Wafer polishing system

The wafer polishing system is disclosed. The wafer polishing system may comprise a polishing unit; a slurry distribution unit mounted on the polishing unit and distributing a slurry flowing into the polishing unit for wafer polishing; a slurry tank connected to the slurry distribution unit and storing the slurry; a slurry pump connected to the polishing unit and the slurry tank for transferring the slurry from the slurry tank to the polishing unit; a first circulation line in which one side is connected to the slurry tank; a second circulation line in which one side is connected to the other side of the first circulation line and the other side is connected to the slurry distribution unit; and a cleaning liquid supply unit connected to the second circulation line for supplying a cleaning liquid flowing through the second circulation line.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 to Korea Application No. 10-2017-0000828 filed in Korea on Jan. 3, 2017 which is hereby incorporated in its entirety by reference as if fully set forth herein.

TECHNICAL FIELD

Embodiments relate to a wafer polishing system.

BACKGROUND

Recently, the high integration of semiconductors has increased the processing and storage capacity of information per unit area. This has led to demands for large diameter semiconductor wafers, miniaturization of circuit line width, and multilayer wiring. In order to form a multi-layered wiring on a semiconductor wafer, high-level flatness of the wafer is required, and a wafer flattening process is required for such high-level flatness.

One of the wafer flattening processes is a wafer polishing process. The wafer polishing process is a step of polishing the upper and lower surfaces of the wafer with a polishing pad. The wafer polishing process is carried out using a polishing system having a polishing unit provided with an upper plate, a lower plate and a means for supplying polishing slurry to the polishing unit.

A pipe connected to the polishing unit for supplying the slurry to the polishing unit may be provided in the polishing system. However, the abrasive grains contained in the slurry may be adhered to the inside of the pipe to clog the pipe.

Furthermore, when such adhered slurry falls off and flows into the polishing unit, it may cause damage to the object to be polished and the polishing unit. Therefore, a solution to this problem is required.

SUMMARY

In one embodiment, a wafer polishing system may comprise a polishing unit; a slurry distribution unit mounted on the polishing unit and distributing a slurry flowing into the polishing unit for wafer polishing; a slurry tank connected to the slurry distribution unit and storing the slurry; a slurry pump connected to the polishing unit and the slurry tank for transferring the slurry from the slurry tank to the polishing unit; a first circulation line in which one side is connected to the slurry tank; a second circulation line in which one side is connected to the other side of the first circulation line and the other side is connected to the slurry distribution unit; and a cleaning liquid supply unit connected to the second circulation line for supplying a cleaning liquid flowing through the second circulation line.

In another embodiment, a wafer polishing system may comprise a polishing unit; a slurry distribution unit mounted on the polishing unit and distributing a slurry flowing into the polishing unit for wafer polishing; a slurry tank connected to the slurry distribution unit and storing the slurry; a slurry pump connected to the polishing unit and the slurry tank for transferring the slurry from the slurry tank to the polishing unit; a first circulation line in which one side is connected to the slurry tank; a second circulation line in which one side is connected to the other side of the first circulation line and the other is side connected to the slurry distribution unit; a cleaning liquid supply unit connected to the second circulation line for supplying a cleaning liquid flowing through the second circulation line; a flow control valve disposed in the second circulation line; a flow meter disposed in the second circulation line; a controller electrically connected to the flow control valve and the flow meter; an alarm electrically connected to the controller; and a drain line connected to the second circulation line for draining the cleaning liquid remaining in the second circulation line.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings. While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. However, the disclosure should not be construed as limited to the embodiments set forth herein, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments. In the drawings, sizes and shapes of elements may be exaggerated for convenience and clarity of description.

It may be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another. In addition, terms particularly defined in consideration of construction and operation of the embodiments are used only to describe the embodiments, but do not define the scope of the embodiments.

It will be understood that when an element is referred to as being “on” or “under” another element, it can be directly on/under the element, and one or more intervening elements may also be present. When an element is referred to as being “on” or “under,” “under the element” as well as “on the element” can be included based on the element.

In addition, relational terms, such as “on/upper part/above” and “under/lower part/below,” are used only to distinguish between one subject or element and another subject and element without necessarily requiring or involving any physical or logical relationship or sequence between such subjects or elements.

In the following, the term “line” refers to a pipe, through which wafer polishing slurry or cleaning liquid may flow. Further, the “automatic valve” is a valve that may be opened or closed using a control device remotely, and the “manual valve” means a valve that allows the operator to manually open or close.

FIG. 1is a view showing a polishing system of one embodiment. As shown inFIG. 1, the polishing system of the embodiment may include a polishing unit100, a slurry distribution unit200, a slurry tank300, a slurry pump400, a first circulation line510, a second circulation line520, a third circulation line530, and a cleaning liquid supply unit600.

In the polishing unit100, a wafer may be polished. For example, an upper plate and a lower plate may be provided in the polishing unit100, the wafer to be polished may be disposed therebetween, and the wafer may be polished by rotating the upper plate and/or the lower plate.

The slurry distribution unit200may be mounted on top of the polishing unit100and may serve to distribute a slurry for wafer polishing to the polishing unit100.

The slurry for wafer polishing may be used in polishing the wafer in the polishing unit100. Such a polishing slurry is provided in a liquid phase in which abrasive particles and liquid are mixed, thus may circulate through a circulation line.

The polishing slurry flows into the slurry distribution unit200and may be uniformly introduced into the polishing unit100through the slurry distribution unit200. When the polishing unit100and the slurry distribution unit200are viewed from above, the slurry distribution unit200may be configured such that a plurality of manifolds is formed radially with respect to the center of the polishing unit100.

Through the plurality of manifolds having such a structure, the polishing slurry may be uniformly introduced into the upper plate and the lower plate disposed in the polishing unit100.

Conventionally, a roller pump including a gear unit is used to introduce the polishing slurry into the polishing unit100. However, when the roller pump is continuously used, in particular the polishing slurry wears out the gear unit, which could lead to malfunction of the roller pump.

Furthermore, the worn particles of the gear unit may damage a slurry transfer tube provided in the roller pump, or the worn particles may flow into the polishing unit100and cause scratches on the wafer surface to be polished.

Therefore, in the embodiment, by replacing the conventional roller pump with the slurry distribution unit200not provided with the gear unit, it is possible to effectively suppress damage of the slurry transfer tube in the roller pump, wafer scratch generation, and the like.

The slurry tank300is connected to the slurry distribution unit200and may store a slurry. Since a large amount of the slurry may be stored the slurry tank300, an agitator may be provided to suppress the phenomenon that particles constituting the slurry are separated from the liquid by sinking the particles.

Although not shown, a make-up line for replenishing the slurry may be provided in the slurry tank300, and the slurry may be replenished to the slurry tank300through the make-up line.

The slurry pump400is connected to the polishing unit100and the slurry tank300, and is capable of transferring the slurry from the slurry tank300to the polishing unit100.

Since the polishing unit100, the slurry tank300and the slurry pump400are connected to each other through the first circulation line510to the third circulation line530, when the slurry pump400pumps the slurry, the slurry may circulate through the polishing unit100and the slurry tank300through the first circulation line510to the third circulation line530.

The first circulation line510may be connected to the slurry tank300at one side and connected to the second circulation line520at the other side and the slurry pump400may be disposed.

The second circulation line520may be connected to the other side of the first circulation line510at one side and connected to the slurry distribution unit200at the other side. The second circulation line520may be connected to a supply line540for supplying a cleaning liquid for cleaning the inside of the second circulation line520and a second drain line730for draining the cleaning liquid. The cleaning liquid may be, for example, de-ionized water.

The third circulation line530may be connected to the polishing unit100at one side and connected to the slurry tank300at the other side, thus the third circulation line530may connect the polishing unit100and the slurry tank300.

The cleaning liquid supply unit600is connected to the second circulation line520and may supply the cleaning liquid flowing through the second circulation line520. The cleaning liquid may be supplied to the second circulation line520for cleaning the inside of the second circulation line520.

After the cleaning process of the second circulation line520is completed, the cleaning liquid remaining in the second circulation line520may be drained to the outside through the second drain line730.

A drain device700may be disposed in the third circulation line530to drain the slurry flowing out from the polishing unit100to the outside. The slurry flowing out of the polishing unit100may include, for example, wafer particles and other foreign substances which are polished off from the wafer.

When a wafer polishing process continues, the content of the above-mentioned wafer particles and other foreign substances in the slurry increases, therefore, it is necessary to replace such a contaminated slurry. Accordingly, the drain device700may drain this contaminated slurry to the outside through a first drain line720connected thereto.

That is, when the contamination degree of the slurry exceeds the reference value, a part or all of the slurry is drained to the outside through the drain device700, and the insufficient slurry may be replenished through the slurry tank300.

The first drain line720is connected to the drain device700and may serve as a path for draining the contaminated slurry flowing out from the drain device700to the outside. A valve V1may be disposed in the first drain line720to close or open the first drain line720.

In addition, a third drain line710may be further included in the embodiment. The third drain line710may be connected to the first circulation line510and disposed below the slurry tank300. If necessary, the slurry stored in the slurry tank300may be drained to the outside through the first drain line710. A valve V2may be disposed in the third drain line710to close or open the first drain line710. The third drain line710, the first drain line720, and the second drain line730may alternatively be referred to as a first drain line710, second drain line720, and third drain line730.

Furthermore, the second drain line730may be further included in the embodiment. The second drain line730, as described above, may serve as a drain for draining the cleaning liquid remaining in the second circulation line520after the completion of the cleaning process of the second circulation line520.

In the embodiment, a flow control valve521and a flow meter523disposed between the slurry distribution unit200and the second drain line730, and disposed in the second circulation line520may be further included.

The flow meter523may measure the flow rate of the slurry supplied to the slurry distribution unit200and the polishing unit100by flowing through the second circulation line520when the wafer polishing step is performed.

The flow control valve521may control the flow rate of the slurry to be within a predetermined range based on the flow rate of the slurry measured by the flow meter523. This flow rate control may be implemented through a controller810, which will be described in detail below.

In the embodiment, a third automatic valve733may be disposed in the second drain line730. The second drain line730may be opened or closed by opening or closing the third automatic valve733.

In the embodiment, a supply line540may be further included. The supply line540may be connected to the second circulation line520at one side and connected to the cleaning liquid supply unit600at the other side. A check valve543, a first manual valve541, and a first automatic valve542may be disposed in the supply line540.

The check valve543may prevent the slurry present in the second circulation line520from flowing back to the cleaning liquid supply unit600. The first manual valve541and the first automatic valve542may be opened or closed to open or close the supply line540.

When the slurry flows backward to the cleaning liquid supply unit600, there is a possibility that various components, devices, etc. constituting the cleaning liquid supply unit600are seriously contaminated and damaged. Therefore, in order to prevent this surely, a check valve543, a first manual valve541, and a first automatic valve542may be disposed in the supply line540.

In the embodiment, a second automatic valve522may be disposed between the first circulation line510and the supply line540, and disposed in the second circulation line520. The second automatic valve522may be opened or closed to open or close the second circulation line520.

When the second automatic valve522is closed, the slurry does not flow through the second circulation line520, therefore the slurry is not supplied to the slurry distribution unit200and the polishing unit100connected to the second circulation line520.

In the embodiment, a first bypass line550may be disposed between the slurry pump400and the second automatic valve522. The first bypass line550may be connected to the first circulation line510at one side and connected to the slurry tank300at the other side. A second manual valve552may be disposed at the first bypass line550.

The first bypass line550may serve to bypass the slurry pumped from the slurry pump400directly to the slurry tank300, when the polishing unit100stops supplying the slurry due to abnormal operation of the polishing system, failure of any part of constituting the polishing system and the like.

In the embodiment, a second bypass line560may be disposed between a branch point of the first bypass line550from the first circulation line510and the second automatic valve522. The second bypass line560may be connected to the first circulation line510at one side and connected to the slurry tank300at the other side.

It is necessary to prevent the slurry from flowing into the second circulation line520and bypass the slurry to the slurry tank300during the course of the second circulation line520cleaning process. Therefore, the slurry may be bypassed to the slurry tank300by using the second bypass line560.

On the other hand, since the cleaning process of the second circulation line520is not an emergency, it may be appropriate to use the second bypass line560without using the first bypass line550when the slurry is bypassed.

A fourth automatic valve564may be disposed in the second bypass line560. As the fourth automatic valve564is opened or closed, the second bypass line560may be opened or closed.

FIG. 2is a view showing the circulation of the slurry for wafer polishing in the course of wafer polishing process inFIG. 1. During the wafer polishing process, the slurry may flow in the direction of the solid arrow.

The slurry flowing out of the slurry tank300is pumped by the slurry pump400while flowing through the first circulation line510, at which time the valve V2provided in the third drain line710may be closed.

The slurry flowing out of the slurry pump400flows through the first circulation line510and into the second circulation line520, at which time the second manual valve552and fourth automatic valves564may be closed.

The slurry flowing into the second circulation line520may flow into the slurry distribution unit200through the second circulation line520. At this time, the second manual valve552is opened, and the first manual valve541, the first automatic valve542, and the third automatic valve733are closed, and the slurry may flow through the flow meter523and the control valve521, and the slurry may flow into the slurry distribution unit200along the second circulation line520.

The slurry flowing into the slurry distributing unit200is uniformly distributed and introduced into the polishing unit100to be used in the wafer polishing process, and the slurry flowing out of the polishing unit100may be returned to the slurry tank300through the third circulation line530.

At this time, the slurry passes through the drain device700disposed in the third circulation line530, and the valve V1disposed in the first drain line720may be closed because the slurry continues to circulate the circulation lines.

FIG. 3is a view showing the flow of a cleaning liquid and a slurry for polishing a wafer in the course of the polishing system cleaning process inFIG. 1. InFIG. 3, hidden line arrows indicate the flow of the cleaning liquid, and solid line arrows indicate the flow of the slurry.

The inside of the second circulation line520directly connected to the slurry distribution unit200and the polishing unit100and supplying the slurry to them needs to be cleaned periodically or aperiodically.

If the inside of the second circulation line520is not cleaned, the slurry may adhere to the inner surface of the second circulation line520, as a result, the second circulation line520may be blocked or the flow rate may be reduced.

When debris from the inner surface of the second circulation line520flows into the polishing unit100after the adhered slurry is grown to a certain size, scratches or other damage may be caused to the wafer, which may result in poor wafer processing.

Therefore, the second circulation line520may be cleaned with a cleaning liquid to solve the above-described problems. Cleaning of the second circulation line520may proceed to the step as follows.

First, the second automatic valve522is closed and the fourth automatic valve564is opened to bypass the slurry to the slurry tank300. In this state, the slurry is not supplied to the second circulation line520after the second automatic valve522.

In addition, the first automatic valve542and the first manual valve541are opened to supply the cleaning liquid to the second circulation line520. At this time, the third automatic valve733is closed to prevent the cleaning liquid from flowing to the second drain line730. In this state, the inside of the second circulation line520is cleaned for a predetermined time.

At this time, the cleaning liquid may flow into the slurry distribution unit200and the polishing unit100through the second circulation line520. The cleaning liquid flowing out of the polishing unit100may be drained to the outside through the drain device700and the first drain line720. Of course, the valve V1disposed in the first drain line720is opened.

It is necessary to drain the cleaning liquid remaining in the second circulation line520after the cleaning of the second circulation line520using the cleaning liquid is completed.

If the wafer polishing process is performed by circulating the slurry again through the second circulation line520while the cleaning liquid remains in the second circulation line520, the slurry may be diluted by the cleaning liquid to lower the polishing ability, which may increase the wafer polishing process time.

In order to solve such a problem, the process of draining the cleaning liquid remaining in the second circulation line520may proceed as follows.

The first manual valve541and the first automatic valve542are closed to block the flow of the cleaning liquid into the second circulation line520. In addition, the third automatic valve733is opened to drain the cleaning liquid remaining in the second circulation line520to the outside through the second drain line730.

In this state, some of the cleaning liquid remaining in the second circulation line520may be drained to the outside through the second drain line730.

The rest of the cleaning liquid may be drained to the outside through the second circulation line520, the slurry distribution unit200, the polishing unit100, a part of the third circulation line530, the drain device700and the first drain line720.

The cleaning liquid remaining in the second circulation line520may be very effectively drained to the outside through the two-directional passages, i.e., the first drain line720and the second drain line730.

After the completion of the drain of the cleaning liquid remaining in the second circulation line520, the second automatic valve522is opened again, the fourth automatic valve564is closed, and the valve V1disposed in the first drain line720is closed. The slurry may be circulated again between the polishing unit100and the slurry tank300, and the polishing process may be carried out again.

In the embodiment, the second circulation line520is cleaned with the cleaning liquid supplied through the supply line540to effectively remove the slurry adhered to the inside of the second circulation line520, clogging of the second circulation line520, poor polishing of the wafer, and the like may be effectively suppressed.

Furthermore, in the embodiment, after the completion of the second circulation line520cleaning process, the cleaning liquid remaining in the second circulation line520may be effectively drained to the outside through the second drain line730. It is possible to effectively suppress the dilution of the slurry by the cleaning liquid remaining in the second circulation line520when the slurry is introduced into the polishing unit100again.

FIG. 4is a view for explaining the control and the alarm of the polishing system of one embodiment. The control and alarm of the polishing system may be performed about the second circulation line520, and may be applied to both the polishing process in which the slurry flows in the second circulation line520and the cleaning process in which the cleaning liquid flows in the second circulation line520.

However, in the following, for example, only the case of the polishing process will be described. It will be apparent to those skilled in the art from the following description that the control and alarm of the polishing system are applied to the cleaning process.

The embodiment may further include the controller810electrically connected to the flow control valve521and the flow meter523and an alarm820electrically connected to the controller810.

The controller810may receive information on the flow rate of the slurry from the flow meter523. The controller810may control the flow rate so that the flow rate of the slurry does not deviate from a predetermined range.

When the controller810sends an operation signal to the flow control valve521, the flow control valve521receiving the operation signal controls the valve opening rate and the like to control the flow rate of the slurry.

A flow rate range including the upper and lower limits of the slurry flow rate flowing through the second circulation line520may be set and input to the controller810. The flow rate range may be set differently when the slurry flows and when the cleaning liquid flows.

When the flow control valve521cannot control the slurry flow rate and the flow rate of the slurry flowing through the second circulation line520is out of the setting range, the alarm820may be operated.

That is, when the flow rate of the slurry flowing through the second circulation line520is out of a predetermined range, the controller810sends an operation signal to the alarm820, and the alarm820may operate.

The operation of the alarm820may be implemented in various ways such as a warning sound, a warning light, a warning indication on a display device connected to the alarm820, and the like.

In the embodiment, the flow control valve521may used to adjust the flow rate of the slurry or the cleaning liquid within a predetermined range, so that the polishing system may be stably operated.

Furthermore, when the flow rate control valve521cannot control the flow rate, if the flow rate of the slurry or the cleaning liquid deviates from a predetermined range, the alarm unit820operates and the operator may take quick and effective measures.

While only a few have been described above with respect to the embodiments, various other forms of implementation are possible. The technical contents of the above-described embodiments may be combined in various forms other than mutually incompatible technologies, and may be implemented in a new embodiment through this.