DE102013205822A1 - A chemosensitive field effect transistor and method of making a chemosensitive field effect transistor - Google Patents

Abstract

The invention relates to a chemosensitive field effect transistor with a semiconductor substrate (102), a source contact (110), a drain contact (112), a gate insulating layer (114), a first gate electrode (116) and a further electrode ( 418). The semiconductor substrate (102) has a first contact area (104), a second contact area (106) and a channel area (108) arranged between the first contact area (104) and the second contact area (106). The source contact (110) makes electrical contact with the semiconductor substrate (102) in the first contact region (104). The drain contact (112) makes electrical contact with the semiconductor substrate (102) in the second contact region (106). A gate insulating layer (114) is arranged opposite to the channel region (108) on a surface of the semiconductor substrate (102). A first gate electrode (116) is connected to the gate insulating layer (114), the gate insulating layer (114) and the first gate electrode (116) forming a gate stack that is sensitive to at least one chemical species. A further electrode (418) is connected to the gate insulating layer (114), the gate insulating layer (114) and the further electrode (418) forming a gate stack which is not sensitive to the at least one chemical species.

Description

State of the art

The present invention relates to a chemosensitive field effect transistor, to a method for operating a chemosensitive field effect transistor and to a method for producing a chemosensitive field effect transistor.

Semiconductor devices (GaN, SiC, ...), MIS (metal-insulator-semiconductor), FET (field effect transistor), etc. are known. Also known is the use of such devices for gas sensing (ChemFET). The focus of previous investigations is on gas sensitivity. Typically, a drift of the offset is observed. This offset drift is based on different causes with different time constants.

These include, for example, the generation, loading and discharge of interface states, the redistribution of free charge carriers from traps, the removal of free charge carriers from traps by tunneling, the generation of defects, mobile charges in the dielectrics and changes in the semiconductor, which are comparatively low for weak electrical loads are. Overall, the drift means that spontaneously occurring gas-related signals can be perceived by considering the change, but over a longer period of time no quantitative measurements are possible over a period of hours.

The DE 10 2011 002 854 A1 describes a field effect gas sensor.

Disclosure of the invention

Against this background, the present invention provides a chemosensitive field effect transistor, a method for operating a chemosensitive field effect transistor and a method for producing a chemosensitive field effect transistor according to the main claims. Advantageous embodiments emerge from the respective subclaims and the following description.

A signal of a chemosensitive field-effect transistor may have a temporal change during operation despite the constant concentration of a chemical species to be detected. The change can be called signal drift. The signal drift can be the result of various physical or chemical phenomena in the area of the dielectric layer.

By at least one additional electrode in the region of the dielectric layer of the field effect transistor can be stabilized. The stabilized region can be advantageously used to detect the concentration of the species. Additionally or alternatively, such an additional electrode can be used as a so-called getter electrode, can be removed by the mobile charge carriers from the dielectric layer and held in position. By one or more such additional electrodes, a long-term stable signal can be achieved, whereby an absolute measurement of the concentration of the chemical species is possible. In this way, for example, an absolute measuring gas sensor based on the ChemFET principle can be produced.

A chemosensitive field effect transistor has the following features:
a semiconductor substrate having a first contact region, a second contact region, and a channel region disposed between the first contact region and the second contact region;
a source contact electrically contacting the semiconductor substrate in the first contact region;
a drain contact electrically contacting the semiconductor substrate in the second contact region;
a gate insulating layer disposed on a surface of the semiconductor substrate opposite to the channel region;
a first gate electrode connected to the gate insulating layer, the gate insulating layer and the first gate electrode forming a gate stack sensitive to at least one chemical species; and
at least one further electrode, in particular a second gate electrode and / or a first getter electrode, which is connected to the gate insulating layer, wherein the gate insulating layer and the further electrode form a non-sensitive for the at least one chemical species gate stack.

A chemosensitive field-effect transistor can be understood as meaning a sensor element which is designed to detect a specific chemical species in a medium. The chemosensitive field effect transistor may be referred to as ChemFET. By a species may be understood, for example, a chemical or a substance, in particular a gas. The semiconductor substrate may be a material that can be used both as a carrier material of the chemosensitive field effect transistor and as a functional material of the chemosensitive field effect transistor. Depending on the embodiment of the field-effect transistor, the first contact region and the second channel region may have a different doping than the channel region. A source contact may be a first electrical terminal of the chemosensitive field effect transistor. A drain contact may be a second electrical terminal of the chemosensitive field effect transistor. A gate insulating layer may be electrically insulating. The gate insulating layer may include a dielectric material. The gate insulating layer may be directly connected to the semiconductor substrate. A gate stack which is not sensitive to at least one chemical species can not be influenced by the presence of the species. In contrast, in the case of a gate stack that is sensitive to at least one chemical species, a property, for example a dielectric constant of the gate stack, can be changed by interaction with the species, whereby a current flow through the channel region lying between the drain contact and the source contact can be changed , The chemosensitive field-effect transistor can, for example, map a change in the concentration of the species due to a change in the current flow.

The gate insulating layer may further be disposed opposite to the first contact region and additionally or alternatively opposite to the second contact region on the surface of the semiconductor substrate. As a result, mobile charge carriers can be removed from the gate insulating layer in the direction of at least one of the contact regions. As a result, the baseline drift of the field effect transistor can be reduced.

According to one embodiment, the further electrode may be configured to cause a more homogeneous electric field than opposite the non-sensitive gate stack in operation of the chemosensitive field effect transistor in the channel region opposite the sensitive gate stack. For this purpose, a part of the gate of the field effect transistor can be blocked by the further electrode.

According to one embodiment, the further electrode may be designed to subtract mobile ions from the sensitive gate stack during operation of the chemosensitive field-effect transistor. In this case, the first gate electrode and the further electrode may have different materials. For example, the first gate electrode may be constructed of a species-permeable or porous material. Due to the different materials, the first gate electrode and the further electrode can also be connected in an electrically conductive manner according to one embodiment.

The first gate electrode and the further electrode may be formed from two different materials (possibly different material structure). The first gate electrode and the further electrode may be located over the channel or channel region on the same dielectric layer. The first nonsensitive electrode may be over the depleted area. The other gas sensitive electrode may be over the enrichment area. The electrodes are electrically isolated.

According to one embodiment, the first gate electrode and the further electrode may be arranged on a surface of the gate insulating layer facing away from the semiconductor substrate. As a result, a simple structure of the field effect transistor is made possible. According to one embodiment, mutually facing end portions of the first gate electrode and the further electrode may touch. Alternatively, mutually facing end portions of the first gate electrode and the further electrode may be spaced from each other. If the electrodes are spaced apart from each other, they can have different electrical potentials.

The further electrode may be electrically connected to the first gate electrode.

According to a further embodiment, the further electrode, which is formed, for example, as a second gate electrode, may be arranged inside the gate insulating layer. As a result, the first gate electrode and the second gate electrode may also overlap.

The first gate electrode may be arranged on a surface of the gate stack facing away from the semiconductor substrate, and the further electrode may be embedded in the gate insulating layer. For example, the first gate electrode may be located on top of the gate stack, and the second gate electrode may be embedded in the dielectric or different dielectrics.

By way of example, the first gate electrode may extend from a side of the gate insulating layer facing the first contact region towards a side of the gate insulating layer facing the second contact region. The second gate electrode may extend from a side of the gate insulating layer facing the second contact region toward a side of the gate insulating layer facing the first contact region. In this way, the channel region can be completely or partially covered by the first gate electrode and the second gate electrode. In this case, only the region of the channel region not covered by the second gate electrode can be relevant for the sensor operation of the field effect transistor.

According to one embodiment, the further electrode ( 818 ) as a getter electrode ( 818 ) and a second getter electrode ( 820 ) may be provided across the source and drain of the field effect transistor for gettering of movable ions.

According to one embodiment, the first gate electrode and the further electrode, which may in particular be formed as a second gate electrode, may be arranged opposite to the channel region. By arranging both gate electrodes at the level of the channel region, a portion of the entire gate of the field effect transistor for the sensing of the species can be blocked.

According to a further embodiment, the first gate electrode opposite to the channel region and the further electrode, which may be formed in particular as a first getter electrode, be arranged opposite to the first contact region. In this way, mobile charge carriers can be drawn to the first contact region and thus removed from the sensing region of the field effect transistor. Alternatively, the first getter electrode may be disposed opposite to the second contact region. In this case, mobile charge carriers can be pulled to the second area of the charge.

Accordingly, the first getter electrode may be disposed opposite to the first contact region, and the chemosensitive field effect transistor may include a second getter electrode disposed opposite to the second contact region. In this case, the gate insulating layer and the second getter electrode can form another gate stack that is not sensitive to the at least one chemical species. As a result, mobile charge carriers of different charges can be removed from the sensitive gate stack.

A corresponding chemosensitive field effect transistor can advantageously be used as an absolute measuring gas sensor.

A method of fabricating a chemosensitive field effect transistor comprises the following steps:
Providing a semiconductor substrate having a first contact region, a second contact region, and a channel region disposed between the first contact region and the second contact region;
Providing a source contact electrically contacting the semiconductor substrate in the first contact region;
Providing a drain contact electrically contacting the semiconductor substrate in the second contact region; Arranging a gate insulating film opposite to the channel region on a surface of the semiconductor substrate;
Bonding a first gate electrode to the gate insulating layer to form a gate stack sensitive to at least one chemical species through the gate insulating layer and the first gate electrode; and
Connecting at least one further gate electrode, in particular a second gate electrode and / or a first getter electrode, with the gate insulating layer to form through the gate insulating layer and the further electrode for the at least one chemical species non-sensitive gate stack ,

The structure of the chemosensitive field-effect transistor has the following components:
a semiconductor substrate having a first contact region, a second contact region, and a channel region disposed between the first contact region and the second contact region;
a source contact electrically contacting the semiconductor substrate in the first contact region;
a drain contact electrically contacting the semiconductor substrate in the second contact region;
a gate insulating layer opposite to the channel region on a surface of the semiconductor substrate;
a first gate electrode having the gate insulating layer for forming a gate stack sensitive to at least one chemical species through the gate insulating layer and the first gate electrode; and
at least one further electrode, in particular a second gate electrode and / or a first getter electrode, which is connected to the gate insulating layer to form through the gate insulating layer and the further electrode for the at least one chemical species non-sensitive gate stack ,

The individual components can be produced using known methods.

The invention will now be described by way of example with reference to the accompanying drawings. Show it:

1 a representation of a chemosensitive field effect transistor;

2 a diagram of a characteristic of a chemosensitive field effect transistor;

3 a characteristic field of different characteristics of chemosensitive field-effect transistors;

5 to 10 Representations of chemosensitive field effect transistors according to embodiments of the present invention; and

11 a flowchart of a method for producing a chemosensitive field effect transistor according to an embodiment of the present invention.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similarly acting, wherein a repeated description of these elements is omitted.

1 shows a representation of a chemosensitive field effect transistor. The chemosensitive field effect transistor has a semiconductor substrate 102 with a first contact area 104 , a second contact area 106 and a channel area 108 , a source contact 110 (S-), a drain contact 112 (D +), a gate insulating layer 114 and a gate electrode 116 (G). The channel area 108 is between the first contact area 104 and the second contact area 106 arranged. The first contact area 104 and the second contact area 106 have a first doping n +. The channel area 108 has a second doping p. The source contact 110 contacts the semiconductor substrate 102 in the first contact area 104 electric. The drain contact 112 contacts the semiconductor substrate 102 in the second contact area 106 electric. The gate insulating layer 114 is in the channel area 108 on a surface of the semiconductor substrate 102 arranged. The gate electrode 116 is on one of the semiconductor substrate 102 opposite side of the gate insulating layer 114 arranged and of the semiconductor material 102 electrically isolated. The sensitive, possibly porous electrode 116 with the dielectric 114 show chemosensitivity. In the canal area 108 a charge distribution is shown which occurs during normal operation of the chemosensitive field effect transistor. Thus shows 1 a chemosensitive field effect transistor in the form of a FET device with typical field distribution in the operating range of the chemosensitive field effect transistor as a ChemFET sensor.

2 shows a diagram of a capacity-voltage curve (CV) 200 a chemisensitive MetalI Insulator Semiconductor (MIS) structure with a saturation region 202 and a linear range 204 , The diagram shows a significant hysteresis caused by moving ions. Especially here, the moving charges have a significant effect on the signal, in the form of an offset drift of a ChemFET sensor.

3 shows typical characteristics of a contaminated field effect transistor (drain-source current via drain-source voltage for different gate voltages). The differences to the uncontaminated transistor can be seen in the saturation region. Here occur without contamination only minor changes in the current with an increase in the drain-source voltage. 3 however, shows strong changes due to the contaminations. Shown is a saturation region 302 and a linear range 304 ,

4 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor has, as shown by 1 described, a semiconductor substrate 102 on, this is a first contact area 104 , a second contact area 106 and one between the first contact area 104 and the second contact area 106 arranged channel area 108 having. According to this embodiment, the first contact area 104 a doping n ++, the second contact area 106 a doping n ++, the channel region 108 a doping n and the remaining area of the substrate 102 a doping p- up.

A source contact 110 contacts the semiconductor substrate 102 in the first contact area 104 and thus forms a first terminal of the field effect transistor. A drain contact 112 contacts the semiconductor substrate 102 in the second contact area 106 and thus forms a second terminal of the field effect transistor.

At the height of the canal area 108 and each slightly overlapping with the first contact area 104 and the second contact area 106 is a gate insulating layer 114 on a surface of the substrate 102 arranged. Adjacent to the insulating layer 114 is at the height of the first contact area 104 a first passivation layer (and insulation layer) 421 on the surface of the substrate 102 and at the level of the second contact area 106 a second passivation layer (and insulation layer) 422 on the surface of the substrate 102 arranged.

A first gate electrode 116 extends from the first passivation layer 421 along a the substrate 102 remote surface of the gate insulating layer 114 in the direction of the second passivation layer 422 ,

A second gate electrode 418 extends over the second passivation layer 422 and starting from the second passivation layer 422 along a the substrate 102 remote surface of the gate insulating layer 114 towards the first passivation layer 421 ,

According to this embodiment, the gate insulating layer 114 exemplified a layer structure of three superimposed layers 431 . 432 . 433 on.

The first gate electrode 116 forms together with the between the first gate electrode 116 and the substrate 102 lying section of the gate insulating 114 a gate stack sensitive to at least one chemical species. In this case, for example, the first gate electrode 116 and additionally or alternatively one of the layers 431 . 432 . 433 the gate insulating layer 114 be influenced by the species.

The second gate electrode 418 forms together with the between the second gate electrode 418 and the substrate 102 lying portion of the gate insulating layer 114 a non-sensitive for at least one chemical species gate stack. In this case, for example, the second gate electrode 418 impermeable to the species.

Mutually facing end portions of the first gate electrode 116 and the second gate electrode 418 are according to this embodiment by a distance 441 spaced apart. The second gate electrode 418 has an active overlap 442 with the channel area 108 on.

Thus, the channel area becomes 108 in a section of a sensitive gate stack 116 . 431 . 432 . 433 and in another portion of a non-sensitive gate stack 418 . 431 . 432 . 433 covered. The sensitive gate stack 116 . 431 . 432 . 433 is used in the operation of the field effect transistor for sensing a species, for example for gas sensing. Through the non-sensitive gate stack 418 . 431 . 432 . 433 a part of the entire gate of the field effect transistor is blocked for the sensing of the species.

The first gate electrode 116 and the second gate electrode 418 are in the area of the gate insulating layer 114 electrically isolated from each other. During operation of the field effect transistor, at the first gate electrode 116 a different voltage than at the second gate electrode 418 issue.

5 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor corresponds to the basis of 4 described field effect transistor, with the difference that the first gate electrode 116 and the second gate electrode 418 touch. The first gate electrode 116 and the second gate electrode 418 extend over the entire length of the channel area 108 and the gate insulating layer 114 , The second gate electrode 418 has an active overlap 442 with the channel area 108 on.

According to this embodiment, the second gate electrode extends 418 over the middle of the gate insulating layer 114 In addition, therefore, has a greater extent than the first gate electrode 116 on.

The first gate electrode 116 and the second gate electrode 418 are on the surface of the gate insulating layer 114 electrically conductive interconnected. During operation of the field effect transistor, that corresponds to the first gate electrode 116 applied voltage V _gate1 at the second gate electrode 418 applied voltage V _gate2 . The first gate electrode 116 and the second gate electrode 418 have different materials according to this embodiment.

6 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor corresponds to the basis of 4 described field effect transistor, with the difference that although the first gate electrode 116 on a the substrate 102 remote surface of the gate insulating layer 114 is arranged, the second gate electrode 418 however, within the gate insulation layer 114 is arranged. According to this embodiment, the second gate electrode extends 418 in the from the substrate 102 furthest layer 433 the gate insulating layer 114 , In the further course, the second gate electrode extends 418 over a the substrate 102 remote surface of the second passivation layer 422 ,

Depending on the embodiment of the field effect transistor, mutually facing end portions of the first gate electrode 116 and the second gate electrode 418 with respect to its longitudinal direction in the region of the gate insulating layer 114 be at the same height, overlap each other or be spaced from each other. According to this embodiment, the first gate electrode 116 and the second gate electrode 418 an overlap 643 on. The second gate electrode 418 has an active overlap 442 with the channel area 108 on.

The first gate electrode 116 and the second gate electrode 418 are in the area of the gate insulating layer 114 electrically isolated from each other. During operation of the field effect transistor, at the first gate electrode 116 a different voltage than at the second gate electrode 418 issue.

7 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor corresponds to the in 1 shown field effect transistor, with the difference that in 7 shown field effect transistor has a multilayer gate insulating layer 114 and a second gate contact 418 having.

The gate insulating layer 114 has two layers according to this embodiment. A first location 734 the gate insulating layer 114 is directly on a surface of the semiconductor substrate 102 and a second location 735 the gate insulating layer 114 is on the first location 734 arranged.

About one of the semiconductor substrate 102 remote surface of the gate insulating layer 114 the first gate electrode extends 116 , The second gate electrode 418 extends between the first layer 734 and the second location 735 in the gate insulating layer 114 into it.

The second gate electrode 418 is from the first gate electrode 116 through the second layer 735 electrically isolated. The second gate electrode 418 extends in the longitudinal direction of the extension of the gate insulating layer 114 over a portion of the gate insulating layer 114 , Over a residual region of the gate insulating layer 114 only the first gate electrode extends 116 , The second gate electrode 418 starts on one side of the drain contact 112 and extends toward the source contact 110 , In this case, the second gate electrode extends 418 just over half the length of the canal area 108 ,

In a portion of the gate insulating layer 114 in which is the first gate electrode 116 and the second gate electrode 418 does not overlap through the first gate electrode 116 and the gate insulating layer 114 a, for example, formed for a gas-sensitive gate stack. In another section of the gate insulating layer 114 in which is the first gate electrode 116 and the second gate electrode 418 overlap is through the first gate electrode 116 , the second gate electrode 418 and the gate insulating layer 114 formed a non-sensitive gate stack.

To achieve stable operation of the field effect transistor, the field effect transistor is typically operated in saturation. Here one finds the typical charge carrier density distribution, as in 1 is shown schematically. The gate 114 is influenced by the gas. The field between gate 114 and channel 108 is from Source 110 to drain 112 not constant. Thus you get different sensitivities depending on the position.

In the embodiment shown here in the multi-gate structure, effects due to mobile charges from the depletion region or saturation region become due to an additional electrode in the form of the second gate electrode 418 which is close to that of the first contact area serving as the source 110 is led, eliminated. Through the second gate electrode 418 becomes a gas-sensitive area with locally almost constant field in the channel 108 realized.

Due to a high channel resistance in the area under the second gate electrode 418 will reach that field 751 under the first gate electrode 116 opposite the semiconductor 102 , outside the second gate electrode 418 is almost constant and only in one field 752 under the second gate electrode 418 sets a voltage curve. It is true that the at the second gate electrode 418 applied voltage smaller than that at the first gate electrode 116 voltage is applied. Further, the thicknesses of the second gate electrode are 418 and the first gate electrode 116 differently. As a result, foreign ion influences from the area below the second gate electrode 418 no longer to the sensor signal serving as a signal or channel current of the field effect transistor.

The effect of gas, mobile ions and impurities due to different E fields is thus minimized. Small changes in gas potential only affect the channel flow near the source region. The field in the remaining area is then not dependent on the sensor operation.

8th shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor has, as shown by 1 described, a semiconductor substrate 102 on, this is a first contact area 104 , a second contact area 106 and one between the first contact area 104 and the second contact area 106 arranged channel area 108 having. According to this embodiment, the first contact area 104 a doping n ++, the second contact area 106 a doping n ++, the channel region 108 a doping n and the remaining area of the substrate 102 a doping p- up.

A source contact 110 contacts the semiconductor substrate 102 in the first contact area 104 and thus forms a first terminal of the field effect transistor. A drain contact 112 contacts the semiconductor substrate 102 in the second contact area 106 and thus forms a second terminal of the field effect transistor.

At the height of the canal area 108 and each overlapping with the first contact area 104 and the second contact area 106 is a gate insulating layer 114 on a surface of the substrate 102 arranged. Adjacent to the insulating layer 114 is at the height of the first contact area 104 a first passivation layer 421 on the surface of the substrate 102 and at the level of the second contact area 106 a second passivation layer 422 on the surface of the substrate 102 arranged.

A first gate electrode 116 extends along a the substrate 102 remote surface of the gate insulating layer 114 over the entire canal area 108 and overlaps with the first contact areas 104 as well as something with the second contact area 106 ,

A first getter electrode 818 extends from the first passivation layer 421 along a the substrate 102 remote surface of the gate insulating layer 114 towards the first gate electrode 116 , The first getter electrode 818 is thus opposite to the first contact area 104 arranged. The first getter electrode 818 has a width 844 on. Between the first gate electrode 116 and the first getter electrode 818 there is a distance 845 ,

Corresponding to the first getter electrode 818 extends a second getter electrode 820 starting from the second passivation layer 422 along a the substrate 102 remote surface of the gate insulating layer 114 towards the first gate electrode 116 , The second getter electrode 820 is thus opposite to the second contact area 106 arranged. A distance 846 between the second getter electrode 820 and a boundary of the channel area 108 (Ohm / active limit) is in 8th shown.

According to this embodiment, the gate insulating layer 114 exemplified a layer structure of three superimposed layers 431 . 432 . 433 on.

The first gate electrode 116 forms together with the between the first gate electrode 116 and the substrate 102 lying portion of the gate insulating layer 114 a gate stack sensitive to at least one chemical species. In this case, for example, the first gate electrode 116 and additionally or alternatively one of the layers 431 . 432 . 433 the gate insulating layer 114 be influenced by the species.

The first getter electrode 818 and the second getter electrode 820 are designed to remove mobile ions from between the first gate electrode 116 and the channel area 108 lying portion of the gate insulating layer 114 pull away.

9 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor corresponds to the in 1 shown field effect transistor, with the difference that in the im 9 shown field effect transistor, the gate insulating layer 114 far beyond the first contact area 104 and far beyond the second contact area 106 extends. For example, more than half of the surface of the first contact area 104 and more than half of the surface area of the second contact area 106 from the gate insulating layer 114 be covered. In the area of the canal area 108 has the gate insulating layer 114 another layer on, located on the surface of the semiconductor substrate 102 only in the area of the channel area 108 located. As another difference to that in 1 the field effect transistor shown in FIG 9 shown field effect transistor, corresponding to 8th a first getter electrode 818 and a second getter electrode 820 on. The first getter electrode 818 is in the range of the first contact area 104 on a first contact area 104 remote surface of the gate insulating layer 114 arranged. The second getter electrode 818 is in the range of the second contact area 106 on a second contact area 106 remote surface of the gate insulating layer 114 arranged. Thus, the first getter electrode 818 and the second getter electrode 820 in contrast to the first gate electrode 116 outside the area of the canal 108 arranged.

According to one embodiment shows 9 a Multigateaufbau with side getter electrodes in the form of the first getter electrode 818 and the second getter electrode 820 , which are designed to possibly getter mobile charge carriers. Through between the first getter electrode 818 and the second getter electrode 820 Applied lateral fields become movable charges according to their charge to the respective getter electrode 818 . 820 pulled and stored according to an embodiment in a getterndes material.

10 shows a representation of a chemosensitive field effect transistor according to an embodiment of the present invention. The field effect transistor is constructed as the basis of 7 described field effect transistor and additionally has the first getter electrode 818 on, on a continuation of the gate insulating layer 114 over the first contact area 104 is arranged, as it is based on 9 is described.

This results in a field effect transistor with a multi-gate construction, the advantages of the two, for example on the basis of 7 and 9 combined concepts. Such a field effect transistor thus has the two gate electrodes 116 . 418 and the first getter electrode 818 on.

Due to the structure of semiconductor devices presented here, the baseline drift due to mobile charges or ions or other impurities can be reduced, so that a quantitative gas measurement is possible.

Presented are Sensorrealisierungsvarianten that can provide, for example, a stabilized distribution of mobile defects and / or additional contamination during operation, such as metal ions such. B. Na + (sodium ions), K + (potassium ions) intercept and thus improve the component performance over its lifetime.

With reference to the preceding figures, different transducer realization variants have been presented with regard to the gate design. In addition to the exhaust gas resistance in the gas-sensitive gate stack as stable as possible with respect to mobile charges, reloading of traps or defects in the operating state is achieved. Optionally, ionic impurities are added to the gate during operation 114 invade, rendered harmless.

The embodiments show enhancement field effect transistors. The concepts shown and described are also applicable to depletion field effect transistors or tunnel field effect transistors. Design details can be executed application-specific.

The approach presented here can be used in all sensors with field-effect-based components, especially in semiconductor-based gas sensors with transistor (MIS) (metal-insulator-semiconductor).

11 shows a flowchart of a method for producing a chemosensitive field effect transistor according to an embodiment of the present invention.

In one step 1101 a semiconductor substrate is provided. As described with reference to the preceding figures, the semiconductor substrate has a first contact region, a second contact region and a channel region arranged between the first contact region and the second contact region. In one step 1103 For example, a source contact is electrically contacted at the first contact region. In one step 1105 For example, a drain contact is electrically contacted at the second contact region. In one step 1107 For example, a gate insulating film is disposed opposite to the channel region on a surface of the semiconductor substrate. In one step 1109 For example, a first gate electrode is connected to the gate insulating layer to form a gate stack sensitive to at least one chemical species through the gate insulating layer and the first gate electrode. In one step 1111 For example, at least one second gate electrode is connected to the gate insulating layer to form a gate stack that is not sensitive to the at least one chemical species by the gate insulating layer and the second gate electrode.

The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment. Said method steps can also be carried out in a sequence other than that described.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102011002854 A1 [0004]

Claims (12)

A chemosensitive field effect transistor comprising: a semiconductor substrate ( 102 ), which has a first contact area ( 104 ), a second contact area ( 106 ) and one between the first contact area ( 104 ) and the second contact area ( 106 ) channel region ( 108 ) having; a source contact ( 110 ), which the semiconductor substrate ( 102 ) in the first contact area ( 104 ) contacted electrically; a drain contact ( 112 ), which the semiconductor substrate ( 102 ) in the second contact area ( 106 ) contacted electrically; a gate insulating layer ( 114 ), which are opposite to the channel area ( 108 ) on a surface of the semiconductor substrate ( 102 ) is arranged; a first gate electrode ( 116 ), with the gate insulating layer ( 114 ), wherein the gate insulating layer ( 114 ) and the first gate electrode ( 116 ) form a gate stack sensitive to at least one chemical species; and at least one further electrode ( 418 ; 818 ), in particular a second gate electrode ( 418 ) and / or a first getter electrode ( 818 ), with the gate insulating layer ( 114 ), wherein the gate insulating layer ( 114 ) and the further electrode ( 418 ; 818 ) form a non-sensitive for the at least one chemical species gate stack. A chemosensitive field-effect transistor according to claim 1, wherein the first gate electrode ( 116 ) and the further electrode ( 418 ; 818 ) are formed of two different materials. Chemosensitive field-effect transistor according to one of the preceding claims, in which the further electrode ( 418 ; 818 ) electrically connected to the first gate electrode ( 116 ) connected is. A chemosensitive field-effect transistor according to one of the preceding claims, wherein the first gate electrode ( 116 ) on a semiconductor substrate ( 102 ) facing away from the gate stack and the further electrode ( 418 ; 818 ) in the gate insulating layer ( 114 ) is embedded. Chemosensitive field-effect transistor according to one of the preceding claims, in which the further electrode ( 818 ) especially as a getter electrode ( 818 ) and a second getter electrode ( 820 ) is provided across the source and drain of the field effect transistor for gettering movable ions. A chemosensitive field-effect transistor according to one of the preceding claims, wherein the first gate electrode ( 116 ) and the further electrode ( 418 ; 818 ) and possibly the second getter electrode ( 820 ) on a semiconductor substrate ( 102 ) facing away from the surface of the gate insulating layer ( 114 ) are arranged. Chemosensitive field-effect transistor according to one of Claims 1 to 5, in which the further electrode ( 418 ) in particular as a second gate electrode ( 418 ) and within the gate insulating layer ( 114 ) is arranged. A chemosensitive field-effect transistor according to one of the preceding claims, wherein the first gate electrode ( 116 ) and the further electrode ( 418 ), which in particular as a second gate electrode ( 418 ) is formed, opposite to the channel region ( 108 ) are arranged. A chemosensitive field-effect transistor according to one of claims 1 to 7, wherein the first gate electrode ( 116 ) opposite the channel region ( 108 ) and the further electrode ( 818 ), which in particular as a first getter electrode ( 818 ) is formed, opposite to the first contact area ( 104 ) are arranged. A chemosensitive field-effect transistor according to claim 6, wherein said second getter electrode ( 820 ) opposite to the second contact area ( 106 ), wherein the gate insulating layer ( 114 ) and the second getter electrode ( 820 ) form another gate stack that is not sensitive to the at least one chemical species. Procedure ( 900 ) for producing a chemosensitive field-effect transistor, the method ( 900 ) comprises the following steps: providing ( 1101 ) of a semiconductor substrate ( 102 ), which has a first contact area ( 104 ), a second contact area ( 106 ) and one between the first contact area ( 104 ) and the second contact area ( 106 ) channel region ( 108 ) having; Provide ( 1103 ) of a source contact ( 110 ), which the semiconductor substrate ( 102 ) in the first contact area ( 104 ) contacted electrically; Provide ( 1105 ) of a drain contact ( 112 ), which the semiconductor substrate ( 102 ) in the second contact area ( 106 ) contacted electrically; Arrange ( 1107 ) a gate insulating layer ( 114 ) opposite the channel region ( 108 ) on a surface of the semiconductor substrate ( 102 ); Connect ( 1109 ) of a first gate electrode ( 116 ) with the gate insulating layer ( 114 ) to pass through the gate insulating layer ( 114 ) and the first gate electrode ( 116 ) form a gate stack sensitive to at least one chemical species; and connect ( 1111 ) at least one further electrode ( 418 ; 818 ), in particular a second gate electrode ( 418 ) and / or a first getter electrode ( 818 ), with the gate insulating layer ( 114 ) to pass through the gate insulating layer ( 114 ) and the further electrode ( 418 ; 818 ) form a non-sensitive for the at least one chemical species gate stack. Use of a chemosensitive field effect transistor according to one of claims 1 to 10 as an absolute measuring gas sensor.

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