CMOS COMPATIBLE CAPACITIVE ABSOLUTE PRESSURE SENSORS

• US 20180022600A1
• Filed: 07/19/2017
• Published: 01/25/2018
• Est. Priority Date: 07/19/2016
• Status: Active Grant

• Current Assignee: King Abdul AZIZ City For Science and Technology
• Original Assignee: King Abdul AZIZ City For Science and Technology
• Inventors: ALSAIARY, TARIQ SALIM, ALHOMOUDI, IBRAHIM ABDULLAH
• Granted Patent: US 10,556,791 B2
• Time in Patent Office: Days
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 7/02 containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS] B81B7/04 takes precedence
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 2203/0742 Interleave, i.e. simultaneously forming the micromechanical structure and the CMOS circuit
• CPC Class Codes: G01L 19/0076 using buried connections
• CPC Class Codes: G01L 19/147 Details about the mounting of the sensor to support or covering means
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0045 Diaphragm associated with a buried cavity
• CPC Class Codes: G01L 9/0054 integral with a semiconducting diaphragm
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

Monolithic integration of microelectromechanical systems (MEMS) sensors with complementary oxide semiconductor (CMOS) electronics for pressure sensors is a very challenging task. This is primarily due to the requirement for a very high quality thin diaphragm to provide the pressure dependent MEMS deformation that can be sensed and, when seeking absolute rather than relative pressure sensors, a sealed reference cavity. Accordingly, a new manufacturing process is established based upon back-etching and bonding of a monolithic absolute silicon carbide (SiC) capacitive pressure sensor. Beneficially, the process embeds the critical features of the MEMS within a shallow trench formed within the silicon substrate and then processing the CMOS circuit. The process further benefits as it maintains that those elements of the MEMS element fabrication process that are CMOS compatible are implemented concurrently with those CMOS steps as well as the metallization steps. However, the CMOS incompatible processing is partitioned discretely.

Claims

1. A method comprising:

manufacturing a first portion of a microelectromechanical systems (MEMS) element for monolithic integration with a complementary oxide semiconductor (CMOS) integrated circuit (IC) using a high temperature MEMS processing process;

manufacturing the CMOS integrated circuit;

manufacturing a second portion of the MEMS element at least one of during and subsequent to the CMOS integrated circuit;

wherein

the second portion of the MEMS element is formed with a low temperature MEMS processing.

2. The method according to claim 1, wherein

the first portion of the MEMS element is formed within a trench formed within the surface of a substrate within which the CMOS element is subsequently formed.

3. The method according to claim 1, wherein

the first portion of the MEMS element is formed within a trench formed within a substrate within which the CMOS element is to be formed;

and

the surface of the substrate is planarized post-formation of the first portion of the MEMS element such that the CMOS processing exploits contact photolithography.

4. The method according to claim 1, wherein

at least one of the initial high temperature MEMS processing and subsequent low temperature MEMS processing includes a structural material forming part of the MEMS element or another MEMS element, wherein

the structural material is selected from the group comprising silicon, silicon dioxide, silicon nitride;

silicon oxynitride, carbon, aluminum oxide, and silicon carbide.

5. The method according to claim 1, wherein

the low temperature MEMS processing results in a maximum substrate temperature of at least one of 25°

C., 50°

C., 100°

C., 200°

C., 250°

C., 300°

C., and 350°

C.

6. A device comprising:

a first portion of a microelectromechanical systems (MEMS) element within a trench formed within a substrate comprising a complementary oxide semiconductor (CMOS) integrated circuit (IC);

the CMOS integrated circuit;

a second portion of the MEMS element formed upon a predetermined region of the substrate and overlapping a predetermined portion of the first portion of a microelectromechanical systems (MEMS) element within the trench.