JPS6114563A - Semiconductor composite sensor - Google Patents

Abstract

PURPOSE:To measure density and pressure simultaneously as to many items by structuring the substrate of the titled sensor which has a field effect type semiconductor sensor and a semiconductor pressure sensor formed on the same substrate so that single-crystal silicon is grown on an insulating material by an epitaxial method. CONSTITUTION:An (n<->) type single-crystal silicon epitaxial grown layer 5, (p<->) diffused piezoresistance 3, (n<->) type single-crystal silicon epitaxial grown layer 6, SiO2 layer 10, and environment-resisting insulating layer (e.g. Si3N4) 11 are formed successively on the insulating substrate 1 (e.g. sapphire), and a diaphragm part 2 is formed to constitute a pressure sensor. Further, while an island-shaped silicon layer is formed, a (p<+>) type diffused lead part 4 connecting the resistance 3 and a metallic layer 13 for a lead contact, (p<+>) type drain diffused area 7, source diffused area 8, and (n<+>) type earth area 9 are formed. Further, a channel part 15 is formed of an SiO2 layer and then a chemically sensitive film 12 is formed thereupon to constitute the field effect type sensor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor composite sensor that can simultaneously measure the concentration of chemical substances and pressure. The present invention relates to a semiconductor composite sensor that utilizes the piezoresistive effect for pressure measurement.

[Background technology]

Traditionally, gate insulated field effect transistors (MI5
A semiconductor sensor has been proposed that utilizes the structure of an FET (FET) to measure the ionic activity and the concentration of chemical substances in an electrolyte. These are IonSensit
ive Field Effect Transist
or (l5FET) or Chemical FET
It is called (CHEMFET), and is
17 etc. have descriptions regarding these matters.

On the other hand, various configurations of silicon diaphragm type semiconductor pressure sensors have been proposed that utilize the piezoresistance effect in which the resistance value changes when mechanical stress is applied to the semiconductor.

These sensors both use silicon substrates, so
By making full use of recent advanced silicon IC manufacturing technology, it is possible to miniaturize and integrate compensation circuits, and various new applications have been proposed. For example, in medical applications, a sensor may be attached to the tip of a catheter and inserted into a blood vessel to directly and continuously measure information inside the body. That is,
Measurement of ion concentration in blood by CHEMFET, acetylcholine, urea, penicillin, etc. using a biofunctional material as a sensitive membrane, and intravascular or intracardiac blood pressure measurement using a pressure sensor. Continuous in-body measurement using these CHEMFET and pressure sensors individually is also very effective, but from a clinical medical point of view, it is extremely important to monitor blood pressure at the same time as measuring ion concentration and other substance concentrations. It becomes data.

Although this is possible by simultaneously installing a CHEMFET and a semiconductor pressure sensor in one catheter,
Installing individual sensors within the same catheter requires very complicated manual work, and is almost impossible to implement in actual practice.

As a solution to overcome these problems, the patent application 1983-
A semiconductor composite sensor has been proposed in No. 288880/2. As shown in the cross-sectional view of the structure in Figure 5, these devices have a structure in which a layer selectively sensitive only to a specific substance to be measured is provided on the gate portion of an insulated gate field effect transistor on the same semiconductor substrate. It has a structure that incorporates two types of sensors into one element: a field-effect semiconductor sensor and a semiconductor pressure sensor that uses a diffused resistor formed on a diaphragm as a pressure sensing part.

By the way, when this sensor is actually used, the pressure-sensitive diaphragm and chemically sensitive layer are directly exposed to the atmosphere to be measured, and
Lead contact parts etc. must be completely insulated and isolated from the atmosphere to be measured. For this purpose, the sensor element itself must be resistant to atmosphere. When using a silicon substrate, complicated processes are required to obtain atmospheric resistance, and the area required just to obtain atmospheric resistance on the surface of the element is also large, which makes it difficult to achieve ultra-small size. Although there are some results, there are many problems such as yield.

[Purpose of the invention]

An object of the present invention is to provide an ultra-small semiconductor composite sensor that can simultaneously measure the concentration and pressure of multiple chemical substances and can be attached to the tip of a catheter.

[Structure of the invention]

The most important feature of the present invention is that by using an insulating material as the substrate of the sensor, it is possible to reliably and easily obtain atmospheric resistance as a sensor element. This is SOI (S
ion In5ulator) structure. The SOI structure is one in which single-crystal silicon is directly formed on a single-crystal insulator such as sapphire using heteroepitaxial techniques and advanced technology. In particular, those using sapphire are called 5O8 (Ston on 5apphire).
).

The present invention will be explained below with reference to the drawings.

FIG. 1 is a plan view showing the structure of a semiconductor composite sensor as an embodiment of the present invention. Figure 2 is a cross-sectional view taken along the dashed line a-a' in Figure 1, and Figure 8 is b-b.
FIG. 4 is a sectional view taken along line C-C'.

The semiconductor composite sensor of this embodiment has a structure in which one field-effect semiconductor sensor and one semiconductor composite sensor are incorporated.

In fact, when using such a semiconductor composite sensor, it is only necessary to incorporate one semiconductor pressure sensor, and even if multiple semiconductor pressure sensors are incorporated, it is only expected that the accuracy will improve slightly by averaging the output values of each sensor. However, field-effect semiconductor sensors are very effective because they enable simultaneous measurement of multiple items by incorporating a large number of sensors formed with various sensitive films.

In the figure, the size of the sensor is 1.5 mm, and the thickness of the button is 0.5 mm.
The thickness of the 35 skin diaphragm portion is assumed to be 20 μm.

In this example, an insulating substrate (1) (for example, sapphire)
On Cζ, a first n'''' type single crystal silicon epitaxial growth layer (5) is formed, and on its surface, four p-type diffused piezoresistors (3) are formed. The basic structure is that the second n-type single crystal silicon epitaxial growth layer (6) is completely formed. Moreover, the structure in which the p-type diffused piezoresistor (3) is embedded in the n-type silicon layer (5, 6) is that the piezoresistor (3) is electrically completely isolated from the sensor surface. By separating, electrical disturbance caused by the atmosphere to be measured
The piezoresistor (3) prevents the detected pressure value from becoming unstable.

11 In this embodiment, unnecessary silicon layers are removed by etching to form island-shaped silicon layers having a predetermined pattern. When the silicon layer is formed into an island shape in this way, it can be completely protected by covering it with an atmosphere-resistant insulating layer αD. This atmosphere-resistant insulating layer must have a thickness of about 100 OX in the part below the chemically sensitive layer μs in the channel section α, but it is appropriate to have a thickness of about 1 μm in other parts. In addition, the material is 5isN4yAl!, which can be formed at low temperatures using plasma CVD. BOa+ SiOxNy+
AJOxNy, PSG (Phosph.

−5ilicate P2O55ins ) + Pb
O-Al! QOa・5i04 (Lead-Alumi
no-8ilicate) + PbO-B2O5・
510g (Lead-Boro-5ilicate
) r Pb()AI! gOa・BgOa・5i02
(Lead-Alumino-Boro-8ilic
A single-layer structure of polyimide resin or a multi-layer structure of a combination thereof can be considered.

The etching solution for forming the island shape is preferably an alkaline etching solution such as hydrazine or ethylenediamine, and 5iOs+ is suitable as the etching mask at this time.

With the island-like silicon layer formed in this way, a p-type diffusion lead part (4) connecting the diffused piezoresistor (3) and the metal layer for lead contact (to), and a p+-type drain q An n+ type grounding region (9) is formed near the source diffusion region (8) to ground the diffusion region (7), the saw/diffusion region (8), and the substrate.

The Sing Q□ that is finally formed is different from the 5i02 that was initially formed for etching into an island shape, and was re-formed after completely removing that 5iOi, and its thickness is 500 to 1000 A. In the channel portion αQ, it is used as a gate oxide film.

The chemically sensitive film □□□ only needs to be formed to cover at least the channel portion, and strict masking is not required.

Possible types of this sensitive film are listed together with the measurement target shown in brackets: St 6N4 rA
1gOs+Ta5O5 [crocodile ion], various NAS (N
ago -Al gos-5ing synthesis) glass [Na+ ion] palinomycin fixed membrane (K+ ion), various crown ether fixed membranes [K+ ion, Ag+
ion, TI + ion etc, l urease [[[
[, l.

Examples include a 7base-immobilized membrane [neutral lipid], a penicillinase-immobilized membrane [penicillin], an anti-albumin antibody-immobilized membrane [albumin], and an acetylcholinesterase-immobilized membrane [acetylcholine]. .

Furthermore, when forming multiple types of sensitive films at the same time, it is also conceivable to form a hydrophobic organic polymer film that is not sensitive to any chemical substance in order to be used as a reference electrode. Possible examples of such a polymer film include polyethylene, polypropylene, polyvinyl chloride Teflon, and the like.

The insulating layer α4 is used as a mask for forming the diaphragm portion. Etching using ultrasonic energy may be considered as a method for forming the diaphragm, but the most common method is etching with hot phosphoric acid using Sing as an insulating layer. The method for forming this 5i02 is SiH
A preferred method is to form the film by heating it from 300°C to 500°C in the atmosphere of 4 and 02, and then reheating it to 800°C or higher to make it dense.

〔Effect of the invention〕

The present invention uses only the minimum necessary semiconductor layer to form a chemical sensor that utilizes the electric field effect of semiconductors and a pressure sensor that utilizes the piezoresistive effect, and the other parts are made of a single crystal insulator such as sapphire. By doing so, the greatest feature is that the 7-insulator element itself essentially obtains extremely excellent insulation and atmosphere resistance. Therefore, even if it is applied as a catheter tip-type composite sensor, its implementation is significantly easier than with conventional semiconductor composite sensors. Furthermore, its long-term reliability is incomparably superior to cases where insulation is obtained using epoxy resin or silicone resin.

In addition, compared to the case where a silicon wafer is processed eight-dimensionally to form an insulating film on the surface of the sensor element to obtain atmospheric resistance, the process is relatively simpler and requires less etching. Since the available area can be used, the number of sensor elements that can be manufactured from a wafer of the same area increases dramatically.

Furthermore, since the silicon layers are separated into islands, they can be completely insulated from each other. Therefore, it is easy to install an electric circuit together with the sensor on the same chip, and it is possible to incorporate an electric circuit into the intelligent It is fully compatible with sensors.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the structure of a semiconductor composite sensor in which a field effect semiconductor sensor and a semiconductor pressure sensor are simultaneously formed on a substrate in which single crystal silicon is epitaxially grown on an insulating material, which is an embodiment of the present invention. It is a diagram. Second
The figure is a sectional view taken along dashed line a-a' in Fig. 1, similarly, Fig. 3 is a sectional view taken along b-b(), and Fig. 4 is a sectional view taken along dashed line a-a'.
It is a sectional view at -c'. FIG. 5 is a sectional view showing the basic configuration of a semiconductor composite sensor using a silicon single crystal substrate according to the prior art. 1. Insulating substrate (for example, sapphire substrate) 2. Diaphragm part 3. Diffused piezoresistance (p'' type) Raw diffusion lead part (p raw type) 5. Single crystal silicon epitaxial growth layer (n-type) Part 1 6 , single crystal silicon epitaxial growth layer (n-type) part 2 7, drain diffusion region (p-type) 8, source diffusion region (p-type) 9, grounding diffusion region (n-type) 10, 5iOs+ layer 11, Atmospheric resistant insulating layer (e.g. 5iaN4) 1'
ii2. Chemically sensitive layer 13, lead contact metal layer 14, insulating layer (for example, SiOg) 15, channel portion J6. Silicon single crystal substrate Ya1 Figure 5

Claims (2)

[Claims] (1) A field-effect semiconductor sensor in which a layer selectively sensitive to a specific substance to be measured is provided on the gate part of a gate-insulated field-effect transistor, and a semiconductor that uses a diffused resistor formed on a diaphragm as a pressure-sensitive part. A semiconductor composite sensor in which at least one pressure sensor is formed on the same substrate, wherein the substrate has a structure in which single crystal silicon is epitaxially grown on an insulating material. (2) The semiconductor composite sensor according to claim 1, wherein the insulating material is sapphire.