JP2003347282A - Method for plasma treatment and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for plasma which can suppress a rise in the temperature of an object to be treated by decreasing the quantity of radiation energy from a dielectric window to the object and an apparatus therefor. <P>SOLUTION: The surface of the dielectric window 3 of the plasma treatment apparatus which is opposed to the object is recessed to the side of the object 5. <P>COPYRIGHT: (C)2004,JPO

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 such as dry etching, sputtering and CVD used in the manufacture of electronic devices such as semiconductor devices and liquid crystal panels, and an apparatus therefor.

[0002]

2. Description of the Related Art In general, a plasma processing apparatus using an inductively coupled plasma source, which is used in a thin film deposition apparatus or the like,
As shown in the schematic cross-sectional view of FIG. 8, the inside of the chamber 31, which is a vacuum vessel, is evacuated, and a process gas such as oxygen gas flows into the chamber 31 from the gas inlet 32, and the dielectric window 33 A high-frequency current is supplied from an upper high-frequency power supply 35 to a conductor line (antenna coil) 34 disposed outside the dielectric window 33 via the dielectric window 33. Thus, an induced electromagnetic field is formed inside the chamber 31 and the process gas is turned into plasma to generate plasma. As a result, a predetermined process such as etching is performed on the semiconductor wafer, which is the workpiece 37 placed on the wafer support 36. The wafer support 36 is provided on a lower electrode 39 connected to a lower high-frequency power supply 38.

[0003] A heat shield plate 40 is provided between the dielectric window 33 and the object 37, and the heat shield plate 40 reduces the radiant heat transfer to the object 37, By cooling the dielectric window 33, the amount of radiation heat transfer is reduced. Further, fine dust and the like separated from the processing object 37 by the processing are exhausted from the exhaust port by the exhaust unit 41.

The uniformity of the plasma in the plasma processing apparatus largely depends on the distribution of the plasma determined by the shape of the conductor line (antenna coil) 34 and the shape of the dielectric window 33. For this reason, various shapes of the antenna coil 34 and the dielectric window 33 have been proposed.

The surface of the dielectric window 33 with respect to the workpiece 37 is generally formed in a parallel plane as disclosed in Japanese Patent No. 3114873, for example. Alternatively, as disclosed in Japanese Patent Application Laid-Open No. Hei 10-27785, the dome is formed in an upwardly convex shape.

In any case, when the object 37 is processed, the dielectric window 33 is heated by infrared rays emitted from the plasma or collisions of ions and electrons. Normally, the temperature of the dielectric window 33 is higher than the temperature of the workpiece 37 placed on the cooled wafer support 36.
Therefore, the processing target 37 receives the radiant energy from the dielectric window 33 and is consequently heated.

[0007]

In recent years, there has been a strong demand for high-speed response performance and high integration of semiconductor chips in terms of performance. Therefore, with the combination of aluminum as the wiring material and SiO ₂ as the interlayer insulating film used in the wiring process of the conventional semiconductor chip, as the pattern becomes finer, both the response speed and the power consumption become desired. Performance cannot be obtained. As a countermeasure for this,
The use of copper (Cu), which is a wiring material having a lower electric resistance value, and an interlayer insulating film made of a low dielectric constant film (Low-k) have been attracting attention as an interlayer insulating film. is there. However, at the time of processing using these materials, low-temperature processing is required to prevent deterioration of the Cu and Low-k materials.

In this case, a high-frequency current is supplied from an upper high-frequency power supply 35 to a conductor line 34 disposed outside the dielectric window 33 via a dielectric window 33 in a plasma processing apparatus as shown in FIG. When an induced electromagnetic field is formed inside the chamber 31 and the oxygen gas which is a process gas inside the chamber 31 is turned into plasma to process a semiconductor wafer which is an object to be processed 37 inside the chamber 31, the temperature of the semiconductor wafer is increased. Increases, oxidation (CuO conversion) of the Cu surface is promoted. As a result, problems such as an increase in the electric resistance value are caused. Further, since the Low-k film has a large linear expansion coefficient, if a temperature rise occurs during the processing, the processed shape after the processing is deformed, which causes a wiring failure or the like.

The temperature of the semiconductor wafer may be increased by the heat of the plasma itself, by heat from a heated gas, heat generated by a chemical or physical reaction on the surface of the workpiece, or dielectric heat. Radiation heat transfer from the body window 33 is exemplified.

Among the causes of these temperature rises, the radiant heat transfer from the dielectric window 33 converts the process gas inside the chamber 31 into plasma through the dielectric window 33 and causes the process gas inside the chamber 31 to be processed. When the object 37 is processed, the dielectric member forming the dielectric window 33 is heated by the plasma, so that the temperature of the object 37 increases due to radiant heat transfer from the dielectric window 33 to the object 37. Occurs, and this temperature rise may be a problem.

As a countermeasure, as shown in FIG. 8, a heat shield plate 40 is provided between the dielectric window 33 and the object 37, and the heat shield plate 40 allows the radiation transmission to the object 37. Although the heat is alleviated and the amount of radiated heat transfer is reduced by cooling the dielectric window 33, the installation of the heat shield plate 40 is not preferable because the number of components constituting the chamber 31 increases. In addition, materials that can be used in such an environment are generally expensive materials, which leads to an increase in the cost of the apparatus. Further, there is a problem that the cost is required when the chamber 31 is cleaned, and the assembly takes time.

When cooling the dielectric window 33,
The cooling mechanism is required, which also leads to an increase in the number of parts and an increase in the cost of the apparatus, which is not preferable.

The present invention has been made based on these circumstances, and a plasma processing method capable of suppressing a rise in the temperature of an object to be processed by reducing the amount of radiant energy from the dielectric window to the object to be processed. And its equipment.

[0014]

According to the first aspect of the present invention, an object to be processed is placed inside a chamber in which a dielectric window is partially formed, facing the dielectric window, In a plasma processing method in which an induced electromagnetic field is introduced into the chamber through the dielectric window to convert the supplied plasma gas into plasma, and a predetermined process is performed on the workpiece, the induced electromagnetic field is introduced. In this case, the heat radiation from the dielectric window is reduced.

According to the second aspect of the present invention,
A chamber provided with an object to be processed therein and having a dielectric window partially formed therein, a gas inlet for introducing a process gas into the chamber, exhaust means for exhausting the inside of the chamber, A plasma processing apparatus having means for exciting a field, wherein a shape of a surface of the dielectric window facing the object to be processed is formed in a convex shape toward the object to be processed. Device.

According to the third aspect of the present invention,
The convex shape of the dielectric window may be a spherical shape.

Further, according to the means of the present invention,
The convex shape of the dielectric window is a conical shape.

According to the fifth aspect of the present invention,
A chamber provided with an object to be processed therein and having a dielectric window partially formed therein, a gas inlet for introducing a process gas into the chamber, exhaust means for exhausting the inside of the chamber, A plasma processing apparatus having means for exciting a field, wherein a surface of the dielectric window facing the object to be processed is a plane inclined with respect to the surface of the object to be processed. Device.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

The inventor of the present invention has proposed a plasma processing apparatus for performing a plasma process on a semiconductor wafer or the like. Lower temperature (for example, about 50 ° C)
Of radiant heat transfer by radiant energy to the object to be treated, and
We have studied ways to reduce the amount of heat transfer due to the radiation. As a result, by reducing the view factor (representing the geometric relationship between the two surfaces) of the surface of the dielectric window facing the object, the amount of radiant heat transfer from the dielectric window to the object is reduced. Confirmed that it can be done.

FIG. 1 shows radiant heat transfer of the amount of radiant energy from the dielectric window whose temperature has risen to the object to be processed.
This will be described with reference to the schematic explanatory diagram shown in FIG.

When a high-frequency current is supplied from the upper high-frequency power supply 1 to the conductor line (antenna coil) 2 to radiate a high frequency from the conductor line 2 and generate plasma inside the chamber 4 through the dielectric window 3, the dielectric High frequency induction heating of body window 3 itself, infrared rays emitted from plasma, ions,
The dielectric window 3 is heated by the collision of electrons. At this time,
Since the temperature of the dielectric window 3 is higher than the temperature of the workpiece 5 cooled by the cooling means (not shown), the workpiece 5 facing the dielectric window 3 emits radiant energy from the dielectric window 3. , Resulting in a rise in temperature.

At this time, assuming that the opposing surfaces of the dielectric window 3 and the workpiece 5 are surfaces 1 and 2, respectively, the amount of heat transfer by radiation between the two surfaces (surfaces 1 and 2) is expressed by the following equation. expressed.

[0024] _{^{Q = σ (T 1 4 -T}} 2 4) · A 1 F 12 ······ ( Equation 1) Q: the amount of heat transferred subtracted as seen from one side sigma: Stefan-Boltzmann constant _{T 1} : Absolute temperature of surface 1 T ₂ : Absolute temperature of surface 2 A ₁ : Area of surface 1 F ₁₂ : View factor between surface 1 and surface 2 Further, the view factor (geometric relationship between the two surfaces) is as follows: It becomes the formula of.

(Equation 1) F ₁₂ : View factor for each small area element of surface 1 A ₂ : Area of surface 2 φ ₁ : Angle from normal of small area element of surface 1 to counterpart small area element φ ₂ : Small area element of surface 2 The angle s from the normal line to the counterpart minute area element; the distance between the minute surfaces of the surface 1 and the surface 2 where the area of the workpiece 5 is constant and the dielectric window 3
Assuming that the area of the object> the area of the object 5 and the surface temperature of the dielectric window 3 are also equal, as shown in a schematic diagram in FIG. 2, the shape of the dielectric window 3a with respect to the object 5 is flat. ,
As shown in FIG. 1, a comparison will be made with the case where the shape of the dielectric window 3 is a spherical shape with a downward convex shape.

If the view factor when the shape of the dielectric window 3a is a plane is an F _plane , and the view factor when the shape of the dielectric window 3 is a downwardly convex spherical shape is an F _{spherical surface} , the following equation is obtained. Thus, the F _{plane is} greater than the F4 _{spherical surface} (Equation 3).

Therefore, according to (Equation 1), the amount of heat received by the workpiece 5 is smaller when the dielectric window 3a has a downwardly convex spherical shape than when the dielectric window 3a has a flat shape. . As a result, the surface of the dielectric window 3 with respect to the processing target 5 is formed to have a spherical shape with a downward convex shape, so that the temperature rise of the processing target 5 can be suppressed.

In the above (Equation 1), in order to clearly explain the effect due to the difference in view factor, that is, the difference in the shape of the dielectric windows 3 and 3a, the dielectric windows 3 and 3a and the workpiece 5 are explained. It is considered that the material and the surface roughness are constant, and the term of the emissivity specific to the material is omitted.

Also, from (Equation 3), the dielectric windows 3, 3a
Since the surface facing the object 5 has a smaller shape factor than a flat surface, the spherical shape is not limited to the above-mentioned downwardly convex spherical shape. As shown in FIG. 3, a dome-shaped spherical surface (concave surface) is also conceivable in which the surface facing the workpiece 5 of the dielectric window 3b is convex upward. In this case, the shape of the dielectric window 3
Since the area per unit area of b with respect to the workpiece 5 increases, the same effect as in the case of a downwardly convex spherical surface is obtained. However, since the concave surface functions as a concave mirror and condenses light, heating by the concave surface is added. Therefore, it is not preferable because the overall heating is higher than the planar shape.

As shown in FIG. 4, the surface of the dielectric window 3c facing the object 5 is not limited to a spherical surface having a downward convex shape.
A similar effect can be obtained by forming a conical shape downward.

When the heat capacity of the dielectric window 3 is constant, the amount of radiated heat per unit area is maximized in a parallel plane which is the opposite of the planes. Even if a plane is formed,
The amount of radiant heat per unit area can be reduced.
However, their shape is only advantageous with respect to the reduction of heat transfer from the dielectric window 3, and other requirements of the plasma processing apparatus need to be considered individually. Therefore, it is necessary to select the shape of the lower surface of the dielectric window 3 in consideration of various requirements as a plasma processing apparatus.

For example, as shown in a schematic view of FIG. 5, a flat dielectric window 3d can be arranged to be inclined with respect to the workpiece 5. However, in this case, in order to compensate for the uniformity of the plasma inside the chamber 4, it is necessary to take a countermeasure such as devising the shape of the antenna coil 2 in accordance with the uniformity.

Usually, it is difficult to treat (Equation 2) analytically, and the analytical solution is limited to a relatively simple shape such as between two parallel or vertical plates. A method using the Monte Carlo method has been used to determine the shape factor of an arbitrary shape, but the calculation time is extremely long and the accuracy is not sufficient.

On the other hand, the method of calculating (Equation 2) by numerical integration is often used because it can be applied to an arbitrary shape and sufficient accuracy can be obtained. In general, MS method, LS method and AI method are known as their solutions. (For example, as literature, ASME HTD-Vo
l. 72, p45) Next, a plasma processing apparatus based on the above findings will be described below with reference to the schematic diagram of the high-frequency inductively coupled plasma processing apparatus shown in FIG.

The chamber 4, which is a processing container, has a lower electrode 6, which is a cathode electrode, provided therein. The lower electrode 6 is formed by processing a good conductor such as a metal so as to also have a function as an electrode, and the upper surface for mounting the workpiece 5 such as a wafer is flattened on the upper surface thereof, and the lower electrode 6 is insulated. A wafer support 7 to be processed is provided. The lower electrode 6 is connected to a lower high-frequency power supply 8. The lower high-frequency power supply 8 is independently controllable, and its output power is variable so that the bias voltage as a source of anisotropy in the plasma processing can be adjusted, and the lower high-frequency power supply 8 has a frequency of about 20 MHz to 400 KHz. Used.

The chamber 4 is formed of a metal such as aluminum so that the chamber 4 can be grounded. However, depending on a target process, there is a chamber 4 which is protected by using a liner such as quartz on its inner surface.

A dielectric window 3 is provided on a ceiling part of the wall of the chamber 4. This dielectric window 3
In order to efficiently transmit the alternating electromagnetic field to the plasma processing space inside the chamber 4, it is formed of an insulating member such as ceramic or quartz containing alumina having a high dielectric constant as a main component.

The shape of the dielectric window 3 has a small view factor in order to reduce the amount of heat transferred from the dielectric window 3.
That is, the lower surface forms a part of a spherical surface having a downward convex shape. Alternatively, as shown in a side sectional view in FIG. 4, a dielectric window 3c whose lower surface side is formed in a conical shape downward may be used. They can be set arbitrarily according to the processing cost and the desired amount of radiant heat.

In order to maintain a pressure lower than the atmospheric pressure (vacuum of a predetermined degree of vacuum) inside the chamber 4, process gas is supplied to the chamber 4 from the gas inlet 9 via a pipe. An apparatus (not shown) and a vacuum pump (not shown) are connected. This allows the inside of the chamber 4 to be controlled to an arbitrary pressure when performing processing on the workpiece 5.

As the process gas supplied from the process gas supply device into the chamber 4, a gas obtained by mixing an appropriate amount of a diluent gas with a reactive gas such as a CF-based gas or a silane gas is used. Further, an exhaust unit 11 is provided below the chamber 4.

On the other hand, on the atmospheric side of the dielectric window 3, there is a conductor line (antenna coil) 2 connected to an upper high-frequency power supply 1 for inducing an induced electromagnetic field inside the chamber 4, such as copper or the like. An antenna coil 2 made of a conductive material such as aluminum is provided. The antenna coil 2 may be in contact with the dielectric window 3 or may be installed at a certain distance from the dielectric window 3. Also, an upper high-frequency power supply connected to the antenna coil 2
1 has a variable output power, and its maximum output power is large for exciting and maintaining the plasma. The frequency is about 5 MHz to 510 MHz.

When a workpiece 5 such as a semiconductor wafer is processed by the plasma processing apparatus having the above configuration, first, the workpiece 5 is set on the wafer support 7 by a transfer means (not shown). Depending on the target processing process, the lower electrode 6 is provided below the wafer support 7 and the lower high-frequency power source 8 is provided.
Ion energy or the like is incident on the object 5 through a matching circuit (not shown). The wafer support 7 may have no lower electrode 6 depending on the process to be processed, or may be formed by using an electrostatic chuck on the wafer support 7 in order to control the temperature of the workpiece 5. In some cases, the processing object 5 is adsorbed, and cooling and heating are performed with a refrigerant or the like.

On the other hand, an induction magnetic field is generated from an upper high frequency power supply 1 having a frequency of several kHz to several MHz and a matching circuit (not shown) provided above the chamber 4 through the antenna coil 2 and the dielectric window 3. By generating the plasma and generating plasma in the chamber 4, plasma processing such as formation of a deposited film on a semiconductor wafer as the processing target 5 and etching is performed.

When this plasma treatment is performed, the dielectric window 3 is heated by high-frequency induction due to the incident high frequency, or is heated by the collision of infrared rays, ions and electrons emitted from the plasma. When a temperature difference occurs between the dielectric window 3 and the object 5 to be processed, thermal energy is transmitted by radiation.

On the other hand, when the temperature of the workpiece 5 is limited due to the use of members corresponding to the performance requirements of the semiconductor device, particularly when processing at a low temperature is required, such a case is obtained. In a simple plasma process, a rise in the temperature of the workpiece 5 due to radiation from the dielectric window 3 is a significant problem. In general, when low-temperature processing is performed, the wafer support 7 and the lower electrode 6 are provided with a temperature control mechanism for the object 5 to be processed. Even in this case, it is preferable that the radiation heat from the dielectric window 3 is smaller. In addition, the energy consumption of the temperature control mechanism can be reduced.

As described above, the dielectric window 3 has a small view factor in order to reduce the amount of radiant heat transfer, and the lower surface side may form a part of a downwardly convex spherical surface, or the lower surface side may have a lower surface side. It is formed in a conical shape downward. Thereby,
The amount of radiant heat transfer from the dielectric windows 3 and 3a to the workpiece 5 is reduced. As a result, good plasma processing can be performed on the workpiece 5.

In the above-described embodiment, a high-frequency inductively coupled plasma processing apparatus has been described. However, a plasma processing apparatus using a microwave and a slot antenna 12 as shown in a schematic side view in FIG. The same operation can be obtained by using a dielectric window 3 having a similar shape. In FIG. 7, the same reference numerals are given to the same functional portions as in FIG. 6, and their individual descriptions are omitted.

That is, the plasma processing by the plasma processing apparatus using the microwave and the slot antenna 12 is performed as follows. First, the inside of the chamber 4 is evacuated via the exhaust means 11. Subsequently, the processing gas is supplied through a gas inlet 9 provided around the chamber 4.
A process gas is introduced into the chamber 4 at a predetermined flow rate. Next, a conductance valve (not shown) provided in the exhaust unit 11 is adjusted to maintain the inside of the chamber 4 at a predetermined pressure.

Subsequently, desired power is supplied from a microwave power supply (not shown) to the inside of the chamber 4 via the waveguide 13. At this time, the microwave introduced into the waveguide 13 is split right and left by the E-branch, and propagates with a guide wavelength longer than free space. 1/2 or 1 of the guide wavelength
The high-density plasma is generated by the microwaves transmitted through the dielectric window 3 through the slot antenna 12 installed at every / 4 and introduced into the chamber 4. In this state, the microwave incident on the interface between the dielectric window 3 and the plasma cannot propagate into the plasma, but propagates at the interface between the dielectric window 3 and the plasma as a surface wave. The surface waves introduced from the adjacent slot antennas 13 interfere with each other and form an antinode of the electric field every half of the wavelength of the surface wave. A high-density plasma is generated by the antinode electric field due to the surface wave interference. The process gas introduced from the gas inlet 9 is excited and ionized by the generated high-density plasma, activated by a reaction, and uniformly treats the surface of the workpiece 5 placed on the wafer support 7. . At this time, radiant heat from the high-density plasma or the dielectric window 3 that is rising in temperature in contact with the plasma is generated by the shape of the dielectric windows 3 and 3a, which is a curved surface or a conical surface having a downwardly convex shape with a small form factor. Are formed, so that the irradiation of radiation heat to the processing object 5 is suppressed.

In each of the above-described embodiments, a case has been described in which a semiconductor wafer is used as an object to be processed.
Alternatively, it may be electrically insulating.

As described above, according to the above-described embodiment, when performing the plasma processing in the plasma processing apparatus,
The amount of radiant energy from the dielectric window to the object to be processed can be reduced, and the temperature rise of the object to be processed can be suppressed. Therefore, copper (Cu) which is a wiring material having a low electric resistance value can be used for a semiconductor device, and an interlayer insulating film made of a low dielectric constant film (Low-k) can be used as an interlayer insulating film. Thus, a highly integrated semiconductor device can be manufactured.

[0051]

According to the present invention, the amount of radiant energy from the dielectric window to the object to be processed is reduced, whereby the temperature rise of the object to be processed can be suppressed. Thus, a highly integrated semiconductor device can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of radiation heat transfer of a radiation energy amount from a dielectric window to an object to be processed.

FIG. 2 is a schematic diagram when the shape of a dielectric window is flat.

FIG. 3 is a schematic diagram of a dome-shaped spherical surface in which a dielectric window faces a workpiece.

FIG. 4 is a schematic diagram of a conical surface of a dielectric window facing an object to be processed.

FIG. 5 is a schematic diagram in which a surface of a dielectric window facing a workpiece is inclined by a flat plate.

FIG. 6 is a schematic view of an embodiment of a plasma processing apparatus according to the present invention.

FIG. 7 is a schematic view of an embodiment of a plasma processing apparatus according to the present invention.

FIG. 8 is a schematic diagram of a conventional plasma processing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upper high frequency power supply, 2 ... Conductor line (antenna coil), 3, 3a-3d ... Dielectric window, 4 ... Chamber, 5 ...
Workpiece, 6 ... Lower electrode, 7 ... Wafer support, 8 ... Lower high frequency power supply, 9 ... Gas inlet, 11 ... Exhaust means, 12 ...
Slot antenna, 13 ... waveguide

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4K029 BD01 DC28 DC35                 4K030 CA04 CA12 FA04 KA15 KA30                       KA46 LA18                 5F004 BA20 BD04 BD05 DA26 DB08                       DB23 EB03

Claims (5)

[Claims] An object to be processed is placed inside a chamber in which a dielectric window is partially formed, facing the dielectric window, and an induction electromagnetic field is applied to the inside of the chamber through the dielectric window. In the plasma processing method in which the plasma gas introduced and supplied to the substrate is turned into plasma and a predetermined process is performed on the object to be processed, radiant heat from the dielectric window is reduced when the induction electromagnetic field is introduced. A plasma processing method characterized in that: 2. A chamber provided with an object to be processed therein and having a dielectric window partially formed therein, a gas inlet for introducing a process gas into the chamber, and an exhaust for exhausting the inside of the chamber. Means, and a plasma processing apparatus having means for exciting an induction electromagnetic field, wherein a shape of a surface of the dielectric window facing the object to be processed is formed to be convex toward the object to be processed. Characteristic plasma processing apparatus. 3. The plasma processing apparatus according to claim 2, wherein the convex shape of the dielectric window is a spherical shape. 4. The plasma processing apparatus according to claim 3, wherein the convex shape of the dielectric window is a conical shape. 5. A chamber provided with an object to be processed therein and having a dielectric window formed in a part thereof, a gas inlet for introducing a process gas into the chamber, and an exhaust for exhausting the inside of the chamber. Means, and a plasma processing apparatus having means for exciting an induction electromagnetic field, wherein a surface of the dielectric window facing the workpiece is a plane inclined with respect to a facing surface of the workpiece. Characteristic plasma processing apparatus.