JPH07302694A - Plasma processing device - Google Patents

Abstract

PURPOSE:To make possible plasma processes of both of an ion type and a radical type in simple constitution by separating a helical antenna coil along an outer circumference of a semi-spherical reaction chamber into an upper and a lower coils, and adjusting an inductance and an actuation range of the lower coil as desired. CONSTITUTION:In a plasma processing device 19, a helical antenna coil 25 is provided along an outer circumference of a semi-spherical reaction chamber comprising dielectric, where the coil 25 is separated into an upper and a lower coils 26, 27. A tapping position is set at a lower end of the coil 26 through a switch 29, an inductance is adjusted, and a substrate W is disposed in an actuation space of the coil 25. Air is discharged from an air discharge hole 24 to form high vacuum in the reaction chamber, and oxygen gas or the like at a specified pressure is introduced from a gas introducing port 33, so a surface hardened layer on the substrate W becomes hard to be peeled by an ion type plasma process. Next, as the tap position is set at the coil 27 at an upper end, the plasma cannot reach the substrate W, so ashing or the like of the substrate W is performed by a radial process without damaging its surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus used for etching, ashing, deposition, surface modification of a semiconductor substrate, and particularly to a hemispherical reaction chamber effective for generating high density plasma. The present invention relates to a helical antenna type plasma processing apparatus used.

[0002]

2. Description of the Related Art Various plasma processing apparatuses are widely used for processing a substrate by generating plasma under reduced pressure in conventional etching, ashing, deposition, surface modification, etc. of a semiconductor substrate in the process of manufacturing an LSI. There is.

For example, ashing for stripping a used resist after etching or ion implantation process is an extremely important application field of a plasma processing apparatus in a manufacturing process of an LSI. For example, see (1) "Monthly Semiconductor Worl".
d July 1993, pp. 164-175 ”, and reference (2)“ Monthly Semiconductor World 1991.
March issue, pp. 153-159 ", and reference (3)" Monthly publication
Semiconductor World Special Issue '94 Latest Semiconductor Process Technology, pp. 197-203 ”discusses various problems related to resist ashing by plasma. Another problem is how to efficiently and completely remove a resist whose surface layer has been altered / cured by etching or ion implantation.

In order to solve this problem, first, a plasma treatment with ion bombardment, which is effective for peeling off the deteriorated hardened layer, is performed, and then ashing mainly based on a radical reaction is performed to avoid damage due to ashing. Two-stage ashing, such as peeling, is proposed.
As one method of realizing this, as described in Document (3), a two-stage plasma ashing device in which two chambers, an RIE chamber and a microwave downflow chamber, are joined, or Document (4) “Monthly Semicond”.
uctor World extra number '94 latest semiconductor process technology No. 22
As described in "Pages 6 to 227", a two-stage plasma ashing apparatus has been developed which combines the RIE ashing function and the microwave downflow ashing function in one chamber.

[0005]

However, in the two-stage plasma ashing apparatus described in Documents (3) and (4), the two-stage plasma ashing apparatus has both the RIE ashing function and the microwave downflow ashing function. Different types of power supplies are needed. In particular, the apparatus according to the document (3) requires a substrate transfer mechanism between two separated chambers, which not only complicates the apparatus configuration but also increases the number of particles generating elements. In addition, the increase in device price due to the complexity of the device has been a problem that cannot be overlooked.

That is, in the conventional two-stage plasma ashing apparatus, since the biggest obstacle is that the apparatus structure is complicated, it has been desired to provide a two-stage plasma ashing apparatus which avoids the complication of the apparatus as much as possible. . As a result, not only the ashing apparatus but also the plasma processing apparatus in general, a simple two-step plasma processing apparatus that can be applied to other processes that require both ionic plasma and radical plasma, or an ionic plasma with a single apparatus It has been desired to provide a plasma processing apparatus capable of selecting either plasma radical plasma or radical plasma.

The present invention has been made in view of the above circumstances, and is capable of performing both ionic plasma processing and radical plasma processing, and provides a simple plasma processing apparatus having a simple apparatus configuration. The purpose is to do.

[0008]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems by improving a helical antenna type plasma processing apparatus. A plasma processing apparatus using a helical antenna is described in Reference (5) "Basics and Practice of High-Density Plasma Processing" (Proceedings of the Japan Society of Applied Physics, Plasma Electronics Subcommittee, Osaka University, Nov. 18, 1993).
As described in (19th), it easily generates a high-density plasma.

In the present invention, the helical antenna coil installed in a winding shape from the upper part to the lower part along the outer circumference of the hemispherical reaction chamber is divided into an upper coil and a lower coil, and the inductance of the lower coil is adjusted by the adjusting means. By adjusting the, the ionic and radical properties of the plasma acting on the substrate can be controlled.

The plasma processing apparatus 1 shown in FIGS. 3A and 3B has a single helical antenna coil 3 which is not divided into hemispherical reaction chambers 2, and the electric characteristics of the coil are fixed. It was done. In this case, whether the interaction between the plasma P and the substrate W is ionic or radical is mainly governed by the held position (height) of the substrate W. That is, as shown in FIG. 3A, when the substrate W is held in the plasma generating portion of the helical antenna coil 3, the surface of the substrate W is strongly exposed not only to radicals but also to charged particles such as electrons and ions. To be done.
On the contrary, as shown in FIG. 3B, in the state where the substrate W is held away from the plasma generating part, the short-lived ions rarely reach the substrate W, and the surface of the substrate W has a plasma P It is mainly affected by long-lived radicals, which can maintain their activity even in a place far away from. Therefore, it is possible to select whether the interaction is ionic or radical by the upper and lower positions of the substrate W, but in this method, the uniformity of the plasma and the arbitrary ratio of the ionic and radical properties, Precise control is difficult to achieve.

FIG. 2A is a diagram showing a schematic structure of the plasma processing apparatus 4 according to a second aspect of the present invention. The tapping position of the lower coil 6 is switched by the changeover switch 5 to change the inductance and the operating range of the lower coil 6. It is variable. Further, FIG. 2B is a diagram showing a schematic configuration of the plasma processing apparatus 7 according to claim 3, wherein the inductance of the lower coil 8 is arbitrarily set by a variable inductance circuit 9 coupled in parallel with the lower coil 8. It is variable. Further, FIG. 2C is a diagram showing a schematic configuration of the plasma processing apparatus 10 according to the fourth aspect, in which the tapping position changeover switch 11 and the variable inductance circuit 12 are used together.

[0012]

When the present invention is applied to ashing of a resist having a surface-hardened layer formed by ion implantation, for example, the plasma processing apparatus 4 using the adjusting means shown in FIG. explain. Lower coil 6
Is set to a position where the inductance is maximum (the lower end of the lower coil 6), and the processed substrate W is placed in the working space of the coil. Next, the reaction chamber 13 is evacuated to a high vacuum from the exhaust port 14 by a high vacuum evacuation system, and, for example, oxygen gas or a mixed gas of hydrogen and steam effective for peeling the surface hardened layer is kept at a predetermined pressure while maintaining a predetermined gas It is introduced from the inlet 15. When a predetermined high-frequency power is applied from the high-frequency power supply 16 in this state, plasma is generated in the working space of the helical antenna coil 18 extending from the upper coil 17 to the lower coil 6, and the processed substrate W is held in the plasma, so that ionicity is generated. The strong action facilitates the peeling of the surface-hardened layer.

If the surface hardened layer is peeled off after a predetermined time, the application of high frequency power is once stopped and the tapping position is set to a position where the inductance is minimized (lower coil 6).
To the upper side) of the processing substrate W so that the processing substrate W is not directly exposed to plasma. Next, high frequency power is applied again while the processing gas is kept at a predetermined pressure. In such a state, the resist peeling of the processed substrate W proceeds mainly by a radical reaction. As a result, it is possible to realize low-damage resist stripping that is less affected by charged particles such as ions.

As shown in FIG. 2B, the operation is also achieved in the case of the plasma processing apparatus 7 in which the inductance of the lower coil 8 is arbitrarily changed by the variable inductance circuit 9 connected in parallel to the lower coil 8. Similarly, the variable inductance circuit 9 enables continuous selection of ionic and radical ratios. The plasma processing apparatus 10 shown in FIG. 2C has the characteristics of the plasma processing apparatuses 4 and 7 shown in FIGS. 2A and 2B, and a plasma processing apparatus capable of more precise control is provided. Can be realized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an ashing device 19 shown as an example of the plasma processing apparatus according to claim 2 in which the tapping position of the lower coil is switched. In FIG. 1, the reaction chamber 20
Is made of transparent quartz and has a diameter of 350 mm. Exhaust system 23 is 4
The turbo molecular pump 21 of 50 liter / sec is used as the main exhaust pump, and the ultimate pressure is -10 ^-5 Torr. Further, a mechanical booster pump 22 is connected to the latter stage of the turbo molecular pump 21, and these two pumps 21,
The inside of the reaction chamber 20 is exhausted to a high vacuum through the exhaust port 24 by 21.

The helical antenna coil 25 is used in the reaction chamber 2
It is installed in a winding shape from the upper part to the lower part along the outer circumference of 0. And a series of helical antenna coils 25
Is divided into an upper coil 26 and a lower coil 27, and the divided position is set to a predetermined height from the wafer W (substrate) surface on the stage 28. Further, a changeover switch 29 (adjusting means) is connected to the lower coil 27, and the inductance of the lower coil 27 can be adjusted by switching the tapping position with the upper end or the lower end of the lower coil 27. .

A matching box 30 and a high frequency power source 31 are sequentially connected to the upper end of the upper coil 26. The high frequency power source 31 has a frequency of 400 kHz and a maximum output of 1.
The one with 5kW is used. A shower head 34 connected to the gas introduction system 32 via an introduction pipe 33 is installed above the reaction chamber 20.
The reaction gas is supplied from 4 into the reaction chamber 20.

A stage 28 is installed inside the reaction chamber 20 at a height substantially corresponding to the lower end of the lower coil 27, and a resist coated wafer W is held on the upper surface of the stage 28. There is. Here, the resist used as a sample is a P (phosphorus) high-dose ion-implanted resist, and the dose amount is 1 × 10 ¹⁶ / cm ² . Also,
The thickness of the resist is about 1 μm, of which the upper side is about 0.
The deterioration hardening layer has a thickness of about 3 μm.

When the resist ashing is performed using the apparatus having the above-mentioned structure, the reaction gas is H ₂ + H ₂ O within the range of the ashing conditions of the first step for peeling off the deteriorated hardened layer.
(Several to 10%), Reaction pressure is 10 to several 10 mTorr, Substrate temperature is 170 to 200 ° C., Applied high frequency power is several 100 W
And set. Then, within the range of the ashing condition of the second step for peeling off the non-altered layer, the reaction gas is O ₂ + H ₂ O (0
Flow rate of 100 to 300 sccm, reaction pressure of 10 to several tens of mTorr, substrate temperature of 170 to 200 ° C.,
The applied high frequency power is set to about 1kW.

As a result of performing ashing under these ashing conditions, 0.2 to 0.4 μm is obtained for the alteration hardened layer.
An ashing speed of m / min and 1-3 μm / min was obtained for the unaltered layer. Further, the surface appearance of the wafer after ashing was confirmed by observing the surface with a scanning electron microscope after ashing, with a good amount of residue.

In this embodiment, the lower coil 2
Although an example using the changeover switch 29 for switching the tapping position as the inductance adjusting means of 7 has been described, the present invention is not limited to this configuration, and as described above, the variable inductance circuit connected in parallel to the lower coil is used. Needless to say, the configuration used may be a combination of a changeover switch and a variable inductance circuit. Further, the present invention is not limited to the ashing device,
It is also possible to apply to other plasma processing apparatuses such as an etching apparatus and a deposition apparatus.

[0022]

As described above in detail, in the plasma processing apparatus according to the present invention, the helical antenna coil is divided into two, and the changeover switch for changing the tapping position of the lower coil and the lower coil are arranged in parallel. By adjusting the inductance of the lower coil by any one of the combined variable inductance circuit and the combined use of the changeover switch and the variable inductance circuit, the plasma acting on the substrate with only a single reaction chamber and high frequency power source can be adjusted. It enables control and selection of ionicity and radicality. As a result, a process that requires a combination of an ionic ashing reaction and a radical ashing reaction, such as peeling of a resist on which an altered hardened layer is formed by high-dose ion implantation, that is, ionic and radical It is possible to provide a plasma processing apparatus having a simple configuration and a low cost for both processes requiring plasma processing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an ashing device (plasma processing device) according to an embodiment of the present invention.

FIG. 2 is a diagram showing three examples of the inductance adjusting means of the lower coil in the plasma processing apparatus of the present invention.

FIG. 3 is a diagram showing a plasma generation state in a reaction chamber in the plasma processing apparatus.

[Explanation of symbols]

 1, 4, 7, 10 Plasma processing device 2, 13, 20 Reaction chamber 3, 18, 25 Helical antenna coil 5, 11, 29 Changeover switch 6, 8, 27 Lower coil 9, 12 Variable inductance circuit 17, 26 Upper coil 19 Ashing equipment (plasma processing equipment) W Wafer (substrate) P Plasma

Claims (4)

[Claims] 1. A plasma and its active species generated in the reaction chamber by a helical antenna coil installed in a winding shape from the upper part to the lower part along the outer circumference of a hemispherical reaction chamber made of a dielectric material In a plasma processing apparatus for acting on a substrate held below a room, the helical antenna coil is divided into an upper coil and a lower coil, and the inductance of the lower coil and the working range of the lower coil are arbitrarily set. A plasma processing apparatus, characterized in that adjustment means for adjusting is provided. 2. The plasma processing apparatus according to claim 1, wherein the adjusting unit includes a changeover switch for changing a tapping position of the lower coil. 3. The plasma processing apparatus according to claim 1, wherein the adjusting unit is composed of a variable inductance circuit connected in parallel to the lower coil. 4. The plasma processing apparatus according to claim 1, wherein the adjusting unit includes a changeover switch for changing a tapping position of the lower coil, and a variable inductance circuit connected in parallel with the lower coil. A plasma processing apparatus characterized by being configured in combination.