JPS59175727A - Plasma etching apparatus - Google Patents

Abstract

PURPOSE:To uniform the physical characteristics of semiconductor wafer at the holding place and obtain the uniform etching characteristic by disposing the coolant path not only to the circumferencial side of lower electrode but also at the center side thereof. CONSTITUTION:A coolant path 23 is guided to the area near the circumference of electrode 21 along the circumference of semiconductor wafer holding place 221 from the coolant path entrance 23a provided at the center of lower electrode 21 and it is thereafter disposed along the external half circumference of the wafer holding positions 221-226. Moreover, the path 23 is folded to the inside along the circumference of the holding position 226 and then extended along the internal half circumference of the holding positions 226-221. Thereafter, it is disposed so that it is fed back to the coolant path exit 23b provided at the center of electrode 21. Since the path 23 is almost symmetrically disposed respectively to the holding places 221-226, the physical characteristics are uniformed within the range of respectively holding positions 221-226 and uniformly of etching rate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in plasma etching equipment used for manufacturing semiconductor devices such as ICs and LSIs.

[Technical background of the invention]

FIG. 1 is a sectional view showing an example of a conventional plasma etching apparatus. In the figure, 1 is a vacuum container made of stainless steel. An upper electrode 2 and a lower electrode 3, which constitute parallel plate electrodes, are arranged to face each other so as to form a part of the vacuum vessel 1. The upper and lower electrodes 2 and 3 are electrically insulated from the vacuum vessel 1 and the Teflon rings 4 and 5. Further, a gas introduction pipe 6 is connected to the upper electrode 2, and an exhaust pipe 7 is provided to the vacuum vessel 1, which is connected to an exhaust system having, for example, an oil diffusion pump and a rotary pump. On the other hand, a high frequency power source 8 is connected to the lower electrode 3, and the upper electrode 2 and the vacuum vessel 1 are grounded. Further, a carbon susceptor 9 is provided on the first lower electrode 3, and a semiconductor wafer 10 to be etched is placed on the susceptor 9. The reason why the susceptor 9 is provided is to prevent heavy metal contamination of the semiconductor wafer 10. A water cooling pipe 11 for cooling is provided on the lower surface of the lower electrode 3, and a similar water cooling pipe 12 is also provided on the upper electrode 2.
is installed.

When using the above-mentioned plasma etching apparatus, 4 fathoms of CF reaction gas introduced into the vacuum vessel 1 from the gas introduction pipe 6 is turned into plasma by the high frequency electric field between the parallel plate electrodes 2 and 3, and the plasma gas is applied to the semiconductor wafer 12. After reacting with the etching force, it is discharged from the system through the exhaust pipe 7.

Incidentally, in the conventional plasma etching apparatus described above, the water cooling pipe 11 on the lower surface of the lower electrode 3 is arranged as shown in FIG. As shown in the figure, a plurality of semiconductor wafers 10 are placed along the inner side of the periphery of the lower electrode 3.

Then, the water-cooled pipe 11 is installed in the radial direction of the internal electrode 3 from the water-cooled pipe inlet 11a provided at the center of the lower electrode 3, and is piped along the outer half circumference of the semiconductor wafer 10. The cold water pipe is arranged so as to return to the cold water pipe outlet 11b provided at the center of the pipe. Therefore, the cold water pipe 11 is not provided in the inner half circumference of the semiconductor wafers 10 .

[Problems in the Background Art] As described above, in the conventional plasma etching apparatus, the cold water pipes 11 on the lower surface of the lower electrode are arranged asymmetrically at the mounting position of the semiconductor wafer. The physical characteristics of the wafer were non-uniform between the peripheral edge of the electrode where the cold water pipe 11 was not provided and the center side of the electrode where the cold water pipe 11 was not provided. In this case, the physical characteristics that cause non-uniformity include not only the temperature but also the impedance of the lower electrode 3 due to the influence of water in the cold water pipe 1. For this reason,
Ueno - Since the potential distribution in the vicinity of the mounting position is non-uniform, the etching speed of the semiconductor wafer differs between the outer peripheral side and the center side of the lower electrode 3, and there is a problem that uniform etching cannot be performed. Ta.

[Purpose of the invention]

The present invention was developed in view of the above circumstances, and it is possible to improve the arrangement pattern of the coolant passages in the lower electrode to uniformize the physical characteristics at the semiconductor wafer mounting position, thereby obtaining uniform etching characteristics. A plasma etching apparatus is provided.

[Summary of the invention]

The plasma etching apparatus according to the present invention is a parallel plate in which a plurality of semiconductor wafers are simultaneously placed on a lower electrode provided with a refrigerant passage for cooling via a susceptor, and the semiconductor wafers are plasma etched. The plasma etching apparatus is characterized in that the coolant passage is disposed not only on the periphery side of the lower electrode but also on the center side along the periphery of the semiconductor wafer 1-mounting position.

In the plasma etching apparatus of the present invention, the symmetry of the refrigerant passage at the semiconductor wafer mounting position is improved, so that physical characteristics can be made uniform, and therefore uniform etching characteristics can be obtained.

[Embodiments of the invention]

Hereinafter, a non-embodiment of the plasma etching apparatus according to the present invention will be described.

FIG. 3 is a plan view showing an arrangement pattern of coolant passages in a lower electrode in a plasma etching apparatus according to an embodiment of the present invention. In the figure, 21 is a lower electrode, and 22+ to 22 degrees are mounting positions for the semiconductor wafer. The refrigerant passage 23 is connected from the refrigerant passage 23h provided at the center of the lower electrode 21 to the semiconductor mounting position 221.
After being drawn out to the vicinity of the periphery of the lower electrode 21 along the periphery of the wafer, they are arranged in a wavy manner along the outer half of the wafer mounting positions 21+ to 226.

Furthermore, the coolant passage 23 is turned inward along the periphery of the wafer placement position 2211, and this time the coolant passage 23
The refrigerant passage outlet 23bFC is disposed at the center of the lower electrode 21 and returns to the refrigerant passage outlet 23bFC.

The plasma etching apparatus of this embodiment has a lower electrode 21
The structure is similar to that of the conventional plasma etching apparatus shown in FIG. 1, except that the coolant passage 23 is arranged as described above.

An example in which the plasma etching apparatus of the above embodiment is applied to etching a semiconductor wafer will be described.

First, an etching sample shown in FIG. 4 was prepared. That is,
The surface of a single crystal wafer 31 with a diameter of 4 inches was thermally oxidized to form an oxide film 32 with a thickness of 1000X. Subsequently, a polycrystalline silicon layer was deposited by low pressure vapor deposition (LPGVD) using 7 runs (5in4) of thermal decomposition (750°C), and then further deposited to a film thickness of 6000°C by diffusing phosphorus at 1000°C.
Seven layers 33 of n-type polycrystalline silicon of X were formed. Next, an I-shaped di-ZF turn 34 was formed to serve as an etching mask.

The thus produced etching sample shown in FIG. 4 was etched using the plasma etching apparatus of the above embodiment and a conventional plasma etching apparatus. In either case, the etching conditions are as follows.

・Reactive gas ct2: 20 SCCM H2: 6 SCCM ・Pressure 10 Pa ・Applied power 13.56 MHz t 0.25 W/cm2・
Etching time: 3 minutes After the above plasma etching, the etched sample was treated with a mixture of sulfuric acid and hydrogen peroxide solution.
After removing the turn 34, the film thickness in the etched region of the polycrystalline silicon layer 33 is measured using a crystal step.
The etching rate was also determined by the film thickness. FIG. 5 and Table 1 show the results of the etching test.

Table 1 Note that FIG. 5 shows the etching speed of the center of the lower electrode and the etching mask position.
This corresponds to points A and B in the figure and FIG.

From this test result, in the plasma etching apparatus of the above-mentioned embodiment, the coolant passage 23 is located at the semiconductor wafer mounting position 2.
2. Since the wafers are arranged substantially symmetrically with respect to each of the wafer placement positions 22. It was revealed that the physical properties were made uniform within the range of ~226, and the uniformity of the etching rate was improved.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to obtain remarkable effects such as uniformity of physical characteristics in a plasma etching apparatus, thereby suppressing variations in etching speed.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of conventional plasma etching, and FIG. 2 is an illustration of cold water pipe arrangement at the lower electrode of a conventional plasma etching apparatus. Plan view showing turn, 3rd
The figure is a plan view showing a coolant passage arrangement pattern in a lower electrode of a plasma etching apparatus according to an embodiment of the present invention;
Fig. 4 is a cross-sectional view showing the sample used in the etching test, and Fig. 5 shows a comparison of the results of etching tests conducted on a plasma etching apparatus according to an embodiment of the present invention and a conventional plasma etching apparatus. It is a line diagram. 2 No. Lower electrode, 221 to 226 Semiconductor wafer placement position, 23 Coolant passage, 23a Coolant passage inlet, 23b Coolant passage outlet. Applicant's agent Patent attorney Takehiko Suzue No. 211 @ 311 No. 4 - Figure 5

Claims (1)

[Claims] In a parallel plate plasma etching apparatus, a plurality of semiconductor wafers are simultaneously placed on a lower electrode provided with a refrigerant passage for cooling via a car sensor segmenter, and the semiconductor wafer is plasma etched. A plasma etching apparatus characterized in that the lower electrode is disposed along the periphery of the semiconductor wafer mounting position not only on the periphery side but also on the center side.