JP3940819B2 - Semiconductor wafer surface shape measuring apparatus and surface shape measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor wafer surface shape measuring apparatus and a surface shape measuring method for measuring the shape of the surface of a semiconductor wafer such as a silicon wafer with high accuracy.
[0002]
[Prior art]
A semiconductor wafer such as a silicon wafer is mainly used as a substrate of a semiconductor device. In a semiconductor manufacturing process, a circuit pattern of the semiconductor device is formed on the semiconductor wafer by using an exposure apparatus and subjected to fine processing. It has been broken. In the case of forming such a fine pattern, the semiconductor wafer that is a workpiece is required to have a high degree of flatness with less unevenness than the depth of focus of the exposure apparatus. Therefore, when a semiconductor wafer is manufactured as a product, the inspection of the flatness is one of important quality inspections.
[0003]
Currently, the following two methods are taken as methods for measuring the flatness of a semiconductor wafer. One is a method of holding a semiconductor wafer in the same manner as when it is mounted on the exposure apparatus and measuring the surface shape of the held state. Another method is a method in which the thickness of the semiconductor wafer is measured and the back surface reference is obtained by calculation, and then the state held in the exposure apparatus is virtually obtained to calculate the flatness. Each of these methods has its own characteristics, but at present, a method of calculating the flatness by measuring the thickness is generally used. This is because the method can be measured in a non-contact manner and is preferable from the viewpoint of foreign matter adhering to the back surface of the wafer.
[0004]
In the case of a surface shape measuring apparatus using a pair of opposed laser displacement meters, the pair of laser displacement meters is disposed on a fixed stage with a predetermined distance therebetween, and a semiconductor wafer is held in a space therebetween. The semiconductor wafer is held so that its main surface is perpendicular to the line connecting the laser displacement meters facing each other, and is relatively moved in two axial directions in the XY direction in the main surface. It is controlled to sample data related to the shape at a plurality of measurement points on the front and back surfaces of the semiconductor wafer. The shape data obtained in this way is compared with a reference sample with a known thickness to determine the thickness of the entire wafer surface, and a virtual back surface reference is calculated to determine the flatness of the semiconductor wafer.
[0005]
[Problems to be solved by the invention]
When performing such high-precision flatness measurement, it is necessary to accurately align the spot position of the laser displacement meter being used, and to adjust the parallelism of the laser light from the laser displacement meter accurately. is there. However, the pair of laser displacement meters is only fixed on the fixed stage with screws, and the beam emission direction of the laser light cannot be finely adjusted. If the beam emission directions of the laser beams of the pair of laser displacement meters are not parallel but slightly deviated, the obtained data lacks accuracy, and meaningful quality inspection cannot be performed.
[0006]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned technical problems, and an object thereof is to provide a semiconductor wafer surface shape measuring device and a surface shape measuring method for measuring the surface shape of a semiconductor wafer with high accuracy. To do.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the semiconductor wafer surface shape measuring apparatus for measuring the surface shape of the semiconductor wafer of the present invention,
A holding unit that holds the semiconductor wafer to be measured, and a measuring unit that is disposed to face the main surface of the semiconductor wafer held by the holding unit and measures the shape of the main surface of the semiconductor wafer. on the sensor base of the unit measuring apparatus, the opposite to the semiconductor wafer front and back surfaces are a pair spaced apart by a predetermined distance, the measuring means is supported on said sensor base, hand measurement is characterized by having a position angle adjustment means to adjust the angle of the measuring means moves the projection in three-dimensional directions.
[0008]
As an example, the the holding portion of the semiconductor wafer is provided with a movable member operated by moving in parallel the semiconductor wafer in a plane, said measuring means a pair of laser displacement which is placed to face the semiconductor wafer The position angle adjusting means adjusts the position of the measuring means so that the amount of reflected light of the pair of laser displacement meters disappears at the end of the semiconductor wafer moved by the moving member.
Further , the position angle adjusting means is configured by using an orthogonal triaxial mechanism such as an xyz stage capable of adjusting the position of the measuring means , and more preferably, the position angle adjusting means is a position of the measuring means . And an xyz-θ stage whose angle can be adjusted.
[0009]
In addition, a measuring method according to the present invention that achieves the above-described object is a method for measuring the surface shape of a semiconductor wafer . measurements Teto which a pair spaced apart by a predetermined distance on the sensor base opposite to the semiconductor wafer front and back surfaces is the position angle adjusting means for moving the angle of the three-dimensional directions is adjusted, measuring the The position of the measurement point on the semiconductor wafer and the measurement direction are adjusted, and the shape of the main surface of the semiconductor wafer is measured by the measurement means after the adjustment.
[0010]
As a preferred form thereof, the holding unit is capable of translating the semiconductor wafer in a plane by a moving member, and the measurement hand throw uses a pair of laser displacement meters arranged to face the semiconductor wafer. The position angle adjusting means adjusts the position of the measuring means so that the amount of reflected light of the pair of laser displacement meters disappears at the end of the semiconductor wafer moved by the moving member.
The position of the measurement point on the semiconductor wafer is adjusted by the orthogonal three-axis mechanism, the measuring direction is adjusted by the angle adjusting mechanism. Further, in order to adjust the measuring direction, and adjusting the zero point by using the variation in the thickness is less than the measurement accuracy of the laser displacement gauge block gauge.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A semiconductor wafer surface shape measuring apparatus and surface shape measuring method according to an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are views showing a surface shape measuring apparatus for a semiconductor wafer according to this embodiment. FIG. 1 is an enlarged perspective view of a pair of laser displacement meters as main parts. FIG. It is a side view of the surface shape measuring apparatus of a semiconductor wafer.
[0012]
As shown in FIG. 2, the surface shape measuring apparatus according to the present embodiment has, as its main structure, a pair that functions as a holding unit 31 attached to the measuring apparatus main body 30 and a part of a laser displacement meter that forms the measuring means. Laser sensor blocks 11, 12, and xyz-θ stages 21, 22 which are position angle adjusting means for supporting the laser sensor blocks 11, 12. A silicon wafer 1 as a semiconductor wafer is mounted on the holding portion 31 such that its main surface is vertical, and a pair of laser sensor blocks 11 and 12 are disposed on the silicon wafer 1 so as to face both main surfaces. ing. The pair of laser sensor blocks 11 and 12 are mounted on xyz-theta stages 21 and 22 that move in a three-dimensional direction and adjust their angles.
[0013]
The measuring apparatus main body 30 has moving members 35 and 36 for translating and scanning the silicon wafer 1 in a plane on an upright portion 34 upright on a base 32 attached using a plurality of feet 33. It is attached. The moving member 35 is for moving the silicon wafer 1 supported between the arms 37 in the vertical direction, and the moving member 36 is for moving the silicon wafer 1 in the horizontal direction. The moving member 35 is fixed to the upright portion 34, and a moving member 36 is attached to a movable part of the moving member 35. The movable part of the moving member 36 is connected to the arm 37 via the arm base end member 38. The arm 37 is configured so that the edge of the silicon wafer 1 is sandwiched between the tips of a pair of curved flat-plate arms extended substantially downward, and is opened and closed each time the silicon wafer 1 is replaced. Here, the holding portion 31 is a mechanism for holding the silicon wafer 1, and mainly includes an arm 37, an arm base end member 38, a pair of moving members 35 and 36, an upright portion 34, a base 32, and the like. Is included. Further, the silicon wafer 1 is scanned for measurement over the entire surface thereof by the moving members 35 and 36. An example of the scanning is shown in FIG.
[0014]
FIG. 1 shows a pair of laser sensor blocks 11 and 12. Each of the laser sensor blocks 11 and 12 can emit a laser beam and receive the laser beam to measure the distance to the object to be measured by a non-contact method. As shown in FIG. 1, the pair of laser sensor blocks 11 and 12 have their laser light emission directions, that is, measurement directions opposed to each other, and are arranged at a predetermined distance so that they exist in a space between them. It is possible to detect the thickness and surface shape of an object with extremely high speed and high accuracy. Each of the laser sensor blocks 11 and 12 sends a measurement data signal to an analysis device (not shown) via the cable 23, and the analysis device analyzes the data instantaneously, and the surface shape and thickness of the object, in this case, the silicon wafer 1. Output data about.
[0015]
In this embodiment, such a pair of laser sensor blocks 11 and 12 are supported by xyz-theta stages 21 and 22 which are position angle adjusting means, respectively, so that the position and angle can be adjusted. Each of the xyz-θ stages 21 and 22 has tables 13 and 14 and support columns 15 and 16, respectively. The laser sensor blocks 11 and 12 are fixed on the tables 13 and 14, respectively. The column portions 15 and 16 are attached to the upper end of the sensor base 39 of the measurement apparatus main body 30. Then, as a mechanism for moving these tables 13, 14, an x table and an x table guide shaft that are movable in a horizontal direction (x direction) perpendicular to the main surface of the silicon wafer, and a silicon wafer perpendicular to the x direction. An orthogonal three-axis mechanism having a y table and a y table guide shaft movable in a horizontal direction (y direction) in the in-plane direction of the main surface, and a z table and a z table guide shaft movable in a vertical direction (z direction) And a rotation axis as an angle adjustment mechanism for finely adjusting the laser beam emission direction of each of the laser sensor blocks 11 and 12 within a horizontal plane. The x table guide shaft of each of the xyz-theta stages 21 and 22 is connected to the x axis adjustment knob 17, the y table guide axis is connected to the y axis adjustment knob 18, and the z table guide axis is the z axis adjustment knob. 19 is connected. The rotation axes of the xyz-θ stages 21 and 22 are connected to the rotation adjustment knob 20. By rotating these knobs 17, 18, 19, and 20, the position and angle of each laser sensor block 11 and 12 can be finely adjusted.
[0016]
When measuring the surface shape of the silicon wafer 1 using the surface shape measuring apparatus of this embodiment having such a configuration, first, the focal length of the laser light from the laser sensor blocks 11 and 12 is determined on the silicon wafer 1. In order to adjust the position, orthogonal three-axis mechanisms of the xyz-theta stages 21 and 22 are used, and in order to adjust the parallelism of the laser beam, each x The angle adjustment using the rotation adjustment knob 20 of the −yz−θ stages 21 and 22 is performed. In particular, fine adjustment of the angle in the measurement direction greatly contributes to improving accuracy, as will be described later.
[0017]
When measuring the surface shape, zero adjustment (calibration) of the sensor is performed. In the surface shape measuring apparatus of the present embodiment, the position and angle are adjusted in order to measure the surface shape of the silicon wafer 1. For example, the zero adjustment of the sensor can be advanced by the following method. . First, a block gauge 40 as shown in FIG. 3 is used to adjust the parallelism, and then the focal position is adjusted using the edge of the silicon wafer 1.
[0018]
Specifically, a block gauge 40 whose thickness variation (including warpage) is less than the accuracy of the surface shape measuring device (for example, 5/100 microns) is held by a slidable jig (not shown). As shown in FIG. 3, it is interposed between a pair of laser sensor blocks 11 and 12. The jig is operated to slide the block gauge 40 so that the position of each laser spot from the laser sensor blocks 11 and 12 is on the end of the block gauge 40. At that position, the orthogonal triaxial mechanism in the x-axis direction of the xyz-θ stages 21 and 22 of the laser sensor blocks 11 and 12 is operated so that the focal position is on the block gauge 40. To match.
[0019]
Next, the block gauge 40 is moved little by little in the opposite direction, and the outputs from the pair of laser sensor blocks 11 and 12 are confirmed. On the basis of the output data from either one of the sensors, the xyz-theta stages 21 and 22 are arranged so that the display (output value) from each laser sensor block 11 and 12 matches. The rotation adjustment knob 20 is adjusted. The adjustment of the rotation adjustment knob 20 is to adjust the angle of the laser sensor blocks 11 and 12 in the measurement direction, and the parallelism is achieved by matching the displayed values.
[0020]
When such parallelism adjustment is performed between the laser sensor blocks 11 and 12, the silicon wafer 1 is held between the arms 37 in a state where actual measurement is performed, and this time the silicon wafer 1 is moved in the X direction ( The laser beam spot is guided to the vicinity of the edge of the silicon wafer 1. The sensors of the laser sensor blocks 11 and 12 cannot detect reflected light at the end of the silicon wafer 1. Therefore, while moving the silicon wafer 1 by a small amount in the outer peripheral direction, the position where the sensors of the laser sensor blocks 11 and 12 cannot detect the reflected light of the laser beam is confirmed. The y stage (X direction on the wafer) of the xyz-θ stages 21 and 22 is adjusted. Next, the same method is also performed in the Y direction of the wafer (corresponding to the z-axis direction of the xyz-θ stage), and the Z-stages of the xyz-θ stages 21 and 22 are adjusted. . By such zero point adjustment, the measurement positions and measurement angles of the pair of laser sensor blocks 11 and 12 are finely adjusted, and high-precision measurement is possible.
[0021]
Next, the effect of fine adjustment of the position and angle of the surface shape measuring apparatus of the present embodiment will be described based on experiments conducted by the present inventors with reference to FIGS. FIG. 5 and FIG. 6 show the three-dimensional image of the data from the laser displacement meter. FIG. 5 shows the flatness measured without fine adjustment. FIG. 6 shows the flatness with fine adjustment. It is measured. In the example of FIG. 5, the overall shape of the surface of the silicon wafer shows a characteristic jump almost symmetrically from the vicinity of the center, and it is shown that the accuracy of the portion is deteriorated. On the other hand, as shown in FIG. 6, in order to measure the flatness of the silicon wafer 1, the spot position and parallelism (angle of the emission direction) of the laser sensor blocks 11 and 12 are adjusted. 5, there is no characteristic jump as shown in FIG. 5, and it can be seen that the accuracy is improved accordingly.
[0022]
7 and 8 are similar data, and the output values in the respective regions of the silicon wafer 1 are shown as the results of scanning. The numerical values shown in FIG. 7 are obtained by measuring the flatness without fine adjustment, and FIG. 8 is obtained by measuring the flatness with fine adjustment. It is shown that the data obtained by measuring the flatness with fine adjustment (FIG. 8) is a highly accurate data with lower numerical values and less errors.
[0023]
As described above, with the recent high integration of semiconductor devices, the level of flatness required for semiconductor wafers has become increasingly severe. However, as in the surface shape measuring device of this embodiment, in actual measurement, By finely adjusting the focal position of the laser beam and its parallelism, it is possible to reliably measure the required flatness. In particular, it is effective not only for measuring the flatness of semiconductor wafers that are currently required, but also for measuring the flatness of next-generation semiconductor wafers, and can be an important elemental technology for manufacturing high-quality products. .
[0024]
In the above-described embodiment, the surface shape of the semiconductor wafer is measured using a pair of laser displacement meters. However, other displacement sensors such as a capacitance sensor or an atomic force probe are used as the measuring means. It may be configured. In this embodiment, the xyz-θ stage is used, but it is also possible to use a position angle adjusting unit that scans in another direction.
[0025]
【The invention's effect】
As is apparent from the above description, according to the surface shape measuring apparatus and surface shape measuring method of the semiconductor wafer of the present invention, the surface shape measurement accuracy is greatly improved, and the flatness required for current and next-generation semiconductor wafers. Measurement corresponding to quality becomes possible.
[Brief description of the drawings]
FIG. 1 is an enlarged perspective view of a main part of an example of a surface shape measuring apparatus for a semiconductor wafer according to the present invention.
FIG. 2 is a side view showing the entire apparatus of an example of a surface shape measuring apparatus for a semiconductor wafer according to the present invention.
FIG. 3 is a plan view showing a pair of laser sensor blocks and a block gauge used for zero point adjustment in the semiconductor wafer surface shape measuring apparatus of the present invention.
FIG. 4 is a conceptual diagram showing a method for scanning a semiconductor wafer.
FIG. 5 is a three-dimensional view based on output data of an example in which the flatness of a silicon wafer is measured without fine adjustment.
FIG. 6 is a three-dimensional view based on output data of an example of measuring the flatness of a silicon wafer by performing fine adjustment according to the present invention.
FIG. 7 is a diagram showing output data on a silicon wafer in an example in which the flatness of the silicon wafer is measured without fine adjustment.
FIG. 8 is a diagram showing output data on a silicon wafer in an example in which the flatness of the silicon wafer is measured by performing fine adjustment according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon wafer 11, 12 Laser sensor block 21, 22 XYZ- (theta) stage 31 Holding part 40 Block gauge

Claims (8)

In a semiconductor wafer surface shape measuring device for measuring the surface shape of a semiconductor wafer,
A holding unit for holding a semiconductor wafer to be measured;
A measuring hand throw arranged to face the main surface of the semiconductor wafer held by the holding unit and measure the shape of the main surface of the semiconductor wafer ,
A pair of the measuring means are disposed on the sensor base of the measuring device, facing the front and back surfaces of the semiconductor wafer and spaced apart by a predetermined distance,
The said measuring means is supported on the sensor base, the surface shape of the semiconductor wafer characterized by having a position angle adjustment means to adjust the angle of the measuring means moves the measurement unit in three-dimensional directions measuring device. Wherein the holding portion of the semiconductor wafer is provided with a movable member operated by moving in parallel the semiconductor wafer in a plane, said measuring means is constituted by a pair of laser displacement meter which is placed to face the semiconductor wafer ,
2. The position angle adjusting means adjusts the position of the measuring means so that the amount of reflected light of the pair of laser displacement meters disappears at an end of the semiconductor wafer moved by the moving member. The surface shape measuring apparatus as described.   3. The surface shape measuring apparatus according to claim 1, wherein the position angle adjusting means uses an orthogonal triaxial mechanism capable of adjusting the position of the measuring means.   3. The surface shape measuring apparatus according to claim 1, wherein the position angle adjusting unit includes an xyz- [theta] stage capable of adjusting a position and an angle of the measuring unit. In the semiconductor wafer surface shape measuring method for measuring the surface shape of the semiconductor wafer,
After holding the semiconductor wafer to be measured on the holder,
A pair of measuring means arranged on the sensor base of the measuring device so as to face both the front and back surfaces of the semiconductor wafer and separated by a predetermined distance is measured by a position angle adjusting means for adjusting the movement and angle in a three-dimensional direction. the position and the measurement direction of the measuring points on the semiconductor wafer to adjust to,
A method for measuring a surface shape of a semiconductor wafer, comprising: measuring a shape of a main surface of the semiconductor wafer by the measuring means after the adjustment. The holding part is capable of moving the semiconductor wafer in a plane by a moving member, and the measuring means uses a pair of laser displacement meters arranged to face the semiconductor wafer ,
Claims wherein at the end of the semiconductor wafer to be moved in the moving member, said position angle adjusting means so that the reflected light amount of the pair of laser displacement meter disappears is characterized that you adjust the position of the measuring means 5. The surface shape measuring method according to 5. Position of the measurement point on the semiconductor wafer is adjusted by the orthogonal three-axis mechanism, a surface shape measuring method according to claim 5 or claim 6, wherein the measurement direction is characterized by being adjusted by the angle adjusting mechanism. 7. The surface shape measuring method according to claim 6, wherein , for adjustment of the measuring direction, zero point adjustment is performed using a block gauge whose thickness variation is equal to or less than the measuring accuracy of the laser displacement meter.

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