JPH06314665A - Plasma treating method - Google Patents

Abstract

(57) [Abstract] [Purpose] When a target object is processed in a plasma atmosphere using the energy of a helicon wave, the plasma density on the target object is made uniform. A plasma is generated in a plasma generation chamber 20 by an electromagnetic coil 25 and an antenna 22 to which a high frequency in the RF band is applied. By the operation of the auxiliary electromagnetic coils 41 and 42 below the susceptor 33 in the plasma processing chamber 30,
When the electron cyclotron resonance region is formed on the semiconductor wafer W on the susceptor 33, the plasma density in the electron cyclotron resonance region becomes high. [Effect] The plasma density can be controlled by a slight difference in magnetic field strength at a small level, and the plasma density on the object to be processed can be made uniform. Partial adjustment is also possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method for processing an object to be processed in plasma by a helicon wave.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor element manufacturing process, for example, various plasma processes such as etching process are performed on an object to be processed, for example, a semiconductor wafer in the plasma atmosphere by generating plasma in the process chamber. However, in recent years, with the progress of miniaturization of patterns applied to this type of object to be processed, it has been required to perform plasma processing with higher accuracy under the sub-half micron unit.

In order to meet such demands, a plasma source for generating a high density plasma is being developed, and a plasma device using electron cyclotron resonance (ECR) as disclosed in Japanese Patent Publication No. 3-43774 is proposed. Has been done.

However, the plasma device utilizing the electron cyclotron resonance (ECR) is 2.45 GH.
a waveguide for propagating a microwave of z, or 875 Ga
A large electromagnet is required to form a magnetic field as large as uss, and the size of the entire device has become extremely large.

Among these, as a plasma source that has recently been drawing attention, there is one that uses a helicon wave. This applies a magnetic field to a cylindrical chamber, applies a high frequency to a spiral antenna provided in the vicinity of this chamber, and excites plasma using the energy of the magnetic field and the helicon wave generated by this high frequency. Therefore, high density plasma can be generated. A plasma device using this helicon wave is about to be put into practical use.

However, in the method having the above-mentioned structure, the generated plasma diffuses toward the object to be processed. Therefore, separately from the above-mentioned magnetic field forming apparatus for plasma generation, a multi-pole magnetic field is separately formed on the side surface of the processing chamber. It has been proposed to provide an apparatus, form a multipole magnetic field in the processing chamber by the multipole magnetic field forming apparatus, and confine the generated plasma with this multipole magnetic field.

[0007]

By the way, recently, objects to be processed such as semiconductor wafers have become larger in diameter and larger in size, and therefore, when the objects to be processed are processed in a plasma atmosphere, generated plasma is generated. , Must be homogenized over a large area. Therefore, when the plasma is excited by utilizing the energy of the helicon wave to process the object to be processed, some means for uniformizing the plasma is required.

However, the method of forming the multi-pole magnetic field in the processing chamber and confining the generated plasma with the multi-pole magnetic field as described above has a problem that control for plasma homogenization cannot be performed. More specifically, when the plasma density is uneven on the object to be processed, it cannot be controlled to correct it depending on the location and make it uniform as a whole.

From this point of view only, that is, to make the plasma uniform, an air-core coil is further provided on the outer periphery of the plasma excitation coil provided on the outer periphery of the helicon wave generator to form a double coil as a whole. It may be possible to cancel the magnetic field on the object to be processed, but this causes a problem that control of helicon plasma excitation and control of the magnetic field on the object to be processed cannot be controlled independently.

Therefore, it is necessary to control the magnetic field in the vicinity of the object to be processed by other means so as to make the plasma uniform, but in order to correct the density of the plasma, for example, a strong magnetic field is applied in the vicinity of the object to be processed. If it is formed, the problem of device destruction due to charge-up will occur. Therefore, a weak magnetic field is necessary in order to realize the homogenization of plasma by utilizing the magnetic field.

The present invention has been made in view of the above problems, conditions, etc., and provides a new plasma processing method which enables control for homogenization by using electron cyclotron resonance. The purpose is to do.

[0012]

According to the experiments and consideration by the inventors, it was confirmed that the plasma density can be greatly changed by using the electron cyclotron resonance with a slight magnetic field difference. Therefore, in the present invention, such a principle is utilized to control the plasma density on the surface of the object to be processed. When using electron cyclotron resonance, the magnetic field in the vicinity of the object to be processed was set to a low level, and further attention was paid to downsizing of the apparatus.

Therefore, according to the present invention, as described in claim 1, plasma is generated by utilizing the energy of the electromagnetic wave generated by the alternating electric field and the magnetic field, and the plasma is generated with respect to the object in the processing chamber under the plasma atmosphere. In the method of applying the treatment according to 1., the alternating electric field is high frequency, preferably 1 MHz.
The configuration is characterized in that it is created by applying a high frequency power of about 1 GHz, and further an electron cyclotron resonance region is formed in the vicinity of the object to be processed.

According to the experiments conducted by the inventors, for example, if a spiral antenna is used for generating a helicon wave and the antenna is appropriately rotated, the magnetic field intensity for generating the helicon wave plasma is adjusted. Thus, it was confirmed that an electron cyclotron resonance region was formed near the object to be processed.

Furthermore, in order to further partially correct the density of the plasma density in such a method, the method of claim 2
The auxiliary magnetic field forming means may be separately provided, and the auxiliary magnetic field forming means may be configured to form the electron cyclotron resonance region in the vicinity of the object to be processed.

[0016]

As a high frequency used for creating an alternating electric field for plasma excitation, for example, a high frequency in the RF band of 13.56 MHz can be used. At this time, when an electron cyclotron resonance region is formed near the object to be processed. The magnetic flux density in the resonance region may be small, for example, 10 to 20.
It suffices if a magnetic field of about G can be formed. Therefore, the magnetic field forming device for forming the magnetic field for generating the helicon wave plasma can be made smaller than the conventional one. Further, as described in claim 2, even when the auxiliary magnetic field forming means is separately provided, the electromagnetic coil or the like used for the auxiliary magnetic field forming means can be made small.

The relationship between the magnetic field and the plasma density when, for example, electron cyclotron resonance occurs is shown in the graph as shown in FIG. Figure 1 shows 13.56MHz
In the case of application, the horizontal axis shows the magnetic field strength, and the vertical axis shows the outline of the characteristics when the saturated ion current representing the plasma density is taken. The peak A in this characteristic graph is (depending on the shape of the antenna, , Around 10 G), which is the electron cyclotron resonance point, and as can be seen from the graph, the plasma density sharply decreases in the range C of the part to the right of the peak A and conversely increases in the range B. The magnetic field strength is stronger than B, and the plasma density shows a substantially flat characteristic. Further, the characteristic curves shown in the above graph have substantially the same characteristics even if the distance from the center of the electromagnetic coil in the magnetic field forming device for forming the magnetic field for generating the helicon wave plasma is taken on the horizontal axis. Therefore, if such characteristics are used,
If the plasma density is uneven on the object to be processed, it is possible to correct it.

For example, in the case of using the conventionally proposed helicon wave plasma source, since the plasma generation chamber is provided above the processing chamber for processing the object to be processed, the generated plasma is diffused and the object to be processed is diffused. Therefore, the plasma density tends to become rougher in the peripheral portion of the object to be processed. In such a case, if the plasma density of the peripheral portion of the object to be processed is increased, as a result, the density of the plasma density is corrected and the plasma density on the object to be processed is made uniform.

[0019] A description will be given of this invention, for example, in the peripheral portion of the specimen W ₀ as shown in FIG. 2, A portion of the characteristic graph shown in FIG. 1 (electron cyclotron resonance point) is formed, so as to form the D portion of the characteristic graph shown in FIG. 1 on the target object W ₀ heart, by forming the electron cyclotron resonance region on the workpiece W, the workpiece W ₀ It is possible to make the plasma density on the object W ₀ uniform by increasing the density of only the peripheral portion without changing the plasma density of the central portion.

Further suitable auxiliary magnetic field forming means as described in claim 2, for example, if suitably arranged coil or the like, to form a substantially conical with respect to the workpiece W ₀ as shown in FIG. 3, for example, A portion (electron cyclotron resonance point) in the graph shown in FIG. 1 is formed, and C in the graph is formed in the central portion.
Can be formed, and the plasma density in the central portion is canceled out by the superposition of the A portion and the C portion, and as a result is almost unchanged. As a result, the density of only the peripheral portion is increased and, as a result, the workpiece W is processed. The plasma density above ₀ can be made uniform.

In view of such action and effect, according to the second aspect, even if the density of the plasma density is concentric, for example, in a continuous state of the density, the electron cyclotron resonance region corresponding to the plurality of auxiliary magnetic field forming means is concentric. The plasma density can be made uniform by forming a plurality of cells.

By the way, since electromagnetic waves have high energy,
When the object directly collides with the object to be processed, the object to be processed may be destroyed by the impact at that time. In this respect, the electron cyclotron resonance region has a property that it is difficult for such an electromagnetic wave to propagate, so that the electron cyclotron resonance region should be formed so as to cover the object W ₀ above, for example, as shown in FIG. For example, it is possible to prevent the direct hit of the helicon wave, and it is possible to prevent the destruction of the object W ₀ .

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 schematically shows the configuration of a plasma device 1 used for implementing the present embodiment. , The upper plasma generation chamber 20 and the plasma generated in the lower plasma generation chamber 20 and subject to treatment such as etching on an object to be processed, for example, the semiconductor wafer W, by the plasma generated in the plasma generation chamber 20 It has a plasma processing chamber 30 for performing.

The plasma generating chamber 20 has, for example, a substantially cylindrical shape as a whole, and an upper part thereof is formed in a bell jar 21 having a dome shape. The bell jar 21 has an outer periphery so as to surround the bell jar 21. Spiral antenna 2
2 are arranged. High frequency power from the high frequency power supply 24, for example, a high frequency power having a frequency of 13.56 MHz and a power of 1 to 2000 W is applied to the antenna 22 via the blocking capacitor 23.

A main electromagnetic coil 25 for forming a magnetic field for plasma generation is arranged on the outer periphery of the antenna 22, and a direct current from a power source 26 is applied to the inside of the plasma generation chamber 20. A static magnetic field of, for example, 1 to 600 Gauss for exciting the plasma is configured to be formed in the vertical direction. A processing gas introduction port 27 is provided at the top of the bell jar 21, and an inert gas such as Ar or a processing gas such as C from a separately provided gas source 28 is provided.
HF ₃ is configured to be introduced into the processing chamber 20.

On the other hand, the plasma processing chamber 30 is formed in a processing container 31 which is made of a material such as aluminum and is grounded, and is configured so that a processing gas can be introduced. An exhaust port 32 is provided below the side wall of the plasma processing chamber 30, and a predetermined reduced pressure atmosphere is generated in the plasma processing chamber 30 by exhaust means such as a vacuum pump (not shown) communicating with the exhaust port 32. For example, 1.0 × 10
It is possible to set and maintain ^{-3 to} 1.0 Torr.

A susceptor 3 for mounting and holding the semiconductor wafer W in the plasma processing chamber 30.
3 is provided. The susceptor 33 is made of a material such as aluminum, and is connected to a high frequency power source 35 via a matching box 34 outside the processing container 31. For example, RF bias is excited by applying high frequency power of 13.56 MHz. Is configured.

Under the susceptor 33, annular auxiliary electromagnetic coils 41 and 42 having different diameters are arranged in order from the inside so as to be concentric with the susceptor 33. Each of the auxiliary electromagnetic coils 41 and 42 is independently excited by a power source 43 outside the processing container 31, and is configured to form a predetermined magnetic field near the semiconductor wafer W. In the present embodiment, these auxiliary electromagnetic coils 41, 42 make it possible to form a magnetic field of about 5 to 20 Gauss on the semiconductor wafer W in two concentric circular rings having different diameters.

Plasma device 1 for carrying out the present embodiment
Has the above configuration, and its operation will be described by taking an etching process as an example. First, a semiconductor wafer W to be etched is provided in the plasma apparatus 1 via a gate valve (not shown). It is carried into the plasma processing chamber 30 from the load lock chamber (not shown), and is placed and held on the susceptor 33. As a holding means, for example, an electrostatic chuck or the like can be used.

Thereafter, Ar or a predetermined process gas such as CHF ₃ is introduced from the process gas inlet 27 into the plasma generation chamber 20.
The inside of these plasma generation chamber 20 and plasma processing chamber 30 is
A predetermined reduced pressure atmosphere, for example, 3 mTorr is maintained.
In this state, a high frequency power of 13.56 MHz is applied to the antenna 22 by the high frequency power supply 24 so that the plasma generation chamber 20
When the main electromagnetic coil 25 is excited by the power supply 26 to form a magnetic field of, for example, 650 Gauss in the plasma generation chamber 20 while generating an electric field therein, plasma due to a helicon wave is generated in the plasma generation chamber 20. Then, while being spirally moved, it is diffused and introduced toward the semiconductor wafer W in the plasma processing chamber 30. As a result, the semiconductor wafer W is etched.

In this embodiment, the high frequency power supply 35 is used for the susceptor 33, for example, 13.56 MHz.
Since it is configured to be able to apply the RF bias of, this RF can be applied depending on the processing gas used and the reduced pressure atmosphere.
By appropriately applying a bias, it is possible to control the acceleration of ions in the plasma and perform an appropriate etching process according to the object to be processed.

For example, when it is found that the plasma density of the outermost peripheral portion of the semiconductor wafer W is lower than that of the central portion, the plasma density of the outermost peripheral portion may be increased. For example, by energizing the outer auxiliary electromagnetic coil 42, the semiconductor wafer W
If the electron cyclotron resonance region is formed on the outermost peripheral portion of the surface, the plasma density on the outermost peripheral portion is increased, and as a result, the plasma density on the semiconductor wafer W is made uniform. According to the configuration of the plasma device 1 described above,
The electron cyclotron resonance could be generated at around 15 Gauss.

In this case, when the density gradient between the central portion and the outermost portion is steep or conversely slow, the A portion, the C portion, and the D portion in the graph shown in FIG. By using it, the excitation level of the auxiliary electromagnetic coil 42 is appropriately adjusted to adjust the magnetic field strength in the vicinity of the semiconductor wafer W,
Thereby, the formation location of the electron cyclotron resonance region may be changed appropriately. By such an operation, it is possible to partially adjust the plasma density for homogenization according to the coarse density of the plasma density, that is, the density gradient.

Furthermore, according to the plasma device 1,
Since the independent auxiliary electromagnetic coil 41 is also provided on the inner circumference of the auxiliary electromagnetic coil 42, even if the plasma density on the semiconductor wafer W is different, for example, when the semiconductor wafer W is wavy when viewed from the side surface, the auxiliary electromagnetic coil 41 is assisted accordingly. By appropriately operating the electromagnetic coil 41, it is possible to correct such a wavy density difference.

When there is a difference in plasma density that does not require such partial adjustment, the auxiliary electromagnetic coils 41 and 42 are not used, and the antenna 22 is arranged to rotate or move around the bell jar. Main electromagnetic coil 25 for plasma excitation
Also by adjusting the excitation level, the electron cyclotron resonance region is formed on the semiconductor wafer W, and the plasma density of the plasma density can be reduced by using the portions A, C, and D in the graph shown in FIG. It is possible to implement controls.

In practice, the plasma apparatus 1 is used to form an electron cyclotron resonance region in the vicinity of the surface of the semiconductor wafer W only by the main electromagnetic coil 25 for plasma excitation without using the auxiliary electromagnetic coils 41 and 42. The results are shown in FIG. FIG. 5 shows electrons when the horizontal axis represents the vertical distance from the center of the main electromagnetic coil 25 (X in FIG. 4) toward the semiconductor wafer W, and the vertical axis represents the saturation ion current representing the plasma density. A comparison between the case where there is no cyclotron resonance (thin line in the graph) and the case where there is electron cyclotron resonance (thick line in the graph) is shown when the power of the high-frequency power supply 24 is changed.

According to the above graph, when there is no electron cyclotron resonance, the plasma density decreases as the distance from the center of the main electromagnetic coil 25 increases, but when there is electron cyclotron resonance, the plasma density at the resonance point concerned increases. The density is high. That is, according to the graph shown in FIG. 5, there is a peak at about 350 mm from the center of the main electromagnetic coil 25, and the position of this peak is the electron cyclotron resonance point. By the way, the magnetic field strength at this point is 14 Ga
It was uss. In addition, such a characteristic is that the high frequency power source 2
It can also be confirmed from the graph that the power does not change even when the power of 4 is changed.

According to yet another experiment, the magnetic field strength in the plasma generation chamber 20 by the main electromagnetic coil 25 was set to 400
The characteristics similar to those in the above graph were obtained even when the Gauss was lowered, and at this time, a peak was observed at about 280 mm from the center of the main electromagnetic coil 25. The magnetic field strength of the peak was about 16 Gauss.

Therefore, even if the auxiliary electromagnetic coils 41 and 42 are not used, the magnetic field strength in the vicinity of the semiconductor wafer W is appropriately adjusted by the main electromagnetic coil 25 to cause electron cyclotron resonance on the semiconductor wafer W. It is possible to correct the plasma density.

Although the auxiliary electromagnetic coils 41 and 42, which are the auxiliary magnetic field forming devices in the above-described embodiments, are both installed inside the plasma processing chamber 30, the present invention is not limited to this, that is, outside the plasma processing chamber 30, that is, the processing container 31. It may be installed outside.

The present invention can also be applied to a conventional Herringco wave plasma apparatus using a multipole magnetic field.

Furthermore, in the above embodiment, the case where the etching process is performed on the semiconductor wafer W as the object to be processed is not limited to this, but the present invention is not limited to this, and other plasma processes such as ashing process and CVD process are performed. Can also be applied to.

[0043]

According to the present invention, when various treatments are applied to an object to be treated by plasma using the energy of herringo waves, a slight difference in magnetic field strength at a small level is utilized to cause an effect on the object to be treated. It is possible to make the plasma density uniform by controlling the plasma density. Further, since the electron cyclotron resonance used when controlling the plasma density is realized under a small magnetic field strength in the RF band, the magnetic field forming device used also uses the conventional electron cyclotron resonance. It can be smaller than other types of devices. Furthermore, according to the present invention, it is possible to prevent the helicon wave from hitting the object to be processed directly and protect the object to be processed.

Particularly, according to claim 2, it is possible to finely and partially control the plasma density. Moreover, such control can be performed completely independently of the magnetic field forming device for generating the helicon wave plasma.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between magnetic field strength and plasma density for explaining the principle of the present invention.

FIG. 2 is an explanatory diagram of an object to be processed when controlling the plasma density using the present invention.

FIG. 3 is an explanatory diagram of an object to be processed when controlling the plasma density using the present invention.

FIG. 4 is an explanatory view schematically showing a plasma device used in an example of the present invention.

FIG. 5 is a graph showing a relationship between distance and plasma density in each of the case where electron cyclotron resonance is generated and the case where electron cyclotron resonance is not generated according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma device 20 Plasma generation chamber 21 Belger 22 Antenna 24 High frequency power supply 25 Electromagnetic coil 27 Processing gas introduction port 28 Gas source 30 Plasma processing chamber 31 Processing container 32 Exhaust port 33 Susceptor 41 Auxiliary electromagnetic coil 42 Auxiliary electromagnetic coil W Semiconductor wafer

Claims (2)

[Claims] 1. A method of generating plasma by utilizing the energy of a helicon wave generated by an alternating electric field and a magnetic field, and subjecting an object in a processing chamber to the processing under the plasma atmosphere, high-frequency power is applied. A plasma processing method, characterized in that the alternating electric field is created by applying, and further an electron cyclotron resonance region is formed in the vicinity of the object to be processed. 2. The plasma processing method according to claim 1, wherein an auxiliary magnetic field forming means is separately provided and the auxiliary magnetic field forming means forms an electron cyclotron resonance region in the vicinity of the object to be processed.