JPS6276632A - Surface treatment device - Google Patents

Abstract

PURPOSE:To carry out a surface treatment continuously without exposing a substrate to be treated to the atmosphere by providing a first container for subjecting the surface of the substrate to be treated to a pretreatment by a means not accompanying bombardment of ion particles, a second container for performing a surface treatment by optical excitation in a gas atmosphere, and a transportation mechanism for transporting the substrate to be processed between those containers. CONSTITUTION:For example, CF4 gas is introduced into a first reactor 1 and it is held at about 0.1 torr. An electron beam 10 is caused to go by above a wafer in parallel to that and CF4 gas is dissociated to remove a natural oxide film on the surface of the wafer. The reactor 1 is evacuated again and the wafer is introduced into a second reactor 16 by a transportation mechanism 24 without being exposed to the atmosphere. For example, Cl2 is introduced as an etching gas and a pressure is held at about 100 torr. A light 23 from an XeCl excimer laser as a light source optically dissociates Cl2 efficiently and the irradiation beam promotes etching. Accordingly, as the natural oxide film is not produced again after a pretreatment, the good-reproducibility etching becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface treatment apparatus that performs surface treatment on semiconductor devices, and particularly relates to a surface treatment apparatus that utilizes optical excitation.

(Technical background of the invention and its problems) In recent years, with the rapid development of semiconductor integrated circuits, technology for removing organic impurities and heavy metals from the surface of a semiconductor substrate before forming the circuit has become important. In other words, many semiconductor integrated circuits today utilize the characteristics of the semiconductor surface to form transistors and capacitors by diffusing specific impurities or locally forming dielectric films or conductive thin films. Therefore, if a circuit is constructed with organic matter or heavy metal impurities present on the surface, the electrical characteristics of the circuit will become extremely unstable or highly variable, resulting in several thousand It becomes impossible to manufacture integrated circuits that require equal characteristics of the elements.For example, heavy metal rot acts as a capacitor.
Impurity units are formed in 5i02, and have a large effect on the threshold value of a transistor or the charge retention time of a capacitor.

Currently, such surface treatments include sulfuric acid and hydrochloric acid.

Dangerous strong acids such as hydrogen peroxide mixtures or hydrofluoric acid solutions are often used. In addition, a large amount of ultrapure water (water from which minute particles, impurities, bacteria, etc. have been removed) is used for cleaning after processing.
Furthermore, the treatment tank requires expensive high-purity quartz. Additionally, large-scale equipment is required to treat waste liquid. Therefore, many attempts have been recently reported to perform this pretreatment in a vacuum or in a specific gas atmosphere. but,
For example, methods using plasma using high-frequency power may cause damage such as crystal defects to the semiconductor substrate due to charged particles, and effective means have not yet been developed.

On the other hand, as damage-free surface treatment methods, etching and thin film forming techniques using photoexcitation reactions have recently been proposed. However, these etching, deposition techniques, etc. that utilize chemical reactions on the surface are significantly influenced by the surface condition of the substrate to be processed. For example, in the method of etching Si using chlorine atoms excited by ultraviolet light, a natural oxide film on the surface (several 100% oxidation, which occurs when Si is left in the atmosphere,
1! ! ), the mere presence of this will prevent etching from proceeding. Further, even in the technique of selectively forming a W film on the surface of 81 by thermally dissociating W F s gas, selective deposition cannot be performed if a natural oxide film exists. Therefore, with current apparatuses that process a substrate and then leave it in the atmosphere for the next surface treatment, it is impossible to handle the photoexcitation process as described above.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its objectives are (1) surface treatment in a gas atmosphere, and then continuous surface treatment by optical excitation without exposing the substrate to the atmosphere; The object of the present invention is to provide a surface treatment apparatus that can perform surface treatment and realize high performance of semiconductor integrated circuits.

(Summary of the Invention) The gist of the present invention is to perform pretreatment to remove natural oxide films, impurities, etc. on the surface of a substrate to be treated by a reaction that does not involve the impact of charged particles, and then expose this substrate to the atmosphere. A light beam that dissociates or ionizes a specific processing gas is irradiated onto the substrate to be processed or near its surface placed in the gas to generate active species of the gas. The purpose of this method is to perform surface treatment on the substrate by reaction with the active species.

That is, the present invention provides a surface treatment apparatus for surface-treating a substrate to be treated, which includes a first container for pre-treating the surface of the substrate to be treated by a means that does not involve the impact of charged particles, and a gate valve connected to the first container. a second container connected in vacuum to perform surface treatment on the substrate to be processed by optical excitation in a predetermined gas atmosphere; and a transport mechanism to transport the substrate to be processed between the first and second containers. It was designed to provide a.

〔Effect of the invention〕

According to the present invention, the surface of a semiconductor substrate can be cleaned in a gas atmosphere without using a solution such as a strong acid. Therefore, it is possible to sufficiently handle cases that cannot be treated with solutions, such as very fine grooves in future VLSIs. In addition, by appropriately selecting the energy of the excitation beam according to the gas and setting it to a relatively low gas excitation energy level, irradiation damage to the substrate to be processed can be reduced compared to when using plasma or the like. .

In addition, after the surface has been treated to remove impurities, it is transported in a vacuum and the next surface treatment is performed continuously, which prevents contamination of the substrate to be treated and the formation of a natural oxide film after the first treatment. can. Therefore, it is possible to perform highly accurate and clean processing with reproducibility in the next processing, and the performance of the semiconductor device is improved.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a surface treatment apparatus according to a first embodiment of the present invention, and FIG. 2 is a view taken along the arrow AA in FIG. 1. In the figure, reference numeral 1 denotes a first reaction vessel for performing pretreatment, and within this vessel 1 is arranged a susceptor 3 on which a substrate 2 to be treated is placed. The susceptor 3 is kept at a constant temperature by a temperature control mechanism (not shown). The container 1 also includes a gas inlet 4 for introducing gas and a gas inlet 4 for introducing gas into the container 1.
A gas exhaust port 5 is provided for exhausting the inside.

Here, the gas introduced into the container 1 may be appropriately selected from a reducing gas such as H2, an oxidizing gas such as 02, and a reactive gas containing a halogen element.

On the right side of the container 1, a vacuum container 6 is arranged which is vacuum connected through a slit 13. In this container 6,
An electron gun 9 is housed therein. Further, the inside of the container 6 is maintained at a high vacuum by an exhaust lower connected to a dedicated exhaust device, or an inert gas is introduced through a gas inlet 8, thereby making it possible to generate a stable electron beam 10 for a long time. I did it like that.

Further, in the figure, 11 is an absorption metal plate for measuring the current of the electron beam, 12 is a gas flow meter, and 67 is a DC or AC power source.

A second reaction vessel 16 for performing surface treatment is connected to the left side of the first reaction vessel 1 via a gate valve 15 . A light introduction window 20 is provided in the upper part of the second reaction vessel 16.
For example, light 23 from an xecxx ximer laser (wavelength: 308 nm) 22 is irradiated onto the substrate 19 to be processed. After the second reaction vessel 16 is evacuated to a high vacuum through the exhaust port 17, gas is introduced through the flow controller 21. Although not shown, the susceptor 18 is provided with a heating or cooling means to appropriately control the temperature of the substrate. Further, numeral 24 in the figure is a wafer transport mechanism, which is driven from outside the chamber by a vacuum seal 25.

On the right side of the first reaction vessel 1, a substrate to be processed 2 is exposed from the atmosphere.
A vacuum vessel 26 into which 7 is introduced is arranged. The upper wall 30 of this vacuum container 26 has a structure that can be removed in order to introduce a substrate 27 to be processed. Further, 31 is a wafer transport mechanism, which after evacuation is performed from the exhaust port 29,
Gate 1<) Rev 33 is opened to introduce into the first reaction vessel 1. Further, a vacuum container (not shown) for releasing the substrate to be processed into the atmosphere is arranged on the side surface of the second reaction container 16. Its configuration is exactly the same as the vacuum container 26 for introducing wafers.

Next, an example of photoexcitation etching using the above apparatus will be explained.

First, a wafer is introduced into this apparatus and placed in the first reaction vessel 1, and then CF4 gas is introduced into the first reaction vessel 1, the valve of the exhaust port 5 is adjusted, and the inside of the vessel 1 is opened. 0.1 [t
orr]. Thereafter, an electron beam 10 is passed in parallel above the wafer to dissociate the CF4 gas and remove the natural oxide film on the wafer surface.

Figure 3 shows the state near the wafer surface. Figure 3(a)
As shown in the figure, a 5i02 film 36 and a natural oxide film 38 having a thickness of 3000 mm and serving as an etching mask are formed on the surface of the Si wafer 37. 35 is the introduced CF4 gas, and 34 is an electron beam. Here, the acceleration energy of the electron beam may be set to be higher than the dissociation energy of CF4, but acceleration of several [KeV] is required in order to advance the electron beam over the entire surface of the wafer. At this time, by applying, for example, a DC voltage to the substrate 37 from the power supply 67 shown in FIG.
By drawing positive ions, etc. to the substrate side, processing speed can be increased.

After the above process, the reaction vessel 1 is evacuated again and the wafer is transferred! fil 124 into the second reaction vessel 16 through the gate valve 15.

Here, for example, CQ2 is introduced as an etching gas, and the pressure is maintained at 100 [torr]. Xe light source
(The light from the excimer laser has a wavelength of 308 nm and efficiently photodissociates CQ2. Furthermore, the irradiated light promotes etching, forming grooves 41 of <Si> as shown in FIG. 3(b). be done.

Here, the slope of the side wall of the groove 41 is 3i (10
0) This is because when the substrate 37 is etched with light, a (111) plane that is difficult to be etched appears. In this etching, the ratio of the etching speeds of 3i and 8102 is almost infinite, and SiO2 cannot be etched. Therefore, etching will not proceed unless even a small amount of the native oxide film is removed.

As described above, according to this embodiment, the pretreatment can be performed without using a solution, and furthermore, a natural oxide film is not formed again after the pretreatment, so that etching with good reproducibility is possible. After etching, the wafer is taken out into the atmosphere through a vacuum chamber for taking out the wafer. This procedure is repeated one wafer at a time to proceed with etching.

Moreover, FIG. 3(C) is an example in which W was selectively deposited after the process shown in FIG. 3(a), in which the temperature of the substrate was raised and W F 5 gas was introduced. W 60 grows selectively on the exposed portion 59 of Sl, and W does not grow on 5iOz 36. In this example as well, a small amount of native oxide film acts as a barrier to W growth, and this embodiment enables a process with constant reproducibility. Furthermore, the contact resistance at the junction between Sl and W is also stabilized.

Note that this embodiment can be modified in various ways.

For example, even if H2 is introduced into the first reaction vessel 1, S
iO2 can be removed. Further, by introducing O2 or oxidizing CO, it is possible to remove sludge or heavy metals attached to the surface by converting them into oxides or metal carbonyls. In the case of such impurities, they often penetrate to the surface layer of the semiconductor substrate, and in addition to the above-mentioned gases, there are also gases that can etch the semiconductor substrate.
For example, F2, CF4), etc. may be introduced together. Furthermore, in the second reaction vessel 16, the wavelength of the irradiation light is selected in accordance with the gas to be introduced so as to dissociate the gas. In addition to etching, SiH+ may be introduced and an a-8i film may be deposited by photo-CVD or Sl may be epitaxially grown.

It is also easy to use for oxidation pretreatment etc. In either case, the quality of the obtained film can be significantly improved by performing pretreatment in advance in the first reaction vessel 1 according to the intended use and immediately starting the above process without exposing it to the atmosphere. Improved Fig. 4 is a schematic configuration diagram showing a second embodiment of the present invention. This embodiment is an example in which an electron beam and light are used simultaneously in the first vacuum container 1. The electron beam 10 is formed into a sheet and passes above the substrate 3 to be processed, while, for example, ultraviolet light 43 is irradiated perpendicularly to the entire surface of the substrate 3 to promote the reaction.

FIG. 5 is a schematic configuration diagram showing the configuration of main parts of a third embodiment of the present invention. In this embodiment, an electron optical system 44 is provided above the first vacuum container 1, and the native oxide film is removed only in that portion while irradiating an electron beam 48 along a desired circuit pattern. In this case, light introduction! It is preferable to introduce ultraviolet light 47 through 20 or use a sheet-shaped electron beam to supplement gas excitation in the gas phase. here,
Reference numeral 45 indicates a separate wafer scanning structure.

FIG. 6 is a schematic configuration diagram showing the configuration of main parts of a fourth embodiment of the present invention. This example is an example in which the second reaction vessel is made of quartz, allowing processing at relatively high temperatures. here,
In the figure, 49 is a quartz tube, 50 is a heater, 51
is a wafer, and 52 is a susceptor made of quartz. Gas is introduced through the inlet 53 and exhausted through the exhaust port 54. 55
56 is a gate valve, and 56 is a first conveyance mechanism. Since the other vacuum containers are made of SUS, 5B is used to seal the quartz and SUS. This device can also be used in cases where high temperatures are used, such as thermal CVD or impurity diffusion, so there is concern about contamination in a metallic vacuum container.

FIG. 7 is a schematic diagram showing the main structure of a fifth embodiment of the present invention. This embodiment is an example in which a pattern is projected onto a wafer placed inside the second reaction vessel 16 of FIG. 1 to selectively perform surface treatment. mercury lamp 6
The light of 1 passes through the lens 63 from the reflecting mirror 62 and hits the quartz plate 6.
A pattern 65 formed on 4 is irradiated with light. The light that has passed through the light passing portion is irradiated onto the wafer 2 through a lens 66 and a window 67. With this method, etching, deposition, etc. can be selectively performed only on the light irradiated portion. For example, an AQ pattern can be formed by introducing trimethylaluminum as a gas. Furthermore, if an etching gas is introduced, selective deposition can be performed only on the light irradiated areas. Also in this method, this second reaction vessel 16
This can be achieved with good reproducibility by performing pretreatment (removal of organic matter on the surface of oxide film removal 1) corresponding to the next process in the first reaction vessel 1 before introducing the sample into the first reaction vessel 1.

Note that the present invention is not limited to the embodiments described above. The substrate material is not limited to Sl, but may also be germanium or I.
All materials used in semiconductor devices can be used, including composite materials such as nP and GaAS, dielectric films such as nitride films and oxide films, metal films such as titanium, tungsten, aluminum, and molybdenum, and their silicide films. It can be applied to surface cleaning and subsequent treatment.

In addition, by lowering the energy of the electron beam or passing it above the wafer in parallel without directly irradiating it, irradiation damage can be reduced compared to methods using plasma.
It can also be used to process the upper layer of a wafer on which devices have already been fabricated.

In addition, in the present invention, the substrate to be processed is transferred to the reaction vessel for the next step without being exposed to the atmosphere, so it is a clean dry process, and semiconductor devices that will become even finer and thinner in the future. Of course, it is suitable for the production of
This method can easily accommodate the increasing automation of manufacturing processes year by year, and is an alternative to pretreatment technology using liquids, which is one of the bottlenecks in automation. Further, the present invention further provides a third aspect of the present invention.
By connecting the fourth reactor to the reaction vessel, it is possible to proceed with all LSI processes one wafer at a time, providing great expandability.

In the above embodiment, is an electron beam as the excitation beam.

Although an example using a light beam has been shown, in the present invention, it is possible to replace these with an ion beam, a neutral atomic or molecular beam, etc. as appropriate. For example, by selectively irradiating the surface of the substrate with an ion beam using an ion beam optical system having a configuration similar to the electron optical system shown in FIG. 5, the surface layer can be partially modified or removed. In particular, when an ion beam is used, physical sputtering action can be utilized, which is characterized by selective etching deposition.
It is extremely effective for substances that are difficult to remove by chemical reactions with excited species.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

1 to 3 are for explaining the first embodiment of the present invention, and FIG. 1 is a schematic configuration diagram showing the overall configuration, and FIG. 2 is a view taken in the direction of arrow A-A in FIG. 3 are process sectional views for explaining the operation, FIG. 4 is a schematic diagram showing the main part configuration of the second embodiment of the present invention, and FIG. 5 is a diagram of the third embodiment of the present invention. FIG. 6 is a schematic configuration diagram showing the configuration of the main parts of the fourth embodiment of the present invention, and FIG. 7 is a schematic diagram showing the configuration of the main parts of the fifth embodiment of the present invention. It is a diagram. 1... first reaction container, 16... second reaction container,
2.19, 27.51...substrate to be processed (wafer), 1
0.34.48...Electron beam, 3.18.28°5
2... Susceptor, 15.33.55... Gate valve, 23.39.43.47... Light, 24.31°4
5.56...Wafer transport mechanism, 37...3i wafer, 36...5iOz mask, 41...Etching groove. Applicant's agent Patent attorney Takehiko Suzue ↓ Figure 5 Figure 7

Claims (4)

[Claims] (1) A first container for pre-processing the surface of a substrate to be processed by a means that does not involve the impact of charged particles; A surface treatment apparatus comprising: a second container for surface-treating a substrate to be treated; and a conveyance mechanism for conveying the substrate to be treated between the first and second containers. (2) The surface treatment according to claim 1, wherein the second container is provided with a mechanism for irradiating light perpendicularly or parallel to the surface of the substrate to be treated. Device. (3) The surface treatment apparatus according to claim 2, wherein the light is scanned over the substrate to be treated or is irradiated onto the entire surface of the substrate to be treated. (4) The first container is for removing a natural oxide film on the surface of the substrate to be processed, and the second container is for etching or forming a thin film on the surface of the substrate to be processed. The surface treatment apparatus according to claim 1, characterized in that: