JPH01143221A - Manufacture of insulating thin film - Google Patents

Abstract

PURPOSE:To perform film formation control which exhibits excellent repeatability over a wide area, by performing alternately two processes: a process to allow a hydride containing at least one silicon atom or its radial thereof to stick fast to the surface of a substrate and the process to supply an element or more at least out of elements: nitrogen or oxygen or gases of compound thereof. CONSTITUTION:First of all, mono-silane is introduced in the side of a reaction chamber 1 by operating a three-way valve 2 for two sec. to make mono-silane attach on a substrate 4. Then, the three-way valve 2 is closed at the side of the reaction chamber for a second and a gas in the reaction chamber is replaced and then, ammonia is introduced in the reaction chamber 1 by operating the three-way valve 3 to nitrify an absorption layer which is formed by the first process. After carrying out the second process, the gas in the reaction chamber is replaced again for a second and after that, its process reverts to the first process. A treatment cycle consisting of these procedures are repeated as often as the times predetermined. In such a case, the film thickness of a growth is correctly in proportion to the number of cycle and its repeatability can be confirmed as well and the resultant film formation of an atomic layer order can be controlled. The film thickness distribution in this substrate is extremely uniform as such it is within + or -1%.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing an insulating thin film.

[Conventional technology]

In recent years, insulating thin films have become extremely important as a means to miniaturize, improve performance, and improve the performance of electronic devices and elements. I started doing it. In particular, the performance of insulating thin films containing silicon, such as gate insulating films of thin film transistors, various semiconductor devices, and insulating thin films for capacitors, has a great influence on device characteristics. Furthermore, insulating thin films used for passivation and interlayer insulation are essential for improving reliability. Conventionally, such insulating thin films have been manufactured by chemical methods such as chemical vapor deposition techniques and coating methods under normal pressure or reduced pressure, and physical methods such as vacuum evaporation methods and sputtering methods.

[Problem that the invention seeks to solve]

As the range of applications for insulating thin films expands, there is an increasing need to form films uniformly and with good reproducibility on large-area substrates. This is a particularly important problem in thin film elements for displays. Conventional technology requires precise control of gas flow and pressure during film formation, evaporation amount,
Careful management of numerous manufacturing parameters was required, including input power, substrate temperature and its distribution, consideration of gas flow, and substrate rotation. In addition, film thickness was indirectly controlled by accurately controlling the film formation time.

As described above, there are a wide variety of thin film manufacturing parameters, and great efforts are being made to control them.However, as substrates become larger, it is becoming increasingly difficult to form insulating thin films with uniform thickness with good reproducibility. It's coming. In particular, insulating thin films for display panels require a very large substrate, and variations in film thickness, for example, affect the performance and reliability of the panel. Furthermore, new devices using ultra-thin film all-I, which have been actively researched in recent years, can control the growth rate on the order of 1 atom! Manufacturing technology that performs this process accurately and with good reproducibility is essential. However, it has been difficult to satisfy these requirements using conventional techniques.

An object of the present invention is to provide a new method for manufacturing an insulating thin film, which enables film formation control on the order of atomic layers with good reproducibility over a wide area.

[Means for solving problems]

The method for producing an insulating thin film of the present invention includes a first step of supplying and adhering a hydrogen compound containing at least one silicon element or its radical to the substrate surface, and a step of applying nitrogen, nitrogen, or a hydrogen compound thereof to the substrate surface. All characteristics of at least one of the following compound gases:

[Effect]

The first step in the structure of the present invention is a step of adsorbing a silicon compound or its radicals onto the surface of the substrate in a layered manner. In this step, the coverage of the adsorption layer may become less than 1 due to insufficient adsorption energy, steric hindrance between adsorbed molecules, or thermal desorption from the surface. Even in such a case, it is most important to select, for example, the temperature of the growth substrate, the introduced silicon compound, or its radical species so as to prevent the formation of island-like growth in the Volmer-Weber style. That is, if manufacturing conditions are selected so that the adsorption energy to the underlying layer to which the silicon compound or its radical species is adsorbed is higher than the adsorption energy to the already formed adhesion layer, a layered adsorption layer will be formed. If such a two-dimensional suction book is formed, even if the coverage is less than 1, it is possible to form a uniform thin film by repeating the first and second steps of the present invention by <9 times.

The second step of the present invention is a step of oxidizing or nitriding the adsorption layer made of the silicon compound or its radical species formed in the first step. This oxidation or nitridation of the adsorption layer is performed by supplying at least one of nitrogen, oxygen, or a compound gas thereof onto the adsorption layer to cause a surface reaction. Since the reaction occurs only in the surface adsorption layer, the reaction proceeds quickly at a relatively low temperature, and no undesirable secondary reactions occur after the reaction is completed.

In the first step, even if slight variations in gas supply amount occur at the location or during the film formation time, multi-layered adsorption layers will not be formed in a portion. In addition, a two-dimensional adsorption layer is formed in the first step.
If the manufacturing conditions are slightly changed in the second step, a uniform silicon oxide or silicon nitride molecular layer will be formed. That is, since the present invention uses the functions of forming an adsorption layer and oxidizing or nitriding the adsorption layer, it is possible to form an insulating layer uniformly over a wide range,
Furthermore, by repeating the first step and the second step, the thickness of the grown film can be controlled on the order of atomic layers. Moreover, the thickness of the grown film can be determined accurately and reproducibly by the number of repetitions of each step.

As described above, the present invention enables precise control of the thickness of an insulating thin film on a large-area substrate. Further, the prior art requires careful control of manufacturing parameters, making automation and labor-saving difficult. As described above, in the manufacturing method according to the present invention, even if there is a slight variation in manufacturing parameters, the thickness of the grown film does not change, making it possible to automate and save labor in manufacturing. Furthermore, the reproducibility of the insulating thin film thickness can be improved, and as a result, the performance of elements such as thin film transistors can also be improved.

In addition, since the first and second steps' (11-1 cycles) are used to grow thin films on the order of atomic layers, the time required for film formation is longer than that of conventional techniques; Even if a large number of substrates are processed at once, a uniform insulating thin film can be formed, so the overall throughput of the present invention is by no means lower than that of the prior art.

〔Example〕

Hereinafter, examples of the present invention will be explained with reference to FIG. 7f.

FIG. 1 is a block diagram of an insulating thin film manufacturing apparatus used in a first embodiment of the present invention, in which monosilane and ammonia are used as starting materials. The reaction chamber 1 made of quartz can be evacuated to 10 Torr or less, and the three-way valves 2 and 3 are controlled by a microcomputer and are operated so that monosilane and ammonia can be alternately introduced into the reaction chamber 1. The reaction chamber 1 has a structure that can accommodate a large number of large substrates 4, and the substrates 4 are heated by an electric furnace 5 at a temperature of about 00°C. Reaction chamber 1, three-way valve 2
．． The exhaust gas pipe side in No. 3 is evacuated using separate vacuum pumps.

Here, a nitride film formed on single crystal silicon substrate 4 will be described. First, the reaction chamber 1 containing the substrate 4e was evacuated with a vacuum pump to a temperature below IO-' Torr, and then the entire substrate was heated to 350° C. using the electric furnace 5. Stabilize by flowing into the monosilane and ammonia supply pipes. Both flow rates f# were 39 secM. Argon A
A purge gas of r is flowed into the reaction chamber 1, and the pressure of the reaction chamber 1 is f.
Adjust the flow rate adjusting pulp 7 and main valve 12t so that it is around I Torr.

At this time, the pressure in the monosilane and ammonia supply lines was from several Torr to several tens of Torr.

First, the three-way valve 2t is operated for 2 seconds to introduce monosilane into the reaction chamber 1, and this monosilane is deposited on the substrate 4 (first step). Next, the gas in the reaction chamber is replaced by using the three-way valve 2 as a side valve for one second, and the three-way valve 3 is further operated to introduce ammonia into the reaction chamber 1, which absorbs the adsorbed gas formed in the first step. The second step is to nitride the layer. After the second step is completed, the gas in the reaction chamber is replaced again for one second, and then the process returns to the first step. These steps are repeated for a predetermined number of cycles as 'tl cycles.

In this case, although one molecular layer was not grown in one cycle, the thickness of the grown film was accurately proportional to the number of cycles, and its reproducibility was confirmed, indicating that film formation can be controlled on the order of atomic layers. The film thickness distribution within this substrate was extremely uniform within ±is.

Although monosilane was used in this example, a similar effect could be obtained using disilane, and a silicon oxide film could also be formed using oxygen instead of ammonia. Furthermore, silicon oxynitride could also be formed from a mixed gas of N: and N20. In this way, a silicon-based insulating thin film can be formed using a combination of various gases.

Similar effects were obtained when the substrate temperature ranged from 200 to 600°C, but below 200°C, the adhesion rate and surface reaction decreased, resulting in almost no film growth, and above 600°C, the attached monosilane decomposed. This was inappropriate because the process progressed to three-dimensional growth.

FIG. 2 is a block diagram of an insulating thin film manufacturing apparatus used in a second embodiment of the present invention. The device used in this example is basically the same as that shown in FIG. 1, except that the radical generator 21.2
2 have been newly added.

Radicals are generally generated by discharge caused by external stimulation such as high frequency, direct current, or microwave, and in this example, microwave discharge was used. Furthermore, monosilane was used as a raw material in the first step, a mixed gas of oxygen and nitrogen was used in the second step, and the substrate 4 was a glass substrate. In the same manner as in Example 1, several glass substrates 4 were placed in a reaction chamber 1 and the chamber 1 was evacuated, and then the substrate temperature was heated to 150° C. in an electric furnace 5.

The manufacturing procedure is the same as in the first example, in which monosilane radicals are supplied for 2 seconds, followed by a 1 second scum replacement period. Argon was used as the replacement gas, but there was no change even with nitrogen. Further, the radicals of the mixed gas are supplied for 2 seconds, and the gas is replaced again for 1 second. The above series of steps is one cycle, and is repeated a predetermined number of times.

As a result, the film formed was a highly insulating gold-containing silicon oxynitride thin film with very few defects such as pinholes, and the film thickness distribution within the glass substrate was within ±1%.

This grown film thickness was accurately proportional to the number of cycles, and its reproducibility was also good.

Furthermore, even if only one of the radical generators is operated,
A similar effect 'f: could be obtained. In addition, the raw material used in the first step is disilane, and the gas used in the second step is a mixed gas of oxygen, nitrogen, and ammonia, a mixed gas of ammonia and N20, or various combinations such as only oxygen or only nitrogen. I was able to get the same effect even though I did it.

Furthermore, by forming radicals, the mating temperature could be lowered.

FIG. 3 is a block diagram of an insulating thin film manufacturing apparatus used in a third alternative embodiment of the present invention. In this case, the gases used in the second step, ammonia and oxygen, are supplied by separate three-way valves 31. Pressure adjustment valve 32. The structure is such that it can be introduced from the flow meter 33. The substrate 4 is made of single crystal silicon and is heated to about 300°C. First, disilane is completely supplied for 2 seconds, gas replacement is performed for 1 second, then only ammonia is introduced for 2 seconds, and gas replacement is performed for 1 second. This series of procedures is defined as a first cycle, and after repeating the first cycle r six times, the process moves to the second cycle. In the second cycle, disilane is supplied for 1 and 2 seconds, gas exchange is performed for 1 second, then only oxygen is introduced for 2 seconds, and sludge replacement is performed for 1 second. After repeating this second cycle twice, the process returns to the first cycle.

As described above, the first and second vehicles are treated as one cycle, and the cycle is repeated a predetermined number of times.

In this example, the grown film thickness was accurately proportional to the number of cycles, and its reproducibility was also high. The thin film thus formed had a dielectric breakdown electric field comparable to that of silicon oxide, and also had a high dielectric constant.

Furthermore, it has a barrier effect against ions comparable to that of silicon nitride, and can be used for gate insulating layers, capacitors, etc.

Incidentally, the gas used in the first step may be monosilane or the like, and the gas used in the second step may be used in various combinations depending on the purpose, and similar effects could be obtained. Furthermore, by radicalizing the supplied gas, it was possible to form a film even at a somewhat low temperature, and the quality of the film did not change much even if the gas was radicalized.

〔Effect of the invention〕

As explained above, the insulating thin film manufacturing method of the present invention controls the grown film thickness on the order of atomic layers. Further, even if a large-area substrate was processed many times, it was possible to form a uniform thin film with good reproducibility. Furthermore, a uniform thin film could be formed without any special equipment modifications such as gas flow or substrate rotation.

Therefore, the structure of the manufacturing equipment is simpler than the conventional one. On the other hand, since the film thickness can be controlled accurately with cycle control,
The entire process was automated and labor-saving. The throughput of the entire process was not significantly different from that of the conventional method.

The silicon-based insulating thin film formed according to the present invention had excellent insulation properties and had very few defects such as pinholes.

The present invention can be applied to many applications such as thin film transistors, but by taking advantage of the fact that the film thickness can be controlled on the order of atomic layers, new applications such as the production of devices with superlattice structures are also possible.

[Brief explanation of the drawing]

Figures 1, 2 and 3 are schematic diagrams of the insulating thin film manufacturing apparatus used in the first, second and third embodiments of the present invention. , 2.3.31... Three-way valve, 4... Board, 5... Electric furnace, 6,7
, 8.32... Pressure adjustment pulp, 9,1011
1, 16・°゛・°°Pressure gauge, 12... Main pulse 7', 13, 14, 15.33... Flow meter, 2
1.22... Radical generator. Agent Patent Attorney Oto Uchihara

Claims (1)

[Claims] A first step of supplying and adhering a hydrogen compound containing at least one silicon element or its radical to the substrate surface, and a second step of supplying at least one of nitrogen, oxygen, or a gaseous compound thereof to the substrate surface. 1. A method for producing an insulating thin film, comprising alternating the steps of