JPH01239851A - Thin film forming device - Google Patents

Abstract

PURPOSE:To form a film having less plasma damage and less internal stress on a base, to form a film having less internal stress to cope with an increase in the diameter of a wafer, and to suppress the mixture amount of hydrogen, by providing means for applying a voltage between a reduced electrode and a reaction vessel to generate a plasma, and means for radiating the base with light. CONSTITUTION:Means for holding one or more bases 3 therein, a reaction vessel 2 having two gas inlets 4a, 4b for introducing gas thereinto, electrodes 1 having 1/10 or less of the area of the inner wall of the vessel 2 and mounted near one inlet 4a, means 5 for generating a plasma in the gas introduced into the vessel 2, and means 6 for radiating the base 3 held in the vessel 1 with ultraviolet, visible or infrared light not absorbed by the introduced gas are provided. For example, the area of the electrode 1 is 200cm<2>, the area of the vessel 2 is 5000cm<2>, and their area ratio is 0.04. A 6-inch Si base is employed as the base 3, and a Xe lamp is employed as a light source 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thin film forming apparatus used for forming an insulating film of a semiconductor element, for example.

[Prior Art] Currently, CVD apparatuses occupy an important position as thin film forming apparatuses used for forming insulating films of semiconductor devices, particularly LSIs.

A thermal CVD device is commonly used as a CVD device.

Formation of the Si3N4 film using a thermal CVD apparatus is performed, for example, as follows. placed in the reaction vessel, 7
A mixed gas of monosilane and ammonia is fed onto the substrate heated to 50 to 950° C. and maintained at a pressure of several Torr. Then, a chemical reaction due to thermal decomposition occurs on the substrate, and a Si and N4 film is deposited and formed on the substrate. In addition, Si3
N4@ is used as a mask for selective oxidation and a capacitor insulating film.

Further, the formation of a PSG-based film using a thermal CVD apparatus is performed, for example, as follows. A mixed gas of monosilane, oxygen or nitrous oxide, and a doping gas such as phosphine is fed onto a substrate placed in a reaction vessel and heated to 350 to 450°C.
Maintain pressure at 0 Torr. Then, a chemical reaction due to thermal decomposition occurs on the substrate, and a PSG-based film is deposited and formed on the substrate. Note that this PSG-based film is used as an interlayer insulating film.

However, for applications such as forming a passivation film after AfL wiring, lowering the temperature is essential, and thermal CVD equipment is not sufficient. Therefore, plasma CVD apparatuses are used for such applications.

As a plasma CVD device, a parallel plate plasma CV
D device is known.

Formation of a P-3iN film using this apparatus is performed, for example, as follows. A mixed gas of monosilane, ammonia, and nitrogen was heated to 0. Under the pressure of an ITorr table, the gas is introduced between symmetrical parallel plate electrodes of a capacitor type, and a high frequency voltage is applied to these electrodes to generate plasma. These gases are excited and decomposed into excited active species. Active species, 250~
P-S by depositing on a substrate heated to 300°C
Form an iN film. P-SiN films are used as passivation films for semiconductor devices.

[Problems to be Solved by the Invention] However, the above-described parallel plate type plasma CVD apparatus also has the following problems.

■Due to damage caused by ions in the plasma, the electrical properties of films and elements formed on the substrate (e.g. dielectric strength,
(interface state density) is deteriorated compared to when formed using a thermal CVD apparatus.

(2) Internal stress is generated in the film due to the insertion reaction peculiar to the plasma CVD apparatus, and the anti-migration characteristics of the underlying Aj2 wiring are deteriorated. In particular, when the wiring width becomes finer due to higher integration of elements, migration may cause disconnection of the wiring.

■In order to obtain a uniform film thickness, it is necessary to maintain a uniform plasma density, which becomes increasingly difficult as wafer diameters increase.

■Hydrogen is easily mixed into the film, and the threshold voltage fluctuates due to the diffusion of this hydrogen to the gate.

[Means for Solving the Problems] The gist of the present invention is to provide a reaction vessel having means for holding one or more substrates inside and two gas introduction ports for introducing gas into the inside. and; 1 of the inner wall area of the reaction vessel
/10 or less and an electrode installed near one side of the inlet; means for applying a voltage between the reaction vessel and the electrode to turn the gas introduced into the reaction vessel into plasma; A thin film forming apparatus comprising: a means for irradiating the substrate held in the reaction vessel with ultraviolet light, visible light, or infrared light that is not absorbed by the introduced gas.

[Effect] The constituent elements of the present invention will be explained below along with their effects.

One of the features of the present invention is that the electrode is provided near the inlet of one gas introduction tube, and the area of the electrode is 1/10 or less of the inner wall area of the reaction vessel. .

The present inventor investigated the cause of the deterioration of the electrical properties of films formed using conventional plasma CVD equipment, and found that
We thought that damage caused by ion bombardment might be the cause.

Further research was conducted to find out why such damage caused by ion bombardment occurs. As a result, we obtained the knowledge that in conventional plasma CVD equipment, the plasma intensity does not differ much between the vicinity of the electrode and the vicinity of the substrate, and therefore the plasma intensity near the substrate is also quite strong, causing damage to the film. Ta.

Therefore, we worked hard to find a way to avoid this damage, and found that by making the area of the electrode smaller than the inner wall area of the reaction vessel and applying a voltage between the electrode and the reaction vessel, the plasma could be reduced. The strength is strong near the electrode and becomes weaker near the substrate, and as a result, the above damage can be avoided, and the present invention has been completed.

Based on the above knowledge, we investigated specifically what area ratio would avoid the above damage.

As a result, it was found that it was possible to avoid the above damage by setting the value of electrode area/inner wall area of the reaction vessel (hereinafter referred to as area ratio) to 1/1° or less. .

In addition, this area ratio is preferably 0.02 to 0.06, more preferably 0.04 to 0.05.

Further, when the area ratio is set to 1/10 or less, internal stress within the film due to insertion reaction is reduced, and therefore migration resistance is improved.

Furthermore, it is possible to accommodate larger diameter substrates simply by increasing the size of the reaction vessel without changing the specifications of the electrodes.

Another feature of the present invention is that it includes means for irradiating the substrate held within the reaction vessel with ultraviolet light, visible light, or infrared light that is not absorbed by the introduced gas. By this means, when the substrate is irradiated with ultraviolet light, visible light, or infrared light, desorption of hydrogen is promoted, suppressing the incorporation of hydrogen that causes fluctuations in threshold voltage, and making it possible to form a dense film. becomes.

Examples of such light sources include Hg lamps, Xe, etc., Xe-Hg, etc., W, etc., halogen lamps, or N.
Eximer lasers include 2 laser, Ar laser, YAG laser, and C02 laser. Of course, any laser other than these may be used as long as it is not absorbed by the source gas.

In the present invention, examples of substrates on which a thin film can be formed include silicon substrates, compound semiconductor substrates such as GaAs, dielectric substrates such as AJ2203, and metal substrates such as AIL.

In addition, the thin film to be formed is, for example, 02 or N20.
and SiO film using S i H4, 5f2H6, S i H2Cl12 or SiF4, H2 or rare gas and S
iH,,5t2Ha,5iH2Cλ2 or S i H
a-St (amorphous silicon) film using 4 etc.,
Examples include a p-5i (polycrystalline silicon) film, a c-5i (single-crystalline silicon) film, a metal nitride film using a gas containing hydrogen or a rare gas, and metal atoms, and an oxide film.

The plasma generating means may be a high frequency, a microwave, a magnet, or a combination thereof.

[Example] An embodiment of the present invention will be described below with reference to FIG.

In Figure 1, 1 is an electrode whose area is 200c
It was set as rn'. 2 is a reaction container, and this reaction container is grounded. The area of the reaction vessel was 5000 cm'. Therefore, the area ratio is 0.04. 3 is a substrate, and in this example, a 6-inch silicon substrate was used. 4a and 4b are gas inlet ports, 4a is the upper part of the reaction vessel 2, and the electrode 1
It is installed near the. 5 is a means for applying a voltage between the reaction vessel 2 and the electrode 1 to generate plasma. 6 is a light source, and in this example a Xe lamp was used.

An example of forming a thin film using this apparatus will be described below, and examples of the present invention will be explained in more detail.

240sec of nitrogen gas inlet 4a as raw material gas
Then, monosilane was flowed for 40 seconds from the gas inlet 4b. The operating pressure was maintained at 10'' Torr.

Plasma was generated by applying a high frequency voltage of 13.56 MHz at lkw between the capacitively coupled electrode 1 and the reaction vessel 2. At this time, the electron density in the dense plasma (existing near the electrode) was I x 10''/crd
, 5×1o9/crn'' on substrate 3.

On the other hand, the light source 6 irradiated the substrate 1 with light of 0.6 W/cm'. Note that this irradiation increases the substrate surface temperature to 300°C.
I kept it.

When deposited for 5 minutes under the above conditions, 5500±
A 150-layer thick SiN film was formed.

In other words, the variation in film thickness was as small as about ±2.5%.

The film formed as described above was evaluated.

■Electrical characteristics Dielectric strength voltage: 10MV/cm Interface state density: 1 x 1011/Cm2 ■Internal stress Internal stress is 4x 10-8 dyn/crr? [It was a tensile stress.

(2) Others The density of the film was as high as 3.1 g/am'', so the etching rate with buffered hydrofluoric acid was as good as 10 persons/min.The hydrogen content was 5 moJZ%.

[Comparative Example] Using a conventional parallel plate type plasma CVD apparatus, film formation was carried out under the following conditions to obtain SiN@ with the best characteristics.

Film-forming conditions SiH4:6secm NH,:30secm Operating pressure: 0.57Torr RF power: 100W ■Electrical characteristics Dielectric strength voltage: 6MV/cm Interface state density: 5×1011/Cm2 ■In the same method as the internal stress example When the internal stress was evaluated, the internal stress was 1 to ax 109 dyn/cm' [compressive stress].

■Other density is 2.6g/crn', etching speed with buffered hydrofluoric acid is 300 people/min, hydrogen content is 30mo1%
Met.

That is, compared to the thin film of the present invention, the film quality of the comparative example was clearly not good.

[Effects of the Invention] As described above, according to the present invention, the following effects can be obtained.

(2) Since the substrate is separated from the strongest part of the plasma, there is less plasma damage to the substrate and a film with excellent electrical properties can be formed.

(2) A film with low internal stress can be formed, and therefore, it is possible to fabricate a semiconductor element with fewer disconnections in the AJ2 wiring when increasing integration.

■It is possible to accommodate larger diameter wafers simply by increasing the size of the reaction vessel.

■The amount of hydrogen mixed in can be suppressed, suppressing fluctuations in threshold voltage. .

■It is possible to form a dense film.

[Brief explanation of the drawing]

FIG. 1 is a conceptual configuration diagram showing an apparatus according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Electrode, 2... Reaction container, 3... Substrate, 4a
. 4b... Gas introduction port, 5... Plasma generation means, 6
···light source.

Claims (1)

[Claims] Means for holding one or more substrates therein;
a reaction vessel having two gas introduction ports for introducing gas into the interior; an electrode having an area of 1/10 or less of the inner wall area of the reaction vessel and installed near one of the introduction ports; means for applying a voltage between the reaction vessel and the electrode to turn the gas introduced into the reaction vessel into plasma; A thin film forming apparatus comprising: a means for irradiating visible light or infrared light; and a means for irradiating visible light or infrared light.