Process for fabricating a micromechanical structure made of silicon carbide including at least one cavity

Patent metadata

Field	Value
Publication number	US-10472230-B2
Application number	US-201716091384-A
Country	US
Kind code	B2
Filing date	Apr 6, 2017
Priority date	Apr 6, 2016
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

A process for fabricating a micromechanical structure made of silicon carbide including a cavity, from a stack including a first silicon-carbide layer and a silicon layer on the first silicon-carbide layer, the process including shaping the silicon layer so as to form a discrete silicon structure on the first silicon-carbide layer. The process further includes, after the shaping of the silicon layer, a carbonization to initiate the removal of the discrete silicon structure; depositing a second silicon-carbide layer; and an annealing step, the discrete silicon structure being entirely removed at the end of the annealing.

First claim

The invention claimed is:

1. A process for fabricating a micromechanical structure made of silicon carbide comprising a cavity, from a stack including a first silicon carbide layer and a silicon layer on the first silicon carbide layer, said process comprising:
a step of shaping the silicon layer so as to form a discrete silicon structure on the first silicon carbide layer, and after the step of shaping the silicon layer:
a carbonization step initiating the removal of the discrete silicon structure;
a step of depositing a second silicon carbide layer;
an annealing step;

the discrete silicon structure being entirely removed at the end of the annealing step.

2. The process according to claim 1 , wherein the step of shaping the silicon layer is directly followed by a second annealing step.

3. The process according to claim 1 , further comprising a thermal transition step between the carbonization step and the step of depositing the second silicon carbide layer during which the temperature changes from a first temperature equal to the temperature of the carbonization step to a second temperature equal to the temperature of the step of depositing the second silicon carbide layer.

4. The process according to claim 3 , further comprising a waiting step between the thermal transition step and the step of depositing the second silicon carbide layer.

5. The process according to claim 1 , wherein the temperature during the step of depositing the second silicon carbide layer and/or the annealing step is comprised between 1100° C. and 1400° C.

6. The process according to claim 1 wherein the duration of the annealing step is chosen as a function of the width, the length and/or the thickness of the discrete silicon structure.

7. The process according to claim 1 , wherein the carbonization step is carried out under an atmosphere comprising a hydrocarbon gas.

8. The process according to claim 1 , wherein the stack further includes a substrate; said process including, before the step of shaping the silicon layer:
a step of depositing a first silicon carbide layer on the substrate;
a step of depositing a silicon layer on the first silicon carbide layer;
the step of depositing a first silicon carbide layer and the step of depositing a silicon layer making it possible to obtain the stack including a first silicon carbide layer and a silicon layer on the first silicon carbide layer.

9. The process according to claim 8 , wherein the substrate forming the first layer of the stack is selected from a silicon, sapphire, aluminium nitride, silicon carbide or gallium nitride substrate.

10. The process according to claim 1 , wherein the shaping step is carried out so as to form in the silicon layer a plurality of linking elements and a plurality of discrete structures, each linking element of the plurality of linking elements joining at least one first discrete structure of the plurality of discrete structures to a second discrete structure of the plurality of discrete structures.

11. A microelectromechanical system sensor including a micromechanical structure made of silicon carbide comprising a cavity sealed by a silicon carbide membrane obtained using a process according to claim 1 .

12. The sensor according to claim 11 , wherein said sensor is a piezoresistive or capacitive pressure sensor.

13. The sensor according to claim 11 , wherein said sensor is a chemical sensor including at least one layer sensitive to a chemical compound to detect, said sensitive layer being deposited on said membrane.

14. A method comprising providing a sensor, as defined in claim 11 in or on an organic tissue.

15. A method comprising providing a sensor, as defined in claim 11 in a radiative environment.

Assignees

• Centre Nat Rech Scient
• Univ Tours

Inventors

• Alquier Daniel
• Khazaka Rami
• Michaud Jean François
• Portail Marc

Classifications

• B81C1/00047 Primary

  Cavities · CPC title

• B81B2203/0315

  Cavities · CPC title

• B81B3/0021

  Transducers for transforming electrical into mechanical energy or vice versa (dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00) · CPC title

• B81C2201/0116

  Thermal treatment for structural rearrangement of substrate atoms, e.g. for making buried cavities · CPC title

• B81C1/00476

  removing a sacrificial layer (B81C1/00912 takes precedence) · CPC title