JPS61135126A - Equipment of plasma treatment - Google Patents

Abstract

PURPOSE:To enable forming a thin film at a low temperature and at a great speed by again squeezing a plasma flow which is expanding at the position of a sample with the magnetic field formed by an electromagnet or a permanent magnet provided at the opposite side of a plasma source against the sample. CONSTITUTION:A microwave generated from a magnetron 11 is guided to a discharge tube 14 through an isolator 12 and a power monitor 13. An electron which resonates and is absorbed by an electron which makes a cyclotron motion by the magnetic field formed with an electromagnet 15 excites, dissociates and ionizes an reactive gas introduced in a vacuum container 16 from a reactive gas source 17 and makes plasma. A plasma flow is carried along the line of magnetic force and arrives at a substrate 19. An electromagnet 20 is provided at the back of the substrate 19 against the plasma flow and is so excited that the direction of the magnetic field is the same with that of the electromagnet 15. The plasma flow is carried by the line of magnetic force formed with the electromagnet 15 and is going to be gradually expanded from a beam state but the electromagnet 20 can squeeze the expanding plasma flow again at near the substrate 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a plasma processing apparatus, and in particular, to directly react a chemically active plasma stream with a metal atomic stream to form a metal compound on a substrate to be processed. The present invention relates to a plasma processing apparatus suitable for depositing.

[Background of the invention]

In the manufacture of ICs and LSIs, insulating films such as 5102 and Si3N4 are often used as interlayer insulating films, charge storage insulating films, and gate insulating films.
Conventionally, CVD (Chemical Vapor Dep.
High-temperature processes such as the oxidation method and the thermal oxidation method are used. However, this method requires high-temperature heat treatment at nearly 100°C, so it cannot be applied to places where high-temperature heat treatment is not preferred, such as the final process of LSI manufacturing. This process cannot be applied to

To address the shortcomings of such high-temperature CVD processes,
Recently, plasma CVD using reactive gas plasma has been developed.
(hereinafter referred to as PCVD) technology is attracting attention. This involves simultaneously supplying a reactive gas containing Si as a component atom, such as monosilane (St H4), and gases such as oxygen, nitrogen, and ammonia into a container made of stainless steel, etc. This is a technique in which plasma is generated by applying a high electric field of direct current or alternating current from the outside while keeping the gas in a diluted state, and deposits Si 2 O, Si3N4, etc. on the substrate. Using this PCVD method, it is possible to form an insulating film at a temperature near room temperature, but a serious drawback of the formed film is that it contains a large amount of hydrogen. This hydrogen is 5IH4 and NH3
It is produced as a byproduct when PCV decomposes, and is easily released outside the film in high-temperature CVD methods, but
In method D, since the substrate temperature is low, it remains in the film. Hydrogen in this film becomes a trap source for electrons injected into the insulating film, causing fluctuations in flat band voltage and threshold voltage. In particular, as devices become increasingly finer and insulating films become thinner, electrons are more likely to be injected, and hydrogen in the film becomes a serious problem for the long-term reliability of devices.

By the way, "Plasma enhanced beam d" by R. P. H. Chang et al. of Bell Laboratories.
position of thin films a
low temperatures', J, Va
c, Sci+Techno1. B 1 (4),
Oct.-Dec., 1983. According to a document titled p935, a method known as the activated reactive vapor deposition method is used, in which a reaction gas containing no elements other than those forming the thin film is turned into plasma, and this is used to deposit metal (semiconductor).
Using a method that generates a compound by reacting with steam, 5i
n2. It has been reported that by forming a thin film such as Aut03, an insulating film containing almost no impurities such as hydrogen and having good electrical characteristics can be obtained.

Figure 2 shows the apparatus used by Chang et al. (J, Va
c.

Sci, Technol, Vol. 14.
NcLl + Jan, /Feb, 197L p27
8) In the figure, the plasma source 21 has an elongated column-like shape and is independent from the sample processing chamber 22. Around and in the center of this column are electrodes for RF excitation (not shown).
An electromagnetic coil 23 is provided on the outside for creating an axial magnetic field. The plasma generated in the plasma source 21 is confined by this magnetic field and guided to the sample processing chamber 22.

In this device, although spatter on the wall of the plasma source tube is suppressed by the confining magnetic field, the plasma flow spreads in the chamber of the sample processing chamber, the plasma sputters on the chamber wall, and the material flying from the wall covers the sample. There is a concern that it will be contaminated. In addition, since it is necessary to move the evaporation source away from the sample to avoid interference with the plasma, the deposition rate is 15A/1 in the case of a Sin film.
It is suppressed to min.

[Object of the Invention] The object of the present invention is to eliminate sample contamination due to tube wall spatter;
Another object of the present invention is to provide a plasma processing apparatus that can form a thin film at a high temperature and at a high temperature.

[Summary of the invention]

In the activated reactive vapor deposition method using plasma, the third
As shown in the figure, a plasma source 32 and an evaporation source 31 are used at the same time, and the most important technical challenge is to eliminate their interference. That is, when an electron beam heating type is used as an evaporation source, a high voltage of 4 to 10 is applied to the electrode portion of the evaporation source, making it impossible to operate in a plasma atmosphere. Furthermore, if metal (semiconductor) vapor is irradiated onto the plasma source side, the discharge may become unstable.

As a countermeasure to the above problem, it may be possible to spatially separate the plasma source and the evaporation source, but in that case, both would necessarily be far from the sample 33, and the chamber wall would be affected by the spread of the plasma flow. This results in a decrease in sputtering and deposition rate.

Therefore, in the present invention, in addition to the electromagnet for magnetic confinement on the plasma source side, an electromagnet or a permanent magnet is provided on the opposite side of the sample from the plasma source, and the magnetic field formed by the electromagnet is used to suppress the plasma flow that is about to spread at the sample position. The structure is to narrow it down again. With this configuration, the plasma becomes a stable beam, which suppresses tube wall sputtering and interference of the plasma with the evaporation source, making it possible to solve the above-mentioned problems.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a block diagram of a plasma processing apparatus having a magnetic field microwave plasma source in which the present invention is implemented.

In the figure, 2) 45G generated from magnetron 11
The Hz microwave is guided to the discharge tube 14 through an isolator 12) and a power monitor 13, and is resonantly absorbed by electrons moving in a cyclotron due to a magnetic field formed by an electromagnet 15. The electrons that have obtained energy from the microwave excites the reactive gas introduced into the vacuum container 16 from the reactive gas source 17, dissociate and ionize it, and create plasma. The plasma flow is transported along magnetic lines of force formed by the electromagnet 15, reaches the substrate 19, reacts with metal vapor irradiated from the electron beam heating evaporation source 18, and performs plasma processing on the substrate.

Reference numeral 20 is an electromagnet that is a feature of the present invention, and the substrate 1
It is provided behind the plasma source 9 and is excited so that the direction of the magnetic field is the same as that of the electromagnet 15. As mentioned above, the plasma flow is transported by the magnetic lines of force formed by the electromagnet 15, and the beam shape gradually tries to spread, but by providing the electromagnet 20, the plasma flow that is about to spread near the substrate 19 can be stopped. You can narrow it down again.

In the above embodiment, an electromagnet is used to form the magnetic field that constricts the plasma, but it is clear that a permanent magnet may be used instead of the electromagnet.

Next, a specific example of processing performed using the plasma processing apparatus according to the present invention will be described.

Processing Example 1: First, an example in which a 5in2 film was deposited on a Si substrate will be described. The apparatus used had the configuration shown in FIG. Oxygen is introduced into the vacuum chamber 16 as a reaction gas to generate plasma. By irradiating Si vapor onto the substrate 19 using an electron beam heating evaporation source I8 provided at the bottom of the vacuum chamber 16, Si and 02 plasma are generated. React and place 5in2 on the board
A film is formed. The treatment is 02 gas 1.5 x 10-
'Discharge was performed under the conditions of Torr, microwave, and 100W.

In the above example, the distance between the evaporation source and the substrate was significantly increased from 30 cm to 15 cm by narrowing the plasma flow. Further, since the Si vapor was effectively irradiated onto the substrate and did not reach the plasma source side, the discharge was also stabilized.

FIG. 4 shows the infrared absorption spectrum of the formed film. From the same figure, 5i seen around the wave number 108108O'
It can be seen that the magnitude and position of the -0 stretching vibration absorption peak are close to those of the thermal oxide film, indicating that a dense 5102 film is formed. Furthermore, the etch rate with the P-etching solution was 5 A/sec, which was about three times that of the thermal oxide film, even though the substrate was not heated. Furthermore, impurity analysis using an ion microanalyzer confirmed that there was no heavy metal contamination due to chamber wall sputtering.

Processing example 2: Next, nitrogen is introduced as a reaction gas, and nitrogen plasma and S
An example in which a Si3N4 film is formed by reaction with i vapor will be described. The same apparatus as in Processing Example 1 was used for this.

FIG. 5 shows the emission spectrum from nitrogen plasma when discharge was performed at a nitrogen gas pressure of I.times.10-' Torr and a microwave power of 50 W. In this spectrum, in addition to light emission from N2 molecules, light emission from N2+ molecular ions is also observed, and by applying a negative bias to the substrate, the energy of this movement can be effectively utilized.

Fig. 6 shows nitrogen gas pressure I x 1O-4Torr, microwave power 140W, Si evaporation source power 200W,
The infrared absorption spectrum of the Si3N4 film formed under the conditions of a negative substrate bias of 300 V and a substrate temperature of 300° C. is shown. In this spectrum, 5i-N at wave number 840 cm-'
Bond-based absorption is observed, and S! It can be seen that a 3N4 film is formed. Also, 5i at wave number 2150cm-'
No absorption based on -N bonds was observed, indicating that the film contained almost no hydrogen.

Furthermore, the results of depositing Si3N4 on the step portion showed that the step coverage was also excellent.

This is considered to be an effect of the kinetic energy of the ions.

[Effects of the Invention] According to the present invention, a high-quality thin film without sample contamination due to tube wall sputtering can be formed at a sufficient temperature at a sufficient deposition rate in a plasma processing apparatus without any complicated equipment configuration. becomes possible.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a plasma processing apparatus using magnetic field microwave plasma, which is an embodiment of the present invention, Fig. 2 is a schematic diagram showing an example of a conventional plasma processing apparatus, and Fig. 3 is an activation reaction FIG. 4 is a diagram showing the infrared absorption spectrum of a 5i02 film formed using the apparatus according to the present invention, and FIG. 5 is a schematic diagram for explaining the principle of the chemical vapor deposition method. FIG. 6 is a diagram showing the emission spectrum of nitrogen plasma.
FIG. 3 is a diagram showing an infrared absorption spectrum of a 3N4 film. Explanation of symbols

Claims (4)

[Claims] (1) The discharge section has a discharge section that generates plasma, an evaporation source that evaporates metal or its alloy, an electromagnet that generates a magnetic field for plasma confinement, and a vacuum container that holds the substrate to be processed inside. A plasma processing apparatus for processing a substrate using plasma generated by a plasma processing apparatus, wherein one or more electromagnets or permanent A plasma processing apparatus characterized in that a magnet is arranged and a plasma flow is narrowed by a magnetic field formed by the electromagnet or permanent magnet. (2) In the plasma processing apparatus according to claim 1, the substrate to be processed is irradiated with a plasma flow and an evaporated metal atom flow simultaneously or alternately, in order to process the substrate using plasma. A plasma processing apparatus characterized in that the metal or its compound is deposited on a substrate to be processed. (3) In the plasma processing apparatus according to claim 2, an ion extraction electrode for increasing the kinetic energy of charged particles in the plasma or a means for applying an electric field to the substrate is provided, and the irradiation effect of the charged particles is A plasma processing apparatus characterized by improved adhesion and density of a deposited film on a substrate to be processed. (4) Any one of claims 1 to 3
In the plasma processing apparatus described in 1., metal oxides or nitrides are deposited on the substrate to be processed by using oxygen or nitrogen, or a mixed gas containing either of them as a main component, as a gas for generating a plasma flow. Characteristic plasma processing equipment.