RU2061233C1 - Fat-based gas-sensitive detector - Google Patents

Abstract

FIELD: microelectronics. SUBSTANCE: detector has silicon substrate with source and drain areas. There is a layer of thin dielectric between the areas. Gate is disposed onto the layer. Holes are made into thick dielectric layer for making contacts with source and drain areas. There is a polysilicon film onto the thin dielectric layer between gate and thick dielectric layer. Silicon dioxide layer is deposited onto the thin dielectric layer. The film is made in form of a loop or a frame. Width of the film does not excess distance of boundary of the thick dielectric layer to boundary of spatial charge area of drain and source. The gate is made of catalytically active metal. EFFECT: improved reliability of operation. 2 dwg

Description

 The invention relates to microelectronics and can be used in primary converters of gas concentrations.

 Known gas-sensitive sensor based on a field-effect transistor [1] The sensor heater is made on a single crystal with a gas-sensitive transistor in the form of a layer of semiconductor material, isolated from the transistor by a p - n junction and is located next to the transistor. The disadvantage of this device is the large power consumed by the heater, which is due to the design of the sensor.

 The closest technical solution to the proposed device is a gas-sensitive sensor based on a field-effect transistor [2] A known gas-sensitive sensor contains a silicon substrate with source and drain areas, a thick dielectric layer above them, a gate dielectric layer between them and a gate electrode located above the thin dielectric layer. In this case, holes for contacts to the drain and source regions are made in the thick dielectric layer.

 However, in the specified device in one element of the gate of the transistor combines the functions of heating, control and gas sensitivity. This leads to a deterioration in the sensitivity and performance of the device.

 The technical problem that should be solved by the invention is such a structural embodiment of the device, which would improve the sensitivity and speed of the device. In the proposed invention, this problem is solved due to the fact that the gas-sensitive sensor is based on a field-effect transistor containing a silicon substrate with drain and source regions, a thick dielectric layer above the drain and source regions, a thin dielectric layer between them, on which the gate is located, and in the layer thick dielectric holes are made for contacts to the areas of drain and source. Moreover, unlike the prototype, the device additionally contains a polysilicon film with a layer of silicon dioxide deposited on it, and the specified film has the shape of a loop or frame and is located on a thin dielectric layer between a gate made of a catalytically active metal and a thick dielectric layer, and the width is polysilicon film does not exceed the distance from the boundary of the thick dielectric layer to the boundary of the space charge region of the drain and source.

 A polysilicon film serves as a heater for a gas-sensitive sensor, the heating current of which is supplied through the contact pads.

 In FIG. 1 shows a section, in FIG. 2 is the topology of a crystal fragment of a primary converter of gas concentration of a gas-sensitive sensor based on a field-effect transistor.

 The gas-sensitive sensor contains a silicon substrate 1, source 2 and drain regions 2, a thick dielectric 4, contacts 5 to regions 2, 3, a gate insulator 6, a polysilicon film 7 in the form of a loop or frame, a catalytic metal layer 8, silicon dioxide layer 9, contact pads 10, 11, 12, 13, and 14. On silicon pad 1, source and drain areas 2, 3 are made, covered with a thick dielectric layer 4 on which contacts 5 are made to regions 2, 3 and which is removed between these regions. In place of the removed thick dielectric 4, a thin layer of gate dielectric 6 is deposited, on which, in places adjacent to the source and drain regions 2, 3, a polysilicon film 7 is applied in the form of a loop or frame, and silicon dioxide layer 9 is applied to the polysilicon film 7; a layer 8 of a catalytic metal is deposited on the layer 9 and the open part of the gate dielectric 6. Regions 2, 3, source and drain, contacts 5 are connected to the contact pads 12, 13, respectively, a polysilicon film 7 with contact pads 10, 11, and a layer 8 of catalytic metal with a contact pad 14.

 To bring the primary converter into working condition, voltage is applied to the contact pads 10, 11, which ensures a predetermined gate potential and the sensor’s operating temperature, and information on gas concentration is removed from the contact pads 12, 13, 14.

 The new design of the gas-sensitive sensor provides galvanic isolation of the heating element from the remaining elements of the crystal, separation of the functions of gas sensitivity, control, heating, and thereby increase the sensitivity and speed. In addition, the isolation of the catalytic metal layer from the drain and source regions provides increased reliability, and the structural design of the heater reduces the power consumption and obtains the required value of its resistance over a wide range.

Claims (1)

 A field-effect transistor-based gas sensor containing a silicon substrate with drain and source regions, a thick dielectric layer above the drain and source regions, a thin dielectric layer between them, on which the gate is located, and holes are made in the thick dielectric layer for contacts to the drain and source regions characterized in that it further comprises a polysilicon film with a layer of silicon dioxide deposited on it, the film being in the form of a loop or frame and located on a thin dielectric layer between an admixture made of a catalytically active metal and a thick dielectric layer, and the width of the polysilicon film does not exceed the distance from the boundary of the thick dielectric layer to the boundary of the space charge region of the drain and source.

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