JPH0997786A - Plasma processing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a specimen to be uniformly processed as prescribed even if plasma generating conditions are varied. SOLUTION: In this method (device A1), processing gas is introduced into a vacuum chamber 4 where a high-frequency power is applied through a processing gas introducing pipe 5, and plasma is generated. When a specimen 9 fixed on a mount 10 inside the vacuum chamber 4 is processed by plasma, an induction-coupled RF antenna 1 is used as a high-frequency power generating source, a bellows 11, a stepping motor 12, and a shaft 13 are provided to move the mount 10 vertical to the processed surface of the specimen 9 so as to change a distance between a plasma generating region and the specimen 9. By this constitution, a specimen can be uniformly processed as prescribed even if plasma generating conditions are changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and an apparatus thereof, and more particularly to a plasma processing method and an apparatus thereof used in a manufacturing process of semiconductor integrated circuits and the like.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, CV
Many plasma processes such as D and etching are performed. As a method of generating the plasma, a method using a device called a parallel plate has been the mainstream. In addition, as the diameter of wafers has increased, the processing has changed from a batch type in which several wafers are processed at a time to a single wafer mode in which one wafer is processed at a time. One of the items required for such a sheet-type device is a reduction in processing time. That is, in order to increase the wafer throughput, the processing time for each wafer must be shortened. In order to shorten the processing time, it is generally effective to increase the plasma density. However, in the case of the parallel plate type, the density is 1 × 10 ⁹
There is a limit of about cm ^-3 . Therefore, 1 × 10 ¹⁰ cm ^-3
An apparatus using a plasma source such as an ECR, a helicon, or an inductively coupled type capable of generating a higher density plasma has been developed (see Japanese Patent Laid-Open No. 3-79025). Another of the items required for the single-wafer type device is to uniformly generate a plasma in order to uniformly perform the processing within the wafer surface. The demand for uniform plasma becomes more severe as the diameter of the wafer increases.

By the way, among the above three high-density plasma sources, the ECR and the helicon use a magnetic field by a coil or a magnet, but the inductively coupled type does not use a magnetic field. When a magnetic field is used, the homogeneity of the plasma largely depends on the magnetic flux density distribution of the magnetic field, and it is necessary to design the optimum magnetic field to generate a uniform plasma. This magnetic field design requires a great deal of effort because the optimum magnetic field is not well understood. Further, the use of the magnetic field coil itself causes the device to be large and complicated. On the other hand, when no magnetic field is used, that is, in an inductively coupled device,
The homogeneity is determined by the plasma generation region and the consumption region, that is, the antenna structure and the structure of the sample and the vacuum container. Therefore, it is easier to predict the homogenization and it is easier to downsize the device, as compared with the device with a magnetic field. For this reason, inductively coupled devices have recently been rapidly commercialized. FIG. 6 shows a schematic configuration of an example of such a conventional inductively coupled plasma processing apparatus A0. The apparatus A0 operates as follows. In FIG. 6, in the vacuum container 4 to which high frequency power is applied from the RF antenna 1,
The processing gas is introduced from the processing gas introduction pipe 5 to generate plasma. Then, the sample 9 fixed on the mounting table 10 in the vacuum container 4 is plasma-processed by this plasma.

[0004]

However, the conventional inductively coupled plasma processing apparatus A0 as described above has the following problems. In plasma processing, plasma generation conditions may be changed during processing of one sample. For example, in the case of etching, conditions that place importance on the processing speed and etching shape are used during just etching until the film to be processed is almost completely etched and the underlying film is exposed. After that, at the time of over-etching to etch the "residual" remaining in the stepped portion, etc., a condition with high selectivity with respect to the base film is used so as not to etch the base film. In this way, processing may be performed in two steps. Further, in the etching of polysilicon, the step of removing the natural oxide film formed on the sample surface may be included in the step before the above-mentioned two steps, and the processing may be performed in three steps. In such cases, it is especially required that the uniformity does not change between steps even if the plasma generation conditions are changed. However, in an inductively coupled plasma that does not use a magnetic field, the homogeneity depends on the plasma generation condition itself, so if the plasma generation condition changes, the homogeneity naturally changes. Therefore, it was not possible to deal with the case where the plasma treatment had several steps. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma processing method and an apparatus thereof that can ensure desired uniformity even when the plasma generation conditions change. Is.

[0005]

To achieve the above object, the first invention is to introduce a processing gas into a vacuum container to which high frequency power is applied to generate plasma, and the plasma causes the inside of the vacuum container to be generated. In the plasma processing method for plasma-processing a sample fixed on the mounting table, the plasma processing method is characterized in that the plasma processing is performed by changing the distance between the plasma generation region and the sample. Further, an inductively coupled RF antenna is used as a source of the high frequency power, and the distance is changed by moving the RF antenna and / or the mounting table in a direction perpendicular to the processing surface of the sample. Is a plasma processing method. A second invention is a plasma processing method in which a processing gas is introduced into a vacuum container to which high-frequency power is applied to generate plasma, and the plasma fixes the sample fixed on the mounting table in the vacuum container. 2. In the plasma processing method, the inductively coupled RF antenna is used as a source of the high frequency power, and the plasma processing is performed by changing the number of coils of the RF antenna. A third aspect of the present invention is a plasma processing apparatus for introducing a processing gas into a vacuum container to which high frequency power is applied to generate plasma, and plasma-processing a sample fixed on a mounting table in the vacuum container by the plasma. 2. In the plasma processing apparatus, a distance changing mechanism for changing the distance between the plasma generation region and the sample is provided. A fourth invention is a plasma processing apparatus for introducing a processing gas into a vacuum container to which high frequency power is applied to generate plasma, and plasma-processing a sample fixed on a mounting table in the vacuum container by the plasma. In the above plasma processing apparatus, an inductively coupled RF antenna is used as a source of the high frequency power, and a coil number changing mechanism for changing the number of coils of the RF antenna is provided.

[0006]

DETAILED DESCRIPTION OF THE INVENTION

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
It should be noted that the following embodiments and examples are merely examples embodying the present invention and are not of the nature to limit the technical scope of the present invention. Here, FIG. 1 is a schematic diagram showing a schematic configuration of an apparatus A1 to which the plasma processing method according to the embodiments and examples of the first and third inventions (first example) can be applied, and FIG. 2 shows steps. Explanatory drawing showing profiles of 1 and 2, FIG.
FIG. 4 is an explanatory diagram showing a schematic configuration of the test apparatus A1 ′ and a test result by the test apparatus A1 ′. FIG. 4 shows a plasma processing method according to another embodiment and example (second example) of the first and third inventions. The schematic diagram which shows the schematic structure of the applicable apparatus A2, FIG. 5: The outline of the apparatus A3 which can apply the plasma processing method which concerns on embodiment and Example (3rd Example) of 2nd, 4th invention. It is a schematic diagram which shows a structure. The same reference numerals are used for elements common to the schematic diagram showing the schematic configuration of the example of the conventional plasma processing apparatus A0 shown in FIG.

In the plasma processing method according to the first aspect of the present invention, a processing gas is introduced into a vacuum container to which high-frequency power is applied to generate plasma, and the plasma fixes the plasma on the mounting table in the vacuum container. This is the same as the conventional example in that the sample is plasma-treated. However, the first method of the present invention differs from the conventional example in that the plasma treatment is performed by changing the distance between the plasma generation region and the sample. A third invention is an apparatus to which the method of the first invention can be applied, and is provided with a distance changing mechanism for changing the distance. A concrete example A1 thereof is shown in FIG. 1 (first embodiment). Example). In FIG. 1, reference numeral 1 denotes an RF antenna, and in this example, one turn (1
Turn), but may be several turns. Reference numeral 2 denotes an RF power source for plasma generation, which often uses a frequency of 13.56 MHz. Here, the power supply includes the matching circuit. Reference numeral 3 denotes a quartz window, which is a dielectric window for propagating the electromagnetic field induced by the antenna into the vacuum chamber. Reference numeral 4 is a vacuum container, 5 is a processing gas introducing pipe, and 6 is a flow control valve. An exhaust pipe 7 is provided with a vacuum pump (not shown). Reference numeral 8 denotes a pressure control valve, which controls the pressure in the vacuum container by controlling the exhaust amount with the valve. Reference numeral 9 is a sample, that is, a wafer. Reference numeral 10 is a mounting table, which is equipped with a clamp or an electrostatic chuck to fix the sample. Reference numeral 14 is an RF power source for applying a high frequency bias to the sample, and a frequency of several hundred kHz is often used. Here, a matching circuit is also included.
The present device A1 has these components (reference numbers 1 to 10, 1).
4) is the same as the conventional device 0. However, in the device A1, the bellows 11, the stepping motor 12, and the shaft 1 corresponding to the distance changing mechanism are further included.
It also has 3.

Hereinafter, a case of performing a two-step etching process using the apparatus A1 will be described. The film to be etched is polysilicon which is the gate material of the MOS transistor. (Plasma generation condition in step 1) -RF power for plasma generation: 800 W-Processing gas: C12 + HBr-Processing gas flow rate: 100 sccm (Cl2: HBr = 2)
0:80) -Pressure: 30 mTorr-Bias RF voltage Vpp: 200 v (plasma generation condition in step 2) -Plasma generation RF power: 800 W-Processing gas: C12 + HBr + 02-Processing gas flow rate: 105 sccm (Cl2: HBr: O)
2 = 70: 30: 5) -Pressure: 15 mTorr-RF voltage for bias Vpp: 300v

Step 1 is a step of just etching until the polysilicon is almost etched to expose SiO2 which is a base film, and step 2 is an over-etching step of etching the "residual" remaining in the step portion. . Step 1 generally has a high etching rate,
It is desirable that the etching condition be good. In this case, the etching rate is 7800 Å / min, and etching can be performed in a vertical shape. On the other hand, in step 2, it is desirable that the selection ratio of SiO2 is high so as not to etch the exposed base film, and there is no abnormal shape such as a notch characteristically generated during overetching. In this case, the selection ratio is 100 and no abnormal shape is observed. However, changes in the plasma uniformity can be observed. For example, the uniformity of the ion saturation current Isat measured by the Langmuir probe within the radius of an 8-inch wafer is max. ~ Min. It has changed greatly as follows. Step 1 ... ± 5.7% Step 2 ... ± 16.2%

The profile of the ion saturation current Isat in the radial direction of the wafer at this time is as shown in FIG. That is, the profile of step 1 has a valley shape having a peak slightly off center from the edge of the wafer, while the profile of step 2 has a peak shape having a peak near the center. Such changes are due to changes in plasma generation conditions themselves. Next, it was verified that such a change in uniformity could be suppressed by moving the mounting table in the height direction and changing the distance between the plasma generation source (plasma generation region) and the sample. First, we show the results of measuring the plasma density profile with respect to the height of the mounting table. FIG. 3A shows a test apparatus A1 'used for such measurement, in which the ion saturation current I is measured by a Langmuir probe which can scan in the radial direction of a wafer mounted directly on the sample.
The sat was measured. In this device A1 ', the mounting table is not movable, but by inserting a spacer in a part of the side wall of the vacuum container, the distance between the plasma generation source and the sample is changed to move the mounting table. It is possible to obtain the same effect as in the case. The distance between the plasma generation source and the sample is 3 cm without the spacer. The test result is shown in FIG. In the figure, the horizontal axis is the distance from the wafer center, and the vertical axis is the ion saturation current Isat.
Is the relative value of. When the spacer is not inserted (h = 0 cm), a valley shape having a peak appears at the edge of the wafer, h
It can be seen that as the distance increases to 3 cm and 5 cm, the profile gradually changes to a mountain-shaped profile with a peak in the center. Such changes in profile are caused by changes in the positions of the inner wall of the vacuum container and the sample surface where plasma is consumed. The results were measured under the following conditions. The gas type is different from that in the etching process, but the tendency is the same regardless of the type of gas used, although the absolute value is different. is there.

-RF power for plasma generation: 500 W-Processing gas: Ar-Processing gas flow rate: 100 sccm-Pressure: 50 mTorr Therefore, when the profile changes from the valley type in step 1 to the mountain type in step 2 as described above, In order to make the step 2 also a valley type, the mounting table may be lifted and brought close to the RF antenna. However, how close you should be
It is necessary to measure and determine under the plasma conditions of step 2. Regarding the timing of moving the mounting table, for example, after step 1 is finished, the plasma is once turned off, and the mounting table is moved to reset the pressure while changing the gas flow rate ratio. Then, the plasma is turned on again and the process proceeds to step 2. The mechanism that can move the mounting table in the first embodiment can be replaced with a mechanism that can move the RF antenna sealed in vacuum. FIG. 4 shows a specific example A2 of such a device (second embodiment). In FIG. 4, 15 is a quartz container, which seals the RF antenna 1 in a vacuum,
Moreover, it is a dielectric container for propagating electromagnetic waves into the vacuum container 4.

In addition to the method of sealing the antenna in a vacuum and moving only the antenna as in the example of this figure, a bellow is attached to a part of the side wall of the vacuum container to move the vacuum container itself. May be. As described above, in the devices A1 and A2 of the first and second embodiments, the mounting table and / or the RF antenna moves in the height direction, and the distance between the plasma generation source and the sample can be changed. . Therefore, even if the plasma generation conditions are changed by performing two or more steps per sample with inductively coupled plasma, one of the other factors that determine the uniformity in inductively coupled plasma is the structure of the vacuum container. Can be changed, so that desired uniformity can be ensured. Subsequently, the second and fourth inventions will be described. The plasma processing method according to the second invention is different from the conventional example in that an inductively coupled RF antenna is used as a source of high-frequency power and the number of coils of the RF antenna is changed to perform plasma processing.

A fourth invention is a device to which the second invention can be applied, and is provided with a coil number changing mechanism for changing the number of coils of the antenna. A concrete example A3 thereof is shown in FIG. (Third embodiment). As shown in FIG. 5, 2
Double RF antennas 1 and 1'are provided so that these circuits can be switched by the switch 16 (the switch 16 corresponds to the coil number changing mechanism). When the profile of the plasma density is changed from the valley type to the mountain type between the steps as in the first embodiment, it is made closer to the mountain type by using the 1'antenna in step 1, and in step 2 it is 1 Use the antenna of to make it closer to the valley type. As described above, the profile of the plasma density can be changed by arranging the RF antenna not only in a single circuit but also in a circuit configuration of double or more and switching the distribution of the high frequency current flowing through these circuits. Therefore, the structure of the plasma generation region, which is one of the other factors that determine the homogeneity in the inductively coupled plasma, even if the plasma generation conditions are changed by performing two or more steps of the inductively coupled plasma. Since it can be changed, desired uniformity can be ensured. By applying some or all of the first to third embodiments in combination, it is possible to increase the degree of freedom of the conditions for maintaining the uniformity.

[0014]

Since the plasma processing method and the apparatus therefor according to the present invention are configured as described above, desired uniformity can be ensured even when the plasma generation conditions change. As a result, it is possible to deal with the case where the plasma processing involves several steps.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an apparatus A1 to which a plasma processing method according to embodiments and examples (first example) of the first and third inventions can be applied.

FIG. 2 is an explanatory diagram showing profiles of steps 1 and 2.

FIG. 3 is an explanatory diagram showing a schematic configuration of a test apparatus A1 ′ and a test result therefor.

FIG. 4 is a schematic diagram showing a schematic configuration of an apparatus A2 to which a plasma processing method according to other embodiments and examples (second example) of the first and third inventions can be applied.

FIG. 5 is a schematic diagram showing a schematic configuration of an apparatus A3 to which a plasma processing method according to embodiments and examples (third example) of the second and fourth inventions can be applied.

FIG. 6 is a schematic diagram showing a schematic configuration of an example of a conventional plasma processing apparatus A0.

[Explanation of symbols]

A1 to A3 ... Plasma processing apparatus 1, 1 '... RF antenna 4 ... Vacuum container 5 ... Processing gas introduction tube 9 ... Sample 10 ... Mounting table 11 ... Bellows (corresponding to a part of distance changing mechanism) 12 ... Stepping motor (distance) 13 ... Shaft (corresponding to part of distance changing mechanism) 15 ... Quartz container (corresponding to part of distance changing mechanism) 16 ... Switch (corresponding to coil number changing mechanism)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H05H 1/46 H05H 1/46 L

Claims (5)

[Claims] 1. A plasma processing method in which a processing gas is introduced into a vacuum container to which high-frequency power is applied to generate plasma, and the plasma fixes a sample fixed on a mounting table in the vacuum container. A plasma processing method characterized in that the plasma processing is performed by changing the distance between the plasma generation region and the sample. 2. An inductively coupled RF antenna is used as a source of the high frequency power, and the RF antenna and / or
2. The plasma processing method according to claim 1, wherein the distance is changed by moving the mounting table in a direction perpendicular to the processing surface of the sample. 3. A plasma processing method in which a processing gas is introduced into a vacuum container to which high-frequency power is applied to generate plasma, and the plasma fixes the sample fixed on a mounting table in the vacuum container. , In addition to using an inductively coupled RF antenna as the source of high-frequency power,
A plasma processing method, wherein plasma processing is performed by changing the number of coils of the RF antenna. 4. A plasma processing apparatus for plasma-processing a sample fixed on a mounting table in the vacuum container by introducing a processing gas into the vacuum container to which high-frequency power is applied to generate plasma. A plasma processing apparatus comprising a distance changing mechanism for changing the distance between the plasma generation region and the sample. 5. A plasma processing apparatus for plasma-processing a sample fixed on a mounting table in the vacuum container by introducing a processing gas into the vacuum container to which high-frequency power is applied to generate plasma. , In addition to using an inductively coupled RF antenna as the source of high-frequency power,
A plasma processing apparatus comprising a coil number changing mechanism for changing the number of coils of the RF antenna.