JPS60165728A - Forming method for thin film - Google Patents

Abstract

PURPOSE:To obtain a thin film of high quality by emitting visible or near ultraviolet rays in the absorption zone of halogen gas to reactive gas containing raw material gas and halogen element to excite the halogen gas and colliding it with the raw material gas to activate the raw material gas. CONSTITUTION:The density of raw material gas SiC4H12 is suitably selected, the gas is mixed with O2, the density of reactive gas Cl2 is selected, fed into a reaction chamber, which is evacuated from an outlet 17, and the entire gas pressure is held at 10Torr or higher. When a pulse laser light 19 having 308nm or longer of wavelength is emitted vertically or horizontally to a sample 12, a thin organic film 21 of high quality may be efficiently accumulated. The raw material gas employs silane and organic silanes, hydrogenated Ge and organic Ges, phosphine and organic phosphines, borane and organic boranes, arsine and organic arsines, organic metal compounds and halogen derivatives thereof, which are mixed with O2 or N2. The emitted light is condensed on the sample, and scanned over the entire surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a thin film using a photochemical reaction.

[Problems with technical foresight of the invention]

In recent years, as the integration of semiconductor integrated circuits has progressed, conventional two-dimensional circuits are approaching the limit of their degree of integration. Therefore, in order to overcome this limit and further increase the degree of integration, it is desired to establish a manufacturing technology for three-dimensional circuits such as multilayer wiring and three-dimensional integrated circuits.

Here, in order to create a three-dimensional circuit, it is essential to form thin films such as interlayer insulating films, semiconductor thin films, and even metal wiring films without damaging the underlying circuit board.

Conventional III film forming methods include vapor deposition method, CVD method,
A plasma CVD method, a photo CVD method, or the like is used. However, in the case of the PCVN vapor deposition method, in order to obtain a homogeneous thin film, it is necessary to maintain the substrate at aiIi temperature, which may cause phase n diffusion between the metal wiring layer and the semiconductor junction, or change the impurity distribution in the semiconductor. etc. have negative effects. In addition, in the plasma CVD method, charged particles in the plasma are accelerated by the potential difference generated between the plasma and the substrate and impact the substrate, which causes defects on the substrate and deteriorates electrical characteristics. There is.

In contrast, the photo-CVD method is capable of forming thin films at low temperatures and does not generate high-energy charged particles.
This technique is expected to overcome the problems of the above methods. However, in the photo-CVD method, most of the gases that are the raw materials for thin films do not absorb light in the visible or near ultraviolet regions;
It is necessary to use short wavelength light in the vacuum ultraviolet region to activate the source gas. When vacuum ultraviolet light is used, the light source and the window material for guiding the light into the reaction vessel are special and expensive, and when it passes through the air, it generates ozone, which is harmful to the human body, so there are some precautions when handling it. Caution is required. Further, the conventional photo-CVD method has problems such as a slow thin film deposition rate at low temperatures.

Incidentally, there is a method of incorporating mercury vapor as a sensitizing material to increase the thin film jff deposition rate, but if heavy atoms such as mercury are incorporated into the film, it has an adverse effect on the electrical characteristics of the integrated circuit element. Furthermore, even in the mercury sensitization method, the wavelength is 200 [n
However, it was not possible to solve the above-mentioned problems because it was necessary to use violet light with a short wavelength of less than m].

[Purpose of the invention]

An object of the present invention is to provide an m-film forming method that can efficiently form a high-quality thin film using light in the visible or near ultraviolet region and can contribute to higher integration of semiconductor devices.

[Summary of the invention]

The gist of the present invention is to introduce a reactive gas containing a halogen element together with the raw material gas instead of using light that directly excites the gas as a means of activating the raw material gas. The method involves exciting the halogen gas by irradiating it with visible or near ultraviolet light, and activating the source gas by collision between the excited halogen gas and the source gas.

That is, the present invention provides a method for forming a thin film by depositing a thin film on a sample by a photochemical reaction, in which the sample is mixed with a reactive gas containing a raw material to be deposited on the sample and a reactive gas containing at least a halogen element. 5- This is a method in which the mixed gas is exposed to a gas atmosphere and light that dissociates the reactive gas is irradiated into the mixed gas.

(Effects of the Invention) According to the present invention, by mixing a halogen gas that absorbs this type of light into a raw material gas that does not absorb visible or near ultraviolet light, it is possible to indirectly excite the raw material gas with the above light. Therefore, optical CvD can be achieved using visible or near-ultraviolet light, which is easy to handle, without using vacuum ultraviolet light.Furthermore, the deposition rate of the )w film can be made sufficiently high.

That is, when the raw material gas and the halogen gas react, J:
Thus, hydrogen in the raw material gas is replaced by halogen to produce a halogenated derivative. These halogen derivatives have a large molecular weight compared to the raw material gas, so their vapor pressure is generally low.
It condenses on the substrate surface to form a thin liquid film. This liquid layer has the effect of increasing the concentration of the raw material gas on the surface of the M plate and promoting the reaction by further dissolving the raw material gas. Therefore, a higher film growth rate can be obtained compared to the normal photo-CVD method.

6- [Embodiment of the invention] Figure 1 shows a thin film forming apparatus U used in an embodiment method of the invention.
FIG. In the figure, reference numeral 11 denotes a vacuum container (reaction container) constituting a reaction chamber, and a susceptor 13 on which a sample substrate 12 is placed is disposed within this container 11. Also,
The container 11 has gas inlet ports 14 and 15 for introducing raw material gas to be deposited, a gas inlet port 16 for introducing a reactive gas containing a halogen element, and a gas inlet port 16 for exhausting the gas in the container 11. A gas exhaust port 17 is provided. On the other hand, above the container 11, a light beam 118 is provided for dissociating reactive gas such as halogen. This light source 18
For example, is a pulse excimer laser with a wavelength of 308 [nm], 8 o pulses per second, and an average output of 2 [W/ctml
It is used in The light 19 from the light 8118 is passed through a light passing window 2o provided on the upper wall of the container 11.
The light is guided into the container 11 through the beam, and is irradiated perpendicularly to the upper surface of the sample 12.

Next, 8) 1 will be explained about the thin film forming method using the above apparatus. The raw material is also tetramethylsilane (S I
Using a mixed gas of C4L112) and oxygen (02), and using 1n element (CI2) as the reactive gas, a rough test $II
A 3i substrate was used for the W board 12 and 1. Here, the material of the sample substrate is one that is not etched by C1 radicals. First, only the raw material gas is introduced into the container 11 without using the reactive gas, and the total gas pressure is reduced to 5Q.
[torr].

In this case, all of the above raw material gases are transparent to light with a wavelength of 308 [nm], and even when irradiated with light, they do not react (,
1 did not occur, and the SiO2 film did not accumulate. On the other hand, when chlorine gas of 5 [vol. The dependence on the concentration of tetramethylsilane is shown in Figure 3.10Te!・Up to a concentration of ramedelsilane of 4 [VOI%], the Jrt product velocity increases with increasing concentration of tetramethylsilane, reaching a maximum of 400 [VOI%] per minute. ]'s film 1 "is accumulated, but 4 [vo1%
], an oily liquid will adhere to the surface between the rows and s +
Deposition of 02 occurred and it became female, and at 8 [VOI%] all <
jft does not multiply. Figure 4 shows that the tetramethylsilane concentration is 3.
．． 2 [vol 1%], the deposition rate does not show dependence on chlorine concentration. j "The deposition rate is maximum at a chlorine concentration of 2.5 [vo1%], and the 5i02 film 21 in the
E Yuzu did it.

When we measured the infrared absorption spectroscopy of the film thus obtained, we found that
A strong absorption of 81-0 bond was observed and 8102I! It was confirmed that there was an accumulation of Also, when observed under a microscope, bubbles may be mixed in the film depending on the gas concentration, and the higher the tetramethylsilane and chlorine concentration, the more bubbles there are and the mv4 deteriorates, but the effect is greater with chlorine concentration, and chlorine gas 2.
5 [vo1% co, tetramethylsilane 3.2rvo1%
], an extremely good quality film was formed. This I1 product is A
- When analyzed using gel spectroscopy, carbon and trace amounts of chlorine were detected in the black upper layer of the surface. However, these signals disappear immediately when the sample is processed using xenon ion sputtering, and no carbon or chlorine is incorporated into the film. Also,
The signal strength ratio of oxygen, silicon, and 9- in the film is 11.
O2).

All of the above experiments were conducted with the U plate temperature at room temperature, but when the substrate temperature was set to 100 [° C.], the 5102 film was not deposited. Therefore, if the light passing window 20 is heated to 100 [°C] or more, it is possible to prevent the 8102 film from adhering to the window 20, thereby preventing the SiO2 film from adhering to the window 20.
It is possible to prevent a decrease in the amount of light irradiated into the container 11 due to the adhesion of No. 2.

By the way, in this example, chlorine gas is considered to promote the reaction between tetramethylsilane and oxygen in the following two ways. The first is that chlorine gas, which is in an excited state by absorbing light, collides with tetramethylsilane molecules or oxygen molecules and exchanges energy, producing tetramethylsilane or oxygen molecules in an excited state. These excited source gases collide with each other and react, producing a SiO2 film as a product of 1t1 and 1! Ru. This series of reactions is expressed, for example, by the following reaction formula.

=10− CI 2 +hν→C12x・・・・・・・・・・・・
・・・・Old・・・・・・・■Si C4Hs 2 +
Cl2H-+SiC41-1t2NtCI
2 N......■ 02 +C12H-+Q2 H+CI 2...
・Old...■'Si G4H+ 2 H+802-
+S I02+4GO2+61~120...■ Si 041-1t 2 +02 x+702→810
2+4GO2+61-120...■' Tetramethylsilane produces 8102 through either or both of the reaction routes of ■→■→■ or ■→■'→■' and deposits it on the substrate.

On the other hand, the second point is explained as follows. That is,
Hydrogen atom or methyl Mtr in TeI-ramethylsilane
Mjlkshi-r, Example 1. i' S i CH2Cl
Chlorinated tetramethylsilanes such as (CH3)3 having a low vapor pressure are formed, but because of their low vapor pressure, they condense on the substrate and form an extremely thin liquid film.

Since this film is easily decomposed and removed by irradiation with light, it can be used as a 1 m film for lithography. Chlorinated teiramethylsilane (
SiC4H+ 2-N GIN) promotes the reaction (■→■ or ■'→■') on the substrate by dissolving Te1-ramethylsilane and oxygen, increasing the deposition rate of the SiO2 film. is formed mainly on the surface of the substrate rather than in the gas phase, which has the effect of improving the adhesion between 5iO21! and the substrate and improving the quality of !I9.Furthermore, the window 20 is ℃], the chlorinated tetramethylsilanes will not condense on the window 20, so the SiO2 film deposited on the window 20 will only be exposed to the gas phase reaction. by Si
Since the production rate of the O2 film is low, the adhesion of 8102 to the window 20 poses almost no problem. Even if it is assumed that a certain amount of S i 02 adheres to the window 20 over a long period of time, the 5102 film produced by the gas phase reaction has poor adhesion (because the nails are weak, it can be easily wiped off with a cloth or the like).

In addition, when the concentration of chlorine gas and teramethylsilane gas is increased, bubbles are formed in the 5 iOz film and the film becomes rough. This is thought to be due to the following reasons.
Increasing the amount of tetramethylsilane has the effect of increasing the partial pressure of chlorinated tetramethylsilane, which is the product of reaction (1). On the other hand, increasing the chlorine concentration increases the chlorine partial pressure ratio of chlorinated tetramethylsilane and increases the molecular size, but this has the effect of lowering the vapor pressure of chlorinated tetramethylsilane. Both of the above two effects increase the concentration of chlorinated tetramethylsilane on the substrate, but an unnecessarily large amount of chlorinated tetramethylsilane
02 film, deteriorating the film quality of 5102J[.

As described above, according to this embodiment, S I G4tl+ 2
By mixing a reactive gas consisting of CI2 into a raw material gas consisting of
1 can be deposited. Therefore, compared to conventional optical CVD using vacuum ultraviolet light, the light source is easier to handle and the cost of the apparatus can be reduced. In addition, as mentioned above, by mixing CI2, the deposition rate can be significantly increased by 13-30% compared to the conventional method, which is extremely effective for manufacturing three-dimensional circuits.

FIG. 5 is a schematic diagram showing a thin film forming apparatus used in another example method. This device differs from the device shown in FIG. 1 in the direction of light irradiation. That is, the light source 1
8 was placed on the left side of the container 11, and the light 19 was irradiated parallel to the sample substrate 12. In this way, the substrate 12
Even without direct irradiation with light, the SiO2 film 21 could be deposited at approximately the same deposition rate as in the case of direct irradiation with light.

But I! The quality was clearer when the light was directly irradiated onto the sample substrate.

Note that the present invention is not limited to the embodiments described above. For example, instead of irradiating the sample all at once as a means of irradiating the sample with the light, as shown in FIG.
A rectangular beam having a length longer than the major axis of the sample may be used, and the beam may be scanned over the entire sample area relative to the sample. Furthermore, by using a small-diameter rectangular beam as shown in FIG. 7, it is also possible to selectively form a thin film on the sample. Further, the light source is not limited to a coherent laser, but a non-coherent light source such as a mercury lamp can also be used. Furthermore, the light source does not necessarily need to be placed outside the container, but may be placed inside the container.

In addition, as the raw material gas,' is silane or organic silanes other than tetramethylsilane or halogenated organic silanes instead of tetramethylsilane, and N20 instead of oxygen.
5I02191 can also be deposited using an oxidizing agent such as. Furthermore, as the reactive gas, it is also possible to use fluorine, bromine, iodine, etc. in addition to chlorine. In addition, by changing the combination of raw material gases, S l
Thin films other than 0.02 can be deposited. for example,
A silicon thin film is formed using only silane, organic silanes, and their halogen derivatives as the raw material gas, and nitrogen is added to the silicon thin film.

It is also possible to deposit a silicon nitride thin film using a combination of nitrogen-containing gases such as ammonia and hydrazine. Furthermore, by replacing silane, organic silanes, and their halogen derivatives with hydrogenated compounds or organic compounds of elements other than silicon, such as germanium, phosphorus, boron, arsenic, aluminum, and gallium, and their halogen derivatives, these elements can be The present invention is also effective when depositing thin films of single substances, oxides, and nitrides. Also, by combining scum containing gallium and gas containing arsenic, 1! In particular, it is also possible to deposit compound semiconductors such as J: lypotium arsenide. Furthermore, by adding a small amount of gas containing phosphorus, boron, etc., it is also possible to deposit a thin film doped with these elements. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of the drawing]

Fig. 1 shows a thin film forming apparatus used in a method according to an embodiment of the present invention. is a characteristic diagram showing the dependence of the stacking velocity on the tera-methylsilane concentration14 in the thin film J,
Fig. 4 is a characteristic diagram showing the dependence of the thin film Iff on the chlorine gas concentration, Fig. 5 is a schematic diagram showing the thin film forming apparatus used in other examples, and Figs. 6 and 7 are modified examples, respectively. It is a perspective view for explaining. 11... Vacuum container, 12... Sample substrate, 13...
4ft? Pig, 14.15.16...Gas inlet,
17...Gas exhaust port, 1st...Light source, 19...Light, 20...Light passing window, 21...S l 02 II
. Applicant's agent Patent attorney Takehiko Suzue 17- Figure 1 Figure 2 Figure 1 Figure 3 Tomo Mete Luciran Notomo [voL%J □ Figure 4

Claims (8)

[Claims] (1) In a thin film forming method in which a thin film is formed on a sample by a photochemical reaction, the sample is mixed with a raw material gas containing the raw material to be deposited on the sample and a reactive gas containing at least a halogen element. A method for forming III, which comprises exposing the mixed gas to an atmosphere and irradiating the mixed gas with light that dissociates the reactive gas. (2) The thin film forming method according to claim 1, wherein the sample is not etched by the radicals of the reactive gas. (3) The raw gas is silane and organic silanes. Organometallic compounds such as germanium hydride and organogermanims, phosphines and organophosphines, borane and organoboranes, arsine and organoarsines, organoaluminums, organogalliums, and halogen derivatives thereof. A thin film forming method according to claim 1. (4) The method for forming a soft thin film as set forth in claim 3, wherein the raw stone scum is a mixed gas with oxygen or nitrogen. (5) The i# film forming method according to claim 1, wherein the light is coherent or incoherent. (6) The sheath II of claim 1, wherein the light is directed perpendicularly or parallel to the sample.
The method for forming a thin film according to item M. (7) The light is focused on the sample, and the light focusing area is scanned over the entire surface of the sample relative to the sample. Thin film forming method described in section. (8) The thin film forming method according to claim 1, wherein the total pressure of the mixed gas of the raw material gas and the reactive gas is set to 1 o [torr1 or more.