JP2840858B2 - Wafer inspection method and inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a wafer inspection method and an inspection apparatus that can quickly inspect the surface roughness, thickness and warpage of a semiconductor wafer after grinding the semiconductor wafer with a grinder or the like, and can be effectively used by being incorporated in an automatic grinding apparatus. It is.

[Prior art]

In general, in the surface grinding of a semiconductor wafer with a grindstone, the quality of the processed product depends on the roughness of the processed surface, the uniformity of the thickness after processing, the warpage of the processed product, other micro crystal defects, etc. Be evaluated. As for inspection means for quality control in this type of surface grinding, particularly for inspection of surface roughness and thickness, there is known an automatic grinding apparatus in which each of these sensors is separately arranged. I have. For example, a configuration disclosed in Japanese Patent Application Laid-Open No. 63-207559 by the same applicant is well known as a conventional example.
In this conventional example, a detecting means for detecting the thickness of the wafer is provided near a grinding portion of a chuck table in a grinding unit, and a detecting means for surface roughness is provided near a measuring table in a cleaning unit.
However, means for detecting the warped state of the wafer after the grinding is not provided, and the above is a problem of the crystal material itself before cutting into a wafer. Detection is possible.

[Problems to be solved by the invention]

As is apparent from the conventional example, a means for detecting the thickness of the wafer after grinding and a means for detecting the surface roughness are provided, but each is provided in a separate unit, and each part is provided. Has been detected in some places. Therefore, the data of the quality control in the surface grinding of the wafer is performed as data for detecting the processing state in each part, and is not data for each individual wafer, but is data for each individual wafer. In such a case, it is necessary to reassemble each data, which is a troublesome task. In particular, since the detection of the thickness of the wafer ground by the grindstone is performed in a state where the wafer is attracted to the chuck table, the entire distortion and warpage of the wafer cannot be detected. As shown in FIG. 4, when the wafer a is ground with a grindstone, a large number of fine cracks b are inevitably generated on the ground surface, and the generation of the cracks b is generated on the wafer a by warping. appear. Conversely, the depth or amount of the crack b can be determined in the warped state, and at the same time, the state of the grindstone can be determined. Therefore, the problem is that not only the surface roughness and thickness but also the state of warpage are detected as quality control data in wafer surface grinding, and the state of work in each process is checked to improve the quality control. Have.

[Means for Solving the Problems]

As a specific means for solving the problem of the above-mentioned conventional example, the present invention captures the surface of the chuck table with a first sensor,
The position is detected by the detecting means and stored in a memory as first data. The ground wafer is placed on the chuck table with the ground surface facing up, and is not held in close contact with the chuck table. The surface of the chuck table is detected and its position is detected by the detection means, stored in a memory as second data, the wafer on the chuck table is held in close contact with the chuck table, and the same sensor is captured by the first sensor.
The position is detected by the detecting means and stored in a memory as third data, and the warpage of the wafer is calculated based on the second and third data among the data stored in the memory. A wafer inspection method characterized by calculating the thickness of the wafer based on the data of (1) and (2), after the wafer on the chuck table is held in close contact with the chuck table, the surface of the wafer is measured by a second sensor. In addition to detecting the roughness, the chuck table and the first and second sensors are relatively moved in the horizontal direction, the wafer is inspected at two or more sites, and the chuck table is suctioned. Therefore, the above-mentioned detections can be performed accurately and promptly. Further, as a specific device for carrying out the above method, the present invention provides a chuck table for holding a wafer, and a sensor arm which is opposed to the surface of the chuck table and which can move in a direction relatively approaching or separating from the chuck table. The sensor arm is provided with a first sensor for detecting the thickness and warpage of the wafer held on the chuck table, and a second sensor for detecting the surface roughness of the wafer, Provided is a wafer inspection device, wherein a position detection means for detecting the position of the sensor arm is provided, wherein the chuck table is rotatable and has a function of holding the wafer by suction, The sensor arm can swing in parallel to the surface of the chuck table. The inspection apparatus is incorporated in a grinding apparatus for grinding the surface of a wafer, and continuously inspects the thickness and distortion of the wafer ground in the grinding process. Immediately judge pass / fail and feed back the judgment or detection data to the grinding device to manage the grinding mode or jig status at each grinding site, ie, the abrasion state of the grinding wheel, the clogging state, the contact state with the wafer, etc. You can do it.

【Example】

Next, the present invention will be described in more detail with reference to the illustrated embodiment. Reference numeral 1 denotes a chuck table, which is appropriately rotated in a predetermined direction via a rotary shaft 2 similarly to a commonly used one. And the rotation axis 2
A switching valve 3 communicating with the vacuum means and a switching valve 4 communicating with blowing means for releasing the suction holding and ejecting the air for applying suction to the chuck table surface and holding the suction through the inside. These switching operations are performed selectively and automatically as appropriate. A sensor arm 5 is disposed above the chuck table 1, and the base of the sensor arm 5 is a support shaft 6.
A first sensor 7 of a capacitance type for electrically detecting the thickness and warpage of the wafer at the tip end thereof, and a second sensor for optically detecting the surface roughness of the wafer. And two sensors 8. The rotation and the vertical movement of the support shaft 6 are performed by driving or detecting means A, and the position of the rotation and the vertical movement is properly detected. That is, the pulse motor 9 is engaged with the lower end of the support shaft 6, the sensor arm 5 is selectively rotated, and the tip is driven so that the tip is located substantially at the center of the upper portion of the chuck table 1. Is detected. Further, the support shaft 6 is rotatably and slidably held by a holder member 10 via a bearing mechanism 11. The bearing mechanism 11 is a stroke ball bearing for rotation and linear motion, in which the support shaft 6 freely rotates without eccentricity or blurring, and slides quickly in the vertical direction. A drive shaft 12 is disposed on the holder member 10 in parallel with the support shaft 6, and upper and lower ends of the drive shaft 12 are
The bearings 15 and 16 of the frames 13 and 14 provided on the bearing 10 respectively bear the bearings, and the lower end of the drive shaft 12 is engaged with a driving pulse motor 17. A screw portion 12a is provided near the upper end of the drive shaft 12, and a horizontal member 18 having a substantially central portion engaged with the screw portion 12a is provided. One end of the horizontal member 18 is rotatable on the support shaft 6. Are engaged via a bearing member 19 and via a stopper member 20 so as not to slide. Furthermore,
At the other end of the horizontal member 18, a position detecting means B for detecting the vertical movement of the sensor arm 5 is provided. That is, the position detecting means B is provided in a hanging state or a linear scale 21.
And a reading head for reading the scale of the linear scale
The read head 22 is provided on the holder member 10 side in proximity to the linear scale 21. In the figure, reference numeral 23 denotes a ground semiconductor wafer, and 24 denotes a sub-table, which has substantially the same level and conditions as the chuck table 1, and is disposed at a position close to the chuck table. .

[Description of operation]

The wafer inspection apparatus of the present invention having the above configuration is used as a measurement or inspection unit incorporated with an appropriate grinding unit and a cleaning unit, and the inspection is performed by setting an inspection point in advance and storing the memory. deep. For example, regarding inspection of wafer warpage, partial distortion, and thickness, the first sensor 7 is brought close to the center of the chuck table 1 and a plurality of locations around the center, respectively.
The distance or the height is detected by the linear scale 21 and the read head 22, and a voltage value or a frequency at a certain level at the position is stored in memory to set an inspection point. In this case, the pulse motor 9 and the driving pulse motor 17 are driven, and the chuck table 1 is intermittently rotated at each inspection point corresponding thereto, and the detection data indicating the distance or height at each position is stored in the memory. This is stored, and this is used as the first data. Then, in an actual inspection, after the wafer 23 is ground and cleaned, the wafer 23 is mounted on the chuck table 1 with a ground surface up by an appropriate transport means. In this state, the pulse motor 9 is driven to rotate the support shaft 6 by a predetermined amount based on the memory of the inspection point, and the sensor arm 5
Is positioned substantially at the center of the upper portion of the chuck table 1, and at this position, data for detecting the degree of warpage of the wafer 23 is first stored. That is, by driving the drive pulse motor 17 to rotate the drive shaft 12 and lower the horizontal member 18, the support shaft 6, the sensor arm 5 and the linear scale 21 are lowered, and the first sensor 7 Gradually approaches the wafer 23. Then, when the voltage value or frequency detected by the first sensor 7 matches the stored detection data, the value of the linear scale 21 is read by the read head 22, and this is stored in the memory as second data. Next, the switching valve 3 is opened to apply a suction action to the chuck table surface to cause the wafer 23 to be suction-held, and in this state, the drive pulse motor 17 is driven again. By moving the sensor arm and rotating the chuck table, the first sensor 7 is gradually approached to the wafer 23 in the same manner as described above, and the voltage value or frequency detected by the first sensor 7 for each inspection point is stored in the memory. When the data coincides with the detected data, the values of the linear scales 21 are read by the reading head 22 and stored in a memory as third data. Then, by comparing the respective detection data stored in these memories, the warpage and thickness of the wafer 23 can be accurately detected. That is, of the detection data stored in the memory, the warp of the wafer is detected by the second data and the third data, and the thickness of the wafer can be detected by the first data and the third data. In addition, in the state where the wafer 23 is sucked, the second sensor 8 is also operated simultaneously with the detection of the thickness to detect the roughness of the ground surface of the wafer 23 at each point. In this case, the detection by the second sensor 8 is performed in substantially the same manner as in the conventional example. Each detection data obtained in this way is compared with data as a wafer which is set and stored in advance, and is made into data about each wafer to be inspected, based on the data, the state of the grinding wheel, The state of contact with the wafer can be grasped, and a signal based on the data can be fed back to control the entire grinding system, that is, to instruct an exchange of a grinding wheel, an instruction for dressing, an instruction to lower the grinding wheel, and the like. The quality of the inspected wafer 23 is determined based on the detection data, and the good wafer is conveyed to be stored in a predetermined wafer cassette as in the conventional example. It is transported to another system. or,
Since the sub-table 24 is installed at the same level and under the same conditions as the chuck table 1, it is possible to use the sub-table 24 at any time to check the data of the chuck table, for example, during a wafer inspection.

【The invention's effect】

As described above, in the wafer inspection method according to the present invention, the surface of the chuck table is captured by the first sensor,
The position is detected by the detecting means and stored in a memory as first data. The ground wafer is placed on the chuck table with the ground surface facing up, and is not held in close contact with the chuck table. The surface of the chuck table is detected and its position is detected by the detection means, stored in a memory as second data, the wafer on the chuck table is held in close contact with the chuck table, and the same sensor is captured by the first sensor.
The position is detected by the detecting means and stored in a memory as third data, and the warpage of the wafer is calculated based on the second and third data among the data stored in the memory. By calculating the thickness of the wafer based on the above data, especially by inspecting the degree of wafer warpage, the depth or amount of cracks generated during grinding different from surface roughness can be detected. It is possible to check the condition of the grindstone and to suppress the generation of defective wafers, thereby achieving an excellent effect of improving quality control. Further, after the wafer on the chuck table is held in close contact with the chuck table, the surface roughness of the wafer is detected by the second sensor, and the chuck table and the first and second sensors are relatively moved in the horizontal direction. To inspect the wafer at two or more sites, and hold the wafer in close contact with the chuck table by sucking the wafer.
By detecting the thickness of the wafer, the inspection can be performed even more accurately, and the excellent effect that the quality control can be further improved can be achieved. Further, a wafer inspection apparatus for performing the above method includes a chuck table for holding the wafer, and a sensor arm which is opposed to the surface of the chuck table and which can move in a direction relatively approaching or separating from the chuck table. A first arm for detecting the thickness and warpage of the wafer held on the chuck table.
And a second sensor for detecting the surface roughness of the wafer, and a position detecting means for detecting the position of the sensor arm are provided. Since the required inspection on one wafer can be performed accurately at one place, data for each wafer can be easily collected, and the data is fed back to facilitate the management of grinding wheels and the like in a grinding device. Play. The chuck table is rotatable and has a function of sucking and holding the wafer and a function of releasing the suction holding, and the sensor arm can swing in parallel with the surface of the chuck table. The inspection apparatus can be incorporated in a grinding apparatus for grinding a surface of a wafer, and continuously inspects the thickness of the wafer ground in the grinding process without contacting the wafer. The quality of the wafer can be determined more accurately and promptly based on the data based on the data, and the data can be fed back to control the cutting mode or the state of the jig at each cutting portion, which is an excellent effect.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a wafer inspection apparatus according to the present invention, FIG. 2 is a schematic plan view of the apparatus, and FIG. 3 is a wafer on a chuck table in the apparatus. FIG. 4 is an enlarged sectional view showing a part of a general wafer after grinding. DESCRIPTION OF SYMBOLS 1 ... Chuck table 2 ... Rotating shaft, 3, 4 ... Switching valve 5 ... Sensor arm, 6 ... Support shaft 7 ... First sensor, 8 ... Second sensor 9 ... Pulse motor, 10 Holder member 11 Bearing mechanism 12 Drive shaft 12a Screw part 13, 14, Frame 15, 16, 19 Bearing part 17 Pulse motor 18 for driving 18 Horizontal member, 20 stopper member 21 linear scale 22 reading head 23 semiconductor wafer 24 subtable A driving or detecting means B position detecting means

Claims (7)

(57) [Claims] The surface of a chuck table is captured by a first sensor, and its position is detected by a detecting means.
The data is stored in a memory, and the ground wafer is placed on the chuck table with the ground surface facing up, and the surface is caught by the first sensor without being held in close contact, and the position is detected by the detection means. Detected, stored in a memory as second data, holding the wafer on the chuck table in close contact with the chuck table, capturing the same site with the first sensor,
The position is detected by the detecting means and stored in a memory as third data, and the warpage of the wafer is calculated based on the second and third data among the data stored in the memory. A method for inspecting a wafer, comprising calculating a thickness of the wafer based on the above data. 2. The wafer inspection method according to claim 1, wherein the surface roughness of the wafer is detected by a second sensor after the wafer on the chuck table is held in close contact with the chuck table. 3. The apparatus according to claim 1, wherein the chuck table and the first and second sensors are relatively moved in the horizontal direction, and the wafer is inspected at two or more portions.
(2) The wafer inspection method described in (2). 4. The method according to claim 1, wherein the wafer is held in close contact with the chuck table by sucking the wafer.
(2) The method for inspecting a wafer according to (3). 5. A chuck table for holding a wafer;
A sensor arm facing the surface of the chuck table and movable in a direction relatively approaching or separating from the chuck table, wherein the sensor arm has a thickness and a warp of a wafer held by the chuck table. A first sensor for detecting the surface of the wafer; a second sensor for detecting the surface roughness of the wafer; and a position detecting means for detecting the position of the sensor arm. . 6. The chuck table is rotatable and has a function of holding the wafer by suction, and a function of releasing the suction from the wafer. The sensor arm is arranged in parallel with the surface of the chuck table. The wafer inspection apparatus according to claim 5, wherein the wafer inspection apparatus can swing. 7. The wafer inspection apparatus according to claim 5, wherein the apparatus is incorporated in a grinding apparatus for grinding a surface of a wafer.