MEMS device having a suspended diaphragm and manufacturing process thereof

• US 9,233,834 B2
• Filed: 06/26/2014
• Issued: 01/12/2016
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Faralli, Dino, Ferrari, Paolo, Castoldi, Laura Maria
• Primary Examiner(s): WOJCIECHOWICZ, EDWARD JOSEPH
• Application Number:
  US14/316,504
• Publication Number:
  US 20150001651A1
• Time in Patent Office: 565 Days
• Field of Search: 257/417
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2207/115 Protective layers applied directly to the device before packaging
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: B81B 7/0016 Protection against shocks or vibrations, e.g. vibration damping
• CPC Class Codes: B81B 7/0058 for protecting against damages due to external chemical or mechanical influences, e.g. shocks or vibrations
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B81C 3/00 Assembling of devices or systems from individually processed components
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48145 the bodies being stacked
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

A MEMS device wherein a die of semiconductor material has a first face and a second face. A diaphragm is formed in or on the die and faces the first surface. A cap is fixed to the first face of the die and has a hole forming a fluidic path connecting the diaphragm with the outside world. A closing region, for example a support, a second cap, or another die, is fixed to the second face of the die. The closing region forms, together with the die and the cap, a stop structure configured to limit movements of the suspended region in a direction perpendicular to the first face.

Claims

1. A MEMS device comprising:

a first die of semiconductor material having a first face and a second face, the first die having;

a suspended region;

a trench;

a peripheral region that is separated from the suspended region by the trench;

elastic elements located in the trench and elastically coupling the suspended region to the peripheral region;

a diaphragm formed in the first die or coupled to the suspended region and facing the first face; and

a stop structure on the second face;

a first cap coupled to the first die, facing the first face of the first die and overlying the first die at least over the suspended region and the trench;

a fluidic path that fluidly couples the diaphragm to an environment external to the device; and

a closing body fixed to the second face of the first die and facing the stop structure, the closing body and the stop structure configured to limit movement of the suspended region above a threshold value in a direction perpendicular to the first face.

2. The MEMS device according to claim 1, wherein the suspended region, the peripheral region, and the elastic elements of the first die are monolithic.

3. The MEMS device according to claim 1, wherein the closing body is at least one of a second die of semiconductor material, a rigid body, and a printed-circuit board.

4. The MEMS device according to claim 1, wherein:

the peripheral region has a first thickness and the suspended region has a second thickness smaller than the first thickness,

an air gap extends underneath the suspended region, and

the stop structure further comprises a stem extending from the suspended region into the air gap, the stem having an first area in a plane parallel to the first face of the first body and being spaced apart from the closing body, the suspended region having a second area that is greater than the first area of the stem.

5. The MEMS device according to claim 3, wherein the stem is monolithic with the suspended region.

6. The MEMS device according to claim 1, wherein the peripheral region has first thickness and the suspended region has a second thickness, the first and second thicknesses being substantially the same, the MEMS device further comprising a spacer layer arranged between the peripheral region and the closing body that delimits a space between the first die and the closing body.

7. The MEMS device according to claim 1, comprising a through hole that extends through the first cap.

8. The MEMS device according to claim 1, comprising a packaging material laterally enclosing portions of the first die and the first cap.

9. The MEMS device according to claim 8, wherein a support is fixed to the closing body, portions of the closing body being surrounded by the packaging material and including a processing circuit.

10. The MEMS device according to claim 1, forming at least one of a pressure sensor, a humidity sensor, a flow sensor, an environmental sensor, a gas sensor, a microfluidic device, and a miniaturized microphone.

11. An apparatus comprising:

a processing unit;

an input/output interface coupled to the processing unit;

a memory device coupled to the processing unit; and

a MEMS device including;

a semiconductor die having a first face and a second face, the semiconductor die having;

a suspended region;

a peripheral region;

elastic elements that elastically couple the suspended region to the peripheral region; and

a diaphragm formed in the semiconductor die or coupled to the suspended region and facing the first face;

a first cap coupled to the semiconductor die and forming a cavity between the first face of the semiconductor die and the first cap, the cavity located above the diaphragm, the first cap including an opening that places the cavity in fluid communication with an environment external to the MEMS device;

a closing body fixed to the second face of the semiconductor die; and

a stop structure configured to limit movement of the suspended region above a threshold value in a direction perpendicular to the first face, the stop structure located on the second face of the semiconductor die.

12. The apparatus according to claim 11, wherein the suspended region, the peripheral region, and the elastic elements are monolithic.

13. The apparatus according to claim 11, wherein the peripheral region has a first thickness between the first face to the second face, and the suspended region has a second thickness between the first face to the second face, the second thickness being less than the first thickness.

14. A process for manufacturing a MEMS device, the process comprising:

forming, in a semiconductor die having a first face and a second face, a suspended region and a peripheral region separated by a trench, a stop structure on the second face, wherein the suspended region is elastically coupled to the peripheral region by elastic elements located within the trench, the suspended region supporting a diaphragm facing the first face, and a fluidic path fluidly coupling the diaphragm to an environment external to the device;

fixing a first cap to the semiconductor die so that the first cap faces the first face of the semiconductor die;

fixing a closing body to the second face of the semiconductor die and facing the stop structure, the closing body and the stop structure configured to limit movement of the suspended region above a threshold value in a direction perpendicular to the first face.

15. The process according to claim 14, wherein removing selective portions of the semiconductor die comprises releasing the suspended region and the elastic elements.

16. The process according to claim 14, wherein fixing a first cap comprises forming a composite wafer by fixing a first wafer to a plurality of semiconductor dice on a second wafer, the process further comprising thinning the first wafer, and dicing the composite wafer to obtain a plurality of MEMS sensors.

17. The process according to claim 16, comprising removing selective portions of the second wafer from the first face to define suspended regions and elastic elements prior to fixing the second wafer to the first wafer and forming the stem in the second face of the second wafer prior to dicing the composite wafer.

18. The process according to claim 16, wherein forming the stop structure comprises forming a cavity from the second face of the second wafer under the diaphragm, the cavity being in fluid communication with the trench and laterally surrounding the stem extending from the suspended region.

19. The process according to claim 16, further comprising thinning the second wafer from the second face of the second wafer prior to forming the stem.

20. The process according to claim 16, wherein fixing a closing region comprises fixing a third wafer to the second wafer prior to dicing the composite wafer.

21. The process according to claim 14, comprising:

fixing the closing body to a support; and

forming a package material that encloses, together with the support, the second die, the closing region, the first die, and the cap.