JP6683277B1 - Method for measuring thickness of semiconductor wafer and double-sided polishing apparatus for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring the thickness of a semiconductor wafer, which can measure the thickness of the semiconductor wafer with high accuracy and fast feedback immediately after completion of double-side polishing. A method of measuring the thickness of a semiconductor wafer having both sides polished by using a polishing slurry, the method comprising: immersing the semiconductor wafer having both sides polished in ozone water; A method of measuring the thickness of a semiconductor wafer, comprising: the step of drying the semiconductor wafer performed; and the step of measuring the thickness of the dried semiconductor wafer. [Selection diagram] Figure 1

Description

  The present invention relates to a semiconductor wafer thickness measuring method and a semiconductor wafer double-side polishing apparatus.

  Along with the miniaturization of semiconductor circuit line width, the flatness required for a semiconductor wafer (hereinafter, also simply referred to as “wafer”) which is the substrate has become more and more strict. Under such circumstances, when polishing a large-diameter wafer, a double-sided polishing method, which is superior in processing accuracy, is adopted instead of the conventional single-sided polishing.

  Here, in the double-sided polishing apparatus, it is known that the flatness of the wafer after polishing changes depending on the thickness of the wafer at the time of polishing, that is, the relationship between the finished thickness of the wafer and the thickness of the carrier (for example, Patent Document Reference 1).

  For example, if the finished thickness is made thicker than the thickness of the carrier, the pressure at the outer peripheral portion of the wafer becomes higher than that at the central portion due to the influence of the sinking of the wafer into the polishing cloth due to the polishing load. As a result, polishing of the outer peripheral portion of the wafer is promoted and the outer peripheral portion becomes thinner than the central portion, so-called outer peripheral sag occurs, and the overall shape is likely to be convex.

  Conversely, if the finished thickness is made thinner than the thickness of the carrier, the pressure at the outer peripheral portion of the wafer becomes smaller than that at the central portion due to the so-called retainer effect that alleviates the effect of the carrier sinking into the polishing cloth. . As a result, the peripheral edge of the outer peripheral portion of the wafer becomes thicker than the central portion, and the overall shape tends to be concave. Therefore, conventionally, the flatness of the wafer is adjusted by adjusting the finished thickness of the wafer with respect to the thickness of the carrier. In order to polish a wafer with high flatness, it is necessary to finish the wafer with an optimum thickness for the thickness of the carrier. Therefore, it is necessary to measure the thickness of the wafer after double-side polishing.

  In this case, there is a method in which the wafer is loaded into a double-sided polishing apparatus and collected, and is dried using an automatic transfer robot to measure the wafer thickness in-line (see Patent Document 2).

JP-A-5-177539 JP, 2013-94954, A

  By the in-line measurement as described in Patent Document 2, the flatness can be measured by fast feedback, and the next polishing thickness can be determined. By improving the in-line measurement accuracy, it is possible to improve the accuracy of adjusting the flatness of the semiconductor wafer and realize faster feedback.

  However, conventionally, when the thickness of the semiconductor wafer is measured immediately after the double-side polishing is completed, the measurement accuracy is low.

  In view of such a problem, it is an object of the present invention to provide a semiconductor wafer thickness measuring method capable of measuring the thickness of a semiconductor wafer accurately and with fast feedback immediately after the completion of double-side polishing. Another object of the present invention is to provide a double-sided polishing apparatus capable of measuring the thickness of such a semiconductor wafer.

  In order to achieve the above object, the present invention is a semiconductor wafer thickness measuring method for measuring the thickness of a semiconductor wafer double-side polished using a polishing slurry, the double-side polished semiconductor wafer, ozone water A method for measuring the thickness of a semiconductor wafer, comprising: a step of immersing, a step of drying the semiconductor wafer that has been immersed, and a step of measuring the thickness of the dried semiconductor wafer.

  In such a method for measuring the thickness of a semiconductor wafer, the semiconductor wafer after double-side polishing can be protected with an oxide film by immersing the semiconductor wafer whose double-side polishing has been performed in ozone water. Therefore, the thickness of the semiconductor wafer can be measured more accurately. Also, this method can be performed simply and quickly.

  Further, in the method for measuring the thickness of a semiconductor wafer of the present invention, the polishing slurry may contain a high molecular weight cellulose derivative.

  As described above, even when the polishing slurry containing the high molecular weight cellulose derivative is used, the high molecular weight cellulose derivative can be easily and quickly removed by having the ozone water immersion step. The thickness of the semiconductor wafer can be measured more accurately.

  Further, in the semiconductor wafer thickness measuring method of the present invention, it is preferable that the ozone concentration of the ozone water is 5 ppm or more.

  By using ozone water having such an ozone concentration, the semiconductor wafer can be treated more effectively.

  Further, the step of immersing in ozone water is preferably 10 seconds or more.

  By immersing the semiconductor wafer in ozone water for such a time, the semiconductor wafer can be treated more effectively.

  Further, the method for measuring the thickness of a semiconductor wafer according to the present invention may include a step of immersing the double-side polished semiconductor wafer in pure water before the step of immersing in the ozone water.

  In this way, by having the step of immersing the semiconductor wafer in pure water before the ozone water immersion step, it is possible to perform a simple cleaning before the ozone water immersion, so that the treatment of the semiconductor wafer with ozone water can be performed more reliably. It can be carried out.

  Further, the present invention is a double-sided polishing apparatus for double-sided polishing of a semiconductor wafer, and polishing slurry supply means for supplying a polishing slurry used in double-sided polishing of the semiconductor wafer, and for immersing the semiconductor wafer in ozone water. 2. A double-sided polishing apparatus for a semiconductor wafer, comprising: an ozone water immersion tank, a drying means for drying the semiconductor wafer, and a thickness measuring means for measuring the thickness of the semiconductor wafer.

  With such a double-side polishing machine, it is possible to quickly and in-line measure the thickness of the semiconductor wafer after the double-side polishing of the semiconductor wafer by the double-side polishing machine. Since the ozone water immersion treatment can be performed by the method described above, the thickness of the semiconductor wafer can be measured more accurately.

  In the double-sided polishing apparatus for semiconductor wafers of the present invention, the polishing slurry supply means may supply, as the polishing slurry, one containing a polymer cellulose derivative.

  Thus, even in the case of a double-sided polishing apparatus using a polishing slurry containing a high molecular weight cellulose derivative, it is possible to perform ozone water immersion treatment in an ozone water immersion tank, so that the thickness measurement of semiconductor wafers can be performed more accurately. It can be carried out.

  The semiconductor wafer double-side polishing apparatus of the present invention may further include a pure water immersion tank for immersing the semiconductor wafer in pure water.

  By providing the pure water immersion tank in this way, the semiconductor wafer can be immersed in pure water before it is immersed in ozone water, so that the semiconductor wafer can be more reliably treated with ozone water. .

  In the method for measuring the thickness of a semiconductor wafer according to the present invention, the semiconductor wafer immediately after the double-side polishing can be protected with the oxide film by immersing the double-side polished semiconductor wafer in the ozone water. Therefore, the thickness of the semiconductor wafer can be measured more accurately. Also, this method can be performed simply and quickly. Thereby, the method for measuring the thickness of the semiconductor wafer inline can be provided. As a result, it becomes possible to measure the thickness of the semiconductor wafer with quick feedback, which leads to improvement of the flatness of the semiconductor wafer. Further, the double-sided polishing apparatus of the present invention can quickly measure the thickness of such a semiconductor wafer.

It is a flowchart which shows the outline of the thickness measuring method of the semiconductor wafer of this invention. It is a graph which shows the result of the thickness measurement of the semiconductor wafer after double-side polishing, (a) is a graph which shows the thickness distribution of the semiconductor wafer when it does not have an ozone water immersion process, (b) is the present invention 3 is a graph showing a thickness distribution of a semiconductor wafer in the case of including an ozone water immersion step according to the semiconductor wafer thickness measuring method of FIG. It is a graph which shows the relationship of the density of ozone water in an ozone water immersion process, and the measurement accuracy in thickness measurement of a semiconductor wafer. It is a schematic diagram showing an example of composition of a double-sided polish device of a semiconductor wafer of the present invention. It is a schematic diagram showing an example of the composition of the double-sided polisher which is a part which constitutes the double-sided polisher of the semiconductor wafer of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present invention is a semiconductor wafer thickness measuring method for measuring the thickness of a semiconductor wafer double-side polished using a polishing slurry, the step of immersing the double-side polished semiconductor wafer in ozone water, and performed dipping It is a semiconductor wafer thickness measuring method having a step of drying a semiconductor wafer and a step of measuring a thickness of the dried semiconductor wafer.

  This method for measuring the thickness of a semiconductor wafer of the present invention is a double-sided polishing apparatus for double-sided polishing of a semiconductor wafer, and a polishing slurry supply means for supplying a polishing slurry to be used for double-sided polishing of the semiconductor wafer, and the semiconductor wafer with ozone water. It can be carried out by a double-side polishing apparatus for a semiconductor wafer, which comprises an ozone water immersion tank for immersing the semiconductor wafer, a drying means for drying the semiconductor wafer, and a thickness measuring means for measuring the thickness of the semiconductor wafer. The configuration of this double-sided polishing machine will be further described with reference to FIGS. 4 and 5.

  FIG. 4 is a conceptual diagram showing an outline of an example of the configuration of the double-sided polishing apparatus for semiconductor wafers of the present invention. As shown in FIG. 4, the double-side polishing apparatus 100 has a double-side polishing machine 10 for double-side polishing the semiconductor wafer W. FIG. 4 shows a state in which the wafer W polished by the double-side polishing machine 10 is recovered by the wafer transfer means 70 such as an automatic transfer robot. The double-sided polishing apparatus 100 further includes an ozone water immersion tank 40 for immersing the semiconductor wafer W in the ozone water 42, a drying means 50 for drying the semiconductor wafer W, and a thickness measuring means 60 for measuring the thickness of the semiconductor wafer W. . The double-sided polishing apparatus 100 may further include a pure water immersion tank 30 for immersing the semiconductor wafer W in pure water 32.

  FIG. 5 is a schematic cross-sectional view showing an example of the configuration of the double-side polishing machine 10 which is a part of the double-side polishing apparatus 100 for a semiconductor wafer of the present invention. In the double-sided polishing apparatus of the present invention, the structure of the double-sided polishing machine, which is the part for double-sided polishing of the semiconductor wafer W, is not particularly limited, but for example, a 4-way double-sided polishing machine 10 as shown in FIG. 5 can be used. The double-sided polishing machine 10 includes an upper surface plate 11 and a lower surface plate 12 which are provided to face each other vertically. Polishing cloths 13 are attached to the upper and lower surface plates 11 and 12, respectively. A sun gear 14 is provided at the center between the upper surface plate 11 and the lower surface plate 12, and an internal gear 15 is provided at the peripheral edge portion. The outer peripheral teeth of the carrier 21 are meshed with the tooth portions of the sun gear 14 and the internal gear 15, and the carrier 21 rotates on its axis as the upper surface plate 11 and the lower surface plate 12 are rotated by a drive source (not shown). While revolving around the sun gear 14. At this time, both surfaces of the wafer W held by the holding holes 22 of the carrier 21 are simultaneously polished by the upper and lower polishing cloths 13. When polishing the semiconductor wafer W, the polishing slurry supply means 16 supplies the polishing slurry 17 to the polishing surface of the wafer W.

  FIG. 1 shows an outline of the semiconductor wafer thickness measuring method of the present invention.

  First, as shown in FIG. 1A, double-side polishing of a semiconductor wafer is performed using a polishing slurry. In this double-side polishing step, the double-side polishing of the semiconductor wafer W can be performed using the double-side polishing machine 10 shown in FIGS. At this time, as shown in FIG. 5, the polishing slurry supply means 16 can supply the polishing slurry 17 to the polishing surface of the wafer W. The present invention is particularly preferable when the polishing slurry 17 at this time contains a high molecular weight cellulose derivative.

  Next, as shown in FIG. 1B, the double-side polished semiconductor wafer is recovered from the double-side polishing machine. At this time, as shown in FIG. 4, the semiconductor wafer W can be recovered from the double-side polishing machine 10 by using the wafer transfer means 70 such as an automatic transfer robot. Further, also in the subsequent steps, the semiconductor wafer W can be transferred by the wafer transfer means 70.

  The semiconductor wafer thus collected from the double-side polishing machine is immersed in ozone water as shown in FIG. 1C, but in the present invention, the semiconductor wafer W is immersed in the ozone water immersion step before the ozone water immersion step. It may have a step of immersing in pure water (pure water immersing step). This pure water immersion step can be performed by immersing the semiconductor wafer W in the pure water 32 contained in the pure water immersion tank 30 shown in FIG.

  In the ozone water immersion step after the wafer recovery step (or after the wafer recovery step and the pure water immersion step), the semiconductor wafer W is immersed in the ozone water 42 stored in the ozone water immersion tank 40 shown in FIG. This can be done by In this ozone water immersion step, the ozone concentration of the ozone water 42 is preferably set to 5 ppm or more, and more preferably set to 10 ppm or more. When the ozone concentration is 5 ppm or more, the semiconductor wafer can be more reliably protected by the oxide film, and the polymeric cellulose derivative can be removed. When the ozone concentration is 10 ppm or more, the thickness measurement accuracy is remarkably improved. The upper limit of the ozone concentration of the ozone water 42 is not particularly limited and may be contained up to the saturated concentration, but from the economical aspect, it can be 100 ppm or less.

  In the ozone water immersion step, the time for immersing the semiconductor wafer W in the ozone water 42 is preferably 10 seconds or longer, more preferably 30 seconds or longer, and particularly preferably 1 minute or longer. If the ozone water immersion step is performed for such a time, the surface of the semiconductor wafer W can be sufficiently treated. On the other hand, this ozone water immersion step does not need to be performed for an unnecessarily long time from the viewpoint of productivity. Therefore, the time of the ozone water immersion step can be 5 minutes or less.

  In the ozone water immersion step, the semiconductor wafer W may be immersed in the ozone water 42 for each wafer or for a plurality of wafers at the same time. This is the same even when immersed in pure water 32.

  After performing the ozone water immersion step, the semiconductor wafer is dried as shown in FIG. This drying step can be performed using the drying means 50 shown in FIG. This drying may be performed for each silicon wafer W or may be performed simultaneously for a plurality of silicon wafers. As the drying means 50, any known drying means for drying a semiconductor wafer can be used.

  After performing the drying step, the thickness of the dried semiconductor wafer is measured as shown in FIG. In this thickness measurement, the thickness measuring means 60 shown in FIG. 4 can be used. As the thickness measuring means 60, a known semiconductor wafer thickness measuring device can be used. For example, a spectroscopic interference laser displacement meter SI-F series manufactured by Keyence Corporation can be used.

  In order to prevent and protect the semiconductor wafer W whose both surfaces are polished from being corroded by a polishing slurry or the like, a polymer cellulose derivative is usually attached to the semiconductor wafer W. This polymeric cellulose derivative is usually added to the polishing slurry itself. The high molecular weight cellulose derivative is, for example, hydroxyethyl cellulose.

  As described above, the semiconductor wafer recovered after being double-side polished by the double-side polishing machine usually has a high molecular weight cellulose derivative attached thereto. In the method for measuring the thickness of a semiconductor wafer of the present invention, the surface of the wafer is simply sunk by immersing the semiconductor wafer after recovery (undried semiconductor wafer immediately after recovery) in ozone water (or pure water and ozone water). The high molecular weight cellulose derivative containing the agglomerated silica attached to the can be removed. Further, the surface of the semiconductor wafer can be protected by the oxide film by the action of ozone water. Even in the case of a semiconductor wafer to which a polymer cellulose derivative is not attached, the surface of the semiconductor wafer can be protected with an oxide film by the action of ozone water on the wafer surface activated by polishing. Therefore, the thickness of the semiconductor wafer can be measured with high accuracy by drying after the ozone water immersion step.

  The method of the present invention can be carried out simply and quickly. Thereby, the method for measuring the thickness of the semiconductor wafer inline can be provided. That is, as shown in FIG. 4, the thickness of the semiconductor wafer can be quickly measured in the double-side polishing apparatus 100. As a result, it becomes possible to measure the thickness of the semiconductor wafer with quick feedback, which leads to improvement of the flatness of the semiconductor wafer.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples.

(Examples 1 to 5)
According to the flow of FIG. 1, the thickness of the semiconductor wafer after double-side polishing was measured. First, as a semiconductor wafer W to be double-sided polished, a silicon wafer was prepared as follows. First, a single crystal ingot pulled up by a single crystal pulling apparatus according to the Czochralski method was sliced to obtain an as-sliced wafer. After chamfering the edge of this as-sliced wafer, it was lapped and etched to remove residual strain. Thus, a CW wafer having a diameter of 300 mm was prepared.

  Next, the CW wafer was double-side polished by a double-side polishing machine 10 as shown in FIG. 5 in an amount sufficient to remove the strain caused by the lapping process (FIG. 1A). A colloidal silica polishing agent was used as the polishing slurry. This polishing slurry contained a high molecular weight cellulose derivative.

  Next, the polished semiconductor wafer W was recovered using an automatic transfer robot (wafer transfer means 70) (FIG. 1 (b)). The polymer wafer derivative for protecting the semiconductor wafer W after double-side polishing collected here from being corroded from a polishing slurry agent was attached. Each of the collected semiconductor wafers was immersed in ozone water 42 (FIG. 1C). Here, as the conditions for immersing in the ozone water 42, the ozone concentration was shaken in the range of 2 to 20 ppm, and the immersing time was 30 seconds for evaluation. The ozone concentration is 2 ppm in Example 1, the ozone concentration is 5 ppm in Example 2, the ozone concentration is 7 ppm in Example 3, the ozone concentration is 10 ppm in Example 4, and the ozone concentration is 20 ppm in Example 5. After being immersed in the ozone water 42, the wafer W was dried (FIG. 1D) and the thickness was measured (FIG. 1E was performed). A spectral interference laser displacement meter SI-F series manufactured by Keyence Corporation was used for in-line thickness measurement here.

(Comparative example)
The thickness of the semiconductor wafer was measured in the same manner as in Examples 1 to 5 except that the semiconductor wafer W was not immersed in the ozone water 42. That is, under the above polishing conditions, double-side polishing was performed, wafers were collected, dried, and thickness was measured.

  In FIG. 2, when it is immersed in 10 ppm ozone water (“with ozone”, Example 4, FIG. 2B) and when not immersed in ozone water (“no ozone”, comparative example, FIG. 2 (a)). ), The result of measuring the thickness distribution of the semiconductor wafer is shown.

  It can be seen that in the comparative example of “without ozone”, noise is present, whereas in the example of “with ozone”, the cross-section thickness line of the semiconductor wafer of the measurement result is smooth.

  FIG. 3 shows the results of evaluation of the correlation between ozone concentration and measurement accuracy. As a parameter for evaluating the measurement accuracy of the semiconductor wafer, an average of differences between adjacent data was used for the data of the measurement result.

  As can be seen from FIG. 3, the measurement accuracy can be improved by immersing in ozone water containing ozone. Further, it can be seen that by increasing the ozone concentration of the ozone water, the contamination of the wafer surface is improved, and thereby the noise of the measurement result is reduced. It can also be seen from FIG. 3 that the ozone concentration of 5 ppm or more is preferable for improving the measurement accuracy, and the ozone concentration of 10 ppm or more is more preferable because the measurement accuracy is further improved. In particular, it is considered that the measurement accuracy of 1 nm or less is sufficient, and the ozone concentration of 10 ppm or more is sufficient to obtain the desired accuracy.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to the present invention. It is included in the technical scope of the invention.

10 ... Double-side polishing machine, 11 ... Upper surface plate, 12 ... Lower surface plate, 13 ... Abrasive cloth,
14 ... Sun Gear, 15 ... Internal Gear,
16 ... Polishing slurry supply means 17 ... Polishing slurry,
21 ... Carrier, 22 ... Holding hole,
30 ... Pure water immersion tank, 32 ... Pure water,
40 ... Ozone water immersion tank, 42 ... Ozone water,
50 ... Drying means, 60 ... Thickness measuring means, 70 ... Wafer carrying means,
100 ... Double-side polishing machine,
W ... Semiconductor wafer.

Claims (4)

A method for measuring the thickness of a semiconductor wafer, which comprises measuring the thickness of a semiconductor wafer that has been double-side polished using a polishing slurry containing a polymeric cellulose derivative ,
Immersing the double-side polished semiconductor wafer in ozone water having an ozone concentration of 5 ppm or more for 10 seconds or more ;
A step of drying the semiconductor wafer subjected to the immersion,
And a step of measuring the thickness of the dried semiconductor wafer. Before the step of immersing the ozone water, the double-sided polished semiconductor wafer, the semiconductor wafer thickness measuring method according to claim 1, characterized in that it comprises a step of immersion in pure water. A double-side polishing apparatus for double-side polishing a semiconductor wafer,
As the polishing slurry used when polishing the semiconductor wafer on both sides, a polishing slurry supply means for supplying those containing a high molecular weight cellulose derivative ,
An ozone water immersion tank for immersing the semiconductor wafer in ozone water having an ozone concentration of 5 ppm or more for 10 seconds or more ;
Drying means for drying the semiconductor wafer,
And a thickness measuring unit for measuring the thickness of the semiconductor wafer. The double-side polishing apparatus for a semiconductor wafer according to claim 3, further comprising a pure water immersion tank for immersing the semiconductor wafer in pure water.

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