CN112405305A

CN112405305A - Single-side polishing device and method

Info

Publication number: CN112405305A
Application number: CN202011309902.5A
Authority: CN
Inventors: 郭宇轩
Original assignee: Xian Eswin Silicon Wafer Technology Co Ltd; Xian Eswin Material Technology Co Ltd
Current assignee: Xian Eswin Silicon Wafer Technology Co Ltd; Xian Eswin Material Technology Co Ltd
Priority date: 2020-11-20
Filing date: 2020-11-20
Publication date: 2021-02-26

Abstract

The invention provides a single-side polishing device and a single-side polishing method, and belongs to the technical field of semiconductors. A single-side polishing apparatus comprising: the fixing part is used for fixing the wafer to be polished; the polishing head is positioned above the fixing part and is used for polishing the wafer; the control pins are distributed on the periphery of the wafer and used for fixing the edge of the wafer; the plurality of spray heads are positioned below the fixing part and used for spraying liquid to the surface of one side, away from the polishing head, of the wafer; and the control mechanism is used for controlling the pressure of the liquid according to the position of the polishing head and the shape of the surface of the wafer. The invention can improve the surface flatness of the wafer.

Description

Single-side polishing device and method

Technical Field

The invention relates to the technical field of semiconductors, in particular to a single-side polishing device and a single-side polishing method.

Background

Single crystal silicon as a base material for semiconductor device production has very strict requirements on flatness, roughness, metal, particles, and the like of its surface, and in order to satisfy these requirements, it is required to be achieved by chemical mechanical polishing.

In the single crystal silicon wafer process flow, Chemical Mechanical Polishing (CMP) is a very important process, sometimes referred to as Chemical Mechanical planarization. So-called chemical mechanical polishing, generally, a single crystal silicon wafer is mounted on a wafer carrier and brought into contact with a polishing layer of a polishing pad, the polishing pad is rotated at a high speed, a polishing medium (e.g., slurry) is dispensed onto the polishing pad and sucked into a gap between the semiconductor wafer and the polishing layer, the semiconductor wafer is rubbed against the polishing pad by the pressure of a pressure device, and is ground to remove excess material, and finally, the ground surface of the semiconductor wafer is polished and a flat surface is obtained.

With the recent increase in higher performance and higher integration density and demand of semiconductor devices, there has been an increasing demand for improving productivity and surface quality in CMP of semiconductor wafers, wherein how to improve the flatness of the polished surface of the semiconductor wafer after final polishing is the focus of research in the current chemical mechanical polishing process.

Disclosure of Invention

The invention aims to provide a single-side polishing device and a single-side polishing method, which can improve the surface flatness of a wafer.

To solve the above technical problem, embodiments of the present invention provide the following technical solutions:

in one aspect, an embodiment of the present invention provides a single-side polishing apparatus, including:

the fixing part is used for fixing the wafer to be polished;

the polishing head is positioned above the fixing part and is used for polishing the wafer;

the control pins are distributed on the periphery of the wafer and used for fixing the edge of the wafer;

the plurality of spray heads are positioned below the fixing part and used for spraying liquid to the surface of one side, away from the polishing head, of the wafer;

and the control mechanism is used for controlling the pressure of the liquid according to the position of the polishing head and the shape of the surface of the wafer.

In some embodiments, the plurality of showerheads are arranged along a diameter of the wafer.

In some embodiments, the control mechanism is specifically configured to determine the pressure of the liquid according to the following equation:

p1 is 0.4 × (value of wafer measurement point-initial position of control pin)/range of wafer surface measurement point × 100;

p2 is 0.3 × (value of wafer measurement point-initial position of control pin)/range of wafer surface measurement point × 100;

p3 is 0.3 × (value of wafer measurement point-initial position of control pin)/range of wafer surface measurement point × 100;

the value of the wafer measuring point is the thickness of the wafer at the position of the orthographic projection of the center of the polishing head on the wafer, the initial position of the control pin is the minimum distance between the center point of the control pin and the side surface of the wafer far away from the polishing head, the difference between the maximum thickness and the minimum thickness of the wafer with extreme difference of the wafer surface measuring points is obtained, P1 is the pressure of liquid sprayed by a target nozzle, P2 is the pressure of liquid sprayed by a first nozzle on one side of the target nozzle, P3 is the pressure of liquid sprayed by a second nozzle on the other side of the target nozzle, and the distance between the target nozzle and the center point of the polishing head is the closest.

In some embodiments, the apparatus further comprises:

and the polishing liquid supply pipeline is positioned above the fixed part and used for supplying polishing liquid to the surface of the wafer.

In some embodiments, the flow rate of the polishing solution is 0.7 to 1.4 l/min.

In some embodiments, the liquid is water.

In some embodiments, the spacing between adjacent jets is 5-10 mm.

The embodiment of the invention also provides a single-side polishing method, which is applied to the single-side polishing device and comprises the following steps:

fixing the wafer to be polished by using the fixing part;

controlling the polishing head to descend until a polishing pad of the polishing head is contacted with the surface of the wafer, and enabling the polishing head to reciprocate left and right to polish the wafer;

fixing the edge of the wafer by using a plurality of control pins distributed on the periphery of the wafer;

and controlling the pressure of the liquid by using a control mechanism according to the position of the polishing head and the shape of the surface of the wafer.

In some embodiments, the method comprises:

and supplying the polishing solution to the surface of the wafer at a flow rate of 0.7-1.4l/min by using the polishing solution supply pipeline.

The embodiment of the invention has the following beneficial effects:

in the scheme, the plurality of spray heads are arranged below the fixing part, liquid can be sprayed to the surface of one side, away from the polishing head, of the wafer in the polishing process, and the control mechanism controls the pressure of the liquid according to the position of the polishing head and the shape of the surface of the wafer, so that the pressure between the local area of the wafer and the polishing head is adjusted, the removal rates of different areas of the wafer are consistent, and the flatness of the surface of the wafer can be improved.

Drawings

FIG. 1 is a schematic structural view of a single-side polishing apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic bottom view of a single-side polishing apparatus according to an embodiment of the present invention;

FIG. 3 is a schematic distribution diagram of a showerhead according to an embodiment of the present invention;

FIG. 4 is a schematic view of a wafer metrology site in accordance with an embodiment of the present invention;

FIG. 5 is a graph illustrating the thickness of a wafer.

Reference numerals

100 a main body of a rotating shaft; 110 a rotating shaft; 120. 121, 122, 123, 124, 125, 126, 127 control pins; 200 a rotation shaft of the polishing head; 210 a polishing pad; 300 a polishing liquid supply pipeline; 400 wafers; 500 wafer measurement points; 700 spray head.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the embodiments of the present invention clearer, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention, are within the scope of the invention.

The existing single-side chemical mechanical polishing is to clamp and process a wafer through an adsorption pad, the processing process has high requirements on the flatness of a wafer fixing part, and the adsorption pad has high correlation on the optimization of the flatness of the surface of the wafer and the surface shape of the wafer, so that the adsorption pad has high requirements.

Due to the limitation of the adsorption pad, the removal rates of different areas of the wafer are not consistent, so that the flatness of the wafer is deteriorated to a certain extent.

An embodiment of the present invention provides a single-side polishing apparatus, including:

the fixing part is used for fixing the wafer to be polished;

In this embodiment, a plurality of nozzles are arranged below the fixing portion, so that liquid can be sprayed onto the surface of one side of the wafer, which is far away from the polishing head, in the polishing process, and the control mechanism controls the pressure of the liquid according to the position of the polishing head and the shape of the surface of the wafer, so that the pressure between the local area of the wafer and the polishing head is adjusted, the removal rates of different areas of the wafer are consistent, and the flatness of the surface of the wafer can be improved.

Three, four or more nozzles can be arranged below the fixing part, the pressure between the local area of the wafer and the polishing head can be more accurately adjusted when the number of the nozzles is larger, but the product cost is increased at the same time, in some embodiments, 7-20 nozzles can be arranged below the fixing part, and the number of the nozzles can be increased along with the increase of the size of the wafer.

In some embodiments, the distances between the adjacent nozzles are the same, the distance between the adjacent nozzles can be 5-10mm, and when the distance between the nozzles adopts the above value, the pressure between the local area of the wafer and the polishing head can be accurately adjusted, so that the removal rates of different areas of the wafer are consistent, and the flatness of the surface of the wafer can be improved.

Because the wafer is circular, and rotates in the polishing process, consequently can be with a plurality of shower nozzles along a diameter of wafer arranges, just so can guarantee that shower nozzle spun liquid covers whole wafer, can also reduce the quantity of shower nozzle simultaneously, reduce product cost. The liquid sprayed by the spray head can be water or other liquid which does not pollute the wafer, and the liquid is water, so that the cost is low.

Through the formula, the pressure of the liquid sprayed by the spray head can be controlled according to the position of the polishing head and the shape of the surface of the wafer, the pressure between the local area of the wafer and the polishing head is adjusted, the removal rates of different areas of the wafer are ensured to be consistent, and the flatness of the surface of the wafer can be improved.

In some embodiments, the apparatus further comprises:

and the polishing liquid supply pipeline is positioned above the fixed part and used for supplying polishing liquid to the surface of the wafer. During polishing, the wafer is fixed in a rotatable carrier, and a polishing pad is placed on a rotatable platform, and the wafer and the polishing pad move mutually under the action of certain pressure and polishing liquid, so that the surface of the wafer is highly planarized. The polishing solution supply pipeline is positioned above the fixing part, and directly supplies polishing solution to the surface of the wafer during polishing, wherein the polishing solution is milky colloid with uniformly dispersed colloidal particles and mainly plays roles in polishing, lubricating and cooling. The polishing solution can be divided into acidic polishing solution and alkaline polishing solution according to acidity and alkalinity, and can be divided into metal polishing solution and nonmetal polishing solution according to application scenes. With basic SiO₂Polishing liquid, for example, contains an abrasive (SiO) as an important component₂Colloidal particles), alkali, deionized water, surfactants, oxidants, stabilizers, and the like. SiO 2₂The colloidal particles mainly function to perform mechanical friction and adsorb corrosion products, and can be 1-100nm in size. The alkaline solution mainly plays a role in corrosion in the polishing process, and the alkaline solution is usually organic amine due to the fact that metal ions such as Na +, K + and the like are prevented from being introduced, and the pH value of the alkaline solution is generally 9.4-11.1. The oxidizing agent is used to accelerate the corrosion reaction rate, since Si itself reacts slowly with alkali, while SiO₂The reaction rate with alkali is fast, and the oxidizing agent can oxidize the surface Si, so that the fast corrosion speed is obtained. The surfactant is used for insoluble particles to prevent colloidal particles from coagulating and precipitating.

The polishing pad is a loose and porous material, has certain elasticity, can be made of polyurethane materials, and mainly has the functions of storing and transmitting polishing liquid, providing certain pressure for a wafer and mechanically rubbing the surface of the wafer. The polishing pad has mechanical property similar to sponge and porous property, and the surface has special grooves, so that the polishing uniformity can be improved.

In some embodiments, the flow rate of the polishing solution may be 0.7 to 1.4 l/min. When the flow rate of the polishing solution is 0.7-1.4l/min, the polishing requirement can be met, and the polishing solution can not splash because of overlarge flow rate.

In one embodiment, as shown in fig. 1, a single-side polishing apparatus includes: a fixing portion for fixing a wafer 400 to be polished, wherein 110 is a rotation axis of the fixing portion, 100 is a main body of the rotation axis, and a rotation direction of the rotation axis 110 is determined according to a processing technology and is not limited to clockwise or counterclockwise; a polishing head located above the fixing portion, the polishing head including a rotation shaft 200 and a polishing pad 210, the rotation direction of the rotation shaft 200 being determined according to the processing technology and not limited to clockwise or counterclockwise; a plurality of control pins 120 distributed around the periphery of the wafer 400, wherein the circle is an enlarged schematic view of the control pins 120, and the control pins 120 are used for fixing the edge of the wafer 400; a polishing liquid supply line 300 above the fixed portion; a plurality of shower heads 700 are disposed under the wafer 400, and the shower heads 700 can spray water with a pressure ranging from 0kpa to 100 kpa.

As shown in fig. 2, in one specific example, 7 control pins may be uniformly distributed on the periphery of the wafer 400: 121. 122, 123, 124, 125, 126, 127. In this embodiment, all the control pins have the same size, and the center points are located on the same horizontal plane.

Referring to fig. 3, which is a schematic view illustrating distribution of the showerhead according to an embodiment of the present invention, a plurality of showerheads 700 are arranged along a diameter of the wafer 400.

As shown in fig. 4, which is a schematic distribution diagram of the wafer measurement points 500 on the surface of the wafer 400, a plurality of wafer measurement points 500 may be uniformly distributed on the surface of the wafer 400, and since the wafer 400 is circular, the wafer measurement points 500 may be arranged along the diameter of the wafer 400; the distance between the wafer measurement points 500 may be about 1mm, and since the surface topography of the wafer 400 is symmetrical, the topography of the wafer 400 may be determined by measuring data from the wafer measurement points 500 over several diameters.

The thickness of the wafer measured in nm at the location of a measurement point 500 on a diameter is shown in fig. 5, where a circle represents a measurement point 500 on the wafer.

When polishing, the robot arm first takes out the wafer from the wafer cassette, places the wafer in the center of the clamping device, and returns to the original position after the wafer 400 is fixed by the fixing portion. The polishing head starts to rotate (the rotating speed can be 20-50rpm/min) and slowly descends to a specified position, so that the polishing pad 210 on the surface of the polishing head is ensured to be in contact with the surface of the wafer 400, meanwhile, the polishing liquid starts to continuously supply liquid according to a specified supply amount (the flow rate can be 0.7-1.4l/min), and the polishing head reciprocates left and right to polish the wafer 400.

When the polishing head moves uniformly from left to right, and reaches different wafer measuring points 500, the control mechanism controls the pressure of the liquid sprayed by the spray head 700 according to the thickness of the wafer at the wafer measuring point 500 and the positions of the control pins, and is specifically used for determining the pressure of the liquid according to the following formula:

By controlling the pressure of the liquid sprayed by the spray head 700, the pressure between the wafer and the polishing head at the corresponding position can be adjusted, and the flatness of the surface of the wafer can be improved.

fixing the wafer to be polished by using the fixing part;

In some embodiments, the apparatus further comprises:

and the polishing liquid supply pipeline is positioned above the fixed part and used for supplying polishing liquid to the surface of the wafer. The flow rate of the polishing solution can be 0.7-1.4 l/min. When the flow rate of the polishing solution is 0.7-1.4l/min, the polishing requirement can be met, and the polishing solution can not splash because of overlarge flow rate.

It should be noted that, in the present specification, all the embodiments are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the embodiments, since they are substantially similar to the product embodiments, the description is simple, and the relevant points can be referred to the partial description of the product embodiments.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element or intervening elements may be present.

In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present disclosure, and all the changes or substitutions should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A single-side polishing apparatus, comprising:

the fixing part is used for fixing the wafer to be polished;

2. The single-side polishing apparatus as recited in claim 1, wherein the plurality of nozzles are arranged along a diameter of the wafer.

3. A single-side polishing apparatus as set forth in claim 2 wherein said control mechanism is specifically configured to determine the pressure of the liquid according to the following equation:

4. The single-side polishing apparatus as recited in claim 1, further comprising:

5. The single-side polishing apparatus as claimed in claim 4, wherein the flow rate of the polishing liquid is 0.7 to 1.4 l/min.

6. A single-side polishing apparatus as set forth in claim 1 wherein said liquid is water.

7. A single-sided polishing apparatus as claimed in claim 2, wherein the spacing between adjacent jets is 5-10 mm.

8. A single-side polishing method applied to the single-side polishing apparatus according to any one of claims 1 to 7, comprising:

fixing the wafer to be polished by using the fixing part;

9. A single-side polishing method as claimed in claim 8, wherein said control mechanism is specifically adapted to determine the pressure of said liquid according to the following formula:

10. The single-side polishing method according to claim 8, applied to the single-side polishing apparatus according to claim 4, comprising: