KR20070037434A - Remote chamber methods for removing surface deposits - Google Patents

Abstract

The present invention is directed to an improved remote plasma cleaning method for removing surface deposits from a surface, such as the interior of a deposition chamber used to manufacture an electronic device. Improvements include the addition of a nitrogen source to a feed gas mixture consisting of oxygen and carbon fluoride. The improvement also includes pretreatment of the inner surface of the passageway from the remote chamber to the surface stack by activating a pretreatment gas mixture consisting of a nitrogen source and passing the active pretreatment gas through the passageway.

CVD, PECVD, carbon fluoride, plasma, surface stacks, process chambers, remote chambers

Description

Remote chamber method for removing surface stacks {REMOTE CHAMBER METHODS FOR REMOVING SURFACE DEPOSITS}

The present invention is directed to a method for removing a surface stack by using an active gas produced by remotely activating a gas mixture consisting of oxygen, carbon fluoride, and nitrogen sources. In particular, the present invention relates to a method for removing surface deposits from the interior of a chemical vapor deposition chamber by using an active gas produced by remotely activating a gas mixture consisting of oxygen and perfluorocarbon compounds, and a nitrogen source.

Remote plasma sources for the generation of fluorine atoms are widely used for chamber cleaning in the semiconductor processing industry, in particular for cleaning chambers used for chemical vapor deposition (CVD) and plasma chemical vapor deposition (PECVD). The use of a remote plasma source prevents some of the corrosion of the internal chamber material resulting from in-situ chamber cleaning where the cleaning is performed by creating a plasma discharge in the PECVD chamber. Although capacitive and inductively coupled RF and microwave remote sources have been developed for this kind of use, the industry is rapidly moving to transformer-coupled inductively coupled sources where the plasma has an annular configuration and acts as a secondary coil of the transformer. . The use of low frequency RF power allows the use of a magnetic core that enhances inductive coupling to capacitive coupling, thereby allowing more efficient transfer of energy to the plasma without excessive ion bombardment that limits the lifetime inside the remote plasma source chamber. Allow.

The semiconductor industry has initially moved away from the mixture of carbon fluoride with oxygen for chamber cleaning, which was the main gas used for field chamber cleaning for a number of reasons. First, the emissions of global warming gases from such processes are generally much higher than the nitrogen trifluoride (NF ₃ ) process. NF ₃ dissociates more readily upon release and is not significantly formed by recombination of product species. Therefore, low levels of global warming gas emissions can be more easily achieved. In contrast, fluorocarbons are species that are more difficult to degrade upon release and recombine to form tetrafluorocarbons (CF ₄ ) that are much more difficult to degrade than other fluorocarbons.

Second, it was common for fluorocarbon discharges to produce “polymer” laminates that required more frequent wet cleaning to remove the buildup that accumulates after repeated dry cleaning. The propensity of the fluorocarbon wash to laminate the "polymer" occurs to a greater extent in remote washes where no ion collisions occur during the wash. This observation discouraged the industry from developing industrial processes based on fluorocarbon feed gases. In fact, PECVD equipment manufacturers have tested remote cleaning based on fluorocarbon discharges, but are currently unsuccessful because of polymer deposition in the process chamber.

However, if two drawbacks as described above can be solved, fluorocarbon gases are preferred because of their low cost and low toxicity.

Previous work has been done on nitrogen-added perfluorocarbon / oxygen discharges to enhance the etching of silicon nitride. Reinforcement is considered as a result of the formation of NO by a discharge that reacts with N on the silicon nitride surface, followed by effective fluorination of the Si atoms to form volatile products. Mr. H. C. H. Oh et al. Surface and Coatings Technology 171 (2003) 267.

The present invention is directed to a method for removing a surface stack, the method comprising (a) using sufficient power for a sufficient time for the gas mixture to reach a neutral temperature of at least about 3,000 K to form an active gas mixture, Activating in a remote chamber a gas mixture comprising an oxygen, carbon fluoride, and nitrogen source and having a molar ratio of oxygen and carbon fluoride of at least 1: 3, and (b) contacting the active gas mixture with a surface stack to Removing at least a portion of the surface stack.

The present invention also relates to a method for removing a surface stack, wherein the surface stack includes various silicon oxygen compounds called silicon, doped silicon, tungsten, silicon dioxide, silicon carbide, and low K material. Selected from the group consisting of: (a) activating in a remote chamber a gas mixture comprising an oxygen, carbon fluoride, and nitrogen source and wherein the molar ratio of oxygen to carbon fluoride is at least 1: 3, and (b ) Contacting the active gas mixture with a surface stack to remove at least a portion of the surface stack.

The invention also relates to a method for removing a surface stack, the method comprising: (a) activating a pretreatment gas mixture comprising a nitrogen source in a remote chamber, and (b) remotely activating the active pretreatment gas mixture. Contacting at least a portion of the interior surface of the passage from the chamber to the surface stack, and (c) cleaning the gas mixture containing oxygen and carbon fluoride and having a molar ratio of oxygen to carbon at least 1: 3 in the remote chamber. Activating, (d) passing the active wash gas mixture through the passage, and (e) contacting the active wash gas mixture with a surface stack to remove at least a portion of the surface stack. do.

1 is a schematic diagram of an apparatus useful for carrying out the present process.

2A and 2B are graphs of the effect of N ₂ addition on 125 sccm Zyron ^® 8020 on (a) etch rate and (b) power consumption.

3A and 3B are graphs of the effect of N ₂ addition on 250 sccm Zyron ^® 8020 on (a) etch rate and (b) power consumption.

4 is a graph of the effect of N ₂ addition on 250 sccm Zyron ^® 8020 on COF ₂ emissions, measured by FTIR.

FIG. 5 is a graph of the effect of N ₂ addition on 250 sccm Zyron ^® 8020 on various waste discharges as measured by FTIR.

6 is a graph of etch rate change due to intermittent N ₂ addition.

7A is a graph of the effect of N ₂ pretreatment on various waste discharges as measured by FTIR.

7B is a graph of the effect of N ₂ pretreatment on etch rate of Zyron ^® 8020.

The surface laminates to be removed in the present invention include materials generally deposited by chemical vapor deposition or plasma chemical vapor deposition or similar processes. Such materials include silicon, doped silicon, silicon nitride, tungsten, silicon dioxide, silicon nitride, silicon carbide, and FSG (fluorosilicate glass) and Black Diamond (Applied Materials), Coral ) (Including Novellus Systems) and Aurora (ASM International) and various silicon oxygen compounds called low K materials such as SiCOH or PECVD OSG.

One embodiment of the present invention is to remove a surface stack from the interior of a process chamber used to manufacture an electronic device. Such process chamber may be a chemical vapor deposition (CVD) chamber or a plasma chemical vapor deposition (PECVD) chamber.

The process of the present invention includes an activation step that uses sufficient power to form an active gas mixture. Activation can be accomplished by any means that allows the achievement of large fractions of dissociation of the feed gas, such as RF energy, DC energy, laser irradiation, and microwave energy. The neutral temperature of the resulting plasma depends on the power and the residence time of the gas mixture in the remote chamber. In the present invention, it has been found that the addition of nitrogen gas helps the absorption of RF power. Under certain power inputs and conditions, the neutral temperature will be higher at longer residence times. Here, a good neutral temperature is at least about 3,000 K. Under appropriate conditions (considering power, gas component, gas pressure and gas residence time), a neutral temperature of at least about 6000 K can be achieved for example in octafluorocyclobutane.

The active gas is formed in a remote chamber very close to the process chamber outside the process chamber. The remote chamber is connected to the process chamber by any means that permits the transfer of active gas from the remote chamber to the process chamber. The remote chamber and the means for connecting the remote chamber with the process chamber are comprised of materials known in the art to contain an active gas mixture. For example, aluminum and stainless steel are commonly used for chamber components. Occasionally, Al ₂ O ₃ is coated on the inner surface to reduce surface recombination.

Gas mixtures that are activated to form active gases include oxygen, nitrogen sources, and carbon fluoride. Carbon fluoride of the present invention is referred to herein as a compound consisting of C and F. Preferred carbon fluorides in the present invention are perfluorocarbon compounds. Perfluorocarbon compounds in the present invention are referred to herein as compounds composed of C, F, and optionally oxygen. Such perfluorocarbon compounds include tetrafluoromethane, hexafluoroethane, octafluoropropane, hexafluorocyclopropane, decafluorobutane, octafluorocyclobutane, carbonyl fluoride, and octafluorotetrahydrofuran. Including but not limited to. Preferred gas mixtures have an oxygen to carbon fluoride molar ratio of at least 1: 3. Better gas mixtures have an oxygen to carbon fluoride molar ratio of at least about 2: 1 to 20: 1.

The "nitrogen source" of the present invention is referred to herein as a gas capable of generating nitrogen atoms under the discharge conditions of the present invention. Examples of nitrogen sources include, but are not limited to, N ₂ , NF ₃ , and all kinds of nitrogen oxides such as NO, N ₂ O, NO _2, and the like.

The gas mixture activated to form the active gas may further comprise a carrier gas such as argon and helium.

A preferred embodiment of the present invention is a method for removing a surface stack from the interior of a process chamber used to manufacture an electronic device, the method comprising (a) a gas mixture of at least about 3,000 K to form an active gas mixture. Using a sufficient power for a sufficient time to reach the neutral temperature, activating in the remote chamber a gas mixture comprising an oxygen, perfluorocarbon compound, and nitrogen source, wherein the molar ratio of oxygen and perfluorocarbon is at least 1: 3; (b) contacting the active gas mixture with the interior of the deposition chamber to remove at least a portion of the surface stack.

In the present invention, it has been found that nitrogen gas can dramatically increase the etching rate. In one embodiment of the invention, the perfluorocarbon compound is octafluorocyclobutane (Zyron ^® 8020) manufactured by DuPont. As explained in the example shown below, in the absence of nitrogen gas, Zyron ^® 8020 generated low etch rates and high COF ₂ emissions. The etch rate begins to improve at a small amount of nitrogen, which saturates when the nitrogen addition exceeds a certain amount (see Figures 2 and 3). Nitrogen addition also increases power consumption and reduces COF ₂ emissions (see FIGS. 2 and 4).

It has also been found that under similar conditions of the present invention, the shortcomings of perfluorocarbon compounds, namely global warming gas emissions and polymer lamination, can be overcome. In the experiments of the present invention, no significant polymer stack was found on the interior surface of the chamber. Global warming gas emissions were also very low, as shown in FIG.

It has also been found that some pretreatment of the inner surface of the passage from the remote chamber to the surface stack can increase the etch rate. In the present invention, pretreatment is achieved by activating a pretreatment gas mixture consisting of a nitrogen source and passing the active pretreatment gas through the passage. In one embodiment as described in Example 4, the passage from the remote chamber to the surface stack was pretreated for 3 seconds by the mixture of active nitrogen and argon gas. After pretreatment, the etch rate started at a high level.

Alternatively, the system can be used to alter the surface located in the remote chamber by contact with fluorine atoms and other components from the source.

The following examples illustrate the invention but are not intended to be limiting.

Yes

1 shows a schematic diagram of a remote plasma source and apparatus used to measure etch rate, plasma neutral temperature, and exhaust emissions. The remote plasma source is a commercial annular MKS ASTRON ^® ex reactive gas generator unit manufactured by MKS Instruments, Andover, Massachusetts. The feed gas (eg, oxygen, carbon fluoride, nitrogen source, argon) was introduced into the remote plasma source from the left side, passed through the annular discharge portion, and discharged by 400 kHz high frequency power to form an active gas mixture. Oxygen is produced by Airgas with 99.999% purity. Carbon fluoride is Zylon ^® 8020 manufactured by DuPont with at least 99.9 volume percent octafluorocyclobutane. The nitrogen source is, in the example, nitrogen gas produced by air gas at grade 4.8, and argon is produced by air gas at grade 5.0. The active gas then passes through the aluminum water-cooled heat exchanger to reduce the heat load on the aluminum process chamber. The wafer covered with the surface stack was placed on a temperature controlled mount in the process chamber. Neutral temperature is measured by an optical emission spectrometer (OES), where the rotational vibration transition bands of binary species such as C ₂ and N ₂ are theoretically fitted to yield a neutral temperature. B., incorporated herein by reference. B. Bai and H. See H. Sawin's Journal of Vacuum Science & Technology A 22 (5), 2014 (2004). The etch rate of the surface stack by the active gas is measured by interferometer equipment in the process chamber. N ₂ gas is added at the inlet of the pump to dilute the product to an appropriate concentration for FTIR measurements and to reduce the stagnation of the product in the pump. FTIR was used to measure the concentration of species in the pump exhaust.

Example 1

The feed gas consisted of O ₂ , Zyron ^® 8020 (C ₄ F ₈ ), Ar, and N ₂ , O ₂ flow rate 1542 sccm, Ar flow rate 2333 sccm, C ₄ F ₈ flow rate 125 sccm , N ₂ flow rates are 0, 200, 400 and 600 sccm, respectively. Chamber pressure is 2 Torr. The feed gas was activated to a neutral temperature above 5000 K by 400 kHz RF power. The active gas then entered the process chamber to etch the SiO ₂ surface stack on the mount whose temperature was controlled to 200 ° C. The results are shown in FIG.

Example 2

The feed gas consisted of O ₂ , Zyron ^® 8020 (C ₄ F ₈ ), Ar, and N ₂ , O ₂ flow rate 1750 sccm, Ar flow rate 2000 sccm, C ₄ F ₈ flow rate 250 sccm , N ₂ flow rates are 0, 100, 200, 300, 400, 500 and 600 sccm, respectively. Chamber pressure is 2 Torr. The feed gas was activated to a neutral temperature above 5000 K by 400 kHz RF power. The active gas then entered the process chamber to etch the SiO ₂ surface stack on the mount whose temperature was controlled to 200 ° C. The results are shown in FIG. In this experiment, the COF ₂ concentration in the perpump exhaust was monitored by FTIR and is shown in FIG.

Example 3

The initial feed gas consisted of O ₂ , Zyron ^® 8020 (C ₄ F ₈ ), Ar, an O ₂ flow rate of 1750 sccm, an Ar flow rate of 2000 sccm, and a C ₄ F ₈ flow rate of 250 sccm. Chamber pressure is 2 Torr. The mount on which the SiO ₂ surface stack was on was controlled at 100 ° C. Exhaust gases of C ₄ F ₈ , CO, CO ₂ , C ₂ F ₆ , C ₃ F ₈ , CF ₄ , COF ₂ , N ₂ O, NF ₃ , and SiF ₄ were monitored by FTIR and shown in FIG. 5. have. The plasma was ignited by 400 kHz RF power at 250 seconds and the neutral temperature rose to about 5500 K. There was no N ₂ addition at the start, the etch rate was low (see FIG. 6), the COF ₂ emissions were high and the CO ₂ emissions were low. At 720 seconds, 100 sccm of N ₂ was added to the feed gas. As a result, the etch rate jumped, COF ₂ emissions dropped, and CO ₂ emissions increased immediately. At 1280 seconds, the N ₂ flow was stopped. Etch rates, COF ₂ emissions, and CO ₂ emissions were all restored to their previous levels. 200 sccm of N ₂ flow was added starting at 2100 seconds and stopped at 2780 seconds. The same type of change was repeated. At 3100 seconds, the C ₄ F ₈ flow was stopped for 5 seconds. After the drop in etch rate and COF ₂ and CO ₂ emissions, the system recovered and continued to transition. Power was interrupted at 3600 seconds. From FIG. 5, it can be expected that the addition of 200 sccm of N ₂ increases the etching rate to the same level as the addition of 100 sccm of N ₂ was done. However, it was observed that the etching rate decreased slightly due to the roughness change of the film after the first 2 μm of the surface laminate was etched.

Example 4

The pretreatment gas mixture consisted of 100 sccm N ₂ and 2000 sccm Ar. It was activated by 400 kHz RF power and the neutral temperature was about 2000 K. Starting at 100 seconds and continuing for 3 seconds, the active gas passed from the remote chamber to the process chamber with the SiO ₂ surface stack on a mount whose temperature was controlled at 100 ° C. Next, a gas mixture consisting of 1750 sccm O ₂ and 250 sccm Zyron ^® 8020 (C ₄ F ₈ ) was added. The wash gas mixture was activated by 400 kHz RF power and the neutral temperature was about 5500 K. Process chamber pressure was 2 Torr. The mount on which the SiO ₂ surface stack was on was controlled at 100 ° C. Exhaust gases of C ₄ F ₈ , CO, CO ₂ , C ₂ F ₆ , C ₃ F ₈ , CF ₄ , COF ₂ , N ₂ O, NF ₃ , and SiF ₄ were monitored by FTIR and shown in FIG. 7A. have. After pretreatment, the etch rate started at a high level as shown in FIG. 7B and the COF ₂ emissions were low. In the cleaning gas mixture containing N ₂ , the system was maintained at a high etch rate. At the time point of about 500 seconds, N ₂ was removed from the wash gas mixture, slowing down the etch rate and slowly increasing the COF ₂ emissions. At the time of 1850 seconds, 100 sccm of N ₂ was added back to the wash gas mixture. As a result, the etch rate jumped, COF ₂ emissions dropped, and CO ₂ emissions increased immediately. Power was interrupted at 3160 seconds.

Claims (16)

Method of removing surface stacks, (a) using a sufficient power for a time sufficient to allow the gas mixture to reach a neutral temperature of at least about 3,000 K to form an active gas mixture, comprising a source of oxygen, carbon fluoride, and nitrogen, Activating a gas mixture of at least 1: 3 in a remote chamber; (b) contacting the active gas mixture with the surface stack to remove at least a portion of the surface stack. The method of claim 1, wherein the surface stack is removed from the interior of a deposition chamber used to manufacture an electronic device. The method of claim 1, wherein the power is generated by an RF source, a DC source, or a microwave source. The method of claim 1, wherein the nitrogen source is nitrogen gas, NF ₃ , or nitrogen oxides. The method of claim 1, wherein the fluorocarbon is a perfluorocarbon compound. 6. The perfluorocarbon compound according to claim 5, wherein the perfluorocarbon compound is selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, octafluorocyclobutane, carbonyl fluoride, and perfluorotetrahydrofuran. Method of removing surface stack. The method of claim 1, wherein the gas mixture further comprises a carrier gas. 8. The method of claim 7, wherein the carrier gas is at least one gas selected from the group of gases consisting of argon and helium. The method of claim 1, wherein the pressure in the remote chamber is between 0.01 to 20 torr. The surface laminate of claim 1 wherein the surface stack is selected from the group consisting of various silicon oxygen compounds called silicon, doped silicon, silicon nitride, tungsten, silicon dioxide, silicon nitride, silicon carbide, and low K material. Method of removing surface stack. The method of claim 1, wherein the molar ratio of oxygen and carbon fluoride is at least about 2: 1 to about 20: 1. Method of removing surface stacks, The surface stack is selected from the group consisting of silicon, doped silicon, tungsten, silicon dioxide, silicon carbide, and various silicon oxygen compounds called low K materials, The method, (a) activating in a remote chamber a gas mixture comprising an oxygen, carbon fluoride, and nitrogen source, wherein the molar ratio of oxygen to carbon fluoride is at least 1: 3; (b) contacting the active gas mixture with the surface stack to remove at least a portion of the surface stack. The method of claim 12, wherein the surface stack is removed from the interior of a deposition chamber used to manufacture an electronic device. 13. The method of claim 12, wherein the nitrogen source is nitrogen gas, NF ₃ , or nitrogen oxides. 13. The method of claim 12, wherein said fluorocarbon is a perfluorocarbon compound. Method of removing surface stacks, (a) activating a pretreatment gas mixture comprising a nitrogen source in a remote chamber; (b) contacting the active pretreatment gas mixture with at least a portion of the interior surface of the passageway from the remote chamber to the surface stack; (c) activating in the remote chamber a cleaning gas mixture comprising oxygen and carbon fluoride, wherein the molar ratio of oxygen to carbon fluoride is at least 1: 3; (d) passing the active wash gas mixture through the passage; (e) contacting the active wash gas mixture with the surface stack to remove at least a portion of the surface stack.

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