JP3028082B2 - Porous gettering substrate, method of manufacturing the same, and method of storing silicon substrate using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gettering material for preventing surface contamination of a silicon single crystal substrate caused by molecules of gaseous contaminants in a process of manufacturing a semiconductor device, and a method for manufacturing such a gettering material. About the method.

Further, according to the present invention, as a measure for preventing a reduction in device manufacturing yield in a device manufacturing process, a gas contaminant during the manufacturing process is obtained by using a gettering substrate having a specific form among such gettering materials. The present invention relates to a method of storing a silicon substrate, a wafer, and the like while removing the same.

[0002]

2. Description of the Related Art In devices such as dynamic memories, miniaturization of single elements has progressed with an increase in storage capacity, and single elements have been increasingly integrated on a wafer as an integrated circuit. In particular, a MOS field effect transistor (MO) that performs the switching function of a single element
In SFETs), the thickness in the thickness direction is reduced according to the scaling law in accordance with the miniaturization of the laminated film in the vertical and horizontal directions, and the gate oxide film formed by thermally oxidizing the silicon surface has an extremely thin film equivalent to several tens of angstroms. Oxide insulating films have been used.

[0003] Since the density of defects generated in the gate oxide film greatly affects the production yield of devices, it is necessary to suppress the occurrence of defects. It is well known that ensuring the cleanliness of the silicon substrate surface prior to thermal oxidation is important for suppressing the occurrence of defects when forming such an extremely thin gate oxide film.

As a factor affecting the generation of defects in a gate oxide film, the prevention of heavy metal nuclei during the device manufacturing process and the prevention or elimination of nuclei of microdefects generated in the old days have been discussed in a clean room. Countermeasures were studied from the viewpoint of equipment technology and gettering technology for pollutant removal.

Conventionally, two types of gettering of heavy metal contamination and minute defects have been put to practical use. One is to form a porous silicon layer or a polycrystalline silicon layer on the back surface of a single crystal silicon substrate used for device manufacturing as shown in FIG. A so-called intrinsic gettering method of the type in which a crystal defect is generated inside the substrate and a heavy metal or the like is diffused into the crystal defect in a solid phase and absorbed.
48128).

Another type uses damage formed by mechanical scratching on the back surface of a silicon substrate by a sand blast method, a diamond blade, or the like, or, as shown in FIG. 6A, the main surface of a single crystal silicon substrate. A so-called extrinsic method in which a laser beam such as an argon laser is applied to a surface portion other than the device to locally form damage (porosity), and a heavy metal or the like is absorbed into the damage during heat treatment of doping impurities. -A gettering method (for example, Japanese Patent Application Laid-Open No. 1-196836).

However, recently, apart from such a problem of contamination by heavy metals and the like, the adsorption of contaminant molecules from the gas phase in a clean room to the surface of a silicon substrate has become a problem as one factor for lowering the production yield of devices. For example, the 43rd
At the Annual Meeting of the Japan Society of Applied Physics, Keihide Wakayama et al. Reported that cyclic dimethylsiloxane generated from the sealing material of building materials for clean rooms was adsorbed on the silicon substrate surface (lecture number 27P-F-11, proceedings of the lecture, 2nd volume, p. 702, 1996). Also by Koichiro Saga et al., BHT contained in plastic of silicon box storage plastic box
(Antioxidants) and additives such as DBP (plasticizer) vaporize and adsorb to the silicon substrate surface (see 27P-F-
12, 2nd volume, p. 702, 1996).

There are various problems and it is difficult to apply the conventional gettering technique as it is to the adsorption of the contaminant from the gas phase to the silicon substrate. First, in the intrinsic gettering method, gettering
Since a crystal defect inside the silicon substrate is used as a sink, there is no effect on gettering of contaminants adsorbed on the crystal surface. This is because the rate at which light molecules of gaseous contaminants adsorbed on the crystal surface diffuse into the crystal is extremely slow, making it difficult to reach crystal defects.

On the other hand, in the extrinsic gettering method, a damage formed on a surface portion or a back surface of a silicon substrate other than a device formation region is used as a gettering sink, but the efficiency of adsorption of gas molecules is low. .
This is because, in many cases, the substrate surface that plays the role of the gettering sink is not exposed to the gas phase due to coating or the like, and even if it is exposed, the ratio between the device manufacturing area and the gettering sink area is several times at most. Because it is only.

Further, generally, in an impurity semiconductor,
Since the adsorption of gas molecules having an electron affinity depends on the concentration of the dopant that generates carriers in the silicon substrate, the silicon substrate surface may exhibit selectivity for the adsorption of gas molecules. As a result, adsorption to the back surface of the substrate that is to be a gettering sink does not occur, and adsorption to the device forming region on the surface having the conductivity type opposite to that of the back surface may occur. Recently, since complementary MOS transistors are frequently used as devices, such selective adsorption is an important problem in a manufacturing process.

When a substance different from silicon, such as activated carbon or a metal catalyst, which is usually used as an adsorbent for trace gas components, is used as a gettering material, the substance itself becomes a solid contaminant to the silicon substrate. Is concerned that
Not practical.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a gettering material which can efficiently getter gas contaminants generated from a clean room building material, a plastic member of a wafer storage container, and the like by using a material of the same quality as a silicon substrate. It is an object of the present invention to provide a practical method for producing such a gettering material.

[0013] The present invention also provides a storage method for improving the manufacturing yield in a device manufacturing process by suppressing gas-phase contamination during storage of a silicon substrate using a specific form of the gettering material. It is an issue.

[0014]

According to the present invention, unlike the prior art in which contaminants in a silicon substrate are kept away from a semiconductor element formation region, the ability to adsorb gas molecules existing outside the silicon substrate is increased. A novel gettering substrate, a method for manufacturing the same, and a method for storing a silicon substrate using the same are provided.

That is, the present invention has a porous silicon layer and a pn junction formed by introducing a dopant into the porous silicon layer, and at least one surface of the porous silicon layer having the pn junction has Preferably, the invention is a gettering substrate which is cleaned and activated by heat treatment at about 1100 ° C. in a reducing gas or a halogen gas, or a gas obtained by diluting either of them with an inert gas. In the present invention, the inert gas is a rare gas, a nitrogen gas, or a mixed gas composed of two or more of these.

In the present invention, by using a silicon substrate of the same type as the silicon substrate for device manufacturing as a material of the gettering material, it is possible to basically prevent solid phase contaminants such as heavy metals from being introduced into a clean room or a storage container. Preventing.

Next, in the present invention, since the porous silicon layer is formed on one or both sides of the substrate, the inner wall surface of the pores of the porous silicon layer participates in the adsorption, and the porous silicon layer functions to adsorb gas molecules. This significantly increases the area required.

In the present invention, unlike the known gettering material, the function of the pn junction formed by injecting the dopant into the porous layer formed previously is considered as follows. That is, in FIG. 4A, when n-type impurity ions such as phosphorus are implanted later into the p-type porous layer 10 formed earlier, the depth at which the ions reach depends on the implantation location. The pn junction surface 12 formed in the porous layer is not a conventional flat surface but a complicated curved surface.

For example, when ions are implanted at points A and C in FIG. 4A, ions penetrate through holes and are effectively implanted deeply. On the other hand, when implanted at points B and D, the implant is shallow because it passes through a crystal without vacancies. Further, although impurities diffuse by the subsequent annealing (heat treatment), the impurities cannot diffuse across the holes, so that the diffusion direction is spatially limited so as to bypass the holes. With these two factors,
A microscopic structure in which regions of the same or different conductivity type as the substrate are present in the porous layer in a complicatedly interlaced manner is obtained. As a result, not only the effect of increasing the surface area by making it porous,
It is considered that the appearance of the surface of the region having various energy levels on the wall surface of the hole exerts an adsorption effect on gas molecules having various electron affinities.

Further, in the present invention, the surface of the porous layer is cleaned and activated, whereby the surface is energetically excited,
An effective gettering action can be exerted on a wide range of target gas pollutants.

[0021] Next, the second present invention provides a method for forming an arc discharge in an inert gas containing at least one of rare gas and nitrogen with respect to a pn junction in a porous layer of the gettering substrate. An invention of a gettering substrate characterized in that charges are injected using electron beam irradiation or other means that produces the same effect.

It should be noted that the gettering substrate described above has a certain area itself as illustrated at points X and Y in FIG. It is considered that there is a region of a form three-dimensionally wrapped in a region of a conductivity type opposite to the conductivity type of.

When electrons are injected into such a region as described above, the pn junction is forward-biased at point Y, but is reverse-biased at point X, so that the equivalent electron shown in FIG. As shown in the circuit diagram, a change in potential due to charge injection can be held. Therefore, the gettering substrate of the present invention has a uniform planar pn junction obtained by anodizing a silicon substrate on which a pn junction has been previously formed, as is conventionally known. Therefore, the action on the potential energy (potential distribution) of the gettering surface is also unique and effective.

In a third aspect of the present invention, the surface of the porous silicon layer having a pn junction of the gettering substrate is exposed to a plasma atmosphere of hydrogen gas or a gas obtained by diluting hydrogen with an inert gas. This is an invention of a gettering substrate formed by activating the surface of a porous silicon layer.

The effect of the plasma treatment is that when the surface of a porous layer having a pn junction inside is exposed to a plasma atmosphere composed of electrons and ions, the change in potential due to the introduction of electric charges is maintained as described above. It is believed that the layer surface is more activated.

Next, the present invention relates to a method for manufacturing a gettering substrate. According to the present invention, after forming a porous layer by anodizing one or both surfaces of a silicon substrate, a dopant which produces a conductivity type different from the conductivity type of the silicon substrate is added. After introducing and forming a pn junction in the porous layer, the surface of the porous layer having the pn junction is heat-treated in a reducing gas or a halogen gas, or a gas obtained by diluting either of them with an inert gas. It is an invention of a method for manufacturing a gettering substrate, wherein the gettering substrate is activated by cleaning.

In the present invention, the effect of the method of introducing the dopant after forming the porous layer first is that as described above, the introduction depth is not uniform depending on the location, and as a result, the pn junction surface becomes macroscopic. That is, a complicated curved surface is formed instead of a flat surface. In addition to this, the leading end portion of the introduction depth forms a region complicatedly disturbed microscopically through the pores in the porous material. By realizing such a complicated structure of the joint surface which has not been seen in the prior art, a concentration distribution can be given to the carrier impurities in the porous material. This makes it possible to cope with various electron affinities of gas molecules, and increases the probability that a porous portion having a gettering ability capable of adsorbing gas molecules having a specific electron affinity always exists.

Further, a second present invention relating to a manufacturing method includes:
Electric charge is injected into the pn junction in the porous silicon layer of the gettering substrate obtained by the above-described method in an inert gas by using arc discharge, electron beam irradiation, or a means having an equivalent effect. An invention of a method for manufacturing a gettering substrate, characterized in that:

A third aspect of the present invention relating to a manufacturing method is as follows.
The surface of the porous silicon layer including the pn junction of the gettering substrate obtained by the above-described method is exposed to a plasma atmosphere of hydrogen gas or a gas obtained by diluting hydrogen with an inert gas to form a porous silicon layer having the pn junction. An invention of a method for manufacturing a gettering substrate, comprising activating a surface of a layer.

The present invention also relates to the use of a gettering substrate. In a semiconductor device manufacturing process, when a silicon substrate used for device manufacturing is stored, a dedicated gettering substrate obtained from the same type of silicon substrate as the silicon substrate is used. And a gas contaminant in the container is adsorbed to the gettering substrate, thereby providing a method of storing a silicon substrate for manufacturing a semiconductor device.
It is convenient and preferable that the silicon substrate and the gettering substrate have the same shape to be stored together in the storage container.

Lastly, the present invention relating to the reprocessing of the used gettering substrate, according to the present invention, adsorbs gaseous contaminants during storage in a container together with a silicon substrate in a clean room as described above. The invention of the method for regenerating each gettering substrate, wherein the gettering substrate is taken out of the container and heat-treated (annealed) in a reducing gas such as hydrogen under reduced pressure.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A gettering substrate according to one embodiment of the present invention will be described with reference to FIG. A p-type porous silicon layer 10 is formed on the surface of a p-type silicon substrate 8 by anodization, and a carrier impurity that gives a conductivity type n opposite to the conductivity type p of the substrate is ion-implanted into the porous layer 10. By implanting to form the N ⁺ region 11, a pn junction 12 is formed in the porous layer. Next, the N
⁺ Region surface so as to be exposed to a reducing gas such as silane 110
The surface is cleaned and activated by heating at about 0 ° C. to obtain the gettering substrate of the present embodiment.

The p-type porous silicon layer 10 and N
^{The +} region 11 may be formed on only one side of the silicon substrate 8, or may be formed on both sides as necessary. In the case of forming on one side, the p-type porous silicon layer 10 or the N ⁺ region 1
1 may be formed. However, in this case, the contaminants adsorbed may be separated from the porous layer by the subsequent wet etching process or the like, and may adhere to the device formation region. It is preferable to form a porous layer on one side or both sides.

The structure of the present embodiment may be such that the pn junction 12 is formed by forming the substrate 9 and the porous layer 40 as n-type and forming the P ⁺ region 41 by ion implantation or the like as shown in FIG. good. At this time, by adjusting the implantation depth, the P ⁺ region 41 was formed inside the n-type porous layer 40 as illustrated in FIG. 2, and the pn junctions 12 were formed on both surfaces of the P ⁺ region. Things are also useful.

As illustrated in FIG. 3, an n-type porous layer 40 is formed on the n-type substrate 9 and a P ⁺ region 41 is formed by the first ion implantation.
It is also useful to form the N ⁺ region 43 by performing the second ion implantation from the surface side of the substrate using the carrier impurity opposite to the first ion implantation. By annealing this, the mutual diffusion of both types of impurities is promoted, and the P ⁺ region 4
It is more useful to form a low-concentration compensation region 42 at the boundary between 1 and the N ⁺ region 43 by carrier compensation of both types of impurities.

Next, in the embodiment of the manufacturing method, the anodization is performed by applying a DC or AC voltage by arranging a silicon substrate and an electrode to face each other in a hydrofluoric acid-based electrolyte solution, or by applying any other methods known in the art. Method.

In the embodiment of the manufacturing method, the dopant is introduced by a diffusion method in which impurity vapor is diffused from the surface of the porous layer into the inside of the porous layer in a diffusion furnace, or an ion implantation in which an ionized dopant is injected under an acceleration voltage. Other than the law,
Includes all methods known in the art.

Further, in the embodiment of the manufacturing method, the cleaning activation of the surface of the porous layer is performed by hydrogen gas, silane (SiH ₄ ).
Or a halogen gas such as chlorine, or a gas obtained by diluting any of them with nitrogen gas or a rare gas such as helium or argon (that is, a Group 0 element of the periodic table). This is performed by heating to about 1100 ° C. for a short time. The heating may be carried out in an atmosphere of the above-mentioned gas at normal pressure.

Another embodiment of the manufacturing method is to inject a charge into the pn junction in the porous layer of the gettering substrate having the above structure and function. The charge injection step is performed after heat treatment in a reducing atmosphere to clean and activate the porous layer surface. This is because the electric conductivity of a semiconductor such as silicon depends on the temperature. Therefore, when charge injection is performed first, a spatial change in electric conductivity occurs due to a heat treatment involving a large temperature change around 1100 ° C. Is thought to escape.

In the embodiments of the present invention, the means for injecting electric charges includes a method of irradiating electrons with an electron beam gun, a method of arc discharge, and all other equivalent means capable of injecting electric charges.

In another embodiment of the present invention, the plasma treatment of the surface of the porous layer including the pn junction of the gettering substrate is performed after the surface is heat-treated in a reducing atmosphere. This is because, if the plasma treatment is performed first, it is considered that the electric conductivity introduced by the plasma escapes due to the spatial change in the electrical conductivity caused by the heat treatment involving a large temperature change as described above.

In the embodiment of the present invention, the plasma processing is performed by using a high frequency power in a hydrogen gas or a gas obtained by diluting hydrogen with nitrogen or a rare gas using a dry etch apparatus, a plasma CVD apparatus, or the like usually used in a device manufacturing process. And all other techniques used in the art.

Next, a method of storing a silicon substrate for manufacturing a device according to an embodiment of the present invention will be described with reference to FIG. In a clean room, a silicon substrate storage container 23 accommodates a large number of device manufacturing silicon substrates 21 together with one or a few gettering substrates of the same quality and the same shape as a dummy wafer, and closes the lid 22. 3-4
Store for days. The defect rate of the device manufactured using the silicon substrate thus stored in the storage container is greatly reduced as shown in the first embodiment.

Some examples will be described to explain the embodiments of the present invention in more detail, but the present invention is not limited to these examples. In particular, for convenience of explanation, a silicon semiconductor is mainly described, but the essence of the technical idea of the present invention widely applies to a simple semiconductor such as germanium and a compound semiconductor such as gallium arsenide. Here, sccm (Stream cubic centi) in the unit of gas flow rate
The term "meter perminutes" represents a gas volume Ncm ^{3 in} terms of standard conditions flowing per minute, and the flow rate is electrically controlled by the mass flow device in this unit. In addition, the ion cm ^{−2 in} the dose amount unit of the ion implantation represents the number of charged particles to be dosed / cm ² . On the other hand, the unit of electron beam irradiation amount, mC / cm ² , represents the total amount of irradiation charge per unit area (milli-coulomb).

Example 1 Production Example 1 of Gettering Substrate The back surface was masked with a Teflon film, the diameter was 6 inches, and the resistivity was 1
A 0-ohm-cm p-type single-crystal silicon substrate and a Pt electrode plate are arranged facing each other in an electrolyte solution, and anodization is performed by applying a pulsed alternating current having a voltage of ± 5 V, a pulse width of 1 ms, and a frequency of 500 Hz. Then, a porous layer was formed only on one side of the silicon substrate. At this time, the silicon substrate and the electrode were brought into contact with each other over the entire main surface of the substrate, and only one surface was subjected to anodizing treatment. Here, a hydrofluoric acid-based solution having a weight ratio of ethanol: hydrofluoric acid: water = 1: 1: 2 was used as the electrolyte solution.

With respect to the p-type porous layer thus obtained,
An accelerating voltage of 150 keV with phosphorus (P) as a dopant;
Ions were implanted at a dose of 5E15 ions cm ^-2 to form a pn junction in the porous layer.

Next, a decompression RTP device (Rapid Th)
thermal processor), the above-mentioned pn
The substrate having the junction was subjected to a heat treatment at a temperature of 1100 ° C. for 60 seconds while being exposed to a reduced pressure of 50 Torr in a hydrogen gas to clean and activate the surface.

Evaluation of gettering function Two gettering substrates of the present invention manufactured as described above were used.
As shown in FIG. 5, it was housed in a substrate storage container together with 48 device manufacturing silicon substrates in a stage before the gate oxide film was formed in a clean room, and stored for 100 hours. After that, a gate oxide film is formed to have a thickness of 7 mm.
M having a MOS capacitance pattern of 10 mm ² in nm
OSFETs were manufactured and the manufacturing yield was evaluated. As an evaluation method, the ratio of defective products with an initial withstand voltage showing a transistor breakdown electric field of 8 MV / cm or less was used. When stored using the gettering substrate of Production Example 1, pMOS and nM
The OS had an initial breakdown voltage failure rate of 2% or less, and very good results were obtained without any difference between the two. As Comparative Evaluation, Production Example 1
When the silicon substrate is stored without putting the gettering substrate obtained in the above in a container, the initial breakdown voltage failure rate is 34% for pMOS,
In the case of nMOS, it was 46%, and the excellent effect of the gettering substrate of this example was clearly shown.

Regeneration of Gettering Function The gettering substrate of Production Example 1 used for storage of wafers as described above was again heat-treated under reduced pressure in hydrogen gas to clean and activate the surface. Thereafter, as a result of using for storage as described above, the defective rate was almost equal to that of the first time. In addition, it was effective to perform the cleaning activation process immediately before using for storage. It was found that the gettering substrate of this example was easily regenerated by performing the cleaning activation treatment, and that the substrate could be repeatedly used in a practically preferable manner.

Example 2 Production Example 2 of Gettering Substrate Using an n-type single-crystal silicon substrate, anodization was performed in the same manner as in Example 1 to form an n-type porous layer, and boron (B) was used as an impurity. ) Was implanted at an acceleration voltage of 250 keV with a dose of 2E16 ions cm ⁻² and 900 in a nitrogen atmosphere.
Annealing was performed at 30 ° C. for 30 minutes to diffuse impurities, thereby forming a P ⁺ region. Since the ion implantation depth is increased to about 650 nm, the P ⁺ region 41 can be formed in the porous layer as shown in FIG. 2, and the pn junction surface is formed on the upper and lower surfaces of the P ⁺ region. Was completed. Thereafter, the surface is cleaned and activated by heat treatment in a hydrogen gas atmosphere in the same manner as in Example 1.
A gettering substrate of this example was obtained.

Evaluation of Gettering Function When the gettering substrate of Production Example 2 was evaluated in the same manner as in Example 1, the defect rate was equivalent to that of Example 1. It can be seen that the internal configuration of the gettering substrate of this embodiment is effective.

Example 3 Production Example 3 of Gettering Substrate Using an n-type single-crystal silicon substrate, anodization and boron doping were performed in the same manner as in Example 2, and the surface of the porous silicon layer was further formed. Arsenic (As) from the side with an acceleration voltage of 1
N ⁺ regions 43 were formed by ion implantation at 20 keV and a dose of 5E15 ions cm ⁻² . Put this in a nitrogen atmosphere 1
000 annealed 40 minutes at ℃ encourage mutual diffusion of the dopant, the low density compensation region due to the compensation of mutual carrier impurity at the boundary of the P ⁺ region and the N ⁺ region as shown in FIG. 3 42
Was formed. Thereafter, the surface was cleaned and activated in the same manner as in Example 1 to obtain a gettering substrate of the present invention.

Evaluation of Gettering Function The gettering substrate of Production Example 3 was evaluated in the same manner as in Example 1, and the defect rate was equivalent to that of Example 1. It can be seen that the internal configuration of the gettering substrate of this embodiment is effective.

Example 4 Production Example 4 of Gettering Substrate In the same manner as in Example 1, anodization and phosphorus doping were performed using a p-type single crystal silicon substrate, and pn was formed in the porous layer.
A bond was formed and a clean activation treatment was performed in a reducing gas. Next, using a parallel plate type dry etching apparatus, the hydrogen gas flow rate was set to 100 sccm, and the argon gas flow rate was set to 300 sccm.
In a controlled atmosphere, a high-frequency power of 13.56 MHz was applied to the pn junction surface in the porous layer at a pressure of 10 Torr, and plasma treatment was performed for 15 minutes to obtain a gettering substrate of the present invention.

Evaluation of Gettering Function The gettering substrate of Production Example 4 was evaluated in the same manner as in Example 1, and the defect rate was equivalent to that of Example 1. Further, the particles (dust having a size of about 1 micron or less) trapped on the wafer by the dust measuring device on the wafer using the laser beam scattering measurement.
When the number was measured, it was as small as about 30 pieces. It can be seen that the activation treatment of the adsorption surface by improving the surface potential using the plasma treatment of this embodiment is effective.

Example 5 Production Example 5 of Gettering Substrate Anodization and phosphorus doping were performed using a p-type single crystal silicon substrate in the same manner as in Example 1, and pn was formed in the porous layer.
A bond was formed and a clean activation treatment was performed in a reducing gas. On the other hand, the electron injection of about 1 mC / cm ² is performed from the surface side of the porous layer using an electron beam gun at an accelerating voltage of 30 keV in a nitrogen gas, thereby injecting electric charge into the pn junction, and Was obtained.

Evaluation of Gettering Function The number of trapped particles was measured using the gettering substrate of Production Example 5, and as a result, about 30 particles were obtained. It was confirmed that the gettering substrate of this example was as useful as the gettering substrate of Production Example 4. It can be seen that the potential distribution improvement according to this embodiment is effective.

[0058]

According to the gettering substrate of the present invention, since the porous layer having the pn junction is formed inside,
As a result of enlarging the surface for adsorbing molecules of gaseous contaminants, gas-phase contamination on the silicon substrate for device manufacturing can be suppressed.

According to the gettering substrate obtained by the manufacturing method of the present invention, by forming the porous layer and then forming the pn junction surface, the tip portion into which impurities are introduced can be microscopically formed through holes. As a result of the formation of a complicated disordered region, a gettering function effective for gas phase contaminants having various electron affinities can be secured.

According to the gettering substrate into which the electric charge is injected according to the present invention, the electric potential is locally held on the adsorption surface by the electric charge injection, and as a result, the electric potential distribution can be generated on the gettering substrate surface. It is possible to solve the problem that the adsorption efficiency of the corresponding gas is reduced depending on the substrate surface potential.

The gettering substrate of the present invention can be regenerated by using an existing device manufacturing apparatus by a method such as heat treatment in hydrogen gas or treatment with plasma of an inert gas. It is highly practical because it can be used repeatedly.

According to the storage method using the gettering substrate of the present invention, gettering at room temperature is possible, so that a high degree of cleanliness required for device manufacture can be always maintained.

[Brief description of the drawings]

FIG. 1 is a structural cross-sectional view schematically illustrating a gettering substrate according to an embodiment of the present invention.

FIG. 2 is a structural cross-sectional view schematically illustrating a gettering substrate (Example 2) according to another embodiment of the present invention.

FIG. 3 is a structural cross-sectional view schematically illustrating a gettering substrate (Example 3) of still another embodiment of the present invention.

FIG. 4 is a structural cross-sectional view schematically illustrating an operation of an embodiment of the gettering substrate of the present invention, and an equivalent electronic circuit diagram schematically illustrating the above-described operation.

FIG. 5 is a sectional view of a storage container illustrating the method for storing a silicon substrate of the present invention.

FIG. 6 is a structural cross-sectional view schematically illustrating a conventional gettering substrate, and a structural cross-sectional view schematically illustrating another conventional gettering substrate.

[Explanation of symbols]

Reference Signs List 8 p-type silicon substrate 9 n-type silicon substrate 10 p-type porous layer 11 N ⁺ region 12 pn junction 21 device manufacturing silicon substrate 22 storage container lid 23 storage container silicon substrate support 24 gettering substrate 30 of the present invention Silicon substrate 31 Damaged layer 32 Crystal defect layer 33 Laser beam such as Ar 40 n-type porous layer 41 P ⁺ region 42 Low concentration compensation region 43 N ⁺ region

Claims (13)

(57) [Claims] 1. A porous silicon layer comprising: a porous silicon layer; and a pn junction formed by introducing a dopant into the porous silicon layer. The surface of the porous silicon layer having the pn junction is subjected to a cleaning activation treatment. A gettering substrate, characterized in that: 2. The cleaning activation treatment includes a heat treatment at about 1100 ° C. in an atmosphere in which at least one of a reducing gas and a halogen gas is diluted with at least one of a rare gas and a nitrogen gas. The gettering substrate according to claim 1, wherein: 3. The gettering substrate according to claim 1, wherein the porous silicon layer having the pn junction is formed on both surfaces of the silicon substrate. 4. The gettering substrate according to claim 1, wherein the porous silicon layer having a pn junction is formed on at least one surface of a silicon substrate having no device formation region. . 5. The gettering substrate according to claim 1, wherein an electric charge is injected into a pn junction in the porous silicon layer. 6. The porous silicon layer having a pn junction is activated by exposing the surface of the porous silicon layer to a plasma atmosphere of a hydrogen gas or a gas obtained by diluting hydrogen with a rare gas or at least one of nitrogen. The gettering substrate according to claim 1 or 2, wherein 7. A gettering substrate for absorbing contaminants, comprising: a porous layer formed on at least one surface of the substrate; and a pn junction surface provided in the porous layer.
The gettering substrate, wherein the pn junction surface is a curved surface having a first portion formed deep from the surface of the porous layer of the substrate and a second portion formed shallow. 8. A gettering substrate for absorbing a contaminant, comprising: a porous layer formed on at least one surface of the substrate; a first pn junction surface provided in the porous layer;
A gettering substrate provided in the porous layer and having a second pn junction surface formed deeper than the first pn junction surface. 9. A method of forming a porous layer by anodizing at least one surface of a silicon substrate, and introducing a dopant having a conductivity type different from the conductivity type of the silicon substrate into the porous layer. A pn junction is formed in the layer, and the surface of the porous layer on which the pn junction is formed is heat-treated in an atmosphere in which at least one of a reducing gas and a halogen gas is diluted with at least one of a rare gas and nitrogen to activate the cleaning. A method for manufacturing a gettering substrate. 10. A pn junction in a porous layer of a gettering substrate obtained by the method according to claim 9, wherein an arc discharge and an electron beam are carried out in an inert gas containing at least one kind of a rare gas or nitrogen. A method for manufacturing a gettering substrate, comprising: injecting charges using irradiation or a means that produces an equivalent effect. 11. The surface of a porous layer having a pn junction of a gettering substrate obtained by the method according to claim 9 is diluted with hydrogen gas or an inert gas containing at least one of rare gas and nitrogen. A method for manufacturing a gettering substrate, comprising activating a surface of a porous layer by exposing to a plasma atmosphere of a gas. 12. A semiconductor substrate on which a device is formed,
11. The substrate according to claim 9, wherein the substrate is of the same kind as the semiconductor substrate.
A method for storing a silicon substrate for manufacturing a semiconductor device, comprising: storing in a storage container together with a gettering substrate manufactured by the method according to 1; and adsorbing gas contaminants in the storage container to the gettering substrate. 13. The gettering method according to claim 1, wherein the gettering substrate used in gettering is cleaned and activated by heat treatment or plasma treatment under reduced pressure in a reducing gas. Substrate recycling method.