TWI900113B - Method of processing brittle materials - Google Patents

Abstract

A method of processing brittle materials to address the difficulty of fine processing brittle materials. The method comprises: providing a workpiece essentially composed of a brittle material, wherein the workpiece has a machining region and a non-machining region on a machining surface; covering the non-machining region with a mask while leaving the machining region exposed and uncovered by the mask; subjecting the machining region to abrasive jet machining using a sandblasting unit; and removing the mask from the machining surface. The present invention can achieve effective fine machining of brittle materials applicable to semiconductor processes.

Description

Brittle material processing methods

The present invention relates to a method for processing brittle materials, and in particular to a method for processing brittle materials using a sandblasting method for punching.

In recent years, packaging technology has garnered significant attention in the semiconductor industry to maintain Moore's Law. For example, some companies have developed 3D stacking technologies, such as chip-on-wafer and wafer-on-wafer, to further enhance computing performance. Furthermore, compared to substrates made of organic materials, the manufacturing process for materials like glass and ceramics is more environmentally friendly and readily available. They also offer advantages such as superior flatness, stability, oxidation resistance, heat dissipation, and an expansion coefficient closer to that of silicon. Consequently, some companies are hoping to replace existing organic substrates with materials like glass and ceramics to enhance performance.

However, the silicon, glass, and ceramics commonly used in these wafers are all brittle materials with high hardness and susceptibility to cracking. This presents processing challenges, such as when slicing stacked wafers or forming fine structures such as circuit trenches and vias on brittle substrates. For example, cutting methods can cause cracks and fracturing in brittle materials, impacting process quality; laser etching can cause thermal stress and deformation; dry etching is time-consuming and costly; and wet etching is difficult to handle with chemicals and can cause environmental pollution.

In view of this, conventional methods for processing brittle materials still need to be improved.

To solve the above-mentioned problem, the present invention aims to provide a brittle material processing method suitable for cutting wafers made of brittle materials such as silicon wafers.

A second object of the present invention is to provide a brittle material processing method suitable for processing substrates made of brittle materials such as glass and ceramics.

Throughout this disclosure, directional terms or similar terms, such as "upper," "inner," "outer," and "lateral," are primarily used with reference to the directions in the accompanying drawings. These directional terms or similar terms are intended solely to facilitate the description and understanding of the various embodiments of the present invention and are not intended to limit the present invention.

The use of the quantifiers "a" or "an" in the elements and components described throughout this invention is merely for convenience and to provide a general understanding of the scope of the invention. They should be interpreted in this invention to include one or at least one, and the singular concept also includes the plural, unless it is obvious that it means otherwise.

The brittle material processing method of the present invention comprises: providing a substrate, the substrate being mainly composed of a brittle material, and having a processing area and a non-processing area on a processing surface of the substrate; covering the non-processing area with a mask and leaving the processing area uncovered by the mask; punching the processing area with a sandblasting unit to form a circuit trench and/or a hole in the substrate; removing the mask from the processing surface; and filling the circuit trench and/or the hole with a conductive paste and sintering the conductive paste to form a wire and/or a guide hole; wherein, covering the non-processing area with a mask and leaving the processing area exposed; Covering the processed area so that it is uncovered by the mask is performed by at least one of a masking method, a laminating method, and a coating method. In the masking method, a mask having an opening pre-formed therein is applied to the processed surface, with the opening corresponding to the processed area. In the laminating method, the processed surface has a plurality of non-processed areas, and a plurality of masks are placed on each non-processed area, with the shape and size of each mask corresponding to each non-processed area. In the coating method, a mask precursor is applied to the processed surface to form the mask, and then the portion of the mask corresponding to the processed area is removed.

The brittle material processing method of the present invention is suitable for precision machining related to semiconductor manufacturing processes. It can be applied to dicing wafers made of brittle materials such as silicon wafers, or to grooving and drilling substrates made of brittle materials such as glass and ceramics. It is not susceptible to cracking, fracturing, or thermal stress deformation of these brittle materials, while taking into account cost and environmental considerations. Furthermore, it can effectively form fine lines/holes and ensure the conductivity of these lines/holes.

The brittle material processing method of the present invention may further include forming a dielectric layer on the surface of the circuit trench and/or the hole. This improves the bonding strength between the conductive material and the substrate.

The brittle material processing method of the present invention may further include stacking a plurality of substrates having the conductive lines and/or vias formed thereon, and forming a multi-layer redistribution layer using the conductive lines and/or vias. This allows for the formation of a redistribution layer with conductive lines/vias having a high aspect ratio, making it suitable for multi-layer 3D stacked packaging.

The brittle material processing method of the present invention may further include stacking a plurality of substrates having the circuit trenches and/or holes formed therein, then filling the circuit trenches and/or holes with a conductive paste from the outermost substrate and sintering the conductive paste to form a wire and/or a via. The wires and/or vias are then used to form a multi-layer redistribution layer. This allows for the formation of a redistribution layer with wires and/or vias having a high aspect ratio, making it suitable for multi-layer 3D stacked packaging.

S1: Provide workpiece step

S2: Covering mask step

S3: Sandblasting step

S4: Remove the mask step

S5: Dielectric layer formation step

S6: Forming wires/vias

S7: Stacking Step

S8: Stacking Step

1: Workpiece waiting to be processed

11: Processing surface

11a: Processing Area

11b: Non-processing area

2: Mask

2a: Opening

3: Sandblasting unit

31: Spray nozzle

P: SMT machine

M: Mask front drive

L: Laser

[Figure 1] Flowchart of the steps of the brittle material processing method of the present invention.

[Figure 2] Schematic diagram of the implementation of the brittle material processing method of the present invention.

[Figure 3] Schematic diagram of the implementation of the masking method in the brittle material processing method of the present invention.

[Figure 4] Schematic diagram of the implementation of the bonding method in the brittle material processing method of the present invention.

[Figure 5] Schematic diagram of the coating method in the brittle material processing method of the present invention.

To make the above and other objects, features, and advantages of the present invention more clearly understood, the following describes preferred embodiments of the present invention in detail with reference to the accompanying drawings. Elements designated by the same symbols in different figures are considered identical and their descriptions are omitted. It should also be noted that the size ratios of the elements in the drawings are for illustration only and do not represent actual dimensions.

Referring to FIG. 1 , the brittle material processing method of the present invention may include: a workpiece providing step S1 , a mask covering step S2 , a sandblasting step S3 , and a mask removal step S4 .

In the step S1 of providing a workpiece, as shown in FIG2 , a workpiece 1 to be processed is provided. The workpiece 1 to be processed can be, for example, a wafer or a substrate. The substrate can be, for example, an interposer, an IC carrier, or a substrate of a circuit board or other component. However, as long as it is a substrate for directly or indirectly connecting an IC chip and an electronic device, the present invention is not limited thereto. The workpiece 1 to be processed is mainly composed of a brittle material. Specifically, when the workpiece 1 to be processed is the wafer, the brittle material is, for example, silicon, silicon carbide, aluminum nitride, etc., but is not limited thereto; when the workpiece 1 to be processed is the substrate, the brittle material is, for example, glass, ceramic (another example is aluminum nitride ceramic or other ceramic), etc., but is not limited thereto. Furthermore, in addition to being primarily made of the brittle material, the wafer or substrate may also be formed of other materials to form transistors, circuits, and other structures. Therefore, those skilled in the art will understand the meaning of "the workpiece 1 being primarily composed of a brittle material" in the present invention.

As shown in Figure 2, the workpiece 1 has a processing surface 11. The processing surface 11 includes a processing area 11a and a non-processing area 11b. The processing area 11a may correspond to the portion of the workpiece 1 to be further processed by sandblasting. For example, if the workpiece 1 is a wafer, the processing area 11a may correspond to the scribe line (or dicing channel) on the wafer. If the workpiece 1 is a substrate, the processing area 11a may correspond to the portion of the substrate to be further grooved or drilled.

In the masking step S2, as shown in Figure 2, the non-processed area 11b is covered with a mask 2, leaving the processed area 11a uncovered and exposed. The mask 2 can be made of a resin such as polyvinyl alcohol (PVA) or polymethyl methacrylate (PMMA), but the present invention is not limited to such a material as long as it has a certain degree of wear resistance (sandblasting resistance). Specifically, the masking step S2 can be performed using at least one of the following methods: a masking method, a lamination method, and a coating method.

Referring to Figure 3 , in this masking method, a mask 2 pre-formed with an opening 2a is aligned and placed over the processing surface 11, with the opening 2a corresponding to the processing area 11a on the workpiece 1. This leaves the processing area 11a uncovered by the mask 2 and exposed, while the non-processing area 11b is covered by the mask 2. For example, in one embodiment, the workpiece 1 can be a wafer, and the mask 2 covers the wafer. The mask 2 is formed with a plurality of parallel slits, with the slits corresponding to the scribe lines of the wafer.

Referring to Figure 4 , in this placement method, the processing surface 11 has a plurality of non-processed areas 11b, and a plurality of masks 2 are placed on each non-processed area 11b. The shape and size of each mask 2 correspond to each non-processed area 11b. This ensures that each non-processed area 11b is covered by the mask 2, while the processing area 11a is exposed. This placement method can be performed using a pick and place machine (P). The mask 2 can be an adhesive film or affixed with an adhesive material, but is not limited thereto.

Please refer to Figure 5. In the coating method, a mask precursor M is first coated on the processing surface 11 to form the entire mask 2, and then the portion of the mask 2 corresponding to the processing area 11a is removed, thereby leaving the processing area 11a uncovered by the mask 2 and exposed, and the non-processing area 11b is covered by the mask 2. For example, the mask precursor can be a resin solution containing a resin such as polyvinyl alcohol or polymethyl methacrylate and a volatile solvent. The mask precursor can be applied to the processing surface 11 by spin coating or slit coating. After the volatile solvent evaporates, the entire mask 2 is formed. The portion of the mask 2 corresponding to the processing area 11a is then removed by laser lithography or optical lithography (not shown).

In the covering mask step S2, workers can also combine two or more methods, including the masking method, the placement method, and the coating method, according to actual needs, to ensure that the non-processing area 11b is covered by the mask 2 and the processing area 11a is not covered by the mask 2 and is exposed.

In the sandblasting step S3, as shown in FIG2 , a sandblasting unit 3 is used to perform a punching process on the processing area 11a. For example, the workpiece 1 can be cut, grooved, or drilled. The sand material used in the sandblasting step S3 can be, for example, gold steel sand (silicon carbide), aluminum oxide, zirconium oxide, or other high-hardness alloys, high-entropy materials, etc., but is not limited thereto. The sand material can have a particle size of 0.2μm~15μm, or a particle size of 0.2μm~5μm, or a particle size of 5μm~15μm, and can have a hardness of 3200~4400Hv. In one embodiment, the sandblasting unit 3 sprays the sand material through a nozzle 31. The nozzle 31 can be shaped, for example, elongated or circular. Those skilled in the art can adjust parameters such as the sandblasting pressure, duration, and distance between the nozzle 31 and the workpiece 1 based on the material of the workpiece 1 and the desired processing depth.

As shown in Figure 2, the brittle material processing method of the present invention utilizes the mask 2 to protect the non-processing area 11b from being eroded by the sandblasting process. This allows only the processing area 11a to be processed. For example, when the workpiece 1 is a substrate, the processing area 11a can be eroded to form a circuit trench and/or a hole by grooving and/or drilling the substrate. The width of the circuit trench can be greater than 10μm, and the diameter of the hole can be greater than 10μm. The hole can be either a through hole or a blind via.

For another example, when the workpiece 1 is a wafer, the processing area 11a (corresponding to the wafer's scribe lines) can be punched to cut the wafer into a plurality of bare dies. In this case, the mask 2 can be formed with a plurality of parallel slits. During sandblasting, the wafer is first sandblasted along the slits, then the mask 2 is rotated 90 degrees and sandblasted again along the slits, thereby cutting the wafer into a plurality of square bare dies. However, the present invention is not limited to this rotation angle. In one embodiment, the workpiece 1 may also be a plurality of wafers aligned and stacked together, with the mask 2 formed on the outermost wafer surface of the stack. Thus, through the sandblasting step S3, the plurality of wafers can be cut into a plurality of multi-layer bare dies.

In the mask removal step S4, the mask 2 is removed from the processing surface 11. The mask removal step S4 can be performed by laser, water washing, low-temperature debonding, etc., which are methods known in the art to which the present invention belongs and will not be described in detail here.

In the brittle material processing method of the present invention, workers can also repeatedly perform the mask covering step S2, the sandblasting step S3, and the mask removal step S4 according to actual needs to achieve the desired processing depth.

When the workpiece 1 is the substrate, the brittle material processing method of the present invention may further include a dielectric layer formation step S5 to form a dielectric layer on the surface of the circuit trench and/or the hole. The dielectric layer may be, for example, a metal such as nickel, vanadium, or titanium, or an alloy of these metals (e.g., nickel-vanadium alloy). The present invention is not limited to this material as long as the dielectric layer can improve the bonding between the substrate and the conductive material (e.g., copper). Furthermore, if the bonding between the substrate and the conductive material is sufficient, this step may be omitted. In step S5 of forming the dielectric layer, the worker can choose to form the dielectric layer using methods known in the art, such as sputtering, electroplating, coating, and deposition, depending on the dielectric layer's raw materials. In one embodiment, after forming the dielectric layer, a plasma treatment can be used to activate the dielectric layer's surface to further enhance bonding with the conductive material described later.

When the workpiece 1 is a substrate, the brittle material processing method of the present invention may further include a conductive line/via forming step S6, in which a conductive paste is filled into the wiring trench and/or the hole and sintered to form the conductive line and/or the via. The conductive paste may be, for example, a conductive copper paste, a conductive silver paste, or other paste containing a conductive component, but is not limited thereto. In the conductive line/via forming step S6, the conductive paste may be filled into the wiring trench and/or the hole using a scraper, for example, and sintered using infrared heating, electromagnetic induction heating, or other methods, causing the conductive paste to solidify and adhere to the substrate, thereby forming the conductive line and/or the via on the substrate. It should be noted that when sintering is performed using infrared heating, the conductive paste contains infrared absorbing materials; when sintering is performed using electromagnetic induction heating, the conductive paste contains magnetic materials. In one embodiment, after forming the conductive lines and/or vias, laser trimming can be used to remove unintended connections to prevent short circuits.

When the workpiece 1 is a substrate, the brittle material processing method of the present invention may further include a stacking step S7, in which a plurality of substrates having the conductive lines and/or vias formed thereon are stacked to form a multi-layer redistribution layer (RDL). Specifically, the worker may pre-design the positions of the conductive lines and/or vias so that the plurality of aligned and stacked substrates can form a multi-layer RDL using the conductive lines and/or vias. The multi-layer RDL is used to reroute the chip's multiple I/O terminals, thereby contributing to a smaller package size and a higher degree of integration. Furthermore, by forming the wires/vias at predetermined locations on each substrate and then aligning and stacking the substrates, multiple wires/vias can be combined to form a composite wire/via, compared to methods that require slotting/drilling a single substrate. This allows for wires/vias with a higher aspect ratio.

In one embodiment, workers may first stack multiple substrates with the wiring trenches and/or holes formed therein (but not yet filled and sintered with the conductive paste). Then, the conductive paste is filled into the wiring trenches and/or holes from the outermost substrate and sintered to form the conductive lines and/or vias. These conductive lines and/or vias are then used to form the multi-layer redistribution wiring layer, thereby achieving a high aspect ratio for the conductive lines/vias. Alternatively, in one embodiment, workers may first fill the wiring trench with conductive paste and sinter it to form the wires. Multiple substrates with the wires and/or holes formed thereon are then stacked. The conductive paste is then filled into the holes from the outermost substrate and sintered to form the vias. The wires and vias are then combined to form a multi-layer redistribution layer, thereby achieving wires/vias with a high aspect ratio.

When the workpiece 1 is a plurality of wafers, the brittle material processing method of the present invention may further include a stacking step S8 to stack the plurality of layers of bare die. This can form a 3D stacked die, thereby achieving functions such as integrating multiple chips, reducing package size, and shortening signal transmission distances.

In summary, the brittle material processing method of the present invention is suitable for precision machining related to semiconductor manufacturing processes. It can be applied to dicing wafers made of brittle materials such as silicon wafers, or to grooving and drilling substrates made of brittle materials such as glass and ceramics. It is not susceptible to cracking, fracturing, or thermal stress deformation of these brittle materials, and it takes both cost and environmental considerations into account, which is the effectiveness of the present invention.

While the present invention has been disclosed using the preferred embodiments described above, they are not intended to limit the present invention. Any modifications and alterations made by one skilled in the art without departing from the spirit and scope of the present invention are still within the technical scope protected by the present invention. Therefore, the scope of protection of the present invention includes all modifications within the meaning and equivalent scope of the appended patent applications. Furthermore, if the above-mentioned embodiments can be combined, the present invention includes any combination of embodiments.

1: Workpiece waiting to be processed

11: Processing surface

11a: Processing Area

11b: Non-processing area

2: Mask

3: Sandblasting unit

31: Spray nozzle

Claims (4)

A brittle material processing method includes: providing a substrate primarily composed of a brittle material, having a processing area and a non-processing area on a processing surface of the substrate; covering the non-processing area with a mask and leaving the processing area uncovered by the mask; punching the processing area with a sandblasting unit to form a circuit trench and/or a hole in the substrate; removing the mask from the processing surface; and filling the circuit trench and/or the hole with a conductive paste and sintering the conductive paste to form a wire and/or a via; wherein covering the non-processing area with the mask and leaving the processing area uncovered by the mask is performed by at least one of a masking method, a placement method, and a coating method. In the masking method, a mask with an opening pre-formed therein is applied to the processing surface, where the opening corresponds to the processing area. In the pasting method, the processing surface has a plurality of non-processing areas, and a plurality of masks are placed in each non-processing area, with the shape and size of each mask corresponding to each non-processing area. In the coating method, a mask precursor is coated on the processing surface to form the mask, and then the portion of the mask corresponding to the processing area is removed. The brittle material processing method of claim 1 further includes forming a dielectric layer on the surface of the circuit trench and/or the hole. The brittle material processing method of claim 1 further includes stacking a plurality of substrates formed with the conductive lines and/or the vias, and forming a multi-layer redistribution layer using the conductive lines and/or the vias. The brittle material processing method of claim 1 further includes stacking a plurality of substrates having the circuit trench and/or the hole formed thereon, filling the circuit trench and/or the hole with a conductive paste from the outermost substrate and sintering the conductive paste to form a wire and/or a via, and forming a multi-layer redistribution layer using the wire and/or the via.