JPH0774115A - Plasma treatment system - Google Patents

Abstract

PURPOSE:To provide a plasma system for subjecting an object to uniform, fine processing while keeping it from contaminants by generating a high-density plasma in a high vacuum where no plasma can be produced by means of a parallel-plate structure. CONSTITUTION:A plasma system comprises a container 11, in which a susceptor 12 is provided for holding a semiconductor wafer W that is treated with process gas supplied from a gas feeder; and four coils 13A on the outside of the container 11, which produces high-frequency electromagnetic radiation in parallel with the wafer so that the resulting electromagnetic field may generate a plasma from the process gas.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art A plasma processing apparatus generates a plasma by performing vacuum discharge in a processing container in which a processing gas exists.
The plasma is utilized to perform a predetermined process on the object to be processed. Conventionally, this plasma processing apparatus has been widely used in a semiconductor manufacturing process such as a sputtering process, an ashing process, a CVD process, or an etching process.

As such a plasma processing apparatus, for example, a plasma processing apparatus provided with parallel plate electrodes has been conventionally known. This plasma processing apparatus includes a processing container that forms a decompressed space by vacuum evacuation, a lower electrode that is disposed below the processing container and holds a semiconductor wafer as an object to be processed, and is opposed to the lower electrode. It comprises an upper electrode provided and a high frequency power source for generating a plasma by applying a high frequency voltage between these upper electrodes. Further, a receiving port for receiving the processing gas is formed on the upper surface of the upper electrode, and a gas supply hole for supplying the received gas into the processing container is dispersedly formed on the lower surface thereof. Supply the processing gas into the processing container,
The processed gas is configured to be discharged from an exhaust port formed in the processing container.

Therefore, in order to plasma-process a semiconductor wafer using the above-mentioned plasma processing apparatus, a plasma processing gas is supplied from a gas supply hole into a processing container whose pressure is reduced to a low vacuum, and a lower electrode is supplied by a high frequency power source. A high-frequency voltage is applied between the upper electrode and the upper electrode to generate plasma by the discharge between them, and a predetermined plasma treatment is performed on the semiconductor wafer on the lower electrode 2 by the activated species of the plasma. There is.

[0005]

However, in the case of the conventional plasma processing apparatus having the parallel plate electrode structure as described above, a high frequency voltage is applied to the upper and lower electrodes in the processing container, and a high voltage is applied between these electrodes. Since the plasma is generated by discharging, the discharge gas pressure is restricted by the relationship between the discharge starting voltage, the distance between the electrodes, and the gas pressure, and as the gas pressure that stably generates the plasma between the upper and lower electrodes. Has a problem that the pressure is about 0.5 Torr and the degree of vacuum is the limit, and plasma cannot be generated under a high vacuum higher than that. Further, recently, semiconductor wafers have become more and more microfabricated, and it has become necessary to form grooves with finer and deeper shapes.However, in the conventional plasma processing apparatus, the processing pressure is relatively high, so that active species do not interact with each other. However, there is a problem in that it is impossible to go straight ahead due to the collision with the above, which hinders fine processing of the semiconductor wafer, and cannot meet such recent demands for fine processing.

The present invention has been made to solve the above-mentioned problems, and it is possible to generate a high density plasma even under a high vacuum, which cannot be generated by a parallel plate electrode structure, and further, a semiconductor wafer or the like. It is an object of the present invention to provide a plasma processing apparatus capable of performing uniform ultrafine processing on a target object without contaminating the target object.

[0007]

A plasma processing apparatus according to claim 1 of the present invention supports an object to be processed by a processing gas supplied from a gas supply section provided in a processing container. The processing gas is provided with a support disposed in the processing container, and a high-frequency electromagnetic field is formed in parallel with the object to be processed in synchronization with the high-frequency voltage by applying a high-frequency voltage, and the processing gas is plasma-treated. A plurality of inducing means for generating a changing electromagnetic wave are provided on the outer circumference of the processing container.

The plasma processing apparatus according to a second aspect of the present invention is the plasma processing apparatus according to the first aspect of the invention, wherein the processing container is at least one wall surface of the processing container that is arranged to face the plurality of guiding means. The part is made of a dielectric material.

Further, in the plasma processing apparatus according to claim 3 of the present invention, in the invention according to claim 1 or 2, high frequency voltages having a phase difference are applied to the plurality of induction means. To form a high-frequency rotating electromagnetic field in the processing container.

A plasma processing apparatus according to a fourth aspect of the present invention is the plasma processing apparatus according to any one of the first to third aspects of the invention, wherein the plurality of guiding means are provided via an electrostatic coupling preventing member. Provided in the processing container.

Further, in a plasma processing apparatus according to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the gas supply section faces the object to be processed. The gas supply holes are evenly distributed and arranged on the surface made of a dielectric material.

[0012]

According to the first aspect of the present invention, when the processing gas is supplied from the gas supply unit into the processing container and the high frequency voltage is applied to the plurality of induction means, electromagnetic waves are generated. The plasma of the processing gas can be homogenized by making the processing gas into plasma and forming a high-frequency electromagnetic field in parallel along the surface to be processed of the object to be processed by the plurality of guiding means.

According to a second aspect of the present invention, in the invention according to the first aspect, the processing container is at least one wall surface of the processing container that is arranged to face the plurality of guiding means. Since the portion is formed of the dielectric material, the high frequency electromagnetic field can be formed inside the processing container without shielding the high frequency electromagnetic field by the wall surface of the processing container.

According to the invention of claim 3 of the present invention, in the invention of claim 1 or 2,
Since the plurality of inducing means are applied with high frequency voltages having a phase difference with each other to form a high frequency rotating electromagnetic field in the processing container, the high frequency electromagnetic field is parallel to the surface to be processed of the object to be processed. The plasma of the processing gas can be homogenized by rotating at high speed.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the plurality of guiding means are provided via an electrostatic coupling preventing member. Since the electrostatic coupling component of the electromagnetic waves from the plurality of guiding means does not enter the processing container by the electrostatic coupling preventing member, it is possible to prevent charging on the inner surface of the processing container. it can.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the gas supply section faces the object to be processed. Since it has gas supply holes evenly distributed on the surface made of a dielectric material, the inner surface in contact with the plasma generation area is made of a dielectric material, and the electromagnetic waves generated by a plurality of induction means are not disturbed in the plasma generation area. It uniformly acts on the processing gas replenished from the supply holes, and thereby a uniform plasma can be generated.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in FIGS. As shown in FIG. 1 and FIG. 2, the plasma processing apparatus of this embodiment includes a processing container 11 that can keep a high vacuum by sealing the inside from the outside, and a processing object that is disposed in the processing container 11 and is an object to be processed. And a conductive susceptor 12 for horizontally holding the semiconductor wafer W with the surface to be processed facing up. A plurality of induction means, for example, four coils 13A, which generate a high-frequency rotating electromagnetic field B described later and generate electromagnetic waves in this magnetic field to generate plasma inside the processing container 11, are provided. . It is preferable that the central axis of the processing container 11, the central axis of rotation of the high-frequency rotating electromagnetic field B, and the center of the semiconductor wafer W be arranged so that the respective members described later coincide with each other.

Further, as shown in FIG. 1, the processing container 11 has an applying section 11A for applying the high frequency rotating magnetic field B.
And a processing unit 11B that is connected below the applying unit 11A and that processes the semiconductor wafer W on the susceptor 12 with plasma by a high-frequency rotating electromagnetic field. The applying unit 11A is formed of a cylindrical material made of an insulating material or a dielectric material such as quartz or ceramics, and has a cylindrical body with an open upper end and a lower end. The processing unit 11B is made of a conductive material such as aluminum. It is made of a flexible material and has a cylindrical body with a closed lower end. This processing unit 11B
Has an opening formed on the upper surface so as to match the inner diameter of the applying portion 11A, and the applying portion 11A is attached to this opening via a sealing member 14 such as an O-ring so as to keep the inside airtight. Has been. And this processing unit 11B
The inner surface of the is anodized and grounded to maintain the ground potential. In addition, the applying unit 11
A gas supply unit 11 for supplying a processing gas to the upper opening of A
C is attached via a seal member 14 such as an O-ring, and the seal member 14 is configured to maintain airtightness inside. In the gas supply unit 11C, the surface forming the processing unit 11B is formed of a dielectric material such as quartz or ceramics, and the other portion is formed as a flat hollow disk made of a conductive material such as aluminum. Has been done. A gas supply port 11D is formed at the center of the upper surface of the gas supply unit 11C,
Further, a plurality of gas supply holes 11E for uniformly supplying the processing gas supplied from the gas supply port 11D into the processing container 11 are formed on the lower wall made of a dielectric material in a dispersed manner. These gas supply holes 11E can be formed in various modes with respect to inner diameter and arrangement as required. Further, the processing section 11B is provided with an exhaust port 11F which communicates with an exhaust means 50 such as a vacuum pump, and is configured to exhaust the processed gas and the like from the exhaust port 11F. By providing a plurality of exhaust ports 11F in the processing unit 11F so as to be rotationally symmetrical, it is possible to suppress the bias of plasma in the processing unit 11F. The gas supply unit 11C is also grounded similarly to the processing unit 11B.

Further, the susceptor 12 has the applying section 11
Like B and the gas supply unit 11C, it is made of anodized aluminum. Further, the susceptor 12 includes a capacitor 15 and a matching circuit 16
Further, a high frequency power supply 17 for applying a high frequency voltage of, for example, 13.56 MHz is connected, and the susceptor 12 is negatively self-biased by the high frequency voltage during plasma processing. This bias voltage can be adjusted by appropriately controlling the voltage applied from the high frequency power source 17 according to the processing content of the semiconductor wafer W,
The semiconductor wafer W can be subjected to a desired plasma treatment by this adjustment voltage.

The four coils 1 which are the above-mentioned induction means
3A surrounds the applying section 11A from four sides,
A high frequency power source 13B is connected to each A, and a high frequency voltage of several 100 kHz to 100 MHz, for example, 13.56 MHz is applied by each high frequency power source 13B. Then, by the high-frequency power supplies 13B, for example, the coils 13A on the right side of FIG.
High-frequency voltage with a phase difference of / 2 (right coil 13A
Each voltage is Vsinωt counterclockwise with reference to
Vsin (ωt + π / 2), Vsin (ωt + π), and Vsin (ωt + 3π / 2)) are respectively applied to the four coils 13A, and a high-frequency rotating electromagnetic field B is formed in the applying unit 11A. Is configured to. Further, each of the coils 13A has a role as an antenna for generating electromagnetic waves or electromagnetic energy for plasma generation by the power supplied from the respective high frequency power supply 13B, and the power supplied is, for example, 500.
~ 3 KW is preferred. Therefore, in the following description, the coil 13A will also be referred to as the antenna 13A, if necessary. In this embodiment, the coil 13A is a one-turn coil formed by bending one metal wire along the outer surface of the applying section 11A as shown in FIG. These coils 1
As shown in FIGS. 1 to 3, 3A is attached to the outer peripheral surface of the application unit 11A via a cylinder 51 (see FIG. 3) formed of, for example, a ferrite material. The cylindrical body 51 has a function of preventing electrostatic coupling with the applying section 11A that is charged during processing and preventing an electrostatic coupling component of electromagnetic waves generated from the antenna 13A from entering the applying section 11A. Have Although the high frequency power supply 13B is connected to only one coil 13A in FIG. 3, the high frequency power supply 13B is actually connected to the other coil 13A as shown in FIGS.
B is connected. Therefore, the cylindrical body 51 eliminates the possibility that a negative potential is generated on the inner peripheral surface of the applying portion 11A, and as a result, there is no sputtering phenomenon on the inner wall of the applying portion 11A due to the negative potential, and the material of the inner wall of the applying portion 11A is plasma. It is possible to prevent mixing of impurities due to the material of the inner surface of the processing container 11 without being ejected inside. The cylindrical body 51 may be omitted, but in that case, each coil 13A may be directly attached to the outer peripheral surface of the applying portion 11A, or may be attached at a predetermined interval from the outer peripheral surface of the applying portion 11A. May be. Also, each coil 13A
Is preferably formed as a one-turn coil or a two-turn coil as described above so as not to increase its impedance, but is not necessarily limited to such a shape. In addition, in FIGS.
3C is a matching circuit.

Then, the applying section 1 is formed by the coil 13A.
The high frequency rotating electromagnetic field B generated in the plasma generation region in 1A extends horizontally and is orthogonal to the electric field E formed between the susceptor 12 and the gas supply unit 11C. The processing gas is ionized by the action of the high-frequency rotating magnetic field B and the electromagnetic wave and / or electric field from the coil 13A to generate plasma, and the density of the plasma is increased. for that reason,
Even in a high vacuum of 0.005 Torr or less, a homogeneous and high-density plasma can be obtained from the processing gas. Since the horizontal high-frequency rotating magnetic field B is used to generate this plasma, the lines of magnetic force do not cross the semiconductor wafer W, and no eddy current is generated in the semiconductor wafer W. Therefore, there is no possibility that the electric current in the semiconductor wafer W will flow out through the susceptor 12, and as a result, there will be no risk of causing trouble such as disconnection of wiring.

Next, the operation of plasma processing using the above plasma processing apparatus will be described. First, the processing container 11
After the semiconductor wafer W is placed horizontally on the susceptor 12 inside with the surface to be processed facing up, the inside of the processing container 11 is exhausted through the exhaust port 11.
After evacuating to a high vacuum of, for example, 0.005 Torr or less through F, while continuing the evacuation, a processing gas such as an etching gas or a film forming gas is supplied from the gas supply hole 11E of the gas supply unit 11C into the processing container 11. And 4 more coils 1
A high frequency voltage is applied from 3A. As a result, the application unit 11
A horizontal high-frequency rotating magnetic field B is generated in A, and electromagnetic waves are supplied from each coil 13A to generate plasma of a processing gas. At this time, since the high-frequency voltage of each coil 13A has a phase difference of π / 2 in the counterclockwise direction, the application direction of the high-frequency electromagnetic field B also sequentially rotates in the counterclockwise direction and rotates in the applying unit 11A. An electromagnetic field B, that is, a high frequency rotating electromagnetic field B is formed. Then, the action of this high-frequency rotating electromagnetic field B homogenizes the plasma. At this time, in the applying unit 11A, the electrons generated by the electromagnetic field formed by each antenna 13A generate an E × B drift, so that a higher density plasma is generated. The high-density and homogeneous plasma formed in this way covers the semiconductor wafer W on the susceptor 12, and ions in the plasma are extracted toward the semiconductor wafer W side due to the potential difference between the plasma potential and the self-bias potential of the susceptor 12. Predetermined plasma processing is performed on the semiconductor wafer W. At this time, since the gas is continuously supplied from the gas supply unit 11C in the applying unit 11A while the exhaust is continued, the processing gas is sequentially replenished to the plasma to maintain the uniform plasma and the already generated plasma. The plasma is supplied downward to accelerate the plasma treatment.

As described above, according to the present embodiment, the processing container 1 is constituted by the four coils 13A outside the processing container 11.
Since the high-frequency rotating electromagnetic field B is formed in the applying section 11A of No. 1 and the electromagnetic wave is supplied to generate the plasma, the plasma is generated without being restricted by the gap length between the parallel plate electrodes as in the conventional case. Plasma can be generated even if the inside of the processing container 11 is at a high vacuum of about 1 to 2 digits, for example, 0.005 Torr or less, compared to the conventional case. Can be done. Also, the processing container 11
Since there is no electrode for plasma generation inside, there is no fear of generating impurities in the processing container 11, and the semiconductor wafer W is not contaminated. Moreover, according to the present embodiment, since the plasma is rotated during the processing of the semiconductor wafer W, it is possible to always maintain a uniform plasma, and thus it is possible to perform a uniform plasma processing on the entire surface of the semiconductor wafer W. . Further, according to the present embodiment, since the surfaces of the applying portion 11A for applying the high-frequency rotating electromagnetic field B and the gas supplying portion 11C facing the semiconductor wafer W are formed of an insulating material (dielectric material) such as quartz, 4 coils 13
The electromagnetic field from A is not shielded by the application unit 11A, a good high-frequency rotating electromagnetic field B can be formed in the application unit 11A, and the electromagnetic wave from each coil 13A is disturbed in the plasma generation region. It is possible to generate and maintain a homogeneous plasma. Further, according to this embodiment, since each coil 13A is provided in the processing container 11 via the cylindrical body 51 which is an electrostatic coupling preventing member, the electrostatic coupling component of the electromagnetic waves from the four coils 13A is treated. The cylindrical body 51 prevents the inside of the container 11 from entering, thereby preventing the inner surface of the processing container 11 from being charged, and thus the processing container 1
1 Processing container 11 by preventing the sputtering phenomenon on the inner surface
It is possible to prevent impurities from being mixed due to the material of the inner surface. Furthermore, since the parts other than the application part 11A of the processing container 11 are made of a conductive material such as aluminum, it is possible to prevent electrification in these parts and ensure safety.
It also has excellent workability. Further, in the high-frequency rotating electromagnetic field B, the magnetic lines of force extend parallel to the surface to be processed of the semiconductor wafer W and do not intersect with the semiconductor wafer W, so there is no risk of generating an eddy current in the semiconductor wafer W, and the semiconductor wafer There is no risk that the current at W will flow out through the susceptor 12,
As a result, there is no risk of causing a failure such as disconnection of wiring.

In the above embodiment, the induction means constituted by individually connecting the high frequency power source 17 to each of the four coils 13A has been described. However, they are separated from each other by 180 ° in opposite positions, that is, in the circumferential direction. A pair of coils 13 in position
A, 13A, and these coils 13A, 13A
Alternatively, a high frequency voltage having a 180 ° phase shift may be applied. In this case, a rotating magnetic field is not formed in the applying unit 11A, but a magnetic field oscillating in the horizontal direction can be formed to generate plasma similar to the rotating magnetic field. In this case, if each coil 13A is wound in the opposite direction, a common high frequency power source can be used.

Also, as shown in FIG. 4, four coils 1
Of the 3A, two coils 13A arranged to face each other,
13A makes a pair, and one of them is a high-frequency power source 13
Similarly, the other pair of coils 13A and 13A are connected to one high frequency power source 13B by connecting to B, and the two high frequency power sources are driven at the same frequency with a phase difference of π / 2 to generate a high frequency rotating electromagnetic field. It may be generated. Further, the guiding means used in the present invention, the structure is not particularly limited as long as it can form an electromagnetic field moving at high speed by rotation or vibration in a plane substantially parallel to the surface to be processed, For example, a high frequency voltage having a phase difference of 2π / 3 may be applied to each of three coils arranged 120 ° apart in the circumferential direction, and a high frequency rotating electromagnetic field may be generated by these coils. Further, the number of coils may be four or more.

Further, although the vertical type processing container is described in the above embodiment, it is not always necessary to horizontally support the object to be processed such as a semiconductor wafer, and for example, a horizontal type processing container for vertically supporting and processing. May be adopted. Also,
A plurality of objects to be processed may be housed in these processing containers and processed simultaneously.

[0027]

As described above, according to the invention described in claim 1 of the present invention, a plurality of induction means are provided in the processing container, and by applying a high frequency voltage, the object to be processed is synchronized with the high frequency voltage. Since an electromagnetic field is formed parallel to the body and an electromagnetic wave is generated that turns the processing gas into plasma, parallel plate electrode structure cannot generate plasma, so high density plasma is generated even under high vacuum. In addition, a uniform high-frequency electromagnetic field can be formed parallel to the surface to be processed of the object to be processed such as a semiconductor wafer in parallel with the surface to be processed, and plasma processing can be performed uniformly on the object to be processed. It is possible to provide a plasma processing apparatus capable of performing the above.

Further, according to the invention of claim 2 of the present invention, in the invention of claim 1, the processing container is at least one of wall surfaces of the processing container arranged to face the plurality of guiding means. Since the part is made of the dielectric material, it is possible to form a stable high-frequency electromagnetic field in the processing container to further homogenize the plasma and to provide a plasma processing apparatus having excellent safety and processability.

Further, according to the invention of claim 3 of the present invention, in the invention of claim 1 or 2,
Since the plurality of inducing means are applied with high frequency voltages having a phase difference with each other to form a high frequency rotating electromagnetic field in the processing container, the high frequency electromagnetic field is parallel to the surface to be processed of the object to be processed. It is possible to provide a plasma processing apparatus that can rotate at high speed to homogenize the plasma of the processing gas.

Further, according to the invention described in claim 4 of the present invention, in the invention described in any one of claims 1 to 3, the plurality of guiding means are connected via an electrostatic coupling preventing member. Since it is provided on the outer circumference of the processing container, the electrostatic coupling component of the electromagnetic waves from the plurality of inducing means is prevented from entering the processing container by the electrostatic coupling preventing member, thereby preventing charging on the inner surface of the processing container. Further, it is possible to provide a plasma processing apparatus capable of preventing the sputtering phenomenon on the inner surface of the processing container and preventing the mixing of impurities due to the material on the inner surface of the processing container.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the gas supply section faces the object to be processed. Since it has gas supply holes evenly distributed on the surface made of a dielectric material, the inner surface in contact with the plasma generation area is made of a dielectric material, and the electromagnetic waves generated by a plurality of induction means are not disturbed in the plasma generation area. It is possible to provide a plasma processing apparatus that uniformly acts on the processing gas replenished from the supply holes and thereby generates a uniform plasma.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a plasma processing apparatus of the present invention.

FIG. 2 is a horizontal sectional view of the plasma processing apparatus shown in FIG.

FIG. 3 is a perspective view showing a plurality of induction means of the plasma processing apparatus shown in FIG.

FIG. 4 is a view corresponding to FIG. 2, showing another embodiment of the plasma processing apparatus of the present invention.

[Explanation of symbols]

 W Semiconductor Wafer (Processing Object) B High-Frequency Electromagnetic Field 11 Processing Container 11A Applying Section 11B Processing Section (Parts Other than Applying Section) 11C Gas Supply Section (Surface facing Processing Target) 11E Gas Supply Hole 12 Susceptor (Support) ) 13A guiding means 51 cylindrical body (electrostatic coupling preventing member)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/3065

Claims (5)

[Claims] 1. A support provided in the processing container for supporting an object to be processed by a processing gas supplied from a gas supply unit provided in the processing container,
By applying a high-frequency voltage, a high-frequency electromagnetic field is formed in parallel with the object to be processed in synchronization with the high-frequency voltage, and a plurality of induction means for generating electromagnetic waves that turn the processing gas into plasma are provided on the outer periphery of the processing container. A plasma processing apparatus, which is provided in the. 2. The plasma processing apparatus according to claim 1, wherein in the processing container, at least a part of a wall surface of the processing container arranged to face the plurality of guiding means is formed of a dielectric material. 3. The plurality of inducing means forms a high frequency rotating electromagnetic field in the processing container by applying a high frequency voltage having a phase difference to each other. Plasma processing equipment. 4. The plasma processing apparatus according to claim 1, wherein the plurality of guiding means are provided in the processing container via an electrostatic coupling preventing member. 5. The gas supply unit according to claim 1, wherein the gas supply unit has gas supply holes arranged evenly on a surface of the dielectric material facing the object to be processed. The plasma processing apparatus described in any one of the above.