JPH03174725A - Method of removing metal - Google Patents

Abstract

PURPOSE:To enable easy removal of metals such as iron and nickel causing pollution of a substrate, in dry atmosphere, by a method wherein the substrate polluted with heavy metals is set in a reaction vessel, a mixed gas of a carbon monoxide and a gas containing halogen atoms is introduced into the vessel and thereafter the mixed gas is activated in a state wherein the inside of the vessel is pressurized to be at 1 bar or above. CONSTITUTION:A substrate 3 polluted with heavy metals is set in a reaction vessel, a mixed gas of a carbon monoxide and a gas containing halogen atoms is introduced into the vessel and thereafter the mixed gas is activated in a state wherein the inside of the vessel is pressurized to be at 1 bar or above. This method enables very easy removal of the heavy metals not only in the surface of the substrate, but also on the side inside the surface, in a dry atmosphere, and consequent attainment of the substrate of high purity.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to cleaning of a substrate in the manufacturing process of a semiconductor device,
Particularly related to metal contamination removal technology.

(Prior Art) In the manufacture of semiconductor devices, dry etching has been promoted, but dry cleaning has not been done at all. The main reason for this is not that there is no demand for drying, but that it is technically difficult.

That is, in the manufacture of semiconductor devices, impurities that adhere to the surface or must be removed by cleaning before each process are organic contamination, metal contamination, and native oxide film. Methods have been reported for removing organic matter, such as using oxygen plasma or using ozone under ultraviolet light irradiation. Furthermore, a method has been proposed in which the natural oxide film is made to act on a dry atmosphere of HF gas. However, although metal contamination is caused by dry etching, sputtering, etc., there has been no report that it has been removed by dry processing.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned conventional problems. The purpose of the present invention is to provide a method for easily removing the substances in a dry atmosphere.

[Configuration of the Invention (Means for Solving the Problems) The invention of Section 1 of the present application includes a first step of installing a substrate contaminated with heavy metals in a reaction container, and a step of placing carbon monoxide and halogen atoms in the container. The second introducing the mixed gas with the containing gas
and a third step of activating the mixed gas in a state where the inside of the container is pressurized to 1 atmosphere or more.

The invention of Section 2 of the present application includes a first step of installing a substrate contaminated with heavy metals in a reaction container, and a step of pressurizing the inside of the container to 1 atmosphere or more after introducing carbon monoxide into the container. a second step of activating the carbon monoxide to act on the substrate; evacuating the carbon monoxide in the container and introducing a gas containing halogen atoms; activating the gas to act on the substrate; After evacuating the gas containing halogen atoms in the container and introducing carbon monoxide,
The method is characterized by comprising a fourth step of activating the carbon monoxide and causing it to act on the substrate while the inside of the container is pressurized to 1 atmosphere or more.

The invention of Section 3 of the present application includes a first step of installing a substrate contaminated with heavy metals in a reaction container, and a step of pressurizing the inside of the container to 1 atmosphere or more after introducing carbon monoxide into the container. a second step of activating the carbon monoxide to act on the substrate; evacuating the carbon monoxide in the container; and introducing a mixed gas of nitrogen monoxide and a gas containing a halogen atom into the container.・After that, a third step of activating the mixed gas while pressurizing the inside of the container to 1 atmosphere or more, and a step of repeating the second and third steps at least once after evacuating the mixed gas. It is characterized by comprising four steps.

The invention of Section 4 of the present application includes a first step of installing a substrate contaminated with heavy metals in a reaction container, and a step of pressurizing the inside of the container to 1 atmosphere or more after introducing carbon monoxide into the container. a second step of activating the carbon monoxide to act on the substrate, and after exhausting the carbon monoxide in the container and introducing nitrogen monoxide into the container, pressuring the inside of the container to 1 atmosphere or more. a third step of activating the nitrogen monoxide under pressure and acting on the substrate; evacuating the nitrogen monoxide in the container and introducing a gas containing halogen atoms into the container; a fourth step of activating and acting on the substrate; and a fifth step of repeating the second to fourth steps at least once after exhausting the gas containing halogen atoms in the container. It is characterized by:

As the means for activating the gas, for example, ultraviolet light in a wavelength range that absorbs gas containing halogen atoms or T E
A method using light irradiation such as a CO2 laser, a method of discharging using any one of high frequency power, microwaves, DC power, and shock waves under reduced pressure can be employed. In particular, when activating by electrical discharge, discharge is performed in a container different from the reaction container,
The active species generated in the separate container may be introduced into the container via piping or the like. Furthermore, as the active species, those in the penning process by rare gas atoms in a metastable state generated by discharge of rare gas may be used.

Examples of the gas containing halogen atoms include CF
Examples include gases containing fluorine atoms such as 2, F2, and NF3. As the gas containing fluorine atoms, the above-mentioned N
In addition to F3, there are SF6 and BF3, but when SF6 is used, its dissociated component S is on the substrate surface, and BF3
When B is used, its dissociated component B adheres to the substrate surface, and it is necessary to remove these components again. Therefore, N F 3 is useful because foreign matter does not adhere to the substrate.

(Operation) According to the invention of Section 1 of the present application, a substrate contaminated with heavy metals is placed in a reaction container, and a mixed gas of carbon monoxide and a gas containing halogen atoms is introduced into the reaction container. By activating the mixed gas while pressurizing the inside of the container to 1 atmosphere or more, active CO acts on the heavy metals present on the substrate surface to generate carbonyl compounds. Such carbonyl compounds of heavy metals have a high vapor pressure or have sublimation properties, so they can be easily removed from the substrate surface.

In addition, along with the production of the carbonyl compound, the substrate surface is etched by the gas containing activated halogen atoms, and heavy metals located inside the surface are exposed.
Licarbonyl compounds are produced by the action of the active CO and are similarly removed. Therefore, not only the substrate surface but also
Heavy metals inside the surface can be removed very easily in a dry atmosphere, resulting in a highly clean substrate.

According to the invention of Section 2 of the present application, after the first step of placing the substrate contaminated with heavy metals in the reaction container, carbon monoxide is introduced into the container and the inside of the container is pressurized to 1 atmosphere or more. By performing the second step of activating the carbon monoxide in this state, active CO acts on the heavy metals present on the substrate surface to generate carbonyl compounds.

Next, by exhausting the carbon monoxide in the container, carbonyl compounds of heavy metals having high vapor pressure or sublimation properties can be easily removed from the substrate surface. After evacuation, a third step of activating the gas is performed after introducing a gas containing halogen atoms, whereby the substrate surface is etched by the activated gas containing halogen atoms, and the inside of the substrate is etched from the surface. Heavy metals located on the side are exposed.

After exhausting the gas containing halogen atoms in the container and introducing carbon monoxide, by performing a fourth step of activating the carbon monoxide while pressurizing the inside of the container to 1 atmosphere or more. , C active against heavy metals exposed in the above step
A carbonyl compound can be generated by the action of O, and can be easily removed from the substrate surface.

Therefore, not only heavy metals on the surface of the substrate but also on the inside from the surface can be removed very easily in a dry atmosphere to obtain a highly clean substrate.

In the invention of Section 2 of the present application described above, by repeating the third and fourth steps, it is possible to obtain an even more cleaned substrate.

According to the invention of Section 3 of the present application, after the first step of placing a substrate contaminated with heavy metals in a reaction container, carbon monoxide is introduced into the container and the inside of the container is pressurized to 1 atmosphere or more. By performing the second step of activating the carbon monoxide in the 0 state, the active CO acts on the heavy metal present on the substrate surface to generate a carbonyl compound.

Next, after exhausting the carbon monoxide in the container and introducing a mixed gas of nitrogen monoxide and a gas containing a halogen atom into the container, the mixture is carried out while the inside of the container is pressurized to 1 atmosphere or more. By carrying out the third step of activating the gas, the gas containing activated nitrogen monoxide and halogen atoms acts on the carbonyl compound of the heavy metal to generate a nitrosylated halogen compound. Such nitrosylated halogen compounds of heavy metals have high vapor pressure or sublimation properties, and therefore can be easily removed from the substrate surface.

Additionally, along with the production of the nitrosylated halogen compound,
The substrate surface is etched by a gas containing activated halogen atoms, and heavy metals located inside the surface are exposed.

Next, by evacuating the mixed gas and performing a fourth step in which the second and third steps are repeated at least once, the heavy metals exposed in the step can be converted into 21 trosylated halogen compounds, and the substrate surface can be easily removed from Therefore, it is possible to remove not only the surface of the substrate but also the heavy metals inside the surface very easily in a try atmosphere to obtain a highly clean substrate.

According to the invention in Section 4 of the present application, after the first step of placing a substrate contaminated with heavy metals in a reaction container, carbon monoxide is introduced into the container, and the inside of the container is pressurized to 1 atmosphere or more. By performing the second step of activating the carbon monoxide in this state, active CO acts on the heavy metals present on the substrate surface to generate carbonyl compounds.

Next, after exhausting the carbon monoxide in the container and introducing nitrogen monoxide into the container, a third step of activating the nitrogen monoxide while pressurizing the inside of the container to 1 atmosphere or more is performed. By doing so, activated nitrogen monoxide acts on the carbonyl compound on the surface of the substrate, allowing it to be converted into a nitrosylated compound.

Next, the nitrogen monoxide in the container is exhausted, and a gas containing halogen atoms is introduced into the container. The gas containing the converted halogen atoms acts to produce a di-rosylated halogen compound. Such nitrosylated halogen compounds of heavy metals have high vapor pressure or sublimation, so
Can be easily removed from the substrate surface. Further, as the nitrosylated norylogen compound is produced, the substrate surface is etched by the gas containing the activated norogen atoms, and heavy metals located inside the surface are exposed.

Next, by exhausting the gas containing the halogen atoms and performing a fifth step in which the second to fourth steps are repeated at least once, the heavy metals exposed in the step can be converted into a nitrosylated halogen compound, Can be easily removed from the substrate surface. Therefore, not only heavy metals on the surface of the substrate but also on the inside from the surface can be removed very easily in a dry atmosphere to obtain a highly clean substrate.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Explain.

FIG. 1 is a schematic diagram showing a metal removal apparatus used in an embodiment of the present invention. Inside the stainless steel reaction vessel 1,
A sample stage 2 is provided. The inner wall of the reaction vessel 1 is
The container is covered with a quartz plate to prevent stainless steel, which is the container material, from being sputtered and contaminating the substrate during sputtering. Pins 4 for fixing the substrate 3 are implanted on the upper surface of the sample stage 2. A heater 5 for heating the substrate 3 and a thermocouple 6 for detecting temperature are embedded in the sample stage 2, respectively.

The sample stage 2 is normally grounded, but has a structure that allows it to be electrically floating. A discharge electrode 7 is arranged in the container 1 facing the sample stage 2. This electrode 7 is made of nickel, and its periphery is finished with a calculated curvature. Further, the electrode 7 is connected to a current introduction terminal 8. Furthermore, six sets of capacitors 9 are arranged around the electrode 7, forming pairs of capacitors 9 facing each other in order to spread the discharge uniformly. At the tips of these capacitors 9, there is a small electrode IO
The structure is such that a discharge is first generated in this gap, and the ultraviolet light generated from the discharge serves as a trigger to start the main discharge.

Furthermore, windows 11 and 12 for irradiating light are provided in the reaction vessel 1 in a direction of 45 degrees from the sample stage 2. When irradiating with ultraviolet light, a quartz window is attached and the ultraviolet light source 13 is placed outside the window.

When irradiating with TEACO laser light, a ZnS window material is attached and the laser light is introduced. The reaction vessel 1
An activation mechanism 15 is attached via a gate valve 14 to the activation mechanism 15 . The activation mechanism 15 includes a discharge tube 16 made of quartz, a microwave cavity resonator 17 and a waveguide 18 provided in the discharge tube 16, and a microwave power supply connected to the waveguide 17. It consists of 19. In the activation mechanism 15 having such a structure, gas is introduced from the gas inlet 20, microwaves are applied to cause discharge, and the generated activated species are introduced into the reaction vessel 1. Further, a vacuum pump 21 for exhausting gas is connected to the reaction vessel 1 via a valve 22.

Next, a method for manufacturing a Si substrate contaminated with heavy metals used in this example will be described below. The metal removal method will be explained below.

First, a p-type Si crystal Si substrate with a (100) plane is placed in a parallel plate dry etching device, and a covering material such as a quartz plate or an induced polymer film is usually provided to prevent the stainless steel from being directly exposed to plasma. The chamber material, stainless steel, is exposed directly to the plasma. Argon gas was flowed into this etching device for 180 seconds.
Introduced with a pressure of 0.01 torrs and high frequency power of 2 W.
/Cn2 for 20 minutes. When the Si substrate subjected to such treatment was analyzed by Auger electron spectroscopy, the results shown in FIG. 2(A) were obtained. This figure 2 (A
) clearly indicates that the Si substrate was contaminated with iron and nickel. FIG. 2(B) is a spectrum after the surface of a Si substrate was sputtered very slightly using an Ar ion beam. Iron and nickel are still detected. This shows that iron and nickel 6 are not only attached to the surface, but also invade near the surface layer of the Si substrate due to ion bombardment.

Example 1 First, the Si substrate 3 contaminated with heavy metals was fixed on the sample stage 2 in the reaction vessel 1, and the Si substrate 3 was heated to 300° C. by the heater 5 embedded in the sample stage 2. Next, 30% carbon monoxide was poured into the reaction vessel through the discharge tube IB.
sec+n, chlorine was introduced at a flow rate of 5 sec until the pressure in the container 1 reached 5 atm. Continuing, reaction vessel 1
Ultraviolet light emitted from a 500 W Hg-Xe lamp was introduced into the chamber through a quartz window 11. At this time, the ultraviolet light was focused using a lens.

After performing this treatment for 20 minutes, the gas was evacuated using the vacuum pump 21, nitrogen was further purged into the reaction vessel l, and S
The i-substrate 3 was exposed to the atmosphere.

Auger analysis was performed on the Si substrate taken out from reaction vessel 1. As a result, peSNi
It was confirmed that the amount of metals such as

7 In addition, the above-mentioned process was repeated multiple times, and Fe
The signal intensity was measured. As a result, as shown in FIG. 4, it was confirmed that the metal on the Si substrate could be removed extremely well by repeating the process three or more times.

Example 2 First, the Si substrate 3 contaminated with heavy metals was fixed on the sample stage 2 in the reaction vessel 1, and the Si substrate 3 was heated to 300° C. by the heater 5 embedded in the sample stage 2. Next, the reaction vessel 1 is heated while the Si substrate 3 is maintained at 300°C.
Carbon monoxide is passed through the discharge tube 16 into the 5SCCI111
Chlorine was introduced at a flow rate of 2 sec and He was introduced at a flow rate of 50 sec until the pressure in the container 1 reached 3 atm. Next, a DC voltage of 50 kV was applied across the capacitor 9 from the current introduction terminal 8 through the discharge electrode 7 to cause a discharge in the reaction vessel 1 at 15 pulses for 1 second. After this treatment was carried out for 10 minutes, the gas was evacuated using the vacuum pump 21, nitrogen was further purged into the reaction vessel 1, and the Si substrate 3 was exposed to the atmosphere.

Eighth die analysis was performed on the Si substrate taken out from reaction vessel 1. As a result, as shown in Figure 3 above,
It was confirmed that metals such as Fe and Ni were significantly reduced.

Example 3 First, the Si substrate 3 contaminated with heavy metals was fixed on the sample stand 2 in the reaction vessel l, and the Si substrate 3 was heated to 350°C by the heater 5 embedded in the sample stand 2 (first process).

Next, while the Si substrate 3 was maintained at 350° C., carbon monoxide was introduced into the reaction vessel 1 through the discharge tube 16 until the pressure in the vessel 1 reached 5 atmospheres. Continuing, 50k is applied between the capacitor 9 from the current introduction terminal 8 through the discharge electrode 7.
A DC voltage of V was applied to cause a discharge in reaction vessel 1 at 15 pulses for 1 second. This treatment was performed for 10 minutes (second step).

Next, after exhausting carbon monoxide using the vacuum pump 21, chlorine gas was introduced into the reaction vessel through the discharge tube 16 for 30 seconds.
ecm, and the pressure inside the container 1 was set to 0.2 torr.
It was held at r. When flowing chlorine gas through the discharge tube 16, a 200 W microwave was applied using a 2.54 GHz microwave power source 19 to cause discharge within the discharge tube 16. This microwave discharge causes chlorine gas to dissociate, producing chlorine atoms. The chlorine atoms flow toward the reaction vessel 1 through the discharge tube 16 and act on the Si substrate 3. This chlorine treatment was carried out for I minutes. Thereafter, the introduction of chlorine gas was stopped, and the Si substrate 3 was heated to 350° C. by the heater 5 in the sample stage 2 and left for 5 minutes (Third King's Degree).

Next, after performing the second step described above again, the gas was evacuated using the vacuum pump 21, nitrogen was further purged into the reaction vessel 1, and the Si substrate 3 was exposed to the atmosphere.

The surface of the Si substrate taken out from reaction vessel 1 was analyzed by XPS. As a result, as shown in FIG. 5, a chlorine peak was observed, and it was confirmed that although chlorine remained on the surface, the peaks of metals such as iron and nickel had decreased. Carbon and oxygen signals are observed, but this is due to exposure to atmospheric air during processing and analysis.

Additionally, some zero oxygen is released from the quartz tube during the discharge within the quartz tube. Therefore, it is possible that the surface was oxidized. In this case, electrical discharge is a means to dissociate chlorine. In addition, as a means for dissociating chlorine, a Penning process may be used in which chlorine is mixed with a rare gas such as Ar, and the metastable state of the rare gas is utilized.

Example 4 First, the Si substrate 3 contaminated with heavy metals was fixed on the sample stand 2 in the reaction vessel 1, and the Si substrate 3 was heated to 350°C by the heater 5 embedded in the sample stand 2 (first process).

Next, while the Si substrate 3 was maintained at 350° C., carbon monoxide was introduced into the reaction vessel I through the discharge tube 1B until the pressure in the vessel I reached 5 atmospheres. Next, 50kV is applied between the capacitor 9 from the current introduction terminal 8 through the discharge electrode 7.
A DC voltage of 1 was applied to generate a discharge of 15 pulses for 1 second in the reaction vessel 1. This treatment was performed for 10 minutes (second step).

Next, after exhausting carbon monoxide using the vacuum pump 21, a mixed gas of nitrogen monoxide and chlorine gas (mixing ratio 1:1) is introduced into the reaction vessel through the discharge tube 16 until the pressure inside the vessel 1 is 3 atm. It was introduced so that Subsequently, discharge was performed for 10 minutes under the same conditions as in the second step. after that,
The introduction of nitrogen monoxide and chlorine gas was stopped, and the Si substrate 3 was heated to 350° C. by the heater 5 in the sample stage 2 and left for 5 minutes (third step).

Next, after performing the second and third steps described above again, the gas was evacuated using the vacuum pump 21, nitrogen was further purged into the reaction vessel 1, and the Si substrate 3 was exposed to the atmosphere.

Auger analysis was performed on the Si substrate taken out from reaction vessel 1. As a result, Fe, N
It was confirmed that metals such as i were significantly reduced.

Example 5 First, the Si substrate 3 contaminated with heavy metals was fixed on the sample stand 2 in the reaction vessel l, and the Si substrate 3 was heated to 150°C by the heater 5 embedded in the sample stand 2 (first
process).

2 Next, while the Si substrate 3 was heated to 150° C., carbon monoxide was introduced into the reaction vessel 1 through the discharge tube 16 until the pressure reached 5 atmospheres. Subsequently, a DC voltage of 50 kV was applied across the capacitor 9 from the current introduction terminal 8 through the discharge electrode 7 to cause discharge in the reaction vessel 1 at 15 pulses for 1 second. This treatment was performed for 10 minutes (second step).

Next, after exhausting the carbon monoxide in the reaction vessel 1, the Si
With the substrate 3 heated to 150° C., nitrogen monoxide was introduced into the reaction vessel 1 through the discharge tube i6 until the pressure in the vessel i reached 6 atmospheres. Subsequently, discharge was performed for 10 minutes under the same conditions as in the second step.

Thereafter, the nitrogen monoxide was exhausted, and the Si substrate 3 was heated to 300° C. by the heater 5 in the sample stage 2 and left for 10 minutes (third step).

Next, chlorine gas was introduced into the reaction vessel 1 through the discharge tube 6 to bring the pressure inside the reaction vessel 1 to 100 torr, and then ultraviolet light emitted from a 500 W Hg-Xe lamp was introduced through the quartz window 11. At this time, the ultraviolet light was focused using a lens. After performing this treatment for 13 minutes, the gas was exhausted using the vacuum pump 21 (fourth step).

Next, after performing the second to fourth steps described above again, the gas was evacuated using the vacuum pump 21, nitrogen was further purged into the reaction vessel 1, and the Si substrate 3 was exposed to the atmosphere.

The surface of the Si substrate taken out from reaction vessel 1 was analyzed. As a result, as in the other examples already mentioned, the amount of metal was reduced, and it was confirmed that this method is effective as a means for removing soil from metal.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to remove not only the surface of the substrate but also heavy metals inside the surface very easily in a dry atmosphere to obtain a highly clean substrate. It is possible to provide a method for removing metal.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one form of a metal removal apparatus used in an example of the present invention, and FIGS. 2 (A) and (B) are auger removal of heavy metal-contaminated Si4 substrate surface used for detailed explanation of the present invention. Spectrum diagram from analysis, Figure 3,
FIGS. 4 and 5 are characteristic diagrams showing the results of analyzing the surface of a Si substrate after metal removal treatment in an example of the present invention. I... Reaction container, 2... Sample stand, 3... Substrate, 5
... Heater, 7... Discharging electrode, ... Capacitor, IL 12... Window, (3... Ultraviolet source, 15...
・Activation mechanism, 16...Discharge tube, 19...Microwave power supply, 21...Vacuum pump.

Claims (4)

[Claims] (1) A first step of installing a substrate contaminated with heavy metals in a reaction container, a second step of introducing a mixed gas of a gas containing carbon monoxide and halogen atoms into the container, and a third step of activating the mixed gas in a state where the gas mixture is pressurized to 1 atmosphere or more. (2) A first step of installing a substrate contaminated with heavy metals in a reaction container, and after introducing carbon monoxide into the container, the carbon monoxide is a second step of activating and acting on the substrate; and a third step of evacuating carbon monoxide in the container, introducing a gas containing halogen atoms, and activating the gas to act on the substrate. After exhausting the gas containing halogen atoms in the container and introducing carbon monoxide, the carbon monoxide is activated and acts on the substrate while the inside of the container is pressurized to 1 atmosphere or more. A method for removing metal, comprising a fourth step. (3) A first step of installing a substrate contaminated with heavy metals in a reaction container, and after introducing carbon monoxide into the container, the carbon monoxide is a second step in which carbon monoxide in the container is exhausted and a mixed gas of nitrogen monoxide and a gas containing halogen atoms is introduced into the container; a third step of activating the mixed gas while pressurized to 1 atmosphere or more; and a fourth step of repeating the second and third steps at least once after exhausting the mixed gas. A metal removal method characterized by: (4) A first step of installing a substrate contaminated with heavy metals in a reaction container, and after introducing carbon monoxide into the container, the carbon monoxide is a second step of activating and acting on the substrate, and after exhausting carbon monoxide in the container and introducing nitrogen monoxide into the container, pressurizing the inside of the container to 1 atmosphere or more; A third step of activating the nitric oxide to act on the substrate.
a fourth step of evacuating nitrogen monoxide in the container, introducing a gas containing halogen atoms into the container, and activating the gas to act on the substrate; A method for removing metal, comprising a fifth step of repeating the second to fourth steps at least once after exhausting the gas containing atoms.