JP3204145B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating plasma using microwaves, and etching, ashing, CVD (Chemical Vapor Deposition), etc. on a semiconductor element substrate or a glass substrate for a liquid crystal display (LCD). The present invention relates to a plasma processing apparatus for performing a process.

[0002]

2. Description of the Related Art In an LSI manufacturing process, it is widely practiced to apply external energy to a reaction gas to generate a plasma, and to perform processing such as etching, ashing, and CVD using the plasma. In particular, a dry etching technique using plasma is an indispensable basic technique for this LSI manufacturing process.

[0003] In recent years, these plasma treatments have included 13.5
In addition to a device that generates plasma using a high frequency of about 6 MHz, a device that generates plasma using microwaves has been used. This is because it is easier to generate high-density plasma by using a microwave than by using a high frequency of about 13.56 MHz.

However, a plasma processing apparatus using microwaves generally has a problem that it is difficult to uniformly generate plasma over a wide area. In order to solve this problem, the present applicant has proposed a plasma processing apparatus using a dielectric layer (Japanese Patent Laid-Open No. 62-5600).

FIG. 15 is a schematic sectional view showing a conventional plasma processing apparatus using a dielectric layer.

A sample table 15 is provided inside the reaction vessel 11 (reaction chamber 12), and a microwave introduction window 14 is provided above the reaction vessel 11 so as to face the sample table 15. The chamber 12 is hermetically sealed. A dielectric layer 32 is provided facing the microwave introduction window 14 with the hollow portion 31 interposed therebetween. Quartz glass (SiO ₂ ) or alumina (Al ₂ O ₃ )
Is used.

[0007] The microwave is oscillated in a microwave oscillator 35 and is introduced into the dielectric layer 32 via a waveguide 34. An electric field is formed below the dielectric layer 32 by the microwave propagating through the dielectric layer 32, and the electric field passes through the microwave introduction window 14 and is introduced into the reaction chamber 12. The introduced gas is excited to generate a plasma. With this plasma, the surface of the sample S is subjected to plasma processing such as etching.

This device has an advantage that the plasma can be uniformly generated in a wide plane area by increasing the areas of the microwave introduction window 14 and the dielectric layer 32.

[0009]

However, in a conventional plasma processing apparatus using a dielectric layer, plasma is generated in a wider area than the sample in order to ensure uniformity of the plasma processing speed within the sample surface. The configuration is such that Therefore, there is a problem that the plasma density is reduced as a whole and the plasma processing speed of the sample is reduced, and a problem that the etching of a fine hole pattern is not performed vertically to the bottom of the hole (deterioration of pattern removability). Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention improves the plasma processing speed of a sample by increasing the plasma density of a region irradiated to the sample, and improves the fine hole pattern. It is an object of the present invention to provide a plasma processing apparatus capable of improving the pattern removability in etching.

[0011]

The plasma processing apparatus of the present invention is provided for a microwave waveguide, and is provided with a dielectric layer disposed along an upper side surface of the apparatus and substantially in parallel with the dielectric layer. A plasma processing apparatus comprising: a microwave introduction window, and a sample stage arranged inside the microwave introduction window so as to face the microwave introduction window, and a reaction vessel for generating plasma therein, wherein the plasma stage is opposed to the sample stage of the microwave introduction window. It is characterized in that the thickness of the region to be thinned is smaller than the outside.

The "area facing the sample stage" referred to here means "the area facing the sample mounting surface on the sample stage".

In the above-described apparatus using a dielectric layer, microwaves are introduced and propagated in the dielectric layer, and microwaves leaking from the dielectric layer are introduced into the reaction vessel through a microwave introduction window. are doing. That is, the intensity of the microwave in the reaction vessel depends on the distance from the dielectric layer and the thickness of the microwave introduction window.

Therefore, the present inventors conducted a test focusing on the thickness of the microwave introduction window, and as a result, by partially reducing the thickness of the microwave introduction window, the plasma was strong under the thin region. It was confirmed that this occurred, and the present invention was completed.

That is, in the plasma processing apparatus of the present invention, the thickness of the microwave introduction window in a region directly facing the sample on the sample stage is made thinner than the outside thereof. Therefore, the plasma in this region irradiated to the sample on the sample stage is generated more strongly than the plasma in the region irradiated to the other regions, so that the plasma density distribution can be efficiently processed for the sample. As a result, it is possible to improve the plasma processing speed of the sample and to improve the pattern removability in etching a fine hole pattern.

Further, the plasma processing apparatus of the present invention changes the plasma density distribution by making the thickness of the microwave introduction window different depending on the position, with the portion facing the sample as the center. Therefore, by appropriately selecting the distribution according to the position of the thickness of the microwave introduction window, not only can the uniform plasma processing be performed on the sample, but also, if necessary, the plasma processing speed in the central portion of the sample can be increased. You can also.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) (Overall Configuration of Apparatus) FIG. 1 is a schematic longitudinal sectional view of a first embodiment of a plasma processing apparatus according to the present invention. In the figure, reference numeral 11 denotes a reaction vessel having a hollow rectangular parallelepiped shape, which is made of a metal such as aluminum or stainless steel.

A reaction chamber 12 is provided inside the reaction vessel 11. A microwave introduction window 14 in which a concave portion 14a is formed in a portion facing the sample S is provided at an upper portion of the reaction vessel 11 via an O-ring 20, and the reaction chamber 12 is hermetically sealed. I have.

In the reaction chamber 12, a sample stage 15 is disposed at a position facing the microwave introduction window 14, and the sample S is placed on the sample stage 15. The sample stage 15 is provided with a mechanism (not shown) such as an electrostatic chuck for holding the sample S, a constant temperature medium circulation mechanism (not shown) for holding the sample S at a predetermined temperature, and the like. The sample table 15 is fixed on a base 16, is insulated from the reaction vessel 11 by an insulating member 18, and the periphery of the sample table 15 is covered by a plasma shield member 17.

The reaction vessel 11 is provided with a gas introduction hole 25 for introducing a gas into the reaction chamber 12 and an exhaust port 26 connected to an exhaust device (not shown). The peripheral wall of the reaction vessel 11 can be heated to a predetermined temperature by a heater (not shown).

Above the reaction vessel 11, a dielectric layer 32 whose upper part is covered with a metal plate 33 made of aluminum or the like is provided so as to face the microwave introduction window 14. A microwave oscillator 35 is connected to the dielectric layer 32 via a waveguide 34. The dielectric layer 32 is made of a material having a small dielectric loss, such as a fluororesin, polyethylene, or polystyrene. As the frequency of the microwave, for example, 2.45 GHz is used.

(Microwave introduction window) Microwave introduction window 1
Reference numeral 4 denotes heat-resistant and microwave-permeable quartz glass (SiO ₂ ) or alumina (Al) having small dielectric loss.
_It may be formed of a dielectric such as ₂ O ₃ ).

In order to make the thickness of the portion of the microwave introduction window 14 facing the sample S thinner than the outer portion thereof, a concave portion is formed by, for example, shaving the portion of the microwave introduction window 14 facing the sample S. Just do it. It is more effective to provide the recess on the reaction chamber 12 side, but it may be provided on the side facing the dielectric layer 32.

The shape of the concave portion may be any shape such as a circle or a rectangle in plan view, and may be determined in consideration of the shape of the sample and the uniformity of the plasma processing speed in the sample surface. For example,
In many cases, such as when processing silicon wafers, it is preferable to use a circular shape.

The diameter of the concave portion may be determined according to the purpose, for example, for the purpose of uniform plasma processing or for the purpose of increasing the plasma processing speed at the center of the sample. In order to improve the uniformity, it is usually preferable that the diameter be about 1.0 to 1.2 times the diameter of the sample. When it is particularly desired to increase the plasma processing speed at the center of the sample, it is usually preferable that the plasma processing speed is about 0.9 times or less the diameter of the sample.

The depth of the concave portion may be determined in consideration of the target plasma processing speed and its uniformity. For example, when the purpose is to improve the plasma processing speed, usually, when the thickness of the microwave introduction window is 30 mm,
The depth of the recess is preferably 4 mm or more. When the thickness of the microwave introduction window is 20 mm, the depth of the recess is 2 m.
m or more. That is, the depth of the recess is preferably about 0.1 times or more the thickness of the microwave introduction window. However, microwave introduction windows of any thickness, when the remaining thickness is 10 mm or less,
Since a problem occurs in the strength, it is preferable to determine the depth of the concave portion so that the thickness is further increased.

FIGS. 2A and 2B are schematic views showing an example of the microwave introduction window, wherein FIG. 2A is a sectional view and FIG. 2B is a bottom view.
The microwave introduction window 14 of this example is provided with a circular concave portion 14a (diameter DA, depth HA) at a central portion facing the sample S.

FIG. 3 is a schematic sectional view showing another example of the microwave introduction window. The microwave introduction window 14 may be composed of a plurality of members such as a window main body 14d and an annular portion 14e shown in FIG.

FIG. 4 is a schematic sectional view showing still another example of the microwave introduction window. Microwave introduction window recess 1
4a may have a stepped shape as shown in FIG. 4 (a) or a tapered shape as shown in FIG. 4 (b).

The concave portion 14a of the microwave introduction window is
It may be arc-shaped.

FIG. 5 is a schematic sectional view showing an example of a microwave introduction window having a concave portion formed on the side facing the dielectric layer. As described above, it is more effective to provide the recess on the reaction chamber 12 side, but it may be provided on the side facing the dielectric layer.

(Plasma Processing Method) A case in which plasma processing such as etching is performed on the surface of the sample S by using the plasma processing apparatus thus configured will be described with reference to FIG.

The reaction chamber 12 is evacuated from the exhaust port 26, and then gas is supplied to the reaction chamber 12 from the gas inlet 25.

A microwave is oscillated from a microwave oscillator 35, and the microwave is introduced into the dielectric layer 32 through a waveguide 34. The microwave leaking from the dielectric layer 32 penetrates the microwave introduction window 14 to generate plasma in the reaction chamber 12 and etch the sample S.

At this time, a concave portion 14a is provided in a portion of the microwave introduction window directly above the sample S, which is thinner than other portions and has a higher microwave electric field strength, so that the plasma density in this region is increased. As a result, the plasma processing speed of the sample S can be increased.

Further, the plasma density distribution can be changed by changing the shape of the concave portion 14a of the microwave introduction window (changing the distribution depending on the position of the thickness of the microwave introduction window 14), so that more uniform plasma processing can be performed. Can be applied to the sample, and conversely, if necessary, the plasma processing speed at the center of the sample S can be increased.

(Embodiment 2) (Overall Configuration of Apparatus) FIG. 6 is a schematic longitudinal sectional view of a second embodiment of the plasma processing apparatus of the present invention.

This apparatus performs plasma processing while applying a high frequency to the sample S. In addition to the apparatus configuration shown in FIG. 1, a high frequency power supply 28 and a counter electrode 21 connected to the sample table 15 are provided. . The counter electrode 21 is provided at the periphery of the microwave introduction window 14 so as to protrude from the peripheral wall of the reaction vessel 11 and serves as a ground electrode for the sample table 15 to which a high frequency is applied. By forming the counter electrode 21 in such a shape, a stable bias potential can be generated in the sample S. This counter electrode 21 is made of aluminum or the like whose surface is anodized. As the frequency of the high-frequency power supply 28, 400 kHz, 13.56 MHz, or the like is used.

In this device, a microwave transmission area limiting plate 23 is further provided on the microwave introduction window 14. The microwave transmission region limiting plate 23 is provided with a hole 23a in the center of a metal plate such as aluminum, which limits the region where microwaves are introduced into the reaction chamber 12 and generates plasma in a predetermined region. It is.

(Microwave introduction window portion) FIG. 7 is a schematic sectional view showing an example of the microwave introduction window portion.

The microwave introduction window 14 of this example is provided with an annular convex portion 14b (inner diameter DA1, outer diameter DA2), so that not only a circular concave portion 14a (diameter DA1, depth HA1) is formed, but also a facing portion. The tip 21a of the electrode is protected from plasma.

The microwave introduction window 14 having such a shape not only increases the plasma density in the region on the sample S, but also prevents the surface of the tip 21a of the counter electrode from being sputtered, and The number of occurrences can also be reduced.

FIG. 8 is a schematic sectional view showing another example of the microwave introduction window portion.

The microwave introduction window 14 may be shaped as shown in this figure to protect the tip 21a of the counter electrode from plasma.

FIG. 9 is a schematic sectional view showing still another example of the microwave introduction window portion.

When the generation of particles does not cause any particular problem, the microwave introduction window 14 having no portion for protecting the tip 21a of the counter electrode from the plasma may be used as shown in FIG.

(Plasma Processing Method) A case in which plasma processing such as etching is performed on the surface of the sample S by using the plasma processing apparatus thus configured will be described with reference to FIG.

The reaction chamber 12 is evacuated from the exhaust port 26, and then gas is supplied to the reaction chamber 12 from the gas inlet 25.

The microwave is oscillated from the microwave oscillator 35, and the microwave is introduced into the dielectric layer 32 through the waveguide 34. Microwaves leaking from the dielectric layer 32 pass through the microwave introduction window 14 and generate plasma in the reaction chamber 12.

Almost simultaneously with the plasma generation, the high-frequency power source 2
A high frequency is applied to the sample stage 15 using 8 to generate a bias voltage on the surface of the sample S. While controlling the energy of ions in the plasma by this bias voltage, the sample S
The surface of the sample is irradiated with ions, and the sample S is subjected to plasma processing such as etching.

At this time, a concave portion is provided just above the sample S in the microwave introduction window, and is thinner than other portions, so that the microwave electric field intensity is increased. Therefore, the plasma density in this region can be increased, the plasma processing speed of the sample S can be improved, and the pattern removability can be improved in etching a fine hole pattern.

Further, by making the shape of the concave portion of the microwave introduction window appropriate, the uniformity of the plasma processing speed can be improved.

If the shape of the microwave introduction window is designed to protect the surface of the counter electrode, the tip of the counter electrode can be further prevented from being sputtered, and the number of generated particles can be reduced.

The plasma processing apparatus of this example is suitable for processing in which control of ions is particularly important, for example, in the step of etching a hole pattern of a silicon oxide film (SiO ₂ ).

[0056]

An embodiment of the present invention will be described. The plasma processing apparatus used in this embodiment is the one shown in FIGS. The microwave introduction window was made of quartz, and had seven shapes shown in Table 1. The frequency of the microwave is 2.45 GHz, and the frequency of the high frequency is 400 kHz.
z.

[0057]

[Table 1]

(Test 1) The etching rate of the silicon oxide film was measured using microwave introduction windows having different recess depths HA1. Window A (HA1 = 12 mm) and window B (HA1
= 2 mm) and a window G (HA1 = 0 mm) were etched using a 6-inch silicon wafer on which a silicon oxide film of 1 μm was formed as a sample. The etching conditions are as follows. Gas used: C
HF ₃ , microwave power: 1300 W, high frequency power: 6
00W.

FIG. 10 is a graph showing the measurement results of the etching rate for each window.

It has been confirmed that the etching rate can be increased by increasing the recess depth HA1.

(Test 2) Using a microwave introduction window provided with a concave portion and a microwave introduced window not provided with a concave portion, a silicon oxide film was etched with a 0.4 μm hole pattern, and the etched cross-sectional shape was observed. Then, the pattern missing property was evaluated. The microwave introduction windows used are window B (with a recess) and window G (without a recess) in Table 1. The sample used had a silicon oxide film having a thickness of 1.5 μm formed on a 6-inch silicon wafer, and a resist pattern having 0.4 μm holes formed thereon. At each time of a predetermined integrated plasma discharge time, the sample is etched,
For the etched sample, use a scanning electron microscope (S
EM) was used to observe the etched cross-sectional shape. The etching conditions are as follows. Gas used: CHF ₃ and CO, microwave power: 1300 W, high frequency power:
600W.

FIGS. 11A and 11B are schematic diagrams of observation photographs of the cross-sectional shape of the etching with respect to the window B (example of the present invention). FIG. 11A shows a plasma discharge after 20 minutes, FIG. Is etched after 970 minutes of plasma discharge. The center is at the center of the wafer, and the periphery is at a position 10 mm from the edge of the wafer.

FIG. 12 is a schematic view of an observation photograph of the cross-sectional shape of the etching with respect to the window G (comparative example). As in FIG. 11, (a) is after 20 minutes of plasma discharge and (b) is after 570 minutes of plasma discharge. , (C) are etched after 970 minutes of plasma discharge. 11, the center is the center position of the wafer, and the periphery is 10 mm from the edge of the wafer.
In the position.

As can be seen from FIG. 11, in the example of the present invention,
Even when the plasma discharge time was long, a vertical hole could be formed, and the pattern escape property was good.
In contrast, as can be seen from FIG. 12, in the comparative example,
When the plasma discharge time is short (FIG. 12A), a vertical hole can be formed, but as the plasma discharge time becomes longer (FIG. 12B, FIG. 12B).
(C)), the shape of the hole was tapered, and the pattern removability was deteriorated.

That is, it was confirmed that the provision of the concave portion could improve the pattern removability during etching.

(Test 3) The silicon oxide film was etched using microwave introduction windows having different diameters DA1 of the concave portions,
The in-wafer uniformity of the etching rate (etching rate uniformity) was measured. Window A, Window C, Window D, Window E in Table 1
And five types of microwave introduction windows, ie, window F, were tested. The sample and etching conditions are the same as those in Test 1.

FIG. 13 shows the concave diameter D of the microwave introduction window.
FIG. 9 is a view showing a measurement result of etching rate uniformity with respect to A1. The dotted line in the figure indicates a window F without a concave portion.
It is a result of (comparative example).

By setting the diameter DA1 of the concave portion in the range of 150 mm to 180 mm, the window F without the concave portion (Comparative Example)
It was confirmed that the uniformity of the etching rate was improved as compared with.

(Test 4) Using a window A in which the tip of the counter electrode is protected and a window G in which the tip of the counter electrode is not protected (Comparative Example), plasma is generated, and the time change of the number of particles is measured. Measure. The number of particles was determined to be 0.2 μm or more on a 6-inch wafer. The plasma generation conditions are as follows. Gas used: CHF ₃ and CO 2, microwave power: 1300
W, high frequency power: 600W.

FIG. 14 is a diagram showing a change in the number of particles with respect to the plasma discharge time.

In the window A (Example of the present invention), the number of particles on the wafer was less than 50 and stable. On the other hand, in the window G (Comparative Example), after a predetermined time, the number of particles on the wafer exceeded 100.

That is, it was confirmed that the provision of the tip protection portion of the counter electrode can suppress the increase in the number of particles.

[0073]

As described in detail above, the plasma processing apparatus of the present invention improves the plasma processing speed of a sample by increasing the plasma density in a specific region, and improves the pattern processing in etching a fine hole pattern. The detachability can be improved. Further, by optimizing the shape of the concave portion provided in the microwave introduction window, the uniformity of the plasma processing speed can be improved.

Further, when it is necessary to provide an electrode or the like in the vicinity of the microwave introduction window, the electrode or the like can be protected, and the number of particles can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a first embodiment of a plasma processing apparatus according to the present invention.

FIGS. 2A and 2B are schematic diagrams showing an example of a microwave introduction window of the plasma processing apparatus of the present invention, wherein FIG. 2A is a cross-sectional view and FIG.

FIG. 3 is a schematic sectional view showing another example of the microwave introduction window of the plasma processing apparatus of the present invention.

FIG. 4 is a schematic sectional view showing still another example of the microwave introduction window of the plasma processing apparatus of the present invention.

FIG. 5 is a schematic sectional view showing still another example of the microwave introduction window of the plasma processing apparatus of the present invention.

FIG. 6 is a schematic longitudinal sectional view of a second embodiment of the plasma processing apparatus of the present invention.

FIG. 7 is a schematic sectional view showing one example of a microwave introduction window portion of the plasma processing apparatus of the present invention.

FIG. 8 is a schematic sectional view showing another example of a microwave introduction window portion of the plasma processing apparatus of the present invention.

FIG. 9 is a schematic sectional view showing still another example of the microwave introduction window portion of the plasma processing apparatus of the present invention.

FIG. 10 is a diagram showing a measurement result of an etching rate for microwave introduction windows having different recess depths.

11A and 11B are schematic diagrams of observation photographs of an etching cross-sectional shape with respect to a window B (example of the present invention). FIG.
At 0 minutes, (b) is after 570 minutes of plasma discharge, and (c) is at 970 minutes after plasma discharge.

12A and 12B are schematic diagrams of observation photographs of an etching cross-sectional shape with respect to a window G (Comparative Example). FIG.
(B), after 570 minutes of plasma discharge, and (c), after 970 minutes of plasma discharge.

FIG. 13 is a diagram showing a measurement result of etching rate uniformity with respect to a concave portion diameter DA1 of the microwave introduction window.

FIG. 14 is a diagram showing a change in the number of particles with respect to a plasma discharge time.

FIG. 15 is a schematic cross-sectional view showing a conventional plasma processing apparatus using a dielectric layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Reaction container 12 Reaction chamber 14 Microwave introduction window 14a Concavity 14b Convex part (counter electrode tip protection part) 14c Convex part (counter electrode tip protection part) 14d Window main body 14e Annular part 15 Sample stand 16 Base 17 Plasma shield member 18 Insulating member 19 O-ring 20 O-ring 21 Counter electrode 21 a Tip of counter electrode 23 Microwave transmission region limiting plate 23 a Hole 25 Gas introduction hole 26 Exhaust port 31 Hollow part 32 Dielectric layer 33 Metal plate 34 Waveguide 35 Microwave oscillator 41 resist 42 silicon oxide film 43 silicon

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-106994 (JP, A) JP-A-8-236296 (JP, A) JP-A-9-232099 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/3065 C23C 16/511 H01L 21/205

Claims (1)

(57) [Claims] 1. The upper side of the device for microwave waveguides
Arranged along the dielectric layer, opposite the dielectric layer Ryakutaira
A plasma processing apparatus comprising: a microwave introduction window provided in a row ; and a reaction stage in which a sample stage is disposed inside so as to face the microwave introduction window and generates plasma therein. A plasma processing apparatus, wherein the thickness of a region of the window facing the sample stage is thinner than the outside thereof.