JP2008119698A - Method and apparatus for drilling hole in substrate with co2 laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for drilling a hole in a substrate with laser, by which drilling of a minute hole diameter suitable for MEMS is made possible using comparatively inexpensive CO<SB>2</SB>laser, while no damage is caused to a workpiece and no swelling or the like in the periphery of a drilled hole is caused, and a pitch between holes can be reduced. <P>SOLUTION: In the method for drilling the hole using the CO<SB>2</SB>in the substrate by irradiating it with CO<SB>2</SB>laser, fused components of the workpiece are sucked during the irradiation of the laser beam 28. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method and apparatus for drilling holes in a substrate such as glass and ceramics with a CO ₂ laser (carbon dioxide laser), and more particularly to glass for anodic bonding in the field of MEMS (micro electromechanical system), and more particularly to a through electrode. The present invention relates to a method and an apparatus for making a hole in a working glass.

  Conventionally, in the MEMS field, functional elements (microdevices) having both electrical and mechanical elements such as pressure sensors, acceleration sensors, optical devices, and various switches have been formed on a silicon substrate, etc. It is manufactured by sealing with.

  Conventionally, the glass substrate and the silicon substrate are bonded using an adhesive. However, the functional element portion is prevented from being contaminated by the volatile component of the adhesive during bonding, and the package of the functional element portion is evacuated. In order to achieve smooth operation of the functional elements, oxidation prevention, and heat insulation effect, recently, bonding is performed by a method called anodic bonding which does not use an adhesive (see, for example, Patent Document 1).

  The anodic bonding is a bonding method in which a glass substrate and a silicon substrate are bonded to each other by electrostatic attraction generated at the interface between the glass substrate and the silicon substrate by heating the glass substrate and the silicon substrate while applying voltage. is there.

  Recently, in order to further miniaturize the above MEMS parts, a through hole is formed in the glass substrate, a through electrode is provided through the through hole, and the electrode is directly taken from the glass substrate. ing.

  From the above, in the production of MEMS parts, it is important to form fine through holes with high accuracy in a glass substrate. In addition, high-speed and low-cost processing has been demanded for mass productivity.

  Conventionally, various methods such as the following have been used to form a through hole in the glass substrate. For example, 1) spinning drill, 2) ultrasonic processing, 3) sand blast, 4) wet etching, 5 Examples thereof include dry etching and 6) femtosecond laser.

Further, using a CO ₂ laser, drilling of glass or ceramics used for an inkjet head or the like is also performed (for example, see Patent Document 2).
JP 2004-358603 A (paragraph 0058) JP 2004-291026 A (Claim 1, Claim 2)

By the way, the above-mentioned conventional method for forming a through hole in a glass substrate has the following problems.
1) Spinning drills require time for drilling, and for MEMS, there is a problem that the diameter of the drill must be reduced or the pitch between holes cannot be reduced.
2) Ultrasonic machining has problems that it is difficult to make small holes (minimum hole diameter is 0.35 mm) and that the pitch between holes cannot be reduced.
3) Sandblasting requires a mask, takes time for drilling, cannot drill small holes (the depth cannot exceed the opening diameter), and cannot narrow the pitch between holes. The inside of the opened hole is rough, and there is a problem that the airtightness in the package of the functional element portion cannot be maintained when anodic bonding is performed, and there is a problem that is not suitable for anodic bonding.
4) Wet etching requires a mask, requires time for drilling, cannot narrow the pitch between holes, and is not suitable for deep drilling (processing depth: 0.2 mm at the maximum). There was a problem that the end of the.
5) The dry etching requires a mask, takes time for drilling, and has a problem that the apparatus is very expensive.
6) The femtosecond laser has a problem that it takes time to make a hole and the apparatus is very expensive.

Also, performing a method of Patent Document 2 relates to drilling by a low-cost CO ₂ laser, as is described in the patent literature 2, normally, simply drilled holes in the glass with a CO ₂ laser In this case, the processing heat will cause distortion in the glass, etc., and cracks will occur, so the periphery of the processing part is heated with a laser other than the processing laser or infrared rays, and the temperature gradient of the processing part and its surroundings. Disclosed is a method of reducing distortion and reducing cracks by reducing the above.

  However, when two types of lasers are used as in Patent Document 2, the cost of the apparatus is doubled or the respective control mechanisms are required, and the cost of the apparatus increases and the control mechanism becomes complicated. There is a problem that adjustment becomes difficult.

  Moreover, the drilling process by patent document 2 or a general laser is performed by evaporating a to-be-processed object with the heat | fever of the irradiated laser, or scattering a molten component with assist gas.

  However, in the method of evaporating the workpiece in the processed part as described above and the method of scattering the molten component with the assist gas, a large amount of heat must be applied to the perforated part, and the area of the molten part is also large. As a result, the hole diameter becomes large, or the melted portion scatters around the processed portion, so that a bulge or the like occurs around the hole.

  For this reason, the above method has a problem that it is not suitable for microfabrication such as MEMS. In particular, when a swell occurs around the through-hole, when the swell is used as a through-electrode, the swell must be removed, resulting in a high processing cost.

  In addition, the method using two types of lasers in Patent Document 2 has a problem that it takes time to process because the workpiece is heated until the workpiece is melted and the surrounding area is heated, and is not suitable for mass production. If a large number of holes are continuously drilled, a large amount of heat is applied, and there is a problem that the glass substrate is distorted and cracks occur in the glass substrate. There is a problem of not opening.

Here, the conventional CO ₂ laser processing method will be described with reference to FIGS. 15 to 17. First, as shown in FIG. 15, the glass substrate 43 sucked and fixed by the suction table 42 on the processing table 41 is used. The laser beam 46 collected by the condensing lens 45 inside the nozzle 44 is drilled into the glass substrate 43 through the opening at the tip of the nozzle 44, and assists from the assist gas introduction pipe 47. A gas 48 is introduced.

  FIG. 16 shows the principle of drilling of the glass substrate 43 according to the conventional method. In the solid 49 in the normal state constituting the glass substrate 43, the temperature rapidly rises around the portion hit by the laser beam 46, and the workpiece As shown in the temperature distribution, the melting point mp of the glass is exceeded in the vicinity of the center to become a melt 50, and the temperature of the melt 50 further rises due to the irradiation of the laser beam 46 and exceeds the boiling point bp of the glass near the center. Vaporizes and turns into plasma vapor 51.

  The conventional apparatus is configured as described above. Next, the state of the glass substrate 43 in a state of being drilled by laser light will be described with reference to FIG. 17. First, as shown in FIG. The glass substrate 43 in the vicinity of the focal point of the laser beam 46 irradiated through the section 52 has a temperature exceeding the melting point mp and becomes a melt 50 from the solid 49, and the melt 50 is further irradiated with the laser beam 46. The temperature of the central portion of the liquid 50 exceeds the boiling point bp and vaporizes to form plasma vapor 51, which is discharged from the inside of the glass substrate 43 to form holes.

As shown in FIG. 17 (b), plasma vapor 51 is formed in the center of the melt 50 at a higher temperature and exceeding the boiling point bp, and is provided at the nozzle tip 52 to blow off the plasma vapor 51 in this state. The assist gas 48 is introduced from the assist gas introduction pipe 47 described above, and the assist gas 48 is injected from the nozzle tip 52.
In addition to the above, the assist gas 48 injects oxygen gas or the like to promote drilling, or prevents the plasma vapor 51 from entering from the nozzle tip 52 and causing the condensing lens 45 to be fogged. Has been used for.

  The melting of the glass substrate 43 proceeds downward with the two-layer structure of the plasma vapor 51 formed from the melt 50 by heat and the melt 50 around it, but the melting area is closer to the upper surface where the heated time is longer And the melting proceeds in an inverted conical shape as a whole.

  When the glass substrate 43 is irradiated with the laser beam 46 to form the melt 49 of the solid 49, the solid 49 of the glass substrate 43 is removed and an inverted conical hole is formed. As shown in FIG. Reaches the lower surface of the glass substrate 43, the irradiation of the laser beam 46 is terminated. At this time, the melt 50 accumulated on the peripheral wall of the hole falls by gravity or the blowing of the assist gas 48, and the lower part of the inverted conical shape is formed. Then, it cools and hardens, and breaks the shape of the hole 53 formed through the glass substrate 43 or closes the lower penetration.

As described above, the conventional processing method using a relatively inexpensive CO ₂ laser has a problem that it is not suitable for fine processing and mass productivity. In addition, various methods other than the above-described CO ₂ laser can be used for mass production, cost, etc. There were no suitable methods for MEMS parts due to various problems.

Therefore, the object of the present invention is to use a CO ₂ laser that is relatively inexpensive and has a good beam quality among various types of lasers, and is capable of drilling with a small hole diameter suitable for MEMS. It is an object of the present invention to provide a method and apparatus for drilling a substrate with a CO ₂ laser that does not cause damage, does not generate swells around the opened holes, and can reduce the pitch between the holes.

In order to solve the above-described problems, the invention of claim 1 is a method of piercing a substrate by irradiating a CO ₂ laser, and performing CO ₂ while sucking a molten component of a workpiece when irradiating a laser beam. This is a method of drilling a substrate with a laser.

According to a second aspect of the present invention, in the method for drilling a substrate with the CO ₂ laser according to the first aspect, a configuration is adopted in which an annealing process is performed after the drilling.

According to a third aspect of the present invention, there is provided an apparatus for piercing a substrate by irradiating a CO ₂ laser. A nozzle component that irradiates a laser beam opposite to the workpiece is irradiated with a molten component of the workpiece during the laser beam irradiation. This is a drilling device for a substrate with a CO ₂ laser provided with a suction member capable of sucking.

The substrates in the above inventions are particularly applicable to, for example, glass substrates and ceramic substrates, particularly anodic bonding glass substrates in the MEMS field, but are not limited thereto, and drilling with a CO ₂ laser is possible. Includes all possible materials.

  In addition, the annealing treatment is performed by heating near the glass transition point of the substrate (for example, about 600 ° C. with a glass substrate) to correct distortion in the substrate due to drilling.

  According to the first or third aspect of the present invention, by sucking the perforated portion at the time of laser beam irradiation, the workpiece can be sucked and removed in a water tank-like state before the workpiece is completely melted, and the hole diameter is increased. In addition, it can be processed in a short time without causing swell.

  In addition, since it is not necessary to apply more heat than necessary during processing, it is possible to minimize the occurrence of distortion due to heat on the work piece, and the state of the hole after processing is less altered and smooth and accurate. Become.

  In addition, since there is little distortion of the work piece, even if the pitch between the holes is reduced, the work piece will not be cracked, chipped, etc. From the point that smooth and accurate through holes can be formed in the short time described above. For example, when applied to a glass substrate in the MEMS field, a minute through hole suitable for conduction is formed.

Furthermore, since a CO ₂ laser that is relatively inexpensive to use is used, and the workpiece is not distorted without using a heat source or the like, drilling can be performed at low cost.

  According to the second aspect of the present invention, by annealing the substrate after drilling, distortion during processing of the substrate can be further reduced, and for example, a glass substrate having a through hole suitable for MEMS or the like is provided. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 and FIG. 2 show an embodiment of an example of a drilling device for a MEMS glass substrate to which the present invention is applied. On a rail 2 that extends in the horizontal direction in the figure on a machine base 1. Further, the transfer robot 3 is provided so as to be movable along the rail 2 by an appropriate means (not shown), and the pre-processing glass substrate housed on the machine base 1 is also stored using the arm of the transfer robot 3. The glass substrate 8 can be transferred, delivered, and received to each part of the part 4, the suction rotation table 5, the processing table 6, and the processed glass substrate storage unit 7.

  The unprocessed glass substrate storage unit 4 stores the glass substrate 8 in a stacked manner in order to transfer the unprocessed glass substrate 8 to the transport robot 3, and can sequentially transfer the glass substrate 8 from the upper surface to the transport robot 3.

  The processed glass substrate storage unit 7 receives a glass substrate 8 ′, which is punched on the processing table 6 and transported to the next process, from the transfer robot 3 and stores it in an overlapping manner.

  The suction rotation table 5 rotates by sucking and rotating the glass substrate 8 transported from the pre-processing glass substrate storage unit 4 by the transport robot 3, and is necessary for drilling by known means using the alignment sensor 9. The resulting glass substrate 8 is positioned.

  The processing table 6 can be moved up and down by an elevating cylinder 11 provided in a machine frame 10 provided on the machine base 1, and a suction table 12 is fixed on the processing table 6, and the glass after positioning. The substrate 8 is sucked and fixed on the upper surface, and a drilling process using a laser is performed on the sucked glass substrate 8.

  Two columns 13 and 13 are erected adjacent to each other near the processing table 6 in the machine frame 10, and a rail 14 extending in the horizontal direction is provided between the columns 13 and 13 so as to connect the upper ends of the columns. A fixed frame 16 integrated with a slider 15 slidably fitted to the rail 14 is provided. The fixed frame 16 can be moved along the rail 14 together with the slider 15 by appropriate means (not shown). It has become.

  A rail 17 that is horizontal and orthogonal to the rail 14 is fixed to the fixed frame 16, and the front end of the rail 17 extends forward from the fixed frame 16, and is slidably fitted to the rail 17. The slider 18 is provided with a rail 19 extending in the vertical direction, and the rail 19 is movable along the rail 17 in the horizontal direction along with the slider 18 by an appropriate driving means (not shown). .

  A laser oscillator 21 for fixing a hole in the glass substrate 8 by a laser beam is fixed to a slider 20 fitted to the rail 19 so as to be movable up and down by sliding. Includes a shutter 22 for blocking laser light, a mirror 23 for reflecting laser light to a predetermined position, a nozzle 24 facing a portion of the glass substrate 8 to be drilled, and a tip of the nozzle 24 adsorbing to the glass substrate 8. A suction pad 25 as a suction member made of silicone rubber or the like, an assist gas introduction tube 26 for introducing an assist gas, and a suction tube 27 for performing a suction action of the suction member are integrated with the slider 20 together with the laser oscillator 21. Is provided.

  By moving the slider 15, slider 18, and slider 20 on the rail 14, rail 17, and rail 19 by controlled driving means, the nozzle 24 is movable in the X, Y, and Z axis directions, and is attracted. The pad 25 is brought close to the surface of the glass substrate 8 on the suction table 12 and sucked, or the nozzles 24 are moved in the horizontal direction sequentially after being processed to a plurality of predetermined positions where the glass substrate 8 is to be drilled. The nozzle 24 is separated from the finished glass substrate 8.

  FIG. 3 is an enlarged view of the vicinity of the tip of the nozzle 24 when drilling the glass substrate 8 that is suction-fixed on the suction table 12 on the processing table 6, and is irradiated by the laser oscillator 21. The laser beam 28 guided into the nozzle 24 by the shutter 22 and the mirror 23 is condensed by the condenser lens 29 in the nozzle 24, passes through the tip opening of the nozzle 24, and is fixed to the tip of the nozzle 24. Adjustment is made so as to focus on the vicinity of the surface of the glass substrate 8 sucked by the suction pad 25 through the suction pad fixing holder 30 and the opening 31 at the center of the suction pad 25.

  The suction table 12 does not exist below the portion of the glass substrate 8 where the hole is to be drilled, and an appropriate gap (1 to 3 mm) is provided between the lower surface of the glass substrate 8 and the processing table 6. To.

  Further, the suction pad 27 is sucked through the suction pipe 27 and a negative pressure higher than the spray pressure of the assist gas introduction pipe 26 is generated, so that the glass substrate 8 generated from the surface of the glass substrate 8 has a water tank shape. The molten component is sucked and discharged to the outside through the hole 31 at the center of the suction pad 25 and the suction pad fixing holder 30, and the suction negative pressure is, for example, about 400 mmHg to 760 mmHg, but is not limited thereto. However, it is only necessary to apply a negative pressure to the suction pad 25 portion and suck the molten component, and the suction pad 25 can be appropriately changed depending on the conditions of the drilling process.

  Further, an assist gas 32 made of air, nitrogen, oxygen, argon gas or the like is introduced into the nozzle 24 from the assist gas introduction pipe 26, and is ejected from the tip of the nozzle 24 toward the suction pad fixing holder 30. The molten component sucked up by the suction pad 25 is prevented from fogging the condenser lens 29.

  FIG. 4 shows the principle of drilling the glass substrate 8 with a laser beam. The glass constituting the glass substrate 8 is a solid 33 in a normal state, whereas the vicinity of the focal point of the laser beam 28 is centered on the focal point. As shown in the temperature distribution of the workpiece, the temperature of the glass substrate 8 rapidly rises, and near the center exceeds the melting point mp of the glass to form a water tank-like melt 34. The melt 34 is a suction tube 27 as described above. Is sucked through the suction pad 25 due to the negative pressure, and does not evaporate beyond the boiling point bp.

  The apparatus of the present invention is configured as described above. Next, the state of the glass substrate 8 in the state of drilling with a laser beam will be described with reference to FIG. 5. First, as shown in FIG. The glass substrate 8 in the vicinity of the focal point of the laser beam 28 irradiated through the opening 31 of the pad fixing holder 30 and the suction pad 25 has a temperature exceeding the melting point mp and becomes a melt 34 from the solid 33, and the laser beam 28 is irradiated. Simultaneously with the suction by the suction tube 27, the melt 34 is sucked upward through the opening 31 as shown by the arrow in the figure.

  As shown in FIG. 5B, after the melt 34 is sucked, a hole 35 is formed by removing the glass of the glass substrate 8, and the bottom of the hole 35 is irradiated with a laser beam 28 to form glass. As the temperature rises, the solid 33 becomes a melt 34, and the melt 34 is continuously absorbed upward.

  As shown in FIG. 5C, the glass is removed to form a hole 35 by forming the solid 33 into the melt 34 by irradiating the glass substrate 8 with the laser beam 28 and sucking the melt 34 upward. When the hole portion 35 reaches the lower surface of the glass substrate 8, it becomes a through hole, and the punching process of this part is completed, and the suction pad 25 moves to the next processing part and repeats the punching process for a predetermined number of times. become.

Examples of drilling a 300 μm thick glass substrate with a CO ₂ laser were performed under the conditions shown in Table 1 (Examples 1 to 4). Moreover, it carried out on the conditions (Comparative Examples 1-5) as shown in Table 1 with respect to the glass substrate of the thickness of 300 micrometers similarly as a comparative example.

  In addition, FIGS. 6 to 14 show enlarged cross-sectional photographs of the glass substrates on which Examples 1 to 4 and Comparative Examples 1 to 5 were performed.

In the column of Table 1, “Pyrex (registered trademark)” in the column of “Glass” is one type of borosilicate glass and a registered trademark of Corning, and “Lithium-containing” is one type of borosilicate glass and contains lithium. It is a relatively hard glass (Asahi Glass Co., Ltd. product: SW-YY).
“Upper suction” is suction performed by the suction member of the present invention.
“Lower suction” is the suction of the melt from the bottom of the through hole on the lower surface of the substrate.
The “upper blow” blows off the molten component or gas on the upper surface of the substrate with the assist gas.
The “annealing process” was performed at about 600 ° C.
“Hole opening” was evaluated as “◯” when the through hole was opened, and “X” when the through hole was not opened.
“Usage level” represents the suitability for MEMS use (hole condition, hole diameter, cracks, rise, distortion, comprehensive evaluation). Very good ◎, good ○, difficult to use △ (depending on the application) Can be used after processing, etc.), unusable was marked as x.

As shown in the description of Table 1 and the cross-sectional photographs shown in FIGS. 6 to 9, the first embodiment of the present invention has a small difference between the upper hole diameter and the lower hole diameter, and the holes are smooth. It was excellent in the proper use for use.
The glass of Example 2 is obtained by processing hard lithium-containing glass, but there is little difference between the upper hole diameter and the lower hole diameter, the holes are smooth, and excellent in suitability for MEMS use. It was.
In the sample subjected to the annealing treatment of Example 3, no layer due to distortion of the glass substrate was found around the formed through hole (see the photograph in FIG. 8).
In Example 4, the holes were continuously drilled at a pitch of 100 μm, and even if the pitch between the holes was reduced, the holes could be drilled with high accuracy, and the glass substrate was not distorted. No chipping occurred (see the photograph in FIG. 9).

As shown in the description of Table 1 and the cross-sectional photographs shown in FIGS. 10 to 14, the comparative example 1 has a larger difference between the upper hole diameter and the lower hole diameter than the examples, and is used for MEMS. Processing such as shape correction inside the hole is necessary, and there is a problem that the pitch cannot be narrowed when drilling continuously.
In Comparative Example 2, a bulge is formed in the lower part due to lower suction, and the use for MEMS requires a polishing process on the surface of the glass substrate, which has a problem of time and cost.
In Comparative Example 3, the assist gas was blown, but the difference between the upper hole diameter and the lower hole diameter was larger than that of the Example, and for use for MEMS, processing such as shape correction inside the hole by processing was required. In addition, there is a problem that the pitch cannot be narrowed when continuously drilling holes.

Moreover, the thing of the comparative example 4 is what processed hard lithium containing glass, and the comparative example 5 added the upper blow further, but both block the hole which the melt formed, and use it. I couldn't.
Thus, it is very difficult to drill holes in hard lithium-containing glass by conventional processing methods.

It is an apparatus top view showing one Embodiment of this invention apparatus. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. It is a principal part expanded sectional view of this invention. It is explanatory drawing showing the principle of this invention. (A) (b) (c) is an enlarged explanatory view showing the present invention. It is a cross-sectional photograph of the glass substrate which performed the drilling process of Example 1. 4 is a cross-sectional photograph of a glass substrate that has been subjected to drilling in Example 2. FIG. It is a cross-sectional photograph of the glass substrate which performed the drilling process of Example 3. It is a cross-sectional photograph of the glass substrate which performed the drilling process of Example 4. It is a cross-sectional photograph of the glass substrate which performed the drilling process of the comparative example 1. It is a cross-sectional photograph of the glass substrate which performed the drilling process of the comparative example 2. It is a cross-sectional photograph of the glass substrate which performed the drilling process of the comparative example 3. It is a cross-sectional photograph of the glass substrate which performed the drilling process of the comparative example 4. It is a cross-sectional photograph of the glass substrate which performed the drilling process of the comparative example 5. It is an expanded sectional view showing the conventional laser processing method. It is explanatory drawing showing the conventional process principle. (A) (b) (c) is explanatory drawing showing the conventional processing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Machine stand 2 Rail 3 Transfer robot 4 Unprocessed glass substrate storage part 5 Suction rotation table 6 Processing table 7 Processed glass substrate storage part 8 Glass substrate 8 'Processed glass substrate 9 Alignment sensor 10 Machine frame 11 Lifting cylinder 12 Suction table 13 Support 14 Rail 15 Slider 16 Fixed frame 17 Rail 18 Slider 19 Rail 20 Slider 21 Laser oscillator 22 Shutter 23 Mirror 24 Nozzle 25 Adsorption pad 26 Assist gas introduction tube 27 Suction tube 28 Laser beam 29 Condensing lens 30 Adsorption pad fixing holder 31 Opening part 32 Assist gas 33 Solid 34 Melt 35 Hole part mp Melting point bp Boiling point

Claims (3)

In CO ₂ method a hole laser by irradiating the substrate, drilling method to the substrate in the CO ₂ laser and performs with suction melting component of the workpiece during the irradiation of the laser beam. _{2. The} method of drilling a substrate with a CO2 laser according to claim 1, wherein annealing is performed after the drilling. In a device that punctures a substrate by irradiating a CO ₂ laser, a suction member is provided at the nozzle portion that irradiates a laser beam opposite to the workpiece and can suck the molten component of the workpiece when the laser beam is irradiated. A substrate drilling apparatus using a CO ₂ laser.

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