JPH10289798A - Plasma-etching method, plasma-etching device and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly maintain an optimum magnetic field status on a sample at all times by forming the first magnetic field in a vacuum vessel for generating a plasma, and the second magnetic field in the vicinity of a sample, and controlling the second magnetic field, depending on the status of the first magnetic field. SOLUTION: A silicon wafer 10 as an etching object is fastened to a sample stage 32 and, then the internal pressure of a plasma generation chamber 12 and a reaction chamber 14 is decompressed to a prescribed pressure level. Then, reaction gas is introduced to the plasma generation chamber 12 and the reaction chamber 14. Thereafter, coils 22, 24 and 26 are electrically energized to form magnetic field in the plasma generation chamber 12, and a microwave is introduce from a circular waveguide 16 to the plasma generation chamber 12. According to this construction, a plasma is generated on an ERC surface 100, and the plasma is taken out into the reaction chamber 14, due to the action of a divergent magnetic field. In addition, the plasma is made to be irradiated the surface of the silicon wafer 10 on the sample stage 32, thereby etching the silicon wafer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing technique for performing processes such as etching and thin film formation in a process of manufacturing electronic parts and semiconductor elements by using plasma.

[0002]

2. Description of the Related Art In a plasma processing apparatus, microwaves are introduced into a vacuum vessel containing a small amount of reaction gas, and a gas discharge is generated in the vacuum vessel to generate plasma. And
By irradiating the surface of the sample substrate with the plasma, processes such as etching and thin film formation are performed. Such a plasma processing apparatus is being studied as being indispensable for manufacturing a highly integrated semiconductor device. Especially,
Electron cyclotron resonance (ECR: El
An ECR plasma processing apparatus using ectron cyclotron resonance has been put to practical use as an apparatus capable of generating highly active plasma under a low gas pressure region.

In order to improve the processing quality in a plasma processing apparatus, it is important that the plasma has a uniform density over the entire range of the sample. In particular, when the processing area of a sample becomes large, such as a semiconductor wafer having a diameter of 300 mm, which has been developed in recent years, it is more important than ever to maintain a uniform plasma (particularly, ion) intensity distribution on the sample. However, it has been difficult to maintain plasma uniformity on the sample. For example, if the sample is irradiated with plasma generated in a vacuum vessel using a divergent magnetic field in which the strength of the magnetic field weakens with an appropriate gradient toward the sample, the processing surface of the sample is used. The distribution of the magnetic flux density above becomes non-uniform. In addition, the plasma in the vacuum container is basically illuminated on the sample by being constrained by the magnetic field (divergent magnetic field) in the vacuum container. Because it becomes noticeable, the plasma on the sample is not completely uniform.

[0004] If the distribution of plasma particles on the sample is not uniform, a high ion density region and a low ion density region are formed on the sample.
Inconveniences such as deterioration of processing speed uniformity or anisotropy occur. In addition, a potential difference may be generated on the sample, a current may flow, and a semiconductor element formed on the sample may be broken. On the other hand, in the CVD process, the thickness of the film formed on the semiconductor substrate becomes uneven, and uniform film formation becomes difficult. If the plasma processing of the semiconductor substrate is not performed uniformly, the performance of the finally manufactured semiconductor device deteriorates.

[0005] JP-B-6-4052, JP-A-63-484
75, JP-A-6-216046 and the like disclose a method of making the magnetic flux density distribution on a sample table uniform using a permanent magnet. By such a method, a plasma having a uniform density can be obtained over the entire processing surface of the sample.

[0006]

However, the uniformity of the plasma on the sample is affected not only by the magnetic field near the sample stage but also by the magnetic field generated by the plasma generating electromagnetic coil.
That is, the interaction between the magnetic field formed for plasma generation and the magnetic field near the sample determines the magnetic flux density distribution on the sample. For this reason, even if the strength and position of the permanent magnet in the vicinity of the sample table are set to the optimum state, when the current value of the electromagnetic coil for plasma generation is changed later, the optimum magnetic flux density distribution is obtained on the sample table. May not be possible.

The present invention has been made in view of the above circumstances, and provides a plasma processing method capable of always maintaining an optimum magnetic field state on a sample even when a magnetic field for generating plasma is changed. As a first object.

It is a second object of the present invention to provide a plasma processing apparatus which can always maintain an optimum magnetic field state on a sample even when a magnetic field for generating plasma is changed.

Further, even when the magnetic field for plasma generation is changed in the plasma processing step, good plasma processing can be achieved by always maintaining an optimum magnetic field state on the semiconductor substrate, and a high-quality semiconductor can always be obtained. It is a third object to provide a method of manufacturing a semiconductor substrate which enables manufacture of a device.

[0010]

In order to solve the above problems, in a plasma processing method according to a first aspect of the present invention, a first magnetic field for generating a plasma in a vacuum vessel (12, 14) is provided. At the same time, a second magnetic field is formed near the sample (10) in order to control the plasma distribution near the sample (10). Then, the second magnetic field is controlled according to the state of the first magnetic field.

According to a second aspect of the present invention, there is provided a plasma processing apparatus comprising: first magnetic field forming means (22, 2) for forming a first magnetic field for generating plasma in a vacuum vessel (12, 14);
4, 26) and a second magnetic field forming means (42) for forming a second magnetic field near the sample (10) in order to control the plasma distribution near the sample (10). Furthermore, the first
Magnetic field control means (4) for controlling the position of the second magnetic field forming means (42) in order to adjust the second magnetic field according to the state of the magnetic field
4, 46).

In the above-described plasma processing apparatus, the magnetic field control means (44, 46) controls the second direction in a direction parallel to and / or orthogonal to the direction in which the plasma travels.
The position of the magnetic field forming means (42) can be adjusted. Further, the second magnetic field forming means (42) can be arranged between the inner wall of the vacuum vessel (12, 14) and the sample (10). Further, the second magnetic field forming means (50)
It may be arranged outside the vacuum vessel (12, 14).

In a method of manufacturing a semiconductor device according to a third aspect of the present invention, a first magnetic field for generating plasma is formed in a vacuum vessel (12, 14) when a plasma processing step is performed. A second magnetic field is formed near the semiconductor substrate (10) to control the plasma distribution near the semiconductor substrate (10). Then, the second magnetic field is controlled according to the state of the first magnetic field.

[0014]

In the present invention, since the second magnetic field near the sample stage is controlled in accordance with the magnetic field state such as the intensity and distribution of the magnetic field for plasma generation, the magnetic field for plasma generation is changed as necessary. Also in this case, it is possible to optimally set the magnetic flux density distribution on the sample. For example, when changing the magnetic field for plasma generation in order to change the plasma density or the rough distribution of the processing, in consideration of the change in the magnetic field,
The second magnetic field is controlled so that the magnetic flux density distribution on the sample is totally optimal. As a result, it is possible to irradiate the sample with plasma having a uniform density distribution, and the plasma processing quality is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to examples. In the embodiments described below, the technical idea of the present invention is applied to plasma processing of a silicon wafer which is a part of a manufacturing process of a semiconductor device.

[0016]

FIG. 1 shows a configuration of a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus of the present embodiment includes:
A predetermined plasma process such as etching is performed on a silicon wafer 10 having a diameter of 12 inches, and includes a hollow cylindrical plasma generation chamber 12 for generating plasma, and a reaction chamber 14 communicating with the plasma generation chamber 12. ing.
As the sample processed by the present apparatus, various samples requiring uniform plasma processing, such as an 8-inch wafer, other than the silicon wafer 10 having a diameter of 12 inches, can be used. A circular waveguide 16 connected to a microwave oscillator (not shown) such as a magnetron is connected to the upper part of the plasma generation chamber 12.
Hz) is led to the plasma generation chamber 12 via the circular waveguide 16.

A microwave introduction window 20 is arranged between the circular waveguide 16 and the plasma generation chamber 12. The microwave introduction window 20 is made of a microwave transmitting material such as quartz glass, and is designed to hermetically seal the plasma generation chamber 12. Outside the plasma generation chamber 12, three-stage coils 22, 24, and 26 are arranged so as to include a connection portion of the circular waveguide 16 and concentrically surround the connection portion.
These coils 22, 24, and 26 receive a necessary current from the current supply unit 40, apply an axial magnetic field having a magnetic flux density of 875 gauss into the plasma generation chamber 12, and cause an ECR phenomenon. I have. In the reaction chamber 14,
A sample stage 32 for holding the silicon wafer 10 by fixing means such as electrostatic suction is provided.

A ring-shaped permanent magnet 42 is provided between the inner wall of the reaction chamber 14 and the sample table 32 so as to surround the sample table 32. The permanent magnet 42 prevents the diffusion of the plasma to the inner wall of the reaction chamber 14, and the coils 22, 24, 26 for generating the plasma.
The height can be adjusted according to the state of the magnetic field formed by this. That is, the coils 22, 24, 26
The position in a direction parallel to the direction in which the plasma travels can be adjusted according to the value of the current supplied to the plasma. The position of the permanent magnet 42 can be set based on the ion current density distribution on the wafer 10 by simulation or actual measurement.

FIGS. 2A and 2B show a permanent magnet 42 and a driving mechanism for driving the same up and down. The permanent magnet 42
It is installed on an elevating platform 44 that can move up and down,
It can be moved up and down by a drive unit 46 such as a motor.
In this embodiment, the height of the permanent magnet 42 is
Is set as a relative height (h) with respect to the upper surface.

On the side wall of the reaction chamber 14, the plasma generation chamber 1
An exhaust pipe 34 for exhausting the gas in the reaction chamber 14 and the reaction chamber 14 is provided, and the plasma generation chamber 12 and the reaction chamber 14 are maintained in a high vacuum state by evacuation from the exhaust pipe 34. Further, the reaction chamber 14 is provided with a gas supply pipe 36 for supplying a reaction gas required for plasma generation. Further, although not shown, the plasma generation chamber 12
A coolant path is formed around the coolant passage, and the plasma generation chamber 12 is cooled by cooling water (coolant) circulating through the coolant path.

Next, the overall operation of this embodiment will be described. When etching the polysilicon film formed on the silicon wafer 10 using the apparatus of the present embodiment, first, the silicon wafer 10 to be processed is fixed on the sample stage 32, By evacuation, the internal pressures of the plasma generation chamber 12 and the reaction chamber 14 are reduced to a predetermined pressure. Next, the plasma generation chamber 1 is connected to the gas supply pipe 36.
2 and a reaction gas (Cl ₂ / O ₂ ) are introduced into the reaction chamber 14, and the internal pressure of the plasma generation chamber 12 and the reaction chamber 14 is set to 1 × 1.
Keep around 0 ^-3 Torr.

Thereafter, a magnetic field is formed inside the plasma generation chamber 12 by energizing the coils 22, 24, and 26, and a microwave is introduced into the plasma generation chamber 12 from the circular waveguide 16 through the microwave introduction window 20. I do. This microwave has a frequency f = 2.45 GHz (wavelength λ = about 12.
2 cm) and a power of 1000 W.

When microwaves are introduced into the plasma generation chamber 12, the reaction gas is resonantly excited on the ECR surface 100 to generate plasma. Main coil 22, 24, 2
The magnetic field formed by the magnetic field 6 is a divergent magnetic field whose magnetic flux density decreases toward the reaction chamber 14 side, and the plasma generated in the plasma generation chamber 12 is drawn into the reaction chamber 14 by the action of the divergent magnetic field, and the sample is The surface of the silicon wafer 10 on the table 32 is irradiated to perform etching.

On the other hand, when a thin film is formed on the silicon wafer 10 using the apparatus of the present embodiment, a predetermined source gas is introduced through the gas supply pipe 36 in addition to the above-described procedures.
The plasma generated by the gas is applied to the silicon wafer 1
Irradiate to zero. As a result, a thin film of a substance generated by the reaction of the source gas is formed on the surface of the silicon wafer 10. Also in such thin film formation, plasma having a uniform density is generated, and the film thickness distribution of the thin film formed on the surface of the silicon wafer 10 is equalized. As a result, the quality and performance of the finally manufactured semiconductor device are improved. Here, the semiconductor device includes a semiconductor element itself such as a transistor and a completed semiconductor device such as a RAM.

In the above plasma processing such as etching and CVD, the microwave power is set to 1.4 kW.
, And 60 sccm of Ar is introduced as a reaction gas into the reaction chamber 14, the internal pressures of the plasma generation chamber 12 and the reaction chamber 14 are maintained at 1 × 10 ⁻³ Torr, and the coils 22, 24, 26
Permanent magnet 4 when the current supplied to the magnet is all 40 A
The optimum height h0 (reference height) of No. 2 is set to 20 mm (FIG. 2).
A). FIG. 3 shows the ion current density distribution on the wafer 10 in such a state.

Next, the current supplied to the coils 22, 24 and 26 is changed to 40A, 20A and 0A. Such a change is performed, for example, for the purpose of widening a process window in consideration of a processing shape in etching of polysilicon. As described above, the coils 22, 24, 2
When the current supplied to 6 changes, the magnetic field in plasma generation chamber 12 and reaction chamber 14 changes accordingly. On the other hand, as shown in FIG. 2A, when the height of the permanent magnet 42 is kept at the reference height h0, the ion current density distribution on the wafer 10 is as shown in FIG. It becomes quite uneven.

On the other hand, in this embodiment, the coils 22 and
The height of the permanent magnet 42 is adjusted by driving the lifting platform 44 by the drive unit 46 according to the current value to the 24 and 26. That is, as shown in FIG.
The height of the permanent magnet 42 with respect to 2 is lowered 15 mm below h0, and h is set to 35 mm. Wafer 1 at this time
FIG. 5 shows the ion current density distribution on zero. As can be seen, the overall ion current density is slightly lower than in the case shown in FIG. 4 (when the height of the permanent magnet 42 is not adjusted), but the uniformity is significantly improved.

As described above, according to the present embodiment, since the height of the permanent magnet 42 is adjusted according to the current values of the coils 22, 24, and 26, the magnetic field used for generating and extracting plasma is used. Is changed, the magnetic flux density distribution on the wafer 10 can be set optimally. That is, since the position of the permanent magnet 42 is controlled so that the magnetic flux density distribution on the wafer 10 is totally optimized, plasma with a uniform density distribution can be applied to the wafer 10. The plasma processing quality is improved. Then, the quality of the semiconductor device finally manufactured using the wafer 10 thus processed is improved.

In the above-described embodiment, the permanent magnet 42 is moved in parallel with the direction in which the plasma travels. However, the permanent magnet 42 may be moved in a direction perpendicular to the direction in which the plasma travels. For example, as shown in FIG. 6, ring-shaped permanent magnets 48a, 48b, 48 divided into seven as permanent magnets.
Using magnets c, 48d, 48e, 48f, and 48g, these magnets 48a to 48g are respectively moved in the radial direction. The arc-shaped permanent magnets 48a to 48g are arranged so as to surround the sample table 32 similarly to the permanent magnet 42 used in the previous embodiment, and change the current value supplied to the coils 22, 24, and 26. The diameter is changed according to.

As in the case shown in FIGS. 3 to 5, the microwave power was set to 1.4 kW, 60 sccm of Ar was introduced into the reaction chamber 14 as a reaction gas, and the plasma generation chamber 12 and the reaction chamber 14 is maintained at 1 × 10 ^-3 Torr, and the current supplied to the coils 22, 24, 26 is all 4
The inner diameter of the permanent magnet 42 at 0 A is 200 mm (solid line). Thereafter, the current supplied to the coils 22, 24, 26 is changed to 40A, 20A, 0A. At this time,
As shown by the broken line in the figure, the radius is expanded by 20 mm and the radius 220
mm. By such control, it is possible to obtain substantially the same effects as in the above embodiment. In this example,
Although the permanent magnets 48a to 48g of seven divisions are used, the number of divisions is not limited to seven divisions.

FIG. 7 shows a configuration of a plasma processing apparatus according to another embodiment of the present invention. This embodiment has substantially the same configuration as the embodiment shown in FIG. 1, except that only the positions of the permanent magnets (42, 50) arranged near the sample table 32 are changed. That is, in the present embodiment, the permanent magnet 5
0 is arranged outside the reaction chamber 14 instead of inside, thereby facilitating the movement of the permanent magnet 50. Further, it is possible to arrange a permanent magnet inside the sample stage 32 as needed.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and does not depart from the gist of the technical idea of the present invention shown in the claims. Various changes are possible within the scope.
For example, when the permanent magnet arranged near the sample stage 32 has a yoke, it is preferable that the yoke itself is movable. In this case, if necessary, only the magnet may be moved, or only the yoke may be moved, or both the magnet and the yoke may be moved. When the positions of both the magnet and the yoke are changed, each of them may be driven independently.

[0033]

As described above, according to the present invention, it is possible to optimally set the magnetic flux density distribution on the sample even when the magnetic field used for generating and extracting plasma is changed. As a result, it is possible to irradiate the sample with plasma having a uniform density distribution, and the plasma processing quality is improved. Further, the quality of a semiconductor device finally manufactured using the wafer 10 thus processed is improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a schematic configuration of a plasma processing apparatus according to an embodiment of the present invention.

FIGS. 2A and 2B are side views (partial cross-sections) showing the configuration near the sample stage of the embodiment shown in FIG. 1 and explaining the operation of the embodiment. .

FIG. 3 is a graph used to explain the operation of the embodiment, and shows an ion current density distribution on a wafer.

FIG. 4 is a graph used to explain the operation of the example, and shows an ion current density distribution on a wafer.

FIG. 5 is a graph used to explain the operation of the example, and shows an ion current density distribution on a wafer.

FIG. 6 is a plan view showing a main part of another embodiment of the present invention, showing a configuration of a split type permanent magnet.

FIG. 7 is a schematic diagram showing a configuration of a plasma processing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Silicon wafer (sample) 12 ... Plasma generation chamber (vacuum container) 14 ... Reaction chamber (vacuum container) 22, 24, 26 ... Coil 42, 48a-48g, 50 ... Permanent Magnet 44 ・ ・ ・ Elevating table 46 ・ ・ ・ Drive unit

Claims (7)

[Claims] 1. A plasma processing method for performing a predetermined plasma process by irradiating a sample placed in a vacuum container with plasma, wherein a first magnetic field for generating the plasma is formed in the vacuum container. Forming a second magnetic field near the sample to control the plasma distribution near the sample;
Controlling the second magnetic field according to the state of the first magnetic field. 2. A plasma processing apparatus for performing a predetermined plasma process by irradiating a sample placed in a vacuum container with plasma, wherein a first magnetic field for generating the plasma is formed in the vacuum container. A first magnetic field forming means; a second magnetic field forming means for forming a second magnetic field in the vicinity of the sample so as to control a plasma distribution in the vicinity of the sample; And a magnetic field control means for controlling a position of the second magnetic field forming means to adjust a second magnetic field. 3. The plasma processing apparatus according to claim 2, wherein said magnetic field control means is configured to adjust a position of said second magnetic field forming means in a direction parallel to a traveling direction of said plasma. . 4. The plasma according to claim 2, wherein the magnetic field control means is configured to adjust a position of the second magnetic field forming means in a direction orthogonal to a direction in which the plasma travels. Processing equipment. 5. The plasma processing apparatus according to claim 2, wherein said second magnetic field forming means is disposed between an inner wall of said vacuum vessel and said sample. 6. The apparatus according to claim 2, wherein said second magnetic field forming means is disposed outside said vacuum vessel.
Or the plasma processing apparatus according to 4. 7. A method for manufacturing a semiconductor device, comprising: a plasma processing step of performing a predetermined plasma processing by irradiating a plasma to a semiconductor substrate disposed in a vacuum vessel; Forming a first magnetic field for generating the plasma therein; forming a second magnetic field near the semiconductor substrate to control a plasma distribution near the semiconductor substrate; Controlling the second magnetic field according to the state of the semiconductor device.