JPH0334208B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a plasma processing apparatus that performs film formation or etching by applying a high frequency electric field to a substrate electrode on which a sample is placed in plasma. [Prior Art] Various plasma application technologies have been developed to realize miniaturization and higher density of LSIs. Examples of devices that form films include plasma CVD devices, sputtering devices, and ECR (electron cyclotron resonance) devices. Recently, high-frequency voltage is applied to the substrate on which the sample is placed in these film-forming devices.
Bias application technology that performs etching at the same time as film formation is attracting attention. Among them, bias sputtering technology (CYTing: ``Study of planarized''
sputter−deposited SiO ₂ ” J.Vac.Sci.,
Technol., 15, May/June 1978, pp1105~
1112) and bias ECR technology (K. Machida and
H.Oikawa: “New Planarization Technology
Using Bias−ECR Plasma Deposition”
Extended Abstracts of Conference on
SSDM, Tokyo, 1985, pp329-332) is attracting attention. These methods involve forming a flat insulating film on the uneven surface of a semiconductor substrate on which electrodes and wiring are formed, or depositing metal, etc. into contact holes formed on the insulating film to draw out the wiring. It can be easily embedded.
For this reason, these technologies are considered to be one of the most important technologies for future VLSI production. FIG. 6 is a schematic side sectional view showing a conventional bias sputtering device. Reference numeral 1 denotes a film forming chamber in which film forming and etching are performed, and is connected to a vacuum pump via an exhaust system 2. 3 is a gas introduction mechanism for introducing sputter gas, and 15 is a valve thereof.
The target 4 and the substrate electrode 5 are surrounded by shield plates 8 and 9 electrically connected to the film forming chamber 1. The film forming chamber 1 is grounded, the target 4 is connected to the RF matching box 10 and the RF power source 12, and the substrate electrode 5 is connected to the RF matching box 11 and the RF power source 1.
3 and are respectively grounded. To operate this device, first 1
4 is set on the substrate electrode 5. Then valve 1
5 is opened and sputter gas is introduced into the film forming chamber 1 to a predetermined pressure. After that, RF power supply 12
When turned on, RF power is applied to the target 4 to generate plasma, which sputters the target 4 to deposit a desired thin film on the sample 14. On the other hand, when the RF power source 11 is turned on, RF power is applied to the substrate electrode 5 and the sample 14 is sputter etched. FIG. 7 is a schematic side sectional view showing a conventional bias ECR device. 21 is a bias power supply such as RF,
22 is a substrate electrode, 23 is a plasma generation chamber, 24 is a film forming chamber, 25 and 26 are gas introduction mechanisms, and 27 is a quartz plate. In this device, first, active or inert gas is introduced into the plasma generation chamber 23 from the gas introduction mechanism 25, and ions are generated using microwaves or the like. Then, these ions are transferred to magnet coil 2.
The sample 28 is transported to the film forming chamber 24 by the magnetic field generated by the sample 9 , and a film is deposited on the sample 28 placed on the substrate electrode 22 . Note that in this case, film formation may be performed by supplying other gases or the like from the gas introduction mechanism 26 provided in the film forming chamber 24. In this device, as in the case of the bias sputter device described above, the substrate electrode 22
By applying an RF voltage to the sample 28, the sample 28 is etched by ions. [Problems to be Solved by the Invention] However, in a bias sputtering apparatus as shown in FIG. 6, a quartz plate is used as the target 4, and a semiconductor element including A1 wiring is mounted on a Si wafer as the sample 14. When using something, A
Part of one wiring was severely deformed, and in severe cases, it was blown out. In addition, in the same device,
A quartz plate was used as the target 4, and a polycrystalline Si gate MOS capacitor with a gate oxide film of 200 Å thick formed on a Si wafer was used as the sample 14.
After depositing 1.5 μm of SiO ₂ by applying a 3.5 KW RF electric field, when etching was performed by applying a 0.6 KW RF electric field to the substrate electrode 5, as shown in Table 1, as the gate area became larger, the gate There was a problem that the oxide film was destroyed and the gate leakage yield decreased significantly.

[Means for solving problems]

The plasma processing apparatus of the present invention has been developed in view of the above-mentioned problems, and includes an electrode that is electrically insulated from the substrate electrode and arranged near the outer periphery of the sample. [Operation] Surges caused by abnormal discharge are absorbed by the electrodes placed near the outer periphery of the sample. In addition, the presence of this electrode suppresses local potential fluctuations on the sample surface, keeping the sample surface potential constant, and furthermore, the locally high ion and electron distribution caused by magnetic field lines is almost uniform on the sample surface. become. [Example] Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 1 is a schematic side sectional view showing an embodiment of the present invention applied to a bias sputtering device.
Components that are the same as those of the bias sputtering device shown in FIG. 6 are given the same reference numerals and detailed explanations will be omitted. In the apparatus of this embodiment, a sample 1 is placed around the substrate electrode 5.
An electrode 16 is provided so as to surround 4,
This point is different from the conventional device shown in FIG. This electrode 16 has a bottomed cylindrical shape with an opening at the center of the bottom surface, and covers the substrate electrode 5 in an inverted state. The opening 16' of the electrode 16 is wider than the sample 14, and the electrode 16 is larger than the sample 14 when viewed from above.
is arranged so as to fit inside the opening 16'. Further, the electrode 16 is electrically insulated from the film forming chamber 1 by an insulator 17, and is grounded via a switch 18 and a variable voltage source 19. In this embodiment, Mo is used as the material for the electrode 16. In this configuration, a quartz plate is used as the target 4, and A1 is placed on the Si wafer as the sample 14.
Film formation was performed using a device equipped with a semiconductor element including wiring. That is, as in the conventional apparatus shown in FIG. 6, first, a sample 14 on which a thin film is to be deposited is set on the substrate electrode 5. Then, the valve 15 is opened to introduce sputter gas into the film forming chamber 1 to a predetermined pressure. Thereafter, the RF power source 12 is turned on, RF power is applied to the target 4 to generate plasma, and the target 4 is sputtered to deposit a film on the sample 14. While performing such film deposition, on the other hand, the RF power supply 11 is turned on.
By applying RF power to the substrate electrode 5, the sample 14 is sputter etched to form a desired film. At this time, no melting of the A1 wiring was observed regardless of whether the switch 18 was open or closed. That is, neither when the electrode 16 was electrically floated to a plasma potential nor when a voltage of about 0 to several volts was applied to the electrode 16, the A1 wiring was not fused as in the conventional case. Next, with the switch 18 open, a polycrystalline Si gate MOS capacitor with a gate oxide film of 100 Å thick formed on a Si wafer is used as a sample, and a sample is placed on the target 4.
Table 2 shows the gate yield when RF power of 3.5 KW was applied to deposit SiO ₂ to a thickness of 1.5 μm, and then etching was performed by applying RF power of 0.6 KW to the substrate electrode 5.

〔Effect of the invention〕

As explained above, according to the plasma processing apparatus of the present invention, surges caused by abnormal discharge are absorbed by the electrode placed near the outer periphery of the sample, and local potential fluctuations on the sample surface are suppressed by the presence of this electrode. The potential on the sample surface is kept constant, and
The locally high distribution of ions and electrons caused by lines of magnetic force becomes almost uniform on the sample surface. Therefore, regardless of the power applied to the substrate electrode on which the sample is placed, damage to the sample can be significantly reduced. As a result, bias sputtering technology and bias ECR technology, which had problems with poor yields due to damage, can be brought to a practical stage. In addition, these bias application techniques perform film deposition and etching at the same time, resulting in a low relative film deposition rate and a reduction in throughput, which is another major practical problem. This makes it possible to significantly improve throughput.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view showing an embodiment in which the present invention is applied to a bias sputtering device, and FIG. 2 is a schematic side sectional view showing an embodiment in which the present invention is applied to a bias ECR device. , FIG. 3 is a graph showing the relationship between the RF power applied to the substrate electrode 22 and the gate leakage yield, FIGS. 4 and 5 are plan views showing an example of the electrode 30 or 16, and FIG. 6 is a graph showing a conventional bias spacing. a schematic side sectional view showing the ivy device;
FIG. 7 is a schematic side sectional view showing a conventional bias ECR device. 5, 22... Substrate electrode, 13, 21... RF power supply, 14, 28... Sample, 16, 30... Electrode.

Claims (1)

[Claims] 1. In a plasma processing apparatus that applies a high frequency electric field to a substrate electrode in plasma and forms a film or etches a sample placed on the substrate electrode,
A plasma processing apparatus characterized in that an electrode electrically insulated from the substrate electrode is arranged near the outer periphery of the sample.