JP2004186404A - Plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus for forming a gas pressure and a plasma density symmetrically on a board independently of the shape or the like of a processing chamber so as to attain uniform surface treatment. <P>SOLUTION: The plasma processing apparatus comprises a processing chamber having a board mount means for mount on the board and a gas discharge means placed in opposition to the board mount means in the inside of the chamber, and an exhaust means for the inside of the processing chamber. A gas introduced into the inside of the processing chamber is processed to plasma by the gas discharge means so as to process the board. A plasma shield for surrounding the board mount means and the gas discharge means are placed in the processing chamber in axial symmetry, a plurality of hole or slit shaped gas ducts penetrated through the plasma shield are placed to a lower part from the mount face of the board mount means of the plasma shield, and the gas is exhausted through an exhaust passage formed between the shield plate and the wall of the processing chamber. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus such as an etching apparatus, an ashing apparatus, and a plasma CVD apparatus used for manufacturing a semiconductor device.
[0002]
[Prior art]
Higher performance and higher integration of semiconductor devices are becoming more and more advanced, and accordingly, fine processing technology with more excellent in-plane uniformity and higher reliability and thin film formation technology with higher quality and better film thickness uniformity are required. Have been. In the case of a plasma processing apparatus, it is necessary to equalize the gas pressure and the plasma density on the substrate surface in order to increase the in-plane uniformity of the processing. For this reason, a plasma shield and a gas flow control plate are provided. Various apparatus configurations such as a plasma processing apparatus have been proposed. In addition, in order to form a high-quality thin film and perform high-precision etching, an apparatus capable of controlling ion energy and achieving in-plane uniformity under various processing conditions such as gas flow rate and gas pressure is required. .
[0003]
Such a situation will be specifically described using an etching apparatus as an example.
For example, C ₄ F ₈ When etching is performed using a processing gas such as that described above, when the gas pressure is increased, active species generated by decomposition of the processing gas by plasma or the like and reaction products with the substrate are easily polymerized, and the generated polymer adheres to the substrate. Etching may occur. In addition, when the flow rate of the processing gas is small, active species having high reactivity with the resist such as F radicals increase, and the resist pattern may be thinned, so that a desired pattern may not be obtained. For this reason, in the etching of a submicron region, for example, in the case of a 200 mm substrate, a low pressure of about several Pa and a flow rate of about 600 sccm are required. It is necessary to make the density uniform. Further, in order to improve productivity, a device capable of maintaining such uniformity for a long period of time is required.
[0004]
FIG. 4 is an example of an etching apparatus provided with a plasma shield (Japanese Patent Laid-Open No. 2000-30896). In a processing chamber 100, an upper electrode 101 and a lower electrode 102 on which a substrate 104 is placed are arranged. The matching circuits are connected to high-frequency power supplies 105 and 106 via 107 and 108, respectively. A converging ring (plasma shield) 103 is provided so as to surround a region between the upper electrode 101 and the lower electrode 102 where plasma is generated. A processing gas is introduced from a gas inlet 109, high-frequency power is supplied from a high-frequency power supply 105 to the upper electrode 101 to generate plasma, high-frequency power of a different frequency is supplied to the lower electrode, and a DC bias applied to the substrate 104 is reduced. The substrate can be etched while being controlled.
Here, the concentration ring 103 is formed by stacking a plurality of donut-shaped thin plates and optimizing the interval between the thin plates to reduce the gas pressure inside the concentrated ring to a low pressure of, for example, several Pa, thereby enabling finer pattern etching. At the same time, the plasma is confined inside the converging ring to make the plasma density uniform.
[0005]
The etching apparatus shown in FIG. 5 (JP-A-8-279399) is an apparatus in which a DC bias generated on a substrate is reduced by using a plasma shield.
A lower electrode 102 on which a substrate 104 is placed is provided below the processing chamber 1, and is connected to a high-frequency power supply 105. Further, a plurality of gas discharge ports 108 are provided above the lower electrode 102, and gas introduced into the processing chamber passes through an area 109 provided around the lower electrode below the processing chamber 100 to form an exhaust port. Discharged from 110. Around the lower electrode, a plasma screen 103 having a number of slits 103a is disposed so as to partition the processing chamber horizontally. Here, the width of the slit 103a is set to a size such that plasma does not leak to the region 109 side.
When plasma is generated by supplying high-frequency power to the lower electrode 102, the DC bias potential of the substrate 104 is determined by the ratio of the area of the lower electrode 102 to the area of the ground potential where the plasma contacts, so that the plasma screen 103 is provided. By reducing the area of the ground potential with which the plasma contacts, the sheath potential (DC bias potential of the substrate) on the substrate 104 placed on the lower electrode can be reduced. That is, it is possible to manufacture a high-performance device by reducing the energy of ions incident on the substrate and reducing the damage of the substrate by ions.
[0006]
[Problems to be solved by the invention]
However, when the above etching apparatus was examined in detail, it was found that there were the following problems.
In the apparatus shown in FIG. 4, in order to lower the gas pressure inside the concentration ring 103, it is necessary to increase the distance between the thin plates to a certain degree or more. (For example, asymmetry caused by the position of the exhaust port), the gas pressure on the substrate surface becomes asymmetric, and the etching uniformity is reduced.
Further, since the concentration ring is placed above the substrate, if the film attached to the concentration ring is separated and scattered due to stress, the film adheres to the substrate. Therefore, when the pattern is further miniaturized, the etching failure becomes more prominent. In addition, when the gas pressure difference between the inside and outside of the concentrating ring becomes small, there is a problem that a film adheres to the inner wall of the processing chamber and the like. Since the ratio of returning to the inside increases, there has been a problem that the components of the gas constituting the plasma change with time and the processing uniformity on the substrate surface is reduced.
[0007]
On the other hand, in the apparatus configuration shown in FIG. 5, the hole diameter of the slit formed in the plasma screen 103 is not more than 0.5 mm in the sheath thickness. However, when the slit diameter is increased in order to increase the flow rate, the conductance increases and the processing chamber increases. When there is asymmetry in the inner shape of the substrate 100, there is a problem that a difference in conductance due to the asymmetry causes a difference in gas pressure, the gas pressure near the substrate becomes non-uniform, and the etching uniformity decreases.
Further, since the plasma screen is placed near the substrate, there is a problem that the film adhering to the plasma screen is peeled off as in the case of FIG. Further, since the slit film in contact with the plasma easily adheres, frequent cleaning has to be performed to maintain the etching reproducibility. In addition, in the apparatus configuration shown in FIG. 5, the exhaust means is disposed immediately below the processing chamber. However, since the distance between the lower electrode and the cooling mechanism or the matching circuit is increased, the cooling response is reduced and the etching performance is reduced. There are problems such as lowering.
[0008]
As described above, the conventional etching apparatus has advantages and disadvantages, and currently does not meet the above requirements. This situation is not limited to the etching apparatus, but also applies to other plasma processing apparatuses such as a plasma CVD apparatus and an ashing apparatus.
[0009]
The present invention has been completed in order to solve the above problems by examining in detail the structure of the gas exhaust path and the plasma shield and their arrangement positions. That is, an object of the present invention is to provide a plasma processing apparatus which makes the gas pressure and plasma density on a substrate symmetrical and enables uniform surface treatment regardless of the internal shape of the processing chamber. It is another object of the present invention to provide a plasma processing apparatus capable of performing a stable surface treatment by suppressing film adhesion to a hole or the like of a plasma shield itself and maintaining a constant conductance for a long period of time. Furthermore, a plasma processing apparatus that suppresses film adhesion to the plasma shield and the inner wall of the processing chamber, greatly extends the cleaning cycle, and is excellent in productivity. It is an object to provide a high plasma processing apparatus.
[0010]
[Means for Solving the Problems]
A plasma processing apparatus according to the present invention includes a processing chamber having therein a substrate mounting means for mounting a substrate thereon, and a gas releasing means disposed opposite to the substrate mounting means, and an exhaust means for exhausting the inside of the processing chamber. In the plasma processing apparatus for processing the substrate by converting a gas introduced into the processing chamber into a plasma by the gas releasing unit, the substrate mounting unit and the gas releasing unit are axially symmetrically surrounded. A plasma shield is arranged, and a plurality of hole-shaped or slit-shaped gas passages penetrating the plasma shield are provided below the mounting surface of the substrate mounting means of the plasma shield, and the shield plate and the wall of the processing chamber are provided. The gas is exhausted through an exhaust path formed between the gas passages.
[0011]
As described above, the inside of the processing chamber is divided and divided by the plasma shield symmetrical around the substrate central axis, and the gas is discharged to the outer exhaust passage through the small holes or slits provided below the plasma shield. The gas flow is symmetrical about the substrate central axis, and the gas pressure and plasma density on the substrate can be made uniform.
That is, since the conductance of the exhaust path formed outside the plasma shield is larger than the conductance of many gas ventilation paths, the pressure inside the plasma shield is higher than that of the exhaust path, and the gas on the substrate becomes higher. The pressure uniformity is improved. Here, the pressure difference in the exhaust path is preferably 30% or less of the pressure at the peripheral portion of the substrate, more preferably 10%. Within this range, the gas pressure uniformity is further improved, and the in-plane uniformity of the processing is further improved.
[0012]
Further, since the gas passage is provided below the substrate mounting surface, the plasma density in the gas passage is reduced, and the amount of film deposited in the gas passage can be significantly reduced. Therefore, the conductance of the gas passage can be appropriately maintained for a long time, and the cleaning cycle can be extended. From this viewpoint, the position of the gas passage is preferably formed at least 10 mm below the substrate mounting surface, more preferably at least 30 mm below.
In addition, since the plasma shield can be attached to a position distant from the substrate surface, even if the adhered film is peeled off, it does not adhere to the substrate, and defects caused by particles can be avoided.
[0013]
The plasma shield is not limited to a cylindrical shape, and its inner diameter and / or outer diameter may be changed below the substrate mounting surface. Further, a portion where the plasma shield is parallel to the mounting surface may be provided, and the gas passage may be formed in the parallel portion. These may be selected as appropriate according to the internal shape of the processing chamber and the required conductance of the exhaust passage.
[0014]
In the present invention, the hole diameter of the hole or the short side of the slit is preferably from 0.7 mm to 4 mm, more preferably from 1.5 to 2.5 mm. With this range, it is possible to prevent the plasma from seeping out to the exhaust passage side, prevent film deposition on the inner wall of the processing chamber, and maintain a desired conductance for a long time. Further, a ratio of a length of the hole to a hole diameter or a ratio of a depth to a short side of the slit is preferably 4 or less.
In the plasma processing apparatus of the present invention, a plurality of exhaust ports may be provided axially symmetrically on the bottom wall of the exhaust path, or exhaust ports may be provided on the entire exhaust path.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view showing one configuration example of the etching apparatus of the present invention, and FIG. 2 is a transverse sectional view.
As shown in FIG. 1, in a processing chamber 1, an upper electrode 9 having a large number of gas emission holes 9a and a lower electrode 5 on which a substrate 7 is placed are arranged to face each other. And is fixed to the processing chamber via the The upper electrode 9 is connected to a first high-frequency power source 10 for plasma generation and connected to a gas supply system 8 including a valve 13, a mass flow controller 12, and the like, and can supply a predetermined flow rate of gas toward the substrate. It has a configuration. On the other hand, the lower electrode 5 is provided with an electrostatic chuck 5a for electrostatically adsorbing a substrate on an upper portion thereof, and a coolant passage 14 for cooling the substrate is formed inside. The periphery is covered with an insulating cover 5b. The lower electrode 5 is connected to a second high frequency power supply 11 for controlling the bias of the substrate and a DC power supply 22 for electrostatic attraction of the substrate. The refrigerant is supplied through the introduction pipe 14a and discharged through the discharge pipe 14b. A blocking capacitor 23 and a high-frequency cut filter 24 are mounted between the second high-frequency power supply 11 and the DC power supply 22 and the lower electrode 5 to prevent mutual interference.
An exhaust port is provided at one end in the processing chamber, and the turbo pump 2 is connected.
[0016]
A cylindrical plasma shield 3 is mounted around the substrate so as to surround the upper electrode 9 and the lower electrode 5 in an axially symmetric manner. The inside of the processing chamber is divided by the plasma shield 3. In the lower part of the plasma shield 3, a large number of hole-shaped or slit-shaped gas passages 4 are formed. The shape and the number of the gas passages 4 allow a gas at a predetermined flow rate to flow therethrough, and the plasma is supplied inside. The gas pressure is determined so as to be confined and increase outside.
Therefore, the gas released from the many gas discharge holes 9a of the upper electrode flows toward the substrate 7, and the space (inside exhaust passage) 3a between the lower electrode 5 and the plasma shield 3, the gas passage 4, the plasma shield The gas is exhausted to the outside by the turbo pump 2 through a space (outside exhaust passage) 3b between the pump 3 and the inner wall of the processing chamber and an exhaust passage 3c near the pump. As described above, since the gas passage 4 of the plasma shield does not allow plasma to pass through and has a hole with a small conductance, the flow is restricted and the internal pressure increases, and the gas pressure inside the plasma shield becomes axially symmetric. The pressure distribution in the plasma shield is not affected by the shape of the outer exhaust passage (or the processing chamber). That is, since the asymmetry of the inside shape of the processing chamber is canceled, the symmetry of the gas pressure and various characteristics of the plasma around the central axis of the substrate can be increased, and etching with excellent in-plane uniformity can be performed.
[0017]
Although the conductance of the outer exhaust passage 3b reaches the turbo pump due to the internal shape of the processing chamber 1, the conductance of the plasma shield is designed to be sufficiently smaller than the conductance of these outer exhaust passages. The pressure within can be axisymmetric. Here, the conductance of the exhaust path may be determined so that the pressure difference between the outer exhaust path and the peripheral pressure of the substrate is preferably 30% or less, more preferably 10% or less. By doing so, the etching uniformity is further improved, and the etching uniformity can be maintained for a long time.
[0018]
Next, an etching method using the etching apparatus of FIG. 1 will be described. The robot hand holding the substrate is inserted through the gate valve 6, and the substrate is placed on a push-up pin (not shown) of the lower electrode. Subsequently, the push-up pins are lowered, the substrate 7 is placed on the electrostatic chuck 5a, and this is electrostatically attracted using the DC power supply 22. Next, after reducing the pressure of the processing chamber 1 to a predetermined pressure using a back pump (not shown) and a turbo pump 2, process gas is supplied into the processing chamber 1 from the lower surface of the upper electrode 9 via the gas supply mechanism 8. To a predetermined pressure. Thereafter, a high-frequency power in the VHF band (for example, 60 MHz) is applied to the upper electrode 9 from the first high-frequency power supply 10, and a high-frequency power in the HF band (for example, 1.6 MHz) is applied to the lower electrode 5 from the second high-frequency power supply. . A relatively high-density plasma is generated by the high frequency power in the VHF band, and an etchant is generated. On the other hand, by applying high frequency power in the HF band to the lower electrode, the ion energy can be controlled independently of the plasma density, and the desired etching process is performed.
[0019]
At this time, the plasma is prevented from diffusing by the plasma shield 3 and does not leak to the outer exhaust passage 3b. Further, even if the film adhered to the plasma shield is separated and scattered due to the stress of the film, the film is not adhered to the substrate since the distance from the substrate is large, so that etching defects and the like can be avoided. Further, since the gas passage of the plasma shield can be kept away from the plasma, the amount of the film formed on the hole of the plasma shield can be reduced, and the change of the etching processing condition due to the blockage of the hole can be suppressed.
[0020]
With the apparatus configuration as described above, the cleaning cycle inside the processing apparatus is greatly extended. For example, in the apparatus shown in FIG. 4, it was necessary to perform plasma cleaning every about 20 hours of running. Continuous running for more than an hour becomes possible.
[0021]
The position of the gas passage is preferably 10 mm or less, more preferably 30 mm below the substrate surface. When the thickness is 10 mm or less, the plasma density decreases, the amount of b attached to the holes decreases, and the gas pressure and the uniformity of the plasma density can be stably maintained over a longer period.
[0022]
Further, the hole diameter of the holes is preferably 0.7 to 4 mm, and the length thereof is preferably an aspect ratio of 4 or less. When the diameter of the hole is 4 mm or less, diffusion of plasma beyond the plasma shield can be more effectively prevented. Further, by setting the thickness to 0.7 mm or more, a change in conductance due to adhesion and peeling of the film to the holes can be suppressed, and an appropriate conductance can be maintained for a long time. When the hole diameter is 1.5 mm to 2.5 mm, the operation of the apparatus can be performed for 200 hours or more.
Here, if the plasma shield 3 becomes too thick, it is necessary to increase the diameter of the hole in order to secure the conductance, and the plasma may leak out. To prevent this, the aspect ratio obtained by dividing the length of the hole by the diameter of the hole is desirably 4 or less. Further, when the plasma shield is thickened, the volume of the exhaust path is restricted, and the conductance of the exhaust path may be reduced depending on the shape of the inside of the processing chamber.
[0023]
Next, specific examples of the shape, arrangement, and structure of each member when the apparatus configuration of FIG. 1 is applied to an etching apparatus for a 200 mm substrate will be described. Here, the gas flow rate is set to 600 sccm (Ar: C ₄ F ₈ : O ₂ = 600: 20: 1) and the pressure on the substrate is 3 Pa.
The outer diameter of the cover 5b covering the lower electrode 5 is 310 mm, the inner diameter of the plasma shield 3 is 440 mm, the outer diameter is 444 mm, and the distance from the substrate center of the inner wall of the processing chamber opposite to the turbo pump 2 in the outer exhaust path is 322 mm. . Therefore, the width of the outer exhaust passage 3b is 100 mm, and the height is 100 mm. The height of the gas passage forming portion is 54 mm.
[0024]
The pressure difference in the outer exhaust passage having the above structure can be obtained as follows by applying the relational expression between the conductance and the shape of the rectangular exhaust pipe.
That is, the conductance that makes 1/4 turn from the plasma shield outer exhaust passage 3b on the opposite side of the turbo pump 2 is about 0.5 m. ³ / Sec.
The conductance C of the exhaust pipe is
C = 309 · k · (a · b) ² / ((A + b) · L) (1)
Where a and b are the vertical and horizontal lengths of the cross section of the exhaust pipe, and L is the length. When the length of a quarter of the circumference of the outer exhaust path from the pump opposite side is L, the conductance C is calculated from k = 1.115. ³ / Sec. Gas flow rate Q (= 600 sccm = 1 Pa · m ³ / Sec), the amount of gas discharged through the gas passage to the 1/4 circumference is 1/4, and the gas diffuses uniformly through each gas passage, so that the effective gas flow rate flowing through the outer circumference is averaged. Can be assumed to be 1/2 of that. As a result, the flow rate Q ′ flowing through the 周 turn becomes １ ／ of the total flow rate Q.
From this, the pressure difference ΔP in the outer exhaust passage is
1/8 = C · ΔP = 0.5 · ΔP
Thus, ΔP = 0.25 Pa.
Therefore, by disposing the plasma shield having the above structure, the pressure difference in the outer exhaust passage can be reduced to 1/10 or less of the pressure near the substrate. That is, in addition to the conductance restriction by the gas passage of the plasma shield, high gas pressure uniformity can be obtained on the substrate, and etching with excellent in-plane uniformity can be performed.
[0025]
Next, the number of gas passages when forming a gas passage having a hole diameter of 1.5 mm in the plasma shield is estimated.
The conductance C of a short cylinder in the molecular flow region is given by:
C = k ・ 121 ・ D ³ / L (m ³ / Sec)
Here, D is the diameter of the hole (= 1.5 mm), L is the length (= 2 mm), and k is a constant determined by L and D, and is about 0.43 in this case.
From the above equation, the conductance C of one gas passage is 8.78 × 10 ^-5 m ³ / Sec. Flow rate 600sccm (= 1Pa ・ m ³ / Sec), it is sufficient to open 5700 gas passages in the plasma shield 3 to obtain 3 Pa or less and 2 Pa with a margin. At this time, the pressure difference (about 3 Pa) in the plasma shield 3 is much larger than the pressure difference 0.25 Pa in the outer exhaust passage 3b, and a uniform gas pressure on the substrate 4 can be realized. Based on the 2 Pa obtained by the plasma shield, the opening degree of the main valve 2 a or the variable orifice (not shown) of the turbo pump 2 can be adjusted to obtain a gas pressure of 3 Pa on the substrate.
As described above with reference to specific examples, in any processing chamber having any internal shape, a plasma shield is attached, and the shape and arrangement of the plasma shield, and the shape and number of gas passages are appropriately selected. Thereby, the gas pressure and the plasma density on the substrate can be made uniform for the desired flow rate and gas pressure.
[0026]
Next, a part of an experiment conducted on the relationship between the position and shape of the gas passage and the maintenance cycle (the time until the film becomes attached and running becomes impossible) in the apparatus shown in FIG. 1 will be described below.
The position of the upper end of the gas passage is 35 mm from the substrate mounting surface of the lower electrode. The shape of the plasma shield plate is cylindrical as shown in FIG. 3 (a). When a circular hole is formed, if the diameter of the hole exceeds 4 mm, the plasma diffuses beyond the plasma shield, and When the thickness was about 0.7 mm, the membrane came into contact with the hole in 100 hours, and the membrane was peeled off and the conductance changed. When the hole diameter was in the range of 1.5 mm to 2.5 mm, stable treatment for 200 hours or more was possible.
Further, by setting the upper end position of the gas passage to 30 mm or less from the substrate mounting surface, the plasma density in the gas passage portion is reduced, and the amount of adhesion is reduced. On the other hand, it was found that the amount of adhesion increased when the distance was within 10 mm from the substrate mounting surface, and that the conductance was reduced in about 100 hours even with a hole diameter of 2.5 mm.
[0027]
In the apparatus shown in FIG. 1, a cylindrical plasma shield was used. However, the plasma shield is not limited to this as long as it has an axially symmetric shape. Can be used. Also, similarly, various forms and shapes of gas passages can be used. These examples will be described with reference to FIG.
FIG. 3A is a schematic cross-sectional view in which a part of the cylindrical plasma shield shown in FIG. 1 is enlarged, and is an example in which a hole 31 is formed in the thickness direction of the plasma shield. (B) shows a cylindrical shield in which a hole is formed obliquely. By making the hole slant in the longitudinal direction, even if the film adhered in the hole is peeled off, it is discharged to the outside and the decrease in conductance is suppressed. Can be. (C) and (d) show that the radius of the gas passage forming portion of the cylindrical plasma shield is increased or decreased downward. In the figure, the radius is changed linearly, but it may have a curvature and be shaped like a bowl, for example. (E) and (f) show a plasma shield plate in which two cylinders of different radii are connected, and a gas passage is formed in a portion horizontal to the bottom wall. In these cases, the problem that the peeled film closes the hole and reduces the conductance is alleviated. (G) is an example in which the outer diameter of the plasma shield in the gas passage is increased.
[0028]
Further, the gas passage may have any shape such as a hole shape and a slit shape. The hole shape includes, for example, a rectangular shape such as a square, a rectangle, a parallelogram, or a trapezoid in addition to a circle or an ellipse. Further, the slit shape refers to a shape having a rectangular cross section and one side thereof being larger than the other side. The slit-shaped gas passage is formed, for example, by stacking plates horizontally or vertically at predetermined intervals. Further, a configuration in which donut-shaped disks are stacked at predetermined intervals may be adopted.
[0029]
For example, as shown in FIG. 3 (g), when donut-shaped disks having different outer diameters are overlapped to form a slit-shaped gas passage, the specific number of slits is as follows. Can be obtained as follows.
That is, the conductance C of the slit is
C = k · 309 · a ² ・ B / L
Where a is the distance between the disks, b is the inner circumference, and L is the width of the disk (ie, the thickness of the plasma shield in the gas passage). Here, if a = 2 mm, b = 440 · π mm, and L = 6 mm, k = 0.52. Therefore, to obtain a flow rate of 600 sccm and a gas pressure of 2 Pa, the number of gaps is three. The aspect ratio (= L / a) is desirably 4 or less for the same reason as in the case of holes.
[0030]
In the apparatus shown in FIG. 1, the gas exhausted from the inner exhaust passage 3a is exhausted through the outer exhaust passage 3b. However, an exhaust port is provided on the bottom wall of the outer exhaust passage, and the turbo pump is connected to the processing chamber. It is good also as a structure arrange | positioned at the lower part. In this case, the exhaust ports may be arranged axially symmetrically, or may be provided on the entire outer periphery of the plasma shield.
[0031]
Although the above description has been given of the processing chamber in which the outside of the plasma shield is asymmetric, it is needless to say that the present invention can be applied to the case where the outside of the plasma shield is symmetric. Since the outside gas pressure is reduced, the adhesion of the film to the outside exhaust passage or the like can be reduced, and the generation of dust due to the film peeling can be suppressed.
In addition, a part of the plasma shield may be cut at a portion where the plasma disappears, or a gap may be provided between the plasma shield and the bottom wall, so that a larger flow rate of gas can be flowed. However, depending on the size of the gap or the like, the uniformity of the gas pressure on the substrate may be reduced. In this case, the distance between the plasma shield and the lower electrode may be reduced. That is, the shape and arrangement of the plasma shield may be optimized so as to reduce the conductance of the internal exhaust passage.
In addition, the material of the plasma shield of the present invention includes quartz, aluminum fluoride, silicon nitride, an insulator such as aluminum nitride or the like, which is coated with an insulating material or another material to increase the plasma resistance, silicon, carbon, and the like. A scavenger material made of a compound is preferably used. The surface of the plasma shield may be subjected to a treatment such as blast treatment or thermal spraying, so that the surface is roughened and the adhered film is hardly peeled off.
[0032]
In the above embodiments, the etching apparatus has been described as an example. However, in the case of other plasma processing apparatuses such as a plasma CVD apparatus and an ashing apparatus, the gas pressure and the plasma density can be similarly increased by providing a plasma shield plate. Can be improved, and a thin film having more excellent film thickness uniformity can be formed. Further, the present invention is not limited to the capacitive coupling type, and can be applied to an inductive coupling type plasma apparatus. Further, a microwave or the like may be used as a plasma generation energy source.
[0033]
【The invention's effect】
As described above, when the present invention is used, plasma and gas can be axially symmetric with respect to the center of the substrate regardless of the internal shape of the processing chamber. In particular, this effect is important because the plasma does not become axially symmetric unless the gas pressure and gas species are not axially symmetric with respect to the center of the substrate. In addition, since it is difficult to form a film on the plasma shield and the processing chamber, not only generation of dust can be suppressed, but also a change in conductance with time due to film adhesion can be suppressed, and the apparatus can be operated for a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic front sectional view showing a configuration example of a plasma processing apparatus of the present invention.
FIG. 2 is a schematic cross-sectional view of FIG.
FIG. 3 is a schematic sectional view showing a structure of a plasma shield.
FIG. 4 is a schematic sectional view showing a conventional plasma processing apparatus.
FIG. 5 is a schematic sectional view showing a conventional plasma processing apparatus.
[Explanation of symbols]
1,100 processing room,
2 turbo pump,
3,103 plasma shield,
4 gas passages,
5, 102 lower electrode,
5a electrostatic chuck,
6 Gate valve,
7,104 substrates,
8 gas supply system,
9a gas discharge holes,
9, 101 upper electrode,
10, 11, 105, 106 high frequency electrodes,
14 refrigerant passage,
20, 21 insulator,
22 DC power supply.

Claims (8)

A processing chamber having therein a substrate mounting means for mounting a substrate and a gas discharging means disposed opposite to the substrate mounting means, and an exhaust means for exhausting the inside of the processing chamber; In a plasma processing apparatus for processing the substrate by converting a gas introduced into the processing chamber into plasma by the means,
A plasma shield surrounding the substrate mounting means and the gas releasing means is disposed axially symmetrically, and a hole-shaped or slit-shaped gas penetrating through the plasma shield below the mounting surface of the substrate mounting means of the plasma shield. A plasma processing apparatus, wherein a plurality of passages are provided, and a gas is exhausted through an exhaust passage formed between the shield plate and a wall of the processing chamber. 2. The plasma processing apparatus according to claim 1, wherein the conductance of the exhaust path is set so that a pressure difference in the exhaust path is 30% or less of a pressure at a peripheral portion of the substrate. 3. The plasma processing apparatus according to claim 1, wherein the gas passage is formed at least 10 mm below a height of the mounting surface. The plasma processing apparatus according to any one of claims 1 to 3, wherein an inner diameter and / or an outer diameter of the plasma shield is changed below a height of the mounting surface. The plasma processing apparatus according to claim 4, wherein the plasma shield has a portion parallel to the mounting surface, and the gas passage is formed in the parallel portion. The plasma processing apparatus according to claim 1, wherein a diameter of the hole or a short side of the slit is set to 0.7 mm to 4 mm. The plasma processing apparatus according to any one of claims 1 to 6, wherein a ratio of a length of the hole to a hole diameter or a ratio of a depth to a short side of the slit is 4 or less. The plasma processing apparatus according to any one of claims 1 to 7, wherein an exhaust port is formed on the bottom wall of the exhaust path on the entire circumference, or a plurality of exhaust ports are provided axially symmetrically. .

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