JP3393424B2 - Method for manufacturing solid-state imaging device and solid-state imaging 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 solid-state imaging device manufacturing method and a solid-state imaging device. The present invention is, for example,
It is suitable for highly miniaturized and highly integrated CCD image pickup device manufacturing process or CCD image pickup device.

[0002]

2. Description of the Related Art A solid-state image pickup device, which is abbreviated as CCD, is used for an image pickup section of an 8 mm video camera for consumer use, for example. The degree of integration is 1/2 inch and has 400,000 pixels on the market, and the density and miniaturization are progressing. Such high density,
Along with the progress of miniaturization, the structure thereof is generally as shown in FIG. A brief description of these manufacturing processes is as follows.

First, a light receiving portion 101 is formed in a substrate 100, and a poly-Si (polysilicon) electrode 102 for charge transfer is formed thereon. On top of that, as an interlayer insulating film, for example, PSG (phosphosilicate glass (Phospho
A film 103 called Silicate Glass)) is formed.
Then, an Al (aluminum) film is formed on the entire surface, and only the light receiving portion 101 is opened by photolithography and dry etching to form an Al light shielding film 104. Then, a plasma SiN film is formed as the passivation film 105, and a flattening film 106 is formed by spin coating. After that, the light collecting portion 107 called an on-chip lens
Is formed. A general manufacturing method is used except that the flattening film 106 is formed by spin coating.

[0004]

However, the above-mentioned conventional method has a problem to be solved. That is, in the flattening step of the manufacturing process of the solid-state imaging device, in order to make the flattened shape sufficient, the spin coat film is formed to be considerably thick, and the self-flattening effect is used to obtain flatness. Therefore, absorption of light occurs when light passes through the flattening film,
There was a problem that the sensitivity was lowered.

An object of the present invention is to prevent such a decrease in sensitivity, and to obtain a solid-state image pickup device having a sensitivity higher than this.

[0006]

In order to achieve the above object, in the invention of the method for manufacturing a solid-state image pickup device of the present application, at least one thin film formed on a substrate is subjected to chemical mechanical polishing to make the substrate substantially horizontal. In planarizing in the direction, the light-shielding film formed on the substrate is modified to form a polishing inhibiting layer for the chemical mechanical polishing. Further, according to the invention of the solid-state imaging device of the present application, in a solid-state imaging device in which at least one thin film is formed on a substrate, the light-shielding film formed on the substrate is modified as a polishing suppression layer for chemical mechanical polishing. The substrate is flattened in a substantially horizontal direction near the upper end of the modified light shielding film.

[0007]

In the present invention, chemical mechanical polishing, which is being used in the silicon semiconductor manufacturing process, is effectively used instead of the conventional planarization method. At that time, in order to obtain a favorable flattened shape, a suppression layer for the chemical mechanical polishing is provided.
Here, the inhibition layer means a layer whose chemical mechanical polishing rate is sufficiently smaller than that of the chemical mechanical polishing film. Further, the process is simplified by modifying the light-shielding film that must be formed in the solid-state imaging device and using it as the suppression layer.

The chemical mechanical polishing method is used for, for example, mirror polishing of a silicon wafer (substrate). The physical action of abrasive particles called a slurry and the chemical action of the solvent that suspends it are used to flatten the thin film. In other words, the portion of the substrate protruding in the substantially horizontal direction is polished by the above action to achieve flatness. By using this method, the insulating film of the solid-state imaging device can be flattened to a desired shape. Since the self-planarizing effect is not used unlike the conventional method, it is not necessary to form the insulating film thick. Therefore, it is possible to obtain a solid-state image pickup device structure having a good flattening shape and having less deterioration in sensitivity.

However, some measures have been taken to achieve perfect flattening by this method. This is because the flattening film of the solid-state imaging device is made of, for example, O ₃ / TEOS, and is soft as a material. If this is polished as it is, it is difficult to control the polishing stop position and the film thickness is not stable. Therefore, the present inventor has focused on the shape of the solid-state imaging device. That is, as described above, in the solid-state imaging device, the Al light shielding film is projected so as to surround the light receiving portion. Therefore, in the present invention, this light-shielding film is used as a layer for suppressing chemical mechanical polishing. By doing so, the upper surface of the suppression layer film serves as a reference surface, and complete flattening can be easily achieved.

Further, since it is possible to save the trouble of forming a new deterrent layer, there is no possibility that productivity will be significantly lowered. However, aluminum is generally used for this light-shielding film, and the film itself has no hardness. Therefore, in this class,
The rate of chemical mechanical polishing with the layer to be polished, i.e.
The deterrent ability cannot be large. Therefore, in the present invention, the aluminum film is further modified. This improves hardness and improves the deterrence ability of the deterrent layer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below.
First, the reforming will be described. The modification of the light-shielding film can be achieved, for example, by converting aluminum into sialon or boehmite. First, sialon can be easily formed by surface treatment of aluminum. Moreover, its mechanical strength and hardness are large. Boehmite (Al OOH), which is a hydrate of aluminum, can be easily formed by immersing aluminum in warm water. Like Sialon, it has high mechanical strength and hardness. Therefore, if these modification treatments are applied,
The rate of chemical mechanical polishing, that is, the deterrent ability is large,
A flattened shape with good reproducibility can be realized.

Next, a polishing apparatus for carrying out the present invention will be described. An example of the device is schematically shown in FIG. The polishing plate 3 called a platen rotates about the shaft 4. A polishing cloth 9 called a pad is placed on the polishing plate 3, and a slurry supply system 10 is arranged on the polishing cloth 9, and the slurry 2 is stored therein.
The slurry 2 is supplied onto the polishing cloth 9 from the slurry supply port 1.

The Si substrate 5 is attached to the carrier 6. The carrier 6 also rotates about the shaft 7, and the substrate 5 attached thereto is pressed against the polishing plate 3 while rotating. The number of rotations of the polishing plate 3 and the carrier 6, the pressure of the polishing pressure adjuster 8, the supply amount of the slurry 2 and the like are adjusted to perform polishing. These are just examples,
The present invention is not limited to these examples such as the substrate mounting method, the platen, the number and configuration of carriers, and the structure of pads. Specific examples will be given below.

[0014]

Example 1 In this example, O ₃ / TEO is used as a planarizing film.
The S film and the light-shielding film material Al used as the suppression layer were modified into sialon, and were flattened by the chemical mechanical polishing method. FIG. 1A shows a schematic cross section before the flattening process, and FIG. 1B shows a schematic cross section after the flattening process. That is, Si substrate 1
00 to form a light receiving portion 101 on which a charge transfer layer is formed.
A poly-Si electrode 102 was formed, and a PSG film was formed thereon as an interlayer insulating film. After forming an Al film on the front surface,
Only the light receiving portion was opened by photolithography and dry etching to form an Al light shielding film 104. The Al light shielding film 104 was patterned by using the lithography and the dry etching method.

The Al light-shielding film 104 was plasma-treated under the following conditions to form a sialon film 108 on the surface. The thickness of the sialonized film 108 was about 50 nm. Gas: Si H ₄ / O ₂ / N ₂ O = 10/30/50 sccm Temperature: 380 ° C. Pressure: 6.7 Pa RF density: 0.08 W / cm ² Further, a plasma Si N film was formed as the passivation film 105. All were carried out by the usual method except for sialonization of the Al film.

Next, a flattening film 106 was formed by an atmospheric pressure CVD apparatus. The conditions were as follows. Gas: O ₃ / TEOS = 350/14 sccm Temperature: 380 ° C. Pressure: Atmospheric pressure At this time, the film had the film-forming characteristics and became a self-reflow shape, as shown in FIG. 1 (a).

Next, using the polishing apparatus shown in FIG. 2, the planarization film 106 was chemically mechanically polished under the following conditions. At this time, the polishing time was set so that the chemical mechanical polishing was stopped at the position of the sialonized film 108 which was the restraining film (the polishing time required for the thickness t of the flattening film 106 plus alpha). Polishing plate speed: 50 rpm Carrier speed: 17 rpm Polishing pressure: 8 psi Polishing pad temperature: 30-40 ° C Slurry flow rate: 225 ml / min

This polishing condition is a general polishing condition for the insulating film. Since polishing is performed in a basic atmosphere here, the slurry was used by suspending it in KOH / water / alcohol. The result is that the sialonized light-shielding film 1
Polishing stopped at 08, and good flattening processing as shown in FIG. 1B was completed.

[0019]

Embodiment 2 In this embodiment, an O ₃ / TEOS film is used as a flattening film, and an Al film as a light-shielding film is modified into boehmite and used as a suppression layer. The structure is the same as that of the first embodiment shown in FIG. The same FIG. 1 is cited. First, the same process as in Example 1 was performed until the Al light-shielding film 104 was formed.

Next, the Al light-shielding film 104 was treated with hot water under the following conditions to boehmite the surface (108). The thickness of the boehmite film 108 was about 50 nm (in Example 1, reference numeral 108 is a “sialonized” film, but since the same FIG. 1 is cited, the same reference numeral is applied to this “boehmite” film). 108 is used). The temperature of hot water is 80
℃. It is also possible to add sodium aluminate to warm water as needed.

After that, the passivation film 105 and the planarization film 106 were formed under the same procedure and conditions as in Example 1. The shape at this time was as shown in FIG. Further, the chemical mechanical polishing of the flattening film 106 was performed under the same procedure and conditions as in Example 1. At this time, similarly, the polishing time was adjusted so that the chemical mechanical polishing was stopped at the position of the boehmite conversion film 108, which was the above-mentioned inhibition film. As a result, polishing was stopped at this boehmite film 108, and good planarization processing as shown in FIG.

The present invention is of course not limited to the three embodiments described above, and the structure, conditions, etc. can be changed as appropriate without departing from the spirit of the present invention.

[0023]

As described above, in the present invention, the light-shielding film formed on the substrate is modified and used as the polishing inhibiting layer for chemical mechanical polishing. Therefore, it is possible to form a good flattened shape, which was a bottleneck by the conventional method, and to realize it with good reproducibility due to the existence of the stable polishing inhibiting layer. In addition, there is no need to add significant processes. As a result, a high-performance solid-state imaging device having a flattened shape can be mass-produced with high reliability and at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of an embodiment.

FIG. 2 is a front view schematically showing an example of a chemical mechanical polishing apparatus.

FIG. 3 is a sectional view schematically showing the configuration of a conventional solid-state image sensor.

[Explanation of symbols]

1 Slurry supply port 2 slurry 3 Polishing plate

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Claims (6)

(57) [Claims] 1. A method of manufacturing a solid-state imaging device, comprising: performing chemical mechanical polishing on at least one thin film formed on a substrate to planarize the substrate in a substantially horizontal direction. method for manufacturing a solid-state imaging device by <br/> modified, characterized in that includes the step of forming an abrasive preventing layer for the chemical mechanical polishing a light-shielding film improves the hardness was. 2. The method for manufacturing a solid-state imaging device according to claim 1, wherein the light-shielding film is aluminum or an aluminum alloy, and the modification is sialonization of the aluminum. 3. The method for manufacturing a solid-state imaging device according to claim 1, wherein the light shielding film is aluminum or an aluminum alloy, and the modification is boehmite conversion of the aluminum. 4. In a solid-state imaging device having at least one thin film formed on a substrate, a light-shielding film formed on the substrate is modified to improve hardness as a polishing inhibiting layer for chemical mechanical polishing. The one or more layers with the upper end of the modified light-shielding film as a reference surface.
Solid-state imaging device , wherein the thin film is planarized in a substantially horizontal direction. 5. The solid-state imaging device according to claim 4, wherein the modified light-shielding film is sialon. 6. The solid-state imaging device according to claim 4, wherein the modified light-shielding film is boehmite.