JP4112822B2 - Plasma processing equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus that performs a surface treatment such as etching on a square substrate such as a liquid crystal glass substrate.
[0002]
[Prior art]
In recent years, the demand for rectangular substrates such as liquid crystal panels or organic EL panels for displays has increased, and among these, the size of these rectangular substrates has been increasing.
[0003]
An example of various plasma processing apparatuses used in the manufacturing process of a liquid crystal panel or an organic EL panel using such a square substrate, as shown in FIG. 1, is a vacuum processing tank in which plasma processing is performed. 2 and a transfer chamber 3 for transferring to the next process, which are connected via a gate valve 4.
[0004]
Then, in the vacuum processing chamber 2 of such various plasma processing apparatuses 1, a rectangular lower electrode 107 is provided corresponding to the shape of the rectangular substrate as shown in FIG. Since many of the lower electrodes use an aluminum plate as a base material and are subjected to alumite treatment from the standpoints of surface insulation and corrosion resistance, the corners of the four corners of the lower electrode 107 are corners. In order to prevent the alumite film from becoming thin at the corners and to ensure anodizing, the corners of the four corners are chamfered in an arc shape or a spherical shape, as shown in FIG. Has been given. This chamfering also has an effect of preventing abnormal discharge due to concentration of discharge at sharp corners.
[0005]
In addition, as shown in FIG. 7, an insulating cover 112 such as an alumina block is provided around the lower electrode 107. Due to the recent increase in size of the substrate, a ring-shaped integrated body is required in terms of cost and handling. The insulating blocks 112a-d are arranged so as to be in contact with each other at two junctions 112k provided at the four corners of the lower electrode 107.
[0006]
[Problems to be solved by the invention]
However, in a low-pressure process used for recent microdevice processing, for example, a process of 10 Pa or less, the chamfering of R2 or less as described above may cause discharge concentration at the corners of the lower electrode.
[0007]
Thus, the conventional small chamfering is insufficient to prevent the concentration of discharge at the edge portion, which causes the plasma to become unstable.
[0008]
Further, even in a structure in which the periphery is covered with an insulating cover using an alumina block, the divided portions of the insulating cover 112 installed around the lower electrode 107 are in contact with the four corners of the lower electrode. From 112k, the discharge easily enters the corner, and the discharge tends to concentrate due to the discharge wrapping around the corner.
[0009]
For this reason, the corner portion of the lower electrode is easily damaged, and although the corner portion is chamfered, it is slightly chamfered, so that the adhesion of the alumite film is not sufficient. In this way, since the adhesion of the alumite to the base material is poor, there is no great effect on the wraparound of the discharge, and the phenomenon that the alumite coating at the corners breaks down due to the concentration of discharge and peels occurs. .
[0010]
In this way, when the alumite film is peeled off, the insulating property is lost only in that portion, so that current flows intensively and adversely affects the plasma state. For this reason, there was a problem that the apparatus stopped due to an error and the operating rate was greatly reduced.
[0011]
The present invention has been made in view of the above circumstances, and solves the above-described problems. When performing plasma processing such as etching using a square substrate such as liquid crystal, the present invention can be used in any process pressure region. An object of the present invention is to provide a plasma processing apparatus capable of preventing the occurrence of abnormal discharge at the corner of the lower electrode on which the mold substrate is installed and performing stable plasma processing.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in a plasma processing apparatus that performs plasma processing by exciting plasma in a sealed vacuum chamber, an electrode having corner portions of four corners on which a square substrate is placed has a corner portion. A chamfered portion having a chamfering amount equal to or greater than R3 is formed, the periphery of the electrode is covered with a plurality of divided insulating blocks, and the junction of the insulating block is a region excluding the corners of the electrode The insulating block has a structure having a concavo-convex portion at a joint location, and the insulating block is arranged by fitting the concavo-convex portion of the block facing each other.
According to such a configuration, even if discharge wraps around from the divided portion, since it is not a corner portion of the lower electrode but a linear portion, it is difficult to reach the corner portion directly and abnormal discharge is prevented. Further, since the chamfering amount or the chamfering radius of the lower electrode where the discharge tends to concentrate is a chamfering amount equal to or larger than R3 and larger than the chamfering amount of the corner of the substrate to be processed, However, the concentration of discharge to the lower electrode is drastically reduced because the concentration is directed toward the substrate to be processed having sharper corners than the lower electrode. Further, since the substrate to be processed has lower conductivity than the lower electrode, abnormal discharge is less likely to occur. For this reason, it is possible to prevent abnormal discharge and perform stable and highly reliable discharge.
[0021]
According to a second aspect of the present invention, in a plasma processing apparatus for performing plasma processing by exciting plasma in a sealed vacuum chamber, an insulating block in which a periphery of a lower electrode on which a substrate to be processed is placed is divided into a plurality of parts The insulating block is formed so that the joint portion is located in a region excluding the corner portion of the lower electrode.
[0022]
According to such a configuration, even if discharge wraps around from the divided portion, since it is not a corner portion of the lower electrode but a straight portion, it is difficult to reach the corner portion directly, and abnormal discharge can be prevented.
[0023]
Preferably, the lower electrode is configured such that the chamfering amount of the corner portion is larger than the chamfering amount of the corner portion of the substrate to be processed.
[0024]
According to this configuration, in addition to the above effects, it is possible to further suppress abnormal discharge.
[0025]
A third aspect of the present invention is a plasma processing method for exciting plasma in a sealed vacuum container and performing plasma processing on a surface of a substrate to be processed disposed on a lower electrode disposed in the vacuum container. The lower electrode is composed of a conductive electric member that has been subjected to insulation treatment while leaving at least a part of the surface as a conductive surface region. Between the lower electrode and the upper electrode disposed in the vacuum vessel, under an exhaust process for exhausting to a pressure of A plasma excitation start step for applying a voltage to excite plasma between the lower electrode and the upper electrode; and an insulation treatment step for insulating the conductive surface region of the lower electrode after the plasma excitation start step When Wherein after the insulating treatment process, wherein the includes a plasma treatment step of performing a plasma process to the substrate to be treated at the desired processing conditions that plasma treatment can be made to the target substrate.
[0026]
According to such a configuration, it is possible to extremely effectively prevent abnormal discharge by leaving a part of the conductive surface and forming a current escape path at the time of plasma excitation in which abnormal discharge is most likely to occur.
[0027]
Preferably, the insulating treatment step is an insulating treatment step of introducing an oxidizing gas into the vacuum vessel to insulate the conductive surface region.
[0028]
According to such a configuration, it is possible to perform insulation efficiently only by switching the gas, and it is possible to perform plasma processing with high working efficiency, stability, and high reliability.
[0029]
Desirably, the conductive member is made of aluminum, and the insulating treatment step includes a step of performing an alumite treatment on the conductive surface region.
[0030]
According to such a configuration, anodizing can be easily and efficiently performed, and it is possible to perform insulation efficiently only by gas switching without the need for an additional device, and the work efficiency is high, and it is stable and highly reliable. Plasma processing can be performed.
[0031]
Desirably, when performing processing such as etching by exciting plasma in a sealed vacuum chamber, the four corners of the lower electrode on which the square substrate as the object to be processed is placed are chamfered at the four corners of the square substrate. At least the chamfering of at least R3 is performed.
[0032]
According to such a configuration, the occurrence of abnormal discharge can be prevented particularly at the corners of the lower electrode on which the square substrate is installed.
[0033]
In the fourth aspect of the present invention, the lower electrode is composed of a conductive electrical member that has been subjected to insulation treatment in a state where at least a part of the surface is left as a conductive surface region. A lower substrate and a vacuum vessel are disposed under a non-processing condition in which a substrate to be processed is installed and evacuated to a desired pressure, and plasma processing is not performed on the substrate to be processed. A plasma excitation starting step for applying a voltage between the upper electrode and exciting the plasma between the lower electrode and the upper electrode; and after the plasma excitation starting step, the conductive surface region of the lower electrode A coating step of coating the substrate with an insulating member, and a plasma processing step of performing plasma processing on the substrate to be processed under processing conditions that allow the substrate to be processed to be subjected to desired plasma processing after the coating step. And wherein the door.
[0034]
According to such a method, it is only necessary to cover the insulating member after the discharge is stabilized, so that abnormal discharge can be prevented and highly reliable plasma treatment can be performed.
[0035]
Here, the chamfering is not limited to the R processing, but as shown in the explanatory view of FIG. 6, a linear removal region having a chamfering width A and a chamfering width B (A ≦ B) is formed linearly. It is also included. Here, the chamfering amount of the chamfering process refers to the size of the long side B of the removal area, or the radius R of the removal area in the case of R machining.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1
In the first embodiment of the present invention, as shown in FIG. 3, in the plasma processing apparatus that performs plasma processing by exciting plasma in a sealed vacuum chamber, the lower electrode 7 on which the substrate to be processed is placed is The chamfer radius of the corner portion of the substrate mounting surface is configured to be larger than the chamfer amount of the corner portion 11e of the substrate 11 to be processed. Further, the periphery of the lower electrode is covered with an insulating cover 12 composed of insulating blocks 12a to 12d divided into a plurality, and the insulating block is a region where the junction 12k excludes the corner of the lower electrode 7. It is formed so that it may be located in.
[0037]
FIG. 1 shows the external appearance of the vacuum processing tank 2 of the plasma processing apparatus 1 as described above. A square substrate such as a liquid crystal glass substrate transferred from the outside passes through the transfer chamber 3. It is transferred into the vacuum processing tank 2 and is subjected to plasma processing such as etching in the inside sealed by the gate valve 4.
[0038]
FIG. 2 is a diagram showing the internal structure of the vacuum processing tank 2 according to the first embodiment of the present invention, in which an upper electrode 6 is attached to a lid 5 that can be opened and closed, and a substrate to be processed is the counter electrode. A lower electrode 7 on which a glass square substrate is installed is disposed. The lower electrode 7 is made of an aluminum plate, and the surface thereof is alumite treated in consideration of insulation retention and corrosion resistance.
[0039]
The lower electrode 7 is installed on a water cooling plate 8 and indirectly cools the substrate to be processed by circulating cooling water in the water cooling plate 8. Further, a high-frequency matching unit 9 and a high-frequency power source 10 are attached to the lower electrode 7. By applying RF high frequency (13.56 MHz) to the lower electrode 7, plasma is excited in the vacuum processing tank 2 to perform etching or etching. The surface treatment such as film formation is performed.
[0040]
In FIG. 3, the corners 7e at the four corners of the surface on which the square substrate 11 of the lower electrode 7 is installed are arc-shaped chamfered to prevent abnormal discharge due to concentration of discharge, as in the conventional example. However, in this embodiment, the chamfering amount of the lower electrode 7 is not less than the largest chamfering amount of the four corners of the square substrate 11 and is chamfered by R3 or more.
[0041]
Here, the upper limit of the chamfer dimension is not particularly defined as long as the patterns on the substrate are all equal and are in an environment where plasma processing such as etching is performed. This is in order to be sufficient to prevent abnormal discharge in a low-pressure process used for recent microdevice processing, for example, a process of 10 Pa or less. In addition, an insulating cover 12 composed of four insulating blocks 12a to 12d made of alumina is installed around the lower electrode 7, and is divided into two or more from the viewpoint of cost and handling. Although it is the same as that of the conventional example, it is divided, and the joint portion 12k avoids the corners of the four corners of the surface on which the square substrate 11 of the lower electrode 7 is installed, and corresponds to each side of the square substrate. It is the feature that it is arrange | positioned so that it may come to the position which carries out. The position to be divided is not particularly limited as long as it does not contact the corner. This is in consideration of the intrusion of the electric discharge from the joint, and even if there is an electric wrap around, it is far from the edge of the corner of the lower electrode, and the edge is subjected to R machining, so the electric discharge There is no concentration.
[0042]
On the other hand, in the conventional example, since the joining portion is located at the corner portion, abnormal discharge is likely to occur at the corner portion of the lower electrode due to the entrance of the discharge from the joining portion.
[0043]
As described above, according to the plasma processing apparatus of the first embodiment of the present invention, the chamfering amount of the corner portion of the lower electrode where discharge tends to be concentrated is larger than the chamfering amount of the corner portion of the substrate to be processed. Therefore, even if the discharge is concentrated, it will be concentrated toward the substrate to be processed with sharper corners than the lower electrode, and the possibility of the concentration of discharge on the lower electrode is drastically reduced. To do.
[0044]
Further, since the substrate to be processed has lower conductivity than the lower electrode, abnormal discharge is less likely to occur. For this reason, it is possible to prevent abnormal discharge and perform stable and highly reliable discharge.
[0045]
In addition, since the joint portion of the insulating block that covers the periphery of the lower electrode on which the substrate to be processed is placed is located in a region excluding the corner portion of the lower electrode, there is a discharge wrap around from the joint portion. Even so, since it is not a corner portion of the lower electrode but a straight portion, it is difficult to reach the corner portion directly and abnormal discharge is unlikely to occur.
[0046]
Moreover, in this structure, as is clear from FIG. 3A, the bent portion is configured so that the joining line does not become a straight line, and the intrusion path such as moisture is lengthened to prevent intrusion. FIG.3 (b) is a figure which shows the AA cross section of Fig.3 (a).
[0047]
The chamfering amount is desirably R3 or more, but it is sufficient that the chamfering amount is larger than the chamfering amount of the substrate to be processed.
[0048]
Further, when the insulating cover is used, the chamfering amount of the lower electrode is not necessarily larger than the chamfering amount of the substrate to be processed.
[0049]
In the first embodiment, the case where the peripheral edge of the lower electrode is covered with an insulating cover made of an assembly of insulating blocks has been described. However, the present invention can also be applied to a case where the insulating cover is not formed.
Embodiment 2
As a second embodiment of the present invention, a plasma processing apparatus for etching a substrate to be processed, which is a rectangular substrate smaller than the lower electrode, on the lower electrode 17 will be described.
[0050]
In this example, as shown in FIG. 4 which is an enlarged explanatory view of the main part, when the lower electrode is larger, the corner of the lower electrode is positioned inside the outer end of the substrate to be processed. A large number of chamfers are formed to increase the chamfering amount. Here, it is assumed that no insulating cover is provided.
[0051]
According to such a configuration, since the corner of the lower electrode is configured to be located inside the outer end of the substrate to be processed, the edge of the corner of the lower electrode is not exposed to the plasma, and Since the coating is protected by the processing substrate, concentration of discharge is prevented.
[0052]
Note that the substrate to be processed is usually chamfered at one corner to form an orientation flat surface for positioning, but may be formed so that the corner is larger than the corner having the largest chamfer amount.
Embodiment 3
Next, as a third embodiment of the present invention, a part of the surface of the lower electrode 7 is not subjected to an alumite treatment in advance to leave a conductive region, and is covered with an alumite layer 18 that is an insulator after plasma excitation. A plasma processing method that suppresses abnormal discharge during plasma excitation will be described.
[0053]
Abnormal discharge at the corners of the lower electrode occurs because the peak voltage during plasma discharge exceeds the withstand voltage value of the alumite layer on the surface of the corners, and the alumite breaks down and peels off, It has been found that the peak voltage shows a very large value immediately after the start of plasma excitation.
[0054]
Therefore, in this embodiment, a part of an arbitrary surface of the lower electrode 17 is not subjected to an alumite treatment and is left as a conductive region 17s, and an electrically conductive portion is formed, and active under a peak voltage immediately after plasma excitation. In order to prevent abnormal discharge due to discharge concentration at the corners, the current is leaked.
[0055]
The plasma processing apparatus described in the first embodiment is used, and as shown in FIG. 5A, the substrate to be processed is installed in a vacuum processing tank (see FIG. 1), and a desired pressure and Exhaust so that Here, a hole 12h is formed in the insulating cover 12, and a conductive region 17s not subjected to an alumite treatment is formed in a region corresponding to the hole 12h.
[0056]
Next, as shown in FIG. 5B, the surface of the substrate to be processed is prevented from being etched, for example, by keeping the temperature of the lower electrode below a predetermined value, such as non-processing conditions for suppressing the plasma processing on the substrate to be processed. And a high frequency voltage is applied between the upper electrode 6 and the lower electrode 17, and a voltage is applied between the lower electrode and the upper electrode disposed in the vacuum processing tank, and the lower electrode Plasma is excited between the upper electrode and the upper electrode. Since the region left as the conductive surface region 17s without any alumite treatment being applied to a part of the arbitrary surface of the lower electrode 17 electrically constitutes a conductive portion, it is just after the plasma excitation. The current can be actively leaked under the peak voltage. For this reason, abnormal discharge due to discharge concentration at the corners is prevented.
[0057]
When the peak voltage is lowered, an oxidizing gas such as oxygen is slightly introduced to oxidize the conductive surface region 17s to form an alumite layer 18s. As a result, the entire surface of the lower electrode is covered with the alumite layer.
[0058]
Then, evacuate again, exhaust the oxidizing gas out of the vacuum processing tank, introduce and replace the inert gas, further evacuate until the desired degree of vacuum is reached, and raise the temperature of the lower electrode. As shown in FIG. 5C, plasma processing is started on the square substrate 11 which is the substrate to be processed.
[0059]
According to this method, it is possible to prevent abnormal discharge extremely effectively by leaving a part of the conductive surface and forming a current escape path at the time of plasma excitation in which abnormal discharge is most likely to occur. When the peak voltage drops, it is only a little in time. When the conductive surface is oxidized by introducing an oxidizing gas, the entire surface of the lower electrode is insulated, and then the normal plasma treatment is performed. Is possible.
[0060]
According to this method, it is possible to easily and efficiently anodize the insulating region on the lower electrode surface by simply switching the gas without requiring an additional device, and it is possible to work efficiently. Therefore, it is possible to perform plasma processing which is high, stable and reliable.
Embodiment 4
Next, as a fourth embodiment of the present invention, a conductive surface region is not formed in advance on a part of the surface of the lower electrode 7 and is covered with an insulator 13 after plasma excitation. Next, a plasma processing method that suppresses abnormal discharge during plasma excitation will be described.
[0061]
Although it is the same as that of the said 3rd Embodiment, when insulatingly covering the electroconductive area | region of the lower electrode surface after discharge stabilization, it replaces with the method of the said 3rd Embodiment which forms an insulating film in this embodiment. In addition, after the plasma is stabilized, an insulating material is placed to cover the conductive surface region.
[0062]
That is, in this embodiment, as in the third embodiment, a part of an arbitrary surface of the lower electrode 17 is not subjected to an alumite treatment and is left as a conductive surface region 17s, and an electrically conducting portion is provided. The current is actively leaked under the peak voltage immediately after plasma excitation to prevent abnormal discharge due to discharge concentration at the corners.
[0063]
As in the third embodiment, the plasma processing apparatus is the same as that described in the first embodiment. As shown in FIG. 6A, the object to be processed is placed in a vacuum processing tank (see FIG. 1). A substrate is placed and evacuated to a desired pressure. Here, the insulating cover 12 is formed small enough to expose the outer peripheral portion of the lower electrode, and a conductive region 17p that is not subjected to alumite treatment is formed in a region corresponding to the outer peripheral portion.
[0064]
Next, as shown in FIG. 6 (b), a high frequency voltage is applied between the upper electrode 6 and the lower electrode 17, and between the lower electrode and the upper electrode disposed in the vacuum processing tank. A voltage is applied to excite plasma between the lower electrode and the upper electrode. Since the region left as the conductive surface region 17p without any alumite treatment being applied to a part of the arbitrary surface of the lower electrode 17 electrically constitutes a conductive portion, it is immediately after plasma excitation. The current can be actively leaked under the peak voltage. For this reason, abnormal discharge due to discharge concentration at the corners is prevented.
[0065]
When the peak voltage is lowered, the outer insulating block 13 is moved inward so as to cover the outer peripheral portion of the insulating cover 12. As a result, the conductive surface region of the lower electrode surface is covered with the outer insulating block 13.
[0066]
And as shown in FIG.5 (c), the plasma processing to the square substrate 11 which is a to-be-processed substrate is started.
[0067]
According to this method, it is possible to prevent abnormal discharge extremely effectively by leaving a part of the conductive surface and forming a current escape path at the time of plasma excitation in which abnormal discharge is most likely to occur. Just in time, when the peak voltage drops, the entire lower electrode surface is insulated by moving the insulating block and covering the surface of the conductive region, and then the normal plasma treatment can be performed. It becomes.
[0068]
According to this method, the present invention can also be applied to a case where a material that cannot easily form an insulating film such as an oxide film or a nitride film is used as the lower electrode. Compared with the third embodiment, the lower electrode can be applied. There is also an advantage that the selection range of materials is widened.
[0069]
In addition, the number of gas supply and discharge times can be reduced, and it is possible to perform stable and highly reliable plasma processing with high work efficiency.
[0070]
As described above, according to the present invention, the conduction portion on the arbitrary surface can be covered with an insulator such as alumina to stabilize the discharge.
[0071]
According to such a configuration, it is possible to prevent the occurrence of abnormal discharge at the corner of the lower electrode on which the square substrate is installed, regardless of the pressure region.
[0072]
【The invention's effect】
As described above, according to the present invention, the chamfered amount of the corner of the lower electrode on which the substrate to be processed is placed is larger than the chamfered amount of the corner of the substrate to be processed. Therefore, even under any pressure, abnormal discharge can be prevented and stable and reliable discharge can be performed.
[0073]
In addition, according to the present invention, the insulating block that covers the periphery of the lower electrode on which the substrate to be processed is placed is formed so that the bonding portion is located in a region excluding the corner portion of the lower electrode. Even if there is a wraparound of the discharge, since it is not a corner of the lower electrode but a straight portion, it is difficult to reach the corner directly, and abnormal discharge can be prevented.
[0074]
Further, according to the method of the present invention, any pressure region can be obtained by forming an electrically conductive portion on any part of the lower electrode surface without applying alumite treatment and covering with an insulator after plasma excitation. Even in this case, abnormal discharge can be prevented from occurring at the corners of the lower electrode on which the square substrate is installed.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a structure of a vacuum processing tank 2 of the plasma processing apparatus 1 according to the embodiment of the present invention. Explanatory drawing explaining the plasma processing apparatus of 1 embodiment. FIG. 4 is explanatory drawing explaining the plasma processing apparatus of the 2nd Embodiment of this invention. FIG. 5 is the plasma processing method of the 3rd Embodiment of this invention. FIG. 6 is a process explanatory view showing a plasma processing method according to a fourth embodiment of the present invention. FIG. 7 is a perspective view showing a configuration of a lower electrode and an insulating cover of a conventional example. FIG. Top view of substrate [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Vacuum processing tank 3 Vacuum transfer chamber 4 Gate valve 5 Cover body 6 Upper electrode 7 Lower electrode 8 Water cooling plate 9 High frequency matching device 10 High frequency power supply 11 Square substrate 12 Insulating cover 12k Joining location 12a, 12b, 12c 12d Insulating block 13 Insulating block 17 Lower electrode 18 Anodized layer 111 Square substrate 112 Insulating cover 112k

Claims (1)

In a plasma processing apparatus for performing plasma processing by exciting plasma in a sealed vacuum chamber,
The electrode having the corners of the four corners on which the square substrate is placed forms a chamfered portion where the corner portion has a chamfering amount equal to or greater than R3, and the periphery of the electrode is covered with an insulating block divided into a plurality of parts. The insulating block is formed so as to be located in a region excluding the corners of the electrode, the insulating block has a concavo-convex portion at the bonding portion, and the insulating block A plasma processing apparatus, wherein the uneven portions of the block to be fitted are fitted together.

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