JP6166137B2 - Charged particle beam equipment - Google Patents

Description

  The present invention relates to a charged particle beam apparatus.

  A charged particle beam apparatus such as a scanning electron microscope (CD-SEM) uses a signal (secondary electrons or reflected electrons) obtained by scanning a charged particle beam on the sample, This is an apparatus for forming the observed image. An example of a sample to be measured using a CD-SEM is a semiconductor device wafer.

  Semiconductor devices are being miniaturized and multilayered to improve device and circuit performance. With the miniaturization and multilayering of semiconductor devices, new materials, structures, processes, and the like are used, and accordingly, outgas is easily generated from the semiconductor device sample. Outgas is a gas released from a semiconductor device sample by, for example, the photoresist itself or a residual gas after the etching process.

  When outgas is generated from the semiconductor device sample, the atmospheric pressure in the sample chamber rises. As a result, there is an increased possibility that defects such as the primary electrons are scattered and the resolution is deteriorated or discharge is generated. In the current CD-SEM, all the semiconductor wafers to be measured are evacuated for a longer time than usual in the pre-exhaust chamber, and the effects of outgassing are suppressed by measures such as evacuating to a lower pressure. ing.

  The following Patent Document 1 describes a technique for suppressing the replacement frequency of a valve body that blocks between an atmosphere surrounding an electron source and an atmosphere in a sample chamber. In this document, the preliminary exhaust chamber is evacuated (preliminary exhaust), and when the pressure in the preliminary exhaust chamber reaches a predetermined value, it is determined whether or not the time required for the vacuum exhaust exceeds a predetermined value. Further, based on whether the exhaust time exceeds a predetermined value, it is determined how much molecules etc. are released from the sample, etc., and the valve mode (valve opening) is determined according to the determination result. (See paragraph 0040).

JP 2012-028280 A

  Using a method in which all semiconductor device samples are evacuated in the pre-exhaust chamber for a longer time than usual or evacuated to a lower pressure, even a sample that does not release outgas (normal wafer) takes a longer time than usual. It will be evacuated. Therefore, the throughput of the charged particle beam apparatus is undesirably lowered.

  In Patent Document 1, the amount of outgas is determined based on the time required for evacuation in the preliminary exhaust chamber, and the opening degree of the valve body is adjusted according to the determination. The valve body is provided to protect the electron source from the influence of residual gas under the premise that the sample is transported into the sample chamber. However, even if the electron source is protected from the residual gas, if the residual gas remains in the sample chamber, there is still a possibility that primary electrons will be scattered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a charged particle beam apparatus with high throughput while suppressing the influence of residual gas remaining in a sample chamber.

  The charged particle beam apparatus according to the present invention transports the sample into the sample chamber and does not reach it when the atmospheric pressure in the auxiliary exhaust chamber reaches the first atmospheric pressure after the first time has elapsed since the start of preliminary exhaust. In this case, it is determined whether or not the atmospheric pressure in the auxiliary exhaust chamber reaches a second atmospheric pressure lower than the first atmospheric pressure before the second time elapses after the preliminary exhaust is started.

  The charged particle beam apparatus according to the present invention detects a sample that generates outgas, and when detected, switches to an evacuation sequence for suppressing the influence. As a result, for samples that do not generate outgas, it is possible to suppress the influence of samples that generate outgas while securing throughput through normal operation.

1 is a side view illustrating a configuration of a transport system of a charged particle beam device 100 according to Embodiment 1. FIG. 4 is a flowchart illustrating an operation in which the charged particle beam device 100 transports a sample 8 from the preliminary exhaust chamber 5 to the sample chamber 2. It is an example of a user interface screen presented by the control unit 12 in step S206. It is a side view which shows the structure of the charged particle beam apparatus 100 which concerns on Embodiment 2. FIG.

<Embodiment 1>
FIG. 1 is a side view showing a configuration of a transport system of a charged particle beam device 100 according to Embodiment 1 of the present invention. A sample (semiconductor device wafer) 8 is stored in the hoop 7. When conveyance of the sample 8 to the sample chamber 2 is started, the hoop 7 is moved into the mini environment 6. The sample 8 is taken out from the hoop 7 and is carried into the mini environment 6.

  Next, the valve 10 that separates the mini-environment 6 and the preliminary exhaust chamber 5 is opened, and the sample 8 is transferred into the preliminary exhaust chamber 5 under atmospheric pressure. At this time, the sample chamber 2 is in a high vacuum state by the vacuum pump 11, and the valve 9 separating the preliminary exhaust chamber 5 and the sample chamber 2 is closed.

  When the sample 8 is carried into the preliminary exhaust chamber 5, the valve 10 is closed, and the vacuum pump 11 evacuates the preliminary exhaust chamber 5 while the valve 9 is closed. At this time, first, a dry pump is used for roughing from atmospheric pressure. At a time point after the atmospheric pressure in the preliminary exhaust chamber 5 has dropped to a predetermined atmospheric pressure, further evacuation is performed using a turbo pump. When the air pressure in the preliminary exhaust chamber 5 reaches the same pressure as the sample chamber 2, the valve 9 is opened. The pressure in the preliminary exhaust chamber 5 is measured by a pressure gauge 13.

  Next, the sample 8 is transferred onto the electrostatic chuck 4 on the stage 3 in the sample chamber 2. Finally, the valve 9 is closed, the sample 8 is moved below the column 1, and the charged particle beam is irradiated onto the sample 8 to perform the inspection. The control unit 12 controls the entire operation of the charged particle beam apparatus 100 such as the transport system, the vacuum pump 11 and the charged particle beam source. The control unit 12 includes a display device such as a display that displays a screen interface for a user to input an operation instruction to the charged particle beam device 100.

  The preliminary exhaust chamber 5 is a local space for carrying the sample 8 into the high vacuum sample chamber 2 and is designed to have a volume as small as possible. By performing degassing treatment suitable for the sample material in the preliminary exhaust chamber 5, the atmospheric pressure in the preliminary exhaust chamber 5 can be switched between atmospheric pressure and high vacuum at high speed.

  When the sample 8 is inspected under the column 1, the above-described problem does not occur if the sample does not generate outgas (normal wafer), but if the sample generates outgas (outgas wafer), In particular, the air pressure on the surface side of the sample 8 rises locally. Due to this, the primary electrons are scattered, so that the resolution may be deteriorated or discharge may be generated. If the resolution deteriorates, the sample 8 cannot be inspected normally, and the sample 8 that has been produced as designed is judged as defective, or the sample 8 that is not produced as designed is judged as a non-defective product. There is a possibility of obtaining an inspection result. When discharge occurs, the sample 8 itself is broken, and the sample 8 must be discarded depending on the degree of breakage.

  FIG. 2 is a flowchart for explaining the operation of the charged particle beam apparatus 100 for transporting the sample 8 from the preliminary exhaust chamber 5 to the sample chamber 2. Hereinafter, each step of FIG. 2 will be described.

(FIG. 2: Step S201)
The vacuum pump 11 roughens the inside of the preliminary exhaust chamber 5 from the atmospheric pressure using a dry pump. At this time, since the pressure is reduced from the atmospheric pressure, a large amount of existing gas exists in the preliminary exhaust chamber 5. Therefore, the time required to reach the atmospheric pressure at which the main pulling can be started is substantially constant regardless of whether the wafer is a normal wafer or an outgas wafer. When the atmospheric pressure in the preliminary exhaust chamber 5 reaches a level at which main pulling can be started, the vacuum pump 11 pulls the internal pressure in the preliminary exhaust chamber 5 to the same level as that in the sample chamber 2 using a turbo pump.

(FIG. 2: Steps S202 to S204)
The vacuum pumping by the turbo pump is a pressure reduction from the middle vacuum state, and is less than when the existing gas in the preliminary exhaust chamber 5 is roughly drawn. Therefore, the time required for the pressure in the preliminary exhaust chamber 5 to reach a predetermined pressure varies between when outgas is generated (normal wafer) and when it does not occur (outgas wafer). The controller 12 uses this difference to determine whether or not the sample 8 generates outgas. Specifically, it is determined whether or not the atmospheric pressure in the preliminary exhaust chamber 5 reaches the first atmospheric pressure within a first time after starting the vacuum exhaust. When it reaches, it is determined that the sample 8 does not generate outgas (normal wafer), and the sample 8 is transferred to the sample chamber 2 (S203). If not reached, it is determined that the sample 8 generates outgas (outgas wafer) (S204), and step S205 and subsequent steps (evacuation sequence for outgas wafer) are performed.

(FIG. 2: Step S205)
The controller 12 reaches the second atmospheric pressure in which the atmospheric pressure in the preliminary exhaust chamber 5 is lower than the first atmospheric pressure within a second time longer than the first time after starting the vacuum exhaust in the preliminary exhaust chamber 5. Determine whether or not. If it has reached, it is determined that the inside of the preliminary exhaust chamber 5 has been sufficiently depressurized, and the process proceeds to step S203 to transport the sample 8 to the sample chamber 2. If not, step S206 and subsequent steps are performed.

(FIG. 2: Step S205: Supplement 1)
In this step, the pre-evacuation chamber 5 is evacuated to a second atmospheric pressure lower than the first atmospheric pressure because the atmospheric pressure in the sample chamber 2 slightly rises due to outgas when the sample 8 is inspected in the sample chamber 2. This is because the atmospheric pressure of the charged particle beam device 100 is set to a level that is safe enough to operate safely.

(FIG. 2: Step S205: Supplement 2)
The inspection time of a semiconductor device wafer is usually about several minutes. When the sample 8 is inspected for a longer time, outgas may gradually accumulate in the sample chamber 2 and exceed the allowable amount. In this case, it is necessary to devise such that the sample 8 is periodically returned to the preliminary exhaust chamber 5 and evacuated again.

(FIG. 2: Step S206)
When the atmospheric pressure in the preliminary exhaust chamber 5 does not reach the second atmospheric pressure within the second time after starting the vacuum exhaust, the sample 8 is considered to generate a large amount of outgas. Therefore, the control unit 12 continues the evacuation without providing a time limit until the atmospheric pressure in the preliminary exhaust chamber 5 reaches the third atmospheric pressure that is equal to or lower than the second atmospheric pressure. The reason for not providing the time limit is that the optimum evacuation time is not necessarily determined in advance according to the amount of outgas generated. Even a semiconductor device wafer that does not generate outgas may generate outgas only by slightly changing the structure, material, process, and the like. In addition, the amount of outgas generated may change. Therefore, when the amount of outgas generated from the sample 8 is large, it is considered that it is simpler and safer to evacuate to the third pressure even if the throughput is somewhat sacrificed. Therefore, in this step, the preliminary exhaust chamber 5 is continuously evacuated to the third atmospheric pressure.

(FIG. 2: Step S206: Supplement)
However, it may not always be desirable from the viewpoint of throughput to continue evacuation of all the samples 8 to the third atmospheric pressure. Therefore, the control unit 12 can provide a user interface for the user to select whether or not to execute this step. For example, the control unit 12 displays an operation screen illustrated in FIG. 3 described later on a display connected to the charged particle beam device 100. In the operation screen, the user can select whether or not to stop the vacuum exhaust in the preliminary exhaust chamber 5. The operation screen and the following step S207 can be omitted. If omitted, only step S208 is performed.

(FIG. 2: Step S207)
When the user instructs to stop the vacuum exhaust on the operation screen described in step S206, the control unit 12 stops the vacuum exhaust in the preliminary exhaust chamber 5 according to the instruction, and discharges the sample 8 from the preliminary exhaust chamber 5. To do. Thereafter, the control unit 12 ends this flowchart and starts this flowchart again for the next sample 8.

(FIG. 2: Step S208)
When the user does not instruct to stop the vacuum exhaust in step S207, or when step S207 is omitted, the control unit 12 determines whether the atmospheric pressure in the preliminary exhaust chamber 5 has reached the third atmospheric pressure. If it has reached, it is determined that the pressure has been sufficiently evacuated to a level that does not hinder the occurrence of outgassing from the sample 8, and the process proceeds to step S203, where the sample 8 is transported to the sample chamber 2. If not, the process returns to step S207 and the same process is repeated.

(FIG. 2: Step S208: Supplement 1)
In step S206, since the vacuum pumping using the turbo pump is continued, the turbo pump may break down earlier than usual. In order to avoid this, the control unit 12 does not use the operation screen described in step S206, but within a third time longer than the second time after starting the vacuum exhaust in the preliminary exhaust chamber 5. In addition, it may be determined whether or not the atmospheric pressure in the preliminary exhaust chamber 5 reaches the third atmospheric pressure. That is, in this step, when the third atmospheric pressure is not reached within the third time, the control unit 12 stops the vacuum exhaust in the preliminary exhaust chamber 5 and discharges the sample 8 from the preliminary exhaust chamber 5. Since this step is for the sample 8 that generates a large amount of outgas, the third time must be set sufficiently long.

(FIG. 2: Step S208: Supplement 2)
Whether or not to implement the method described in Supplement No. 1 above is desirably selectable by the user on the operation screen described in step S206, for example. Further, although the method described in Supplement 1 above protects the turbo pump by the operation of the control unit 12, it is desirable that the turbo pump itself has a self-monitoring function using a thermometer or the like.

(FIG. 2: Step S208: Supplement 3)
Even if the second atmospheric pressure and the third atmospheric pressure are set to the same value, there may be no problem in the operation of the charged particle beam device 100. This is because, depending on the amount of outgas generated, if the second atmospheric pressure is set to a sufficiently low value, it is considered that it is not necessary to continue evacuation beyond that.

(FIG. 2: Steps S205 and S208: Supplement)
If the second atmospheric pressure is not reached within the second time in step S205, or if the third atmospheric pressure is not reached within the third time in step S208, the control unit 12 stops evacuating the preliminary exhaust chamber 5 (the sample thereof). The test 8 may be forcibly discharged), or the sample 8 may be forcibly discharged, or a warning signal to that effect may be issued and specific measures may be delegated to a user operation or a host system. By stopping the inspection, the risk of primary electron scattering and discharge can be avoided, but the inspection of the sample 8 in the process is delayed. If the process has a low correlation with the yield of the semiconductor device, there is no particular problem, but if the correlation is high, it may be desirable to continue the inspection with knowledge of the risk. Therefore, as described in step S <b> 206, it is desirable that the user's instruction can be left to determine whether or not to continue the inspection.

  FIG. 3 is a screen example of a user interface presented by the control unit 12 in step S206. When the user presses the “unload” button, the control unit 12 assumes that the user has instructed to stop the evacuation of the preliminary exhaust chamber 5. In addition, the atmospheric pressure in the preliminary exhaust chamber 5 and the elapsed time after starting the vacuum exhaust in the preliminary exhaust chamber 5 may be displayed together. For example, when the air pressure does not sufficiently decrease even though the evacuation time is sufficient, the user can press the unload button to stop the inspection. Furthermore, if the third atmospheric pressure is not reached within the third time, it may be possible to select whether or not to evacuate the preliminary exhaust chamber 5 forcibly.

<Embodiment 1: Summary>
As described above, in the charged particle beam apparatus 100 according to the first embodiment, when the atmospheric pressure in the preliminary exhaust chamber 5 reaches the first atmospheric pressure within the first time, the sample 8 does not generate outgas or outgas. It is determined that the generated amount is not to hinder the operation of the charged particle beam apparatus 100, and the sample 8 is transported to the sample chamber 2. Thereby, since it is not necessary to carry out excessive evacuation with respect to all the samples 8, it can suppress that the throughput of the charged particle beam apparatus 100 is impaired.

  Further, in the charged particle beam device 100 according to the first embodiment, when the atmospheric pressure in the preliminary exhaust chamber 5 does not reach the first atmospheric pressure within the first time, the evacuation is continued further than the first time. It is determined whether or not the second atmospheric pressure lower than the first atmospheric pressure is reached within a long second time. When the second atmospheric pressure is reached, the sample 8 is transferred to the sample chamber 2. Thereby, even if it is the sample 8 which generate | occur | produces outgas, since the process by the charged particle beam apparatus 100 can be continued, the fall of a throughput can be suppressed.

  Further, in the charged particle beam device 100 according to the first embodiment, when the atmospheric pressure in the preliminary exhaust chamber 5 does not reach the second atmospheric pressure within the second time, the evacuation is further continued to be equal to or lower than the second atmospheric pressure. It is determined whether or not the third atmospheric pressure is reached. For example, this operation is effective when it is desired to continue the processing even when the sample 8 generates outgas.

  Further, in the charged particle beam device 100 according to the first embodiment, when the evacuation is continued until the atmospheric pressure in the preliminary exhaust chamber 5 becomes equal to or lower than the second atmospheric pressure, the user uses the operation screen described in FIG. The vacuum exhaust can be stopped by manual operation. Thereby, it can be left to a user's judgment whether the process with respect to the said sample 8 is continued. Furthermore, it is possible to allow the user to select whether or not the evacuation is forcibly terminated when the third time has elapsed. Thereby, a certain amount of automatic processing can be performed while satisfying the user's wishes. Moreover, damage to the vacuum pump 11 can be prevented.

<Embodiment 2>
In the first embodiment, the configuration example has been described in which it is determined whether or not the preliminary exhaust is continued using the atmospheric pressure measured by the pressure gauge 13 installed in the preliminary exhaust chamber 5. The reason for using the pressure gauge 13 is to measure the amount of outgas generated from the sample 8 by the atmospheric pressure in the preliminary exhaust chamber 5. Instead of this or in combination with this, the same operation as that of the first embodiment can be realized by measuring the outgas composition material itself. In the second embodiment of the present invention, a configuration example thereof will be described.

  FIG. 4 is a side view showing the configuration of the charged particle beam apparatus 100 according to the second embodiment. In the second embodiment, a substance sensor 14 is disposed in the preliminary exhaust chamber 5 instead of or in combination with the pressure gauge 13. The substance sensor 14 can be configured using, for example, a residual gas analyzer that detects an outgas composition substance that is known to be generated from the sample 8 in advance.

  The control unit 12 can determine whether or not to continue the vacuum exhaust in the preliminary exhaust chamber 5 based on the remaining amount of the composition material of the outgas detected by the material sensor 14. For example, in step S202, instead of the first atmospheric pressure, the first remaining amount of the outgas composition material corresponding to this can be used as the determination criterion in the same step. That is, when the remaining amount of the outgas composition material reaches the first remaining amount within the first time, the process proceeds to step S203. Similarly, in the other steps, the atmospheric pressure used as the threshold value may be appropriately replaced with the remaining amount of the outgas composition material.

  When the pressure gauge 13 and the substance sensor 14 are used in combination, the respective detection values can be used in combination by a technique such as using one of the detection values preferentially or weighted average of the detection values.

  The present invention is not limited to the embodiments described above, and includes various modifications. The above embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment. The configuration of another embodiment can be added to the configuration of a certain embodiment. Further, with respect to a part of the configuration of each embodiment, another configuration can be added, deleted, or replaced.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part of them, for example, by an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function can be stored in a recording device such as a memory, a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  1: column, 2: sample chamber, 3: stage, 4: electrostatic chuck, 5: preliminary exhaust chamber, 6: mini-environment, 7: hoop, 8: sample, 9-10: valve.

Claims (7)

A charged particle beam apparatus for irradiating a sample with a charged particle beam,
A sample chamber in which the sample is placed,
A preliminary exhaust chamber adjacent to the sample chamber;
A pump for evacuating the sample chamber and the preliminary exhaust chamber;
A pressure gauge for measuring the pressure in the preliminary exhaust chamber;
A transport system for transporting the sample from the preliminary exhaust chamber to the sample chamber;
A control unit for controlling the pump and the transport system;
With
The controller is
Before transporting the sample from the preliminary exhaust chamber to the sample chamber, the pump is used to evacuate the preliminary exhaust chamber and the sample chamber,
If the air pressure in the auxiliary exhaust chamber reaches the first atmospheric pressure after the first time has elapsed since the start of vacuum exhaust in the auxiliary exhaust chamber, the sample is transferred from the auxiliary exhaust chamber to the sample chamber. ,
If the air pressure in the auxiliary exhaust chamber does not reach the first atmospheric pressure after the first time has elapsed since the start of the vacuum exhaust in the auxiliary exhaust chamber, the vacuum exhaust in the auxiliary exhaust chamber is started after the vacuum exhaust is started. By further evacuating the preliminary exhaust chamber until a second time longer than the first time elapses, it is determined whether or not the atmospheric pressure in the preliminary exhaust chamber reaches a second atmospheric pressure lower than the first atmospheric pressure. And when it reaches | attains, the said sample is conveyed from the said preliminary | backup exhaust chamber to the said sample chamber, and when it does not reach | attain, the signal to that effect is output. The controller is
When the atmospheric pressure in the auxiliary exhaust chamber does not reach the second atmospheric pressure until the second time has elapsed since the start of vacuum exhaust in the auxiliary exhaust chamber, the atmospheric pressure in the auxiliary exhaust chamber is equal to or lower than the second atmospheric pressure. The charged particle beam apparatus according to claim 1, wherein the evacuation in the preliminary exhaust chamber is continued until the third atmospheric pressure is reached. The charged particle beam device comprises:
A display device for displaying a screen interface used by a user to give a command to the control unit;
The controller is
In order to input a stop instruction for instructing to stop the vacuum exhaust in the preliminary exhaust chamber while the preliminary exhaust chamber is evacuated until the atmospheric pressure in the preliminary exhaust chamber reaches the third atmospheric pressure. Display a stop instruction screen used by the
The charged particle beam apparatus according to claim 2, wherein when the stop instruction is received via the stop instruction screen, the vacuum exhaust in the preliminary exhaust chamber is stopped. The controller is
By further evacuating the preliminary exhaust chamber until a third time longer than the second time elapses after the start of vacuum exhaust in the preliminary exhaust chamber, the atmospheric pressure in the preliminary exhaust chamber is changed to the second atmospheric pressure. It is determined whether or not the following third atmospheric pressure is reached, and if reached, the sample is transferred from the preliminary exhaust chamber to the sample chamber, and if not reached, the vacuum exhaust in the preliminary exhaust chamber is stopped. The charged particle beam apparatus according to claim 3. The controller is
On the stop instruction screen, evacuation in the preliminary exhaust chamber is continued until the stop instruction is given, or a third time longer than the second time has elapsed since the start of vacuum exhaust in the preliminary exhaust chamber. An interface for inputting a selection instruction for selecting whether or not to evacuate the preliminary exhaust chamber if the atmospheric pressure in the preliminary exhaust chamber does not reach the third atmospheric pressure by
5. The charged particle beam apparatus according to claim 4, wherein when the selection instruction is received, a time for continuing the vacuum evacuation in the preliminary exhaust chamber is controlled according to the instruction. The said control part displays the elapsed time after starting the vacuum exhaustion in the said preliminary | backup exhaust chamber on the said stop instruction | indication screen, and the measurement result by the said pressure gauge. The charged particle beam apparatus according to 1. A charged particle beam apparatus for irradiating a sample with a charged particle beam,
A sample chamber in which the sample is placed,
A preliminary exhaust chamber adjacent to the sample chamber;
A pump for evacuating the sample chamber and the preliminary exhaust chamber;
A substance sensor for measuring a residual amount of a substance generated from the sample in the preliminary exhaust chamber;
A transport system for transporting the sample from the preliminary exhaust chamber to the sample chamber;
A control unit for controlling the pump and the transport system;
With
The controller is
Before transporting the sample from the preliminary exhaust chamber to the sample chamber, the pump is used to evacuate the preliminary exhaust chamber and the sample chamber,
When the remaining amount in the preliminary exhaust chamber reaches the first residual amount before the first time has elapsed since the start of vacuum exhaust in the preliminary exhaust chamber, the sample is removed from the preliminary exhaust chamber to the sample chamber. Transport to
If the remaining amount in the preliminary exhaust chamber does not reach the first remaining amount before the first time has elapsed since the start of vacuum exhaust in the preliminary exhaust chamber, vacuum exhaust in the preliminary exhaust chamber is started. Until the second time longer than the first time elapses, the remaining amount in the auxiliary exhaust chamber is lower than the first remaining amount by further evacuating the auxiliary exhaust chamber. The charged particle beam apparatus is characterized in that it determines whether or not the sample reaches the sample chamber, and when the sample reaches the sample chamber, the sample is transported from the preliminary exhaust chamber to the sample chamber.

Images