JPH1131640A - Method for manufacturing stuck soi substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a substrate flat by polishing a single-crystalline silicon layer on an insulation film to a first predetermined thickness and dry-etching it to a second predetermined thickness and then polishing it until the insulation film is exposed. SOLUTION: A single-crystalline silicon layer 32 is ground to a thickness of 3-5 μm ±0.5 μm, for example and then is etched by dry etching to a thickness of 0.5-1.0 μm. Next, the whole surface of the single crystal silicon layer 32 is polished at the same time by a selective polishing method with the use of an insulation film 34 as a stopper, until the convex insulation film 34 is exposed and polishing is stopped, when the single crystal silicon layer 32 is polished to the top surface of the insulation film 34. A thin film SOI(silicon-on-insulator) structure having the single-crystalline silicon layer 32 formed into island shape on the insulation film 34 is formed in this manner. Since the amount of polishing is extremely small, unevenness in polishing and hence polishing variation are hardly produced and even if the unevenness in polishing is produced, the polishing variation is small and hence the substrate can be plavarized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a bonded SOI
More specifically, the method for manufacturing a substrate suppresses the occurrence of unevenness on the substrate surface due to uneven polishing, and manufactures a bonded SOI substrate having good flatness and a flat surface over the entire surface of the substrate with high productivity. It is about the method.

[0002]

2. Description of the Related Art An SOI (Silicon On Insulator) structure is a structure having a single crystal silicon layer on an insulating film. The insulating film enables complete isolation between elements and reduces junction capacitance and wiring capacitance. It is said that it is convenient for manufacturing an integrated circuit element having a high density and excellent high-speed operation or an optical functional element exhibiting excellent characteristics. As used herein, the term “SOI substrate” refers to a substrate having an SOI structure, that is, as shown in FIG. 3, a thin-film single-crystal silicon layer 24 formed in an island shape in a concave portion of an insulating layer 22 on a supporting substrate 20. This is called an SOI substrate 26. The SOI structure may be a single-crystal silicon layer 28 formed in a thin comb shape on the insulating layer 22, as shown on the left side of FIG.

[0003] SOI substrates can be manufactured by various methods.
The production of a substrate is evaluated as a method capable of producing an SOI substrate having a single crystal silicon layer having the best crystallinity and forming an element having excellent characteristics from the substrate, and development is proceeding. Here, with reference to FIG.
A method for manufacturing an OI substrate will be described. 4 (a) to 4 (e)
[FIG. 2] is a cross-sectional view of a substrate in each manufacturing step of a bonded SOI substrate. As shown in FIG. 4A, a plurality of recesses 12 are formed on the surface of an element forming substrate 10 made of a single crystal silicon wafer having a mirror-finished surface according to a predetermined pattern by a photolithography technique. Next, an insulating film 14 such as a SiO ₂ film is formed on the entire surface of the concave portion 12. Then, as shown in FIG. 4 (b), SiO ₂ film 1
4, another layer, for example, a polycrystalline silicon layer 16 is formed to fill the recess 12, and the surface of the polycrystalline silicon layer 16 is flattened. Instead of the polycrystalline silicon layer, a layer having another composition, for example, an insulating film may be used. Next, as shown in FIG. 4C, a support substrate 18 made of mirror-finished silicon is brought into surface contact with the flattened polycrystalline silicon layer 16 and bonded to the element formation substrate 10, and the substrate 10 and the substrate And 18 are combined. Next, as shown in FIG. 4D, the bonded element forming substrate 10 is formed into a layer thickness of a required SOI layer + 3 to 5 μm.
Grind to a layer thickness of. Here, the necessary thickness of the SOI layer refers to the thickness of a single-crystal silicon layer having an SOI structure formed in an island shape. For grinding, for example, a grinding device 52 as shown in FIG. 5 is used. As shown in FIG. 5, the grinding device 52 has a resin bond (grinding stone obtained by mixing diamond and a range) 56 on the lower surface. And a rotating wafer holder 58 that rotates around a rotation axis while holding the rotating shaft. In the grinding, the substrate 10 is vacuum-adsorbed to the rotating wafer holder 58 and held upward, and the resin grindstone 54 is pressed against the substrate W while rotating, and the substrate 10 is ground by the resin bond 56. Further, as shown in FIG. 4E, the SiO ₂ film 14 is exposed and necessary SOI
Until the structure can be formed, the substrate 10 is polished to form a bonded SOI substrate 19. In order to polish, the substrate 10 is vacuum-adsorbed and held on the rotating wafer holder, and the substrate 10 held by the rotating wafer holder is pressed while rotating while polishing is supplied onto the rotating polishing pad.

When fabricating an SOI substrate by a bonding method, it is said that polishing is necessary for the following two reasons. First, in the process of grinding, 3
Grinding damage of about 5 μm occurs on the ground surface. For example, the sharp corners of the diamond abrasive grains come into contact with the ground surface, causing large scratches or deep cuts on the ground surface of the substrate 10. Therefore, it is necessary to remove the grinding damage by performing polishing. Secondly, since only the grinding process results in rough cutting, and the planarization, flattening and smoothing of the surface of the SOI structure are insufficient, it is necessary to perform polishing as a finishing process. Therefore, in the polishing, the upper surface and the same plane of the SiO ₂ film 14 upper surface and the surrounding single crystal silicon thin layer 10 of the recess of the SiO ₂ film 14 formed in an island shape on the SOI substrate 19 bonded 4 It is of the utmost importance that it is on top and flat and free of polishing damage. The term “planarization” in this specification means that the upper surface of the single-crystal silicon thin layer 10 and the upper surface of the peripheral SiO ₂ film 14 are on the same plane. In other words, in the conventional method for manufacturing a bonded SOI substrate, the grinding process is stopped when the thickness of the SOI layer reaches the required layer thickness of the SOI layer + 3 to 5 μm, and 3 to 5 μm generated by the grinding process. Then, the ground surface which has been subjected to grinding damage and has unevenness in flatness is polished, and a flat and smooth SOI layer is obtained by polishing with a variation of a margin of ± 10%.

[0005]

However, in the above-mentioned conventional method for manufacturing a bonded SOI substrate, even if a single-crystal silicon layer having a flattened ground surface is obtained even though grinding damage is caused in the grinding process. However, in the next polishing step, since the single-crystal silicon layer having a thickness of 3 to 5 μm is polished, polishing unevenness inevitably occurs in a size proportional to the single-crystal silicon layer to be polished. Occurs. As a result, in-plane variation occurs in the thickness distribution of the single-crystal silicon layer, and the SO
It was difficult to obtain an I structure.

As a method for solving the problem of uneven polishing caused by the conventional method for manufacturing a bonded SOI substrate, Japanese Patent Application Laid-Open No.
-102540, the method disclosed in
The E method (Plasma Assisted Chemical Etching) has been proposed. However, both the method of the above-mentioned publication and the PACE method,
In this method, a surface to be polished is scanned to detect a convex portion, and the convex portion is locally removed by plasma etching or polishing to flatten the surface. Therefore, it takes time for scanning and removing processing to scan the substrate surface to detect the convex portion and remove the detected convex portion to make the surface flat. As a result, there is a problem that it is difficult to improve productivity. Further, since a scanning device and a control device for the scanning device are required, there is a problem that the processing device becomes large-scale and the cost increases.

Accordingly, an object of the present invention is to provide a method for manufacturing an SOI substrate having an SOI layer having a flattened substrate surface, which is further flattened as compared with the conventional method, by a bonding method. That is.

[0008]

In order to achieve the above object, a method for manufacturing a bonded SOI substrate according to the present invention comprises:
The single crystal silicon substrate is patterned to form a concave portion of a predetermined pattern on the surface of the single crystal silicon substrate, an insulating film is formed along the concave wall and the substrate surface, and another layer is formed on the entire surface of the substrate. The single crystal silicon substrate and another support substrate are bonded together so that the flattened upper surface is in surface contact with another support substrate, and then the single crystal silicon substrate is exposed until the insulating film is exposed. Grinding to produce an SOI substrate provided with a thin film SOI structure on a supporting substrate, wherein the thickness of the single crystal silicon layer on the insulating film forming the thin film SOI structure becomes a first predetermined thickness. A grinding step of grinding the single-crystal silicon layer, and then a step of etching the single-crystal silicon layer by dry etching until the thickness of the single-crystal silicon layer reaches a second predetermined thickness;
Then, a finishing step of polishing the single crystal silicon layer until the insulating film is exposed.

When the thickness of the thin film single crystal silicon layer is 0.03-
In an SOI structure having a thickness of 0.1 μm and an insulating film thickness of about 400 to 800 nm, the first predetermined thickness and the second predetermined thickness are actually 3 to 5 μm and 0.5 to 0.5 μm, respectively.
1.0 μm may be sufficient. The grinding method and the dry etching method applied in the grinding step and the etching step are, respectively,
A known grinding method and etching method may be used. The polishing method applied in the finishing step is a known polishing method,
The P method and other commonly used methods. Preferably, in the finishing step, polishing is performed by a selective polishing method for polishing a single crystal silicon layer using the insulating film as a polishing stopper.

[0010]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment of a method for manufacturing a bonded SOI substrate according to the present invention, and FIG.
FIGS. 3A to 3C are cross-sectional views of the substrate in each step of the embodiment. First, as shown in FIG.
As shown in (c), a support substrate made of silicon is brought into surface contact with the flattened polycrystalline silicon layer on the element formation substrate and bonded to the element formation substrate, and the element formation substrate and the support substrate are combined. The substrate 30 is manufactured. As shown in FIG. 1A, the bonded substrate 30 is composed of, in order from the top, a single-crystal silicon layer 32, an insulating film 34, a polycrystalline silicon layer 36, and a silicon support substrate 38. ing. The thickness of the insulating film 34 is 600 nm,
4 has a depth of 0.03 to 0.1 μm. First,
The single crystal silicon layer 32 of the bonded substrate 30 is ground by a known grinding method. In the grinding step, as shown in FIG. 1A, the thickness of the single-crystal silicon layer is 3 to 5 μm ± 0.
The single crystal silicon layer 32 is ground to a thickness of 5 μm. Here, the thickness of the single crystal silicon layer refers to the thickness from the upper surface of the SiO ₂ film 34 in the recess 40 to the upper surface of the single crystal silicon layer 32.

Next, as shown in FIG. 1B, the single crystal silicon layer 32 is etched by dry etching so that the thickness of the single crystal silicon layer remains 0.5 to 1.0 μm. Dry etching is performed by a plasma etching method, an RIE method, or the like. At the time of etching, the processing time is set in advance by calculating the etching time backward from the etching rate. Next, the single crystal silicon layer 32 is polished by the selective polishing method using the insulating film 34 as a stopper until the convex insulating film 34 is exposed, as shown in FIG.
A thin film SOI structure having a single crystal silicon layer formed in an island shape on the insulating film is formed. Thus, an SOI substrate 39 can be obtained. In this embodiment, the thickness of the single-crystal silicon layer to be polished in the polishing step is 0.5 to 1.
0 μm, and the polishing amount is much smaller than that of the conventional method, so that polishing unevenness and therefore polishing variation hardly occur.
Also, even if it occurs, the variation amount is small, and the planarization, flattening and smoothing SOI are much better than those of the conventional substrate.
A substrate with a structure can be provided. Further, in the present embodiment, since the entire polished surface of the single-crystal silicon layer is simultaneously polished, the time required for polishing is shorter than in the method of locally removing the projections of the polished surface, so that the productivity is reduced. high,
Moreover, the equipment cost and the grinding cost are low. Further, dishing due to overpolishing can be suppressed, and the variation in the SOI layer is reduced, which is extremely advantageous for reducing the thickness of the SOI structure.

The selective polishing method is a polishing method in which the entire surface of the single-crystal silicon layer 32 is simultaneously polished using the insulating film 34 as a polishing stopper, and the polishing is completed when the polishing reaches the upper surface of the insulating film 34. The configuration and operation of the polishing apparatus 40 for polishing the bonded substrate 30 by the selective polishing method will be described with reference to FIG. As shown in FIG. 2, the polishing apparatus 40 for the selective polishing method includes a wafer holder 42 that rotates and holds the bonded substrate 30 by vacuum suction, a polishing platen 44, and a polishing pad bonded to the upper surface thereof. And a nozzle 50 for supplying a polishing liquid L onto the polishing pad 46. The polishing pad 46 can be used according to the required hardness of the abrasive, from a super-hard platen such as a ceramic plate to a soft cloth of suede-type foamed polyurethane. When polishing, first, the bonded substrate 30 to be polished is faced down and the wafer holder 42 is
To be held. Next, the polishing pad 46 is
While supplying the polishing liquid L thereon, the surface to be polished of the substrate is brought into surface contact with the polishing pad 46, and is rotated to simultaneously polish the entire surface to be polished of the substrate. As the polishing liquid L, an alkaline polishing liquid that does not chemically react with the SiO ₂ film but chemically reacts with the single crystal silicon is used. The silicon layer can be selectively polished by the chemical reaction selectivity of the polishing liquid.

As in the above-described embodiment, the single-crystal silicon layer 32 of the bonded substrate 30 is ground until the thickness thereof becomes 5 μm, and then the thickness of the single-crystal silicon layer 32 becomes 1.0 μm.
When dry-etching to a thickness of μm and finally performing the polishing process, the variation in dry etching allowance is ± 5%
± 10% to ± 15%
When the size of the irregularities on the final substrate surface is calculated, the result is as follows. 4μm × 0.05 × 2 + 1μm × 0.1 × 2 = 0.6μ
m On the other hand, when an SOI substrate is manufactured by a conventional method and the single crystal silicon layer is ground in the grinding step until the thickness of the single crystal silicon layer becomes 5 μm, the thickness of the single crystal silicon layer polished in the polishing step is 5 μm. If 5 μm is polished, a variation of ± 10% is generated, so that the size of the unevenness on the substrate surface of the SOI structure is 5 μm × 0.1 × 2 = 1 μm. As can be seen from the above calculations, according to the method of the present invention, it is possible to provide an SOI substrate whose surface unevenness is smaller than that of the conventional method.

[0014]

According to the present invention, when an SOI substrate is manufactured by a bonding method, a single crystal silicon layer is thinned by etching after a grinding step, and polishing is performed in a final finishing step. In the present invention, since the thickness of the single-crystal silicon layer to be polished is much smaller than that of the conventional method, it is possible to minimize the occurrence of uneven polishing. Thus, the polishing can be performed without deteriorating the grinding accuracy, so that a uniform thin film SOI structure can be obtained. Further, since a uniform thin film SOI layer can be obtained over the entire surface of the substrate, the product yield is improved. Also, unlike local polishing, the entire substrate surface is polished,
Processing time is short, and productivity is improved. Further, since a uniform thin SOI layer can be formed, the thickness of the bonded SOI substrate having a thickness of 0.1 μm or less can be reduced.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views of a substrate in respective steps of an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a selective polishing apparatus.

FIG. 3 is a cross-sectional view illustrating a configuration of an SOI substrate.

FIG. 4 is a cross-sectional view of a substrate in each step of a conventional method for manufacturing a bonded SOI substrate.

FIG. 5 is a schematic diagram showing a configuration of a grinding device.

[Explanation of symbols]

10 ... element forming substrate, 12 ... recess, 14 ... insulating film, 16 ... polycrystalline silicon layer, 18 ... support substrate, 1
9 bonded SOI substrate, 20 support substrate, 22
... insulating film, 24 ... thin film single crystal silicon layer, 26 ...
SOI substrate, 28 single crystal silicon layer formed in a thin comb shape, 30 bonded substrate, 32 single crystal silicon layer, 34 insulating film, 36 polycrystalline silicon layer, 38 ... Support substrate, 39 ... SOI substrate, 40 ...
Polishing device for selective polishing, 42 Wafer holder 44
… Polishing table, 46… polishing pad, 48… polishing table,
50 ... Nozzle, 52 ... Grinding device, 54 ... Resin grindstone, 56 ... Resin bond 56, 58 ... Rotary wafer holder.

Claims (3)

[Claims] 1. A single crystal silicon substrate is patterned to form a recess having a predetermined pattern on a surface of the single crystal silicon substrate.
An insulating film is formed along the concave wall and the substrate surface, another layer is formed on the entire surface of the substrate, the upper surface is flattened, and the flattened upper surface is brought into surface contact with another supporting substrate. In a method for manufacturing an SOI substrate having a thin-film SOI structure over a support substrate, a single-crystal silicon substrate is ground until a crystalline silicon substrate and another support substrate are bonded to each other, and then the insulating film is exposed. A grinding step of grinding the single-crystal silicon layer until the thickness of the single-crystal silicon layer on the insulating film forming the thin-film SOI structure reaches a first predetermined thickness; A step of etching the single crystal silicon layer by dry etching until a predetermined thickness of 2 is obtained, and a finishing step of polishing the single crystal silicon layer until the insulating film is exposed. Method for manufacturing an SOI substrate 2. The bonding SO according to claim 1, wherein in the finishing step, polishing is performed by a selective polishing method.
Method for manufacturing I substrate. 3. The method according to claim 1, wherein the first predetermined thickness and the second predetermined thickness are:
3. The bonded SO according to claim 1, wherein the thickness is 3 to 5 [mu] m and 0.5 to 1.0 [mu] m, respectively.
Method for manufacturing I substrate.