CN114506812A - Inertial sensor and preparation method thereof - Google Patents
Inertial sensor and preparation method thereof Download PDFInfo
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- CN114506812A CN114506812A CN202111616431.7A CN202111616431A CN114506812A CN 114506812 A CN114506812 A CN 114506812A CN 202111616431 A CN202111616431 A CN 202111616431A CN 114506812 A CN114506812 A CN 114506812A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00349—Creating layers of material on a substrate
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00023—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems without movable or flexible elements
- B81C1/00095—Interconnects
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
- B81C1/00523—Etching material
- B81C1/00531—Dry etching
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
- G01C21/166—Mechanical, construction or arrangement details of inertial navigation systems
Abstract
Disclosed are an inertial sensor and a method for manufacturing the same, the method comprising: forming a first dielectric layer and a first conductive layer on a first substrate; forming a first opening in the first conductive layer to expose a portion of the surface of the first dielectric layer; forming a protective layer on the first conductive layer, wherein the protective layer covers a part of the first conductive layer, the side wall of the first opening and the surface of the first dielectric layer exposed by the first opening; forming a second dielectric layer with a second opening on part of the first conductive layer and part of the protective layer; forming a second conductive layer on the second dielectric layer, wherein the second conductive layer fills the second opening; forming a first bonding structure on the second conductive layer; patterning the second conductive layer to form a third opening; removing part of the second dielectric layer through the third opening to form a cavity and a movable mass block; and removing the first conductive layer in the cavity and the protective layer exposed on the surface of the first dielectric layer. The inertial sensor and the preparation method thereof ensure the reliability of the inertial sensor through the protective layer.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to an inertial sensor and a preparation method thereof.
Background
Surface technology is one of the most common manufacturing processes of micro-electro-mechanical systems (MEMS), which uses a semiconductor substrate as a base to prepare a three-dimensional micromechanical structure through multiple thin film depositions and pattern processing.
Taking an inertial sensor as an example, the sensor includes a Device patch (Device) and a Cap patch (Cap) bonded together. The device slice sequentially comprises a first substrate, a first dielectric layer, a first conducting layer, a second dielectric layer, a second conducting layer and a bonding structure from bottom to top. The first conductive layer and the second conductive layer are patterned conductive layers. The patterned first conductive layer is used as a wiring and a capacitance plate of the detection capacitor; the patterned second conductive layer forms a proof mass. And removing the second dielectric layer below the mass block to form a cavity, and simultaneously releasing the mass block to enable the mass block to be movable.
The second dielectric layer is removed by using gaseous hydrofluoric acid (HF), the second dielectric layer (silicon dioxide) is selectively etched by the hydrofluoric acid in an isotropic manner, and since the first conductive layer is a patterned conductive layer, a part of the first dielectric layer below the first conductive layer is exposed, and during the fumigating process, the hydrofluoric acid removes a part of the first dielectric layer below the first conductive layer through gaps of the patterned first conductive layer, thereby reducing the reliability of the device.
The fumigation amount of the first medium layer is reduced as much as possible by ensuring that the mass is movable by controlling the fumigation rate and the fumigation time, but the first medium layer can still be damaged.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an inertial sensor and a method for manufacturing the same, in which a protective layer is introduced on a first conductive layer to protect a first dielectric layer, thereby ensuring the reliability of the inertial sensor.
In a first aspect, the present invention provides a method for manufacturing an inertial sensor, the method comprising:
forming a first dielectric layer and a first conductive layer on a first substrate;
forming a first opening in the first conductive layer to expose a portion of the surface of the first dielectric layer;
forming a protective layer on the first conductive layer, wherein the protective layer covers a part of the first conductive layer, the side wall of the first opening and the surface of the first dielectric layer exposed by the first opening;
forming a second dielectric layer with a second opening on part of the first conductive layer and part of the protective layer;
forming a second conductive layer on the second dielectric layer, wherein the second conductive layer fills the second opening;
forming a first bonding structure on the second conductive layer;
patterning the second conductive layer to form a third opening;
removing part of the second medium layer through the third opening to form a cavity and a movable mass block;
and removing the first conductive layer in the cavity and the protective layer exposed from the surface of the first dielectric layer.
Preferably, before the first conductive layer in the cavity and the protective layer exposed on the surface of the first dielectric layer are removed, the protective layer is not present outside the region enclosed by the cavity.
Preferably, before the first conductive layer in the cavity and the protective layer exposed on the surface of the first dielectric layer are removed, the wiring and pressure point area of the first conductive layer outside the area enclosed by the cavity is free from the protective layer.
Preferably, before the first conductive layer in the cavity and the protective layer exposed on the surface of the first dielectric layer are removed, the protective layer is not present between the contact surfaces of the second conductive layer and the first conductive layer within the region enclosed by the cavity.
Preferably, the materials of the protective layer, the first conductive layer and the second conductive layer are the same.
Preferably, the material of the protective layer, the first conductive layer and the second conductive layer is polysilicon.
Preferably, the thickness ratio of the first conductive layer to the protective layer is 10: 1-50: 1.
Preferably, the thickness ratio of the second conductive layer to the protective layer is 200: 1-1000: 1.
Preferably, the thickness of the protective layer is 0.02-0.06 micrometer.
Preferably, the thickness of the first conductive layer is 0.4-1.2 microns.
Preferably, the thickness of the second conductive layer is 15-30 microns.
Preferably, the deposition temperature of the first conductive layer and the protective layer is 520-620 ℃.
Preferably, the first conductive layer in the cavity and the protective layer exposed on the surface of the first dielectric layer are removed by dry etching.
Preferably, CF is used4And O2And carrying out dry etching on the protective layer.
Preferably, a part of the second dielectric layer is removed through the third opening by a hydrofluoric acid vapor phase fumigation process to form a cavity and a movable mass.
Preferably, the method further comprises the following steps:
forming a second bonding structure on the first surface of the second substrate;
forming a groove on a first surface of a second substrate;
and bonding the first bonding structure of the first substrate and the second bonding structure of the second substrate at high temperature to form a sealed cavity.
A second aspect of the present invention provides an inertial sensor comprising:
a first substrate;
a first dielectric layer located on the first substrate;
the first conducting layer is positioned on the first dielectric layer, a first opening is formed in the first conducting layer, and a part of the surface of the first dielectric layer is exposed out of the first opening;
a protective layer on a portion of the first conductive layer;
a second dielectric layer on the first conductive layer, the second dielectric layer having a cavity therein;
a patterned second conductive layer on the second dielectric layer, the second conductive layer in the cavity being a movable mass;
a first bonding structure on the second conductive layer;
wherein the protective layer within the area enclosed by the cavity is only located between the contact surfaces of the first conductive layer and the second conductive layer.
Preferably, the protective layer is absent from the region enclosed by the cavity.
Preferably, the protective layer is arranged outside the area enclosed by the cavity, and the protective layer does not cover the wiring and the pressure point area of the first conductive layer.
Preferably, the materials of the protective layer, the first conductive layer and the second conductive layer are the same.
Preferably, the material of the protective layer, the first conductive layer and the second conductive layer is polysilicon.
Preferably, the thickness ratio of the first conductive layer to the protective layer is 10: 1-50: 1.
Preferably, the thickness ratio of the second conductive layer to the protective layer is 200: 1-1000: 1.
Preferably, the thickness of the protective layer is 0.02-0.06 micrometer.
Preferably, the thickness of the first conductive layer is 0.4-1.2 microns.
Preferably, the thickness of the second conductive layer is 15-30 microns.
Preferably, the method further comprises the following steps:
a second substrate;
a second bonding structure located on the first surface of the second substrate;
a groove located on the first surface of the second substrate;
the first surface of the second substrate is opposite to the second conductive layer, and the second bonding structure is located on the first bonding structure and encloses the first substrate and the second substrate to form a sealed cavity.
According to the inertial sensor and the preparation method thereof, the protective layer is introduced on the first conductive layer, and the first dielectric layer positioned below the first conductive layer is not corroded by hydrofluoric acid (HF) due to the protection of the protective layer, so that the integrity of the first dielectric layer is ensured.
Further, the embodiment of the present invention removes the protective layer on the first conductive layer opposite to the movable mass (i.e., the protective layer exposed on the surfaces of the first conductive layer and the first dielectric layer in the cavity), without affecting the line width of the effective electrode plate of the first conductive layer.
Further, in the process of forming the protective layer, the protective layer covers the surface of part of the first conductive layer, the side wall of the first opening and the surface of the first dielectric layer exposed through the first opening, and only the protective layer in the region surrounded by the subsequent cavity is reserved, so that the first conductive layer (wiring and pressure point region) outside the region surrounded by the cavity is prevented from being short-circuited, the requirement on the photoetching precision is low, and the method is simple.
Furthermore, after the hydrofluoric acid (HF) fumigation is completed, the first conductive layer in the cavity and the protective layer on the surface of the first dielectric layer are removed, so that corresponding stress is not increased, and a tube core is not deformed in subsequent processing steps (such as annealing), thereby causing a test error.
In a preferred embodiment, the protective layer is made of the same material as the first conductive layer and the second conductive layer. Due to the fact that the materials of the first conducting layer and the second conducting layer are the same, the protective layer cannot be corroded when hydrofluoric acid (HF) corrodes the second medium layer, and therefore the first medium layer can be protected; meanwhile, the second conducting layer in contact with the protective layer is electrically connected with the first conducting layer through the protective layer, and the normal work of the inertial sensor cannot be influenced.
In a preferred embodiment, the thickness of the protective layer is much smaller than that of the second protective layer, and the time required for etching the protective layer is short, so that the etching thickness of the second conductive layer is not influenced on the second conductive layer.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
FIG. 1 shows a schematic diagram of a prior art inertial sensor;
FIGS. 2 a-2 b are cross-sectional views illustrating a mid-stage of a prior art inertial sensor fabrication process;
FIG. 3 shows a schematic structural diagram of an inertial sensor of an embodiment of the invention;
fig. 4a to 4m show sectional views of stages in the manufacturing process of an inertial sensor according to an embodiment of the invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. In addition, certain well known components may not be shown.
The present invention may be embodied in various forms, some examples of which are described below.
FIG. 1 shows a schematic diagram of a prior art inertial sensor; as shown in fig. 1, the inertial sensor 100 includes a Device patch (Device)110 and a Cap patch (Cap) 120 bonded together. The device slice 110 sequentially includes, from bottom to top, a first substrate 111, a first dielectric layer 112, a first conductive layer 113, a second dielectric layer 114, a second conductive layer 115, and a bonding structure 116. The cap plate 120 is bonded to the device wafer 110 by the bonding structures 116.
The first dielectric layer 112 and the second dielectric layer 114 are insulating layers, wherein the first dielectric layer 112 is located between the first substrate 111 and the first conductive layer 113, and is used for supporting the first conductive layer 113 and electrically isolating the first conductive layer 113 from the first substrate 111. The second dielectric layer 114 is located between the first conductive layer 113 and the second conductive layer 115, and is used for supporting the second conductive layer 115 and electrically isolating the first conductive layer 113 from the second conductive layer 115.
The first conductive layer 113 and the second conductive layer 115 are patterned conductive layers. Wherein the patterned first conductive layer 113 includes a capacitor plate of the detection capacitor and a wiring and pressure point region; the patterned second conductive layer 115 forms a proof mass 115 a. A portion of the second dielectric layer 114 under the mass 115a is removed to form a cavity 1141, and the mass 115a is released so that the mass 115a is movable. When the mass block 115a is displaced, the distance between the mass block and the first conductive layer 113 is changed, so that a capacitance signal in the Z-axis direction can be detected, and the distance between the mass block and the sidewall electrode is changed, so that a capacitance signal in the X/Y-axis direction can be detected, and the inertia can be detected.
The first dielectric layer 112 has an opening 1121, the opening 1121 is formed simultaneously in the process of forming the cavity 1141, and the existence of the opening 1121 may reduce the reliability of the inertial sensor 100. The formation of the opening 1121 will be described in detail with reference to fig. 2a and 2 b.
Fig. 2 a-2 b show cross-sectional views of a prior art inertial sensor during a middle stage of its fabrication.
As shown in fig. 2a, a first dielectric layer 112, a patterned first conductive layer 113, a patterned second dielectric layer 114, a second conductive layer 115, and a patterned bonding structure 116 are sequentially formed on a first substrate 111, and the second conductive layer 115 is etched to form a patterned second conductive layer 115.
The patterned first conductive layer 113 includes a capacitor plate of the detection capacitor, and a wiring and pressure point region; the patterned second conductive layer 115 forms a proof mass 115 a.
As shown in fig. 2b, a hydrofluoric acid (HF) fumigation process is used to remove a portion of the second dielectric layer 114 between the first conductive layer 113 and the second conductive layer 115 through the patterned second conductive layer 115, so as to form the cavity 1141, thereby forming the movable mass block 115 a.
During the process of removing the second dielectric layer 114, hydrofluoric acid (HF) may simultaneously etch the exposed first dielectric layer 112 through the gap of the patterned first conductive layer 113, so as to form the opening 1121.
Although the amount of fumigation of first dielectric layer 112 can be minimized by controlling the fumigation rate and fumigation time, damage to first dielectric layer 112 can still result. Therefore, it is necessary to widen the line width of the first conductive layer 113, but this increases parasitic capacitance and decreases the reliability of the device.
Fig. 3 shows a schematic structural diagram of an inertial sensor according to an embodiment of the present invention, and as shown in fig. 3, an inertial sensor 200 includes a Device patch (Device)210 and a Cap patch (Cap) 220 bonded together. The device slice 210 sequentially includes, from bottom to top, a first substrate 211, a first dielectric layer 212, a first conductive layer 213, a protective layer S, a second dielectric layer 214, a second conductive layer 215, and a first bonding structure 216.
The first dielectric layer 212 and the second dielectric layer 214 are insulating layers, wherein the first dielectric layer 212 is located between the first substrate 211 and the first conductive layer 213, and is used for supporting the first conductive layer 213 and electrically isolating the first conductive layer 211 from the first substrate. The second dielectric layer 214 is located between the first conductive layer 213 and the second conductive layer 215, and is used for supporting the second conductive layer 215 and electrically isolating the first conductive layer 213 from the second conductive layer 215.
In a specific embodiment, the first substrate 211 is, for example, a silicon substrate; the first dielectric layer 212 and the second dielectric layer 214 are, for example, silicon dioxide (SiO)2)。
The first conductive layer 213 and the second conductive layer 215 are patterned conductive layers, wherein the first conductive layer 213 has a first opening a therein, and the patterned first conductive layer 113 includes a capacitor plate of a detection capacitor and a wiring and a pad region. The first opening a penetrates through the first conductive layer 213 and exposes a portion of the upper surface of the first dielectric layer 212. The second conductive layer 215 has a third opening C therein, and the patterned second conductive layer 215 forms a mass. A portion of the second dielectric layer 214 under the mass is removed to form a cavity 2141, and the mass is released so that it can move to form a movable mass 215 a. When the movable mass block 215a is displaced, the distance between the movable mass block and the first conductive layer 213 is changed, so that a capacitance signal in the Z-axis direction can be detected, and the distance between the movable mass block and the sidewall electrode is changed, so that a capacitance signal in the X/Y-axis direction can be detected, and the inertia can be detected.
In a specific embodiment, the first conductive layer 213 and the second conductive layer 215 are, for example, polysilicon.
When a portion of the second dielectric layer 214 is removed to form the cavity 2141, the protective layer S covers the first conductive layer 213 in the cavity 2141 and the sidewall and the bottom wall of the first opening a in the first conductive layer 213, and protects the first dielectric layer 212 exposed through the first opening a, so as to prevent hydrofluoric acid from corroding the first dielectric layer 212, ensure the integrity of the first dielectric layer 212, and improve the reliability of the inertial sensor. After the cavity 2141 is formed, the portion of the protection layer S exposed on the surfaces of the first conductive layer 213 and the first dielectric layer 212 in the cavity 2141 is removed, and only the portion between the contact surfaces of the second conductive layer 215 and the first conductive layer 213 remains in the region surrounded by the cavity 2141.
Due to the protection of the protection layer S, the first dielectric layer 212 is not affected by hydrofluoric acid (HF), so that the integrity of the first dielectric layer 212 is ensured, and compared with the prior art, the line width of the first conductive layer 213 does not need to be increased, so that parasitic capacitance is not additionally increased, and the parasitic capacitance is reduced while the reliability of the device is ensured.
In one embodiment, the protection layer S is made of the same material as the first conductive layer 213, such as polysilicon. Since the same material as the first conductive layer 213 is used, hydrofluoric acid (HF) does not corrode the protective layer S, thereby protecting the first dielectric layer 212; the second conductive layer 215, which is in contact with the protective layer S at the same time, is electrically connected to the first conductive layer 213 via the protective layer S, without affecting the normal operation of the inertial sensor.
The first bonding structure 216a is a patterned conductive layer, and the first bonding structure 216a is used for bonding with the cap sheet 220. The second conductive layer 215 further includes a first pressure point 215b separated from the movable mass 215a, and the inertial sensor 200 further includes a second pressure point 216b, the second pressure point 216b is electrically connected to the first conductive layer 213 through the first pressure point 215b, and the second pressure point 216b is used for subsequent package wire bonding. The first bond structure 216a is formed in the same step as the second pressure point 216 b. The first bonding structure 216a is selected from any one of silicon, glass, metal, and alloy, such as aluminum. The cap sheet 220 includes a second substrate 221 and a second bonding structure 222, the second substrate 221 has a recess 2211 therein, and the cap sheet 220 and the device wafer 210 are bonded to each other through the first bonding structure 216a and the second bonding structure 222.
The first bonding structure 216a of the device chip 210 and the second bonding structure 222 of the cap chip 220 are both annular structures, the first bonding structure 216a and the second bonding structure 222 are in contact with each other, and the groove 2211 is opposite to the movable mass 215a of the second conductive layer 215 to form a sealed cavity, so that the air pressure in the cavity can be controlled conveniently, and meanwhile, the structure inside the inertial sensor is prevented from being affected by the external environment to cause poor working stability.
The second substrate 221 is a semiconductor substrate, such as a silicon substrate; the second bonding structure 222 is selected from any one of silicon, glass, metal, and alloy, so as to realize any one of silicon-glass electrostatic bonding, silicon-silicon direct bonding, metal thermocompression bonding, or metal solder bonding with the first bonding structure 216a, in this embodiment, the second bonding structure 222 is, for example, germanium.
Fig. 4a to 4g are sectional views showing stages in the manufacturing process of the inertial sensor according to the embodiment of the present invention, and the method for manufacturing the inertial sensor according to the embodiment of the present invention will be described in detail with reference to fig. 4a to 4 g.
As shown in fig. 4a, the method starts with a first substrate 211, and a first dielectric layer 212 is formed on the first substrate 211.
In this step, the surface of the first substrate 211 is provided, for example, by depositionThe first dielectric layer 212 is formed. In a specific embodiment, the first substrate 211 is, for example, a silicon substrate, and the first dielectric layer 212 is, for example, silicon dioxide (SiO)2) The thickness of the first dielectric layer 212 is, for example, 2.5 μm.
As shown in fig. 4b, a first conductive layer 213 having a first opening a is formed on the first dielectric layer 212.
In this step, a first conductive layer 213 is formed, for example by deposition, on said first dielectric layer 212. Forming a resist layer on a surface of the first conductive layer 213, patterning the resist layer using a photolithography process to form a resist mask, and etching the first conductive layer 213 through the resist mask to form a first opening a penetrating the first conductive layer 213. After the first opening a of the first conductive layer 213 is formed, the resist mask is removed by solvent dissolution or ashing.
The patterned first conductive layer 213 includes a fixed plate of the sensing capacitor as well as wiring and a pad area. The first opening a exposes a portion of the surface of the first dielectric layer 212.
In one embodiment, the first conductive layer 213 is deposited at 520-620 degrees Celsius, for example, and the thickness of the first conductive layer 213 is 0.4-1.2 microns, for example, 0.8 microns.
As shown in fig. 4c-1, a protective layer S is formed on the first conductive layer 213.
In this step, a protective layer S is formed on the first conductive layer 213, for example, by deposition. The protective layer S covers a portion of the surface of the first conductive layer 213, the sidewall of the first opening a, and the surface of the first dielectric layer 212 exposed through the first opening a, so as to protect the surface of the first dielectric layer 212 exposed through the first opening a during the subsequent process of removing at least a portion of the second dielectric layer 214 to form the cavity 2141.
The material of the protective layer S is the same as that of the first conductive layer 213, and the preparation conditions are the same. However, the thickness of the protective layer S is much smaller than the thickness of the first conductive layer 213, and the ratio of the thickness of the protective layer S to the thickness of the first conductive layer 213 is 1:10 to 1:50, for example, 1: 20.
In a specific embodiment, the material of the protective layer S is the same as the first conductive layer 213, and the protective layer S is formed by deposition at 520-620 ℃. The thickness of the protective layer S is 0.02-0.06 micrometer, for example 0.04 micrometer.
Further, for example, photolithography and etching processes are used to remove the protective layer S in the area of the pad and the wire of the first conductive layer 213, and only the protective layer S in the area surrounded by the subsequent cavity is remained, i.e., the protective layer S is not left outside the area surrounded by the subsequent cavity 2141, so as to prevent the wire and the pad area from being short-circuited. It is to be understood that after the cavity 2141 is formed, the protection layer S exposed in the cavity 2141 is removed, so that the protection layer S only needs to cover the pad and the wiring region of the first conductive layer 213 outside the region surrounded by the cavity 2141, and the protection layer S in other regions may be remained, i.e., at least the pad and the wiring region of the first conductive layer 213 are removed.
In other embodiments, a fourth opening S-1 may also be formed in the protection layer S within the area enclosed by the subsequent cavity, and during the subsequent formation of the second conductive layer 215, a portion of the second conductive layer 215 can form a direct contact with the first conductive layer 213 via the fourth opening S-1, that is, the protection layer S is not present between the contact surfaces of the second conductive layer 215 and the first conductive layer 213 within the area enclosed by the subsequent cavity 2141, as shown in fig. 4 c-2.
As shown in fig. 4d, a second dielectric layer 214 having a second opening B is formed on the first conductive layer 213 and the protective layer S.
In this step, a second dielectric layer 214 is formed, for example, by deposition, on the surfaces of the first conductive layer 213 and the protective layer S. Forming a resist layer on the surface of the second dielectric layer 214, patterning the resist layer by using a photolithography process to form a resist mask, and etching the second dielectric layer 214 through the resist mask to form a second opening B penetrating through the second dielectric layer 214, wherein the protective layer S and a part of the surface of the first conductive layer 213 are exposed through the second opening B. After the second opening B of the second dielectric layer 214 is formed, the resist mask is removed by solvent dissolution or ashing.
In one embodiment, the second dielectric layer 214 is an insulating layer, such as silicon dioxide (SiO)2) The thickness of the second dielectric layer 214 is, for example, 1.6 μm.
As shown in fig. 4e, a second conductive layer 215 is formed on the second dielectric layer 214.
In this step, a second conductive layer 215 is formed on the surface of the second dielectric layer 214, for example, by epitaxial growth. The epitaxial growth may be atmospheric or low pressure epitaxial growth. The second conductive layer 215 covers the surface of the second dielectric layer 214, fills the second opening B, and contacts the surface of the passivation layer S and the surface of the first conductive layer 213 exposed through the second opening B. The material of the protective layer S is also the same as that of the second conductive layer 215. Since the protective layer S is made of the same material as the first conductive layer 213 and the second conductive layer 215, the second conductive layer 215 is electrically connected to the first conductive layer 213 via the protective layer S, and anchor support is achieved.
The second conductive layer 215 is, for example, polysilicon. The thickness of the second conductive layer 215 is much greater than the thickness of the protective layer S, in a specific embodiment, the thickness of the second conductive layer 215 is 15 to 30 micrometers, for example, 20 micrometers, and a ratio of the thickness of the second conductive layer 215 to the thickness of the protective layer S is 200:1 to 1000:1, for example, 500: 1.
As shown in fig. 4f, a patterned first bonding structure 216a and a second pressure point 216b are formed on the second conductive layer 215.
In this step, a first bonding structure 216a and a second pressure point 216b are formed on the surface of the second conductive layer 215, for example, by deposition and etching, and the first bonding structure 216a is a ring-shaped structure.
The first bonding structure 216a is selected from any one of silicon, glass, metal, and alloy, so as to realize any one of silicon-glass electrostatic bonding, silicon-silicon direct bonding, metal thermocompression bonding, and metal solder bonding.
In a particular embodiment, the first bond structure 216a is, for example, a single layer composed of aluminum, or a stack of layers composed of aluminum and germanium. The thickness of the first bonding structure 216a is, for example, 1.5 μm.
As shown in fig. 4g, the second conductive layer 215 is etched to form a third opening C through the second conductive layer 215 to form the desired movable mass 215 a.
In this step, a resist layer is formed on the surface of the second conductive layer 215, the resist layer is patterned by a photolithography process to form a resist mask, and the second conductive layer 215 is etched through the resist mask to form a third opening C, thereby forming the movable mass 215 a.
As shown in fig. 4h, a portion of the second dielectric layer 214 is removed through the third opening C to form a cavity 2141.
In this step, the second dielectric layer 214 is fumigated by using gaseous hydrofluoric acid (HF), and the hydrofluoric acid selectively etches the second dielectric layer 214 in an isotropic manner, wherein the protective layer S and the second conductive layer 215 are not corroded by the hydrofluoric acid and serve as an etching barrier layer. The area within the dashed line frame of fig. 4h is the area enclosed by the cavity 2141.
In this embodiment, the protection layer S is made of the same material (polysilicon) as the first conductive layer 213 and the second conductive layer 215, and is not corroded by hydrofluoric acid (HF) in this step, so as to protect the first dielectric layer 212 under the protection layer S. Due to the protection of the protection layer S, the first dielectric layer 212 is not affected by hydrofluoric acid (HF), so that the integrity of the first dielectric layer 212 is ensured, and compared with the prior art, the line width of the first conductive layer 213 does not need to be increased, so that parasitic capacitance is not additionally increased, and the parasitic capacitance is reduced while the reliability of the device is ensured.
As shown in fig. 4i, the exposed portion of the protection layer S on the inner surface of the cavity 2141 is removed.
In this step, the protective layer S is removed by, for example, dry etching. Etching gases, e.g. using CF4And O2. Wherein the dry etch does not etch the first dielectric layer 212.
In this embodiment, the second conductive layer 215 is made of the same material as the protective layer S, and when the protective layer S is etched, the second conductive layer 215 is also etched, but since the protective layer S is thin (for example, 0.04 μm), the time required for etching the protective layer S is short (for example, 30 seconds); and the thickness of the second conductive layer 215 is much greater than that of the protection layer S, so the etched thickness has negligible effect on the second conductive layer 215. In addition, the influence on the sidewall of the third opening C of the second conductive layer 215 can be compensated by increasing the line width.
After etching, the protection layer S in the region surrounded by the cavity 2141 only remains a portion located between the second conductive layer 215 and the contact surface of the first conductive layer 213, wherein the second conductive layer 215 is electrically connected to the first conductive layer 213 through the protection layer S because the protection layer S is made of the same material as the first conductive layer 213 and the second conductive layer 215.
In the embodiment of the present invention, the first conductive layer 213 of the portion opposite to the movable mass 215a is an effective electrode plate of the detection capacitor, and the embodiment of the present invention removes the protective layer S on the first conductive layer 213 opposite to the movable mass 215a, so that the line width of the effective electrode plate of the first conductive layer 213 is not affected.
After the above steps, the fabrication of the device wafer 210 is completed, and the process of fabricating the cap wafer 220 is as follows, the fabrication of the cap wafer 220 starts with the second substrate 221.
As shown in fig. 4j, a patterned second bonding structure 222 is formed on the first surface of the second substrate 221.
In this step, the second bonding structure 222 is formed on the first surface of the second substrate 221, for example, by deposition and etching, and the second bonding structure 222 is a ring-shaped structure.
The second bonding structure 222 is selected from any one of silicon, glass, metal, and alloy, so as to realize any one of silicon-glass electrostatic bonding, silicon-silicon direct bonding, metal thermocompression bonding, and metal solder bonding.
In a particular embodiment, the second bond structure 222 is, for example, a single layer composed of germanium, or a stack composed of aluminum and germanium. The thickness of the second bond structure 222 is, for example, 1 micron.
As shown in fig. 4k, a groove 2211 is formed on the first surface of the second substrate 221.
In this step, a resist layer is formed on the first surface of the second substrate 221, the resist layer is patterned using a photolithography process to form a resist mask, and the second substrate 221 is etched through the resist mask to form the groove 2211.
As shown in fig. 4l, the device chip 210 and the cap chip 220 are bonded.
In this step, the first surface of the second substrate 221 is opposite to the second conductive layer 215, the device chip 210 and the cap chip 220 are bonded at a high temperature through the first bonding structure 216a and the second bonding structure 222, and at the high temperature, the first bonding structure 216a (aluminum) and the second bonding structure 222 (germanium) are melted with each other, so that the device chip 210 and the cap chip 210 are bonded with each other to form a sealed cavity, which facilitates control of air pressure in the cavity and simultaneously prevents the structure inside the inertial sensor from being affected by the external environment to cause poor working stability.
As shown in fig. 4m, at least a portion of the second substrate 221 is removed, exposing the second pressure point 216 b; and removing at least a portion of the second conductive layer 215 to form a separated first pressure point 215 b.
In this step, the second pressure point 216b (aluminum layer) is used as a hard mask to etch and form the first pressure point 215 b.
The second pressure point 216b is electrically connected to the first conductive layer 213 through the first pressure point 215b, and the second pressure point 216b is used for subsequent package wire bonding.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (27)
1. A method of making an inertial sensor, the method comprising:
forming a first dielectric layer and a first conductive layer on a first substrate;
forming a first opening in the first conductive layer to expose a portion of the surface of the first dielectric layer;
forming a protective layer on the first conductive layer, wherein the protective layer covers a part of the first conductive layer, the side wall of the first opening and the surface of the first dielectric layer exposed by the first opening;
forming a second dielectric layer with a second opening on part of the first conductive layer and part of the protective layer;
forming a second conductive layer on the second dielectric layer, wherein the second conductive layer fills the second opening;
forming a first bonding structure on the second conductive layer;
patterning the second conductive layer to form a third opening;
removing part of the second medium layer through the third opening to form a cavity and a movable mass block;
and removing the first conductive layer in the cavity and the protective layer exposed from the surface of the first dielectric layer.
2. A method of manufacturing an inertial sensor according to claim 1, wherein the protective layer is absent from the cavity outside the region enclosed by the cavity before the first conductive layer in the cavity and the protective layer exposed from the surface of the first dielectric layer are removed.
3. The method of claim 1, wherein the protective layer is absent from the routing and pad regions of the first conductive layer outside the region enclosed by the cavity prior to removing the first conductive layer in the cavity and the protective layer exposed from the surface of the first dielectric layer.
4. A method of manufacturing an inertial sensor according to claim 2 or 3, wherein the protective layer is not present between the contact surfaces of the second conductive layer and the first conductive layer within the region enclosed by the cavity before the protective layer exposed on the surfaces of the first conductive layer and the first dielectric layer in the cavity is removed.
5. The method of manufacturing an inertial sensor according to claim 1, wherein the protective layer, the first conductive layer and the second conductive layer are made of the same material.
6. The method of manufacturing an inertial sensor according to claim 1, wherein the material of the protective layer, the first conductive layer and the second conductive layer is polysilicon.
7. The method of manufacturing an inertial sensor according to claim 1, wherein a thickness ratio of the first conductive layer to the protective layer is 10:1 to 50: 1.
8. The method of manufacturing an inertial sensor according to claim 1, wherein a thickness ratio of the second conductive layer to the protective layer is 200:1 to 1000: 1.
9. The method of claim 1, wherein the protective layer has a thickness of 0.02 to 0.06 μm.
10. The method of manufacturing an inertial sensor according to claim 1, wherein the first conductive layer has a thickness of 0.4 to 1.2 μm.
11. The method of manufacturing an inertial sensor according to claim 1, wherein the thickness of the second conductive layer is 15 to 30 μm.
12. A method of manufacturing an inertial sensor according to claim 1, wherein the first conductive layer and the protective layer are deposited at a temperature of 520 to 620 degrees celsius.
13. The method of claim 1, wherein the first conductive layer in the cavity and the exposed protective layer on the surface of the first dielectric layer are removed by dry etching.
14. A method of manufacturing an inertial sensor according to claim 13, characterized in that CF is used4And O2And carrying out dry etching on the protective layer.
15. The method of claim 1, wherein a portion of the second dielectric layer is removed through the third opening by a hydrofluoric acid vapor fumigation process to form a cavity and a movable mass.
16. The method of manufacturing an inertial sensor according to claim 1, further comprising:
forming a second bonding structure on the first surface of the second substrate;
forming a groove on a first surface of a second substrate;
and bonding the first bonding structure of the first substrate and the second bonding structure of the second substrate at high temperature to form a sealed cavity.
17. An inertial sensor, characterized in that the inertial sensor comprises:
a first substrate;
a first dielectric layer located on the first substrate;
the first conducting layer is positioned on the first dielectric layer, a first opening is formed in the first conducting layer, and a part of the surface of the first dielectric layer is exposed out of the first opening;
a protective layer on a portion of the first conductive layer;
a second dielectric layer on the first conductive layer, the second dielectric layer having a cavity therein;
a patterned second conductive layer on the second dielectric layer, the second conductive layer in the cavity being a movable mass;
a first bonding structure on the second conductive layer;
wherein the protective layer within the area enclosed by the cavity is only located between the contact surfaces of the first conductive layer and the second conductive layer.
18. An inertial sensor according to claim 17, characterised in that the cavity encloses an area free of the protective layer.
19. An inertial sensor according to claim 17, characterised in that the cavity encloses an area with the protective layer outside, and the protective layer does not cover the wiring and pressure point areas of the first conductive layer.
20. An inertial sensor according to claim 17, characterised in that the material of the protective layer, the first conductive layer and the second conductive layer is the same.
21. An inertial sensor according to claim 17, characterised in that the material of the protective layer, the first conductive layer and the second conductive layer is polysilicon.
22. An inertial sensor according to claim 17, characterised in that the ratio of the thickness of the first conductive layer to the protective layer is 10:1 to 50: 1.
23. An inertial sensor according to claim 17, characterized in that the ratio of the thickness of the second conductive layer to the protective layer is 200:1 to 1000: 1.
24. An inertial sensor according to claim 17, characterised in that the protective layer has a thickness of 0.02 to 0.06 microns.
25. An inertial sensor according to claim 17, characterised in that the first conductive layer has a thickness of 0.4 to 1.2 microns.
26. An inertial sensor according to claim 17, characterised in that the thickness of the second conductive layer is 15-30 microns.
27. The inertial sensor of claim 17, further comprising:
a second substrate;
a second bonding structure located on the first surface of the second substrate;
a groove located on the first surface of the second substrate;
the first surface of the second substrate is opposite to the second conducting layer, the second bonding structure is located on the first bonding structure, and the first substrate and the second substrate are enclosed to form a sealed cavity.
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| CN116909092A (en) * | 2023-09-07 | 2023-10-20 | 苏州敏芯微电子技术股份有限公司 | Inertial sensor and manufacturing method thereof |
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| CN116909092A (en) * | 2023-09-07 | 2023-10-20 | 苏州敏芯微电子技术股份有限公司 | Inertial sensor and manufacturing method thereof |
| CN116909092B (en) * | 2023-09-07 | 2023-11-17 | 苏州敏芯微电子技术股份有限公司 | Inertial sensor and manufacturing method thereof |
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