KR100480030B1 - Manufacturing method of thin film bulk acoustic resonator and filter - Google Patents

Abstract

The present invention relates to a thin film film bulk acoustic resonator (FBAR) and a filter, and particularly, to etch AlN thin film without excessive etching and loss of lower electrode when manufacturing FBAR and filter applied to next generation mobile communication terminal. It relates to a thin film FBAR and a filter manufacturing method suitable for. Conventionally, since the AlN thin film is etched by wet or dry etching during FBAR device fabrication, the AlN thin film is excessively etched when wet etching is used, and the lower electrode is easily etched when using dry etching. There was a problem with difficulty and low yield. In view of the above problems, the present invention includes forming a lower electrode, a piezoelectric dielectric, and an adhesive thin film metal layer on a substrate, and then applying a photoresist pattern; Removing the adhesive thin film metal layer exposed according to the photoresist pattern and etching the piezoelectric dielectric exposed according to the pattern consisting of the photoresist and adhesive thin film metal layer by a dry etching method until a lower electrode is exposed; Etching the remaining portion of the exposed piezoelectric dielectric by a wet etching method; It provides an FBAR and filter manufacturing method comprising the step of removing the remaining photoresist and thin film metal layer to prevent excessive etching and lower electrode etching of the AlN thin film to facilitate the process of FBAR and filter, the effect of increasing the yield have.

Description

MANUFACTURING METHOD OF THIN FILM BULK ACOUSTIC RESONATOR AND FILTER}

The present invention relates to a film bulk bulk acoustic resonator (FBAR, hereinafter referred to as FBAR) and a filter, and in particular, excessive etching and lower electrode loss of AlN thin film in the manufacture of FBAR and filter applied to the next-generation mobile communication terminal. A thin film FBAR and a method of making a filter that are suitable for etching without.

Bandpass filters (BPFs) and duplexers (DPXs), which are one of the key components used in telecommunication terminals including mobile phones, are devices that extract frequencies desired by users from many airwaves, and are currently used in dielectrics including surface acoustic wave (SAW) resonators. I'm using a filter. However, due to limitations in size and high frequency band characteristics, FBAR filters will be gradually applied to information communication terminals.

The FBAR filter has a wide frequency band, a small size, and a very small power consumption, which will contribute to miniaturization and low power of information and communication components.

Let's look at the core structure of this FBAR thin-film resonator.

FIG. 1 is a basic structure of a FBAR thin film resonator element, which is a portion of the resonator element formed on a substrate, although not shown, wherein a piezoelectric dielectric material 2 is positioned between the lower electrode 1 and the upper electrode 3.

The lower electrode 1 is formed on a silicon (Si) or gallium arsenide (GaAs) substrate (not shown), and a piezoelectric dielectric material 2 such as ZnO or AlN is deposited thereon. After that, the upper electrode 3 is formed on the upper side, and a bulk acoustic wave is generated to generate a resonance.

FIG. 2 illustrates an example in which a filter is applied by applying the FBAR device and then applied to a mobile communication terminal. The FBAR devices are serially and parallelly configured to configure transmit / receive band pass filters (TxBPF, RxBPF) as shown. It can be seen that it is connected and used.

The FBAR can be miniaturized to less than one hundredth of the size of the dielectric filter and the lumped constant (LC) filter, and the insertion loss is much smaller than the surface acoustic wave device, and the usable power is also large. In addition, since it can be embedded in a MMIC (Monolithic Microwave Integrated Circuit), it is possible to implement a one-chip RF filter and to have high frequency characteristics, thereby being applied to a next generation information communication terminal.

One of the features of FBAR is the low cost, since hundreds of filters can be manufactured simultaneously on one semiconductor substrate.

One of the most difficult processes in the fabrication of the FBAR device is a technique for etching the piezoelectric dielectric (eg, AlN) thin film.

In general piezoelectric dielectric etching, a photoresist mask is applied on the piezoelectric dielectric, and then dry or wet etching is performed.

3 illustrates a wet etching method of a conventional piezoelectric dielectric etching method, and is etched through an etching material such as phosphoric acid after applying a photoresist pattern.

3A illustrates that the lower electrode 11 and the piezoelectric dielectric 12 are sequentially formed on the semiconductor substrate 10, and then the photoresist pattern PR is applied. An insulating layer may be formed therebetween to insulate the lower electrode 11 from the semiconductor substrate 10.

Next, as shown in FIG. 3B, the piezoelectric dielectric 12 is patterned by wet etching using the photoresist pattern PR. The piezoelectric dielectric 12 is made of a material such as AlN. When wet etching with an etchant such as human body, the etching speed in the horizontal direction is 10 to 15 times faster than in the vertical direction, thus overetching as shown. do.

This causes a short circuit with the lower electrode when forming the upper electrode as shown in FIG. 3c, so the conventional method has a poor yield.

In addition, when the junction between the photoresist pattern and the piezoelectric dielectric is not good, the junction is also etched.

In the case of dry etching, in addition to the above-described method, gas is used, and since the etching rate in the vertical direction is good (1: 1 in the horizontal direction), the etching according to the photoresist pattern is performed vertically. However, there is a problem that the selective etching is not easy because the etching gas is etched to the lower pattern.

Therefore, the AlN thin film etching process in manufacturing the FBAR device is one of the biggest factor to lower the manufacturing yield of the FBAR filter.

As described above, since the AlN thin film is etched by wet or dry etching during the fabrication of FBAR devices, when the wet etching is used, the AlN thin film is excessively etched so that the lower electrode is easily exposed, and when using dry etching, the lower electrode is etched. As a result, the process was difficult and the yield was low.

In view of the above problems, the present invention improves the adhesion between the photoresist pattern and the AlN thin film formed by forming a thin metal layer on the AlN thin film, and applies the dry and wet etching to the over-etching and lower electrode etching of the AlN thin film. It is an object of the present invention to provide a thin film bulk oakistic resonator and a filter manufacturing method for preventing the same.

The present invention for achieving the above object comprises the steps of applying a photoresist pattern after forming a lower electrode, a piezoelectric dielectric, an adhesive thin film metal layer on a substrate in turn; Removing the adhesive thin film metal layer exposed according to the photoresist pattern and etching the piezoelectric dielectric exposed according to the pattern consisting of the photoresist and adhesive thin film metal layer by a dry etching method until a lower electrode is exposed; Etching the remaining portion of the exposed piezoelectric dielectric by a wet etching method; And removing the remaining photoresist and the thin film metal layer.

The thin film metal layer is formed using a metal having good adhesion, such as Cr or Ti, the depth of the piezoelectric dielectric etched through the dry etching is preferably not more than 80% of the lower layer is exposed.

When described in detail with reference to the accompanying drawings an embodiment of the present invention thin film FBAR and a filter manufacturing method configured as described above are as follows.

4A to 4E are cross-sectional views of a thin film FBAR and a filter manufacturing process according to the present invention. As shown therein, a thin film metal layer is formed on a substrate 20, a lower electrode 21, and an AlN piezoelectric dielectric 22 formed thereon. (23) depositing a photoresist pattern (PR) for depositing and separating FBAR elements thereon (FIG. 4A); Etching the exposed thin metal layer 23 using the photoresist pattern PR to expose a portion of the AlN piezoelectric dielectric 22 to be etched later (FIG. 4B); Etching at least 80% of the AlN piezoelectric dielectrics 22 exposed by the pattern consisting of the photoresist PR and the thin film metal layer 23 by a dry etching method (FIG. 4C); Etching the remaining portion of the exposed AlN piezoelectric dielectric 22 by a wet etching method (FIG. 4D); The photoresist PR and the thin film metal layer 23 are removed (FIG. 4E).

Hereinafter, the thin film FBAR and the filter manufacturing method of the present invention configured as described above will be described in more detail.

First, as shown in FIG. 4A, the lower electrode 21 and the AlN piezoelectric dielectric 22 are formed on the substrate 20, and then the photoresist pattern to be formed is adhered to the AlN piezoelectric dielectric 22. In order to improve the quality of the thin-film metal layer 23 having good adhesion, such as Cr or Ti and then to form a photoresist pattern (PR) on the top. As a result, the risk of the etching gas or the etchant flowing into the interface between the photoresist pattern PR and the AlN piezoelectric dielectric 22 may be extremely reduced during the etching process.

The substrate 20 may be a general silicon (Si) or gallium arsenide (GaAs) substrate, but a low loss substrate such as glass or ceramic may be used.

In addition, as will be described later, an insulating layer may be inserted between the substrate 20 and the lower electrode 21, and an air gap or a membrane layer may be additionally configured according to the FBAR filter to be manufactured. have. These specific embodiments will be described later with reference to embodiments of the present invention.

Next, as shown in FIG. 4B, the upper portion of the AlN piezoelectric dielectric 22 is exposed by etching and removing the thin film metal layer 23 according to the formed photoresist pattern PR.

Next, as shown in FIG. 4C, 80% or more of the AlN piezoelectric dielectrics 22 exposed by the pattern formed of the photoresist PR and the thin film metal layer 23 are etched by a high density plasma dry etching method. . In the dry etching method, since the vertical etching rate is good, the AlN piezoelectric dielectric 22 is not excessively etched because it is almost vertically etched. At this time, the lower electrode 22 is not exposed.

Next, as shown in FIG. 4C, the remaining portion of the AlN piezoelectric dielectric 22 etched through the dry etching is etched by a wet etching method to etch the AlN piezoelectric dielectric 22 without etching the lower electrode 22. ) Can be completely etched.

Finally, the FBAR devices may be individually configured by removing the remaining photoresist PR and the thin film metal layer 23.

As described above, the present invention performs wet etching to remove the remaining AlN piezoelectric dielectric 22 and expose the lower electrode 22 after most of the AlN piezoelectric dielectric 22 is etched by dry etching with good vertical etching rate. Therefore, the difficulty of the process becomes very easy and the state of the resultant product is much superior to the conventional dry or wet etching method.

Now, embodiments of the methods of manufacturing the various FBAR filters by applying the present invention will be described with the drawings.

5A to 5E are cross-sectional views of an FBAR filter manufacturing process constructed by etching an AlN thin film using the inventive thin film FBAR and filter manufacturing process, and an insulating layer and an air gap are applied thereto.

As shown in FIG. 5A, an insulating layer (SiNx, SiO 2) 31 is formed on the substrate 30 to insulate the lower electrode, and then the sacrificial layer 32 is deposited on the substrate 30. The sacrificial layer 32 uses silicon, polysilicon, PSG, BPSG, etc. and will then be removed leaving an air gap.

Next, as shown in FIG. 5B, the sacrificial layer 32 is patterned to form a lower electrode 33 thereon.

Next, as shown in FIG. 5C, the AlN piezoelectric dielectric 34 is formed on the lower electrode 33, and then the AlN piezoelectric dielectric 34 is patterned using the present invention. That is, the AlN piezoelectric dielectric 34 is cleanly patterned using the process procedure described with reference to FIG. 4 while not damaging the exposed portion of the lower electrode 33.

Next, as shown in FIG. 5D, an upper electrode 35 is formed on the formed AlN piezoelectric dielectric 34 pattern and the lower structure, and then patterned in consideration of connection with the lower electrode 33 of another FBAR device. do.

Next, as shown in FIG. 5E, an additional metal on the upper electrode 35 of the selected FBAR element is selected to give a resonator frequency difference by selecting one of the series resonator or the parallel resonator to implement the filter composed of the FBAR elements. (add metal) 36 is deposited. Thereafter, the sacrificial layer 32 is finally removed by wet etching to form an air gap 32 ′.

Through the above-described method, it is possible to produce a resonator having an air gap 32 'and no membrane and a filter using the same. In this process, the AlN piezoelectric dielectric 34 is patterned through the present invention, so that the process is easy and the production yield is improved. Is improved.

Let's look again at Figure 5b. Here, after forming the sacrificial layer 32 and before forming the lower electrode 33 thereon, a membrane layer such as silicon nitride or ONO (oxide / nitride / oxide) may be further formed. The process is similar to that of Figures 5C-5E.

Therefore, the present invention can be commonly applied to the manufacture of a filter using an insulating layer, an air gap, and a map brain appropriately.

6A and 6B are configured slightly differently from the above-mentioned filter, and FIG. 6A is almost similar to the filter configured through FIG. 5, but uses a low loss substrate such as glass or ceramic as the substrate 40.

FIG. 6B illustrates a case in which the membrane layer is further applied to the configuration of FIG. 5. In this case, a low loss substrate such as glass or ceramic is used as the substrate 50. The illustrated AlN piezoelectric dielectric 54 pattern may have a wider width to achieve mechanical stability.

In the case of using the glass or ceramic substrate as described above, since the sacrificial layer can be directly formed without the insulating layer, there is almost no loss of the substrate, thereby improving the characteristics of the filter.

7A to 7E are process flow charts illustrating a method of manufacturing a filter in which an air gap is positioned in the etched portion after partially etching the silicon substrate, differently from the methods described above.

As shown in FIG. 7A, the substrate 60 is partially etched and the insulating layer 61 is deposited. The etched portion is a portion which will be an air gap later, and is configured to be positioned inside the substrate differently from the above-described configuration.

Next, as shown in FIG. 7B, the sacrificial layer 62 is formed on the structure, and then chemically polished so that the substrate is flat.

Thereafter, a lower electrode 63 is formed on the structure.

Next, as shown in FIG. 7C, the AlN piezoelectric dielectric 64 is formed on the structure, and the AlN piezoelectric dielectric 64 is patterned using the present invention. That is, here, the AlN piezoelectric dielectric 64 is cleanly patterned using the process procedure described with reference to FIG. 4 while not damaging the exposed portion of the lower electrode 63.

Next, as shown in FIG. 7D, an upper electrode 65 is formed on the formed AlN piezoelectric dielectric 64 pattern and the lower structure, and then patterned in consideration of connection with the lower electrode 63 of another FBAR device. do.

The frequency of the resonator is then changed by depositing additional metal 66 on a portion of the upper electrode 63 according to the filter to be constructed.

Finally, as shown in FIG. 7E, the sacrificial layer 62 is removed by wet etching to form an air gap 62 ′.

7 may further add a membrane layer on the sacrificial layer 62 and the substrate 60 polished before forming the lower electrode 63.

FIG. 8A illustrates a case in which the substrate 70 is used as glass or ceramic as described above. FIG. 8B illustrates the upper electrode 85 and the lower electrode in order to compensate for interconnect vulnerabilities between the FBARs after forming the structure of FIG. 7. In this embodiment, the conductive metal material 87 is deposited on the portion 81. In addition to this, the interconnects can be configured outside the filter.

FIG. 9 illustrates embodiments of adjusting a thickness of an upper electrode by applying or etching an additional metal in a method of changing a frequency of the formed resonator.

It is assumed that the left one of the basic resonator elements shown in FIG. 9A is used for the parallel resonator and the right one for the series resonator.

As shown in FIG. 9B, there is a method of depositing and forming an additional metal AM on the upper electrode 93 on the left side, which is basically applied to the above-described methods.

In addition, as applied to FIG. 9C, there is a method of forming an additional metal (AM) first before forming the upper electrode 93.

In addition, as applied to FIG. 9D, after forming the upper electrode 93, there is a method of controlling the thickness by etching only the upper electrode 93 of the right element to form a series resonator by dry etching.

Through the above method, the frequency difference between the center frequencies of the resonator is several MHz to several tens of MHz.

FBARs and filters constructed through the aforementioned methods use the piezoelectric dielectric etching method of the present invention, and it should be noted that the present invention can be applied to many other methods in addition to the aforementioned methods.

10A to 10C illustrate a post-tunning method when a resonance frequency of an FBAR device and a filter formed by using the present invention is different from the design, and using a fine shadow mask (MK) as shown in FIG. 10A. Plasma etching or deposition on top of the configured FBAR filter, plasma etching or deposition on the back of the FBAR filter configured as shown in Figure 10b using a fine shadow mask (MK), and configured as shown in Figure 10c The method of performing plasma etching or vapor deposition on the additional metal part of an FBAR filter is mentioned. The resonant frequency is changed by changing the mass of the formed resonator, thereby changing the mechanical movement of the resonator.

As described above, the present invention improves the adhesion between the photoresist pattern and the AlN thin film formed by forming a thin metal layer on the AlN thin film, and prevents excessive etching and lower electrode etching of the AlN thin film by cross-applying dry etching and wet etching. By providing a new etching method of the AlN thin film to facilitate the process of the filter using FBAR and FBAR, it has the effect of increasing the yield.

1 is a cross-sectional view of an FBAR device.

2 is a diagram illustrating filters applied with FBAR to a mobile communication terminal.

3 is a flowchart of a conventional FBAR device manufacturing process

4 is a flow chart of the FBAR device manufacturing process of the present invention.

5 is a flowchart of an FBAR filter manufacturing process embodiment to which the FBAR device manufacturing process of the present invention is applied.

FIG. 6 illustrates FBAR filter manufacturing embodiments to which the FBAR device manufacturing process of the present invention is applied.

7 is a flowchart of another embodiment of the FBAR filter manufacturing process to which the present invention FBAR device manufacturing process is applied.

8 illustrates FBAR filter manufacturing embodiments to which the FBAR device manufacturing process of the present invention is applied.

9 shows examples of frequency adjustment of an FBAR filter to which the FBAR device fabrication process of the present invention is applied.

10 illustrates post-processing embodiments of an FBAR filter to which the FBAR device fabrication process of the present invention is applied.

*** Explanation of symbols for main parts of drawing ***

20: substrate 21: lower electrode

22: piezoelectric dielectric 23: thin film metal layer

PR: Photoresist

Claims (8)

Applying a photoresist pattern after sequentially forming a lower electrode, a piezoelectric dielectric, and an adhesive thin film metal layer on the substrate; Removing the adhesive thin film metal layer exposed according to the photoresist pattern and etching the piezoelectric dielectric exposed according to the pattern consisting of the photoresist and adhesive thin film metal layer by a dry etching method until a lower electrode is exposed; Etching the remaining portion of the exposed piezoelectric dielectric by a wet etching method; And removing the remaining photoresist and the thin film metal layer. The method of claim 1, wherein the thin film metal layer is formed by using a highly adhesive metal containing Cr or Ti. The method of claim 1, wherein a depth of the piezoelectric dielectric etched through the dry etching is 80% or more. The method of claim 1, wherein the piezoelectric dielectric is made of AlN. The method of claim 1, further comprising forming an insulating layer between the substrate and the lower electrode to form an insulation layer before forming the lower electrode. The method of claim 1, wherein an air gap is further formed at the bottom of the lower electrode by forming and then etching the sacrificial layer before forming the lower electrode. The method of claim 1, further comprising forming a membrane layer between the lower electrode and the lower structure before forming the lower electrode. The thin film of claim 1, wherein a portion of the substrate is etched before forming the lower electrode, and then a sacrificial layer is formed on the etched portion and then removed, thereby forming an air gap on the lower electrode lower substrate. Bulk Ocostic Resonator and Filter Manufacturing Method.