JPS63122123A - Microwave plasma processor - Google Patents

Abstract

PURPOSE:To accelerate uniformly the processing of a material to be processed by forming an interval between a discharge tube and a reflecting end at 1/8 or more of the wavelength of a microwave in a tube and providing uniformizing means for uniformizing the discharge amount of active particles to a processing chamber. CONSTITUTION:A reflecting end 10 having a plurality of holes of small diameter is attached to the lower hole of a circular waveguide 7, and a discharge tube 6 having a recess parallel to a sample base plate 13 is attached to the upper hole of the tube 7. Further, a rectangular waveguide 2 is provided through a step converter 5 to efficiently convert the rectangular microwave to a circular microwave transmission mode. An interval between the tube 6 and the end 10 is set to lambdag/8 or more to generate an efficient plasma. Since the whole surface of a wafer 13 can be uniformly ashed by providing the end 10 and the wafer 12 in parallel, the wafer 12 can be rapidly and uniformly processed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave plasma processing apparatus, and particularly to a microwave plasma processing N apparatus suitable for etching semiconductor substrates and depositing silane.

[Conventional technology]

As described in Japanese Patent Application Laid-Open No. 59-103340, the conventional device is equipped with a magnetron at the other end of a waveguide attached around the circumference of the discharge tube, and a reflective disk or reflective cylinder at the opening of the discharge tube. The microwaves from the magnetron were reflected by a reflecting disk or cylinder to efficiently generate plasma within the discharge tube.

[Problem that the invention seeks to solve]

The above conventional technology does not take into consideration the positional relationship between the reflective end and the discharge tube and the shape of the discharge tube or the reflective end, and has problems in terms of plasma generation efficiency and uniformity of processing speed of the processed material. .

In terms of plasma generation efficiency, the plasma generation efficiency of the incident wave injected into the discharge tube is low, with a
It was found that there were more than % reflected waves. For this reason,
As described in JP-A-59-103340, the microwave power injected into the discharge tube is reflected by a reflecting disk or cylinder, and the reciprocating microwave power is used effectively to increase plasma generation efficiency. However, it has been found that the plasma generation efficiency varies greatly depending on the distance from the discharge tube to the reflective end, that is, the distance through which the microwave power injected into the discharge tube passes.

Regarding the uniformity of the processing speed of the object to be processed, if the object to be processed is etched by generating plasma in a conventional hemispherical discharge tube, the etching rate will be non-uniform. This is because strong plasma is generated along the spherical surface of the discharge tube, and by the time the active particles created in the plasma generation section reach the object to be processed, they mainly lose energy due to collisions with neutral particles and become inactive. It is thought that the number of active particles decreases rapidly as the distance between the object to be processed and the plasma generating section increases along the spherical surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microwave plasma processing apparatus that can process an object quickly and uniformly.

[Means for solving problems]

The above purpose is to provide a plasma generation chamber to which a processing gas is supplied and which is evacuated to a predetermined pressure, a processing chamber that communicates with one side across the plasma generation chamber, and a plasma generation chamber that is connected to the opposite side of the processing chamber. a waveguide having a microwave generation source at the other end, the plasma generation chamber is configured by being provided between the plasma generation chamber and the waveguide and cut off from the atmosphere; The distance between the discharge that transmits the microwaves from the plasma generation chamber and the reflection end that is provided on the side opposite to the discharge tube of the plasma generation chamber and that reflects the microwaves is set to be at least h of the tube wavelength of the microwaves, and the plasma generation chamber This is achieved by providing a homogenizing means for uniformly discharging the active particles generated in the processing chamber.

[For production]

While supplying processing gas to a plasma generation chamber formed by cutting off the atmosphere, the pressure is reduced and maintained at a predetermined level, microwaves are generated from a microwave generation source, and the microwaves are guided to the plasma generation chamber through a waveguide. , and enter the plasma generation chamber via a discharge tube. The standing wave of the incident microwave is reflected at a reflection end provided at a distance of ⅛ wavelength or more from the inner wall of the discharge tube, creating a large electric field on the inner surface of the discharge tube and generating plasma near the inner surface of the discharge tube. The active particles generated in the plasma have as few collisions as possible with neutral particles until they pass through the reflection end and enter the processing chamber by the homogenizing means.
It is adjusted so that it enters the entire surface of the processing chamber uniformly. As a result, the object to be processed can be processed quickly and uniformly.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 shows a microwave plasma processing apparatus.

A reflecting end 10 having a plurality of small-diameter holes is attached to the lower opening of the circular waveguide 7, and a sample stage parallel to the reflecting end 10 is mounted on which the object to be processed, in this case a wafer ν, is placed. 13
A processing chamber 11 is provided.

A heater 14 is provided at the bottom of the sample stage 13 and indirectly heats the wafer.

A discharge tube 6 having a concave surface parallel to the sample stage 13 is attached to the upper opening of the circular waveguide 7, and a step conversion mechanism is installed to efficiently convert the microwave transmission mode from rectangular to circular. A rectangular waveguide 2 is provided through a vessel 5. A magnetron 1, which is a microwave generation source, is attached to the upper end of the waveguide 2. 3 is an isolator for absorbing reflected waves returning within the rectangular waveguide 2;
is the reflection of the microwave transmitted through the rectangular waveguide 2! This is a stub type matching device that performs impedance matching of a load for cursing.

In this case, the plasma generation chamber is a circular waveguide 7° reflection end 1
0 and the discharge tube 6.

9 is a cooling water channel for cooling the circular waveguide 7;
is a processing gas inlet for supplying processing gas into the plasma generation chamber. An exhaust device (not shown) is connected to the lower part of the processing chamber 11, and the processing chamber 11 and the plasma generation chamber are evacuated to a predetermined pressure. 15 is discharge tube 6
This is a cooling gas inlet that introduces cooling gas for cooling.

In this case, the magnetron 1 has a frequency of 2.45 GHz, the rectangular waveguide 2 has a standard size that can transmit TElo mode, and the circular waveguide 7 has a size of 113111+1 (for example, TB1□ mode) that does not cut off microwaves. In this case, it should be 72111111 or more.)
A material made of quartz (alternatively, alumina or the like can also be used) is used for the discharge tube 6 which is permeable to microwaves and forms a plasma generation chamber. Further, the distance between the discharge tube 6 forming the plasma generation chamber and the reflection end 10 is set to approximately λF/4 (40 Mm), which is equal to or more than the tube wavelength λF (156,7 mm) (7) 1/ of the microwave. The length of the cylindrical portion is also approximately λy/4 (40tl#).

The hole in the reflective end 10 has a size of 101111 (for example, 72-111 in the case of Tgo mode) that can cut and reflect microwaves.
The following is fine. ).

In the above configuration, the wafer on which one photoresist is to be processed is placed on the sample stage B, 2005 ccy of 02 gas is introduced into the circular waveguide 7 as a processing gas, and the pressure is applied to the I
When 02 gas plasma is generated in the plasma generation chamber by applying a 700W microwave and impedance matching the load using the stub type matching device 4 while maintaining the Torr, as shown in the figure, the discharge tube 6 Plasma was generated in the vicinity of the inner surface, and as shown in FIG. 2, ashing processing was performed almost uniformly and at a high etching rate over the entire surface of the Kuehesha.

This is because the surface of the discharge tube 6 is parallel to and has approximately the same area as the sample stage 13, that is, parallel to the entire surface of the wafer, so that the active particles in the plasma generated on the inner surface of the discharge tube 6 are When exiting into the processing chamber 11 through the hole at the reflective end,
The active particles mainly collide with the neutral particles in the plasma generated at the same time in the plasma generation chamber, losing energy and becoming inactive particles, but the distance the active particles take to reach the wafer surface is It is thought that since the number of active particles reaching the wafer is approximately the same, the etching rate becomes uniform.

In order to confirm this, ashing of photoresist was performed using the apparatus shown in FIG. In this figure, the same reference numerals as in FIG. 1 indicate the same members, and the difference between this figure and FIG. The point is that the parallel plate-shaped discharge tube 6a is used, and the height of the circular waveguide 7 is changed to form a circular waveguide 7a.

Using the apparatus configured as described above, 20,011 ccM of 02 gas is introduced into the circular waveguide 7a, and while the pressure is maintained at ITorr, 500 W of microwave is applied to measure the distance #l between the discharge tube 6a and the wafer. As a result of changing the ashing of Uninor Hill, as shown in Figure 4, the etching speed was 11111! It was found that as the value increases, it decreases rapidly. Also, from this experiment, an approximate formula can be found as follows: y=y0・e−(102~o, os)(x−!o)
It turns out that it can be expressed as .--.--.lit.

Note that here, y is the etching amount at the distance Plx, and 3'O is the etching amount at the distance 111xO.

In addition, the high etching rate was achieved by setting the distance between the discharge tube 6 and the reflecting end 10 to about 14, which is the tube wavelength λ2 of the microwave, as shown in FIG. This is considered to be because the electric field intensity Ex near the inner surface of the discharge tube 6 becomes maximum due to the microwaves incident on the discharge tube 6 and the microwaves reflected at the reflection end 10, thereby improving plasma generation efficiency.

In order to confirm this, the discharge tube 6 and the reflective end 1 shown in FIG.
When the reflected power Pr was determined by variously changing the distance Ld from 0 to 0, as shown in Fig. It can be seen that the reflected power Pr becomes large when it reaches the minimum and is less than Ld40■. In other words, the interval La corresponds to the in-tube wavelength λ of the microwave, and it can be seen below that the reflected power is large and does not contribute effectively to plasma generation. Furthermore, this tendency becomes more apparent as the input power Pf increases, and tends to be alleviated as the input power Pf decreases.

Further, in this case, the efficiency of plasma generation reached the maximum when the distance Ld was 49 mm, and it was not possible to generate plasma when Ld was 10 mm.

Note that the plasma generation efficiency is maximum at λy / 1/8 or more, but the shorter the interval Ld, the shorter the distance to the wafer, which increases the probability that the number of remaining active particles will increase, so it is not practical. In the upper case, the optimum distance Ld is λP/8 or more, more specifically, λP/8 to λp/4. However, if it is brought closer to a wafer discharge tube, λy / 1
A high etching rate can be obtained even when the etching rate is /8 or more.

As described above, according to this embodiment, by setting the distance between the discharge tube 6 and the reflective end 10 to be 2978 or more, uniform ashing can be performed over the entire surface of the wafer. This has the advantage of being able to process quickly and uniformly.

Next, another embodiment of the present invention will be described with reference to FIGS. 7 to 9.

In Fig. 7, the same reference numerals as in Fig. 1 indicate the same members, and the difference between this figure and Fig. 1 is that the discharge tube 6 is shaped like a hemisphere, and the distance from the wafer to the wafer expands outward from the center of the wafer. The use of the discharge tube 6b and the reflection of $10
As shown in FIG. 8, a reflection jllOa is provided with a plurality of holes that become larger from the center toward the outside.

Since the shape of the discharge tube 6b is hemispherical, the aperture ratio of the hole in the reflective end 10a is such that the distance from the central lowest end of the discharge tube 6b to the periphery is 501111 in this case.
11, the amount of active particles reaching wafer n is not uniform over the entire surface of wafer n, so the amount of etching in each part of wafer n was predicted using equation (1) above, and the Sekiguchi rate was changed accordingly. In this case, the reflective end 10J
The aperture ratio of the peripheral portion of No. 1 is approximately 10 times that of the center.

When a wafer was subjected to an ashing process using the apparatus with the above configuration under the same conditions as the apparatus shown in Figure 1 above, the etching process was almost uniform over the entire surface of the wafer, as shown in Figure 9 (b). Can be ashed at a rate.

FIG. 9(A) shows the case where the reflection 410 m is ashed using the apparatus shown in FIG. 7 with the hole size uniform as in the case of the apparatus shown in FIG. In this case, it is clearly seen that the distance between the discharge tube 6b and the wafer plate increases from the center toward the outside, and the etching rate also decreases.

As described above, according to this book and other embodiments, even if the distances from the wafer 6b are not equal, the aperture ratio of the reflective end 10a can be changed depending on the distance from the discharge tube 6b to the wafer ν. Since the amount of active particles reaching the wafer can be made almost uniform over the entire surface of the wafer, the wafer can be processed uniformly as in the previous embodiment. Also, the hemispherical lower end of the discharge tube 6b and the reflection j! 110
By setting the distance from a to λF/8 or more, efficient plasma generation can be achieved in the same way as in the first embodiment, and the wafer processing speed can be increased.

Note that although a downwardly convex discharge tube is used in this embodiment, an upwardly convex discharge tube may also be used.

However, this is disadvantageous because the distance between the wafer and the inner surface of the discharge tube becomes long.

In addition, the length of the cylindrical portion of the discharge tube 6 in the above figure '@1 is λp
/ 4 in order to increase the area of the inner surface of the discharge tube 6 and increase the absorption efficiency of microwaves that contribute to plasma generation. Nagawate cicada, 1! This results in an increase in the size of the wafer and an increase in the distance from the inner surface of the discharge tube (plasma generation part) to the wafer, which actually reduces the effect.

Furthermore, although this embodiment has been described in the case of etching a wafer, it can also be applied to the case of generating deposits on a wafer using plasma.

〔Effect of the invention〕

According to the present invention, the distance between the discharge tube and the reflection end is set to 1/8 or more of the tube wavelength of the microwave, and the equalizing means is provided to uniformize the amount of active particles released into the processing chamber. There is an effect that the processed material can be processed more thoroughly and uniformly.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing a microwave plasma processing apparatus that is an embodiment of the present invention. The second cause is a diagram showing the etching state by the apparatus shown in FIG. 1. FIG. Fig. 4 is a diagram showing the experimental results using the device on the third side, Fig. 5 is a diagram showing the microwave standing wave electric field between the discharge tube and the reflecting end, and Fig. 6 is a diagram showing the electric field of the microwave standing between the discharge tube and the reflective end. A diagram showing the relationship between the distance to the reflection end and the reflected power of microwaves, FIG. 7 is a longitudinal cross-sectional view showing a microwave plasma processing apparatus according to another embodiment of the present invention, and FIG. FIG. 9 is a plan view of the reflective end viewed from the direction A, and is a diagram showing the etching state when the aperture ratio of the reflective end is made the same and when the aperture ratio is changed by the apparatus of FIG. 7. l... Magnetron, 2... Rectangular waveguide, 6... Discharge tube, 7... Circular waveguide, 10
・・・・・・Reflection end,■...tsu I no 1 啼-kokoq-Lilithy group L Figure 46 Prisoner

Claims (1)

[Claims] 1. A plasma generation chamber to which a processing gas is supplied and is evacuated to a predetermined pressure, a processing chamber communicating with one side across the plasma generation chamber, and the other end connected to the side opposite to the processing chamber of the plasma generation chamber. a waveguide having a microwave generation source in the plasma generation chamber; a discharge tube provided between the plasma generation chamber and the waveguide and transmitting the microwave from the microwave generation source; A distance between a reflecting end provided on the opposite side of the discharge tube and reflecting the microwave is set to 1/8 or more of the tube wavelength of the microwave, and active particles generated in the plasma generation chamber are uniformly discharged into the processing chamber. A microwave plasma processing apparatus characterized by being provided with a homogenizing means.