JP2000054150A - Plasma treating device and plasma treating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the film thickness controllable at high precision in thin film working of a substrate of a large area by previously monitoring the treating amounts of the plural places in the surface layer region of the substrate to be treated, thereby controlling the intensity of irradiation with microwaves corresponding to the respective positions and controlling the treating amounts on the surface of the substrate to be treated. SOLUTION: At first, a silicon wafer is set to a substrate supporting stand 121 via a wafer load-unload chamber 130. Next, a gate valve 123 is opened, the inside of a reaction vessel 120 is evacuated by a turbo-molecular pump for evacuation, and the pressure is controlled to about <=0.01 mPa. A prescribed amt. of gas is fed to a reaction vessel 120 from a gas feeding system 140 via a nozle 141, the pressure in the reaction vessel 120 is controlled to form a prescribed atmosphere, and microwaves are applied via each wave guide 125 (a) to (d) to generate plasma. At this time, the treating amounts of the plural places in the surface region of the wafer 110 is previously monitored to control the intensity of irradiating with the microwaves at each position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field microwave plasma processing apparatus, and more particularly to a control method suitable for uniformly and reproducibly processing a large area substrate or a plurality of substrates.

[0002]

2. Description of the Related Art Various kinds of thin film processing by plasma etching, plasma CVD and the like are used to manufacture electronic devices and micromachines such as semiconductor devices, thin film transistors (TFT-LCD) for liquid crystal displays, solar cells, semiconductor sensors, photosensitive drums for copying machines, and the like. Widely used for In order to increase the size of these electronic devices and reduce the manufacturing cost, the substrate size tends to be larger. For example, in a silicon semiconductor device, the size of a silicon wafer as a substrate is
0mmφ is used and in the near future 300mmφ, 40mm
0 to 450 mmφ is planned. For liquid crystal displays, the size of the glass substrate is 550 mm x 650 mm, 6
50 mm x 830 mm, and more than 1000 mm square will be used in the future.

To cope with the uniform processing of these large-area substrates, the conventional techniques are (1) to make the main factors of the plasma processing speed such as generation of plasma uniform by controlling the distribution of the lines of magnetic force, and (2) the reaction. Various measures have been proposed, such as making the flow of gas in the container uniform, selecting a raw material gas whose reaction on the substrate surface is rate-determining, and (3) rotating the substrate and electrodes.

[0004] Related to these, for example,
(1) JP-A-2-83924, JP-A-3-6380, JP-A-8
-191061, JP-A-9-22793, JP-A-8-92765,
(2) JP-A-8-236300, JP-A-8-102460, JP-A-9-22797, JP-A-9-36098, (3) JP-A-8-679
No. 95, JP-A-8-264513 and the like.

[0005]

Although various apparatuses and manufacturing methods have been proposed as described above, they are not sufficient for achieving a higher uniformity in a further increase in area.

In processing by plasma etching or thin film deposition by plasma CVD, the plasma processing state and speed are determined by the electron density of the plasma, the electron temperature, the dissociation rate constant of the source gas molecules due to the collision of high-speed electrons, and the dissociation of the source gas molecules. It is determined by the mean free path of generated radicals, establishment of adhesion and reaction of generated radicals, desorption rate of gas generated by the reaction, and the like. In addition, these factors include the type and composition ratio of the source gas, its supply amount and its timing and flux distribution, substrate temperature, microwave irradiation intensity and its pulse modulation,
It is a function of the process conditions such as the frequency and intensity of the bias applied to the substrate, the geometry of the reaction vessel, the reaction pressure, and the surface condition of the substrate. It needs to be well controlled. However, it is practically impossible to accurately control all of these functions in mass production. For example, the ratio of the power actually absorbed by the plasma to the input power of the microwave is a function of the density, and the function is non-linear. Therefore, the input power and the plasma (electron) density are complicated non-linear (density jump). , Hysteresis).

When a substrate having a different surface state or a film having a different composition is etched or deposited, the parameter survey of the etching or film forming process must be performed again each time.

An object of the present invention is to provide a plasma processing apparatus and a plasma processing method which are excellent in large area uniformity / reproducibility and productivity.

[0009]

In order to accurately control the state and speed of the plasma processing, first, a plurality of locations on the surface of the substrate to be processed are locally monitored, and then the above-described function of each function is added to each location. It is effective to feed back the most appropriate process conditions. Monitoring can be performed in-process (in parallel with the progress of the processing of the process and feedback of process conditions during the process) or in-line (evaluated items determined after completion of each process, and process the next lot) Feedback on conditions) can be applied. The function of the process conditions that is effective and can be controlled locally at high speed is
This is the microwave irradiation intensity.

That is, the object is to locally monitor the surface of a substrate to be processed in-process and control the irradiation intensity of microwaves corresponding to each position,
The uniformity and reproducibility of the plasma processing amount on the substrate surface are improved.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<Embodiment 1> FIGS. 1A and 1B are schematic views of vertical and horizontal cross sections of a magnetic field microwave plasma CVD apparatus 100 according to the present invention.

The reaction vessel 120 is made of an aluminum alloy (3.
5% magnesium containing), an inner diameter of 410 mmφ, a height of 136 mm, and one silicon wafer 110 of 300 mmφ can be set.

A wafer loading / unloading chamber 130 with a transfer robot 131 for taking in and out the silicon wafer 110 is provided on the side surface, and a turbo molecular pump 124 for evacuation is provided via a gate valve 123 for pressure adjustment at a lower portion.
Is provided. Turbo molecular pump for vacuum evacuation 1
24 has a pumping speed of 4500 liters / s. When the reaction gas supply rate is 1000 ml / min, the pumping speed is 0.2 Pa (1.5
mTorr).

On the side surface, four windows 126 (a) to 126 (d) made of quartz for introducing microwaves are provided.
A microwave oscillator (omitted in the drawing) is connected via 5 (a) to 5 (d). 2.45G microwave oscillator
Hz, 1.5 kW each, 10-100% duty variable type, aluminum rectangular microwave waveguide 125
(a) to (d) transmit the fundamental mode microwave.
A magnet 127 for ECR (Electron Cyclotron Resonance) formation is arranged around the quartz windows 126 (a) to 126 (d). Magnets 128 for forming a caps magnetic field for confining the generated plasma are arranged on the upper and side surfaces of the reaction vessel. The magnets 127 and 128 are made of samarium-cobalt (residual magnetic flux density of about 11000 G) and are arranged around the side surface and the upper surface of the reaction vessel 120. The magnetic flux density on the inner surface of the quartz window 126 (a) to (d) for microwave introduction is ECR.
It is about 1800 G, which exceeds 875 G for formation, while it is set to 20 G or less in the vicinity of the surface of the silicon wafer to prevent device damage.

A plurality of gas nozzles 141 are installed in the reaction vessel, and are connected to a gas supply system 140.

Inside the reaction vessel 120, a substrate support 121 for setting the silicon wafer 110 is provided, which is connected to a high frequency power supply 122. The substrate support table 121 is of a bipolar electrostatic chuck type with helium gas cooling.
56MHz, 5kW and 100-600kHz, 5kW are equipped and can be switched.

First, the silicon wafer 110 is set on the substrate support 121 through the wafer loading / unloading chamber 130. Next, the inside of the reaction vessel 120 is closed with a gate valve 123.
Is opened, and vacuum evacuation is performed by the evacuation turbo molecular pump 124. The ultimate pressure is 0.01 mPa or less.

A predetermined amount of gas from a gas supply system 140 is supplied through a nozzle 141. The control of the pressure in the reaction vessel 120 is performed by adjusting the gate valve 123.

After adjusting the inside of the reaction vessel 120 to a predetermined atmosphere, microwaves are irradiated through the waveguides 125 (a) to 125 (d) to generate plasma.

The application of the high frequency 122 to the substrate support table 121 is used at the time of depositing and filling the film into the grooves (concave portions) on the surface having fine irregularities by using the sputter etching of the deposited film.

FIG. 2 is a schematic diagram of a partial cross section of a basic structure of a multilayer wiring interlayer insulating film for VLSI formed according to the present invention.

This is a film forming substrate in which a silicon oxide film (SiO ₂ ) 20 and a lower wiring layer 30 mainly composed of aluminum (Al) are formed on a silicon wafer 10 having a diameter of 300 mm and an active layer formed thereon. The lower wiring layer 30
It has a three-layer structure of molybdenum silicide (thickness: 60 nm) -aluminum [containing 0.5% copper and silicon] (800 nm) -molybdenum silicide (40 nm). Wiring width 0.5 μm, wiring interval 0.4 μm, wiring thickness 0.9
μm 2, and the aspect ratio of the wiring groove 35 is 2.25.

An interlayer insulating film 40 was deposited by the high-density plasma CVD method of the present invention. The plasma state and process conditions are as follows.

Reaction gas supply amount Monosilane gas (SiH ₄ ) 160 ml / min Oxygen gas (O ₂ ) 220 ml / min Argon (Ar) 400 ml / min Reaction pressure 0.4 Pa Temperature of silicon wafer not controlled (during reaction, plasma irradiation Microwave (2.45 GHz) irradiation intensity 1.0 kW x 4 substrate-applied bias (400 kHz) 2.6 kW The high-frequency bias is applied to the substrate only in the plasma. Argon ions collide with the accelerated deposited film on the substrate, and the overhanging portions of the deposited film are selectively sputter-etched to fill (embed) the fine grooves 35 between the wirings and form a flat surface layer. This is for filming. For this reason, the film forming rate is reduced to about 65 to 70% of the case where the sputter etching is not performed without applying the substrate high frequency bias.

Under the above reaction conditions, a silicon oxide film having a thickness of 700 nm can be formed in a reaction time of 80 s. The quality of the deposited film and the characteristics at room temperature are as follows.

Film formation speed 525 nm / min Dielectric breakdown strength ≧ 8.5 MV / cm Resistivity 2 × 10 ¹⁵ Ω-cm Dielectric constant (at 1 MHz) 4.1 ± 0.1 Foreign matter density (≧ 0.3 μm) ≦ 0 .02 pcs / cm ² No plasma damage (from the shift of VI characteristics of MOS device with antenna ratio of 20,000) Etching rate by buffered hydrofluoric acid 0.8 nm / s (HF: NH ₄ F = 1: 10) Heated desorption gas analysis (contained Moisture content) Equivalent to thermal oxide film (dry oxygen) Refractive index 1.456 to 1.465 Peak wavenumber of infrared absorption spectrum (Si-O bond) 1078 to 1080 / cm (Si-H bond) Below detection limit (< 1 × 10 ¹¹ / cm ³ ) As described above, the measured values of the dielectric breakdown strength, the resistivity, and the results of the plasma damage evaluation sufficiently satisfy the basic properties of the interlayer insulating film. Further, the dense film is verified from the etching rate by buffered hydrofluoric acid, the refractive index, and the infrared absorption spectrum (Si-O bond). The moisture content is determined by thermal desorption gas analysis or infrared absorption spectrum (Si-H bond) analysis, and the moisture content is determined by thermal oxidation (dry oxidation) of silicon used in conventional semiconductor devices as a highly reliable film. It is equivalent to a film, and when these are combined, it can be evaluated as a high-quality dense film.

The uniformity of film thickness and film quality will be described.

FIG. 3A shows a case where the input from each of the four microwave inlets is 1.0 kW according to a normal method.
4 shows a distribution of deviation from the average value of the deposited film thickness in a 300φ wafer. The deviation from the average value within the wafer is +10 to -8%. Observation in detail reveals that the vicinity of the microwave introduction ports (a) and (b) indicated by arrows is thick, and the vicinity of (c) and (d) is relatively thin. As described above, the cause of this distribution includes factors such as plasma distribution, gas flow distribution, substrate temperature distribution, and distribution of substrate surface treatment.

With respect to the uniformity, the conventional method has been improved in order to make these factors uniform. On the other hand, in the present invention, the variation of various factors is corrected by the irradiation intensity of the microwave to achieve uniformity. In view of the above measurement results, the input from each of the four microwave introduction ports (a) to (d) is 0.85 k.
W, 0.9 kW, 1.1 kW, 1.0 kW. FIG.
(2) shows the distribution of the deviation from the average value of the deposited film thickness in the 300φ wafer when corrected by the irradiation intensity of each microwave according to the present invention. ± 4 deviation from average value in wafer
It can be seen that the percentage is greatly improved. Further, it was confirmed that the film thickness distribution between the wafers could be secured ± 4%. Further, as a result of measuring the distribution of the refractive index of the deposited film as a representative value of the film quality, 1.46 ± 0.006 was confirmed both within the wafer and between the wafers, demonstrating the uniformity and reproducibility.

<Embodiment 2> FIG. 4 is a schematic view of a vertical cross section of a large-area magnetic field microwave plasma oxidizing apparatus 200 according to the present invention. The configuration of the device is basically the same as that shown in FIG. 1, and differences will be mainly described.

The reaction vessel 220 has an inner diameter of 820 mmφ and a height of 2 mm.
20 mm, 300 mmφ silicon wafer 210
Can be set. 4 quartz windows 2 for microwave introduction
Reference numeral 26 is provided on the shoulder of the reaction vessel 220. The substrate support 221 is connected to a DC power supply 222.

A feature of the present apparatus is that an in-process measuring device 250 for film thickness by light (laser) interferometry is installed, and the measurement result can be fed back to the output of the microwave oscillator. The irradiation light is visible He-Ne laser
(λ = 632.8 nm), but as the wavelength becomes shorter,
The interference cycle is short, the measurement accuracy is improved, and it is suitable for thin films.
The light absorption by the deposited film increases and the sensitivity decreases.

The flow rate of oxygen gas is adjusted to a pressure of 10 Pa
Irradiation of about 1 kW was performed from each of the four entrance windows while controlling the microwave power of 2.45 GHz at four locations to generate oxygen plasma having a density of about 10 ¹² n / cm ³ . In addition, a DC voltage of 1 kV was applied to the substrate to improve the oxidation rate. The substrate temperature during oxidation is maintained at about 350 ° C., and a relatively thick oxide film can be formed with low stress by low-temperature and high-speed oxidation.

A silicon oxide film having a thickness of 750 nm was formed for an oxidation time of 10 minutes. The film thickness distribution is within ± 3% in both the wafer and the lot. The film thickness distribution when the film thickness was not controlled in-process was ± 5% in the wafer and ± 8% in the lot, demonstrating the effectiveness of the in-process control.

<Embodiment 3> TFT for liquid crystal display
An example in which the present invention is applied to a (thin film transistor) panel manufacturing process will be described.

In order to install a large glass substrate of size 650 × 830, the diameter of the reaction chamber is 1150 mm, and the number of microwave entrance windows is the same as that shown in FIG. For the in-process measurement of the film thickness, an ellipsometry (ellipsometry) was installed in addition to the light (laser) interferometry as in FIG. This is because the ellipsometry has excellent measurement accuracy for an extremely thin film of polycrystal or amorphous silicon.

FIG. 5 is a schematic diagram of a cross-sectional structure of a basic structure of a positive coplanar type microcrystalline silicon TFT for a high definition display incorporating a peripheral driving circuit. The film was formed by the following process.

(A) The surface of a glass substrate 300 was covered with a silicon oxide film (SiO ₂ ) 310. This is to prevent impurities in the glass substrate from radiating to the outside and deteriorating the characteristics of the TFT. A film thickness of 400 ± 50 nm was deposited by microwave plasma CVD using monosilane and oxygen as source gases without in-process control of the film thickness. The reason why the film thickness is not controlled in-process is that the accuracy of the film thickness is not required in this step, and it is to prevent the film from adhering to the monitor part and to reduce the maintenance frequency. .

(B) Next, a silicon film 320 was deposited. A film thickness of 60 ± 3 nm was deposited by microwave plasma CVD using monosilane as a source gas. Since the thickness of this silicon is an important factor in the characteristics of the TFT,
The thickness of the deposited film was measured by ellipsometry, and the result was fed back to the output of the microwave and controlled in-process, whereby the inside of the substrate could be kept within ± 5%. In such a large-surface active thin film, the film thickness distribution is limited to ± 10% without in-process control.

(C) Subsequently, in the same reaction chamber, the silicon film 320 on the substrate was irradiated with hydrogen plasma. In the hydrogen plasma, the raw material gas is hydrogen, the microwave output is 1.5 kW, and the plasma density is about 5 × 10 ¹² n / cm ^3.
High density. At this time, the substrate is heated to about 450 ° C. under plasma irradiation. As a result, the silicon film is changed from an amorphous state to a microcrystal (microcrystal) having a uniform orientation and grain size.
Thereby, the mobility of electrons, which is one of the important characteristic values for the TFT, is improved to ^{20 to} 60 cm ² / V · s,
In addition, uniformity and reproducibility are improved.

(D) The silicon film 320 is processed into a predetermined pattern by photolithography and dry etching.

(E) A silicon oxide film (SiO ₂ ) 330 as a gate insulating film and a polycrystalline silicon film 340 as a gate electrode are both deposited by a plasma CVD method and formed into a predetermined pattern by photolithography and dry etching. Process.

(F) Phosphorus is doped into the exposed portion of the silicon film 320 of the microcrystal by plasma doping, and laser annealing is performed to obtain an n-type.

(G) Silicon oxide film 35 for carry-up
0 is deposited and processed into a predetermined pattern by photolithography and dry etching.

(H) Thus, the basic structure of the TFT can be formed. Thereafter, the TFT panel is processed through the steps of aluminum wiring 360 for source / drain electrodes, transparent electrode (ITO), dielectric film for storage capacitor and transparent electrode, etc. Can be formed.

In the embodiments of the present invention, the application of the present invention to plasma CVD and plasma oxidation for a multilayer wiring interlayer insulating film of a semiconductor device and plasma CVD of a silicon film for a display device has been described. However, the present invention is not limited to this. Not
It is also effective for manufacturing large-area devices such as solar cells and photosensitive drums. Also, plasma nitridation is used as the plasma process, low dielectric constant film such as amorphous carbon, high dielectric constant film such as BST (barium strontium titanate), ferroelectric dielectric film such as PZT, diamond film, various metal films, etc. Applicable with dry etching.

[0048]

According to the present invention, (1) high-accuracy film thickness control becomes possible in thin film processing on a large-area substrate,
(2) Uniformity and reproducibility of the formed thin film can be secured,
(3) Since the control of the thin film processing apparatus is easy and the productivity is excellent, there is a great effect in improving the yield and characteristics of semiconductor devices and display devices, especially large area substrate devices.

[Brief description of the drawings]

FIG. 1 is a schematic view of a vertical and horizontal section of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view of a partial cross section of a semiconductor device formed by performing the manufacturing process of the present invention.

FIG. 3 is a graph showing experimental results of film thickness distribution in a large-area wafer before and after applying the present invention.

FIG. 4 is a schematic sectional view of a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 5 is a schematic view of a partial cross section of a semiconductor device formed by performing the manufacturing process of the present invention.

[Explanation of Signs] 100 : Magnetic Field Microwave Plasma CVD Apparatus, 11
0, 210: silicon wafer, 120, 220: reaction vessel, 125, 225: microwave waveguide, 126, 22
6. Quartz window for microwave introduction, 127, 128, 22
7,228 ... magnet, 141,241 ... gas nozzle, 20
0 : Magnetic field microwave plasma oxidizer, 250: Film thickness in-process measurement equipment.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/3065 H05H 1/46 C 21/31 H01L 21/265 F H05H 1/46 21/302 B F term (Reference) 4K029 AA06 AA09 BA35 BA46 BC05 BD01 BD08 CA00 CA05 DC48 GA02 KA09 4K030 AA06 AA14 AA16 BA27 BA29 BA44 BA46 CA04 CA06 DA04 DA08 EA06 FA02 GA02 GA12 HA01 HA06 HA08 JA13 KA30 KA39 KA41 LA02 DB11 DA11 DD01 DG20 DM29 DM36 DM38 DN01 5F004 AA01 5F045 AA09 BB02 DP04 EH03 GB04

Claims (5)

[Claims] 1. A gas supplied from a gas nozzle provided in a vacuum reaction vessel is formed around microwaves irradiated from a plurality of inlets provided around the vacuum reaction vessel and the inlet. In the method of forming a plasma by electron cyclotron resonance with the applied magnetic field and performing plasma processing on the surface of the substrate to be processed installed on the support in the vacuum reaction vessel with the plasma, a plurality of surface layer regions of the substrate to be processed are previously formed. A plasma processing method characterized in that a processing amount in a surface of a substrate to be processed is controlled by monitoring a processing amount at a location and thereby controlling a microwave irradiation intensity corresponding to each position. 2. A gas supplied from a gas nozzle provided in a vacuum reactor is formed around microwaves irradiated from a plurality of inlets installed around the vacuum reactor and the inlet. A plasma processing apparatus that forms a plasma by electron cyclotron resonance using an applied magnetic field, and performs plasma processing on the surface of the substrate to be processed, which is installed on a support in a vacuum reaction vessel, using the plasma. In-process measurement of the processing amount at the point, and the measured value is fed back to the control device of the microwave oscillator to control the irradiation intensity of the microwave corresponding to each position, and the processing target installed in the reaction vessel. A plasma processing apparatus for controlling a processing amount in a surface of a substrate. 3. The plasma processing apparatus according to claim 2, wherein the plasma processing apparatus is one of a plasma CVD apparatus, a plasma etching apparatus, a plasma oxidizing / nitriding apparatus, and a plasma doping apparatus. 4. A gas supplied from a gas nozzle provided in a vacuum reaction vessel is formed around microwaves irradiated from a plurality of inlets provided around the vacuum reaction vessel. In the plasma processing method of forming plasma by electron cyclotron resonance by the applied magnetic field and performing plasma processing on the surface of the substrate to be processed installed on the support in the vacuum reaction vessel with the plasma, a plurality of surface layer regions of the substrate to be processed are provided. A plasma processing method comprising: in-process measuring a processing amount at a point; and feeding back the measured value to a control device of a microwave oscillator to control a microwave irradiation intensity corresponding to each position. 5. The plasma processing method according to claim 4, wherein the method is one of plasma CVD, plasma etching, plasma oxidizing / nitriding, and plasma doping.