CN111446089B - MEMS switch structure and manufacturing method - Google Patents
MEMS switch structure and manufacturing method Download PDFInfo
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- CN111446089B CN111446089B CN202010170824.9A CN202010170824A CN111446089B CN 111446089 B CN111446089 B CN 111446089B CN 202010170824 A CN202010170824 A CN 202010170824A CN 111446089 B CN111446089 B CN 111446089B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H1/00—Contacts
- H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
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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
- B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
- B81C1/0015—Cantilevers
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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
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
- B81C1/00444—Surface micromachining, i.e. structuring layers on the substrate
- B81C1/00468—Releasing structures
- B81C1/00476—Releasing structures removing a sacrificial layer
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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
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Abstract
The invention discloses a MEMS switch structure, comprising: the control electrode, the first connecting electrode and the second connecting electrode are arranged on the first medium layer, and the conductive support column and the second medium layer are arranged on the first medium layer; when voltage is applied to the control electrode, the cantilever beam is attracted to generate downward elastic deformation, so that the free end of the cantilever beam slides out of the first clamping groove and falls into the second clamping groove to close the switch; when the voltage applied to the control electrode is cancelled, the cantilever beam generates upward elastic recovery under the action of self tensile stress, so that the cantilever beam slides out of the second clamping groove and falls into the first clamping groove to open the switch. The invention can realize the switch with ultra-low power consumption and the circuit function thereof.
Description
Technical Field
The invention relates to the technical field of semiconductor integrated circuits and sensors, in particular to a high-performance low-power-consumption MEMS switch structure and a manufacturing method thereof.
Background
Conventional CMOS circuits typically use MOS transistors to form switches to control the opening and closing of the circuit. However, when the MOS transistor switches are operated, a certain amount of energy is consumed due to gate electrode leakage, channel resistance, and the like, which adversely affects low power consumption control of the circuit, especially, the influence is greater for larger and larger scale circuits.
Disclosure of Invention
The present invention is directed to overcoming the above-mentioned deficiencies of the prior art and to providing a MEMS switch structure and method of manufacture.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a MEMS switch structure comprising:
the first dielectric layer is provided with a control electrode, a first connecting electrode and a second connecting electrode;
the conductive support column and the second dielectric layer are arranged on the first dielectric layer, the lower end of the support column is connected with the second connecting electrode, the upper end of the support column is connected with the conductive cantilever beam, the lower surface of the cantilever beam is provided with a protruding conductive contact, the side surface of the second dielectric layer is provided with a first clamping groove and a second clamping groove which are connected up and down, and the free end of the cantilever beam falls into the first clamping groove when the switch is in an open state;
when a voltage is applied to the control electrode, the cantilever beam is attracted to generate downward elastic deformation, so that the free end of the cantilever beam slides out of the first clamping groove and falls into the second clamping groove, the contact is contacted with the first connecting electrode, and the switch in a closed state is formed; when the voltage applied to the control electrode is cancelled, the cantilever beam generates upward elastic recovery under the action of self tensile stress, so that the free end of the cantilever beam slides out of the second clamping groove and falls into the first clamping groove, and the contact is separated from the first connecting electrode to form a switch in an open state.
Further, the cantilever beam material is a metal material with tensile stress.
Further, the contact is a solid structure with a triangular or inverted trapezoidal cross section.
Furthermore, the contact is of a multilayer structure with a triangular or inverted trapezoidal section, and the multilayer structure is of a spring structure consisting of multiple layers of planar metal patterns and conductive through holes connected among the planar metal patterns of each layer.
Further, the first clamping groove and the second clamping groove are provided with concave arc-shaped groove surfaces.
A method of manufacturing a MEMS switch structure, comprising the steps of:
providing a substrate with a first dielectric layer, and forming a first connecting electrode, a control electrode and a second connecting electrode on the first dielectric layer in parallel;
forming a second dielectric layer on the surface of the first dielectric layer, patterning the second dielectric layer to expose a first connecting electrode, a control electrode and a second connecting electrode on the first dielectric layer, and simultaneously forming a first clamping groove and a second clamping groove which are vertically connected with each other on the vertical side surface of the second dielectric layer facing the first connecting electrode;
forming one to many sacrificial layers on the first dielectric layer, stopping the final surface of the sacrificial layer at the height when the first card slot is partially exposed, forming a conductive contact structure on the sacrificial layer and downwards entering the sacrificial layer, so that the contact corresponds to a position above the first connecting electrode, forming a support pillar structure on the sacrificial layer and downwards entering the sacrificial layer, stopping the bottom of the support pillar on the second connecting electrode, and forming a cantilever beam structure on the final surface of the sacrificial layer, so that one end of the cantilever beam is connected with the support pillar, and the free end of the cantilever beam further extends into the first card slot after being connected with the contact;
and removing the sacrificial layer through a release process to form the switch structure in an open state when the free end of the cantilever beam is clamped in the first clamping groove.
Further, when patterning the second dielectric layer, the method specifically includes:
forming a cavity with two arc-shaped concave side walls which are connected up and down in the second dielectric layer through isotropic etching, and stopping etching on the first dielectric layer to expose the first connecting electrode, the control electrode and the second connecting electrode; the first clamping groove and the second clamping groove are formed by two arc-shaped concave surfaces which are positioned on the side wall of the cavity and are connected up and down.
Further, the cantilever beam is formed to be a metal cantilever beam with tensile stress.
Further, the formed contact is a solid structure with a triangular or inverted trapezoidal cross section, and the forming method specifically comprises the following steps:
forming a sacrificial layer on the first dielectric layer, covering the second dielectric layer with patterns, and then reducing the final surface of the sacrificial layer to the height of one-third to two-thirds of the first clamping groove when the sacrificial layer is exposed by utilizing a back-etching process;
forming a triangular or inverted trapezoidal groove structure which downwards enters the sacrificial layer on the surface of the sacrificial layer, so that the groove is correspondingly positioned above the first connecting electrode;
and filling metal in the groove, and forming the contact structure in the groove.
Further, the formed contact is a multilayer structure with a triangular or inverted trapezoidal section, the multilayer structure is a spring structure formed by multiple layers of planar metal patterns and conductive through holes connected between the metal patterns of each layer, and the forming method specifically comprises the following steps:
sequentially forming a plurality of sacrificial layers on the first dielectric layer, and alternately forming metal patterns and through holes in the sacrificial layers of each layer; the metal patterns in the sacrificial layer at the lowest layer are enabled to have a triangular or inverted trapezoidal cross-sectional structure, the area of each layer of metal patterns from bottom to top is sequentially increased, the two through holes in the upper layer and the lower layer of any layer of metal patterns are respectively arranged on the upper surface and the lower surface of two opposite ends of the layer of metal patterns, the final surface of the sacrificial layer at the uppermost layer is positioned at the height when one third to two thirds of the first clamping groove are exposed, and the multilayer structure is connected with the cantilever beam through one metal pattern or through hole formed in the sacrificial layer at the uppermost layer.
It can be seen from the above technical solutions that the present invention controls the closed and open states of the switch by using the suction force generated by the cantilever beam acting as the switch blade when a voltage is applied and the elastic restoring force of the cantilever beam itself when the voltage is cancelled, and locks the cantilever beam in the two states of the switch by using the first and second slot structures disposed in the vertical direction with respect to the cantilever beam, so that the switch state is maintained by continuously applying the voltage as in the conventional switch when the switch is in the open state, and the magnitude of the applied voltage is reduced by using the locking force of the second slot structure to the cantilever beam when the switch is in the closed state, thereby implementing the switch with ultra-low power consumption and its circuit functions.
Drawings
Fig. 1 is a schematic structural diagram of a MEMS switch according to a preferred embodiment of the invention.
Fig. 2 is a schematic diagram of a spring type contact structure according to a preferred embodiment of the invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In the following detailed description of the embodiments of the present invention, in order to clearly illustrate the structure of the present invention and to facilitate explanation, the structure shown in the drawings is not drawn to a general scale and is partially enlarged, deformed and simplified, so that the present invention should not be construed as limited thereto.
In the following detailed description of the present invention, please refer to fig. 1, in which fig. 1 is a schematic diagram of a MEMS switch structure according to a preferred embodiment of the present invention. Referring to fig. 1, which shows the switch in an open state, a MEMS switch structure of the present invention is disposed on a first dielectric layer 10, and utilizes a MEMS microbridge structure 20 on the first dielectric layer 10 to form a blade structure of the switch.
Please refer to fig. 1. The first dielectric layer 10 is provided with a first connecting electrode 11 and a second connecting electrode 13 for connecting both ends of a blade of the switch. A control electrode 12 is also provided on the first dielectric layer 10 between the first connection electrode 11 and the second connection electrode 13. The first connection electrode 11, the second connection electrode 13 and the control electrode 12 may further be connected into the control circuit of the switch. The control circuit may employ, for example, a CMOS circuit structure, and knowledge of the CMOS circuit is understood with reference to the prior art.
The surface of the first dielectric layer 10 is provided with a MEMS micro-bridge structure 20 having a cantilever structure, which includes a conductive support pillar 22 and a conductive cantilever 21 connected to the upper end of the support pillar 22. The cantilever beam 21 (equivalent to the bridge surface of the MEMS microbridge structure 20) serves as a knife structure of the switch, and the supporting column 22 serves as a connecting structure between a fixed end of the knife and the control circuit, and is used for supporting the cantilever beam 21, so that the cantilever beam 21 is suspended on the first dielectric layer 10.
The support pillars 22 are vertically arranged on the first medium layer 10; the lower end of the supporting column 22 is connected to the second connecting electrode 13, and the upper end of the supporting column 22 is connected to the fixed end of the cantilever beam 21.
The structure of the support posts 22 may be the same as or similar to the structure of the support posts 22 in the conventional MEMS microbridge structure 20. Can be understood with reference to the prior art.
The cantilever beam 21 is provided on a lower surface thereof with a conductive contact 23 protruding downward, and the contact 23 is located at a position corresponding to a position above the first connection electrode 11 and spaced apart from the first connection electrode 11 by a certain distance. The contact 23 is preferably disposed on a side proximate to the free end 211 of the cantilever beam 21, but at a distance from the end of the free end 211 of the cantilever beam 21. The position of the contact 23 on the cantilever beam 21 and the suspension height range of the lower end of the contact 23 are ensured to be at a proper position where the contact 23 can form effective contact with the first connecting electrode 11 when the cantilever beam 21 is forced to bend and deform downwards.
A second dielectric layer 30 is also arranged on the surface of the first dielectric layer 10; the second dielectric layer 30 faces at least the free end 211 of the cantilever beam 21 and is disposed on one side thereof. The side surface of the second dielectric layer 30 facing the free end 211 of the cantilever beam 21 is provided with a first slot 31 and a second slot 32 in the vertical direction, and the first slot 31 and the second slot 32 are connected up and down on the side surface of the second dielectric layer 30. The free end 211 of the cantilever beam 21 falls into the first card slot 31 when the switch is in the on state; the cantilever beam 21 is made of a metal material having a tensile stress, and may be made of, for example, platinum metal having a tensile stress. When the free end 211 of the cantilever beam 21 falls into the first slot 31, the free end 211 of the cantilever beam 21 will abut against the inner wall of the first slot 31 under the action of tensile stress, so as to be locked by the first slot 31. Similarly, when the cantilever beam 21 slides on the side surface of the second dielectric layer 30 due to elastic deformation (bending), and falls into the second slot 32 from the first slot 31, the free end 211 of the cantilever beam 21 can also abut against the inner wall of the second slot 32 under the action of tensile stress, so as to be locked by the second slot 32.
The contact 23 is disposed on the cantilever beam 21 at a position that ensures that when the free end 211 of the cantilever beam 21 falls into the first card slot 31 or the second card slot 32, the contact 23 and the first card slot 31 or the second card slot 32 will not interfere with each other.
The first dielectric layer 10 and the second dielectric layer 30 may be formed using conventional dielectric materials.
In a preferred embodiment, the first and second locking grooves 31 and 32 may have a concave arc-shaped groove surface structure in the vertical direction, as shown in fig. 1. At this time, a state of mutual engagement is formed between the arc-shaped groove surface of the first card slot 31 and the arc-shaped groove surface of the second card slot 32, so that a sharp protrusion 33 toward the free end 211 of the cantilever beam 21 is formed at the engagement position of the arc-shaped groove surface of the first card slot 31 and the arc-shaped groove surface of the second card slot 32, so that the free end 211 of the cantilever beam 21 can conveniently fall into the second card slot 32 (the first card slot 31) to be locked when sliding out of the first card slot 31 (the second card slot 32).
As an alternative embodiment, the contact 23 may take the form of a solid (solid) structure having a triangular or inverted trapezoidal cross-section, as shown in fig. 1. Thus, the lower end of the contact 23 is formed in a sharp shape, and the contact 23 can be easily separated from the first connection electrode 11 by the stress of the cantilever beam 21 when the switch is turned on.
The contact 23 may be made of the same metal material as the cantilever beam 21. Or may be formed using other conventional switch contact materials.
Please refer to fig. 2. As a preferred embodiment, the contact 23 may also employ a multi-layer structure 231 and 237 having a triangular or inverted trapezoidal cross-section. The multilayer structure 231-237 may adopt a spring structure composed of multiple layers of planar metal patterns 231, 233, 235, and 237 and conductive vias 232, 234, and 236 connected between the layers of planar metal patterns 231, 233, 235, and 237.
In this spring structure, the metal pattern 231 of the lowermost layer may have a triangular or inverted trapezoidal cross section, and the metal patterns 233, 235, and 237 of the respective layers located above the metal pattern 231 of the lowermost layer are sequentially increased in area, so that the overall multi-layer structure constituting the spring may have a triangular or inverted trapezoidal outer shape.
Meanwhile, two through holes for connection, which are positioned on the upper layer and the lower layer of any metal pattern, are respectively arranged on the upper surface and the lower surface of two opposite end parts of the metal pattern. For example, the first via 232 disposed above the lowermost metal pattern (first metal pattern) 231 may be located at the left end of the lowermost metal pattern 231, and the upper end of the first via 232 is connected to the left end of the second metal pattern 233; the second via hole 234 formed on the second metal pattern 233 is located at the right end of the second metal pattern 233, and the upper end of the second via hole 234 is connected to the right end of the third metal pattern 235; the third via 236 is located at the left end of the third layer metal pattern 235, and the upper end of the third via 236 is connected to the left end of the fourth layer metal pattern 237.
Thus, the metal patterns 231, 233, 235, and 237 of the respective layers are formed in an end-to-end configuration through a series of through holes 232, 234, and 236 as viewed from the direction of the drawing, thereby forming a spring structure. The metal pattern 231 at the lowermost layer is suspended, and the metal pattern 237 at the uppermost layer is connected and fixed to the lower surface of the cantilever beam 21. Alternatively, the metal pattern 237 at the uppermost layer may be integrated with the cantilever beam 21, i.e., the uppermost layer of the spring structure is a through hole 236 structure, and the upper end of the through hole 236 is connected to the lower surface of the cantilever beam 21 for fixing. In this way, when the lowermost metal pattern 231 is subjected to a vertical compressive or tensile force, since the metal patterns 233, 235, and 237 and the through holes 232, 234, and 236 (excluding the metal pattern or the through hole connected to the cantilever beam 21) on the upper layer are all in a suspended state, a certain amount of contraction or extension (deformation) is generated under the compressive or tensile force, and therefore, when the switch is closed and the lower end of the contact 23 is pressed against the surface of the first connecting electrode 11, even if the cantilever beam 21 fluctuates up and down to some extent due to the need to find a locking point in the second engaging groove 32, the lower end of the contact 23 can be ensured to effectively contact the surface of the first connecting electrode 11.
The layers of metal patterns 231, 233, 235, and 237 in the contact 23 may be formed using the same metal material as the cantilever beam 21. Or may be formed using other conventional switch contact materials. The vias in the contacts 23 may be filled with the same metallic material as the cantilever beam 21. Or may be formed using other conventional via metal materials.
The working principle of the switch of the invention is that, in a normal state, the switch is in an open state, the cantilever beam 21 is in a certain tensile stress state (namely in a certain elastic bending state), and the free end 211 of the cantilever beam 21 falls into the first slot 31 and is restrained by, for example, an arc-shaped inner wall of the first slot 31 and locked under the action of the tensile stress.
When the switch needs to be closed, a certain voltage is applied to the control electrode 12 below the cantilever beam 21, the cantilever beam 21 is attracted by the action of the electric field, and elastic deformation approaching the control electrode 12 downwards is generated, so that the free end 211 of the cantilever beam 21 slides out of the first clamping groove 31 and falls into the second clamping groove 32 due to the stress, and a locking point between the free end and the inner wall of the clamping groove is found in the second clamping groove 32 under the combined action of the stress and the voltage. In the process, the contact 23 will be driven to move downwards until an effective contact with the first connecting electrode 11 occurs, turning the switch on and forming a switch in a closed state. At this time, the locking force of the second locking groove 32 to the cantilever beam 21 can be utilized to reduce the voltage applied to the control electrode 12, and the purpose of reducing consumption can be achieved only by overcoming the restoring force of the cantilever beam 21.
When the switch needs to be turned on, the voltage applied to the control electrode 12 is cancelled, the cantilever beam 21 generates upward elastic recovery under the action of self tensile stress due to the fact that the attraction effect generated by the electric field is lost, so that the free end 211 of the cantilever beam 21 slides out of the second clamping groove 32 and falls into the first clamping groove 31 and is locked by the first clamping groove 31, and the contact 23 is separated from the first connecting electrode 11 under the driving of the rising of the cantilever beam 21, so that the switch in the on state is formed.
As another alternative, an auxiliary electrode opposite to the control electrode 12 may be further disposed above the cantilever beam 21, so that when the switch needs to be opened, the cantilever beam 21 is provided with the necessary attraction force by applying a proper voltage to the auxiliary electrode, so that the cantilever beam 21 can be flexibly rebounded to fall into the second card slot 32 to be locked under the action of the self elastic restoring force by the attraction force generated by the smaller voltage from the auxiliary electrode. At this time, the voltage applied to the auxiliary electrode can be canceled.
In addition, when the auxiliary electrode is present, the proper self-stress magnitude required when the cantilever beam 21 falls into the first and second slots 31 and 32, respectively, can be adjusted by adjusting the height of the supporting column 22, the length of the cantilever beam 21, and the like.
A method for fabricating a MEMS switch structure according to the present invention is described in detail with reference to fig. 1.
A MEMS switch structure fabrication method of the present invention can be used to fabricate a MEMS switch structure such as the solid (solid) structure contact 23 of fig. 1 having a triangular or inverted trapezoidal cross-section, and can include the steps of:
firstly, a substrate with a first dielectric layer 10 is provided, a first connecting electrode 11, a control electrode 12 and a second connecting electrode 13 can be formed on the first dielectric layer 10 in parallel by adopting a CMOS conventional process, the first connecting electrode 11, the control electrode 12 and the second connecting electrode 13 are isolated by the first dielectric layer 10, and the formed first connecting electrode 11, the control electrode 12 and the second connecting electrode 13 are connected with a CMOS switch control circuit on the substrate.
Next, a second dielectric layer 30 is deposited on the surface of the first dielectric layer 10.
Then, the second dielectric layer 30 is etched to form a cavity in the second dielectric layer 30 corresponding to the areas where the first connection electrode 11, the control electrode 12, and the second connection electrode 13 are located, and the etching is stopped on the first dielectric layer 10 to expose the first connection electrode 11, the control electrode 12, and the second connection electrode 13. A first cavity with an arc-shaped concave side wall is formed in the second dielectric layer 30 through isotropic etching; then, the side wall of the first cavity is protected, and a second cavity with an arc-shaped concave side wall is formed in the second dielectric layer 30 below the first cavity continuously through isotropic etching, and the etching of the second cavity is stopped on the first dielectric layer 10, so that the first connection electrode 11, the control electrode 12 and the second connection electrode 13 are exposed. The first cavity and the second cavity formed in this way are connected up and down, and a first clamping groove 31 and a second clamping groove 32 for locking the cantilever beam 21 can be formed by two arc-shaped concave surfaces respectively positioned on the side walls of the first cavity and the second cavity.
Since the first and second locking grooves 31 and 32 for locking the cantilever beam 21 are located at the position facing the free end 211 of the cantilever beam 21, the pattern of the second dielectric layer 30 located at the extra portion outside the effective locking region can be removed or retained without affecting other processes.
Then, a sacrificial layer is deposited on the first dielectric layer 10, and the second dielectric layer 30 is covered by a pattern.
Then, the final surface of the sacrificial layer is lowered to a height at which the first card slot 31 on the side surface of the second dielectric layer 30 is partially exposed by using the etching back process. For example, the exposed height of the first card slot 31 may be one-third to two-thirds. Preferably, the exposed height of the first card slot 31 may be two fifths to three fifths. Optimally, the exposed height of the first card slot 31 may be half, and it should be noted that the exposed portion of the first card slot 31 does not need to be very precise, and the final surface of the sacrificial layer is located approximately in the middle area of the first card slot 31 to meet the usage requirement.
Next, a triangular or inverted trapezoidal first trench structure is formed on the surface of the sacrificial layer by photolithography and etching processes, and the first trench is located at a position corresponding to the position above the first connection electrode 11.
And, using photolithography and etching processes, a second trench structure is formed on the surface of the sacrifice layer down into the sacrifice layer, and the bottom of the second trench is stopped on the second connection electrode 13.
Next, a metal layer is deposited on the surface of the sacrificial layer, and the first trench and the second trench are filled, thereby forming a contact 23 structure having a triangular or inverted trapezoidal cross section in the first trench, and a support pillar 22 structure connecting the second connection electrode 13 in the second trench.
Then, the metal layer is patterned, and a cantilever beam 21 is formed on the surface of the sacrificial layer, wherein one end of the cantilever beam is connected with the support pillar 22, the other end of the cantilever beam is a free end 211, and the free end 211 further extends into the first slot 31 after being connected with the contact 23, so as to serve as a knife structure of the switch. The contact 23, the supporting column 22 and the cantilever beam 21 are made of the same metal material.
It should be noted that when the cantilever beam 21 is formed by patterning the metal layer, the free end 211 of the cantilever beam 21 is separated from the inner wall of the first card slot 31.
The distance from the lower end of the contact 23 to the first connection electrode 11, and the position of the contact 23 on the cantilever beam 21, may be determined by model calculation or experiments according to the set height of the cantilever beam 21 and the position thereof when the contact is bent to fall into the second card slot 32.
Finally, the sacrificial layer is removed by a release process, so as to form the switch structure in an open state when the free end 211 of the cantilever beam 21 is clamped in the first clamping groove 31 and locked.
As an example, the material of the second dielectric layer 30 may be a C-based material, and the material of the sacrificial layer may be a Si-based material. Or, the material of the second dielectric layer 30 may be Si-based material, and the material of the sacrificial layer may be C-based material. I.e. a larger etching selection ratio between the second dielectric layer material and the sacrificial layer material should be satisfied.
The following describes in detail a method for manufacturing a MEMS switch structure having contacts 23(231 and 237) with triangular or inverted trapezoidal cross-section according to the present invention with reference to fig. 1 and 2.
The invention relates to a manufacturing method of a MEMS switch structure with a triangular or inverted trapezoidal section multilayer spring structure contact 23, which comprises the following steps:
firstly, a substrate with a first dielectric layer 10 is provided, a first connecting electrode 11, a control electrode 12 and a second connecting electrode 13 can be formed on the first dielectric layer 10 in parallel by adopting a CMOS conventional process, the first connecting electrode 11, the control electrode 12 and the second connecting electrode 13 are isolated by the first dielectric layer 10, and the formed first connecting electrode 11, the control electrode 12 and the second connecting electrode 13 are connected with a CMOS switch control circuit on the substrate.
Next, a second dielectric layer 30 is deposited on the surface of the first dielectric layer 10.
Then, the second dielectric layer 30 is etched to form a cavity in the second dielectric layer 30 corresponding to the areas where the first connection electrode 11, the control electrode 12, and the second connection electrode 13 are located, and the etching is stopped on the first dielectric layer 10 to expose the first connection electrode 11, the control electrode 12, and the second connection electrode 13. First, a first cavity with an arc-shaped concave side wall is formed in the second dielectric layer 30 through isotropic etching; then, the side wall of the first cavity is protected, and a second cavity with an arc-shaped concave side wall is formed in the second dielectric layer 30 below the first cavity continuously through isotropic etching, and the etching of the second cavity is stopped on the first dielectric layer 10, so that the first connection electrode 11, the control electrode 12 and the second connection electrode 13 are exposed. The first cavity and the second cavity formed in this way are connected up and down, and a first clamping groove 31 and a second clamping groove 32 for locking the cantilever beam 21 can be formed by two arc-shaped concave surfaces respectively positioned on the side walls of the first cavity and the second cavity.
Since the first and second locking grooves 31 and 32 for locking the cantilever beam 21 are located at the position facing the free end 211 of the cantilever beam 21, the pattern of the second dielectric layer 30 located at the extra portion outside the effective locking region can be removed or retained without affecting other processes.
Next, a first sacrificial layer is deposited on the first dielectric layer 10, so that the surface of the first sacrificial layer is located at a thickness position where the middle of the second card slot 32 is exposed.
Next, a first layer trench structure of a triangular shape or an inverted trapezoidal shape is formed on the surface of the first layer sacrificial layer by using photolithography and etching processes, and the first layer trench is located at a position corresponding to the position above the first connection electrode 11. Then, the first layer trench is metal-filled, and a first layer (lowermost layer) metal pattern 231 is formed in the first layer trench.
Next, a second sacrificial layer is deposited on the first sacrificial layer, and a first via 232 is formed in the second sacrificial layer by using photolithography and etching processes, stopping on the first metal pattern 231, and locating the first via 232 at the left end position of the first metal pattern 231 shown in fig. 2. Then, the first via 232 is via-metal filled.
The vias formed may be angled via structures (as shown in fig. 2) or conventional vertical via structures.
The steps are repeated, and the second metal pattern 233, the second through hole 234, the third metal pattern 235 and the third through hole 236 are respectively formed in each sacrificial layer on the first through hole 232 through step-by-step deposition of the sacrificial layers, and finally the fourth metal pattern 237 is formed on the third through hole 236, so that the spring contact 23 with the four-layer structure is formed. In the above process, the areas of the first layer metal pattern 231 to the fourth layer metal pattern 237 are sequentially increased; meanwhile, the left end of the second metal pattern 233 is connected to the first via 232, the second via 234 is connected to the right end of the second metal pattern 233, the right end of the third metal pattern 235 is connected to the second via 234, the third via 236 is connected to the left end of the third metal pattern 235, and the left end of the fourth metal pattern 237 is connected to the third via 236. The contact 23 structure having four metal patterns 231, 233, 235, and 237 as shown in fig. 2 is finally formed.
Wherein, when forming the fourth metal pattern 237 in the uppermost sacrificial layer, the deposited uppermost sacrificial layer covers the second dielectric layer 30 pattern; next, the final surface of the uppermost sacrificial layer is lowered to the height of the exposed portion of the first card slot 31 on the side surface of the second dielectric layer 30 by using the etching back process. For example, the exposed height of the first card slot 31 may be one-third to two-thirds. Preferably, the exposed height of the first card slot 31 may be two fifths to three fifths. Optimally, the exposed height of the first card slot 31 may be about half. A fourth metal pattern trench is formed in the uppermost sacrificial layer, and a second trench is formed on the uppermost sacrificial layer down to stop on the second connection electrode 13.
Next, a metal layer is deposited on the surface of the uppermost sacrificial layer, and the fourth metal pattern trench and the second trench are filled, so that a fourth metal pattern 237 is formed in the fourth metal pattern trench, the contact 23 of the four-layer spring structure having a triangular or inverted trapezoidal cross section is completed, and the supporting post 22 connected to the second connection electrode 13 is formed in the second trench.
Then, the cantilever beam 21 is formed by patterning the metal layer, and the free end 211 of the cantilever beam 21 is clamped in the first clamping groove 31 to form the switch structure in the open state when locked by removing each sacrificial layer through a release process.
The above description is only a preferred embodiment of the present invention, and the embodiments are not intended to limit the scope of the present invention, so that all equivalent structural changes made by using the contents of the specification and the drawings of the present invention should be included in the scope of the present invention.
Claims (10)
1. A MEMS switch structure, comprising:
the first dielectric layer is provided with a control electrode, a first connecting electrode and a second connecting electrode;
the conductive support column and the second dielectric layer are arranged on the first dielectric layer, the lower end of the support column is connected with the second connecting electrode, the upper end of the support column is connected with the conductive cantilever beam, the lower surface of the cantilever beam is provided with a protruding conductive contact, the side surface of the second dielectric layer is provided with a first clamping groove and a second clamping groove which are connected up and down, and the free end of the cantilever beam falls into the first clamping groove when the switch is in an open state;
when a voltage is applied to the control electrode, the cantilever beam is attracted to generate downward elastic deformation, so that the free end of the cantilever beam slides out of the first clamping groove and falls into the second clamping groove, the contact is contacted with the first connecting electrode, and the switch in a closed state is formed; when the voltage applied to the control electrode is cancelled, the cantilever beam generates upward elastic recovery under the action of self tensile stress, so that the free end of the cantilever beam slides out of the second clamping groove and falls into the first clamping groove, and the contact is separated from the first connecting electrode to form a switch in an open state.
2. The MEMS switch structure of claim 1, wherein the cantilever beam material is a metallic material having a tensile stress.
3. The MEMS switch structure of claim 1, wherein the contact is a solid structure having a triangular or inverted trapezoidal cross-section.
4. The MEMS switch structure of claim 1, wherein the contact is a multi-layered structure having a triangular or inverted trapezoidal cross-section, the multi-layered structure being a spring structure composed of a plurality of layers of planar metal patterns and conductive vias connecting between the layers of the planar metal patterns.
5. The MEMS switch structure of claim 1, wherein the first and second card slots have concave arcuate slot surfaces.
6. A method of manufacturing a MEMS switch structure according to claim 1, comprising the steps of:
providing a substrate with a first dielectric layer, and forming a first connecting electrode, a control electrode and a second connecting electrode on the first dielectric layer in parallel;
forming a second dielectric layer on the surface of the first dielectric layer, patterning the second dielectric layer to expose a first connecting electrode, a control electrode and a second connecting electrode on the first dielectric layer, and simultaneously forming a first clamping groove and a second clamping groove which are vertically connected with each other on the vertical side surface of the second dielectric layer facing the first connecting electrode;
forming one to many sacrificial layers on the first dielectric layer, stopping the final surface of the sacrificial layer at the height when the first card slot is partially exposed, forming a conductive contact structure on the sacrificial layer and downwards entering the sacrificial layer, so that the contact corresponds to a position above the first connecting electrode, forming a support pillar structure on the sacrificial layer and downwards entering the sacrificial layer, stopping the bottom of the support pillar on the second connecting electrode, and forming a cantilever beam structure on the final surface of the sacrificial layer, so that one end of the cantilever beam is connected with the support pillar, and the free end of the cantilever beam further extends into the first card slot after being connected with the contact;
and removing the sacrificial layer through a release process to form the switch structure in an open state when the free end of the cantilever beam is clamped in the first clamping groove.
7. The method for manufacturing the MEMS switch structure according to claim 6, wherein the patterning of the second dielectric layer specifically includes:
forming a cavity with two arc-shaped concave side walls which are connected up and down in the second dielectric layer through isotropic etching, and stopping etching on the first dielectric layer to expose the first connecting electrode, the control electrode and the second connecting electrode; the first clamping groove and the second clamping groove are formed by two arc-shaped concave surfaces which are positioned on the side wall of the cavity and are connected up and down.
8. The method of fabricating a MEMS switch structure as defined by claim 6 wherein the cantilever beam formed is a metallic cantilever beam with tensile stress.
9. The method for manufacturing a MEMS switch structure according to claim 6, wherein the contact is formed as a solid structure having a triangular or inverted trapezoidal cross section, and the method specifically includes:
forming a sacrificial layer on the first dielectric layer, covering the second dielectric layer with patterns, and then reducing the final surface of the sacrificial layer to the height of one-third to two-thirds of the first clamping groove when the sacrificial layer is exposed by utilizing a back-etching process;
forming a triangular or inverted trapezoidal groove structure which downwards enters the sacrificial layer on the surface of the sacrificial layer, so that the groove is correspondingly positioned above the first connecting electrode;
and filling metal in the groove, and forming the contact structure in the groove.
10. The method of claim 6, wherein the contact is formed as a multi-layer structure having a triangular or inverted trapezoidal cross-section, and the multi-layer structure is a spring structure composed of a plurality of planar metal patterns and conductive vias connecting between the metal patterns, and the method specifically comprises:
sequentially forming a plurality of sacrificial layers on the first dielectric layer, and alternately forming metal patterns and through holes in the sacrificial layers of each layer; the metal patterns in the sacrificial layer at the lowest layer are enabled to have a triangular or inverted trapezoidal cross-sectional structure, the area of each layer of metal patterns from bottom to top is sequentially increased, the two through holes in the upper layer and the lower layer of any layer of metal patterns are respectively arranged on the upper surface and the lower surface of two opposite ends of the layer of metal patterns, the final surface of the sacrificial layer at the uppermost layer is positioned at the height when one third to two thirds of the first clamping groove are exposed, and the multilayer structure is connected with the cantilever beam through one metal pattern or through hole formed in the sacrificial layer at the uppermost layer.
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