JPH06318583A - Flattening method for wafer surface and chemical and mechanical polishing equipment used therefor - Google Patents

Abstract

PURPOSE:To enable flattening a wafer surface by chemical and mechanical polishing in a mass process, and improve the yield, the reliability, and the pro ductivity of semiconductor products. CONSTITUTION:A lower layer insulating film 13 which has a specified thickness and contains an end point detection component is formed on the upper surface of a wafer 1 having step-differebces caused by forming wirings, and a polishing layer 15 is formed on the upper surface of the lower layer insulating film 13. By a chemical and mechanical polishing method using slurry containing abrasive material and an abrasive cloth, the polishing layer 15 is polished to flatten the wafer 1 surface. The slurry waste liquor generated by polishing is analyzed from time to time in the course of polishing. The eluation of end point detection component, which is contained in only the base layer 13 against the polishing layer 15, to the slurry waste liquor is detected. When the evaluation of the end point detection component is detected, the polishing is ended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for flattening a wafer surface and a chemical mechanical polishing apparatus used in the method, and more particularly to a method for flattening the upper surface of a wafer having a step in a manufacturing process of a semiconductor device forming a laminated structure. The present invention relates to a method of embedding an insulating film and planarizing by chemical mechanical polishing, and a chemical mechanical polishing apparatus used in this method.

[0002]

2. Description of the Related Art In recent years, with the high integration and high functionality of devices, miniaturization and multi-layering of device structures have been progressing.
Due to the complicated device structure, the step difference on the surface of the element formed on the wafer is becoming higher in aspect. The step having a high aspect ratio not only narrows the limit of lithography, but also partially thins the film thickness of the wiring formed in the upper layer or applies a local stress to the wiring. Therefore, the technique of filling the above steps with an insulating film and flattening them is important not only for expanding the limit of lithography but also for improving the yield and reliability of semiconductor products.

The above-mentioned flattening technique involves spin coating a sol containing SiO ₂ (hereinafter referred to as SOG: Spin On Glass).
And referred) and, O ₃ -TEOS (ozone - _{tetraethoxysilane: Si (OC 2 H 5)} 4) there is a CVD method or the like using the gas. In the above method, the CV of silane (SiH ₄ ) gas is used.
As compared with the insulating film formed by D, an insulating film having excellent step coverage is formed.

However, even with the above method, it is difficult to obtain an insulating film having a completely flat surface, and the larger the aspect ratio of the step of the underlying layer, the thicker the film for improving the flattening effect. The via hole formed in the thickened insulating film has a very large aspect ratio, which makes it difficult to establish conduction.

Therefore, a technique for thinning and flattening an insulating film thickened by increasing the aspect ratio of the underlying step by chemical mechanical polishing is being developed.

[0006] This method, first, as shown in FIG. 5 (1), for example, the upper surface of the wafer 5 produced in step by forming the wiring 502, etc., the O ₃ as shown in FIG. 5 (2) -TE
Insulating film 50 excellent in step coverage by the OSCVD method or the like
3 is formed. Next, as shown in FIG. 5C, the insulating film 503 is polished from above by chemical mechanical polishing until it reaches a predetermined film thickness. In this chemical mechanical polishing, the surface of the wafer 5 is brought into direct contact with a polishing cloth attached to a rotary polishing machine, and the surface of the wafer 5 is polished by using a slurry containing an abrasive. Is obtained. Then, as shown in FIG. 5D, an upper wiring film 504 is formed on the upper surface of the insulating film 503 whose surface is flattened to obtain a good laminated structure.

[0007]

However, the above method has the following problems. That is, in chemical mechanical polishing, there is no means for directly measuring the polished film thickness. Therefore, it is necessary to control the film thickness by, for example, the polishing time. However, even if the polishing time is constant, the insulating film 503
The polishing rate changes greatly depending on the degree of surface irregularity, deterioration of the polishing cloth, and the state of the slurry. Therefore, the above-mentioned flattening method cannot be used in the mass process because there is a risk of insufficient polishing or excessive polishing.

In view of the above, the present invention provides a method for flattening a wafer surface that solves the above problems and a chemical mechanical polishing apparatus used for the method, thereby improving the yield and reliability of semiconductor products, Enables flattening of the wafer surface by dynamic mechanical polishing in a mass process,
The purpose is to improve the productivity of semiconductor products.

[0009]

In order to achieve the above object, a first wafer surface flattening method of the present invention is a polishing layer made of an insulating film on the upper surface of a wafer having a step on the surface due to formation of wiring. Is a method for flattening a wafer surface by chemical mechanical polishing using a slurry containing a polishing agent and a polishing cloth, and has the following steps. First, while polishing the polishing layer, a slurry waste liquid generated by polishing is analyzed at any time along the progress of polishing,
With respect to the polishing layer, the component contained only in the underlayer of the polishing layer is used as the endpoint detection component, and the elution of the endpoint detection component into the slurry waste liquid is detected. Then, when the elution of the endpoint detection component is detected, the polishing is finished.

A second wafer surface flattening method of the present invention is the same as the first method, wherein the base layer of the polishing layer is a lower layer insulating film containing an end point detection component formed on the upper surface of the wafer. Alternatively, it is a thin film containing an end point detection component formed on the upper surface of the lower insulating film.

A third method of flattening a wafer surface according to the present invention is the method of the first method, wherein the slurry reacts with the end point detection component eluted in the slurry waste liquid to produce a color. It is characterized by going out.

Further, in the chemical mechanical polishing apparatus used in the first or second wafer surface flattening method and having a rotary polishing plate having the polishing cloth adhered to the upper surface thereof, the upper surface of the rotary polishing plate is A liquid collecting groove for collecting the slurry waste liquid is provided outside the polishing cloth and along the outer periphery of the rotary polishing plate.

[0013]

In the chemical mechanical polishing carried out by the first method for flattening the surface of the wafer, the components constituting the polishing layer are eluted in the slurry. Then, when the polishing reaches the base layer of the polishing layer, the endpoint detection component contained in the base layer is eluted into the slurry. In the above method, the slurry waste liquid is analyzed along with the progress of polishing, and the polishing is terminated when the end point detection component eluted in the slurry waste liquid is detected.
Therefore, the surface of the wafer flattened by polishing is
The uppermost part of the base layer of the polishing layer is exposed.

In the second method of flattening the surface of the wafer,
Polishing is stopped by detecting when the lower insulating film or a thin film formed on the upper surface of the lower insulating film appears on the surface by polishing. Therefore, the surface of the wafer flattened by polishing is covered with the lower insulating film.

In the third method for flattening the surface of the wafer,
When the polishing reaches the underlayer and the endpoint detection component contained in the underlayer elutes in the slurry, the endpoint detection component in the eluted state reacts with the reagent in the slurry to develop color. Therefore, elution of the end point detection component into the slurry waste liquid is detected.

Further, in the chemical mechanical polishing apparatus of the present invention,
Slurry waste liquid generated with the progress of chemical mechanical polishing is collected by a centrifugal force in a liquid collecting groove provided in the rotary polishing machine.

[0017]

EXAMPLES Examples of the wafer surface flattening method of the present invention will be described below. FIG. 1 is a sectional view of an essential part of a wafer for explaining a first embodiment of the present invention. As shown in FIG. 1A, the wafer 1 whose surface is flattened has wirings 12 formed on the upper surface of a semiconductor substrate 11 made of, for example, silicon. Due to the wiring 12, a step having a high aspect ratio is formed on the surface of the wafer 1.

The surface of the wafer 1 having the steps formed as described above is flattened according to the following procedure. First, Fig. 1
As shown in (2), the lower insulating film 13 is formed on the upper surface of the wafer 1.
Is deposited to a predetermined thickness. The lower insulating film 13 is a glass layer in which an end point detection component such as B (boron), P (phosphorus), As (arsenic) is contained in SiO ₂ , and a BPSG film containing B having a thickness of 4000 Å, for example. It is deposited by the CVD method.

Then, a polishing layer 15 containing no end point detecting component is formed on the upper surface of the lower insulating film 13. Polishing layer 15
Is made of a glass layer such as NSG, and is deposited by SOG or O ₃ -TEOSCVD method having excellent step coverage. The film thickness of the polishing layer 15 is such a thickness that the step portion formed on the surface of the wafer 1 is sufficiently buried by the deposited polishing layer 15, and is, for example, 16000Å.

Then, the wafer 1 is set in a chemical mechanical polishing apparatus, and chemical mechanical polishing is performed from the upper surface of the polishing layer 15 with a slurry containing a polishing agent and a polishing cloth. In the chemical mechanical polishing, the slurry waste liquid generated by the polishing is analyzed at any time along with the progress of the polishing, and the endpoint detection component eluted in the slurry is detected.

Further, the detection of the end point detection component is carried out by, for example, sending the slurry waste liquid generated during polishing to an atomic absorption spectrometer as needed and monitoring the absorption by the end point detection component.

When the end point detection component eluted in the slurry is detected by the analysis of the slurry waste liquid, the end point is judged as the polishing end point as shown in FIG. 1 (3), and the polishing is completed. To do.

When the surface of the wafer 1 on which the step is formed is flattened according to the above procedure, the polishing layer 15 is polished by chemical mechanical polishing, so that the polished surface has good flatness.

With the progress of the chemical mechanical polishing, the components constituting the polishing layer 15 are eluted into the slurry. Then, when the polishing reaches the uppermost portion of the lower insulating film 13, the end point detection component contained in the lower insulating film 13 begins to elute into the slurry. Since the end point detection component eluted in the slurry is detected by the analysis of the slurry waste liquid which is performed at any time along with the progress of polishing, polishing is performed on the uppermost part of the lower insulating film 13 when the end point detection component is detected. Is judged to have reached. Since the polishing is stopped at the above point, the wafer 1 is in a state in which the lower layer insulating film 15 having a predetermined thickness is formed on the uppermost portion of the wiring 12.

Then, on the surface of the wafer 1 which has been flattened as described above and covered with the lower insulating film 13 and the insulating film of the polishing layer 15 remaining after polishing, for example, as shown in FIG. The wiring film 17 is formed to obtain a laminated structure.

Next, the chemical mechanical polishing apparatus used for polishing the polishing layer 15 in the above Example 1 will be described with reference to FIG.
FIG. 2 is a perspective view of a main part of the rotary polishing platen 2 of the chemical mechanical polishing apparatus. The rotary polishing platen 2 rotates in one direction with a center 21 of the plate as an axis, and a removable polishing cloth 22 is closely attached to the upper surface thereof. On the upper surface of the rotary polishing machine 2,
A liquid collecting groove 23 for collecting the slurry waste liquid is provided along the periphery of the rotary polishing plate 2.

The liquid collecting groove 23 is provided with a straw-shaped liquid collecting device 24 for drawing out the slurry waste liquid in the liquid collecting groove 23. The upper opening of the liquid collecting device 24 is widely formed in a funnel shape along the shape of the liquid collecting groove 23, and opens in a direction facing the rotating direction of the rotary polishing platen 2. An ampoule 25 is placed at the lower end of the liquid collecting device 24.

In the above chemical mechanical polishing apparatus, the polishing cloth 22
And the polishing surface of the wafer 1 to be polished are brought into direct contact with each other, and the rotary polishing plate 2 is rotated while dropping the slurry containing the polishing agent to polish the wafer 1. At that time, the slurry waste liquid is collected in the liquid collecting groove 23 at any time by the rotation of the rotary polishing plate 2,
It is pumped out from the liquid collecting device 24 and accumulated in the ampoule 25. Therefore, the slurry waste liquid can be analyzed at any time by immersing the sample collection nozzle of the atomic absorption spectrometer, for example, in this ampoule 25.

Next, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 3A, the surface of the wafer 3 to be flattened is provided with the wiring 32 as in the first embodiment.
The formation of the step forms a step having a high aspect ratio.

The surface of the wafer 3 having the steps formed as described above is flattened according to the following procedure. First, FIG.
As shown in (2), the lower insulating film 33 is formed on the upper surface of the wafer 3.
Is deposited to a predetermined thickness. As the lower insulating film 13, for example, an NSG film is formed by plasma CVD. Also,
The film thickness of the lower insulating film 33 is, eg, 3000 Å.

Next, a thin film 34 is formed on the upper surface of the lower insulating film 33, for example, B ₂ O ₃ glass or glass containing a large amount of B ₂ O ₃ glass. Then, the polishing layer 35 is deposited on the upper surface of the thin film 34 by the method excellent in step coverage like the first embodiment until the step on the surface of the wafer 3 is filled. The polishing layer 35 may be made of the same material as the lower insulating film 33.

Then, using the chemical mechanical polishing apparatus used in the first embodiment, the polishing layer 35 of the wafer 3 is polished by chemical mechanical polishing as in the first embodiment. In this case, The slurry used for polishing is neutral. In the polishing, similarly to the first embodiment, the slurry waste liquid is analyzed at any time along with the progress of the polishing, and B ₂ O ₃ glass eluted in the slurry is detected as the end point detection component.

The B ₂ O ₃ glass becomes boric acid when it is eluted into the slurry by polishing, so that the waste liquid of the slurry exhibits weak acidity. Therefore, a neutralization titration reagent such as BTB solution is prepared in the ampoule 25 shown in FIG. Then, the time when the BTB liquid is colored yellow due to the dropping of the slurry waste liquid is determined as the polishing end point, and the polishing is finished.

When the surface of the wafer 3 having a step difference is flattened according to the above procedure, the surface of the wafer 3 exposed by polishing can have good flatness as in the first embodiment. Further, similarly to the first embodiment, it is determined that the polishing reaches the uppermost portion of the thin film 34 at the time when the end point detection component is detected, and the polishing is stopped at this time.
Is the lower insulating film 3 having a predetermined thickness with respect to the uppermost part of the wiring 32.
5 has been formed.

Then, an upper wiring film 37 is formed on the surface of the wafer 3 flattened as described above, for example, as shown in FIG.

In the second embodiment, when the wiring 32 is made of a refractory metal such as W (tungsten), annealing is applied after the flattening. As a result, the B ₂ O ₃ glass forming the thin film 34 dissolves in the upper and lower insulating films such as NSG films, and there is no fear of contamination.

In the second embodiment, the thin film 34 is not limited to the B ₂ O ₃ glass or the glass containing a large amount of B ₂ O ₃ glass, but may be Al, Zn, Mg, Ni.
Alternatively, the end point detection component may be formed of any of these metals. In this case, the reagent used to detect the end point detection component is, for example, a chelate reagent that forms a chelate compound with the metal used in the thin film 34. As a result, the metal that begins to elute in the slurry when the polishing reaches the thin film 34 and the above-mentioned reagent form a chelate compound, and the coloration due to the formation of the chelate complex is exhibited, so that the polishing end point is detected. .

However, when a metal material is used for the thin film 34 and the upper wiring film 37 is formed on the flattened upper surface of the wafer 3 as described above, the thin film 34 that remains in the insulating film without being polished.
Therefore, it is necessary to prevent conduction with the upper layer wiring formed by the upper layer wiring film 37 as much as possible.

Next, a third embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4A, a step having a high aspect ratio is formed on the surface of the wafer 4 to be planarized by the formation of the wiring 42 as in the first and second embodiments.

The surface of the wafer 4 having the steps formed as described above is flattened according to the following procedure. First, FIG.
As shown in (2), the polishing layer 45 is formed on the upper surface of the wafer 4. The polishing layer 45 is made of an insulating film such as NSG formed by a method excellent in step coverage like the first and second embodiments. The film thickness of the polishing layer 45 is set so that the step portion formed on the surface of the wafer 4 is sufficiently embedded.

Then, using the chemical mechanical polishing apparatus used in the first embodiment, the polishing layer 45 of the wafer 4 is polished in the same manner as in the first and second embodiments, and the slurry waste liquid is analyzed. . In the polishing, since the underlying layer of the polishing layer 45 is the wiring 42, the end point detection component is selected from the materials forming the wiring 42. The detection of the end point detection component eluted in the slurry is carried out by the atomic absorption analysis shown in the first embodiment or the color reaction with the reagent shown in the second embodiment.

When the end point detection component eluted in the slurry is detected by the analysis of the slurry waste liquid, the end point is judged as the polishing end point as shown in FIG. 4C, and the polishing is completed. To do.

When the surface of the wafer 4 having a step difference is flattened according to the above procedure, the flattened surface of the wafer 4 which is revealed by polishing is obtained as in the first and second embodiments. Further, similarly to the first and second embodiments, it is determined that the polishing reaches the uppermost portion of the wiring 42 at the time when the end point detection component is detected, and the polishing is stopped at this time, so the wafer 4 is The upper surface of the wiring 42 is exposed, and the polishing layer 45 left unpolished between the adjacent wirings 42 is buried.

On the surface of the wafer 4 flattened as described above, an upper insulating film 46 is formed, for example, by C as shown in FIG. 4 (4).
By forming about 5000 Å by the VD method or the like, a flat insulating film having a predetermined film thickness can be obtained on the upper surface of the wafer 4. Then, an upper wiring film 47 is formed on the upper surface of the upper insulating film 46, for example, as shown in FIG.

In the second and third embodiments described above, when the end point detection component is detected by a color reaction, as shown in FIG.
By disposing the ampoule 25 shown in 1 above in the absorptiometer, the end point detection component in the slurry waste liquid can be automatically detected.

Further, in the second and third embodiments, when the detection of the end point detection component is performed by a color reaction, a reagent that changes color by reacting with the end point detection component eluted in the slurry by polishing is used. It may be contained in the slurry in advance. In this case, the surface of the wafer can be flattened by the above method using a normal chemical mechanical polishing apparatus, and the elution of the end point detection component can be detected extremely quickly. However, if a chelate compound or the like remains on the polishing cloth, it becomes difficult to detect the polishing end point on the wafer to be flattened next time. Therefore, it is necessary to clean the polishing cloth or replace the polishing cloth each time polishing is performed.

Further, in the above-mentioned first to second embodiments, the case where the detection of the end point detection component eluted in the slurry waste liquid is carried out by the atomic absorption or the color reaction by the reagent is explained. However, the present invention is not limited to this.

The method of flattening the wafer surface according to the first to third embodiments is also effective for controlling the polishing rate of the wafer surface by chemical mechanical polishing. In this case, even if the above method is not performed every time each wafer is polished, the above method can be performed once per lot or once a day, etc., and the change in the polishing rate can be known.

[0049]

As described above in detail in the embodiments,
According to the method of flattening a wafer surface according to claim 1 of the present invention, by analyzing the slurry waste liquid generated during the chemical mechanical polishing of the wafer surface, good flatness of the wafer surface can be obtained without excess or deficiency of polishing. Obtainable. Further, according to the wafer surface flattening method of the second aspect of the present invention, the wafer surface flattened by polishing can be covered with the lower insulating film having a predetermined thickness. Therefore,
When forming an element on the upper surface of the wafer, it is not necessary to newly form an interlayer insulating film. Further, according to the wafer surface flattening method of claim 3, a color reaction between a reagent previously contained in the slurry and an end point detection component eluted into the slurry by polishing rapidly causes the end point of polishing. Can be detected. Then, according to the chemical mechanical polishing apparatus of the present invention, the slurry waste liquid generated as the polishing progresses is sequentially collected in the liquid collecting groove provided on the rotary polishing plate. Therefore, the slurry waste liquid can be analyzed at any time along with the progress of polishing. As described above, the present invention is expected to improve the reliability and yield of semiconductor products,
Since the flattening of the wafer surface by chemical mechanical polishing can be performed by a mass process cell, it is expected that the productivity will be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view illustrating a first embodiment.

FIG. 2 is a perspective view of a main part of a chemical mechanical polishing apparatus.

FIG. 3 is a schematic sectional view illustrating a second embodiment.

FIG. 4 is a schematic sectional view illustrating a third embodiment.

FIG. 5 is a schematic sectional view illustrating a conventional example.

[Explanation of symbols]

 1, 3, 4 Wafer 12, 32, 42 Wiring 13 Lower layer insulating film (underlayer) 15, 35, 45 Polishing layer 33 Lower layer insulating film 34 Thin film (underlayer)

Claims (4)

[Claims] 1. A polishing layer formed of an insulating film is formed on the upper surface of a wafer having a step on the surface by forming wiring, and the polishing layer is formed by a chemical mechanical polishing method using a slurry containing a polishing agent and a polishing cloth. A method of flattening a wafer surface to be polished, wherein the polishing layer is polished, and a slurry waste liquid generated by the polishing is analyzed at any time along the progress of polishing, and only the underlying layer of the polishing layer is compared with the polishing layer. It has a step of detecting the elution into the slurry waste liquid of the end point detection component with the contained component as the end point detection component, and a step of finishing polishing at the time of detecting the elution into the slurry waste liquid of the end point detection component. A characteristic method for planarizing a wafer surface. 2. The wafer surface flattening method according to claim 1, wherein the base layer of the polishing layer is a lower insulating film containing an endpoint detection component formed on the upper surface of the wafer, or the upper surface of the lower insulating film. A method of flattening a wafer surface, which is a thin film containing an end point detection component formed in step 1. 3. The method of planarizing a wafer surface according to claim 1, wherein the slurry contains a reagent that reacts with the end point detection component eluted in the waste liquid of the slurry to develop a color. A method of planarizing a wafer surface. 4. A chemical mechanical polishing apparatus for use in the method for flattening a wafer surface according to claim 1 or 2, comprising a rotary polishing plate having the polishing cloth adhered to the upper surface thereof. A chemical mechanical polishing apparatus, wherein a liquid collection groove for collecting the slurry waste liquid is provided on the upper surface outside the polishing cloth and along the outer periphery of the rotary polishing plate.