JPH0654773B2 - Surface treatment method and apparatus used therefor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface treatment method used in a manufacturing process of electronic devices and the like and an apparatus used therefor.

(Prior Art) Conventionally, for example, a natural oxide film is formed on the Si surface, which is
In addition to becoming a protective film on the Si surface, it sometimes becomes an obstacle. That is, it becomes an insulating layer, which makes it difficult to perform regular crystal growth, and when forming a metal electrode or the like, the contact resistance increases due to this insulating layer. As a conventional technique for solving this, in order to remove the natural oxide film, wet etching with hydrofluoric acid, high-temperature heat treatment at 800 ° C. or higher, or physical sputtering with Ar ions was used.

(Problems to be Solved by the Invention) In the wet etching method, if an oxide film is present in other portions, it is also etched, and the target process shape cannot be secured. On the other hand, the high temperature heat treatment cannot be used when the distribution of impurities in the semiconductor is redistributed due to the high temperature or when a material that cannot withstand the high temperature is on the same substrate. Physical sputtering by Ar does not prevent damage by physical sputtering.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and form a protective film surface on which a natural oxide film is less likely to occur, and a method capable of removing the protective film at low temperature and with low damage if necessary. Is to provide a device that can be used for these.

(Means for Solving the Problems) According to the present invention, the oxide film on the surface of the sample is exposed to the discharge of halocarbon gas under a condition capable of being etched, and is then etched in the same chamber or in a chamber connected in vacuum. Then, the surface treatment method is characterized in that the discharge condition is changed to a condition in which a layer containing carbon serving as a surface protective film can be deposited, and the sample is exposed to discharge.

Further, according to the present invention, the oxide film on the surface of the sample is exposed to the discharge of halocarbon gas under the condition that the oxide film can be etched and etched, and the discharge condition is continuously protected in the same chamber or in a chamber connected in vacuum. Change the conditions to deposit a layer containing carbon to form a film, expose the sample to discharge, to form a protective film, before the next step, introduce a gas that can etch the protective film, irradiate light,
A surface treatment method is obtained, characterized in that the protective film is removed by etching, and subsequently, the following steps are performed in the same chamber or a chamber connected in a vacuum.

Further, according to the present invention, in a vacuum chamber, a device having a power source for introducing a gas to generate plasma and an electrode is capable of automatically changing the pressure in two or more steps every predetermined time. A surface treatment device characterized by being capable of performing

Further, according to the present invention, a device having a power source for introducing gas and generating plasma and an electrode in a vacuum chamber, wherein the gas pressure is automatically changed in two or more steps every predetermined time. A surface treatment device having a means and a window capable of transmitting light, and a gas capable of decomposing by light and generating a halogen can be introduced and vacuum exhausted, and the surface protective film formed by the surface treatment device can be irradiated with light in the gas. A surface treatment apparatus equipped with a function capable of etching and having a desired manufacturing apparatus provided in the same chamber or a chamber connected in a vacuum is obtained.

(Operation) The present invention has solved the problems of the prior art by adopting the above configuration. For example, after the dry etching, in the case where the film forming step is performed next, an oxide film is formed on the surface in the step of removing the resist serving as the etching mask. In the first invention of the present application, this sample is used under certain conditions, such as CF ₄ + H ₂ and CH.
Exposure to plasma of halocarbon gas such as F ₃ or gas containing it, first remove the surface oxide film by etching, and as it is, in the same device or in a chamber connected in vacuum under different conditions. Exposure to a plasma of halocarbon gas, at which time a polymer layer containing carbon is deposited on the surface.

In the second invention of the present application, after depositing the polymer layer, a sample is put in a film forming apparatus in the next step, for example, a film forming step. This film forming apparatus is provided with an apparatus capable of generating halogen radicals by light such as a halogen gas, and removes the polymer layer and also removes the dry etching damage layer mixed in during the previous dry etching. I will end up. A sample is placed in the same chamber or in a film forming chamber connected in vacuum to form a film. Then, there is no dry etching damage, and since oxygen in the atmosphere is not left in the carbon-containing polymer of the present invention, there is no oxide layer. That is, the clean surface can be used in the next step. Since this plasma treatment is anisotropic, there is no dimensional change.

As shown in the third invention of the present application, the surface protective film has a power source for generating plasma and electrodes, and discharges a halocarbon gas in the apparatus.
The discharge gas pressure can be automatically changed in two or more steps. That is, the oxide film on the surface is etched by the first discharge, and then the discharge pressure is changed so that the polymer layer containing carbon is deposited on the surface to grow the surface protective film. Fourth application
In the invention of, for example, if a film forming step is entered, a device capable of removing the protective film by light irradiation in a halogen gas capable of etching the surface protective film before film formation is connected to a film forming device in a vacuum. Keep it. The problems of the prior art have been solved by using the method and apparatus of the present invention.

(Example) First, a first example of the present application will be described.

FIG. 1 shows an example in which the method of the present invention is applied to a conventional process in which resist ashing is performed after SiO ₂ etching and then CVD film formation is performed. First, in FIG. 3A, SiO ₂ 12 was etched with a resist mask 11 using a CF ₄ type gas.
Then, the etched surface is a contamination layer (contamination layer, hereinafter abbreviated as a contamination layer) on the Si substrate 13.
14 are formed. This layer contains sputtered substances during etching, particularly oxygen and carbon from the resist, or fluorine and carbon contained in the gas.
The contamination layer 14 was found to be about 150Å by SIMS analysis. Further, as a result of resist ashing in the oxygen plasma shown in (b) of FIG. Next, as it is, in order to remove this contamination layer 14 by photo-etching, first, a natural oxide film on the contamination layer with an aqueous solution of HF, or on the contamination layer due to oxygen that may have been sputtered into the mask during etching The thin oxide film must be removed.
Then the wet process comes in and the required Si
Up to O ₂ 12 is etched. Therefore, in the present invention, after the resist 11 is ashed by the oxygen plasma of FIG. 1 (a),
CHF ₃ is poured into the dry etching equipment, and it is 30 at about 70 mTorr.
Surface treatment is performed by raising plasma for 2 seconds. Then apply pressure 15
Increase to about 0 mTorr and discharge for about 1 minute. The discharge output was constant at 0.08 W / cm ² . Then, the thin oxide film on the contamination layer 14 on the Si substrate 13 is removed, and the processing protection layer 15 shown in FIG. 2 (b) whose surface is replaced with carbon and fluorine is formed. This processing protection layer 15 has a thickness of 50 to 100.
The thickness is about Å, and the contamination layer when the SiO ₂ 12 shown in FIG.
No oxide remains on this surface when exposed to the atmosphere. That is, oxygen is removed in the form of CO and CO ₂ . As described above, the surface treatment apparatus of the third invention of the present application is to automatically perform etching of an oxide film and deposition of a polymer layer containing carbon. FIG. 2 shows its block diagram. The vacuum chamber 21 has a gas inlet 22, an electrode 23, and an RF power source 25. The exhaust pump 24 exhausts the gas through the conductance valve 27. The discharge pressure is set and input in the personal computer 28 in advance over time. The first discharge pressure is read by the pressure gauge 26, and its signal determines the opening ratio of the conductance valve 27 via the personal computer 28. Under the second pressure condition, the signal indicating the end of the first discharge time is output from the personal computer 28 to change the aperture ratio of the conductance valve 27. At this time, this can be changed at the time of programming, but the signal of the pressure gauge 26 and the signal of the conductance valve 27 are exchanged in the personal computer at intervals of about 1 to 2 seconds to finally set the second pressure. There is no problem if the discharge is maintained during the first and second pressure changes.

Next, an embodiment of the second invention of the present application will be described. In this embodiment, the polymer layer is deposited and then the film formation step is performed.
The apparatus of the invention is used. This device includes a device capable of irradiating deep UV light while flowing Cl ₂ or F ₂ gas in a vacuum, such as an excimer laser device or a Hg lamp. In Fig. 1 (c), Cl ₂ gas was flown while the vacuum was exhausted, and the pressure was 600 mT.
When orr is irradiated with Deep UV light, Cl ₂ gas is decomposed by Deep UV light and Cl radical is generated. The generated Cl radicals can easily etch the processing protection layer 15 and the contamination layer 14 that is the base thereof.

The photo-etching rate can be changed by Cl ₂ partial pressure, and if the pressure is 600 mTorr, the etching rate is about 70-100 Å / min. It takes 1 to 2 minutes to remove the contamination layer of about 150 Å. FIG. 3 shows the concentration of carbon and fluorine during the etching of the contamination layer during the Cl ₂ photoetching time, which was measured by Auger analysis. It can be seen that the processing protective layer and the contamination layer are removed by etching for about 2 minutes. Carbon concentration drops to almost the same level as carbon pollution caused by carbon dioxide in the air. The etching rate of the surface protective film containing carbon is shown in FIG. It is removed at a rate of about 3400Å per minute. The device of the fourth invention of the present application will be described.
FIG. 5 shows the configuration diagram. This is a normal CVD equipment 56
A vacuum chamber 51 is attached via a gate valve to a wafer tray 54 provided therein, and a light source 52 capable of irradiating the sample with ultraviolet light through a quartz window 53, an exhaust pump 57,
There is a gas inlet 54. The sample with the above-mentioned surface protective film is put into the vacuum chamber 51, a gas is made to flow while evacuating, and light is irradiated. After the etching is completed, the wafer is sent to the CVD device 56 in a vacuum through a gate valve, and normal CVD is performed. The photo-etching characteristics are the same as described above.

Next, based on this principle, the Si surface is easily oxidized, but the treatment protective layer formed by the plasma treatment of the present invention is extremely difficult to be oxidized. An example showing this is shown below.

FIGS. 6 (a) to 6 (d) show Auger spectra after etching with various etching gases. When a carbon-free gas such as Cl ₂ or XeF _{2 in} (a) and (b) is used, oxygen in the atmosphere is adsorbed and the oxide remains on the surface. On the other hand, when the gas containing carbon (c) or (d) is used, carbon is present on the surface and oxygen is
Evaporates into CO and CO ₂ . Therefore, no oxide remains on the surface. In fact, the photo-etching rate is extremely low with the gases (a) and (b). From this also, the layer containing carbon is less likely to be oxidized, and as a result, the contamination layer can be removed without damaging the underlying Si substrate or the like in the photoetching process at low temperature and low damage.

In the above example, Cl ₂ gas was flown while evacuating, and DeepU
Although the V light was irradiated, the treatment protective layer 15 and the contamination layer 14 can be removed even by introducing Cl ₂ gas into the chamber, stopping vacuum evacuation, and setting a Cl ₂ atmosphere to perform Deep UV irradiation.

Further, Cl ₂ gas may be introduced into the chamber to be adsorbed on the sample surface, Cl ₂ gas may be exhausted, and this adsorbed gas may be irradiated with Deep UV. In this case, the etching rate is lowered, but the controllability of the etching rate is improved.

(Effect of the Invention) According to the first invention of the present application, a method for forming a surface protective film in which a surface oxide film is not formed even when exposed to the outside air is obtained. According to the second invention of the present application, in addition to this, a method of removing this film at low temperature and low damage was obtained. These effects are
It can be sufficiently confirmed from the result of the Auger analysis of FIG. 3 and the result of the photoetching of Table 1 described above. Further, FIG. 7 shows the dimensional change by the plasma treatment of the present invention and the dimensional change of the conventional wet HF etching. There is almost no dimensional change in the lateral direction which is a process problem after the plasma treatment.

This method can also be used naturally for a surface protective film before crystal growth, and a sample surface free of carbon and other impurities can be obtained at low temperature and with low damage, so that a natural oxide film of a conventional technique in a semiconductor process or the like can be obtained. The big problem of removal has been completely improved.

[Brief description of drawings]

1 (a) to 1 (c) are schematic cross-sectional views showing an embodiment of the present invention, FIG. 2 is an apparatus configuration diagram of a third invention of the present application, and FIG. 3 shows effects of the present invention. It is a figure of the Auger analysis result which shows a mode of removal of impurities, such as carbon. FIG. 4 is a diagram showing the photo-etching rate of the surface protective film. FIG. 5 is a block diagram of the device according to item 4 of the present application. FIG. 6 is an Auger analysis diagram of the Si surface after etching with various etching gases. FIG. 7 is a diagram showing the dimensional change of SiO ₂ after each treatment examined by SEM photographs. 11 …… Resist mask, 12 …… SiO ₂ 13 …… Si substrate, 14 …… Contour layer 15 …… Process protection layer, 16 …… Deep UV light 21 …… Vacuum chamber, 22 …… Gas inlet 23 …… Electrode , 24 …… Exhaust bomb 25 …… RF power supply, 26 …… Pressure gauge 27 …… Conductance valve 28 …… Personal computer, 51 …… Vacuum chamber 52 …… Light source, 53 …… Quartz window 54 …… Wafer tray, 55… … Gas inlet 56 …… CVD equipment, 57 …… Exhaust pump

Claims (4)

[Claims] 1. A sample is exposed to a discharge of a halocarbon gas or a gas containing the same under the condition that an oxide film on the surface of the sample can be etched, and is then etched in the same chamber or in a chamber connected in a vacuum, followed by discharge. A surface treatment method, characterized in that the conditions are changed to a condition in which a layer containing carbon serving as a surface protective film can be deposited, and the sample is exposed to an electric discharge. 2. A sample is exposed to a discharge of a halocarbon gas or a gas containing the same so that the oxide film on the surface of the sample can be etched, and then the sample is continuously discharged in the same chamber or in a chamber connected in a vacuum. The conditions are changed to a condition in which a layer containing carbon serving as a surface protective film can be deposited, the sample is exposed to discharge, a protective film is formed, and a gas capable of etching the protective film is introduced before the next step,
A surface treatment method, which comprises irradiating light to remove the protective film by etching, and subsequently performing the following step in the same chamber or in a chamber connected in a vacuum. 3. A device having an electrode and a power supply for introducing plasma in a vacuum chamber to generate plasma, and means for automatically changing the gas pressure in two or more steps every predetermined time. A surface treatment device having. 4. A device having an electrode and a power source for introducing plasma in a vacuum chamber to generate plasma, and a means for automatically changing the gas pressure in two or more steps every predetermined time. A surface treatment device having a window that can transmit light, and a gas that decomposes by light and can generate a halogen can be introduced and vacuum exhausted, and the surface protective film formed by the surface treatment device can be etched by light irradiation in the gas. A surface treatment apparatus which is equipped with a desired manufacturing apparatus which is equipped with a function and is connected in the same chamber or in a vacuum.