TWI859679B - Plasma flow control apparatus, and plasma etching machine and homogeneity optimization method of the same - Google Patents

Abstract

The present application discloses a plasma flow control apparatus, and a plasma etching machine and a homogeneity optimization method of the plasma etching machine. The plasma etching machine includes a plasma reaction chamber, a wafer support platform and a plasma flow control apparatus. The plasma flow control apparatus includes a first annular body, a second annular body and an annular connector. The first annular body, the second annular body and the annular connector are arranged around the straight line A. The annular connector is located in a spacing space and connects the first annular body and the second annular body to form a flow control chamber together with the first annular body and the second annular body. The first annular body is close to the air inlet of the plasma reaction chamber, and the second annular body is close to the wafer support platform. The wafer placement area of the wafer support platform is located in the projection area of the inner hole of the first annular body on the wafer support platform, and is also located in the projection area of the inner hole of the second annular body on the wafer support platform. The application can improve the etching uniformity, and can alleviate the problem of waste caused by the direct suction of air flow by the vacuum pump.

Description

Plasma current control device, plasma etching machine and uniformity optimization method thereof

The present invention relates to the field of semiconductor production technology, in particular to a plasma current control device, which can be applied to a plasma etcher and can be used to optimize the etching uniformity of the plasma etcher.

Plasma etching machines are used in the semiconductor industry. The basic principle is that under vacuum and low pressure, the radio frequency generated by the inductively coupled plasma (ICP) radio frequency power source is output to the annular coupling coil, and a certain proportion of mixed etching gas is coupled to generate high-density plasma through fluorescence discharge. Under the action of the radio frequency (RF) of the lower electrode, these plasmas bombard the wafer substrate, and the chemical bonds of the semiconductor in the wafer substrate drawing area are broken, generating volatile substances with the etching gas, which are separated from the substrate in the form of gas and are pumped away from the vacuum pipeline.

At present, there is uneven distribution of plasma during the operation of plasma etcher, and the gas flow is dispersed throughout the plasma reaction chamber, causing part of the gas flow to be directly pumped away by the vacuum pump, resulting in unnecessary waste and poor etching uniformity of the wafer. Taking metal aluminum etching as an example, the uniformity of metal aluminum etcher on the market is generally above 8%.

Therefore, how to overcome the above disadvantages is a technical problem that technicians in this field need to solve.

In order to solve the above technical problems, the present invention provides a plasma flow control device, which includes a first annular body, a second annular body and an annular connector; the first annular body, the second annular body and the annular connector are all arranged around a straight line A; the first annular body and the second annular body are spaced from each other along the straight line A to form a space between them; the annular connector is located in the space and connects the first annular body and the second annular body, and together with the first annular body and the second annular body, forms a flow control cavity; the inner hole of the first annular body forms an inlet for plasma to enter the flow control cavity, and the annular connector is provided with an outlet for plasma to flow out of the flow control cavity.

In an implementation of a plasma flow control device, the outer circumference of the second annular body is smaller than the outer circumference of the first annular body.

In one implementation of the plasma flow control device, the first annular body and the second annular body are both plate-shaped structures.

In one implementation of a plasma flow control device, the annular connector includes a plurality of connecting columns, each of which is arranged around the straight line A in sequence and at intervals, and the outlet is formed between adjacent connecting columns.

The present invention also provides a plasma etching machine, the plasma etching machine comprises a plasma reaction chamber, a wafer support platform and any one of the plasma flow control devices described above; the wafer support platform is located between the air inlet and the air outlet of the plasma reaction chamber, and the plasma flow control device is located between the air inlet of the plasma reaction chamber and the wafer support platform. , the first annular body of the plasma flow control device is close to the air inlet of the plasma reaction chamber, and the second annular body is close to the wafer support platform; the wafer placement area of the wafer support platform is located within the projection area of the inner hole of the first annular body on the wafer support platform, and is also located within the projection area of the inner hole of the second annular body on the wafer support platform.

In one implementation of the plasma etching machine, there is a gap between the outer periphery of the first annular body and the outer periphery of the second annular body and the side wall of the plasma reaction chamber or the inner lining side wall of the plasma reaction chamber.

An implementation of a plasma etcher, the plasma etcher further includes a bias electrode and a bias electrode cover, the bias electrode cover is fixed inside the plasma reaction chamber and covers the bias electrode, and the second annular body is supported and fixed on the bias electrode cover or supported and fixed on the inner lining of the plasma reaction chamber.

An implementation of a plasma etching machine, the plasma etching machine further includes a flow guide cover, a pressure control valve and a vacuum pump, the inlet of the flow guide cover is connected to the exhaust port of the plasma reaction chamber, the outlet of the flow guide cover is connected to the pressure control valve, and the pressure control valve is connected to the vacuum pump.

An implementation of a plasma etcher, the plasma etcher further comprises a shielding cover fixed outside the plasma reaction chamber, the shielding cover and the plasma reaction chamber enclose a shielding chamber; the plasma etcher further comprises a coupling coil disposed in the shielding chamber, a ceramic dielectric window disposed in the shielding chamber and located between the coupling coil and the air inlet of the plasma reaction chamber, and a nozzle penetrating the ceramic dielectric window for injecting process gas into the plasma reaction chamber.

The present invention also provides a method for optimizing the uniformity of a plasma etching machine, which optimizes the etching uniformity of the plasma etching machine by adjusting the inner hole size of the first annular body of the plasma flow control device, and/or adjusting the outer circumference size of the second annular body of the plasma flow control device, and/or adjusting the height size of the annular connector of the plasma flow control device.

In the present invention, when the plasma etching machine is working, the gas flow first enters the interior of the plasma reaction chamber from the gas inlet. Since the first annular body is arranged close to the gas inlet of the plasma reaction chamber, most of the gas flow enters the interior of the flow control chamber from the inner hole of the first annular body. Since the wafer placement area of the wafer support table is located within the projection area of the inner hole of the first annular body on the wafer support table and the projection area of the inner hole of the second annular body on the wafer support table, Therefore, the inner hole of the first annular body can concentrate the airflow more densely in the area facing the wafer, and the plasma in the concentrated airflow can fall on the wafer, etching the wafer with high density. At the same time, under the blocking effect of the cavity wall of the flow control cavity, the plasma will stay on the wafer for a longer time, so that it can fully participate in the etching, thereby improving the etching uniformity and alleviating the problem of airflow being directly sucked away by the vacuum pump and causing waste.

101: The first ring

102: Second Ring

103a: Connecting column

103b: Outlet

103: Ring connector

200: Plasma reaction chamber

201a: Exhaust port

201b: Cylindrical support part

201: Cavity

202a: Air intake

202: Cavity cover

203: Lining

301: Wafer support platform

302: Wafer

303: Wafer focusing ring

401: Bias electrode

402: Bias electrode cover

403: Biased RF power supply

404: Bias matching network

501: fairing

502: Pressure control valve

503: Vacuum pump

600: Shielding cover

701: Coupled coil

702: Excitation source RF power supply

703: Excitation source matching network

800: Ceramic dielectric window

901: Nozzle

902: Air source

A: Straight line

Figure 1 is a cross-sectional view of an embodiment of the plasma etching machine provided by the present invention;

Figure 2 is a three-dimensional cross-sectional view of part of the structure in Figure 1;

Figure 3 is a comparison of the gas flow distribution before and after the plasma etching machine uses a plasma flow control device.

In the past, plasma etcher had uneven distribution of plasma during operation, and the gas flow was dispersed throughout the plasma reaction chamber, causing part of the gas flow to be directly pumped away by the vacuum pump, resulting in unnecessary waste and poor etching uniformity of the wafer. Taking aluminum etching as an example, the uniformity of aluminum etcher on the market is generally above 8%.

To this end, the present invention provides a plasma flow control device, which can be applied to a plasma etcher, and can improve the etching uniformity of the plasma etcher and reduce the amount of gas used under the same etching conditions. In addition, the present invention also provides a plasma etcher using the plasma flow control device and a method for optimizing the uniformity of the plasma etcher.

In order to enable technical personnel in this technical field to better understand the technical solution of the present invention, the plasma current control device, plasma etcher and uniformity optimization method of the plasma etcher provided by the present invention are further described in detail below in combination with diagrams and specific embodiments.

As shown in Figure 1, the plasma etching machine includes a plasma reaction chamber 200, a wafer support table 301 for supporting a wafer 302, and a plasma flow control device. The plasma reaction chamber 200 has a chamber body 201 and a chamber cover 202. The bottom wall of the chamber body 201 is provided with an exhaust port 201a, and the chamber cover 202 is provided with an air inlet 202a.

The wafer support platform 301 is fixed inside the plasma reaction chamber 200. The wafer placement area of the wafer support platform 301 is located between the air inlet 202a and the air exhaust port 201a of the plasma reaction chamber 200.

The plasma flow control device is fixed inside the plasma reaction chamber 200. The plasma flow control device is located between the air inlet 202a of the plasma reaction chamber 200 and the wafer placement area of the wafer support platform 301.

The plasma flow control device includes a first annular body 101, a second annular body 102 and an annular connector 103. The first annular body 101, the second annular body 102 and the annular connector 103 are all arranged around the straight line A. The first annular body 101 and the second annular body 102 are spaced apart from each other along the straight line A, and a space is formed therebetween. The first annular body 101 and the second annular body 102 can adopt a plate-like structure for easy layout.

The annular connector 103 is located in the space between the first annular body 101 and the second annular body 102 and connects the first annular body 101 and the second annular body 102. The annular connector 103, the first annular body 101 and the second annular body 102 together enclose a flow control cavity.

The inner hole of the first annular body 101 forms an inlet for the plasma to enter the flow control chamber. The annular connector 103 is provided with an outlet 103b for the plasma to flow out of the flow control chamber. In conjunction with FIG. 2, the annular connector 103 is a split structure, including a plurality of connecting columns 103a, each connecting column 103a is arranged in sequence around the straight line A, and the outlet 103b is formed between adjacent connecting columns 103a. Of course, the annular connector 103 can also be set as an integrated structure.

The first annular body 101 is close to the air inlet 202a of the plasma reaction chamber 200, and the second annular body 102 is close to the wafer support platform 301. The wafer placement area of the wafer support platform 301 is located within the projection area of the inner hole of the first annular body 101 on the wafer support platform 301, and is also located within the projection area of the inner hole of the second annular body 102 on the wafer support platform 301.

When the plasma etching machine is working, the gas flow first enters the plasma reaction chamber 200 from the gas inlet 202a. Since the first annular body 101 is arranged close to the gas inlet 202a of the plasma reaction chamber 200, most of the gas flow enters the flow control chamber from the inner hole of the first annular body 101. The plasma in the gas flow passes through the inner hole of the second annular body 102 and falls on the wafer to etch the wafer. Then this part of the gas flow is discharged from the flow control chamber through the outlet 103b of the annular connector 103, and then discharged from the exhaust port 201a of the plasma reaction chamber 200.

Since the wafer placement area of the wafer support platform 301 is located within the projection area of the inner hole of the first annular body 101 on the wafer support platform 301 and the inner hole of the second annular body 102 is within the projection area of the wafer support platform 301, the inner hole of the first annular body 101 can concentrate the airflow more densely in the area facing the wafer, and the plasma in the concentrated airflow can fall on the wafer, and the wafer is etched at a high density. At the same time, under the blocking effect of the cavity wall of the flow control cavity, the plasma will stay on the wafer for a longer time, so that it can fully participate in the etching, thereby improving the etching uniformity and alleviating the problem of airflow being directly sucked away by the pump and causing waste.

As shown in Figure 3, Figure 3 is a comparison diagram of the airflow distribution before and after the plasma etching machine adopts the plasma flow control device. It can be seen from the figure that after adopting the above-mentioned plasma flow control device, the airflow distribution is more concentrated, and the airflow can flow to the wafer more concentratedly.

Specifically, there is a gap between the outer periphery of the first annular body 101 and the outer periphery of the second annular body 102 and the side wall of the chamber 201 of the plasma reaction chamber 200 or the side wall of the inner liner 203 of the plasma reaction chamber 200. That is, when the plasma reaction chamber is not provided with the inner liner 203, the gap is formed between the outer periphery of the first annular body 101 and the outer periphery of the second annular body 102 and the side wall of the chamber 201 of the plasma reaction chamber 200; when the plasma reaction chamber 200 is provided with the inner liner 203, the gap is formed between the outer periphery of the first annular body 101 and the outer periphery of the second annular body 102 and the side wall of the inner liner 203 of the plasma reaction chamber 200.

In the illustrated embodiment, the plasma reaction chamber 200 is provided with an inner liner 203, which is embedded in the cavity 201 of the plasma reaction chamber 200. The bottom wall of the inner liner 203 divides the cavity 201 of the plasma reaction chamber 200 into two upper and lower chambers. The upper chamber and the lower chamber are connected through a through hole (not shown in the figure) on the bottom wall of the inner liner 203.

There is a gap between the outer periphery of the first annular body 101 and the outer periphery of the second annular body 102 and the side wall of the chamber 201 of the plasma reaction chamber 200 or the side wall of the inner liner 203 of the plasma reaction chamber 200. During the etching process, particles can fall from the gap, which can avoid particle accumulation and help improve etching uniformity.

Specifically, the outer circumference of the second annular body 102 is smaller than the outer circumference of the first annular body 101. In this way, when the gas flows out from the outlet 103b of the annular connector 103, it can smoothly pass through the gap between the first annular body 101 and the side wall of the chamber 201 of the plasma reaction chamber 200 or the side wall of the inner liner 203 of the plasma reaction chamber 200 to flow to the exhaust port 201a, so that the exhaust resistance is small and the exhaust is smooth, which is more conducive to improving the etching uniformity.

Specifically, the plasma etcher using the above plasma flow control device can optimize the uniformity of the plasma etcher by adjusting the inner hole size of the first annular body 101, and/or adjusting the outer peripheral size of the second annular body 102, and/or adjusting the height size of the annular connector 103 (i.e. the size along the straight line A) under different process conditions.

Adjusting the inner hole size of the first annular body 101 can change the degree of airflow concentration of the plasma flow control device. Adjusting the outer peripheral size of the second annular body 102 can change the residence time of the airflow in the flow control cavity of the plasma flow control device. Adjusting the height size of the annular connector 103 can change the speed at which the airflow tends to be discharged from the flow control cavity. The degree of concentration, residence time and airflow discharge speed can all affect the etching uniformity.

Continue to refer to Figure 1. The plasma etcher also includes a bias electrode 401, a bias electrode cover 402, a bias RF power supply 403, and a bias matching network 404. The bias electrode 401, the bias matching network 404, and the bias RF power supply 403 are sequentially connected through wires, and the bias electrode 401 provides the bias required for etching.

In the illustrated embodiment, the middle of the bottom wall of the cavity 201 of the plasma reaction chamber 200 bulges into the cavity to form a cylindrical support portion 201b, and the bias electrode 401 is supported by the cylindrical support portion 201b. The wire passes through the inside of the cylindrical support portion 201b and is connected to the external bias RF power supply 403 and the bias matching network 404. The cylindrical support portion 201b plays a supporting role on the one hand, and plays a guiding role on the other hand, guiding the airflow to the exhaust port 201a on the bottom wall of the cavity 201.

The bias electrode cover 402 is fixed inside the plasma reaction chamber 200 and covers the bias electrode 401. In the illustrated embodiment, the second annular body 102 is supported and fixed on the bias electrode cover 402. Specifically, the middle part of the second annular body 102 bulges into the flow control chamber to form a bulge, so that a groove is formed corresponding to the side surface of the second annular body 102 away from the first annular body 101, and the top of the bias electrode cover 402 is fixedly sleeved through the groove. The bulge is provided to facilitate the fixation of the second annular body 102 and the bias electrode cover 402, and at the same time, the bulge can play a role in blocking the flow, which is conducive to prolonging the residence time of the plasma on the wafer. In other embodiments, the second annular body 102 may also be supported and fixed to the inner liner 203 of the plasma reaction chamber.

In addition, a step is provided on the top surface of the bias electrode cover 402 to support and limit the wafer focusing ring 303.

The plasma etching machine also includes a flow shroud 501, a pressure control valve 502 and a vacuum pump 503. The inlet of the flow shroud 501 is connected to the exhaust port 201a of the plasma reaction chamber 200, the outlet of the flow shroud 501 is connected to the pressure control valve 502, and the pressure control valve 502 is connected to the vacuum pump 503. The vacuum pump 503 provides the negative pressure required for etching, and the pressure control valve 502 regulates the pressure.

The plasma etching machine also includes a shielding cover 600. The shielding cover 600 is fixed outside the plasma reaction chamber 200 and covers the air inlet 202a of the plasma reaction chamber 200. The shielding cover 600 and the plasma reaction chamber 200 enclose a shielding chamber.

The plasma etching machine also includes a coupling coil 701, an excitation source radio frequency power supply 702, and an excitation source matching network 703. The coupling coil 701, the excitation source matching network 703, and the excitation source radio frequency power supply 702 are sequentially connected through wires. The coupling coil 701 is arranged in a shielded chamber.

The plasma etching machine also includes a ceramic dielectric window 800, a nozzle 901 and a gas source 902. The ceramic dielectric window 800 is arranged in the shielding chamber and is located between the coupling coil 701 and the gas inlet 202a of the plasma reaction chamber 200. The nozzle 901 is penetrated through the ceramic dielectric window 800 and is connected to the gas source 902 to inject process gas into the plasma reaction chamber. The process gas generates plasma under the action of the coupling coil 701.

In summary, the core idea of the present invention is to set a plasma flow control device inside the plasma reaction chamber of the plasma etcher, and by designing the structure and layout of the plasma flow control device, the effects of improving the etching uniformity of the plasma etcher and alleviating the gas flow are achieved.

The above examples are used to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. It should be pointed out that without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

101: The first ring

102: Second Ring

103: Ring connector

200: Plasma reaction chamber

201a: Exhaust port

201b: Cylindrical support part

201: Cavity

202a: Air intake

202: Cavity cover

203: Lining

301: Wafer support platform

302: Wafer

303: Wafer focusing ring

401: Bias electrode

402: Bias electrode cover

403: Biased RF power supply

404: Bias matching network

501: fairing

502: Pressure control valve

503: Vacuum pump

600: Shielding cover

701: Coupled coil

702: Excitation source RF power supply

703: Excitation source matching network

800: Ceramic dielectric window

901: Nozzle

902: Air source

A: Straight line

Claims (20)

A plasma flow control device is arranged inside a plasma reaction chamber of a plasma etcher, wherein the plasma flow control device comprises a first annular body, a second annular body and an annular connecting body; the first annular body, the second annular body and the annular connecting body are arranged around a straight line (A); the first annular body and the second annular body are spaced apart from each other along the straight line (A), and a space is formed between them; the annular The connector is located in the space and connects the first annular body and the second annular body, and together with the first annular body and the second annular body, forms a flow control cavity; the inner hole of the first annular body forms an inlet for the plasma entering the plasma reaction cavity from the air inlet of the plasma reaction cavity to enter the flow control cavity, and the annular connector is provided with an outlet for the plasma to flow out of the flow control cavity. A plasma flow control device as described in claim 1, wherein the outer circumference of the second annular body is smaller than the outer circumference of the first annular body. The plasma flow control device as described in claim 1, wherein the first annular body and the second annular body are both plate-shaped structures. The plasma flow control device as described in claim 1, wherein the annular connector includes a plurality of connecting posts, each of which is arranged in sequence and at intervals around the straight line (A), and the outlet is formed between adjacent connecting posts. The plasma flow control device as described in claim 1, wherein the annular connector is an integrated structure. A plasma etching machine, comprising a plasma current control device as described in any one of claims 1 to 5. The plasma etching machine as described in claim 6, wherein the plasma etching machine further comprises a plasma reaction chamber and a wafer support platform, the wafer support platform is located between the air inlet and the air outlet of the plasma reaction chamber, and the plasma flow control device is located between the air inlet of the plasma reaction chamber and the wafer support platform. A plasma etching machine as described in claim 7, wherein the first annular body of the plasma flow control device is close to the air inlet, and the second annular body is close to the wafer support platform. A plasma etching machine as described in claim 8, wherein the wafer placement area of the wafer support table is located within the projection area of the inner hole of the first annular body on the wafer support table, and is also located within the projection area of the inner hole of the second annular body on the wafer support table. The plasma etching machine as described in claim 8, wherein there is a gap between the outer periphery of the first annular body and the outer periphery of the second annular body and the side wall of the plasma reaction chamber or the inner lining side wall of the plasma reaction chamber. The plasma etcher as described in claim 10, wherein the plasma etcher further comprises a bias electrode and a bias electrode cover, the bias electrode cover is fixed inside the plasma reaction chamber and covers the bias electrode, and the second annular body is supported and fixed on the bias electrode cover or supported and fixed on the inner lining of the plasma reaction chamber. The plasma etching machine as described in claim 11, wherein the inner liner is embedded in the cavity of the plasma reaction chamber, and the bottom wall of the inner liner divides the cavity of the plasma reaction chamber into two upper and lower chambers, and the upper chamber and the lower chamber are connected through the through hole on the bottom wall of the inner liner. The plasma etching machine as described in claim 11, wherein a step is also provided on the top surface of the bias electrode cover for supporting and limiting the wafer focusing ring. The plasma etcher as described in claim 11, wherein the middle of the bottom wall of the plasma reaction chamber bulges into the chamber to form a cylindrical support portion, the bias electrode is supported by the cylindrical support portion, and the wire passes through the inside of the cylindrical support portion and is connected to the external bias RF power supply and bias matching network. The plasma etching machine as described in claim 7, wherein the plasma reaction chamber has a chamber body and a chamber cover, the bottom wall of the chamber body is provided with an exhaust port, and the chamber cover is provided with an air inlet. The plasma etching machine as described in claim 11, wherein the plasma etching machine further comprises a flow shroud, a pressure control valve and a vacuum pump, the inlet of the flow shroud is connected to the exhaust port of the plasma reaction chamber, the outlet of the flow shroud is connected to the pressure control valve, and the pressure control valve is connected to the vacuum pump. The plasma etcher as described in claim 16, wherein the plasma etcher further comprises a shielding cover fixed outside the plasma reaction chamber, the shielding cover and the plasma reaction chamber enclose a shielding chamber; the plasma etcher further comprises a coupling coil disposed in the shielding chamber. The plasma etching machine as described in claim 17, wherein the plasma etching machine further includes an excitation source radio frequency power supply, an excitation source matching network, and the coupling coil, the excitation source matching network and the excitation source radio frequency power supply are sequentially connected through wires. The plasma etching machine as described in claim 17, further comprising a ceramic dielectric window, a nozzle and a gas source, wherein the ceramic dielectric window is arranged in the shielding chamber and is located between the coupling coil and the gas inlet of the plasma reaction chamber, and the nozzle is penetrated through the ceramic dielectric window and connected to the gas source, and is used to inject process gas into the interior of the plasma reaction chamber. A method for optimizing the uniformity of a plasma etching machine as described in any one of claims 6 to 19, characterized in that the etching uniformity of the plasma etching machine is optimized by adjusting the inner hole size of the first annular body of the plasma flow control device, and/or adjusting the outer circumference size of the second annular body of the plasma flow control device, and/or adjusting the height size of the annular connector of the plasma flow control device.

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