JP5163366B2 - Frequency adjustment device - Google Patents

Description

  The present invention relates to an apparatus for adjusting a frequency by etching an element formed on a wafer with an ion beam.

  Conventionally, a method of adjusting the frequency of a piezoelectric element by etching the piezoelectric element with an ion beam is known. At that time, in order to improve productivity, a method of forming or arranging a plurality of elements on a wafer and simultaneously adjusting the frequency of the plurality of elements is employed. In such a frequency adjusting apparatus, masking (shielding) is performed with a pattern mask so that an ion beam is not irradiated on other than the desired element, and a predetermined mask hole is selectively opened and closed on the pattern mask to ion the target element. Some have a shutter for adjusting the beam irradiation time (see, for example, Patent Document 1).

  FIG. 9 shows an example of a prior art frequency adjusting device, in which a piezoelectric substrate (wafer) 151 is disposed on a movable stage 150, and a pattern having a mask hole 152a for selectively exposing a target piezoelectric element 151a thereon. A mask 152 is disposed, and a shutter 153 is disposed thereon. The shutter 153 is driven to open and close in the direction of the arrow, and by closing the mask hole 152a, the ion beam B irradiated from above can be shielded.

  The ion beam B is generated by an ion gun, and the irradiation direction of each ion beam B is adjusted to be as perpendicular to the wafer as possible, but has a slight diffusion angle. The shutter 153 is stopped near the mask hole 152a in the open position. Therefore, as shown in FIG. 9, a part of the diffused ion beam B may be reflected by the end surface 153a of the shutter 153 or may be sputtered by the end surface 153a of the shutter 153. When such reflected ions b1 and sputtered particles (recoil particles) b2 are incident on the piezoelectric element 151a, the piezoelectric element 151a is etched more than desired, or an unexpected deposit adheres to the piezoelectric element 151a. Adversely affects the surface of the product.

  FIG. 10 shows the relationship between the opening width of the mask hole and the etching amount by the ion beam. A shutter is close to the left side of the mask hole. As can be seen from FIG. 10, the etched recess does not have a flat bottom surface and is uneven. This is considered to be caused by an ion beam or recoil particles reflected by the end face of the shutter. If there is such variation in the etching amount, the amount of frequency change due to etching differs depending on the shape of the electrode and the position where the ion beam is irradiated, leading to a decrease in frequency adjustment accuracy.

To solve the above problem,
(1) Increase the retreat distance of the shutter so that the influence of reflected ions and recoil particles does not reach the piezoelectric element.
(2) The thickness of the shutter is made extremely thin to reduce the influence of ions incident on the shutter end face.
Etc., but each has drawbacks.

In the case of (1), the ions and recoil particles reflected by the shutter end face are not completely the same as the incident angle of the ion beam and take a wide range of emission angles, so that the influence on the piezoelectric element is not exerted. Need to be evacuated sufficiently. However, when the retracting distance of the shutter is increased, the entire shutter mechanism is increased. In the prior art, the electrodes are arranged in a matrix and the frequency of a plurality of elements is adjusted at the same time. However, the enlargement of the entire shutter mechanism reduces the integration of the shutter and reduces the efficiency. Further, if the shutter retract distance is increased, the operation time is increased accordingly, so that the time lag increases and the adjustment accuracy decreases.
In the case of (2), since the shutter is also etched by the ion beam, it is not practical in terms of life if the thickness of the shutter is extremely reduced.
JP 2001-36370 A

  An object of the present invention is to provide a frequency adjusting device that can reduce the influence of reflected ions and recoil particles on the shutter end face and can accurately adjust the frequency.

In order to achieve the above object, the present invention provides a pattern mask having a mask hole that is disposed on a wafer provided with a plurality of elements and selectively exposes the target element, and the wafer through the mask hole. An ion gun for etching that irradiates an ion beam with respect to, a shutter that is arranged between the pattern mask and the ion gun, selectively opens and closes a predetermined mask hole, and adjusts the ion beam irradiation time of the target element; The end face of the shutter is inclined in a reverse taper shape with respect to the traveling direction of the ion beam so as to have an inclination angle larger than the diffusion angle of the ion beam. I will provide a.

  In the present invention, since the end face of the shutter has an inverse taper shape having an inclination angle larger than the diffusion angle of the ion beam, the upper edge of the end face protrudes forward and the lower edge is in a position retracted backward. Therefore, the ion beam that pours from above can be shielded by the upper edge, and the ion beam can be prevented from entering the end face. As a result, reflected ions and recoil particles are not generated at the shutter end face, and variations in etching amount can be reduced. Further, only by changing the shape of the end face of the shutter, there is no need to increase the retracting distance of the shutter or reduce the thickness of the shutter, so that problems caused by them do not occur.

  Various types of shutter end face shapes are conceivable. In the present invention, being inclined in a reverse taper shape with respect to the ion beam traveling direction means being inclined in the diffusion direction with respect to the ion beam traveling direction. Specifically, the shutter end surface may be a flat inclined surface having a certain inclination angle, a concave curved surface shape, a convex curved surface shape, or a stepped shape, and may be inclined as a whole. That's fine. Among them, when the end surface is a flat inclined surface having a certain inclination angle, even when the shutter is etched by the ion beam and the thickness of the shutter is reduced, the shape change is small, and the life of the shutter with respect to the ion beam is sufficient. Is the most effective.

It is preferable that the end surface on the moving direction side of the shutter is inclined in a reverse taper shape with respect to the ion beam traveling direction. For example, when a plurality of shutters are arranged in close proximity to each other, when one adjacent shutter is closed and the other shutter is open, ions or recoil particles reflected by the end face of the closed shutter are applied to adjacent elements. May be incident. In that case, by making the end surface on the moving direction side into an inversely tapered shape, it is possible to prevent the reflected ions and recoil particles from entering the adjacent elements, and the frequency can be adjusted with high accuracy while improving the integration. .

  Moreover, it is good also as a structure where the end surface of the side orthogonal to the moving direction of a shutter inclines in reverse taper shape with respect to the ion beam advancing direction. For example, when a plurality of shutters are arranged close to each other in parallel, when one of the adjacent shutters is closed and the other shutter is open, the light is reflected on the side surface of the closed shutter (the end surface on the side orthogonal to the moving direction). Ions and recoil particles may enter the adjacent element. In that case, by making the side surface of the shutter into an inversely tapered shape, it is possible to prevent the reflected ions and recoil particles from entering the adjacent elements, and the frequency can be adjusted with high accuracy while improving the integration.

  The inclination angle of the end face of the shutter is preferably in the range of 5 ° to 45 °. The ion beam diffusion angle is determined in accordance with the ratio of the spread amount at a position that is a predetermined ratio (for example, 5%) of the maximum etching amount and the distance from the pattern mask to the wafer. Degree. Thus, by setting the inclination angle of the end face of the shutter to 5 ° to 45 °, the possibility that the ion beam hits the end face of the shutter is reduced, and the generation of reflected ions and recoil particles can be suppressed.

  As described above, according to the present invention, since the end face of the shutter for adjusting the ion beam irradiation time is formed in a reverse taper shape having an inclination angle larger than the diffusion angle of the ion beam, the ion beam may hit the end face of the shutter. And the generation of reflected ions and recoil particles can be suppressed. As a result, the variation in etching amount can be reduced, and it is not necessary to increase the retracting distance of the shutter or reduce the thickness of the shutter, thereby eliminating problems such as an increase in the size of the shutter mechanism and a shortened life. it can.

  Hereinafter, preferred embodiments of the present invention will be described based on examples.

  1 and 2 show an example of a frequency adjusting device according to the present invention. The frequency adjusting device 1 includes a processing chamber 2 having a hermetically sealed structure, and a vacuum pump 4 is connected to the side of the processing chamber 2 via an opening / closing door 3. By driving the vacuum pump 4, the inside of the processing chamber 2 is kept at a predetermined degree of vacuum. An etching ion gun 5 is installed on the ceiling of the processing chamber 2. As shown in FIG. 1, the ion gun 5 can irradiate an ion beam B having a substantially constant intensity per unit area downward within a predetermined range.

  A movable stage (conveying means) 6 is provided at the bottom of the processing chamber 2, and a wafer 10 is positioned and held thereon. The wafer 10 is made of, for example, a piezoelectric substrate, and an area 10a having a plurality of elements as one unit is densely arranged in a matrix at a constant pitch P, as shown in FIG. Note that one area 10a is not limited to including a plurality of elements, and may be composed of one element. The movable stage 6 can carry the wafer 10 intermittently in the direction of arrow A at intervals of the pitch P of the area 10a. The frequency of each area 10a of the wafer 10 at the previous stage sent to the frequency adjusting apparatus is set in a state shifted in advance in the direction opposite to the frequency change direction by the ion beam irradiation, and the target value is obtained by the ion beam irradiation. It is adjusted in the direction approaching. Etching by ion beam irradiation may be anything that can adjust the frequency, such as an electrode or a protective film formed on the wafer 10. The frequency of each area 10a of the wafer 10 is measured in advance, and the amount of frequency deviation with respect to the target value is obtained individually.

  Above the movable stage 6, a shutter base 11 is installed at a fixed position and horizontally. At the center of the shutter base 11, an opening 11a having a size substantially corresponding to the ion beam irradiation range by the ion gun 5 is formed. A pattern mask 15 that blocks an ion beam other than the target area is positioned and fixed in the opening 11 a of the shutter base 11. The pattern mask 15 is preferably supported as close to the wafer 10 as possible. A plurality of mask holes 15 a are formed in the pattern mask 15 independently for each area 10 a of the wafer 10. The size of each mask hole 15a is determined according to the distance between the pattern mask 15 and the wafer 10 and the diffusion angle of the ion beam, but is set substantially equal to the size of each area 10a. The mask holes 15a in this example are provided in two rows in the direction orthogonal to the wafer transfer direction and alternately shifted in the wafer transfer direction (A direction) so that the process for one row of the wafer 10 is performed in two stages. ing. That is, the odd-numbered and even-numbered mask holes are provided shifted in the A direction (transport direction). The mask holes on the downstream side (left side) in the transport direction correspond to the odd-numbered areas, and the mask holes on the upstream side (right side) in the transport direction correspond to the even-numbered areas. An interval d that is the same as one row (= P) of the area 10a is provided between the left mask hole 15a and the right mask hole 15a. Note that the spacing d in the A direction between the left and right mask holes 15a is not limited to one row and may be a plurality of elements, and can be arbitrarily selected according to the allocation of areas.

  A shutter mechanism 20 is provided on the shutter base 11. The shutter mechanism 20 includes a plurality of solenoids 12 fixed on the shutter base 11 on both sides of the opening 11a. Each solenoid 12 is connected to a shutter 14 via a shaft 13, and each shutter 14 is individually operated in the horizontal direction by the respective solenoid 12. The solenoid 12 is preferably provided with a main body provided with a coil, a yoke, and the like, and a shaft 13 that operates integrally with the movable iron core, and is capable of operating the shaft 13 at two positions of opening and closing by energizing the coil. For example, what can operate | move in several tens msec or less between an open position and a closed position is good. Each shutter 14 is provided corresponding to each mask hole so that each mask hole 15a can be opened and closed individually. That is, the left shutter 14 is operated in the opposite direction so as to open and close the left mask hole 15a and the right shutter 14 is opened and closed. The width and length of the shutter 14 are larger than the vertical and horizontal dimensions P of the mask hole so that the mask hole 15a can be completely covered. The movements of the movable stage 6 and the solenoids 12 are controlled by the control device 16 so as to adjust the frequency of the area in one row in the direction orthogonal to the wafer transfer direction in a plurality of stages. The control device 16 stores a frequency shift amount with respect to a target frequency in each area of the wafer 10 in association with an ion beam irradiation time.

  After the wafer 10 is transferred below the pattern mask 15, all shutters are opened, and all areas are irradiated with ion beams through the mask holes 15a. Then, the shutter is sequentially closed from the shutter corresponding to the area where the desired irradiation time (irradiation time corresponding to the frequency shift amount) has elapsed, and after all the shutters are closed, the wafer 10 is transferred by one pitch in the transfer direction. The

  FIG. 3 shows details of the shutter mechanism 20. The end surface 14a on the moving direction side of the shutter 14 is a flat inclined surface having a reverse taper shape with respect to the ion beam traveling direction, and the inclination angle θ is larger than the diffusion angle of the ion beam B. Here, the inclination angle θ is an angle inclined in the diffusion direction of the ion beam with respect to the vertical plane. Thus, by making the end surface 14a of the shutter 14 have a reverse taper having an inclination larger than the diffusion angle of the ion beam B, the ion beam B is incident on the shutter end surface 14a when the shutter 14 has the mask hole 15a opened. And the occurrence of reflected ions and recoil particles on the shutter end surface 14a can be prevented.

FIG. 4 is a diagram for defining the diffusion angle of the ion beam. The etching amount (depth) and the spread in the width direction when the object 10 is irradiated with the ion beam B through the mask hole 15a of the mask 15 are shown. It represents a relationship. If the distance from the mask 15 to the object 10 is d, and the amount of spread from the mask opening width at a position that is 5% of the maximum etching amount (= −1) is W,
Diffusion angle = tan ^-1 (W / d)
It is represented by For example, when d = 1.5 to 1.7 mm, W = 0.2 to 0.25 mm, and the diffusion angle is about 7 to 8 °. In this embodiment, the inclination angle of the end face 14a of the shutter 14 is set to 30 °, but it may be set in the range of 5 to 45 ° according to the diffusion angle.

  FIG. 5 shows the etching amount when the end surface 14a of the shutter 14 is formed into a reverse taper (θ = 30 °) having an inclination larger than the diffusion angle of the ion beam B. The shutter 14 is stopped near the left side of the mask hole 15a. By making the end surface 14a of the shutter 14 into a reverse taper, the generation of reflected ions and recoil particles on the shutter end surface 14a can be prevented, and the etching mark in the mask hole 15a is nearly rectangular as shown in FIG. Thus, it can be seen that the bottom surface of the etched recess is substantially flat. As is clear from the shutter having the vertical end face shown in FIG. 10, the frequency control accuracy is improved by improving the etching controllability of the element.

  The shutter 14 having the reverse tapered end face 14a needs to be positioned so that the upper edge of the end face 14a does not protrude inside the mask hole 15a as shown by the solid line in FIG. 3 when the mask hole 15a is opened. . On the other hand, when the mask hole 15a is closed, as shown by a broken line in FIG. 3, the upper edge of the end face 14a covers the mask hole 15a, and the ion beam B that has passed through the upper edge is not incident on the mask hole 15a. It is not necessary that the lower edge of the end face 14a completely covers the mask hole 15a.

  FIG. 6A shows a second embodiment of the frequency adjusting device according to the present invention, in which two shutters 14 are arranged so as to face each other, and the end surface 14a on the moving direction side is an inclined surface having a reverse taper shape. It is. In this embodiment, two rows of mask holes 15a are formed in the pattern mask 15 in a direction perpendicular to the moving direction of the movable stage 6, and the mask holes 15a are opened and closed by a pair of shutters 14 that can move in opposite directions. . The two rows of mask holes 15a may be displaced from each other in the direction perpendicular to the paper surface. In FIG. 6, the left shutter 14 closes the left mask hole 15 a of the pattern mask 15, and the right shutter 14 opens the right mask hole 15 a of the pattern mask 15. FIG. 6B is a comparative example in which the end surface 140a of the shutter 140 is a vertical surface.

  As shown in FIG. 6B, when the end surface 140a of the shutter 140 is a vertical surface, only the reflected ions b1 and the recoil particles b2 reflected by the end surface 140a of the right shutter 140 having the mask hole 15a open. In addition, reflected ions b1 and recoil particles b2 reflected by the end surface 140a of the left shutter 140 that closes the mask hole 15a may also enter the object 10a from the mask hole 15a. On the other hand, when the opposite end surfaces 14a of the shutter 14 are reversely tapered as shown in FIG. 6A, the ion beam B is not reflected by the end surface 14a, and is directly passed through the mask hole 15a. Since the light enters the object 10a, the frequency adjustment accuracy is improved.

  FIG. 7 is a cross-sectional view perpendicular to the moving direction of the shutter, showing a modification of the shutter. In the above embodiment, an inclined surface having an inclination angle larger than the diffusion angle of the ion beam is formed on the end surface on the moving direction side of the shutter, but a plurality of shutters 14 are arranged in parallel as shown in FIG. In this case, reverse-tapered inclined surfaces having an inclination angle larger than the diffusion angle of the ion beam may be formed on both side surfaces (end surfaces orthogonal to the moving direction) 14b of the shutter 14. Note that the end surface (end surface on the moving direction side) of the shutter 14 may be similarly an inversely tapered inclined surface. FIG. 7B is a comparative example in which both side surfaces 141a of the shutter 141 are vertical surfaces. In the case of FIG. 7B, for example, when the second shutter 141 from the right side is retracted and the mask hole 15a is opened, the reflected ions and the reflections reflected by the side surfaces 141a of the first and third shutters 141 from the right side are reflected. There is a possibility that the rebound particles are irradiated to the second object 10a from the opened mask hole 15a. On the other hand, if both side surfaces 14b of the shutter 14 are inclined surfaces as shown in FIG. 7A, the ion beam is applied to the side surfaces 14b of both adjacent shutters 14 even when one of the mask holes 15a is open. It is not incident and is not affected by reflected ions or recoil particles. By making the side surface 14b of the shutter 14 in a reverse taper shape in this way, it is possible to prevent the reflected ions and recoil particles from entering the adjacent elements, so that the frequency adjustment can be performed with high accuracy while improving the integration. Yes.

  FIG. 8 shows a modified example of the shutter. (A) is a shutter 14 having an end surface 14a made of a linear inclined surface as shown in the first embodiment, (b) is a shutter 14A having a convex curved end surface 14a1, and (c) is a concave curved end surface 14a2. The shutter 14B, (d) is an example of a shutter 14C having a stepped end face 14a3. The end surfaces of both shutters are inclined in a reverse taper shape with respect to the ion beam traveling direction. Since the upper edge of the shutter end surface protrudes forward and the lower edge is retracted backward, the upper edge shields the ion beam falling from above, preventing the ion beam from entering the end surface. . In particular, in the case of the end face 14a made of a linear inclined surface as shown in FIG. 5A, even if the shutter 14 is etched by an ion beam and the thickness is reduced, the shape change of the end of the shutter 14 is small and the shutter lifetime is reduced. Is the most advantageous.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. In the above embodiment, the shutter has a rectangular shape, and an inclined surface having an inverse taper shape is formed on the end face on the side where the mask hole is opened and closed. However, when the shutter has an opening corresponding to the mask hole, An inversely tapered inclined surface may be formed on the inner surface.

  In the above embodiment, a solenoid is used as an actuator for driving the shutter, and the shutter moves linearly back and forth. However, the present invention can be similarly applied to a case where the shutter swings. The actuator of the present invention may be any actuator that opens and closes the shutter at high speed, and is not limited to a solenoid but may be a VCM (voice coil motor). There are various types of VCM such as a movable coil type and a movable magnet type, and any of them can be used.

  In the above embodiment, the ion beam is irradiated in the vertical direction from the top to the bottom. However, the ion beam may be irradiated in the horizontal direction from the bottom.

It is the schematic of an example of the frequency adjustment apparatus which concerns on this invention. It is the disassembled perspective view which looked at the principal part of the frequency adjusting device shown in FIG. 1 from the ion gun 5 side for etching of FIG. It is an enlarged view of an example of the shutter mechanism shown in FIG. It is a figure for defining the diffusion angle of an ion beam. It is the figure which showed the relationship between the opening width of a mask hole at the time of using the shutter which concerns on this invention, and the etching amount by an ion beam. (A) is an enlarged view of the shutter mechanism in 2nd Example of this invention, (b) is an enlarged view of a comparative example. (A) is an enlarged view of the shutter mechanism in 3rd Example of this invention, (b) is an enlarged view of a comparative example. It is a side view of some examples of the end face shape of a shutter. It is an enlarged view of an example of the conventional shutter mechanism. It is the figure which showed the relationship between the opening width of a mask hole at the time of using the shutter mechanism shown in FIG. 9, and the etching amount by an ion beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frequency adjusting device 2 Processing chamber 5 Ion gun for etching 6 Movable stage 10 Wafer 10a Area (piezoelectric element)
11 Shutter base 12 Actuator 14 Shutter 14a End face (end face on the moving direction side)
14b Side surface (end surface on the side orthogonal to the moving direction)
15 Pattern mask 15a Mask hole 16 Control device 20 Shutter mechanism

Claims (5)

A pattern mask disposed on a wafer provided with a plurality of elements and having a mask hole for selectively exposing the target element;
An ion gun for etching that irradiates the wafer with an ion beam through the mask hole;
In a frequency adjustment apparatus comprising: a shutter that is disposed between the pattern mask and the ion gun, selectively opens and closes a predetermined mask hole, and adjusts an ion beam irradiation time of a target element;
An end face of the shutter is inclined in an inversely tapered manner with respect to the direction of ion beam traveling so as to have an inclination angle larger than the diffusion angle of the ion beam. The frequency adjusting device according to claim 1, wherein an end surface of the shutter is an inclined surface having a constant inclination angle. 3. The frequency adjusting device according to claim 1, wherein an end surface of the shutter in the moving direction is inclined in a reverse taper shape with respect to an ion beam traveling direction. 4. The frequency adjusting device according to claim 1, wherein an end face on a side orthogonal to a moving direction of the shutter is inclined in a reverse taper shape with respect to an ion beam traveling direction. 5. 5. The frequency adjusting device according to claim 1, wherein an inclination angle of an end face of the shutter is in a range of 5 ° to 45 °.

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