JP2004165266A - Plasma etching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma etching device, hardly generating arcing on a substrate or especially a semiconductor wafer under processing. <P>SOLUTION: The plasma etching device is equipped with a chamber 1 for receiving a substrate to be processed or the semiconductor wafer W, a plasma producing means 15 for producing the plasma of processing gas in the chamber 1, a mounting table 2 provided in the chamber 1 to mount the substrate to be processed or the semiconductor wafer W, and an annular member 5 provided around the semiconductor wafer W on the mounting table 2. The outer diameter of the annular member 5 is designed so as to hardly generate arc discharge on the semiconductor wafer W. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma etching apparatus for performing plasma etching on a substrate, particularly a semiconductor wafer.
[0002]
[Prior art]
2. Description of the Related Art In a semiconductor device manufacturing process, plasma etching for etching a semiconductor wafer (hereinafter, simply referred to as a wafer), which is a substrate to be processed, with plasma is frequently used. Various types of plasma etching apparatuses are used, and among them, a capacitively coupled parallel plate plasma processing apparatus is mainly used. Further, a permanent magnet is disposed in such a capacitively coupled parallel plate plasma processing apparatus, and a magnetic field formed by the permanent magnet is applied horizontally to the semiconductor wafer, and a high-frequency electric field perpendicular to the semiconductor wafer is applied. A magnetron plasma processing apparatus that performs etching with extremely high efficiency using the drift motion of electrons generated at the time is also used (for example, Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP-A-6-20794 [Patent Document 2]
JP-A-8-124912
[Problems to be solved by the invention]
By the way, at the time of etching, the portion of the resist film near the plasma sheath is negatively charged, so that the electron from the plasma has a larger momentum in the lateral direction, and a contact hole with a large aspect ratio is formed. In the portion, the electrons hardly reach the contact hole, but the ions are accelerated by the plasma sheath and reach the contact hole, so that the bottom in the contact hole becomes positively charged. On the other hand, electrons and ions reach the space portion and the trench portion where no contact hole is formed without difficulty. As a result, a large potential difference occurs between them. This is called a shading effect. In addition, the DC potential Vdc between the plasma and the plasma differs depending on the portion on the wafer, which also causes a large potential difference in the semiconductor wafer.
[0005]
When a large potential difference is generated due to such a difference in Vdc or a shading effect, a large electric field is formed in the horizontal direction. Therefore, this electric field is generated at the moment when the etching reaches the underlayer, and arc discharge (arcing) may occur on the wafer. When arcing occurs on the wafer in this manner, circuits formed on the wafer are destroyed, causing a reduction in chip yield and generation of particles.
[0006]
The present invention has been made in view of such circumstances, and has as its object to provide a plasma etching apparatus in which arcing hardly occurs on a substrate being processed, particularly on a semiconductor wafer.
[0007]
[Means for Solving the Problems]
The present inventors have repeatedly studied the cause of arcing on the substrate at the moment when a certain layer is removed during plasma etching, and as a result, the lower electrode is provided around the substrate to be processed on the mounting table serving as the lower electrode. It has been found that the outer diameter of the ring-shaped member, the so-called focus ring, is important. In other words, such a ring-shaped member is charged around the substrate to be processed, such as a semiconductor wafer, similarly to the substrate to be processed, and affects the above-described electric field formation. It has been found that arc discharge on the processing substrate is less likely to occur. In particular, when a magnetic field forming means for forming a horizontal magnetic field orthogonal to a high-frequency electric field is provided in the space between the mounting table serving as the lower electrode and the upper electrode, electrons generated on the ring-shaped member are subjected to electric and magnetic fields. Is supplied to the substrate to be processed by drifting, but by appropriately adjusting the outer diameter of the ring-shaped member, it is possible to make the run-up distance of electrons on the ring-shaped member appropriate and make arc discharge difficult to occur. Was found.
[0008]
That is, the present invention provides a chamber for accommodating a substrate to be processed, plasma generating means for generating plasma of a processing gas in the chamber, and a mounting table provided in the chamber and for mounting the substrate to be processed, A ring-shaped member provided around the substrate on the mounting table, wherein the ring-shaped member has an outer diameter set so that arc discharge on the substrate to be processed hardly occurs. Is provided.
[0009]
Further, the present invention provides a chamber for accommodating a semiconductor wafer, a lower electrode provided in the chamber and supporting the semiconductor wafer, an upper electrode provided above and opposed to the lower electrode, and A high-frequency power supply for supplying high-frequency power to the lower electrode to form a high-frequency electric field in a direction perpendicular to the semiconductor wafer surface between the and the upper electrode, a processing gas supply unit for supplying a processing gas into a chamber, In the processing space between the lower electrode and the upper electrode, a magnetic field forming means for forming a magnetic field orthogonal to the direction of the electric field and directed in one direction, comprising a ring-shaped member provided around the lower electrode, An outer diameter of the ring-shaped member is set so that arc discharge on the semiconductor wafer hardly occurs, and a plasma etching apparatus is provided. Specifically, in the case of a semiconductor wafer having a diameter of 200 mm, when the outer diameter of the ring-shaped member is larger than 240 mm and smaller than 280 mm, particularly, 260 mm, arc discharge on the semiconductor wafer hardly occurs. Further, in the case of a semiconductor wafer having a diameter of 300 mm, arc discharge on the semiconductor wafer hardly occurs when the outer diameter of the ring-shaped member is smaller than 380 mm, in particular, 360 mm.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Here, a magnetron RIE plasma etching apparatus will be described as an example. FIG. 1 is a sectional view showing a magnetron RIE plasma etching apparatus according to one embodiment of the present invention. This etching apparatus is airtightly formed, has a stepped cylindrical shape including an upper portion 1a having a small diameter and a lower portion 1b having a large diameter, and has a chamber (processing vessel) 1 whose wall is made of, for example, aluminum.
[0011]
In the chamber 1, a support table 2 for horizontally supporting a semiconductor wafer (hereinafter, simply referred to as “wafer”) W as a substrate to be processed is provided. The support table 2 is made of, for example, aluminum, and is supported by a conductor support 4 via an insulating plate 3. A focus ring (ring-shaped member) 5 made of a conductive material, for example, single-crystal silicon is provided on the outer periphery above the support table 2 with its surface substantially flush with the wafer surface. The outer diameter of the focus ring 5 is set so that arc discharge on the wafer W is unlikely to occur, as described later. As an example, the diameter of the wafer W is set to 200 mm, and the outer diameter of the focus ring 5 is set to a value larger than 240 mm and smaller than 280 mm, specifically, 260 mm.
[0012]
The support table 2 and the support table 4 can be moved up and down by a ball screw mechanism including a ball screw 7, and a drive portion below the support table 4 is covered with a bellows 8 made of stainless steel (SUS). . A bellows cover 9 is provided outside the bellows 8. A baffle plate 10 is provided outside the focus ring 5, and is electrically connected to the chamber 1 through the baffle plate 10, the support 4, and the bellows 8. The chamber 1 is grounded.
[0013]
An exhaust port 11 is formed on a side wall of the lower portion 1 b of the chamber 1, and an exhaust system 12 is connected to the exhaust port 11. By operating a vacuum pump of the exhaust system 12, the pressure inside the chamber 1 can be reduced to a predetermined degree of vacuum. On the other hand, a gate valve 13 that opens and closes the loading / unloading port of the semiconductor wafer W is provided on the upper side wall of the lower part 1 b of the chamber 1.
[0014]
A high-frequency power supply 15 for plasma formation is connected to the support table 2 via a matching unit 14, and a high-frequency power of a predetermined frequency of 13.56 MHz or more (for example, 13.56 MHz or 40 MHz) is supplied from the high-frequency power supply 15 to the support table 2. Is supplied to the support table 2. On the other hand, shower heads 20, which will be described in detail later, are provided in opposition to and above the support table 2 in parallel with each other, and the shower heads 20 are grounded. Therefore, the support table 2 functions as a lower electrode, and the shower head 20 functions as an upper electrode. The distance between these electrodes is preferably less than 50 mm.
[0015]
On the surface of the support table 2, an electrostatic chuck 6 for holding the wafer W by electrostatic attraction is provided. The electrostatic chuck 6 includes an electrode 6a interposed between insulators 6b, and a DC power supply 16 is connected to the electrode 6a. When a voltage is applied to the electrode 6a from the DC power supply 16, the wafer W is attracted by electrostatic force, for example, Coulomb force.
[0016]
A coolant chamber 17 is provided inside the support table 2, and the coolant is introduced into the coolant chamber 17 via the coolant introduction pipe 17 a and discharged from the coolant discharge pipe 17 b to circulate, thereby supporting the wafer W. Cooled through the table 2. Thereby, the processing surface of the wafer W is controlled to a desired temperature.
[0017]
Further, even if the chamber 1 is evacuated by the exhaust system 12 and held in a vacuum, the cooling gas is supplied by the gas introducing mechanism 18 so that the wafer W can be effectively cooled by the refrigerant circulated in the refrigerant chamber 17. It is introduced between the front surface of the electrostatic chuck 6 and the back surface of the wafer W via a gas supply line 19. By introducing the cooling gas in this manner, the wafer W is cooled via the support table 2, and the cooling efficiency of the wafer W can be increased.
[0018]
The shower head 20 is provided on the top wall of the chamber 1 so as to face the support table 2. The shower head 20 is provided with a large number of gas discharge holes 22 on its lower surface, and has a gas inlet 20a on its upper part. A space 21 is formed therein. A gas supply pipe 23a is connected to the gas introduction unit 20a, and the other end of the gas supply pipe 23a is connected to an etching gas supply system 23 that supplies an etching gas. From the etching gas supply system 23, a gas generally used in this field, such as a halogen-based gas, an O ₂ gas, an Ar gas, and a He gas, is supplied as an etching gas. The gas reaches the space 21 of the shower head 20 via the introduction portion 20a, and is discharged from the gas discharge holes 22.
[0019]
On the other hand, around the upper part 1a of the chamber 1, a dipole ring magnet 30 is arranged concentrically. As shown in the horizontal cross-sectional view of FIG. 2, the dipole ring magnet 30 is configured such that a plurality of anisotropic segment columnar magnets 31 are attached to a ring-shaped magnetic casing 32. In this example, 16 cylindrical anisotropic segment columnar magnets 31 are arranged in a ring shape. In FIG. 2, the arrows in the anisotropic segment columnar magnets 31 indicate the directions of magnetization, and as shown in this figure, the directions of magnetization of the plurality of anisotropic segment columnar magnets 31 are slightly shifted. Thus, a uniform horizontal magnetic field B directed in one direction as a whole is formed.
[0020]
Therefore, in the space between the support table 2 and the shower head 20, a vertical electric field E is formed by the high frequency power supply 15 and a horizontal magnetic field B is generated by the dipole ring magnet 30, as schematically shown in FIG. The magnetron discharge is generated by the formed and thus formed orthogonal electromagnetic field. As a result, a plasma of an etching gas in a high energy state is formed, and a predetermined film on the wafer W is etched.
[0021]
Next, an etching operation when a predetermined film on the wafer W is etched using the magnetron RIE plasma etching apparatus configured as described above will be described.
[0022]
Here, the wafer W having the structure shown in FIG. 4 is etched to form the state shown in FIG. Wafer W in FIG. 4, on the Si substrate 41, for example, be an insulating layer 42 made of SiO ₂ is formed, conductive layer 43 is formed which functions as on the example the stopper layer and the electrodes thereof, on which for example SiO ₂ Is formed. Further, a resist film 45 patterned by photolithography is formed thereon. 4 is etched using the resist film 45 as a mask until the hole 46 and the trench 47 reach the conductive layer 43 at the same time, thereby obtaining the semiconductor device shown in FIG.
[0023]
When performing the etching of the structure of FIG. 4 using the apparatus of FIG. 1, first, the gate valve 13 is opened and the wafer W having such a structure is loaded into the chamber 1 and After the mounting, the support table 2 is raised to the position shown in the figure, and the inside of the chamber 1 is evacuated to a predetermined degree of vacuum through the exhaust port 11 by the vacuum pump of the exhaust system 12.
[0024]
Then, while introducing a predetermined etching gas from the etching gas supply system 23, a predetermined high frequency power of 13.56 MHz or more is supplied from the high frequency power supply 15 to the support table 2 as the lower electrode. At this time, the wafer W is sucked and held on the electrostatic chuck 6 by, for example, Coulomb force by applying a predetermined voltage from the DC power supply 16 to the electrode 6a of the electrostatic chuck 6, and the wafer W A high-frequency electric field is formed between the lower electrode and the support table 2. Since a horizontal magnetic field B is formed between the shower head 20 and the support table 2 by the dipole ring magnet 30, an orthogonal electromagnetic field is formed in the processing space between the electrodes where the semiconductor wafers W are present. A magnetron discharge is generated by the drift of the electrons. Then, a predetermined film of the wafer W is etched by the plasma of the etching gas formed by the magnetron discharge.
[0025]
In the etching of the hole 46 and the trench 47, arcing may occur on the wafer W due to a shading effect or the like at the moment when the etching reaches the conductive layer 43. This is related to the outer diameter of the focus ring 5, and by appropriately adjusting the outer diameter of the focus ring 5, arcing on the wafer W can be made less likely to occur. That is, since the focus ring 5 is made of the same material as the wafer W and is charged similarly to the wafer W and affects the formation of an electric field formed in the horizontal direction of the wafer W, the outer diameter of the focus ring 5 is appropriately adjusted. Arcing on the wafer W can be hardly generated. Arcing on the wafer W is likely to occur even if the outer diameter of the focus ring 5 is larger or smaller than an appropriate range.
[0026]
Specifically, when the diameter of the wafer W is 200 mm, arcing can be made difficult to occur when the outer diameter of the focus ring 5 is larger than 240 mm and smaller than 280 mm, particularly 260 mm. Further, when the diameter of the wafer W is 300 mm, arcing can be suppressed when the outer diameter of the focus ring 5 is smaller than 380 mm, especially when the outer diameter of the focus ring 5 is 360 mm.
[0027]
Next, using a magnetron plasma etching apparatus for a 200 mm wafer having the structure shown in FIG. 1, the focus ring 5 was etched with the outer diameter of 240 mm, 260 mm, and 280 mm, and the presence or absence of arcing when the trench 47 shown in FIG. The result of confirming will be described. As the dipole ring magnet 30, a magnet having a magnetic field intensity at the center of the chamber 1 of 6000 μT (60 Gauss) is used. First, the chamber pressure is 5.45 Pa, and the etching gas is CF ₄ / Ar / O ₂ = 0.04 / After supplying at a flow rate of 0.2 / 0.01 L / min and supplying high frequency power of 40 MHz and 600 W to etch the SiO ₂ film as the interlayer insulating layer 44, the pressure in the chamber is 6.67 Pa, and the etching gas is supplied. The TiN film as the conductive layer 43 was etched by supplying CHF ₃ / CO / O _{2 at} a flow rate of 0.04 / 0.34 / 0.002 L / min and supplying a high frequency power of 40 MHz and 1500 W. As a result, when the outer diameter of the focus ring 5 is 280 mm, clear arcing occurs on the wafer W, and even when the outer diameter is 260 mm, arcing occurs slightly when the outer diameter is 260 mm. Did not. From this, it was confirmed that if the outer diameter of the focus ring 5 is set to 260 mm, which is a value larger than 240 mm and smaller than 280 mm, arcing on the wafer W hardly occurs.
[0028]
Next, a description will be given of an experimental result in which an optimum outer diameter of the focus ring 5 is obtained when the diameter of the wafer W is 300 mm.
As the dipole ring magnet 30, a magnet having a magnetic field intensity at the center of the chamber 1 of 12000 μT (120 Gauss) is used, the pressure in the chamber is 4.0 Pa, and the etching gas is CF ₄ / CO / Ar / O ₂ = 0.02 / 0. Etching was performed by supplying a high-frequency power of 1000 W while supplying a flow rate of 0.1 / 0.4 / 0.01 L / min. As a result, arcing occurred on the wafer W when the outer diameter of the focus ring 5 was 380 mm, and no arcing occurred when the outer diameter was 360 mm. From this, it was confirmed that arcing on the wafer W is unlikely to occur when the outer diameter of the focus ring 5 is set to a value smaller than 380 mm and 360 mm.
[0029]
The present invention can be variously modified without being limited to the above embodiment. For example, in the above embodiment, the magnetron RIE etching apparatus has been described as an example, but the present invention is not limited to this, and can be applied to any other type of plasma etching apparatus. Further, the structure of the wafer as the substrate to be processed in the above embodiment is merely an example, and is effective in all cases where arcing may occur.
[0030]
【The invention's effect】
As described above, according to the present invention, arc discharge on the substrate to be processed is unlikely to occur on the ring-shaped member provided around the substrate on the mounting table so as to be substantially flush with the substrate. Since the outer diameter is set as described above, arcing on the substrate to be processed can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a magnetron RIE plasma etching apparatus according to one embodiment of the present invention.
FIG. 2 is a horizontal cross-sectional view schematically showing a dipole ring magnet arranged around a chamber of the apparatus of FIG.
FIG. 3 is a schematic diagram for explaining an electric field and a magnetic field formed in a chamber.
FIG. 4 is a sectional view showing a layer structure of a semiconductor wafer etched by the apparatus of FIG. 1;
FIG. 5 is a sectional view showing a state where the semiconductor wafer of FIG. 4 is etched;
[Explanation of symbols]
1: chamber 2: support table (mounting table, lower electrode)
5; Focus ring (ring-shaped member)
12; exhaust system 15; high-frequency power supply (high-frequency electric field forming means)
20; shower head (upper electrode)
23; etching gas supply system 30; dipole ring magnet W; semiconductor wafer

Claims (9)

A chamber for accommodating the substrate to be processed;
Plasma generation means for generating a plasma of a processing gas in the chamber,
A mounting table provided in the chamber, for mounting a substrate to be processed,
A ring-shaped member provided around the substrate on the mounting table,
An outer diameter of the ring-shaped member is set so that arc discharge on the substrate to be processed hardly occurs. 2. The plasma according to claim 1, wherein the plasma generating unit includes a high-frequency electric field forming unit that forms a high-frequency electric field perpendicular to a surface to be processed of the substrate to be processed in a space above the mounting table. 3. Etching equipment. The plasma generating means, the mounting table as a lower electrode, an upper electrode provided above and facing the mounting table as a lower electrode, applying high-frequency power to the mounting table, the mounting table, 2. The plasma etching apparatus according to claim 1, further comprising: a high-frequency power supply configured to generate a high-frequency electric field perpendicular to a surface to be processed of the substrate to be processed in a space between the upper electrode and the upper electrode. 3. The plasma etching apparatus according to claim 2, further comprising a magnetic field forming unit that forms a horizontal magnetic field orthogonal to a high-frequency electric field in a space between the mounting table and the upper electrode. A chamber for accommodating a semiconductor wafer;
A lower electrode provided in the chamber and supporting the semiconductor wafer;
An upper electrode provided above and opposed to the lower electrode;
A high-frequency power supply for supplying high-frequency power to the lower electrode to form a high-frequency electric field in a direction perpendicular to the semiconductor wafer surface between the lower electrode and the upper electrode;
Processing gas supply means for supplying a processing gas into the chamber;
In the processing space between the lower electrode and the upper electrode, magnetic field forming means for forming a magnetic field orthogonal to the direction of the electric field and directed in one direction,
A ring-shaped member provided around the lower electrode,
The plasma etching apparatus according to claim 1, wherein an outer diameter of the ring-shaped member is set so that arc discharge on the semiconductor wafer hardly occurs. The plasma etching apparatus according to claim 5, wherein the semiconductor wafer has a diameter of 200 mm, and the outer diameter of the ring-shaped member is larger than 240 mm and smaller than 280 mm. The plasma etching apparatus according to claim 6, wherein an outer diameter of the ring-shaped member is 260 mm. The plasma etching apparatus according to claim 5, wherein the semiconductor wafer has a diameter of 300 mm, and an outer shape of the ring-shaped member is smaller than 380 mm. The plasma etching apparatus according to claim 8, wherein an outer diameter of the ring-shaped member is 360 mm.

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