CN107295738B

CN107295738B - Plasma processing device

Info

Publication number: CN107295738B
Application number: CN201610221384.9A
Authority: CN
Inventors: 卫晶; 韦刚; 成晓阳; 昌锡江
Original assignee: Beijing Naura Microelectronics Equipment Co Ltd
Current assignee: Beijing Naura Microelectronics Equipment Co Ltd
Priority date: 2016-04-11
Filing date: 2016-04-11
Publication date: 2020-02-14
Anticipated expiration: 2036-04-11
Also published as: CN107295738A

Abstract

The invention provides a plasma processing apparatus. The plasma processing device comprises a cavity and a radio frequency power supply, wherein the cavity is grounded, an inner bushing is arranged on the inner side of the cavity and connected with the cavity, the radio frequency power supply is used for applying radio frequency power to the inside of the cavity so as to perform plasma processing, the radio frequency power forms a radio frequency path through the plasma and the grounded cavity, and the plasma processing device also comprises a grounding impedance adjusting unit, and the grounding impedance adjusting unit is connected between the inner bushing and the cavity in series or connected between the cavity and the ground in series and used for adjusting the grounding impedance of the radio frequency path. The plasma processing device can adjust the grounding impedance of the radio frequency path, so that the grounding impedance of the radio frequency path can reach the minimum value, the loss of radio frequency power is reduced, high-frequency interference electromagnetic waves introduced into the cavity are avoided, the effective utilization of the radio frequency power is realized, and the anti-interference performance of the cavity and the stability of a plasma state are further improved.

Description

Plasma processing device

Technical Field

The invention relates to the technical field of plasma processing, in particular to a plasma processing device.

Background

Plasma is widely used in the production process of semiconductor devices. In a plasma processing system, a radio frequency power supply transmits radio frequency energy to a reaction cavity through a matching device, the radio frequency energy excites gas with certain air pressure into plasma in the reaction cavity, the excited plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules, free radicals and the like, and the active particles interact with a wafer which is placed in a cavity and exposed to the plasma environment, so that various physical and chemical reactions occur on the surface of a wafer material, the surface performance of the material is changed, and the etching or other technological processes of the wafer are completed.

The plasma equipment widely used at present is an inductively coupled plasma generator (ICP). In an Inductively Coupled Plasma (ICP) generating device, radio frequency power ionizes a gas through an inductive coupling coil to form a plasma. The method can obtain high-density plasma under lower working pressure, and has simple structure and low cost. The rf source generating the plasma (determining the plasma density) can be controlled independently of the substrate table rf source (determining the direction and energy of the particles incident on the wafer) at the same time.

A conventional inductively coupled plasma apparatus is shown in fig. 1, wherein an upper rf power supply 13 applies power to an outer ring and an inner ring of an inductively coupled coil 8 through a first matching unit 6 and a current distribution unit 7, a process gas enters a reaction chamber 1 through a nozzle 10 installed on a quartz dielectric window 9 (a liner in the reaction chamber 1 is not shown), and simultaneously rf energy on the inductively coupled coil 8 is coupled into the chamber 1 through the dielectric window 9 to generate a plasma 14, which acts on a wafer 15, the wafer 15 is placed on an upper portion of an electrostatic chuck 16, and a lower rf power supply 17 applies rf energy to the electrostatic chuck 16 through a second matching unit 12, thereby processing the wafer 15.

Fig. 2 is a simplified side sectional view of the plasma generating chamber shown in fig. 1, in which the focus ring 18 is disposed at the upper edge of the electrostatic chuck 16, the upper flange and the side edge of the liner 111 of the chamber 1 are both in contact with the cavity 110 of the chamber 1, the cavity 110 is grounded, and plays an important role as an rf ground in the plasma generating circuit, and the liner 111 can confine the plasma 14 and protect the inner wall and the bottom of the chamber 1 from being etched. When the upper rf power and the lower rf power are loaded simultaneously, a plasma 14 is generated inside the chamber 1, two rf paths formed by the upper rf power and the lower rf power through the plasma 14 are marked in fig. 2, a first arrow 19 indicates that the upper rf power is loaded to the inductive coupling coil 8 and then coupled to the chamber 1 through the quartz dielectric window 9 to generate the plasma 14, and then grounded through the plasma 14 and the liner 111 to form the upper rf path, and a second arrow 20 indicates that the lower rf power is loaded to the lower electrode (the electrostatic chuck 16) and then grounded through the plasma 14 and the liner 111 in a capacitive coupling manner to form the lower rf path.

The liner 111 and cavity of FIG. 2The chamber body 110 of the chamber 1 is connected, and the chamber body 110 is grounded and serves as an important rf ground in the upper and lower rf paths. The ideal rf path generally requires zero ground impedance, which should be as small as possible in practical application, and the above-mentioned manner of grounding the liner in the plasma chamber introduces an additional grounding capacitor C, i.e. a sheath space charge region is generated between the plasma 14 and the liner 111, and the sheath region forms a potential difference, which can be equivalent to a capacitor C as shown in fig. 3 and 4, thereby introducing an impedance value

The value of the ground impedance is non-zero. Due to the existence of the radio frequency grounding impedance value, corresponding power loss exists when radio frequency power finally passes through a radio frequency ground in the practical application process, and other high-frequency electromagnetic wave interference may be introduced due to the existence of the capacitor C, so that the stability and the state of plasma in the chamber are influenced.

Disclosure of Invention

The present invention is directed to solving the above-mentioned problems of the prior art and provides a plasma processing apparatus. The plasma processing device can adjust the ground impedance of the radio frequency path, so that the ground impedance of the radio frequency path can reach the minimum value under various different plasma processing process conditions, the loss of radio frequency power is reduced, high-frequency interference electromagnetic waves are prevented from being introduced into the cavity, the radio frequency power is effectively utilized, and the anti-interference performance of the cavity and the stability of a plasma state are further improved.

The invention provides a plasma processing device, which comprises a cavity, a liner and a radio frequency power supply, wherein the cavity is grounded, the liner is sleeved on the inner side of the cavity and is connected with the cavity, the radio frequency power supply is used for applying radio frequency power to the cavity to perform plasma processing, the radio frequency power forms a radio frequency path with the grounded cavity through the plasma, and the plasma processing device also comprises a ground impedance adjusting unit, and the ground impedance adjusting unit is connected in series between the liner and the cavity, or is connected in series between the cavity and the ground to adjust the ground impedance of the radio frequency path.

Preferably, the ground impedance adjusting unit includes at least one variable inductor.

Preferably, the ground impedance adjusting unit includes at least one fixed inductor.

Preferably, a total inductance value of the ground impedance adjusting unit

Wherein f is the frequency of the RF power source, and c is the capacitance of an equivalent capacitor formed between the plasma and the liner.

Preferably, the variable inductor comprises a telescopic inductor coil and an adjusting rod, and the axial length of the telescopic inductor coil is adjusted through the adjusting rod, so that the inductance value of the variable inductor is adjusted.

Preferably, the ground impedance adjusting unit is connected in series with the inside lining with between the cavity, scalable inductance coils's both ends are connected respectively the inside lining with the cavity, adjust the pole both ends respectively with the inside lining with cavity swing joint, it can adjust to adjust the inside lining with interval between the cavity, so that scalable inductance coils's axial length along with the inside lining with the change of interval between the cavity changes.

Preferably, the variable inductance includes 5 to 10.

Preferably, the rf power supply comprises a first rf power supply and a second rf power supply, the first rf power supply being configured to generate the plasma within the chamber; the second RF power source is configured to attract the plasma within the chamber.

Preferably, the frequency of the radio frequency power source comprises 400KHz, 2MHz, 13MHz, 27MHz, 40MHz or 60 MHz.

Preferably, the plasma processing apparatus is an inductively coupled plasma processing apparatus or a capacitively coupled plasma processing apparatus.

The invention has the beneficial effects that: the plasma processing device provided by the invention can adjust the grounding impedance of the radio frequency path by arranging the grounding impedance adjusting unit, so that the grounding impedance of the radio frequency path can reach the minimum value under various different plasma processing process conditions, thereby reducing the loss of radio frequency power, avoiding introducing high-frequency interference electromagnetic waves into the cavity, further realizing the effective utilization of the radio frequency power, and further improving the anti-interference performance of the cavity and the stability of the plasma state.

Drawings

FIG. 1 is a schematic diagram of an inductively coupled plasma device according to the prior art;

FIG. 2 is a sectional view of the plasma generation chamber of FIG. 1;

FIG. 3 is a graph of a plasma sheath region potential profile in the plasma apparatus of FIG. 1;

FIG. 4 is an equivalent circuit diagram of the plasma sheath region of FIG. 1;

FIG. 5 is a schematic view showing the structure of a plasma processing apparatus according to embodiment 1 of the present invention;

fig. 6 is a schematic structural diagram of an inductive series branch in the ground impedance adjusting unit in fig. 5;

fig. 7 is an equivalent circuit diagram of the ground impedances of the first rf path and the second rf path in embodiment 1 of the present invention;

fig. 8 is a schematic structural diagram of a variable inductor in embodiment 2 of the present invention;

fig. 9 is a schematic structural view of a plasma processing apparatus according to embodiment 3 of the present invention.

Wherein the reference numbers indicate:

1. a chamber; 11. an inductor series branch circuit; 110. a cavity; 111. a liner; 2. a radio frequency power supply; 21. a first radio frequency power supply; 22. a second radio frequency power supply; 3. a ground impedance adjusting unit; 31. a retractable inductance coil; 32. adjusting a rod; 4. a substrate; 5. a base station; 6. a first matcher; 7. a current distribution unit; 8. an inductive coupling coil; 9. a dielectric window; 10. a nozzle; 12. a second matcher; 13. an upper radio frequency power supply; 14. plasma; 15. a wafer; 16. an electrostatic chuck; 17. a lower radio frequency power supply; 18. a focus ring; 19. a first arrow; 20. a second arrow; l, fixing the inductor; C. a capacitor; h. the axial length of the stretchable inductor coil.

Detailed Description

In order to make the technical solution of the present invention better understood, a plasma processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings and the detailed description.

Example 1:

the embodiment provides a plasma processing apparatus, as shown in fig. 5, which includes a cavity 110 and a radio frequency power supply 2, the cavity 110 is grounded, a liner 111 is sleeved inside the cavity 110 and connected to the cavity 110, the radio frequency power supply 2 is configured to apply radio frequency power to the cavity 110 for plasma processing, the radio frequency power forms a radio frequency path with the grounded cavity 110 through a plasma 14, and the plasma processing apparatus further includes a ground impedance adjusting unit 3, and the ground impedance adjusting unit 3 is connected in series between the liner 111 and the cavity 110 and is configured to adjust ground impedance of the radio frequency path.

By arranging the grounding impedance adjusting unit 3, the grounding impedance of the radio frequency path can be adjusted, so that the grounding impedance of the radio frequency path can reach the minimum value under various different plasma processing process conditions, the loss of radio frequency power is reduced, high-frequency interference electromagnetic waves are prevented from being introduced into the cavity 110, the effective utilization of the radio frequency power is realized, and the anti-interference performance of the cavity 110 and the stability of the state of the plasma 14 are further improved.

In this embodiment, the rf power source 2 includes a first rf power source 21 and a second rf power source 22, and the first rf power source 21 is disposed above the cavity 110 and is configured to apply rf power to the inside of the cavity 110, so as to generate the plasma 14 in the cavity 110. In this embodiment, the first rf power source 21 loads power to the inductive coupling coil 8 through the first matcher 6 and the current distribution unit 7, the process gas enters the cavity 110 through the nozzle 10 installed on the quartz dielectric window 9, and meanwhile, the rf energy on the inductive coupling coil 8 is coupled into the cavity 110 through the dielectric window 9, so that the process gas entering the cavity 110 is ionized to form the plasma 14, which can obtain the high-density plasma 14 at a lower working pressure, and the plasma 14 acts on the substrate 4 placed on the base 5. The rf power output by the first rf power source 21 passes through the plasma 14 in the chamber 110 and is grounded to the chamber 110 to form a first rf path. The second rf power source 22 is disposed below the chamber 110, and is configured to apply rf power to a base stage 5, which is located inside the chamber 110 and supports a substrate 4 to be processed. In this embodiment, the second rf power source 22 loads rf energy to the base station 5 through the second matcher 12, and the second rf power source 22 can generate a negative bias voltage on the base station 5 to attract the plasma 14 in the cavity 110, so that the plasma 14 in the cavity 110 can perform a good processing on the substrate 4. The rf power output by the second rf power source 22 passes through the plasma 14 in the chamber 110 and is grounded to the chamber 110 to form a second rf path.

In the plasma processing apparatus, only one of the first rf power supply 21 and the second rf power supply 22 may be provided.

In this embodiment, the ground impedance adjusting unit 3 includes at least one fixed inductor L, in this embodiment, the fixed inductors L are plural, the plural fixed inductors L are respectively connected in series in plural different inductor series branches, as shown in fig. 5, the inductor series branches are provided with six inductor series branches, the six inductor series branches are respectively connected in series at different positions between the cavity 110 and the substrate 111, and the six inductor series branches are connected in parallel with each other. Fig. 6 shows a series connection structure of a plurality of fixed inductors (e.g., L1, L2 … … Ln) in each inductor series branch. After the ground impedance adjusting unit 3 is connected, the equivalent circuit of the ground impedance of the first rf path and the second rf path is as shown in fig. 7, a capacitor C in fig. 7 is an equivalent capacitor of a sheath space charge region formed between the plasma 14 and the liner 111 in the cavity 110, and the ground impedance adjusting unit 3 is connected in series with the capacitor C to form a series resonant circuit. The series resonant circuit has a ground impedance value of

The ground impedance is adjusted by adjusting the number of fixed inductors L connected to the ground impedance adjusting unit 3The total inductance value of the adjusting unit 3 is obtained by deriving the formula (1) so that the ground impedance of the series resonant circuit is zero when the total inductance value of the adjusting unit 3 is

In the equation (2), f is the frequency of the rf power source 2, and c is the capacitance of the equivalent capacitor formed between the plasma 14 and the liner 111.

The number of fixed inductors L in each inductor series branch is determined by the size of the sheath capacitance formed between the plasma 14 and the liner 111 at the location of connection. Of course, a fixed inductor L may be connected between the chamber 110 and the liner 111, and the ground impedance formed between the plasma 14 and the liner 111 may be adjusted by the fixed inductor L, so that the ground impedance between the plasma 14 and the liner 111 is zero.

In this embodiment, preferably, the number of the inductance series branches in the ground impedance adjusting unit 3 is 5 to 10. By connecting a plurality of fixed inductors L in series in a plurality of inductor series branches, the total inductance value of the ground impedance adjusting unit 3 is finally made to beAnd (4) finishing.

It should be noted that the number of the inductors in this embodiment needs to be determined according to different process conditions of the plasma processing process, and since the state and the flux of the plasma 14 are different under different process conditions, the voltage of the formed sheath space charge region is also different, and the equivalent capacitance value C is also different, so that under different plasma process conditions, the total inductance value of the ground impedance adjusting unit 3 needs to be adjusted accordingly, that is, the number of the fixed inductors L is adjusted, so that the ground impedance value of the series resonant circuit formed by the equivalent capacitance C and the total inductor L is minimized (e.g., zero).

In this embodiment, the frequency of the rf power source 2 may be any frequency such as 400KHz, 2MHz, 13MHz, 27MHz, 40MHz, or 60 MHz.

In this embodiment, the plasma processing apparatus is an inductively coupled plasma processing apparatus or a capacitively coupled plasma processing apparatus.

Example 2:

the present embodiment provides a plasma processing apparatus, which is different from embodiment 1 in that the ground impedance adjusting unit includes at least one variable inductor, and an inductance value of the variable inductor can be adjusted and varied.

In this embodiment, the variable inductor includes a plurality of inductors. Preferably, the variable inductance comprises 5-10. A plurality of variable inductances are respectively connected between the cavity and the lining, and the variable inductances are connected in parallel with each other. It should be noted that, an inductance series branch may also be formed after a plurality of variable inductances are connected in series, and the inductance series branch is connected between the cavity and the liner; a plurality of inductance series branches can be connected between the cavity and the lining, and the inductance series branches are connected in parallel with each other.

It should be noted that the inductance of each variable inductor or the inductance of each inductor series branch is determined according to the size of the sheath capacitor formed between the plasma and the liner at the location where the variable inductor is connected. Of course, a variable inductor may be connected between the chamber and the liner, and the ground impedance formed between the plasma and the liner may be adjusted by the variable inductor so that the ground impedance between the plasma and the liner is zero.

As shown in fig. 8, the variable inductor includes a stretchable inductor coil 31 and an adjustment rod 32, and the adjustment rod 32 adjusts the axial length h of the stretchable inductor coil 31, thereby adjusting the inductance value of the variable inductor. In this embodiment, the ground impedance adjusting unit 3 is connected in series between the liner 111 and the cavity 110, two ends of the scalable inductance coil 31 are respectively connected to the liner 111 and the cavity 110, two ends of the adjusting rod 32 are respectively movably connected to the liner 111 and the cavity 110, and the adjusting rod 32 can adjust the distance between the liner 111 and the cavity 110, so that the axial length h of the scalable inductance coil 31 changes along with the change of the distance between the liner 111 and the cavity 110.

The formula for calculating the inductance of the retractable inductor 31 is:

where μ 0 is a vacuum permeability, μ S is a relative permeability of the magnetic core inside the stretchable inductance coil 31, μ S is 1 in the case of an air-core coil, n is a number of turns of the coil, S represents a sectional area of the coil, h is an axial length of the coil, and the coefficient k depends on a ratio of a radius R of the coil to the axial length h.

As the calculation formula of the inductance value of the stretchable inductor coil 31 shows that the inductance value L decreases when the axial length h of the stretchable inductor coil 31 increases, and increases when the axial length h of the stretchable inductor coil 31 decreases, the adjustment of the inductance value of the variable inductor can be realized by adjusting the axial length h of the stretchable inductor coil 31 through the adjusting rod 32, so that the minimum ground impedance value of the series resonance circuit formed by the capacitance and the variable inductor formed between the plasma and the liner 111 is finally realized.

In this embodiment, the adjusting rod 32 is a locking screw, one end of the locking screw is in threaded connection with the inner liner 111, a threaded hole is formed in the cavity 110 at a position corresponding to the other end of the locking screw, and when the other end of the locking screw is adjusted by using torque to enter the threaded hole, the distance between the inner liner 111 and the cavity 110 changes correspondingly, so that the telescopic inductor coil 31 is compressed or stretched, the axial length h of the telescopic inductor coil 31 is further reduced or increased, and then the adjustment of the inductance value of the variable inductor is realized; after the adjusting is proper, one end of the locking screw is locked through the locking nut, and then the locking screw can be fixed.

It should be noted that the adjustment of the inductance value of the variable inductor may also be performed by adjusting the cross-sectional area of the coil or the number of turns of the coil in the formula (3), and is not limited to the adjustment method in the present embodiment.

Other structures and arrangements of the plasma processing apparatus in this embodiment are the same as those in embodiment 1, and are not described herein again.

Example 3:

the present embodiment provides a plasma processing apparatus, which is different from embodiments 1-2 in that, as shown in fig. 9, a ground impedance adjusting unit 3 is connected in series between a chamber 110 and ground.

In this embodiment, the cavity 110 is grounded through the copper braided strap, and the ground impedance adjusting unit 3 is connected between the cavity 110 and the copper braided strap. The adjustment of the ground impedance of the radio frequency path can also be achieved by connecting the ground impedance adjusting unit 3 in series between the cavity 110 and the copper braided strap.

Other structures and arrangements of the plasma processing apparatus in this embodiment are the same as those in any of embodiments 1-2, and are not described herein again.

Beneficial effects of examples 1-3: the plasma processing apparatus provided in embodiments 1 to 3 can adjust the ground impedance of the rf path by providing the ground impedance adjusting unit, so that the ground impedance of the rf path can reach a minimum value under various different plasma processing conditions, thereby reducing the loss of the rf power, and simultaneously avoiding introducing high-frequency interference electromagnetic waves into the cavity, thereby achieving effective utilization of the rf power, and further improving the anti-interference performance of the cavity and the stability of the plasma state.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. The utility model provides a plasma processing apparatus, includes cavity, inside lining and radio frequency power supply, the cavity ground connection, the inside lining cover is established the cavity is inboard, and with the cavity is connected, radio frequency power supply be used for to apply radio frequency power in the cavity to carry out plasma treatment, radio frequency power passes through plasma and ground connection the cavity forms the radio frequency access, its characterized in that still includes ground connection impedance adjusting element, ground connection impedance adjusting element series connection in the inside lining with between the cavity, be used for adjusting the ground connection impedance of radio frequency access.

2. The plasma processing apparatus of claim 1, wherein the ground impedance adjustment unit comprises at least one variable inductance.

3. The plasma processing apparatus of claim 1, wherein the ground impedance adjustment unit comprises at least one fixed inductor.

4. The plasma processing apparatus according to claim 2 or 3, wherein a total inductance value of the ground impedance adjusting unit

5. The plasma processing apparatus of claim 2, wherein the variable inductor comprises a stretchable inductor coil and an adjustment rod, and an axial length of the stretchable inductor coil is adjusted by the adjustment rod, thereby adjusting an inductance value of the variable inductor.

6. The plasma processing apparatus of claim 5, wherein the ground impedance adjusting unit is connected in series between the liner and the cavity, two ends of the scalable inductance coil are respectively connected with the liner and the cavity, two ends of the adjusting rod are respectively movably connected with the liner and the cavity, and the adjusting rod can adjust a distance between the liner and the cavity, so that an axial length of the scalable inductance coil changes along with a change of the distance between the liner and the cavity.

7. The plasma processing apparatus of claim 2, wherein the variable inductance comprises 5-10.

8. The plasma processing apparatus of claim 1 wherein the rf power supply comprises a first rf power supply and a second rf power supply, the first rf power supply being configured to generate the plasma within the chamber; the second RF power source is configured to attract the plasma within the chamber.

9. The plasma processing apparatus of claim 1, wherein the frequency of the radio frequency power source comprises 400KHz, 2MHz, 13MHz, 27MHz, 40MHz, or 60 MHz.

10. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is an inductively coupled plasma processing apparatus or a capacitively coupled plasma processing apparatus.