JPH03222415A - Discharge reactive device based on rotation magnetic field - Google Patents

Abstract

PURPOSE:To equalize the etching speed in a wafer and enhance pressure resistance on a wafer surface by installing control electrodes to a part around electrodes to which treated components are placed so that a west-side potentiality may be constantly higher than an east-side potentiality as viewed from the direction of electric field. CONSTITUTION:Four control electrodes A, B, C, and D are laid out around a non-grounding electrode 16. Pulsating voltage whose phase is deviated by 90 degree is applied to the control electrodes A, B, C, and D. If a magnetic field is rotated once for two seconds, the frequency of the pulsating voltage is set to 1/2Hz. When the direction of the magnetic field viewed from the direction of the electric field is assumed to be the north-side, it is oscillated so that the potentiality of the control electrodes located on the west side may be higher while the potentiality of the electrodes on the east side way be lowered. This construction makes it possible to eliminate the east side deviation of plasma potentiality induced by rotating magnetic field and equalize the distribution of plasma potentiality, further equalize the etching speed in a wafer 17 and improve pressure resistance of the surface of the wafer 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a discharge reaction device using a rotating magnetic field suitable for use in the manufacture of semiconductor devices such as ICs and LSIs, and particularly in dry etching devices.

(Conventional technology) As the integration of semiconductor integrated circuits increases, there is a demand for miniaturization of devices, and as the development of three-dimensional integrated circuits progresses, the requirements for the dry etching technology necessary for their processing are becoming increasingly strict. ing.

Since the concept of a dry etching method using a rotating magnetic field was announced by Hyman of IBM in 1981, it has been widely used in conjunction with triode reactive ion etching equipment as a method to increase plasma density.

In the magnetron system, where the electric and magnetic fields are orthogonal, the synergistic effect of the electric and magnetic fields causes the electrons to rotate in the direction perpendicular to the plane formed by the electric and magnetic fields (EXB) in a so-called magnetron motion. collides with molecules, improving ionization efficiency and increasing etching rate. In addition, the mobility of electrons is significantly reduced by the magnetic field, and the electron current reaching the electrodes in a DC floating state is reduced, resulting in a low self-bias (lower ion energy colliding with the electrodes), which lowers the ion energy that impinges on the wafer. Damage to the surface can be reduced.

In an apparatus using a rotating magnetic field, high-density plasma is rotated on a wafer by rotating a magnetic field generated by two or three pairs of electromagnetic coils, thereby promoting ionization of the plasma.

(Problems to be Solved by the Invention) However, the conventional device described above has the following problems.

First of all, wafers are becoming larger in diameter, with a maximum diameter of 8 inches, and in order to provide a uniform magnetic field on these large wafers, the magnetic coils must be large, each with a diameter of 1 m or more. It becomes necessary. When it comes to such a large device, considering the floor area and work space of the equipment,
This makes it unusable for current semiconductor manufacturing lines.

Secondly, irrespective of the magnetic field strength distribution, in the parallel plate electrode type magnetron device, electrons move in the ExB direction as described above, so the plasma becomes denser in the same direction. In such a plasma state, even if the plasma potential on the wafer is approximately uniform in the north-south direction if the magnetic force direction is north, in the east-west direction the plasma potential on the east side is higher than on the west side. When the etching shape and etching rate are controlled by the directionality and intensity of the ions, as in reactive ion etching, the ions are accelerated in the dark part of the plasma by the sum of the plasma potential and self-bias, and collide with the film to be etched. Also, the ionic current Ji is Ji= e
As shown by niμiE, it changes in proportion to the product of ion density and ion mobility.

In other words, with respect to the magnetic field, the ion collision strength and quantity are greater at the collecting edge than at the center and at the convex periphery.
The etching rate also becomes significantly non-uniform. The plasma concentration phenomenon mainly depends on the magnetic field strength and reaction pressure. In particular, in order to achieve the high aspect ratio and extremely small pattern size-dependent etching required for next-generation devices, etching in a low-pressure atmosphere is essential, and the density phenomenon caused by the magnetic field becomes noticeable. In addition to the etching speed,
At the outer periphery of the wafer, the central part has a high specific ion collision strength, so it is easily damaged by ion irradiation, and depending on the device, there is a problem that the yield rate at the periphery decreases significantly.

Furthermore, the conventional techniques are unsuitable for large-diameter wafers because of the difference in etching rate between the periphery and center of the wafer to be etched and the periodic changes in ion energy at the periphery. This makes it difficult to independently vary the magnetic field and pressure, and the process window for uniformity tends to be very narrow.

The present invention was made to solve the above problems, and its purpose is to suppress the movement of electrons in plasma, make the distribution of plasma potential uniform, and increase the etching rate in a wafer as a dry etching device. It is an object of the present invention to provide a discharge reaction device using a rotating magnetic field that can more uniformly improve the breakdown voltage on the wafer surface and can generate a uniform film as a plasma CVD device.

(Means for Solving the Problems) The present invention according to the above object includes a vacuum chamber containing an electrode, a gas supply means for supplying a predetermined gas to the inside of the vacuum chamber, and an exhaust means for discharging the gas inside the vacuum chamber. and a discharge reaction apparatus using a rotating magnetic field, which is equipped with an electromagnetic coil that is arranged around a vacuum chamber and generates a rotating magnetic field that rotates in a plane perpendicular to the direction of the electric field. A plurality of electrodes are arranged around the rotating magnetic field, and the rotating magnetic field is rotated so that the potential of the one located on the west side is always higher than the one located on the east side with respect to the north direction of the rotating magnetic field when viewed from the direction of the electric field. It is characterized by the provision of a control electrode whose potential is synchronously controlled.

(Function) If the magnetic field is simply rotated, as described above, the plasma potential on the east side relative to the north direction of the rotating magnetic field increases when viewed from the direction of the electric field.

When the potential of the control electrode placed around the electrode on which the object to be processed is placed increases, the surrounding plasma potential increases. Therefore, by controlling the potential so that the potential of the control electrode located on the west side with respect to the north direction of the rotating magnetic field is always higher than the potential of the control electrode located on the east side, the plasma potential can be made uniform.

(Embodiment) A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a plan view of the tri-etching device 10, and FIG. 2 shows a front sectional view.

In the figure, 14 is a vacuum chamber, CF.

Gas supply port (not shown) for introducing etching gas such as
and a gas exhaust port (not shown) for evacuating the inside of the vacuum chamber 14 and setting a required pressure.

The gas supply port is connected to a gas supply source through a valve, and the gas discharge port is connected to a gas pump through a valve.

Reference numeral 16 denotes a non-grounded electrode for placing a wafer (workpiece 17) disposed in the vacuum chamber 14, to which a high frequency power source 20 is connected via a matching circuit 18 to apply high frequency power. Ru. A ground electrode 22 is provided on the upper wall of the vacuum chamber and is grounded.

1.1' 2.2° are two pairs of electromagnetic coils arranged surrounding the vacuum chamber 14, to which currents with a phase difference of 90° are applied, and the electric field between the non-grounded electrode 16 and the grounded electrode 22 is Rotate the resultant magnetic field generated in orthogonal directions. The rotation speed of this rotating magnetic field is low, approximately one rotation per two seconds.

By applying a rotating magnetic field in this way, high-density plasma can be rotated on the wafer 17, but as mentioned above, if the direction of the magnetic field is one north, the plasma potential is higher on the east side than on the west side. Even if the magnetic field is rotated, the plasma continues to rotate on the wafer 17 with its density remaining unchanged, resulting in the above-mentioned problem.

In this embodiment, four control electrodes A, C, B, and D are arranged around the non-grounded electrode 16 so that their upper surfaces are between the upper surface of the wafer 17 placed on the non-grounded electrode 16 and the path. did.

23 and 24 are insulators.

A DC power supply is connected to each of the four control electrodes A, C, B, D through a low-pass filter, and the phase is 90°.
A pulsating voltage is applied. This pulsating voltage is set to be displaced in synchronization with the rotation of the magnetic field. That is, if the magnetic field rotates once every 2 seconds, the frequency of the pulsating voltage is set to +AHz. For example, control electrodes A, B, C
, D can be a sine wave pulsating voltage. Furthermore, if the direction of the H field as seen from the direction of the electric field with respect to the rotation of the magnetic field is the north side, the control electrodes located on the west side have a high potential and the control electrodes located on the east side have a low potential, so that the cycle is synchronous. do.

It is configured as described above.

Next, the operation of this device will be explained.

First, encinque gas, such as CP, is introduced into the vacuum chamber 14 from the gas supply port, the inside of the vacuum chamber 14 is maintained at 10-'' (Torr), and high-frequency power (1 kW, 13.5 MHz) is applied to the non-grounded electrode 16. When applied, a discharge occurs between the ungrounded electrode 16 and the grounded electrode 22,
Plasma is generated. On the other hand, two pairs of electromagnetic coils 1.1°
2 and 2' to rotate the composite magnetic field. Since this composite magnetic field is generated in a direction perpendicular to the electric field, the electrons undergo magnetron rotational movement, increasing ionization efficiency.

On the other hand, as mentioned above, the four control electrodes A, B, C, D
A pulsating current is applied to the

For example, when the driver setting value of the electromagnetic coil 1.1° 2.2° is (1,0), the magnetic field indicates A, and at the same time, the potential of the control amount pliB on the west side with respect to the direction of the magnetic field is the highest. , the control electrode on the east side has the lowest potential. Also, the driver setting value of the electromagnetic coil 1.1"2.2" is (
, 7071, 707), the magnetic field is directed in a direction rotated 45° clockwise from the above position, and at this time the control electrode A
, it is understood that the potential of the control electrode B is high and the potential of the control electrode C1 is low. In other words, in synchronization with the rotation of the magnetic field, the potential of the four control electrodes A, B, C, and D is such that the control electrode on the west side is always higher than the control electrode on the east side with respect to the direction of the magnetic field (north). Displaced as follows.

When a positive potential is applied to control electrodes A, B, C, and D, the plasma potential near the control electrode increases in proportion to the potential of that electrode.
Conversely, in the case of negative potential, the ion current increases and the plasma potential decreases. This is because the DC electrode acts as a source of electrons or as a remover of excess electrons. That is, the movement of electrons in the EXB direction within the plasma can be suppressed or controlled.

Therefore, as described above, the potentials of the four control electrodes A, B, C, and D are displaced such that the control electrode on the west side is always higher than the control electrode on the east side with respect to the direction of the magnetic field (north). By cycling in this manner, it is possible to eliminate the aforementioned bias of the plasma potential towards the east due to only the rotating magnetic field, thereby making the distribution of the plasma potential uniform,
The etching rate within the wafer becomes more uniform, and the breakdown voltage of the wafer surface is improved.

The plasma potential can be easily adjusted by adjusting the potentials of the four control electrodes A, B, C, and D. As a result of optimal potential adjustment, the plasma potential between north and south and between east and west was within ±IOV at a location 4 inches from the center of the wafer, which was significantly improved. At the same time, the uniformity of the etching rate within the wafer surface has conventionally been within ±10 mm from the edge.
Although there was a variation of 10%, in this example, the variation was ±3.5% except for the 5InI11 part from the edge.
I was able to get it within the acceptable range.

In the above embodiment, four control electrodes A, B, C, and D are arranged, but if the number of electrodes is increased to eight, for example, the plasma potential can be controlled more easily and uniformity can be achieved.

Furthermore, although a high frequency power source is used in the above embodiment, a direct current power source may also be used, and a direct current power source can simplify the configuration of the device.

Furthermore, although the above embodiment has been explained using a dry etching apparatus as an example, it goes without saying that it can also be used as a plasma CVD apparatus.

The present invention has been variously explained above with reference to preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

(Effects of the Invention) As described above, according to the present invention, since the movement of electrons in plasma can be controlled and the distribution of plasma potential can be made uniform, it can be used as a dry etching apparatus to increase the etching rate of the object to be processed. It is possible to more uniformly improve the withstand pressure on the surface of the object to be processed, and furthermore, it is possible to form a film of uniform thickness on the surface of the object to be processed by using it as a plasma CVD apparatus.

[Brief explanation of drawings]

FIG. 1 is an explanatory plan view of the dry etching apparatus, and FIG. 2 is a front sectional view thereof. 10... Dry etching device, 14... Vacuum chamber, 16... Ungrounded electrode,
17... Wafer, 20... High frequency power supply, 2
2... Ground electrode, 1.1 ' 2.2 '... Electromagnetic coil, A, B, C, D... Control electrode. drawing

Claims (1)

[Claims] 1. A vacuum chamber containing an electrode, a gas supply means for supplying a predetermined gas into the vacuum chamber, an exhaust means for discharging the gas within the vacuum chamber, and a vacuum chamber disposed around the vacuum chamber. , a discharge reaction device using a rotating magnetic field, which is equipped with an electromagnetic coil that generates a rotating magnetic field that rotates in a plane perpendicular to the direction of the electric field, in which a plurality of electrodes are arranged around the electrode on which the object to be treated is placed, and the electric field Control in which the electric potential is controlled in synchronization with the rotation of the rotating magnetic field so that the electric potential of the object located on the west side of the rotating magnetic field is always higher than that of the object located on the east side with respect to the north direction of the rotating magnetic field when viewed from the direction of A discharge reaction device using a rotating magnetic field, characterized by being provided with electrodes.