CN203993383U - A kind of ultrasonic polishing device that utilizes the vibration of liquid transfer megahertz level - Google Patents

Abstract

An ultrasonic polishing method and a polishing device thereof utilizing a liquid to transmit megahertz-level vibrations, relating to a polishing method and a device thereof, the method transmits vibrations through a flexible coupling agent, and transmits high-frequency ultrasonic vibrations of a vibrator to a vibration polishing tool; A vibration polishing tool that does not depend on the overall modal analysis and modal design is realized. And this method is applied in the field of silicon wafer polishing, and a set of ultrasonic polishing device using liquid to transmit megahertz vibration is designed, and the piezoelectric ceramic sheet on the vibrator is excited by an alternating voltage of appropriate frequency, and the vibrator will be in the designed mode Resonance in the state, the high-frequency vibration is transmitted to the vibration polishing tool through the coupling agent, and finally the megasonic vibration is transmitted to the polishing liquid, so that the polishing liquid particles can effectively play a role, thereby obtaining a complete surface lattice and ultra-high shape of the polished silicon wafer. Surface accuracy and extremely low roughness. This method of using liquid to transmit vibration makes the addition of vibration more flexible and expands the scope of vibration utilization.

Description

An Ultrasonic Polishing Device Using Liquid to Transmit Megahertz Vibration

technical field

The invention relates to a polishing method and a device thereof, in particular to an ultrasonic polishing device which utilizes liquid to transmit megahertz vibration.

Background technique

Ultra-precision machining is the basis for the development of modern high-tech industries and science and technology. As one of the important fields of ultra-precision machining, ultra-precision polishing is a processing method that uses the mechanical and chemical effects of fine abrasive grains to obtain smooth or ultra-smooth surface quality. . In recent years, for precision chemical mechanical polishing of brittle and hard materials such as silicon wafers, adding ultrasonic vibration to assist polishing has become a hot research issue. The traditional methods of ultrasonic vibration addition are vibration polishing tools that rely on overall modal analysis and modal design. Vibration loading plays a certain role, but this method of addition has great limitations. When external conditions change, It is very likely to cause a change in the resonance frequency, and it is difficult to ensure that the vibrator is always working in a good resonance mode.

Contents of the invention

The object of the present invention is to provide an ultrasonic polishing device that utilizes liquid to transmit megahertz-level vibrations. The device utilizes the non-resonance mode vibration of the vibration polishing tool to assist chemical mechanical polishing, and transmits the high-frequency ultrasonic vibration of the vibrator to the vibration through the coupling agent. On the polishing tool, the vibrator is independent from the vibrating polishing tool, so that the vibration loading is more flexible and greatly expands the range of vibration utilization.

The purpose of the present invention is achieved through the following technical solutions:

An ultrasonic polishing device that uses liquid to transmit megahertz-level vibrations. The device is composed of an ultrasonic vibration attachment system and a polishing machine tool. The ultrasonic vibration attachment system includes three assemblies: a vibrator and a sealing device, a coupling agent, and a vibration polishing tool. Including the upper piece of the pressing device, the lower piece of the pressing device, the current-carrying wire, the sealing ring, the wafer piezoelectric vibrator, the horizontal cantilever support, the coupling agent, the vibration polishing tool, the silicon wafer, the polishing pad, the polishing disc; the vibrator is the excitation voltage frequency For the piezoelectric vibrator above 1MHz, the vibrator is equipped with a sealing device. The vibrator and its sealing device are placed on an external horizontal cantilever support with adjustable height. The vibrator is soaked in the couplant, and the silicon wafer is adsorbed on the vibration polishing tool. The device is located on a polishing disk attached with a polishing pad, and the vibrating polishing tool is provided with a slot structure.

The ultrasonic polishing device that utilizes liquid to transmit megahertz-level vibrations, the ultrasonic vibration chemical-mechanical composite polishing tool includes a wafer piezoelectric vibrator, a horizontal clamp, a sealing ring, a current-carrying wire, an upper plate of a pressing device, and a pressing device Lower film, coupling agent, vibrating polishing tool, object to be polished, polishing liquid, polishing pad, polishing disc; the horizontal support is a cantilever of a four-bar mechanism, and the vibrating polishing tool is located on the polishing disc and positioned with the triangular claws of the polishing machine .

The ultrasonic polishing device using liquid to transmit megahertz-level vibration is characterized in that the vibration polishing tool is in the shape of a cylindrical barrel, and the vibration polishing tool holds a silicon wafer, transmits vibration, and stores a coupling agent.

The ultrasonic polishing device that uses liquid to transmit megahertz-level vibrations, the vibration polishing tool holds a silicon chip, and the bottom of the vibration polishing tool barrel is milled with a groove that is the same shape as the polished silicon chip and has a depth of half the thickness of the silicon chip Align silicon wafers with silicon wafers.

Said ultrasonic polishing device using liquid to transmit megahertz vibration, said polishing disk is located on the polishing machine, and the vibration polishing tool has a certain eccentric distance from the polishing disk.

Advantage and effect of the present invention are:

1. The present invention transmits vibration through a flexible coupling agent, transmits the high-frequency ultrasonic vibration of the vibrator to the vibration polishing tool, separates the vibrator from the vibration polishing tool, the vibrator is in the resonance mode, and the vibration polishing tool is in the forced vibration and non-resonance mode , breaking the shackles of the resonance mode of the vibration polishing tool, realizing a vibration polishing tool that does not depend on the overall modal analysis and modal design, thus making the vibration loading more flexible and expanding the scope of vibration utilization.

2. The megasonic effect of the present invention: the working frequency of the vibrator is above 1MHz. The megasonic has the advantages of high energy density, strong penetrating ability, good linearity, and higher energy utilization rate. It also belongs to high-frequency ultrasonic vibration. noise.

3. The vibration energy utilization rate of the present invention is high: in the existing ultrasonic vibration-assisted polishing, the vibration is transmitted to the polishing pad, and then the vibration is transmitted to the polishing liquid, so that the polishing liquid particles can play a role, and the polishing pad has a strong vibration absorption characteristics, the vibration energy loss is large, but the present invention directly loads the vibration on the silicon chip, and the energy utilization efficiency of the vibration is high.

Description of drawings

Fig. 1 is a diagram of a vibrator sealing device of the present invention;

Fig. 2 is an ultrasonic polishing device using liquid to transmit megahertz vibration according to the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments shown in the accompanying drawings.

The invention proposes a new ultrasonic vibration method in machining, which transmits the vibration through a flexible coupling agent, and transmits the high-frequency ultrasonic vibration of the vibrator to the vibration polishing tool; the vibrator and the vibration polishing tool are independent, breaking the existing vibrator and vibration polishing tool. The restraint of the resonance mode of the tool achieves the purpose of independent design of the vibrator, realizes the vibration polishing tool that does not depend on the overall modal analysis and modal design, makes the addition of vibration more flexible, and expands the scope of vibration utilization. Applying this vibration additional method to silicon wafer polishing, a set of ultrasonic polishing device using liquid to transmit megahertz vibration is designed. This device is composed of two parts: ultrasonic vibration additional system and polishing machine system. Device, coupling agent, and vibration polishing tool are three assemblies. The vibrator is a piezoelectric vibrator with an excitation voltage frequency above 1MHz. Since the working surface of the vibrator is immersed in water, a corresponding sealing device is designed for it. The vibrator and its sealing device Placed on an external height-adjustable horizontal cantilever support 7, adjusting the height of 7 can realize the adjustment of the distance between the vibrator and the vibration polishing tool. The vibrator is immersed in the coupling agent, and the high-frequency vibration generated is directly transmitted to the vibration polishing tool 9 through the coupling agent 8. On the vibration polishing tool 9, the silicon wafer is adsorbed on the vibration polishing tool, and the whole device is located on the polishing pad. On the optical disc, the groove structure of the vibration polishing tool ensures the co-operation of the silicon wafer and the vibration polishing tool. The polishing disc rotates around the main shaft of the polishing machine, and at the same time, the nozzle of the polishing machine sprays the polishing liquid to complete the polishing process. The design of the vibrator does not need to consider the influence of the external environment on its natural frequency. The high-frequency vibration generated by the vibrator is transmitted to the vibrating polishing tool through the coupling agent in contact with it, and finally the megasonic vibration is transmitted to the polishing liquid, so that the polishing liquid particles can effectively play a role , so as to obtain a complete surface lattice, ultra-high surface accuracy and extremely low roughness of the polished silicon wafer. The design and operation of the vibrator are independent of the vibration polishing tool. The vibrator is in the resonance mode, the coupling agent transmits the vibration, and the vibration polishing tool is in the forced vibration and non-resonance mode, which breaks the restriction of the resonance mode of the vibration polishing tool and realizes the independence of the vibrator. Design, the vibration polishing tool can be replaced independently after wear and tear, and the vibrator can still be recycled.

Ultrasonic vibration chemical-mechanical composite polishing tool consists of three parts: ultrasonic vibrator, coupling agent, and vibratory polishing tool. Coupling agent, vibration polishing tools, objects to be polished, polishing liquid, polishing pads, polishing discs; the vibration source is a disk-shaped megasonic piezoelectric vibrator, and the operating frequency of the vibrator is above 1MHz. Megasonic has high energy density and penetrating ability Strong, good linearity and other advantages; the megasonic vibration generated by the vibration source is transmitted to the flexible coupling agent, which avoids the contact wear between the vibration source and the vibration polishing tool, and the coupling agent can reduce the loss of vibration on the transmission medium interface; vibration polishing The tool has multiple functions such as transmitting vibration, holding silicon wafer, storing couplant, etc. The vibration polishing tool is used as a fixture to hold the silicon wafer, that is, the silicon wafer is adsorbed on the vibration polishing tool. The groove structure makes the silicon wafer go together with the vibration polishing tool Rotation, the vibration polishing tool and the polishing disc have a certain eccentricity, so that the vibration polishing tool not only revolves around the axis of the polishing disc, but also rotates around its own axis, and the vibration polishing tool is floating, which makes the polishing more uniform and avoids the silicon wafer. warping etc. Finally, the megasonic vibration is transmitted to the polishing liquid, so that the polishing liquid particles can effectively function, so as to obtain a complete surface lattice, ultra-high surface accuracy and extremely low roughness of the polished silicon wafer.

The invention generates megahertz-level ultrasonic waves from a vibration source, and transmits them to a vibrating polishing tool through a selected coupling agent, so as to add ultrasonic vibration to the vibrating polishing tool. This method uses the transmission characteristics of vibration. In order to reduce the attenuation of vibration during transmission, three points should be paid attention to: 1. The requirements of the vibration source. The vibration frequency of the vibration source should be relatively high (the frequency should be above 1MHz), which is Because, in the case of a certain amplitude, the higher the frequency, the greater the energy density, and the better the effect of vibration addition, and in the same medium, the higher the frequency of vibration, the shorter the wavelength, the better the directionality; 2. The coupling agent Choose, the vibration is transmitted from the vibration source to the vibration polishing tool through a flexible coupling agent, there are two interfaces, because the high-frequency ultrasonic has a good linear shape, it is easy to generate reflection at the interface of the two media and cause energy loss , it is necessary to select the appropriate coupling agent according to the acoustic impedance of the two media to reduce the loss of energy; third, because the wavelength of high-frequency ultrasound is very short, it attenuates very quickly in the gas environment, so vibration polishing tools and There should be no gas barrier between the workpieces to be processed, and liquid should be used to discharge the air, so that the processed objects can be adsorbed on the vibration polishing tool.

The ultrasonic vibration adding method and device can be applied in various machining processes. Now the present invention is applied in the polishing process. Aiming at the polishing of silicon wafers, a set of ultrasonic polishing device using liquid to transmit megahertz vibration is designed.

Example:

The ultrasonic polishing device that uses liquid to transmit megahertz vibration is composed of two parts: the ultrasonic vibration additional system and the polishing machine system. The vibration additional system includes three assemblies: vibrator and sealing device, coupling agent and vibration polishing tool. It consists of six parts (see Figure 1); the polishing machine system is composed of the object to be polished (silicon wafer), polishing liquid, polishing pad, and polishing disc (see Figure 2).

In the figure: 1-screw; 2-upper piece of compression device; 3-lower piece of compression device; 4-electric wire; 5-sealing ring; 6-disc piezoelectric vibrator; 7-horizontal cantilever support; 8-coupling agent; 9-vibration polishing tool; 10-silicon wafer; 11-polishing pad; 12-polishing liquid; 13-polishing disk.

The working surface of the disc piezoelectric vibrator of the present invention is immersed in the liquid environment. In order to prevent the liquid from penetrating into the electrode surface and causing a short circuit, a sealing device is designed to seal it, and the upper piece 2 and the lower piece 3 are fastened by bolts 1 , so that the sealing ring 5 is extruded and deformed to achieve the effect of sealing. Apply an excitation of an alternating voltage of a suitable frequency to the piezoelectric ceramic sheet (the frequency of the excitation voltage is above 1MHz), and the vibrator will resonate in the designed mode to generate high-frequency vibration. The high-frequency vibration is transmitted to the coupling agent in contact with it, and the megasonic vibration propagates forward in the form of longitudinal waves in the coupling agent 7, and the vibration is transmitted to the vibration polishing tool through the coupling agent. The vibration polishing tool 9 is designed into a cylindrical barrel shape, and the barrel The bottom milling has the same shape as the polished silicon wafer, and the depth is half the thickness of the silicon wafer to align the silicon wafer. It has multiple functions such as transmitting vibration, clamping the silicon wafer, and storing coupling agent. The vibration polishing tool is used as a fixture To install silicon wafers, first apply a layer of water, then stick the silicon wafers on it, and squeeze to remove the air inside, so that the silicon wafers can be adsorbed on the vibrating polishing tool. The vibratory polishing tool turns together. In order to avoid direct contact between the vibrator and the vibrating polishing tool and reduce unnecessary wear and tear, the vibrator and the sealing device are located on the external horizontal cantilever support 7, which is a cantilever of a four-bar mechanism. By adjusting the horizontal cantilever support Height, to achieve the purpose of adjusting the distance between the vibrator and the vibration polishing tool; the vibration polishing tool card is seated on the polishing disc, and is positioned with the triangular claw of the polishing machine, the polishing disc is located on the polishing machine, rotates around the main shaft of the polishing machine, vibrating polishing There is a certain eccentric distance between the tool and the polishing disc, so that the vibration polishing tool not only revolves around the axis of the polishing disc, but also rotates around its own axis, and the vibration polishing tool is floating, which makes the polishing more uniform and avoids the warping of silicon wafers and other problems . The vibration passes through the vibration polishing tool and the silicon wafer, and finally the megasonic vibration is transmitted to the polishing liquid, so that the polishing liquid particles can effectively function, thereby obtaining a complete surface lattice, ultra-high surface accuracy and extremely low roughness of the polished silicon wafer .

Claims (5)

1. An ultrasonic polishing device that utilizes liquid to transmit megahertz-level vibrations is characterized in that the device is composed of an ultrasonic vibration additional system and a polishing machine tool, and the ultrasonic vibration additional system includes a vibrator and a sealing device, a coupling agent, and a vibration polishing Three assemblies of the tool, including the upper piece of the pressing device, the lower piece of the pressing device, the conductive wire, the sealing ring, the piezoelectric vibrator of the wafer, the horizontal cantilever support, the coupling agent, the vibration polishing tool, the silicon wafer, the polishing pad, and the polishing disc ; The vibrator is set as a piezoelectric vibrator with an excitation voltage frequency above 1MHz, and the corresponding vibrator is provided with a sealing device. The vibrator and its sealing device are placed on an external horizontal cantilever support (7) with adjustable height, and the vibrator is soaked in the coupling agent. , the silicon wafer is adsorbed on the vibrating polishing tool, the whole device is located on a polishing disc with a polishing pad attached, and the vibrating polishing tool is provided with a slot structure. 2. A kind of ultrasonic polishing device utilizing liquid to transmit megahertz-level vibration according to claim 1, characterized in that, said ultrasonic vibration chemical mechanical composite polishing tool includes a wafer piezoelectric vibrator, a horizontal clamp, a sealing ring, and a live wire , the upper piece of the pressing device, the lower piece of the pressing device, the coupling agent, the vibration polishing tool, the object to be polished, the polishing liquid, the polishing pad, and the polishing disc; the horizontal cantilever support is a cantilever of a four-bar mechanism, and the vibration polishing tool is stuck on the polishing disc and positioned with the triangular jaws of the polisher. 3 . The ultrasonic polishing device using liquid to transmit megahertz vibration according to claim 1 , wherein the vibration polishing tool is in the shape of a cylindrical barrel, and the vibration polishing tool is clamped on a silicon wafer. 4 . 4. A kind of ultrasonic polishing device utilizing liquid to transmit megahertz-level vibration according to claim 3, characterized in that, the vibration polishing tool clamps the silicon chip, and the bottom of the vibration polishing tool barrel is milled with the same shape as the polished silicon chip. 1. The groove with a depth of half the thickness of the silicon wafer positions and holds the silicon wafer. 5 . The ultrasonic polishing device using liquid to transmit megahertz vibration according to claim 1 , wherein the polishing disc is located on the polishing machine, and the vibration polishing tool and the polishing disc have a certain eccentricity. 5 .