JPH02265241A - Method and apparatus for surface treatment - Google Patents

Abstract

PURPOSE:To uniformly remove an oxide by a method wherein a counter member which has been installed so as to face a specimen is held at a temperature lower than that of the specimen, a thin film by a gas of a salt containing a halogen element is deposited, the specimen is then held at a temperature lower than that of the counter member, the thin film is sublimated and a thin film is deposited again on the surface of the specimen. CONSTITUTION:The following are provided: a vacuum container 11 which can be evacuated to produce a vacuum; a discharge tube 14 which is coupled to a microwave power supply 17 and which is for exciting a gas of a salt containing a halogen element from a gas introduction part 12a. In addition, a counter member 16 which faces a specimen stage 15 and the whole of a specimen 18 and whose area is larger than the area of the specimen 18 is installed. Before an oxide on the surface of the specimen 18 is etched, a temperature of the counter member 16 is held to be lower than the temperature of the specimen 18; the counter member 16 is exposed to the gas containing the halogen element; a thin film produced by the gas is deposited on the surface. After that, the temperature of the specimen 18 is held to be lower than that of the counter member 16; the thin film which has been deposited on the counter member 16 is deposited again on the whole surface of the specimen 18; after that, a heating operation is executed; the oxide of the specimen 18 is removed. Thereby, the oxide can be removed uniformly and efficiently.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Field of Application) The present invention relates to a surface treatment apparatus and a surface treatment method in the manufacturing process of semiconductors, and in particular to dry etching of oxides on the surfaces of semiconductors and metals. It relates to a surface treatment method for removing and a surface treatment device.

(Prior art) In the semiconductor manufacturing process, when forming microscopic elements, selective etching is used to selectively etch a specific material relative to other materials, and selective etching is used to selectively etch a thin film only on the surface of a specific material. Techniques such as selective deposition are important to form . Such selective etching and selective deposition are often performed, for example, between semiconductors or metals and their oxides. As an example of selective deposition, W (tungsten) is not deposited on the silicon oxide film by keeping the substrate temperature at an appropriate level using WF6 and a nitrogen-based gas.
There are some that can be deposited only on top. However, natural oxide films are usually easily formed on the surfaces of semiconductors and metals due to exposure to the atmosphere, and unless this is removed, the etching and deposition selectivity will be substantially reduced. Natural oxide films also have process problems such as deteriorating the film quality of crystal films and oxide films formed by crystal growth and thermal oxidation, inhibiting impurity diffusion, and becoming a source of dust. Therefore, it is desirable to remove it in such cases.

The present inventors developed a thin film of salt containing a halogen element as a method and apparatus for removing semiconductor and metal oxides, which are problematic in semiconductor manufacturing processes, without damaging the sample. We have previously proposed a technique in which the oxide is removed by heating after forming it on the sample surface (Japanese Patent Application No. 63-327594). However, this technique also cannot be applied to large-area samples such as 8-inch wafers. Therefore, it was difficult to uniformly remove the oxide.

This is because the a degree of the gas introduced into the vacuum container depends on the distance from the gas inlet, so the thin film formed on the sample surface is thicker in the region near the gas inlet and thinner in the far region. This is because they are formed non-uniformly depending on the location on the surface.

Furthermore, the formation of the thin film itself particularly depends on the manner in which the ionic crystal in the gas phase grows on the surface of the sample.

That is, under normal conditions, the gas phase is dilute with respect to the sample surface, and therefore, reflecting the surface condition of the sample, the thin film is not uniform and becomes an island-like deposit, resulting in oxide There was a problem that the removal could not be carried out uniformly.

(Problems to be Solved by the Invention) As mentioned above, in the method of forming a thin film made of a halide salt and removing it by heating, it is difficult to uniformly form a thin film over the entire surface of the sample. This is difficult, and depending on the conditions, the thin film may not be uniform and may form islands, resulting in the problem that the oxide cannot be removed uniformly.

The present invention has been made in consideration of the above circumstances, and its purpose is to form the thin film uniformly over the entire surface of the sample, thereby removing oxides with good uniformity throughout the surface of the sample. Another object of the present invention is to provide a surface treatment apparatus and a surface treatment method that can uniformly remove oxides without forming a thin film into islands, and can perform subsequent steps favorably.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention exposes a sample on which an oxide is exposed on the surface to a salt gas containing a halogen element, and then heats the sample. A surface treatment method for etching away the oxide by etching away the oxide on the sample surface, the temperature of a facing member provided facing the entire sample surface being adjusted to the temperature of the sample. a first step of holding the sample at a relatively low temperature relative to the sample and exposing the opposing member to a gas containing a halogen element to deposit a thin film generated by the gas on the surface; After redepositing the thin film deposited on the opposing member in the first step over the entire surface of the sample by keeping the temperature relatively low, the sample is heated to remove oxides from the sample. A surface treatment method (first invention) characterized in that a sample having an oxide exposed on the surface is used as a first gas and a salt gas containing a halogen element;
A surface treatment characterized by comprising a step of exposing the sample to a second gas that liquefies and dissolves the first gas, and then a step of heating the sample to remove oxides from the sample. The method (second invention) includes a sample stage capable of heating and cooling on which a sample with an oxide exposed on the surface is placed, and an opposing member capable of heating and cooling provided facing the entire surface of the sample. A surface treatment apparatus (third invention) characterized by comprising: a vacuum container capable of being evacuated and equipped with a means for introducing a salt gas containing a halogen element into the vacuum container; a vacuum container that can be evacuated into which a sample exposed on the surface is stored; a first gas introducing means for introducing a salt gas containing a halogen element into the vacuum container; A second gas introduction means for introducing a second gas that dissolves a salt gas containing an element, and an exhaust means for exhausting the gas introduced by the first and second gas introduction means. A characteristic surface treatment apparatus (fourth invention) is provided.

(Function) According to the first and third inventions of the present application, a thin film generated by a salt gas containing a halogen element is deposited by keeping the opposing member provided facing the sample at a lower temperature than the sample. Then, by keeping the sample at a lower temperature than the opposing member, the thin film can be sublimated and re-deposited uniformly and efficiently on the sample surface, so that subsequent oxides from the sample can be removed uniformly.

According to the second and fourth inventions of the present application, the salt gas (first gas) containing a halogen element is uniformly dissolved on the sample surface by the second gas that liquefies on the sample. The thin film is not non-uniform, so oxides from the sample can be removed uniformly.

(Example) Examples of the surface treatment apparatus and surface treatment method according to the present invention will be described in detail with reference to the drawings.

Figure 1 is part 3 of the present application. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for explaining an embodiment of a surface treatment apparatus according to the invention.

This device includes a vacuum container (11) that can be evacuated, and a salt gas containing a halogen element (11) coupled to a microwave power source (17) and introduced from a gas inlet (12a). a discharge tube (first gas) that excites a discharge tube (first gas)
14), and further inside the vacuum container (ii) is a sample stage (15) on which a sample (18) such as a wafer is placed, and an area larger than the sample area so as to face the entire sample. A stainless steel plate having the same structure is provided as a facing member (16). Here, the facing member (1
6) is preferably a material that is not corroded by gas, such as Cu, AJ2
Materials such as Further, silicon or the like may be used as the material to which the thin film is easily adsorbed, or it may be laminated with the above-mentioned non-corrosive material.

Furthermore, the wall of the container (11) may be used as the opposing member, as long as the opposing member has a structure that allows it to be substantially close to the sample. (13) is an exhaust port (13) connected to exhaust means (not shown) for exhausting the introduced gas. In addition, the sample stage (J5) and the opposing member (16) can be cooled, for example, with a refrigerant or heated with a heater, and the temperature can be freely changed, for example, between -100°C and 200°C. It is configured so that

The surface treatment device also includes a transport mechanism (not shown) for transporting the vacuum container and the treatment device for the next step after removing oxides so that the sample is not exposed to the atmosphere before moving to the next step.
It would be even better if it could be transported via. Further, the vacuum container is provided with a vacuum preliminary chamber (not shown) for storing a sample before removing oxides.

Next, an embodiment of the surface treatment method according to the first invention of the present application using the apparatus according to the embodiment according to the first invention of the present application will be described in detail with reference to the drawings.

FIG. 2 shows a cross-sectional view of the process in the case of forming a contact hole in a semiconductor substrate as the above embodiment.

First, as shown in FIG. 2(a), a P-type silicon substrate (2
1) An oxide film (22) with a thickness of 1.3 μm as an insulating film on top
was deposited by the CVD method, and then a resist film (23) was applied. Next, as shown in FIG. 2(b), the resist film (23) is exposed, developed and patterned by a normal photolithography process, and then subjected to reactive ion etching using a mixed gas of CF and H2. Using the pattern of the resist film (23) as a mask, the oxide film (22
) was formed with a contact hole (24). Next, as shown in FIG. 2(C), after removing the resist (23), the PO
A diffusion layer (25) was formed by a diffusion process using CJ3 gas.At this time, a natural oxide film (2B) was formed in the contact area.The sample that underwent the above process is shown in Figure 1. It was placed in the preliminary chamber of the surface treatment equipment, and the inside was evacuated.

Next, after cooling the opposing member (16) of the device to -50°C, NNF3105C is introduced from the gas inlet (12a).

NH3100ScM was introduced into the discharge tube (14) at 2.4
A 5 GHz microwave was applied to discharge and decompose the introduced salt gas containing a halogen element. When this treatment was carried out for 10 minutes, a thick NH, F film was formed on the entire surface of the opposing member (16). Thereafter, the sample is transferred from the preliminary chamber into the vacuum container, placed on the sample stage (15) of the vacuum container (11), and the temperature of the opposing member (16) is set to be relatively higher than that of the sample, and the NH4F 120℃, the temperature at which the film sublimates
When the temperature was raised to 100, a part of the thin film that had been formed on the surface of the opposing member sublimated and redeposited on the sample (18) to a thickness of about 40 mm, so that a thin film was uniformly formed on the sample surface. Ta.

This is because the thin film deposited on the opposing member has a high concentration, so the thin film sublimated by heating becomes a highly concentrated atmosphere on the sample surface, and the sample surface is at a lower temperature than the opposing member regardless of the state of the sample surface. redeposit evenly. At this time,
In order to uniformly form a thin film on the sample, it is important that the opposing member has a larger area so as to face substantially the entire surface of the sample, as in the apparatus of the embodiment of the present application.

Further, even if the thickness of the film deposited on the opposing member is uneven depending on the location, the film sublimates uniformly throughout during sublimation. Furthermore, although the distance between the facing member and the sample depends on the conditions when depositing the thin film on the sample, it is important to keep the distance closer (for efficient deposition).

Here, a thin film having a thickness of about 2,000 layers is formed on the facing member (16). It took about 5 minutes,
Thirty samples could be successfully processed until the thin film thus formed was sublimated and disappeared.

After the thin film was formed on the sample, by raising the temperature of the sample to, for example, about 120° C., the thin film evaporated and the natural oxide film formed in the contact hole of the sample was easily removed. .

Next, the effect of forming a thin film on the sample using a facing member as in the embodiment of the present invention (A) will be compared to the effect of forming a thin film directly on the sample without using a facing member as in the conventional case (B). This will be explained below by comparison with .

FIG. 3 shows the thickness ( person).

As can be seen from the figure, in the conventional example (B), the thickness of the thin film becomes thinner and more uneven as the distance from the gas outlet increases. Further, it took about 10 minutes to form a thin film of sufficient thickness.

On the other hand, according to Example (A) of the present invention, it was found that the thin film had a uniform thickness regardless of the distance from the gas outlet, and therefore, the oxides of the sample were uniformly removed by subsequent heating. be done.

That is, in the apparatus shown in FIG. 1, when the temperature of the sample stage was raised and the sample was heated at approximately 120° C. for 2 minutes, the thin film formed on the substrate of the contact hole (24) as shown in FIG. 2 (d) of the stage. It sublimates together with the natural oxide film that was formed on the surface.
It was removed evenly.

Next, the sample from which the natural oxide film has been removed is transported into a sputtering device without being exposed to the atmosphere, and an AJ-8t alloy film (27), for example, is placed in the contact hole (24) as shown in FIG. 2(e). Embedded.

When the contact resistance of the sample formed according to the above example was measured, it was found that the contact resistance was as low as about 80Ω/hole over the entire contact hole. On the other hand, when a thin film is directly formed on the sample without forming a thin film on the opposing member, the contact resistance at high places is about 300 J2/hole, reflecting the thin film distribution shown in Figure 3. Therefore, the contact resistance was non-uniform.

Therefore, according to this example, it was possible to remove the natural oxide film of the contact hole over the entire sample. In addition, since a highly concentrated thin film is once deposited on the entire surface of the opposing member, it is lifted up and bloomed on the sample facing the opposing member, and redeposited on the sample surface, which is efficient and allows for the formation of a predetermined film. The time required for thick deposition could be reduced to about 1/10 compared to the case where it was formed directly on the sample surface.

In this example, the metal buried in the contact hole (24) was AJ2-Si alloy, but other metals may also be used.
Further, the forming method may also be a selective CVD method. For example, instead of the Aβ-Si alloy, a tungsten film may be formed by selective CVD. In this case, since the natural oxide film (26) in the contact hole has been removed, the oxide film (22) and the contact Good selectivity can be obtained.

Next, an embodiment of the apparatus according to the fourth invention of the present application will be described with reference to FIG. Basically, it is the same as the apparatus according to the first embodiment of the invention described above, but the major difference is that the opposing member (i
e), but instead includes a second gas inlet (12a) for introducing a second gas capable of dissolving the first gas into the vacuum container.

An example method according to the second invention of the present application using this example apparatus will be described. In this embodiment, an example of epitaxial growth of silicon will be described.

First, a silicon substrate (sample) (18), which has been wet-cleaned to remove organic contamination and metal contamination, is placed on the sample stage (15) of the surface treatment apparatus shown in FIG.
After evacuating the inside of the container, 208 CCM of NF3 and 1 mL of N H3 were added as the first gas from the gas inlet (12a).
003CCM is introduced, microwaves are applied to the discharge tube (14), and treatment is performed for 10 minutes. At the same time, an organic compound gas such as C2H50H is introduced from the gas inlet (L2b) as a second gas to dissolve the first gas, and the temperature of the sample stage is lowered while maintaining the inside of the vacuum container at 300 Torr. Lower the temperature of the sample (18) to 150°C.
It was held so that At this time, it was observed that a thin film of NH4F was dissolved on the surface of the sample by C2H and OH.

Next, after stopping the introduction of the first and second gases and evacuating the inside of the container (1st stage), the sample was heated to 150°C.
It was held for 10 minutes. As a result, the thin film formed on the sample surface was removed together with the liquefied C2HsOH, and the sample surface became a completely clean surface with no natural oxide film formed thereon.

Thereafter, the sample is transported into an epitaxial apparatus via a preliminary chamber or the like so as not to be exposed to the atmosphere, and the sample temperature is raised to 900°C, and an epitaxial gas such as 5iH2CJ22 gas is introduced into the apparatus. A silicon layer was epitaxially grown on the surface of the silicon substrate of the sample. When the epitaxial layer formed as described above was observed using a TEM, it was found that a uniform single crystal layer of silicon was formed over the entire sample.

Here, for comparison, when epitaxial growth of silicon was performed after removing the native oxide film without introducing the second gas, crystal defects were observed locally. This was because the thin film formed on the sample surface during the removal of the native oxide film became island-like, and the native oxide film remained locally.

In this way, according to this example, the thin film formed on the sample surface is dissolved by C2HsOH, and is uniformly deposited on the sample surface. Therefore, the natural oxide film can be removed uniformly, and the subsequent steps can be performed satisfactorily.

Further, in this embodiment, the first gas and the second gas were introduced at the same time, but the second gas may be introduced after the first gas is introduced. In this case, an island-like thin film is formed on the sample surface by introducing the first gas;
By subsequently introducing the second gas, the thin film is dissolved and made uniform, so that substantially the same effect as in the embodiment described above can be obtained.

Note that the present invention is not limited to the above-described embodiments.

That is, in the above embodiments, the thin film was formed using discharged gas, but it could also be formed by reacting a gas that spontaneously generates active halogen species with a basic gas, or by using vapor of a halogen salt. good.

In addition, the gas that liquefies and dissolves the thin film is C2H5
In addition to 0H, polar molecules such as water and organic compounds may also be used. Further, the process performed after removing the native oxide film is not limited to the above-mentioned contact formation and epitaxial growth, but can be applied to all cases where it is necessary to uniformly remove semiconductor or metal oxides.

In addition, salt gas containing halogen elements includes either halogen gas, interhalogen gas, ammonia,
hydrazine, amine, phosphine.

It may be a mixed gas formed by a combination with at least one gas selected from aluminium, or a compound gas of a salt containing fluorine, chlorine, bromine, or iodine. Furthermore, what is removed is not limited to the natural oxide film, but may be a normal oxide film.

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

[Effects of the Invention] As described above, according to the present invention, the oxide film can be uniformly and efficiently removed even from a large-area sample having an oxide on the surface, which improves semiconductor device manufacturing. It becomes possible to improve the yield.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the apparatus according to the present invention, FIG. 2 is a process sectional view for explaining the embodiment method according to the present invention, and FIG. 3 is a schematic diagram for explaining the embodiment of the present invention. It is a characteristic diagram for explanation. 11... Vacuum container, 12a, 1.2b...
・Gas inlet, 13...Gas exhaust port, 14...
Discharge tube, 15...sample stage, 18...sample. 16... Opposing member,

Claims (5)

[Claims] (1) A surface treatment method in which a sample on which an oxide is exposed on the surface is exposed to a salt gas containing a halogen element, and then the sample is heated to remove the oxide by etching, the method comprising: Before removing an object by etching, the temperature of an opposing member provided opposite to the entire surface of the sample is kept relatively low with respect to the temperature of the sample, and the opposing member is exposed to a gas containing a halogen element to dry the surface. a first step of depositing a thin film produced by the gas on the counter member, and then maintaining the temperature of the sample relatively low with respect to the counter member to deposit the thin film on the counter member in the first step; 1. A surface treatment method, comprising redepositing a thin film over the entire surface of the sample, and then heating the sample to remove oxides from the sample. (2) exposing the sample with the oxide exposed on the surface to a salt gas containing a halogen element as a first gas, and a second gas that liquefies on the sample and dissolves the first gas;
A surface treatment method comprising the step of: thereafter heating the sample to remove oxides from the sample. (3) The surface treatment method according to claim 2, wherein the second gas is water or an organic compound such as acetone or alcohol. (4) A vacuum exhaust system equipped with a sample stage capable of heating and cooling on which a sample with exposed oxides is placed, and a counter member capable of heating and cooling provided facing the entire surface of the sample. What is claimed is: 1. A surface treatment apparatus comprising: a vacuum container capable of evacuating; and means for introducing a salt gas containing a halogen element into the vacuum container. (5) a vacuum container capable of being evacuated into which a sample with an oxide exposed on the surface is housed; a first gas introduction means for introducing a salt gas containing a halogen element into the vacuum container; a second gas introduction means for introducing a second gas which is liquefied by the gas to dissolve the salt gas containing the halogen element; and an exhaust means for exhausting the gas introduced by the first and second gas introduction means. A surface treatment device comprising: