CN1734724A - Plasma processing method and post-processing method - Google Patents

Abstract

The present invention provides a plasma processing method and a post-processing method capable of preventing not only corrosion in a processing chamber but also corrosion in a transfer system. A plasma processing method for performing plasma processing on an object to be processed in a chamber, comprising: plasmaizing a gas containing at least halogen, and using the first plasma to generate the first plasma to process the object to be processed treatment; after the first plasma treatment, supply oxygen-containing gas into the chamber to generate a second plasma, and process the chamber and the object to be treated; the second plasma treatment will contain at least nitrogen and hydrogen The gas is plasmaized, and the third plasma treatment is performed on the object to be treated after the second plasma treatment with the generated third plasma.

Description

Plasma treatment method and post-treatment method

technical field

The present invention relates to a plasma processing method and a post-processing method, specifically, a plasma processing method and a post-processing method for etching a semiconductor wafer or the like.

Background technique

In the process of dry-etching substrates such as semiconductor wafers with corrosive gases such as hydrogen bromide or chlorine, it is necessary to deal with particles generated by the detachment of reaction products attached to the processing chamber and chamber damage caused by corrosive gases. Corresponding countermeasures are proposed. Therefore, it has been proposed to clean with O ₂ plasma after dry etching (for example, Patent Document 1). Cleaning with this _O2 plasma is effective for replacing the halogen gas environment in the chamber and for corrosion protection in the chamber. In addition, it is also expected to have the effect of removing the corrosive gas adsorbed on the substrate by spraying.

However, accumulation of reaction products has been observed on substrates after etching treatment. For example, when etching silicon substrates, reaction products such as SiBr ₄ and SiCl ₄ are deposited. It is difficult to completely remove these deposits by the _O2 plasma post-treatment described above.

[Patent Document 1] JP-A-63-5532 (Claims)

As mentioned above, it is difficult to completely remove deposits on the substrate by cleaning with _O2 gas plasma. The above-mentioned deposits remaining on the substrate have the characteristic of generating corrosive gases such as halogen gas in an open air environment. Therefore, when moving to a subsequent process, there is a problem that corrosive gas is generated from deposits on the substrate in the transfer system, causing corrosion of the transfer system. Generally speaking, the inner surface of the chamber where corrosive gas is used for etching and other processing is made of aluminum or aluminum oxide film material, so it constitutes a temporary anti-corrosion measure. Corrosion causes deterioration, which greatly impairs the durability of the entire system. However, little research has been done so far on the corrosion protection of handling systems.

Contents of the invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide a plasma processing method and a post-processing method capable of preventing corrosion not only in a processing chamber but also in a transfer system.

In order to solve the above problems, according to a first viewpoint of the present invention, a plasma processing method for performing plasma processing on an object to be processed in a chamber is provided, which is characterized in that, comprising:

a first plasma treatment for treating an object to be treated with plasma of a gas containing at least a halogen, and using the generated first plasma;

After the first plasma treatment, a gas containing oxygen is supplied into the chamber to generate a second plasma, and the chamber and the object to be processed are treated by the second plasma treatment;

After the second plasma treatment, a gas containing at least nitrogen and hydrogen is plasmatized, and the object to be treated is treated with the generated third plasma.

In this plasma treatment method, by performing the second plasma treatment and the third plasma treatment, not only corrosion in the treatment chamber but also corrosion of the transport system caused by halogen can be prevented.

In the above plasma treatment method, the first plasma treatment to the third plasma treatment may all be performed in the same chamber. At this time, cleaning of the chamber and modification of deposits on the surface of the object to be treated are realized by the all-in-one treatment in a single chamber.

In addition, the above-mentioned first plasma treatment and second plasma treatment may be performed in the same chamber, and the third plasma treatment may be performed in another chamber. At this time, by moving the object to be processed into another chamber, the influence of the halogen gas atmosphere in the chamber where the first plasma processing is performed can be substantially blocked. Accordingly, generation of corrosive gas in the conveyance system can be prevented.

In addition, in the above-mentioned plasma treatment method, the above-mentioned halogen is preferably chlorine or bromine; the above-mentioned gas containing at least nitrogen and hydrogen is preferably ammonia or a mixed gas of nitrogen and hydrogen. At this time, in the third plasma treatment, the silicon halide adhering to the object to be processed is converted into ammonium halide and stabilized. Thus, generation of halogens in the conveyance system can be prevented.

In the above-mentioned plasma treatment method, it is preferable to include a cleaning treatment of wet-cleaning the object to be treated after the above-mentioned third plasma treatment. At this point, the ammonium halide can be easily removed by washing.

In addition, in a preferred aspect of the plasma processing method, the first plasma processing is a plasma etching process on a silicon substrate. At this time, the use of corrosive gas can realize high-efficiency etching, and can prevent corrosion of the chamber and the transfer system.

In addition, according to the second aspect of the present invention, a post-processing method is provided, which is a method of post-processing the object to be processed in the chamber after the processing step using corrosive gas, which is characterized in that it includes:

Supplying gas containing oxygen into the above-mentioned chamber to generate _O2 plasma to treat the above-mentioned chamber and the object to be processed is _O2 plasma treatment;

NH ₃ plasma treatment in which a gas containing at least nitrogen and hydrogen is plasmaized, and an object to be treated after O ₂ plasma treatment is treated with the generated NH ₃ plasma.

In the above-mentioned post-treatment method, the treatment step using the above-mentioned corrosive gas, the above-mentioned O ₂ plasma treatment, and the above-mentioned NH ₃ plasma treatment may all be performed in the same chamber. At this time, the cleaning of the chamber and the modification of the deposits on the surface of the object to be treated are realized through the general-purpose treatment performed in a single chamber.

In addition, the above-mentioned _O2 plasma treatment and _NH3 plasma treatment can also be performed in different chambers. At this time, by moving the object to be processed into another chamber, the influence of the corrosive gas can be blocked. As a result, the modification efficiency of deposits on the surface of the object to be treated during NH ₃ plasma treatment can be improved, and the transfer of corrosive gas to the conveying system can also be reliably prevented.

In the above-mentioned aftertreatment method, when the corrosive gas is a gas containing at least halogen, and the above-mentioned gas containing at least nitrogen and hydrogen is ammonia gas, or a mixed gas of nitrogen gas and hydrogen gas, in the above-mentioned _NH3 plasma treatment, the object to be treated The silicon halide attached to it is converted into ammonium halide and stabilized, so it is possible to prevent the generation of halogen in the conveying system.

In the post-processing method, it is preferable to include a cleaning treatment in which wet cleaning is performed on the object to be processed after the above-mentioned NH ₃ plasma treatment. At this time, the ammonium halide can be easily removed by washing.

In a preferred embodiment of the above-mentioned post-processing method, the processing step using a corrosive gas is an etching process on a silicon substrate. In this case, corrosion protection of the chamber and the handling system can be achieved while performing highly efficient etching using corrosive gas.

The plasma processing method and the post-processing method of the present invention can prevent corrosion caused by halogens in the processing chamber and the transfer system.

Description of drawings

FIG. 1 is a schematic diagram illustrating a state of a wafer surface after a first plasma treatment.

Fig. 2 illustrates a schematic view of the state of the wafer surface at the time of the second plasma treatment.

FIG. 3 is a schematic diagram illustrating the state of the wafer surface after the third plasma treatment.

Fig. 4 shows a schematic configuration diagram of a plasma processing apparatus suitable for carrying out the method of the present invention.

Fig. 5 shows a cross-sectional structural diagram of a processing unit.

Fig. 6 shows a schematic configuration diagram of another plasma processing apparatus suitable for carrying out the method of the present invention.

Symbol Description

1 plasma processing device; 2 processing unit; 3 processing unit; 82, 83 etching processing unit; 84, 85NH ₃ plasma processing unit; 100 plasma processing device; wafer.

Detailed ways

In the present invention, examples of the object to be processed include substrates such as semiconductor wafers.

The "gas containing at least halogen" used in the plasma processing method of the present invention is a gas containing a halogen element such as chlorine or bromine as a constituent, and specific examples thereof include hydrogen bromide gas, hydrogen chloride gas, chlorine gas, and the like. Therefore, as the first plasma treatment, for example, a plasma etching treatment using a halogen gas is mentioned.

In addition, as the "oxygen-containing gas", for example, O ₂ gas, a mixed gas of O ₂ gas and an inert gas such as a rare gas can be used. Therefore, as the second plasma treatment, for example, O ₂ plasma treatment by O ₂ gas plasma can be mentioned. In this second plasma treatment, remove the halogen gas components ( _Cl2 , _HBr , etc.) Replacement of the gas environment, removal of deposits such as SiCl ₄ and SiBr ₄ adhering to the chamber wall.

In the plasma processing method of the present invention, as "the gas containing at least nitrogen and hydrogen", for example, NH ₃ gas, a mixed gas of N ₂ and H ₂ , etc. can be used. Therefore, as the third plasma treatment, for example, NH ₃ plasma treatment by NH ₃ gas plasma or the like can be mentioned.

In the third plasma treatment, silicon halides such as SiCl ₄ and SiBr ₄ (SiX ₄ , where X represents halogen, the same applies hereinafter) deposited on a target object such as a semiconductor wafer due to the first plasma treatment, and the Cl ₂ , HBr, etc. physically adsorbed on the object to be treated are converted into ammonia halides such as NH ₄ Cl, NH ₄ Br (NH ₄ X, where X is the same as above, and the same below). Ammonium halide does not volatilize even in an open air state, so it can suppress the generation of halogen gas in the conveying system and prevent corrosion of the conveying path.

The ammonium halide produced by the third plasma treatment is a water-soluble substance, so it can be easily removed by the wet cleaning process. The cleaning conditions may be the same as those in a normal wet cleaning process.

In the present invention, the first plasma treatment to the third plasma treatment can be carried out in the same chamber. At this time, the halogen gas environment in the chamber generated by the first plasma treatment is replaced and removed by the second plasma treatment. The deposits in the chamber and the halogen molecules adsorbed on the object to be processed are removed, and the deposits can be modified (converted into ammonia halide) by the third plasma treatment.

Alternatively, the first plasma treatment and the second plasma treatment may be performed in the same chamber, and the object to be treated may be moved to another chamber to perform the third plasma treatment. At this time, the second plasma treatment replaces the initial halogen gas environment in the chamber generated by the first plasma treatment, removes deposits in the chamber, and removes halogen gas molecules adsorbed on the object to be processed. In addition, the third plasma treatment modifies only the reaction products deposited on the surface of the object to be treated in other chambers. At this time, the movement of the object to be processed between the chambers is preferably performed under vacuum conditions.

The conditions of the plasma treatment are not particularly limited. For example, the first plasma treatment may be performed for 50 seconds, and the second plasma treatment and the third plasma treatment as post-processing may be performed for about 5 seconds each.

In addition, other treatments may be added in addition to the above first to third plasma treatments, if necessary. For example, when the first plasma treatment is an etching step of a silicon wafer, it is preferable to add a treatment for removing a natural oxide film on the surface of the silicon wafer as a pretreatment.

The post-processing method of the present invention is a post-processing method performed after a treatment step using a corrosive gas. In this post-processing method, the following steps are performed on the object to be processed and the chamber after the corrosive gas treatment: Plasma the gas containing oxygen, and perform O ₂ plasma treatment (cleaning treatment) with the generated O ₂ plasma ; NH ₃ plasma treatment (modification treatment) in which a gas containing at least nitrogen and hydrogen is plasmatized, and the object to be treated is treated with the generated NH ₃ plasma. Here, examples of the treatment using a corrosive gas include plasma etching treatment using a halogen-containing gas, which is the same as the first plasma treatment in the plasma treatment method described above. In addition, the O ₂ plasma treatment can be performed in the same manner as the second plasma treatment in the above plasma treatment method, and the NH ₃ plasma treatment can be performed in the same manner as the third plasma treatment.

Next, the operation of the present invention will be described with reference to FIGS. 1 to 3 . 1 to 3 are schematic diagrams illustrating the principle of the plasma processing method of the present invention. 1 is a diagram showing a cross-sectional state near a substrate surface after a first plasma treatment is performed using a corrosive gas on a semiconductor wafer (hereinafter referred to simply as "wafer") W as an object to be processed. Through the first plasma treatment, adhering substances 201 of halogens such as Cl ₂ or HBr are physically adsorbed on the substrate surface, and deposits 202 made of SiX ₄ (X represents halogens such as chlorine and bromine) and the like are also adsorbed.

If the second plasma treatment is performed after the first plasma treatment, the adsorbate 201 is removed by the _O2 plasma by spraying. As a result, as shown in FIG. 2 , most of the adsorbed substances 201 are removed, but not completely, and the deposits 202 remain on the wafer W almost as they are. In addition, in the inner wall of the chamber after the first plasma treatment, the adsorbate 201 is removed by the same mechanism as in FIG. 2 , and at the same time, the gas atmosphere in the chamber is replaced to prevent corrosion.

Next, the wafer W is subjected to the third plasma treatment. By the action of the NH ₃ plasma, as shown in FIG. 3 , the SiX ₄ in the deposit 202 is changed into ammonium halide (NH ₄ X), and converted into the modified product 203 . In addition, the remaining halogen adsorbed substance 201 is also fixed by the modified substance 203 . The modified product 203 does not generate halogen gas even when exposed to open air in a transport system such as a wafer cassette, and thus can prevent corrosion of the transport system. In addition, NH ₄ X generated by the third plasma treatment is a water-soluble substance and can be easily removed by wet cleaning.

Hereinafter, embodiments of the present invention will be described with reference to a schematic diagram of a specific configuration of a plasma processing apparatus. Fig. 4 is a schematic horizontal sectional view showing a plasma processing apparatus suitable for carrying out the method of the present invention. This plasma processing apparatus performs etching processing and post-processing on a wafer W as an object to be processed under a predetermined vacuum.

This plasma processing apparatus 1 is provided with two processing units 2 and 3, and each processing unit 2 and 3 is configured so as to be able to implement a general-purpose process in which etching and post-processing of each independent wafer W are performed consistently. Each processing unit 2, 3 is respectively connected to the sample load lock chamber 6, 7 through a gate valve (gate valve) G1. On the opposite side of these sample loading and unloading chambers 6, 7 to the processing units 2, 3, a wafer loading and unloading chamber 8 is provided, and on the side of the wafer loading and unloading chamber 8 opposite to the sample loading and unloading chambers 6, 7, a mounting can be provided. Three connection ports 9 , 10 , 11 of wafer cassettes (FOUP (front-opening unified pods)) F accommodating wafer W.

The two processing units 2, 3 communicate with the sample inlet and outlet chambers 6, 7 by opening the respective gate valves G1, and are disconnected from the sample inlet and outlet chambers 6, 7 by closing the respective gate valves G1. In addition, gate valves G2 are also provided at the parts of the sample loading and unloading chambers 6 and 7 that are connected to the wafer loading and unloading chamber 8. The sample loading and unloading chambers 6 and 7 communicate with the wafer loading and unloading chamber 8 by opening the gate valve G2, and the sample loading and unloading chambers communicate with the wafer loading and unloading chamber 8 by closing the gate valves. G2 is disconnected from the wafer loading and unloading chamber 8 .

In the sample loading/unloading chambers 6, 7, between the processing units 2, 3 and the wafer loading/unloading chamber 8, wafer transfer devices 4, 5 for loading and unloading wafers W to be processed are provided, respectively.

A high-efficiency particulate air filter (HEPA filter) (not shown) is provided on the top of the wafer loading and unloading chamber 8, and the clean air passing through the HEPA filter is supplied into the wafer loading and unloading chamber 8 while flowing downward, so that The loading and unloading of the wafer W is carried out in an atmosphere of clean air at atmospheric pressure. On the three connection ports 9, 10, 11 for installing the wafer cassette F in the wafer loading and unloading chamber 8, baffles (shutters) (not shown) are respectively provided, and the wafer cassette F containing the wafer W or an empty wafer The round box F is directly installed on these contact ports 9, 10, 11. After installation, the baffle plate falls off to prevent outside air from entering, and communicates with the loading and unloading chamber 8. In addition, on one side of the wafer loading and unloading chamber 8, an alignment chamber (alignment chamber) 14 is provided, where alignment of the wafer W is performed. On the other side of the wafer loading and unloading chamber 8, a cleaning chamber 15 is provided, where wet cleaning of the wafer W after the plasma treatment is performed.

In the wafer loading/unloading chamber 8 , a wafer transfer device 16 for loading and unloading wafers W into and out of the cassette F and loading and unloading wafers W into and out of the sample loading/unloading chambers 6 and 7 is provided. The wafer transfer device 16 has a multi-joint arm structure and can move on rails 18 along the direction in which the wafer cassettes F are arranged. A pick 17 is placed on the front end of the wafer W for transfer. Control of the entire system, such as the operation of the wafer transfer device 16 , is performed by the control unit 19 .

In such a plasma processing apparatus 1, first, under the atmosphere of clean air maintained at atmospheric pressure, a wafer W is taken out from any one of the wafer cassettes F by the wafer transfer device 16 in the wafer transfer chamber 8 and transferred into the alignment chamber. In the chamber 14, the position of the wafer W is aligned. Next, the wafer W is loaded into any one of the sample loading and unloading chambers 6 and 7, and after the sample loading and unloading chambers 6 and 7 are evacuated, the wafer W in the sample loading and unloading chamber is loaded into the processing unit by the wafer transfer device 4 or 5. In processing unit 2 or 3, etching is performed and post-processing continues in the same processing unit. Thereafter, the wafer is carried into any one of the sample entry and exit chambers 6, 7 by any one of the wafer transfer devices 4, 5, and after the pressure returns to atmospheric pressure, the sample is taken out by the wafer transfer device 16 in the wafer transfer chamber 8. The wafer W is inserted into the cleaning chamber 15 to perform wet cleaning processing. In the cleaning chamber 15, the wafer W is wet-cleaned with a cleaning solution such as water to remove modified NH ₄ X. The cleaned wafer W passes through the wafer transfer device 16 again, and is accommodated in any one of the cassettes F. The above operations are performed on one lot of wafers W to complete the process for one lot.

Next, the processing unit 2 will be described in detail with reference to FIG. 5 . FIG. 5 is a schematic cross-sectional view of the processing unit 2 . In this processing unit 2, as described above, the dry etching treatment as the "first plasma treatment", the subsequent "post-treatment", and the _O2 treatment as the "second plasma treatment" can be performed in the same chamber. Plasma treatment and _NH3 plasma treatment as "third plasma treatment".

In addition, the processing unit 2 is configured as a capacitively coupled parallel plate plasma etching device in which electrode plates are relatively parallel up and down, and one of them is connected to a power source for plasma formation.

The processing unit 2 has, for example, a cylindrical chamber 22 as a processing container formed of aluminum whose surface is thermally sprayed with ceramics, and the chamber 22 is grounded for protection. In the chamber 22 , a wafer W made of, for example, silicon on which a predetermined film is formed is loaded, and a susceptor 23 serving as a lower electrode is provided in a state supported by a supporting member 24 . The support member 24 is supported by a support table 26 of an elevating device (not shown) via an insulating plate 25 made of ceramics or the like, and the base 23 can be elevated by the elevating mechanism. The air part in the center of the lower part of the support table 26 is covered with bellows 27 , and the inside of the chamber 22 is separated from the air part.

A refrigeration chamber 28 is provided inside the support member 24 . In this cooling chamber 28, for example, a refrigerant such as perfluoropolyether (Galden fluids) is introduced and circulated through a refrigerant introduction pipe 28a, and its cold and heat are transferred to the above-mentioned wafer W through the susceptor 23, whereby the wafer W is The processing surface is controlled at the desired temperature. In addition, even if the chamber 22 is kept vacuum, in order to make the coolant circulating in the cooling chamber 28 effectively cool the wafer W, a gas passage 29 for supplying a heat transfer medium such as He gas is provided on the back surface of the wafer W to be processed. This heat transfer medium can effectively transfer the cold and heat of the susceptor 23 to the wafer W, and can precisely control the temperature of the wafer W.

The upper central part of the base 23 is shaped into a convex disc shape, on which an electrostatic clamp 31 is arranged to make the electrodes 32 interposed between insulating materials, and a DC voltage is applied by a DC power supply 33 connected to the electrodes 32, for example, by The wafer W is electrostatically attracted by Coulomb force. A ring-shaped focus ring 35 capable of improving etching uniformity is disposed on an edge portion around the upper end of the susceptor 23 so as to surround the wafer W loaded on the electrostatic chuck 31 .

Above the above-mentioned base 23, a shower head (shower head) 41 functioning as an upper electrode is arranged relatively parallel to the base 23. The shower head 41 is supported on the upper part of the chamber 22 by sandwiching the insulating material 42 , and a plurality of spray holes 43 are provided on the surface 44 facing the base 23 . In addition, there is, for example, a distance of about 30 to 90 mm between the surface of the wafer W and the shower head 41, and this distance can be adjusted by the above-mentioned elevating mechanism.

A gas inlet 46 is provided at the center of the shower head 41 , and a gas supply pipe 47 is connected to the gas inlet 46 , and the gas supply pipe 47 is connected to a gas supply system for supplying etching gas and cleaning gas through a valve 48 . The gas supply system includes a Cl ₂ gas supply source 50 , an NH ₃ gas supply source 51 , and an O ₂ gas supply source 52 , and mass flow controllers 53 and valves 54 are provided on the pipes of these gas supply sources, respectively.

Cl ₂ gas as etching gas, NH ₃ gas as post-processing gas, and O ₂ gas reach the inner space of shower head 41 through supply pipe 47 and gas inlet 46 from the respective gas supply sources of the gas supply system. , is ejected from the gas ejection hole 43.

An exhaust pipe 55 is connected near the bottom of the side wall of the chamber 22 , and an exhaust device 56 is connected to the exhaust pipe 55 . The exhaust device 56 is provided with a vacuum pump such as a turbomolecular pump, thereby being configured to be able to evacuate the inside of the chamber 22 to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. In addition, on the side wall of the chamber 22, there are provided a loading and unloading port 57 for the wafer W and a gate valve G1 for opening and closing the loading and unloading port 57. When the gate valve G1 is opened, the wafer W passes through the loading and unloading port 57 and is connected to the wafer W. Adjacent sample entry/exit chambers 6 (see FIG. 4 ) are conveyed.

A high-frequency power supply 60 is connected to the shower head 41 functioning as an upper electrode, and an adapter 61 is provided on its power supply line. The high-frequency power supply 60 supplies high-frequency power of, for example, a frequency of 60 MHz to the upper electrode shower head 41 to form a high-frequency electric field for plasma formation between the upper electrode shower head 41 and the lower electrode susceptor 23 . In addition, a low-pass filter (LPF) 62 is connected to the shower head 41 .

A high-frequency power source 70 is connected to the base 23 as a lower electrode, and an adapter 71 is connected to the power supply line thereof. The high-frequency power supply 70 supplies, for example, high-frequency power at a frequency of 13.56 MHz to the lower electrode susceptor 23 to introduce ions in the plasma to the wafer W, thereby achieving highly anisotropic etching. In addition, a high-pass filter (HPF) 36 is connected to the base 23 .

When using the device of FIG. 5 for etching, at first, the gate valve G1 is opened, and after the wafer W is carried into the chamber 22 and loaded on the base 23, the gate valve G1 is closed, the base 23 is raised, and the wafer W on the base 23 is adjusted. The distance between the W surface and the shower head 41 is about 30-90 mm. The vacuum pump of the exhaust device 56 exhausts the chamber 22 through the exhaust pipe 55. After decompression in the chamber 22, the DC power supply 33 supplies The electrodes 32 inside the electrostatic chuck 31 apply a DC voltage.

Next, Cl ₂ gas as an etching gas is introduced into the chamber 22 from the Cl ₂ gas supply source 50 . In addition, a high-frequency power of, for example, 60 MHz is applied from the high-frequency power source 60 to the shower head 41, thereby generating a high-frequency electric field between the upper electrode shower head 41 and the lower electrode susceptor 23, and turning _the Cl gas into plasma. . The wafer W is electrostatically attracted to the electrostatic chuck 31 by generating plasma.

The wafer W is etched using the thus obtained plasma of the etching gas. At this time, a high-frequency electrode of a predetermined frequency is applied to the lower electrode susceptor 23 from the high-frequency power supply 70 to guide ions in the plasma to the susceptor 23 side.

In the processing unit 2, when performing cleaning treatment as a post-treatment with O ₂ gas or reforming treatment with NH ₃ gas, O ₂ gas and NH ₃ gas are respectively used as an etching gas instead of Cl ₂ gas. Same plasma treatment.

FIG. 6 is a schematic configuration diagram showing a multi-chamber plasma processing apparatus. As shown in FIG. 6 , this plasma processing apparatus 100 includes etching processing units 82 and 83 for performing etching processing and O ₂ plasma processing on a wafer W, and NH ₃ plasma processing units 84 and 85 for performing ammonia plasma processing. In addition, the plasma processing apparatus 100 has a hexagonal wafer transfer chamber 81, and connection ports 81a, 81b, 81c, and 81d for connecting predetermined processing units are provided on four sides thereof. The etching processing unit 82 is connected to the connection port 81a, the etching processing unit 83 is connected to the connection port 81b, the _NH3 plasma processing unit 84 is connected to the connection port 81c, and the _NH3 plasma processing unit 85 is connected to the connection port 81d.

In addition, on the other two sides of the wafer transfer chamber 81, sample loading and unloading chambers 86 and 87 are respectively provided. One side of these sample loading and unloading chambers 86, 87 opposite to the wafer transfer chamber 81 is provided with a wafer loading and unloading chamber 88, and the side of the wafer loading and unloading chamber 88 opposite to the sample loading and unloading chambers 86, 87 is provided with a Three connection ports 89, 90, 91 of a wafer W's FOUP F.

Etching processing units 82, 83, _NH3 plasma processing units 84, 85, and sample entry and exit chambers 86, 87 are connected through gate valves G3, G4, and communicate with wafer transfer chamber 81 by opening these respective gate valves G3, G4, and pass Close the respective gate valves G3, G4 to disconnect the wafer transfer chamber 81. In addition, a gate valve G5 is also provided at the part of the sample loading and unloading chambers 86 and 87 connected to the wafer loading and unloading chamber 88. The sample loading and unloading chambers 86 and 87 communicate with the wafer loading and unloading chamber 88 by opening the gate valve G5, and the wafer loading and unloading chamber 88 is connected by closing the gate valve G5. G5 is disconnected from the wafer loading and unloading chamber 88 .

In the wafer transfer chamber 81 , corresponding to the etching processing units 82 and 83 , the NH ₃ plasma processing units 84 and 85 , and the sample loading and unloading chambers 86 and 87 , a wafer transfer device 92 for loading and unloading the target wafer W is provided. This wafer transfer device 92 is installed at about the center of the wafer transfer chamber 81, and two blades 94a, 94b for holding the wafer W are provided at the front end of the rotating and telescoping portion 93 capable of rotating and expanding. It is mounted on the rotation-extensible part 93 so as to face in the opposite direction. In addition, the inside of the wafer transfer chamber 81 is maintained at a predetermined degree of vacuum.

The top of the wafer loading and unloading chamber 88 is provided with a high-efficiency particulate air filter (HEPA filter) (not shown), and the clean air passing through the HEPA filter is supplied into the wafer loading and unloading chamber 88 in a downward flow manner. The loading and unloading of the wafer W is carried out in an atmosphere of clean air at atmospheric pressure. The wafer box F of the wafer loading and unloading chamber 88 is installed with three connection ports 89, 90, 91, respectively provided with baffles (not shown), and the wafer box F containing the wafer W or the empty wafer box F are directly connected to the wafer box F. Installed on these connection ports 89 , 90 , 91 , after installation, the baffles can be detached to prevent the intrusion of external air, and at the same time communicate with the wafer loading and unloading chamber 88 . In addition, an alignment chamber 94 is provided on one side of the wafer loading/unloading chamber 88, and alignment of the wafer W is performed here. On the other side of the wafer loading/unloading chamber 88, a cleaning chamber 95 is provided, where wafers W after plasma processing are cleaned.

The wafer loading and unloading chamber 88 is provided with a transport device 96 for loading and unloading wafers W into and out of the cassette F and loading and unloading wafers W into and out of the sample loading and unloading chambers 86 and 87 . The transfer device 96 has a multi-joint arm structure and can move on a rail 98 along the arrangement direction of the wafer cassettes F, and the wafer W is loaded on the front picker 97 for transfer. Control of the entire system, such as the operation of the wafer transfer devices 92 and 96 , is performed by the control unit 99 .

In this plasma processing apparatus 100, first, in a gas environment of clean air maintaining atmospheric pressure, a wafer W is taken out from any one of the wafer cassettes F by the wafer transfer device 96 in the crystal transfer chamber 88 and carried into alignment. In the chamber 94, calibration of the wafer position is performed. Next, the wafer W is carried into either of the sample loading and unloading chambers 86 and 87, and after the sample loading and unloading chamber is evacuated, the wafer W in the sample loading and unloading chamber is taken out by the wafer transfer device 92 in the wafer transfer chamber 81.

Next, the taken-out wafer W is loaded into the etching processing unit 82 or 83 for etching processing, followed by O ₂ plasma processing. Thereafter, the wafer W is taken out from the etching processing unit 82 or 83 by the wafer transfer device 92, loaded into the NH ₃ plasma processing unit 84 or 85, and subjected to NH ₃ plasma processing. That is, in this plasma processing apparatus 100, etching processing and _O2 plasma processing are performed in the etching processing unit 82 or 83, and then, at the original position where the vacuum state is not broken, in the _NH3 plasma processing unit 84 or 85 _NH3 plasma treatment was carried out in . Thereafter, the wafer W is carried into either of the sample loading and unloading chambers 86 and 87 by the wafer loading and unloading device 92, and after returning to atmospheric pressure therein, the wafer W in the sample loading and unloading chamber is taken out by the wafer loading and unloading device 96 in the wafer loading and unloading chamber 88. , into the cleaning chamber 95. In the cleaning chamber 95 , the wafer W is wet-cleaned with a cleaning solution such as water to remove modified NH ₄ X . After cleaning, the wafer W is taken out by the wafer transfer device 96 and accommodated in any one of the cassettes F. The above operations are performed for one set of wafers W, and the processing of one set is completed.

The structures of the etching processing units 82 and 83 and the NH ₃ plasma processing units 84 and 85 in the plasma processing apparatus 100 are basically the same as those in FIG. 5 except for the difference in the gas supply system. That is, the etching processing units 82 and 83 are equipped with a supply system of Cl gas as _an etching gas and a supply system of _O gas as a cleaning gas, and _the NH plasma processing units 84 and 85 are equipped with _NH gas as a reforming gas. supply system. In addition, the etching treatment, O ₂ plasma treatment, and NH ₃ plasma treatment in the plasma processing apparatus 100 can be implemented according to the processing in the processing unit 2 shown in FIG. 5 .

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 and Comparative Examples 1-3

While performing the silicon wafer etching process using corrosive gases HBr and _Cl2 as etching gases, post-processing with _O2 plasma and _NH3 plasma was carried out under varying conditions depending on the type of test, and measurements were made on the wafer and on the transport path (wafer The amount of halogen in the box). In addition, the etching process and post-processing were performed using the apparatus of the same structure as FIG. 5.

The types of tests are shown in Table 1, and the case of not performing post-treatment (Comparative Example 1), the case of only _O2 plasma treatment (Comparative Example 2), and the case of only _NH3 plasma treatment (Comparative Example 3), the case of performing _NH3 plasma treatment after _O2 plasma treatment (Example 1). As the conditions of the plasma treatment, the etching treatment was performed for 50 seconds, and the post-treatment _O2 plasma treatment and _NH3 plasma treatment were performed for 5 seconds each.

The results are shown in Table 1.

Table 1 Comparative example 1 Comparative example 2 Comparative example 3 Example 1 on chip Cl(μg/chip) 14.9 17.8 4266.7 504.7 Br(μg/chip) 13.3 2.0 746.8 2.6 In the cassette Cl(ppm/cassette) 1.5 2.2 0.0 0.2

As shown in Table 1, in Comparative Example 1 without post-treatment and Comparative Example 2 in which only _O2 plasma treatment was performed, the chlorine content in the wafer cassette was high. This is considered to be because chlorine volatilizes from the deposits remaining on the wafer in the open state of the atmosphere, so there is a possibility of corrosion of the transfer system.

In Comparative Example 3 where only _NH3 plasma treatment was carried out, no chlorine was detected in the wafer box, but the content of chlorine and bromine on the wafer was high, thus it is considered that it was modified into ammonium chloride and ammonium bromide. status accumulation. In addition, although not shown in Table 1, it was confirmed that a large amount of deposits remained in the chamber.

On the other hand, in Example 1 in which _O2 plasma treatment was followed by _NH3 plasma treatment, only a trace amount of chlorine (0.2 ppm/cassette) was detected in the pod, showing the method of the present invention It can effectively prevent the corrosion of the handling system. In addition, compared with Comparative Example 3, the amount of halogen on the wafer was significantly reduced and could be completely removed by wet cleaning. In addition, there is almost no accumulation left in the chamber, which can effectively prevent the corrosion of the chamber.

Example 2 and Comparative Example 4

Using corrosive gas HBr and _Cl as etching gas as etching gas While carrying out the silicon wafer etching step, as post-processing, implement O ₂ plasma treatment and NH ₃ plasma treatment, then, carry out wet cleaning to the silicon wafer after processing ( Example 2).

The wet cleaning was carried out for 60 seconds using dilute hydrofluoric acid (DHF) of 5% hydrogen fluoride aqueous solution (HF+H ₂ O) as a chemical solution. In addition, for comparison, when only O ₂ plasma treatment was performed as a post-treatment, cleaning was performed with dilute hydrofluoric acid (DHF) under the same conditions (Comparative Example 4).

An apparatus having the same structure as that shown in FIG. 5 was used for the etching step and post-processing. The plasma treatment time was 50 seconds for the etching treatment, and 5 seconds for the post-treatment O ₂ plasma treatment and NH ₃ plasma treatment. In addition, the time of Comparative Example 4 in which only O ₂ plasma treatment was performed as a post-treatment was 5 seconds + 5 seconds, a total of 10 seconds.

Determination of halogen content on silicon wafers before and after wet cleaning. The amount of halogen on the silicon wafer was obtained by immersing the silicon wafer in 100 mL of water to dissolve the halogen, and measuring the solution by ion chromatography. The results are shown in Table 2.

Table 2 before washing after washing Comparative Example 4 _O2 plasma only Embodiment 2O ₂ plasma+NH ₃ plasma Comparative Example 4 _O2 plasma only Embodiment 2O ₂ plasma+NH ₃ plasma Cl(μg/chip) 18.3 182.2 0.10 0.07 Br(μg/chip) 2.9 18.3 0.06 0.02

As shown in Table 2, in Example 2 in which O ₂ plasma treatment and NH ₃ plasma treatment were performed as post-treatments, a large amount of chlorine and bromine remained on the silicon wafer before wet cleaning. These halogens are considered to be contained in the modified product. However, the content of chlorine and bromine was significantly reduced by wet cleaning, and decreased to the same level as Comparative Example 4 in which only _O2 plasma treatment was performed. From the results, it was confirmed that the halogen-containing modification produced on the wafer by the NH ₃ plasma treatment can be easily removed by wet cleaning.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes are possible. For example, in the above-mentioned embodiment, the plasma etching treatment was exemplified as the first plasma treatment and the treatment using a corrosive gas, but the present invention is not limited thereto, and the same applies to steps using a corrosive gas such as a halogen.

In addition, in the above-mentioned embodiment, the parallel plate type plasma etching apparatus which etches by applying high-frequency power to the upper and lower electrodes was exemplified, but it is not limited thereto. A type of apparatus using high-frequency power, or a magnetron RIE plasma etching apparatus using a permanent magnet. In addition, it is not limited to a capacitively coupled plasma device, and various other types of plasma etching devices such as an inductively coupled type may be used.

Industrial availability

The method of the present invention can be utilized in a process using a corrosive gas in a process such as a manufacturing process of a semiconductor device.

Claims (14)

1. A plasma treatment method is a plasma treatment method for carrying out plasma treatment to an object to be processed in a chamber, characterized in that, comprising: a first plasma treatment in which a gas containing at least halogen is plasmatized, and the object to be treated is treated with the generated first plasma; After the first plasma treatment, supply a gas containing oxygen into the chamber to generate a second plasma, and perform the second plasma treatment for treating the chamber and the object to be processed; A third plasma treatment in which a gas containing at least nitrogen and hydrogen is plasmatized, and the object to be treated after the second plasma treatment is treated with the generated third plasma. 2. The plasma treatment method according to claim 1, characterized in that: The first plasma treatment to the third plasma treatment are all performed in the same chamber. 3. The plasma treatment method as claimed in claim 1, characterized in that: The first plasma treatment and the second plasma treatment are performed in the same chamber, and the third plasma treatment is performed in another chamber. 4. The plasma treatment method according to any one of claims 1 to 3, characterized in that: The halogen is chlorine or bromine, and the gas containing at least nitrogen and hydrogen is ammonia, or a mixed gas of nitrogen and hydrogen. 5. The plasma treatment method as claimed in claim 4, characterized in that: In the third plasma treatment, the silicon halide adhering to the object to be treated is converted into ammonium halide. 6. The plasma processing method as claimed in claim 5, comprising: A cleaning treatment of wet cleaning is performed on the processed object after the third plasma treatment. 7. The plasma treatment method according to any one of claims 1 to 6, characterized in that: The first plasma treatment is a plasma etching treatment of the silicon substrate. 8. A post-processing method, for the object to be processed in the chamber, the post-processing method implemented after the treatment process using corrosive gas, it is characterized in that, comprising: Supplying oxygen-containing gas into the chamber to generate _O2 plasma to treat the chamber and the object to be treated by _O2 plasma treatment; NH ₃ plasma treatment in which a gas containing at least nitrogen and hydrogen is plasmaized, and an object to be treated after O ₂ plasma treatment is treated with the generated NH ₃ plasma. 9. post-processing method as claimed in claim 8, is characterized in that: In the treatment process using the corrosive gas, the O ₂ plasma treatment and the NH ₃ plasma treatment are all performed in the same chamber. 10. post-processing method as claimed in claim 8, is characterized in that: The O ₂ plasma treatment and NH ₃ plasma treatment were performed in different chambers. 11. The post-processing method according to any one of claims 8 to 10, characterized in that: The corrosive gas is a gas containing at least halogen, and the gas containing at least nitrogen and hydrogen is ammonia, or a mixed gas of nitrogen and hydrogen. 12. post-processing method as claimed in claim 11, is characterized in that: In the NH ₃ plasma treatment, the silicon halide adhering to the object to be treated is converted into ammonium halide. 13. post-processing method as claimed in claim 12, is characterized in that, comprises: The object to be processed after the _NH3 plasma treatment is subjected to a cleaning treatment of wet cleaning. 14. The post-processing method according to any one of claims 8 to 13, characterized in that: The processing step using the corrosive gas is etching processing of a silicon substrate.

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