JPH08288265A - Microwave plasma etching system - Google Patents

Abstract

PURPOSE: To perform uniform processing on the entire surface of a wafer by rotatably and hermetically connecting an upper end portion of an outer casing with a lower end portion of a fall portion of a waveguide and rotating the waveguide about the vertical center axis of an etching chamber. CONSTITUTION: A rotating device 32 includes a gear 36 concentrically affixed to a fall portion 16b of a waveguide 16, and a driving gear 40 which is meshed with the gear 36 and is rotated by an electric motor 38 so as to drive the gear 36. The fall portion 16b of the waveguide 16 and an outer easing 20 are hermetic and rotatable between a lower end portion 48 of the fall portion 16b and the outer casing 20. As the electric motor 38 is activated, the waveguide 16 freely rotates about the vertical center axis of the outer casing 20 and therefore about the vertical center axis of an etching chamber. Thus, the direction in which a microwave is introduced can be freely adjusted, and uniformity of the etching rate can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma etching apparatus for introducing a microwave into an etching chamber into which a reaction gas is fed to generate plasma and etching a substrate in the etching chamber. More specifically, the present invention relates to a microwave plasma etching apparatus capable of uniformly processing the entire surface of a large-sized substrate such as a large-diameter wafer.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a microwave plasma etching apparatus is often used for etching a wafer. The conventional microwave plasma etching apparatus will be described below. FIG. 6 is a schematic diagram showing the configuration of a conventional microwave plasma etching apparatus (hereinafter simply referred to as an etching apparatus). As shown in FIG. 6, the conventional etching apparatus is basically an etching chamber 14 which is divided into a magnetron 12 for generating a microwave having a frequency of 2.45 GHz and a quartz bell jar 13 and adjusted to a constant pressure. And magnetron 12
Waveguide 1 for introducing microwave from etching chamber 14 into etching chamber 14
6 and a solenoid coil 18 for generating a magnetic field in the etching chamber 14. The outer box body 20 is a waveguide 16
An airtight box body made of the same material as the above, which houses a quartz bell jar 13 that defines an etching chamber 14 inside,
The solenoid coil 18 is arranged outside. The waveguide 16 includes a horizontal portion 16a having the magnetron 12 at one end, and a descending portion 16b that descends from the other end of the horizontal portion 16a toward the outer box body 20.

The etching chamber 14 is provided with a susceptor 22 on which a wafer W to be etched is placed, and etching gas is introduced from an inlet 24 to the etching chamber 14.
Is introduced into the exhaust gas, is sucked from the exhaust port 26, and is discharged. A high frequency power supply 28 applies a high frequency bias to the susceptor 22 to apply a bias potential. The etching gas generates plasma by the action of the introduced microwave and collides with the wafer W to etch the wafer surface.

[0004]

In the conventional microwave plasma etching apparatus, the etching chamber 14 is used.
The microwave introduced to the wafer is introduced in a certain direction with respect to the wafer and has an eigenmode. for that reason,
The etching rate on the wafer surface tends to be high along the microwave introduction direction and slow in the direction intersecting with it. The eigenmode is a factor mainly determined by the shape of the waveguide 16 that transmits microwaves from the magnetron 12 that is a microwave source to the etching chamber 14. For example, when the waveguide is circular, eigenmodes based on TE ₁₁ mode and TE ₀₁ mode as shown in FIGS. 7A and 7B are obtained, and when the waveguide is rectangular, It becomes an eigenmode based on the TE ₁₀ mode as shown in 7 (c). This microwave eigenmode affects the uniformity of the plasma density generated in the etching chamber, which in turn affects the uniformity of the etch rate applied to the wafer.

As described above, in the conventional microwave plasma etching apparatus in which the microwave introduction direction is constant, the etching rate on the wafer surface is fast along the microwave introduction direction and intersects the introduction direction. Since it is extremely slow, the plasma density becomes non-uniform and it is difficult to improve the in-plane uniformity of the etching rate. If the plasma density is not uniform, the etching rate will be slower at the center of the wafer and faster at the periphery due to the inherent characteristics of each device based on the dimensions, shape, etc. of the waveguide, etching chamber, susceptor, etc. Alternatively, portions where the etching speed is slow and portions where the etching speed is fast are alternately generated in a ring shape from the center of the wafer.

Therefore, a method of changing the eigenmode of the microwave by changing the shape or size of the waveguide to improve the uniformity of the etching process has been conventionally tried. That is, one method is to replace the waveguide or change the internal shape of the waveguide in accordance with the etching condition, and another method is to provide a plurality of waveguides and appropriately It is to select an appropriate waveguide among them. However, it is technically and practically difficult to replace the waveguide or change the internal shape during the treatment process depending on the condition of the etching treatment. The method of providing and selecting an appropriate waveguide among them has a problem that the etching apparatus becomes large and the equipment cost increases. Moreover, it is extremely difficult to adjust the eigenmode of the microwave in real time by the conventional method of adjusting the eigenmode of the microwave by changing the shape and size of the waveguide.

The above-mentioned non-uniformity of the etching process by plasma is particularly remarkable when etching a wafer having a large diameter in recent years, for example, when the process in the direction along which the microwave is introduced is a predetermined process. Indicates that processing in the direction intersecting the direction of introduction of microwaves has failed, and when processing in the center has been performed as specified, processing in the peripheral area has failed, and vice versa. If the processing in the peripheral portion is as specified, the processing in the central portion fails. As a result, it is difficult to improve the yield of semiconductor products, and there has been a demand for the provision of a microwave plasma etching apparatus that can perform uniform etching treatment.

[0008] Therefore, an object of the present invention is to provide a microwave plasma etching apparatus adapted to perform uniform processing over the entire surface of a wafer.

[0009]

The present inventor considers that there is a problem in that the waveguide of the conventional microwave plasma etching apparatus is fixed to the etching chamber, and therefore, the vertical center axis of the etching chamber is considered to be a problem. The present invention has been completed, paying attention to rotating the waveguide around the. In order to achieve the above object, an outer box body containing an etching chamber inside and a magnet arranged outside, a horizontal part having a microwave generator at one end, and the other end of the horizontal part And a waveguide composed of a descending part that descends toward the outer box body, and introduces microwaves into the etching chamber into which the reaction gas is fed through the waveguide and the outer box body to form a plasma. In a microwave plasma etching apparatus that performs etching processing on the substrate in the etching chamber while generating the, the connecting portion between the outer box body and the waveguide is rotatably and airtightly connected to each other, and the vertical central axis of the etching chamber is It is characterized in that the waveguide is rotated around.

In the present invention, the outer casing means a hermetically sealed outer casing having a bell jar which defines the etching chamber accommodated therein and a magnet for generating a magnetic field inside the etching chamber arranged outside thereof. It is connected to the descending part of the waveguide. The rotating means for rotating the waveguide around the central axis in the vertical direction of the etching chamber is not particularly limited, and for example, the rotation driving force is transmitted by a gear mechanism or a belt transmission mechanism. 3 turns
It may be rotated by 60 °, within a certain angle range, eg 0 °
It may be rocked within a range of up to 180 °. Further, as the rotation speed, a speed at which the effect of the present invention is achieved is determined by an experiment.

A preferred embodiment of the present invention comprises a lower end of a descending part of a waveguide and an upper end of an outer casing, each of which has a sliding surface. The connecting portion for connecting each other, the waveguide rotating means provided in the descending portion of the waveguide for rotating the waveguide around the vertical center axis of the etching chamber, and the rotating of the waveguide. Rotation guide means provided in the connection portion for guiding, an upper end portion that supports the horizontal portion of the waveguide, and a support plate fixed to the outer box body so as to extend in the horizontal direction so as to be rotatable. Supporting means for the waveguide having a supported lower end portion.

As long as the present invention is a microwave plasma etching apparatus for introducing a microwave into a process chamber to generate plasma and etching a substrate in the process chamber, the type of reaction gas and the type of substrate to be treated are used. It can be applied regardless of type.

[0013]

According to the invention of claim 1, the upper end of the outer box and the lower end of the descending part of the waveguide are rotatably and airtightly connected to each other, and the waveguide is provided around the vertical center axis of the etching chamber. By rotating the wafer, the introduction direction of the microwave can be freely adjusted with respect to the wafer. Therefore, the density distribution of plasma in the etching chamber can be adjusted freely, and as a result, the uniformity of the etching rate can be improved.

According to the second aspect of the invention, the entire waveguide is smoothly rotated around the vertical center axis of the etching chamber by rotating the descending portion of the waveguide by the rotating means while guiding by the guide means. By supporting the horizontal portion of the waveguide by the supporting means, the waveguide can be smoothly rotated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. Embodiment 1 FIG. 1 is a schematic diagram showing the configuration of the essential parts of Embodiment 1 of a microwave plasma etching apparatus (hereinafter simply referred to as an etching apparatus) according to the present invention. Of the parts shown in FIG. 1, the same parts as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted. In addition to the configuration of the etching device shown in FIG. 6, the present etching device 30 has a waveguide 1 as shown in FIG.
6 includes a rotating device 32 and a supporting device 34 for the waveguide 16. The rotating device 32 includes a gear 36 concentrically attached to the descending portion 16b of the waveguide 16 and a drive gear 40 that meshes with the gear 36 and rotates by the drive of an electric motor 38 to drive the gear 36. It is configured. The electric motor 38 is connected to the etching device 30 via a support mechanism.
Is fixed in place, and the rotating shaft of the gear 40 is rotatably supported by a bearing (not shown) also supported by the supporting mechanism.

The support device 34 includes a horizontal portion 16 of the waveguide 16.
It is composed of a support column 42 that supports b and a support plate 44 that receives the load of the support column 42. An upper end of the support column 42 is fixed to the horizontal portion 16a, and a freely rotating ball 46 is attached to the lower end thereof, so that the circular motion smoothly draws a circle on the support plate 44 by the rotational motion of the ball. Support plate 44
Is fixed to the outer box body 20, and the surface on which the ball 46 moves is finished to be smooth to reduce friction.

The descending portion 16a of the waveguide 16 and the outer casing 20 are rotatable between the lower end 48 of the descending portion 16a and the upper end 50 of the outer casing 20. In the present embodiment, as shown in FIG. 2, the lower end portion 48 of the descending portion 16a is
It has a first annular plate 52 having a sliding surface on the lower side and a cylindrical inner ring plate 54 orthogonal to it in an L shape and having a sliding surface on the outer surface. The upper end portion 50 of the outer box body 20 has a second annular plate 56 having a sliding surface on the upper side that slides with the first annular plate 52, and a cylindrical outer ring that slides with the sliding surface of the inner ring plate 54. And a plate 58. The outer ring plate 58 and the inner ring plate 54 are guides that cooperate to guide the rotation of the lower end portion 16 a of the waveguide 16. It should be noted that each sliding surface may have a ball bearing structure in order to reduce rotational friction.

With the above structure, when the electric motor 38 is started, the waveguide 16 can be freely rotated around the vertical central axis of the outer box body 20, and thus the vertical central axis of the etching chamber 14. . Further, the support device 34 allows the waveguide 16 to rotate in a stable posture.

Second Embodiment The second embodiment is a modification of the rotating device and the supporting device provided in the etching apparatus 30 of the first embodiment, and FIG. 3 shows the structure of the main part of the etching apparatus 60 of the second embodiment. FIG. In this embodiment, the support plate of the first embodiment rotates integrally with the waveguide 16. The rotating device of the present embodiment includes a disk-shaped fixed guide plate 62 attached to the outer box body 20, an annular rotating plate 64 that is guided while sliding on the outer peripheral surface thereof, and a rotating plate 64. A drive gear 66 that meshes with teeth provided on the outer peripheral surface to drive the rotary plate 64, an electric motor 68 that rotates the drive gear 66, and the horizontal portion 16 of the waveguide 16.
It is composed of a connecting column 70 that rotates a together with the rotating plate 64.

Further, in this embodiment, in order to guide the rotation of the descending portion 16b of the waveguide 16, another guide mechanism is provided in addition to the mechanism shown in FIG. It is the descending part 1
6b, which is composed of a disc-shaped upper rotating plate 72 that rotates integrally with it and an annular guide plate 74 that guides the upper rotating plate 72 while sliding on the outer peripheral surface thereof. 74 is fixed in place via a support 76. When the guide mechanism is provided, the inner ring plate 54 and the outer ring plate 58 shown in FIG. 2 can be omitted.

With the above structure, when the electric motor 68 is started, the rotating plate 64 rotates while being guided by the guide plate 62, and the waveguide 16 is integrally formed with the rotating plate 64 via the connecting column 70. Rotate about the vertical central axis of 20, and thus the vertical central axis of the etching chamber 14. Further, the guide mechanism including the upper rotary plate 72 and the guide plate 74 allows the waveguide 16 to rotate in a stable posture and in a stable posture.

Third Embodiment The third embodiment is a modification of the rotating device and the supporting device provided in the etching apparatus 60 of the second embodiment, and FIG. 4 shows the configuration of the main part of the etching apparatus 80 of the third embodiment. FIG. In this embodiment, the rotating plate of the second embodiment is integrally attached to the upper portion of the waveguide 16 and rotates integrally with the waveguide 16. The rotating device of the present embodiment includes a disc-shaped rotating plate 8 attached to the horizontal portion 16a of the waveguide 16.
2 and the rotary plate 82 that meshes with the teeth provided on the outer peripheral surface thereof.
And a drive gear 84 for driving the drive gear 84, and an electric motor 86 for rotating the drive gear 84. Also in this embodiment,
Similar to the second embodiment, a guide mechanism including an upper rotary plate 72 and a guide plate 74 is provided.

With the above structure, when the electric motor 86 is started, the rotary plate 82 rotates, and the waveguide 1 is integrated with the rotary plate 82.
6 rotates in a stable posture around the vertical center axis of the outer box body 20, and thus the vertical center axis of the etching chamber 14.

In the first to third embodiments, since the waveguide 16 smoothly rotates around the vertical center axis of the etching chamber 14, the microwaves on the wafer placed in the etching chamber 14 are , As it is continuously and continuously introduced from all directions, as shown in FIG. 5, the density difference of sparseness and density becomes small and the plasma density distribution in the etching chamber becomes uniform.
The in-plane uniformity of the etching rate is improved. In addition, Example 1
Therefore, in the third embodiment, the waveguide 16 and the outer casing 20 and the connecting portion are located at the uppermost portion of the outer casing 20, but it is not necessarily limited to this. For example, the I-I plane in FIG. 1, that is, the solenoid. Any outer box body 20 above the coil 18 may be used.

[0025]

According to the structure of the present invention, since the waveguide freely rotates about the vertical center axis of the etching chamber,
Microwaves on the wafer arranged in the etching chamber are sequentially and continuously introduced from each direction within the range of the rotation angle. As a result, the difference in density of microwaves becomes small, the density distribution of plasma in the etching chamber becomes uniform, and the in-plane uniformity of the etching rate is improved. Therefore, by using the microwave plasma etching apparatus according to the present invention, even when a large-sized substrate, for example, a large-diameter wafer is processed, the entire surface of the wafer can be uniformly etched.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of a microwave plasma etching apparatus according to a first embodiment.

FIG. 2 is a partial cross-sectional view illustrating a guide unit according to the first embodiment.

FIG. 3 is a schematic diagram showing a main part of a microwave plasma etching apparatus according to a second embodiment.

FIG. 4 is a schematic diagram showing a main part of a microwave plasma etching apparatus according to a third embodiment.

FIG. 5 is a conceptual diagram illustrating that the degree of density of microwaves on a wafer is small.

FIG. 6 is a schematic diagram showing a configuration of a conventional microwave plasma processing apparatus.

7 (a), (b) and (c) are schematic diagrams showing microwave eigenmodes.

[Explanation of symbols]

12 magnetron 13 bell jar 14 etching chamber 16 waveguide 16a horizontal part of waveguide 16b descending part of waveguide 18 solenoid coil 20 outer box 22 susceptor 24 inlet 26 exhaust port 28 high frequency power source 30 microwave according to the present invention Example 1 of plasma etching apparatus 32 Rotating device 34 Supporting device 36 Gear 38 Electric motor 40 Driving gear 42 Supporting column 44 Supporting plate 46 Ball 48 Lower end of waveguide 50 Upper end of outer casing 52 First annular plate 54 Inner ring plate 56 Second annular plate 58 Outer ring plate 60 Embodiment 2 of microwave plasma etching device according to the present invention 62 Guide plate 64 Rotating plate 66 Drive gear 68 Electric motor 70 Connecting column 80 Microwave plasma etching device according to the present invention Example 3 82 Rotating plate 84 Drive gear 86 Electric motor

Claims (2)

[Claims] 1. An outer box containing an etching chamber inside and a magnet arranged outside, a horizontal part having a microwave generator at one end, and an outer box from the other end of the horizontal part. A waveguide composed of a descending part descending toward the body, and a microwave is introduced into the etching chamber into which the reaction gas is fed through the waveguide and the outer casing to generate plasma. At the same time, in a microwave plasma etching apparatus that performs etching processing on the substrate in the etching chamber, the outer box body and the waveguide are connected to each other in a rotatable and airtight manner so that the outer chamber and the waveguide are connected around the vertical center axis of the etching chamber. A microwave plasma etching apparatus characterized in that a waveguide is rotated. 2. A connecting portion, which comprises a lower end portion of a descending portion of a waveguide and an upper end portion of an outer casing, each of which has a sliding surface, and which airtightly connects with each other while slidingly rotating on the surface. , A waveguide rotating means provided in the descending portion of the waveguide for rotating the waveguide around the vertical center axis of the etching chamber, and a connecting portion for guiding the rotation of the waveguide. A rotation guide means provided, an upper end portion that supports the horizontal portion of the waveguide, and a lower end portion that is rotatably supported by a support plate that is fixed to the outer box body so as to extend in the horizontal direction. The microwave plasma etching apparatus according to claim 1, further comprising: a waveguide supporting unit having: