KR20090103681A - Wafer grinding method and wafer grinding machine - Google Patents

Abstract

PURPOSE: A method and an apparatus for grinding a wafer are provided to grind a wafer with target thickness without influence due to a protecting tape. CONSTITUTION: An apparatus for grinding a wafer includes a grinding unit(3), a transfer unit(4), a noncontact thickness gauge, a contact thickness gauge, and a control unit. The grinding unit grinds a wafer(2). The transfer unit transfers the grinding unit for a grinding operation. The noncontact thickness gauge measures wafer thickness before a grinding process. The contact thickness gauge measures wafer thickness using the grinding process. The control unit controls the grinding thickness with reference to a measure data of the noncontact thickness gauge during the grinding process.

Description

Wafer grinding method and wafer grinding device {WAFER GRINDING METHOD AND WAFER GRINDING MACHINE}

The present invention relates to a wafer grinding method and a wafer grinding device.

In recent years, with the ever-increasing trend for high integration and package of semiconductor devices, the thickness of semiconductor chips (dies) is correspondingly decreasing. As a result, the back surface of the wafer is ground by the grinding means before dicing. In order to protect the circuit pattern formed on the front surface of the wafer, the back surface of the wafer is ground with a protective tape attached to the front surface of the wafer.

In addition, the back side of the wafer is polished to remove the warping of the wafer.

As the wafer thickness decreases, the final thickness of the wafer needs to be high precision. The final thickness of the wafer is generally considered to include the thickness of the protective film, but variations in wafer thickness directly affect the final thickness of the wafer.

In this regard, Japanese Unexamined Patent Publication No. 2007-335458 eliminates a protective tape without the influence of nitrides or oxides on the back of the wafer, and precisely measures the thickness of the wafer so that the wafer becomes a target thickness. The means described below is employed.

More specifically, according to Japanese Unexamined Patent Publication No. 2007-335458, during the roughing process, a contact thickness gauge is used to measure the overall thickness of the wafer including the protective tape, and a non-contact thickness gauge is used during the finishing process. The wafer backside is ground by measuring the thickness of only the wafer. Once the target final thickness is reached, the grinding process is terminated to achieve the precise final target thickness.

For example, Japanese Unexamined Patent Publication No. 2007-113980 discloses a non-contact thickness gauge.

According to Japanese Unexamined Patent Publication No. 2007-113980, a hollow cylinder probe for an eddy current displacement gauge is mounted on the lower surface of the gauge body, and a coil is disposed at the front end of the probe. At the lower surface, the laser radiation unit and the laser light receiving unit of the laser displacement gauge are disposed inside the hollow cylinder probe.

The coil generates an AC magnetic field and eddy currents are induced in the metal plate. The change in the coil inductance induced by the eddy current is detected, and the distance L2 from the probe to the metal plate is calculated.

On the other hand, the laser beam is emitted in the laser radiation unit, and the laser beam reflected from the coating surface is detected by the laser receiving unit. By trigonometry, the distance L1 between the laser displacement gauge and the coating surface is calculated. Based on the distances L1 and L2, the thickness of the coating is calculated.

However, during the grinding process, the environment of the wafer grinding surface is not stabilized by the grinding liquid and the grinding sludge, and as disclosed in Japanese Unexamined Patent Publication No. 2007-335458, the use of the non-contact thickness gauge during the finishing process, It contaminates the measuring device and makes it difficult to make stable measurements. Measurements made while the workpiece is not processed are influenced by an oxide film or a nitride film formed on the back surface of the wafer so that the wafer thickness cannot be accurately measured.

The present invention proposes to avoid the above-mentioned problems, and an object of the present invention is to measure the thickness of a wafer after the roughing process and before entering the finishing process by measuring with a non-contact thickness gauge, without being affected by the grinding liquid and the grinding sludge. It is to provide a wafer grinding device that can stably measure bays to produce wafers of a desired thickness.

In order to solve the above-mentioned problems, according to the first teaching of the present invention, a wafer grinding method of grinding a back surface of a wafer by roughing and finishing before dicing, wherein the wafer is contacted with a non-contact thickness gauge before the finishing process after the roughing process. A wafer grinding method is provided, characterized in that the thickness is actually measured.

As a result, in a stable state in which the grinding process does not proceed, the wafer thickness is measured by a non-contact thickness gauge without being affected by the grinding liquid or the grinding sludge.

According to the second teaching of the present invention, during the finishing process, the finishing thickness is finely adjusted based on the actual measurement data obtained from the non-contact thickness gauge before the finishing process, and the wafer thickness is measured by the contact thickness gauge. A wafer grinding method is provided.

Before the finishing process, the fact that the thickness of the wafer alone is actually measured by the non-contact thickness gauge, using a contact thickness gauge such as an in-process gauge during the finishing process, eliminates the influence of the protective tape, thus ensuring that the wafer is at a target thickness with high accuracy. Can be processed.

According to the third teaching of the present invention, after a grinding process performed by grinding the grinding means for holding and grinding a wafer, a transfer means for transferring the grinding means while grinding the wafer, and pushing the grinding means toward the wafer using a transfer means, and While finely adjusting the finishing thickness with reference to the measurement data of the non-contact thickness gauge for measuring the wafer thickness during the finishing process, the contact thickness gauge for measuring the thickness of the wafer during the finishing process, and the finishing process, Wafer grinding apparatus is provided, comprising control means for appropriately measuring wafer thickness with said contact thickness gauge.

The invention will be more fully understood from the description of the preferred embodiment of the invention, as described below in conjunction with the accompanying drawings.

In this way, if a non-contact thickness gauge is used after the roughing process, the wafer thickness can thus be measured in a stable state without being affected by the grinding liquid or the grinding sludge.

Since the thickness of the wafer only is measured prior to the finishing process, the wafer can be ground to the target thickness with high accuracy without being affected by the protective tape even during the finishing process, even with the contact thickness gauge.

1 is a diagram showing a system configuration of a core portion showing an example of a wafer grinding apparatus for performing a finish grinding process of all semiconductor wafer grinding processes according to the present invention.

FIG. 2 is an enlarged cross-sectional view illustrating an example of the wafer to be polished in FIG. 1 and a technique of actually measuring the thickness of the wafer to be polished.

3 is an enlarged cross-sectional view of the core portion illustrating a technique for actually measuring wafer thickness with a non-contact thickness gauge after a roughing process.

FIG. 1 shows an example of a semiconductor wafer grinding device 1 used for semiconductor wafer grinding. The semiconductor wafer grinding apparatus 1 (hereinafter referred to as grinding apparatus 1) is a holding means (to be described later) for holding a semiconductor wafer 2 (hereinafter referred to as wafer 2). And a grinding means 3 for grinding the wafer 2 and a transfer means 4 for grinding-feeding the grinding means 3.

In other words, the grinding process of the wafer 2 employs a machining method that performs a roughing process and a finishing process, and after the roughing process performed in the grinding apparatus (not shown) as a preceding process, the grinding apparatus ( 1) is used.

As shown in FIG. 2, the wafer 2 is composed of, for example, a protective film 5 attached directly to the surface 2a on which the circuit pattern 2c is formed. In other words, the wafer 2 has a configuration in which the protective film 5 is attached directly on the surface 2a on which the circuit pattern 2c is formed, and a support base member (not shown) is further attached thereto. It is.

The wafer 2 is held by, for example, holding means constituting an adsorption plate (chuck) (not shown) just above the upper surface of the rotating plate 7 rotated by the motor 6. In other words, the rotating plate 7 is formed in a disk shape, and the output shaft 8 of the motor 6 is mounted on the same axis as the central axis of the rotating plate 7 on the lower surface of the rotating plate. The rotating plate 7 rotates along the direction of arrow A by the driving force of the motor 6.

The thickness of the wafer 2 is measured by means to be described later. Before the finishing process, for example, the thickness of the wafer 2 is about 750 μm and the thickness of the protective film 5 is about 100 μm.

The grinding means 3 described below is pressed by the conveying means 4 while contacting the back surface 2b constituting the surface of the wafer 2 to be ground so that the wafer 2 has a predetermined thickness of about 30 μm. Grinding

The grinding means 3 is arranged at the front end of the substantially 10 L-shaped ram 10 standing upright on the apparatus body 9.

More specifically, the grinding means 3 is a grinding wheel mounted on the front part of the output shaft 12 of the motor 11 moving in the axial direction by the shaft portion (to be described later) constituting the conveying means 4. (13) is provided. During the process, the output shaft 12 of the motor 11 is mounted on the same axis as the central axis of the grinding wheel 13 on the upper surface of the grinding wheel 13 and in the direction of arrow B by the driving force of the motor 11. Rotate

The grinding wheel 13 grinds the back surface 2b of the wafer 2 held by the adsorption on the rotating plate 7, and is formed of, for example, diamond using a liquid adhesive as a bonding material. By using the liquid adhesive as the bonding material, the grinding wheel is elastic, and the impact when the grinding wheel 13 and the wafer 2 contact each other is alleviated. As a result, the back surface 2b of the wafer 2 can be processed with high precision. The grindstone portion 13a of the grinding wheel 13 is located on the rotating plate 7 facing the rear surface 2b of the wafer 2 held by the suction.

Next, the conveying means 4 for grinding-feeding the grinding means 3 comprises a ball screw 14 or the like. The ball screw 14 is driven by a motor (not shown) via a transfer control unit (to be described later). The grinding wheel 13 can then move in the Z direction with respect to the wafer 2. By transferring the grinding wheel 13 in pressure contact with the back surface 2b of the wafer 2, the back surface 2b of the wafer 2 can be ground by the grinding wheel 13.

The ball screw 14 is fixed on the L-shaped ram 10. Although the ram 10 is shown in a fixed form, the ram 10 of the grinding device 1 may alternatively be movable.

The grinding apparatus 1 for finishing which has the structure mentioned above detects the thickness of the wafer 2 hold | maintained by adsorption on the rotating plate 7 in real time in order to measure the thickness of the wafer 2 during a finishing process. And a detection means 15 as a control system such as a power controller. One example of the detection means 15 is a contact thickness gauge such as an in-process gauge.

In-process gauges are also referred to as so-called touch sensors. The change of the probe constituting the contactor is converted into a voltage signal by a differential transformer, and based on the converted voltage signal, the upper surface of the rotor plate 7 and the back surface 2b of the wafer 2 The interval P1-P2 between them, that is, the thickness of the wafer 2 and the protective film 5 is measured in real time.

The control system of the grinding apparatus 1 is the actual measured value P1-P2 from the detection means 15 which measures the thickness of the wafer 2 by the control unit 17 which controls the motor of the transfer means 4. And a control unit 16 to which a signal associated with is retrieved. Then, referring to the measurement data of the non-contact thickness gauge 20 (see FIG. 3), a control signal is applied to the motor of the transfer means 4 for fine adjustment of the final thickness of the wafer 2. That is to say, one example of the non-contact thickness gauge 20 is a unit that measures the reflection time of infrared light reflected on the interface between the wafer 2 and the protective film 5 using infrared transmission properties through metal and plastic. It is an IR (infrared ray) sensor which measures the thickness of a wafer.

Regarding the grinding device 1 having the above-described configuration, a method of determining the grinding quality at the time of the grinding step and the grinding step will be described below.

First, a wafer 2 is set on a grinding device (not shown) for roughing, and the wafer is roughed. During the roughing process, the wafer thickness is measured in real time by other detection means having a configuration similar to that of the detection means 15 of the finishing grinding device 1.

The grinding liquid and the resulting grinding sludge used during the roughing process are removed from the grinding surface of the wafer 2, and then, using the non-contact thickness gauge 20 (FIG. 3), the thickness of the wafer 2 is measured. . For finishing to be described later, the final measurement data is sent to the control unit 16 of the grinding apparatus 1.

As described above, in the grinding apparatus for roughing, the thickness of the wafer 2 is measured after the roughing process, and accordingly, the thickness of the wafer 2 is non-contact thickness gauge in the absence of the influence of the grinding liquid or the grinding sludge. It can be measured precisely by (20).

Since the thickness of the wafer 2 can be precisely measured after roughing in this manner, the polishing device 1 can be ground to the final target thickness by the finishing grinding device 1.

After the roughing process, the wafer 2 has the rotating plate 7 of the finishing apparatus 1 with the protective film 5 attached on the surface 2a of the wafer 2 and facing downward as shown in FIG. 1. Is maintained above the top surface.

Then, the wafer 2 is rotated by the motor 6 on the one hand, and on the other hand, the grinding wheel of the grinding means 3 mounted on the transfer means 4 at the front end of the ram 10. 13 rotates by the motor 11. Then, power is supplied to the motor 11 in accordance with the control command from the feed control unit 17, and the ball screw 14 is driven to move the grinding wheel 13 downward.

With the grinding wheel 13a of the grinding wheel 13 in contact with the back surface 2b of the wafer 2, the grinding wheel 13 is predetermined for each rotation of the rotary plate 7 to perform the finishing process. Move down by the infeed amount.

During the above-described finishing process, the thickness of the wafer 2 held by the adsorption on the rotating plate 7 is equal to the interval P1-P2 between the upper surface of the rotating plate 7 and the back surface 2b of the wafer 2. It is measured in real time by an in-process gauge as detection means 15 which suitably transmits the associated signal. In order to control the motor of the conveying means 4 of the control unit 16, the signal relating to the intervals P1-P2 is sent to the conveyance control unit 17.

After the roughing process, measurement data on the thickness of the wafer 2 measured using the non-contact thickness gauge 20 is supplied to the transfer control unit 17.

As a result, the thickness measurement data of the wafer 2 obtained using the non-contact thickness gauge 20 and the top surface of the rotating plate 7 and the wafer 2 measured by an in-process gauge suitable for performing the finishing process. The transfer control unit 17 generates a control signal so that the final thickness of the wafer 2 can be finely adjusted and finished to the target thickness of the wafer 2 based on the intervals P1-P2 between the rear surfaces 2b of the substrate. It feeds to the motor of the conveying means 4.

When the grinding process on the back surface 2b is normally completed in the above-described manner, the grinding wheel 13 retreats from the wafer 2, the motor 11 stops, and the rotation of the grinding wheel 13 is stopped. Thereby, the grinding process by the grinding apparatus 1 is complete | finished.

After the grinding process, a polishing process is performed by a polishing apparatus (not shown) in a state where the wafer 2 is fixed on the rotating plate 7 to remove the damaged layer or the like. As a result, damage such as unwanted cracking of the wafer 2 is prevented. The ground wafer 2 is separated from the rotor plate 7 and transported to a subsequent wafer processing process such as coating or dicing.

As described above, in the grinding process of the wafer 2 according to the present embodiment, a roughing process is first performed, and then, before the finishing process, the thickness of the wafer 2 is measured by the non-contact thickness gauge 20. . Accordingly, the grinding surface of the wafer 2 is unlikely to be affected by the grinding liquid used or the generated grinding sludge, unlike during the grinding process. Thus, the thickness of the wafer 2 can be precisely measured by the non-contact thickness gauge 20.

Despite the fact that a contact in-process gauge is used during the finishing process, by using the non-contact thickness gauge 20 to measure the thickness of the wafer 2 only prior to the finishing process, high precision without the influence of the protective tape It is possible to grind the road wafer 2 to a target thickness.

In other words, the non-contact thickness gauge 20 can be protected from errors or damage due to environmental contamination during the grinding process.

The present invention is not limited to the above-described embodiments. For example, instead of the in-process gauge used as the detection means 15, any other measuring means capable of measuring the back position of the wafer 2 fixed on the rotor plate 7 may be used with the same effect. have.

Further, in the above-described embodiment, the thickness was measured by the non-contact thickness gauge 20 on the roughing axis after the roughing process, but the thickness may be measured on the finishing axis before the finishing process, with the same effect.

Although the invention has been disclosed with reference to specific embodiments for purposes of illustration, it will be apparent to those skilled in the art that many modifications may be made without departing from the basic concept and scope of the invention.

Claims (3)

As a wafer grinding method of grinding the back surface of a wafer by roughing and finishing before dicing, After the roughing process and before the finishing process, measuring the thickness of the wafer with a non-contact thickness gauge. The wafer grinding method according to claim 1, wherein during the finishing process, the thickness of the wafer is finely adjusted based on the data obtained from the non-contact thickness gauge before the finishing process, and the wafer thickness is appropriately measured by the contact thickness gauge. Way. As a wafer grinding device, Grinding means for holding and grinding a wafer; Conveying means for conveying the grinding means for the grinding operation; A non-contact thickness gauge for measuring the wafer thickness before the finishing process, after the roughing process performed by pushing the grinding means towards the wafer using a conveying means; A contact thickness gauge for measuring the thickness of the wafer during the finishing process; And a control means for finely adjusting the finishing thickness with reference to the measurement data of the non-contact thickness gauge during the finishing process, and for appropriately measuring the wafer thickness with the contact thickness gauge.