JP2009246323A - Production process for soi substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production process for transparent insulating substrate having a silicon thin film formed on one major surface, i.e. an SOI substrate, having a roughened major surface on the reverse side of a surface where the silicon thin film is formed, while preventing generation of metal impurities or particles, using a simple method. <P>SOLUTION: A production process of an SOI substrate, having a silicon thin film formed on a first major surface of a transparent insulating substrate and a roughened second major surface comprises a step of roughening the second major surface of the transparent insulating substrate so as to obtain a surface roughness of 0.1 μm or more, in terms of Ra value by blowing first abrasive grains, and a step of roughening the second major surface, by blowing second abrasive grains which makes the surface roughness of the second major surface of the transparent insulating substrate finer, in terms of Ra value, than that in the first roughening process when surface roughening is performed under same conditions as those of the first roughening processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an SOI substrate manufacturing method, and more particularly to an SOI substrate manufacturing method in which a silicon thin film is formed on one main surface of a transparent insulating substrate.

  In order to further improve the performance of semiconductor devices, SOI (silicon on insulator, silicon on insulator) substrates have recently attracted attention. In addition, a silicon on quartz (SOQ) substrate and a silicon on glass (SOG) substrate, which are a kind of SOI substrate and the support substrate (handle wafer) is not silicon, are TFT-LCDs and radio frequency (RF) devices, respectively. Other applications to MEMS products are expected (see Patent Document 1).

As the SOQ substrate, for example, a method has been proposed in which a silicon substrate is used as a donor wafer and a quartz substrate is used as a handle wafer to bond these different substrates together. In the bonded substrate manufactured in this manner, the quartz substrate is transparent, and thus there may be a problem in process / evaluation different from a normal SOI substrate manufactured by bonding silicon substrates together.
As one of such problems, when transporting an SOI substrate in which a silicon thin film is formed on a transparent insulating substrate such as an SOQ substrate (hereinafter, sometimes referred to as a transparent SOI substrate) on the apparatus, There was a problem that the optical sensor that recognizes was difficult to recognize.

JP 2006-324530 A

  The present invention has been made in view of such problems, and is a transparent insulating substrate in which a silicon thin film is formed on one main surface, which is opposite to the side on which the silicon thin film is formed. It is an object of the present invention to provide a method for manufacturing an SOI substrate having a rough main surface while suppressing the generation of metal impurities and particles by a simple method.

  The present invention has been made to solve the above-described problem, and a silicon thin film is formed on a first main surface which is one main surface of a transparent insulating substrate, and the first main surface of the transparent insulating substrate is formed. A method of manufacturing an SOI substrate having a roughened second main surface, which is a main surface opposite to the surface, comprising at least a step of preparing a transparent insulating substrate, and at least the transparent insulating substrate In the method for manufacturing an SOI substrate, comprising the step of mirror-finishing the first main surface and the step of forming a silicon thin film on the first main surface of the transparent insulating substrate, the second main surface of the transparent insulating substrate As the second abrasive grains, the first roughening step of roughening the surface roughness by spraying the first abrasive grains so that the surface roughness is 0.1 μm or more in Ra value, When surface roughening is performed under the same conditions as the one surface roughening process The first rough surface is made of abrasive grains such that the surface roughness of the second main surface of the transparent insulating substrate is smaller than that of the first roughening step when compared with the Ra value. And a second roughening step of roughening the second main surface of the transparent insulating substrate after spraying the second abrasive grains. (Claim 1).

If it is the method of roughening by spraying of such a two-step abrasive grain, generation | occurrence | production of a metal impurity and a particle can be suppressed by a simple method and roughening can be performed. As a result, according to the above-described method for manufacturing an SOI substrate, the transparent insulating substrate has a silicon thin film formed on one main surface, and the main surface opposite to the side on which the silicon thin film is formed is rough. The produced SOI substrate can be manufactured by suppressing the generation of metal impurities and particles by a simple method.
In the case of an SOI substrate manufactured in this way, since the back surface of the transparent insulating substrate is rough, the substrate is recognized by the recognition device by scattering the signal from the recognition device using the optical sensor. It is possible to prevent the harmful effect of not being done. In addition, it is possible to prevent slipping during substrate transportation.

In this case, in the second roughening step, it is preferable to perform a roughening treatment so that the surface roughness of the second main surface of the transparent insulating substrate is less than 0.08 μm in Ra value. 2).
In this way, in the second roughening step, if the roughening treatment is performed so that the surface roughness of the second main surface of the transparent insulating substrate is less than 0.08 μm in terms of Ra value, the metal is more effectively used. The generation of impurities and particles can be suppressed and the second main surface of the transparent insulating substrate can be roughened.

In the method for manufacturing an SOI substrate according to the present invention, it is preferable that the hardness of the second abrasive grain is lower than the hardness of the first abrasive grain.
Thus, if the hardness of the second abrasive grains is lower than the hardness of the first abrasive grains, the second main surface of the transparent insulating substrate can be more effectively suppressed from generating metal impurities and particles. Can be roughened.

In the method for manufacturing an SOI substrate according to the present invention, the abrasive grain spraying in the first and second roughening steps can be performed by applying processing energy by air pressure or water pressure.
Thus, in the method for manufacturing an SOI substrate according to the present invention, the processing energy for spraying abrasive grains in the first and second roughening steps can be applied by either air pressure or water pressure. It can select suitably according to other manufacturing conditions.

In the method for manufacturing an SOI substrate according to the present invention, a main component of the first abrasive grains and the second abrasive grains can be at least one of alumina, silicon carbide, and zirconia. ). Further, at least a main component of the second abrasive grain can be a synthetic resin or a vegetable soft grain (Claim 6).
In the method for manufacturing an SOI substrate according to the present invention, the abrasive grains having the above components can be appropriately selected and used.

In the method for manufacturing an SOI substrate according to the present invention, the first roughening step and the second roughening step can be performed at least after the silicon thin film forming step. . Further, at least the step of preparing the transparent insulating substrate, the first roughening step, the silicon thin film forming step, and the second roughening step can be performed in this order. (Claim 8). In addition, the first roughening step and the second roughening step can be performed after the step of preparing the transparent insulating substrate and before the silicon thin film forming step. 9).
As described above, the first roughening step and the second roughening step in the present invention can be performed either before or after the formation of the silicon thin film, and are appropriately set according to other manufacturing conditions. be able to. Further, the first roughening step and the second roughening step can be performed separately before and after the formation of the silicon thin film.

Further, in the method for manufacturing an SOI substrate according to the present invention, it is preferable to perform mirror finishing of the first main surface of the transparent insulating substrate so that the surface roughness is less than 0.7 nm in terms of RMS value. 10).
Thus, if the mirror surface processing of the first main surface of the transparent insulating substrate is performed so that the surface roughness is less than 0.7 nm in terms of the RMS value, the first main surface becomes sufficiently flat. A silicon thin film can be easily formed.

In the SOI substrate manufacturing method according to the present invention, the roughening treatment of the second main surface of the transparent insulating substrate in the first and second roughening steps is finally performed. It is preferable that the average transmittance of light in the wavelength range of 250 to 800 nm in the direction perpendicular to the main surface is 10% or less.
Thus, the roughening treatment of the second main surface of the transparent insulating substrate in the first and second roughening steps is finally performed at 250 to 800 nm in the direction perpendicular to the main surface of the transparent insulating substrate. If the average transmittance of light in the wavelength region is 10% or less, the substrate recognition apparatus can be recognized more reliably.

In the method for manufacturing an SOI substrate according to the present invention, the silicon thin film is formed by implanting hydrogen ions, rare gas ions, or both from at least a silicon substrate or a silicon substrate having an oxide film formed on the surface. An ion-implanted layer is formed, and the ion-implanted surface of the silicon substrate or the silicon substrate on which the oxide film is formed and the first main surface of the transparent insulating substrate are adhered to each other, and the ion-implanted layer is bonded. The silicon substrate or the silicon substrate having an oxide film formed on the surface thereof is peeled off to form a thin film, and a silicon thin film is formed on the first main surface of the transparent insulating substrate. ).
In this way, if the silicon thin film is formed by peeling off after using the ion implanted layer as a boundary after the ion implantation, a thin silicon film with high crystallinity can be formed.

Further, the transparent insulating substrate can be any one of a quartz substrate, a glass substrate, and a sapphire substrate.
The transparent insulating substrate used in the method for manufacturing an SOI substrate of the present invention can be appropriately selected from these according to the purpose of the semiconductor device to be manufactured.

The SOI substrate manufacturing method of the present invention is an SOI substrate (transparent SOI substrate) in which a silicon thin film is formed on a transparent insulating substrate, and the back surface (the main surface on which the silicon thin film is not formed) is rough. The produced SOI substrate can be manufactured by suppressing the generation of metal impurities and particles by a simple method.
And if it is the SOI substrate manufactured in this way, since the surface roughness of the back surface of a transparent insulating board | substrate is large, a board | substrate is made to a recognition apparatus by scattering the signal from the recognition apparatus using an optical sensor. Can be recognized. In addition, it is possible to prevent slipping during substrate transportation.

Hereinafter, the present invention will be described in more detail.
As described above, conventionally, an SOI substrate in which a silicon thin film is formed on a transparent insulating substrate such as an SOQ substrate is not easily recognized by an optical sensor that recognizes the substrate when the SOQ substrate is transported on the apparatus. There was a problem.

In response to such problems, the present inventors have provided the back surface of an SOI substrate (transparent SOI substrate) in which a silicon thin film is formed on a transparent insulating substrate, that is, the main surface on which the silicon thin film of the transparent insulating substrate is formed. It has been found that by roughening the main surface on the opposite side of the substrate, the signal from the recognition device can be scattered in the substrate recognition device using an optical sensor or the like, and the substrate can be easily recognized.
However, a lot of abrasive grains or the like have entered the rough surface of such a substrate, and there is a problem that metal impurities are generated or particles are generated. Therefore, it is conceivable to etch the substrate. However, if the entire substrate is etched, the side opposite to the roughened surface is also etched, so that the flatness is deteriorated or the silicon thin film is formed. Problems such as peeling of the silicon thin film occurred.

The inventors of the present invention have made extensive studies on such problems, and sprayed abrasive grains under the same conditions on the surface opposite to the surface on which the silicon thin film is formed (hereinafter referred to as blasting). Using two types of abrasive grains with different degrees of roughening due to the fact that there are two types of abrasive grains, first of all, the abrasive grain with the higher degree of roughening is sprayed. Later, the inventors have found a method for manufacturing an SOI substrate in which abrasive grains having a smaller degree of roughening are sprayed).
By performing such two-stage blasting, large irregularities are created by the first-stage blasting, and particles (abrasive grains used for blasting, residues during blasting, etc.) are deposited in the concave portions. However, this can be removed by blasting using fine abrasive grains in the second stage. Further, the large unevenness is not corrected by this second stage blasting.
Moreover, since the effect which removes the particle | grains for a big recessed part with the fine abrasive grain as mentioned above is acquired, it turned out that dusting can be prevented by performing two-stage blasting.
And if it is the manufacturing method of the SOI substrate which performs the above-mentioned two-stage blasting, it does not affect the surface on which the silicon thin film is formed, and the generation of metal impurities and particles is suppressed by a simple method. The present invention was completed by conceiving that a transparent SOI substrate having a roughened surface opposite to the surface on which the thin film is formed can be manufactured.

In the present specification, of the main surfaces of the transparent insulating substrate, the main surface on the side where the silicon thin film is formed is referred to as a “first main surface” for convenience, and the main surface opposite to the first main surface is referred to as a “first main surface”. Called the “two main surfaces”.
The overall flow of the present invention will be described. A step of preparing a transparent insulating substrate, a step of mirror-treating one main surface (first main surface) of the transparent insulating substrate, and the mirror-finished first main surface A transparent SOI substrate is manufactured by a process of forming a silicon thin film thereon. In order to manufacture a transparent SOI substrate having a roughened back surface, it is necessary to roughen the second main surface at any stage. In the present invention, the rough surface of the second main surface is used. First, the abrasive grains having the larger degree of roughening are sprayed, and then the abrasive grains having the smaller degree of roughening are sprayed. In the present invention, the roughening by the two-stage blasting can be performed either before or after the formation of the silicon thin film. Moreover, each roughening process by two-stage blasting can also be performed separately before and after the formation of the silicon thin film.

Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings. However, the present invention is not limited to these embodiments.
(First aspect)
FIG. 1 is a flowchart showing an example (first embodiment) of a method for manufacturing an SOI substrate according to the present invention.
Here, an example will be described in which the first roughening step and the second roughening step are performed after the formation of the silicon thin film.

First, as shown in FIG. 1A, a transparent insulating substrate 10 is prepared (step 1-a). As this transparent insulating substrate 10, for example, a quartz substrate sliced from a quartz ingot can be used.
The type of the transparent insulating substrate to which the present invention can be applied is not particularly limited. For example, the transparent insulating substrate can be any of a quartz substrate, a glass substrate, and a sapphire substrate. It can be appropriately selected depending on the purpose.

Next, as shown in FIG. 1B, at least one main surface of the transparent insulating substrate is mirror-finished (step 1-b). Here, the mirror-finished main surface becomes the main surface on the side on which the silicon thin film is to be formed, that is, the first main surface 11. The method of this mirror surface processing is not specifically limited, It processes by combining lapping, an etching, grinding | polishing etc. suitably.
The other main surface, that is, the second main surface 12 is desirably subjected to at least a treatment for suppressing dust generation. Specifically, generation of particles or the like can be suppressed by performing etching after lapping. Moreover, you may perform a mirror surface process similarly to the 1st main surface. In this case, a technique such as double-side polishing that simultaneously processes the first main surface 11 and the second main surface 12 may be used.

  In addition, it is desirable to perform the mirror finish of the first main surface 11 of the transparent insulating substrate 10 so that the surface roughness is less than 0.7 nm in terms of RMS value. With such a surface roughness, the silicon substrate can be bonded with higher strength by bonding or the like, and when the silicon thin film is formed, the crystal of the silicon thin film is generated due to the generation of voids that are unbonded portions. It is possible to effectively prevent the deterioration of sex. On the other hand, the lower limit value of the RMS value of the surface roughness of the first main surface 11 is not particularly limited, and the higher the flatness, the better. However, there is a problem of cost in improving the flatness, and it is practically about 0.1 nm or more. The surface roughness of the second main surface 12 is not particularly limited at this point.

Next, a silicon thin film is formed on the first main surface 11 of the transparent insulating substrate 10. The method for forming the silicon thin film is not particularly limited. For example, the silicon thin film can be formed by a so-called ion implantation separation method as follows.
First, as shown in FIG.1 (c), the silicon substrate 20 is prepared (process 1-c). Further, if necessary, a silicon substrate having an oxide film formed on the surface may be used. In order to improve the state of bonding, it is necessary that the surface to be bonded (bonding surface) has a flatness of a certain level or more. Therefore, at least the surface to be bonded is mirror-polished or the like. For example, the flatness is preferably an RMS value of less than 0.7 nm.

Next, as shown in FIG. 1D, hydrogen ions are implanted into the silicon substrate 20 from the surface (ion implantation surface 22) to form the ion implantation layer 21 (step 1-d).
The ion-implanted layer 21 may be formed by implanting not only hydrogen ions but also rare gas ions or both hydrogen ions and rare gas ions. Other ion implantation conditions such as implantation energy, implantation dose, and implantation temperature may be appropriately selected so that a thin film having a predetermined thickness can be obtained. As a specific example, the temperature of the substrate at the time of implantation is 250 to 400 ° C., the ion implantation depth is 0.5 μm, the implantation energy is 20 to 100 keV, and the implantation dose is 1 × 10 ¹⁶ to 1 × 10 ¹⁷ / cm. It includes be ^two, but not limited thereto.
Note that a single crystal silicon substrate having an oxide film formed on the surface can be used as necessary. By using such a silicon substrate having an oxide film formed on the surface and performing ion implantation through the oxide film, an effect of suppressing channeling of implanted ions can be obtained, and variations in ion implantation depth can be further suppressed. . Thereby, a thin film with higher film thickness uniformity can be formed.

Next, as shown in FIG. 1E, the first main surface 11 of the transparent insulating substrate 10 and the ion-implanted surface 22 of the silicon substrate 20 are brought into intimate contact and bonded together (step 1-e).
The transparent insulating substrate 10 and the silicon substrate 20 are bonded to each other so that the first main surface 11 of the transparent insulating substrate 10 and the ion implantation surface 22 of the silicon substrate 20 are sufficiently flat surfaces as described above. Therefore, for example, if a synthetic quartz substrate and a silicon substrate are used, they can be bonded together by simply bringing them into close contact at room temperature and applying pressure.
However, in order to bond more firmly, it is preferable to do as follows.

That is, it is desirable to perform a surface activation process on the ion implantation surface 22 of the silicon substrate 20 and the first main surface 11 of the transparent insulating substrate 10 in advance. Surface activation treatment may be performed only on one of the ion implantation surface 22 of the silicon substrate 20 and the first main surface 11 of the transparent insulating substrate 10.
At this time, the surface activation treatment can be a plasma treatment. Thus, if the surface activation treatment is performed by plasma treatment, the surface of the substrate that has been subjected to the surface activation treatment is activated due to an increase in OH groups. Therefore, in this state, if the first main surface 11 of the transparent insulating substrate 10 and the ion-implanted surface 22 of the silicon substrate 20 are brought into close contact with each other, the substrates can be bonded more firmly by hydrogen bonding or the like. . In addition, the surface activation treatment can be performed by ozone treatment or the like, and a plurality of kinds of treatments may be combined.

  In the case of processing with plasma, a substrate subjected to cleaning such as RCA cleaning is placed in a vacuum chamber, and after introducing a plasma gas, it is exposed to high-frequency plasma of about 100 W for about 5 to 30 seconds, and the surface is subjected to plasma processing. To do. As the plasma gas, for example, when processing a single crystal silicon substrate with an oxide film formed on the surface, oxygen gas plasma, and when processing a single crystal silicon substrate with no oxide film formed on the surface, hydrogen is used. Gas, argon gas, a mixed gas thereof, or a mixed gas of hydrogen gas and helium gas can be used. In addition, nitrogen gas or the like may be used.

  When processing with ozone, a substrate subjected to cleaning such as RCA cleaning is placed in a chamber into which air is introduced, and after introducing a plasma gas such as nitrogen gas or argon gas, high frequency plasma is generated, The surface is treated with ozone by converting the oxygen in it into ozone.

  In this way, if the surfaces subjected to the surface activation treatment are used as the bonding surfaces, for example, the substrate is brought into close contact at room temperature under reduced pressure or normal pressure, the substrates can be firmly bonded without performing high temperature treatment.

In addition, after bonding this silicon substrate and a transparent insulating substrate, the heat processing process of heat-processing this bonded substrate at 100-300 degreeC can be performed.
Thus, after bonding a silicon substrate and a transparent insulating substrate, the bonded substrate is heat-treated at 100 to 300 ° C., thereby increasing the bonding strength between the silicon substrate and the transparent insulating substrate. it can. In addition, if the heat treatment is performed at such a low temperature, there is little risk of occurrence of thermal strain, cracking, peeling, or the like due to the difference in thermal expansion coefficient due to the different materials. Increasing the bonding strength can reduce the occurrence of defects in the peeling process.

Next, the silicon substrate 20 is separated by the ion-implanted layer 21, and a peeling step for thinning the silicon substrate 20 is performed to form a silicon thin film 31 as shown in FIG. 1 (f) (step 1-f). .
The separation (peeling, thinning) of the silicon substrate can be performed, for example, by applying a mechanical external force.

Next, as shown in FIG.1 (g), the 1st roughening which roughens the 2nd main surface 12 of the transparent insulating board | substrate 10 by spraying a 1st abrasive grain (blasting process). A process is performed (process 1-g).
The abrasive grain spraying in the first roughening step can be performed using a fluid such as air or water and applying processing energy by air pressure or water pressure.
A method of applying processing energy to abrasive grains by air pressure is called air blasting (also called sand blasting), and a method of applying processing energy to abrasive grains by water pressure is called wet blasting.
What type of blasting can be selected can be appropriately selected according to processing conditions for spraying second abrasive grains described later, other manufacturing conditions, and the like.

The first abrasive grains are sprayed so that the surface roughness of the second main surface 12 is 0.1 μm or more in terms of Ra value. In order to spray the abrasive grains so as to have such a surface roughness, for example, the spraying conditions and the like may be determined in advance by experiments or the like, and the actual abrasive grains may be sprayed under the conditions.
As this 1st abrasive grain, the main component can use at least 1 sort (s) of an alumina, a silicon carbide, and a zirconia, for example. Abrasive grains containing these as main components are preferable because of their high hardness and good blasting efficiency.

Next, as shown in FIG. 1 (h), the second abrasive grains are sprayed onto the second main surface 12 of the transparent insulating substrate 10 subjected to the first roughening as described above to roughen the surface. A second roughening step for surface treatment is performed (step 1-h).
The second abrasive grains are sprayed when the second abrasive grains are roughened under the same conditions as the first roughening step described above as the second abrasive grains. Abrasive grains whose surface roughness is smaller than that of the first roughening step when compared with the Ra value are used. Various types of abrasive grains satisfying such conditions can be used.

At this time, it is preferable to make the hardness of the second abrasive grain lower than the hardness of the first abrasive grain. In this way, it is possible to more effectively suppress the generation of metal impurities and particles and roughen the transparent insulating substrate.
Specifically, as the second abrasive grain, as in the first abrasive grain, the main component can be at least one of alumina, silicon carbide, and zirconia.
Further, the main component of the second abrasive grains may be a synthetic resin or vegetable soft grain having a hardness lower than that of the ceramic. As the synthetic resin, for example, a polyamide-based synthetic resin such as nylon (registered trademark), polycarbonate, or the like can be used.
Even when the second abrasive is the same component as the first abrasive, the above conditions can be satisfied by adjusting the average grain size of the abrasive.

  Moreover, in this 2nd roughening process, it is preferable to roughen so that the surface roughness of the 2nd main surface 12 of the transparent insulating board | substrate 10 may become less than 0.08 micrometer in Ra value. For this purpose, for example, the conditions for spraying the second abrasive grains and the like may be determined in advance through experiments or the like, and the actual abrasive grains may be sprayed under those conditions.

  Then, the roughening treatment of the second main surface of the transparent insulating substrate in the first and second roughening steps is performed in a direction perpendicular to the main surface of the transparent insulating substrate 10 (that is, the thickness direction of the substrate). The average transmittance of light in the wavelength range of 250 to 800 nm (hereinafter sometimes referred to as vertical average transmittance) is preferably 10% or less, and particularly preferably 5% or less. With such a vertical average transmittance, the recognition device using the optical sensor can be more reliably recognized. In order to obtain such a vertical average transmittance, it is necessary to determine in advance how the processing conditions in the first roughening step and the second roughening step are the above-mentioned vertical average transmittance. What is necessary is just to perform a roughening process on the conditions, such as obtaining experimentally.

  The vertical average transmittance of the transparent insulating substrate 10 and the surface roughness of the second main surface 12 of the transparent insulating substrate 10 have a certain degree of correlation. The upper limit of the vertical average transmittance of the transparent insulating substrate 10 is preferably as described above, but the lower limit of the surface roughness of the second main surface 12 of the transparent insulating substrate 10 is not particularly limited directly. . Although it depends on other conditions such as the type of the transparent insulating substrate and the performance of the recognition device, for example, the Ra value can be 0.01 μm or more.

Through the steps described above, the SOI substrate 30 having the silicon thin film 31 on the first main surface 11 of the transparent insulating substrate 10 can be manufactured.
Note that the steps 1-a to 1-b and the steps 1-c to 1-d, which are treatments for separate substrates, may of course be reversed in order or performed in parallel.

  As described above, by performing the steps 1-a to 1-h, an SOI substrate in which a silicon thin film is formed on a transparent insulating substrate having a rough back surface is manufactured. In the present invention, in the steps 1-g and 1-h, the second main surface 12 is roughened by dividing the spraying of abrasive grains having different ability to roughen into two stages. Therefore, roughening can be performed by suppressing the generation of metal impurities and particles by a simple method. As a result, according to the above-described method for manufacturing an SOI substrate, the transparent insulating substrate has a silicon thin film formed on one main surface, and the main surface opposite to the side on which the silicon thin film is formed is rough. The produced SOI substrate can be manufactured by suppressing the generation of metal impurities and particles by a simple method.

(Second embodiment)
Next, another example of the method for manufacturing an SOI substrate according to the present invention will be specifically described.
FIG. 2 is a flowchart showing another example (second embodiment) of the method for manufacturing an SOI substrate of the present invention.
Here, an example will be described in which the first roughening step is performed before the formation of the silicon thin film.

  First, as shown in FIGS. 2A to 2B, the transparent insulating substrate 10 is prepared (step 2-a) as in the case of the first aspect described above. At least one main surface (first main surface 11) is mirror-finished (step 2-b). The second main surface 12 is the same as that of the first aspect described above.

Next, as shown in FIG. 2 (c), the second main surface 12 of the transparent insulating substrate 10 is roughened by spraying the first abrasive grains (first roughening step, Step 2-c).
The specific method in the first roughening step is the same as step 1-g of the first aspect except that the silicon thin film is not formed on the first main surface 11 side.

  Next, a silicon thin film is formed on the first main surface 11 of the transparent insulating substrate 10. As the formation method of this silicon thin film formation, for example, an ion implantation separation method or the like can be adopted as in the first embodiment.

  Hereinafter, steps 2-d to 2-g shown in FIGS. 2D to 2G, that is, a series of steps for forming a silicon thin film, are steps 1-c to 1- 1 in the first embodiment. This can be performed in substantially the same manner as in the case of f. However, there is a difference that the second main surface 12 of the transparent insulating substrate 10 is subjected to a single roughening treatment through the first roughening step.

First, as shown in FIG. 2D, the silicon substrate 20 is prepared (step 2-d). Also in this case, a silicon substrate having an oxide film formed on the surface may be used as necessary. Further, at least the surface to be bonded is mirror-polished.
Next, as shown in FIG. 2E, hydrogen ions are implanted into the silicon substrate 20 from the surface (ion implantation surface 22) to form the ion implantation layer 21 (step 2-e). The conditions for ion implantation and the like are the same as in step 1-d of the first embodiment.

  Next, as shown in FIG. 2F, the first main surface 11 of the transparent insulating substrate 10 and the ion-implanted surface 22 of the silicon substrate 20 are brought into close contact and bonded together (step 2-f). The specific bonding method and the like are the same as in the case of the first aspect (step 1-e).

  Next, the silicon substrate 20 is separated by the ion-implanted layer 21, and a peeling step for thinning the silicon substrate 20 is performed to form a silicon thin film 31 as shown in FIG. 2G (step 2-g). . A specific separation method or the like can be performed in the same manner as in the case of the first embodiment (step 1-f).

Next, as shown in FIG. 2 (h), the second main surface 12 of the transparent insulating substrate 10 is subjected to a second roughening treatment by spraying second abrasive grains (second rough surface). Step, step 2-h).
A specific method in the second roughening step is the same as the step 1-h in the first aspect.

Through the steps described above, the SOI substrate 30 having the silicon thin film 31 on the first main surface 11 of the transparent insulating substrate 10 can be manufactured.
Note that the steps 2-a to 2-c and steps 2-d to 2-e, which are processes for separate substrates, may be performed in reverse order or in parallel.

  As described above, by performing steps 2-a to 2-h, an SOI substrate in which a silicon thin film is formed on a transparent insulating substrate having a rough back surface can be manufactured.

(Third embodiment)
Next, another example of the method for manufacturing an SOI substrate according to the present invention will be specifically described.
FIG. 3 is a flowchart showing another example (third aspect) of the method for manufacturing an SOI substrate of the present invention.
Here, an example will be described in which the first roughening step is performed before the formation of the silicon thin film.

  First, as shown in FIGS. 3A to 3B, a transparent insulating substrate 10 is prepared (step 3-a) as in the case of the first and second modes, and the transparent insulating property is prepared. At least one main surface (first main surface 11) of the substrate 10 is mirror-finished (step 3-b). The second main surface 12 is the same as in the first and second embodiments.

Next, as shown in FIG. 3C, the first roughening step is performed as in the second embodiment. The second main surface 12 of the transparent insulating substrate 10 is roughened by spraying the first main grains on the second main surface 12 of the transparent insulating substrate 10 (first roughening step, step 3). -C).
The specific method in the first roughening step is the same as step 1-g of the first aspect except that the silicon thin film is not formed on the first main surface 11 side.

Next, as shown in FIG. 3D, the second main surface 12 of the transparent insulating substrate 10 is subjected to a second roughening treatment by spraying the second abrasive grains (second rough surface). Step, step 2-h).
A specific method in the second roughening step is the same as the step 1-h in the first aspect.

  Next, a silicon thin film is formed on the first main surface 11 of the transparent insulating substrate 10. As the formation method of this silicon thin film formation, for example, an ion implantation separation method or the like can be adopted as in the first embodiment.

  Hereinafter, Steps 3-e to 3-h shown in FIGS. 3E to 3H, that is, a series of steps for forming a silicon thin film, are steps 1-c to 1-f in the first embodiment. In the case of step 2 and steps 2-d to 2-g in the second embodiment, it can be carried out in substantially the same manner. However, there is a difference that the second main surface 12 of the transparent insulating substrate 10 is subjected to two roughening treatments through the first roughening step and the second roughening step.

First, as shown in FIG. 3E, the silicon substrate 20 is prepared (step 3-e). Also in this case, a silicon substrate having an oxide film formed on the surface may be used as necessary. Further, at least the surface to be bonded is mirror-polished.
Next, as shown in FIG. 3F, hydrogen ions are implanted into the silicon substrate 20 from the surface (ion implantation surface 22) to form the ion implantation layer 21 (step 3-f). The conditions for ion implantation and the like are the same as in step 1-d of the first embodiment.

  Next, as shown in FIG. 3G, the first main surface 11 of the transparent insulating substrate 10 and the ion-implanted surface 22 of the silicon substrate 20 are brought into close contact and bonded together (step 3-g). The specific bonding method and the like are the same as in the case of the first aspect (step 1-e).

  Next, the silicon substrate 20 is separated by the ion-implanted layer 21, and a peeling step for thinning the silicon substrate 20 is performed to form a silicon thin film 31 as shown in FIG. 3 (h) (step 3-h). . A specific separation method or the like can be performed in the same manner as in the case of the first embodiment (step 1-f).

Through the steps described above, the SOI substrate 30 having the silicon thin film 31 on the first main surface 11 of the transparent insulating substrate 10 can be manufactured.
Note that the steps 3-a to 3-d and steps 3-e to 3-f, which are processes for separate substrates, may be performed in reverse order or in parallel.

  As described above, by performing steps 3-a to 3-h, an SOI substrate in which a silicon thin film is formed on a transparent insulating substrate having a rough back surface can be manufactured.

As described above, the first roughening step and the second roughening step in the present invention can be performed either after the formation of the silicon thin film (first aspect) or before the formation (third aspect). In addition, the first roughening step and the second roughening step can be performed separately before and after the formation of the silicon thin film (second embodiment).
At this time, there are differences in the respective advantages. For example, if the surface roughening treatment by spraying abrasive grains is performed before the silicon thin film is formed, the silicon thin film is not formed, so that the influence on the crystallinity of the silicon thin film can be prevented. On the other hand, if the roughening step by spraying abrasive grains is after the formation of the silicon thin film, the influence on the flatness of the first main surface before the formation of the silicon thin film can be prevented.
The order of these steps can be appropriately set according to other manufacturing conditions and the like.

  It is possible to spray the abrasive grains on the second main surface 12 of the transparent insulating substrate 10 in three or more stages, but it is desirable to use two stages in view of the cost and the effect obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention, but the present invention is not limited thereto.

Example 1
In the following manner, 30 transparent SOI substrates were manufactured according to the SOI substrate manufacturing method (first embodiment) by the bonding method according to the present invention as shown in FIG.

First, a synthetic quartz substrate 10 having a diameter of 150 mm that was cut out from a synthetic quartz ingot was prepared (step 1-a).
Next, both surfaces of the synthetic quartz substrate 10 were polished (step 1-b). The flatness of both main surfaces was 2 nm in terms of RMS value.

Next, a mirror-polished single crystal silicon substrate having a diameter of 150 mm was prepared as the silicon substrate 20. A silicon oxide film layer having a thickness of 100 nm was formed on the surface of the silicon substrate by thermal oxidation (step 1-c).
Next, hydrogen ions are implanted into the silicon substrate 20 through the formed silicon oxide film layer to form a microbubble layer (ion implantation layer) 21 parallel to the surface at an average ion depth (step 1-). d). The ion implantation conditions are an implantation energy of 35 keV, an implantation dose of 9 × 10 ¹⁶ / cm ² , and an implantation depth of 0.3 μm.

Next, after placing the silicon substrate 20 ion-implanted in the plasma processing apparatus and introducing nitrogen as a plasma gas, parallel plate electrodes having a high frequency of 13.56 MHz and a diameter of 300 mm under a reduced pressure of 2 Torr (270 Pa). A high-frequency plasma treatment was performed for 10 seconds on the ion-implanted surface by applying a high-frequency power of 50 W in between. In this way, the surface activation treatment was performed on the ion implantation surface 22 of the silicon substrate 20.
On the other hand, the synthetic quartz substrate 10 is placed in a plasma processing apparatus, nitrogen gas is introduced as a plasma gas between narrow electrodes, and then a high frequency is applied between the electrodes to generate plasma, thereby causing high frequency plasma processing. For 10 seconds. In this way, the surface activation treatment was also applied to the first main surface 11 of the synthetic quartz substrate 10.

After the silicon substrate 20 and the synthetic quartz substrate 10 that have been subjected to the surface activation treatment as described above are brought into close contact with each other at the room temperature with the surface that has undergone the surface activation treatment as a bonding surface, the back surfaces of both substrates are disposed in the thickness direction. (Step 1-e).
Next, in order to increase the bonding strength, the substrate on which the silicon substrate 20 and the synthetic quartz substrate 10 were bonded was heat-treated at 300 ° C. for 30 minutes.

  Next, an external impact was applied to the ion implantation layer 21 of the silicon substrate 20, and the silicon thin film 31 was formed by sequentially separating the ion implantation layer 21 (step 1-f).

  Next, a roughening treatment was performed by spraying alumina particles having a particle size of # 320 (average particle diameter of about 50 μm) onto the second main surface 12 of the synthetic quartz substrate 10 by air pressure (first roughening step, Step 1-g).

  Next, the second main surface 12 of the synthetic quartz substrate 10 is made by air pressure under the same conditions as in the first roughening step, except that the abrasive grains are alumina particles having a particle size # 2000 (average particle diameter of about 8 μm). The surface roughening process was performed by spraying on (2nd surface roughening process, process 1-h).

In this way, a transparent SOI substrate 30 having the silicon thin film 31 on the first main surface 11 of the synthetic quartz substrate 10 and roughening the second main surface 12 was manufactured. When the transparent SOI substrate 30 was subjected to a recognition experiment using a normal substrate recognition apparatus provided in the device manufacturing apparatus, all the substrates were correctly recognized.
Further, the crystallinity of the silicon thin film 31 was sufficiently good.

(Comparative Example 1)
30 transparent SOI substrates were manufactured in the same manner as in Example 1 except that the surface roughening step by spraying abrasive grains was performed once. The abrasive grains were subjected to a roughening treatment by spraying alumina particles having a particle size of # 320 (average particle diameter of about 50 μm) onto the second main surface 12 of the synthetic quartz substrate 10 by air pressure.

A transparent SOI substrate recognition experiment was performed in the same manner as in Example 1, and all the substrates were correctly recognized.
However, both the crystallinity of the silicon thin film and the dust generation of the entire transparent SOI substrate were worse than those in Example 1.

(Comparative Example 2)
30 transparent SOI substrates were produced in the same manner as in Comparative Example 1 except that alumina particles having a particle size of # 2000 (average particle diameter of about 8 μm) were used for abrasive grain spraying.

The recognition experiment of the transparent SOI substrate was conducted in the same manner as in Example 1, but 20 sheets failed to be recognized.
The crystallinity of the silicon thin film and the dust generation of the entire transparent SOI substrate were comparable to those in Example 1.

(Example 2)
According to the SOI substrate manufacturing method (second embodiment) by the bonding method according to the present invention as shown in FIG. 2, 30 transparent SOI substrates 30 were manufactured.
In addition, it differs from Example 1 only in performing a 1st surface roughening process (process 2-c) before formation of a silicon thin film (process 2-d-2-g).

(Example 3)
According to the SOI substrate manufacturing method (third aspect) by the bonding method according to the present invention as shown in FIG. 3, 30 transparent SOI substrates 30 were manufactured.
In Example 1, the first roughening step (step 3-c) and the second roughening step (step 3-d) are performed by forming a silicon thin film (steps 3-e to 3-h). The only difference is what you do before.

In both Examples 2 and 3, a recognition experiment for the transparent SOI substrate 30 was performed in the same manner as in Example 1, and all the substrates were correctly recognized.
In both Examples 2 and 3, the crystallinity of the silicon thin film 31 was sufficiently good. Further, the dust generation of the entire transparent SOI substrate 30 was at the same level as in Example 1.

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

It is a flowchart which shows an example (1st aspect) of the manufacturing method of the SOI substrate which concerns on this invention. It is a flowchart which shows another example (2nd aspect) of the manufacturing method of the SOI substrate which concerns on this invention. It is a flowchart which shows another example (3rd aspect) of the manufacturing method of the SOI substrate which concerns on this invention.

Explanation of symbols

10 ... Transparent insulating substrate, 11 ... First main surface, 12 ... Second main surface,
20 ... Silicon substrate, 21 ... Ion implantation layer, 22 ... Ion implantation surface,
30 ... Transparent SOI substrate 31 ... Silicon thin film.

Claims (13)

A silicon thin film is formed on the first main surface which is one main surface of the transparent insulating substrate, and the second main surface which is the main surface opposite to the first main surface of the transparent insulating substrate is rough. A method for manufacturing a planarized SOI substrate, comprising:
Preparing a transparent insulating substrate;
Mirror-treating at least the first main surface of the transparent insulating substrate;
Forming a silicon thin film on the first main surface of the transparent insulating substrate,
A first roughening step of roughening the second main surface of the transparent insulating substrate by spraying first abrasive grains such that the surface roughness is 0.1 μm or more in terms of Ra value; ,
When the surface roughness of the second main surface of the transparent insulating substrate is compared with the Ra value when the surface is roughened under the same conditions as the first surface roughening step as the second abrasive grain. Using abrasive grains that are smaller than in the case of the first roughening step, the second abrasive grains are sprayed onto the second main surface of the transparent insulating substrate subjected to the first roughening. And a second roughening step for roughening the substrate. A method for manufacturing an SOI substrate, comprising:   In the second roughening step, the roughening treatment is performed such that the surface roughness of the second main surface of the transparent insulating substrate is Ra value of less than 0.08 μm. The manufacturing method of the SOI substrate as described.   3. The method for manufacturing an SOI substrate according to claim 1, wherein the hardness of the second abrasive grains is lower than the hardness of the first abrasive grains. 4.   The SOI substrate according to any one of claims 1 to 3, wherein the abrasive grains are sprayed in the first and second roughening steps by applying processing energy by air pressure or water pressure. Manufacturing method.   5. The main component of the first abrasive grains and the second abrasive grains is at least one of alumina, silicon carbide, and zirconia. 5. Manufacturing method of SOI substrate.   5. The method for manufacturing an SOI substrate according to claim 1, wherein at least a main component of the second abrasive grain is a synthetic resin or a vegetable soft grain.   The SOI according to any one of claims 1 to 6, wherein the first roughening step and the second roughening step are performed at least after the silicon thin film forming step. A method for manufacturing a substrate.   At least the step of preparing the transparent insulating substrate, the first roughening step, the silicon thin film forming step, and the second roughening step are performed in this order. The method for manufacturing an SOI substrate according to claim 1.   2. The first roughening step and the second roughening step are performed after the step of preparing the transparent insulating substrate and before the silicon thin film forming step. The manufacturing method of the SOI substrate as described in any one of Claim 6 thru | or 6.   10. The mirror processing of the first main surface of the transparent insulating substrate is performed so that the surface roughness is less than 0.7 nm in terms of RMS value. 10. SOI substrate manufacturing method.   The roughening treatment of the second main surface of the transparent insulating substrate in the first and second roughening steps is finally performed at a wavelength of 250 to 800 nm in a direction perpendicular to the main surface of the transparent insulating substrate. The method for manufacturing an SOI substrate according to any one of claims 1 to 10, wherein the average transmittance of light in the region is 10% or less. Forming the silicon thin film, at least,
A silicon substrate or a silicon substrate with an oxide film formed on the surface is implanted with hydrogen ions or rare gas ions or both from the surface to form an ion implantation layer.
The silicon substrate or the surface of the silicon substrate on which the oxide film is formed and the ion-implanted surface of the silicon substrate and the first main surface of the transparent insulating substrate are adhered and bonded together,
The silicon substrate or the silicon substrate having an oxide film formed on the surface thereof is peeled and thinned with the ion implantation layer as a boundary, and a silicon thin film is formed on the first main surface of the transparent insulating substrate. The method for manufacturing an SOI substrate according to any one of claims 1 to 11.   The method for manufacturing an SOI substrate according to any one of claims 1 to 12, wherein the transparent insulating substrate is any one of a quartz substrate, a glass substrate, and a sapphire substrate.

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