JP2000246474A - Machining method by means of laser beams - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove a dross by forming a protective film on a base material, radiating laser beams to it through the protective film, and thereby sticking the dross generated in machining to the protective film. SOLUTION: In a silicon single crystal substrate 10, the area of element such at resistance element and wiring element is formed on the (100) surface; and an A1 film 12 is formed as an electrode pad on an silicon oxide film 11. On the Al film, a silicon oxide film 13 which becomes an Si etching resistant film is formed by a CVD method. Similarly, the silicon oxide film 13 is also formed on the rear face of the silicon single crystal substrate 10. A laser beam is emitted to form an anticipative hole 15 penetrating the Al film 12, with dross 16 generating around the incident and outgoing part of the laser beam. In expanding the lead hole 15 by anisotropic etching, a hole formed by the laser beam on the Al film 12 is also expanded by etching, with the dross automatically removed. A silicon oxide film 18 is formed by CVD on the inner wall of the expanded hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a substrate such as a silicon single crystal substrate or a glass substrate by a laser beam, and more particularly to a method for removing dross or the like.

[0002]

2. Description of the Related Art Conventionally, a substrate such as a silicon single crystal substrate or a glass substrate is irradiated with a laser beam to perform processing such as drilling. For example, a semiconductor wafer is irradiated with laser light to form a through hole.

[0003]

However, when a through hole is formed by processing by irradiating a laser beam, a processing scattered matter (called a dross or debris).
There is a problem in that the heat generation occurs and adheres to the periphery of the base material, thereby lowering the reliability.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a processing method using a laser beam, which makes it possible to easily remove dross generated during processing. Aim.

[0005]

Means for Solving the Problems (1) A processing method using laser light according to one aspect of the present invention includes forming a protective film on a base material and irradiating the base material with the laser light via the protective film. It is. When processing is performed by irradiating the laser beam, dross is generated, but the dross does not directly adhere to the base material, but adheres to the protective film, so that the dross is easily removed and has high reliability. Has become. (2) In a processing method using laser light according to another aspect of the present invention, in the processing method using laser light described in (1) above, protective films are formed on the front surface side and the back surface side of the base material, respectively. Since the protective film is formed on the front surface side and the back surface side of the base material, for example, in the case of forming a through hole, it is possible to avoid direct attachment of dross to both the front surface and the back surface of the base material. . (3) In a processing method using laser light according to another aspect of the present invention, in the processing method using laser light described in (1) and (2) above, the base material is a silicon single crystal substrate. Since the substrate is a silicon single crystal substrate, the protective film can be easily formed.

(4) A processing method using laser light according to another aspect of the present invention is the processing method using laser light described in (1) to (3) above, wherein the laser light is irradiated to form a preceding hole, The through hole is formed by expanding the preceding hole by performing isotropic etching. As the anisotropic etching, both wet etching and dry etching are possible. When a silicon single crystal substrate is used as a base material, any etching is possible, but wet etching (wet crystal anisotropic etching), which has a greatly different etching rate with respect to the crystal orientation of the silicon single crystal, is preferable. Therefore, the following effects can be obtained in the present invention. Since the through hole is formed by irradiating the laser beam and forming the preceding hole and then performing anisotropic etching, there is no restriction that it is difficult to make a thin hole with respect to the thickness, and the high aspect ratio Is obtained. Also, when a through-hole is generated only by laser processing, the processing time is long. However, since the through-hole is formed by enlarging the preceding hole by anisotropic etching, batch processing becomes possible and processing time becomes longer. Can be shortened. In addition, there is little variation in the diameter of the through hole, and the through hole is made uniform. The enlargement of the hole diameter (hole width) of the through hole can be arbitrarily adjusted by adjusting the anisotropic etching time. Further, dross generated by the irradiation of the laser beam and processing dust remaining on the inner wall are automatically removed during the anisotropic etching. Roughness of the inner wall surface due to laser processing is removed by anisotropic etching, and when the substrate is silicon, a smooth crystal plane of silicon is exposed. Therefore, the thickness of the insulating film formed in the insulating film forming step can be reduced. Since a portion to be etched can be exposed by irradiation with laser light, a step of photolithography is omitted, and manufacturing cost can be reduced.

(5) In the processing method using laser light according to another aspect of the present invention, in the processing method using laser light described in (4) above, the surface of the silicon single crystal substrate is a (100) plane or a (100) plane. is there. In the case of a substrate having such a surface, a hole with a high aspect ratio can be formed with high precision by using wet crystal anisotropic etching. (6) In the processing method using laser light according to another aspect of the present invention, in the processing methods using laser light described in (4) and (5) above, the through-hole is for forming an electrode pad of a semiconductor chip. Processing of through holes for forming electrode pads is highly reliable. (7) A processing method using laser light according to another aspect of the present invention is for forming an ink ejection hole of an inkjet head in the processing method using laser light described in (4) and (5) above. Processing of the ink ejection holes is highly reliable. (8) In the processing method using laser light according to another aspect of the present invention, in the processing method using laser light described in (5) above, the through hole is a through hole of a suction valve of a micropump.
The processing of the through hole of the suction valve of the micropump is highly reliable.

(9) In the processing method using laser light according to another aspect of the present invention, in the processing method using laser light described in (2) to (8) above, protective films are respectively formed on the front surface side and the back surface side. Laser light is irradiated from both sides of the substrate. For this reason, the processing time can be reduced. (10) In a processing method using laser light according to another aspect of the present invention, in the manufacturing methods described in (1) to (90) above, the laser light is branched by a phase grating and applied to a substrate. Since a plurality of preceding holes can be formed at the same time, the processing time can be greatly reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. FIG. 5 is a front view of a semiconductor device 40 manufactured by applying the processing method using laser light according to the first embodiment of the present invention. This semiconductor device is configured by stacking semiconductor chips 29 as shown. Note that the semiconductor device 40 includes a semiconductor chip 29
The device is different from a device in which semiconductor chips are arranged on both surfaces of one lead frame in that they are connected and stacked via bumps 30. This semiconductor chip 2
Reference numeral 9 includes, for example, a storage device such as a DRAM and an SRAM, a logic circuit, and the like, and can be stacked on each other to form, for example, a system LSI.

FIGS. 1 to 3 are process diagrams of a method of manufacturing the semiconductor device 40 of FIG. 5, and the manufacturing method will be described with reference to the process diagrams. In the following description, the reference numerals at the beginning of the paragraph correspond to the reference numerals in FIGS.

(A) FIG.
(A) As shown in (b) and (c), a transistor,
An element region 1 of various elements such as a resistance element and a wiring is formed with a (100) plane orientation, and an aluminum film (electrode) 12 as an electrode pad is formed on this plane.
Are formed over the element region 1 and the silicon oxide film 11. 4A, 4B, and 4C are a plan view, a bb sectional view, and a cc sectional view of the semiconductor substrate, respectively. FIGS. 2 to 4 show the periphery of the aluminum film 12 therein. Portions are shown. On the aluminum film 12 arranged as described above, a silicon oxide film 13 serving as an anti-Si etching film is formed by a CVD method (or a PVD method). (B) Similarly, a silicon oxide film 14 is formed on the back surface of the silicon single crystal substrate 10 by a CVD method (or a PVD method). It is to be noted that the back surface itself can be thinned by performing a grinding process or the like on the back surface in a process before this. (C) Irradiate a laser beam to form a preceding hole 15 penetrating through the aluminum film 12. At this time, dross 16 is generated around the laser beam entrance and exit. The conditions of this laser beam and the like are described in the embodiments described later. (D) The preceding hole 15 is enlarged by performing anisotropic etching. At this time, the hole formed by the irradiation of the laser beam on the aluminum film 12 is also enlarged (retracted) by etching,
The dross 16 is also automatically removed. The conditions for the anisotropic etching are described in the examples described later. (E) A silicon oxide film 18 is formed on the inner wall of the hole 17 formed by anisotropic etching by CVD (or PV).
D method). At this time, the oxide film 12a is also formed on the inner wall of the hole of the aluminum film 12. In consideration of coverage, it is preferable to form silicon oxide from both sides using CVD. In the first embodiment, since the oxide film 12a is provided, Cu and Al
Cannot be conducted, and the processing after FIG. 2 (i) is required.

(F) Copper plating is performed to form copper plating layers 19 and 20 on the front and rear surfaces, respectively, and the copper plating material 20a is filled in the hole 17 having the silicon oxide film 18 formed on the inner wall. (G) Photoresists 21 and 22 are formed on the copper plating layers 19 and 20 by photolithography, respectively. (H) Perform copper etching to form copper plating layers 19 and 2
Of 0, other portions except the portions covered by the photoresists 21 and 22 are removed. (I) Resists 23 and 24 are formed by photolithography. For the resist 23, the aluminum film 1
2 is formed so that a part of the silicon oxide film 13 located on the upper surface 2 is exposed to the outside. (J) The silicon oxide film 13 exposed to the outside is removed by dry etching. This dry etching is RI
Using E, 30 ml of CHF3 gas was flowed at a rate of 30 ml / min.
The test was performed for about 10 minutes at a power of 500 mW at 03 mTorr. Note that part of the silicon oxide film 13 remains on the aluminum film 12 due to the dry etching.

(K) Strip resists 23 and 24. (L) Copper plating layer 2 by applying copper plating (electroless) on the entire surface
5 and 26 are formed. (M) Resists 27, 28 on copper plating layers 25, 26
Are formed respectively. (N) Except for the copper plating layers 25 and 26 covered with the resists 27 and 28 by wet copper etching, the copper plating layers 25 and 26 are removed. With the above processing, a semiconductor chip (IC chip) 29 is completed. (O) And copper plating layers 19 and 25, copper plating material 20
a and bumps 30 composed of copper plating layers 20 and 26
A solder 31 or gold is attached to the substrate. (P) The semiconductor chip 29 formed in the same manner as above is placed on the solder 31 and welded. By repeating the above processing, the semiconductor device 40 having a multilayer structure shown in FIG. 5 is obtained.

Although the above description has been made with respect to a silicon single crystal substrate 10 having a (100) plane orientation, the same applies to a silicon single crystal substrate having a (110) plane orientation. Also, an example has been described in which the laser light is irradiated from the front surface of the silicon single crystal substrate 10 when the preceding hole is generated, but this may be irradiated from the back surface side. In that case, the hole diameter on the front surface side is reduced, and the size of the bump can be reduced.

Embodiment 2 FIG. 6 is a process explanatory view of Embodiment 2 of the present invention, and corresponds to FIGS. 1B and 1C. In the second embodiment, a hole 12b is provided in the center of the aluminum film 12 in advance. Thus, the aluminum film 12
Since the holes 12b are provided in the holes, there is no retreat when the laser beam 2 is irradiated. Then, the aluminum film 12 becomes the silicon oxide film 1
Since the silicon oxide film is covered with the silicon oxide film 18, the silicon oxide film 18 is not etched (does not recede) during the anisotropic etching, and the oxide film 12 a is not generated when the silicon oxide film 18 is formed.

Embodiment 3 FIG. 7 is a process explanatory view of Embodiment 3 of the present invention, and corresponds to FIG.
In the third embodiment, similarly to the example of FIG.
2, a hole 12b is provided in advance, and the silicon oxide film 11 is patterned to form a silicon single crystal substrate 1.
Part of 0 is exposed. By doing so, the retraction of the aluminum film 12 can be avoided, and the etching pattern (the shape of the through hole) in the anisotropic etching is standardized.

Embodiment 4 FIG. 8 is a cross-sectional view of an inkjet head manufactured by applying the processing method using laser light according to the fourth embodiment of the present invention, and FIG. 9 is a perspective view of the nozzle plate. This inkjet head 5
Reference numeral 0 denotes a configuration in which a nozzle plate 51 and a glass vibration plate 52 are laminated, an ink tube 53 is attached to the glass vibration plate 52, and a piezoelectric element 54 is provided. The nozzle plate 51 is formed of a silicon single crystal substrate (having a (100) plane or a (110) plane), in which an ink reservoir 55 is formed, and the ink that has entered the ink reservoir 55 is supplied with ink. Mouth 5
6 and into the cavity 57. A glass vibrating plate 52 is attached on the cavity 57, and the vibrating plate 52 vibrates by the piezoelectric element 54. This diaphragm 5
Due to the vibration of 2, the ink in the cavity 57 is ejected from the ink nozzle hole 58, adheres to the recording paper, and is printed.

FIG. 9 is a process chart showing a process of manufacturing the nozzle plate of FIG. 8, and the process will be described with reference to FIG. (A) A thermal oxide film 62 is formed on a silicon single crystal substrate 61. (B) The thermal oxide film 62 is patterned into a shape corresponding to the ink reservoir 55, the ink channel 56, and the cavity 57 by photolithography and hydrofluoric acid etching. (C) The silicon single crystal substrate 61 is etched to a predetermined depth with an alkaline solution to form an ink reservoir 55 and an ink flow path 5.
6 and a cavity 57 are formed. (D) A thermal oxide film 63 is formed on the entire surface by thermal oxidation. (E) Irradiate the laser beam 2 from above the thermal oxide film 63 to form a preceding hole 64 for forming the ink discharge port 58. (F) The discharge port 58 is formed by performing anisotropic etching with an alkaline liquid. Dross is generated when the preceding hole 64 is formed, and the dross is removed by this anisotropic etching.

Embodiment 5 FIGS. 11A and 11B are a plan view and a cross-sectional view of a micropump manufactured by applying the processing method using laser light according to the fifth embodiment of the present invention. This micropump 70 has a silicon single crystal substrate 7
1 is sandwiched between two glass plates 72 and 73, and absorbs fluid from the suction side pipe 711 and discharges the fluid to the discharge side pipe 712.
The principle of operation is that the piezoelectric element 7 attached to the diaphragm 75 formed in the center of the silicon single crystal substrate 71
A voltage is applied to the pressure chamber 4 to bend the pressure chamber 710.
By changing the internal pressure and displacing the suction side valve membrane 76 and the discharge side valve membrane 78 spatially continuous with the pressure chamber 710, the suction valve 77 and the discharge valve 79 are opened and closed,
The fluid is pressure-fed from the suction side pipe 711 to the discharge side pipe 712. The pressure chamber 710 and the suction-side valve membrane 7
The space above 6 and the space below the discharge side valve membrane 78 are continuous.

FIG. 12 shows the silicon single crystal substrate 71 of FIG.
FIG. 4 is a process chart showing the manufacturing process of FIG. (A) A silicon oxide film 84 and 85 having a thickness of 1 micron is formed on a silicon single crystal substrate 81 having a thickness of 280 microns and polished on both sides. (B) Positive photoresists 86 and 87 are applied on the silicon oxide films 84 and 85. Details of the application conditions of the resist film are as follows. First, a resist is applied to the silicon oxide film 84 by spin coating, and then prebaked to form a resist film 86.
Next, a resist is similarly spin-coated on the silicon oxide film 85 and prebaked at 100 degrees Celsius for 30 minutes to form a resist film 87. This means that the resist film 86 has been prebaked for a total of 40 minutes. (C) Next, the resist film 87 is subjected to pattern exposure and development corresponding to a through-hole (not shown) connecting the through-hole 714 and the pressure chamber 710 with the space above the suction-side valve film 76 to form a resist pattern 88. But not post-baked. The reason is that another pattern formation (exposure, phenomenon) is performed later on the resist films 86 and 87.

(D) Next, the silicon oxide film 85 is selectively etched with a hydrofluoric acid-based etchant. Since the resist films 86 and 85 used as etching masks for hydrofluoric acid have not been subjected to high-temperature baking (post-baking), the remaining film remains photosensitive.
Without exfoliation, pattern processing by pattern exposure and phenomenon is performed in the next step. (E) The resist film 86 is subjected to pattern exposure corresponding to the suction side valve film 76, the diaphragm 75, the suction side valve film 76 and the like, and the resist film 87 is subjected to the suction side valve film 76, the suction valve 77,
Pattern exposure corresponding to the diaphragm 75, the discharge-side valve film 78, the discharge valve 79, and the like is performed, and then the phenomena of the resist films 86 and 87 are simultaneously performed to form resist patterns 810 and 811. (F) Next, a laser beam is irradiated to irradiate the portion corresponding to the through hole 714 of the silicon oxide film 85 with the laser beam 2 to form the preceding hole 714a.

(G) Next, anisotropic etching with an alkaline solution is performed. Here, for example, the concentration is 25% by weight. Etching was performed using a KOH aqueous solution at a temperature of 80 degrees Celsius. The diameter of the preceding hole is enlarged by this etching, and a hole 714b corresponding to the above-described through hole 714 is formed. The dross generated when the preceding hole is formed is removed by the anisotropic etching. (H) Further, anisotropic etching with an alkaline solution is performed, and portions of the oxide films 84 and 85 having a thickness of, for example, 0.08 μm disappear and the silicon base is exposed,
The underlying silicon is etched continuously, and FIG.
The suction valve film 76, the suction valve 77, the diaphragm 75, the discharge side valve film 78, the discharge valve 79, etc. are formed.

Embodiment 6 FIG. 13 is a diagram showing a configuration of an apparatus when a preceding hole is formed in a silicon single crystal substrate by laser light in each of the above embodiments. Laser light source 90
From the laser beam reach the phase grating 93 via the beam expander 91 and the reflection mirror 92. Then, the light is branched by the phase grating 93 and irradiated on the silicon single crystal substrate 10 through the condenser lens 94.

FIGS. 14A and 14B are explanatory diagrams showing the state at this time. In this example, the laser light is branched into four in a phase grating 93 and irradiated on the silicon single crystal substrate 10 to form a preceding hole 95. This branching is performed, for example, first in the X direction and then in the Y direction by switching directions (by relative movement between the phase grating 93 and the silicon single crystal substrate 10). Alternatively, the X direction and the Y direction may be simultaneously branched by the phase grating 93. Since a plurality of preceding holes 95 can be simultaneously formed in this manner, the processing time can be reduced. Further, two-dimensional branching is also possible. In this case, one chip or one wafer can be processed at a time.

[0025]

EXAMPLE In this example, a preceding hole was formed by irradiating a laser beam under the conditions shown in Table 1 below. In each case, a leading hole having a high aspect ratio was obtained.

[0026]

[Table 1]

The etching conditions when the diameter of the preceding hole is enlarged by anisotropic etching are as follows. <Etching conditions> (Example of wafer (100) plane × plate thickness 550 μm) Etching solution: 35% K0H Chemical temperature: 80 ° C. Etching time: 1 hour (short holes if short, all (110) faces long) In addition, as an etching solution, an organic alkali etching solution such as hydrazine, EPW (ethylenediamine-pyrocatechol-water), TMAH (tetramethylammonium hydroxide), or the like can be used instead of the KOH solution. .

[Brief description of the drawings]

FIG. 1 is a process diagram (part 1) of a method for manufacturing a semiconductor device to which a processing method using a laser beam according to a first embodiment of the present invention is applied;

FIG. 2 is a process drawing (part 2) subsequent to FIG. 1;

FIG. 3 is a process drawing (part 3) subsequent to FIG. 2;

FIG. 4 is a plan view, a bb cross-sectional view, and a cc cross-sectional view of the semiconductor substrate of FIG. 1;

FIG. 5 is a front view of a semiconductor device manufactured by applying the processing method using laser light according to the first embodiment.

FIG. 6 is a process explanatory view of a second embodiment of the present invention.

FIG. 7 is an explanatory view of a process according to the third embodiment of the present invention.

FIG. 8 is a cross-sectional view of an inkjet head manufactured by applying a processing method using a laser beam according to a fourth embodiment of the present invention.

FIG. 9 is a perspective view of the nozzle plate of FIG. 8;

FIG. 10 is a process chart showing a process of manufacturing the nozzle plate of FIG. 8;

11A and 11B are a plan view and a cross-sectional view of a micropump manufactured by applying a processing method using a laser beam according to a fifth embodiment of the present invention.

FIG. 12 is a process chart showing a manufacturing process of the silicon single crystal substrate of FIG. 11;

FIG. 13 is a diagram showing a configuration of an apparatus when a preceding hole is formed in a silicon single crystal substrate by laser light in each of the above embodiments.

FIG. 14 is an explanatory view showing a processing state of FIG. 13;

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Yotsuya 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Katsuharu Arakawa 3-3-5 Yamato Suwa City, Nagano Prefecture Seiko Epson In-house F-term (reference) 4E068 AA04 AF01 CD02 CD04 CF03 CG00 DA00 DA02 DA11 5F004 AA09 BB03 DB01 DB32 EA37 EB02 EB08 5F033 HH07 HH08 HH11 HH13 JJ11 KK11 MM30 NN40 QQ08 QQ09 QQ13 QQQQ QV QQ QQ QQ Q

Claims (10)

[Claims] 1. A processing method using laser light, comprising forming a protective film on a base material and irradiating the base material with laser light via the protective film. 2. The processing method using a laser beam according to claim 1, wherein a protective film is formed on each of the front side and the back side of the substrate. 3. The method according to claim 1, wherein the substrate is a silicon single crystal substrate. 4. The method according to claim 1, wherein the preceding hole is formed by irradiating a laser beam, and the through hole is formed by expanding the preceding hole by performing anisotropic etching. A processing method using the laser light described above. 5. The method according to claim 1, wherein the surface of the silicon single crystal substrate is (10
5. The processing method using a laser beam according to claim 4, wherein the surface is a (0) plane or a (110) plane. 6. The processing method according to claim 4, wherein the through hole is for forming an electrode pad of a semiconductor chip. 7. The processing method according to claim 4, wherein the through holes are for forming ink ejection holes of an ink jet head. 8. The processing method according to claim 4, wherein the through hole is for forming a through hole of a valve of a micropump. 9. The processing by laser light according to claim 2, wherein the laser light is irradiated from both surfaces of the base material having the protective film formed on the front surface and the back surface, respectively. Method. 10. The processing method using a laser beam according to claim 1, wherein the laser beam is branched by a phase grating and irradiated onto the substrate.