JPS61191955A - Semiconductor sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a sensor suitable for volume production at a low cost, by forming a plurality of sensor elements on an Si substrate separately after the Si substrate is joined on the surface of a base body without the use of an adhesive. CONSTITUTION:An Si substrate is adhered is adhered on to the tip surface of an Si base body 11 with the surface thereof machined flat in a clean atmosphere, joined together directly through a SiO2 film 13 by heating up to higher than 200 deg.C and then, a plurality of sensors are formed on the Si substrate 12 separately. Then, the Si portion is removed except for the area where the sensor elements were formed and the exposed surface of the Si substrate is covered with an insulation film 17 for passivation made of Si3N4 or the like. The base body 11 is divided into respective sensor elements by dicing. This enables the passivation of the entire elements without any special process such as outline machining thereof to achieve the complete insulation without exposing Si of the elements to the cut section.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor sensor, and more particularly to a structure of a semiconductor sensor whose elements are directly exposed to a solution and a method for manufacturing the same.

[Technical background of the invention and its problems]

Semiconductor sensors, especially 15FETs whose elements directly touch the solution
In this case, it is necessary to insulate the entire device. To date, the following two methods have been typical as methods for insulating the entire element.

(1) A method of covering the entire element with a passivation film such as SigN+.

(2) A method using an m5os substrate in which Si is epitaxially grown on a sapphire substrate.

However, this type of method has the following problems.

That is, in the first method, before forming the passivation film, the outer shape of the element must be cut out (actually, the element is etched to leave a diagonal shape) so that the groove can be formed on the entire outer periphery.

For this reason, the process becomes complicated, and there are other problems such as a reduction in the strength of the wafer due to handling, and the risk of contamination from the etching solution (because an alkaline etchant is normally used, the wafer cannot be used in the normal process after etching). be. Therefore, the currently widely used wafer scale semiconductor manufacturing line cannot be used, and it is not suitable for mass production.

In the second method, a sapphire substrate 51 as shown in FIG.
After forming an element on the upper Si layer 52, the Si layer other than the element is removed by etching to expose the sapphire substrate 51. After that, a passivation film 5 of S:3N4 etc. is applied to the entire surface.
3, and the element portion is completely covered with sapphire and a passivation film. If this method is used, there is no need to process the external shape of the device, and the device can be cut out from the wafer by normal dicing (the cut surface is Si3
The element is insulated with only N+ and sapphire appearing). Although this is an excellent method, the S
In addition to requiring many man-hours to create an oS wafer and making it expensive, there is also the possibility of contamination by A° C. from the sapphire substrate.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a structure of a semiconductor sensor that can be realized at low cost without using an SO8 substrate, and is suitable for mass production, and a method for manufacturing the same. Our goal is to provide the following.

[Summary of the invention]

The gist of the present invention is to form a semiconductor sensor using direct bonding technology of Si wafers without using an adhesive.

That is, the present invention provides a semiconductor sensor in which the element itself is directly exposed to a solution, etc., in which a sensor element is formed by bonding to a base whose surface is processed to be flat and the center of the surface of this base without using an adhesive. Si substrate and at least this S
and an insulating film formed to cover the exposed surface of the i-substrate.

Further, the present invention provides a method for manufacturing a semiconductor sensor having the above structure, in which a substrate having a flat surface and a silicon
The substrate is placed in close contact with the substrate in a clean atmosphere, and in this state it is heated for 200
['C] After bonding the base body and the Si substrate by heating to a temperature above ['C], a plurality of sensor elements are formed on the Si substrate in a spaced manner, and then S
In this method, the i-portion is removed, at least the exposed surface of the Si substrate is coated with an insulating film, and then the substrate is diced and divided into individual sensor elements.

In the present invention, a direct bonding technique for Si wafers is used, but the following bonding method may be used for this bonding. In other words, the surfaces of S (wafers, etc.) to be bonded are mirror-polished to a surface roughness of 500 [mm] or less, and then the polished surfaces are made hydrophilic by washing with water or the like.Then, the surfaces that have become hydrophilic are brought into close contact with each other. , By heating to 200 ['C] or higher in this state, a strong direct bond can be obtained.

In the present invention, the Si on one side of this bonded wafer is 10 to 30
Polish and rub, leaving a thickness of [μm]. and,
A device is formed on this Si surface, and unnecessary Si portions are removed by etching. After that, Si3N4, Al2O3. T
An inorganic insulating film such as az Os is applied to the entire surface to provide passivation.

If the process up to this point is performed on a wafer scale and then diced, the silicon in the element portion will not be exposed on the cut surface and can be completely insulated.

(Effects of the Invention) According to the present invention, the entire device can be passivated without special processes such as processing the device external shape.Furthermore, there is no need to use an SO8 substrate, etc., so there is no need to increase manufacturing costs. Nor.

Therefore, mass production of semiconductor sensors can be realized, and manufacturing costs can be reduced.

[Embodiments of the invention]

FIG. 1 is a plan view showing a schematic structure of an 15FET according to an embodiment of the present invention, and FIG. 2 is a cross section taken along arrow A-A in FIG. It is a diagram. Si substrate 1
A Si substrate 12 is directly bonded to the upper surface of the substrate 1 with an SiO2 film 13 interposed therebetween.

The Si substrate 12 is selectively formed at the center of the surface of the Si substrate 11. A source 14 and a drain 15 are formed on the surface of the Si substrate 12 by impurity diffusion. Further, on the upper surface of the Si substrate 12, a gate oxide film (S
in2 film) 16 is formed. A 5isN+ film 17 is formed as a passivation film on the entire upper surface of the bonded Si base 11 and Si substrate 12.

With such a structure, the device formed on the Si substrate 12 is completely covered with the 5iO2113 and Si3N+ film 17, and the device is completely passivated.

FIGS. 3(a) to 3(d) are cross-sectional views showing the manufacturing process of the sensor of the above embodiment. First, as a Si substrate, the thickness is 400 mm.
[μTrL] Si wafers (3 inch diameter, P type, 8 concentration 10”/Q13) 11.12 were prepared, and each surface to be bonded was mirror polished to a surface roughness of 500 [person] or less. Next, , the surface of the first Si substrate 11 has a thickness of 1000 [
After forming the thermal oxide film 13, the first and second S
The i-substrate was made hydrophilic by washing with water or the like. Next, the third
As shown in Figure (a), the substrates 11 and 12 were brought into close contact with each other in a clean atmosphere, and in this state, the substrates 11 and 12 were bonded together by heating to a temperature of 200°C or more.

Next, as shown in FIG. 3(b), the upper second Si substrate 12 was polished to a thickness of 30 μml and finished by lapping. As a result, the Si substrate 12 is
This will be the i-board. .

Next, as shown in FIG. 3(C), impurities were selectively diffused into the Si substrate 12 to form a source 14 and a drain 15. As a result, the gate width is 400 [μTrL],
A gate with a gate length of 20 [μTrL] is formed. Note that this structure does not require a channel stopper because the isolation between the source and drain other than the gate portion is complete. Further, in this step, a plurality of FET elements were formed separately from each other. Thereafter, the Si other than the element portion was removed by etching to expose the Si substrate 1113.

Next, as shown in FIG. 3(d), after gate oxidizing the device gate portion to form a gate oxidation layer 1116 with a thickness of 500 mm, a Si3N+ film 17 is formed on the entire surface by CVD to a thickness of 800 mm. ] I was disciplined. Thereafter, the Si3N+ film 17 and the SiO2 film 16 in the contact formation area were removed by etching, and a contact pad (not shown) was formed by vapor deposition. Thereafter, the sensor was cut into individual sensors by dicing, thereby obtaining the shapes shown in FIGS. 1 and 2.

The thus formed 15FET exhibited a sensitivity of about 50 [mV/PH] as an H+ ion sensor, similar to conventional sensors, and no dielectric breakdown was observed even after long-term use.

As described above, according to this embodiment, an 15FET whose element portion is completely passivated can be manufactured on a normal wafer scale semiconductor manufacturing line. Furthermore, S
There is no need to use an O8 substrate, and only a Si substrate is sufficient. For this reason, mass production of 15FET is possible,
The manufacturing cost can be significantly reduced.

Further, the Si layer on the element forming side can be formed sufficiently thick. For example, if a typical 3-inch wafer is used, 4
A thickness of 50 [μ7rL] is possible.

Therefore, deep diffusion is possible, and there are also advantages such as being able to reduce wiring resistance up to the contact point. On the other hand, in SO8, since it is a deposited layer formed by epitaxial growth, there is a limit to its thickness, and it was not possible to form it thicker than about 20 [μyyt].

Note that the present invention is not limited to the embodiments described above. For example, the number of elements formed on the same chip is not limited to one, and two or more elements may be formed.

In this case as well, the insulation isolation between the elements is perfect, and there is no need for a channel stopper other than the gate portion, making multiplication easy.

Furthermore, without removing all of the Si substrate other than the element area, a diffused resistance layer 18 is formed by leaving a part of the Si substrate as shown in FIG. 4, and this diffused resistance layer 18 realizes a sensor with a built-in heater. becomes possible. In addition, the passivation film is partially made of Si3N+, but is also made of SiO2.
2゜S i N, Afiz 03 or Ta205
It is possible to use an insulating film such as Furthermore, it is also possible to use an insulating substrate instead of the Si substrate as long as it can be directly bonded to the Si substrate on which the element is formed.

It is. In this case, since the substrate itself is an insulator, Si
The Si02 film between the substrate and the base body can also be omitted. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a schematic configuration of a semiconductor sensor according to an embodiment of the present invention, and FIG. 2(a) is a view taken along arrow A-A in FIG.
2(b) is a sectional view taken along arrow 8-8 in FIG. 1, FIGS. 3(a) to 3(d) are sectional views showing the manufacturing process of the above embodiment sensor, and FIG. 4 is a modified view. A sectional view for explaining an example, FIG. 5 is a sectional view showing a schematic configuration of a conventional SO8 structure semiconductor sensor. 11... First Si substrate, 12... Second Si substrate (Si substrate), 13... SiO2! II, 14-'/
- source, 15... drain, 16... gate oxide film,
17...Si3N+ film (passivation insulation II
), 18... Diffused resistance layer. Applicant's agent Patent attorney Takehiko Suzue jl! 1 Figure 2 (a) (b) Figure 3 Figure 4 Figure 5 Procedural amendment May 20, 1985, indication of case 16 Japanese Patent Application No. 1983-33101 2 Title of invention Semiconductor sensor and Manufacturing method 3, relationship with the amended case Patent applicant (307) Toshiba Corporation 4, Agent 11 Mori Building 6, 1-26-5 Toranomon, Minato-ku, Tokyo;
Target of amendment 7, content of amendment (1) The description of the scope of claims is corrected as shown in the attached sheet. (2) From page 5, line 15 to line 16 of Mei IRiI, the phrase “joined in the center of the surface” was replaced with [
"It is joined by direct bonding without using adhesive on the surface." (The ``joining method'' is written on page 6, line 12 of the 3 specifications,
Correct to "direct bonding method." (In the 14th line of page 6 of the specification, it should be 500 [in] or less") should be changed to 500 [in] or less, preferably 50
[Enter] Below” and correct it. ■ On page 10, line 4 of the specification, the phrase ``Formation part wo'' is corrected to ``Formation part no''. (a) Insert the following sentence between line 9 and line 10 of page 11 in the details layer. Next, other embodiments of the present invention will be explained. This is an example in which a large number of sensor elements are formed on the same substrate, and is basically the same as the previous embodiment.Therefore, the explanation will be given with reference to FIG. 1 and the second factor. Similar to the example, the Si substrate 1 is placed on the top surface of the Si substrate 11.
The Si substrate 12 is directly bonded to the Si substrate 12 via the silicon substrate 13 . Here, a plurality of sets of Si substrates 12 are formed on the surface of the Si base 11. Also, as in the previous embodiment, S
A source 14 and a drain 15 are provided on the surface of the i-substrate 12.
A gate oxide film 16 is formed on the upper surface of the Si substrate 12, and a Si3N+17 film is formed on the entire upper surface of the Si substrate 11 and the Si substrate 12, respectively. With such a structure, the device formed on the Si substrate 12 is completely covered with the 5iOzll113 and 313N+- film 17, and the device is completely destroyed. Therefore, even if a large number of elements are formed on the same substrate, they will not affect each other, which is convenient for detecting many types of components. The manufacturing process of the above example sensor is as follows. First, as a Si substrate, a Si wafer (3 inch diameter, P type, B concentration 10''/4'') with a thickness of 20° [μ7FL] was used.
11. For 1.1 and 12., each surface to be joined is mirror polished to a surface roughness of 50 [mm] or less. Next, a thermal oxide film 1 with a thickness of 1 [μm] is formed on the surface of the first Si substrate 11.
3, the first and second Si substrates are made hydrophilic by washing with water or the like. Subsequently, the substrates 11 and 12 are brought into close contact with each other in a clean atmosphere, and heated to 1100['C] in this state to bond each of the substrates 11 and 12 together. Next, the upper second Si substrate 12 is polished to a thickness of 10 [μm] to give it a mirror finish. As a result, the 5i substrate 12 becomes a thin Si substrate. Next, as in the previous embodiment, the source 14 and drain 15 are formed by impurity diffusion, and then the S other than the element portion is
i is removed by etching to expose 5iO2Si113. Subsequently, gate oxidation 11116 and Si3N+j!
After forming 17, 5t3N+ film 1 of the contact forming part
7 and 5102 films 16 are etched away and contact pads are deposited. Thereafter, the shapes shown in FIGS. 1 and 2 are obtained by cutting out individual sets by dicing. Even in the thus formed 15FET, as in the previous embodiment, as an H+ ion sensor, the power of about 50 [mv/
pH], and no dielectric breakdown is observed even after long-term use. Note that on sensors other than H+ ions,
For example, quaternary ammonium salts, palinomycin, etc.
Disperse and coat in C. In this case, C-,
◆Ions etc. without the influence of other elements (C2- is 10°1~
104mol/1. K"4; tl 0' ~ 10'
(mol/n concentration range). 2. Claims (1) A base whose surface is processed to be flat, a Si substrate on which a sensor element is formed by [111[LL] bonding without using m1 adhesive on this base, and at least this 1. A semiconductor sensor comprising: an insulating film formed to cover an exposed surface of a Si substrate. (2) The semiconductor sensor according to claim 1, wherein the base body is a Si base body, and the Si substrate is bonded to the 5iti body through an oxide film. (3) The semiconductor sensor according to claim 1, wherein the base body is an insulator. A semiconductor sensor according to claim 1. (5) A substrate and a Si substrate each having a flat surface.
The substrate is placed in close contact with the substrate in a clean atmosphere, and in this state it is heated for 200
['C] A step of joining the base body and the Si substrate by heating to a temperature above ['C], a step of forming a plurality of sensor elements on the Si substrate in a spaced manner, and then a step of bonding the base body and the Si substrate by heating to a temperature above ['C]; A semiconductor sensor characterized by comprising the steps of removing the '+ part, then covering at least the exposed surface of the Si substrate with an insulating film, and then dicing the base to divide it into individual sensor elements. manufacturing method. (61 Using a 5i substrate as the substrate 4, S1!!
6. The method of manufacturing a semiconductor sensor according to claim 5, wherein the plate is bonded to the Si substrate via an oxide film. (7) Claim 51N, characterized in that an insulator is used as the base! ! A method for manufacturing a semiconductor sensor. (8) The insulating film is SiO2 or SiN. The method for manufacturing a semiconductor sensor according to claim 5, characterized in that S i3N4 , Al1z Os, or Taz Os is used. Applicant's agent Patent attorney Takehiko Suzue

Claims (8)

[Claims] (1) A base whose surface is processed to be flat, a Si substrate on which a sensor element is formed by bonding to the center of the surface of this base without using an adhesive, and at least this Si substrate.
A semiconductor sensor comprising: an insulating film formed to cover an exposed surface of a substrate. (2) The semiconductor sensor according to claim 1, wherein the base is a Si base, and the Si substrate is bonded to the Si base via an oxide film. (3) The semiconductor sensor according to claim 1, wherein the base is an insulator. (4) The insulating film is SiO_2, SiN, Si_3
The semiconductor sensor according to claim 1, characterized in that the semiconductor sensor is N_4, Al_2O_3 or Ta_2O_5. (5) The substrate and the Si substrate, both of which have flat surfaces, are brought into close contact with each other in a clean atmosphere, and heated to 200°C in this state.
] A step of joining the base body and the Si substrate by heating the above, a step of forming a plurality of sensor elements on the Si substrate in a spaced manner, and then removing a Si portion other than the area where the sensor elements are formed. A method for manufacturing a semiconductor sensor, comprising the steps of: coating at least the exposed surface of the Si substrate with an insulating film; and then dicing the substrate to separate it into individual sensor elements. (6) The method of manufacturing a semiconductor sensor according to claim 5, characterized in that a Si substrate is used as the substrate, and the Si substrate is bonded to the Si substrate via an oxide film. (7) The method for manufacturing a semiconductor sensor according to claim 5, wherein an insulator is used as the base. (8) As the insulating film, SiO_2, SiN, S
i_3N_4, Al_2O_3 or Ta_2O_5
A method for manufacturing a semiconductor sensor according to claim 5, characterized in that the method uses: