TWI598974B - Non-destructive evaluation method for wafer-level piezoelectric material and equipment for measurement of the same - Google Patents

Description

Non-destructive wafer level piezoelectric material evaluation method and measurement equipment

SUMMARY OF THE INVENTION The present invention is directed to a non-destructive wafer level piezoelectric material evaluation method and measurement apparatus that employs a non-element region for measurement to derive the results from the bulk acoustic wave component.

According to the piezoelectric material, a piezoelectric material refers to a crystal material that exhibits a voltage between both end faces when subjected to pressure. The piezoelectric material is widely used in sensor components due to its advantages of large output, small displacement, fast response, fast energy conversion, low price, and no electromagnetic interference, such as seismic sensors, force, velocity and acceleration. Measuring elements and electroacoustic sensors are used in many applications. The piezoelectric material has a piezoelectric effect due to the special arrangement of atoms in the crystal lattice, which causes the material to have a coupling effect between the stress field and the electric field.

The so-called piezoelectric effect (Piezoelectricity) is a phenomenon in which a mechanical energy exchanges with electrical energy. When the piezoelectric material is subjected to physical pressure, the electric dipole moment in the material body is shortened by compression. At this time, the piezoelectric material resists this change and generates an equal amount of positive and negative charges on the opposite surface of the material to maintain the original state. . This phenomenon of polarization due to deformation is called "positive piezoelectric effect". The positive piezoelectric effect is essentially a process in which mechanical energy is converted into electrical energy.

According to the specific material form, it can be divided into two types: piezoelectric block material and piezoelectric film. Due to the size of the film, the piezoelectric effect is difficult to measure due to the size, and the manufacturer cannot perform the performance evaluation at the material manufacturing stage when producing related products for piezoelectric applications. Here are a few examples of the development of measuring piezoelectric material properties to understand the current technology for measuring piezoelectric materials, as follows:

1. Patent No. I427290 of the Republic of China Patent Publication No. I427290 provides a gas detecting device and method thereof, and discloses a gas sensing device and method thereof, in particular, capable of simultaneously sensing at least in a low concentration environment. A gas comprising a first surface acoustic wave device (SAW device) having a piezoelectric substrate, a pair of transducers and an external circuit, the pair of transducers being a first transducer and a first The two transducers are respectively formed on two ends of the piezoelectric substrate, and the first transducer generates surface acoustic waves on the piezoelectric substrate, and the external circuit is electrically connected to the pair of switches. And a second surface acoustic wave component having the first surface acoustic wave component, a sensing film having a hole formed on each of the pair of transducers, and a control device Controlling only one external circuit at a time in the device When the film adsorbs the sensing object, the film transmits the surface acoustic wave to the second transducer, and the object is subjected to quantitative analysis or qualitative analysis by the surface acoustic wave variation.

2. Patent Publication No. 536868 of the Republic of China, which provides a method for processing a piezoelectric substrate of a surface acoustic wave device, and discloses a method for processing a piezoelectric substrate of a surface acoustic wave device, the surface acoustic wave device comprising a piezoelectric substrate The input electrode and the output electrode of the surface are composed of a circuit pattern of an input finger electrode and an output finger electrode of the surface finger electrode by a process such as an optical development technique or a screen printing technique on the surface of the piezoelectric substrate, and The design variation of the density of the pattern and the composition of the component, after matching the surface wave triggering/receiving device (such as a reflector, etc.) on the finger electrode, can be combined to generate different operating frequencies for its application, and at the same time, at the pressure The back surface of the electric substrate is subjected to sand blasting with appropriate roughness to create a rough surface of an appropriate degree, and the block wave signal excited by the input finger electrode can be effectively suppressed to improve the chain wave of the band pass band. The signal is suppressed in response to the band and is rejected by the output finger electrode.

3. The application of the Republic of China Patent Publication No. 201234436 provides a "wafer-level process for the cavity of a surface acoustic wave filter", which uses atomic layer deposition (ALD) to the piezoelectric layer of a surface acoustic wave (SAW) filter. And a layer of material (such as alumina) is deposited on the interdigital transducer (IDL) as a passivation and adhesion promoting layer and a photopolymer layer (such as a dry epoxy film) is used to define a cavity for the SAW filter. . The ALD layer serves to protect the IDT from potential corrosion caused by polymer layers and/or moisture, while at the same time providing stable operation of the SAW filter by protecting the piezoelectric layer without signaling Displacement. The cavity has a wall formed of a photopolymer that provides a simple and cost effective SAW process.

It is known from the above-mentioned technical features of the prior art that the publication No. I427290 refers to a device and method for simultaneously sensing at least one low-concentration object by using a surface acoustic wave (SAW) array type oscillating circuit, mainly integrating piezoelectric material characteristics, The surface acoustic wave characteristic, the film characteristic, and the external related circuit integrated detection device can simultaneously detect at least one object to be tested in a low concentration environment; and the publication No. 536868 discloses a piezoelectric material used in a surface acoustic wave element. A piezoelectric substrate is fabricated, and a surface finger electrode is designed on the piezoelectric substrate for signal processing, and the special processing method of the present invention is applied to the piezoelectric substrate of the device, thereby effectively reducing the surface finger electrode The effect of the bulk wave generated while the surface acoustic wave is excited on the frequency response of the design element; further, Japanese Patent No. 201234436 discloses an IDT and pressure for protecting a surface acoustic wave device having an electrode system containing at least two metal electrodes during operation. The electrical surface is not subject to corrosion and undergoes frequency displacement. However, none of the above techniques can perform effective and accurate measurement data without damaging the wafer.

The main object of the present invention is to provide a method for evaluating the piezoelectric effect constant of a film material on a production line, which enables a manufacturer to produce a bulk acoustic wave piezoelectric element in a film production stage. The evaluation, that is, the piezoelectric performance evaluation during the film material manufacturing process, can avoid the waste of the subsequent micro-electromechanical process due to the uneven quality of the film.

The main purpose of the above non-destructive wafer level piezoelectric material evaluation method of the present invention is achieved by the following specific technical means:

The method mainly comprises taking a non-element region of the wafer to complete the surface acoustic wave component through a single-layer photomask process, and measuring the surface acoustic wave component through a device to obtain a frequency response result, thereby deriving the result to obtain a piezoelectric Coefficient, electromechanical coupling coefficient, etc., and after being brought into the mathematical operation relationship, can further extend the performance of the bulk acoustic wave component; according to this method, the surface acoustic wave component can be quickly completed on the production line, and the feedback result of the frequency response is obtained. The electrical information judgment, the evaluation of the piezoelectric coefficient, can provide the parameters of the manufacturer's various piezoelectric application products, and provide the instant film characteristics judgment on the production line and the process, which can reduce the production cost and non-destructive detection. The merits of the actor.

The non-destructive wafer-level piezoelectric material evaluation method as described above, wherein the non-element region is a specified characteristic test region, which means that the region is exclusively for film physical property testing, and is not a region for final component fabrication.

The non-destructive wafer level piezoelectric material evaluation method as described above, wherein the single layer mask process comprises the steps of: a) cleaning the substrate; b) one-time evaporation; c) exposure; d) generating; ) secondary evaporation; f) detachment.

The non-destructive wafer level piezoelectric material evaluation method as described above, wherein the frequency response result is brought into a mathematical operation relationship, and the performance of the bulk acoustic wave element can be further extended. The mathematical expression is as follows:

A non-destructive wafer level piezoelectric material evaluation method as described above, wherein the bulk acoustic wave element is obtained by the following expression: , N _p is number of IDT finger pairs, C _s is capacitance per finger-pair , d _e is the effective resonant cavity length Here, C _T =N _p C _S =N _p C _O W

The main purpose of the above-described non-destructive wafer level piezoelectric material evaluation measuring apparatus of the present invention is achieved by the following specific technical means:

The utility model comprises a measuring platform and a network analyzer; wherein the measuring platform is for placing a wafer of the surface acoustic wave component to be tested, and the measuring platform is provided with a cantilever, the cantilever group is provided with a probe for measuring the high frequency component The probe is located at the surface acoustic wave component of the wafer to be tested, and the probe is connected to the network analyzer to transmit the measurement signal to the network analyzer for data analysis, thereby obtaining the frequency response result of the surface acoustic wave component.

A non-destructive wafer level piezoelectric material evaluation measurement device as described above, wherein the probe includes a signal line and ground to form a good connection between the wafer and the network analyzer Ground effect.

A non-destructive wafer level piezoelectric material evaluation measuring device as described above, wherein the measuring platform employs a lifting platform.

(1)‧‧‧Measurement platform

(11)‧‧‧Cantilever

(2) ‧ ‧ probe

(3)‧‧‧Network Analyzer

(A) ‧‧‧ Wafer

(A1)‧‧‧Surface acoustic wave components

First: Schematic diagram of the process of the present invention

Second: Schematic diagram of the architecture of the measuring device used in the present invention

Third: Schematic diagram of the frequency response of the surface acoustic wave device of the present invention

Fourth: Schematic diagram of the frequency performance of the bulk acoustic wave component of the present invention

For a more complete and clear disclosure of the technical content, the purpose of the invention and the effects thereof achieved by the present invention, the following is a detailed description, and please refer to the illustrated drawings and drawings: please refer to the first The figure and the second figure are respectively a schematic diagram of the flow chart of the non-destructive wafer level piezoelectric material evaluation method of the present invention and the architecture of the measuring device used in the measuring method of the present invention. The steps include: (S1) taking a non-element region of a wafer; (S2) passing the non-element region of the wafer through a single-layer photomask process to obtain a surface acoustic wave component; (S3) the surface acoustic wave component is measured by a device to obtain a frequency response result; (S4) the frequency response result is calculated by a mathematical operation relationship, and the bulk acoustic wave component of the wafer level piezoelectric material can be obtained. Performer.

Referring to the first to second figures, in the implementation, the present invention intercepts the non-element area of the wafer (A) for detection, and adopts the non-element area to achieve the structure without destroying the original wafer (A). The non-element region of the wafer (A) is applied as a single-layer photomask process. The flow of the single-layer photomask process is exemplified by the following steps: a) cleaning the substrate; b) one-time evaporation; Exposure; d) generation; e) secondary evaporation; f) detachment; however, this single-layer reticle process is not required, as long as a single-layer reticle process technology can obtain a surface acoustic wave component (A1) .

Then, the evaluation method of the present invention mainly performs the frequency response result by performing the surface acoustic wave component (A1) through a measuring device, and the measuring device comprises: a measuring platform (1), which is an up-and-down adjustment lifting platform. The measuring platform (1) is for placing the wafer (A) of the surface acoustic wave component (A1) to be tested, and the measuring platform (1) is mounted with a cantilever (11), and the cantilever (11) is set up with a measurement The probe (2) of the high-frequency component is such that the probe (2) is located at the surface acoustic wave component (A1) of the wafer (A) to be tested; and a network analyzer (3) is connected to the probe (2). The probe (2) transmits the measured signal to the network analyzer (3) for data analysis, thereby obtaining the frequency response result of the surface acoustic wave component (A1); in addition, the probe (2) includes the signal line and the ground To make the wafer (A) and the network analyzer (3) form a good ground. effect.

Through the above measuring device, the network analyzer (3) analyzes the frequency response result of the surface acoustic wave element (A1), thereby deriving the result to obtain the piezoelectric coefficient, the electromechanical coupling coefficient, etc., and bringing the mathematical operation relationship After the formula, the performance of the bulk acoustic wave element can be further extended.

Then, the frequency response result of the surface acoustic wave element (A1) is obtained by the above measurement, and the frequency response result is brought into a mathematical operation relationship, and the performance of the bulk acoustic wave element can be further extended. The mathematical expression is as follows:

Where K ² represents the electromechanical coupling coefficient; Insertion loss (IL) represents the insertion loss (dB) = Bulk acoustic wave components: Here, C _T =N _p C _S =N _p C _O W

Where G _a (f ₀ ) is the radiation conduction of the center frequency f ₀ ; Cs is the electrostatic capacity N _p of the IDT (the number of finger electrodes) is number of IDT (finger electrodes) finger pairs; C _s (the logarithm of the finger capacitance) Is capacitance per finger-pair; d _e is the depth at which the acoustic wave is incident on the reflective gate; Cr is the static capacitance value of the finger electrode itself; Lr is the equivalent inductance value; fp-fs is the displacement of the two resonance frequencies Quantity, fp represents the parallel resonance value; fs represents the series resonance value; C _T represents the electrostatic capacity of the IDT; C ₀ represents the Cs per unit length; through the above operation, it is known that the surface acoustic wave element (A1) analyzes the frequency response result The piezoelectric coefficient, the electromechanical coupling coefficient, and the like are obtained, and after being brought into the mathematical operation relation, the value expressed by the bulk acoustic wave element can be obtained.

The above are only some of the embodiments of the present invention and are not intended to limit the present invention. It is intended that the spirit of the invention and the features of the invention may be included in the scope of this patent.

It can be seen from the above components and implementation description that the present invention has the following advantages as compared with the prior art:

1. The present invention is a non-destructive wafer-level piezoelectric material evaluation method and measuring device, which enables a manufacturer to complete the evaluation of the piezoelectric properties of the film at the film forming stage when the bulk acoustic wave piezoelectric element is produced on the production line. That is, the piezoelectric performance evaluation of the film material during the manufacturing process can avoid the waste of the subsequent micro-electromechanical process due to the uneven quality of the film.

2. The present invention is a non-destructive wafer-level piezoelectric material evaluation method and measuring device, mainly through an extension comparison method, that is, a surface acoustic wave component can be completed by a single-layer photomask, and the test piece is measured. The frequency response, the measurement frequency response result is inversely obtained to obtain the piezoelectric coefficient, the electromechanical coupling coefficient, etc., and after being brought into the mathematical operation relationship, the performance of the bulk acoustic wave component can be further extended.

3. The present invention is a non-destructive wafer-level piezoelectric material evaluation method and measuring device, wherein the surface acoustic wave component can be quickly completed on the production line, and the electrical information is judged by the result of the frequency response. The evaluation of the piezoelectric coefficient can provide the parameters of the manufacturer's various piezoelectric application products for parameter setting, and provide instant judgment of film characteristics on the production line and in the process.

4. The present invention is a non-destructive wafer level piezoelectric material evaluation method and measuring device, which has the advantages of reducing production cost and non-destructive detection.

In summary, the embodiments of the present invention can achieve the expected use efficiency, and the specific technical means disclosed therein have not been seen in similar products, nor have they been disclosed before the application, and have completely complied with the patent law. The regulations and requirements, the application for invention patents in accordance with the law, and the application for review, and the grant of patents, are truly sensible.

(S1) ‧ ‧ steps

(S2) ‧ ‧ steps

(S3) ‧ ‧ steps

(S4) ‧ ‧ steps

Claims (5)

A non-destructive wafer-level piezoelectric material evaluation method, which mainly takes a non-element region of a wafer, passes the non-element region of the wafer through a single-layer mask process, to obtain a surface acoustic wave component, and allows the The surface acoustic wave component is measured by a device to obtain a frequency response result, and the frequency response result is brought into a mathematical operation relationship, and the mathematical operation formula is as follows: Among them, K ² represents the electromechanical coupling coefficient; Insertion loss (IL) represents the insertion loss (dB), and the performance of the bulk acoustic wave component of the wafer level piezoelectric material can be obtained by calculation. The non-destructive wafer-level piezoelectric material evaluation method described in claim 1, wherein the non-element area is a specified characteristic test area, which means that the area is exclusively for film physical property testing, not the final component. The area of production. The non-destructive wafer-level piezoelectric material evaluation method described in claim 1 or 2, wherein the frequency response result feedback can obtain the electrical information judgment of the piezoelectric coefficient and the electromechanical coupling coefficient, and the piezoelectricity is achieved. The evaluator of the coefficient. For example, the non-destructive wafer-level piezoelectric material evaluation method described in claim 1 wherein the performance of the bulk acoustic wave element is as follows: Here, C _T =N _p C _s =N _p C _O W; wherein G _a (f ₀ ) is the radiation conduction of the center frequency f ₀ ; C _s is the electrostatic capacity N _p of the IDT (the number of finger electrodes) Is number of IDT (finger electrode) finger pairs; C _s (finger capacitance logarithm) is capacitance per finger-pair; d _e is the depth of the sound wave incident on the reflective gate; C _r is the finger electrode itself Static capacitance value; L _r represents the equivalent inductance value; f _p -f _s represents the displacement of the two resonance frequencies, f _p represents the parallel resonance value; f _s represents the series resonance value; C _T represents the electrostatic capacity of the IDT; C ₀ represents C _s per unit length. The non-destructive wafer-level piezoelectric material evaluation method described in claim 3, wherein the obtained piezoelectric coefficient evaluation can provide parameter setting for the piezoelectric application product, and provide the production line, Instant film characteristics judger in the process.