JPH04199708A - Plasma etching method - Google Patents

Abstract

PURPOSE:To enable a reduction of a reproducibility of a plasma etching to be suppressed, and to prevent a capability of a vacuum exhaust system from lowering, by cleaning the inside of a vacuum container through the plasma of CHF3 in the process before opening the vacuum container when introducing a substrate to be etched in the vacuum container, and by removing B2O3, and further, by reducing from the air the moisture to be stuck on B2O3 particles. CONSTITUTION:The inside of an etching container 1 is cleaned by a plasma, through discharging a reducing gas 7 in the container 1. Then, solid particles generated in the foregoing process are cleaned by the plasma of a CHF3 gas 8. Then, after providing a member 6 to be etched in the etching container 1, a plasma etching is applied to the member 6 to be etched by discharging the reducing gas 7, and the member 6 to be etched is taken out from the etching container 1, and further, these processes are performed successively. Thereby, the plasma etching method capable of removing B2O3 stuck on the insides of a vacuum container and vacuum exhaust system is obtained, and the plasma etching, which is stable in a long period of time, can be achieved.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention is applicable to GaAs, AQGaAs, InGaAs, etc.
This invention relates to a plasma etching method for semiconductor crystals such as As and InAQAg.

(Prior art) Halogen gas with high electronegativity and electron affinity is used for plasma etching of semiconductor crystals such as GaAs, AUGaAs, or InGaAs, and among them, BCQ and CQ2 are used because of the low boiling point of the reaction product. .

Since B(43 gas is a reducing gas, it is known to act as an agent for etching the native oxide film and removing oxygen from the residual gas, thereby preventing a decrease in the etching rate and a delay in the etching start time.

At the same time, the reducing action of BCQ3 mentioned above also works with boron dioxide (B20).
3). This B20. It adheres to the inner walls of vacuum containers or vacuum exhaust systems, etc., and is highly hygroscopic in the atmosphere, so it adsorbs moisture when opening and closing the vacuum container.

This moisture is also reduced to BCQ3 gas and B20.
continues to accumulate.

FIG. 4 shows the self-bias (VDC) after the start of etching using BC43 plasma.

This voltage is a negative bias generated on the cathode due to the difference in mobility between electrons and ions, and it changes depending on the plasma state. In a vacuum vessel to which a large amount of B2O3 has adhered, VDC rises after plasma discharge starts and takes a certain amount of time to stabilize. This is because BCff and plasma are used to remove moisture adsorbed by B2O3 by reduction action immediately after discharge. This variation in VDC depends on the amount of B, 0□ deposited, and therefore reduces the reproducibility of etching using BCQ and plasma. As an example, the etching depth after 5 minutes from the start of etching changes greatly as shown in FIG.

Furthermore, the etching surface is contaminated by B201 particles and the function of the vacuum evacuation device is deteriorated.

(Problems to be Solved by the Invention) As mentioned above, since moisture and oxygen are removed in plasma etching using DC (J3 gas), the reproducibility of etching is reduced due to B and 03 contamination generated thereby. Additionally, there is a serious problem that causes a decline in the functionality of the vacuum evacuation device.

The present invention has been made in consideration of the following circumstances, and an object of the present invention is to provide a plasma etching method capable of removing B2O3 attached to a vacuum container and a vacuum evacuation system.

[Structure of the invention]

(Means for Solving the Problems) The plasma etching method according to the present invention includes a step of discharging a reducing gas into an etching container and plasma cleaning the inside of the etching container, and then removing solid particles generated in the above step. A step of plasma cleaning, and then a step of placing the member to be etched in the etching container, discharging a reducing gas, performing plasma etching on the member to be etched, and taking out the member to be etched from the etching container are successively carried out. It is characterized by

(Function) In the present invention, when a substrate to be etched is introduced into a vacuum container, B2O3 is removed by performing CLLF and plasma cleaning before opening the vacuum container, so that B2O3 is removed from the atmosphere. Significantly reduces water adsorption on particles.

Therefore, B(, 1320 produced by the reduction action of Q3
3 Contamination is suppressed and B2O3 accumulation does not progress.

(Example) An example of the plasma etching method according to the present invention will be described below with reference to the drawings.

- Reactive Ion Etching with parallel plate reactors as an example;
FIG. 1 shows an etching apparatus applied to RIE (hereinafter abbreviated as RIE). In the RIE apparatus shown in FIG. 1, a substrate 6 to be etched is placed between an electrode 3-1- connected to a high-frequency power source 4 in a vacuum chamber 1, and plasma is generated between the substrate 6 and the ground electrode 2. A gas flow controller 7.8 is installed for introducing, for example, CHF3 gas together with the etching gas BCQ.

The etching method of the present invention is shown below.

First, a vacuum is drawn without placing a substrate to be etched, and then discharge is performed using plasma of BCR gas 7, which is referred to as plasma cleaning here. This dry discharge allows the reduction of BCQ and plasma to remove moisture and oxygen in the vacuum chamber 1, which impede etching.

Next, plasma cleaning is performed continuously using CHF3 gas 8. By this plasma cleaning, the above 13c
ρ is generated by the reduction action of
Decomposes and removes B2O3 adhering to the inner walls of etc. This B2
0. is decomposed by F radicals and F ions of CHF and is evacuated.

After this ClIF5 plasma cleaning, vacuum vessel 1
The substrate 6 to be etched is placed with the opening opened, and after vacuum cleaning is performed, BCQ3CH3 gas plasma etching is performed. At this time, since 8203 in vacuum container 1 has been removed, there is no moisture adsorbed by 8203 when the vacuum container is opened.

FIG. 2 shows an example of VOC after the start of plasma etching according to the present invention. CHF, B2O by plasma cleaning
3 is removed, it is clear that fluctuations in VDC caused by removal of moisture adsorbed by 8203 are suppressed. This is noticeable compared to FIG. 4, which shows the conventional example.

Figure 3 shows the change in the etching depth for each run (5 minutes after the start of plasma etching according to the present invention), but even if the number of runs is increased, the accumulation of B2O3 does not progress and the vDc always fluctuates. Since it was suppressed, etching could be performed with good reproducibility.

In this embodiment, etching in an RIE apparatus having a parallel plate reactor has been described, but the invention can also be applied to plasma etching in other plasma etching apparatuses.

Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, residual moisture and oxygen can be removed by the reducing action of BCΩ3, and the resulting B2O3 contamination can be removed at the same time, thereby suppressing a decrease in the reproducibility of plasma etching. In addition, it is possible to prevent the performance of the vacuum evacuation system from deteriorating, and stable plasma etching can be achieved over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an RIE apparatus used in an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the time change of self-bias (VDC) measured in an embodiment of the present invention = 7-. FIG. 3 is a diagram showing an example of the change in etching depth for each run 5 minutes after the start of etching by RIE in the embodiment of the present invention, and FIG. 4 is a diagram showing a conventional example corresponding to FIG. 2 above. , FIG. 5 is a diagram showing a conventional example corresponding to FIG. 3 above. l...Vacuum container 2...Ground electrode 3.
...Lower electrode 4...High frequency power supply 5...
Vacuum exhaust system 6...Substrate to be etched 7.
・BCQ3 gas flow rate controller 8... CHF3 gas flow rate controller agent Patent attorney Oku NorifuμikσA) Figure 5

Claims (1)

[Claims] A step of plasma cleaning the inside of the etching container by discharging a reducing gas into the etching container, then a step of plasma cleaning the solid particles generated in the step, and then placing a member to be etched in the etching container. A plasma etching method in which the steps of subsequently performing plasma etching on the member to be etched by discharging a reducing gas and taking out the member to be etched from the etching container are successively performed.