US20150099423A1

US20150099423A1 - TSV Wafer Thinning Controlling Method and System

Info

Publication number: US20150099423A1
Application number: US14/253,484
Authority: US
Inventors: Feng Jiang; Haiyang Gu; Hongwen HE
Original assignee: National Center for Advanced Packaging Co Ltd
Current assignee: National Center for Advanced Packaging Co Ltd
Priority date: 2013-06-17
Filing date: 2014-04-15
Publication date: 2015-04-09
Also published as: CN103346099A; CN103346099B

Abstract

A TSV wafer thinning controlling method and system is provided, which can improve the accuracy of the wafer thinning technique. The system includes a chuck table used for carrying a wafer and a grinding device used for thinning the wafer; and further includes: an infrared sensor equipped on the chuck table or grinding device, and a measurement feedback system connected with the infrared sensor and the grinding device; wherein, the infrared sensor comprises an infrared emitting and receiving circuit, signal amplifying and filtering circuit and a data processor.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from CN Patent Application Serial No. 201310240770.9, filed on Oct. 9, 2013, the entire contents of which are incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present invention is related to micro-electronics technology, especially related to a TSV wafer thinning controlling method and system.

BACKGROUND OF THE INVENTION

With high requirement of electronic products, the size of chips becomes thinner and thinner. However, traditional solutions as decreasing the distance between the interconnection lines is restricted by physical properties of materials and processing equipments. The concept of TSV (Through Silicon Via) is proposed based on status in quo.
TSV process can realize the 3D interconnection between wafers (chips) or between a chip and a substrate by producing metal columns in wafers, which can greatly reduce the package thickness. Compared with the traditional stacking techniques including the bonding technique, this interconnection method has increased the 3D stacking density and reduced packaging dimension, thus it can greatly improve the speed of the chip and reduce the power consumption. TSV process is therefore widely considered as the fourth generation of packaging technology and becomes one of the key techniques for the high density packaging.
TSV is a process starts with producing a conductive metal column and then thinning the backside of the wafer through grinding. The aim of the thinning process is to minimize the distance from the backside of the wafer to the bottom of the metal column, which is normally within the range of 1˜5 μm in practical.
Normally, there are two ways to measure the thickness of the wafer during the thinning technique:
Contacting measurement: one end of a contact point is connected to wafers and the other end is connected with a reference point, to obtain the thickness of the whole wafer.
Non-contacting measurement: an optical sensor is used to gain the thickness of the whole wafer without contacting the wafer. The key point is to measure the thickness from the backside of the wafer to the front of the metal layer.
Though the distance from the bottom of the conductive metal column to the backside of the wafer can be calculated by applying the above two thickness measurement methods, errors exist in both the depth of the holes punched on the wafer and the depth of the conductive metal column deposition. Considering of which, the distance from the bottom of the conductive metal column to the backside of the wafer cannot be precisely measured, which will further influence subsequent processing.
To solve the problems described above, it is necessary to provide a TSV wafer thinning controlling method and system based on infrared technology so as to improve the accuracy of the wafer thinning technique.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a TSV wafer thinning controlling method and system, which can improve the accuracy of the wafer thinning technique.
A TSV wafer thinning controlling method provided is applied to a thinning process of a TSV wafer, wherein, an infrared sensor is set on a grinding device and the method includes:
setting an initial value of the distance from the backside of a TSV wafer to the bottom of via-holes;
launching infrared rays and receiving reflected waves;
filtering reflected waves of the bottom of the via-holes in the TSV wafer and calculating the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process;
comparing the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process with the initial value;
generating a signal to terminate the thinning processing when the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process equal to the initial value.
A TSV wafer thinning controlling system provided includes a chuck table used for carrying a wafer and a grinding device used for thinning the wafer; wherein, the system further includes:
an infrared sensor equipped on the chuck table or grinding device,
a measurement feedback system connected with the infrared sensor and the grinding device;
wherein, the infrared sensor comprises an infrared emitting and receiving circuit, signal amplifying and filtering circuit and a data processor.
By using the technical schemes of the present invention, the distance from the backside of the TSV wafer to the bottom of the via-holes can be measured via the infrared sensor, and the invention has following merits: non-contacting measurement with high accuracy is effectively implemented; the distance from the backside of the TSV wafer to the bottom of the via-holes, other than thickness of the whole wafer, is accurately managed, which is helpful for following wafer processing.

BRIEF DESCRIPTION OF THE DRAWINGS

To give a further description of the embodiments in the present invention or the prior art, the appended drawings used to describe the embodiments and the prior art will be introduced as follows. Obviously, the appended drawings described here are only used to explain some embodiments of the present invention. Those skilled in the art can understand that other appended drawings may be obtained according to these appended drawings without creative work.

FIG. 1 illustrates the flow chart of the TSV wafer thinning controlling method based on infrared technology according to an embodiment of the present invention;

FIG. 2 illustrates the schematic diagram of the TSV wafer thinning controlling system based on infrared technology according to an embodiment of the present invention;

FIG. 3 illustrates the top view of a chuck table in an embodiment according to an embodiment of the present invention;

FIG. 4 illustrates the theory of measuring the distance from the TSV wafer to the bottom of the via-holes according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention are described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments by which the invention may be practiced. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the scope of the invention to those skilled in the art. Among other things, the present invention may be embodied as systems, methods or devices. The following detailed description should not to be taken in a limiting sense.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrase “in one embodiment” as used herein does not necessarily refer to the same embodiment, though it may. Furthermore, the phrase “in another embodiment” as used herein does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.
In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on”. The term “coupled” implies that the elements may be directly connected together or may be coupled through one or more intervening elements. Further reference may be made to an embodiment where a component is implemented and multiple like or identical components are implemented.
While the embodiments make reference to certain events this is not intended to be a limitation of the embodiments of the present invention and such is equally applicable to any event where goods or services are offered to a consumer.
Further, the order of the steps in the present embodiment is exemplary and is not intended to be a limitation on the embodiments of the present invention. It is contemplated that the present invention includes the process being practiced in other orders and/or with intermediary steps and/or processes.
As shown in FIG. 1, a TSV wafer thinning controlling method based on infrared technology according to an embodiment of the present invention includes following steps:
Step 1: an infrared sensor is calibrated, the location of the infrared sensor on a grinding device is decided, the infrared sensor is fixed on the grinding device and the initial value of the distance from the backside of the TSV wafer to the bottom of via-holes is set;
Step 2: the back-thinning technique is applied to the TSV wafer;
Step 3: the infrared sensor launches infrared rays and receives the reflected waves;
Step 4: reflected waves of the bottom of the via-holes in the TSV wafer are filtered by a data processor and the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is calculated;
Step 5: the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is compared with the initial value in real time;
Step 6: the processing is terminated when the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is equal to the initial value.
Similarly, a TSV wafer thinning controlling system based on infrared technology, which includes a chuck table used for carrying and a grinding device used for thinning the wafer, is provided. An infrared sensor used for measuring the distance from the backside of the TSV wafer to the bottom of the via-holes is equipped on the chuck table or grinding device. A measurement window is set at the bottom of the infrared sensor and a measurement feedback system is connected with the infrared sensor.
The measurement feedback system is also connected with the grinding device. Once the signal indicating that the distance from the backside of the TSV wafer to the bottom of the via-holes is equal to the initial value is generated by the infrared sensor and transferred to the grinding device via the measurement feedback system, the grinding device stops working.
As shown in FIG. 2, the schematic diagram of the TSV wafer thinning controlling system based on infrared technology according to an embodiment of the present invention is illustrated. The system includes a chuck table 10 and a grinding device 20. The TSV wafer 30 is put on the chuck table 10, and the grinding device 20 is adapted to thin the backside of the TSV wafer 30. Preferably, there is a protective tape 11 set on the chuck table 10, and the TSV wafer 30 is put on the protective tape 11, so as to reduce the damage produced by the chuck table to the front structure of TSV wafer during the thinning process.
FIG. 3 illustrates the top view of a chuck table in an embodiment according to an embodiment of the present invention. In the present embodiment, there are three carrying units in the chuck table. The quantity of the carrying units may be different in other situations.
The grinding device 20 includes a transmission shaft 21 and a chassis 22 for fixing and connecting. The chassis 22 includes several grinding units 23 and the thinning process of TSV wafer is implemented by the grinding units 23.
In an embodiment of the present embodiment, an infrared sensor 40 is fixed on the chassis 22 of the grinding device 20 through an installation unit 24. In another embodiment, the infrared sensor 40 may be fixed directly onto the grinding device 10. A measuring window 41 is set below the infrared sensor 40 and the measuring window 41 includes a blowing device or deionized water injection device. The measuring window 41 will blow or reject deionized water during measuring to minimize the interference and therefore increase the accuracy of measurement.
In an embodiment of the present embodiment, the infrared sensor 40 includes an infrared emitting and receiving circuit, signal amplifying and filtering circuit, a data processor, and a measurement feedback system connected with the infrared sensor 40. When measuring, the infrared sensor emits infrared rays through the infrared emitting and receiving circuit and certain number of reflected waves are then received. The signal amplifying and filtering circuit amplifies the reflected wave signals and eliminates clutter out from the reflected waves. Then the data processor filters reflected waves from the bottom of the TSV wafer via-holes, and calculates the distance from the backside of the TSV wafer to the bottom of the via-holes.
In an embodiment of the present embodiment, the TSV wafer thinning controlling method based on infrared technology may include following steps:
Step 1′: a calibration and record of an infrared sensor is carried out, the location of the infrared sensor on a grinding device is decided, the infrared sensor is fixed on the grinding device and the initial value of the distance from the backside of the TSV wafer to the bottom of the via-holes is set.
The infrared sensor is fixed onto a chassis of the grinding device, the chassis and the infrared sensor will move simultaneously through a transmission shaft. Grinding units on the chassis will thin the backside of the TSV wafer.
Since the backside of the wafer need be etched after the thinning process so as to expose the TSV conductive column, Normally it is prefer to keep the distance from the backside of the TSV wafer to the bottom of the via-holes larger than 1 μm, especially within 1˜20 m. The initial value should be set as smaller than the thickness of the TSV wafer before thinning, in an embodiment, the initial value is set as 5 μm.
Step 2′: the back-thinning technique is applied to the TSV wafer.
The back-thinning technique involves one or more processes from coarse grinding, fine grinding and polishing Preferably, the backside of the TSV wafer should be treated by coarse grinding, fine grinding and polishing.
In an embodiment of the present embodiment, a TSV wafer with a thickness of 700 μm is chosen, the wafer may be made from silicon or glass. The TSV conductive column is made from copper and 200 μm high. The back-thinning technique mentioned above is adapted to grind the TSV wafer.
Step 3′: the infrared sensor launches infrared rays and receives the reflected waves;
Preferably, the infrared rays emitted from the infrared sensor are near infrared wave.
Step 4′: reflected waves of the bottom of the via-holes in the TSV wafer is filtered by a data processor and the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is calculated;
The measurement theory of the infrared sensor is illustrated in FIG. 4. The infrared sensor emits infrared rays R1, R2 and the infrared rays reflect and refract at the same time at the surface of the wafer. For example, the infrared ray R1 partially reflects at the backside of the wafer; the infrared ray R2 partially refracts at the backside of the wafer, and the infrared ray refracted reflects at the bottom of the TSV conductive column and then refracts out of the TSV wafer. At this situation, there will form two beams of interfered light after the reflection and/or refraction of the infrared rays R1 and R2. Hence, the distance from the backside of the TSV wafer to the bottom of the via-holes can be calculated through the refraction law.
Step 5′: the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is compared with the initial value in real time.
The measuring frequency is equal to or larger than 50 times/sec. The distance from the backside of the TSV wafer to the bottom of the via-holes currently obtained from each measurement is compared with the initial value which is 5 μm. Larger measuring frequency of the infrared sensor will generate better real-time performance of thinning craft and higher accuracy.
Step 6′: the processing is terminated when the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process is equal to the initial value.
While the infrared sensor detects a distance as 5 μm, the back-thinning of the TSV wafer is terminated through measurement feedback system.
From the above descriptions, it can be seen that by using the technical schemes of the present invention, the distance from the backside of the TSV wafer to the bottom of the via-holes can be measured via the infrared sensor, and the invention has following merits:
Non-contacting measurement with high accuracy is effectively implemented;
The distance from the backside of the TSV wafer to the bottom of the via-holes, other than thickness of the whole wafer, is accurately managed, which is helpful for following wafer processing.
For those skilled in the art, they should aware that obviously the present invention has not only the details in the embodiments above, meanwhile, they should be capable of implementing the present invention in other specific forms without deviating the spirit and basic features of the present invention. Therefore, the embodiment is exemplary and non-restrictive under whichever circumstances. The region of the present invention is restricted by the claims attached other than the illustrations above. Considering of which, all the adjustments in accordance with the principle and the scope of claims are considered to be within the protection scope of the present invention. Any signs in the drawings of the claims should not be considered as the restriction to the claims referred.
Moreover, it should be understood that although this literature is described in embodiments, however, not each embodiment has merely one independent technical scheme. This way of description is used barely for clarity. For those skilled in the art, this literature should be considered as an entirety. Technical schemes from each embodiment could be properly combined and form as other embodiments that can be understood by those skilled in the art.

Claims

1. A TSV wafer thinning controlling method, applied to a thinning process of a TSV wafer, wherein, an infrared sensor is set on a grinding device and the method comprises:

setting an initial value of the distance from the backside of a TSV wafer to the bottom of via-holes;

launching infrared rays and receiving reflected waves;

filtering reflected waves of the bottom of the via-holes in the TSV wafer and calculating the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process;

comparing the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process with the initial value;

generating a signal to terminate the thinning processing when the distance from the backside of the TSV wafer to the bottom of the via-holes during the thinning process equal to the initial value.

2. The method of claim 1, wherein, the thinning process comprises one or more processes from coarse grinding, fine grinding and polishing

3. The method of claim 1, wherein, the initial value is set as smaller than the thickness of the TSV wafer before thinning

4. The method of claim 3, wherein, the initial value is larger than 1 μm.

5. The method of claim 1, further comprising:

calibrating the infrared sensor.

6. A TSV wafer thinning controlling system comprising a chuck table used for carrying a wafer and a grinding device used for thinning the wafer; wherein, the system further comprises:

an infrared sensor equipped on the chuck table or grinding device,

a measurement feedback system connected with the infrared sensor and the grinding device;

wherein, the infrared sensor comprises an infrared emitting and receiving circuit, signal amplifying and filtering circuit and a data processor.

7. The system of claim 6, further comprises: a measurement window set at the bottom of the infrared sensor.

8. The system of claim 7, wherein, the measuring window comprises a blowing device or deionized water injection device.

9. The system of claim 6, wherein, the lowest position of the infrared sensor is higher than the lowest position of the grinding device.

10. The system of claim 6, further comprising: a protective tape set on the front side surface of TSV wafer.

11. The system of claim 6, wherein the grinding device comprises a transmission shaft and a chassis for fixing and connecting.

12. The system of claim 11, wherein the chuck table comprises three carrying units, and/or the chassis comprises several grinding units.

13. The system of claim 11, wherein the infrared sensor is fixed on the chassis of the grinding device through an installation unit.

14. The system of claim 6, wherein the infrared sensor is fixed directly onto the grinding device.

15. The method of claim 6, wherein, the measuring frequency of the infrared sensor is equal to or larger than 50 times/sec.

16. The method of claim 6, wherein, the infrared sensor emits near infrared wave.