JPH02207528A - Plasma chemical reaction film forming equipment and its method - Google Patents

Abstract

PURPOSE:To control reaction in vapor phase, and form a film having little irregularity on a substrate surface by individually introducing a plurality of reactive gases into a plasma generating chamber, introducing a first gas into the vicinity of a slit, and introducing a second gas into the gap between the slit and a wafer. CONSTITUTION:Microwave is generated by a magnetron 3, and supplied to a cavity resonator 1 through a waveguide 2; microwave energy of large amplitude is radiated from a slit on a slit plate 5 to a plasma generating chamber 6. A first gas and a second gas are supplied to the plasma generating chamber 6 after passing gas reservoirs 14, 14' from gas introducing inlets 13, 13'. In a high density plasma generating region adjacent to the slit, N2 or N2O, e.g., is introduced, and SiH4 or Si2H6 is introduced into the gap between a wafer and the slit. Hence, decomposition and activation of N2 or N2O progress, and the plasma secondarily decomposes SiH4 or Si2H6. As the result, reaction in vapor phase can be reduced as compared with the case where mixed gas is supplied from one part, so that uniform CVD film formation free from unevenness on a wafer 12 can be realized.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the production of semiconductor devices using low-temperature plasma, and in particular to plasma CVD for forming an insulating film etc. on the surface of a substrate.
(Chemical reaction film formation) apparatus and method thereof.

[Conventional technology]

Plasma CVD (chemical reaction film deposition) equipment that uses low-temperature plasma can be broadly classified as using a technology that generates plasma by applying a high-frequency voltage of about 10 KHz to 30 M7 to one side of parallel plate electrodes in a vacuum. things (semiconductor research 18
i P 121- P 170. Semiconductor research 19;P
225-P. 267) and one that uses a technique of introducing 2.45G7 microwaves into a vacuum chamber to generate plasma. Conventionally, among these, techniques using parallel plate electrodes have been mainly used.

On the other hand, with the miniaturization of semiconductor devices, it has become a problem that device characteristics are affected by bombardment of ions in plasma during thin film formation. Furthermore, in order to improve processing capacity, it is required to increase the film formation rate.

In order to increase the film formation rate, it is necessary to increase the plasma density and radical (active particles immediately before ionization) concentration.

To achieve this, measures are taken to increase the input energy. Other means of increasing the flow rate of the reaction gas may be considered, but if the energy remains constant, the amount of gas decomposed will also remain constant, and the film formation rate will become saturated. Therefore, increasing energy is essential.

With parallel plate electrodes, increasing the input energy, that is, the high-frequency power, increases the deposition rate, but the energy of the ions colliding with the substrate increases, causing a problem that the electrical characteristics of the semiconductor element deteriorate.

Further, due to the occurrence of abnormal discharge, there are problems such as a decrease in gas decomposition efficiency and deposits on the walls of the reaction chamber being incorporated into the substrate surface as impurities.

Therefore, increasing the density of plasma and appropriately controlling ion energy will be essential for future plasma processing.

When generating plasma using microwaves, even if the microwaves generated by a magnetron are radiated into a low-pressure plasma generation chamber, the electric field strength of the microwaves is insufficient, so it is not possible to supply energy to the ionization energy level of electrons. It is difficult to generate plasma.

Therefore, in order to generate plasma using microwaves, there is a method to match the cyclotron frequency at which electrons rotate in a plane perpendicular to the magnetic field and the microwave frequency to create a resonance state and supply energy to the electrons, and a method to supply energy to the electrons. There are two methods: increasing the amplitude of microwaves by radiating them into a resonator, and increasing the electric field strength to supply energy to electrons. The former is a magnetic field microwave wave or E CR (E 1
ectronCyclotron Re5onanc
e) method, and is disclosed in Japanese Patent Application Laid-open No. 13480/1983. The latter is disclosed in Japanese Patent Application Laid-Open No. 56-96841 and Japanese Patent Application Laid-Open No. 63-103088 proposed by the authors.
This is what was shown in the publication.

In plasma generated by microwaves, energy is directly supplied to electrons from the microwaves, so the seal voltage formed between the plasma and the substrate hardly changes. Therefore, by applying a high frequency voltage to the electrode on which the substrate is placed and arbitrarily controlling the voltage between the sheaths, it is possible to control the high plasma density and appropriate ion energy necessary for high speed.

However, in the ECR method, as shown in JP-A-56-13480, when a high-frequency voltage is applied to an electrode on which a substrate is placed, there is no ground electrode on the opposite side of this electrode, so the high-frequency current flows from the surroundings. There is a problem in that the effect of ion energy flowing between the substrate and the processing chamber is strong around the substrate and weak at the center, making it impossible to process the entire substrate under uniform conditions.

In order to solve the above problems and to form a film at high speed with appropriate ion energy, the authors published Japanese Patent Application Laid-Open No. 63-103088.
We proposed a plasma processing device that radiates microwaves inside a cavity resonator from a slit, as described in the above publication. This method will be explained.

Generally, when microwaves propagate in a waveguide or a cavity resonator, which is considered to be a type of waveguide, a current corresponding to the electric field and magnetic field flows on the surface of the waveguide.

Therefore, if a slit is provided in a part of the waveguide to cross this current, charges will accumulate at both ends of the slit, and this will change as the microwave travels, causing the electric field between both ends of the slit to change, causing the waveguide to pass through the waveguide. Microwaves are radiated to the outside.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, since microwaves are radiated from the slit to the plasma generation chamber, high-density plasma is generated near the slit, and becomes less dense as it moves away from the slit. This tendency becomes more pronounced as the pressure inside the plasma generation chamber increases, for example from 5 PIL to 50 Pa.

The conventional gas supply method is to introduce a mixed reaction gas from one location. Therefore, the decomposition and activation of the reactive gas is promoted in the high-density plasma region, and the reaction in the gas phase progresses in that region. As a result, the film formed on the substrate surface had large irregularities.

The higher the pressure, the larger the unevenness becomes.

The main purpose of the present invention is to provide a plasma chemical reaction film forming apparatus and method for suppressing reactions in the gas phase and forming a film with less irregularities on the surface of a substrate, in order to solve the problems of the prior art described above. It is about providing.

A second object of the present invention is to provide a plasma chemical reaction film forming apparatus that reduces the temperature change of the substrate during film formation and obtains uniform film quality between the initial stage and the end of film formation. be.

The third object of the present invention is to prevent thermal deformation of the slit plate,
An object of the present invention is to provide a plasma chemical reaction film forming apparatus that can always perform stable CVD film formation.

[Means to solve the problem]

That is, in order to achieve the main object of the present invention, a plurality of gas introduction means for individually introducing reactive gases into the plasma generation chamber are provided. The first gas is introduced near the slit where high-density plasma is generated, and the second gas is introduced between the slit and the wafer.

Further, in order to achieve the second object, the present invention provides a heat source that irradiates the substrate obliquely from the periphery of the substrate.

Alternatively, the surface of the substrate is preheated with N2 or N20 plasma immediately before film formation to reduce temperature changes in the substrate during film formation.

Further, in order to achieve the third object of the present invention, a cooling means is provided by flowing gas into the gap between the microwave window and the slit to prevent thermal deformation of the slit plate.

Further, by providing a guide path between the microwave window and the slit to guide the cooling gas to the center of the slit plate, thermal deformation of the slit plate can be further prevented.

[Effect]

In the present invention, a gas other than SiH or 5i2H, such as N2 or N20, is used in the high-density plasma generation region near the slit.
into the Si between the wafer and the slit. , Si, H
By introducing G, N is reduced in the high-density plasma generation region.
The decomposition activation of 2, N, and 0 progresses, and the plasma secondarily decomposes S i H4, Si, and H, near the wafer.
As a result, reactions in the gas phase can be significantly reduced compared to when a mixed gas is supplied from one location, and uniform CVD film formation without irregularities can be performed on fine semiconductor elements.

The second invention is that when the substrate is directly heated by a lamp heater, heat transfer occurs by radiation, and the temperature rise time is much shorter than that of heat transfer mediated by gas molecules between the substrate and the substrate mounting table. fast. Therefore, the temperature difference between the substrate at the beginning of film formation and at the end of film formation can be reduced, and CVD film formation with uniform film quality can be performed on fine semiconductor elements. Also, by heating the substrate with N2 or N20 plasma immediately before film formation, the temperature of the substrate at the start of film formation can be increased, and the temperature difference between the initial and final stages of film formation can be reduced. , it is possible to perform CVD film formation with uniform film quality on a fine semiconductor element.

In addition, the third invention is capable of cooling the slit plate by flowing a cooling gas such as N2 between the slit plate and the microwave window, preventing thermal deformation of the slit plate, and ensuring a constant flow from the slit to the processing chamber. Microwaves can be introduced. In particular, the temperature of the slit plate is high at the center and low at the periphery, so it is necessary to guide the cooling gas to the center of the slit.Therefore, a guide passage is provided between the slit and the microwave window so that the gas flows to the center of the slit. In this way, thermal deformation of the slit plate is prevented.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIGS. 1 and 2 are diagrams showing a schematic configuration of an embodiment of the thin film forming apparatus of the present invention. That is, the cavity resonator 1 is E.

, mode, and microwaves are supplied from a magnetron 3 through a waveguide 2. The waveguide 2 is mounted eccentrically with respect to the circular cavity resonator 1 in order to improve coupling with the E0□ mode. There is a separation plate (ceramic plate) on the other side of the circular cavity resonator 1.
4 and a slit plate (electromagnetic coupling means) 5 are fixed.

A plasma generation chamber 6 is connected below it. Note that the structure is sealed in vacuum by a separation plate (ceramic plate) 4.

The planar structure of the slit plate 5 is E as shown in FIG. 3, 5b. 1
There is a ring-shaped to triple slit opening in the direction perpendicular to the electric field of the mode. That is, there are 2 to 2 slit openings with a width of 5 to 20 mm at equal intervals on the circumference of φ60 to φ350 strokes.
Ten pieces are arranged, and the opening area is 2.5d to 130d. The length of each slit 5c is 2.45G) (When using a microwave of z, the length of each slit 5c is set to 60na or more, which corresponds to 1/2 wavelength of the microwave, in order to allow the microwave to be emitted from the slit.)

In the plasma generation chamber 6 (FIGS. 1 and 2), there is a substrate mounting table (or electrode) 7. Gas supply hole 13.13' gas exhaust pipe 1
0 is the default. The substrate mounting table (or electrode) 7 is made of insulating material 8
In the case of plasma CVD, it is not necessary to connect the electric current g11 to the substrate mounting table 7.

However, even in plasma CVD, in the case of bias sputtering or the like, it is necessary to connect a high frequency power source 11 or the like during etching. A first gas for plasma processing (for example, N2 or N20 or an inert gas) and a second gas (for example, SiH4 or Si) are supplied to the gas supply holes 13.13' from first and second gas sources (not shown), respectively. , H,) can be supplied only at a set flow rate.

A vacuum pump (not shown) is connected to the gas exhaust pipe 10, so that the pressure inside the plasma generation chamber can be controlled at 1 to 1 O-3 Torr.

The magnetron 3 is operated to oscillate microwaves, which are supplied to the cavity resonator 1 through the waveguide. The microwave energy whose amplitude has been increased within the cavity resonator is radiated into the plasma generation chamber 6 through the slits of the slit plate 5 at a microwave radiation power density of I W/ad to 40 W/cJ. Since the amplitude of the microwave radiated to the plasma generation chamber 6 is large in the cavity resonator 1, the plasma is lit and maintained even if the plasma generation chamber 6 does not have a cavity resonator structure.

It is also necessary to lower the microwave radiation impedance and to minimize the influence on the stub tuner etc. provided in the waveguide 2. Therefore, the area of the slit opening is preferably 2.5 cd or more, and most preferably 5 aJ or more.

Further, the relationship between the radial pitch P of the slit openings and the gap G between the lower surface of the separation plate 4 and the surface of the substrate 12 is preferably P/G=about 1 to about 5, most preferably P/G=about 1.5
By setting the ratio to about 2.5, uniform plasma can be generated over the entire surface of the substrate 12. In particular, in the case of this embodiment, unlike the ECR method, there is no magnet, so the microwave is diffused and radiated from the slit opening.

Therefore, the microwave is diffused at an intensity of about sin θ with respect to the angle θ with respect to the hanging axis with the slit opening as the center. Therefore, a dimension in which P/G is approximately 2 allows plasma to be generated most uniformly.

The first gas (for example, Na, N, or O is an inert gas) is supplied from the gas introduction hole 13 through the gas reservoir 14 and from the blow-off hole 15 into the plasma generation chamber 6 . A second gas (for example, S i H4 or Si, H,) is similarly supplied from the gas introduction hole 13' through the gas reservoir 14' and from the blow-off hole 15'. The blow-off holes 15 and 15' are 24 holes with a diameter of 0.5 m that are equally spaced on the circumference. An appropriate angle of the blow-off hole can be selected depending on film-forming conditions such as pressure and gas flow rate. The gas reservoir 14°14' is formed with a ring-shaped space, and each blow-off hole ts, ts
This is an accumulator that keeps the gas pressure constant around the circumference so that the same flow rate of gas is blown out from '. The closer the plasma density is to the slit plate 5, the higher the density is, and the further away from the slit plate 5, the lower the density. Blowout hole 1 of first gas introduction means
5 is directed near the slit plate 5, and N2 or N
When microwaves are introduced by flowing 20 or inert gas, a high-density plasma of the first gas of N2 or N20 is generated near the slit plate 5. Furthermore, if a second gas of SiH4 or 5i2H is introduced from the second gas introduction means, S is generated by the plasma of the first gas of N2 or N,O.
The iH4 or Si2H6 second gas is excited and plasma CVD produces N2 or N20 and SiH4 or 5i2H,
is decomposed and a Si◯ film is formed on the wafer 12. In this way, N2 or N20 is selected as the first gas, and S i H4 or 5i2H is selected as the second gas. In this case, compared to the case where the mixture is supplied from one gas supply means.

There is little reaction in the gas phase, and a SiOx film with small surface irregularities can be formed on the substrate surface.

Next, an embodiment of the present invention for reducing the temperature change of the substrate 12 will be described using the same FIG. 1.

That is, there is a method in which the substrate is heated by a resistance wire heater 20 embedded in the substrate mounting table 7. In this case, due to the low pressure atmosphere, there was a problem in that heat transfer between the substrate 12 and the mounting table 7 was poor, and it took a long time for the temperature to rise to the set temperature after the substrate 12 was placed on the mounting table 7. . FIG. 7 shows the results of measuring the temperature rise of the substrate 12 after it was placed on the mounting table 7 using a thermal lightning pair. It can be seen that the lower the pressure, the gentler the temperature rise curve. For example, 30 seconds after placing the substrate at 5 Pa, plasma is ignited and the film is formed for 1 minute 3.
When running for 0 seconds, the substrate temperature will go from 100℃ to 2006C+
It changes up to α. α is the amount by which the substrate is heated by the plasma. If the temperature change of the substrate is large as described above, the film quality will be different between the initial stage of film formation and the end of film formation, which is not preferable. Therefore, a lamp heater 17 was installed around the substrate 12. The lamp heater is a ring-shaped halogen lamp surrounded by an axially symmetrical groove-shaped reflection mirror 18.

Therefore, the light from the lamp obliquely illuminates the substrate (wafer) 12 from around it and heats it. lamp heater 1
7, the substrate 12 is rapidly heated, so the temperature at the start of deposition can be increased, and the difference in temperature between the substrate at the beginning and end of deposition can be reduced. Furthermore, temperature changes in the substrate can be further reduced by turning off the power to the lamp heater or reducing its output at the same time as the start of film formation. This is because the temperature decrease due to the decrease in the output of the lamp heater 17 and the temperature increase due to plasma generation are canceled out, and the temperature remains constant. You may do so. Further, it may be used in combination with the resistance wire heater of the substrate mounting table, in which case the lamp output can be reduced and a long-life far-infrared heater can also be used. In this embodiment, the lamp heater 17 is installed in the low pressure inside the plasma generation chamber, but it is also possible to install the lamp heater 17 in the atmosphere by vacuum sealing the space between the substrate and the lamp heater with quartz glass.

Furthermore, the temperature of the substrate 12 can be similarly raised by generating plasma of a non-film-forming gas immediately before film formation. When forming a Si film, N2 or N20 plasma is used. For N2 plasma, microwave power is 500W, 2
5P (Wafer temperature rises by 50 degrees in 30 seconds under L condition.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 and 5. A hole 21 for introducing gas is formed in the side wall of the cavity resonator 1 shown in FIG. 4, and communicates with the gap between the slit plate 5 and the separation plate (ceramic plate) 4. N2 was used as a cooling gas. The N2 gas that has passed through the hole 21 passes through the gap between the slit plate 5 and the separation plate 4, and passes through the slit 5c.
The air flows into the cavity resonator 1 and is exhausted through a hole 23 formed in the center of the upper part of the cavity resonator. Therefore, the slit plate 5 can be cooled and thermal deformation due to heating from plasma can be prevented. Other embodiments are shown in FIGS. 5 and 6. The temperature rise of the slit plate 5 due to plasma is highest at the center of the slit plate 5. Therefore, it is efficient for the cooling gas to flow to the center of the Surin 1 to the plate 5. Therefore, as shown in FIGS. 5 and 6, an elongated projection 5d was formed on the slit plate 5 so that a gas flow path could be formed when the projection was brought into close contact with the microwave window. In FIG. 5, an arc-shaped elongated protrusion is formed around the outermost slit 5c to prevent gas flowing in from the surroundings from flowing out from the outermost slit 5c. In FIG. 6, a guide protrusion 5d is formed so that the gas flows more precisely from the sulin 1 to the center.

〔Effect of the invention〕

As explained above, according to the present invention, there are effects as described below.

■ As a means of introducing gas into the plasma generation chamber,
A first gas introduction means introduced near the slit and a second gas introduction means introduced between the slit and the wafer are provided,
Gases are supplied individually, and the plasma of the first gas causes the second
By using the method of exciting the gas, reactions in the gas phase of the film-forming gas can be suppressed, so that the unevenness of the film formed on the substrate surface can be reduced.

■ Since a substrate heating means is provided that irradiates the substrate with a lamp heater from around the substrate, the temperature of the substrate at the start of film formation can be increased, reducing the temperature difference between the beginning and end of film formation. Changes in film quality can be prevented. The same effect as above can also be obtained by heating the substrate with N2 or N20 plasma immediately before film formation.

■ Gas flows through the gap between the slit plate and the microwave window, which has the effect of cooling the slit plate and prevents thermal deformation of the slit plate.

[Brief explanation of the drawing]

1 and 2 are a sectional view and a partially sectional perspective view showing one embodiment of the present invention, FIG. 3 is a plan view showing a slit plate, and FIG. 4 is a sectional view showing another embodiment of the present invention. 5 and 6 are plan views each showing a slit plate portion showing other embodiments of the present invention, and FIG. 7 is a cross-sectional view showing a portion of the cavity resonator shown in FIG. FIG. 3 is a characteristic diagram showing changes in substrate surface temperature over time. ...Cavity resonator, 2...Waveguide, 5...
Slit plate, 5c...Slit opening, 5d.
...Protrusion, 6...Plasma generation chamber, 7...
・Substrate mounting table, 12...Substrate, 13, 13'・
...Gas introduction hole, 14.14'...Gas reservoir. 15, 15'...Blowout hole, 17...Lamp heater, 20...Resistance wire heater. 17 --- Rania's first step? Fig. b Fig. L - 8 P1 8 + ash container 4 - 1 minute volume i + and 5 - 11 1)... Throat, throat tile Zl ---'IfK977°' 4xJL Ri C ---
Sri Soto? 3---Ladle and S

Claims (1)

[Claims] 1. A microwave source, a waveguide connected to the microwave source, a cavity resonator that resonates the microwave guided by the waveguide, and a microwave resonator placed on an electrode. A plasma processing chamber for chemically forming a film on a substrate, a separation plate for isolating the plasma processing chamber and the cavity resonator, and supplying resonant microwaves from the cavity resonator to the plasma processing chamber. an electromagnetic coupling means for individually introducing two or more gases into the plasma processing chamber, a first gas introduction port facing near the electromagnetic coupling means, and a second gas introduction A plasma chemical reaction characterized by comprising a plurality of gas introduction means installed such that an opening faces toward the substrate side from the first gas introduction port, and for suppressing a reaction in the gas phase of the film forming gas. Film deposition equipment. 2. Among the plurality of gas introducing means, N as the first gas
A gas containing at least one selected from _2, N_2O, NH_3, and an inert gas, and S as the second gas.
2. The plasma chemical reaction film forming apparatus according to claim 1, wherein the gas is a gas containing at least one selected from iH_4 and Si_2H_6, or a mixture of this gas with N_2 or an inert gas. 3. Chemical vaporization for a microwave source, a waveguide connected to the microwave source, a cavity resonator that resonates the microwave guided by the waveguide, and a substrate placed on the electrode. A plasma processing chamber for reaction film formation, a separation plate for isolating the plasma processing chamber and the cavity resonator, and an electromagnetic coupling means for supplying resonant microwaves from the cavity resonator to the plasma processing chamber. A plasma chemical reaction film forming apparatus comprising: a gas introducing means for introducing a chemical vaporization reaction film forming gas into the plasma processing chamber; and a heating means for heating the substrate. 4. The plasma chemical reaction film forming apparatus according to claim 3, wherein the heating means includes a heat source around the substrate, and the substrate is heated by radiation from the heat source. 5. The plasma chemical reaction film forming apparatus according to claim 3, wherein the heating means is configured to heat the substrate by treating the surface of the substrate with plasma of a non-film forming gas. 6. The plasma chemical reaction film forming apparatus according to claim 3, characterized in that the heating means is configured to be controlled. 7. A microwave source, a waveguide connected to the microwave source, a cavity resonator that resonates the microwave guided by the waveguide, and a chemical vaporization reaction on the substrate placed on the electrode. A plasma processing chamber for film formation, a separation plate for isolating the plasma processing chamber and the cavity resonator, and an electromagnetic coupling means for supplying resonant microwaves from the cavity resonator to the plasma processing chamber. , characterized by comprising a gas introducing means for introducing a chemical vaporization reaction film forming gas into the plasma processing chamber, and a cooling means for flowing a gas between the separating plate and the electromagnetic coupling means for cooling. Plasma chemical reaction film deposition equipment. 8. The plasma chemical reaction film forming apparatus according to claim 7, further comprising a guide for guiding the gas to the center of the electromagnetic coupling means as the cooling means. 9. Resonating microwaves guided from a microwave source through a waveguide by a cavity resonator separated from the plasma processing chamber by a separation plate, and supplying the resonated microwaves through an electromagnetic coupling means; More than one type of gas is individually introduced into the plasma processing chamber to suppress reactions in the gas phase of the film-forming gas, and chemical vaporization is performed on the substrate placed on the electrode installed in the plasma processing chamber. A plasma chemical reaction film formation method characterized by reaction film formation. 10. As gases to be introduced individually, N_2, N_2O,
A gas containing at least one selected from NH_3 and an inert gas, and a gas containing at least one selected from SiH_4 and Si_2H_6, or this gas contains N_2,
10. The plasma chemical reaction film forming method according to claim 9, wherein the gas is a mixture of an inert gas or an inert gas.