Planarization method and device

Abstract

The invention provides a planarization method and equipment, and the method specifically comprises the steps: putting a to-be-polished workpiece into a sealed container, and pouring a polishing solution which is corrosive to the to-be-polished workpiece into the container; after the container is sealed, vacuumizing is conducted, the to-be-polished workpiece is completely immersed in the polishing solution, kinetic energy is given to particles in the polishing solution, the particles in the polishing solution impact the to-be-polished workpiece, and polishing of the to-be-polished workpiece is achieved; according to the method, micro-morphology surface polishing can be achieved, the machining problem is solved, the manufacturing flux is improved, and the process cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing technology, and in particular relates to a planarization method and equipment. Background Technology

[0002] Currently, polishing the sidewalls of workpieces with special morphologies, particularly in the semiconductor or advanced packaging fields such as TSV sidewall polishing, sidewall polishing of conventional laser-processed workpieces, and relatively small and precise parts, requires high equipment performance and has a long process time. Traditionally, the most practical method for polishing workpieces is surface thermal oxidation combined with etching removal. However, this significantly increases product costs and production cycles in mass production. How to quickly achieve mass production that is controllable and low-cost is a key core process that needs to be solved in the manufacturing process, and it is also a critical issue that needs to be addressed for polishing other irregularly shaped surfaces.

[0003] Conventional semiconductor fabrication processes, employing optimized etching rates and steps, can achieve the conchoidal texture on the sidewalls of TSV microvias, reducing roughness. Alternatively, oxidation followed by etching can gradually reduce sidewall roughness. However, production efficiency is affected by each individual process step, failing to solve the problem of high efficiency and low cost. Furthermore, batch processing has long cycles and places high demands on equipment condition. In laser processing, polishing laser-cut surfaces also suffers from high efficiency and low cost due to the small size and inconvenience of handling parts. In machining, conventional polishing methods are currently unsuitable for scenarios requiring high sidewall roughness on tiny parts. Summary of the Invention

[0004] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a planarization method and apparatus.

[0005] Technical solution: This invention discloses a planarization method, specifically as follows:

[0006] Place the workpiece to be polished into a sealed container and pour a corrosive polishing liquid into the container.

[0007] After sealing the container, a vacuum is drawn until the workpiece is completely immersed in the polishing liquid.

[0008] The particles in the polishing slurry are given kinetic energy, causing them to impact the workpiece to be polished, thus achieving the polishing of the workpiece.

[0009] Furthermore, ultrasonic waves or megasonic waves are used to impart kinetic energy to the particles in the polishing slurry.

[0010] Furthermore, this method also maximizes the kinetic energy of the particles in the polishing fluid by pressurizing or evacuating the container, thereby accelerating the polishing of the workpiece surface.

[0011] A planarization device includes a cavity, an ultrasonic generator, and a mounting frame. The cavity is provided with a liquid inlet, a liquid outlet, and an air extraction port. The cavity is provided with a partition layer that divides the cavity into upper and lower parts. The ultrasonic generator is located in the lower part of the cavity and is disposed on the bottom surface of the partition layer.

[0012] Place the workpiece to be polished in the placement rack, open the top cover of the cavity, and place the placement rack on the upper part of the cavity;

[0013] Close the top cover of the cavity to seal the cavity;

[0014] The corrosive polishing fluid is added to the cavity through the fluid inlet;

[0015] The cavity is evacuated by the air extraction valve to remove air bubbles from the surface and holes of the workpiece to be polished, so that the workpiece to be polished is in complete contact with the polishing liquid.

[0016] Turn on the ultrasonic generator to give kinetic energy to the particles in the polishing fluid;

[0017] After polishing is completed, the polishing liquid is discharged through the drain port.

[0018] Furthermore, the air extraction port can also serve as an air filling port. After the ultrasonic generator is turned on, nitrogen gas is injected into the cavity through the air extraction port, thereby adjusting the kinetic energy of the particles in the polishing fluid impacting the workpiece to be polished.

[0019] Furthermore, valves are provided on the liquid inlet, liquid outlet, and air extraction port to control the inflow or outflow of liquid or gas.

[0020] Furthermore, the device also includes a liquid level sensor and a vacuum sensor; the liquid level sensor is used to detect whether the polishing fluid in the cavity has reached a preset value, and the vacuum sensor is used to detect the vacuum level in the cavity.

[0021] Beneficial effects: Different types of solutions and ratios can be selected according to different materials of the workpiece. The process of this invention does not limit the preparation method or morphology of the workpiece. This invention can realize batch processing, especially for semiconductor and advanced packaging process wafers and related morphological workpieces, it can realize the micro-morphological surface polishing, solve their processing problems, increase manufacturing throughput and reduce process costs. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 This is a structural diagram of the device of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail, but the scope of protection of the present invention is not limited to the embodiments described.

[0025] The method of this invention mainly involves immersing the workpiece to be polished in a specific polishing solution. This solution has a certain corrosion rate on the workpiece material. Utilizing the sealing function of a container, a vacuum is first created inside the container to remove air bubbles from the workpiece surface, ensuring the workpiece is completely submerged in the polishing solution. After completion, the ultrasonic function is activated, the ultrasonic power is set, and the pressure inside the container is adjusted simultaneously. Increasing or decreasing the pressure within the cavity appropriately regulates the "acoustic flow effect" and "cavitation effect" generated by the ultrasound, enhancing the kinetic energy of the particles in the polishing solution. This achieves chemical-mechanical polishing of the workpiece surface protrusions, resulting in flattening of the workpiece. This invention can improve the surface undulations of the workpiece, reduce protrusions and peaks, and significantly improve product quality and performance.

[0026] The workpiece to be polished can be made of silicon wafers, SOI wafers, glass sheets, ceramic sheets, etc., and there are no restrictions on the material or shape. It can be round or square, etc. In the following text, the workpiece is used as a typical representative and is referred to as such.

[0027] A surface of a workpiece can be prepared by methods such as ICP dry deep silicon etching, laser ablation, or laser-induced humidified etching. During the workpiece preparation process, it can be masked by photoresist, dielectric masking, or other materials, or by using laser equipment to import the drawing into the equipment without masking, or by machining. This surface is not limited to the outer surface of the workpiece, but can also include the inner surface of the workpiece and all its surfaces.

[0028] The polishing slurry used can be a conventional semiconductor CMP process polishing slurry, or a mixture of a specific liquid and a solid powder, such as organic solvents, water, acids, alkalis, silicon oxide, cerium oxide, silicon carbide, aluminum oxide and other solid powders, which have a certain corrosive, softening or passivating effect on the material to be polished.

[0029] like Figure 1 As shown, specific embodiments of this invention are illustrated below:

[0030] First, a silicon wafer is prepared. After photolithography and ICP dry plasma deep silicon etching are completed, a three-dimensional morphology with shell-like protrusions on the sidewalls is formed. The range of the sidewall protrusions is in the range of tens to hundreds of nanometers. The spacing of the protrusions is related to the etching rate and is usually in the range of 0.1 to 5 micrometers. Wafers with this feature will have slightly different morphologies depending on the process flow.

[0031] The appropriate polishing slurry is selected based on the material of the workpiece to be polished. Since the three-dimensional morphology is mainly prepared on silicon wafers, the present invention selects a conventional silicon polishing slurry. The main components of this polishing slurry are alkaline components such as TMAH or NaOH, as well as silicon dioxide powder particles, with a particle size usually in the tens of nanometer range.

[0032] According to the processing method requirements, a container that can hold the solution is used. This container can achieve a sealed state and can be vacuumed or pressurized after sealing.

[0033] Place the workpiece to be processed into the container described above, add polishing liquid, and ensure that the workpiece is submerged in the solution.

[0034] Seal the container and begin evacuating it to create negative pressure inside the container cavity. As the gas on the surface of the workpiece gradually expands and is extracted, the polishing liquid completely submerges the workpiece.

[0035] By activating the ultrasonic / megason function, the tiny silicon oxide particles in the polishing slurry generate a certain amount of kinetic energy through the "acoustic flow effect" and "cavitation effect" under the action of ultrasound. This energy continuously impacts the sidewalls of the three-dimensional silicon substrate, achieving erosion and polishing of the sidewalls. Furthermore, the alkaline corrosion process enhances the polishing effect.

[0036] By pressurizing or evacuating, the pressure inside the container chamber is changed, altering the "acoustic flow effect" and "cavitation effect" of the liquid under ultrasound, maximizing the impact kinetic energy of the particles, and accelerating the impact on the workpiece surface.

[0037] After completion, restore the chamber to atmospheric pressure, open the chamber, remove the polished workpiece, rinse it clean in time to remove the polishing liquid from the surface, and complete the surface polishing of the workpiece.

[0038] The workpiece in the specific embodiments of this invention patent can be, specifically, a silicon wafer, an SOI wafer, a glass sheet, a ceramic sheet, etc., regardless of material or shape, and can be circular or square, etc. In the above embodiments, a silicon-based workpiece is used as a typical example for illustration. The polishing slurry can be, specifically, a silicon polishing slurry, a silicon carbide polishing slurry, a copper polishing slurry, or other CMP-specific polishing slurries. Alternatively, a solution with corrosive properties to the material of the workpiece can be prepared by adding appropriate solid powders, such as silicon oxide, aluminum nitride, cerium oxide, diamond powder, etc.

[0039] The planarization device of the present invention, such as Figure 2 As shown: It includes a cavity, an ultrasonic generator, and a mounting frame. The cavity is provided with a partition layer, which divides the cavity into upper and lower parts. The ultrasonic generator is located in the lower part of the cavity and is set on the bottom surface of the partition layer.

[0040] Place the workpiece to be polished in the placement rack, open the top cover of the cavity, and place the placement rack on the upper part of the cavity;

[0041] The cavity can be sealed by closing the top cover of the cavity and using the vacuum cavity sealing ring.

[0042] The corrosive polishing fluid is added to the cavity through the fluid inlet;

[0043] The cavity is evacuated by the air extraction valve to remove air bubbles from the surface and holes of the workpiece to be polished, so that the workpiece to be polished is in complete contact with the polishing liquid.

[0044] Turning on the ultrasonic generator causes the tiny particles in the liquid to vibrate, gaining kinetic energy. Under the action of micro-corrosion in the liquid, the particles simultaneously impact the workpiece to be polished, accelerating the polishing rate and effect.

[0045] After polishing is completed, the polishing liquid is discharged through the drain port.

[0046] In one embodiment of the present invention, the air extraction port can also serve as an air filling port. After the ultrasonic generator is turned on, nitrogen gas is injected into the cavity through the air extraction port, so that the pressure in the cavity is gradually changed to a preset value. The pressure range in the cavity can be controlled from 100Pa to 100KPa (10 atmospheres), thereby adjusting the kinetic energy of the particles in the liquid impacting the workpiece to be polished, and achieving the purpose of accelerating polishing.

[0047] In one embodiment of the present invention, valves are provided on the liquid inlet, liquid outlet, and air extraction port, and the inlet or outlet of liquid or gas is controlled by the valves.

[0048] In one embodiment of the present invention, the device further includes a liquid level sensor and a vacuum sensor; the liquid level sensor is used to detect whether the polishing fluid in the cavity has reached a preset value, and the vacuum sensor is used to detect the vacuum level in the cavity.

[0049] After polishing reaches the preset time (effect), the pressure inside the cavity is adjusted to normal pressure by opening the nitrogen filling valve (exhaust port), the ultrasonic generator is turned off, the cavity cover is opened, the workpiece is taken out, the polishing liquid is cleaned and removed, and the disc is dried to complete the entire polishing process.

[0050] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the scope of the patent. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. The application scenarios of this invention are not limited to silicon wafers and silicon-based material-related processes, but also include surface polishing of irregularly shaped machined workpieces. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this patent should be included within the protection scope of this patent.

Claims

1. A planarization method, characterized in that, Specifically: Place the workpiece to be polished into a sealed container and pour a corrosive polishing liquid into the container. After sealing the container, a vacuum is drawn until the workpiece is completely immersed in the polishing liquid. The particles in the polishing slurry are given kinetic energy, causing them to impact the workpiece to be polished, thus achieving the polishing of the workpiece.

2. The planarization method according to claim 1, characterized in that, Ultrasonic waves or megasonic waves are used to impart kinetic energy to the particles in the polishing slurry.

3. The planarization method according to claim 1, characterized in that, This method also maximizes the kinetic energy of particles in the polishing fluid by pressurizing or evacuating the container, thereby accelerating the polishing of the workpiece surface.

4. A planarization device, characterized in that, Includes a cavity, an ultrasonic generator, and a mounting frame. The cavity is equipped with a liquid inlet, a liquid outlet, and an air extraction port. The cavity is equipped with a partition layer that divides the cavity into upper and lower parts. The ultrasonic generator is located in the lower part of the cavity and is positioned on the bottom surface of the partition layer. Place the workpiece to be polished in the placement rack, open the top cover of the cavity, and place the placement rack on the upper part of the cavity; Close the top cover of the cavity to seal the cavity; The corrosive polishing fluid is added to the cavity through the fluid inlet; The cavity is evacuated by the air extraction valve to remove air bubbles from the surface and holes of the workpiece to be polished, so that the workpiece to be polished is in complete contact with the polishing liquid. Turn on the ultrasonic generator to give kinetic energy to the particles in the polishing fluid; After polishing is completed, the polishing liquid is discharged through the drain port.

5. A planarization device according to claim 1, characterized in that, The air extraction port can also be used as an air filling port. After the ultrasonic generator is turned on, nitrogen gas is filled into the cavity through the air extraction port, thereby adjusting the kinetic energy of the particles in the polishing fluid impacting the workpiece to be polished.

6. A planarization device according to claim 1, characterized in that, The liquid inlet, liquid outlet, and air extraction port are all equipped with valves, which control the inflow or outflow of liquid or gas.

7. A planarization device according to claim 1, characterized in that, The device also includes a liquid level sensor and a vacuum sensor; the liquid level sensor is used to detect whether the polishing fluid in the cavity has reached a preset value, and the vacuum sensor is used to detect the vacuum level in the cavity.

Images