JPH0474666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to chemically sensitive semiconductor sensors, particularly field effect semiconductor sensors.

In recent years, research on chemically sensitive sensors that utilize the electric field effect of semiconductors has become active. This utilizes the fact that the conductivity near the surface of the semiconductor changes in response to changes in the electric field generated at the interface between the semiconductor and the solution.
Transistor).

However, the conventionally used ISFET
have been manufactured using single crystal silicon as a material, but single crystal silicon has the drawback of being mechanically brittle. Therefore, when installing an ISFET in an actual chemical sensor structure, such as a catheter, (1) First, solder the lead wire to the ISFET.

(2) Store the ISFET-lead wire in the catheter,
Electrically insulate everything other than the sensing part. (3) Next, connect the connector to the other end of the lead wire. This required complex processes that were difficult to automate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor sensor that overcomes the drawbacks of conventional sensors, is capable of automation, and is easy to assemble into a sensor structure.

According to the present invention, at one end of a heat-resistant polymer film having an elongated planar shape, a substrate region made of P-type amorphous silicon, and an n-type drain region on one side sandwiching the substrate region; A source region having a doping polarity opposite to that of the substrate region and a P-type ground region are formed on the other side across the substrate region, a drain electrode is provided at an end of the drain region, and a source region and a ground region are formed. A source electrode is provided at the end of the region so as to short-circuit both, and at least the substrate region is coated with a chemically selective sensitive film, and the drain region, source region, ground region, and other parts of the film surface are covered with a chemically selective sensitive film. A chemically sensitive semiconductor sensor characterized in that part or all of the sensor is covered with an electrically insulating film can be obtained.

Next, an embodiment of the semiconductor sensor of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the ISFET of the present invention, in which a substrate region 2 made of amorphous silicon constituting a sensor portion covered with a chemically selective sensitive film is formed at one end of an elongated heat-resistant film 1. A drain region 3 is provided on one side of the substrate region, and a source region 4 is provided on the other side, and a ground region 9 is provided extending on the film 1 so as to be in contact with and along the source region. The other end of the drain region is covered with a drain electrode 5, and the source region and the ground region are short-circuited to each other by the source electrode 6. The drain electrode and the source electrode are connected to lead wires 7 and 8 formed on the film and extended to the other end of the film, respectively, and a wire connection portion 14 is provided at the other end of the lead wire. It is being 2. FIGS. 1 to 4 are cross sections taken along lines aa, bb, cc, and dd in FIG. 1, respectively. Figure 2 1 is a cross-sectional view taken along line a-a.
The cross-sectional structure of the ISFET gate section is shown. 1 is an elongated heat-resistant polymer film, 2 is a P-type amorphous silicon region of the substrate portion, 3 is an n-type drain region,
4 is an n-type source region, 10 and 11 are electrical insulating films made of SiO ₂ film and Si ₃ N ₄ film, and this ISFET with SiO ₂ film or Si ₃ N ₄ film on the substrate surface is a PH
Can be used as a sensor. A chemically selective sensitive film 12 sensitive to various chemical substances can be coated on the surface of an electrically insulating film made of a SiO ₂ film and a Si ₃ N ₄ film coated on a substrate region. This chemically selective sensitive film is a film that causes a change in interfacial potential by reaction with a specific chemical species, and is a film in which SiOxNy, Al ₂ O ₃ , SiOxNy, Al ₂ O ₃ ,
Ta ₂ O ₅ or PH-sensitive silicone rubber, etc.
PH-sensitive membrane, K ⁺ ion-sensitive membrane such as polyvinyl chloride containing valinomycin, Na ⁺ ion-sensitive membrane such as NAS glass, etc.
Immunization consisting of ion-sensitive membranes, Ca ²⁺ ion-sensitive membranes such as didecyl phosphate-containing polyvinyl chloride, specific substrate-sensitive membranes such as enzyme-immobilized polymers, and polymers immobilized with immune substances (e.g. antigens, antibodies, haptens). It is possible to coat a material-sensitive film or the like. Figure 2 2
is a cross-sectional structure taken along line bb, showing the drain and source regions 3 and 4 formed on the heat-resistant polymer film 1.
and a P-type grounding region 9 provided along the source region and a SiO ₂ insulating film 10 formed on its surface.
and a Si ₃ N ₄ insulating film 11. FIG. 2 3 shows a cross-sectional structure of the bonding part c-c, in which lead wires 7 and 8 are formed in close contact with each other on the heat-resistant polymer film 1, and a wire is provided on the upper surface of the lead wire at the end of the drain region. A drain electrode 5, a source electrode 6 that short-circuits the ground region 9 and the source region 4 are formed. Their surfaces are similar to the bb section
It is covered with a SiO ₂ film 10 and a Si ₃ N ₄ film 11. This eliminates the need to solder the drain and source terminals and lead wires, significantly simplifying the manufacturing process of the sensor structure. FIG. 2 shows a cross-sectional structure of the lead wire portion dd, in which lead wire portions 7 and 8 are formed on the heat-resistant polymer film 1.

For example, the ISFET may have a drain region, a source region, and a ground region extending from a substrate region provided at one end of an elongated film to the other end, and a drain electrode and a source electrode may be provided at the other end of the film. Wiring can then be accomplished by insulating a lead wire to the electrode and covering the connection portion with resin.

The polymer film used in the semiconductor sensor of the present invention needs to be heat resistant.
As explained later, the production of amorphous silicon requires
Requires a temperature of 200 to 400°C. Therefore, the polymer film must be stable at 200 to 400°C. As such a polymer film, a polyimide film such as polyimide, polyamideimide, polyesterimide, polyamino bismaleimide, etc. is used.

Next, a method for manufacturing the semiconductor sensor shown in FIG. 1 will be explained with reference to FIGS. 1 to 4. First, as shown in FIG. 3, lead wires are connected to the drain electrode 5 and the source electrode 6 by the method disclosed in Utility Model Application Publication No. 57-105959, for example, on the elongated heat-resistant polymer film 1. Form 7 and 8. As the material of the lead wire, metals such as copper, aluminum, platinum, gold, silver, nickel, molybdenum, and various other alloys can be used. Next, as shown in FIG. 3, a P-type amorphous silicon portion 13 is patterned on the film. This amorphous silicon is usually formed by a plasma reaction. As the plasma reaction, either an inductive coupling method or a capacitive coupling method may be used. Monosilane, hydrogen, and a trace amount of diborane are used as the gas atmosphere, and the total pressure of the gas is 0.01 to 10 mmHg, preferably 0.1 to 5 mmHg. At this time, the substrate temperature (in this case, the temperature of the heat-resistant polymer film) is preferably 200 to 350°C. A frequency of 13.56 MHz is usually used as the high frequency. Amorphous silicon is formed by arc discharge,
Other methods such as CVD and sputtering may also be used. Such a method for producing amorphous silicon is described, for example, in Japanese Patent Application Laid-open Nos. 56-98819 and 56-100126. The thickness of the amorphous silicon layer is preferably 0.1 to 3 μm. The amorphous silicon produced in this way is non-crystalline and consists of silicon and hydrogen. The hydrogen content in this is usually 15 atomic % or less. After forming the amorphous silicon, a predetermined pattern is formed by ordinary photolithography. Next, as shown in FIG. 3, the substrate portion 2 is masked with a photoresist, and phosphorus is ion-implanted into the region where the drain region 3 and source region 4 are to be formed to make this region n-type. As shown in FIG. 4, the area other than the area where the ground area 9 will be formed is masked and boron ions are implanted into this area to make this area P-type. After that, the area other than the substrate area is masked with photoresist and phosphorus is implanted into the substrate area. Inject ions and adjust threshold voltage. Next, after removing the photoresist, an insulating layer SiO ₂ is formed over the entire amorphous silicon layer.
The SiO ₂ layer can also be created by low-temperature oxidation of amorphous silicon (oxidation temperature below 450°C), but it is also possible to create it by low-temperature CVD (SiH ₄ + O ₂ ), sputtering targeting SiO ₂ , or electron beam evaporation of SiO ₂ . It can be created even if it is twisted. In either case, the substrate temperature is preferably 200 to 450°C. The thickness of the SiO ₂ insulating film is preferably 200 to 3000 Å.
Next, a Si ₃ N ₄ insulating film layer is further formed on the SiO ₂ layer. This Si ₃ N ₄ film can also be produced by plasma CVD, sputtering targeting Si ₃ N ₄ , or Si ₃ N ₄ film.
It can be created by electron beam evaporation. In this case as well, the substrate temperature is preferably 200 to 450°C. Also, the thickness of the Si ₃ N ₄ insulating film is 200 to 3000 mm.
Å is preferred. In this way, the surface of the amorphous silicon semiconductor portion can be covered with the insulating film of SiO ₂ and Si ₃ N ₄ . This ISFET can be used as a PH sensor. Finally, on the surface of the board
A PH sensitive film other than Si ₃ N ₄ or another chemically sensitive film is coated on the Si ₃ N ₄ layer of the substrate portion.

Next, another embodiment of the ISFET of the present invention will be described with reference to FIG. FIG. 4 is a plan view of the ISFET, and a substrate region 2 made of amorphous silicon that constitutes a sensor section covered with a chemically selective sensitive film 12 is formed at one end on the elongated heat-resistant film 1. A drain region 3, a source region 4, and a ground region 9 are provided only on both sides. A drain electrode 7 is provided on the upper surface of the drain region, and a source electrode 8 is provided on the upper surfaces of the source region 4 and the ground region 9, and these electrodes are connected to lead wires 7 and 8 extending to the other end of the film, respectively. has been done. A wire connection portion 14 is provided at the other end of the lead wire. FIG. 5 shows cross-sectional structures taken along lines aa and bb in FIG. 4, respectively. Figure 5 1 shows the gate part (chemically sensitive part) of a semiconductor element.
1 is a heat-resistant polymer film,
2 is a P-type amorphous silicon region of the substrate portion, 3
and 4 are n-type amorphous silicon drain and source regions, 9 is a P-type ground region, and 7'
and 8' are the drain and source electrode metals, respectively, and 1
0 is a SiO ₂ film, 11 is a Si ₃ N ₄ film, and 12 is a chemically selective sensitive film. The ground region 9 can be made of metal that forms the source electrode 8'.

FIG. 52 is a cross-sectional structure taken along line bb in FIG. 4.
This part is an electrode lead part, and includes electrode lead parts 7 and 8 connected to the drain electrode 7' and source electrode 8' formed on the heat-resistant polymer film 1, and the SiO ₂ insulating film 10 formed on the surface thereof. , and a Si ₃ N ₄ insulating film 11 formed thereon. By being covered with these insulating films, the lead portions of the drain and source electrodes are completely insulated.
The manufacturing process of this structure is further simplified than that of the ISFET shown in FIG. Note that the drain region 3 and source region 4 made of n ⁺ amorphous silicon may be omitted, and the drain electrode metal 7' and source electrode metal 8' may be directly coated on the surface of the amorphous silicon region 2 of the substrate portion. In this case, the manufacturing process is further simplified.

The manufacturing method of the ISFET shown in Figure 5 is shown in Figure 6.
Shown in 3.

First, as shown in FIG. 6, amorphous silicon 2 which is undoped or doped with diborane (P type when doped with diborane) is formed on a heat-resistant polymer film 1 by plasma CVD. The thickness is preferably 0.1 to 3 μm. Next, amorphous silicon doped with phosphine is formed on the amorphous silicon 2, and as shown in FIG.
form a pattern. Note that the drain region 3 and source region 4 may be omitted. Next, the drain electrode metal 7', the drain electrode lead part 7, the source electrode metal 8', the ground region, and the source electrode lead part 8 are simultaneously formed by a conventional method such as vapor deposition or sputtering, and are then formed by photolithography as shown in FIG. 6.
Create a predetermined pattern like this. The electrode metal is the first
This is as described in the case of ISFET in the figure. The subsequent steps are the same as for the ISFET shown in Figure 1.

The sensor thus produced can be assembled into the circuit shown in FIG. 7 to measure the amount of chemical substances in the measurement liquid. This circuit is a source follower circuit, and the comparison electrode 40 is grounded. A constant voltage V _D is applied to the drain 41 of the sensor,
A constant current circuit 43 is connected between the drain 41 and the source 42.
A constant current is flowing. When the semiconductor sensor 44 and reference electrode 45 are inserted into a liquid to be measured, such as a blood vessel, the Si ₃ N ₄ film coated on the substrate area of the sensor interacts with hydrogen ions in the liquid to be measured, and the semiconductor Changing the interfacial potential of the substrate region of the sensor. As the interface potential changes, the source potential Vs changes. Therefore, by measuring the potential between the output terminal 47 and the comparison electrode 45, the hydrogen ion concentration in the measurement liquid can be measured.

FIG. 8 shows a multi-sensor in which a plurality of sensors 20, 21, 22, 23 are formed on the same heat-resistant polymer film 1. The surface of the substrate region of each sensor is coated with films 24, 25, 26, 27 that are selectively sensitive to different chemical substances. By providing a plurality of substrate regions on a single film in this way, the amounts of different chemical substances in a solution can be measured independently and simultaneously with one device. FIG. 9 shows a chemically sensitive sensor 30, a comparison electrode 31 that does not respond to the chemical activity in the solution but responds only to the potential of the electrolyte, and a pseudo reference electrode 32 for conductivity bias in a single structure. This is an example of a composite sensor provided on a heat-resistant polymer film 1,
As the reference electrode, a sensor whose substrate region is coated with a non-porous hydrophobic organic polymer film such as tetrafluoroethylene can be used, as described in, for example, JP-A-54-81897. Furthermore, a metal deposited on a polymer film can be used as the pseudo reference electrode. Since such a composite sensor can be extremely miniaturized, it can be particularly used as a sensor inserted into a living body.

As described above, since the semiconductor sensor of the present invention has flexible amorphous silicon formed on a heat-resistant polymer film, it is easy to fabricate a sensor structure, and it can be used by inserting it into a narrow site, for example, in a living body. Since the sensor is flexible, it can be easily inserted into a living body, making it extremely useful in practice.
Furthermore, when mass-producing sensors, it is possible to manufacture sensors at extremely low cost by arranging a large number of sensors on a large area heat-resistant polymer film using the method described above, and finally separating them into individual sensors. It has excellent effects such as:

[Brief explanation of drawings]

FIG. 1 is a plan view of the semiconductor sensor of the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a plan view of each step of the method for manufacturing the sensor shown in FIG. 1. FIG. 4 is a plan view showing another embodiment of the semiconductor sensor of the present invention, FIG. 5 is a cross-sectional view thereof, and FIG. FIG. FIG. 7 is a measurement circuit diagram using the sensor of the present invention, and FIGS. 8 and 9 are cross-sectional views showing a composite sensor.

Claims (1)

[Claims] 1. A substrate region made of P-type amorphous silicon is provided at the end of a heat-resistant polymer film having an elongated planar shape, and an n-type drain is provided on one side of the substrate region. an n-type source region and a p-type ground region are formed on the other side of the substrate region, a drain electrode is provided at the end of the drain region, and a drain electrode is provided at the end of the source region and the ground region. A source electrode is provided to short-circuit both, and at least the substrate region is covered with a chemically selective sensitive film, and the drain region, the source region, the ground region, and part or all of the other film surfaces are electrically insulated. A chemically sensitive semiconductor sensor characterized by being coated with a film. 2. A plurality of substrate regions are provided at an end portion of a heat-resistant polymer film, and the surface of each of the plurality of substrate regions is coated with a different chemically selective sensitive film. chemically sensitive semiconductor sensors. 3. The chemically sensitive semiconductor sensor according to claim 1, wherein the heat-resistant polymer film is a polyimide film. 4. The chemically sensitive semiconductor sensor according to claim 1, wherein the electrical insulating film is a two-layered film composed of silicon oxide and silicon nitride.