JP2001110765A - Highly accurate wafer, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a highly accurate wafer by which a high flatness can be obtained by removing minute waving about several nm to several hundred nm in amplitude produced by etching, when manufacturing a wafer. SOLUTION: After application of film solution such as wax or the like to produce a film on the rear of a wafer, the coated side is pressed against the master flat plane having a required flatness to give the flatness of that master flat plane to it through a film 0.5 μm or under in thickness, and this film-stuck face side is fixed by, for example, vacuum suction or template system, and it is processed with polishing or CMP or the like, whereby the minute waving produced in the preprocess or in etching can be removed, and a highly accurate wafer having a high flatness can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-precision wafer which improves the flatness of the surface of a semiconductor or ceramic wafer and improves the yield in the wiring technology of a highly integrated LSI manufacturing process. After applying a thin film solution for forming a thin film, the coated side is pressed against a required reference plane to impart flatness to the reference plane, and the thin film sticking side is fixed by vacuum suction or a template method and polished. High-precision wafer that obtains high flatness by CMP or CMP and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a method of manufacturing a semiconductor wafer such as silicon includes 1) a slicing step of slicing a single crystal ingot pulled by a single crystal pulling apparatus to obtain a thin disk-shaped wafer; A chamfering step for preventing chipping or cracking of the wafer, 3) a lapping step for flattening the chamfered wafer, 4) an etching step for removing a processing strain layer generated on the wafer by the processing, and 5). A chamfered portion polishing step for finishing and polishing the chamfered portion, 6)
A polishing step of polishing the wafer on one side or both sides,
7) After the final polishing of the wafer, 8) final cleaning is performed to obtain a final product, or 9) epitaxial growth is performed to obtain a final product.

Conventionally, etching before the polishing step, that is, general etching using hydrofluoric acid, nitric acid, acetic acid or the like,
The surface of the wafer had minute undulations of several nm to several hundred nm in amplitude.

Polishing is performed after the above-mentioned etching. For example, in the case of single-side polishing, a polishing method of attaching a wax to a ceramic plate or a polishing method of vacuum suction or a template method is often used.

[0005] In detail, in the former method, wax is applied to the back side of the wafer and pressed against a heated ceramic plate with a stamper. Thereafter, the plate is cooled and the wafer is fixed. Due to the fluidity of the wax, the wax enters into a large gap between the wafer and the plate with respect to the undulation and warpage of the wafer, and the undulation on the back surface of the wafer is reduced.

[0006] In the latter vacuum suction, the back surface of the wafer is forcibly suctioned to a flat chuck portion. Therefore, even if the wafer undulates, there is no gap between the wafer and the chuck portion during polishing. In the template type, if a soft material such as cloth is used as the material for chucking the wafer,
The undulation can be absorbed on the back side of the wafer, but if a hard material is used, the undulation is forcibly absorbed without absorbing the undulation as in the case of vacuum suction.

That is, the shape of the wafer 1 is as shown in FIG. Here, the surface to be a product is shown as front surface f, and the back surface is shown as b. When polishing or CMP,
The back surface of the wafer is in an undulating state. Figure 4
B, as shown in FIG.4C, this is forcibly fixed to the vacuum chuck 10 or the template 11 which is an ideal flat holding portion,
Polishing and CMP are performed by pressing against the polishing cloth 12. After the processing is completed, when the wafer 1 is detached from the holding section, the surface has a wavy shape.

[0008] As described above, undulations cannot be removed by vacuum suction or template-type polishing. In each case, the wafer to be polished is fixed directly on a flat chuck by vacuum suction or a wafer guide, so the internal stress is released when the wafer separates from the wafer holding part after polishing, and the undulation of the wafer is reduced. It will return to its original state, and undulation will remain on the wafer surface.

After these processes, exposure is performed in order to form a wiring pattern in a device process. At this time, the surface undulation of the wafer causes a pattern break in the design rule of 256 Mbits or less.

[0010]

As a technique for removing relatively large undulations, a flat base plate is sucked on a vacuum chuck, a wafer is attached to the base plate via wax, and the wafer is polished to polish the polished surface. A method has been proposed in which flattening is performed and the obtained flat surface side is adsorbed to a vacuum chuck, and the previous wax side is polished and flattened (Japanese Patent Laid-Open No. 8-66850).

[0011] The above method is performed to remove a large level of undulation such as warpage formed by slicing in the grinding of a wafer immediately after slicing.
It cannot remove minute undulations of several nm to several hundred nm in amplitude.

That is, a general single-sided mirror-finished wafer is usually subjected to etching because of the necessity of finishing the back surface into an etched surface. As described above, this etching causes minute undulations on the back surface of the wafer, which are transferred to the mirror surface during polishing. These minute undulations are becoming a problem with recent miniaturization of device designs.

An object of the present invention is to remove a minute waviness having an amplitude of about several nm to several hundreds of nm formed by etching when manufacturing a wafer, and to provide a method for manufacturing a high-precision wafer capable of obtaining high flatness. The purpose is to provide.

[0014]

As a result of various studies on a polishing method for the purpose of removing minute waviness, the inventor applied a thin film solution such as a wax for forming a thin film on the back surface of the wafer, and then applied the polishing solution to the back side of the wafer. By pressing on a reference plane having a required flatness, through a thin film having a thickness of 0.5 μm or less, the flatness of the reference plane is imparted, and the thin film sticking surface side is fixed by, for example, vacuum suction or a template method, Polishing and CMP
By working in such a manner, it has been found that minute undulations generated in the previous process and etching can be removed, and a high-precision wafer having high flatness can be manufactured, and the present invention has been completed.

That is, according to the present invention, a thin film solution for forming a thin film is applied to the back surface of a wafer, the coated side is pressed against a reference plane, and after the flatness of the plane is given, the wafer is peeled off from the reference plane. Using a high-precision wafer for polishing, the thin film attachment surface is the fixed side of the polishing device, the other main surface is wrapped, CM
This is a method for manufacturing a high-precision wafer characterized by obtaining high flatness by polishing or polishing.

Further, according to the present invention, in the above configuration, the thickness is
0.5μm or less thin film is wax, adhesive, resist, SOG
The present invention proposes a high-precision wafer for polishing characterized by being one of films.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, after a thin film solution for forming a thin film is applied to the back surface of a wafer, the coated side is pressed against a required reference plane to impart flatness to the reference plane. The main surface is wrapped, CMP or polished on the other main surface with the thin film application surface as the fixed side of the processing equipment.In the wafer manufacturing process, undulations in the processing immediately before the final product is eliminated. Is most effective.

In the present invention, the undulation is not a large level such as a warp, but an unevenness having an amplitude of several nm to several hundreds of nm, which can be detected by the magic mirror method. If the amplitude of the undulation is several tens of nm or more, it can be detected even by a shape measuring device such as an interferometer system, a capacitance system, or a photoelectric system.

In the present invention, a semiconductor bare wafer, a semiconductor wafer, a quartz wafer, a ceramic wafer, or the like can be used as the wafer.

The present invention will be described in detail with reference to the drawings. On the surface b, which is the back surface of the wafer 1 having undulation as shown in FIG.
Solution 3 capable of forming a thin film, for example, wax, resist, S
Nozzle 2 with solution of OG film and other materials capable of forming thin film
And spin coating.

Before the solvent in the solution evaporates and solidifies as a thin film, immediately after heating for a thermoplastic film, immediately before heating for a thermosetting film, or after applying an elastic coating agent, As shown in 1B, the thin film 4 side of the wafer 1 is pressed against a surface plate 5 having an ideally flat surface (reference plane).

As shown in FIG. 1B, after the wafer 1 is pressed, the wafer 1 is separated from the reference plane of the surface plate 5 with the thin film 4 attached to the wafer 1. For example, it is possible to adopt a method in which a spatular jig, which is generally commercially available and widely used, is inserted between the reference plane of the surface plate 5 and the thin film 4 and peeled. As a result, the thin film 4 adhered to the back surface b of the wafer 1 is pressed against the reference plane, so that a high-precision polishing wafer having the flatness of the reference plane can be obtained.

The thin film 4 adhered to the back surface b of the wafer 1 is pressed against a reference plane, and the adhered surface b of the thin film 4 is processed using a polishing wafer provided with flatness of the reference plane. By lapping, polishing, or CMP processing the wafer surface f as the fixed side of the apparatus as shown in FIGS. 2A and 2B, it is possible to obtain an ideal flat high precision wafer without undulation.

In the present invention, if the thin film 4 on the back surface is too thick, it becomes difficult to stick it strictly parallel to the surface plate 5, and this may cause a loss of global flatness.
The thickness is desirably thin, preferably 0.5 μm or less, and most preferably about 0.1 to 0.2 μm to remove fine undulations. Further, the thin film on the back surface may be used as it is or may be peeled off, depending on the type of product and the type of required post-process.

In the present invention, the ideally flat surface
(Reference plane) means that the surface is not rough, for example, Ra 0.3 μm
In the following, a plate having a surface roughness of preferably 0.1 μm or less, a plate having a precision level such as a mounting plate used for polishing silicon, and a surface plate can be used. The material is not particularly limited, but in the case of a semiconductor bare wafer, alumina, SiC and the like are preferable.

[0026]

Example 1 After performing etching, spin-coating a bonding wax on a surface to be a back surface of a silicon semiconductor bare wafer having fine undulations, and then heating and re-melting the wax film. The thin film side of the wafer was pressed against a reference flat plate made of a SiC plate (Ra = 0.2 μm or less). Before coating, the surface of the wafer was subjected to a water-repellent treatment so that the film was completely attached to the wafer side.

After the wafer was pressed, the wafer was peeled off from its flat surface with the thin film attached to obtain a high-precision wafer for polishing. Next, as described in FIG. 2, the surface of the wafer was
processed.

After that, when microscopic irregularities on the surface were observed with a magic mirror device, no fine irregularities were observed, and a wafer having an ideal flat surface without fine undulations could be manufactured. Thereafter, the wax on the back surface was removed by washing, but there was no change in the surface shape.

Comparative Example 1 After the above-described Example 1 according to the present invention and the polishing of the conventional method were performed in the same manner as in Example 1 except that the pressing was not performed on such an ideally flat surface (reference plane), FIG. 4 shows the result of measuring the site flatness of the wafer. The measurement is performed by the capacitance method, and the maximum value of SFQR at 25 mm square is described.

As is apparent from FIG. 3, the flatness of the wafer according to the first embodiment of the present invention is superior to that of the conventional method.

[0031]

According to the present invention, an ideally flat wafer without fine waviness can be manufactured by a simple method. For example, a silicon wafer from which such fine undulations have been removed can be used as a high-precision wafer that does not cause problems such as pattern breakage in LSI device process technology of 256 Mbits or later.

[Brief description of the drawings]

FIG. 1A is an explanatory diagram showing a coating method for forming a thin film, and FIG. 1B is a process explanatory diagram showing a method for attaching to a flat surface after applying a thin film according to the present invention and then peeling off.

FIG. 2A is an explanatory diagram illustrating a method of polishing by a vacuum suction type using a polishing wafer according to the present invention, and FIG. 2B is an explanatory diagram similarly illustrating a polishing method of a template type.

FIG. 3 is a graph comparing the site flatness measurement results of a wafer obtained by a conventional method and a wafer obtained by the present invention.

FIG. 4A is an explanatory diagram showing a cross-sectional state of a wafer after an etching process, and FIGS. 4B and 4C are explanatory diagrams showing steps of a conventional vacuum suction type and template type polishing method using a wafer.

[Explanation of symbols]

 1 Wafer 2 Nozzle 3 Solution 4 Thin film 5 Surface plate 10 Chuck 11 Template 12 Polishing cloth b Back side f Front side

Claims (6)

[Claims] 1. A high-precision wafer for polishing, in which a thin film adhered to a back surface of a wafer is pressed against a reference plane to impart flatness to the reference plane. 2. The high-precision wafer for polishing according to claim 1, wherein the thickness of the thin film is 0.5 μm or less. 3. A high-precision polishing wafer for applying a thin film solution for forming a thin film on the back surface of a wafer, pressing the coated side against a reference plane, and peeling off the reference plane after the flatness of the plane is imparted. Manufacturing method. 4. A polishing wafer in which the thin film adhered to the back surface of the wafer is pressed against a reference plane and the flatness of the plane is imparted, and the thin film adhered surface is used as a fixed side of the processing apparatus and the other main surface is used. A method for manufacturing high-precision wafers that obtains high flatness by lapping, CMP, or polishing the surface. 5. The thin film is made of wax, adhesive, resist, SOG
5. The method for producing a high-precision wafer according to claim 4, wherein the method is any of a film. 6. The method for manufacturing a high-precision wafer according to claim 4, wherein the wafer is fixed by vacuum suction or a template method.