Crystal growth doping apparatus and crystal growth doping method

A crystal growth doping apparatus and a crystal growth doping method are provided. The crystal growth doping apparatus includes a crystal growth furnace and a doping device that includes a feeding tube inserted to the furnace body along an oblique insertion direction, and a storage cover and a gate tube that are disposed in the feeding tube. The feeding tube extends from an outer surface thereof to form a placement opening, and the placement opening is recessed from an edge thereof to form an upper recessed portion and a lower recessed portion along the oblique insertion direction. The storage cover includes a storage tank and a handle. When the storage cover is disposed in the gate tube body, the gate tube body is configured to isolate an inner space of the feeding tube from the placement opening.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 110128823, filed on Aug. 5, 2021. The entire content of the above identified application is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a crystal growth apparatus and a crystal growth method, and more particularly to a crystal growth doping apparatus and a crystal growth doping method.

BACKGROUND OF THE DISCLOSURE

In a crystal growth process, a certain amount of dopant is doped into a silicon crystal melt through a doping device of a conventional silicon wafer crystal growth apparatus, so that the resistivity required for a target silicon crystal can be provided. However, a storage cover that includes dopant therein is mostly taken out from, or placed in the doping device in a manual manner, which may cause contamination of quartz tubes, decreased doping efficiency, and dopant and internal contamination of the doping device.

Furthermore, in the silicon wafer crystal growth apparatus, since a quartz inner tube of the doping device is inclined relative to a crystal growth furnace, when the storage cover is taken out from or placed in the doping device, the storage cover can easily hit and cause damage to a structure of an opening of the doping device.

SUMMARY OF THE DISCLOSURE

In response to the above-referenced technical inadequacies, the present disclosure provides a crystal growth doping apparatus and a crystal growth doping method.

In one aspect, the present disclosure provides a crystal growth doping apparatus, and the crystal growth doping apparatus includes a crystal growth furnace and a doping device. The crystal growth furnace includes a furnace body and a crucible that is disposed in the furnace body and configured to accommodate a melting raw material. The doping device includes a feeding tube, a storage cover, and a gate tube body. The feeding tube is inserted to the furnace body along an oblique insertion direction that is inclined relative to a horizontal direction, in which the feeding tube extends from an outer surface thereof to form a placement opening, and the placement opening is recessed from an edge thereof to form an upper recessed portion and a lower recessed portion along the oblique insertion direction. The storage cover is detachably disposed in the feeding tube, in which the storage cover includes a storage tank and a handle formed on an outer surface of the storage tank. The gate tube body is disposed in the feeding tube, in which the storage cover is detachably disposed in the gate tube body, and when the storage cover is disposed in the gate tube body, the gate tube body is configured to isolate an inner space of the feeding tube from the placement opening.

In another aspect, the present disclosure provides a crystal growth doping method, which is configured to be implemented with a doping device that is inserted in a crystal growth furnace along an oblique insertion direction, in which the crystal growth furnace includes a crucible therein, and the crucible is configured to accommodate a melting raw material, and in which the doping device includes a feeding tube, a gate tube body that is disposed in the feeding tube, and a storage cover that is detachably disposed in the gate tube body, and the feeding tube extends from an outer surface thereof to form a placement opening. The crystal growth doping method includes a gate opening step, a storage cover removing step, a material storage step, a storage cover placement step, a gate closing step, and a doping step. The gate opening step includes having a door opening member enter the feeding tube from the placement opening and abut against a gate tube opening of the gate tube body, the door opening member pushing the gate tube body along the oblique insertion direction such that the gate tube body is moved away from the placement opening of the feeding tube, and having the door opening member engage with the feeding tube. The storage cover removing step includes having a removal member pass through the placement opening so as to hook a handle of the storage cover onto the removal member, and taking the storage cover outside of the feeding tube from the placement opening along the oblique insertion direction. The material storage step includes placing a dopant in the storage cover. The storage cover placement step includes hooking the handle and placing the storage cover into the feeding tube with the removal member. The gate closing step includes separating the door opening member from the gate tube opening of the gate tube body, so as to move the gate tube body along the oblique insertion direction and isolate an inner space of the feeding tube from the placement opening. The doping step includes moving the feeding tube to allow the storage cover to be adjacent to the melting raw material, so that the dopant is heated and vaporized and enters the melting raw material.

Therefore, in the crystal growth doping apparatus and the crystal growth doping method provided by the present disclosure, by virtue of a storage cover being detachably disposed in the feeding tube, and when the storage cover is disposed in the gate tube body, the gate tube body being configured to isolate an inner space of the feeding tube from the placement opening, internal pollution problems of the dopant and the crystal growth doping apparatus can be prevented, and when the dopant is taken out from or placed in the crystal growth doping apparatus, the placement opening of the feeding tube can be prevented from being hit, which may cause the feeding tube to break.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring toFIG.1toFIG.14, an embodiment of the present disclosure provides a crystal growth doping apparatus100and a crystal growth doping method S100. For ease of understanding the crystal growth doping method S100, the structure of each component of the crystal growth doping apparatus100will be described in sequence, and the crystal growth doping method S100will be described in due course.

As shown inFIG.1, the crystal growth doping apparatus100includes a crystal growth furnace1and a doping device2that is disposed to the crystal growth furnace1, and the crystal growth furnace1includes a furnace body11and a crucible12that is disposed in the furnace body11and configured to accommodate a melting raw material200.

It should be noted that, in the present embodiment, the crystal growth furnace1is applied in a Czochralski process to perform a crystal growth process, and the crystal growth furnace1can be used to produce products such as crystal ingots, crystal rods, or monocrystalline silicon, but the present disclosure is not limited thereto. For example, in other embodiments not shown in the present disclosure, the crystal growth furnace1can be applied in a Bridgman-Stockbarger process to perform the crystal growth process.

As shown inFIG.1andFIG.12, the doping device2includes an outer tube21which is disposed on the furnace body11along an oblique insertion direction F2that is inclined relative to a horizontal direction F1, a feeding tube22that is inserted to the furnace body11along the oblique insertion direction F2, a magnetic moving mechanism23that is movably mounted on the outer tube21, a gate tube body24that is disposed in the feeding tube22, a storage cover25that is detachably disposed in the feeding tube22, a removal member26that is detachably disposed to the furnace body11, and a door opening member27that is detachably disposed to the furnace body11.

Specifically, from an outside toward an inside of the doping device2, the magnetic moving mechanism23, the outer tube21, the feeding tube22, the gate tube body24, and the storage cover25are sequentially disposed to the doping device2. In addition, relative to the outer tube21, the storage cover25, the removal member26, and the door opening member27are detachably mounted or disposed to the outer tube21and other elements that are tubular.

It should be noted that an angle between the horizontal direction F1and the oblique insertion direction F2is between 30° and 45°, but the present disclosure is not limited thereto. In brief, the angle can be adjusted according to practical requirements.

It should be noted that for ease of illustration, the outer tube21, the feeding tube22, the magnetic moving mechanism23, and the gate tube body24are sequentially described herein, then the storage cover25, the removal member26, and the door opening member27will be described.

As shown inFIG.1andFIG.2, the outer tube21includes an outer tube body211and an operating tube212that extends along the horizontal direction F1from the outer tube body211, and the operating tube212has an operating tube opening2121and a surrounding protrusion2122which is disposed to the operating tube opening2121and located at an end of the operating tube212relatively away from the outer tube body211.

In addition, the operating tube opening2121is configured for the storage cover25to enter an inside of the outer tube body211of the outer tube21from an outside of the crystal growth furnace1, and the surrounding protrusion2122is configured for the door opening member27to engage thereto, so that the door opening member27can be detachably mounted to the surrounding protrusion2122.

More specifically, in the present embodiment, the operating tube212is a flange tube, the operating tube opening2121has a flange plate structure (not shown in the figures) that is disposed at an outer edge thereof, and the surrounding protrusion2122is formed on a side surface of the flange plate structure relatively away from the outer tube body211, but the present disclosure is not limited thereto. For example, in other embodiments not shown in the present disclosure, the operating tube212can also be a tube of another type (e.g. a spiral tube or a square tube).

As shown inFIG.1toFIG.3, part of the feeding tube22is disposed in the outer tube21, and part of the feeding tube22is disposed in the furnace body11and adjacent to the melting raw material200. In addition, the feeding tube22includes a placement opening221that extends from an outer surface thereof, a dowel222that is formed on an inner side surface of the feeding tube22, a feeding tube opening223that is formed at an end of the feeding tube22, and an inclined tube224that is connected to an inside of the feeding tube22.

It should be noted that, as shown inFIG.4, the placement opening221has a shrinkage groove2211, an upper recessed portion2212, and a lower recessed portion2213, and the upper recessed portion2212and the lower recessed portion2213are connected to the shrinkage groove2211. In addition, in the present embodiment, the upper recessed portion2212and the lower recessed portion2213are respectively half oval and half circular in shape.

Furthermore, the upper recessed portion2212and the lower recessed portion2213are configured to provide a relatively spacious moving space for the removal member26, so that the storage cover25can be placed in the feeding tube22from the shrinkage groove2211with the removal member26and without the shrinkage groove2211being hit.

It should be noted that the placement opening221is recessed from an edge thereof to form the upper recessed portion2212and the lower recessed portion2213along the oblique insertion direction F2, and the shrinkage groove2211is located between the upper recessed portion2212and the lower recessed portion2213, but the present disclosure is not limited thereto. For example, in other embodiments of the present disclosure, the shape of the upper recessed portion2212and the lower recessed portion2213can be adjusted according to practical requirements.

Furthermore, in the present embodiment, the shrinkage groove2211has two rounded corners2211athat are formed on two sides thereof along a direction that is perpendicular to the oblique insertion direction F2, and each of the two rounded corners2211ais between 120° and 180°. In addition, the shrinkage groove2211and the two rounded corners2211acan be used to increase the structural strength of the feeding tube22and effectively decrease the stress that is applied on the feeding tube22during operation, but the present disclosure is not limited thereto. For example, in other embodiments not shown in the present disclosure, the shrinkage groove2211can also be provided without the two rounded corners2211a.

It should be noted that, as shown inFIG.3andFIG.4, the dowel222and the placement opening221are respectively formed at opposite sides of the feeding tube22, and a distance that is between the dowel222and the lower recessed portion2213is greater than a distance that is between the dowel222and the upper recessed portion2212. In addition, the dowel222can be used to limit a relative position between the gate tube body24and the feeding tube22.

It should be noted that, as shown inFIG.1toFIG.3, the feeding tube opening223is adjacent to the lower recessed portion2213and near to the crucible12, and the inclined tube224is partially disposed in the feeding tube opening223. In addition, an outer diameter of the inclined tube224is not greater than an inner diameter of the feeding tube22, the inclined tube224has two ends that respectively form a flat tube opening2241and an inclined tube opening2242, and the flat tube opening2241is disposed in the feeding tube opening223.

Specifically, the flat tube opening2241is located in the feeding tube22, and a cross-section of the flat tube opening2241is not parallel to a melting surface201of the melting raw material200. In addition, the inclined tube opening2242is located outside the feeding tube22, and a cross-section of the inclined tube opening2242is parallel to the melting surface201.

As shown inFIG.1, the inclined tube opening2242is adjacent to the melting surface201, and the cross-section of the inclined tube opening2242and the melting surface201have a vertical distance L there-between, and the vertical distance L is not greater than 5 mm. Furthermore, in the present embodiment, the vertical distance L is preferably between 1 mm and 5 mm, and the vertical distance L is more preferably between 1 mm and 3 mm.

It should be noted that, by virtue of “the cross-section of the inclined tube opening2242and the melting surface201having a vertical distance L there-between, and the vertical distance L being not greater than 5 mm,” the storage cover25can be as close as possible to the melting surface201and receive more heat energy in a certain period of time, so as to increase the doping efficiency of the crystal growth doping apparatus100.

As shown inFIG.1,FIG.5, andFIG.6, the magnetic moving mechanism23includes an outer magnetic sleeve231that is movably disposed on an outer surface of the outer tube21, an inner magnetic sleeve232that is movably disposed on an inner side surface of the outer tube21, a plurality of adsorbed members233that are movably disposed between the inner side surface of the outer tube21and the inner magnetic sleeve232, and a plurality of magnetic members234that are disposed on a side surface of the outer magnetic sleeve231relatively distant from the outer side surface of the outer tube21.

In addition, the adsorbed members233correspond in position to the magnetic members234, and the feeding tube22is disposed at and abuts against an inner side surface of the magnetic moving mechanism23.

Specifically, when the feeding tube22is disposed in the outer tube21, the inner magnetic sleeve232covers around part of the outer surface of the feeding tube22, and the adsorbed members233are disposed on a side surface of the inner magnetic sleeve232relatively distant from the feeding tube22. In addition, the outer magnetic sleeve231covers part of the outer surface of the outer tube21, and the magnetic members234are disposed on the side surface of the outer magnetic sleeve231relatively distant from the outer tube21.

Furthermore, the quantity of the adsorbed members233and the quantity of the magnetic members234are the same and preferably four, respectively. In the present embodiment, the adsorbed members233and the magnetic members234can respectively be iron members and magnets.

It should be noted that the magnetic moving mechanism23is configured to move the feeding tube22. Specifically, the magnetic members234can be operated outside of the outer tube21and moved, so that the feeding tube22that is covered by the inner magnetic sleeve232can be correspondingly moved. Accordingly, when the feeding tube22is operated without opening the crystal growth doping apparatus100, problems such as pollution can be prevented.

As shown inFIG.3, the gate tube body24forms a gate tube opening241on an end thereof, and the gate tube opening241is recessed along the oblique insertion direction F2to form a long groove242. In addition, in the oblique insertion direction F2, the long groove242and the placement opening221each have a length, and the length of the long groove242is not less than the length of the placement opening221.

Furthermore, in the present embodiment, the length of the long groove242is defined as a long groove length242a, the length of the placement opening221is defined as a placement port length221a, and a ratio of the long groove length242ato the placement port length221ais between 1.3 and 2.

More specifically, the ratio of the long groove length242ato the placement port length221acan be between 1.3 and 1.5, 1.5 and 1.8, and 1.8 and 2.0. In the present embodiment, the ratio of the long groove length242ato the placement port length221ais preferably between 1.5 and 1.8. Accordingly, the structural strength of the gate tube body24still can be maintained to a certain extent when the gate tube body24has the long groove242formed thereon.

It should be noted that, when the gate tube body24is disposed in the feeding tube22, the gate tube body24is configured to isolate an inner space of the feeding tube22from the placement opening221, so that the inside of the feeding tube22is isolated from the outside thereof. In addition, as shown inFIG.3, the dowel222can be disposed in the long groove242, and when the storage cover25is not disposed in the feeding tube22, the dowel222engages to an end of the long groove242relatively distant from the gate tube opening241, so that the gate tube body24is maintained in the same position for a long time.

Descriptions regarding the outer tube21, the feeding tube22, the magnetic moving mechanism23, and the gate tube body24are concluded herein. The storage cover25, the removal member26, and the door opening member27will be sequentially described next in conjunction with description of the outer tube21, the feeding tube22, the magnetic moving mechanism23, and the gate tube body24.

As shown inFIG.7, the storage cover25includes a storage tank251, a handle252that is formed on an outer side surface of the storage tank251, a loading opening253that corresponds in position to the handle252, and a loading tube254that is recessed toward an inside of the storage tank251from the loading opening253. In addition, the loading opening253is configured for a dopant300to enter the storage tank251, and the loading tube254and an inner side wall of the storage cover25jointly form the storage tank251.

It should be noted that, as shown inFIG.7andFIG.14, when the storage cover25is disposed in the feeding tube22, the gate tube body24is engaged to the dowel222, and the storage cover25is detachably disposed in the gate tube body24. When the storage cover25is disposed in the gate tube body24, a side surface of the storage cover25relatively distant from the handle252is detachably disposed to (engages to) the flat tube opening2241. In other words, the side surface of the storage cover25adjacent to the loading opening253abuts the flat tube opening2241.

It should be noted that, as shown inFIG.1,FIG.7, andFIG.14, in the present embodiment, the dopant300is solid, and when the storage cover25abuts the flat tube opening2241, the heat emitted by the melting raw material200is transmitted to the dopant300by thermal radiation and conduction, so that the dopant300is heated and vaporized.

In continuation of the above, the vaporized dopant300overflows from the loading opening253and reaches the melting surface201of the melting raw material200for doping through the flat tube opening2241and the inclined tube opening2242.

As mentioned above, if a dopant that reaches the melting surface201of the melting raw material200is solid, the solid dopant is different from the vaporized dopant300, and a doping apparatus for the solid dopant is different from the crystal growth doping apparatus100of the present disclosure.

As shown inFIG.8, the removal member26includes a removal grip261, a first rod body262that is connected to the removal grip261, and a first recessed portion263formed at an end of the first rod body262relatively distant from the removal grip261. In addition, the removal member26can be used to enter the placement opening221of the feeding tube22from the operating tube opening2121of the operating tube212, and the removal member26is configured to take out the storage cover25from the feeding tube22and hook and support the handle252with the first recessed portion263.

It should be noted that, an end of the first rod body262is adjacent to the first recessed portion263, and the end of the first rod body262and a length direction of the first rod body262have a first oblique angle θ1there-between that is between 8° and 12°. In addition, in the present embodiment, the first oblique angle θ1is preferably 10°, but the present disclosure is not limited thereto, and the first oblique angle θ1is without special limitations. Specifically, the first oblique angle θ1is located on an opposite side of a bottom surface of the first recessed portion263, and by virtue of “the end of the first rod body262and a length direction of the first rod body262having a first oblique angle θ1,” the removal member26can easily take out the storage cover25.

As shown inFIG.9, the door opening member27includes a door opening grip271, a second rod body272that is connected to the door opening grip271, a second recessed portion273which is formed at an end of the second rod body272relatively distant from the door opening grip271, and an engagement portion274which is located at another end of the door opening member27relatively distant from the second recessed portion273.

As shown inFIG.11, the door opening member27is configured to enter the gate tube body24from the operating tube opening2121of the operating tube212to detachably abut the gate tube opening241of the gate tube body24with the second recessed portion273, then the door opening member27is configured to push the gate tube body24along the oblique insertion direction F2so that the gate tube body24is moved away from the placement opening221.

It should be noted that, as shown inFIG.9, an end of the second rod body272is adjacent to the second recessed portion273, and the end of the second rod body272and a length direction of the second rod body272have a second bevel angle θ2there-between that is between 13° and 17°. In addition, in the present embodiment, the second bevel angle θ2is preferably 15°, but the present disclosure is not limited thereto, and the second bevel angle θ2is without special limitations.

It should be noted that, in the present embodiment, the door opening member271is semi-annular, and the engagement portion274is disposed on the door opening member271. After the door opening member27pushes the gate tube body24so that the gate tube body24is moved away from the placement opening221, the engagement portion274is configured to engage with the operating tube opening2121of the operating tube212, so as to maintain a distance between the gate tube body24and the placement opening221, and the first rod body262of the removal member26is configured to pass through the door opening member271and then enter the placement opening221of the feeding tube22.

Descriptions regarding the crystal growth doping apparatus100are concluded herein, and the crystal growth doping method S100that is implemented with the crystal growth doping apparatus100will be described, but the present disclosure is not limited thereto. In other words, the crystal growth doping method S100of the present embodiment can also be implemented with other crystal doping apparatuses.

It should be noted that descriptions of the crystal growth doping method S100is similar to that of the crystal growth doping apparatus100, and similarities (e.g., the feeding tube22) between the descriptions of the crystal growth doping method S100and the crystal growth doping apparatus100will not be reiterated herein.

As shown inFIG.10, the crystal growth doping method S100sequentially includes a gate opening step S1, a storage cover removing step S3, a material storage step S5, a storage cover placement step S7, a gate closing step S9, and a doping step S11.

As shown inFIG.10andFIG.11, in the gate opening step S1, the door opening member27can be used to enter the feeding tube22from the placement opening221to abut the gate tube opening241of the gate tube body24, and the door opening member27can be used to push the gate tube body24along the oblique insertion direction F2, so that the gate tube body24is moved away from the placement opening221of the feeding tube22. Accordingly, the door opening member27engages to the feeding tube22.

Specifically, in the gate opening step S1, the second rod body272of the door opening member27enters the gate tube body24from the operating tube opening2121of the operating tube212to detachably abut the gate tube opening241of the gate tube body24with the second recessed portion273, then the door opening member27pushes the gate tube body24along the oblique insertion direction F2so that the gate tube body24is moved away from the placement opening221.

In continuation of the above, the engagement portion274of the door opening member27engages to the operating tube opening2121of the operating tube212, so as to maintain a distance between the gate body24and the placement opening221.

As shown inFIG.10andFIG.12, in the storage cover removing step S3, the removal member26is configured to pass through the lower recessed portion2213of the placement opening221, the removal member26hooks the handle252of the storage cover25, then the storage cover25is took outside the feeding tube22from the placement opening221along the oblique insertion direction F2.

Specifically, in the storage cover removing step S3, the first rod body262of the removal member26passes through the door opening member271to enter the placement opening221and then passes through the lower recessed portion2213, and the removal member26hooks and supports the handle252with the first recessed portion263, then the storage cover25is took outside of the feeding tube22from the placement opening221along the oblique insertion direction F2.

As shown inFIG.7andFIG.10, in the material storage step S5, the dopant300is placed in the storage tank251of the storage cover25. Specifically, the dopant300is placed in the storage tank251from the loading opening253and through the loading tube254, and when the dopant300is in the storage tank251, the dopant300is disposed between the loading tube254and the inner side wall of the storage cover25. Accordingly, the dopant300does not easily fall out of the loading opening253.

As shown inFIG.10, in the storage cover placement step S7, the removal member26hooks the handle252and then passes through the lower recessed portion2213, so that the storage cover25can be placed in the feeding tube22. In addition, as shown inFIG.14, when the storage cover25is disposed in the feeding tube22, the side surface of the storage cover25and adjacent to the loading opening253abuts the flat tube opening2241.

As shown inFIG.10andFIG.13, in the gate closing step S9, the door opening member27and the gate tube opening241of the gate tube body24separate from each other, so that the gate tube body24moves along the oblique insertion direction F2to isolate the inner space of the feeding tube22from the placement opening221.

As shown inFIG.10andFIG.14, in the doping step S11, the magnetic moving mechanism23moves the feeding tube22, so that the storage cover25is adjacent to the melting raw material200. Accordingly, the dopant300is heated and vaporized, so as to enter the melting raw material200.

Beneficial Effects of the Embodiment

In conclusion, in the crystal growth doping apparatus100and the crystal growth doping method S100provided by the present disclosure, by virtue of “a storage cover25being detachably disposed in the feeding tube22, and when the storage cover25is disposed in the gate tube body24, the gate tube body24being configured to isolate an inner space of the feeding tube22from the placement opening221,” internal pollution problems of the dopant300and the crystal growth doping apparatus100can be prevented, and when the dopant300is took out from or placed in the crystal growth doping apparatus100, the placement opening221of the feeding tube22can be prevented from being hit, which may cause the feeding tube22to break.

Furthermore, by virtue of “the loading tube254being recessed toward an inside of the storage tank251from the loading opening253, and the loading tube254and an inner side wall of the storage cover25jointly forming the storage tank251,” the dopant300does not easily fall out of the loading opening253.

Furthermore, by virtue of “the shrinkage groove2211having two rounded corners2211athat are formed on two sides thereof along a direction that is perpendicular to the oblique insertion direction F2, and each of the two rounded corners2211abeing between 120° and 180°,” the structural strength of the feeding tube22can be increased, and the stress that is applied on the feeding tube22during operation can be effectively decreased.

Furthermore, by virtue of “the magnetic moving mechanism23being configured to move the feeding tube22,” the feeding tube22can be operated without opening the crystal growth doping apparatus100, and problems such as pollution can be prevented.

Furthermore, by virtue of “the placement opening221having a shrinkage groove2211, an upper recessed portion2212, and a lower recessed portion2213, and the upper recessed portion2212and the lower recessed portion2213being connected to the shrinkage groove2211,” when the removal member26enters the placement opening221, sufficient space for movement is provided to the removal member26, so that the storage cover25can be placed in the feeding tube22from the shrinkage groove2211with the removal member26and without the shrinkage groove2211being hit.

Furthermore, by virtue of “the ratio of the long groove length242ato the placement port length221abeing between 1.3 and 2,” when the gate tube body24engages to the dowel222, the gate tube body24is configured to isolate the inner space of the feeding tube22from the placement opening221, and when the gate tube body24has the long groove242formed thereon, the structural strength of the gate tube body24still can be maintained to a certain extent.