CN111952231A

CN111952231A - Charge transfer device and related plasma system

Info

Publication number: CN111952231A
Application number: CN201910398362.3A
Authority: CN
Inventors: 刘建; 韦刚
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing Naura Microelectronics Equipment Co Ltd
Priority date: 2019-05-14
Filing date: 2019-05-14
Publication date: 2020-11-17
Also published as: WO2020228407A1; TW202109681A; TWI738250B

Abstract

A charge transport device for use in a plasma system, the plasma system including a chamber and a lower electrode disposed in the chamber, the plasma system being configured to machine a workpiece disposed on the lower electrode, the lower electrode including an electrode for generating a chucking force to hold the workpiece during machining of the workpiece, and a heater for providing a heat source to the workpiece during machining of the workpiece via an AC power source and an AC voltage provided by a filter device coupled between the AC power source and the heater, the charge transport device being configured to selectively transfer charge on the heater, the charge transport device including a first terminal coupled between the AC power source and the heater and a second terminal, the second terminal is coupled to a reference voltage terminal.

Description

Charge transfer device and related plasma system

Technical Field

The present invention relates to an apparatus, and more particularly, to a charge transfer device and related plasma system.

Background

During the processing of wafers, electrostatic chucks are widely used to support, secure, and cool wafers. When the wafer is processed, the electrostatic chuck generates electrostatic adsorption force to the wafer by direct current voltage to achieve a fixed effect, however, after the process is finished, the residual charges on the electrostatic chuck also generate electrostatic adsorption force to the wafer to cause a sticking phenomenon, so that when the processed wafer is taken away, the wafer is deviated and inclined due to the electrostatic adsorption force, and even the wafer taking fails.

Disclosure of Invention

The present invention discloses a charge transfer device and related plasma system to solve the problems of the background art, such as improper wafer adhesion on an electrostatic chuck.

According to an embodiment of the present invention, a charge transfer device for a plasma system is disclosed, the plasma system includes a chamber and a lower electrode disposed in the chamber, the plasma system is configured to process a workpiece disposed on the lower electrode, the lower electrode includes an electrode and a heater, wherein the electrode is configured to generate an attraction force to fix the workpiece when the workpiece is processed, the heater is configured to provide a heat source to the workpiece when the workpiece is processed by the workpiece through an ac power source and an ac voltage provided by a filter device coupled between the ac power source and the heater, the charge transfer device is configured to selectively transfer charges on the heater, the charge transfer device includes a first terminal and a second terminal, the first terminal is coupled between the ac power source and the heater, the second terminal is coupled to a reference voltage terminal.

According to an embodiment of the present invention, a plasma system including a chamber for processing a workpiece disposed in the chamber is disclosed, and includes an ac power source, a filtering device, a lower electrode, and a charge transfer device. The alternating current power supply is used for providing alternating current voltage. The filtering device is coupled with the alternating current power supply and is used for filtering the alternating current voltage. The lower electrode is coupled to the AC power source and the filter device, and includes an electrode and a heater. The electrode is used for generating an adsorption force to fix the workpiece when the workpiece is machined. The heater is used for receiving the alternating voltage filtered by the filtering device to provide a heat source. The charge transfer device is coupled to the heater and is used for selectively transferring charges on the heater, and the charge transfer device comprises a first end point and a second end point. The first terminal is coupled between the AC power source and the heater, and the second terminal is coupled to a reference voltage terminal.

Drawings

FIG. 1 is a schematic diagram of a plasma system in accordance with one embodiment of the present invention.

FIG. 2A is a schematic diagram of a bottom electrode according to an embodiment of the invention.

FIG. 2B is a schematic diagram of a ceramic layer in a bottom electrode according to an embodiment of the invention.

FIG. 2C is a schematic view of a heating layer in the bottom electrode according to an embodiment of the invention.

Fig. 3 is a schematic diagram of a charge transfer device according to an embodiment of the invention.

Fig. 4 is a schematic diagram illustrating an operation of a charge transfer device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a plasma system in accordance with another embodiment of the invention.

Detailed Description

The following disclosure provides various embodiments or illustrations that can be used to implement various features of the disclosure. The embodiments of components and arrangements described below serve to simplify the present disclosure. It is to be understood that such descriptions are merely illustrative and are not intended to limit the present disclosure. For example, in the description that follows, forming a first feature on or over a second feature may include certain embodiments in which the first and second features are in direct contact with each other; and may also include embodiments in which additional elements are formed between the first and second features described above, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or characters in the various embodiments. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Moreover, spatially relative terms, such as "under," "below," "over," "above," and the like, may be used herein to facilitate describing a relationship between one element or feature relative to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass a variety of different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Although numerical ranges and parameters setting forth the broad scope of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain standard deviations found in their respective testing measurements. As used herein, "about" generally refers to actual values within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range. Alternatively, the term "about" means that the actual value falls within the acceptable standard error of the mean, subject to consideration by those of ordinary skill in the art to which this application pertains. It is understood that all ranges, amounts, values and percentages used herein (e.g., to describe amounts of materials, length of time, temperature, operating conditions, quantitative ratios, and the like) are modified by the term "about" in addition to the experimental examples or unless otherwise expressly stated. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, these numerical parameters are to be understood as meaning the number of significant digits recited and the number resulting from applying ordinary carry notation. Herein, numerical ranges are expressed from one end to the other or between the two ends; unless otherwise indicated, all numerical ranges set forth herein are inclusive of the endpoints.

When a plasma system is to process a workpiece (e.g., a wafer), such as by etching the workpiece (e.g., a wafer), the workpiece (e.g., a wafer) is positioned on a lower electrode of the plasma system by a robot arm for processing. The lower electrode typically has an electrostatic chuck to which the plasma system delivers a dc voltage of about one to five kilovolts, which causes electrostatic attraction of the workpiece (e.g., wafer) to be secured to the lower electrode during processing. After the machining is completed, the plasma system performs de-chuck (de-chuck) operation, and more particularly, the plasma system transmits a reverse dc voltage to the electrostatic chuck to remove the attraction of the charges in the lower electrode to the workpiece (e.g., wafer).

However, the desorption operation can neutralize only a part of the electric charges, and the desorption operation is difficult to control. If the time for removing the chucking operation is too long, the reverse pressurization may occur, and thus, as the mass production proceeds, the electric charge inside the electrostatic chuck is accumulated and the distribution unevenness becomes more and more significant, resulting in an increasing attraction force of the residual electric charge to the local part of the workpiece (e.g., wafer). Therefore, after the workpiece (e.g. wafer) is processed, when the plasma system controls the thimble in the lower electrode to lift the workpiece (e.g. wafer), the workpiece (e.g. wafer) is prone to shift due to the attraction of residual charges, and if the workpiece (e.g. wafer) is seriously taken out, the wafer fails to be taken out. The invention discloses a charge transmission device applied to a plasma system and the related plasma system to avoid the possible deviation condition when a workpiece (such as a wafer) is taken out after the processing is finished.

FIG. 1 is a schematic diagram of a plasma system 1 in accordance with one embodiment of the present invention. In the present embodiment, the plasma system 1 is used for processing a workpiece (e.g., a wafer), and the plasma system 1 may be an etching apparatus for etching the workpiece (e.g., the wafer) by using plasma, for example. As shown in fig. 1, the plasma system 1 includes a chamber 10, a lower electrode 11 disposed in the chamber 10, an alternating current power supply 12, a filter device 13, and a charge transfer device 14. A workpiece (e.g., a wafer) is placed on the lower electrode 11 for machining.

Referring to fig. 2A, fig. 2A is a schematic diagram of the lower electrode 11 according to an embodiment of the invention. The lower electrode 11 may optionally include a ceramic layer 21, a heating layer 22, and a base 23, wherein the ceramic layer 21 houses the aforementioned electrostatic chuck for holding a workpiece (e.g., a wafer) during processing; heater layer 22 is used to control the temperature of a workpiece (e.g., a wafer). The susceptor 23 has a cooling liquid therein for temperature control of a workpiece (e.g., a wafer) in cooperation with the heating layer 22, and one end of the susceptor 23 is grounded. The ceramic layer 21, the heating layer 22 and the base 23 are bonded together by an adhesive. For example, the ceramic layer 21, the heating layer 22 and the base 23 are bonded by silicon. One of ordinary skill in the art will readily recognize that the components included in the lower electrode 11 are exemplary only and are not intended to limit the present invention.

Referring to fig. 2B, fig. 2B is a schematic diagram of a ceramic layer 21 according to an embodiment of the invention. The ceramic layer 21 includes ceramics 211 and 213 and an electrode 212. When the plasma system 1 transmits a DC voltage of one thousand to five kilovolts to the electrode 212, the electrode 212 generates electrostatic attraction force to hold a workpiece (e.g., a wafer). Referring to FIG. 2C, FIG. 2C is a schematic view of heating layer 22 according to an embodiment of the present invention. Heating layer 22 includes a heat spreader plate 221, insulating

layers

222 and 224, and a heater 223. The uniform heating plate 221 serves to make the temperature distribution of the heating layer 22 more uniform. The heater 223 generates heat as a heat source by the ac voltage. The isolation layers 222 and 224 serve as high temperature protection layers to prevent damage to other components or devices within the plasma system 1 when the heat generated by the heater 223 is too high. In certain embodiments, the insulating

layers

222 and 224 comprise polyamide. In this embodiment, an adhesive is used to bond the heat spreader plate 221 and the insulating layer 222. For example, the heat spreader 221 and the insulating layer 222 are bonded by silicone.

During the processing of a workpiece (e.g., a wafer), the electrode 212 is applied with a dc voltage, which continuously charges the equivalent capacitance formed by each of the ceramic layers 21 (including the ceramics 211 and 213 and the electrode 212) and the heating layer 22 (including the soaking plate 221, the insulating

layers

222 and 224, and the heater 223), and polarization voltages are generated between the layers and exist. Because the heating layer 22 uses more glue layers and heat-resistant resin materials, the thickness is larger, the capacitance is smaller, correspondingly, the voltage partial pressure generated on the heater 223 is larger, and the polarization charge is more. Even if the de-chucking operation is performed at the end of the process, the formed polarized charges cannot be completely removed, thereby causing the aforementioned electrostatic chucking force, resulting in a risk of the lift pin of the lower electrode 11 shifting when the work piece (e.g., wafer) is lifted up. The charge transfer device 14 disclosed in the present invention can effectively remove the residual charge, thereby avoiding the above situation.

With continued reference to fig. 1, the AC power source 12 is configured to generate an AC voltage AC, and transmit the filtered AC voltage AC 'to the heater 223 through the filtering device 13 coupled between the AC power source 12 and the heater 223, and the heater 223 receives the AC voltage AC' to generate heat. The filter 13 includes an inductor, and since the lower electrode 11 is in an rf environment when a workpiece (e.g., a wafer) is processed, the inductor inside the filter 13 can filter the rf electric field on the electrode 212, so as to prevent the rf electric field from interfering with the AC voltage AC provided by the AC power supply 12. The charge transfer device 14 is used for selectively transferring the charge on the heater 223, and the charge transfer device 14 includes a first terminal N1 and a second terminal N2, wherein the first terminal N1 may be coupled between the ac power source 12 and the heater 223. In the present embodiment, the first terminal N1 is coupled between the ac power source 12 and the filtering device 13. The second terminal N2 is coupled to the reference voltage terminal 15. In the present embodiment, the reference voltage terminal 15 is a ground terminal. The residual charge on the heater 223 can be effectively removed by forming a path for discharging between the heater 223 and the ground terminal through the charge transfer device 14.

One of ordinary skill in the art will readily recognize that the plasma system 1 may have other necessary devices and components for processing a workpiece (e.g., a wafer). For example, the plasma system 1 should have an upper RF power source and a lower RF power source for exciting the reaction gas in the chamber 10 into plasma for processing the workpiece (e.g., wafer). For example, the lower electrode 11 further includes a pin for controlling the pin to be lifted to lift up a workpiece (e.g., a wafer) at the end of processing the workpiece (e.g., the wafer) by the plasma system 1, so as to facilitate the robot entering the chamber 10 to take out the workpiece (e.g., the wafer). For simplicity, FIG. 1 depicts only those devices and components that are relevant to the inventive spirit of the present invention.

Fig. 3 is a schematic diagram of the charge transfer device 14 according to an embodiment of the invention. The charge transfer device 14 includes an impedance 141 and a switch 142, wherein the impedance 141 is coupled between a first terminal N1 and a second terminal N2, and more specifically, one terminal of the impedance 141 is coupled to the first terminal N1 through the switch 142, and another terminal of the impedance 141 is coupled to the second terminal N2. In the present embodiment, the impedance 141 may be a resistor. The resistance of the impedance 141 may be larger than a specific value, so that the AC current AC output by the AC power supply 12 is not too large to cause device damage. In some embodiments, the impedance 141 has a value greater than 200 kilo-ohms. In detail, after the machining of the workpiece (e.g. wafer) is finished, the electrode 212 is disconnected from the adsorption of the dc voltage, and at this time, the switch 142 is activated, so that the residual interlayer polarization charges on the heater 223 can be directly conducted to the ground through the path formed by the charge transfer device 14. Thus, by activating switch 142, charge transfer device 14 conducts the residual charge on heater 223 through impedance 141 to reference voltage terminal 15, which greatly reduces the residual amount of polarized charge on heater 223. One of ordinary skill in the art will readily appreciate that the activation or non-activation of switch 142 enables charge transfer device 14 to selectively conduct charge on electrode 212 to reference voltage terminal 15 through impedance 141.

However, the timing of activating the switch 142 is not limited to the end of processing the workpiece (e.g., wafer). For example, during processing of a workpiece (e.g., a wafer), the electrode 212 is applied with a dc voltage for clamping, and the activation switch 142 also enables the polarized charges on the heater 223 to be conducted to the reference voltage terminal 15 through the path formed by the charge transfer device 14 during the negative phase voltage of the ac power source 12.

It should be noted that in other embodiments, the charge transfer device 14 may not include the switch 142, so that the charge transfer device 14 can conduct the polarized charge on the heater 223 to the reference voltage terminal 15 through the impedance 141 during or after the processing of the workpiece (e.g., wafer).

Fig. 4 is a schematic diagram illustrating the operation of the charge transfer device 14 according to an embodiment of the present invention. In the embodiment of fig. 4, switch 142 is in an actuated state. In fig. 4, the equivalent capacitance of the ceramic layer 21 is denoted by C21, and the equivalent capacitances of the soaking plate 221, the insulating layer 222, and the heater 223 in the heating layer 22 are denoted by C221, C222, and C223, respectively. By coupling the charge transfer device 14 between the heater 223 and the ground, since the insulation layer 224 at the bottom of the heater 223 and the glue layer capacitance between the heating layer 22 and the base 23 are located between the heater 223 and the base 23 regarded as being grounded, the insulation layer 224 and the glue layer capacitance between the heating layer 22 and the base 23 can be shielded. In other words, the overall equivalent thickness of heating layer 22 becomes thin. The equivalent capacitance of heating layer 22 will become formed only by the series connection of capacitor C221, capacitor C222, and capacitor C223, the equivalent capacitance of heating layer 22 will therefore become larger, and the partial voltage received by heating layer 22 will become smaller. Thus, the DC voltage carried by the electrode 212 will reduce the polarization charge on the heater 223 during processing of the workpiece (e.g., wafer). In addition, the charge transfer device 14 forms a path for electrical discharge between the heater 223 of the heating layer 22 and the ground, so that the electrode 212 disconnects the attraction of the dc voltage after the processing of the workpiece (e.g., wafer) is completed. At this time, the polarization charges remaining on the heater 223 can be directly conducted to the reference voltage terminal, preferably the ground terminal, through the path formed by the charge transfer device 14. Also as described in the embodiment of fig. 3, not only after the machining process is completed, but also during the machining process of the workpiece (e.g., wafer), the polarized charges on the heater 223 can be conducted to the ground terminal through the path formed by the charge transfer device 14 during the negative phase voltage of the ac power source 12.

It should be understood that the charge transfer device 14 is not limited to be coupled between the ac voltage 12 and the filter device 13 as long as the discharge path is formed between the heater 223 and the ground after the above paragraphs. FIG. 5 is a schematic diagram of a plasma system 5 in accordance with another embodiment of the present invention. As in the embodiment of FIG. 1, plasma system 5 is used to process a work piece (e.g., a wafer), for example, plasma system 5 may be an etching apparatus that utilizes plasma to etch a work piece (e.g., a wafer). As shown in fig. 5, the plasma system 5 includes a chamber 50, a lower electrode 51 disposed in the chamber 50, an ac power source 52, a filter device 53, and a charge transfer device 54. A workpiece (e.g., a wafer) is placed on the lower electrode 51 for processing. The plasma system 5 shown in FIG. 5 is substantially the same as the plasma system 1 except that the charge transport device 54 includes a first terminal N1 'and a second terminal N2', wherein the first terminal N1 'is coupled between the filtering device 53 and the heater 523 of the lower electrode 51, and the second terminal N2' is coupled to the reference voltage terminal 55. Similarly, in the present embodiment, the reference voltage terminal 55 is a ground terminal. After reading the above paragraphs, those skilled in the art should understand how the charge transfer device 54 can form a discharge path between the heater 523 and the ground to remove the residual charge, and the detailed description is omitted here for brevity.

In summary, the present invention discloses a charge transfer device and a related plasma system, which can effectively shield the insulation layer at the bottom of the heater and the glue layer capacitance between the heating layer and the base, in other words, the whole equivalent thickness of the heating layer becomes thinner, the equivalent capacitance of the heating layer becomes larger, and the partial pressure received by the heating layer becomes smaller. Thus, the DC voltage carried by the electrode will reduce the polarization charge on the heater during the processing of the workpiece (e.g., wafer). In addition, the charge transmission device disclosed by the invention forms a discharging path between the heater and the grounding end, so that the polarized charges on the heater can be directly conducted to the ground through the path formed by the charge transmission device, and the risk of deviation when the thimble of the lower electrode jacks up the workpiece (such as a wafer) can be effectively reduced.

Claims

1. A charge transfer device for use in a plasma system, the plasma system including a chamber and a lower electrode disposed in the chamber, the plasma system being configured to machine a workpiece disposed on the lower electrode, the lower electrode including an electrode for generating a suction force to fix the workpiece when machining the workpiece, and a heater for providing a heat source to the workpiece through an AC power source and an AC voltage provided by a filter device coupled between the AC power source and the heater when machining the workpiece,

the charge transfer device is used for selectively transferring the charge on the heater and comprises a first end point and a second end point, wherein the first end point is coupled between the alternating current power supply and the heater, and the second end point is coupled to a reference voltage end.

2. The charge transport device of claim 1, further comprising:

a resistor coupled between the first terminal and the second terminal.

3. The charge transport device of claim 2, further comprising:

a switch coupled between the first terminal and the resistor, wherein the charge transfer device transfers the charge on the heater to the reference voltage terminal when the switch is activated.

4. The charge transport device of claim 1, wherein the first terminal is coupled between the heater and the filtering means.

5. The charge transfer device of claim 1, wherein said first terminal is coupled between said ac power source and said filtering means.

6. A plasma system including a chamber for processing a workpiece disposed in the chamber, comprising:

an alternating current power supply for supplying an alternating current voltage;

the filtering device is coupled to the alternating current power supply and is used for filtering the alternating current voltage;

a lower electrode coupled to the AC power source and the filtering device, comprising:

an electrode for generating an adsorption force to fix the work piece when the work piece is machined; and

the heater is used for receiving the alternating voltage filtered by the filtering device to provide a heat source; and

a charge transfer device coupled to the heater for selectively transferring charge on the heater, the charge transfer device including a first terminal and a second terminal, the first terminal being coupled between the AC power source and the heater, the second terminal being coupled to a reference voltage terminal.

7. The plasma system as claimed in claim 6, wherein said charge transfer device further comprises:

a resistor coupled between the first terminal and the second terminal.

8. The plasma system as claimed in claim 7, wherein said charge transfer device further comprises:

9. The plasma system of claim 6, wherein the first end is coupled between the heater and the filtering means.

10. The plasma system as claimed in claim 6, wherein said first terminal is coupled between said ac power source and said filtering means.