JP2697274B2 - Microwave plasma processing apparatus and operation method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a configuration of a microwave plasma processing apparatus for forming a thin film on a surface of an object to be processed using microwave plasma or etching a surface thereof, and The present invention relates to a method of operating an apparatus when performing a surface treatment of an object to be processed using a microwave plasma processing apparatus.

[Conventional technology]

ECR as an example of conventional microwave plasma processing equipment
(Electron cyclotron resonance) A plasma CVD apparatus is shown in FIG. Microwaves oscillated by a microwave source (not shown) pass through the waveguide 1, pass through the microwave transmission window 2, and are introduced into the plasma generation chamber 3 kept in a vacuum by a vacuum exhaust device (not shown). The plasma generation gas is supplied into the plasma generation chamber 3 through the gas introduction pipe 4, and the action of the microwave and the magnetic field formed in the plasma generation chamber 3 by the excitation coil 5 surrounding the plasma generation chamber 3. Generates microwave plasma.

This plasma moves downward along the divergent magnetic field formed by the exciting coil 5 and is placed in a reaction chamber 7 on a wafer 9 placed on a stage 8 to which RF power can be applied from an RF power supply outside the reaction chamber. Is irradiated. A reaction gas is supplied to the reaction chamber 7 through a gas introduction pipe 10.

In order to efficiently absorb microwaves into the plasma, the plasma generation chamber 3 has a cylindrical cavity structure, and the reaction chamber 7
Is provided with a metal window 6 having an opening of a certain size.

In such a device, for example, using 2.45 GHz, which is usually used industrially as a microwave frequency, a region of 875 gauss of magnetic flux density is formed in the plasma generation chamber,
When nitrogen is used for the plasma generation gas and silane is used for the reaction gas, the plasma generation gas is efficiently ionized by the electron cyclotron resonance effect of the microwave electric field and the magnetic field,
A silicon nitride film is efficiently formed on the wafer. Incidentally, when the film is formed by applying the RF power to the stage,
Densification of film, improvement of step coating, flattening of film at step, etc.
Film formation according to the purpose is possible.

[Problems to be solved by the invention]

In order to increase the film formation rate in the microwave plasma processing apparatus, it is effective to bring the stage 8 closer to the plasma generation chamber 3 and to irradiate the wafer surface with high-density plasma. However, since the plasma generation chamber 3 and the reaction chamber 7 are separated by the window 6, the distance that can be approached is limited, so that the film formation rate cannot be obtained to a certain degree or more.

An object of the present invention is to provide a configuration of a microwave plasma processing apparatus capable of increasing a film forming rate beyond the above-mentioned limit without accompanying a configuration change that causes an increase in cost, such as an increase in complexity and size of the apparatus. It is an object of the present invention to provide a method of operating an apparatus when processing an object to be processed by the apparatus.

[Means for solving the problem]

In order to solve the above-mentioned problem, in the present invention, microwaves are introduced through a microwave transmission window into a plasma generation chamber into which a plasma generation gas is introduced, and a magnetic field is formed in the plasma generation chamber. A microwave plasma processing apparatus that generates microwave plasma and irradiates the surface of a processing object mounted on a stage with the plasma to process the surface is provided. The processing object is formed so as to be able to pass in the axial direction while maintaining a gap, and a linear drive mechanism for moving the stage forward and backward in the axial direction of the plasma generation chamber is provided on the anti-microwave transmission window side, and the load lock chamber and the gate valve are provided. And a delivery chamber in which delivery of the processing object to the stage is performed. The treated surface of the physical object is positioned in the plasma generating chamber shall be a device performed. The specific length of the microwave generation window is defined as the axial length from the surface of the microwave transmission window inside the plasma generation chamber to the end face of the microwave transmission window on the side opposite to the microwave transmission window. / 2 or more, and the distance between the surface to be processed and the microwave transmission window is set to 1/2 of the microwave wavelength when processing the object.
It is preferable that the apparatus be set as follows.

Further, the method of operating the apparatus when processing the object to be processed using this specific apparatus is described in terms of evacuation of the plasma generation chamber and transfer of the object from the load lock chamber to the stage in the transfer chamber which is on standby. After that, operate the linear drive mechanism to advance the stage at a small pitch in the direction of the microwave transmission window, so that the distance between the processing surface of the object to be processed and the microwave transmission window becomes less than half the microwave wavelength. Stop at the appropriate position,
A method for treating an object to be treated while introducing all the gases used for the treatment into the plasma generation chamber.

[Action]

By configuring the microwave plasma processing apparatus as described above and processing the object to be processed by positioning the surface to be processed in the plasma generation chamber, the surface to be processed is subjected to high density plasma irradiation in the plasma generation chamber. Therefore, by introducing the reaction gas into the plasma generation chamber at the time of film formation, a thin film containing the plasma generation gas and the reaction gas as components is formed at a high speed exceeding the limit possible with the conventional apparatus. In this case, an anti-microwave transmitting window side of the plasma generation chamber does not necessarily require a conventional window. This is because the conventional plasma generation chamber is formed as a cavity resonator with a window to efficiently absorb microwaves into the plasma, and a microwave standing wave is formed in the plasma generation chamber using the window as one reflection surface. The plasma generated gas is turned into a plasma in a state where the plasma is generated, but according to the experiments of the present inventor, even if the window is removed, the density of the plasma moving from the plasma generation chamber to the reaction chamber along the diverging magnetic field changes. This is because the amount of plasma generated in the plasma generation chamber is kept constant. As described above, the reason why the plasma generation amount is kept constant regardless of the presence or absence of the window is that once the plasma is formed in the generation chamber, the plasma generation The wavelength of the microwave in the room becomes shorter,
This is because the window no longer satisfies the positional condition for establishing a standing wave, and the microwave is absorbed by the plasma and does not proceed further. Therefore, the plasma is generated more actively as it is closer to the microwave transmission window. The present invention focuses on such a change in the wavelength of the microwave and attenuation in the traveling direction.

Therefore, as a specific configuration of the microwave plasma apparatus, the length of the plasma generation chamber in the axial direction from the surface of the microwave transmission window inside the plasma generation chamber to the end face on the anti-microwave transmission window side is equal to or more than の of the microwave wavelength. And the distance between the surface of the object to be processed and the microwave transmission window is set to an appropriate wavelength equal to or less than 1/2 of the microwave wavelength before plasma formation, that is, the wavelength equal to the microwave wavelength in vacuum. By setting the interval, a position where the electric field strength of the microwave is maximum and thus the amount of plasma generation is maximum is included in the interval, and the film forming speed can be maximized. Moreover,
The height of the plasma generation chamber is much lower than that of the normal size with three half-waves of the standing wave, and the conventional reaction chamber is used as a delivery chamber for delivery of workpieces. Since the size is further reduced, the size of the apparatus body is reduced, and the linear drive mechanism can sufficiently compensate for the increase in the amount of movement of the stage in the axial direction and a relatively large size, thereby suppressing an increase in the cost of the apparatus.

Also, when processing an object to be processed using the microwave plasma processing apparatus having the miniaturized apparatus main body, the stage is moved at a fine pitch, for example, 1 m, in the direction of the microwave transmission window.
The gas type, gas flow rate,
Even if the film forming conditions such as gas pressure change, the position of the processing surface where the film forming speed is maximum, or the position where the film forming speed is sufficiently large and the film thickness distribution becomes more uniform, etc., is most suitable for the purpose. The position of the processed surface can be accurately obtained.

〔Example〕

FIG. 1 shows a configuration of a microwave plasma processing apparatus according to one embodiment of the present invention. In the figure, the same members as those in FIG. 3 are denoted by the same reference numerals. In this embodiment, the window 6 in FIG. 3 is removed, and the plasma generation chamber 3 having the same height as that in FIG. 3 is opened downward, and a delivery for delivering the wafer in vacuum to the flange 3a at the open end. Chamber 11 is attached. The transfer chamber 11 is connected to a load lock chamber (not shown) via a gate valve. In the transfer chamber 11, an exhaust port 13 is formed at a position off the axis of the plasma generation chamber 3, and a hole 14 through which a connecting shaft 15 coupled to a linear drive mechanism is formed is formed on the axis. The connection shaft 15 is coupled to a screw rod 18 of a linear drive mechanism 22 via a flange 17 whose peripheral edge is securely joined to a lower end of the metal bellows 16.
The screw rod 18 repeatedly rotates the ratchet lever 21 that transmits torque only in one rotation direction after determining the rotation angle of one operation, and turns the fixing nut 19 in one direction via the gear 20. By moving, it moves forward or backward at a fine pitch without rotating around the axis. The operation can be facilitated by using a pulse motor in which the amount of rotation of the shaft is obtained in proportion to the number of input pulses, instead of the ratchet lever 21.

A reaction gas introduction pipe 10 is attached to the plasma generation chamber 3 in addition to the plasma generation gas introduction pipe 4, and when a thin film is formed on the surface of the wafer 9, the plasma generation gas is introduced from each of these two introduction pipes. And a reaction gas are introduced simultaneously.

Here, the behavior of microwaves and plasma generation in the plasma generation chamber will be described. The accidental electrons in the plasma generation chamber consist of the microwave electric field E and the external magnetic field B generated by the exciting coil.
Cyclotron motion is performed by the action of this, and it collides with gas molecules to ionize them. Microwave frequency f = 2.45
When the frequency is GHz and the magnetic field intensity B is 875 gauss, the electron cyclotron frequency coincides with the microwave frequency, so that electron cyclotron resonance (ECR) occurs and the number of electron processes increases. By setting the gas pressure in the plasma generation chamber at around 1 mTorr, ionization efficiency is improved, and high-density plasma can be obtained.

The shape of the plasma chamber has a cylindrical cavity structure to efficiently absorb microwaves into the plasma. For example, when a microwave propagates in a rectangular waveguide in the TE ₁₁ mode, when the inner diameter of the plasma chamber is 290 mm and the height is 190 mm, a standing wave of the TE ₁₁₃ mode is generated in the plasma chamber, and an antinode in the traveling direction of the microwave. (FIG. 4 (a)). The electric field intensity E of the microwave is perpendicular to the direction in which the microwave travels. Since the electric field intensity is highest at the position of the antinode, the ionization efficiency becomes maximum at this position, and a high-density plasma can be obtained. Since the film formation rate is higher as the plasma density is higher, a film formation rate higher than the conventional one can be obtained by forming a film at this position. It the distance between the microwave transmitting window and the surface to be processed λ _0/2 (λ ₀ is the wavelength of the microwave in a vacuum) always includes the position of the antinode if, even plasma density is temporarily out of its position Since it is not 0 but larger than the plasma density in the conventional reaction chamber, it is possible to increase the film formation rate.

The dielectric constant ε of the plasma is different from the dielectric constant ε _{0 in} vacuum and is given by the following equation.

ω _ce : electron cyclotron frequency = 2.8 × 10 ⁶ × B (H
z) ω: microwave frequency = 2.45 × 10 ⁹ (Hz) For example, magnetic flux density B = 1000 gauss, electron density Ne = 1 × 10 9
^{At 10} cm ^-3 , ε = 1 + 0.94 = 1.94.

Therefore, the wavelength λ of the microwave in the plasma at B and Ne is given by λ _{0 where} the wavelength of the microwave in the cylindrical cavity in vacuum is λ _0. Becomes

Since the wavelength [lambda] becomes shorter as the plasma density increases, a large film forming rate can be obtained by bringing the surface to be processed closer to the vacuum transmission window 2 within the range of 0 to [lambda] / 2.

FIG. 2 shows a modification of the above embodiment. In this example, the plasma generation chamber 3 has a height corresponding to the TE ₁₁₁ mode of the microwave, that is, a height substantially equal to a half wavelength of the microwave, and is considerably reduced to about 1/3 of the above-described embodiment. Have been. Again the distance between the surface to be processed and the microwave transmission window 2 of the wafer 9 is maintained at lambda _0/2 or less, compared with the above-described embodiment, the device body is further miniaturized, also with this,
The linear drive mechanism is also downsized.

The microwave plasma processing apparatus shown in FIGS. 1 and 2 is an etching apparatus only by using a plasma generation gas as an etching gas. The present invention also includes this etching apparatus.

〔The invention's effect〕

As described above, in the present invention, microwaves are introduced through a microwave transmission window into a plasma generation chamber into which an axisymmetrically formed plasma generation gas is introduced, and a magnetic field is formed in the plasma generation chamber. A microwave plasma processing apparatus that generates microwave plasma and irradiates the surface of the object to be processed placed on the stage with the plasma to process the surface is performed. An object is formed so as to be able to pass in the axial direction while maintaining a gap, and a linear drive mechanism for moving the stage forward and backward in the axial direction of the plasma generation chamber is provided on the anti-microwave transmission window side, and a load lock chamber and a gate valve are interposed. And a delivery chamber in which the workpiece is delivered to the stage inside. Since the apparatus is located in the plasma chamber, the surface of the object to be processed is irradiated with high-density plasma in the plasma generation chamber, and a film formation rate that cannot be reached by the conventional apparatus having a reaction chamber can be obtained. it can.

Microwaves in plasma have a shorter wavelength than in vacuum, and are absorbed by the plasma and do not proceed further.Plasma is generated more actively near the microwave transmission window. The axial length of the plasma generation chamber from the surface of the microwave transmission window inside the plasma generation chamber to the end face of the anti-microwave transmission window side is formed to be half or more of the microwave wavelength, and Sometimes the distance between the surface to be treated and the microwave transmission window is
By setting the device to 1/2 or less, the position where the electric field intensity is maximum and therefore the plasma generation amount is maximum within the interval between the surface to be processed and the microwave transmission window is included, and the deposition rate can be maximized. It can be. In addition, the height of the plasma generation chamber is significantly lower than that of a normal chamber having three standing wave half-wave numbers, and the conventional reaction chamber is provided for delivery of the workpiece. Since the size of the chamber is further reduced, the size of the apparatus main body becomes smaller, and the linear drive mechanism can sufficiently compensate for the increase in the amount of movement of the stage in the axial direction and a relatively large size, thereby suppressing an increase in the cost of the apparatus.

The method of operating the apparatus when processing an object to be processed using the microwave plasma processing apparatus having this miniaturized apparatus main body is described below. After the workpiece is transferred to the stage, the linear drive mechanism is operated and the stage is advanced at a small pitch in the direction of the microwave transmission window, and the distance between the processing surface of the workpiece and the microwave transmission window becomes microwave. Stop at an appropriate position where the wavelength is 1/2 or less, and operate the processing object while introducing all the gases used for the processing into the plasma generation chamber, so the position of the processing surface of the processing object The setting is performed at a fine pitch, and the gas type, gas flow rate,
The position of the surface to be processed that is most suitable for the purpose, such as the position where the film forming speed is maximum even if the film forming conditions such as gas pressure change, or the position where the film forming speed is sufficiently large and the film thickness distribution is more uniform. Can be obtained with high accuracy.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a microwave plasma processing apparatus according to one embodiment of the present invention, FIG. 2 is a longitudinal sectional view of an apparatus showing a modification of the embodiment of FIG. 1, and FIG. FIG. 4 is a longitudinal sectional view showing a configuration example of a microwave plasma processing apparatus, and FIG. 4 is a view for explaining a state of microwaves in a plasma generation chamber formed as a cylindrical cavity resonator, and FIG. FIG. 4B shows the wavelength before generation, and FIG. 4B shows the wavelength after plasma generation and the attenuation in the axial direction. 1: waveguide, 2: microwave transmission window, 3: plasma generation chamber, 4:
Plasma production gas introduction pipe, 5: excitation coil, 8: stage,
9: wafer (object to be processed), 10: reaction gas introduction pipe, 11: transfer chamber, 22: linear drive mechanism.

Claims (3)

(57) [Claims] A microwave is introduced through a microwave transmitting window into a plasma generation chamber into which a plasma generation gas is introduced, and a magnetic field is formed in the plasma generation chamber to generate microwave plasma. In a microwave plasma processing apparatus for processing a surface by irradiating a surface of an object to be treated with plasma with a stage, an anti-microwave transmission window side of the plasma generation chamber is arranged such that the stage and the object to be processed maintain an air gap and are axially aligned. And a linear drive mechanism for moving the stage forward and backward in the axial direction of the plasma generation chamber on the anti-microwave transmission window side, and communicates with the load lock chamber via a gate valve to form a stage inside. A transfer chamber for transferring the object to be processed, and the processing surface is positioned in the plasma generation chamber when the object is processed. Microwave plasma processing apparatus according to claim. 2. The microwave plasma processing apparatus according to claim 1, wherein the plasma generation chamber extends in the axial direction from the surface of the microwave transmission window on the plasma generation chamber side to the end face on the anti-microwave transmission window side. The microwave is formed to have a length equal to or more than 1/2 of the microwave wavelength, and the gap between the surface to be processed and the microwave transmission window is set to be equal to or less than 1/2 of the microwave wavelength when processing the object to be processed. Plasma processing equipment. 3. A method for operating an apparatus when processing an object to be processed using the apparatus according to claim 2, wherein the plasma generation chamber is evacuated to a standby state in a transfer chamber from a load lock chamber. After the workpiece is transferred to the middle stage, the linear drive mechanism is operated to advance the stage at a very small pitch in the direction of the microwave transmission window, and the distance between the processing surface of the workpiece and the microwave transmission window becomes smaller. A method for operating a microwave plasma processing apparatus, comprising: stopping at an appropriate position that is equal to or less than half of a wave wavelength, and processing an object to be processed while introducing all gases used for processing into a plasma generation chamber.