JP5303412B2 - Inspection apparatus and wafer chuck cleaning method - Google Patents

Description

  The present invention relates to a surface inspection apparatus and a surface inspection method, for example, a surface inspection apparatus and a surface inspection method for inspecting a substrate such as a semiconductor wafer, a magnetic disk, or a liquid crystal display element as an inspection target.

  In a semiconductor manufacturing process, if dust is present on a substrate (semiconductor wafer), it may cause defects such as wiring insulation failure or short circuit. These dusts are generated in various states such as those generated from moving parts such as transport devices, those generated from the human body, those generated by reaction in the processing device by process gas, and those containing chemicals and materials. It is mixed. The same applies to the manufacturing process of a magnetic disk or a liquid crystal display element, and adhesion of generated dust to a substrate (magnetic disk or liquid crystal display element) causes a defect.

  Therefore, by detecting and managing the dust on the substrate surface using a surface inspection device in the manufacturing process, the dust generation status of each manufacturing device and the cleanliness of each process are monitored and controlled. We are trying to control yield reduction. However, even in such a surface inspection apparatus, there is no generation of dust from the movable part or the like, and there is a concern that dust adheres to the substrate to be inspected (substrate to be inspected) as in other processes.

  As a conventional technique for suppressing the adhesion of dust to such a substrate to be inspected, as described in Patent Document 1, a target placed on an XY stage (stage) disposed on a support base in a casing is used. In an apparatus for inspecting an inspection substrate with a laser microscope, a ventilation port is provided above a substrate to be inspected placed on a stage, and two exhaust ports connected to a fan are connected to the side of the stage and below the support base. It is known that an air flow (down flow) from the upper side to the lower side of the substrate to be inspected is generated by disposing the substrate on the substrate to be inspected, and adhesion of dust generated from the movable portion of the stage to the substrate to be inspected is known.

  Further, in Patent Document 2, an apparatus that images and inspects a substrate to be inspected placed on an XY stage (stage) arranged in a clean box with an optical unit is positioned on the side of the stage of the clean box. By providing an open area that leads to the outside on the side surface, and by providing an overhanging part that protrudes toward the stage side at a height that is approximately equal to the lower end of the stage inside the clean box, clean air is supplied into the clean box. A device that guides air from a clean air unit to be supplied in the direction of the stage to pass over the substrate to be inspected and suppresses adhesion of dust generated in the clean box to the substrate to be inspected is disclosed.

  Further, in Patent Document 3, in an apparatus for inspecting an object to be inspected placed on an XY stage (stage) arranged in a case using an illumination device and a detection device, air supplied into the case by a suction device is disclosed. A device that guides an object to be inspected in parallel by an air guide panel is disclosed.

  Although the improvement in cleanliness in the inspection chamber is as described above, the wafer chuck alone holding the semiconductor wafer at the time of inspection moves in the direction of minimizing the contact area with the wafer in each semiconductor manufacturing apparatus. At that time, a wafer edge grip type chuck (also referred to as a side chuck) is used. By holding the wafer end face by line contact without contacting the front and back of the wafer, dust and contact traces generated by contacting the wafer are minimized.

Japanese Patent Laid-Open No. 7-230037 JP 2001-118896 A JP 2005-140778 A

  In gripping a substrate to be inspected by the edge grip method, there is always a contact between the substrate to be inspected and a component to be inspected by the substrate. As a result of the contact, some damage is given to the softer one of the inspected substrate and the inspected substrate gripping component. As a result of the stacking, the softer one of the inspected substrate and the inspected substrate gripping part is scraped or the like, and is generated as dust having a diameter of several tens of nanometers or more and floats or stays. In addition, there is an inspected substrate gripping component that becomes a movable part in the immediate vicinity of the inspected substrate. As long as the inspected substrate gripping component is a movable part, generation of dust due to friction or the like is inevitable by any method.

  Therefore, regular maintenance (cleaning, etc.) is indispensable for the edge grip type chuck, and in some cases, it must be periodically replaced. However, when performing maintenance such as cleaning, it is necessary to attend work education in advance, and the possibility of unevenness in work cannot be denied as long as people perform work. In addition, it is necessary to consider the risk of attaching new dust, scratching, and destroying parts through humans. For the reasons described above, regardless of the manual cleaning or replacement of the chuck itself, when the edge grip chuck is maintained, the apparatus stop time becomes longer, resulting in a decrease in yield.

  The present invention has been made in view of the above, and by automatically removing dust generated in the vicinity of the gripping portion of the substrate to be inspected, the adhesion of dust to the substrate to be inspected is suppressed and is stabilized by automation. An object is to provide a surface inspection apparatus and a surface inspection method that can be used.

  In order to solve the above problems, the present invention is characterized in that the wafer chuck is moved rearward from the inspection optical system, and the wafer chuck is cleaned behind the inspection optical system.

  Another feature of the present invention is that the flow rate of air supplied to the wafer chuck and the exhaust amount of air supplied to the wafer chuck are controlled.

  In the present invention, the dust generated on the inspected board gripping component is automatically removed, so that the adhesion of the dust to the inspected board can be suppressed, so the apparatus stop time is shortened (close to maintenance-free). Increases equipment availability.

It is a see-through | perspective side view which shows the outline of the whole structure of the surface inspection apparatus which concerns on embodiment of this invention. 1 is a perspective plan view showing an outline of an overall configuration of a surface inspection apparatus according to an embodiment of the present invention. It is a perspective view which extracts and shows the edge grip type chuck | zipper in the surface inspection apparatus of FIG. It is a see-through | perspective side view which shows the standby state of the surface inspection apparatus which concerns on embodiment of this invention. It is a see-through | perspective side view which shows the to-be-inspected board receiving state of the surface inspection apparatus which concerns on embodiment of this invention. It is a see-through | perspective side view which shows during the test | inspection operation | movement of the surface inspection apparatus which concerns on embodiment of this invention. It is a see-through | perspective side view which shows the cleaning operation | movement of the surface inspection apparatus which concerns on embodiment of this invention. It is a perspective view which extracts and shows the wafer chuck and cleaning unit in the surface inspection apparatus during cleaning operation.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 8.

<Embodiment>
FIG. 1 is a perspective side view showing an overall schematic configuration of the surface inspection apparatus according to the present embodiment.

  1, the surface inspection apparatus according to the present embodiment includes a case 14 that separates the inside and the outside of the surface inspection apparatus, and a detection unit 13 that is provided inside the case 14 and performs surface inspection of a substrate to be inspected.

  The detection unit 13 cleans the air supplied by the fan (not shown) that supplies air into the sample chamber 17 in which the substrate to be inspected (for example, a semiconductor wafer) 1 is placed and surface inspection is performed. A fan filter unit (hereinafter FFU) 3 provided with a filter (not shown), an exhaust port A (11) provided with an opening for sucking air inside the sample chamber 17, and an exhaust port A (11) An exhaust fan unit A (9) that sucks air inside the sample chamber 17 and discharges it to the outside of the case 14 is provided. The sample chamber 17 is completely surrounded by the optical system support 16 in which the illumination optical system 8 is installed, the support 15, the exhaust-side support 26, and the FFU 3.

  In this manner, clean air is supplied by the FFU 3 and dust and the like are discharged from the exhaust port A11 in the downstream area, so that the sample chamber 17 is kept at a high cleanliness. Further, by controlling the flow rate balance between the FFU 3 and the exhaust port A11, the pressure in the sample chamber 17 is always set higher than the pressure outside the case 14 (for example, a clean room). If the sample chamber 17 is maintained at a positive pressure, dirty air or the like outside the sample chamber 17 does not enter the sample chamber 17. That is, the detection unit 13 functions as a clean box because the inside of the sample chamber 17 is set at a higher positive pressure than the outside of the case 14 and is maintained at a high cleanliness level.

  That is, in order for a certain area to function as a clean box, it must have a unit for supplying highly purified air and an exhaust port on one side of the enclosed space, and must be more positive than the surroundings.

  The detection unit 13 is placed on a stage unit 12 on which a semiconductor wafer (hereinafter simply referred to as a wafer) 1, which is an example of a substrate to be inspected, a support unit 15 that supports the stage unit 12, and a wafer chuck 7. Illumination optical system 8 that irradiates illumination light onto the wafer (inspected substrate) 1, detection optical system 2 that detects light (scattered light, diffracted light, reflected light, etc.) from the wafer 1, and illumination optical system 8 And an optical system support 16 that supports the detection optical system 2. In the detection optical system 2, a sample chamber 17, which is a space where the wafer 1 is placed and surface inspection is performed, is surrounded by a cover (not shown), and the cover, the support unit 15, and the optical system. A sample chamber 17 is defined by the support 16.

  The stage unit 12 includes a disk-shaped wafer chuck 7 that holds the wafer 1 by an edge grip method, a rotating mechanism 4 that rotationally drives the wafer chuck 7 in the circumferential direction, and a vertical direction that moves the rotating mechanism 4 in the vertical direction. A moving mechanism 6 and a horizontal moving mechanism 5 for moving the vertical moving mechanism 6 in the horizontal direction are provided. In the surface inspection, while the illumination optical system 8 irradiates the surface of the wafer 1 with illumination light, the wafer chuck 7 holding the wafer 1 is rotated by the rotation mechanism 4 at a high speed in the circumferential direction and horizontally by the horizontal movement mechanism 5. By moving, the surface of the wafer 1 is scanned with illumination light.

  The FFU 3 has an air supply port for supplying clean air to the side surface of the sample chamber 17 facing the stage 12, and is arranged so that the supplied clean air is supplied to the entire sample chamber 17 evenly. ing.

  The exhaust port A11 has a plurality of openings for exhausting the air in the sample chamber 17, and is arranged at the end opposite to the FFU 3 of the wafer chuck 7 so that the opening faces the FFU 3. It is desirable that In addition, the plurality of openings of the exhaust port A <b> 11 are arranged on the upper and lower sides of the wafer 1 placed on the wafer chuck 7 or at the same height as the wafer 1. The air sucked by the exhaust port A11 becomes one flow in the middle of the exhaust duct 24 between the exhaust port A11 and the exhaust fan unit A9, and is discharged to the outside of the case 14 through the exhaust fan unit A9.

  Next, the edge grip method will be described.

  A schematic diagram is shown in FIG. The wafer 1 is placed on a wafer cradle portion 22 constituting the wafer chuck 7, but only the edge portion of the wafer 1 is in contact with the wafer cradle portion 22. A proper number of gripping pieces 23 for gripping the wafer 1 are provided on the circumference of the wafer 1. When gripping the wafer 1, the gripping piece 23 is also in contact with only the edge portion of the wafer 1. The gripping piece 23 is opened / closed or stored so as not to hinder the operation of the wafer 1 when the wafer 1 is placed on the wafer chuck 7 or collected.

  A normal inspection operation of the surface inspection apparatus configured as described above will be briefly described.

  FIG. 4 is a diagram waiting for the wafer 1 to be carried. The shutter 20 is lowered and the delivery port 21 is opened.

  In FIG. 5, the wafer 1 is placed on the wafer chuck 7, the shutter 20 is raised, and the delivery port 21 is closed.

  FIG. 6 shows a state in which the inspection is started. While the rotation mechanism 4 is rotating the wafer chuck 7 on which the wafer 1 is placed to an appropriate number of revolutions, the vertical movement mechanism 6 is moved to an appropriate height, and during that time the horizontal movement mechanism 5 is loaded on the wafer 1. The wafer chuck 7 is moved to a position immediately below the detection optical system 2 and inspection is started.

  After completion of the inspection, while the rotation mechanism 4 stops rotating, the vertical movement mechanism 6 moves to an appropriate height, and the horizontal movement mechanism 5 moves the wafer chuck 7 on which the wafer 1 is placed to the delivery port 21. The shutter 20 is lowered and the wafer 1 is recovered from the wafer chuck 7.

  The effect in this Embodiment comprised as mentioned above is demonstrated.

  In the conventional surface inspection apparatus, the generation of dust must be eliminated in the sample chamber 17, or it must never be adhered to the wafer 1 even if it occurs. This is a natural performance of the surface inspection apparatus, but it is very difficult to maintain and improve this performance. In particular, from the wafer chuck 7 that always comes into contact with the wafer 1, generation of dust due to contact with the wafer 1 and generation of dust from the mechanism portion of the gripping piece 23, which is a movable portion in the immediate vicinity of the wafer 1, are very problematic. Yes.

  When a person wipes the dust with a cloth or the like, there is a risk that new dust is generated due to friction with the cloth or fibers remain and become new dust. In addition, not only the edge grip method but generally the wafer chuck 7 is a high-precision processed part. Therefore, if the wafer chuck 7 is frequently replaced, the cost becomes enormous, the apparatus stop time becomes long, and the yield decreases and the cost increases. .

  Therefore, it is possible to improve the yield by installing an automatic cleaning unit inside the clean box and performing regular cleaning. In addition, the maintenance time can be greatly shortened and the risk of manual work can be eliminated. From the above, periodic chuck replacement work is not required, and the total apparatus stop time is significantly shortened, and the maintenance cost is greatly reduced.

  The cleaning operation using the cleaning unit installed above will be described.

  As the cleaning unit, an air outlet 19 for blowing out high cleanliness air that has passed through the high-performance air filtration filter 27, and an exhaust outlet B18 are arranged in the sample chamber 17 at a position where the blown air is efficiently sucked. An exhaust duct 24 and an exhaust fan unit B10 for passing the air sucked by B18 are added. The performance of the high-performance air filtration filter is, for example, “0.01 μm collection efficiency 100%”. In addition, the air outlet 19 and the exhaust outlet B18 are preferably installed at the most downstream position inside the sample chamber 17 (immediately before the exhaust outlet A11). It is desirable. As for the exhaust port B18, it is desirable that the air outlet 19 be in a directly facing position or the same direction as the exhaust port A11.

  FIG. 7 shows a state where the wafer chuck 7 is cleaned. The shutter 20 is raised and the delivery port 21 is closed.

  While the wafer 1 is not placed on the wafer chuck 7, a predetermined position is determined by using each operation unit of the stage unit 12 until the contact portion of the wafer chuck 7 with the wafer 1 efficiently hits the air blown from the air blowing port 19. Move to the cleaning position. However, at this time, no air is blown out from the air blowing port 19, and the exhaust fan unit B10 is not performing the exhausting operation. At this time, the flow rate (flow velocity) of the air blown from the FFU 3 and the exhaust air flow rate (flow velocity) of the exhaust fan unit A9 that exhausts air from the exhaust port A11 are controlled, and the flow velocity of the air inside the sample chamber 17 is calculated / experimented. Control to the optimum value for cleaning obtained from.

  FIG. 8 shows a schematic view during cleaning. If it moves to a cleaning position, air will blow out from the air blowing outlet 19, and exhaust fan unit B10 will start exhaust operation simultaneously. As shown in FIG. 8, the wafer chuck 7 rotates slowly so that the air blown out from the air blowing port 19 uniformly hits the contact area with the wafer 1.

  When the air blown from the air blowing port 19 hits the contact portion of the wafer chuck 7 with the wafer 1, dust that has been generated and accumulated in the previous inspection operation is blown off. The dust thus blown is sucked from the exhaust port B18, passes through the exhaust duct 24, and is discharged out of the sample chamber by the exhaust fan unit B10. At this time, the number of rotations of the wafer chuck 7, the flow velocity / pressure of the air blown from the air blowing port 19, the flow velocity / pressure sucked by the exhaust port B18, and the like are all controlled to appropriate values. In addition, since the gripping piece 23 is an active part, the wafer chuck 7 stops rotating for a specified time at each gripping piece position, or the gripping piece 23 is opened and closed during the cleaning operation. Conceivable.

  Here, the cleaning position is provided at a downstream position inside the sample chamber 17, and the blowing direction of the air blowing port 19 is the same as the blowing direction of the FFU 3. Further, the exhaust port B18 is installed in the same direction as the exhaust port A11. As described above, even if there is dust that cannot be sucked out by the exhaust port B18, the dust flows up from the exhaust port A11 through the exhaust duct 24 by riding on the flow inside the sample chamber 17 created by the FFU 3 and the exhaust port A11. Since it is discharged via the fan unit A9, contamination inside the sample chamber 17 due to scattered dust can be prevented. Further, since the flow velocity of the air inside the sample chamber 17 is controlled to the optimum value, the blown dust is exhausted from the exhaust port A11 without diffusing into the sample chamber 17.

  When the cleaning of the wafer chuck 7 is completed, the air blowing from the air blowing port 19 stops and the rotation of the wafer chuck 7 also stops. The stage unit 12 is moved to the standby position shown in FIG. 4 using each operation unit of the stage unit 12. At this time, the shutter 20 remains closed, and the exhaust fan unit B10 continues the exhaust operation. While the cleaning is completed and waiting, the flow rate inside the sample chamber 17 is kept at the optimum value for cleaning. Even during standby, the flow rate inside the sample chamber 17 is maintained at the optimum value for cleaning, so that the cleanliness inside the sample chamber 17 can be returned to the optimum value for the inspection operation in a short time. However, the exhaust operation of the exhaust fan unit B10 may be stopped depending on conditions.

  The shutter 20 remains closed and the exhaust fan unit B10 continues the exhaust operation until the standby time confirmed in advance by calculation and experiment. However, the exhaust operation of the exhaust fan unit B10 may be stopped depending on conditions. When the prescribed waiting time has passed, the shutter 20 is lowered to open the transfer port 21, and at the same time, the exhaust fan unit B10 is stopped.

  By the above operation, the wafer chuck 7 is cleaned automatically and non-contactly.

  In order to install and utilize the cleaning unit, a dedicated item must be provided on the operation screen (or operation surface) of the apparatus.

  When provided on the operation screen, it is desirable to provide it on the maintenance screen. This is because the number of people who can operate the device on the maintenance screen is limited to those who have received special education. When it is provided on the operation surface, it is preferably provided inside the door with a controlled key. The key in this case is preferably managed by a person who has received special education. In any case, it is desirable for a person who has received a special education to control the cleaning unit.

  The operation screen (or the operation surface, here, unified to the operation screen) includes the cleaning timing, the flow rate of air blown from the air outlet 19 (flow velocity), the flow rate of air exhausted from the exhaust port B18 (flow velocity), and FFU3. The flow rate (velocity) of the air blown from the air, the flow rate (velocity) of the air exhausted from the exhaust port A11, the number of rotations of the wafer chuck 7 during cleaning, the stop location and stop time of the rotating wafer chuck 7, and the gripping piece 23 It should be possible to set the opening / closing and speed of the door, the waiting time after the end of cleaning, etc. However, these items are basically set to optimum values, and can be changed when a problem occurs or the environment changes.

  The following items should be selected and set for cleaning. (1) a fixed time every day, (2) after inspecting a predetermined number of wafers, (3) after a predetermined sequence is completed, (4) manual start, and (5) individual operation. (4) “Manual start” means that a person who has received a special education presses a button such as “start cleaning” in the operation screen to start a cleaning operation with a predetermined content. (5) Individual operation means that the operations of all the mechanism units necessary for the cleaning work are individually operated.

<Other embodiments>
Although the embodiments of the present invention have been described above, these embodiments can be variously modified and combined within the spirit of the present invention. For example, the back surface of the wafer to be inspected can be kept clean by using the back surface suction method instead of the edge grip method and cleaning the entire suction surface. Alternatively, it is possible to clean not only the wafer chuck but also other dust generating factors.

  Further, the fluid to be sprayed onto the substrate to be inspected may be replaced with pure water, alcohol, or the like instead of high clean air, or after cleaning with pure water, alcohol, or the like, high clean air may be sprayed and dried.

  The installation positions of the air outlet 19 and the exhaust port B18 in the sample chamber 17 do not have to be limited to the downstream position in the sample chamber 17 (immediately before the exhaust port A11).

  The wafer chuck 7 may also be an operation system using an XY stage instead of a rotary system.

  As a method of controlling the flow rate inside the sample chamber 17 to the optimum value for cleaning, the FFU 3 and the exhaust fan unit A are not controlled, but a rectifying plate (not shown) installed in the sample chamber 17 in advance is controlled. The flow rate inside the sample chamber 17 may be controlled to the optimum value for cleaning.

1 Wafer 2 Inspection optical system 3 FFU
4 Rotating mechanism 5 Horizontal moving mechanism 6 Vertical moving mechanism 7 Wafer chuck 8 Illumination optical system 9 Exhaust fan unit A
10 Exhaust fan unit B
11 Exhaust port A
12 Stage unit 13 Detection unit 14 Case 15 Support unit 16 Optical system support unit 17 Sample chamber 18 Exhaust port B
19 Air outlet 20 Shutter 21 Delivery port 22 Wafer receiving base 23 Grip piece 24 Exhaust duct 25 Cleaning unit 26 Exhaust side support 27 High performance air filter

Claims (9)

In an inspection device for inspecting a substrate,
A fan filter unit;
An inspection optical system disposed behind the air flow from the fan filter unit;
A cleaning unit disposed behind the inspection optical system;
An exhaust port disposed behind the cleaning unit;
And an exhaust unit connected to the exhaust port. The inspection apparatus according to claim 1,
An inspection apparatus for controlling the flow rate of the fan filter unit and the flow rate of the exhaust unit. The inspection apparatus according to claim 1,
Has a wafer chuck for mounting said substrate,
The cleaning unit is an inspection apparatus that supplies air, pure water, or alcohol to the wafer chuck. The inspection apparatus according to claim 1 ,
A wafer chuck for mounting the substrate;
The cleaning unit is an inspection apparatus that supplies pure water or alcohol to the wafer chuck and then supplies air to the wafer chuck. The inspection apparatus according to claim 1,
The cleaning unit is an inspection device having a filter. The inspection apparatus according to claim 3, wherein
The movable portion of the wafer chuck, when the air from the cleaning unit or the pure water or the alcohol, is supplied, the inspection device for opening and closing operation. Move the wafer chuck backward from the inspection optical system against the air flow from the fan filter unit ,
A wafer chuck cleaning method for cleaning the wafer chuck behind the inspection optical system. The method for cleaning a wafer chuck according to claim 7,
Cleaning of the wafer chuck for controlling the exhaust volume of air supplied to the flow rate and the wafer chuck of the air supplied to the wafer chuck. The method for cleaning a wafer chuck according to claim 7,
The cleaning unit is a cleaning method for a wafer chuck in which pure water or alcohol is supplied to the wafer chuck and then air is supplied to the wafer chuck .

Images