JP2004099965A - Anodic chemical conversion apparatus and method, substrate manufacturing method, and substrate treatment device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably and tightly attach an electrode to a back side of a substrate in a device for holding the back side of the substrate by a holding part and bringing the electrode into contact with the back side of the substrate to treat the substrate. <P>SOLUTION: A circular recess 211a is formed in a bottom part of an anodic chemical conversion tank 211. A lower electrode 222 is disposed in the recess 211a, and a positive electrode 221 is fixed on the lower electrode 222. In other words, the positive electrode 221 is fixed to the anodic chemical conversion tank 211 via the lower electrode 222. An adsorption pad 251 is disposed around the recess 211a. An adsorption surface of the adsorption pad 251 and a contact surface of the positive electrode 221 are in the same plane. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an anodizing apparatus, an anodizing method, a substrate manufacturing method, and a substrate processing apparatus and a substrate processing method.
[0002]
[Prior art]
Porous silicon is available from A.I. Uhlir and D.M. R. Turner discovered during the study of single crystal silicon biased to a positive potential in an aqueous solution of hydrofluoric acid and electropolishing it.
[0003]
Then, utilizing the highly reactive nature of porous silicon, application of the porous silicon to an element isolation process in the manufacture of a silicon integrated circuit has been studied. A complete isolation technology (FIPOS) using a porous silicon oxide film has been studied. : Full Isolation by Porous Oxidized Silicon and the like have been developed (K. Imai, Solid State Electron 24, 159, 1981).
[0004]
Recently, a technique for applying a direct bonding technique of growing a silicon epitaxial layer on a porous silicon substrate and bonding the substrate to an amorphous substrate or a single crystal silicon substrate via an oxide film has been developed. (JP-A-5-21338).
[0005]
As another application, porous silicon has attracted attention as a photoluminescent or electroluminescent material that emits light by itself (Japanese Patent Application Laid-Open No. 6-338631).
[0006]
An anodizing apparatus for forming a porous silicon layer on a silicon substrate by anodizing is disclosed in JP-A-2000-277478. FIG. 1 is a diagram illustrating a part of the anodizing apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-277478. An anodizing apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-277478 has an anodizing tank 505 having an opening at the bottom and a suction pad 507 around the opening, and a negative electrode disposed above the substrate 500 to be processed. 501 and a plus electrode 502 pressed against the lower surface of the substrate 500.
[0007]
The plus electrode 502 is brought into contact with the substrate 500, and the minus electrode 501 is arranged above the substrate 500. When the anodizing tank 505 is filled with the electrolyte solution 506, a current is applied between the plus electrode 502 and the minus electrode 501. By flowing, the surface of the substrate 500 on the side of the minus electrode 501 is made porous by anodizing, and a porous silicon layer is formed.
[0008]
[Patent Document 1]
JP 2000-277478 A
[Problems to be solved by the invention]
In the anodizing apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-277478, the entire surface of the plus electrode 502 should be in close contact with the lower surface of the substrate 500 in order to form a uniform porous layer on the substrate. Further, it is not preferable that the electrolyte solution leaks from between the substrate 500 and the suction pad 507. Such a requirement can be satisfied by increasing the processing accuracy of the raising / lowering mechanism of the positive electrode 502.
[0009]
However, when the processing accuracy of the raising / lowering mechanism of the plus electrode 502 is poor, the entire surface of the plus electrode 502 cannot be brought into close contact with the substrate 500 as emphasized in FIG. In such an anodizing apparatus, when the pressing force of the positive electrode 502 against the substrate 500 is increased in order to bring the entire surface of the positive electrode 502 into close contact with the substrate 500, as shown in FIG. May be separated from the adsorption pad 507, and the electrolyte solution may leak from that part.
[0010]
That is, in the anodizing apparatus described above, in which the back surface of the substrate is sucked and held by the suction pad and the plus electrode is driven to contact the back surface of the substrate, the plus electrode must be positioned with high precision. For example, it is difficult to surely make the plus electrode adhere to the substrate without causing the holding failure of the substrate.
[0011]
The present invention has been made in view of the above background, and for example, in an apparatus for processing the substrate by holding the back surface of the substrate with a holding portion and contacting the back surface of the substrate with an electrode, the back surface of the substrate An object of the present invention is to ensure that the electrode is in close contact with the electrode.
[0012]
[Means for Solving the Problems]
A first aspect of the present invention relates to an anodizing apparatus, which includes a holding unit that contacts a back surface of a substrate to be processed and holds the substrate, and a negative electrode that is arranged to face the substrate. Anodization tank for filling an electrolyte solution between the substrate and the minus electrode, and a plus electrode fixed inside the anodization tank, wherein the plus electrode is in contact with the back surface of the substrate. It has a contact surface.
[0013]
According to a preferred embodiment of the present invention, for example, it is preferable that the holding section includes a suction member that sucks and holds the substrate, and the suction member has flexibility. Here, it is preferable that the suction member is configured to be deformed according to a suction operation of the substrate, and the substrate is held by the suction member in a state where the back surface thereof is in contact with the plus electrode.
[0014]
Alternatively, the holding unit includes an adsorbing member for adsorbing and holding the substrate, and a flexible member arranged to define a position of the adsorbing member, wherein the flexible member performs a suction operation of the substrate by the adsorbing member. Accordingly, it is preferable that the suction member has flexibility to allow the back surface of the substrate to come into contact with the plus electrode.
[0015]
According to a preferred embodiment of the present invention, it is preferable that the holding portion has a ring shape, and the plus electrode is disposed inside the holding portion.
[0016]
According to a preferred embodiment of the present invention, it is preferable that the apparatus further includes a drive mechanism for separating the substrate from the holding unit and moving the substrate out of the anodizing tank. Here, it is preferable that the driving mechanism has a pin for pushing the substrate in a direction from the positive electrode to the negative electrode to move the substrate out of the anodizing tank.
[0017]
According to a preferred embodiment of the present invention, the holding section preferably holds the substrate substantially horizontally.
[0018]
According to a preferred embodiment of the present invention, the apparatus preferably further includes a mechanism for supplying a cleaning liquid to the substrate to clean the substrate after the substrate has been subjected to anodizing treatment.
[0019]
According to a preferred embodiment of the present invention, the apparatus preferably further includes a mechanism for removing a liquid attached to the substrate.
[0020]
The second aspect of the present invention can be regarded as a method of anodizing a substrate using the above-described anodizing apparatus.
[0021]
A third aspect of the present invention relates to a method for manufacturing a substrate, the method comprising the steps of forming a porous layer on the surface of a substrate according to the above-described anodizing method, and having at least a semiconductor layer on the porous layer. Forming a first substrate; bonding a second substrate to a surface of the first substrate on the semiconductor layer side to form a bonded substrate; Separating into two substrates.
[0022]
A fourth aspect of the present invention relates to a substrate processing apparatus, the apparatus comprising: a holding portion that contacts a back surface of a substrate to be processed and holds the substrate; and a first electrode that is arranged to face the substrate. And an anodizing tank for filling an electrolyte solution between the substrate and the first electrode; and a second electrode fixed inside the anodizing tank, wherein the second electrode is provided on the substrate. It has a contact surface that contacts the back surface.
[0023]
The fifth aspect of the present invention can be understood as processing a substrate using the above-described substrate processing apparatus.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0025]
FIG. 4 is a diagram showing a configuration of an anodizing apparatus (substrate processing apparatus) according to a preferred embodiment of the present invention. The anodizing apparatus 200 of this embodiment can perform a series of processes including anodizing, cleaning, and drying. Therefore, according to the anodizing apparatus 200, it is not necessary to transport the substrate between the apparatuses to individually perform the anodizing treatment, the cleaning treatment, and the drying treatment. 3) There is no possibility of dropping the substrate, and 3) the size of the apparatus can be reduced.
[0026]
The anodizing apparatus 200 is configured to horizontally support and process the substrate 100 to be processed. Therefore, according to the anodizing apparatus 200, for example, when the substrate 100 is received from the transfer robot that holds and transfers the substrate horizontally, the substrate 100 is not rotated (for example, made vertical), Since a series of processes can be performed, the efficiency of operating the substrate 100 can be improved. However, the present invention is also applicable to an apparatus that processes a substrate by arranging the substrate so that its surface is along the vertical direction.
[0027]
The anodizing apparatus 200 has an anodizing tank 211 made of an insulating material. The anodizing tank 211 is supported on a support 213 by a support member 212. The anodizing tank 211 has a circular recess 211a for disposing a circular plus electrode 221 and a lower electrode (second plus electrode) 222 at the bottom thereof, and an annular suction pad is provided around the circular recess 211a. (Holder) 251 is provided. The size and shape of the suction pad 251 are determined so as to suction the peripheral portion of the back surface of the substrate 100 to be processed (here, the surface on which the porous layer is to be formed is called the front surface, and the back surface is called the back surface). I have. An annular groove 251a is formed in the suction pad 251. The groove 251a is connected to a vacuum pump (not shown) through a suction hole 251b.
[0028]
A lower electrode 222 is fixed in the depression 211a, and a plus electrode 221 is fixed on the lower electrode 222. The positive electrode 221 is configured such that the position of the contact surface that contacts the substrate 100 to be processed matches the position of the back surface of the substrate 100 held by the suction pad 251. Here, since the plus electrode 221 is fixed on the lower electrode 222 and the lower electrode 222 is fixed to the bottom of the anodizing tank 211, the position (height) of the surface (that is, the contact surface) of the plus electrode 221 is set. Always coincides with the position (height) of the back surface of the substrate 100 on which the back surface is sucked and held by the suction pad 251. Therefore, according to this embodiment, the entire surface of the contact surface of the plus electrode 221 can be securely brought into close contact with the back surface of the substrate 100, and the sealing by the suction pad 251 can be ensured.
[0029]
By bringing the entire contact surface of the positive electrode 221 into close contact with the back surface of the substrate, the thickness of the porous layer formed on each substrate is made uniform, the dispersion of the porous layer between the substrates is reduced, and the anodization is poor. Can be reduced.
[0030]
It is preferable that at least a portion of the positive electrode 221 that is in contact with the substrate 100 be made of a material having the same quality as the substrate 100, that is, a silicon material. This silicon material preferably has a low specific resistance. By configuring the positive electrode 221 with a silicon material, it is possible to prevent the silicon substrate 100 from being contaminated with the material of the positive electrode 221. Since the positive electrode 221 does not come into contact with a treatment liquid for anodization (for example, an HF-containing solution), even if the positive electrode 221 is made of a silicon material, the possibility that its surface is deteriorated is low.
[0031]
An annular groove 221a for vacuum suction is provided on the front surface of the plus electrode 221 to suck the back surface of the substrate 100. The groove 221a is connected to a vacuum pump (not shown) through the suction hole 221b.
[0032]
The lower electrode 222 disposed below the plus electrode 221 is an electrode for applying the same voltage to the entire surface of the plus electrode 221. The lower electrode 222 is preferably provided with a mechanism for attaching and detaching the plus electrode 221. This is useful for facilitating the operation of replacing the plus electrode 221 when the plus electrode 221 is contaminated or damaged.
[0033]
When performing the anodizing treatment, the minus electrode 201 is arranged above the front surface of the substrate 100 whose back surface is sucked by the suction pad 251. The negative electrode 201 is connected to an electrode driving mechanism (for example, a motor) 204 by connecting members 202 and 203, and when the negative electrode 201 is unnecessary or obstructive, the negative electrode 201 is appropriately connected to the outside of the tank by the electrode driving mechanism 204. Moved to a different place.
[0034]
In order to prevent gas (typically, hydrogen gas) generated from the surface of the silicon substrate 100 during the anodization process from accumulating below the negative electrode 201, a large number of holes 201a are formed in the negative electrode 201. Is provided. Instead of providing such a hole 201a in the negative electrode 201, it is also effective to form the negative electrode 201 in a mesh shape. Here, if gas accumulates in the lower part of the negative electrode 201, no current flows in that part, which may reduce the efficiency of the anodizing treatment or prevent uniform treatment of the substrate 100.
[0035]
The negative electrode 201 is preferably made of a material that is resistant to a treatment liquid for anodization. For example, when an HF-containing solution is used as a treatment liquid for anodization, the negative electrode 201 is preferably made of HF-resistant material such as platinum.
[0036]
When the substrate 100 is subjected to anodizing treatment, a positive potential is applied to the lower electrode 222 (and the positive electrode 221 electrically connected to the lower electrode 222), and a negative potential is applied to the negative electrode 201. A current flows from the substrate 221 to the negative electrode 201 via the substrate 100 and an electrolyte solution (for example, an HF-containing solution) 280, and the surface (negative electrode side) of the silicon substrate 100 is made porous.
[0037]
The operation of the substrate 100 inside and above the anodizing tank 211 is performed by the substrate operation mechanism 240. The substrate operation mechanism 240 has a plurality of elevating pins 243 that support the substrate to be processed and the processed substrate from the back surface. The lifting pin 243 contacts the back surface of the substrate 100 through a through hole 211b formed in a circular groove 211a at the bottom of the anodizing tank 211. Since the through-hole 211b is formed inside the annular adsorption pad 251, the electrolyte solution and the cleaning liquid do not leak from the bottom of the anodizing tank 211 during the anodizing treatment and the cleaning treatment.
[0038]
The lifting pin 243 is connected by a connecting member 244, and further connected to a piston rod 242 of the lifting mechanism 241.
[0039]
The anodizing tank 211 is provided with a supply port 261 for the electrolyte solution and a discharge port 262 for the electrolyte solution and the cleaning solution.
[0040]
Outside the anodizing tank 211, a robot 270 that provides a substrate to be processed to the anodizing tank 211 and transfers the processed substrate from the anodizing tank 211 to another apparatus or a substrate container (for example, a wafer carrier). Is arranged. The robot 270 is arranged, for example, on the support base 270. The robot 270 preferably has a robot hand 271 configured to suck and hold the back surface of the substrate. By employing such a robot hand 271, the surface of the substrate to be processed (the surface on which the porous layer is to be formed) is contaminated, or the porous layer of the substrate on which the porous layer is formed is contaminated or damaged. Can be prevented.
[0041]
A cleaning / drying mechanism 300 for cleaning and drying the substrate after the anodizing treatment is disposed above the anodizing tank 211. The cleaning / drying mechanism 300 is driven by a driving mechanism including a lifting mechanism and the like. That is, when the negative electrode 201 is rotated by the electrode driving mechanism 204 or when the robot 270 operates the substrate above the anodizing tank 211, the cleaning / drying mechanism 300 is, for example, It is moved to a predetermined upper evacuation position.
[0042]
Next, an operation of the anodizing apparatus according to the preferred embodiment of the present invention and a processing procedure thereby will be described with reference to FIGS. Here, FIG. 4 is a diagram showing a state of the anodizing treatment, FIG. 5 is a diagram showing a state of the transfer of the substrate between the robot 270 and the elevating pins 243, and FIG. FIG. 7 is a diagram illustrating a state of a cleaning process, and FIG. 7 is a diagram illustrating a state of a drying process (removal of a cleaning liquid) of a substrate after the cleaning process.
[0043]
First, as shown in FIG. 5, the elevating mechanism 241 raises the elevating pins 243 to a predetermined height, while the robot 270 sucks and holds a part of the back surface of the substrate 100 by the robot hand 271 to move the substrate 100 to the elevating pins 243. Place on top. Next, the robot 270 evacuates the robot hand 271. Next, the elevating mechanism 241 lowers the elevating pins 243 until the back surface of the substrate 10 contacts the suction surface of the suction pad 251 and the contact surface of the plus electrode 211 at the bottom of the anodizing bath 211.
[0044]
Next, the pressure in the annular groove 251 a formed on the surface of the suction pad 251 is reduced by a vacuum pump (not shown) through the suction hole 251 b, so that the substrate 100 is suctioned to the suction surface of the suction pad 251. As a result, the bottom of the anodizing tank 211 is sealed, and a state in which the electrolyte solution 280 for anodizing can be filled therein is obtained. Further, the pressure in the annular groove 221a formed on the surface of the plus electrode 221 is reduced by a vacuum pump (not shown) through the suction hole 221b, so that the substrate 100 is adsorbed on the surface of the plus electrode 221. In this state, the entire contact surface of the plus electrode 221 is in close contact with the back surface of the substrate 100.
[0045]
Next, as shown in FIG. 4, an anodizing electrolyte solution (typically, an HF-containing solution) 280 is supplied into the anodizing tank 211 through the supply port 261 to fill and discharge the inside of the tank with the electrolyte solution 280. While discharging the electrolyte solution 280 through the port 262, the electrolyte solution 280 is circulated by a circulation system (not shown).
[0046]
In a state where the electrolyte solution 280 is circulated, a voltage is applied between the minus electrode 201 and the plus electrode 221 by a power supply device (not shown), and the silicon substrate 100 is anodized. By this processing, the surface of the silicon substrate 100 is made porous, and a porous silicon layer is formed.
[0047]
Next, the application of the voltage and the supply of the electrolyte solution 280 are stopped, and all the electrolyte solutions 280 in the anodizing tank 211 are discharged through the discharge port 262.
[0048]
Next, a cleaning liquid (for example, pure water) is supplied to the negative electrode 201 from the nozzle of the cleaning / drying mechanism 300 to wash the negative electrode 201, and then the negative electrode 201 is removed from the anodizing tank 211 by the electrode driving mechanism 204. Move to a suitable place. When cleaning the negative electrode 201, the cleaning / drying mechanism 300 may be moved to a position near the negative electrode 201.
[0049]
Next, as shown in FIG. 6, the cleaning / drying mechanism 300 is lowered to a predetermined position by a driving mechanism (not shown), and a cleaning liquid (for example, pure water) is supplied from the nozzle of the cleaning / drying mechanism 300 onto the substrate 100. Thus, the substrate 100 is cleaned. The cleaning liquid used for cleaning is discharged through the discharge port 262.
[0050]
Next, as shown in FIG. 7, a drying gas (for example, nitrogen gas) is supplied onto the substrate 100 from a nozzle of the cleaning / drying mechanism 300, and thereby the cleaning liquid attached to the substrate 100 is removed. Thus, a series of processes including the anodizing process, the cleaning process, and the drying process is completed.
[0051]
In this embodiment, the cleaning mechanism and the drying mechanism are integrated, but they may be provided separately.
[0052]
Next, the processed substrate 100 is taken out from the anodizing tank 211. Specifically, after releasing the suction of the substrate 100 by the suction pad 251 and the plus electrode 221, as shown in FIG. 5, the lifting mechanism 241 raises the lifting pin 243 to a predetermined height, while the robot 270 moves the robot hand. The 271 is extended to the receiving position of the substrate 100, and a part of the back surface of the substrate 100 is suction-held by the robot hand 271 and then transferred to another apparatus or a substrate container (for example, a wafer carrier).
[0053]
By repeating the above processing for a plurality of substrates, a plurality of substrates can be processed. Here, the anodizing treatment, the cleaning treatment, and the drying treatment are performed by one anodizing apparatus 200, but all or a part of these processings may be performed by another apparatus. Alternatively, in addition to the anodizing treatment, the cleaning treatment, and the drying treatment, another treatment (for example, a cleaning treatment before the anodizing treatment) may be performed by one anodizing apparatus 200.
[0054]
As described above, by fixing the plus electrode 221 to the inside of the anodizing tank 211 via the lower electrode 222, the position (height) of the surface (that is, the contact surface) of the plus electrode 221 can be adjusted by the suction pad 251. Is always kept constant so as to match the position (height) of the back surface of the substrate 100 held by suction. Therefore, according to this embodiment, the entire surface of the contact surface of the plus electrode 221 can be securely brought into close contact with the back surface of the substrate 100, and the sealing by the suction pad 251 can be ensured.
[0055]
Next, an improved example of the suction pad (holding portion or suction member) 251 will be described.
[0056]
FIG. 8 is a diagram showing a first improved example of the suction pad (holding portion or suction member). Note that, in FIG. 8, related parts are extracted and described, and other components are omitted. In the configuration example shown in FIG. 8, a flexible annular suction pad 301 is employed instead of the suction pad 251.
[0057]
An annular groove 301a for vacuum-sucking the substrate is formed on the surface of the suction pad 301. The inside of the groove 301a is depressurized by a vacuum pump (not shown) through the suction hole 251b, so that the substrate is moved to the suction pad 301. Is adsorbed on the adsorption surface.
[0058]
By providing the suction pad 301 with flexibility, when the back surface of the substrate 100 is sucked by the suction pad 301, the back surface of the substrate 100 is brought into contact with the surface (contact surface) of the plus electrode 211 as shown in FIG. Lower to the position where it adheres. That is, according to the configuration example shown in FIG. 8, the accuracy required for processing or attaching the suction pad 301 and the plus electrode 211 is relaxed as compared with the configuration example shown in FIG.
[0059]
Also in this configuration example, since the plus electrode 211 is fixed to the anodizing bath 211 via the lower electrode 222, the position of the contact surface (the surface that contacts the substrate 100) of the plus electrode 211 can be determined with high accuracy. It can be matched to the design position.
[0060]
FIG. 10 is a diagram showing a second improved example of the suction pad (holding portion or suction member). Note that in FIG. 9, relevant parts are extracted and described, and other components are omitted. In the configuration example shown in FIG. 9, instead of the suction pad 251, a suction fit into the hole formed in the bottom of the anodizing tank 211 so as to have a degree of freedom in a vertical direction (a direction perpendicular to the substrate surface). A pad 401 is employed. Below the suction pad 401, a flexible member 402 for regulating the position of the suction pad 401 is arranged.
[0061]
An annular groove 401a for vacuum-sucking the substrate is formed on the surface of the suction pad 401. The inside of the groove 401a is depressurized by a vacuum pump (not shown) through a suction hole 251b, so that the substrate can be removed from the suction pad 401. Is adsorbed on the adsorption surface. Here, the inside of the space 403 is also depressurized with the depressurization in the groove 401a, so that the suction pad 401 moves downward while compressing the flexible member 402 while adsorbing the substrate. Accordingly, with the suction by the suction pad 401, the substrate is lowered to a position where the back surface is in close contact with the surface (contact surface) of the plus electrode 211. That is, according to the configuration example shown in FIG. 10, the precision required for processing or attaching the suction pad 401 and the plus electrode 211 is relaxed as compared with the configuration example shown in FIG.
[0062]
Also in this configuration example, since the plus electrode 211 is fixed to the anodizing bath 211 via the lower electrode 222, the position of the contact surface (the surface that contacts the substrate 100) of the plus electrode 211 can be determined with high accuracy. It can be matched to the design position.
[0063]
The invention applied to the anodizing apparatus described above can also be applied to a processing apparatus for performing processing other than anodizing on a substrate. That is, the present invention is a substrate processing apparatus for processing a substrate between a first electrode and a second electrode, wherein the back surface of the substrate is held by a holding portion, and the first electrode is arranged to face the surface of the substrate. The present invention can be applied to an apparatus in which a second electrode is brought into contact with a back surface of the substrate and an electrolyte solution is filled between the first electrode and the substrate to process the substrate. As an example of the treatment other than the anodization by such an apparatus, for example, a plating treatment can be mentioned.
[0064]
[Application example of processing device]
Hereinafter, as an example in which the above-described anodizing apparatus is applied to a method for manufacturing a semiconductor substrate, a method for manufacturing a substrate such as an SOI substrate will be exemplarily described.
[0065]
FIG. 11 is a diagram illustrating a method for manufacturing a substrate according to a preferred embodiment of the present invention.
[0066]
First, in the step shown in FIG. 11A, a single-crystal Si substrate 11 for forming a first substrate (seedwafer) 10 is prepared, and the main surface thereof is formed using the anodizing apparatus 200 described above. Next, a porous Si layer 12 as a separation layer is formed. The porous Si layer 12 can be formed, for example, by subjecting the single crystal Si substrate 11 to an anodizing treatment (anodic treatment) in an electrolytic solution (chemical conversion solution).
[0067]
Here, as the electrolytic solution, for example, a solution containing hydrogen fluoride, a solution containing hydrogen fluoride and ethanol, a solution containing hydrogen fluoride and isopropyl alcohol, and the like are preferable. More specifically, as the electrolytic solution, for example, a mixed solution obtained by mixing an aqueous HF solution (HF concentration = 49 wt%) and ethanol at a volume ratio of 2: 1 is preferable.
[0068]
Further, the porous Si layer 12 may have a multilayer structure including two or more layers having different porosity. Here, the porous Si layer 12 having a multilayer structure has a first porous Si layer having a first porosity on the surface side, and a second porous Si layer having a second porosity larger than the first porosity below the first porous Si layer. It is preferable to include two porous Si layers. By adopting such a multilayer structure, in the subsequent step of forming the non-porous layer 13, the non-porous layer 13 with few defects can be formed on the first porous Si layer. In a later separation step, the bonded substrate (bonded substrate) can be separated at a desired position. Here, the first porosity is preferably 10% to 30%, more preferably 15% to 25%. Further, the second porosity is preferably 35% to 70%, more preferably 40% to 60%.
[0069]
When the above mixed solution (hydrofluoric acid with 49 wt% HF: ethanol = 2: 1) is used as the electrolyte solution, for example, the current density is 8 mA / cm. ² The first layer (surface side) is generated under the conditions of a treatment time of 5 to 11 min, and then a current density of 23 to 33 mA / cm. ² It is preferable to form the second layer (inside) under the conditions of a processing time of 80 sec to 2 min.
[0070]
As described above, by using the above-described anodizing apparatus 200 to form the porous layer 12, it is possible to reduce the contamination of the first substrate 10 by the metal eluted from the anode arranged in the processing tank. it can.
[0071]
Next, it is preferable to perform at least one of the following steps (1) to (4). Here, (1) and (2) are preferably performed in order, (1), (2) and (3) are performed in order, or (1), (2) and (4) are performed in order. More preferably, (1), (2), (3), and (4) are most sequentially performed.
[0072]
(1) Step of forming protective film on pore wall of porous Si layer (pre-oxidation step)
In this step, a protective film such as an oxide film or a nitride film is formed on the hole walls of the porous Si layer 12, thereby preventing the holes from becoming coarse due to the subsequent heat treatment. The protective film can be formed, for example, by performing a heat treatment (for example, preferably at 200 ° C. to 700 ° C., more preferably at 300 ° C. to 500 ° C.) in an oxygen atmosphere. Thereafter, it is preferable to remove an oxide film and the like formed on the surface of the porous Si layer 12. This can be performed, for example, by exposing the surface of the porous Si layer 12 to a solution containing hydrogen fluoride.
[0073]
(2) Hydrogen baking step (pre-baking step)
In this step, heat treatment is performed on the first substrate 1 on which the porous Si layer 12 has been formed at 800 ° C. to 1200 ° C. in a reducing atmosphere containing hydrogen. By this heat treatment, pores on the surface of the porous Si layer 12 can be sealed to some extent, and if a natural oxide film exists on the surface of the porous Si layer 12, it can be removed.
[0074]
(3) Trace material supply process (pre-injection process)
When the non-porous layer 13 is grown on the porous Si layer 12, the supply of the raw material of the non-porous layer 13 is made to be very small in the initial stage of the growth, and the non-porous film 13 is grown at a low speed. Is preferred. By such a growth method, migration of atoms on the surface of the porous Si layer 12 is promoted, and pores on the surface of the porous Si layer 12 can be sealed. Specifically, the supply of the raw material is controlled so that the growth rate is 20 nm / min or less, preferably 10 nm / min or less, and more preferably 2 nm / min or less.
[0075]
(4) High temperature baking process (intermediate baking process)
By performing the heat treatment in a reducing atmosphere containing hydrogen at a temperature higher than the processing temperature in the hydrogen baking step and / or the trace material supply step, further sealing and planarization of the porous Si layer 12 can be performed. Can be realized.
[0076]
Next, in a first stage of the process shown in FIG. 11B, a first non-porous layer 13 is formed on the porous Si layer 12. Examples of the first non-porous layer 13 include a single-crystal Si layer, a polycrystalline Si layer, an Si layer such as an amorphous Si layer, a Ge layer, a SiGe layer, a SiC layer, a C layer, a GaAs layer, a GaN layer, and an AlGaAs. A layer, an InGaAs layer, an InP layer, an InAs layer, and the like are preferable.
[0077]
Next, in a second stage of the process shown in FIG. 11B, SiO 2 is formed on the first non-porous layer 13 as a second non-porous layer. ₂ A layer (insulating layer) 14 is formed. Thereby, the first substrate 10 is obtained. SiO ₂ The layer 14 is, for example, O ₂ / H ₂ It can be generated under the conditions of an atmosphere, 1100 ° C., and 10 to 33 min.
[0078]
Next, in a step shown in FIG. 11C, a second substrate (handle wafer) 20 is prepared, and the first substrate 10 and the second substrate 20 are separated from each other. A bonded substrate (bonded substrate) 30 is produced by closely contacting at room temperature so as to face each other.
[0079]
Note that the insulating layer 14 may be formed on the single-crystal Si layer 13 side as described above, may be formed on the second substrate 20, or may be formed on both. When the first substrate and the second substrate are brought into close contact with each other, the state shown in FIG. However, as described above, by forming the insulating layer 14 on the side of the first non-porous layer (for example, a single-crystal Si layer) 13 serving as an active layer, the first substrate 10 and the second substrate 20 Can be kept away from the active layer, so that a higher quality semiconductor substrate such as an SOI substrate can be obtained.
[0080]
After the substrates 10 and 20 are completely adhered to each other, it is preferable to perform a process for strengthening the bonding between them. As an example of this processing, for example, 1) N ₂ Heat treatment was performed in the atmosphere at 1100 ° C. for 10 minutes. ₂ / H ₂ The heat treatment (oxidation treatment) in an atmosphere at 1100 ° C. for 50 to 100 minutes is preferably performed. In addition to or instead of this treatment, an anodic bonding treatment and / or a pressure treatment may be performed.
[0081]
As the second substrate 20, a Si substrate, and a SiO substrate ₂ A substrate on which a layer is formed, a light-transmitting substrate such as quartz, sapphire, or the like is preferable. However, the second substrate 20 need only have a sufficiently flat surface to be bonded (bonded), and may be another type of substrate.
[0082]
Next, in a step shown in FIG. 11D, the bonded substrate (bonded substrate) 30 is separated at a portion of the porous layer 12 having weak mechanical strength. As the separation method, various methods can be adopted. For example, a method using a fluid, such as a method of driving a fluid into the porous layer 12 or a method of applying a static pressure to the porous layer 12 with the fluid, is used. preferable.
[0083]
By this separation step, the transfer layer (the non-porous layer 13 and the insulating layer 14) of the first substrate 10 is transferred onto the second substrate 20. When only the non-porous layer 13 is formed on the porous layer 12 of the first substrate 10, the transfer layer is only the non-porous layer 13.
[0084]
In the step shown in FIG. 11E, the porous layer 12 ″ on the second substrate 20 after the separation is selectively removed by etching or the like. Thus, the non-porous layer 13 is provided on the insulating layer 14. For example, when the non-porous layer 13 is a semiconductor layer, such a semiconductor layer is called an SOI layer (Semiconductor On Insulator), and a substrate having such an SOI layer is an SOI layer. Called the substrate.
[0085]
Further, the porous layer 12 'on the single-crystal Si substrate 11 of the first substrate 10' after the separation is selectively removed by etching or the like. The single-crystal Si substrate 11 obtained in this manner can be used again as a substrate for forming the first substrate 10 or as a second substrate 20.
[0086]
[Application example of semiconductor substrate]
Next, an example of a method of manufacturing a semiconductor substrate manufactured by the above manufacturing method will be described.
[0087]
FIG. 12 is a diagram illustrating a method of manufacturing a semiconductor device using a semiconductor substrate that can be manufactured by applying the method of manufacturing a substrate according to the preferred embodiment of the present invention.
[0088]
First, an SOI substrate having a semiconductor layer as the non-porous layer 13 and an insulating layer as the non-porous layer 14 is manufactured by applying the above-described substrate manufacturing method. Then, the non-porous semiconductor layer (SOI layer) 13 on the buried insulating film 14 is patterned in the shape of an island, or an oxidation method called LOCOS or the like is used to form the active region 13 ′ where the transistor is to be formed and the element isolation region 54. Is formed (see FIG. 12A).
[0089]
Next, a gate insulating film 56 is formed on the surface of the SOI layer (see FIG. 12A). As a material of the gate insulating film 56, for example, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, hafnium oxide, titanium oxide, scandium oxide, yttrium oxide, gadolinium oxide, lanthanum oxide, zirconium oxide, and the like And the like are preferred. The gate oxide film 56 can be formed, for example, by oxidizing the surface of the SOI layer or depositing a substance on the surface of the SOI layer by a CVD method or a PVD method.
[0090]
Next, a gate electrode 55 is formed on the gate insulating film 56 (see FIG. 12A). The gate electrode 55 is made of, for example, polycrystalline silicon doped with a P-type or N-type impurity, a metal such as tungsten, molybdenum, titanium, tantalum, aluminum, or copper, or an alloy containing at least one of these, molybdenum silicide, Metal silicides such as tungsten silicide and cobalt silicide, and metal nitrides such as titanium nitride, tungsten nitride and tantalum nitride can be used. The gate insulating film 56 may be formed by stacking a plurality of layers made of different materials, such as a polycide gate. The gate electrode 55 may be formed, for example, by a method called salicide (self-aligned silicide), may be formed by a method called a damascene gate process, or may be formed by another method. Through the above steps, the structure shown in FIG. 12A is obtained.
[0091]
Next, an N-type impurity such as phosphorus, arsenic, or antimony or a P-type impurity such as boron is introduced into the active region 13 'to form a source / drain region 58 having a relatively low concentration (see FIG. 12B). ). The impurities can be introduced by, for example, ion implantation and heat treatment.
[0092]
Next, after an insulating film is formed so as to cover the gate electrode 55, the insulating film is etched back to form a sidewall 59 on the side of the gate electrode 59.
[0093]
Next, impurities of the same conductivity type as described above are again introduced into the active region 13 'to form the source and drain regions 57 having a relatively high concentration. Through the above steps, the structure shown in FIG. 12B is obtained.
[0094]
Next, a metal silicide layer 60 is formed on the upper surface of the gate electrode 55 and the upper surfaces of the source and drain regions 57. As a material of the metal silicide layer 60, for example, nickel silicide, titanium silicide, cobalt silicide, molybdenum silicide, tungsten silicide, or the like is preferable. These silicides are formed by depositing a metal so as to cover the upper surface of the gate electrode 55 and the upper surfaces of the source and drain regions 57, and thereafter, by subjecting the metal to a reaction with silicon under the heat treatment, Of the metal by removing an unreacted portion with an etchant such as sulfuric acid. Here, if necessary, the surface of the silicide layer may be nitrided. Through the above steps, the structure shown in FIG. 12C is obtained.
[0095]
Next, an insulating film 61 is formed so as to cover the upper surface of the silicided gate electrode and the upper surfaces of the source and drain regions (see FIG. 12D). As a material of the insulating film 61, silicon oxide containing phosphorus and / or boron is preferably used.
[0096]
Next, as necessary, a contact hole is formed in the insulating film 61 by a CMP method. KrF excimer laser, ArF excimer laser, F ₂ Applying photolithography technology using an excimer laser, electron beam, X-ray, etc., to form a rectangular contact hole with a side of less than 0.25 microns or a circular contact hole with a diameter of less than 0.25 microns Can be.
[0097]
Next, a conductor is filled in the contact hole. As a method for filling the conductor, a film of a refractory metal or a nitride thereof serving as the barrier metal 62 is formed on the inner wall of the contact hole, and then a conductor 63 such as a tungsten alloy, aluminum, an aluminum alloy, copper, or a copper alloy is formed. , CVD, PVD, plating and the like are preferable. Here, the conductor deposited higher than the upper surface of the insulating film 61 may be removed by an etch-back method or a CMP method. Prior to filling the conductor, the surface of the silicide layer in the source and drain regions exposed at the bottom of the contact hole may be nitrided. Through the above steps, a transistor such as an FET can be formed in the SOI layer, and a semiconductor device having a transistor having a structure illustrated in FIG.
[0098]
Here, when the thickness and the impurity concentration of the active layer (SOI layer) 10 ′ are determined so that a depletion layer spreading below the gate insulating film reaches the upper surface of the buried insulating film 14 by applying a voltage to the gate electrode, the gate electrode is formed. The transistor operates as a fully depleted transistor. When the thickness and impurity concentration of the active layer (SOI layer) 10 'are determined so that the depletion layer does not reach the upper surface of the buried oxide film 14, the formed transistor operates as a partially depleted transistor.
[0099]
【The invention's effect】
According to the present invention, in a device for processing the substrate by holding the back surface of the substrate with the holding portion and bringing the electrode into contact with the back surface of the substrate, for example, the electrode is securely adhered to the back surface of the substrate be able to.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a partly extracted and described anodizing apparatus disclosed in Japanese Patent Application Laid-Open No. 2000-277478.
FIG. 2 is a view for explaining a problem in the case where the machining accuracy of a positive electrode lifting / lowering mechanism is low.
FIG. 3 is a drawing for explaining a problem in the case where the processing accuracy of a positive electrode lifting / lowering mechanism is low.
FIG. 4 is a diagram showing a configuration of an anodizing apparatus and a state of an anodizing treatment according to a preferred embodiment of the present invention.
FIG. 5 is a diagram showing how a substrate is transferred between a robot and a lifting pin.
FIG. 6 is a diagram illustrating a state of a cleaning process of the substrate after the polar chemical conversion process.
FIG. 7 is a diagram illustrating a state of a drying process (removal of a cleaning liquid) of a substrate after a cleaning process.
FIG. 8 is a diagram showing a first improved example of a suction pad (holding unit).
FIG. 9 is an enlarged view of a part of FIG. 9;
FIG. 10 is a view showing a second modification of the suction pad (holding unit).
FIG. 11 is a diagram illustrating a method of manufacturing a substrate according to a preferred embodiment of the present invention.
FIG. 12 is a diagram illustrating a method of manufacturing a semiconductor device according to a preferred embodiment of the present invention.
[Explanation of symbols]
500 substrates
501 Negative electrode
502 plus electrode
505 Anodizing chemical tank
506 Electrolyte solution
507 Suction pad
100 substrates
201 Negative electrode
202, 203 connecting member
204 electrode drive mechanism
211 Anodizing chemical tank
211a hollow
211b hole
212 support member
213 Support
221 plus electrode
221a groove
221b suction hole
222 lower electrode
222a groove
222b suction hole
240 Substrate operation mechanism
241 lifting mechanism
242 piston rod
243 lifting pin
251 suction pad
251a groove
251b Suction hole
261 supply port
262 discharge port
270 robot
271 Robot Hand
280 electrolyte solution
Positive electrode structure
300 washing / drying mechanism
301 Suction pad
301 groove
401 Suction pad
401a groove
402 Flexible member
403 Space
10 First substrate
11 Single crystal Si substrate
12 Porous Si layer
13 Single crystal Si layer
14 Insulating layer
20 Second substrate
30 Laminated substrate (bonded substrate)

Claims (14)

An anodizing apparatus,
A holding unit that contacts the back surface of the substrate to be processed and holds the substrate,
A negative electrode arranged to face the substrate;
Anodizing tank for filling an electrolyte solution between the substrate and the negative electrode,
A positive electrode fixed inside the anodization tank,
Wherein the positive electrode has a contact surface that contacts the back surface of the substrate. 2. The anodizing apparatus according to claim 1, wherein the holding unit includes a suction member that suctions and holds the substrate, and the suction member has flexibility. 3. The said adsorption | suction member is comprised so that it may deform | transform with the adsorption | suction operation | movement of a board | substrate, The said board | substrate is hold | maintained by the said adsorption | suction member in the state which contacted the said plus electrode with the back surface. 3. The anodizing apparatus according to 2. The holding unit,
An adsorption member for adsorbing and holding the substrate;
A flexible member arranged to define the position of the suction member,
Wherein the flexible member has a flexibility that allows the back surface of the substrate to contact the plus electrode by moving the suction member in accordance with the suction operation of the substrate by the suction member. The anodizing apparatus according to claim 1. The anodizing apparatus according to any one of claims 1 to 4, wherein the holding unit has a ring shape, and the positive electrode is disposed inside the holding unit. The anodizing apparatus according to any one of claims 1 to 5, further comprising: a driving mechanism that separates the substrate from the holding unit and moves the substrate out of the anodizing tank. The anodizing apparatus according to claim 6, wherein the driving mechanism has a pin for pushing the substrate in a direction from the positive electrode to the negative electrode to move the substrate out of the anodizing tank. The anodizing apparatus according to any one of claims 1 to 7, wherein the holding unit holds the substrate substantially horizontally. The anodizing method according to any one of claims 1 to 8, further comprising a mechanism for supplying a cleaning liquid to the substrate after the substrate has been subjected to anodizing treatment to clean the substrate. apparatus. The anodizing apparatus according to any one of claims 1 to 9, further comprising a mechanism for removing a liquid attached to the substrate. An anodizing method, comprising anodizing a substrate using the anodizing apparatus according to any one of claims 1 to 10. A substrate manufacturing method,
Forming a porous layer on the surface of the substrate according to the anodizing method according to claim 11;
Forming a first substrate having at least a semiconductor layer on the porous layer;
Forming a bonded substrate by bonding a second substrate to a surface of the first substrate on the semiconductor layer side;
Separating the bonded substrate into two substrates at the portion of the porous layer;
A method of manufacturing a substrate, comprising: A substrate processing apparatus,
A holding unit that contacts the back surface of the substrate to be processed and holds the substrate,
A first electrode disposed to face the substrate;
An anodizing tank for filling an electrolyte solution between the substrate and the first electrode;
A second electrode fixed inside the anodizing tank,
Wherein the second electrode has a contact surface that contacts a back surface of the substrate. A substrate processing method comprising processing a substrate using the substrate processing apparatus according to claim 13.

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