阅读说明：本技术 等离子体处理装置和等离子体处理方法 (Plasma processing apparatus and plasma processing method ) 是由 池田太郎 久保敦史 镰田英纪 山本伸彦 于 2020-09-04 设计创作，主要内容包括：本发明提供一种等离子体处理装置和等离子体处理方法,在基板的背面进行局部的成膜。该等离子体处理装置具有：处理容器；基板保持机构,其配置于所述处理容器内,并保持基板；电介质窗,其配置于所述基板保持机构的下方；以及相控阵天线,其配置于所述电介质窗的下方,并放射多个电磁波。(The invention provides a plasma processing apparatus and a plasma processing method, which can perform local film formation on the back surface of a substrate. The plasma processing apparatus includes: a processing vessel; a substrate holding mechanism which is disposed in the processing container and holds a substrate; a dielectric window disposed below the substrate holding mechanism; and a phased array antenna which is disposed below the dielectric window and radiates a plurality of electromagnetic waves.)

1. A plasma processing apparatus includes:

a processing vessel;

a substrate holding mechanism which is disposed in the processing container and holds a substrate;

a dielectric window disposed below the substrate holding mechanism; and

and a phased array antenna which is disposed below the dielectric window and radiates a plurality of electromagnetic waves.

2. The plasma processing apparatus according to claim 1,

the substrate holding mechanism further includes a sensor for measuring a degree of curvature of the substrate held by the substrate holding mechanism.

3. The plasma processing apparatus according to claim 2,

the phase control device further includes a control unit that controls the phases of the plurality of electromagnetic waves radiated from the phased array antenna based on the degree of curvature of the substrate measured by the sensor.

4. The plasma processing apparatus according to claim 3,

further comprising a gas supply unit for supplying a gas to a space between the dielectric window and the substrate in which plasma is generated,

the control unit controls the film formation on the back surface of the substrate according to the degree of curvature of the substrate by plasma generated from the gas in the space.

5. The plasma processing apparatus according to claim 4,

the control unit controls the back surface of the substrate to form a film by changing the phase of the electromagnetic waves in accordance with time.

6. The plasma processing apparatus according to any one of claims 1 to 5,

the substrate holding mechanism is connected with the driving mechanism,

the substrate holding mechanism is movable in the vertical direction in the processing container by the driving mechanism.

7. The plasma processing apparatus according to any one of claims 1 to 6,

the perpendicular distance from the phased array antenna to the dielectric window is greater than λ/4 relative to the wavelength λ of the electromagnetic wave.

8. The plasma processing apparatus according to any one of claims 1 to 7,

the phased array antennas each have a monopole antenna.

9. The plasma processing apparatus according to any one of claims 1 to 8,

a distance from a center of the phased array antenna to a center of an adjacent phased array antenna with respect to a wavelength λ of the electromagnetic wave is less than λ/2.

10. The plasma processing apparatus according to any one of claims 1 to 9,

the frequency of the plurality of electromagnetic waves is 100MHz or more.

11. The plasma processing apparatus according to claim 10,

the frequency of the electromagnetic waves is 1 GHz-3 GHz.

12. A plasma processing method performed by a plasma processing apparatus having a processing container, a substrate holding mechanism arranged in the processing container and holding a substrate, a dielectric window arranged below the substrate holding mechanism, and a phased array antenna arranged below the dielectric window and radiating a plurality of electromagnetic waves, the plasma processing method comprising:

holding a substrate to the substrate holding mechanism;

controlling phases of a plurality of the electromagnetic waves radiated from the phased array antenna;

radiating each of the plurality of electromagnetic waves whose phases are controlled from the corresponding phased array antenna into the processing container;

supplying a gas to a plasma-generating space between the dielectric window and the substrate; and

and forming a film on the back surface of the substrate based on information indicating a degree of curvature of the substrate by the plasma generated in the space.

13. The plasma processing method according to claim 12,

the information indicating the degree of warpage of the substrate is a measured value of any one of a state of a back surface of the substrate, a state of a front surface of the substrate, or a film thickness of the back surface of the substrate.

14. The plasma processing method according to claim 12 or 13,

the method includes measuring a degree of curvature of a substrate for a dummy substrate whose surface has been formed under predetermined film forming conditions, measuring a degree of curvature of a substrate for each substrate whose surface has been formed under the film forming conditions, or measuring a degree of curvature of a substrate for at least one of a plurality of substrates whose surfaces have been formed under the film forming conditions.

Technical Field

The present invention relates to a plasma processing apparatus and a plasma processing method.

Background

Since a film obtained by film formation in a process such as 3D NAND is thick, warpage of a substrate tends to increase. When the substrate is bent, the pattern is deviated in the exposure step, which is problematic. If the stress on the substrate can be reduced to flatten the substrate, the problem of pattern deviation in the exposure process can be solved.

As a method of reducing stress to a substrate, for example, patent document 1 proposes a method of reducing stress applied to a substrate after an element is formed by forming a film not only on a front surface but also on a back surface of the substrate.

Documents of the prior art

Patent document

Patent document 1: U.S. patent application publication No. 2015/0340225

Disclosure of Invention

Problems to be solved by the invention

The present disclosure provides a plasma processing apparatus and a plasma processing method capable of performing local film formation on a back surface of a substrate.

Means for solving the problems

According to one embodiment of the present disclosure, there is provided a plasma processing apparatus including: a processing vessel; a substrate holding mechanism which is disposed in the processing container and holds a substrate; a dielectric window disposed below the substrate holding mechanism; and a phased array antenna which is disposed below the dielectric window and radiates a plurality of electromagnetic waves.

ADVANTAGEOUS EFFECTS OF INVENTION

According to one aspect of the present disclosure, a local film formation can be performed on the back surface of the substrate.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a plasma processing apparatus according to an embodiment.

Fig. 2 is a diagram showing an example of a phased array antenna according to an embodiment.

Fig. 3 is a diagram for explaining phase control according to an embodiment.

Fig. 4 is a diagram showing an example of a scanning pattern of film formation by the phase control according to the embodiment.

Fig. 5 is a diagram showing an example of the position of an optical sensor of the plasma processing apparatus according to the embodiment.

Fig. 6 is a view showing an example of the plane a-a in fig. 5.

Fig. 7 is a diagram showing another example of the position of the optical sensor of the plasma processing apparatus according to the embodiment.

Fig. 8 is a diagram showing another example of the position of the optical sensor of the plasma processing apparatus according to the embodiment.

Fig. 9 is a flowchart showing an example of the plasma processing method according to the embodiment.

Fig. 10 is a diagram showing an example of electric field distribution in the dielectric window according to the embodiment.

Fig. 11 is a diagram illustrating an example of the effect of the plasma processing method according to the embodiment.

Description of the reference numerals

1: a processing vessel; 2: a phased array antenna; 3: a substrate holding mechanism; 5: a dielectric window; 6: a microwave output section; 7: a phaser; 8: a control unit; 9: a base plate; 10: a plasma processing apparatus; 11: a monopole antenna; 12: a heating source; 121: an inner conductor; 122: an outer conductor; 125: a radiation unit; w: a substrate.

Detailed Description

Hereinafter, a mode for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description thereof may be omitted.

[ plasma processing apparatus ]

A plasma processing apparatus 10 according to an embodiment will be described with reference to fig. 1. Fig. 1 (a) is a schematic cross-sectional view showing an example of a plasma processing apparatus 10 according to an embodiment. Next, a microwave plasma processing apparatus will be described as an example of the plasma processing apparatus 10. Fig. 1 (c) shows a microwave plasma processing apparatus according to a comparative example (hereinafter referred to as a plasma processing apparatus 20).

A plasma processing apparatus 10 according to one embodiment shown in fig. 1 (a) includes a processing container 1 for accommodating a substrate W such as a wafer. The plasma processing apparatus 10 performs a predetermined plasma process such as a film forming process or an etching process on the substrate W by using plasma generated by a microwave.

The processing container 1 is a substantially cylindrical container and is grounded. The opening of the bottom surface of the processing container 1 is closed by the bottom plate 9, whereby the inside of the processing container 1 can be kept airtight. The processing container 1 and the bottom plate 9 are made of a metal material such as aluminum or stainless steel.

A substrate holding mechanism 3 for holding the substrate W is provided in the processing container 1. Examples of the material constituting the substrate holding mechanism 3 include a dielectric (e.g., ceramics such as quartz and alumina). The substrate holding mechanism 3 may be provided with an electrostatic chuck for electrostatically attracting the substrate W, a temperature control mechanism, and the like. A drive mechanism 4 is connected to the substrate holding mechanism 3. The substrate holding mechanism 3 can be moved in the vertical direction within the processing container 1 by the driving mechanism 4, thereby adjusting the height of the substrate W.

An exhaust pipe, not shown, is connected to the processing container 1, and an exhaust device including a vacuum pump is connected to the exhaust pipe. When the evacuation device is operated, the inside of the processing container 1 is evacuated, and thereby the inside of the processing container 1 is depressurized to a predetermined degree of vacuum. A not-shown carrying-in/out port for carrying in and out the substrate W and a not-shown gate valve for opening and closing the carrying-in/out port are provided in a side wall of the processing container 1. Seven (only three are shown in fig. 1) phased array antennas 2 for radiating microwaves into the processing container 1 are provided on the base plate 9. The phased array antenna 2 radiates electromagnetic waves, such as microwaves.

Fig. 2 shows an example of the phased array antenna 2. The phased array antenna 2 is in the form of a coaxial cable, and includes an inner conductor 121, an outer conductor 122 outside the inner conductor 121, and a dielectric 123 such as teflon (registered trademark) provided therebetween. The distal end of the phased array antenna 2 is configured as a monopole antenna 11 including an inner conductor 121 protruding by a length D. The size (length D) of the monopole antenna 11 varies depending on the frequency of the electromagnetic wave. For example, when the frequency of the microwave is 300MHz to 3GHz, the length D is several tens mm to several hundreds mm.

The monopole antenna 11 is exposed to the internal space of the processing container 1 from the end of the dielectric member 123 which is located at the same level as the inner surface 9a of the bottom plate 9, whereby microwaves are radiated into the processing container 1 from the radiation unit 125. However, the inner conductor 121 may not protrude from the dielectric 123. In this case, a notch portion where the outer conductor 122 does not exist is formed at the distal end of the phased array antenna 2, and microwaves are radiated from the radiation port at the distal end of the inner conductor 121 into the processing chamber 1 through the notch portion. For example, the antenna constituting the phased array antenna 2 may be an antenna different from a monopole antenna, such as a helical antenna.

With this configuration, the microwave is output from the microwave output unit 6, subjected to phase control by the phase shifter 7 in accordance with the control of the control unit 8, and then radiated into the processing container 1. The number of phased array antennas 2 is not limited to seven, and may be two or more, but more preferably three or more.

Returning to fig. 1 (a), the phased array antennas 2 are arranged at substantially equal intervals as follows: the distance P from the center of each phased array antenna 2 to the center of the adjacent phased array antenna 2 with respect to the wavelength λ of the microwave is smaller than λ/2. The dielectric window 5 is disposed below the substrate holding mechanism 3 so as to be separated from the phased array antenna 2 and the substrate holding mechanism 3. The dielectric window 5 is made of, for example, quartz or alumina (Al)₂O₃) And ceramics, fluorine-based resins such as polytetrafluoroethylene, and polyimide resins. The dielectric window 5 is a partition plate that divides the inside of the processing chamber 1 into a space U above the dielectric window 5 and a space V below the dielectric window 5. The space V is an atmospheric space, and the space U is a vacuum space.

A free space of about several tens mm to several hundreds mm exists in the space V above the phased array antenna 2, and plasma is generated in the space U through the dielectric window 5 provided above the free space. The vertical distance H from the bottom plate 9 to the lower surface of the dielectric window 5 with respect to the wavelength λ of the microwave is larger than λ/4. The phased array antenna 2 radiates microwaves into the space V. Seven microwaves radiated from the seven phased array antennas 2 propagate to the space V. In the space V, seven microwaves are collected and synthesized. The synthesized microwave is transmitted through the dielectric window 5 and propagated in the space U.

A plurality of gas supply ports 15 are arranged at equal intervals in the circumferential direction on the side wall of the processing container 1 above the dielectric window 5, and the plurality of gas supply ports 15 are connected to a gas supply portion 16. The gas supplied from the gas supply portion 16 is uniformly introduced into the space U from the plurality of gas supply ports 15. In the space U, a local plasma is generated from the gas supplied from the gas supply unit 16 by the power of the synthesized microwave, and a film is formed on the back surface of the substrate W by the local plasma. As a result, the film S is formed in a spot on the region of the back surface of the substrate W where the plasma is generated.

A heating source 12 is disposed at the top of the processing vessel 1. The heat source 12 may be formed of a plurality of LEDs (light emitting diodes), for example. The heat source 12 heats the substrate W by a plurality of LEDs.

The plasma processing apparatus 10 has a control unit 8. The control unit 8 may be a computer including a storage unit such as a processor and a memory, an input device, a display device, and an input/output interface for signals. The controller 8 controls each part of the plasma processing apparatus 10. The control unit 8 manages the plasma processing apparatus 10 by an operator performing an input operation of a command using an input device. The control unit 8 visually displays the operation status of the plasma processing apparatus 10 by a display device. The storage unit stores a control program and process data. Causing the processor to execute a control program to execute various processes in the plasma processing apparatus 10. The processor executes a control program to control each part of the plasma processing apparatus 10 according to process data. The processor of the control unit 8 controls the phase shifter 7 provided for each phased array antenna 2 to control the phase of the microwave radiated from the radiation unit 125.

When performing plasma processing in the plasma processing apparatus 10 having this configuration, first, the substrate W is carried into the processing container 1 through the carrying-in/out port from the opened gate valve while being held by the carrying arm.

When the substrate W is conveyed to above the substrate holding mechanism 3, the substrate holding mechanism 3 is raised from the conveying arm to place the substrate W on the substrate holding mechanism 3. After the substrate W is carried in, the gate valve is closed. The pressure inside the processing container 1 is maintained at a predetermined vacuum degree by an exhaust device. The gas is introduced into the space U above the dielectric window 5, and microwaves of controlled phases are radiated from the seven phased array antennas 2 into the space V. This enhances the electric field at a predetermined position of the dielectric window 5, and can control the distribution of plasma when the gas is converted into plasma in the space U. The controller 8 forms a predetermined film S on the back surface of the substrate W in accordance with the degree of warpage of the substrate W by using the generated plasma. The predetermined film S may be SiN or SiO₂And the like.

As shown in fig. 1 (c), in the plasma processing apparatus 20 according to the comparative example, the phases of the microwaves emitted from the seven antennas 200 are the same. Therefore, in the plasma processing apparatus 20 according to the comparative example, when plasma is generated above the dielectric window 5 by the electric field of the microwave, the electric field distribution is affected by the arrangement pattern of the seven antennas 200. As a result, as shown in fig. 1 (d), the intensity of the plasma distribution is generated according to the arrangement pattern of the antenna 200. That is, the plasma processing for the substrate W is easily affected by the arrangement pattern of the antennas 200 and becomes uneven.

However, the arrangement pattern of the antenna 200 is a physical arrangement, and it is difficult to change the preset arrangement. Therefore, in the present embodiment, the electric field distribution in the dielectric window 5 is controlled by radiating microwaves from below the dielectric window 5 so as to control the phases of the plurality of microwaves, independently of the arrangement of the phased array antenna 2. Thus, the plasma processing apparatus 10 capable of controlling the plasma distribution is provided.

That is, the plasma processing apparatus 10 according to the present embodiment shown in fig. 1 (a) controls the phase of the microwave radiated from each of the seven phased array antennas 2 by using the phase shifter 7 under the control of the control unit 8. This allows the microwaves radiated from each of the seven phased array antennas 2 to interfere with each other, thereby increasing the electric field strength at an arbitrary position. Thereby, plasma is locally generated, whereby plasma distribution can be highly controlled.

For example, in fig. 1 (a), the microwaves injected from the seven phased array antennas 2 are phase-controlled to interfere with the microwaves propagating through the space V, and the electric field intensity of the microwaves is increased on the right side of the dielectric window 5 by combining a plurality of microwaves. As a result, as shown in fig. 1 (b), a plasma distribution in which plasma is concentrated is obtained in the space U and on the right side of the substrate W, and the film S can be formed in a spot manner on the right side of the substrate W.

[ phase control ]

Next, the phase control of the microwave is described with reference to fig. 3. Fig. 3 is a diagram for explaining phase control performed by the control unit 8 provided in the plasma processing apparatus 10 according to the embodiment. Fig. 3 (a) shows a relationship between microwaves radiated from one of the phased array antennas 2 (in this example, the phased array antenna 2a) and a focal position O of the dielectric window 5 at which an electric field is to be concentrated. When the position where the focal position O is suspended on the surface of the base plate 9 is denoted by O ', the distance from the focal position O to the position O' on the surface of the base plate 9 is denoted by Z, and the position of the radiation point of the microwave radiated from the phased array antenna 2a is denoted by X, the following expression (1) is established.

[ number 1 ]

K in formula (1) is the wave number of an electromagnetic wave including a microwave, and is represented by the reciprocal of the wavelength λ of the electromagnetic wave, that is, k is 1/λ. δ (X) represents a phase of an electromagnetic wave (microwave in the present embodiment) emitted from the emission point X.

When the formula (1) is modified, the formula (2) for obtaining the phase δ (x) of the electromagnetic wave is obtained.

Number 2

Based on equation (2), the phase δ (X) of the electromagnetic wave emitted from the emission point X is calculated from the wave number k, the distance Z, and the emission point X of the electromagnetic wave. Equation (2) depicts the curve of fig. 3 (b).

The condition for mutually enhancing the phases of the microwaves radiated from the two or more phased array antennas 2 at the focal position O will be described with reference to (c) of fig. 3. The seven phased array antennas 2 are set as phased array antennas 2a, 2b, 2c, 2d, 2e, 2f, and 2g, and in fig. 3 (c), the phased array antennas 2 are shown as being arranged in the lateral direction with the phases separated for the convenience of description, which is different from the actual positional relationship of the phased array antennas 2.

The control unit 8 controls the radiation points x of the microwaves radiated from the phased array antennas 2a to 2g_a～x_gControlling the phase delta (x) of each microwave radiated from the phased array antennas 2a to 2g_a)～δ(x_g) So that the phases of the microwaves at the focal position O coincide with each other.

Since the radiation points X of the phased array antennas 2a to 2g are different, as shown in formula (2), the phase δ (X) of the microwaves radiated from the phased array antennas 2a to 2g is shifted at the focal position O unless the phase is controlled. As a result, even if any of the microwaves of the phased array antennas 2a to 2g is in a condition where the phases are mutually intensified at the focal position O, any other microwaves are in a condition where the phases are mutually weakened at the focal position O. In contrast, in the present embodiment, the phases δ (x) of the microwaves radiated from the phased array antennas 2a to 2g are controlled individually_a)～δ(x_g) The phases can be mutually intensified at the focal position O. For example, the phase of the microwaves radiated from the phased array antennas 2a, 2b, and 2c shown in fig. 3 (c) is conditioned to be mutually enhanced because the antinodes of the phases of the microwaves coincide with each other, and the nodes coincide with each other. However, even if the control is made under the condition that the phases of the microwaves radiated from the phased array antennas 2a, 2b, and 2c are mutually enhanced, the microwaves may be radiated from the phased array antennasThe phase of at least one of the microwaves emitted from the lines 2d to 2g is a condition for attenuating each other. In this case, the phases of the seven microwaves may not be mutually intensified at the focal position O.

In contrast, in the present embodiment, the phases of the microwaves radiated from the phased array antennas 2c, 2d, 2e, 2f, and 2g are also controlled so as to be mutually intensified. Accordingly, the phases of the respective microwaves are controlled so that the phases of the seven microwaves are mutually intensified at the focal position O of the dielectric window 5, and the electric field of the microwaves can be controlled so as to be concentrated at the focal position O.

However, instead of performing this control for all seven microwaves, the control for mutually enhancing the phase focal positions O of the microwaves may be performed for at least two microwaves output from the phased array antennas 2a to 2 g. For example, in the phased array antenna 2, the number of antennas that do not control the phase of the microwave may be one or more. In the above description, although one focal position O is provided in the dielectric window 5, the present invention is not limited to this, and control may be performed to mutually strengthen the phases at two or more focal positions O in the dielectric window 5 at the same timing.

Further, as shown in fig. 1, the distance P from the center of one phased array antenna 2 to the center of the adjacent phased array antenna 2 is smaller than λ/2 with respect to the wavelength λ of the microwave. This is because, when the distance (interval) between adjacent phased array antennas 2 is larger than λ/2, the microwaves cannot be converged at the focal position O of the dielectric window 5, and control for mutually increasing the phases of the microwaves at the focal position O cannot be performed.

The above-described focusing of the microwave by the phase control is not accompanied by a mechanical operation, and thus the control can be performed at a very high speed. In principle, the focal position O can be moved in time by high-speed control to the same extent as the frequency of the microwave. This enables the phased array antenna 2 to perform phase control at high speed. As a result, the distribution of the electric field of the microwave in the dielectric window 5 can be controlled at high speed, and plasma can be locally generated in the space U above the dielectric window 5.

In the focusing of the microwave, the smaller the distance between the substrate holding mechanism 3 and the dielectric window 5, the smaller the diameter of the spot indicating the in-focus state of the microwave, and the local plasma is generated. Therefore, by moving the substrate holding mechanism 3 in the vertical direction by the driving mechanism 4 and adjusting the interval between the substrate holding mechanism 3 and the dielectric window 5, it is possible to irradiate a desired portion of the back surface of the substrate W with local plasma and perform film formation at a predetermined position. This reduces local stress on the substrate W. The control unit 8 acquires the bend distribution of the substrate W from the optical sensor 13, the optical monitor, and the like, calculates the film formation position and the film thickness based on the acquired measurement values, and controls the phased array antenna 2 based on the calculation result so as to form a film having a desired film thickness at the film formation position on the back surface of the substrate W.

Fig. 4 is a diagram illustrating an example of phase control performed by the control unit 8 according to the embodiment. The control unit 8 controls the region where plasma is generated by changing the phases of the plurality of microwaves with time. In the example of fig. 4, the control unit 8 controls the phases δ (x) of the microwaves emitted from the seven phased array antennas 2a, 2b, 2c, 2d, 2e, 2f, and 2g, respectively, by using the phasers 7 (only one is shown in fig. 4)_a)～δ(x_g) Mutually enhanced at the focal position C. Thus, a case where control is performed so that the electric field of the microwave becomes strong at the spot portion Ar centered on the focal position C is schematically shown.

The control unit 8 controls the phase δ (x) of the microwave at high speed by using the phase shifter 7_a)～δ(x_g) The focal point position C is scanned in the radial direction L1, the circumferential direction L2, or the like on the surface of the dielectric window 5. Thus, by moving the focal position C and the in-focus portion Ar at a high speed, plasma can be locally generated in the space U above the dielectric window 5.

The control unit 8 controls the phase δ (x) of the microwave by changing the phase shifter 7_a)～δ(x_g) To change the moving speed of the in-focus portion Ar. This enables the average electric field distribution per unit time to be freely controlled. For example, the change control unit 8 controls the phase δ (x) of the microwave_a)～δ(x_g) To make cokeThe point alignment portion Ar is moved slowly on the outer peripheral side of the dielectric window 5, and the in-focus portion Ar is moved more quickly on the inner peripheral side than on the outer peripheral side. This makes it possible to make the integrated value of the electric field intensity on the outer periphery side of dielectric window 5 stronger than the integrated value of the electric field intensity on the inner periphery side. Further, the plasma distribution can be freely controlled, for example, the plasma density on the outer peripheral side above the dielectric window 5 can be controlled to be higher than the plasma density on the inner peripheral side.

[ sensor position ]

The plasma processing apparatus 10 includes a sensor for measuring the degree of curvature of the substrate W held by the substrate holding mechanism 3. The sensor will be described with reference to fig. 5 to 8, taking the optical sensor 13 as an example. Fig. 5 is a diagram showing an example of the position of the optical sensor 13 of the plasma processing apparatus 10 according to the embodiment. Fig. 6 is a view showing an example of the plane a-a in fig. 5. Fig. 7 is a diagram showing another example of the position of the optical sensor 13 in the plasma processing apparatus 10 according to the embodiment. Fig. 8 is a diagram showing another example of the position of the optical sensor 13 in the plasma processing apparatus 10 according to the embodiment.

The optical sensor 13 shown in fig. 5 to 8 measures the degree of warpage of the substrate W. The information indicating the degree of curvature of the substrate W may be a measured value of any one of the state of the front surface Us of the substrate W, the state of the back surface Ds of the substrate W, or the thickness of the film S formed on the back surface Ds of the substrate W. In the plasma processing apparatus 10 shown in fig. 5 to 8, a film is formed on the back surface Ds of the substrate W so that the substrate W is flattened by reducing the stress of the substrate W while measuring the degree of curvature of the substrate W by the optical sensor 13. As a measuring device for measuring the degree of warpage of the substrate W, the optical sensor 13 and the control unit 8 may be combined, or a measuring device in which the optical sensor 13 and the optical monitor are integrated may be attached to the processing container 1.

In the example of fig. 5, a plurality of optical sensors 13 are attached to the top of the processing container 1. The number of optical sensors 13 is shown as an example on the a-a plane of fig. 5, i.e., in (a) to (c) of fig. 6. In the example of fig. 6 (a), the number of the optical sensors 13 is nine in total, one is provided at the center of the top, and eight are provided so as to surround the periphery of the optical sensor 13 at the center. In the example of fig. 6 (b), the number of the optical sensors 13 is five in total, wherein one is provided at the center of the top, and four are provided equidistantly around the optical sensor 13 at the center. In the example of fig. 6 (c), the number of the optical sensors 13 is thirteen in total, nine of them are provided at the positions shown in fig. 6 (a), and four of them are provided at equal intervals on the outer periphery thereof.

Returning to fig. 5, the control unit 8 causes light of a predetermined frequency to enter the surface Us of the substrate W from the plurality of optical sensors 13 through the transmission window 14 through which the light is transmitted. Then, the reflected light of the plurality of lights on the surface Us of the substrate W is received by a light receiver, not shown, and the state of the substrate W is directly measured from the state of the received light. Accordingly, the bending state of the surface Us of the substrate W can be directly measured, and thus the measurement accuracy is high. Further, the measurement accuracy is higher as the number of the optical sensors 13 is larger, but the cost is also higher. Therefore, the bent state of the substrate W can be measured by disposing at least five optical sensors 13 at the positions shown in fig. 6 (b), and an increase in cost can be suppressed. On the other hand, in consideration of the measurement accuracy, it is preferable to dispose nine optical sensors 13 at positions shown in fig. 6 (a), and it is more preferable to dispose thirteen optical sensors 13 at positions shown in fig. 6 (c).

In the example of fig. 7, an optical sensor 13 is attached to a side wall of the processing container 1. The optical sensor 13 is capable of changing the orientation of the optical axis. The optical sensor 13 allows light to enter from the side wall of the processing container 1 through the transmission window 14 obliquely with respect to the back surface Ds of the substrate W in order to measure the bent state of the substrate W. The orientation of the optical axis is changed to scan the back surface Ds of the substrate W with light. The reflection of the light is received by the light receiver 17 through the transmission window 14 on the opposite side. The bending state of the substrate W is measured based on the state of the received light. In this case as well, the measurement accuracy is high because the curved state of the substrate W is directly measured from the reflection of the incident light.

However, the bent state of the substrate W may be indirectly measured by measuring the thickness of the film S on the back surface Ds of the substrate W using a film thickness meter. For example, in the example of fig. 8, the optical sensor 13 is attached to the bottom plate 9 of the processing container 1. Light of a predetermined frequency is incident from the bottom of the processing container 1 through the transmission window 14 from the plurality of optical sensors 13. The light passes through the dielectric window 5, enters the rear surface Ds of the substrate W, and is reflected. The reflected light is received by a light receiver, not shown, and the film thickness formed on the back surface Ds of the substrate W is measured in accordance with the state of the received light. The correlation between the film thickness and the curved state (warpage) of the substrate W is measured in advance, and stored in the control unit 8 as a relational expression and information indicating the correlation. Therefore, by measuring the film thickness of the back surface of the substrate W, the bending state of the substrate W can be indirectly predicted.

As described above, the information indicating the degree of warpage of the substrate W can be acquired based on the result of measuring any one of the state of the front surface Us of the substrate W, the state of the back surface Ds of the substrate W, or the film thickness of the back surface of the substrate W using the optical sensor 13. The control unit 8 controls the phases of the plurality of microwaves radiated from the phased array antenna 2 based on information indicating the degree of curvature of the substrate W measured by the optical sensor 13.

The substrate to be measured for the warp state by the optical sensor 13 may be a dummy substrate whose surface has been formed under the same film formation conditions as the production substrate W, may be each production substrate W, or may be at least one of the plurality of substrates W. The substrate W may be the first substrate W of the substrate group, the last substrate W of the substrate group, or the like. However, the substrate to be measured is not limited to this.

For example, when the substrates W are processed under the same film formation conditions, the measured values obtained by measuring the bending states of the dummy substrates on which the films are formed on the front surface Us under the same film formation conditions may be used for the control of forming the films on the rear surface Ds of all the substrates W on which the films are formed on the front surface Us under the same film formation conditions. However, the present invention is not limited to this, and for example, even when the substrates W are processed under the same film formation conditions, the film formation of the rear surface Ds may be controlled based on the measurement result of each substrate W while performing measurement for each substrate W. Thus, even when the bending state differs for each substrate, the film S having an appropriate thickness can be formed in an appropriate region of the back surface Ds of the substrate W, and the stress can be reduced for each substrate W to eliminate the bending.

The plasma processing apparatus 10 may not be provided with a measuring device such as the optical sensor 13. In this case, after the film is formed on the surface Us of the substrate W based on the predetermined film formation conditions, the substrate W may be conveyed to an unillustrated orienter, light may be incident on the surface of the substrate W while the substrate W is rotated by the orienter, and the degree of curvature of the substrate W may be measured by reflection of the light. The measurement value is transmitted from the control unit provided in the orienter to the control unit 8 of the plasma processing apparatus 10. Thus, the control unit 8 controls the phases of the plurality of microwaves radiated from the phased array antenna 2 based on the received measurement value indicating the degree of curvature of the substrate W.

[ plasma treatment method ]

Next, an example of a plasma processing method performed by the plasma processing apparatus 10 will be described with reference to fig. 9. Fig. 9 is a flowchart showing an example of the plasma processing method according to the embodiment. The present process is controlled by the control unit 8. In the plasma processing method SW shown in fig. 9, the film may be formed on the back surface of the dummy substrate W from the first sheet and on the back surface of the product substrate W from the second sheet.

When the present process is started, the controller 8 loads the substrate W into the process container 1 and holds the substrate W in the substrate holding mechanism 3 to prepare the substrate W (step S1). Next, the controller 8 measures the bending state of the substrate W by the optical sensor 13 (step S2). Next, the controller 8 supplies gas from the gas supply unit 16 (step S3). Next, the control unit 8 outputs microwaves from the microwave output unit 6 (step S4).

Next, the control unit 8 controls the phases of the microwaves radiated from the seven phased array antennas 2 based on the measurement values indicating the bending state of the substrate W by using the phase shifter 7 (step S5). Thereby, the microwaves, the phases of which are controlled, are radiated from the phased array antennas 2 into the processing container 1. The microwaves with their phases controlled interfere with each other in the space V, and the microwaves are focused. This generates local plasma between the dielectric window 5 and the substrate holding mechanism 3. The controller 8 performs partial film formation on the back surface Ds of the substrate W by the partial plasma (step S6).

Next, the control unit 8 determines whether or not to end the film formation process (step S7). When it is determined that the film formation process is not to be ended, the control unit 8 measures the bent state of the substrate W again by the optical sensor 13 (step S8). Then, the controller 8 controls the phases of the microwaves emitted from the seven phased array antennas 2 based on the measurement results using the phase shifter 7 (step S5), and performs partial film formation on the back surface Ds of the substrate W (step S6). In step S7, the controller 8 repeats the processes of steps S5 to S8 until it determines that the film formation process is ended, and the controller 8 ends the present process when it determines that the film formation process is ended. If it is determined that the warp state of the substrate W is within the allowable range based on the measurement result in step S8, the controller 8 may terminate the film formation process in step S7 without performing steps S5 to S6. At the end of this process, the output of the microwaves is stopped, and the supply of the gas is stopped.

According to this plasma processing method, the curved state of the substrate is measured, and the measurement result is fed back to each phased array antenna 2 provided on the back surface side of the substrate W to control the phase of each microwave. Thus, the stress on the substrate W can be reduced by forming the film on the predetermined region of the back surface Ds of the substrate W.

The substrate W having a rear surface formed by the above-described processing method may be transferred to another processing container, the bent state of the substrate W may be measured again, and if the substrate W has a bend outside a predetermined allowable range, the substrate W may be transferred to the plasma processing apparatus 10 again, and the film may be formed on the rear surface Ds of the substrate W again.

[ simulation result of phase control ]

Fig. 10 (b) and (c) show an example of simulation results of the electric field distribution in the dielectric window 5 according to the embodiment when the control unit 8 controls the phases of the microwaves output from the nineteen phased array antennas 2 by using the phase shifters 7 as shown in fig. 10 (a).

As the simulation conditions, microwaves of the same power are radiated from the nineteen phased array antennas 2. The electric field intensity of the microwaves shown in (a) to (c) of fig. 10 is indicated by the dark portions.

Fig. 10 (b) is an electric field intensity distribution when the phase δ (x) of the microwave is controlled so that the in-focus portion Ar centered on the focal position C1 is formed in the vicinity of the center of the dielectric window 5.

Thereafter, as shown in (C) of fig. 10, as a result of controlling the phases δ (x) of the microwaves so that the phases are mutually enhanced at the focal position C2 of the dielectric window 5, the electric field of the microwaves becomes stronger at the in-focus portion Ar centered on the focal position C2. This simulation confirmed that the phase control enabled free focus control.

As described above, according to the plasma processing apparatus 10 of the present embodiment, the electric field distribution in the dielectric window 5 can be changed without being limited by the arrangement of the phased array antenna 2. Thus, the phase control enables free focus control and free control of the plasma distribution.

As shown in fig. 11, the warp of the substrate W can be eliminated by this control. For example, when the substrate W is warped in a bowl shape so that the center thereof is recessed, the film is formed on the entire back surface Ds of the substrate W. In this case, the film thickness Se on the outer periphery of the film S is made thicker than the film thickness Sc on the center side. This reduces the stress on the substrate W, thereby flattening the substrate W.

However, the film formation method is not limited to this, and for example, the film formation may be performed on the center side of the back surface Ds of the substrate W, but not on the outer peripheral side. In addition, the film formation may be performed on the outer peripheral side of the back surface Ds of the substrate W depending on the curved state of the substrate W, but not on the center side.

Whether the film formed on the rear surface Ds is a compressive stress film or a tensile stress film varies depending on not only the type of the film but also the film forming conditions even in the case of the same type of film. Therefore, by setting at least one of the film formation position, the type of film, and the film formation condition to be appropriate based on the measurement result indicating the curved state of the substrate W, the curved state of the substrate W can be eliminated and the substrate W can be flattened.

The plasma processing apparatus 10 of the present disclosure is described by taking as an example a plasma processing apparatus that emits microwaves, but is not limited thereto. The phased array antenna 2 included in the plasma processing apparatus 10 of the present disclosure is not limited to radiating microwaves, and may radiate electromagnetic waves having a frequency of 100MHz or higher, such as UHF or the like. More preferably, the phased array antenna 2 can radiate electromagnetic waves having a frequency in a range of 1GHz to 3 GHz. The higher the frequency, the higher the phase control speed can be.

In the above embodiment, the space V above the dielectric window 5 is an air space, but is not limited thereto. For example, the space V below the dielectric window 5 may be filled with a dielectric of the same material as the dielectric window 5 or a different material. By filling the space V with the dielectric, the wavelength of the microwave propagating through the dielectric can be shortened, and therefore the plasma processing apparatus 10 can be made smaller.

In the above embodiment, the space V is an air space, but the space V may be a vacuum space. However, when the space V is a vacuum space, the phase control is performed in the vacuum space, and there is a possibility that plasma is generated in the space V. From the above, the space V is more preferably an air space. Further, by setting the distance between the radiation unit 125 and the dielectric window 5 to be greater than 1/4 of the wavelength λ of the microwave, the microwave can be sufficiently focused through the dielectric window 5.

As described above, according to the plasma processing apparatus and the plasma processing method of the present embodiment, the phased array antenna 2 is provided below the substrate W. This allows the phased array antenna 2 to be feedback-controlled using the result of measuring the bent state of the substrate, thereby locally forming a film on the back surface Ds of the substrate W. This reduces the stress on the substrate W, thereby flattening the substrate W.

The plasma processing apparatus and the plasma processing method according to one embodiment of the present disclosure are not limited to the above embodiments, but are all exemplified in all aspects. The above-described embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above embodiments may have other configurations within a range not inconsistent with the present invention, and may be combined within a range not inconsistent with the present invention.