Dry etching method using laser modification and subsequent peening by impacting with metallic glass nanoparticles.

Abstract

To identify the shortcomings of conventional etching methods and invent a dry etching method to simplify the process and improve environmental protection. [Solution] The dry etching method involves first performing laser modification to embrittle the substrate, and then impacting the substrate with metallic glass nanoparticles in the laser-modified region to form recesses or through-holes within the substrate.

Description

Background Art

[0001] As shown in FIGS. 1 to 3, a conventional wet etching method for etching a substrate is disclosed to be assisted by laser modification. The substrate G is mainly modified, and as shown in FIG. 1, it is embrittled in the modified region M by laser modification on the substrate G. Thereafter, the substrate G is etched with hydrofluoric acid (etchant) A to form a V-shaped tapered recess H as shown in FIG. 2. Thereafter, the etchant continuously corrodes or erodes the substrate G to form a venturi-shaped through-hole V as shown in FIG. 3 for further processing.

[0002] However, such a conventional wet etching method has the following drawbacks.

[0003] 1. At any time when etching the substrate, the etchant gradually erodes the inside of the substrate along a tapered angle that tapers inward as shown in FIG. 2. When etching from the upper surface of the substrate G, an upper recess is formed, and when etching from the bottom surface of the substrate G, a lower recess is formed. Next, the venturi or so-called "waist portion" V is formed after creating a through-hole that penetrates the upper and lower recesses as shown from FIG. 2 to FIG. 3. When such a through-hole is further processed into a vertical cylindrical through-hole, the production complexity and cost will increase accordingly.

[0004] 2. The tapered angle by the etchant is related to the concentration of the etchant. There is a possibility that the higher the etchant concentration, the larger the tapered angle will be. The etchant concentration is also related to the etching rate affected by the etchant. The higher the etchant concentration, the faster the etching rate.

[0005] Therefore, whenever production efficiency needs to be increased, the etchant concentration must be increased to raise the etching rate. However, a higher etchant concentration can lead to a relatively larger taper angle, and such a large taper angle may not be acceptable for very small workpieces that simply require a small taper angle. Thus, optimally controlling the etchant concentration, etching rate, and taper angle on a case-by-case basis can increase complexity.

[0006] 3. Etchantants such as toxic hydrofluoric acid used in processing may be harmful to human health and the environment.

[0007] The inventors identified the shortcomings of conventional etching methods and invented this dry etching method to simplify the process and improve environmental protection. [Overview of the project]

[0008] The object of the present invention is to provide a dry etching method that includes first performing laser modification to embrittle the substrate, and then impacting the substrate with metallic glass nanoparticles in the laser-modified region to form recesses or through-holes within the substrate. [Brief explanation of the drawing]

[0009] [Figure 1] The first step of the conventional wet etching method is shown. [Figure 2] The etching process after Figure 1 is shown. [Figure 3] This shows a circuit board after through-holes have been formed within it. [Figure 4] The first step of the present invention is shown below. [Figure 5] The partially etched substrate shown is a continuation of Figure 4. [Figure 6] This shows a substrate in which vertical through-holes are formed within the substrate according to the present invention. [Modes for carrying out the invention]

[0010] As shown in Figures 4-6, the dry etching method of the present invention includes the following:

[0011] A. Laser modification is performed by applying a laser 2 to the substrate 1 to form a modified region 11 of the substrate 1 as shown in Figure 4, thereby embrittlement of the substrate material. After laser irradiation, such a modified region 11 has a material strength that is more embrittle than the untreated region.

[0012] B. The modified region 11 is peened by dynamically colliding metallic glass nanoparticles 3 in the modified region 11 to form recesses 12 as shown in Figure 5. The side walls of the recesses 12 may be nearly vertical.

[0013] C. Metallic glass nanoparticles 3 are continuously impacted into the modified region 11 that has not yet been peened or cut, forming vertical through-holes 13 that penetrate the substrate, as shown in Figure 6.

[0014] Alternatively, as shown in Figure 5, step B may be omitted, and the metallic glass nanoparticles 3 may be directly and continuously collided in the modified region 11 to form the through-holes 13 from Figure 4 (step A) to Figure 6 (step C).

[0015] Furthermore, by selectively applying and concentrating the dry etching of the present invention on the modified region 11 without affecting the untreated region within the substrate, it is possible to obtain a desired pattern or via that is suitable for excellent microfabrication.

[0016] During laser modification, several factors that may affect the critical value of the laser modification must be considered. For example, laser parameters such as power, wavelength, and pulse duration; substrate material properties such as substrate type, thickness, and surface condition; processing parameters including speed, focal position, and assist gas; and other relevant factors must ensure that the modified areas 11 are precisely cut or perforated without damaging these untreated areas within the substrate 1.

[0017] The substrate 1 may include glass, silicon wafer, quartz, silicon nitride, silicon carbide, alumina, gallium nitride, aluminum nitride, and zirconia.

[0018] The metallic glass particles have the following characteristics: high hardness, high roundness, a shiny surface, and a small particle size (which may be equal to or smaller than 20 microns). The surface roughness (Rz) of the metallic glass particles is smaller than 0.1 micron. No concave cavities, ridges or sharp corners should be formed on the particle surface so that peening on the substrate can be smoothly performed using the metallic glass particles. Due to the above-mentioned characteristics of the metallic glass particles, neither damage nor cleavage is formed on the collision surface of the substrate.

[0019] The hardness of the metallic glass particles needs to be higher than the hardness of the substrate that undergoes collision according to the present invention.

[0020] In addition to the vertical through-holes perforated according to the present invention, many different taper angles may be formed by colliding metallic glass particles against each side wall of each recess.

[0021] By appropriately adjusting the peening angle of the colliding metallic glass particles, the side walls of the recesses of the substrate can be easily formed at a desired taper angle.

[0022] The driving gas for colliding the metallic glass particles includes air, nitrogen or other inert gases. The gas driving pressure can be in the range of 1 to 10 bar. The gas driving speed can be 200 meters per second. The operating parameters may be changed according to the processing requirements.

[0023] The present invention is superior to the conventional wet etching process in the following advantages.

[0024] 1. The collision of the metal glass particles is applied directly and quickly onto the substrate without considering many operations or control parameters required for wet etching processes. Therefore, this process is simpler than wet processes for creating recesses, through holes or vias within the substrate, especially when creating recesses having multiple taper angles, or vertical through holes or vias within the substrate.

[0025] 2. For the promotion of human health and environmental protection, no toxic acids or etchants are used in the present invention.

[0026] 3. The operation and control of the present invention are implemented by easy mechanical or physical methods, rather than complex chemical methods as used in wet etching methods.

[0027] 4. The metal glass particles may be recovered or recycled after the collision for reuse to reduce production costs.

[0028] The present invention may significantly improve the process yield and the reliability of the overall manufacturing, and may overcome drawbacks such as heat affected zones (HAZ), molten burrs, and via blockages as observed in conventional laser-induced processing on substrates without the assistance of collisions of metal glass particles as expected by the present invention.

[0029] Substrates as defined in the present invention may include semiconductor, glass, ceramic, optical elements, MEMS (Micro-Electro-Mechanical Systems) or core substrates, coreless substrates, interposers, RDL (Redistribution Layer) interposers or RDL substrates, or other substrate members that are comprehensively used in any other microstructures.

Claims

1. The steps of laser modification of the substrate by irradiating a region within the substrate with a laser to form a modified region within the substrate, and The step of impacting metallic glass particles onto the modified region within the substrate to form recesses having a specific taper angle or vias or through-holes penetrating the substrate. A dry etching method that includes this.

2. The dry etching method according to claim 1, wherein the metallic glass nanoparticles have a particle size equal to or smaller than 20 microns.

3. The dry etching method according to claim 1, wherein the collision of metallic glass particles is driven by a gas containing air having a driving pressure in the range of 1 to 10 bar and a driving speed equal to or slower than 200 meters per second.

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