JPS61166976A - Surface treatment - Google Patents

Abstract

PURPOSE:To obtain stable radiation light having luminance and active seed and make various effective surface treatments with good quality by using a light source for which high-frequency LTE plasma discharge is used and an active seed source. CONSTITUTION:The 1st gas such as nitrogen is introduced into a discharge tube 6 of a plasma generating mechanism 10. The high-frequency glow discharge arises first then LTE plasma 3 is generated when the impressed high-frequency electric power is increased. This plasma 3 has the high luminance and exhibits the spectral pattern different from the spectral pattern of the DC glow discharge and the many active seeds 18 exist. The radiation light 17 from the LTE plasma 3 and the active seeds 18 are introduced through an electrode 30 into a treating chamber 7. A prescribed reactive material such as gaseous silane is conducted via a valve 11 to an introducing ring 13 and is supplied into the chamber 7 where the material is brought into reaction with the LTE plasma 3. An SiN film, etc., are thereby formed on a base body 16. This method is applicable to etching, optical cleaning, surface reforming, etc., in addition to the film formation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention produces a predetermined amount of synchrotron radiation and active species with good control, and by using these, in particular, insulator films of semiconductor devices, semiconductor The present invention relates to a surface treatment method for surface treatment such as film formation, etching, surface cleaning, surface modification, etc. of films and metal films.

(b) Conventional technology The method of activating a gas through a photochemical reaction and depositing a target substance on the surface of a substrate to form a thin film, etching, surface modification, etc. can be performed at low temperatures. , has shown rapid progress in recent years due to the fact that it is not damaged by the impact of charged particles, its photochemical selectivity enables unprecedented processing, and it is easy to select the reaction process and control film formation. .

Conventionally known photochemical surface treatment methods can be roughly divided into two types. One method uses a discharge lamp as a light source, and the other method uses a laser as a light source. In a method using a discharge lamp, the luminance of the emitted light is generally low, and in a method using a laser, the laser itself is expensive.

In addition, normally, in a processing apparatus, a light source and a processing chamber are separated by a window, and especially in the case of optical CVD, etc., there is a problem in that foreign matter accumulates on this window and the emitted light is attenuated by the N. As an invention to improve this, there is an invention disclosed in Japanese Patent Application Laid-Open No. 16966/1983. This invention is characterized in that the light source section and the processing section are installed in the same container.
It is clear that IC discharge or DC discharge is used. Therefore, its configuration supplies a protective gas for the electrodes,
The contents are aimed at stabilizing the discharge, that is, stabilizing the light source. However, this configuration complicates the device structure and introduces gases that are not directly related to surface treatment into the treatment system, which has the disadvantage of limiting the types of surface treatment or adversely affecting the treatment. be.

Nowadays, process technology using plasma has become indispensable in the process of manufacturing semiconductor devices. This is because of the following reasons.

In general, active species can be created by irradiating a substance with light or electrons, but the active state that can be created by light is either a state in which phototransition is not prohibited, or an interstitial state from the state in which it is not prohibited. Although only active states are generated by crossing or relaxation, active states generated by electron collisions inside plasma or electron beams easily transition to states where optical transition is prohibited, and are different from light. This is because it is possible to produce active species that However, in most of the conventional techniques for film formation using plasma, the substrate is directly immersed in the plasma, which has the disadvantage that charged particles in the plasma impact the substrate, deteriorating the electrical characteristics of semiconductor devices. . Such deterioration is manifested in, for example, variations in vth in MOS, variations in hfe in bipolar, and the like. And as the degree of integration of semiconductor devices has become extremely large as in recent years,
Because even the impact of minute charged particles can cause significant deterioration of electrical properties, there is a particular desire to develop a process that does not cause damage.

(c) Purpose of the Invention The present invention is a novel method for stably producing synchrotron radiation and active species useful for surface treatment, and by using these, high-quality and effective surface treatment can be performed regardless of the type of surface treatment. The purpose is to provide a surface treatment method.

(d) Structure of the Invention This invention generates LTE plasma by flowing a gas that emits radiation of at least a predetermined wavelength into a high-frequency power space that is inductively coupled or capacitively coupled, and
The present invention is configured to use TE plasma as a radiation light source and an active species source, and to perform surface treatment on a predetermined substrate by reacting the LTE plasma with another substance in a surface treatment chamber.

(E) Embodiment FIG. 1 shows an apparatus used in an embodiment of the present invention. 10 is a plasma generation mechanism, 2o is
It is a processing mechanism.

First, the plasma generation mechanism 10 will be explained.

This plasma generation mechanism 1o uses a high frequency (several KHz to several hundred MHz) power source 1. It is composed of a coil 2 and a discharge tube 6, and the high frequency voltage emitted from the electric current 11 is transmitted to the coil 2.
When applied, a discharge occurs inside the discharge tube 6 due to high frequency inductive coupling. When using a frequency in the microwave region (GHz order) as the high frequency, a microwave cavity is installed to surround the discharge tube 6 instead of the coil 2. Then, the first gas is introduced through the valve 4 from the direction of the gas flow 5 into the discharge tube 6 where the discharge has occurred as described above. Further, the discharge tube 6 is usually made of an insulating material, and effective materials include quartz glass or ceramics. If quartz glass is used, there is a risk that the quartz glass will melt as the plasma temperature increases.
The discharge tube 6 may be a double tube made of quartz glass, and cooling water may flow between the two tubes, the inner and outer tubes.

As the applied high-frequency power is increased, a high-frequency glow discharge is first generated, but when even higher power is applied, the plasma is pinched hysterically and L T E
(Local T'herm, al E quili
(br-iu+m local thermal equilibrium) plasma 3 is observed to be generated. This plasma is very bright and often exhibits a different spectral pattern than a normal DC glow discharge. For example, in the case of hydrogen discharge, in normal DC glow discharge or high-frequency glow discharge, there is a continuous spectrum from the visible light range to the ultraviolet light range caused by hydrogen molecules, and in addition to that.

Balmer series and Lyman series emission caused by hydrogen atoms can be observed. However, in this case, the light emitted by hydrogen atoms is relatively weak, so the color of the emitted light is white. However, in LTE plasma 3, the color of the emitted light is red with extremely high brightness. And we know that this is the result of the extremely high brightness of the Balmer system of light emitted by hydrogen atoms. At the same time, although it is not in the visible region and cannot be seen directly in the mouth, the Lyman luminance is also extremely high. Lyman α light has a wavelength of 121.6r+I11, and as is well known, when using light of this wavelength, it is possible to directly decompose silane and disilane, and it is also possible to decompose MgF
It also has the advantage of being able to use optically transparent materials such as LiF and AQ reflectors coated with MgF, making it extremely easy to assemble an optical system, which is very useful. Until now, there was no light source that could extract high-quality Lyman-α light, so this light had not been used much. The high frequency LTE plasma light source of the present invention described above satisfies this point. Note that the first
Gases such as nitrogen, argon, helium, mercury, and mixtures thereof are also useful as well as hydrogen.

Furthermore, when the first gas is hydrogen, the LTE plasma contains dissociated hydrogen atoms and excited states of hydrogen molecules, hydrogen radicals, ions, etc. compared to normal high-frequency glow discharge. There are many active species of

Figures 2 and 3 show the results of vacuum ultraviolet emission spectrometry analysis of nitrogen. Figure 2 shows the emission analysis in the LTE plasma state, and Figure 3 shows the emission analysis in the high-frequency glow plasma state. . The conditions for creating the surface state are 13.56MHz,
2.5kW, pressure cuff 00mTorr, N2 flow rate 30s
It is kept constant at cc11. Around this creation condition, L
Since the two states of TE and high-frequency glow have hysteresis, the zero emission intensity that allows you to compare the states of LTE and high-frequency glow under the same conditions is in arbitrary units in both figures, but the light intensity of 120 nIn When compared with LTE
The luminous intensity is 120 times higher than that of high-frequency glow. Like hydrogen, the LTE plasma has a strong short-wavelength light, and this spectrum can be attributed to light emission from nitrogen atoms, so it is clear that the LTE plasma contains many active species, especially nitrogen radicals. Similar results were obtained not only for nitrogen but also for oxygen. And when comparing high frequency glow discharge and high frequency LTE plasma discharge.

There are the following differences between the two.

(a) In high frequency glow discharge, the light emitting area tends to spread widely, and in high frequency LTE plasma discharge, the light emission has a different spectral pattern. In this plasma discharge, excitation of vibrational and rotational modes is often observed compared to high-frequency glow discharge.

(c) The high-frequency glow discharge state and the high-frequency LTE plasma discharge state often transition in a hysteretic manner using discharge power, discharge pressure, etc. as parameters, and discharge impedance often differs greatly between surface discharges.

(d) High-frequency LTE plasma discharge has very high brightness; the impedance does not change hysterically; therefore, from the impedance alone, high-frequency glow discharge and high-frequency LT
Although it is difficult to distinguish between E plasma discharge and high frequency LTE plasma discharge, the plasma tends to be pinched when it enters a high frequency LTE plasma discharge state, and both discharges can be visually distinguished.

Next, the processing mechanism 2o will be explained. The processing mechanism 20 is
A processing chamber 7 that can be kept airtight if necessary, an introduction ring 13 provided in the processing chamber 7 for introducing a reaction gas, a substrate holder 8 for installing a substrate 16, the discharge tube 6 and the processing chamber 7. and a mesh-like electrode 3° for plasma shielding provided between the two. The structure is such that radiation light 17 and active species 18 from the LTE plasma 3 generated within the discharge tube 6 are introduced into the processing chamber 7 via the electrode 30. A given reactant is supplied to valve 1.
1 from the direction of flow 12 to the inlet ring 13 and is supplied by the inlet ring 13 into the interior of the processing chamber 7 . A temperature controller 9 is installed in the substrate holder 8, and the temperature of the substrate 16 can be adjusted as necessary.

The first gas and the predetermined reactants are vented via valve 14 in the direction of gas flow 15 .

When the plasma generation mechanism 10 and the processing mechanism 20 are installed in the same container, a glow-like plasma spreads around the high-frequency LTE plasma in areas where the pressure is several Torr or less, and this glow-like plasma often spreads in areas where the pressure is low. The plasma spreads to the inside of the processing chamber 7. The electrode 30 is provided to prevent this.

Note that this electrode 30 may be any member as long as it can prevent the spread of glow-like plasma.

Of course, it is not necessarily limited to mesh-like ones. When a voltage is applied to this electrode 30, plasma shielding can be performed more effectively, and charged particles from the plasma can be drawn into the processing mechanism 20 and the charged particles can be actively used for surface treatment.

An example using the apparatus shown in FIG. 1 is shown below. When nitrogen is used as the first gas and silane gas is used as the reactant in the processing chamber 7, SiN
The membrane was created. This SiN film has a substrate temperature of 200°C,
Pressure cuff 00mTorr.

SiH, flow rate 25 sc + i, N, flow rate 200 sc
cm, power 3.5 kW (13,56 MH,) (7) Under the conditions, film formation can be performed at a rate of about 80 people/+*in. Increases proportionally to total flow rate. At present, it is not clear to what extent this film formation rate can be increased.

The formation mechanism of this SiN film is considered to be a reaction between nitrogen radicals generated by the LTE plasma and silane activated (excited and decomposed) by short wavelength light from the LTE plasma.

In another embodiment using the apparatus of FIG. 1, when hydrogen is used as the first gas and silane gas or disilane gas is used as the reactant, a-8i:H
We were able to create a membrane. The reaction mechanism is thought to be that silane or disilane is decomposed by Lyman series short wavelength light from the LTE plasma and an a-5i:H film is produced, but hydrogen radicals from the LTE plasma are auxiliary to this reaction. a-5i: a-5i:
It is also possible that the formation of H film is promoted.

Further, another embodiment using the apparatus shown in FIG. 1 will be shown.

When oxygen is used as the first gas, LTE plasma can be used to create oxygen radicals, ozone, and the like. Using short wavelength oxygen light and oxygen radicals or ozone, organic matter on the surface of the substrate is decomposed into water and carbon dioxide,
Surface cleaning of the substrate surface can be performed. In this case, it goes without saying that the introduction ring 13 and the like are unnecessary.

It goes without saying that if oxygen is used as the first gas, the surface of a certain type of substrate can be oxidized, if hydrogen is used it can be reduced, and if nitrogen is used it can be nitrided.

FIG. 4 shows an apparatus used in another embodiment of the invention. This device is the same as the device shown in FIG. 1 by adding a plasma generation mechanism 10'. That is, the apparatus is composed of two plasma generation mechanisms 10 and 10' and a processing mechanism 20.

Note that the configuration of this plasma generation mechanism 10' and the LTE plasma generation process in the plasma generation mechanism 10' are the same as those of the plasma generation mechanism 10 described in FIG. 1, so a description thereof will be omitted. The LTE plasma 3 generated in the plasma generation mechanism 10'
The emitted light 17' and the active species 18' from ' are electric! 30'
is introduced into the processing chamber 7 through the reactor and reacts with a predetermined reactant.

Note that the shape of the electrode 30' is made into a blind shape so that the LT
The radiation light 17' from the E plasma 3' is blocked, and the active species 1
8 may be introduced into the processing chamber 7.

Even when the apparatus shown in FIG. 4 is used, hydrogen is used as the first gas, nitrogen is used as the second gas, and silane gas or silane gas is used as the reactant in the processing chamber 7, the surface of the substrate 1G is A SiN film was formed.

This generation mechanism is based on the short wavelength light (considered to be Lyman series of hydrogen atoms) from the LTE plasma generated in the plasma generation mechanism 10 and the plasma generation mechanism 10'
It is thought that nitrogen radicals from the LTE plasma generated in the above reaction reacted with the silane. It is also conceivable that hydrogen radicals from the LTE plasma generated in the plasma generation mechanism 10 are also involved in the reaction.

Although the above embodiment is an example in which LTE plasma is created by high frequency inductive coupling, LTE plasma can also be created by high frequency capacitive coupling.

These examples are not intended to be limiting in any way, and the surface treatment method of the present invention can be modified in many ways, including improvements, combinations, and combinations of existing techniques while respecting the gist of the present invention. .

(f) Effects of the invention This invention is as explained above,
By using a light source and an active species source using plasma discharge, it is possible to obtain high-intensity, stable synchrotron radiation and active species.

In addition, the types of surface treatments are much wider than conventional ones, such as the formation of semiconductor films, metal films, insulating films, etc., dry etching, optical cleaning, surface modification, etc., so the areas that contribute to the manufacture of semiconductor devices, etc. It can be said to be an industrially significant invention.

[Brief explanation of the drawing]

1 and 4 are front cross-sectional views of an apparatus used for carrying out an embodiment of the present invention, and FIG. 2 is a graph showing the results of vacuum ultraviolet emission spectroscopy from LTE plasma. Figure 3 is a graph showing the results of vacuum ultraviolet emission spectroscopy from glow plasma. 3・3'----LTE plasma 7-------Processing chamber 10・io'----Plasma generation mechanism 1 G-----
- One substrate 17 ---- Synchrotron radiation 18 ---- Bulk species 20 - One - Processing mechanism 30, 30 - One - Electrode Patent applicant Nichiden Anelva Co., Ltd. Attorney Heelman Kenji Murakami IGI (XJ (9'ljun 'qJ9) Sister's Sword FI0.4

Claims (8)

[Claims] (1) Generate LTE plasma by introducing a gas that emits synchrotron radiation of at least a predetermined wavelength into an inductively coupled or capacitively coupled high-frequency power space, use the LTE plasma as a synchrotron radiation source and an active species source, and perform surface treatment. A surface treatment method comprising performing surface treatment on a predetermined substrate by causing the LTE plasma to react with a predetermined substance in a chamber. (2) A voltage-appliable electrode is disposed between the LTE plasma and the substrate, which transmits synchrotron radiation and active species, while selectively blocking or transmitting charged particles. surface treatment method. (3) The gas is nitrogen, the predetermined substance is monosilane, disilane, and/or a silane derivative, and the SiN film is formed on the surface of the substrate. The surface treatment method according to item 2. (4) Claim 1 or 2, wherein the gas is hydrogen, the predetermined substance is monosilane, disilane, and/or a silane derivative, and a Si film is created on the surface of the substrate. Surface treatment method described in section. (5) The surface treatment method according to claim 1 or 2, wherein the gas is oxygen, the predetermined substance is an organic substance on the surface of the substrate, and the surface of the substrate is cleaned. (6) According to claim 1 or 2, wherein two or more high-frequency power spaces are provided and two or more types of gas are introduced into the spaces to generate two or more LTE plasmas. Surface treatment method. (7) An electrode capable of applying a voltage that can selectively block or transmit charged particles while transmitting synchrotron radiation and the active species is disposed between two or more generated LTE plasmas and the substrate. A surface treatment method according to claim 7, characterized in that: (8) One gas is hydrogen, the other gas is nitrogen, the predetermined substance is monosilane, disilane, and/or a silane derivative, and Si is applied to the surface of the substrate.
9. A surface treatment method according to claim 7 or 8, characterized in that an N film is created.