Abrégé

An apparatus comprising a micromachined (a.k.a. MEMS, Micro Electro Mechanical Systems) silicon flow sensor, a flow channel package, and a driving circuitry, which operates in a working principle of thermal time-of-flight (TOF) to measure gas or liquid flow speed, is disclosed in the present invention. The micromachining technique for fabricating this MEMS time-of-flight silicon thermal flow sensor can greatly reduce the sensor fabrication cost by batch production. This microfabrication process for silicon time-of-flight thermal flow sensors provides merits of small feature size, low power consumption, and high accuracy compared to conventional manufacturing methods. Thermal time-of-flight technology in principle can provide accurate flow speed measurements for gases regardless of its gas compositions. In addition, the present invention further discloses the package design and driving circuitry which is utilized by the correlated working principle.

Classes IPC  ?

• G01F 1/708 - Mesure du temps de parcours d'une distance déterminée
• G01F 1/68 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en utilisant des effets thermiques
• G01F 1/72 - Dispositifs pour la mesure des débits pulsatoires

Abrégé

Many current micromachining devices are integrated with materials such as very thick layer of polyimide (10 to 100 um) to offer essential characteristics and properties for various applications; it is inherently difficult and complicated to provide reliable metal interconnections between different levels of the circuits. The present invention is generally related to a novel micromachining process and structure to form metal interconnections in integrated circuits or micromachining devices which are incorporated with thick polyimide films. More particularly, the embodiments of the current invention relates to formation of multi-step staircase structure with tapered angle on polyimide layer, which is therefore capable of offering superb and reliable step coverage for metallization among different levels of integrated circuits, and especially for very thick polyimide layer applications.

Classes IPC  ?

• H01L 21/302 - Traitement des corps semi-conducteurs en utilisant des procédés ou des appareils non couverts par les groupes pour changer leurs caractéristiques physiques de surface ou leur forme, p. ex. gravure, polissage, découpage

Abrégé

A micromachined thermal mass flow sensor comprises a high mechanical strength polyimide film as a supporting layer of suspending membrane. The polyimide film provides superior thermal insulating properties to reduce the power consumption of device. Due to the tendency of humidity absorption, the polyimide suspending membrane is double side passivated on both top and bottom surfaces to sustain its long term stability from rush and humid working environment. A thin layer of silicon dioxide deposited by plasma enhanced chemical vapor deposition is overlaid between the silicon nitride and polyimide film to enhance the adhesion property of passivation layers to polyimide surface. With such embodiments, a sturdy and robust micromachined thermal mass flow sensor with high measurement accuracy could be formed.

Classes IPC  ?

• G01F 1/68 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en utilisant des effets thermiques

Abrégé

The current invention generally relates to Micro Electro Mechanical Systems (MEMS) thermal mass flow sensors for measuring the flow rate of a flowing fluid (gas/liquid) and the methods of manufacturing on single crystal silicon wafers. The said mass flow sensors have self-cleaning capability that is achieved via the modulation of the cavity of which the sensing elements locate on the top of the cavity that is made of a silicon nitride film; alternatively the sensing elements are fabricated on top of a binary silicon nitride/conductive polycrystalline silicon film under which is a porous silicon layer selective formed in a silicon substrate. Using polycrystalline silicon or the sensing elements as electrodes, an acoustic wave can be generated across the porous silicon layer which is also used for the thermal isolation of the sensing elements. The vibration or acoustic energy is effective to remove foreign materials deposited on top surface of the sensing elements that ensure the accuracy and enhance repeatability of the thermal mass flow sensing.

Classes IPC  ?

• G01F 1/68 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en utilisant des effets thermiques

Abrégé

An integrated mass flow sensor is manufactured by a process of carrying out a micro-machining process on an N or P-type silicon substrate with orientation <100>. This mass flow sensor comprises an upstream thin-film heater, an downstream thin-film heater, and a pair of thin-film heat sensing elements, and a thermally isolated membrane for supporting the heaters and the sensors out of contact with the substrate base. This mass flow sensor is operated with three sets of circuits, a first circuit for measuring a flow rate in a first range of flow rates, a second circuit for measuring a flow rate in a second range of flow rates, and a third circuit in a differential configuration for measuring a flow rate in said first range of flow rates or said second range of flow rates, to significantly increase range of flow rate measurements and provide an optional for concentration measurement, while maintains a high degree of measurement accuracy.

Classes IPC  ?

• G01F 1/00 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu

Abrégé

This invention discloses a mass flow sensor manufactured by applying the micro-electromechanical system (MEMS) process to provide a new and improved mass flow sensor that is a self -calibrated in a time-of -flight manner with configuration to measure the flow velocity directly. The self-calibration of a mass flow rate sensor is achieved by providing an electric pulse to a heater in the flow and determining a temperature variations of the fluid. The method further includes a step of measuring a temperature variation by a temperature sensor disposed at a short distance from the heater. The method further includes a step of correlating the temperature variation measured at the temperature sensor with the temperature variation of the heater to determine a time delay and a corresponding flow velocity.

Classes IPC  ?

• G01F 1/68 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en utilisant des effets thermiques

Abrégé

This invention discloses a mass flow sensor manufactured by applying the micro-electromechanical system (MEMS) process to provide a new and improved mass flow sensor that is a self-calibrated in a time-of-flight manner with configuration to measure the flow velocity directly. The self-calibration of a mass flow rate sensor is achieved by providing an electric pulse to a heater in the flow and determining a temperature variations of the fluid. The method further includes a step of measuring a temperature variation by a temperature sensor disposed at a short distance from the heater. The method further includes a step of correlating the temperature variation measured at the temperature sensor with the temperature variation of the heater to determine a time delay and a corresponding flow velocity.

Classes IPC  ?

• G01F 1/68 - Mesure du débit volumétrique ou du débit massique d'un fluide ou d'un matériau solide fluent, dans laquelle le fluide passe à travers un compteur par un écoulement continu en utilisant des effets thermiques