JPH068133A - Polishing device - Google Patents

Abstract

PURPOSE:To enhance the polishing uniformity of ground surface by further improving uniformity for polishing a semiconductor wafer or the like for a flattening or another purpose. CONSTITUTION:In a polishing device where a substrate is supported on a support table, and the surface of the substrate and/or at least a part of the surface of a material formed on the substrate is polished as a grinding section, a plurality of polishing plates 11 and 12 are provided for polishing the grinding the section, and each of the plates 11 and 12 is constituted in such a way as controllable for a polishing amount.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polishing apparatus. In particular, the present invention relates to a polishing apparatus for polishing various substrates or a substrate on which a material portion such as a thin film is formed and polishing the substrate surface itself and / or the material surface such as the thin film as a portion to be polished. In particular, the present invention can be suitably used for polishing a substrate having a complicated step such as a semiconductor integrated circuit and a thin film formed on the substrate so as to planarize the substrate with good uniformity.

[0002]

2. Description of the Related Art A conventional planarization technique will be described by taking the case of manufacturing a Si semiconductor as an example.

With the miniaturization and ultra-high integration of semiconductor integrated circuits, the progress of multi-layering is remarkable. In order to respond to the demand for satisfactorily implementing the miniaturization / high integration technology typified by such multilayering, the planarization technology centering on the planarization of the interlayer film will become more and more important in the future.

As for the flattening technique, as shown in Table 1 below, various means are considered and implemented. As shown in Table 1, each has problems.

[Table 1]

Here, the problems of the conventional technique will be described by taking the widely used flattening technique by CVD + etchback as an example.

This conventional process, as shown in FIG.
An interlayer film 22 such as SiO _{2 is} thickly deposited on the lower wiring 21 such as Al on the substrate 1 by CVD or the like (FIG. 6).
After (A)), a resist (or a coating film such as SOG)
23 is applied and planarized (FIG. 6 (B)), and then blanket etchback is performed under the condition that the etching rate of the resist 23 and the interlayer film 22 is 1: 1 (etchback indicated by an arrow in FIG. 6C). Is schematically shown), and the flattened shape after resist application is reflected on the shape of the interlayer film 22 (FIG. 6C).

However, this conventional technique has the following problems. The process is complicated. It is difficult to set the etching ratio between the resist 23 and the interlayer film 22 to 1: 1. This is because the resist 23 and the interlayer film 2
Since the area ratio of 2 changes as the etchback progresses (this can be easily guessed by comparing AA ′ and B′-B ′ in FIG. 6C), the microloading effect causes , Because the respective etching rates are slightly different.

In view of the above background, in order to overcome the above-mentioned drawbacks, flattening by polishing has recently been introduced into semiconductor manufacturing techniques such as the Si process. This is a conventional mirror finishing of semiconductor wafers, and recently SOI (Silico)
Non-Insulator) device has been used.

For example, as a reported flattening technique for an interlayer film by polishing, generally, as shown in FIG. 7, an interlayer film 22 is stacked thickly and polished by a polishing apparatus to flatten it. There is something to turn into. In FIG. 7, reference numeral 24
Indicates the machining allowance due to polishing. Other symbols are synonymous with those in FIG.

The polishing apparatus used for this conventional polishing flattening technique has a polishing plate 33 as shown in FIG.
A wafer, which is the material to be polished 35, is set, and the slurry 32
While being supplied from around the material to be polished 35 (wafer). In FIG. 8, 31 is a slurry supply port, 34 is a polishing plate rotating shaft, 36 is a wafer holding sample stage, 37 is its rotating shaft, 38 is an adjustable polishing pressure,
Reference numeral 39 indicates a polishing pad, and 30 indicates a slurry supply system.

However, when this conventional polishing apparatus is used,
As shown in FIG. 9A, it was found that the polishing rate in the wafer, which is the material to be polished 35, has a distribution. Figure 9
Shows the wafer position on the horizontal axis and the remaining film thickness after polishing on the vertical axis, and shows the relationship between the two.

As can be understood from FIG. 9 (a), in the prior art, the film thickness remaining in the central portion of the material to be polished is large,
The periphery is small and uneven. As described above, in the above conventional technique, the degree of polishing is uneven depending on the position of the material to be polished. Generally speaking, the cause of this is that the slurry that is the abrasive is supplied from the periphery,
This is because the slurry is not sufficiently spread to the center of the wafer.

That is, as one of the causes of the large degree of polishing of the outer peripheral portion of the wafer, which is a drawback of the prior art, the slurry is supplied only from the slurry inlet 31 (see FIG. 8),
Next, it can be mentioned that the device structure is such that it flows along the surface of the pad 39 and flows to the outer peripheral portion. With this structure, the supply of the slurry 32 to the polishing surface of the wafer is inevitably made larger in the outer peripheral portion than in the inner peripheral portion of the polishing surface,
Therefore, the uniform slurry is not supplied to the polishing surface. Therefore, the polishing rate at the outer peripheral portion of the polishing surface is higher than that at the inner peripheral portion of the polishing surface, and the polishing surface has a convex lens shape as shown in FIG. 9A.

In order to solve the above problems, the following polishing apparatus has been proposed.

A first example is the one proposed in the published utility model publication No. 754, 1988. This is the wafer polishing pad 39, as shown schematically in FIG.
Then, the small holes 3a are concentrically formed, and the slurry 32 is supplied through the small holes 3a (30 is a slurry supply system) so that the slurry 32 is uniformly applied to the wafer.
To improve the uniformity of polishing.

The second example has already been proposed by the present applicant, and as shown in Japanese Patent Laid-Open No. 100321 of 1990, a wafer polishing pad is made of a porous material having continuous holes. And the same effect as in the first example was obtained.

Compared to the previous polishing apparatus in which the slurry 32 is supplied only from the outer periphery of the wafer (material 35 to be polished) shown in FIG. 8, the above-mentioned improved technique certainly supplies the slurry directly to the wafer surface. With such a structure, the uniformity of polishing within the wafer is improved. For example, as shown in FIG. 9B, it is possible to prevent the shape after polishing from becoming a convex lens shape to some extent.

However, as the wafer to be polished, for example, the wafer becomes larger in diameter, the wafer (the wafer 3 to be polished in FIG.
As for the force of 5) being pressed against the polishing plate (33 in FIG. 8), the center of gravity of the polishing pressure (38 in FIG. 8) is applied more to the center than to the periphery of the wafer, so that the shape after polishing becomes concave. Is concerned. Even if it does not reach that level, sufficient uniformity may not be obtained.

Therefore, in the present situation where the diameter of the wafer is increased and the pattern is miniaturized more and more, the conventionally proposed improvement in uniformity is becoming insufficient, and the polishing rate in the surface of the material to be polished (wafer) is further increased. There is a desire for a polishing apparatus that can be controlled to achieve improved uniformity.

[0020]

At this point, the present inventor has completed the present invention as a result of intensive studies. That is, the present invention is a polishing apparatus for supporting a substrate on a support base and polishing at least a part of the surface of the substrate and / or the material surface formed on the substrate as the portion to be polished. A polishing apparatus characterized by comprising a plurality of plates, each polishing plate being configured to control the polishing amount, and with this configuration, since the above problems can be achieved and polishing with good uniformity can be realized. is there.

It is preferable that the polishing amounts of the plurality of polishing plates can be controlled independently for each plate. It can be set according to the object (target portion) to be polished by each polishing plate. The polishing amount of each polishing plate may be controlled to be the same or different, and is arbitrary.

Each polishing plate may be configured, for example, to be coaxially rotated, or may be configured to be dispersedly rotated with different rotation axes. The directions of rotation may be the same or opposite.

Various means can be used to control the polishing amount.
For example, in the coaxial rotation or the distributed rotation of the polishing plate, the polishing directions can be made different from each other by reversing the rotation directions. Further, the amount of polishing can be controlled by controlling the number of revolutions (rotation speed), the area of the polishing plate, and the pressure applied to the polishing plate.

In particular, it is a preferred embodiment to control the polishing amount by the rotation speed of the polishing plate. In the course of research, the present inventor has found that the number of rotations of the polishing plate is related to the polishing rate, which is also an important factor for completing the present invention.

That is, as the number of rotations of the polishing plate increases, the polishing amount of the material to be polished per unit time generally increases, and therefore the polishing rate increases.

Therefore, the problem that the polishing amount differs between the center of the substrate which is the material to be polished and the periphery of the substrate can be solved by changing the rotation number of the polishing plate at the center and the periphery of the substrate to control the polishing amount. In the present invention, the above-mentioned problems can be solved by forming a plurality of polishing plates and making it possible to control the polishing amount of each, that is, by controlling the polishing rate at the center and the periphery of the substrate, for example.

[0027]

In the present invention, a plurality of polishing plates are provided, and the polishing amount of each polishing plate is controlled by, for example, changing the polishing rate by adjusting the number of revolutions thereof, thereby making the surface to be polished uniform. It can be configured to achieve polishing. Therefore, in the conventional apparatus, the polishing rate is different between the center and the periphery of the substrate, and the polishing amount is not uniform. By using the present invention, the polishing rate is made substantially equal between the center and the periphery of the substrate. As a result, uniform polishing can be realized, and thus a good flattened shape can be formed.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. It should be understood that the present invention is not limited to the examples below.

Embodiment 1 FIG. 1 shows a main part of a first embodiment of the present invention. In this embodiment, two concentric polishing plates 11 and 12 are provided. That is, the disk-shaped first polishing plate 11 and the annular second polishing plate 12 surrounding the disk-shaped first polishing plate 11 are provided, and both are rotated coaxially. The number of rotations is controlled independently, so that the polishing amount can be controlled.

More specifically, each concentric polishing plate is provided with plate rotating shafts 4 and 4 ', and rotation of the first polishing plate 11 inside and the second polishing plate 12 surrounding it is performed. The number can be controlled independently. The inner first polishing plate 11 is rotationally controlled by the central shaft 4, and the outer second polishing plate 12 is controlled.
Controls the rotation by transmitting the rotation of the outer shaft 4'by a gear. In the embodiment of FIG. 1, the first and second polishing plates 1
The rotation directions of 1 and 12 were opposite.

FIG. 2 shows a cross section of the main part of this embodiment. Figure 2
Among them, 26 is a support base, and 25 is a substrate to be polished (wafer) supported by the support base. The support base 26 is rotated by a rotary shaft 27, and its pressure is controlled by a pressure 28.

Reference numeral 29 is a polish pad arranged on each of the polishing plates 11 and 12. Reference numeral 21 is a slurry supply port, and 22 is a slurry.

The pressure of the polishing plate 11 is controlled by the pressure 41 shown in the figure, and the pressure of the polishing plate 12 is controlled by the pressure 42 shown in the figure.

In this apparatus, the rotation speeds of the polishing plates 11 and 12 can be controlled independently by the shafts 4 and 4 ', and the polishing pressures can be controlled independently.

In FIG. 2, as indicated by reference characters a and b, the rotation direction of the second polishing plate 12 located outside advances toward the side of the drawing on the right side of the drawing, and comes to this side of the drawing on the left side. However, this can be reversed.

Further, as shown in FIG. 3, the polishing plate 1
The rotation directions 11a and 12a of
The rotation direction 25a of the wafer can be the opposite direction. This improves the polishing rate.

The substrate 25 is rotating and revolving, and this revolution is eccentric with respect to the rotation axes of the polishing plates 11 and 12. This improves the uniformity of polishing. Further, since the rotation speed and the pressure can be controlled independently, the uniformity is further improved by performing this control.

Further, since the substrate wafer revolves around its axis, the contact between the substrate wafer and the polishing plates 11 and 12 is made uniform. The slurry is also supplied uniformly. These also contribute to the improvement of polishing uniformity.

In this embodiment, as shown in FIGS. 2 and 3,
Although the slurry supply port 21 is arranged outside the track 25b on the outer periphery of the substrate wafer so that the slurry comes there, it may be chased after the substrate if the mechanism is complicated.

In general, the slurry can be configured to follow the direction of revolution of the support table and be uniformly supplied to the entire polishing plate.

In this embodiment, the polishing apparatus as described above was used to polish SiO ₂ formed by CVD on a wafer which is a substrate to be polished under the following conditions. Polishing plate rotation speed: center 37 rpm, peripheral 5
0 rpm Wafer holding sample stage rotation speed: 17 rpm Polishing pressure: 8 psi Slurry flow rate: 225 ml / mi
n Polishing pad temperature: 90 ° C

As a result, the polishing rate becomes uniform,
It was possible to prevent the shape after polishing from becoming a concave lens shape on the entire surface of the wafer.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. The polishing apparatus of this embodiment has a plurality of polishing plates of the same horizontal plane, that is, the inner plate 11 is surrounded by four outer plates 12a to 12d, as shown in FIG. . For rotation control, the rotation of the plate rotation shaft 4 of the internal polishing plate 11 is controlled by the gear 1
3, 3'can be transmitted to the rotary shaft 4'of the external polishing plate 12a. Gear 1 here
Changing the gear ratio of 3, 13 ', polishing plates 11, 12
The rotation ratio of can be changed. In this example, the gear 4a of the buffer is interposed so that the rotation direction is the same.
Of course, although not shown here, the gear ratio may be automatically changed.

In FIG. 4, the polishing plates 11, 1
Although a rotary system is added to the polishing plates other than 2a, they are omitted in the figure. Further, the slurry is configured to be supplied from a small hole formed in the rotating shaft.

When using this polishing apparatus to polish SiO ₂ formed by CVD on a substrate wafer under the same conditions as in Example 1, the polishing rate was made uniform and the shape after polishing was the entire surface of the wafer. As a result, it was possible to suppress the formation of the concave lens shape.

Embodiment 3 FIG. 5 shows the essential parts of a third embodiment. This is an application example of the first invention, in which the rotation of the plate rotation shaft can be transmitted through the chain 4b. The other structure is the same as that of the first embodiment.

Using this polishing apparatus, the SiO ₂ formed on the substrate wafer by CVD was polished under the same conditions as in Example 1. As a result, the polishing rate was uniform, and the shape after polishing was the entire surface of the wafer. As a result, it was possible to suppress the formation of the concave lens shape.

The examples described above including this example are examples for preventing the polishing pressure from becoming higher toward the center and the shape after polishing becomes a concave lens shape. However, it goes without saying that the gist of the present invention is to improve the uniformity of polishing. For example, when a convex lens shape is used, the rotation ratio is reversed to that described above. It goes without saying that the polishing shape can be corrected. In addition, the control of the polishing amount is not limited to the rotation speed and the pressing force, and other means may be used. Further, the uniforming of the polishing amount does not necessarily have to be performed at the center and the periphery of the material to be polished, and it is sufficient to achieve the desired uniformization, and in some cases, in order to make the polishing amount uneven, The invention can also be used.

[0048]

As described above, according to the present invention, it is possible to achieve polishing with a desired polishing distribution, thereby preventing the polishing surface from becoming concave or convex, and realizing uniform and good planarization. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of a first embodiment of the present invention.

FIG. 2 is a diagram showing a cross section of a main part of the same example.

FIG. 3 is a diagram showing an upper surface of a main part of the same example.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing a process of CVD + etchback which is a conventional process.

FIG. 7 is a diagram showing a flattening technique using a conventional polishing apparatus.

FIG. 8 is a diagram showing a conventional polishing apparatus system.

FIG. 9 is a diagram showing a distribution of polishing rates within a wafer.

FIG. 10 is a diagram showing an improved example of a conventional polishing apparatus.

[Explanation of symbols]

11 polishing plate (internal polishing plate) 12, 12a to 12d polishing plate (external polishing plate) 25 substrate to be polished (wafer) 26 support base

Claims (1)

[Claims] 1. A polishing apparatus for supporting a substrate on a support base and polishing at least a part of the substrate surface and / or a material surface formed on the substrate as a polishing target portion, the polishing for polishing the polishing target portion. A polishing apparatus comprising a plurality of plates, each polishing plate being configured to control a polishing amount.