JP2003309101A - Manufacturing method for laminated substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the manufacturing yield of a laminated substrate with no defective blister by reducing the defective blister of the laminated substrate which is represented by a thin-film SOI substrate. <P>SOLUTION: A method comprises a process where at least two substrates are SC-1-rinsed, a process where the rinsed substrate is dried, a process where the dried substrates are jointed, and a process where one of the jointed substrates is made into a thin film. In the process of SC-1-rinsing, the temperature of rinsing liquid is 25-60°C. <P>COPYRIGHT: (C)2004,JPO

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 bonded substrate, and more particularly to a cleaning step before bonding the substrates which are the materials.

[0002]

2. Description of the Related Art Bonded SOI using a bonding method
As a method of manufacturing a (Silicon On Insulator) substrate, a technique of bonding two silicon substrates with a silicon oxide film interposed therebetween, for example, Japanese Patent Publication No. 5-46086.
As disclosed in Japanese Patent Publication No. JP-A-2003-264, an oxide film is formed on at least one of the substrates, and the bonding surfaces are brought into close contact with each other without interposing foreign matter, and then heat treated at a temperature of 200 to 1200 ° C. to increase the bond strength. A method of increasing the number is conventionally known.

The bonded substrate having the bond strength increased by the heat treatment can be subjected to the subsequent grinding / polishing step. Therefore, by grinding and polishing the element manufacturing side substrate to a desired thickness. , S for element formation
An OI layer can be formed.

The bonded SO produced in this way
The I substrate has an advantage that the SOI layer is excellent in crystallinity and the buried oxide film existing immediately below the SOI layer is also highly reliable, but since it is thinned by grinding and polishing, it takes time to thin the film. The material is wasted, and the film thickness uniformity can be obtained only at the target film thickness ± 0.3 μm at most.

On the other hand, high integration of semiconductor devices in recent years,
With the increase in speed, it is required to further reduce the thickness of the SOI layer and improve the film thickness uniformity.
A film thickness and film thickness uniformity of about 0.01 μm are required.

In order to realize a thin film SOI substrate having such a film thickness and film thickness uniformity as a bonded substrate, it is impossible to reduce the thickness by conventional grinding and polishing. As a method, a method called an ion implantation delamination method (or hydrogen ion delamination method) disclosed in Japanese Patent Laid-Open No. 5-211128 has been developed.

Bonding S by this ion implantation separation method
The OI substrate is manufactured by forming an oxide film on at least one of the two silicon substrates and injecting hydrogen ions or rare gas ions from the upper surface of the one silicon substrate to form a microbubble layer inside the silicon substrate. After forming the (encapsulation layer), the ion-implanted surface is brought into close contact with the other substrate through the oxide film, and then heat treatment (peeling heat treatment) is applied to make the microbubble layer the cleavage surface (peeling surface) one substrate. Is peeled into a thin film, and heat treatment (bonding heat treatment) is further applied to firmly bond the two to form an SOI substrate.

According to this method, the peeled surface is a good mirror surface, an SOI substrate having an extremely high uniformity of the SOI layer can be obtained relatively easily, and one of the peeled substrates can be reused, so that the material can be effectively used. It also has the advantage of being usable.

Further, according to this method, the silicon substrates can be directly bonded to each other without interposing the oxide film, and not only when the silicon substrates are bonded to each other, but also quartz and silicon carbide are ion-implanted. It is also used when a substrate having these thin films is manufactured by bonding to an insulating substrate having a different thermal expansion coefficient such as alumina, or by ion-implanting the insulating substrate and bonding to another substrate.

[0010]

In any of the methods for manufacturing a bonded substrate as described above, the substrates, which are single or plural kinds of materials, are usually washed and dried, and then the material substrates are joined together. To do. After that, a heat treatment for increasing the bonding strength of the bonding interface of the bonded substrates is applied to firmly bond them, and then one of the substrates is thinned to manufacture a bonded substrate. In the production of this bonded substrate, when foreign materials such as particles and organic substances are present on the bonding surface of the material substrate when bonding the material substrates, the particles and the organic substances interfere with the bonding of the bonding interface, and the unbonded portion is left on the bonding interface. Will be formed. This causes void defects and blister defects at the bonding interface of the bonded substrate after the bonding heat treatment. In particular, when the bonding strength at the bonding interface is weak, void defects and blister defects are likely to occur even when the bonding heat treatment is performed, and the size thereof tends to increase.

FIG. 2 is a schematic view of a vertical cross section of an SOI substrate as an example of a bonded substrate having these defects. In the SOI substrate, an oxide film 10 and an active silicon layer 9 are laminated on a base substrate 2, but voids 13 and blister defects 12 as shown in the figure cause unbonded portions of these layers.

Therefore, in order to reduce these void defects and blister defects, it has been attempted to adequately manage the cleaning process before bonding and sufficiently remove foreign substances such as particles and organic substances. Even with sufficient control, it is difficult to completely remove the blisters with a diameter of several mm, which are visually observed after thinning, in the plane.
The manufacturing yield of a thin film SOI substrate which is blister-free on the entire surface has not reached a satisfactory level.

In particular, the diameter has increased to 300 mm in recent years.
In manufacturing the above SOI substrate, the conventional diameter of 200
Blister defects occur more frequently than substrates with a size of about mm, and blister-free wafers are 0-20
I could get only about%. Moreover, the size of the blister was as large as 4 mm or more, and the bonding strength at the bonding interface tended to be reduced.

The present invention has been made to solve the above problems, and reduces the blister defect of a bonded substrate represented by a thin film SOI substrate, and the manufacturing yield of the bonded substrate free from blister defects. The purpose is to improve.

[0015]

The present invention for solving the above-mentioned problems is a method for manufacturing a bonded substrate, which comprises a step of SC-1 cleaning at least two substrates, and the washed substrate. Including a step of drying, a step of bonding the dried substrates, and a step of thinning one of the bonded substrates,
The temperature of the cleaning liquid in the SC-1 cleaning step is 25
The method for producing a bonded substrate is characterized in that the temperature is not lower than 60 ° C and not higher than 60 ° C (claim 1).

As described above, when the temperature of the cleaning liquid in SC-1 cleaning is set to 25 ° C. or more and 60 ° C. or less, particles and organic substances can be removed without roughening the bonding surface more than necessary, and the entire surface becomes blister-free. The manufacturing yield of the bonded substrate can be improved. The temperature of the cleaning liquid is set to such a value, when the temperature of the cleaning liquid is lower than room temperature (that is, about 25 ° C.), the effect of removing particles and the like becomes insufficient, and a cooling facility for lowering the temperature below room temperature is required. It is because Also, at temperatures above 60 ° C., the blister reduction effect becomes insufficient.

In this case, it is preferable that the temperature of the cleaning liquid in the SC-1 cleaning is 30 ° C. or higher and 50 ° C. or lower (claim 2). This is because the temperature is preferably 30 ° C. or higher and 50 ° C. or lower in order to further enhance the effect of removing particles and organic substances and further improve the blister-free rate.

In this case, it is preferable that the drying step is a step of sucking and removing water on the surface of the cleaned substrate (claim 3). In this way, in the drying process,
By using a suction drying method of sucking and removing water on the surface of the substrate without using a water replacement method of replacing water on the surface of the substrate with an organic solvent having high volatility such as IPA (isopropyl alcohol) and drying. Since a plurality of substrates can be simultaneously dried by placing a plurality of substrates on the drying pedestal, productivity can be improved. Further, since it is not necessary to use highly flammable IPA or the like used in the water replacement method,
Work safety can also be improved.

In this case, at least one of the substrates used as the material for the bonded substrate can be a silicon substrate with an oxide film (claim 4), and the substrate used as the material for the bonded substrate can be hydrogen or a rare gas. Gas or halogen gas ions may be implanted (Claim 5).

As described above, the substrate used as the material of the bonded substrate is a combination of a plurality of types of substrates depending on the type and use of the device. Among them, a silicon substrate with an oxide film is used, and the substrate of the present invention is used. If a bonded substrate is manufactured by applying a cleaning process, an SOI substrate having a strong bonding strength before heat treatment and a strong bond strength after heat treatment can be obtained, and bonding without contamination, defects, blister defects, and void defects can be obtained. A laminated substrate can be manufactured. In addition, if a silicon substrate into which hydrogen, rare gas or halogen gas ions are implanted is used, the ion implantation delamination method provides an ultrathin and uniform film thickness without contamination, defects, blister defects and void defects. A bonded substrate can be manufactured.

Further, the bonded substrate manufactured by the manufacturing method of the present invention (claim 6) becomes a bonded substrate having no blister defects or void defects at the bonding interface, and has a strong bonding strength and a strong bonding strength. It can be a laminated substrate. In particular, in a large-diameter substrate having a diameter of 300 mm or more, the substrate manufactured by the manufacturing method of the present invention has excellent bonding characteristics.

The present invention will be described in detail below. As the cleaning before bonding, in the usual case, SC-1 cleaning (cleaning with a mixed solution of NH ₄ OH / H ₂ O ₂ / H ₂ O)
Hydrophilicity of the substrate surface, such as SC-2 cleaning (cleaning with a mixed solution of HCl / H ₂ O ₂ / H ₂ O) and sulfuric acid / hydrogen peroxide cleaning (cleaning with a mixed solution of H ₂ SO ₄ / H ₂ O ₂ ). The washings described above are appropriately combined and used according to the purpose.

Among them, the SC-1 cleaning is effective in removing particles, organic substances and the like, and is therefore an essential cleaning in the cleaning step before bonding.
This SC-1 cleaning is also very commonly used in the manufacturing process of silicon substrates and silicon devices.
The use temperature is 70 to 85 ° C. This is traditionally
This is because it has been considered that the cleaning effect cannot be obtained unless the cleaning process is performed at such a high temperature. Therefore, conventionally, SC-1 cleaning has not been performed with a cleaning liquid having a temperature lower than this.

However, the inventors of the present invention produced a thin film SOI by bonding a substrate for bonding which was immersed in the SC-1 cleaning layer for a longer time than usual due to a trouble of the SC-1 cleaning device, to produce a thin film SOI. We encountered the result that the blister occurrence rate was high, and as a result of investigating and analyzing the result, the present invention was completed.

That is, conventionally, if the SC-1 cleaning is more strictly controlled and particles and the like are sufficiently removed,
It was thought that the occurrence of blisters could be prevented. However, with respect to the above results, the present inventors have found that the surface of the substrate to be bonded (oxide film surface or silicon surface) is roughened by being immersed in SC-1 cleaning for a long time,
I thought that led to an increase in blister defects. Therefore, in SC-1 cleaning, it was thought that blister defects could be reduced by cleaning without causing surface roughness of the bonded surface more than necessary.

Then, as a result of studying the conditions of the SC-1 cleaning, the present inventors have completed the present invention with the idea that the SC-1 cleaning is performed at a temperature lower than the temperature usually used. . As described above, conventionally, when the temperature of SC-1 cleaning is lowered, there is concern that the original effect of SC-1 cleaning such as removal of particles and organic substances may be reduced. No lowering and washing was done. However, as a result of investigation by the present inventors, SC as a cleaning process of the substrates to be bonded is performed.
It was found that the cleaning effect of removing particles and the like in the -1 cleaning has almost no effect even if the temperature of the cleaning liquid is lowered from 70 to 85 ° C in the related art to 25 to 60 ° C. And this 60
It was found that the blister generation was remarkably suppressed at the cleaning liquid temperature of ℃ or below. In this case, if the temperature is lowered to less than 25 ° C., the effect of removing particles decreases, and a separate device for cooling the cleaning liquid to a temperature of room temperature or lower is required, so that the effect of removing particles is maintained. Meanwhile, the inventors have found that the temperature of the cleaning liquid is preferably 25 ° C. or higher and 60 ° C. or lower in order to prevent the occurrence of blisters. Especially, the temperature of the cleaning liquid is 30 to 5
It was found that, in the range of 0 ° C., the blister generation rate was particularly reduced, although the effect of cleaning and removing particles was maintained.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for manufacturing a bonded substrate according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a process diagram showing an outline of one embodiment of a method for manufacturing a bonded substrate according to the present invention. Here, an example of manufacturing an SOI substrate using a hydrogen ion peeling method which is one of methods for manufacturing a bonded substrate will be described.

In FIG. 1, two bare substrates are prepared as material substrates (A). As the bare substrate, there are various substrates such as a mirror-polished substrate, an epitaxial substrate, and a heat-treated substrate, and the present invention can be applied regardless of the type. First, the oxide film 10 is formed on the surface of a bare substrate prepared as the bond substrate 1. Hydrogen ions are implanted from the surface of the bond substrate 1 having the oxide film 10 formed on the surface,
The high hydrogen concentration layer 11 is uniformly formed at a desired depth. The depth of the hydrogen high-concentration layer 11 corresponds to the obtained active silicon layer 9 (S
The thickness of the OI layer) will be determined.

Next, a bare substrate is used as the base substrate 2.
Use as it is. Here, the bond substrate 1 is a bare substrate,
The base substrate 2 may be a substrate with an oxide film. Also together
A bare substrate or a substrate with an oxide film may be used. These materials
Particles and organic substances adhering to the surface of the material substrate
Etc., a cleaning process is performed before joining the material substrates.
(B). In this cleaning step, for example, SC-1 cleaning and S
Cleaning such as so-called RCA cleaning that combines C-2 cleaning
I do. In the present invention, in this SC-1 cleaning
The temperature of the cleaning liquid is 25 to 60 ° C, preferably 30 to 50 ° C
Set to. This makes the bonding surface rougher than necessary.
It is possible to remove particles and organic substances without losing
To obtain a blister-free bonded substrate over the entire surface
You can The concentration of the SC-1 cleaning solution in this case is generally
Range used for, for example, NH _FourOH (29wt
%): H_TwoO_Two(30 wt%): H_Two0 = 1: 1: 5
It is sufficient to use 1: 1: 10. This SC-1 cleaning is once
It is not limited to the case of performing only
It is also possible to change the interval and divide into multiple times.

In the subsequent drying step (C), it is preferable to use the suction drying method instead of the water replacement method. This is because the suction drying method does not require the use of an inflammable organic solvent such as IPA and is highly safe. Further, since a plurality of wafers can be processed at the same time, work efficiency is good.

This suction drying method, as shown in FIG.
The substrate W is placed on the dry pedestal 21 where the vacuum suction line 22 is installed.
Is placed vertically, and the vacuum pump 23 sucks clean air existing around both surfaces of the substrate W as an air stream, and at the same time sucks and removes water drops and water films on both surfaces of the substrate W to dry. According to this method, the amount of water on the surface of the substrate can be adjusted to an appropriate amount without being reduced more than necessary.
In addition, since a plurality of substrates can be placed on the drying pedestal, a large number of substrates can be dried at the same time, and thus productivity can be improved.

Next, in the bonding step (D), the surface of the bond substrate 1 and the surface of the base substrate 2 are bonded. At this time,
Since the particle contamination and the organic matter contamination are likely to occur from the atmosphere of the bonding process and the container storing the material substrate, it is desirable to perform the bonding process as soon as possible after performing the cleaning process and the drying process.

In the peeling heat treatment step (E), when the bonded substrates are heat-treated at a low temperature of about 400 to 600 ° C.,
A defect layer is formed in the hydrogen high concentration layer 11 formed in the bond substrate 1. The bond layers are separated in the horizontal direction inside the bond substrate 1, whereby the bond substrate 1 is peeled off. As a result, part of the bond substrate 1 is transferred onto the base substrate 2 as the active silicon layer 9 to become an SOI substrate.

In the bonding heat treatment step (F), in order to enhance the bonding strength at the bonding interface, a bonding heat treatment is performed at 1000 ° C. or higher in an oxidizing atmosphere or a non-oxidizing atmosphere to firmly bond and stabilize. Finally, in the polishing step (G),
Polishing is performed to remove damage on the surface of the SOI layer and improve microroughness. Instead of polishing, heat treatment such as hydrogen annealing may be performed. The SOI substrate 15 by the hydrogen ion peeling method is completed by the above series of steps.

The presence or absence of blister defects can be confirmed by visually observing the SOI substrate after the peeling heat treatment step (E). According to the cleaning method in the manufacturing method of the present invention, it is possible to remove particles and organic substances without roughening the bonded surface more than necessary. Therefore, it is possible to obtain a bonded substrate that is blister-free over the entire surface with high yield. In particular, conventionally, it was possible to obtain a bonded substrate that is entirely blister-free only with a low yield,
The present invention is extremely effective when manufacturing a substrate having a diameter exceeding 300 mm.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples of the present invention and comparative examples, but the present invention is not limited thereto. (Examples and Comparative Examples) Here, an SOI substrate was manufactured by using a hydrogen ion peeling method which is a kind of manufacturing method of a bonded substrate. The manufacturing process was performed up to the peeling heat treatment process (E) in the process diagram shown in FIG. First, a silicon substrate with a diameter of 300 mm on which an oxide film with a thickness of 150 nm is formed is 8 ×
A bond substrate in which 10 ¹⁶ ions / cm ² of hydrogen ions were implanted and a bare silicon substrate were prepared as base substrates. Next, both substrates were washed with sulfuric acid / hydrogen peroxide mixture and then washed under the three conditions shown in Table 1 below (SC-1 cleaning + SC-2 cleaning).
After that, it was thoroughly rinsed with pure water. Subsequently, both substrates were dried using a suction drying method.

[0037]

[Table 1]

In order to confirm the cleaning effect of the substrate subjected to the drying process after the cleaning process before joining the substrates, the number of particles on the substrate of the separately prepared substrate was measured by KLA.
-When measured with a particle counter SP1 manufactured by Tencor Co., it was found that no matter how many substrates were cleaned under any condition, only 10 particles / substrate or less were detected and cleaning was effectively performed. understood.

Next, the oxide film surface of the bond substrate and one surface of the base substrate were bonded at room temperature. Then, heat treatment was performed at 500 ° C. at which the high-concentration hydrogen layer was separated from the bonded substrates, so that the bond substrate was thinned. Thereafter, the surface of the produced SOI wafer was visually inspected under a fluorescent lamp to measure the number and size of blisters and the number of voids, which are shown in Table 2.

[0040]

[Table 2]

As shown in Table 2, the SOI substrates of Example 1 and Example 2 have a high blister-free rate,
No void has been detected. Also, it can be seen that the size of the blister formed on the substrate is as small as 3 mm or less. Therefore, it is understood that the manufacturing method of the present invention can improve the yield of the bonded substrate manufacturing. On the other hand, although the SOI substrate in the comparative example has a small number of voids, it was found that the surface was rough and the blister-free rate was low because SC-1 cleaning was performed at a normal cleaning liquid temperature. Further, the size of the blister generated on the substrate is as large as 4 mm or more, which shows that the manufacturing yield is low.

The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to the present invention. It is included in the technical scope of the invention.

For example, in the above-described embodiment, the case where the bond substrate is thinned by the ion implantation separation method to manufacture the SOI substrate has been mainly described. However, the present invention is not limited to this, and grinding / polishing is performed. Even if the bond substrate is thinned by a method other than the ion implantation separation method such as etching, the steps of cleaning and bonding two substrates are exactly the same, and such a cleaning step is essential. Any method of applying the invention and manufacturing a bonded substrate is within the scope of the present invention.

[0044]

As described above, according to the present invention,
Even with a bonded wafer having a large diameter exceeding 300 mm, it is possible to prevent the occurrence of blister defects and void defects, and it is possible to significantly improve the production yield of the bonded wafer.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a bonded substrate manufacturing method according to the present invention.

FIG. 2 is an explanatory diagram showing a blister defect and a void defect of a bonded substrate.

FIG. 3 is an explanatory diagram showing a suction drying method.

[Explanation of symbols]

1 ... Bond substrate, 2 ... Base substrate, 9 ... Active silicon layer, 10 ... Oxide film, 11 ... Hydrogen high concentration layer, 12 ... Blister defect, 13 ... Void defect, 15 ... SOI wafer 21 ... Drying pedestal, 22 ... Vacuum Suction line, 23 ... Vacuum pump, W ... Substrate (wafer).

Claims (6)

[Claims] 1. A method for manufacturing a bonded substrate, comprising at least a step of SC-1 cleaning two substrates, a step of drying the cleaned substrates, and a step of bonding the dried substrates together. A method for producing a bonded substrate, comprising a step of thinning one of the bonded substrates, wherein the temperature of the cleaning liquid in the SC-1 cleaning step is 25 ° C. or higher and 60 ° C. or lower. 2. The method for manufacturing a bonded substrate according to claim 1, wherein the temperature of the cleaning liquid in the SC-1 cleaning is 30 ° C. or higher and 50 ° C. or lower. 3. The method of manufacturing a bonded substrate according to claim 1, wherein the drying step is a step of sucking and removing water on the surface of the washed substrate. 4. The bonded substrate according to any one of claims 1 to 3, wherein at least one of the substrates which is a material of the bonded substrate is a silicon substrate with an oxide film. Production method. 5. A substrate which is a material of the bonded substrate,
5. The method for manufacturing a bonded substrate according to claim 1, wherein hydrogen, rare gas or halogen gas ions are implanted. 6. A bonded substrate manufactured by the manufacturing method according to any one of claims 1 to 5.