JPH08111402A - Method and apparatus for dry etching - Google Patents

Abstract

PURPOSE: To make it possible to carry out vertical dry etching for a fine pattern accurately with a small rate of damage, by separating a plasma generating unit and a sample stage with a porous plate having fine holes, and applying a high-frequency voltage across the porous plate and an upper electrode put above the porous plate. CONSTITUTION: A high-frequency voltage from a high-frequency power supply 9 is applied across an upper electrode 2 and a porous plate 4. Without applying a DC bias voltage, as in a prior art, across a sample stage 5 for holding a workpiece and a plasma generating unit, ions are generated at an upper space and accelerated. These ions passed through holes 4, in the porous plate 4 has orientation vertical to the porous plate 4 when the ions are cast to the workpiece held on the sample stage 5. As a result, a vertical etching step is carried out accurately for a workpiece under clean conditions with a small rate of damage to a fine pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method and a dry etching apparatus which are used in a semiconductor device manufacturing process or the like and particularly form a fine pattern with high accuracy.

In order to cope with the rapid progress of miniaturization and high integration of semiconductor integrated circuit devices, a processing technique using dry etching has a high anisotropy associated with miniaturization and a uniformity associated with an increase in diameter. Improvement, high selectivity accompanying thinning of various coatings, low damage, cleanliness, etc. are required. Therefore, it is necessary to improve various devices used for manufacturing a semiconductor device so that a fine pattern can be processed accurately.

[0003]

2. Description of the Related Art Conventionally, in dry etching using plasma of a reaction gas, the type of reaction gas and plasma discharge conditions have been optimized in order to process a fine pattern with high accuracy. However, under the conventional conditions, the gas pressure is generally about 10 ^-1 to 10 ^-2 torr, and collision and scattering of ions and active species occur with a relatively high probability, so that side etching is likely to occur.

In order to prevent this undesired side etching and improve the pattern accuracy, a deposition gas is added to the reaction gas, and the sidewall of the pattern is protected by the deposition to perform dry etching or to remove the workpiece. In order to suppress the reaction of the pattern side wall by cooling below freezing, or to isolate the work piece from the plasma generation part and apply a DC bias voltage to the sample stage that holds the work piece in the vertical direction to the work piece. A method of performing vertical dry etching by utilizing accelerated ion collision has been proposed.

[0005]

However, when a dry gas is added while a deposition gas is added to protect the side wall of the pattern, a large amount of deposits are also attached to the inside of the vacuum container, and the deposits become dust. However, it is necessary to clean it. In addition, when the workpiece is cooled below freezing to suppress the reaction of the pattern side wall and dry etching is performed, the etching apparatus becomes large-scale, and the stability of the process when used as a mass production apparatus is a problem. It was.

Furthermore, when a work piece is isolated from the plasma part and dry-etched, when a direct current bias voltage is applied to the sample stage, the work piece is bombarded with ions having high energy. There was a problem that the work piece was damaged. The present invention, without exposing the workpiece to the plasma of the reaction gas, and without applying a DC bias voltage to the sample stage holding the workpiece,
To provide a means for vertically dry etching a fine pattern with low damage and high accuracy by independently controlling ions and active species in plasma that contribute to the dry etching reaction and making them incident on a workpiece. To aim.

[0007]

In the dry etching method according to the present invention, a perforated plate having a plurality of pores is arranged between a plasma generating portion of a reaction gas and a sample table holding a workpiece. , Perpendicular to the perforated plate to the ions and active species generated by the plasma in the plasma that passes through the multiple pores of the perforated plate without applying a DC bias voltage to the sample stage that holds the workpiece. In order to prevent the exposure of the work piece to the plasma of the reaction gas, the process for achieving vertical etching with good characteristics is adopted.

In this case, by applying a high frequency voltage between the upper electrode arranged above the perforated plate and the perforated plate, the ions in the plasma are accelerated and a plurality of pores of the perforated plate are Can be passed through.

Further, in this case, due to the pressure difference generated in the atmosphere between the plasma generating part of the reaction gas and the sample stage holding the workpiece, the plasma is generated by the plasma passing through the plurality of pores of the perforated plate. The active species can be oriented to travel perpendicular to the plate. Further, in this case, by exhausting the atmosphere under the sample table, a large pressure difference can be generated between the plasma generation part of the reaction gas and the sample table holding the workpiece.

In this case, the perforated plate has a thickness of 1
The diameter can be 100 mm or more, the diameter of the pores can be 100 μm or less, and the aspect ratio can be 10 or more. Further, in this case, the ions in the plasma that contribute to the etching reaction and the active species generated by the plasma can be controlled independently.

Further, in the dry etching apparatus according to the present invention, the vacuum container, the plasma generating part of the reaction gas arranged in the vacuum container, and the work piece similarly arranged in the vacuum container are held. The sample table is equipped with a perforated plate having a plurality of fine holes arranged between the sample table for holding the workpiece and the plasma generation part of the reaction gas.

In this case, the thickness of the perforated plate can be 1 mm or more, the diameter of the pores can be 100 μm or less, and the aspect ratio can be 10 or more. Further, in this case, the upper electrode may be disposed on the perforated plate, and a means for applying a high frequency voltage may be connected between the upper electrode and the perforated plate.

Further, in this case, it is possible to provide a means for producing a pressure difference in the atmosphere between the plasma generating part of the reaction gas and the sample stage holding the workpiece. Further, in this case, by providing an exhaust port of the exhaust device under the sample table, a pressure difference can be generated in the atmosphere between the plasma generating part of the reaction gas and the sample table on which the workpiece is placed. Further, in this case, means for independently controlling the ions and active species in the plasma that contribute to the etching reaction can be provided.

[0014]

In the dry etching apparatus of the present invention, the space between the plasma generating part and the sample table holding the workpiece is partitioned by the perforated plate having pores, and the high frequency coil is arranged around the plasma generating part. The upper electrode is disposed above the perforated plate, and the exhaust port of a large-capacity exhaust pump is provided directly below the sample table that holds the workpiece.

In this device, a high-frequency voltage is applied to a high-frequency coil around the plasma generating section to convert the reactive gas into plasma, and a high-frequency wave is generated between the upper electrode and the perforated plate arranged above the perforated plate. By applying the voltage, the ions in the plasma can be made incident on the workpiece through the pores of the perforated plate without applying the DC bias voltage to the sample stage holding the workpiece. That is, when a high-frequency electric field is formed in plasma, electrons with a small mass oscillate up and down following the high-frequency electric field, but ions with a large mass and a positive charge remain in the plasma, and are formed by the plasma with a positive charge. The surrounding electric field having a positive charge of the same polarity is accelerated in the vertical direction by the electric field generated by the electric field, and the ions accelerated downward enter the workpiece through the pores of the perforated plate.

When a pressure difference is generated between the plasma generating part of the reaction gas and the sample table holding the workpiece, the active species generated by the plasma can be made incident on the workpiece by the pressure difference. it can. Also, the thickness of the perforated plate used here is 1 mm or more, and the diameter of the pores is 1 mm.
Aspect ratio (depth / hole diameter) of 10 μm or less
As described above, the active species passing through this hole can be provided with the directionality of traveling perpendicularly to the perforated plate.

By partitioning the plasma generating part and the vicinity of the sample table with the perforated plate in this manner, the workpiece can be kept in a clean environment without being exposed to the plasma that impairs the vertical etching characteristics. By adjusting the high-frequency voltage between the electrode and the perforated plate, and the pressure difference between the plasma generation part of the reaction gas and the sample stage that holds the workpiece, the ions and active species that enter the workpiece can be adjusted. It can be controlled independently, and as a result, it becomes possible to vertically etch a fine pattern with low damage and high accuracy.

Dry etching with the above-mentioned ions
This is a process in which ions with large mass and large kinetic energy collide with the surface of the work piece to sputter the material on the surface. In the dry etching with active species, first, the active species (radicals) are processed. Adsorbed on the surface of
In this step, the accelerated active species collide with the surface to react with the workpiece, and the reaction product is volatilized and released.

In this case, since the ions have a vertical velocity, the work piece is vertically etched by the sputtering due to the kinetic energy, and the active species are accelerated, so that they collide with the facing surface of the work piece. The work piece is vertically etched because it does not collide with the side surface.

Aspects of dry etching with ions,
Since the dry etching mode by active species is different, the dry etching by ions and the dry etching by active species are controlled independently to reduce damage to the work piece, increase the etching rate, and achieve high efficiency and high accuracy. Can be etched vertically.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of a dry etching apparatus according to an embodiment of the present invention. In this figure, 1 denotes a vacuum vessel, 1 ₁ headspace, 1 ₂ the lower space, 2 upper electrode, 3 is the reaction gas inlet, 4 perforated plate, 4 ₁ pore, 5 sample stage, 6 is a large displacement pump, 7 is a high frequency coil, 8 is a first high frequency power supply, and 9 is a second high frequency power supply.

In the dry etching apparatus according to one embodiment of the present invention, the upper wall of the quartz vacuum container 1 is composed of the upper electrode 2 having the reaction gas inlet 3, and the inside of the vacuum container 1 has many diameters of 100 μm. Thickness ₁ with the following pores 4 1
In mm or more, the aspect ratio of 4 10 or more perforated plates (multi-capillary plate), is 2 minutes into the upper space 1 ₁ and a lower space 1 _2, high-frequency coil on the outer periphery of the vacuum chamber 1 which surrounds the upper space 1 ₁ 7 is arranged, a first high frequency power source 8 is connected, and a second high frequency power source 9 is connected between the upper electrode 2 and the perforated plate 4.

Further, the lower space 1 _2, the sample stage 5 for holding a workpiece is provided, the exhaust rate is below the sample stage 5 is an exhaust pump 6 large capacity of about 2,000 to 3,000 l / sec An exhaust port is provided.

[0024] Through the reaction gas inlet port 3, as a reaction gas in the upper space ₁ 1 CHF ₃ / CF _4, respectively 10
0SCCM introduced, the gas pressure in the upper space 1 ₁ 10 ^-1
To about to 10 ^-2 torr, the high frequency coil 7 disposed on the outer periphery of the vacuum chamber 1 which surrounds the upper space 1 _1, Frequency 3.
A high frequency voltage is applied by the first high frequency power supply 8 of 4 MHz to turn the reaction gas into plasma.

Then, by applying a high frequency voltage between the upper electrode 2 and the perforated plate 4 by the second high frequency power source 9 having a frequency of 13.56 MHz, the plasma generating portion and the workpiece are processed as in the case of the prior art. Ions generated in the upper space are accelerated without applying a DC bias voltage between the sample table 5 holding the object, and the perforated plate 4
Multiple passed through pores 4 _1, and remembering direction of progression vertically perforated plate 4 to be incident on the workpiece held on the sample stage 5.

The large displacement pump 6 is used to exhaust the atmosphere under the sample table 5 so that the gas pressure in the vicinity of the sample table 5 is reduced to 1
0 ^-5 to about to 10 ^-6 torr, creating a pressure differential between the sample stage 5 for holding the upper space 1 ₁ and the workpiece in the lower space 1 ₂ for generating a plasma, this pressure difference, the plasma The active species generated by the above are made incident on the workpiece held on the sample table 5.

At this time, the thickness of the perforated plate 4 is 1 mm.
Since the diameter of the large number of pores 4 ₁ formed in the perforated plate 4 is 100 μm and the aspect ratio is 10,
Further, since the pressure difference in the atmosphere between the plasma generation unit and the sample table on which the workpiece is placed is large, the active species generated by the plasma are vertically incident on the workpiece.

In order for the active species to enter the workpiece vertically, it is necessary that the aspect ratio of the pores 4 ₁ formed in the perforated plate 4 be 10 or more.
_If the aspect ratio of ₁ is smaller than 10, the active species cannot be vertically incident. Further, the diameter of the pores 4 ₁ formed in the perforated plate 4 is preferably 100 μm or less, and in the pores 4 _{1 having a} larger diameter, the active species are scattered and directionality cannot be obtained. Moreover, the range of forming pores 4 ₁ of the perforated plate 4, when larger than the outer shape equal to or outer shape of the sample stage 5, thereby improving the uniformity of the dry etching.

The large displacement pump 6 of this embodiment is also used.
With, the product generated by the reaction between the work piece and the active species is quickly evacuated, and new active species are constantly supplied near the surface of the work piece. However, in this case, it is desirable that the large displacement pump 6 be installed directly below the sample stage 5 that holds the workpiece, and the direction of exhaust greatly affects the uniformity of dry etching.

The plasma generating section and the sample stage 5 are partitioned by the perforated plate 4, and ions and active species to be supplied to the workpiece are applied without applying a DC bias voltage to the sample stage 5 holding the workpiece. By independently controlling, for example, in dry etching of an oxide film, the etching rate can be set to 6000 Å / min, the uniformity can be set to ± 2%, and the vertical etching that does not seriously damage the work piece can be performed. It became possible to do.

In this embodiment, the frequency of the first high frequency power source 8 is 3.4 MHz and the frequency of the second high frequency power source 9 is 13.56 MHz. The frequency of the high frequency power source 9 is 3.4
It can be set to MHz or 13.56 MHz, and is not limited to the frequency of this embodiment.

[0032]

As described above, according to the present invention,
By changing the configuration very easily, the fine pattern can be vertically etched with low damage and high accuracy in a clean environment of the work piece, which makes the device such as a semiconductor device finer and highly integrated. However, it greatly contributes to higher performance.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a dry etching apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 Vacuum container 1 ₁ Upper space 1 ₂ Lower space 2 Upper electrode 3 Reactive gas inlet 4 Perforated plate 4 ₁ Pore 5 Sample stage 6 Large displacement pump 7 High frequency coil 8 First high frequency power supply 9 Second high frequency power supply

Claims (12)

[Claims] 1. A perforated plate having a plurality of pores is arranged between a plasma generation part of a reaction gas and a sample table for holding a workpiece, and a DC bias voltage is applied to the sample table for holding the workpiece. Without applying, the ions in the plasma passing through the plurality of pores of the perforated plate and the active species generated by the plasma are made to enter the workpiece by giving a directionality that advances perpendicularly to the perforated plate, A dry etching method characterized by vertically etching a workpiece without exposing it to plasma of a reaction gas. 2. An ion in the plasma is accelerated by applying a high frequency voltage between the upper electrode arranged above the perforated plate and the perforated plate, so that a plurality of pores in the perforated plate are generated. The dry etching method according to claim 1, wherein the dry etching method is performed. 3. The active species generated by the plasma passing through the plurality of pores of the perforated plate are perforated by the pressure difference of the atmosphere between the plasma generation part of the reaction gas and the sample stage holding the workpiece. The dry etching method according to claim 1, wherein the plate has a directionality in which the plate advances vertically. 4. The pressure difference is generated in the atmosphere between the plasma generation part of the reaction gas and the sample table holding the workpiece by exhausting the atmosphere under the sample table. Dry etching method described in. 5. The thickness of the perforated plate is 1 mm or more,
The diameter of the pores is 100 μm or less, and the aspect ratio is 10
The dry etching method according to any one of claims 1 to 4, wherein the dry etching method is as described above. 6. The dry method according to claim 1, wherein the ions in the plasma that contribute to the etching reaction and the active species generated by the plasma are controlled independently. Etching method. 7. A vacuum container, a reaction gas plasma generation unit arranged in the vacuum container, a sample stage for holding a workpiece similarly arranged in the vacuum container, and a reaction gas plasma generation unit. A dry etching apparatus having a perforated plate having a plurality of pores, which is arranged between a plate and a sample table that holds a workpiece. 8. The dry etching apparatus according to claim 7, wherein the thickness of the perforated plate is 1 mm or more, the diameter of the pores is 100 μm or less, and the aspect ratio is 10 or more. 9. The upper electrode is arranged above the perforated plate, and means for applying a high frequency voltage is connected between the upper electrode and the perforated plate. The dry etching apparatus described in. 10. The method according to claim 7, further comprising means for generating a pressure difference in the atmosphere between the plasma generation part of the reaction gas and the sample stage holding the workpiece. The dry etching apparatus described in the item. 11. A pressure difference is generated in the atmosphere between the plasma generation part of the reaction gas and the sample table on which the workpiece is placed by providing an exhaust port of the exhaust device under the sample table. The dry etching apparatus according to claim 10. 12. The method according to claim 7, further comprising means for independently controlling ions in the plasma that contribute to the etching reaction and active species generated by the plasma. The dry etching apparatus described.