JPH1187311A - Plasma-processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma-processing apparatus capable of increasing plasma density of either capacitively coupled plasma or inductively coupled plasma, without losing uniformity of the plasma density by making use of magnetic field. SOLUTION: A processing chamber 11 contains a substrate holder 14 and an rf electrode 13, in which a processing chamber 11 which is either capacitively coupled or inductively coupled plasma is generated. This apparatus includes two magnet rods 12A to 12B provided at outer confronting positions in the processing chamber 11, which has rods generating a substantially flat magnetic field on the surface of the rf electrode 13. Londitudinal axes of the two magnet rods 12A and 12B are parallel to each other. The two magnet rods 12A to 12B are rotated in synchronism around the longitudinal axis by an electric motor 20. The direction of the magnetic field is alternately reversed, following the rotation of the two magnet rods 12A and 12B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus used for chemical vapor deposition using high-density plasma and dry etching of micron-scale elements in an integrated circuit.

[0002]

BACKGROUND OF THE INVENTION Problems to be Solved by Inductively Coupled Plasma (I
CP) and capacitively coupled plasma (CCP) are widely used in the semiconductor industry. The plasma density of the ICP and CCP can be increased by utilizing appropriately configured magnetic fields.

FIGS. 10 and 11 show examples of a CCP to which a magnetic field is applied. This plasma source is commonly called a magnetron plasma source. The plasma source includes a chamber 101 provided with an rf electrode 102 and a substrate holder 103.
It has. The side wall of the chamber 101 has a cylindrical shape. The rf electrode 102 is connected to an rf power generator 106, and the substrate holder 103 is similarly connected to another rf power generator 107. Ceiling wall is gas inlet 104
And the bottom wall has a gas outlet 105. In this plasma source, a circular magnet 10 is wrapped around the cylindrical side wall of the chamber 101 as shown in FIG.
8 are arranged. Due to the circular magnet 108, a relatively weak DC magnetic field (50 to 200 gauss) 10
9 is added in parallel to the surface of the rf electrode 102.

The application of the magnetic field 109 increases the plasma density and lowers the sheath voltage, but the generated plasma is caused by the E × B drift in both the radial and azimuthal directions. And become very uneven. Where E and B are the local DC field strength and magnetic flux density, respectively.

[0005] One of the typical solutions to the above-mentioned problem is to place the circular magnet 108 around an axis 110 of the cylindrical wall of the chamber 101 at a low frequency (eg, 0.5 Hz or 0.5 Hz), as shown in FIG. Lower frequency). Although rotation of the circular magnet 108 about the axis 110 can improve the uniformity of the reaction at the substrate surface, the non-uniformity of the plasma is not eliminated. This is a control issue when magnetron plasma is used in many applications. This is because the non-uniformity of the plasma on the substrate generates a lateral DC current on the substrate surface, which damages the thin film deposited on the surface.

[0006] Both cylindrical and flat type ICPs have
It can be combined with a magnetic field (B) to increase the density and uniformity of the plasma. In these cases, as shown in FIGS. 12 and 13, large annular electromagnets 201, 301 are arranged around the reaction vessels 202, 302 in order to have a fairly uniform axial magnetic field. Reaction vessel 2
02 and related components relate to a cylindrical ICP source, and the reaction vessel 302 and related components relate to a flat plate type ICP source.

However, since the magnetic field extends to the end portions, the plasma density changes on the surface of the substrate placed on the substrate holders 203 and 303. This leads to the problem of charge-up of the substrate surface, whereby the surface is damaged. Therefore, using a magnetic field,
The search for new practical ways to increase the density of the plasma without compromising the uniformity of the plasma is important.

It is an object of the present invention to provide a plasma processing apparatus capable of increasing the plasma density of a capacitively coupled plasma or an inductively coupled plasma without deteriorating the uniformity of the plasma density by applying a magnetic field.

[0009]

According to the present invention, there is provided a plasma processing apparatus comprising: a substrate holder;
An f electrode is provided, and a processing chamber in which a capacitively-coupled or inductively-coupled plasma is generated in a space between the substrate holder and the rf electrode is provided. The plasma processing apparatus generates a magnetic field having a direction that is substantially parallel to the surface of the rf electrode, and is disposed at two opposing locations outside the processing chamber, the two magnet rods having their long axes parallel to each other. And an electric motor for synchronously rotating these two magnet rods around their long axes, and the direction of the magnetic field changes alternately with the rotation of the two magnet rods.

According to the above arrangement, the magnetic field provided by the rotatable magnet rod causes the plasma density to increase in a pulsed manner, and the original uniformity of the plasma density to be increased by E
It does not suffer from × B drift. further,
Since this technique creates a pulsed plasma, this technique can be used to obtain a pulsed plasma without using a pulsed rf current.

In the above arrangement, the length of the magnet rod is preferably larger than the size of the processing chamber.

In the above configuration, the major axes of the two magnet rods are on the same horizontal plane.

In the above arrangement, the poles of each of the two magnet rods facing the processing chamber have opposite polarities when the pole faces are parallel to the processing chamber wall.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below with reference to the accompanying drawings. Details of the present invention will be made clear through the description of the embodiments.

FIGS. 1 and 2 show a typical embodiment of the present invention. 1 shows a side view and FIG. 2 shows a plan view. Both figures show a plasma processing apparatus including a container 11 provided with a magnetic field generating mechanism. The magnetic field generating mechanism includes two magnet rods (permanent magnets) 12 </ b> A and 12 </ b> A disposed outside the container 11.
B. The configuration proposed for the magnetic field generation mechanism is described using a parallel plate capacitively coupled plasma.

The container 11 has an upper electrode (or rf electrode) 13 at an upper position thereof and a lower electrode (or substrate holder) 14 at a lower position thereof. Upper electrode 13
Is connected to an rf power generator (or rf power supply) 15 via a matching circuit 16. The lower electrode 14 is preferably grounded. Further, a gas inlet 17 is provided on the ceiling wall of the container 11, and a gas outlet 1
8 are provided. The side wall of the container 11 is preferably cylindrical.

Each of the two magnet rods 12A and 12B arranged outside the container 11 is provided so as to be rotatable around its axis. As shown in FIG. 2, the axes 12a and 12b of the two magnet rods 12A and 12B are parallel and exist on the same horizontal plane. Magnet rod and container 11
The distance between the cylindrical side walls is not critical and is generally in the range of 50 mm to 400 mm. The longitudinal cross-sectional shape of the magnet rod is likewise not critical, but instead of a circular longitudinal cross-section, a square or rectangular shape is preferred.

The dimensions (height (H) and width (W)) of the longitudinal section of the magnet rod are 5 mm × 10 mm to 100 mm ×
The range is 100 mm. However, other longitudinal cross-sectional dimensions may be used, depending on requirements and practical convenience. The length (L) of the magnet rods 12A and 12B is the container 1
It is larger than one dimension (diameter of the cylindrical side wall). As shown in FIG. 2, by selecting the length of the magnet rods 12A and 12B to such a preferable length,
Can be avoided. Usually, the two magnet rods 12A, 12B have the same dimensions and the same magnetic field strength at their poles. The magnetic field strength at the magnetic pole of the magnet rod is 100 kA / m or more. The magnetic field strength of the magnetic pole is
The magnetic flux density at the center position of A, 12B is 50
Determined to have a magnetic flux density in the range of ２０００2000 Gauss. The exact value of the magnetic field strength must be selected by considering the magnetic flux density required in the plasma and the distance between the two magnet rods 12A, 12B.

As described above, the magnet rods 12A and 12B are arranged at two positions on the opposite sides of the container 11. Shaft 1 of two magnet rods 12A, 12B
A horizontal plane including 2a and 12b exists between the upper electrode 13 and the lower electrode 14. Each magnet rod is rotatably attached to the shaft portion 19 via its shaft. Shaft 19
Is connected to the electric motor 20 via a gear device 21. The magnet rods 12A, 12B are rotated around the shaft 19 by the electric motor 20. The rotation frequency of the magnet rod can be easily changed by using the gear device 21. Normally, the rotation frequency of the magnet rod is 1
It is in the range of １００100 Hz. Further, other frequencies can be used as well.

Each of the magnet rods 12A and 12B is shown in FIG.
As shown in FIG. 2 and FIG. 2, the opposite surface has different magnetic poles (S-pole and N-pole). Initially, the pole faces are arranged to be parallel to a vertical or horizontal plane. When the pole face is vertical, the magnet rods 12A, 1
Each inner pole of 2B has an opposite polarity, so that
As shown in FIG. 3, a horizontal magnetic field is created between the opposing magnetic poles. In FIG. 3, reference numeral 22 denotes the magnet rod 12
A, 12B indicate the horizontal centerlines, 23 indicates their vertical centerlines, and 24 indicates their centers.

In FIG. 3, the magnetic flux density decreases toward the center 24. By selecting appropriate dimensions for the magnet rods 12A, 12B and disposing the magnet rods away from the container 11, the uniformity of the horizontal magnetic field in cross section can be improved.

The rotation frequencies of both the magnet rods 12A and 12B are synchronized. Therefore, the magnet rod 1
Each time 2A, 12B makes a 180 ° (180 degree) rotation, the direction of the magnetic field (B) generated between the two magnet rods 12A, 12B changes in opposite directions. The direction of rotation of each of the magnet rods may be the same or opposite. In each case, a horizontal magnetic field is generated by 180 rotations for each half rotation of the magnet rods 12A, 12B.
The intensity in that direction changes according to the degree angle. However, inside the container 11, what is the magnitude and direction of the magnetic field when the magnetic field becomes weaker? It is different for these two cases. The appropriate direction of rotation is confirmed by experiment.

For example, computer simulation data on magnetic flux is shown in FIGS. 4, 5, 6, 7, and 8.
Is shown in The magnetic field strength at the magnetic poles of the magnet rods 12A and 12B is treated as 945000 A / m. This simulation was performed for different longitudinal cross-sectional dimensions of the magnet rod and for the two magnet rods 12A, 1
Performed on distances between 2B.

FIGS. 4 and 5 show the results of simulating magnetic field lines generated between two magnet rods 12A and 12B provided at a distance of 1000 mm in the region 25. FIG. The horizontal center line 22 and the vertical center line 23 of the two magnet rods 12A and 12B are treated as an X axis and a Y axis, respectively. The dimension of the longitudinal section of the magnet rod is 100m
It is set as mx 100 mm. The length of the magnet rod is assumed to be infinite for simulation processing. In the area 25, as shown in FIG.
The lines representing the magnetic field are denser near the magnetic poles of the magnet rod and become less dense toward the center 24 of the magnet rods 12A, 12B.

FIG. 6 shows different Y values (0 mm, 50 m).
m, 100 mm) shows the change in magnetic flux density expressed as a function of the distance measured from the center 24 to the magnet rod. At Y = 0, the magnetic flux density at the center 24 of the two magnet rods is 121 Gauss. This flux density is sufficient to move the electrons in a spiral orbit. The uniformity of the magnetic field on the X axis is ± (Bmax-Bmin)
/ 2Bave, where Bmax, Bmin,
Bave is the maximum magnetic flux density, the minimum magnetic flux density, and the average magnetic flux density, respectively. FIG. 7 shows a change in the uniformity of the magnetic flux density in the X-axis direction. For example, the uniformity in the X-axis is about ± 8% for a distance of 100 mm from the center 24.

FIG. 8 shows different widths of the magnet rod (W = 10
(mm, 100 mm, 200 mm) shows the change in magnetic flux density expressed as a function of the distance measured from the center 24 of the two magnet rods 12A, 12B. The magnetic field strength at the poles of the magnet rod was treated as 945000 A / m for all of the widths used for the simulation. FIG. 8 clearly illustrates that the magnetic flux density can be changed by changing the dimensions of the longitudinal section of the magnet rod.

The plasma used in the above embodiment is:
It is a parallel plate capacitively coupled rf plasma. The rf power generator 15 applies r to the upper electrode 13 through the matching circuit 16.
Give f power. The frequency of the given rf current is 1 MHz
It can vary from z to 50 MHz, typically 13.56 MHz. The condition of the lower electrode 14 has no direct effect on the proposed mechanism of increasing the plasma density. The lower electrode 14 is directly grounded or grounded via a block capacitor (not shown). If the above-mentioned plasma source is applied to etching, the lower electrode 14 can be connected to another rf power generator.

The shape of the upper electrode 13 and the lower electrode 14 is not important, and they can be made circular or square. The form of the container and the form of the electrode need not necessarily be the same. For example, the container 11 is configured as a square,
On the other hand, the electrodes are configured as circular. The container 11 of the present plasma processing apparatus is preferably made of a dielectric material such as stainless steel, aluminum, or Pyrex glass. Similarly, the shape of the container may be square. The dimensions of the container 11 are not critical and if a cylindrical container is used, the diameter may be between 100 mm and
A range of 400 mm can be taken. If a container having a square shape is used, its dimensions are 10
The value can be in a range from mm × 10 mm to 400 mm × 400 mm.

Next, the operation of the above-described mechanism will be described. The parallel plate CCP generates uniform plasma in the radial direction between the upper electrode 13 and the lower electrode 14. The electric field (E) generated by approaching the upper electrode 13 and the lower electrode 14 is shown in FIG.
, Are perpendicular to these electrodes. When there is no magnetic field, the electrons in the plasma move in a straight line. Therefore, at pressures typically below 10 mTorr, the mean free path of electron-atom collisions is comparable to the size of the vessel. This causes higher electron temperatures, and thereby lower electron-atom collision rates and lower plasma densities.

When the aforementioned magnetic field is applied by the rotatable magnet rods 12A, 12B, the electrons move along a helical trajectory, so that they can move a longer distance (before collision) and consequently The electron atom collision rate is higher. This results in a higher ionization rate and thereby a higher plasma density. When the pole faces are vertical, the lines representing the magnetic field are substantially horizontal and perpendicular to the direction of the electric field. With this configuration of the magnet rods 12A, 12B, the plasma density increases.

When the pole faces are substantially horizontal or perpendicular to the side walls of
The strength of the magnetic field inside is greatly reduced. At this time, the plasma density decreases to a value obtained by simple capacitive coupling.

When a magnetic field is present, the plasma drifts due to ExB along the Z axis, which is perpendicular to both the X and Y axes. However, since the direction of the magnetic field is reversed by each half rotation of the magnet rods 12A, 12B,
The drift of the plasma due to ExB is the same in both directions. For this reason, the time-average uniformity of the plasma in the Z-axis direction is not disturbed by the magnetic field except at the location of the container wall close to the magnet rods 12A, 12B.

In each half rotation of the magnet rods 12A, 12B, the plasma density increases due to the lines of magnetic force (magnetic flux lines) flowing into the container 11. FIG. 9 shows a relationship between the plasma density and the rotation state of the magnet rod 12A or the magnet rod 12B. Rotatable magnet rod 12A,
The magnetic field provided by 12B pulses the plasma density without disturbing the plasma density uniformity due to the E × B drift. The minimum plasma density of the pulsed plasma is a normal CCP plasma density. The maximum plasma density depends on the strength of the magnetic field and the plasma density without the magnetic field. Depending on the strength of the magnetic field, the plasma density can be increased by a factor of 2 to 10. Magnet rod 12A,
The 12B configuration pulsates the plasma density.
The pulse frequency can be easily controlled by changing the rotation frequency of the magnet rod. The width of the pulse can likewise be varied by the mechanical method used for the gear train 21.

Further, by optimizing the arrangement of the magnet rods, it is possible to obtain pulsed plasma having a minimum plasma density of zero. This method is described below.
There is a minimum rf power applied to the top electrode to initiate the CCP. When a magnetic field is present, the minimum rf power can be quite low. Therefore,
By maintaining the rf power applied to the top electrode slightly lower than the rf power required to start the plasma when no magnetic field is present, a pulsed plasma is created by applying the aforementioned alternating magnetic field. Can be
In this case, the minimum plasma density becomes zero. However, if the rotation speed of the magnet rods 12A and 12B increases, the minimum plasma density does not reach zero completely.

[0035]

In the plasma processing apparatus according to the present invention, the alternating magnetic field generated by the two rotatable magnet rods increases the plasma density in a pulsed manner, thereby realizing an increase in the plasma without impairing the uniformity of the plasma density. be able to.

[Brief description of the drawings]

FIG. 1 is a side view of an exemplary embodiment showing a plasma processing apparatus with a magnet rod arrangement for increasing a parallel plate capacitively coupled plasma density.

FIG. 2 is a plan view of the plasma processing apparatus of FIG.

FIG. 3 is a diagram showing directions of an electric field and a magnetic field existing in the plasma processing apparatus.

FIG. 4 is a diagram showing an area for computer simulation of a line representing a magnetic field between two magnet rods.

FIG. 5 is a detailed diagram showing a computer simulation of a line representing a magnetic field.

FIG. 6 is a graph showing the change in magnetic field in the X-axis direction as a function of distance measured from the center of two magnet rods for different Y values.

FIG. 7 is a graph showing the change in the uniformity of the magnetic field in the X-axis direction as a function of the distance measured from the center of the two magnet rods.

FIG. 8 shows two plots for different widths of the magnet rod.
FIG. 7 is a diagram illustrating a change in the strength of a magnetic field in the X-axis direction with respect to a distance measured from the center of one magnet rod.

FIG. 9 illustrates the relationship between plasma density and magnet rod direction.

FIG. 10 is a schematic view showing a first conventional apparatus for magnetron plasma.

FIG. 11 is a plan view showing a ring magnet used in the first conventional device.

FIG. 12 is a schematic diagram showing a second conventional device of a cylindrical ICP to which a magnetic field is applied.

FIG. 13 is a schematic view showing a third conventional device of a flat plate type ICP to which a magnetic field is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Container 12A, 12B Magnet rod 13 Upper electrode (rf electrode) 14 Lower electrode (substrate holder) 15 rf power generator 20 Electric motor 21 Gear device

Claims (4)

[Claims] 1. A plasma processing apparatus comprising a processing chamber in which a substrate holder and an rf electrode are arranged, and a capacitively-coupled or inductively-coupled plasma is generated between the substrate holder and the rf electrode. The processing apparatus includes two magnets disposed at two opposing positions outside the processing chamber so that their major axes are parallel to each other, and creates a magnetic field having a direction substantially parallel to the surface of the rf electrode. A rod, and an electric motor that rotates the two magnet rods around their long axes in synchronization with each other, wherein the direction of the magnetic field repeats reverse rotation with the rotation of the two magnet rods. Plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein a length of said magnet rod is longer than a dimension of said processing chamber. 3. The plasma processing apparatus according to claim 1, wherein the major axes of the two magnet rods are arranged so as to exist on one horizontal plane. 4. The magnetic pole of each of the two magnet rods facing the processing chamber has opposite polarities when the pole face is parallel to a wall of the processing chamber. 2. The plasma processing apparatus according to 1.