KR20110047971A - Method of manufacturing semiconductor device and substrate processing apparatus - Google Patents

Abstract

PURPOSE: A method of manufacturing a semiconductor and an apparatus for processing a substrate are provided to implement an a-Si film having more smooth surface by improving the surface illumination of the a-Si film. CONSTITUTION: In a method of manufacturing a semiconductor and an apparatus for processing a substrate, the bottom opening of an outer tube(1) and an inner tube(2) is tightly sealed up by a seal cap of stainless. A gas supply pipe includes a plurality of nozzles of SiH4/N2 supplying monosilane and a nitrogen gas. The gas supply line supplies a processing gas to an inner tube. A space of a barrel shape is interposed between the outer tube and the inner tube is connected to a discharge pipe. The discharge pipe is connected to a mechanical booster pump and a dry pump.

Description

TECHNICAL FIELD OF THE INVENTION A manufacturing method and substrate processing apparatus for a semiconductor device {METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE AND SUBSTRATE PROCESSING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device and a substrate processing apparatus, and more particularly, to a method for manufacturing a semiconductor device and a substrate processing apparatus for forming an amorphous silicon film.

In the process of manufacturing semiconductor devices, such as IC and LSI, forming a thin film on a board | substrate is performed by the pressure reduction CVD method (chemical vapor deposition method).

In the case of depositing an amorphous silicon film (hereinafter referred to as an a-Si film) on the insulating film, SiH _{4 is} used as the source gas at a temperature range of 480 ° C to 550 ° C or lower. [Monosilane] gas is used. With the miniaturization of semiconductors, there is a demand for improvement of surface roughness of a-Si films, that is, films on smoother surfaces. Patent Literature 1 discloses a technique for improving the surface roughness of a poly-SiGe film.

FIG. 5 shows the transition of the SiH ₄ gas flow rate and the furnace pressure in the conventional film forming sequence. The purpose of the prepurge event (hereinafter referred to as a prepurge process), which is an initial stage of film formation, is to stabilize the SiH ₄ gas at a specified flow rate. The SiH ₄ gas flow rate shown in this example is raised from 0 slm to about 0.8 slm over 15 seconds, and the pressure in the furnace is raised to about 15 Pa over 15 seconds. Process conditions such as pressure and gas flow rate in a depo event (hereinafter referred to as a depot process) which are steps after the initial stage of film formation are determined by the device to be created, and are basically fixed conditions. The SiH ₄ gas flow rate shown in this example is kept constant at 0.8 slm, and the pressure in the furnace is raised to 40 Pa over about 15 seconds from about 15 Pa. In the result of the film formation by the conventional film formation sequence, the surface state result of the a-Si film is shown in the sequence (a) of FIG. 4, the a-Si surface level is 6.8, and the particle is the upper limit of detection ( Since it is over, the improvement of surface roughness is calculated | required.

Patent Document 1. Japanese Patent Laid-Open Publication No. 2009-147388

The problem to be solved by the present invention is to provide a semiconductor device manufacturing method and a substrate processing apparatus which can solve the above-mentioned problems of the prior art and can improve the surface roughness of an a-Si film.

The invention of claim 1, on a substrate a-Si to the deposition film, the reaction pre-purging in order to keep the pressure in the chamber at a high pressure for applying the pressure control step of controlling the pressure, SiH ₄ gas and N ₂ gas (film formation initial ) step, a depot (semiconductor device according includes the step) a step later than the film formation initial step, and the pre-purging process, the flow rate of SiH ₄ gas, characterized in that the less the flow rate of SiH ₄ gas in the depot process It is a manufacturing method.

According to a second aspect of the invention, the pressure (first pressure) of the prepurge process is made higher than the pressure (second pressure) of the depot (process after the film forming initial process) process.

When the first pressure is set to 100 Pa and the second pressure is set to 40 Pa, the surface roughness of the a-Si film can be further improved.

When the upper limit of a 1st pressure exceeds 150 Pa, since it exceeds the apparatus limit pressure, it is unpreferable. Therefore, the 1st pressure can improve the surface roughness of a-Si, and the range of 80-150Pa which is in apparatus limit pressure is preferable.

The second pressure of 40 Pa is preferably lower in pressure in terms of in-plane film thickness uniformity, but higher in pressure in terms of depot rate (film formation rate). As a compromise between them, the second pressure was 40 Pa.

According to a third aspect of the present invention, in the process of forming an a-Si film on a substrate, the pressure of the prepurge (film formation initial) process is higher than the pressure of the depot process after the prepurge process, for example, 100 Pa, and the flow rate of SIH ₄ is increased. Is a step of gradually increasing the flow rate to a prescribed flow rate.

The surface roughness of the a-Si film can be improved by setting the pressure at which the a-Si film is to be formed to be a predetermined pressure, for example, the pressure at the initial stage of the deposition to be 100 Pa, and the pressure at a later stage than the initial stage to form to 40 Pa.

According to the present invention, the surface roughness of the a-Si film can be improved and a smoother surface a-Si film can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is the inclination which shows the substrate processing apparatus by embodiment of this invention.
2 is a schematic view of a reactor structure of a vertical pressure reducing CVD apparatus according to an embodiment of the present invention.
It is a figure which shows the film-forming procedure by the reduced pressure CVD method by embodiment of this invention.
4 is a diagram showing an evaluation result of a sequence of the present invention and a conventional sequence.
FIG. 5 is a diagram showing a transition of SiH ₄ flow rate and pressure during film formation of a conventional a-Si film.
FIG. 6 is a diagram showing a transition of SiH ₄ flow rate and pressure during film formation of an a-Si film according to the first embodiment of the present invention.
Fig. 7 is a graph showing the transitions of the SiH ₄ flow rate and pressure during the film formation of the a-Si film according to the second embodiment of the present invention.

EMBODIMENT OF THE INVENTION Below, embodiment of the manufacturing method of the semiconductor device of this invention is described. First, with reference to FIG. 1, an example of the substrate processing apparatus for implementing the manufacturing method of the semiconductor device of this invention is demonstrated schematically.

On the front side inside the housing 101, a holding tool receiving member for carrying the cassette 100 as a substrate storage container between an external conveying device (not shown) is provided. The cassette stage 105 as a part is provided, The cassette elevator 115 as a lifting means is provided in the rear side of the said cassette stage 105, The conveyance means is provided in the said cassette elevator 115. A cassette transfer machine 114 is provided. On the rear side of the cassette elevator 115, a cassette shelf 109 as a mounting means of the cassette 100 is provided, and the cassette shelf 109 can traverse above the slide stage 122. Is installed. In addition, above the cassette shelf 109, a buffer cassette shelf 110 as a mounting means of the cassette 100 is provided. In addition, a clean unit 118 is provided on the rear side of the buffer cassette shelf 110 so as to allow clean air to flow inside the housing 101.

A processing furnace 202 is provided above the rear part of the housing 101, and a load lock as a hermetically sealed hermetic chamber below the processing furnace 202. The lock chamber 102 is connected by a gate valve 244 as a partition cover, and the front surface of the load lock chamber 102 faces the cassette shelf 109. The load lock door 123 as a boundary means is provided in this. In the load lock chamber 102, the boat elevator as the lifting means for lifting and lowering the boat 217 as the substrate holding means for holding the wafer 200 as the substrate in multiple stages in a horizontal position in the processing furnace 202 ( 121 is internally installed, and the boat elevator 121 is provided with a stainless steel seal cap 219 as a cover to vertically support the boat 217. A transfer elevator as a lifting means (not shown) is provided between the load lock chamber 102 and the cassette shelf 109, and a wafer transfer machine 112 as a transfer means is provided in the transfer elevator.

Hereinafter, a series of operations in the substrate processing apparatus will be described. The cassette 100 conveyed from an external conveying apparatus (not shown) is placed on the cassette stage 105, and the posture of the cassette 100 is changed by 90 ° in the cassette stage 105, and the cassette is It is conveyed to the said cassette shelf 109 or the buffer cassette shelf 110 by the cooperation of the elevating operation | movement of the elevator 115, the transverse movement, and the advancing / removing operation of the said cassette transfer machine 114. As shown in FIG.

The wafer 200 is transferred from the cassette shelf 109 to the boat 217 by the wafer transfer machine 112. In preparation for transferring the wafer 200, the boat 217 is lowered by the boat elevator 121, and the processing furnace 202 is closed by the gate valve 244. Further, purge gas such as nitrogen gas is introduced into the load lock chamber 102 from the purge nozzle 234. After the load lock chamber 102 is subjected to pressure back to atmospheric pressure, the load lock door 123 is opened.

The horizontal slide mechanism 122 moves the cassette shelf 109 horizontally, and positions the cassette 100 to be transferred to the wafer transfer machine 112 so as to be opposed to the wafer transfer machine 112. The wafer transfer machine transfers the wafer 200 from the cassette 100 to the boat 217 by the cooperation of the lifting operation and the coin operation. Transfer of the wafer 200 is performed on several cassettes 100, and after the transfer of a predetermined number of wafers is completed on the boat 217, the load lock door 123 is closed to close the load lock seal. 102 is vacuumed.

After the vacuum suction is completed, gas is introduced from the gas purge nozzle 234, and when the inside of the load lock chamber 102 is pressurized to atmospheric pressure, the gate valve 244 is opened and the boat elevator 121 is opened. As a result, the boat 217 is inserted into the processing furnace 202 and the gate valve 244 is closed. In addition, you may insert the said boat 217 into the said process furnace 202 in the state below atmospheric pressure, without returning the inside of the load lock chamber 102 to atmospheric pressure after completion of vacuum suction.

After the predetermined processing is performed on the wafer 200 in the processing furnace 202, the gate valve 244 is opened, and the boat 217 is drawn out by the boat elevator 121, and The load lock door 123 is opened after the inside of the load lock chamber 102 is returned to atmospheric pressure.

The wafer 200 after processing is transferred from the boat 217 to the cassette stage 105 via the cassette shelf 109 in the reverse order of the above-described operation, and is carried out by an external conveying device (not shown). .

The conveyance operation | movement of the said cassette transfer machine 114 etc. is controlled by the conveyance control means 124. FIG.

The method for manufacturing a semiconductor device according to the present embodiment uses a hot wall vertical reduced pressure CVD apparatus as the substrate processing apparatus described above, and reacts in a processing furnace (hereinafter referred to as a reaction furnace) 202 as a component thereof. Monosilane is used as the gas to form an a-Si film on the wafer.

Fig. 2 shows a schematic diagram of the reactor structure of the hot wall vertical reduced pressure CVD apparatus.

The outer tube 1 and the outer tube made of quartz, which are outer cylinders of the reactor 202, inside the hot wall composed of heaters 6 divided into four zones. 1) The inner inner tube 2 is installed.

Lower openings of the outer tube 1 and the inner tube 2 are sealed with a seal cap 219 made of stainless steel. The plurality of gas nozzles 12 penetrate the seal cap 219. The gas supply pipe is composed of a plurality of SiH ₄ / N ₂ nozzles 12 that supply monosilane and nitrogen gas. By these gas supply pipes 12, the processing gas is supplied into the inner tube 2. In addition, the SiH ₄ / N ₂ nozzle 12 may be composed of a plurality of nozzle parts having different lengths, and the monosilane is also supplied from the middle of the boat 217. It is also called a supply nozzle in the middle.

On the other hand, these gas nozzles 12 are connected to a mass flow controller (MFC, not shown), and are comprised so that the flow volume of the gas to supply can be controlled by a predetermined quantity.

In addition, the tubular space 18 formed between the outer tube 1 and the inner tube 2 is connected to the exhaust pipe 19. The exhaust pipe 19 is connected to a mechanical booster pump (MBP, 7) and a dry pump (DP, 8), and the outer tube 1 and the inner tube 2 are connected to each other. It is configured to discharge the gas flowing through the cylindrical space 18 therebetween. In addition, the exhaust pipe 19 is branched (分岐) on the upstream side of the mechanical booster pump 7, the branch exhaust pipe 20 N ₂ ballast (ballast) N ₂ ballast source via a valve-(16) (源(Not shown), the pressure in the exhaust pipe 19 is detected by the pressure gauge 15 so that the inside of the outer tube 1 is in a reduced pressure atmosphere at a predetermined pressure, and the controller control unit 17 detects the detected value. by is configured to control the valve 16 for N ₂ ballast.

In addition, a quartz boat 217 in which a plurality of wafers 200 are loaded is provided in the inner tube 2. The heat insulation board 5 loaded in the lower part of the boat 217 is for insulating between the boat 217 and the lower part of the apparatus. This boat 217 is supported by the rotating shaft 9 hermetically inserted from the seal cap 219. The rotating shaft 9 is configured to rotate the boat 217 and the wafer 200 held on the boat 217, and a drive control unit (not shown) to rotate the boat 217 at a predetermined speed. Controlled by

Therefore, in the case of forming a-Si, monosilane and nitrogen are introduced into the inner tube 2 from the SiH ₄ / N ₂ nozzle 12, respectively, and the reaction gas rises in the inner tube 2. The tubular space 18 between the two kinds of tubes 1 and 2 is lowered and exhausted from the exhaust pipe 19. When a boat (8 inches, 5.2 mm pitch, 217) loaded with a plurality of wafers 200 is exposed to the reaction gas, by reaction in the gas phase and on the surface of the wafer 200, A thin film is formed on the wafer 200.

Next, the film-forming procedure using the vertical pressure reduction CVD apparatus containing the above-mentioned reaction furnace is shown in FIG. First, the wafer 200 is introduced (step 301), the pressure in the reactor 202 is stabilized at 100 Pa (PRESS-CONT: pressure control process) (step 302), and the boat 217 loaded with the wafer 200 is obtained. ) Is loaded into the reactor 202 (step 303). The inside of the tubes 1 and 2 is exhausted, and an N ₂ purge is carried out in order to remove water, etc. adsorbed to the boat 217 and the tubes 1 and 2 (step 305). Thereafter, the flow rates of the monosilane and the nitrogen gas are set in MFC (not shown), and the N ₂ ballast control by the controller control unit 17 is performed so that the growth pressure is caused by flowing the respective gases into the reactor 202. It stabilizes (step 306). After the growth pressure in the reactor 202 is stabilized, predetermined film formation is performed (step 307). When the film formation is ended and returns the nozzles (12 to 14) inside a N ₂ cycle (cycle) and the purge tube (1,2) with N ₂ the inside to the atmospheric pressure (step 308, step 309). Returning to atmospheric pressure, the boat 217 is unloaded, and the wafer 200 is naturally cooled (steps 310 and 311). Finally, the wafer 200 is taken out from the boat 217 (step 312).

In the semiconductor device manufacturing method of this embodiment, the reactor 202 is a tube 1, 2 for processing a wafer, a heater 6 for heating the wafer 200 in the tube, and a reaction gas in the tube. A SiH ₄ / N ₂ nozzle 12 for supplying monosilane is included, and during the predetermined film formation, only monosilane is supplied from the nozzle 13 into the reaction tube to form an a-Si film on the wafer. .

This film formation is performed by a reduced pressure CVD method in which the controller control unit 17 controls the film formation pressure. In the case of forming an a-Si film on the wafer, the value of the film forming pressure is different from the initial stage of the film forming process (pre-purge process) and the later stage (depot process), for example, the pressure in the furnace of 100 Pa in the pre-purge process. Is added, and in-depth pressure of 40 Pa is applied in the depot process after the prepurge process. As a result, the surface roughness of the a-Si film can be improved.

<Examples>

An a-Si film was formed on the wafer using a vertical pressure reduction CVD apparatus including the reactor shown in FIG. 2.

The film formation is performed by controlling the film formation pressure, the SiH ₄ flow rate and the N ₂ flow rate by the controller control unit 17. Fig. 6 shows the flow of SiH ₄ and N ₂ and the change of the pressure in the reactor in the first embodiment of the present invention. First, in the pressure control process (PRESS-CONT) of ₁ , N ₂ is flowed in order to maintain the pressure in the furnace at a high pressure (100 Pa in this example) in the step of starting to flow SiH ₄ . This pressure control process aims to stabilize the furnace pressure at high pressure before film-forming. In the PREPURGE process of 2, a predetermined amount of 0.5 slm less than the prescribed flow rate of SiH ₄ (0.8 slm in this example) is flowed for about 5 seconds while maintaining the inside of the reactor at a high pressure (100 Pa). _The flow rate is stabilized by flowing a constant amount of 0.2 slm of ₂ . The surface roughness of the a-Si film is determined by the furnace pressure and the flow rate of SiH ₄ in this process. In other words, the smaller the flow rate of SiH ₄ in this pre-purge step, which is the initial stage of film formation, the better the surface roughness, and the higher the pressure, the better the surface roughness. In addition, about the time of this process, although 1 minute was applied in this example, it is not limited to this. In the depot process (DEPO) 3, the furnace pressure is lowered over 30 seconds (40 Pa in this example) to make it constant, and the flow rate of SiH ₄ is increased to 0.8 slm, which is the prescribed flow rate, over 10 seconds to make it constant. . Under this condition, an a-Si film is formed.

FIG. 7 shows the flow of SiH ₄ and N ₂ and the change of the pressure in the reactor in the second embodiment of the present invention. First, in the pressure control process (PRESS-CONT) of ₁ , N ₂ is increased to about 0.2 slm over about 10 seconds in order to maintain the pressure in the furnace at a high pressure (100 Pa in this example) at the stage of flowing SiH ₄ . After letting a certain amount flow. This pressure control process aims to stabilize the pressure in a reaction furnace at high pressure before film-forming. In the pre-purge process (PREPURGE) of 2, while maintaining a high pressure (100 Pa), SiH ₄ is gradually increased to about 0.5 slm less than the prescribed flow rate (0.8 slm in this example) for about 30 seconds, and then a certain amount is passed. ₂ is a constant flow rate of 0.2 slm. As described above, in order to effectively reduce the flow rate of SiH ₄ in the pre-purging step, the flow rate up to the prescribed flow rate is reduced, whereby the surface state of the a-Si film can be improved.

In the first embodiment, 0.5slm is reached over several seconds, but in the present embodiment, the flow rate is dropped by about 1/10 and 0.5slm is reached over about 30 seconds. Therefore, the flow rate of SiH ₄ in the pre-purging process of SiH ₄ can reproduce the ideal low-flow conditions. In the third depot process (DEPO), the pressure in the reactor is lowered (about 100 Pa to 40 Pa in this example) over about 30 seconds, and the flow rate of SiH ₄ is increased to 0.8 slm, which is a specified flow rate. Under this condition, an a-Si film is formed.

4 is a result of evaluating the surface roughness of the a-Si film.

On the other hand, in any sequence, conditions of depot process, SiH ₄ flow rate: 0.8slm, pressure setting: and the common condition of 40Pa. The sequence (a) of FIG. 4 is a conventional sequence, with SiH ₄ flow rate: 0.8 slm and pressure setting: none as the conditions of the prepurge process, and the conditions of the depot process are the above common conditions. As a result of measuring the surface state of a-Si in this case, the surface level was 6.8, and the number of particles was unmeasurable because of overflow.

Next, the sequence (b) of FIG. 4 is a condition of the prepurge process, and the pressure setting is 80 Pa compared to the sequence (a), and the setting is higher than the pressure of the depot process, and the conditions of the depot process are the above common conditions. It was carried out by. As a result of measuring the surface state of a-Si in this case, the surface level was 4.0 and the number of particles was 22,589. That is, it can be seen that there is an effect when the pressure setting of the pre-purging process is performed.

Next, the sequence (c) of FIG. 4 changes only the pressure conditions as the pressure setting: 100 Pa compared with the sequence (b) as conditions of a prepurge process, and the conditions of a depot process are said common conditions. As a result of measuring the surface state of a-Si in this case, the surface level was improved to 3.3 and the number of particles was improved to 14,836. That is, it turns out that it is effective when the pressure of a prepurge process is made large.

Next, the sequence (d) of FIG. 4 is a condition of a prepurge process, and flows N ₂ by 0.5 slm more than the sequence (c), sets the total gas flow rate of SiH ₄ and N ₂ to 1.3 slm, The conditions are the above common conditions. In the surface state measurement result of a-Si in this case, the surface level deteriorated to 4.0, and the number of particles also increased beyond the upper limit of detection. In other words, it can be seen that the surface state of the film tends to deteriorate when the gas flow rate of the prepurge process increases.

Next, the sequence (e) of FIG. 4 flows 0.5 slm of SiH ₄ and 0.2 slm of N ₂ as a condition of the prepurge process, and total gas flow rate of SiH ₄ and N ₂ is 0.7 slm. Therefore, the total gas flow rate is reduced compared to the SiH ₄ gas flow rate in the depot process, and the conditions of the depot process are the above common conditions. As a result of measuring the surface state of a-Si in this case, the surface level was improved to 3.0 and the number of particles was improved to 223. That is, it turns out that it is effective when the gas flow rate of a prepurge process is made smaller than the gas flow rate of a depot process.

Next, as shown in the sequence (e), the sequence (f) of FIG. 4 flows 0.5 slm of SiH ₄ and 0.2 slm of N ₂ as the sequence (e), and the total gas flow rate of SiH ₄ and N ₂ is 0.7 slm. Thus, the total gas flow rate was the same, the flow rate of SiH ₄ was gradually raised to 0.5 slm, which is a prescribed amount, and the conditions of the depot process are the above common conditions. As a result of measuring the surface state of a-Si in this case, the surface level was improved to 2.0, and the number of particles was significantly improved to 55. That is, it can be seen that the effect is more effective when gradually increasing the gas flow rate of the pre-purging process to a prescribed value.

From the above results, the surface roughness of the a-Si film is improved by reducing the flow rate of the SiH ₄ gas in the initial stage of the film forming process to a smaller amount than the flow rate of the SiH ₄ gas in the stage after the initial stage of the film forming process. You can get it. Moreover, an effect can also be acquired by making the pressure in a reaction furnace in the initial stage of a film-forming process into higher pressure than the pressure in the reaction furnace of a later step than the initial stage of a film-forming process. In addition, it can be seen that in the initial stage of the film forming process, as the flow rate to the set flow rate of SiH ₄ is reduced (slowly increased flow rate), further effects can be obtained.

As another example, the present invention can also be applied to a substrate processing apparatus for producing amorphous silicon by doping another gas with respect to SiH ₄ . For example, in the case of B-Dope-poly (SiH ₄ + BCl ₃ ) or B-PolySiGe (SiH ₄ + BCl ₃ + GeH ₄ ), the same effect can be obtained by gradually increasing the method of flowing SiH ₄ gas. .

One… Outer tube,
2… Inner Tube,
12... SiH ₄ / N ₂ nozzles

Claims (6)

In the step of forming an amorphous silicon film on a substrate,
Flowing SiH ₄ at an initial stage of the process using a furnace pressure as a first pressure,
In the step after the initial step, flowing SiH ₄ at a furnace pressure lower than the first pressure;
Method for manufacturing a semiconductor device comprising a. In the process of forming an amorphous silicon film on a substrate,
Flowing SiH ₄ at a first flow rate in an initial stage of the process,
After the initial step of flowing SiH ₄ at a second flow rate greater than the first flow rate
Method for manufacturing a semiconductor device comprising a. In the process of forming an amorphous silicon film on a substrate,
Flowing SIH ₄ at a first flow rate using the furnace pressure as the first pressure in the initial stage of the process;
A step after the initial step of flowing SiH ₄ at a second flow rate greater than the first flow rate, with the furnace pressure being a second pressure lower than the first pressure.
Method for manufacturing a semiconductor device comprising a. With treatment,
A monosilane gas supply unit for supplying monosilane gas,
A pressure controller for controlling the pressure,
The monosilane gas is supplied, and an initial stage of deposition of an amorphous silicon film is formed at a first pressure on the substrate, and after the initial stage of deposition, the monosilane gas supply unit is controlled to form a second pressure higher than the first pressure. And the second controller controls the pressure controller to be lower than the initial deposition pressure.
Substrate processing apparatus comprising a. With treatment,
A monosilane gas supply unit for supplying monosilane gas,
A pressure control unit for controlling pressure,
The monosilane gas is supplied, and an initial deposition of an amorphous silicon film on the substrate is performed by supplying the monosilane gas at a first flow rate, and after the initial deposition, a second amount of the monosilane gas is greater than the first flow rate. Controller control unit for controlling the monosilane gas supply unit to supply at a flow rate
Substrate processing apparatus comprising a. 6. The method of claim 5,
The controller control unit controls the monosilane gas supply unit to gradually increase and supply the first and second flow rates to the first and second flow rates when the monosilane gas is supplied at the first and second flow rates. Substrate processing apparatus.

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