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CN112635349A - Method for measuring thickness of metal film on surface of wafer - Google Patents

Method for measuring thickness of metal film on surface of wafer Download PDF

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Publication number
CN112635349A
CN112635349A CN202011517574.8A CN202011517574A CN112635349A CN 112635349 A CN112635349 A CN 112635349A CN 202011517574 A CN202011517574 A CN 202011517574A CN 112635349 A CN112635349 A CN 112635349A
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wafer
metal film
thickness
measuring
time
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CN112635349B (en
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李辉
梅双
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Yangtze Memory Technologies Co Ltd
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Yangtze Memory Technologies Co Ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10Measuring as part of the manufacturing process
    • H01L22/12Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/768Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
    • H01L21/76838Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2221/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof covered by H01L21/00
    • H01L2221/10Applying interconnections to be used for carrying current between separate components within a device
    • H01L2221/1068Formation and after-treatment of conductors

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

The invention provides a method for measuring the thickness of a metal film on the surface of a wafer, which comprises the following steps: obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the wafer at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; taking the ratio of the height difference to the time difference as the constant parameter; measuring the thickness of the metal film on the surface of the wafer: and acquiring the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring point of the surface of the wafer, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point. The measuring method can monitor the thickness of the metal film on the surface of the wafer in real time, has high measuring accuracy, greatly improves the productivity and saves the cost; in addition, the surface height difference of the two preset points can be obtained without damaging the wafer, the wafer is prevented from being damaged, and the nondestructive measurement method is provided.

Description

Method for measuring thickness of metal film on surface of wafer
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method for measuring the thickness of a metal film on the surface of a wafer.
Background
During the wafer production process, various films, including metal films, are formed on the surface of the wafer. In the metal electroplating process for forming the metal film, the difference of the metal growth rates of a dense area and a loose area of a substrate structure is huge. The thickness of the dense region may be more than twice the thickness of the loose region, which poses a significant challenge to the subsequent metal polishing process. If the difference between the thicknesses of the metal films in the dense area and the loose area of the wafer is too large, the metal film on the surface of the loose area is completely ground during the metal grinding process, the metal film on the surface of the dense area is not removed, and metal residues exist on the surface of the dense area, which can cause the metal interconnection of the layer, thus causing the short circuit of the device and the loss of the function.
At present, a metal coating process station has no means for monitoring the thickness of a metal film in real time. It is usually necessary to measure the thickness of the metal layer after the metal polishing process, and the real-time monitoring is not achieved. Because the thickness of the metal film can not be monitored in real time before the metal grinding process, in order to ensure that the thickness of the metal interconnection line finally reserved in the loose area and the compact area after the metal grinding process meets the requirement, the electroplating thickness is increased when metal is electroplated, the thickness is increased, the electroplating time is correspondingly increased, the output capacity of electroplating equipment is reduced, the material consumption is increased, and the cost is increased; meanwhile, the plating thickness is increased, the yield of metal grinding equipment is reduced in the subsequent metal grinding process, the usage amount of grinding fluid is increased, the productivity is reduced, and the cost is increased.
It can be seen that real-time monitoring of the thickness of the metal film is important to both improve productivity and save cost. Therefore, a new method for measuring the thickness of a metal film on a wafer surface is needed to overcome the above problems.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for measuring the thickness of a metal film on the surface of a wafer.
In order to solve the above problems, the present invention provides a method for measuring the thickness of a metal film on a wafer surface, which comprises the following steps: obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the wafer at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; taking the ratio of the height difference to the time difference as the constant parameter; measuring the thickness of the metal film on the surface of the wafer: and acquiring the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring point of the surface of the wafer, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point.
Further, the wafer comprises a substrate loose area and a substrate compact area, and in the step of obtaining the constant parameter, one preset point is located in the substrate loose area, and the other preset point is located in the substrate compact area.
Further, in the step of obtaining the constant parameter, the method of obtaining the time difference of the sound wave propagating in the metal film on the metal surface is to measure the time of the sound wave propagating in the metal film at each preset point by using a metal ultrafast laser pulse device, and to obtain the time difference by subtracting the obtained two times.
Further, in the step of obtaining the constant parameter, the method of obtaining the difference in surface height at the two preset points is: and carrying out topography measurement on the surface area of the wafer containing the preset points to obtain the surface height difference of the two preset points.
Further, the measuring apparatus used in the step of obtaining the time difference of the acoustic wave propagating in the metal surface metal film at two preset points on the wafer surface is the same as the measuring apparatus used in the step of obtaining the time of the acoustic wave propagating in the metal surface metal film at the measuring points on the wafer surface.
Further, in the step of obtaining the constant parameter, a plurality of preset points are set, the preset points are combined pairwise to obtain a plurality of ratios of the height differences to the time differences, and an average value of the plurality of ratios of the height differences to the time differences is obtained and used as the constant parameter.
Further, in the step of obtaining the constant parameter, a plurality of preset points are set, the preset points are combined pairwise to obtain a plurality of height differences and a plurality of time differences, and a ratio of an average value of the height differences to an average value of the time differences is taken as the constant parameter.
Further, in the step of obtaining the constant parameter, the height difference between the two preset points is greater than a set value.
Further, in the step of measuring the thickness of the metal film on the surface of the wafer, a plurality of measurement points are obtained in a set area of the wafer, the time of the sound wave propagating in the metal film on the surface of the wafer is obtained at each measurement point, an average value of a plurality of times is obtained, and the product of the average value of the plurality of times and the constant parameter is used as the thickness of the metal film in the set area.
Further, in the step of measuring the thickness of the metal film on the surface of the wafer, a plurality of measurement points are obtained in a set area of the wafer, the time of sound wave propagation in the metal film on the surface of the wafer is obtained at each measurement point, the product of the time and the constant parameter is used as the thickness of the metal film at the measurement point, the average value of the thicknesses of the plurality of metal films is obtained, and the average value is used as the thickness of the metal film in the set area.
The invention has the advantages that the thickness of the metal film on the surface of the wafer can be monitored in real time, the measurement accuracy is high, the productivity is greatly improved, and the cost is saved.
The method for measuring the thickness of the metal film on the surface of the wafer can obtain the surface height difference of two preset points without damaging the wafer, thereby avoiding the damage of the wafer and providing a nondestructive measuring method.
Drawings
FIG. 1 is a schematic view illustrating a step of a method for measuring a thickness of a metal film on a wafer surface according to a first embodiment of the present invention;
FIG. 2 is a schematic top view of a wafer surface illustrating a method for measuring a thickness of a metal film on a surface of the wafer according to the present invention;
FIG. 3 is a schematic diagram illustrating a difference between surface heights at a predetermined point A and a predetermined point B of the method for measuring a thickness of a metal film on a wafer surface according to the present invention;
FIG. 4 is a schematic diagram illustrating a step of a method for measuring a thickness of a metal film on a wafer surface according to a second embodiment of the present invention;
FIG. 5 is a schematic top view of a wafer surface showing a method for measuring a thickness of a metal film on the surface of the wafer according to the present invention;
FIG. 6 is a schematic view illustrating a third embodiment of a method for measuring a thickness of a metal film on a wafer surface according to the present invention;
FIG. 7 is a schematic view illustrating a fourth embodiment of a method for measuring a thickness of a metal film on a wafer surface according to the present invention;
FIG. 8 is a schematic top view of a wafer surface showing a method for measuring a thickness of a metal film on the surface of the wafer according to the present invention;
FIG. 9 is a schematic step diagram illustrating a method for measuring a thickness of a metal film on a wafer surface according to a fifth embodiment of the present invention.
Detailed Description
The following describes in detail a specific embodiment of the method for measuring the thickness of a metal film on a wafer surface according to the present invention with reference to the accompanying drawings.
As described in the background, the metal plating process station has no means for monitoring the thickness of the metal film in real time. Usually, the thickness of the metal layer needs to be measured after the metal grinding process, so that the purpose of real-time monitoring cannot be achieved, and in order to make the thickness of the metal interconnection line finally reserved in the loose region and the dense region after the metal grinding process meet the requirement, the electroplating thickness is increased when the metal is electroplated, so that the productivity is reduced, and the cost is increased.
Therefore, the invention provides a method for measuring the thickness of a metal film on the surface of a wafer, which can monitor the thickness of the metal film on the surface of the wafer in real time at a metal coating process site to provide reference for a subsequent metal grinding process, thereby avoiding the formation of an excessively thick metal film in the metal coating process, improving the productivity and saving the cost.
Fig. 1 is a schematic diagram illustrating a method for measuring a thickness of a metal film on a wafer surface according to a first embodiment of the present invention, and referring to fig. 1, the method for measuring a thickness of a metal film on a wafer surface according to the present invention includes the following steps:
step S10, obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the wafer at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; and taking the ratio of the height difference to the time difference as the constant parameter.
In this step, two preset points are set on the wafer surface. Fig. 2 is a schematic top view of a wafer surface, and referring to fig. 2, two preset points a and B are set on the surface of the wafer 100. In the present embodiment, the method of obtaining the constant parameter is specifically described as follows:
at a preset point A, the time t1 when the sound wave propagates in the metal surface metal film is obtained, and at a preset point B, the time t2 when the sound wave propagates in the metal surface metal film is obtained. And (3) obtaining the time difference T of the sound wave propagating in the metal film on the metal surface by differentiating the propagation time T1 at the preset point A with the propagation time T2 at the preset point B. In this embodiment, a metal ultrafast laser pulse device may be used as the measuring device to obtain the propagation times of the acoustic waves at the preset points a and B, and further obtain the time difference. Specifically, laser emitted by the metal ultrafast laser pulse device is irradiated on a preset point A on the metal surface, the laser generates sound waves, the sound waves propagate in the metal layer and return to the preset point A after a period of time t1, and the time t1 is the propagation time of the sound waves in the metal layer at the preset point A; laser emitted by the metal ultrafast laser pulse equipment is irradiated on a preset point B on the surface of the metal, the laser can generate sound waves, the sound waves are transmitted in the metal layer, the sound waves return to the preset point B after a period of time t2, and the time t2 is the transmission time of the sound waves in the metal layer at the preset point B.
In other embodiments of the present invention, other devices known to those skilled in the art may be used as the measuring device.
And obtaining the height of the surface of the wafer at a preset point A, obtaining the height of the surface of the wafer at a preset point B, and obtaining the height difference between the preset point A and the preset point B by making a difference between the height of the preset point A and the height of the preset point B. As shown in fig. 3, which is a schematic diagram of the surface height difference between preset point a and preset point B, the surface height at preset point a is higher than the surface height at preset point B, and the height difference between the two is H. In the present embodiment, the surface area of the wafer including the preset point a and the preset point B is subjected to topography measurement to obtain a surface height difference between the two preset points. For example, an atomic force microscope is used to perform a topography measurement on a wafer surface region including the preset point a and the preset point B, so as to obtain a surface height difference between the two preset points.
And taking the ratio H/T of the height difference H and the time difference T as the constant parameter.
It can be understood that the smaller the values of the height difference H and the time difference T, the greater the influence on the accuracy of the ratio, so that when selecting the preset point a and the preset point B, the larger the height difference H between the preset point a and the preset point B is, so as to improve the accuracy of the constant parameter.
For example, in the present embodiment, the wafer 100 includes a substrate loose region 101 and a substrate dense region 102. When a metal film is formed on the surface of the wafer by electroplating, the thickness of the metal film formed on the surface of the substrate loose area 101 is smaller, and the thickness of the metal film formed on the surface of the substrate dense area 102 is larger, so that the preset point a is selected from the substrate dense area 102, and the preset point B is selected from the substrate loose area 101, so that the height difference H and the time difference T of the preset point a and the preset point B are larger, and the accuracy of the obtained constant parameter is improved.
Step S11, measuring the thickness of the metal film on the wafer surface: and obtaining the time of the sound wave propagating in the metal film on the metal surface at the measuring point of the wafer surface, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point.
In this step, a measurement point is optionally selected on the wafer surface at which the thickness is to be obtained. As shown in FIG. 2, a measurement point X1 is selected on the surface of the wafer substrate bulk region 101. At the measurement point X1, the time t3 at which the acoustic wave propagates in the metal film on the wafer surface is obtained. In the present embodiment, in order to improve the measurement accuracy, the apparatus for obtaining the acoustic wave propagation time at the measurement point X is the same as the measurement apparatus for obtaining the acoustic wave propagation times at the preset points a and B. For example, both employ a metal ultrafast laser pulse apparatus as the measuring apparatus.
The product of the time T3 for the sound wave to propagate in the metal film on the wafer surface and the constant parameter (i.e. the ratio H/T of the height difference H and the time difference T obtained in step S10) is taken as the metal film thickness at the measurement point X1.
If the thickness of the metal film at other measuring points is to be measured again, for example, the thickness of the metal film at the measuring point X2 on the surface of the wafer substrate dense region 102 is measured, at the measuring point X2, the time T4 of the sound wave propagating in the metal film on the wafer surface is obtained, and the product of the time T4 of the sound wave propagating in the metal film on the wafer surface and the constant parameter (i.e., the ratio H/T of the height difference H and the time difference T obtained in step S10) is used as the thickness of the metal film at the measuring point X2.
And so on, the thickness of the metal film at any position on the surface of the wafer can be measured.
The method for measuring the thickness of the metal film on the surface of the wafer can monitor the thickness of the metal film on the surface of the wafer in real time, has high measurement accuracy, greatly improves the productivity and saves the cost. In addition, the method for measuring the thickness of the metal film on the surface of the wafer can obtain the surface height difference of two preset points without damaging the wafer, so that the wafer is prevented from being damaged, and the nondestructive measurement method is provided.
In the first embodiment, only two preset points a and B are selected in the step of obtaining the constant parameter. In order to further improve the accuracy of the measurement, in other embodiments of the present invention, a plurality of preset points may be set in the step of obtaining the constant parameter.
The invention also provides a second embodiment. The second embodiment is different from the first embodiment in that a plurality of preset points may be set in the step of obtaining the constant parameter. Fig. 4 is a schematic diagram illustrating a step of a method for measuring a thickness of a metal film on a surface of a wafer according to a second embodiment of the present invention, referring to fig. 4, the method of the present invention includes the following steps:
step S40, setting a plurality of preset points, combining the preset points two by two to obtain a plurality of ratios of the height difference to the time difference, and obtaining an average value of the plurality of ratios of the height difference to the time difference, and taking the average value as the constant parameter.
For example, as shown in fig. 5, which is a schematic top view of a wafer surface, a preset point a, a preset point B, a preset point C, and a preset point D are set on the wafer surface, where the preset point a and the preset point C are located in a substrate dense region 102, and the preset point B and the preset point D are located in a substrate loose region 101; combining the preset points A and B as a pair, combining the preset points C and D as a pair, and respectively obtaining the ratio of the height difference and the time difference of each pair of combinations; taking the average value of the ratios as the time constant.
It should be understood that in this embodiment, only four preset points are illustrated schematically, and in other embodiments of the present invention, in order to further improve the accuracy of the measurement, four or more preset points may be set according to actual requirements.
Step S41, measuring the thickness of the metal film on the wafer surface: and acquiring the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring point of the surface of the wafer, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point. This step is the same as step S11 of the first embodiment, and is not described again.
The invention also provides a third embodiment. The third embodiment is different from the second embodiment in the method of obtaining the ratio. Fig. 6 is a schematic diagram illustrating a third embodiment of a method for measuring a thickness of a metal film on a wafer surface according to the present invention, referring to fig. 6, the method of the present invention includes the following steps:
step S60, setting a plurality of preset points, combining the preset points in pairs to obtain a plurality of height differences and a plurality of time differences, and taking a ratio of an average value of the height differences to an average value of the time differences as the constant parameter.
For example, as shown in fig. 5, which is a schematic top view of a wafer surface, a preset point a, a preset point B, a preset point C, and a preset point D are set on the wafer surface, where the preset point a and the preset point C are located in a substrate dense region 102, and the preset point B and the preset point D are located in a substrate loose region 101; combining the preset points A and B as a pair, combining the preset points C and D as a pair, and respectively obtaining the height difference and the time difference of each pair of combinations; taking an average of a plurality of the height differences and an average of a plurality of the time differences; and obtaining the ratio of the average value of the height difference to the average value of the time difference, and taking the ratio as the constant parameter.
It should be understood that in this embodiment, only four preset points are illustrated schematically, and in other embodiments of the present invention, in order to further improve the accuracy of the measurement, four or more preset points may be set according to actual requirements.
Step S61, measuring the thickness of the metal film on the wafer surface: and acquiring the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring point of the surface of the wafer, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point. This step is the same as step S11 of the first embodiment, and is not described again.
In the above embodiments, in the step of measuring the thickness of the metal film on the surface of the wafer, only one measurement point is selected and the thickness measurement is performed. In some cases, it is desirable to obtain an average thickness for a given area. Accordingly, the present invention also provides a fourth embodiment. The fourth embodiment is different from the first embodiment in that the fourth embodiment can obtain an average thickness of a certain set area. Fig. 7 is a schematic diagram illustrating a step of a method for measuring a thickness of a metal film on a surface of a wafer according to a fourth embodiment of the present invention, referring to fig. 7, the method of the present invention includes the following steps:
step S70, obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the metal at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; and taking the ratio of the height difference to the time difference as the constant parameter. This step is the same as step S10 of the first embodiment, and is not described again.
Step S71, obtaining a plurality of measurement points in a set region of the wafer, obtaining the time of the acoustic wave propagating in the metal film on the metal surface at each measurement point, obtaining an average value of a plurality of times, and taking the product of the average value of the plurality of times and the constant parameter as the metal film thickness of the set region.
For example, as shown in fig. 8, which is a schematic top view of a wafer surface, a plurality of measurement points X1, X2, X3, X4, and X5 are obtained in a set region 103 (a region encircled by a dashed line frame in the figure) of the wafer; obtaining the time t1, t2, t3, t4 and t5 of the propagation of the sound wave in the metal film on the metal surface at each measuring point; acquiring an average value T of the times T1, T2, T3, T4 and T5; the product of the average value T of the plurality of times and the constant parameter obtained in step S70 is used as the metal film thickness of the setting region 103.
In this embodiment, only 5 measurement points are schematically illustrated, and in other embodiments, a plurality of measurement points, for example, 10 or 20 measurement points, may be selected to improve the accuracy and precision of the measurement.
The invention also provides a fifth embodiment. The fifth embodiment is different from the fourth embodiment in the method of obtaining the average value of the metal film thickness. Specifically, please refer to fig. 9, which is a schematic step diagram of a method for measuring a thickness of a metal film on a wafer surface according to a fifth embodiment of the present invention, wherein the method includes the following steps:
step S90, obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the metal at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; and taking the ratio of the height difference to the time difference as the constant parameter. This step is the same as step S10 of the first embodiment, and is not described again.
Step S91, obtaining a plurality of measurement points in a set region of the wafer, obtaining the time of the sound wave propagating in the metal film on the metal surface at each measurement point, taking the product of the time and the constant parameter as the thickness of the metal film at the measurement point, obtaining the average value of the plurality of metal films, and taking the average value as the thickness of the metal film in the set region.
For example, as shown in fig. 8, in the setting region 103 (the region encircled by the dashed line frame in the figure), a plurality of measurement points X1, C2, C3, C4, and C5 are obtained; obtaining the time t1, t2, t3, t4 and t5 of the propagation of the sound wave in the metal film on the metal surface at each measuring point; the product of the time and the constant parameter obtained in step 90 is taken as the metal film thickness at the measurement point, which is H1, H2, H3, H4 and H5, respectively; the average value of a plurality of metal film thicknesses H1, H2, H3, H4, and H5 is obtained and is taken as the metal film thickness of the set region.
In this embodiment, only 5 measurement points are schematically illustrated, and in other embodiments, a plurality of measurement points, for example, 10 or 20 measurement points, may be selected to improve the accuracy and precision of the measurement.
The method for measuring the thickness of the metal film on the surface of the wafer can monitor the thickness of the metal film on the surface of the wafer in real time, does not damage the wafer, greatly improves the detection speed, improves the productivity and saves the cost.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method for measuring the thickness of a metal film on the surface of a wafer is characterized by comprising the following steps:
obtaining a constant parameter: acquiring the time difference of the sound wave transmitted in the metal film on the surface of the wafer at two preset points on the surface of the wafer; obtaining the surface height difference of the two preset points; taking the ratio of the height difference to the time difference as the constant parameter;
measuring the thickness of the metal film on the surface of the wafer: and acquiring the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring point of the surface of the wafer, and taking the product of the time and the constant parameter as the thickness of the metal film at the measuring point.
2. The method as claimed in claim 1, wherein the wafer includes a substrate loosening region and a substrate compacting region, and in the step of obtaining the constant parameter, one of the preset points is located in the substrate loosening region and one of the preset points is located in the substrate compacting region.
3. The method for measuring the thickness of the metal film on the surface of the wafer according to claim 1, wherein in the step of obtaining the constant parameter, the time difference of the sound wave propagating in the metal film on the surface of the wafer is obtained by measuring the time of the sound wave propagating in the metal film at each preset point by using a metal ultrafast laser pulse device and subtracting the two obtained times to obtain the time difference.
4. The method for measuring the thickness of the metal film on the surface of the wafer as claimed in claim 1, wherein in the step of obtaining the constant parameter, the method for obtaining the surface height difference at the two preset points is: and carrying out topography measurement on the surface area of the wafer containing the preset points to obtain the surface height difference of the two preset points.
5. The method for measuring the thickness of the metal film on the surface of the wafer as claimed in claim 1, wherein the measuring device used in the step of obtaining the time difference of the sound wave propagating in the metal film on the surface of the wafer at two predetermined points is the same as the measuring device used in the step of obtaining the time of the sound wave propagating in the metal film on the surface of the wafer at the measuring points on the surface of the wafer.
6. The method as claimed in claim 1, wherein in the step of obtaining the constant parameter, a plurality of preset points are set, and the preset points are combined two by two to obtain a plurality of ratios of the height difference to the time difference, and an average value of the plurality of ratios of the height difference to the time difference is obtained and used as the constant parameter.
7. The method as claimed in claim 1, wherein in the step of obtaining the constant parameter, a plurality of preset points are set, and the preset points are combined two by two to obtain a plurality of height differences and a plurality of time differences, and a ratio of an average value of the height differences to an average value of the time differences is taken as the constant parameter.
8. The method as claimed in claim 1, wherein in the step of obtaining the constant parameter, the height difference between the two predetermined points is greater than a predetermined value.
9. The method as claimed in claim 1, wherein in the step of measuring the thickness of the metal film on the wafer surface, a plurality of measurement points are obtained in a set region of the wafer, the time of the acoustic wave propagating in the metal film on the surface is obtained at each measurement point, an average value of a plurality of times is obtained, and the product of the average value of the plurality of times and the constant parameter is used as the thickness of the metal film in the set region.
10. The method as claimed in claim 1, wherein in the step of measuring the thickness of the metal film on the wafer surface, a plurality of measurement points are obtained in a set region of the wafer, the time of the sound wave propagating in the metal film on the metal surface is obtained at each measurement point, the average value of the thickness of the plurality of metal films is obtained by taking the product of the time and the constant parameter as the thickness of the metal film at the measurement point, and the average value is taken as the thickness of the metal film in the set region.
CN202011517574.8A 2020-12-21 2020-12-21 Method for measuring thickness of metal film on surface of wafer Active CN112635349B (en)

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