JPS62173723A - Plasma treater - Google Patents

Abstract

PURPOSE:To absorb a surge and the like by the abnormal discharge of plasma, to inhibit the local potential fluctuation of the surface of a sample and to equalize ion-electron distribution on the surface of the sample by arranging an electrode insulated from a substrate electrode near the outer circumferential section of the sample. CONSTITUTION:An electrode 16 is mounted around a substrate electrode 5 so as to surround a sample 14. Consequently, a surge and the like by the abnormal discharge of plasma are absorbed by the electrode 16 disposed near the outer circumferential section of the sample, the partial potential fluctuation of the surface of the sample is inhibited by the presence of the electrode 16 and the potential of the surface of the sample 14 is kept constant, and locally high ion-electron distribution resulting from the line of magnetic force and the like is equalized approximately on the surface of the sample. Accordingly, damage generated in the sample can be reduced largely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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.

[Conventional technology]

Various plasma application technologies have been developed to realize miniaturization and higher density of LSIs. Examples of devices for forming films include plasma CVD devices, sputtering devices, and ECR (electron cyclotron resonance) devices. recently,
A bias application technique that applies a high frequency voltage to a substrate on which a sample is placed in an apparatus for forming these films and performs etching at the same time as film formation is attracting attention. Among them, bias sputtering technology (C, Y, Ttng: rStudy of
planarized sputter-deposit
ed 5iOJ J, Vac, Sci,, Techno
l.

15, May/June 1978. pp1105~
1112) and bias ECR technology (K, Machida
and H, Oikawa: rNew Plana
rtzation Technology tlsin
g Bias-ECRPlasmaDepositio
nJ Extended Abstracts of
the Conference on SSDM, To
kyo, 1985. pp329-332) are the main focus. These methods involve forming a flat insulating film on the uneven surface on which electrodes and wiring are formed on a semiconductor substrate, and forming a metal in contact holes formed on the insulating film to draw out the wiring. etc. can be easily embedded. For this reason, these technologies
It is believed that this will become one of the most important technologies for future VLSI production.

FIG. 6 is a schematic side sectional view showing a conventional bias sputtering apparatus. 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
1 is a gas introduction mechanism for introducing sputtering gas, and 15 is a valve thereof.

The target 4 and the substrate electrode 5 are surrounded by a shield plate 8.9 electrically connected to the film forming chamber l. The film forming chamber 1 is grounded, and the target 4 is connected to the RF matching box 1.
0 and an RF power source 12, the substrate electrode 5 is grounded through an RF matching box 11 and an RF power source 13, respectively. To operate this apparatus, 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 sputtering gas into the film forming chamber 1 to a predetermined pressure. Thereafter, when the RF power source 12 is turned on, RF power is applied to the target 4 to generate plasma, and the plasma sputters the target 4 to deposit a desired thin film on the sample 14. on the other hand,
When the RF power #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 source such as RF, 22 is a substrate electrode, 23 is a plasma generation chamber, 24 is a film forming chamber, 25, 26 is a gas introduction mechanism, and 27 is a quartz plate. In this apparatus, 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 the magnet coil 2.
The substrate electrode 22 is transported to the film forming chamber 24 by the magnetic field generated by 9.
Film deposition is performed on the sample 28 placed above. 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 the case of this device as well, as in the case of the bias sputtering device described above, by applying RF lightning voltage to the substrate electrode 22, the sample 2 is
8 is etched with ions.

[Problem that the invention seeks to solve]

However, in a bias sputtering apparatus as shown in FIG. 6, when a quartz plate is used as the target 4 and a semiconductor element including an AI wiring is mounted on a Si wafer as the sample 14, the Large deformations occurred in some parts, and in severe cases, melting occurred. In addition, in the same apparatus, a quartz plate was used as the target 4, and a polycrystalline Si MOS capacitor with a gate oxide film of 200 mm thick was formed on the Si wafer as the sample 14. 3.5 to target 4
After depositing 1.5 μm of Sing by applying a 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 in that the oxide film was destroyed and the gate leakage yield decreased significantly.

Table 1 In addition, in a bias sputtering apparatus as shown in FIG. 7, a polycrystalline silicon gate MOS in which a gate oxide film with a thickness of 200 mm was formed on a Si wafer was used as sample 28.
Using a device equipped with a capacitor, RF is applied to the substrate electrode 22.
Gate leakage also occurred when film deposition was performed while applying an electric field. In the graph of FIG. 3, the relationship between the RF power applied to the substrate electrode 22 at this time and the gate leakage yield is shown by the circle mark. In the figure, the horizontal axis is the RF power applied to the substrate electrode 22, and the vertical axis is the gate leakage yield. The gate area was 500 μm square, and a leakage current of 10 nA or less was considered a good product.

The problem with such conventional equipment is that the damage to the semiconductor element, which is the sample, is usually caused by damage to the substrate electrode.
Since a high voltage of W/ci or more is applied, it has been thought that there is a strong correlation with the voltage applied to the substrate electrode, and it was thought that the higher the applied voltage, the more fatal the damage. However, on the other hand, in a cylindrical plasma device, which is one type of etching device, the potential applied to the sample is about the same as the plasma potential, and even in RIB (reactive ion etching), which has the largest electric field applied to the sample, o, Even though it was about iW/cIa, damage sometimes became a problem. Based on these facts, the inventor of the present application conducted intensive research and found that the damage to the sample in the conventional apparatus shown in FIGS. 6 and 7 is not directly related to the applied voltage; (2) Large changes in the potential distribution within the sample surface or at the edge of the sample; (3) Local damage caused by magnetic field lines for moving ions, etc. It was determined that the cause was high ion distribution, high electron distribution, or a combination of these.

[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.

[Effect]

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 along with examples.

FIG. 1 is a schematic side sectional view showing an embodiment of the present invention applied to a bias sputtering device, and the same components as those in the bias sputtering device of FIG. The explanation will be omitted.

In the apparatus of this embodiment, an electrode 16 is provided around the substrate electrode 5 so as to surround the sample 14, and this point differs from the conventional apparatus 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. Opening 16' of electrode 16
is wider than the sample 14, and the electrode 16 is arranged so that the sample 14 fits inside the opening 16' when viewed from above. 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, the electrode 16
MO is used as the material.

In such a configuration, film formation was performed using a quartz plate as the target 4 and a sample 14 in which a semiconductor element including At wiring was mounted on a Si wafer. That is, similarly to 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 sputtering gas into the film forming chamber 1 to a predetermined pressure. Thereafter, the RF power source 12 is turned on and RF main 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, turn on the RF power source 11 to apply RF to the substrate electrode 5.
By applying main power, the sample 14 is sputter-etched to form a desired film. At this time, regardless of the open/closed state of the switch 18, no melting of the At wiring was observed.In other words, even when the electrode 16 was electrically floated to a plasma potential, a voltage of about 0 to several V was applied to the electrode 16. Even when .

Next, with the switch 18 open, a polycrystalline StGa 1-M0 S capacitor on which a gate oxide film of 100 nm thick is formed on a Si wafer is used as a sample, and a After applying .5KW RF main power and depositing 1.5μm thick 5iOz,
Table 2 shows the gate yield when etching was performed by applying 0.6 KW of RF main power to the substrate electrode 5.

It can be seen that although the thickness of the gate oxide film is very thin at 100 nm, there is almost no decrease in yield even when the gate area becomes large. Furthermore, even when the electric power applied to the substrate electrode 5 was increased to 1.5 KW, no tendency for damage to increase was observed.

FIG. 2 is a schematic side sectional view showing an embodiment in which the present invention is applied to a bias ECR device, and the same components as the bias ECR device in FIG. In the device of the third embodiment, the explanation of which will be omitted, the substrate electrode 22
A flat ring-shaped electrode 30 is provided on a quartz plate 27 to surround the sample 28, and this point is different from the conventional apparatus shown in FIG. The electrode 30 is the insulator 3
1, it is electrically insulated from the film forming chamber 24 and grounded via a switch 32 and a variable voltage source 33.

In this embodiment, an Al plate is used as the material for the electrode 30.

In such a configuration, film formation was performed using a sample 28 equipped with a polycrystalline silicon gate MOS capacitor in which a gate oxide film with a thickness of 200 mm was formed on an St wafer. That is, like the conventional apparatus shown in FIG. 7, 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. These ions are transported to the film forming chamber 24 by the magnetic field of the magnet coil 29, and the substrate electrode 2
Film deposition is performed on the sample 28 placed on the sample 2 .

Then, by applying an RF lightning voltage to the substrate electrode 22, the sample 28 is etched with ions.

FIG. 3 shows the gate leakage yield of sample 28 in which the film was formed in this manner. The symbol Δ indicates the case where the switch 32 is closed and the electrode 30 is grounded, and the symbol .DELTA. indicates the case where the switch 32 is opened and the electrode 30 is electrically drained. For example, when the RF main power is 400 W, the conventional device shown in FIG. 5 has a yield of about 20%, whereas in this embodiment, when the electrode 30 is grounded,
The yield was over 50%. Further, in this example, when the electrode 30 was used, a high gate leakage yield of about 80% was obtained even when a high RF power of 500 W was applied.

In the above two embodiments, the electrodes 16 and 30 are both formed integrally, but as shown in FIG.
d (16d) may be collected near the outer periphery of the sample 28 (14) and electrically connected to each other. Furthermore, as shown in FIG. 5, the planar shape may have a rectangular outer circumference and a circular inner circumference. Further, in the above embodiment, the center of the inner circumference and the center of the wafer coincide, but they may be unevenly distributed to some extent.

In addition, in the above two embodiments, the present invention is applied to a bias sputtering device and a bias ECR device, respectively, but a high frequency electric field is applied to a substrate electrode in plasma, and a sample placed on the substrate electrode is The present invention can be applied to various other plasma processing apparatuses as long as they perform etching.

〔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. As a result, the potential on the sample surface is kept constant, and the locally high distribution of ions and electrons caused by magnetic lines of force etc. is made 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, which had problems with poor yield due to damage,
Technology can be brought to a practical stage. In addition, these bias application techniques perform film deposition and etching at the same time, which reduces the relative film deposition rate and reduces 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. 39 is a graph showing the relationship between RF power applied to the substrate electrode 22 and gate leakage yield, FIGS. 4 and 5 are plan views showing an example of the electrode 30 or 16, and FIG. 6 is a conventional bias sputtering device. FIG. 7 is a schematic side sectional view showing a conventional bias ECR device. 5.22... Substrate electrode, 13.21... RF main power supply 14.28... Sample, 16.30... Electrode. Patent applicant: Nippon Telegraph and Telephone Corporation Agent: Masaki Yamakawa (1 idiot) Figure 3 RF power CW)

Claims (1)

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