JP3335667B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for planarizing an insulating film or the like by polishing.

[0002]

2. Description of the Related Art Conventionally, colloidal silica has been generally used as a polishing agent in a polishing step for flattening an insulating film or the like in a semiconductor device manufacturing process or the like.

[0003] The colloidal silica silica particles are usually obtained by growing silica particles of several tens nm in an aqueous solution using sodium silicate as a raw material. When used as an abrasive, KOH or NaOH is usually added to a suspension of this in water for the two purposes of adjusting the hydrogen ion concentration for stably dispersing the silica particles and increasing the polishing rate. ing.

[0004] For example, there is a product called Compol 80 manufactured by Fujimi Abrasives Co., Ltd. as such an abrasive. When a silicon oxide film or the like is polished using an abrasive containing an alkali metal as described above, the abrasive in the abrasive becomes Alkali metal diffuses into the silicon oxide film, and in MOS devices, there is a problem that the reliability of the semiconductor device is remarkably reduced, for example, by changing the threshold voltage.

As another colloidal silica-based abrasive,
There are also polishing agents that do not contain alkali metals.Silica particles are grown by pyrolyzing silicic acid tetrachloride or hydrolyzing organosilane and adjusting the hydrogen ion concentration with ammonia or amine. With such an abrasive, there is a problem that the polishing rate of a silicon oxide film or the like is extremely slow and cannot be used practically.

[0006] Conventionally, in the surface polishing of glass for photomasks, the glass surface is polished with an aluminum oxide suspension as primary polishing, and a suspension containing cerium oxide particles having an average particle size of several μm is used as final polishing. Polishing has been used. However, usually, in the manufacturing process of a semiconductor device, the polishing amount of the insulating film is several μm at most.
However, such two or more stages of polishing are not preferred. Further, in the manufacturing process of the semiconductor device, usually, FIG.
(A) As shown in FIG.
The surface formed on the first substrate 1 is covered with an insulating film 52 having a step. At this time, the step shape of the step 51 is reflected on the surface shape of the insulating film 52. Further, as shown in FIG. 3B, the surface steps of the insulating film 52 must be flattened by polishing. However, with cerium oxide particles having an average particle size of several μm, steps of about several hundred nm to several thousand nm are flattened. Whether it can be polished while forming, whether it can be polished without causing scratches on the surface of the insulating film, and whether there is alkali metal contamination as in the case of using colloidal silica, It was not known at all, and no consideration was given to applying the above method to a polishing step in a semiconductor device manufacturing process.

[0007]

As described above, the conventional polishing process using colloidal silica as a polishing agent in the manufacturing process of a semiconductor device or the like has problems such as contamination by an alkali metal and a low polishing rate. It was difficult to use.

In addition, there is a method of using a suspension containing cerium oxide particles for polishing the surface of the glass for a photomask. However, the surface of the insulating film is not scratched and has a thickness of several hundred nm to several thousand nm. It is not known at all whether or not polishing can be performed while flattening the step, and whether or not there is alkali metal contamination, and it is not at all possible to apply the above method to a polishing step in a semiconductor device manufacturing process. Was not taken into account.

The present invention has been made in view of the above circumstances, and an object of the present invention is to use a polishing agent which can be polished at a high speed without being contaminated by an alkali metal. It is intended to facilitate the practical use of the polishing process.

[0010]

[SUMMARY OF] To solve the problems described above the present invention includes the steps of forming an insulating film on a semiconductor substrate, at least a portion of the insulating film where containing cerium oxide
And a step of polishing and removing with a fixed abrasive. Further, the present invention, the predetermined comprising forming an insulating film <br/> on a substrate a step is formed on the surface, the the insulating film of cerium oxide
It is polished by abrasive to provide a method of manufacturing a semiconductor device characterized by a step of flattening.

[0011]

According to the semiconductor device manufacturing method of the present invention,
Since the insulating film, for example, a silicon oxide film or a silicon nitride film is polished with a predetermined abrasive containing cerium oxide,
The insulating film can be polished at high speed.

Further, it has been found that even when the insulating film is polished, no alkali metal contamination is caused inside the insulating film. Further, it was also found that polishing can be performed while flattening steps of about several hundred nm to several thousand nm without causing scratches on the surface of the insulating film.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a semiconductor device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a step of planarizing an interlayer insulating film according to an embodiment of the present invention.

As shown in FIG. 1A, a 1 μm-thick SiO 2 film is formed on a Si substrate 1 on which elements (not shown) are formed.
_{2 A} film 2 is formed. Next, a polysilicon film 3 having a thickness of 500 nm is formed on the SiO ₂ film 2.

Next, as shown in FIG. 1B, a photoresist (photosensitive resin layer) 4 having a thickness of 1.5 μm is applied on the polysilicon film 3, and a mask pattern (not shown) is used. The photoresist 4 is exposed and developed to form a photoresist pattern 4.

Next, as shown in FIG. 1C, using the photoresist pattern 4 as a mask, the polysilicon film 3 is patterned by RIE using CF ₄ gas.

Next, as shown in FIG. 1D, CF ₄ and O
The down-flow type ashing apparatus ashing a photoresist mixed gas of ₂ downstream obtained by microwave discharge, after removing the photoresist pattern 4, Fig. 1
As shown in (e), the entire surface is 1 μm thick as an interlayer insulating film.
Forming a SiO ₂ film 5. Here, a step was formed on the surface of the SiO ₂ film 5 corresponding to the polysilicon wiring 3.

Finally, the SiO ₂ film 5 is polished as shown in FIG. For polishing, an apparatus as shown in the schematic diagram of FIG. 2 was used. As shown in this figure, an abrasive supply pipe 23 is provided at the center of the polishing cloth 22 on the turntable 21.
The turntable 21 is rotated around the axis passing through the center in the direction of the arrow at 100 rpm, and the abrasive is supplied onto the polishing cloth 22 from the tip. Further, the wafer 24 is pressed onto the polishing cloth 22 with a load of 40 kgf, and
To rotate in the direction of the arrow. The powder containing cerium oxide having an average particle diameter of 1.2 μm and a maximum particle diameter of 4.0 μm in the abrasive is obtained by pulverizing and firing bastnaesite, and has a composition of cerium oxide of 50 wt% and other rare earth metals. Oxide of about 37 wt%. Table 1 shows the composition of the powder containing cerium oxide used in this example.

[0019]

[Table 1]

As described above, the surface of the insulating film after being polished with the abrasive containing cerium oxide has been flattened. Also,
When the surface of the insulating film was observed with a differential interference microscope, no damage was observed.

In the same manner as in FIG.
m, powder 1 containing cerium oxide having a maximum particle size of 12.0 μm
In the case of using a suspension of wt% in water, the surface of the insulating film after polishing was flattened. However, when the surface of the insulating film was observed with a differential interference microscope, 10 cm ² was observed. 4 per
Individual wounds were observed.

Further, in the same manner as in FIG.
A powder containing cerium oxide having a particle size of 5 μm and a maximum particle size of 12.0 μm.
Was suspended in water, the surface of the insulating film was observed with a differential interference microscope, and the number of scratches per 10 cm ² was 1.

The results show that the surface of the insulating film can be planarized by polishing with a polishing agent containing cerium oxide, and that the polishing agent containing cerium oxide has a small particle size, preferably a maximum particle size. It can be seen that when the particle size is 4 μm or less, the generation of scratches can be suppressed, and the generation of scratches can be suppressed by changing the firing conditions and softening the hardness of the particles even with an abrasive having the same particle size.

Next, Table 2 shows the film thickness 1 obtained by thermally oxidizing silicon.
μm silicon oxide film and 1 μm thick silicon oxide film containing high concentrations of phosphorus and boron (hereinafter referred to as BPSG)
Was polished with an abrasive in which 1 wt% of a powder containing cerium oxide having an average particle size of 2.5 μm and a maximum particle size of 12.0 μm was suspended in water, and then 0.5 μm was polished. The results are shown. For reference, the results of polishing with Compol 80 are also shown.

[0025]

[Table 2]

When polished by Compol 80, Ref. The level of sodium is about one digit higher than that of a sample not polished (normal value described in the literature), and the level of sodium is higher by two digits or more in the BPSG film.

On the other hand, in the case of polishing with a polishing agent containing cerium oxide, the silicon thermal oxide film and the BPSG film both have a sodium level of Ref. Was not polished, and was equivalent to the value (normal value described in the literature), and no contamination was observed for other elements. Ce is 1 × 10 ¹⁰ atoms / cm ² It was below. The polishing agent containing cerium oxide is obtained by pulverizing and firing bastnaesite as described above, and does not particularly remove alkali metals, but no alkali metal contamination is observed. It can be understood that the polishing agent made of the raw material does not hinder the manufacture of the semiconductor device.

Table 3 shows a thermally oxidized silicon oxide film, a silicon nitride film, and a BPSG film of silicon having an average particle size of 2.
It shows the polishing rate when polishing is performed using an abrasive in which 1 wt% of a powder containing cerium oxide having a maximum particle size of 5 μm and a maximum particle diameter of 12.0 μm is suspended in water. For reference, Compol 80 and 5 wt% silica particles having a particle size of 12 nm are suspended in water, and further, 10 wt% of ammonia is added thereto.
And the case where 0.2 wt% of sodium hydroxide is added is also shown.

[0029]

[Table 3]

In the case of a thermally oxidized silicon oxide film, the polishing rate of Compol 80 is about 110 nm / min.
In addition, when only 5 wt% of silica particles having a particle diameter of 12 nm are suspended in water, the polishing rate is as low as 6 nm / min. In addition, when 0.2 wt% of sodium hydroxide is added, the polishing rate increases to 50 nm / min, and when 10 wt% of ammonia is added, the polishing rate increases to 18 nm / min. However, the effect of ammonia is larger than that of sodium hydroxide. small. Furthermore, when the silicon nitride film and the BPSG film are polished by Compol 80, the polishing speed is 40
nm / min and 200 nm / min.

For example, when removing a thermally oxidized silicon oxide film having a thickness of 500 nm by polishing, the Compol 80 is prepared by suspending 5 wt% of silica particles having a particle diameter of 12 nm in water for about 5 minutes and adding 0.2 wt% of sodium hydroxide to water. % Is about 10 minutes, while adding 10 wt% of ammonia takes about 30 minutes and is not practical.

On the other hand, when 1 wt% of a powder containing cerium oxide having an average particle size of 2.5 μm and a maximum particle size of 12.0 μm is polished with an abrasive suspended in water, the polishing rate of the silicon oxide film is reduced. There 1000 nm / min, the polishing rate of the silicon nitride film is 300 nm / min, the polishing rate of the BPSG film is very fast and 1200 to 1300 nm / min,
The removal rate of the 500 nm film by polishing is about 0.5 minutes and 2 minutes, respectively, which is a practically effective speed for production.

In this embodiment, the polishing agent is obtained by pulverizing and firing bastnasite, and its composition is cerium oxide 50
In the above description, a suspension containing about 37% by weight of a rare earth metal oxide in water was used. However, the abrasive containing cerium oxide can be changed in raw material, production method, concentration of the suspension, and the like. The description of the insulating film to be polished mainly focuses on the silicon thermal oxide film. However, other insulating films such as a silicon oxide film and a nitride film formed by a chemical vapor deposition method, and a conductive film as a part of the insulating film. Is also effective in the case where is formed. Further, the structure of the polishing apparatus is not limited to that described in the embodiment. In addition, various modifications can be made without departing from the scope of the present invention.

[0034]

According to the present invention, an insulating film such as a silicon oxide film or a silicon nitride film can be polished at high speed by using a polishing agent containing cerium oxide. Also,
During the polishing, no alkali metal contamination occurs inside the insulating film. Furthermore, polishing can be performed while flattening a step without causing scratches on the surface of the insulating film. Therefore, in manufacturing a semiconductor device, it becomes easy to put the insulating film polishing process into practical use.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing one embodiment of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a schematic view showing a polishing apparatus used in the present invention.

FIG. 3 is a cross-sectional view showing a conventional polishing step.

[Explanation of symbols]

Reference Signs List 1 Si substrate, 2 SiO ₂ film, 3 polysilicon film, 4 photoresist (photosensitive resin layer), 5 SiO ₂ film, 21 turntable, 22 polishing cloth, 23 abrasive supply pipe, 24 wafer, 51 step, 52 Insulating film.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Riichiro Aoki 72 Horikawacho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture In-house Horikawacho Plant (56) References JP-A-58-61663 (JP, A) JP-A Sho 64-87146 (JP, A) JP-A-59-201756 (JP, A) JP-A-64-45566 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/304 B24B 37/00 C09K 3/14 550

Claims (5)

(57) [Claims] A step of forming an insulating film on a semiconductor substrate;
At least a part of the insulating film is made of Na containing cerium oxide.
A step of polishing and removing particles having a concentration of 100 ppm or less with an abrasive suspended in water . (2) Forming an insulating film on the semiconductor substrate;
At least a part of the insulating film is made of Fe containing cerium oxide.
Polishing with particles of 10,000 ppm or less suspended in water
Polishing and removing with a chemical
Manufacturing method of a semiconductor device. 3. A step of forming an insulating film on a substrate having a step formed on its surface, and forming the insulating film on a substrate containing cerium oxide containing Na.
A step of polishing and flattening with an abrasive in which particles having a concentration of 100 ppm or less are suspended in water . (4) Insulating film on substrate with step formed on the surface
Forming the insulating film and forming the insulating film using Fe containing cerium oxide.
Polishing with particles of 10,000 ppm or less suspended in water
Polishing and flattening with an agent.
A method for manufacturing a semiconductor device. 5. A method of manufacturing a semiconductor device according to any one of claims 1 to 4, wherein the maximum particle size of the particles is 4μm or less.