JPS6235515A - Accumulated film forming method - Google Patents

Abstract

PURPOSE:To obtain a film of high quality without roughing a boundary between the layers of a multilayer film by decomposing raw gas with a radical seed removed by photodecomposing or glow discharging. CONSTITUTION:A reaction chamber 1 and a plasma chamber 4 are evacuated in vacuum therein. A substrate as a support is set in the chamber 1. The substrate in the chamber 1 is heated to the prescribed temperature, and raw gas is supplied into the chamber 1. When the flow rate of the supplied gas arrives at the normal state, light of he prescribed intensity is emitted to the chamber 1 to photodecompose the reaction gas. When the prescribed time is finished, the light emission is stopped, and the gas supply is stopped. The raw gas in the chamber 1 is decomposed with radical seed generated in the chamber 1 and a noncrystal semiconductor thin film is accumulated on the substrate. The series of the operations are all automatically executed by a system controller to accurately control the thicknesses of the layers of the multilayer film.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to amorphous semiconductors and conductors containing semiconductor materials such as silicon and germanium, and SiN and 5i.
The present invention relates to a method for forming a deposited film suitable for forming multiple layers of an insulator such as 02 on a support.

[Prior technology] An ultra-high vacuum is used as an apparatus for producing a single-cell semiconductor multilayer film (a film in which each layer is thin enough to produce a quantum size effect is generally called a semiconductor superlattice). A method using molecular beam epitaxy is well known.

On the other hand, recently, multilayer thin films have also begun to be produced in the field of non-single-crystal semiconductors, but to date, only the glow discharge method has been reported in this field (for example, B. Abeles and T. Tiedje, Physical
Review Letters.

Vo151 N9F11) nt+-wa n01~
- [Problems to be solved by the invention] In devices using the glow discharge method as described above, 1. Normally, RF discharge is used, so at the start of discharge, the discharge becomes unstable due to poor matching with the power source. easy, therefore
In particular, when a thin film is produced by several dozen people, it is extremely difficult to control the film thickness.

In addition, the thin film is directly formed in the discharge atmosphere, and since there are many ion species with high energy in the discharge atmosphere, when forming multiple layers of thin films, these ion species The interface between each layer of the thin film becomes rough.

As described above, it is difficult to produce a high quality amorphous or polycrystalline non-single crystal semiconductor multilayer thin film using the conventional glow discharge method.

[Means for Solving the Problems] The present invention has been made to eliminate the drawbacks of the above-mentioned conventional examples, and includes a reaction vessel, a raw material gas introduction means for introducing raw material gas into the reaction vessel, and , a decomposition means for decomposing the raw material gas in the reaction vessel so as to form a deposited film on a support installed in the reaction vessel, and heating the raw material gas from the raw material gas introducing means before introducing it into the reaction vessel. A deposited film forming apparatus is used, and at least one of the operation timing and the amount of operation of at least one of each of the means is controlled (using a system controller).

[Embodiment] FIG. 1 shows the structure of an embodiment of a deposited film type r& apparatus according to the present invention.

In FIG. 1, 1 is a reaction chamber, and 2 is a front chamber connected to the reaction chamber 1 via a gate valve 3. 4 is a plasma chamber connected to the reaction chamber 1 via a gate valve 5 and a barrier pull orifice 6. Reference numeral 7 denotes an RF or microwave discharge power source for generating plasma discharge within the plasma chamber 4.

8.9 and 10 are exhaust systems for exhausting air from the plasma chamber 41, reaction chamber 1, and front chamber 2, respectively. Exhaust device 8
is connected to the plasma chamber 4 via an exhaust pipe 30, the exhaust device 8 is connected to the reaction chamber 1 via an exhaust pipe 31, and the exhaust device IO is connected to the front chamber 2 via an exhaust pipe 12.

In particular, the reaction chamber required when forming a deposited film! The exhaust device 8 is preferably a combination of a turbo molecular pump or a diffusion pump and a rotary pump so that the exhaust usage can be adjusted according to the internal pressure and the flow rate of the reaction gas.
A combination of a mechanical booster pump and a rotary pump is preferred.

13 is a gate valve provided in the exhaust pipe 30, 17 is a throttle valve provided in the exhaust pipe 31, 15 is a stop valve provided in the exhaust pipe 31 downstream of the valve 17, and 11 is a connecting pipe. But.

Two exhaust pipes 30 and 31 are installed between the gate valve 13 and the exhaust device 8 and between the two valves 15 and 17.
communicate. 14 is a stop valve provided in the connecting pipe 11, and 16 is a stop valve provided in the exhaust pipe 12.

Reference numeral 32 denotes a supply source of raw material gas, and the raw material gas from here is supplied to the plasma chamber 4 via the supply pipe 8 and the branch pipe 33, and is also supplied to the reaction chamber 1 via the supply pipe 18 and the branch pipe 34. be done. Reference numeral 21 denotes a heater installed in the middle of the supply pipe 18, which heats the raw material gas from the gas supply source 32 to, for example, a preset temperature. In addition, 21 may be heated with infrared light such as a halogen lamp, and the temperature can be measured using a thermocouple or CAR9 (Coherent Anti-9
takes Raman 5pectroscapy)
It is measured using methods such as 19 and 20 are branch pipes 3
3 and 34, respectively.

Reference numeral 22 denotes a light source for photodecomposing the reaction gas introduced into the reaction chamber 1, into which light enters through a window provided in the reaction chamber 1. Specifically, as the light source 22, for example,
Examples include low-pressure mercury lamps, Xe lamps, Xe-Hg lamps, excimer lasers, argon lasers, Nd-YAG lasers, and C02 lasers.

35 is a supply source of a reactive gas for generating plasma, and the reactive gas from here is supplied to the plasma chamber 4 via the supply pipe 24. A stop valve 25 is installed in the middle of the supply pipe 24. 23 is a substrate transport mechanism driven by hydraulic pressure, etc., which connects the front chamber 2 and the reaction chamber 1.
The substrate is transported between the two.

35, 38 and 37 are vacuum gauges, and plasma chamber 4
, the degree of vacuum in the reaction chamber 1 and the front chamber 2 is measured.

38 is a quality analyzer for measuring the raw material concentration in the reaction chamber l, and 100 is a thermometer for measuring the temperature of the raw material gas supplied to the reaction chamber l. Reference numeral 101 denotes a thermometer for measuring the temperature of the support on which the thin film is deposited, and is specifically composed of a thermocouple attached to a support holder (not shown) placed in the reaction chamber l. For example, by measuring the temperature of the support holder it is also possible to estimate the temperature of the support supported on it), +02 is a membrane for measuring the thickness of the thin film deposited on the support. It is a thickness gauge, and is comprised of, for example, an ellipsometer or the like inside the body A.

FIG. 2 shows a gas supply source for supplying raw material gas to the reaction chamber 1. As shown in FIG.

In FIG. 2, 40 is a purge gas (N2).

For days 41 to 4, raw material gas (e.g. SiH4, Si2H6
.

8786, PH3, CHa, CFa and NH
3 etc.) is the source. Gas from each gas source 41-48 is 6
Via the pipes 71-7B, each of the three-way valves 81-88. Each mass flow controller 51 to 5B and each three-way valve 6 capable of flow rate control and flow measurement
1 to B8 to the wood pipe 79, mixed appropriately in this main pipe 78, and supplied to the supply pipe 18.

On the other hand, gas from the purge gas source 40 is supplied to the pipes 71 to 78 via the pipe 70 and the three-way valves 81 to 88,
6 pipes 71 to 78 and wood pipe 78 are purged as appropriate. The six valves 61-88, 81-88, 91-98 and each mass blower controller 51-58 are controlled by a system control controller to be described later.

Figure 3 is a conceptual diagram showing the type of control by the system controller and the input information for control. Based on input information (zero constant value) such as film thickness, support (substrate) temperature, and gas temperature, the system controller performs valve opening/closing sequence control, gas pressure control, gas flow rate control, light source/plasma control, and temperature control ( substrate/gas).

FIG. 4 shows an example of the configuration of the system control controller.
The operational procedures of the entire system as shown in FIGS. 7, 8, and 8 are stored in advance in the floppy disk driver 103 as an external storage device,
04's internal memory. 105 is CPU
A driver that drives each valve according to commands from 104, 106 a mass flow controller interface,
111 to 118 are connected to the CP via the interface 10B.
It is a control unit that receives commands from U 104 and controls each mass 70-controller. In addition, the measured value of the flow rate of gas flowing in each pipe 71 to 78 from the flow rate detection means of each mass flow controller 51 to 5 days is determined by each unit 111 to 118 and the inter 7-chair IoFI or spring (:PU 104 Two inputs.

Reference numeral 107 denotes a light source control interface, through which the light source 22 is controlled based on commands from the CPU 104. Reference numeral 108 is a plasma control interface, through which the electricity s7 is controlled based on commands from the CPIJ 104. Reference numeral 109 denotes a temperature control device consisting of a resistance heater or an IR light source provided on the support holder, and controls the temperature of the support (substrate) and the degree of heating of the raw material gas, that is, the electric power value sent to the heater 21, based on commands from the CPU 104. control. The heater 21 is also C
Controlled by PU 104. Connection of each element is performed by, for example, an IEEE 488 bus.

In the above structure, deposition of a single layer film using a photolysis method will first be described with reference to FIG.

First, in step St, the inside of the reaction chamber 1 and the inside of the plasma chamber 4 are evacuated. This is done as follows,
Close stop valves 19, 20.25 and 15° gate valve 3, and close stop valve 14. Scottle valve 1f, gate valve 6 and 13. The barrier pull orifice 5 is opened, and the inside of the reaction chamber 1 and the inside of the plasma chamber 4 are brought to a degree of vacuum of about 1 O-Torr by the exhaust device 8. Note that at this time, the inside of the reaction chamber 1 may be baked using a heater.

Next, in step S2, a substrate serving as a support is placed into the reaction chamber 1. That is, first, open the top lid of the front chamber 2, place the substrate on the substrate transfer mechanism 23 in the front chamber 2 under atmospheric pressure, then close the lid of the second part of the front chamber 2, and close the stop valve. 1B and the exhaust device 10 makes the inside of the front chamber 2 a vacuum of about 10-7 to 10" Torr. Next, the gate valve 3 is opened and the substrate is transferred from the front chamber 2 into the reaction chamber 1 by the substrate transfer mechanism 23. 8, and placed on the substrate holder in the same room i, then return the substrate transport mechanism 23 to the front chamber 2, and close the gate valve 3.

Next, in step S3, the substrate in the reaction chamber 1 is heated to a predetermined temperature. Note that the substrate temperature is usually 100 to 500°C,
Preferably set at 200 to 400°C (thermometer 101
temperature control by referring to measured values).

Next, in step S4, raw material gas is supplied into the reaction chamber 1. That is, by opening the stop valve 20,
A gas supply source 3 supplies at least one type of required raw material gas.
2 into the reaction chamber 1. At this time, the selection of the gas type and the gas flow rate can be performed by controlling the relevant valve in the gas supply source 32, controlling the relevant mass flow controller, and referring to the flow rate detection value, and the gas temperature can be determined as necessary. This can be done by controlling the heater 21 with reference to the measured value of the thermometer 100 accordingly. However, the gas temperature is controlled below the decomposition temperature of the gas.

Next, in step S5, it is determined whether the flow rate (or pressure) of the raw material gas supplied into the reaction chamber 1 has reached the steady state y island.
2 and irradiates light of a predetermined intensity into the reaction chamber 1,
The reaction gas in the reaction chamber 1 is photodecomposed. At this time, since the reaction chamber 1 is evacuated by the exhaust device 8 or 8,
The pressure inside the reaction chamber 1 is maintained at the difference between the supply amount and the exhaust amount of the raw material gas.

Next, in step S7, it is determined whether the light irradiation has been continued for a predetermined period of time, and when the predetermined period of time has ended, step S
8, the light irradiation is stopped, and then, in step S9, the supply of raw material gas into the reaction chamber 1 is stopped. This series of operations is illustrated in FIG. 5. The thickness of the thin film that is decomposed by light irradiation and deposited on the substrate E depends on the type of gas,
Since these parameters depend on the gas flow rate, gas pressure, substrate temperature, type of light source, light intensity, and light irradiation time and are known empirically, these parameters must be entered in advance into the memory in the system controller's CPU. By setting the desired film thickness B! I can be created. In particular, since the amount of thin film deposited is approximately proportional to the light irradiation time, by changing the light irradiation time without changing other conditions, even a film as thin as several tens of layers can be deposited on a substrate with good controllability.

Next, in step SIO, the substrate after thin film deposition is taken out, that is, the inside of the reaction chamber 1 is again heated to 10=Torr~10 Torr.
The vacuum level is set to approximately fITarr, then the gate valve 3 is opened and the substrate is returned to the front chamber 2 by the substrate transfer mechanism 23, the gate valve 3 is closed, and the front chamber 2 is returned to atmospheric pressure to remove the deposited film. Take out the board with the mark on it.

Next, a procedure for depositing an amorphous semiconductor multilayer film on a substrate will be described with reference to FIG. Here, as an example, a case will be considered in which hydrogenated amorphous silicon and hydrogenated amorphous silicon nitride are alternately stacked on a substrate. In order to realize the quantum size effect, it is assumed that each layer has a thickness of 20 layers, a total of 100 layers of 50 layers each are laminated, and a silicon wafer is used as the substrate.

As shown in FIG. 8, the process of placing the substrate at a predetermined position in the reaction chamber 1 and heating it (steps S21 to S523) is the same as described above.

Next, in step S24, raw material gas is supplied into the reaction chamber 1. The raw material gas used is disilane (5i2H6)
, and ammonia (NH3), and the gas temperature is 100 to 200°C. Note that control of the raw material gas will be explained with reference to FIG. First, 5i7H6 and NO3 are mixed by opening and closing the three-way valve at the most downstream side of each line to flow from the vent line 90 to the gas supply pipe 18 side. At this time, the gas mixture ratio is The flow rate can be made variable by controlling the flow rate by a mass flow controller in the line. Here, for example, 5i7H6 is 0.5SCCM
, N1(3 is 5O3CG>!f!).

Next, in step S25, it is determined whether the amount fJi of the raw material gas supplied into one reaction chamber l has reached a steady state,
When this is reached, proceed to step 32G and apply light from a light source, such as a low-pressure mercury lamp, to the reaction chamber! The irradiation is carried out for 11 hours during the irradiation, and in step S27 it is determined whether 20 hydrogenated amorphous silicon nitrides have been deposited on the substrate based on the measured value of the film thickness meter. If 20 people have been deposited, step 928
Next, in step S2, the most downstream three-way valve of the NH3 line is changed to the vent line 90' to prevent NH3 from flowing into the raw material gas (Si2H6).
In step 9, 60 SCG of Si and H6 is flowed, and in step S30, it is determined whether the M gas residue amount has reached a steady state. If it has reached a steady state, the process proceeds to step 531, where the light source light is irradiated for t2 hours, and step Proceed to S32 and judge whether 20 hydrogenated amorphous silicon has been deposited on the substrate (the values 1..17 above are determined by preparing a single layer film in advance and determining the light irradiation time and the deposited amount). (It can be determined by proportional calculation from the film thickness).

If the number reaches 20, the process advances to step S33, and it is determined whether the number of thin film layers is 100. If it is 100, the process proceeds to step S34, and if it is not 100, the process returns to step S24, where 20 pieces of hydrogenated amorphous silicon nitride are deposited, and further 20 pieces of hydrogenated amorphous silicon are deposited thereon.

If the number of thin film stacks reaches 100 in step S33, the process proceeds to step S34 to stop the supply of raw material gas into the reaction chamber 1.Then, the process proceeds to step S35. The substrate after deposition is taken out (see Figure 6).

As described above, a desired amorphous semiconductor multilayer film can be automatically formed on a substrate.

One of the major features of the present invention is flow control, gas mixing,
The temperature TAtr1 and the above series of operations are all automatically performed by the system controller, and the thickness of each layer of the multilayer film can also be accurately controlled.

Here, we have given examples of the production of multilayer films using hydrogenated amorphous silicon and hydrogenated amorphous silicon nitride, but there are also cases where multiple types of gases are used, three or more different deposited films are stacked, or amorphous The procedure for producing a multilayer film consisting of a semiconductor, an insulator, and a metal is the same as above, and the present invention does not care about the type of film to be deposited.

Next, with reference to FIG. 8, a procedure for depositing a crystalline semiconductor fj layer using radical species generated in the plasma chamber 4 instead of photolysis will be described.

Place the substrate in the reaction chamber 1, supply raw material gas into the reaction chamber 1 at an appropriate mixing ratio depending on the film to be deposited, and check whether the gas supplied into the reaction chamber 1 has reached a steady state. The process of determining (steps 341 to 545) is the same as described above.

When the raw material gas supplied into the reaction chamber 1 reaches a steady state in step S45, the process proceeds to step S48, where the radical species generated in the plasma chamber 4 are passed through the gate valve 5 and the barrier pull orifice 6 to the reaction chamber! diffuse within. Note that in order to generate plasma in the plasma chamber 4, for example, Ar, H2,
A reactive gas such as CF is sent through the gas supply pipe 24, and an RF or microwave power source 7 is supplied into the plasma chamber 4.
Power is supplied to cause discharge within the plasma chamber 4.

As a result, the long-lived radical species generated in the plasma chamber are purified through the gate valve 5 and the barrier pull orifice 6. At this time, the ion species are Therefore, only neutral radical species can be extracted. Then, the raw material gas supplied into the reaction chamber 1 from the gas supply pipe 18 is decomposed by the energy of the radical species and deposited on the substrate. Since the source gas is decomposed by radical species rather than ionic species, the flow of the radical species is regulated using the gate valve 5 and the barrier pull orifice B, which does not roughen the surface of the deposited film.

Next, in step S47, it is determined whether the W1 film of a predetermined thickness has been formed on the substrate. When the deposited film has been formed to a predetermined thickness, the supply of raw material gas and radical species into the reaction chamber 1 is stopped in step 548, and step S4
Proceed to step 9 and take out the substrate in the same manner as above.

Note that the above-described light source light and the discharge in the plasma chamber 4 can also be used together.

In the above embodiment, when forming a deposited film on a substrate by photolysis, the source gas is not directly supplied to the reaction chamber l, but instead of being supplied with a stop valve 18. Plasma chamber 4, gate valve 5
．． By supplying the raw material gas through the barrier pull orifice 6, the flow of the raw material gas can also be made uniform by making it a laminar flow.

In addition, even if a film is deposited on the light entrance window of the reaction chamber 1, reducing the light transmittance, in such a case, the etching reaction gas should be replaced in the plasma chamber 4. By discharging, it is also possible to cause the discharge product to flow into the reaction chamber l through the gate valve 5 and the heliapul orifice to etch the inner surface of the window, and also to etch the inner surface of the window! Etching gas is introduced directly into the light source 2.
Etching the inner surface of the window by causing a photo-etching reaction using 2 is also an irradiation technique.

[Effects of Emission 11] As explained above, according to the present invention, when creating a non-condensed semiconductor multilayer thin film on a support, the raw material gas is not decomposed in a glow discharge but is photodecomposed or By decomposing it using radical species extracted from glow discharge, a high-quality film can be obtained without damaging the interface between each layer of the multilayer film. Furthermore, by heating the raw material gas in advance, it has become possible to decompose the raw material gas efficiently.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an embodiment of the deposited film forming apparatus according to the present invention, Fig. 2 is a diagram showing the configuration of the raw material gas supply source, and Fig. 3 is a diagram showing the types of control and control by the system controller. FIG. 4 is a diagram showing an example of the configuration of the system control controller. 5 and 8 are diagrams showing the relationship between supply of source gas and light irradiation, and FIGS. 7, 8, and 8 are diagrams showing an example of a film deposition procedure according to the present invention. 1... Reaction chamber, 2... Front chamber, 3.5.13... Gate valve, 4... Plasma chamber, 6... Barrier pull orifice, 7... RFii source or microwave power source , 8.9. t
o...Exhaust device. 11.12...Exhaust pipe, 14.15.18.25...Stop valve, 17...
Slow, Tor valve, 18.24...Reaction gas supply pipe. 19.20...stop valve, 32.35...gas supply source. 21... Heater. 22... Light source, 23... Substrate transport mechanism, 32.35... Gas supply source, 3B, 37.38... Vacuum gauge, 38... Mass spectrometer, 100.101... Temperature Total, 102...Film thickness meter. -gr3 bar Fig. 5 □B5 opening Fig. 6

Claims (1)

[Scope of Claims] A reaction vessel; a source gas introducing means for introducing a source gas into the reaction vessel; a decomposition means for decomposing the raw material gas in the reactor, and a means for heating the raw material gas from the raw material gas introducing means before introducing it into the reaction vessel, the raw material gas introducing means; A method for forming a deposited film, characterized in that at least one of an operation timing and an operation amount of at least one of the decomposition means and the source gas heating means is controlled by a preset program.