JPH0712770A - Biosensor device and preparation thereof - Google Patents

Abstract

PURPOSE: To realize a low-cost sensor by providing a conductor area spread between contact body areas created on the surface and back of a substrate, and measuring the resistance value between the contact bodies of the back. CONSTITUTION: Dielectric layers (oxide) 23, 24 are formed on the surface and back of a semiconductor substrate (N-type Si). Metallic conductors 26, 28 come into contact with the substrate 22 through an opening part of the layer 23, and are respectively connected to one set of alternately disposed contact body fingers 27, 29. One pair of back contact bodies 30, 32 are formed on the layer 24 to come into contact with the substrate 22 through the contact hole of the layer 24. The contact body 30 comes into ohmic contact with conductor 26. An area 34 is formed by diffusing P-type impurities through the substrate 22. The contact body 32 similarly comes into ohmic contact with the conductor 28 through a conductor area 36. The metallic conductor on the substrate 22 is covered with a polymer emzyme layer 42 and further covered with a polymer coating 44. The layer 42 is made react with the blood of a human body, and the blood sugar value can be detected by measuring the resistance value between the contact bodies 30, 32.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a sensor for medical diagnosis.

[0002]

2. Description of the Related Art In the field of medical diagnosis, the technique of using a sensor is rapidly growing. By using such a sensor, a quick and inexpensive test method, such as knowing the amount of glucose in blood from the measurement of the resistance value, can be obtained.

Prior art sensors are shown in FIGS.
Is shown in. Leads N1 and N2 are created on the surface of the sensor. Enzyme polymer layer L1 and coating layer L2
Is created on the conductor. A drop of blood is applied to the surface of the sensor, and this blood reacts with the enzyme layer L1. The resistance value between the conductors is then measured. This provides a faster, simpler, and more accurate blood glucose readout than current optical methods. One major problem with silicon based sensors is cost. The cost must be very low, since each sensor is used only once and then discarded.

A major problem that must be solved when manufacturing such a sensor is that the polymeric material is very sensitive and requires careful handling.
And when it is made into a pattern, it is difficult to perform necessary heating and treatment with chemicals. Therefore, there is a need for a method of connecting to terminals N1 and N2 without adversely affecting the polymer. One such prior art method is to etch through the wafer and provide the backside with contacts. However, this technique is very expensive to manufacture due to the stress inside the wafer and the resulting damage.

[0005]

1 and 2 are drawings of a biosensor device 10 according to the prior art. Biosensor 10 is typically fabricated on a silicon substrate 12 and has a pair of leads N1 and N2. The conductors N1 and N2 are preferably made of metal. The conductors N1 and N2 are formed on the insulator layer 14 formed on the substrate 12. A polymer enzyme layer 16 is formed on the leads N1 and N2. Then, the polymer protective layer 18 is formed on the polymer enzyme layer 16.

When using this sensor, a blood sample is applied onto the polymer protective layer and the resistance between the conductors N1 and N2 is measured. From this measured resistance value, the level of blood glucose can be known as a result of the interaction between the blood sample and the polymer enzyme.

In order to measure the resistance between the conductors N1 and N2, it is necessary to make connections to these conductors and the backside surface so as not to disturb the outer surface of the sensor 10.

FIG. 3 shows a sensor 2 made according to the present invention.
0 shows a cross-sectional view of 0. This sensor is formed on the semiconductor substrate 22. In the preferred embodiment, semiconductor substrate 22 is N-type silicon. Dielectric layers 23 and 24 are formed on the upper surface and the back surface of the substrate 22, respectively.
The metal leads 26 and 28 contact the substrate 22 through the openings in the dielectric layer 23. Each of the conductors 26 and 28 is also connected to a vertically elongated set of interleaved contactor fingers 27 and 29. The sets of fingers 27 and 29 are interleaved, but they are not in electrical contact with each other.

On top of the dielectric layer 24, a pair of backside contacts 3
0 and 32 are created. This pair of back side contact bodies 30
And 32 through the contact holes of the dielectric layer 24,
Contact the substrate 22. In the preferred embodiment, the dielectric layer 2
3 and 24 are oxides, but dielectric layers 23 and 2
4 can also be another dielectric material.

The backside contact 30 makes ohmic contact with the metal wire 26 through the conductor region 34. Conductor region 34 extends through substrate 22. Conductor region 34 is preferably created by diffusing P-type impurities through substrate 22.

The back contact 32 is likewise provided in the conductor region 3
Through 6 into ohmic contact with the metal conductor 28. Conductor region 36 is preferably created when conductor region 34 is created.

4 to 15 are drawings showing in detail the process sequence of the present invention. It is noted that these detailed drawings of the process sequences are for illustration only and the invention is not limited to this process sequence. In FIG. 4, the process starts for the silicon substrate 22. In the preferred embodiment, the thickness of substrate 22 is from 254 micrometers (10 mils) to 279 micrometers (1
1 mil) and both the top and back surfaces are polished by etching. In the preferred embodiment, it is made on a 76 millimeter (3 inch) wafer, but other sized wafers can be used.

FIG. 5 shows the substrate 22 after the oxidation step has been performed and barrier oxide layers 23 and 24 have been created on the upper and backside surfaces of the substrate. The oxide layers 23 and 24 are
It is preferred to have a minimum thickness of about 8000 Angstroms. The substrate is placed in a dry oxygen atmosphere at about 1100 ° C. for 10 minutes, then in a moist O ₂ atmosphere for 230 minutes, and then in a dry O ₂ atmosphere for 5 minutes.

Next, as shown in FIGS. 6 and 7, an opening 25 is created by etching through the oxide layer 24 on the back surface of the substrate 22. After the opening 25 is created, the silicon substrate 22 is etched to a depth of 2.0 micrometers to 15.0 micrometers, as shown in FIG. The preferred depth of this etch is 10 micrometers. The registration marks 27 made by etching on the silicon substrate 22 are used to align the mask, thus reliably masking the backside of the substrate 22 by diffusion as described below, and the backside contactor Correct alignment with the contacts made on the upper surface of 22 is performed.

The above-described oxide removal and registration etch steps are performed if a structure is present to ensure alignment with subsequent oxide removal steps, or if the alignment is present. It could also be omitted if some kind of marking to ensure that it was provided on the substrate prior to the processing step.

A window 29 is then created through the oxide layers 23 and 24 on the upper and back surfaces of the substrate 22, as shown in FIG. Impurities are then deposited through window 29, as shown in FIG.
Alternatively, impurities are implanted. Then, the impurities are diffused, thereby forming diffusion regions 34 and 36 extending from the upper surface to the back surface of the substrate 22. In the preferred embodiment, this diffusion occurs at a temperature of 1300 ° C. for a period of 157 hours for the P-type material with boron deposited in the window 29. As can be readily seen in the figure, this diffusion step results in conductor regions 34 and 36 of P-type material extending from the upper surface to the back surface of substrate 22.

In yet another embodiment, the window 29 region portion of the back surface of substrate 22 is etched away to reduce the thickness of substrate 22 in the region where the diffused conductor regions are created. This can reduce the diffusion time required for the diffusion from the top surface and the diffusion from the back surface to merge, and also this can reduce the impedance between the top and back surfaces. Can be made smaller.

After the diffusion is complete, the oxide grown during the diffusion process is removed, preferably with a wet HF solution. Then, the substrate 22 as shown in FIG. 10 remains behind. Next, as shown in FIG. 11, oxide layers 23 and 24 are grown on the upper and back surfaces of substrate 22 to a thickness of approximately 1000 angstroms.

Contact windows 37 are then made through the oxide layers 23 and 24, as shown in FIG. 12, and conductors () are then formed on the upper and backside surfaces of the substrate 22. A layer 40, preferably of metal) is created. In the preferred embodiment, chromium is deposited to a thickness of 500 Å and then gold is deposited to a thickness of 500 Å. Instead of chromium, other metals such as titanium can be used.

In some cases, it may be necessary to perform additional process steps to obtain the required ohmic contact between metal layer 40 and P-type diffusion regions 34 and 36. To get a larger ohmic contact,
An additional process step of adding P-type diffusion can be added prior to metallization. Contact body opening 3
After 7 is created, diffusion of P-type impurities is performed during the processing steps, as shown in FIG. Thereafter, the process steps shown in FIGS. 10, 11 and 12 are repeated.

After the metal layer 40 is deposited, it is patterned to create the backside surface contacts 30 and 32. On the upper surface of the substrate 22, metal body fingers 27, 2 interleaved, as shown in FIG.
Nine sets are created.

The metal body fingers 27, 29 can be made, for example, by depositing a layer of chrome, then a layer of gold, and patterning the stack by etching. . Other methods can be used, such as patterning a layer of chrome and then coating it with gold. Instead of chromium, other metals such as aluminum can be used.

In the preferred embodiment, again referring to FIG.
The metal wire on the substrate 22 is coated with a polymer enzyme layer 42, and the polymer enzyme layer 42 is coated with a polymer coating 44.
Is covered with. The polymer enzyme layer 42 reacts with human blood, and the blood glucose level of blood can be known from the measurement of the resistance value between the metal leads 27 and 29.

The enzyme coating 44 and the enzyme layer 42 also serve as a kind of sponge for holding the blood sample in the area of the sensor, so that the blood sample can be read out without escaping from the sensor. .

In use, a small amount of blood sample is used by the sensor 2.
Spread over the surface of 0. The sensor 20 is then attached to a device (not shown) having contacts electrically connected to the back contacts 30 and 32, and the resistance between the back contacts 30 and 32 is measured. To be done. The blood glucose level can be obtained from the measured resistance value.

Another embodiment of the present invention is shown in FIG. To ensure that the sensor works properly,
It is important to completely wet the surface of the sensor. In this alternative embodiment, an auxiliary sensor 40 is created around the sensor 20. The auxiliary sensor 40 is smaller than the main sensor 20, but is preferably made using the same process steps as the sensor 20.

Since reading the sensors is a simple DC resistance measurement, the auxiliary sensors 40 are read out sequentially and their values are compared. If the measurement at auxiliary sensor 40 is not within the pre-specified range, it will indicate to the user that the entire surface of sensor 20 is not wet with blood and the sensor is in error. In yet another embodiment (not shown), the peripheral sensors are distributed.

It is also desirable that the biosensor mounted so that resistance measurements be made be calibrated against the temperature of the biosensor. One example in which temperature compensation is possible is shown in Figure 17a. FIG. 17a shows that in the sensor of FIG. 3, one P-type diffusion region 23 is shorted to the substrate to create a diode 30.
In another embodiment, as shown in Figure 17a, the connection to the substrate is made by etching a larger contact hole 13 '.

Next, the change in voltage with respect to temperature is calibrated (about 2 mV / ° C.). A schematic diagram of this construct is shown in Figure 17b.

A second method of calibrating the sensor for changes in temperature is shown in FIGS. 18a and 18b. In this method, the resistor 32 created by diffusion is
Made in the substrate 12 underneath the connected metal fingers 19. This resistor forms part of the contact between which the resistance is measured. Resistor 3 created by diffusion
2 is created by a well-known diffusion technique. A schematic diagram of a diffusion created resistor is shown in Figure 18b.

A third method is to make a resistor bridge circuit made of diffusion under interdigitated fingers to provide a ratio change of the resistors as the temperature changes. This embodiment would require a reference resistor on the substrate and would also require four terminals.

In the preferred embodiment of the invention, the sensors are separated and packaged so that the individual sensors are available when needed. However, in yet another embodiment, multiple sensors are packaged together as individual unit devices and have circuitry on the substrate itself for selecting individual sensors and making electrical measurements. Carry out.

When a circuit arrangement is made which connects the individual sensors to the detection / measurement circuit, the circuit arrangement is made on the upper surface of the substrate and allows the connection to external circuits from the rear surface through the diffusion area. Alternatively, the circuitry can be made on the backside surface of the wafer and the sensor can be connected to the circuitry through the diffusion area.

In such a device, a multiplexer is provided for electrically selecting the individual sensors, and a microprocessor or equivalent circuit is provided for performing the measurements. The device also has a gasket / cover configured to invoke individual sensors to connect to the blood sample. The microprocessor circuit connects the selected sensor to the processing device. In this way, a device with disposable sensors is obtained, with a sufficient number of sensors that the measurements can be taken for a sufficient length of time.

With regard to the above description, the following items will be further disclosed. (1) creating a region of the second conductivity type on the upper surface of the substrate, creating a region of the second conductivity type on the back surface of the substrate, and from the upper surface of the substrate to the back surface Diffusing the region to create a region of the second conductivity type extending through the substrate.
A method of forming a contact body penetrating a semiconductor substrate of a conductive type. (2) The method according to claim 1, wherein the step of forming the region includes the step of implanting an impurity of a second conductivity type into the region. (3) The method of claim 1, wherein the step of creating the region comprises the step of depositing impurities of a second conductivity type in the region in a furnace.

(4) The method of claim 1, wherein an oxide layer is formed on the upper surface and the back surface of the substrate, and a portion of the oxide layer is etched to form the region. The step of removing further. (5) The method according to the item 1, wherein the step of diffusing the region further includes the step of heating the substrate.

(6) Forming a contact body on the upper surface of the substrate, and forming a conductor region penetrating the substrate from the contact body on the upper surface of the substrate to the back surface of the substrate. And forming a contact body in ohmic contact with the conductor region on the backside surface of the substrate, the method of forming a sensing device on a silicon substrate having a backside contact body.

(7) The method of claim 6, further comprising the step of forming a reactive layer on the upper surface of the substrate. (8) The method of claim 6, wherein the step of creating a conductor region deposits an impurity of a first conductivity type on a region of the upper surface of the substrate; Diffusing the impurities so that a conductor region is created between the region and a region of the backside surface of the substrate.

(9) In the method described in the sixth item, the step of forming a conductor region may include implanting an impurity of the first conductivity type into a region of the upper surface of the substrate, and the step of forming the substrate. Implanting an impurity of the first conductivity type into the region of the backside surface, and injecting impurities into the region of the upper surface of the substrate to the region of the backside surface of the substrate. Diffusing the impurities. (10) The method according to claim 9, wherein the step of performing diffusion includes the step of heating the substrate.

(11) The method of claim 6 wherein the step of diffusing deposits an impurity of the first conductivity type in a region of the upper surface of the substrate and the back surface of the substrate. Depositing an impurity of the first conductivity type in the region, and the impurities in the region so as to diffuse the impurity from a region of the upper surface of the substrate to a region of the back surface of the substrate. Diffusing the method.

(12) A semiconductor substrate having an upper surface and a back surface, a contact body region formed on the upper surface of the substrate, a contact body region formed on the back surface of the substrate, and the substrate. A conductor region extending from the contact region of the upper surface to the contact region of the back surface of the substrate.

(13) A first contact body region and a second contact body region formed on the upper surface of the substrate, and a first contact body region and a second contact body region formed on the back surface of the substrate. And extending through the substrate, each having an ohmic connection between one of the contact body regions of the upper surface of the substrate and one of the contact body regions of the backside surface of the substrate, A biosensor on a semiconductor substrate having a pair of conductor regions.

(14) In the biosensor according to the thirteenth item, one metal lead wire is connected to the first contact body region, and another one metal lead wire is connected to the second contact body region. The biosensor, further comprising a pair of metal leads. (15) In the biosensor according to item 13, there are provided a plurality of vertical metal conductive wires on the upper surface of the substrate,
A first set of the vertical metal conductors is connected to the first contact body region, a second set of the vertical metal conductors is connected to the second contact body region, and a first set of the vertical metal conductors Interspersed between the second set of vertical metal conductors,
The biosensor further comprising.

(16) The biosensor according to the fifteenth item, further comprising a coating formed on the metal wire and reacting with a biological sample placed on the metal wire. . (17) The biosensor according to item 16, wherein the biological sample is blood.

(18) A plurality of pairs of pairs of contact bodies on the upper surface of the substrate and a plurality of pairs of contact bodies on the upper surface of the substrate, respectively. A plurality of pairs of contacts on the backside surface of the substrate and a plurality of pairs of conductor regions extending through the substrate, each conductor region being one on the upper surface of the substrate. A plurality of pairs of the conductor regions, which make ohmic contact between one of the pair of contacts and one of the corresponding pair of contacts on the backside surface of the substrate; One of an analysis circuit on the back surface of the substrate and one of the pairs of contacts on the back surface of the substrate for performing electrical measurements between the contacts on the back surface. Formed on a semiconductor substrate having a circuit selectively connected to the analysis circuit, Biosensor device.

(19) The biosensor device according to the eighteenth item, further comprising a coating body formed on the upper surface of the substrate and reacting with a biological sample arranged thereon. The biosensor device. (20) In the biosensor device according to item 18,
A plurality of sets of interleaved metal leads formed on the upper surface of the substrate, each set associated with and associated with a pair of contacts on the upper surface. The biosensor device further comprising a plurality of sets of interleaved metal leads, each one of the sets being connected to one of the pairs of contacts.

(21) The biosensor device according to item 18, further comprising a device for supplying a biological sample to one of the sensor regions. (22) In the biosensor device according to item 18,
The biosensor device further comprising a circuit for temperature compensation formed on the substrate.

(23) depositing an impurity of one conductivity type on one surface of the substrate and passing through the substrate so that the impurities form a conductive region extending from the upper surface to the back surface of the wafer. Diffusing impurities, and forming a backside surface contact having metal regions on the upper surface of the substrate.

(24) A biomedical sensor (20) is fabricated on a semiconductor substrate (22). Insulated dielectric layers (23, 24) are formed on the upper surface and the back surface of the semiconductor substrate (22). Metal conductor (26, 28)
Contact the substrate (22) through openings in the dielectric layer (23). Each of the conductors (26, 28) also includes a set of inter-positioned longitudinal contact fingers (2
7, 29). A pair of contacts (30, 32) are created on the surface of the substrate (22) opposite the contact fingers (27, 29). A conductive biological sample is placed on top of the interdigitated fingers (27, 29) and electrical measurements can be made by the backside contacts (30, 32). Thereby, the resistance value can be measured.

[Brief description of drawings]

FIG. 1 is a plan view of a prior art biomedical sensor.

2 is a cross-sectional view taken along line 2-2 of FIG.

FIG. 3 is a cross-sectional view of a biomedical sensor made in accordance with the present invention.

4 is a diagram of various stages in a manufacturing process of the sensor of FIG.

5 is a diagram of various stages in a manufacturing process of the sensor of FIG.

6 is a diagram of various stages in a manufacturing process of the sensor of FIG.

7 is a diagram of various stages in a manufacturing process of the sensor of FIG.

8 is a diagram of various stages in a manufacturing process of the sensor of FIG.

9 is a diagram of various stages in a manufacturing process of the sensor of FIG.

10 is a diagram of various stages in a manufacturing process of the sensor of FIG.

11 is a diagram of various stages in a manufacturing process of the sensor of FIG.

12 is a diagram of various stages in a manufacturing process of the sensor of FIG.

13 is a diagram of various stages in a manufacturing process of the sensor of FIG.

14 is a diagram of various stages in a manufacturing process of the sensor of FIG.

FIG. 15 is a diagram of various stages of a manufacturing process of the sensor of FIG.

FIG. 16 is a diagram of yet another embodiment of the present invention.

FIG. 17 is a diagram of yet another embodiment of the present invention.

FIG. 18 is a diagram of yet another embodiment of the present invention.

[Explanation of symbols]

 22 Semiconductor Substrate 23, 24 Dielectric Layer 26, 28 Contact Area on Upper Surface of Substrate 27, 29 Contact Finger 30, 32 Contact Area on Back Side of Substrate 34, 36 Conductor Area

Claims (2)

[Claims] 1. Forming a region of the second conductivity type on an upper surface of a substrate; creating a region of the second conductivity type on a back surface of the substrate; and from the upper surface to the back surface of the substrate. Diffusing the region to form a region of the second conductivity type extending through the substrate, and making a contact through the semiconductor substrate of the first conductivity type. 2. A semiconductor substrate having an upper surface and a back surface, a contact region formed on the upper surface of the substrate, a contact region formed on the back surface of the substrate, and a contact region of the substrate. A conductor area extending from a contact area on the upper surface to a contact area on the back surface of the substrate.