JPH10281807A - Sensor and its creation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor which improves a throughput and which is mounted by using a batch processing technique which shortens the creation of the sensor and the cycle time of a mounting operation. SOLUTION: A sensor 10 is provided with a board 11 and with a cavity 31 which is formed of an adhesive 21 and a filter 22. A detecting element 14 is arranged inside the cavity 31, and electric contacts 17, 18 which are coupled to the detecting element 14 are arranged outside the cavity 31. The filter 22 protects the detecting element 14 from physical damage and contamination during a die cutting-off process and other assembling processes. The filter 22 improves the chemical sensitivity, the selectivity, the response time and the replenishment time of the detecting element 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates generally to semiconductor devices, and more particularly, to sensors.

[0002]

BACKGROUND OF THE INVENTION Mounting a sensor is a labor intensive, time consuming and costly process. For chemical sensors, the mounting process includes cutting the semiconductor substrate into individual chemical sensor chips. The individual chemical sensor chips are then separately glued and assembled in a large metal package, referred to in the art as a T39 package or a T05 package. T05
An example of a package is described in U.S. Patent No. 4,768,070, issued to Takizawa et al. On August 30, 1988. This mounting process of the piece parts is time-consuming and troublesome, and requires careful handling of individual chemical sensor chips that may be contaminated or physically damaged during the mounting process.

[0003] Therefore, there is a need for a sensor that is mounted using a batch processing technique that improves throughput and reduces the cycle time of sensor creation and mounting. Wafer-level package technology produces miniaturized mounted sensors, protecting each sensor chip from contamination and physical damage during subsequent processing.

[0004]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings for a more detailed description, FIG. 1 is a cross-sectional view of an embodiment of a sensor 10. The sensor 10 is a semiconductor component including the substrate 11. Substrate 11 has a surface 19 opposite surface 20 and typically comprises
For example, silicon, III-V compound semiconductor or II-V
It is composed of semiconductor materials such as Group I compound semiconductors. It can be understood that a plurality of sensors can be formed on the substrate 11. For example, FIG. 1 shows a portion of sensors 34 and 35 on substrate 11 adjacent to sensor 10. FIG.
Also shows straight lines 36, 37 which function as delineating lines separating sensor 10 from sensors 34, 35, respectively.

[0005] An insulating layer 32 is provided on the surface 19 of the substrate 11. Insulating layer 32 is preferably a dielectric material such as, for example, silicon oxide or silicon nitride, and can be deposited on substrate 11 using methods well known in the art.

The substrate 11 has an optional recess 12 formed in a portion of the surface 20 to facilitate thermal diffusion of the sensor 10 described below. Recess 12 extends from surface 20 to surface 19 and may expose a portion of insulating layer 32. To ensure a manufacturable process for the sensor 10, the recess 12 is preferably etched into the surface 20 using an anisotropic etchant that etches along a particular crystallographic plane of the substrate 11. The anisotropic etchant must not etch the insulating layer 32 more than the substrate 11. Examples of suitable anisotropic etchants for use on single crystal silicon substrates include, but are not limited to, potassium hydroxide, ammonium hydroxide, cesium hydroxide, hydrazine, ethylenediamine / pyrocatechin and tetramethylammonium hydroxide. Not done.

The sensor 10 has a sensing element 14 supported by the insulating layer 32 and the substrate 11 and located on the recess 12. When the sensor 10 is a chemical sensor, the sensing element 14
It is typically a resistance whose resistance changes when exposed to a particular liquid or gas (not shown). At elevated operating temperatures, the resistivity of sensing element 14 is typically about 1 kOhm to 50 Mohm. As is well known in the chemical sensor art, the presence of a particular liquid or gas is converted by a sensor from a chemical reaction into an electrical signal. For example,
The control circuit (not shown) measures the change in the current or voltage drop across the sensing element 14 so that the sensing element 1
4 can be detected. The control circuitry can be on a different board or
To create an integrated chemical sensor system.

[0008] The sensing element 14 is placed or formed on the insulating layer 32 and the surface 19 of the substrate 11 using methods well known in the art. When the sensor 10 is a chemical sensor, the sensing element 14 is formed of a conductive and chemically sensitive thin film such as a metal oxide, a transition metal or a noble metal. For example, the sensing element 14 may include tin oxide, zinc oxide,
It can be made of titanium oxide or an alloy of platinum and gold. The use of different composition sensing elements 14 allows different liquids or gases to be detected or monitored. Doping the material used for the sensing element 14,
It should be understood that the chemical sensitivity and selectivity of sensing element 14 and sensor 10 can be further enhanced.

The sensing element 14 can be heated by an optional heating element 13 to help initiate a chemical reaction between the sensing element 14 and the desired liquid or gas. Heating element 13 is formed using methods well known to those skilled in the art. For example, heating element 13 may be made of polycrystalline silicon or a metal such as platinum or gold.

As shown in FIG. 1, the heating element 13
In the insulating layer 32, above the recess 12 and below the sensing element 14. It should be understood that the heating element 13 can be placed on a substrate other than the substrate 11. However, it is desirable that both the heating element 13 and the sensing element 14 be placed on the substrate 11 for efficient heating and saving space. The recesses 12 in the substrate 11 assist in heat diffusion or cooling of the heating element 13 and the sensor 10.

Coupling lines 15 and 16 electrically couple features 17 and 18 to sensing element 14, respectively. The coupling lines 15 and 16 are made of a conductive material such as silicide or metal. The coupling lines 15 and 16 are formed on the insulating layer 32 and the surface 19 of the substrate 11 using a method well known in the art.

Features 17 and 18 provide electrical contact for sensing element 14. For example, assembling wire bond wiring,
Combined with features 17,18, it can be a bonding pad. The features 17, 18 are typically made of, but not limited to, a metal such as gold or copper, and include an insulating layer 32 and a substrate 11.
Is applied on the surface 19 by using a sputtering method, an electroplating method, a chemical vapor deposition method or a vapor deposition method.

The adhesive 21 is on the bonding lines 15, 16, on the insulating layer 32, on the surface 19 of the substrate 11, and preferably on the sensing element 1 to avoid contamination of the sensing element 14.
4 and are spaced apart from each other. The adhesive 21 can be any organic or inorganic adhesive material, such as, for example, a solder preform, silk screen epoxy or frit glass. When a conductive adhesive is used as the adhesive 21, a separation layer (not shown) electrically separates the bonding lines 15 and 16 from the adhesive 21.

An adhesive 21 bonds or electrically bonds the insulating layer 32 and the mesh, screen or filter 22 to cover, ie, mount, the sensor 10. As a result, the adhesive 21, the insulating layer 32, the substrate 11, and the filter 22 form the cavity 31. Cavity 31
Can be controlled by the thickness or height of the adhesive 21. As shown in FIG. 1, sensing element 14 is located within cavity 31 and features 17 and 18 are located outside cavity 31.

The filter 22 overlies the insulating layer 32 and the cavity 31 and filters, shields or prevents unwanted particles or chemicals from entering the cavity 31. The filter 22 has a surface 23, an opposing surface 24, contact openings 25 and 30, and filtering holes 26, 27, 28 and 29 functioning as a filtering mechanism of the filter 22. This will be described later in detail.

The filter 22 is preferably a sensing element 1
4 is spatially separated from the sensing element 14 to avoid contamination or damage. Filter 22 must have a suitable thickness to be substantially rigid. This is to prevent elastic deformation that may cause contact with the detection element 14 or damage to the detection element 14.

A wide range of materials as described below can be used for the filter 22. However, filter 2
Many of the materials used for 2 degas chemicals when the operating temperature of the sensor 10 is increased. Filter 22 preferably ensures accurate chemical response of sensor 10 to the environment without degassing chemicals as operating temperatures increase. However, even if the filter 22 degass a chemical substance, the filter 22 should not degas the chemical substance that can be detected by the sensing element 14 so that the sensor 10 can accurately monitor the environment. . Similarly, the adhesive 21, insulating layer 32, substrate 11, bond lines 15, 16 and features 17, 18 must not degas chemicals that can be detected by sensing element 14 at the operating temperature of sensor 10. .

The filter 22 can be comprised of a non-porous material or a porous or breathable material. Possible suitable non-porous materials include, but are not limited to, conventional single crystal silicon substrates, III-V compound semiconductor substrates and II-VI compound semiconductor substrates. Suitable suitable porous or breathable materials include porous silicon substrates, polymer thin films, porous ceramics, glass, charcoal filters, thermosets, alumina,
Examples include, but are not limited to, polyimide, silica, and quartz.

If the filter 22 is comprised of a porous or breathable material, there is an additional filtering mechanism that is not present when the filter 22 is comprised of a non-porous material. Certain liquids or gases can penetrate certain porous or permeable materials and filter holes 26, 27, 28,
It is possible to enter the cavity 31 without passing through 29. As such, a porous or breathable material can extend or enhance the filtering function of the filter 22 over the filtering function of a non-porous material to improve the chemical sensitivity and selectivity of the sensor 10.

[0020] Each porous or breathable material has a different pore size, which can be utilized to provide different sized particles,
Chemicals or molecules can be filtered. Porous or breathable materials can be chemically active.
As an example of a chemically active breathable material, a layer of a metallophthalocyanine polymer can be used in the filter 22 to prevent nitrous oxide from passing through the cavity 31. As an example of a porous material, a compressed charcoal filter can be used for the filter 22 to filter hydrocarbons and prevent them from entering the cavity 31. Further, the polyimide layer is used for the filter 22 to filter out moisture or water vapor and prevent entry into the cavity 31.

Returning to the description of the contact openings 25 and 30 in the filter 22, the contact openings 25 and 30 are located above the features 17 and 18, respectively, in a position for entering these features. If features 17 and 18 function as bonding pads, contact openings 2
5, 30 each have a size of about 50 to 1,000 microns and the assembled wire bond wiring is
5,30, extending through the contact features 17,1
8 to be able to contact each other. The contact openings 25, 30 may also expose die separation regions, shown as straight lines 36, 37 in FIG.

The filtering holes 26, 27, 28,
29 is located above the cavity 31 and the filter 22
Works as a filtering mechanism. Filter 22 is cavity 31
Even if it is possible to have a single hole above the filter 22, the filter 22 should be capable of allowing sufficient gas or liquid flow to enter and exit the cavity 31 while maintaining sufficient filtering as described below. Preferably. The filtering holes 26, 27, 28, 29 preferably each have a diameter smaller than the diameter of the contact openings 25, 30 so that undesired particles do not enter the cavity 31. Thereby, the filter 22 protects the sensing element 14 from physical damage and contamination during substrate dicing and other assembly steps and operation of the sensor 10.

If desired, the filtering holes 26, 27, 28,
Reference numerals 29 each have a diameter on the order of several angstroms to several microns to prevent molecules or chemicals of larger dimensions from entering the cavity 31 and causing a chemical reaction with the sensing element 14. in this way,
The filter 22 is also used as a chemical filter for improving the chemical selectivity and sensitivity of the sensor 10.
For example, suppose that sensor 10 monitors only small hydrocarbon molecules, and sensing element 14 also reacts chemically with small hydrocarbon molecules, larger protein molecules, and larger deoxyribonucleic acid molecules (DNA). In this case, assuming that the filtering holes 26, 27, 28 and 29 each have a diameter of about several angstroms, small hydrocarbon molecules pass through the filtering holes 26, 27, 28 and 29 and react with the sensing element 14. But larger protein and DNA molecules can be used to filter holes 26, 27, 28,
29 and cannot react with the sensing element 14. Therefore, in this example, the chemical selectivity of the sensor 10 is improved.

The filtering holes 26, 27, 28, 29 and the contact openings 25, 30 are ultra-precision machined in the filter 22 before coupling the filter 22 to the substrate 11. Filter hole 2
6, 27, 28, 29 and contact openings 25, 30 can be formed using a wide variety of different chemical and physical methods. Filter holes 26, 27, 2 are formed using, for example, reactive ion etching or mechanical drilling techniques.
8, 29 and contact openings 25, 30 can be formed in the filter 22. Another example is filter 2
2 comprises a non-porous single crystal silicon substrate having a thickness of about 100 to 500 microns, using the same anisotropic etchant used for recess 12 in substrate 11 to filter holes 26, 27, 28, 29 and contact openings 25, 30 can also be etched.

Filter holes 26, 27, 28, 29 and contact openings 25, 30 can be etched from surface 23, from surface 24, or from both surfaces 23, 24. As shown in FIG.
5, 30 and the filtering holes 26 are etched from the surface 23, the holes 27 are etched from the surface 24 and the holes 28, 2
9 is etched from surfaces 23,24. When the holes are etched from both surfaces 23 and 24, the holes are
Numerous or denser holes can be provided as compared to etching only from one of the two surfaces.

With continued reference to FIG. 2, the sensor 10 of FIG.
A partial cross-sectional view of an alternative embodiment of is shown as sensor 40. The sensor 40 of FIG. 2 is similar to the sensor 10 of FIG. 1, and the same reference numbers are used in FIGS. 1 and 2 to indicate the same elements. In FIG. 2, the cavity 4
4 is formed by bonding the insulating layer 32 and the filter 45 using the adhesive 21. The cavity 44 and the filter 45 are, for purposes of illustration, the cavity 31 of FIG.
And the filter 22 are similar to each other.

The filter 45 is constituted by a layer 43 on the support layer 41. The support layer 41 is similar in composition to the filter 22 of FIG. Support layer 4
1 has a plurality of holes 42, which are covered by a layer 43. These holes are similar in purpose to the filtering holes 26, 27, 28, 29 of the filter 22 of FIG.

Layer 43 is made of a porous or breathable material that functions as a selective filter that allows certain chemicals to pass and restricts the passage of other chemicals. Layer 43
Examples of suitable porous and breathable materials are described above.

Layer 43 may be sputtered, squirted, laminated, ejected, or applied to indicator layer 41 to a thickness of about 0.1 to 30 microns after bonding support layer 41 to insulating layer 32. Alternatively, layer 43 may include filter 4
5 can also be provided on the support layer 41 before attaching it to the insulating layer 32. In this alternative method, the filter 45 may be coupled to the insulating layer 32 such that the insulating layer 32 and the substrate 11 are closer to the layer 43 than the support layer 41.
This configuration is not shown in FIG. However, the filter 45
Is preferably coupled to the insulating layer 32, and when the insulating layer 32 and the substrate 11 are positioned closer to the support layer 41 than the layer 43 as shown in FIG. There is no clogging during the operation of 40.

Referring to FIG. 3, a partial cross-sectional view of yet another embodiment of the sensor of FIG. The sensor 60 of FIG. 3 is also similar to the sensor 10 of FIG. 1, and the same reference numbers are used in FIGS. 1 and 3 to indicate the same elements. In FIG. 3, the adhesive 2
1 couples the insulating layer 32 and the filter 61 to form a cavity 62 therebetween. Cavity 62 and filter 61 are similar in purpose to cavity 31 and filter 22, respectively, of FIG.

As described above, the filter 61 is made of a porous or air-permeable material having an appropriate thickness to obtain substantial rigidity in order to prevent the sensing element 14 from being damaged. Unlike the filter 22 of FIG. 1, the filter 61 of FIG. 3 does not have a filtering hole. Filter 61 is similar in composition to layer 43 of FIG. 2 and can have a thickness of about 50 to 500 microns.

The sensors 10, 4 of FIGS. 1, 2 and 3
0 and 60 are conventional metal T05 or T3, respectively.
It has several advantages over prior art sensors implemented in nine packages. For example, the cavities 31, 44, 62 of FIGS. 1, 2 and 3 have a smaller cavity volume than the cavities or encapsulation regions of conventional metal T05 or T39 packages, respectively. Due to the small cavity volume, the sensors 10, 40, 60
Saves space in all applications because it is smaller and less bulky than conventional metal T05 or T39 packages. Sensors 10, 40 and 60 are at least about one inch smaller than conventional metal T05 or T39 packages.
00 times is smaller.

Further, since the cavity volume is small, the cavities 31, 44 and 62 can be more quickly filled with a chemical substance having a critical concentration to be detected by the detecting element 14. Due to the small volume of the cavity,
Critical chemical concentrations can also be removed faster. Therefore, the response time and the refresh time of the sensors 10, 40, and 60 are improved as compared with the related art. As described above, the cavity volume of the cavities 31, 44, 62 can be controlled by the thickness or height of the adhesive 21. The minimum volume required for the cavities 31, 44, 62 depends on the composition and operating temperature of the sensing element 14, the chemicals detected and the rate of diffusion of the environmental gas or liquid into and out of the cavities 31, 44, 62.

Further, the manufacturing process of the sensors 10, 40 and 60 requires less time, costs and labor compared to the prior art. Substrate 11 and filters 22, 4
If 5 or 61 is part of a different semiconductor wafer, the sensor 10 can be created using an automated semiconductor wafer processing apparatus that reduces human intervention and improves manufacturing yield. Thus, the creation of the sensor 10 is compatible with mass production environments.

Thus, the sensors 10, 40, and 60 can be mounted or assembled using wafer-level batch processing, and after hundreds or thousands of sensors are mounted simultaneously on a single semiconductor substrate, Disconnect individual sensors. This wafer-level batch mounting process improves throughput and is more cost-effective than the conventionally laborious and cumbersome steps of separately mounting one sensor at a time.

Furthermore, the wafer level mounting prevents the sensing element 14 from being damaged during die detachment. This is because the sensing element 14 is sealed in the cavity 31, 44 or 62 before the disconnection process. Further, the adhesive 21 and the filters 22, 45, 61
Each of the sensors 10, 40, 60 is stiffened to reduce the possibility of breakage. Therefore, the sensors 10, 40, 60
Is further improved as compared with the prior art.

Thus, it is apparent that the present invention has provided an improved sensor that overcomes the disadvantages of the prior art. Inefficient section assembly in a conventional metal T05 or T39 package is eliminated, and a cost-effective method of reducing cycle time increases mechanical strength and improves manufacturing yield for sensor fabrication. The size of the mounted sensor is about 1 compared to the conventional mounted sensor.
It is about 1/00. In addition, sensor performance is enhanced by improving chemical sensitivity, chemical selectivity, and refresh and response times.

Although the present invention has been particularly shown and described with reference to preferred embodiments, it is to be understood that changes may be made in form and detail without departing from the spirit and scope of the invention. The trader will understand. For example, humidity and temperature sensors can be provided in the cavities 31, 44, 62 to improve the monitoring function of the sensors 10, 40, 60, respectively. In addition, the processes described herein may be used, for example, in a chemical field effect transistor (CHEMFET).
), Surface acoustic wave (SAW) devices, and other types of sensors such as capacitive sensors. Therefore,
The present disclosure is not intended to be limiting. The present disclosure is intended to illustrate the scope of the invention, which is set forth in the following claims.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a sensor according to the present invention.

FIG. 2 is a partial cross-sectional view of an alternative embodiment of the sensor of FIG. 1 according to the present invention.

FIG. 3 is a partial cross-sectional view of another alternative embodiment of the sensor of FIG. 1 according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sensor 11 Substrate 12 Concavity 13 Heating element 14 Detecting element 15, 16 Bonding line 17, 18 Feature 19, 20 Substrate surface 21 Adhesive 22 Filter 23, 24 Filter surface 25, 30 Contact opening 26, 27, 28, 29 Filtering Hole 31 Cavity 34,35 Adjacent sensor 36,37 Drawing line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Margaret El Niffin Number 0142, Tempe, Arizona, USA; 6901 South McLintook Drive 6901 (72) Inventor Pin-chan Liu Scottsdale, Arizona, USA , East Sunnyside Drive 7221

Claims (3)

[Claims] 1. A substrate (11); a sensing element (14) supported by the substrate (11); a filter on the sensing element (14); and coupling the substrate (11) and the filter. A sensor comprising an adhesive (21). 2. A chemically sensitive thin film (14); a filter (22, 45 or 6) overlying and spatially separated from said chemically sensitive thin film (14).
1); a semiconductor substrate (11) under the chemically sensitive thin film (14); and the filter (22, 45).
Or 61) and an adhesive (21) for bonding the semiconductor substrate (11) to the semiconductor substrate (11). 3. A method of making a sensor, comprising: providing a substrate (11); forming a chemically sensitive thin film (14) on said substrate (11);
2, 45 or 61); and adhering the filter (22, 45 or 61) to the substrate (11), wherein the filter (24, 45 or 6) is provided.
Wherein 1) is on the chemically sensitive thin film (14).