-section (the inclined magnetoresistive layer can be formed on a dielectric layer with a slope), and the magnetoresistive layer can be at least one of nickel-iron (NiFe) alloy, nickel-iron-chromium (NiFeCr) alloy, nickel-iron-rubidium (NiFeRb) alloy, or iron-nickel-cobalt (FeNiCo) alloy.

[0031] Step S2: Cover a photoresist on the third metal layer to expose the third metal layer in the target area.

[0032] Reference Figure 3 , which shows a cross-sectional schematic diagram of covering a photoresist on the third metal layer. Exemplarily, as Figure 3 shown, the first metal layer 321 is formed on the substrate 310, the second metal layer 330 is formed on the first metal layer 321, the third metal layer 322 is formed on the second metal layer 330. A photoresist 400 can be covered on the third metal layer 322, and the photoresist 400 in the target area is removed through exposure and development to expose the third metal layer 322 in the target area. Among them, the substrate 310 may include a silicon nitride (SiN) layer, the second metal layer 330 includes an aluminum (Al) layer, the first metal layer 321 includes a tantalum nitride (TaN) layer, and the second metal layer 330 includes at least one metal multi-layer film, and the metal multi-layer film includes a titanium nitride (TiN) layer / titanium (Ti) layer.

[0033] Step S3: Perform a first etching to etch to a target depth in the second metal layer to form a first trench. During the first etching process, by increasing the flow rate ratio of the passivation gas, the first trench is formed with a morphology where the opening width is greater than the bottom width.

[0034] Reference Figure 4 , which shows a cross-sectional schematic diagram after the first etching. Exemplarily, as Figure 4 shown, after the first etching, a first trench 501 is formed. The depth of the first trench 501 reaches the second metal layer 330. During the first etching process, by increasing the flow rate ratio of the passivation gas, the first trench 501 is formed with a morphology where the opening width is greater than the bottom width. Among them, the passivation gas includes trifluoromethane (CHF 3 3), difluoromethane (CH2 F 2 )), octafluorocyclobutane (C 4 F 8 ), fluoromethane (CH 3 F), and nitrogen (N 2 )) or at least one of them, and the flow rate ratio of the passivation gas to the etching gas is from 2:1 to 3:1.

[0035] Step S4: Perform a second etching until reaching the surface of the first metal layer to form a second trench. During the second etching process, by increasing the flow rate ratio of the passivation gas, the second trench is formed with a morphology where the opening width is greater than the bottom width.

[0036] Reference Figure 5 , which shows a cross-sectional schematic diagram after the second etching. Exemplarily, as Figure 5 shown, after the second etching, a first trench 502 is formed. The bottom end of the second trench 502 is the upper surface of the first metal layer 321. During the second etching process, by increasing the flow rate ratio of the passivation gas, the second trench 502 is formed with a morphology where the opening width is greater than the bottom width. Among them, the passivation gas includes trifluoromethane and / or nitrogen, and the flow rate ratio of the passivation gas to the etching gas is from 2:1 to 3:1.

[0037] In summary, in the embodiments of the present application, during the etching process of the metal layer of the three-axis magnetic sensor, by increasing the flow rate ratio of the passivation gas, the etched trench has a morphology where the opening width is greater than the bottom width, thereby slowing down the longitudinal etching at the position covered by the photoresist in the three-dimensional region, alleviating the pitting defect to a certain extent, and improving the yield of the product.

[0038] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A metal layer etching method applied to a three-axis magnetic sensor, characterized in that, it includes: providing a substrate, the substrate includes a three-dimensional region and a two-dimensional region, a magnetic sensor with a three-dimensional topography is formed in the three-dimensional region, a metal layer is formed on the three-dimensional region and the two-dimensional region, the substrate includes a silicon nitride layer, and the metal layer sequentially includes a first metal layer, a second metal layer, and a third metal layer from bottom to top; covering a photoresist on the third metal layer to expose the third metal layer in the target area; performing a first etching to etch to a target depth in the second metal layer to form a first trench. During the first etching process, by increasing the flow rate ratio of the passivation gas, the first trench presents a topography with an opening width larger than the bottom width; performing a second etching to stop etching at the surface of the first metal layer to form a second trench. During the second etching process, by increasing the flow rate ratio of the passivation gas, the second trench presents a topography with an opening width larger than the bottom width; wherein, the passivation gas includes at least one of trifluoromethane, difluoromethane, octafluorocyclobutane, fluoromethane, and nitrogen, and the flow rate ratio of the passivation gas to the etching gas is 2:1 to 3:

1.

2. The method according to claim 1, characterized in that, the magnetic sensor includes an AMR sensor.

3. The method according to claim 2, characterized in that, the AMR sensor includes a magnetoresistive layer that is inclined when observed from a cross-section.

4. The method according to claim 3, characterized in that, the magnetoresistive layer includes at least one of nickel-iron alloy, nickel-iron-chromium alloy, nickel-iron-rubidium alloy, or iron-nickel-cobalt alloy.

5. The method according to claim 4, characterized in that, the second metal layer includes an aluminum layer.

6. The method according to claim 5, characterized in that, the first metal layer includes a tantalum nitride layer.

7. The method according to claim 6, characterized in that, the second metal layer includes at least one metal multi-layer film.

8. The method according to claim 7, characterized in that, the metal multi-layer film includes a titanium nitride layer / titanium layer.

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