JPS6381940A - Measurenent of thickness of wafer - Google Patents

Abstract

PURPOSE:To conduct multipoint thickness measurement at high speed and with high efficiency and high precision by calculating the diameter of a wafer on the basis of movement until the edge of the wafer is detected through a measuring means from a predetermined position and performing the multipoint thickness measurement of the wafer by obtaining movement up to each measuring point on the basis of the calculating value. CONSTITUTION:A semiconductor wafer 1 is set at a prescribed position, and sucked and held by a vacuum chuck 2 from the lower side. The vacuum chuck 2 is moved linearly in the direction of the arrow B. The diameter of the wafer 1 is calculated from the movement of the wafer until the edge of the wafer 1 is detected by edge sensors S1, S2 from a first specified position. Movement until each measurement is acquired on the basis of the calculating value of the diameter, the wafer 1 is shifted by the vacuum chuck 2 at the measureing points, and the thickness of the wafer 1 at the measuring points is measured by a thickness measuring sensor 3. Thickness is measured at multipoints as a plurality of points such as points 6-10. The wafer 1 is returned and transferred in the direction of the arrow B after said measuring point 3, and the thickness of the wafer 1 is also measured at multipoints by the thickness measuring sensor 3 in the same manner as mentioned above during the returning and movement.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a technique for measuring the thickness of a wafer, and in particular to a technique that is effective when applied to measure the thickness at multiple points on a semiconductor wafer. be.

[Conventional technology]

The technology for measuring the thickness of semiconductor wafers is described in "Electronic Materials J, 1981 Special Issue, P70-P71.

By the way, the present inventor studied a multi-point thickness measurement technique for semiconductor wafers. The following are the techniques studied by the present inventor, and the outline thereof is as follows.

That is, when performing multi-point thickness measurement of a semiconductor wafer in an automatic flatness measurement operation of a semiconductor wafer, the first method is to suction and hold the semiconductor wafer on a rotatable vacuum chuck, and then move the top and bottom of the semiconductor wafer. A possible method is to place a non-contact sensor on the semiconductor wafer and measure the thickness at multiple points while rotating the semiconductor wafer.

Second, a method can be considered in which the semiconductor wafer is fixedly held and a plurality of non-contact sensors arranged above the semiconductor wafer are used to measure the thickness at multiple points according to the number of the sensors.

[Problem that the invention seeks to solve]

However, in the first method, when measuring the thickness of the central part of the semiconductor wafer, it is necessary to change the vacuum chuck and perform the measurement while scanning in a zigzag manner.
The inventors have discovered that there are major problems in that the measurement speed is slow and inefficient.

In addition, in the case of the second method, the measurement points are fixed, making it impossible to measure at too many measurement points, and the thickness measurement position accuracy is poor. Found out.

An object of the present invention is to provide a technique that allows multi-point thickness measurement of a wafer to be performed efficiently and at high speed.

Another object of the present invention is to provide a technique that can accurately measure the thickness of a wafer at multiple points.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Failure to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the diameter of a wafer, such as a semiconductor wafer, is calculated based on the mover used to move the wafer from a predetermined position until its edge is detected by the measuring means, and the amount of movement to each measurement point is determined based on the calculated value. It performs multi-point thickness measurements of acid wafers.

[Effect]

According to the above-mentioned means, by determining the diameter of the wafer, the thickness measurement position within the wafer can be accurately determined, and while the wafer is moving relative to the measuring means, the measuring means can measure the thickness at multiple points. can be efficiently measured with a high Mr.

〔Example〕

FIG. 1 is a schematic plan view for explaining a method for measuring the thickness of a semiconductor wafer according to an embodiment of the present invention.

In this embodiment, a semiconductor wafer 1 which is an object to be measured is
(shown by solid lines in FIG. 1) is supplied from six directions of arrows, stopped at a predetermined position, and vacuum-chucking by a vacuum chuck 2 at a position away from the center point 0. As shown by arrow B, the vacuum chuck 2 is capable of linearly reciprocating in a direction orthogonal to the six directions of arrows. In this embodiment, the wafer 1 is held by the vacuum chuck 2, and its orientation flange (OF) is parallel to the direction of arrow A, so that it passes through the center point 0 of the wafer 1 and is perpendicular to the center of the orientation flange (OF). A center line CL extends parallel to the direction of arrow B.

For example, the thickness measuring sensor 3 (measuring means) made of a non-contact sensor such as a capacitance sensor or a laser sensor is arranged on the center line CL on the moving direction side of the orientation flat OF of the semiconductor wafer 1. There is.

In addition, on the center line CL in FIG. 1, two sets of edge sensors St and 82 for measuring the outer circumferential edge of the semiconductor wafer l are arranged on both sides of the thickness measurement sensor 3 and are spaced apart from each other by a length. There is. In FIG. 1, D2 is the distance fi from the edge sensor S1 to the orientation flat OF t of the semiconductor wafer l; Distance between edge sensor S2 and outer edge of semiconductor wafer 1, D4
is the distance between the thickness measurement sensor 3 and the edge sensor S.

Note that 4 in FIG. 1 is a rotary chuck for vacuum suctioning the wafer 1 and rotating it by 90 degrees within its plane.

Next, in order to explain the operation of this embodiment, a semiconductor wafer 1 or 1a is transported from six directions of arrows, stopped at a predetermined position, and a position away from the center point 0 of the wafer l or 1a is moved from below. It is held by vacuum chuck 2.

Next, the vacuum chuck 2 is moved linearly in the direction of arrow B, that is, in the direction of the thickness measurement sensor 3. At this time, edge sensors S and S2 detect the edge of wafer 1 or 1a. Then, from the first predetermined position, the edge sensor S1
．． In S2, the diameter of wafer 1 or 1a is calculated from the amount of wafer movement until the edge of wafer 1 or 1a is detected. Calculation of the diameter Dia of the wafer 1 or 1a at this time is performed, for example, using the following equation.

First of all, for example, in the case of the wafer 1a in FIG. 1, Dia=D+ (D2 Ds) ・
...(1) Also, for example, in the case of wafer 1 in FIG. 1, D+a=D+ + (Ds' D2 )
...The calculation formula (2) can be used.

After determining the diameter of the wafer 1 or 1a in this way, the amount of movement up to each measurement is determined based on the calculated value of the diameter, and the vacuum chuck 2 is moved to move the wafer 1 or la at the measurement point. Wafer 1 or 1 at that measurement point
The thickness of a is measured by the thickness measurement sensor 3. The thickness of the wafer 1 is measured by the thickness measurement sensor 3, for example, for 6 to 10 minutes from the solid line position of the wafer 1 or 1a until its edge is detected by the edge sensor S2 on the left side of FIG. It is performed at multiple points such as points.

When the wafer 1 or 1a reaches the position where the edge is detected by the edge sensor S2 on the left side of FIG. Rotated. After that, the wafer 1 or 1a is again vacuum-chucking with the vacuum chuck 2 and moved back in the direction of arrow B. During the return movement, the thickness of the wafer 1 or 1a is multiplied by the thickness measurement sensor 3 in the same manner as described above. Measure in points.

In these cases, the amount of movement SP, .about.SP1 DEG of the vacuum chuck 2 from the measurement point of the wafer 1 or 1a, such as the edge sensor S1, to the measurement point can be calculated, for example, according to the following equation.

S P + = D4 + D TsSPs =
Da + DT3S 3 Pg = D4 + Dia −D 73SS
P + o ” D4 + Dla D Ts Here, D T3. D T3s indicates the measurement position.

Also, from SP to SPs is the first half of Dia/2 in the measurement of one wafer, from SP to SP.

The figures up to 1 show measurement points in the latter half Dia/2 range, respectively.

As described above, according to this embodiment, the following effects can be obtained.

(1) Calculate the diameter of the wafer from the amount of movement of the wafer in the direction of arrow B from a predetermined position on the wafer 1 or 1a until the edge sensor St, S2 detects the wafer edge, and calculate the amount of movement to each measurement point. By measuring the thickness of the wafer at multiple points, it is possible to accurately determine the thickness measurement points and efficiently perform highly accurate multi-point thickness measurements with just one reciprocating movement of the wafer.

(2) Due to the above (1), measurements can always be carried out reliably without being affected by the displacement of the wafer 1° 1a when the transport is stopped.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the structure of the measurement sensor 3, rotary chuck 4, and vacuum chuck 2 may be different from those of the embodiments described above.

In the above explanation, the invention made by the present inventor was mainly applied to the field of application, which is fully automatic thickness measurement of semiconductor wafers, but the invention is not limited to this, and for example, it can be used to measure other thicknesses. It can also be applied to measurements.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, when moving a wafer such as a semiconductor wafer from a predetermined position in the direction of the measuring means, the diameter of the wafer is calculated based on the amount of movement from the predetermined position until the edge of the wafer is detected by the measuring means, and the diameter of the wafer is calculated. By determining the amount of movement to each measurement point based on the value and measuring the thickness of the semiconductor wafer at multiple points, it is possible to efficiently measure the thickness of the wafer at multiple points at any position. Further, multi-point thickness measurements of semiconductor wafers can be performed accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view illustrating a method for measuring the thickness of a semiconductor device according to the present invention. 1.1a... semiconductor wafer, 2... vacuum chuck,
3... Thickness measurement sensor (measuring means), 4... Rotating chuck, Sl, St... Edge Figure 1

Claims (1)

[Claims] 1. When moving the wafer from a predetermined position in the direction of the measuring means, the diameter of the wafer is calculated based on the amount of movement from the predetermined position until the edge of the wafer is detected by the measuring means; A method for measuring the thickness of a wafer, characterized in that the thickness of the wafer is measured at multiple points by determining the amount of movement to each measurement point based on the calculated value. 2. When measuring the thickness of the wafer, first move the wafer in a direction perpendicular to the orientation flat of the wafer and measure the thickness at multiple points in the orthogonal direction, and then
The wafer is rotated by a predetermined angle in its plane direction, and the wafer is returned in the opposite direction along the moving direction, and the thickness is measured at multiple points in the rotating direction. The method for measuring the thickness of a wafer according to item 1.