KR100755594B1 - Plasma etching apparatus having parallel plate structure of capacitive coupling type and plasma etching method using the same - Google Patents

Abstract

According to the present invention, the plasma etching apparatus includes a processing chamber 2 in which a lower electrode 5 and an upper electrode 21 are disposed therein so as to face each other. At the time of etching, the substrate G to be processed is mounted on the lower electrode 5, the processing gas is introduced into the reduced pressure processing chamber 2, and RF power is applied to the upper electrode 21 to form a plasma. The mounting surface 5a on the lower electrode 5 is formed to mount a rectangular substrate having a long side of 600 mm or more. The frequency of the RF power is above 10 MHz and set below 13.56 MHz.

Description

Plasma Etching Apparatus and Plasma Etching Method with Capacitively Coupled Parallel Plate Structure TECHNICAL FIELD AND PLASMA ETCHING METHOD USING THE SAME             

1 is a graph showing the relationship between the vacuum pressure and Vpp in a processing chamber;

2 is a cross-sectional view schematically showing a plasma etching apparatus for an LCD substrate according to an embodiment of the present invention;

3 is a plan view showing a susceptor (lower electrode) of the plasma etching apparatus shown in FIG. 2;

4 is a graph showing the relationship between frequency and average etch rate of RF power and in-plane uniformity;

5 is a graph showing a characteristic curve indicating a relationship between the frequency of the RF power and the etching rate.

Explanation of symbols for the main parts of the drawings

1: etching apparatus 2: process chamber

3: ground wire 4: susceptor support                 

5: susceptor 7: refrigerant chamber

8: refrigerant introduction pipe 9: refrigerant discharge pipe

14 lift pin 16: focus ring

21: upper electrode 22: electrode support

23 electrode plate 24 discharge hole

25: insulation material 26: gas inlet

27: gas supply pipe 28: valve

29 mass flow controller 30 process gas supply source

31: exhaust pipe 32: gate valve

33: feed rod 35: exhaust device

40: RF power supply 41: matching device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus having a capacitively coupled parallel plate structure for etching a large rectangular to-be-processed substrate such as a liquid crystal display (LCD) substrate and a plasma etching method in the apparatus. In addition, here, an etching means the process which remove | eliminates the object on a to-be-processed board | substrate by chemical and / or physical action.                         

For example, in an LCD manufacturing process, dry etching using plasma is performed with respect to the glass LCD substrate which is a to-be-processed substrate. As a device for performing such plasma etching, it is mainstream to have a capacitively coupled parallel plate structure.

An etching apparatus having a capacitively coupled parallel plate structure includes a processing chamber in which a pair of parallel plate electrodes (upper electrode and lower electrode) is disposed. At the time of etching, a processing gas is introduced into the processing chamber and RF (high frequency) power is applied to at least one of the electrodes. The processing gas is plasmaated by the RF electric field formed between the electrodes by the RF power, and etching is performed on the substrate to be processed by this plasma. In such an etching apparatus, the frequency of 13.56 MHz or its integer multiple is generally used as the frequency of the RF power for plasma generation.

In recent years, the demand for further enlargement has increased for LCD substrates, and an extremely large substrate having one side of 1 m has also been manufactured. In conjunction with the increase in size of the substrate to be processed, when the processing chamber is enlarged, a uniform plasma cannot be obtained, and the uniformity of etching with respect to the substrate to be processed tends to be lowered.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a plasma etching apparatus having a capacitively coupled parallel plate structure capable of uniformly etching a large substrate, and a plasma etching method in the apparatus. The purpose.

A first aspect of the present invention is a plasma etching apparatus having a capacitively coupled parallel plate structure, comprising: an airtight processing chamber configured to accommodate a rectangular substrate to be processed having a long side of 600 mm or more, and supplying a processing gas for etching into the processing chamber. A processing gas supply system, an exhaust system for evacuating the inside of the processing chamber and setting the inside of the processing chamber to a vacuum, and means and electrodes disposed in the processing chamber and grounded, and for mounting the substrate to be processed. A lower frequency electrode, an upper electrode disposed in the processing chamber so as to face the lower electrode, and a (high frequency) electric power having a frequency within a frequency range of 10 MHz or more and less than 13.56 MHz with the upper electrode for plasmalizing the processing gas. It is provided with an RF power supply for supplying.

A second aspect of the present invention is a plasma etching method in a plasma etching apparatus having a capacitively coupled parallel plate structure, wherein a rectangular to-be-processed substrate having a long side of 600 mm or more is housed in an airtight processing chamber and disposed in the processing chamber. Mounting the substrate to be processed on the lower electrode, supplying a processing gas for etching into the processing chamber while evacuating the processing chamber, setting the processing pressure in the processing chamber, and grounding the lower electrode; Supplying RF power having a frequency within a frequency range of 10 MHz or more and less than 13.56 MHz to the upper electrode disposed in the processing chamber so as to face the lower electrode, thereby plasmalizing the processing gas, and And etching the substrate to be processed.

The above and other objects, features, aspects, advantages, and the like of the present invention will become more apparent from the following detailed embodiments described with reference to the accompanying drawings.

The present inventors have studied the cause of the in-plane uniformity of etching in the development process of the present invention in a rectangular to be processed longer than 600 mm long or a square to be processed larger than 600 mm long sides. did. As a result, the present inventors obtained the knowledge as described below.

1 is a graph showing the relationship between the vacuum pressure and Vpp in the processing chamber. As shown in FIG. 1, the minimum value of Vpp exists in the relationship between the vacuum degree (pressure) in a process chamber and the RF voltage Vpp in an electrode. Here, Vpp is a peak-to-peak value of the voltage. According to the experiment, when the substrate size became large, the phenomenon that the minimum value of Vpp shifted to the high vacuum side (low pressure side) was discovered. Empirically, it is known that the plasma density becomes uniform near the minimum value of Vpp. That is, it is considered that the above-described shift of the minimum value of Vpp lowers the uniformity of the plasma and thus lowers the uniformity of etching on the substrate.

From the viewpoint that the plasma density becomes uniform near the minimum value of Vpp, when the minimum value of Vpp is shifted to the high vacuum side (low pressure side) as the size of the substrate increases, the vacuum degree (pressure) in the process chamber is also changed to the high vacuum side (low pressure). Side) is considered to be preferable. However, experiments have shown that in this case, the problem of sputtering of the cathode electrode (upper electrode) and the problem of lowering the plasma density have occurred. As a result of closer examination in order to avoid such a problem, if the frequency of the RF power to be supplied is lower than the conventional 13.56 MHz, the minimum value of Vpp can be shifted to the lower vacuum side (high pressure side). Found.

Therefore, even in the large substrate as described above, if the frequency of the RF power is lower than 13.56 MHz, the minimum value of Vpp can be set within the processing pressure range without causing problems such as sputtering of the cathode electrode and lowering of the plasma density. If plasma etching is performed in the vicinity of the minimum value of Vpp, uniform processing can be performed by a uniform plasma without accompanying the problems described above. In other words, the frequency of the RF power is a phenomenon that the Vpp minimum value is shifted to the lower side of the processing pressure as the size of the substrate is increased, and the processing pressure is high as the minimum value of Vpp is lower than the frequency of the RF power 13.13 MHz. What is necessary is to select to compensate by the phenomenon shifted to the side. However, if the frequency of the RF power is less than 10 MHz, the plasma density itself decreases, and therefore it is necessary to set the frequency to 10 MHz or more.

Further, in the RF mode in which RF power is applied to the lower electrode on which the target object is to be mounted, the above problem is not found because the action of ions in the plasma is the main action of etching. Therefore, the present invention is applied to an RF mode in which RF power is applied to an upper electrode on which an object to be processed is not mounted.

Further, the present invention can be applied irrespective of the size of the substrate as long as the long side has a rectangular (rectangular or square) substrate to be processed having a diameter of 600 mm or more. However, from the design viewpoint of the processing chamber, it is preferable that the substrate to be processed is a rectangular substrate having one side of 3 m or less.

EMBODIMENT OF THE INVENTION Below, the Example of this invention comprised based on such knowledge is demonstrated with reference to drawings. In addition, in the following description, the same code | symbol is attached | subjected about the component which has nearly the same function and structure, and the overlapping description is made only when necessary.

2 is a cross-sectional view schematically showing a plasma etching apparatus for an LCD substrate according to an embodiment of the present invention. FIG. 3 is a plan view illustrating a susceptor (lower electrode) of the plasma etching apparatus shown in FIG. 2. The etching apparatus 1 is comprised as an apparatus which has a capacitively coupled parallel flat plate structure in which the electrode plate opposes up and down parallel, and the power supply for plasma formation was connected to the upper electrode.

The etching apparatus 1 has the airtight processing chamber 2 formed, for example in the shape of the square cylinder which consists of aluminum by which the surface was anodized (anodic oxidation treatment). The processing chamber 2 is configured to accommodate a large rectangular LCD substrate G having a long side of 600 mm or more and 3 m or less. The processing chamber 2 is grounded via the ground wire 3. At the bottom of the processing chamber 2, a susceptor support 4 having a foot shape is disposed. Moreover, on the susceptor support 4, the susceptor 5 for mounting LCD substrate G which is a to-be-processed board | substrate is arrange | positioned. The susceptor 5 is grounded and functions as a lower electrode.

The refrigerant chamber 7 is disposed inside the susceptor support 4. The coolant is introduced into the coolant chamber 7 through the coolant introduction pipe 8, and discharged from the coolant discharge pipe 9 to circulate. Cooling heat of the coolant is transferred to the substrate G via the susceptor 5, whereby the surface to be processed of the wafer W is controlled to a desired temperature.

The susceptor 5 is also formed in the shape of a footnote like the susceptor support 4. The upper center part of the susceptor 5 becomes a convex part, and the upper surface of the convex part becomes the mounting surface 5a for mounting the board | substrate G. As shown in FIG. The mounting surface 5a has substantially the same plane dimension as the substrate G. That is, as shown in FIG. 2, the mounting surface 5a forms a mutually similar shape with the board | substrate G, and has the length L of the long side corresponding to 3 m or less and the length of 600 mm or more of the long side of the board | substrate G. As shown in FIG. In addition, the mounting surface 5a of the susceptor 5 may have a square having a length of 600 mm or more on one side, and in this case, a square substrate G having a length of 600 mm or more on one side is mounted.

From the susceptor 5, as shown in FIG. 3, four lift pins 14 protrude so that up-and-down movement is possible. When the board | substrate G is mounted and removed with respect to the mounting surface 5a, the lift pin 14 protrudes from the mounting surface 5a. The frame-shaped focus ring 16 is disposed at the upper periphery of the susceptor 5 so as to surround the substrate G. As shown in FIG. The focus ring 16 is made of an insulating material such as ceramic.

Above the susceptor 5, an upper electrode 21 having an opposite surface 21a concentric with the mounting surface 5a and facing in parallel is disposed. The opposing surface 21a has a plane dimension substantially the same as the substrate, or a plane dimension larger than the substrate G (larger in this embodiment). The opposing surface 21a is arrange | positioned so that the space | interval may be about 30-300 mm, for example with respect to the mounting surface 5a.

The upper electrode 21 is supported on the upper part of the processing chamber 2 via the insulating material 25. The upper electrode 21 has the electrode plate 23 which comprises the opposing surface 21a, and the electrode support 22 which supports the electrode plate 23 and consists of an electroconductive material, for example, the surface of which is anodized. In order to configure the upper electrode 21 as a shower head, a processing gas head is formed in the electrode support 22, and a plurality of discharge holes 24 are formed in the electrode plate 23.

A gas inlet 26 is formed in the electrode support 22 in the upper electrode 21, and a gas supply pipe 27 is connected to the gas inlet 26. The processing gas supply source 30 is connected to the gas supply pipe 27 via a valve 28 and a mass flow controller 29. The processing gas for etching which is plasma etching is supplied from the processing gas supply source 30.

An exhaust pipe 31 is connected to the bottom of the processing chamber 2, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 is provided with a vacuum pump such as a turbomolecular pump, whereby the inside of the processing chamber 2 can be vacuum sucked up to a predetermined reduced pressure atmosphere. In addition, a port that is opened and closed by the gate valve 32 is formed on the sidewall of the processing chamber 2. In the state in which the gate valve 32 is opened, the board | substrate G is conveyed with the adjacent load lock chamber (not shown) through the port.

The RF power supply 40 is connected to the upper electrode 21 via the matcher 41. This power feeding is performed by the feeding rod 33 connected to the upper center part of the upper electrode 21. The RF power source 40 applies RF power with a frequency in the range of 10 MHz or more and less than 13.56 MHz to the upper electrode 21. Uniform plasma etching can be performed by applying RF power in this range of frequencies.

Next, the processing operation in the etching apparatus 1 will be described taking the case of etching an amorphous silicon film formed on the substrate G as an example.

First, the substrate G, which is the object to be processed, is loaded into the processing chamber 2 from the load lock chamber (not shown) after the gate valve 32 is opened and mounted on the susceptor 5. In this case, the mounting and dismounting of the substrate G are performed by the lift pins 14 provided so as to protrude from the susceptor 5 through the inside of the susceptor 5. Subsequently, the gate valve 32 is closed, and the inside of the processing chamber 2 is vacuum sucked up to a predetermined vacuum degree by the exhaust device 35.

Thereafter, the valve 28 is opened so that the processing gas is supplied from the processing gas supply source 30 while the flow rate is adjusted by the mass flow controller 29. The processing gas is introduced into the upper electrode 21 through the processing gas supply pipe 27 and the gas inlet 26. In addition, the processing gas is uniformly discharged with respect to the substrate G through the discharge hole 24 of the electrode plate 23 as shown by the arrow in FIG. 2. The supply of the processing gas is performed while exhausting the inside of the processing chamber 2, whereby the pressure in the processing chamber 2 is maintained at a predetermined value.

In addition, RF power is applied from the RF power supply 40 to the upper electrode 21, whereby an RF electric field is formed between the upper electrode 21 and the susceptor 5 as the lower electrode. The process gas is excited by the RF electric field, dissociates, and becomes a plasma, and etching is performed by the plasma.

In this case, as in the prior art, when the frequency of the applied RF power is 13.56 MHz or an integral multiple thereof, if the pressure in the processing chamber is the same as in the conventional case, the rectangular board having a long side of 600 mm or more or the square of a large side board having a long side of 600 mm or more is described above. The same problem arises. That is, it is difficult to make the plasma uniform throughout the substrate G, and there is a tendency for nonuniformity of the plasma to occur. This is because, as described above, when the substrate is enlarged, the minimum value of Vpp, which is known to be uniform in the plasma density, is shifted to the high vacuum side (low pressure side).

If the vacuum degree (pressure) in the processing chamber is set to a high vacuum degree (low pressure) by the amount of the shifted minimum value of Vpp, there is a problem that the electrode plate 23 of the upper electrode 21 serving as the cathode electrode is sputtered. Therefore, in order to secure the plasma uniformity while avoiding the problem of sputtering of the electrode plate 23, in this embodiment, the frequency of the RF power applied from the RF power supply 40 to the upper electrode 21 is 10 MHz or more. And less than 13.56 MHz. By making the frequency less than 13.56 MHz in this manner, the minimum value of Vpp can be shifted to the higher voltage side, and the vicinity of the minimum value of Vpp can be avoided without causing a problem that the electrode plate 23 of the upper electrode 21 serving as the cathode is sputtered. Plasma etching can be performed at. Therefore, a uniform process can be performed by a uniform plasma. However, if the frequency is less than 10 MHz, the plasma density itself is lowered and the processing efficiency is lowered. Therefore, the frequency is set to 10 MHz or more.

In the case of the PE mode in which RF power is applied to the upper electrode 21 on which the substrate is not mounted as in the present embodiment, in order to obtain a good plasma state, the pressure in the processing chamber 2 is 13.3 Pa (about 100 mTorr) or more. desirable. The upper limit of the pressure in the processing chamber is usually set within a range in which plasma etching can be performed, for example, about 300 Pa (about 2.26 Torr). Specifically, in the case of normal etching, 25-40 Pa (about 200-300 mTorr) is preferable, and in the case of ashing, 133-200 Pa (about 1-1.5 Torr) is preferable.

Next, the experiment performed in order to confirm the effect of this invention while setting the process conditions of an etching is demonstrated.

An etching experiment was performed on the square LCD substrate of 680 mm x 680 mm using the apparatus shown in FIG. The experiment was conducted with the RF power supplied from the RF power supply set to 2400 W and the frequencies set to 13.56 MHz, 12.0 MHz, and 10.0 MHz. In addition, a mixed gas of SF ₆ , HCl, and He was used as the processing gas, and the pressure in the processing chamber was set to 30 Pa.

4 is a graph showing the relationship between the frequency obtained from this experimental result, the average etching rate of the entire substrate G, and the in-plane uniformity. In FIG. 4, the solid line shows the average etching rate, and the dotted line shows the in-plane uniformity.

As shown in Fig. 4, in the case of 13.56 MHz, the average etching rate of the entire substrate G was 165.4 nm / min, and the in-plane uniformity was ± 24%. In the case of 12.0 MHz, the average etching rate was 242.3 nm / min, and the in-plane uniformity was ± 11%. In the case of 10.0 MHz, the average etching rate was 240.2 nm / min and in-plane uniformity was ± 16%.

5 is a graph showing characteristic curves showing the relationship between the frequency and the etching rate obtained in this experimental result. In FIG. 5, characteristic curve A1 shows the average value of the etching rate in the center part of a to-be-processed substrate, and characteristic curve A2 shows the average value of the etching rate in the periphery of a to-be-processed substrate.

As shown in Fig. 5, the characteristic curve A1 at the center has a peak at almost the center (12 MHz) within the frequency range of 10 MHz to 13.56 MHz, while the characteristic curve A2 has a decrease in frequency within the same frequency range. Accordingly and also intersects with the characteristic curve A1. By selecting the frequencies near the intersections of the characteristic curves A1 and A2 under various conditions under which such characteristic curves A1 and A2 are obtained, it is possible to set the etching conditions of high etching rate and high in-plane uniformity.

4 and 5 show that the etching rate is high and the in-plane uniformity is good at a frequency around 12 MHz. In addition, as an optimum frequency, the etching rate and in-plane uniformity are comprehensively evaluated, and the frequency near the intersection of the characteristic curves A1 and A2 is selected.

As described above, according to the present invention, when the frequency of the RF power supplied to the electrode is 10 MHz or more and less than 13.56 MHz, the plasma can be uniform in plasma etching of a rectangular large substrate having a long side of 600 mm or more. Uniform plasma etching can be performed.

In addition, this invention is not limited to the said Example, A various deformation | transformation is possible. For example, although the embodiment shows the case where the present invention is applied to an etching apparatus of an LCD substrate, the present invention can also be applied to an etching apparatus for processing a substrate of a panel type display apparatus other than an LCD. In addition, in the scope of the idea of the present invention, those skilled in the art can come up with various modifications and modifications, and these modifications and modifications are considered to be within the scope of the present invention.

Claims (12)

A plasma etching apparatus having a capacitively coupled parallel plate structure, An airtight processing chamber configured to accommodate a rectangular to-be-processed substrate having a long side of 600 mm or more; A processing gas supply system for supplying a processing gas for etching into the processing chamber; An exhaust system for evacuating the inside of the process chamber and setting the inside of the process chamber to a vacuum; A lower electrode disposed in the processing chamber and grounded, the lower electrode functioning as a means for mounting the substrate and the electrode; An upper electrode disposed in the processing chamber so as to face the lower electrode; RF power supply for supplying RF (high frequency) power having a frequency within a frequency range of 10 MHz or more and less than 13.56 MHz to the upper electrode to plasma the process gas Plasma etching apparatus comprising a. The method of claim 1, And the processing chamber and the lower electrode are configured to process a rectangular to-be-processed substrate having one side of 3 m or less. The method of claim 1, The lower electrode has a mounting surface having substantially the same planar dimensions as the substrate to be processed, And the upper electrode has an opposing surface that faces the mounting surface at a plane dimension substantially the same as the substrate to be processed or a plane dimension larger than the substrate to be processed. The method of claim 1, The plasma etching apparatus having a frequency of about 12 MHz, The method of claim 1, The frequency of the RF power, ① phenomenon that the minimum value of the peak-to-peak value Vpp of the RF power is shifted to the side of the lower processing pressure as the size of the substrate to be processed increases, The plasma etching apparatus, wherein the minimum value of Vpp is a frequency selected to compensate by the phenomenon that the processing pressure is shifted to the higher side as the frequency of the RF power is lower than 13.56 MHz. In the plasma etching method of the plasma etching apparatus having a capacitively coupled parallel plate structure, Storing a rectangular to-be-processed substrate having a long side of 600 mm or more in an airtight processing chamber, and mounting the to-be-processed substrate on a lower electrode disposed in the processing chamber; Supplying a processing gas for etching into the processing chamber while evacuating the processing chamber, and setting the inside of the processing chamber to a processing pressure; With the lower electrode grounded, RF power having a frequency within a frequency range of 10 MHz or more and less than 13.56 MHz is supplied to the upper electrode disposed in the processing chamber so as to face the lower electrode so as to plasma the process gas. Fair, Etching the substrate to be processed by the plasma Plasma etching method comprising a. The method of claim 6, The substrate to be processed has a plasma etching method of forming a rectangle having one side of 3 m or less. The method of claim 6, The lower electrode has a mounting surface having substantially the same planar dimensions as the substrate to be processed, And the upper electrode has an opposing surface that opposes the mounting surface with a plane dimension substantially the same as that of the substrate or a plane dimension larger than that of the substrate. The method of claim 6, The frequency is about 12 MHz. The method of claim 6, The processing pressure is 13.3 Pa or more and 300 Pa or less. The method of claim 6, The frequency of the RF power is a phenomenon in which the minimum value of the peak-to-peak value Vpp of the RF power is shifted toward the lower side of the processing pressure as the size of the substrate is increased, and The plasma etching method is selected so that the minimum value is compensated by the phenomenon that the processing pressure is shifted to the higher side as the frequency of the RF power is lower than 13.56 MHz. The method of claim 6, The frequency of the said RF power corresponds to the vicinity of the intersection where the 1st and 2nd characteristic curve which respectively shows the relationship between the said frequency and the etching rate in the center part and periphery part of the said to-be-processed board | substrate cross each other in the said frequency range. Plasma etching method selected.

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