JP2001332949A - Method for manufacturing surface acoustic wave element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a surface acoustic wave(SAW) element by which the characteristics of a SAW element can be improved by improving the plurality of a wafer. SOLUTION: This method is provided with a process for forming a wafer 11 by cutting a single crystal material, a process for polishing both surfaces of the wafer 11 into a prescribed thickness, a process for grinding the surfaces 12 of the wafer, a process for mirror-grinding a wafer surface 12 and an element forming process for forming a metal strip electrode 14 on the wafer surface 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a communication filter,
The present invention relates to a method for manufacturing a surface acoustic wave element used for a delay unit, a transmitter, and the like, and more particularly to a method capable of coping with a higher frequency band.

[0002]

2. Description of the Related Art FIG. 8A is a schematic diagram showing the structure of a surface acoustic wave device 1. As shown in FIG. The surface acoustic wave element 1 has a thickness of 500 μm.
The wafer 2 has a diameter of about m, and metal strip electrodes 3 formed on the front surface 2a of the wafer 2 at predetermined intervals. In such a surface acoustic wave element 1, when an external radio wave or sound wave 4 is received, the surface acoustic wave 5 propagating along the surface 2 a of the wafer 2 and the surface acoustic wave 5 Is generated. The bulk wave 6 is further reflected on the back surface 2 b of the wafer 2 to become a reflected wave 7. The reflected wave 7 is a disturbance to the surface acoustic wave 5. Deterred.

[0003] Generally, the wafer 2 exhibits piezoelectricity.
Lithium tantalate (LiTaO) ₃) And Lithium niobate
Titanium (LiNbO₃), Quartz or the like.
This means that voltage is applied to the metal strip electrode 3.
To extract the excited frequency signal from the surface acoustic wave 5
This is because a filter function to make the filter function is obtained. FIG. 8B
Indicates the frequency characteristic of the filter function of the surface acoustic wave element 1.
FIG.

The surface acoustic wave element 1 has been used for a long time as a signal filter for a tuner for television or the like. In recent years, the demand for a filter for mobile communication represented by a mobile phone has been remarkable, and the frequency used has been increasing.

FIG. 9 is a view showing an example of a conventional method of manufacturing a surface acoustic wave device. In the present manufacturing method, after slicing a single crystal ingot, the wafer 2 is formed through processes such as beveling, double-side polishing, and surface mirror polishing.
After cleaning the wafer 2, a metal strip electrode 3 is formed on the surface 2a.

FIG. 10 is a view showing another example of a method of manufacturing a surface acoustic wave device. In the present manufacturing method, in order to reduce the amount of mirror polishing, there is a case where a single-side polishing with fine abrasive grains is performed after the double-side polishing, and then a mirror-polishing is performed.

[0007]

However, the method of manufacturing a surface acoustic wave device described above has the following problems. That is, as the frequency of the surface acoustic wave 5 increases, the line width of the metal strip electrode 3 becomes narrower and finer. Due to the design of the surface acoustic wave element 1, a submicron line width equivalent to that of a semiconductor device is obtained at a frequency of about 2 GHz or more. In addition, the distribution of the line width of the metal strip electrode 3 causes an error with respect to the design frequency of the surface acoustic wave 5. For this reason, even in the manufacturing process of the surface acoustic wave element 1, the flatness of the wafer 2 that can satisfy the fine line width and uniformity of the metal strip electrode 3 in the exposure process is required.

The wafer 2 has a thickness of 500 μm or less,
In order to improve the flat smoothness of the surface 2a, which is the element formation surface, the method of manufacturing the wafer 2 becomes a problem. In particular, a mirror polishing step close to the final step of wafer production becomes a problem. In the mirror polishing, the surface 2a of the wafer 2 is mirror-polished using a nonwoven fabric of polyurethane material and colloidal silica abrasive particles having a particle size of about 0.1 μm or less. Therefore, there is a possibility that the shape may be lost due to pressure non-uniformity, that is, the flatness of the wafer 2 may be reduced.

The use of the wafer 2 having poor flatness impairs the characteristics and manufacturing of the surface acoustic wave device 1 satisfying the submicron line width. For example, if the wafer flatness is inferior as shown in FIG. 8A, a distribution occurs in the line width and the like in the exposure step for forming the metal strip electrode 3, and FIG.
As shown in (1), there is a possibility that the frequency characteristic is improved, and in particular, the error Δ with respect to the selected frequency becomes large.

On the other hand, since the material of the wafer 2 is generally made of lithium tantalate, lithium niobate, or quartz, it has the property of being hard and brittle. For this reason,
When an impact or thermal stress occurs in the wafer processing step and the element formation step, there is a problem that the wafer is easily cracked. Furthermore, since it is a single crystal, it has low strength particularly against impact in the cleavage direction and thermal stress.

An object of the present invention is to provide a method of manufacturing a surface acoustic wave device that can improve the characteristics of the surface acoustic wave device by improving the flatness of the wafer. It is another object of the present invention to provide a method of manufacturing a surface acoustic wave device capable of preventing a crack of a wafer by improving a wafer strength and improving a manufacturing yield.

[0012]

Means for Solving the Problems In order to solve the above problems and achieve the object, a method for manufacturing a surface acoustic wave device according to the present invention is configured as follows.

(1) A cutting step of cutting a single crystal material to form a wafer, a polishing step of polishing both surfaces of the wafer to a predetermined thickness, a grinding step of grinding the wafer surface, and a mirror surface of the wafer surface The method includes a mirror polishing step for polishing and an element forming step for forming elements on the wafer surface.

(2) The method for manufacturing a surface acoustic wave device according to (1), wherein a peripheral edge mirror polishing step of mirror polishing the peripheral edge of the wafer is provided between the grinding step and the mirror polishing step. It is characterized by having.

(3) a cutting step of cutting a single crystal material to form a wafer; a polishing step of polishing both sides of the wafer to a predetermined thickness; a mirror polishing step of mirror polishing both sides of the wafer; And a device forming step of forming a device on the wafer surface.

(4) The method for manufacturing a surface acoustic wave device according to (3), wherein a peripheral edge mirror polishing step of mirror polishing the peripheral edge of the wafer is provided between the polishing step and the mirror polishing step. It is characterized by having.

(5) a cutting step of cutting a single crystal material to form a wafer, a polishing step of polishing both sides of the wafer to a predetermined thickness, and a mirror polishing step of mirror polishing the peripheral portion of the wafer; A mirror polishing step of mirror polishing the wafer surface; and an element forming step of forming elements on the wafer surface.

(6) a cutting step of cutting a single crystal material to form a wafer, a polishing step of polishing both surfaces of the wafer to a predetermined thickness, and a mirror polishing step of mirror polishing the peripheral portion of the wafer; A grinding step of grinding the wafer surface; a mirror polishing step of mirror polishing the wafer surface; and an element forming step of forming elements on the wafer surface.

(7) The method for manufacturing a surface acoustic wave device according to any one of the above (1) to (6), wherein the single crystal material is lithium tantalate.

(8) The method for manufacturing a surface acoustic wave device according to any one of (1) to (6), wherein the single crystal material is lithium niobate.

(9) The method for manufacturing a surface acoustic wave device according to any one of (1) to (6), wherein the single crystal material is quartz.

[0022]

FIG. 1 is an explanatory view showing a manufacturing process of a surface acoustic wave device 10 according to a first embodiment of the present invention. 2A to 2C show the same surface acoustic wave device 1.
FIG. 2 is a view showing processing apparatuses 20, 30, and 40 used for manufacturing the first manufacturing apparatus;
FIG. 3 is an explanatory view showing a manufacturing process of the surface acoustic wave device 10. FIG. 3A is a schematic diagram illustrating the surface acoustic wave device 10, and FIG. 3B is a graph illustrating the frequency characteristics thereof.

The surface acoustic wave device 10 includes a wafer 11 having a thickness of, for example, 500 μm as shown in FIG. The front surface 12 of the wafer 11 is an element formation surface, and the back surface 1
Reference numeral 3 denotes a bulk wave reflection surface. On the surface 12 of the wafer 11, metal strip electrodes 14 are juxtaposed at predetermined intervals. In FIG. 1, reference numerals 12a and 13a denote tapered surfaces provided on the peripheral portion of the wafer 11. In FIG. 3A, α indicates an external radio wave / sound wave, β indicates a surface acoustic wave, γ indicates a bulk wave, and δ indicates a reflected wave.

As shown in FIG. 2A, the processing device 20 includes an air spindle 21 and a grindstone 22 having a 22 ° tapered processing surface driven to rotate by the air spindle 21. The grindstone 22 has a particle size of 1 to 50 μm.
Of diamond diamond particles hardened with a binder.

As shown in FIG. 2B, the processing apparatus 30 places the wafer 11 thereon and
a rotary table 31 rotating at a rotation speed of pm, a feed mechanism 32 disposed opposite to the rotary table 31, an air spindle 33 positioned by the feed mechanism 32 with an accuracy of 0.1 μm, and an air spindle 33. A grindstone 34 that is driven to rotate at 1000 to 3000 rpm. The grindstone 34 has an aluminum base 35 having a diameter of 200 mm and a # 36 provided on the aluminum base 35.
0-1500 diamond (particle size 1-50 μm) and resin
It is formed from a grindstone 36 such as metal vitrified.

The processing device 40 is, as shown in FIG. 2C, an air spindle 41, a surface plate 42 driven to rotate by the air spindle 41, and an elastic body attached to the surface plate 42. A pad 43 made of a nonwoven fabric of a polyurethane material, a support portion 44 for supporting the wafer 11,
An air spindle 45 that rotationally drives the support unit 44 and a supply nozzle 46 that supplies a polishing liquid containing colloidal silica abrasive grains having a particle size of about 0.1 μm or less onto the surface plate 42 are provided.

In the first embodiment, a surface acoustic wave device is manufactured by the following steps. First, a single crystal ingot such as lithium tantalate, lithium niobate, and quartz is cut into a plate shape using a wire saw or an inner peripheral blade, thereby forming a wafer 11 as shown in FIG. Next, as shown in FIG. 3B, the peripheral portion of the wafer 11 is subjected to bevel polishing (chamfering) with a taper of 22 ° by the processing apparatus 20.

Next, the wafer 11 is sandwiched between two rigid platens arranged vertically by a polishing apparatus (not shown), and the wafer 11 is reduced by one from the final finished thickness while supplying loose abrasive grains.
As shown in FIG. 1C, both sides are polished until the thickness becomes 0 to 50 μm. At this stage, the undulation and warpage remaining on the wafer 11 are largely removed. On the back surface 13, the roughness (0.1 to 2 μmRa) obtained by the double-side polishing processing remains until element formation, and the influence on the frequency characteristics can be suppressed by weakening the reflected wave δ.

Next, the surface 12 of the wafer 11 is ground by the processing device 30 as shown in FIG. Since the wafer 11 is cut by the grindstone 34, the wafer 1
Processing is performed while supplying a grinding fluid while giving a cutting speed and a tangential rubbing speed between the wafer and the grinding wheel so as not to generate an overload on 1. For example, a cutting speed of 0.05 to 10
μm / s, tangential rubbing speed between the wafer 11 and the grindstone 10 to 20
The condition range is 0 m / s. Note that the shape of the wafer 11 is determined by the flatness of the wafer chuck surface of the rotary table 31, the feed accuracy and the positional accuracy of the grindstone, and the flatness is 1 μm.
You can finish with: Furthermore, since the load on the wafer 11 is reduced, generation of crack layers and strain layers in the depth direction of the processed surface is extremely small as compared with lapping or the like.

Next, as shown in FIG. 1E, the surface 12 of the wafer 11 is mirror-polished by the processing device 40 to obtain a mirror surface. In the mirror polishing, the surface 12 is mirror-polished using the pad 43 and a polishing liquid. Mirror polishing is a processing method in which an elastic body is pressed against a processing surface by pressing, so that the shape collapse due to non-uniform pressure, that is, the flatness of the wafer 11 corresponding to the removal amount of the mirror polishing is reduced. There is a possibility of inviting. However, since the amount of crack layers and strain layers generated in the depth direction of the processed surface is small due to the use of the above-described grinding, the amount of shaving in mirror polishing can be minimized. That is, the wafer flatness can be improved.

More specifically, the required amount of mirror polishing after the conventional polishing is 10 to 25 μm, whereas the required amount of mirror polishing after the grinding in the present embodiment is 3 to 25 μm.
〜１０10 μm. Therefore, when the shape collapse in the mirror polishing is 10%, the shaving amount is 1
At 0 to 25 μm, the flatness decreases by 1.0 to 2.5 μm, but the shaving amount in the present embodiment is 3 to 10 μm.
μm, which can be suppressed to a decrease in flatness of 0.3 to 1.0 μm.

Next, after processing abrasive grains and foreign matters remaining on the wafer W are removed by washing, the wafer 11 is removed in an element forming step.
A metal strip electrode 14 is formed on the surface 12 as shown in FIG. The metal strip electrode 14 for exciting radio waves and sound waves is formed by processes such as resist application, exposure, development, etching, and resist removal, similarly to the semiconductor element.

As described above, according to the method of manufacturing the surface acoustic wave device according to the first embodiment, the wafer 11 is ground to a more desired thickness by using the grinding process in which the processing damage is smaller than the polishing process. As a result, the amount of mirror polishing removal can be minimized, and a decrease in the flatness of the wafer 11 can be prevented. For this reason, in the element forming process, the parallel and smooth wafer 11 can be used, and the metal strip electrode 14 having a fine line width and a small distribution can be used.
Can be formed. Therefore, as shown in FIG. 3B, it is possible to improve the frequency characteristics of the surface acoustic wave element 10, and particularly to reduce the error Δ with respect to the selected frequency. In addition, since the back surface 13 of the wafer 11 still has surface roughness due to polishing, generation of the reflected wave δ can be minimized.

FIG. 4 is a view showing a manufacturing process of a surface acoustic wave device according to a second embodiment of the present invention.
(B) Processing device 5 used for manufacturing the same surface acoustic wave element
FIG. 4, the same functional portions as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 5A, the processing apparatus 50 includes a grindstone 51 and can mirror-polish the tapered surfaces 12a and 13a. In the figure, θ is the tapered surface 12a,
The angle matches the angle of 13a. Processing device 6
No. 0 is provided with a wrapping tape 61 as shown in FIG. 5B, and the tapered surfaces 12a and 13a can be mirror-polished.

In the method of manufacturing a surface acoustic wave device according to the second embodiment, as shown in FIGS. 4 (a) to 4 (d), similar to the first embodiment, processing,
Performs bevel polishing, double-side polishing, and grinding. Thereafter, as shown in FIG. 4E, the tapered surfaces 12a, 13
The bevel mirror polishing of a is performed, and the mirror polishing of the surface 12 of the wafer 11 is performed as shown in FIG. By mirror-polishing the tapered surfaces 12a and 13a,
Cracks on the tapered surfaces 12a and 13a are reduced as compared with the case where the tapered surfaces 12a and 13a are not mirror-polished. In particular, it is effective for hard and brittle single crystal materials for surface acoustic wave devices, such as lithium tantalate, lithium niobate, and quartz.

In the method of manufacturing the surface acoustic wave device according to the second embodiment, the same effects as those of the above-described first embodiment can be obtained, and therefore, when an impact or thermal stress is applied. Cracks peculiar to hard and brittle materials can be suppressed, and the yield can be improved.

FIG. 6 is a view showing a method of manufacturing a surface acoustic wave device according to a third embodiment of the present invention. 4, the same functional portions as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

6 (a), bevel polishing as shown in FIG. 6 (b), and FIG. 6 (c) in the same manner as in the first embodiment. Polishing is performed as described above. Next, as shown in FIG. 6D, the front surface 12 and the back surface 13 of the wafer 11 are mirror-polished on both sides.
Double-sided mirror polishing is a method in which a nonwoven fabric of a polyurethane material is stuck on two rigid bases arranged vertically, the wafer is sandwiched, and both sides of the wafer 11 are simultaneously mirror-polished while supplying colloidal silica abrasive grains having a particle size of about 0.1 μm. I do. Since the reference surface for pressing the wafer 11 is moving, uniform pressing can be performed by the averaging effect. Therefore, compared with the case where only one side is mirror-polished, the shape collapse is small and a flatter and smoother wafer can be obtained.

Next, as shown in FIG. 6E, the back surface 13 of the wafer 11 is
Grinding. The condition range of the processing device 30 is the same as that of the first embodiment. The surface roughness is set to such an extent that the influence of the reflected wave δ on the frequency characteristics can be prevented.

Next, after washing and removing the processing abrasive grains and foreign matters,
As shown in FIG. 6F, the electrodes 14 are formed on the surface 12 of the wafer 11, and the surface acoustic wave device 10 is completed.

In the method of manufacturing the surface acoustic wave device according to the third embodiment, the same effects as those of the first embodiment can be obtained.

FIG. 4 is a view showing a method of manufacturing a surface acoustic wave according to a fourth embodiment of the present invention. 4, the same reference numerals are given to the same functional portions as those in FIG. 3, and the detailed description thereof will be omitted.

In the method of manufacturing a surface acoustic wave device according to the fourth embodiment, similarly to the above-described third embodiment, the cutting of the wafer 11 shown in FIGS. Processing, bevel polishing, polishing on both sides. Thereafter, as shown in FIG. 7D, the beveled mirror surfaces of the tapered surfaces 12a and 13a are polished, and thereafter, as shown in FIG. I'm trying to do it.

By mirror-polishing the tapered surfaces 12a and 13a, cracks on the tapered surfaces 12a and 13a are reduced as compared with the case where the tapered surfaces 12a and 13a are not mirror-polished. For this reason, cracks peculiar to the hard brittle material when an impact or thermal stress is applied can be suppressed, and the yield can be improved.

Thereafter, as shown in FIG.
Grinding process 3 and element formation are performed as shown in FIG.

In the method of manufacturing a surface acoustic wave device according to the fourth embodiment, the same effects as those of the above-described third embodiment can be obtained, and therefore, when a shock or thermal stress is applied. Cracks peculiar to hard and brittle materials can be suppressed, and the yield can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

[0049]

According to the present invention, the characteristics of the surface acoustic wave element can be improved by improving the flatness of the wafer. Further, by improving the wafer strength, cracking of the wafer can be prevented, and the production yield can be improved.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a view showing a processing apparatus used in the manufacturing method.

FIG. 3A is a schematic diagram of a surface acoustic wave device manufactured by the same manufacturing method, and FIG. 3B is a graph showing frequency characteristics of the surface acoustic wave device.

FIG. 4 is a process chart showing a method for manufacturing a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 5 is a view showing a processing apparatus used in the manufacturing method.

FIG. 6 is a process chart showing a method for manufacturing a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 7 is a process chart showing a method for manufacturing a surface acoustic wave device according to a fourth embodiment of the present invention.

FIG. 8A is a schematic diagram of a surface acoustic wave device manufactured by a conventional manufacturing method, and FIG. 8B is a graph showing frequency characteristics of the surface acoustic wave device.

FIG. 9 is a process chart showing an example of a conventional method for manufacturing a surface acoustic wave element.

FIG. 10 is a process chart showing another example of a conventional method for manufacturing a surface acoustic wave element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Surface acoustic wave element 11 ... Wafer 12 ... Front surface 13 ... Back surface 14 ... Metal strip electrode (element) 20, 30, 40 ... Processing apparatus

Claims (9)

[Claims] A cutting step of cutting a single crystal material to form a wafer; a polishing step of polishing both surfaces of the wafer to a predetermined thickness; a grinding step of grinding the wafer surface; and a mirror polishing of the wafer surface. A method of manufacturing a surface acoustic wave device, comprising: a mirror polishing step of forming a mirror surface; and an element forming step of forming an element on the surface of the wafer. 2. The surface acoustic wave device according to claim 1, further comprising a peripheral mirror polishing step of mirror polishing the peripheral portion of the wafer between the grinding step and the mirror polishing step. Method. 3. A cutting step of cutting a single crystal material to form a wafer; a polishing step of polishing both sides of the wafer to a predetermined thickness; a mirror polishing step of mirror polishing both sides of the wafer; A method for manufacturing a surface acoustic wave device, comprising: a grinding step of grinding to a predetermined surface roughness; and an element forming step of forming an element on the wafer surface. 4. The surface acoustic wave device according to claim 3, further comprising a peripheral edge mirror polishing step of mirror polishing the peripheral edge of the wafer between the polishing step and the mirror polishing step. Method. 5. A cutting step of cutting a single crystal material to form a wafer; a polishing step of polishing both surfaces of the wafer to a predetermined thickness; a mirror polishing step of mirror polishing a peripheral portion of the wafer; A method for manufacturing a surface acoustic wave device, comprising: a mirror polishing step of mirror polishing a wafer surface; and an element forming step of forming an element on the wafer surface. 6. A cutting step of cutting a single crystal material to form a wafer; a polishing step of polishing both surfaces of the wafer to a predetermined thickness; a mirror polishing step of mirror polishing a peripheral portion of the wafer; A method for manufacturing a surface acoustic wave device, comprising: a grinding step of grinding a wafer surface; a mirror polishing step of mirror polishing the wafer surface; and an element forming step of forming an element on the wafer surface. 7. The method according to claim 1, wherein the single crystal material is lithium tantalate. 8. The method according to claim 1, wherein the single crystal material is lithium niobate. 9. The method for manufacturing a surface acoustic wave device according to claim 1, wherein said single crystal material is quartz.