TWI807466B - Susceptor element and plasma processing apparatus - Google Patents

Abstract

The present invention provides a base element for a plasma processing apparatus, comprising a plurality of acoustic emission sensors disposed in the base element. Acoustic emission sensors are able to detect and locate micro-arcing (arcing) phenomena through acoustic propagation.

Description

Susceptor element and plasma processing apparatus

The present invention relates to the technical field of semiconductor processing equipment, in particular to a base element and plasma processing equipment with the base element.

Micromachining of semiconductor substrates or substrates is a well-known technique that can be used to fabricate, for example, processor wafers, memory wafers, micro-electromechanical systems, optoelectronic components, solar cells, and the like. An important step in micromachining manufacturing is the plasma etching step, which is performed inside a reaction chamber into which process gases are fed. The radio frequency source is inductively and/or capacitively coupled to the interior of the reaction chamber to excite the process gas to form plasma for reactive ion etching.

With the continuous reduction of critical dimensions in the process, more stringent process conditions are required, such as higher output RF power, higher bias voltage, etc. These conditions will increase the possibility of voltage breakdown or arcing, which will cause damage to various components in the reaction chamber, and even irreversible failure of the component may occur. Therefore, detecting and locating such arcing events is of great significance to the extension of component life and the optimization and perfection of semiconductor processing processes.

The present invention provides a base element for plasma processing equipment, comprising: a base; an electrostatic chuck disposed above the base for carrying a substrate to be processed; a bonding layer for combining the base with the electrostatic chuck; and a plurality of acoustic emission sensors for detecting arc discharge and locating the position of the arc discharge in the plasma processing equipment.

Preferably, said plurality of acoustic emission sensors is at least three acoustic emission sensors for locating the location of arcing on said electrostatic chuck.

Preferably, the at least three acoustic emission sensors are arranged in the electrostatic chuck, close to the lower surface of the electrostatic chuck.

Preferably, the at least three acoustic emission sensors are arranged in the bonding layer.

Preferably, the at least three acoustic emission sensors are arranged in the base, close to the upper surface of the base.

Preferably, the operating frequency range of the acoustic emission sensor is 10kHz-100kHz.

Preferably, the base component further includes a radio frequency filter and a processing unit, the radio frequency filter is connected to the acoustic emission sensor, and the processing unit receives and processes the filtered electrical signal from the radio frequency filter.

Preferably, the base component also includes a radio frequency filter, a photoelectric converter and a processing unit, the radio frequency filter is connected to the acoustic emission sensor; the photoelectric converter is connected to the radio frequency filter and the processing unit, receives the electrical signal from the radio frequency filter and converts it into an optical signal; the processing unit receives and processes the optical signal from the photoelectric converter.

Preferably, the photoelectric converter is connected to the processing unit through an optical fiber.

The present invention also provides a plasma processing device, comprising: a vacuum reaction chamber; a gas supply device for delivering reaction gas into the vacuum reaction chamber; and the above-mentioned base element, the base element is arranged inside the vacuum reaction chamber.

The present invention also provides a plasma processing device, comprising: a vacuum reaction chamber; a gas supply device for delivering reaction gas into the vacuum reaction chamber; a base disposed inside the vacuum reaction chamber and carrying a substrate to be processed thereon; a plurality of acoustic emission sensors disposed in the base for detecting arc discharge and locating the position of the arc discharge in the plasma processing device.

The present invention provides a base element for plasma processing equipment and the plasma processing equipment, including a plurality of acoustic emission sensors arranged in the base element. Acoustic emission sensors are able to detect tiny plasma discharge phenomena through acoustic propagation. Since the acoustic emission sensor is arranged in the base member close to the substrate, it can better detect the micro-arc discharge between the substrate and the base member or around the substrate than the traditional acoustic emission sensor arranged on the wall of the reaction chamber. In addition, setting more than three acoustic emission sensors can not only detect the micro-arc discharge phenomenon around the substrate, but also accurately locate the specific position of the micro-arc discharge on the substrate or base component through signal processing, thereby providing positive assistance for accurate substrate detection, especially in the process of small critical dimensions.

100: Plasma etching equipment

101: Process chamber side wall

102: base element

103: Gas sprinkler head

104: RF power supply

105: Gas source

106: Vacuum pump

107: Acoustic emission sensor

108: Plasma confinement ring

201: Electrostatic Chuck

202: bonding layer

203: base

204: electrode

210: RF filter

211: processing unit

212: photoelectric converter

P: Plasma treatment area

W: Substrate

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those skilled in the art of the present invention, other accompanying drawings can also be obtained according to these drawings without making progressive changes.

FIG. 1 shows a schematic structural diagram of a plasma processing device according to an embodiment of the present invention.

Fig. 2 is a schematic structural view of the base element in Fig. 1 .

Fig. 3 shows a schematic structural view of a base element according to another embodiment.

Fig. 4 shows a schematic structural view of a base element according to another embodiment.

Fig. 5 shows a schematic structural view of a base element according to another embodiment.

Fig. 6 shows a schematic diagram of locating the position of a micro-arc discharge according to an embodiment of the present invention.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. the embodiment. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art of the present invention without making progressive changes shall fall within the protection scope of the present invention.

Plasma discharge is an event that occurs frequently in plasma processing equipment. When the plasma is excited in the plasma processing chamber, a plasma discharge phenomenon will occur between the parts of the chamber or on the surface of the parts, for example, inside the gas hole of the gas shower head, in the helium through hole or lifting hole of the electrostatic chuck, or between the upper surface of the electrostatic chuck and the lower surface of the substrate to be processed, etc. Plasma discharge satisfies the "Paschen's law", which is a law that characterizes the relationship between the breakdown voltage, gap distance and gas pressure of a uniform electric field gas. Specifically, the breakdown voltage between two objects (for example, electrodes) is a function of the product of the gas pressure and the distance between the two objects. Generally speaking, the relationship between the breakdown voltage and the product is: as the value of the product becomes larger, the breakdown voltage first decreases rapidly to a minimum value and then increases. Therefore, in order to make the breakdown voltage threshold higher, it is necessary to avoid the value of the product of air pressure and distance near the minimum value, that is to say, the larger the value of air pressure and distance, the better. However, because the air pressure is limited by the vacuum environment and the distance is restricted by the structure of the components in the reaction chamber, their product cannot meet the required larger value, so the discharge phenomenon often occurs in the chamber.

Micro-arcing is a form of plasma discharge that can suddenly occur in reaction chambers used to manufacture integrated circuits and damage parts. Micro-arcing typically occurs in substrates, susceptors, electrodes and sputtering targets. It not only reduces the product yield of large integrated circuits, but also reduces the processing efficiency of plasma processing equipment, because the processing equipment must stay for a long time to find the discharge location to repair the damaged parts. Compared with ordinary plasma discharge, micro-arc discharge has a smaller discharge volume and is easily overlooked. However, when micro-arcing occurs around the substrate, even small charges can have a substantial effect on the substrate. In addition, as the critical dimensions in the manufacturing process of large-scale integrated circuits become smaller and smaller, the intensity of micro-arcing between microstructures on the substrate will correspondingly decrease, making it less noticeable. However, defective substrates will proceed to the next step process, resulting in lower yields of finished substrates. Therefore, there is a need to detect and locate the micro-arcing that occurs during such processing.

Micro-arcing events in plasma processing equipment can be effectively detected using an acoustic emission sensor. The acoustic emission sensor is an important part of the acoustic emission detection system, which is based on the piezoelectric effect of the crystal element. The piezoelectric effect is the phenomenon that charges appear on the surface of piezoelectric ceramics when they are deformed by force. The essence of sound wave propagation is a kind of particle motion. When the movement of the particle is transmitted to the contact surface of the sensor, it will drive the protons on the piezoelectric ceramic to move, thereby producing compression and stretching effects on the piezoelectric ceramic, and then converting it into a voltage signal, which is sent to the signal processor to complete the transformation process from sound wave to electrical signal wave. There are four main types of acoustic emission sensors, namely resonant sensors, broadband sensors, differential (differential) sensors, and built-in preamplifier sensors. In acoustic emission detection, mostly resonant acoustic emission sensors and acoustic emission sensors with broadband response are used.

FIG. 1 shows a schematic structural diagram of a plasma processing device according to an embodiment of the present invention, in particular, the plasma processing device is a plasma etching device 100 . The plasma etching equipment 100 has a processing chamber, the processing chamber is substantially cylindrical, and the side wall 101 of the processing chamber is substantially vertical, and the processing chamber has a base element 102 and a gas supply device arranged parallel to each other. In this embodiment, the gas supply device is a gas shower head 103 . Generally, the area between the susceptor 102 and the gas showerhead 103 is the plasma processing area P, and the susceptor 102 and the gas showerhead 103 are fed with high-frequency energy as upper and lower electrodes to ignite and maintain plasma. A substrate W to be processed is placed above the base member 102, and the substrate W may be a semiconductor substrate to be etched or processed or a glass plate to be processed into a flat panel display. Wherein, the base element 102 is used to clamp the substrate W. A plurality of acoustic emission sensors 107 are disposed in the base member 102 for detecting and locating plasma discharges, especially micro-arc discharge events, on the base member 102 or other components in the plasma etching apparatus 100 . The structure and function of the acoustic emission sensor 107 will be described in detail below.

The reaction gas is input from the gas source 105 to the gas shower head 103 in the processing chamber. In one embodiment, the reactive gas can be fluoride gas, oxygen and chlorine one or more gases. One or more RF power sources 104 may be applied to the base member 102 alone or simultaneously to the base member 102 and the showerhead 103 to deliver RF power to these components to generate a large electric field inside the processing chamber. Most of the electric field lines are contained in the plasma processing region P between the susceptor 102 and the gas showerhead 103 , and the electric field accelerates a small number of electrons present inside the processing chamber to collide with gas molecules of the input reaction gas. These collisions result in the ionization of the reactive gases and the excitation of the plasma, which creates a plasma within the processing chamber. The neutral gas molecules of the reactive gas lose electrons when subjected to these strong electric fields, leaving behind positively charged ions. Positively charged ions are accelerated toward the lower electrode, and combined with neutral substances in the substrate to be processed, substrate processing, such as etching, deposition, etc. An exhaust area is provided at a suitable position in the plasma etching chamber, and the exhaust area is connected to an external exhaust device (such as a vacuum pump 106 ) to extract the used reaction gas and by-product gas out of the chamber during the processing. Wherein, the plasma confinement ring 108 is used to confine the plasma in the plasma processing region P. The side wall 101 of the processing chamber is connected to the ground terminal. In this embodiment, the plasma etching apparatus 100 further includes a gas channel disposed in the susceptor member 102 . Wherein, the length of the gas channel is sufficient to penetrate the entire base member 102, and the gas channel has a gas jet at one end close to the substrate W, and the gas jet can blow cooling gas into the back of the substrate W placed thereon to cool the substrate W being processed.

Fig. 2 is a schematic structural view of the base element in Fig. 1 . In order to describe clearly and concisely, the same parts and components as in Fig. 1 are described with the same reference numerals. As shown in FIG. 2 , the base component 102 includes an electrostatic chuck 201 , a bonding layer 202 and a base 203 . The electrostatic chuck 201 is bonded to the base 203 through the bonding layer 203 . The electrostatic chuck 201 carries a substrate W to be processed on its top, and an electrode 204 is embedded in it, and a DC voltage is input to the electrode 204 to generate static electricity to attract the substrate W to be processed above. The electrostatic chuck 201 is generally made of semiconductor or insulating ceramic materials, such as alumina, aluminum nitride, silicon carbide, and the like. Base 203 is usually made of conductive metal material, such as aluminum, Stainless steel or titanium etc. Radio frequency (RF) power is delivered to the susceptor 203 by an RF power supply to ignite the plasma. The bonding layer 202 is used for bonding the electrostatic chuck 201 and the base 203 , and is usually silicone.

In this embodiment, an acoustic emission sensor 107 is also provided on the upper surface of the base 203 . As shown in FIG. 2 , a plurality of (for example, at least three) AE sensors 107 are disposed on the upper portion of the base 203 , and their coupling surfaces are flush with the upper surface of the base 203 and in contact with the bonding layer 202 . The acoustic emission sensor 107 includes a coupling surface, a piezoelectric element and wires. One side of the piezoelectric element is bonded to the coupling surface through conductive glue, and the other side is connected to external devices (such as signal processing unit, filter, etc.) through wires. Piezoelectric elements usually use ceramic wafers such as lead zirconate titanate, barium titanate and lithium niobate, which play the role of acoustic-electric conversion when micro-arc discharge occurs; the coupling surface plays the role of insulating and protecting the piezoelectric element. In another embodiment, the acoustic emission sensor 107 further includes a grounded outer shell, which acts as a shield against electromagnetic interference. In another embodiment, the acoustic emission sensor 107 further includes a damping material, which is arranged around the piezoelectric element inside the outer housing to suppress partial resonance.

Usually, the acoustic impedance in the metal base is close to 10 times that in the insulating material, so the acoustic emission sensor can also be placed in the insulating material such as the electrostatic chuck or bonding layer to measure the micro-arc discharge signal more sensitively. In addition, placing the AE sensor on the electrostatic chuck or bonding layer closer to the substrate can also improve the accuracy of the discharge signal. As shown in FIG. 3 , a plurality of acoustic emission sensors 107 are disposed in the bonding layer 202 between the base 203 and the electrostatic chuck 201 . The upper surface (ie, the coupling surface) of the acoustic emission sensor 107 is in contact with the lower surface of the electrostatic chuck 201 . In another embodiment, the upper surface (ie, the coupling surface) of the emission sensor 107 may not be in contact with the lower surface of the electrostatic chuck 201 . Alternatively, as shown in FIG. 4 , a plurality of acoustic emission sensors 107 are disposed in the electrostatic chuck 201 . Specifically, the acoustic emission sensor 107 is disposed between the electrode 204 in the electrostatic chuck 201 and the lower surface of the electrostatic chuck 201 . In another embodiment, the acoustic emission sensor 107 is disposed between the electrode 204 in the electrostatic chuck 201 and the upper surface of the electrostatic chuck 201 .

Returning to Fig. 2, the other side of the piezoelectric element in the acoustic emission sensor 107 opposite to the coupling side is connected to the external processing unit 211 of the base 203 through a wire, and the processing unit 211 receives And process the converted electric signal from the acoustic emission sensor 107 . Connections can take many forms. For example, each AE sensor 107 is connected to the processing unit 211 through its own wire; or, the wire of each AE sensor 107 is connected to a converging point in the base, and then connected to the processing unit 211 through a bus. A radio frequency filter 210 is disposed between each acoustic emission sensor 107 and the processing unit 211 . The operating frequency of the acoustic emission sensor 107 is in the range of 10 kHz to 100 kHz, while the frequency of the RF power of the plasma processing equipment is greater than 400 kHz. Therefore, the RF power and the signal of the AE sensor 107 can be well decoupled by the RF filter 210 .

Fig. 5 is a schematic structural view of a base element according to another embodiment of the present invention. For clarity and brevity of description, the same components as in the embodiment shown in FIG. 2 are described with the same reference numerals. The difference from the embodiment shown in FIG. 2 is that a photoelectric converter 212 is provided between the radio frequency filter 210 and the processing unit 211 . The photoelectric converter 212 receives the electrical signal from the RF filter 210 and converts it into an optical signal; and sends the optical signal to the processing unit 211 . The photoelectric converter 212 and the radio frequency filter 210 are connected by wires or cables; the photoelectric converter 212 and the processing unit 211 are connected by an optical fiber (the dotted line in the figure), and the optical fiber may be a single-mode optical fiber or a multi-mode optical fiber. Converting the electrical signal received from the acoustic emission sensor 107 into an optical signal and sending it to the processing unit 211 for processing can effectively avoid electromagnetic interference in the radio frequency environment and increase the stability and accuracy of signal transmission for subsequent correct processing.

Arranging three or more acoustic emission sensors in the base element can not only detect the micro-arcing event, but also locate the position of the micro-arcing in the electrostatic chuck. FIG. 6 depicts a schematic diagram of locating the location of a micro-arc discharge according to one embodiment of the present invention. In this embodiment, three AE sensors 107 are provided in the electrostatic chuck 201 . It should be noted that the position of the acoustic emission sensor is not limited. In other embodiments, the acoustic emission sensor can also be disposed in the bonding layer and the base as described above; and the number of the acoustic emission sensor can be greater than three. As shown in FIG. 6 , at time T0 , micro-arc discharge occurs at point P of the electrostatic chuck 201 , and the sound wave propagates around point P at a uniform speed. Three acoustic emission sensors receive at different times For example, the AE sensor A receives the sound wave at the time Ta, the AE sensor B receives the sound wave at the time Tb, and the AE sensor C receives the sound wave at the time Tc. The acoustic emission sensor transmits the signal to the processing unit, and the processing unit records the aforementioned Ta, Tb, and Tc moments. It can be seen that for the acoustic emission sensor A, the micro-arc discharge occurs on the circle with the sensor A as the center and the radius (Ta-T0)×V (V is the speed of sound wave propagation). Similarly, for the acoustic emission sensor B, the micro-arc discharge occurs on the circle with the sensor A as the center and the radius is (Ta-T0)×V (V is the speed of sound wave propagation); for the acoustic emission sensor C, the micro-arc discharge occurs on the circle with the sensor C as the center and the radius is (Tc-T0)×V (V is the speed of sound wave propagation). The intersection point of the three circles is the position P of the micro-arc discharge. Therefore, the processing unit can determine the location where the micro-arc discharge occurs based on the initial position of the AE sensor, the velocity of the sound wave, and the time when each AE sensor receives the sound wave signal.

A base element for use in a plasma etching apparatus is disclosed above, in which base element an acoustic emission sensor is arranged. In fact, this device can also be used in other equipment that utilizes plasma or ion beams for substrate surface treatment, for example, plasma vapor deposition equipment, chemical vapor deposition equipment, and the like. These devices include: a vacuum reaction chamber; a gas supply device for delivering reaction gas into the vacuum reaction chamber; a base disposed inside the vacuum reaction chamber and carrying a substrate to be processed thereon; a plurality of acoustic emission sensors disposed in the base for detecting arc discharge and locating the position of the arc discharge in the plasma processing equipment. Acoustic emission sensors detect and locate micro-arcing.

The present invention provides a base element for a plasma processing apparatus, comprising a plurality of acoustic emission sensors disposed in the base element. Acoustic emission sensors are able to detect tiny plasma discharge phenomena through acoustic propagation. Since the acoustic emission sensor is arranged in the base member close to the substrate, it can better detect the micro-arc discharge between the substrate and the base member or around the substrate than the traditional acoustic emission sensor arranged on the wall of the reaction chamber. In addition, setting at least three acoustic emission sensors can not only detect the micro-arc discharge phenomenon around the substrate, but also through signal processing It can also accurately locate the specific position of the micro-arc discharge on the substrate or base component, thereby providing positive assistance for accurate substrate inspection, especially in the process of small critical dimensions.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present invention. Various modifications and alterations to the present invention will become apparent to those having ordinary skill in the art to which the present invention pertains after reading the above disclosure. Therefore, the protection scope of the present invention should be defined by the appended patent application scope.

100: Plasma etching equipment

101: Process chamber side wall

102: base element

103: Gas sprinkler head

104: RF power supply

105: Gas source

106: Vacuum pump

107: Acoustic emission sensor

108: Plasma confinement ring

P: Plasma treatment area

W: Substrate

Claims (10)

A base element for plasma processing equipment, including: a base; an electrostatic chuck, arranged above the base, for carrying a substrate to be processed; a bonding layer, used for combining the base and the electrostatic chuck; and a plurality of acoustic emission sensors, used for detecting an arc discharge and locating the position of the arc discharge in the plasma processing equipment; wherein the plurality of acoustic emission sensors are at least three of the acoustic emission sensors, used for positioning the position of the arc discharge on the electrostatic chuck. The base component as claimed in claim 1, wherein the at least three acoustic emission sensors are disposed in the electrostatic chuck, close to the lower surface of the electrostatic chuck. The base element as claimed in claim 1, wherein the at least three acoustic emission sensors are disposed in the bonding layer. The base element as claimed in claim 1, wherein the at least three acoustic emission sensors are disposed in the base, close to the upper surface of the base. The base component as claimed in claim 1, wherein the operating frequency range of the acoustic emission sensor is 10kHz-100kHz. The base component as claimed in claim 1, further comprising a radio frequency filter and a processing unit, the radio frequency filter is connected to the acoustic emission sensor, and the processing unit receives and processes a filtered electrical signal from the radio frequency filter. The base component as described in claim 1, further comprising a radio frequency filter, a photoelectric converter and a processing unit, the radio frequency filter is connected to the acoustic emission sensor; the photoelectric converter is connected to the radio frequency filter and the processing unit, receives an electrical signal from the radio frequency filter and converts it into an optical signal; the processing unit receives and processes the optical signal from the photoelectric converter. The base component as claimed in claim 7, wherein the photoelectric converter is connected to the processing unit through an optical fiber. A plasma processing equipment, comprising: a vacuum reaction chamber; a gas supply device for delivering reaction gas into the vacuum reaction chamber; and a base element as described in any one of claims 1-8, the base element is arranged inside the vacuum reaction chamber. A plasma processing equipment, including: a vacuum reaction chamber; a gas supply device, used to transport reaction gas into the vacuum reaction chamber; a base, arranged inside the vacuum reaction chamber and carrying a substrate to be processed thereon; and a plurality of acoustic emission sensors, arranged in the base, for detecting an arc discharge and locating the position of the arc discharge in the plasma processing equipment; wherein the plurality of acoustic emission sensors are at least three acoustic emission sensors, used for locating the position of the arc discharge on the base.