JP2009107905A - Manufacturing method of silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a silicon wafer capable of effectively and efficiently removing an injection damage while suppressing the diffusion of an injected ion. <P>SOLUTION: The manufacturing method of the silicon wafer includes an injection step of performing an ion injection treatment on a substrate 1 consisting of a silicon single crystal and a damage removing step of removing by etching the damage due to the ion injection on the substrate 1 on which the ion injection is performed by performing heat treatment in an atmosphere containing a gaseous hydrogen chloride, an etching removal amount at the damage removing step is a thickness of 5-120% of the maximum concentration depth Rp of Gaussian distribution of injected ion to a depth direction of the substrate 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a silicon wafer, and more particularly to a method for manufacturing a silicon wafer capable of effectively removing damage caused by ion implantation while suppressing diffusion of ions implanted by a short-time heat treatment.

Conventionally, a method using ion implantation has been widely used as a method of diffusing impurities into a silicon substrate. However, in the method using ion implantation, there is a possibility that damage to silicon atoms in the vicinity of the surface of the silicon substrate due to ion implantation may occur, and this damage causes the epitaxial layer to be vaporized on the silicon substrate after ion implantation. When the phase growth is performed, the crystal defects extend to the surface of the epitaxial layer along with the epi growth, and as a result, there is a problem that the silicon crystal defects can be detected on the wafer surface.
In order to solve this problem, conventionally, a method of performing a heat treatment on a wafer to remove damage caused by ion implantation after ion implantation into a silicon substrate has been widely performed. Also, after forming an ion implantation mask on the surface of the first epitaxial layer and performing ion implantation, prior to vapor phase growth of the second epitaxial layer, a heat treatment for crystallinity recovery and carrier activation is performed in a hydrogen atmosphere. A technique to be performed therein has been proposed (see, for example, Patent Document 1).
JP 2001-139399 A

  However, in the method of performing heat treatment for removing damage caused by ion implantation after ion implantation into the silicon substrate, the implanted device diffuses into the silicon substrate due to the heat treatment, and the desired device characteristics cannot be obtained. was there.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a silicon wafer that can effectively and efficiently remove implantation damage while suppressing diffusion of implanted ions. And

In order to solve the above problems, a method for producing a silicon wafer of the present invention includes an implantation step of performing ion implantation on a substrate made of a silicon single crystal,
A damage removing step of etching the substrate surface in order to remove damage caused by ion implantation on the ion-implanted substrate by heat treatment in an etching gas atmosphere having a vacancy implantation effect;
An epitaxial step of forming an epitaxial layer by epitaxial growth.
In the silicon wafer manufacturing method described above, the etching removal amount in the damage removal step is 5 to 120% with respect to the depth Rp that is the maximum concentration position in the substrate depth direction distribution of ions implanted into the substrate. Preferably, the thickness is
In the above-described silicon wafer manufacturing method, the etching gas atmosphere in the damage removing step may include hydrogen chloride gas, and the concentration of the hydrogen chloride gas may be 1 to 50%.
Moreover, in the manufacturing method of the silicon wafer mentioned above, it can be set as the method whose processing time in the said damage removal process is 30 to 120 second.
In the manufacturing method of the silicon wafer mentioned above, it can be set as the method whose process temperature in the said damage removal process is 1000-1210 degreeC.
Moreover, in the manufacturing method of the silicon wafer mentioned above, it can be set as the method of having the protective film formation process which forms the protective oxide film which protects the said board | substrate from the damage by ion implantation before the said implantation process.

According to the method for manufacturing a silicon wafer of the present invention, by performing heat treatment in an etching gas atmosphere having a vacancy injection effect, the substrate surface is etched for damage caused by ion implantation on the ion-implanted substrate. Since there is a damage removal process that removes damage at the same time as silicon, in addition to the damage removal effect due to the removal of the substrate surface area including damage due to etching removal, the vicinity of the substrate surface is constituted by etching gas having a hole injection effect The effect of removing damage caused by increasing the number of vacancies (vacancies) in the silicon single crystal to promote the rearrangement of silicon atoms during the heat treatment can be obtained.
Therefore, the method for producing a silicon wafer of the present invention is very excellent in the effect of removing damage by heat treatment. For this reason, it is possible to obtain an epitaxial wafer having no defect by performing the epi process after the damage removing process of the present invention. In addition, the damage removal process and the epi process of the present invention are performed in the same epi growth furnace, that is, before the epitaxial growth gas is supplied to the epi growth furnace with the substrate to be processed set in the epi growth furnace. By only supplying the etching gas of the present invention, it is possible to perform an epi process continuously after the damage removing process of the present invention, and thereby a high quality epitaxial wafer can be produced at a low cost in an extremely short working time. Can be obtained.

  As described above, in the manufacturing method of the present invention, the effect of removing the damage by the heat treatment is very excellent, so that the damage caused by the ion implantation can be sufficiently removed even if the amount of etching removal in the damage removing process is very small. Specifically, the etching removal amount in the damage removal step can be set to a thickness of 5% to 120% of the maximum concentration depth Rp of the Gaussian distribution of implanted ions in the depth direction of the substrate, preferably The thickness can be 10 to 100%, more preferably 30 to 50%, and still more preferably 30 to 40%. When the etching removal amount is as small as about 5 to 30 to 50% of the maximum concentration depth Rp, it is preferable to employ hydrogen chloride gas as the etching gas. In this case, for example, by heat treatment in nitrogen gas Compared with the case of removing damage due to ion implantation, the heat treatment time can be shortened, so that diffusion of implanted ions can be reduced. For this reason, it is possible to realize a high-quality silicon wafer in which ions are implanted into the substrate with a desired amount of ions.

  Thus, according to the method for producing a silicon wafer of the present invention, when an ion is implanted into a substrate with a desired amount of ions, and an epitaxial layer is grown on the produced silicon wafer. Thus, a high-quality silicon wafer can be obtained, which is very little damaged by ion implantation that causes crystal defects detected in (1). Therefore, a device manufactured using the silicon wafer manufactured according to the present invention has a high quality having desired device characteristics.

In the present invention, when the etching removal amount in the damage removal step is less than 5% of the maximum concentration depth Rp, damage due to ion implantation cannot be sufficiently removed. Further, as the amount of etching removal increases, the damage removal effect is improved, but the heat treatment time and the amount of ions removed by etching removal increase, and the amount of ions serving as a dopant decreases. When the etching removal amount in the damage removal step exceeds 120% of the maximum concentration depth Rp, the amount of ions remaining after the heat treatment becomes too small, and it becomes difficult to obtain the effect due to the ion implantation process. Further, if the etching removal amount exceeds 120% of the maximum concentration depth Rp, the heat treatment time must be lengthened, and there is a possibility that the diffusion of implanted ions cannot be sufficiently suppressed.
Here, the ion (impurity) concentration into which ions are implanted is distributed according to a Gaussian distribution when the substrate thickness (depth) direction is taken on the horizontal axis and the ion concentration is taken on the vertical axis. Therefore, the maximum concentration position Rp is a position (depth) at which the vertex of the Gaussian distribution comes, which is defined by the ion implantation energy.

  In the above-described silicon wafer manufacturing method, the concentration of the hydrogen chloride gas in an atmosphere containing hydrogen chloride gas as an etching gas is set to 1 to 50%, thereby removing damage while suppressing diffusion of implanted ions. Therefore, the etching removal amount in the damage removal process can be controlled with high accuracy. If the concentration of the hydrogen chloride gas in the atmosphere containing hydrogen chloride gas is less than 1%, the etching rate may be slowed to cause a shortage of etching removal, and damage due to ion implantation may not be sufficiently removed. Therefore, it is not preferable. In addition, since the etching rate becomes slow, the heat treatment time has to be lengthened, and because the treatment time becomes long, impurities may diffuse and the desired impurity concentration may not be maintained. This is not preferable because there is a possibility that it cannot be suppressed. If the concentration of the hydrogen chloride gas in an atmosphere containing hydrogen chloride gas exceeds 50%, the etching rate is too high to control the etching removal amount, and the amount of ions remaining after the heat treatment does not become a desired amount. In addition to fears, the surface of the substrate may become rough, and accordingly, crystal defects may be derived in the epitaxial layer during the epi process, which is not preferable.

Moreover, in the silicon wafer manufacturing method described above, by setting the heat treatment time to 30 to 120 seconds, it is possible to accurately control the etching removal amount in the damage removal step while suppressing the diffusion of the implanted ions.
If the heat treatment time is less than 30 seconds, the amount of etching removal becomes insufficient, and damage due to ion implantation may not be sufficiently removed. Further, when the heat treatment time exceeds 120 seconds, in addition to the diffusion of impurities, the amount of ions remaining after the heat treatment is reduced, and there is a possibility that the effect due to the ion implantation treatment cannot be obtained.

Moreover, in the silicon wafer manufacturing method described above, by setting the heat treatment temperature to 1000 to 1210 ° C., it is possible to accurately control the etching removal amount in the damage removal step while suppressing the diffusion of the implanted ions.
When the temperature of the heat treatment is less than 1000 ° C., the etching rate is slow, so that the amount of etching removal becomes insufficient, and damage due to ion implantation may not be sufficiently removed. Further, since the etching rate becomes slow, the heat treatment time has to be lengthened, and there is a possibility that the diffusion of implanted ions cannot be sufficiently suppressed. Further, when the heat treatment temperature exceeds 1210 ° C., slip may occur in the vicinity of the portion indicating the substrate during the heat treatment, the slip may extend to the substrate surface and reach the surface. The strength may decrease, which is not preferable.
Further, if the temperature exceeds 1220 ° C., slip generation and strength reduction are extremely unfavorable, and heat treatment is not performed at 1250 ° C. or higher.

  In addition, in the above-described silicon wafer manufacturing method, by forming a protective oxide film that protects the substrate from damage caused by ion implantation before the implantation step, damage caused by ion implantation can be reduced. In addition to the removal effect, it is possible to obtain a high-quality silicon wafer with less damage due to ion implantation.

  According to the present invention, since the implantation damage can be effectively removed in a short time while suppressing the diffusion of the implanted ions, the ions are implanted into the substrate with a desired amount of ions. A high-quality silicon wafer with very little damage can be obtained at a low cost in a short working time.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

“First Embodiment”
FIG. 1 is a process cross-sectional view for explaining an example of the silicon wafer manufacturing method of the present invention.
In this embodiment, first, as shown in FIG. 1A, as a protective film forming step, a substrate 1 that has been subjected to slicing, chamfering, grinding, etching, polishing, etc. from a silicon single crystal is installed in a heat treatment furnace. By thermally oxidizing the substrate 1 in the furnace, a protective oxide film 2 is formed on the front and back surfaces and the entire side surface of the substrate 1 as shown in FIG. The protective oxide film 2 has a thickness capable of exhibiting a damage reduction effect in ion implantation, as will be described later, and can have a thickness of about 1 to 3 μm, for example.
Here, the drum insulation film formation step can be performed by a batch furnace or the like, and the treatment temperature and treatment time can be set depending on the thickness of the protective oxide film 2 to be formed. In the case of forming the protective oxide film, it can be carried out in the atmosphere under a processing condition of about 1100 ° to 1210 ° for 1 to 5 hours.

Next, as an implantation step, in the ion implantation apparatus equipped with the ion beam generator, as shown in FIG. 1C, the substrate 1 is subjected to ion implantation processing from above the protective oxide film 2 and diffused near the surface of the substrate 1. Layer 3 is formed. Examples of elements to be ion-implanted in this implantation step include boron and the like in the case of a p-type substrate and arsenic, phosphorus, and antimony in the case of an n-type substrate, corresponding to the type of substrate to be formed. be able to.
The ion implantation energy and the amount of ion implantation at this time are defined by how much impurity concentration is distributed in what depth as a silicon wafer to be finally produced.

Thereafter, as a protective film removing step, as shown in FIG. 1D, wet etching for removing silicon oxide with hydrofluoric acid or the like is performed, and the protective oxide film 2 on the entire front and back surfaces and side surfaces of the substrate 1 is completely removed. Thus, the diffusion layer 3 is exposed. Here, the processing conditions such as the concentration of hydrofluoric acid and the processing time can be appropriately set as long as the oxide film can be completely removed, the processing time does not become redundant, surface roughness, etc. occur. As long as the undesirable phenomenon does not occur, it can be appropriately performed.
In order to prevent auto-doping in the epi process, which is a subsequent process, it is possible to remove only the oxide film on the front surface side of the substrate 1 and not to remove the back surface side and the side surface.

When the protective oxide film 2 is as thin as 0.5 μm or less, it is possible to perform this process in an epi growth furnace as the protective film removing step. In this case, it is possible to perform the same process as the natural oxide film removal performed by so-called hydrogen baking or the like in a hydrogen gas before the next damage removing step in the epi growth furnace.
In this case, the gas can be supplied in the epi-growth furnace so as to have the above gas atmosphere, and the processing can be performed under the processing conditions of about 1100 ° to 1210 ° for 5 to 100 minutes. As processing conditions, depending on the thickness of the oxide film, etc., as long as the oxide film can be completely removed, it is not limited to this condition. It can be appropriately performed within a range in which other undesirable phenomenon does not occur. In this case, since a series of steps can be performed only by the processing in the epi growth furnace, the working time can be shortened.

Next, as a damage removing step, as shown in FIG. 1 (e), an ion-implanted substrate is subjected to heat treatment in an atmosphere containing hydrogen chloride gas, which is an etching gas having a vacancy implantation effect, in an epi-growth furnace. Damage due to ion implantation on 1 is removed.
In the damage removing step, by etching a region having a depth range described later from the surface of the substrate 1, damage removal is directly performed by removing the substrate surface region including damage, and an etching gas is used. By using a gas having a vacancy injection effect, the number of vacancies (vacancies) in the silicon single crystal constituting the vicinity of the surface of the substrate 1 increases, and the rearrangement of silicon atoms is promoted during the heat treatment. The damage can be removed from the surface of the substrate 1 to the depth range described later. As a result, when the epitaxial layer is grown, the damage can be removed to a state where there is no crystal defect on the surface of the epitaxial layer.

In this embodiment, the etching allowance (removal amount) in the damage removal step, that is, the decrease amount of the thickness of the substrate 1 in the depth (thickness) direction is the Gauss of implanted ions with respect to the depth direction of the substrate 1. The thickness is set to 5 to 120%, preferably 10 to 100%, more preferably 30 to 50%, and still more preferably 30 to 40% of the maximum concentration depth Rp of the distribution. The amount of etching removal can be controlled by appropriately adjusting the concentration of hydrogen chloride gas in the atmosphere containing hydrogen chloride gas, the heat treatment time, and the heat treatment temperature.
The concentration of the hydrogen chloride gas in the atmosphere containing hydrogen chloride gas is preferably 1 to 50%, the heat treatment time is preferably 30 to 120 seconds, and the heat treatment temperature is 1000 to 1210 ° C. It is desirable that
The atmosphere containing the etching gas in the damage removing step is one in which oxygen gas is purged and contains, for example, 1 to 50% hydrogen gas and / or inert gas in addition to hydrogen chloride gas. be able to.

  As a result, a silicon substrate 1A is obtained in which ions are implanted into the substrate at a desired ion concentration / distribution, and damage from the ion implantation is removed.

  Thereafter, in the epi growth furnace, the supply of the etching gas is stopped, and an epitaxial layer forming gas such as a silane system is supplied. As shown in FIG. A predetermined epitaxial layer 4 is grown on the substrate 1A, and the thermal oxide film 2 on the back surface and the side surface is removed as shown in FIG. 1G to obtain a silicon wafer W provided with the epitaxial layer 4. it can. In the present embodiment, since the epitaxial layer 4 is grown on the silicon substrate 1A with very little damage due to ion implantation, a silicon wafer with very few crystal defects detected when the epitaxial layer 4 is grown is obtained. Is possible.

  The present invention is not limited to the above-described example. For example, in the above-described embodiment, the implantation step is performed after the protective oxide film 2 is provided. However, the protective oxide film 2 may not be provided. . Even in the case where the protective oxide film 2 is not provided, in the present invention, damage due to ion implantation can be sufficiently removed in the damage removing step. Further, when the protective oxide film 2 is not provided, the manufacturing process can be simplified and the number of heat treatments can be reduced.

“Second Embodiment”
In the second embodiment, only the parts different from the above-described first embodiment will be described, and redundant description will be omitted. In the first embodiment described above, the manufacturing method for forming the diffusion layer 3 on the entire surface of the substrate 1 has been described. In the second embodiment, the diffusion layer 3 is selectively formed on a part of the surface of the substrate 1. A manufacturing method will be described.

FIG. 2 is a process sectional view for explaining another example of the method for producing a silicon wafer of the present invention.
In this embodiment, first, a substrate 1 made of silicon single crystal is prepared as shown in FIG. 2A, and then a CVD method or the like is applied over the entire surface of the substrate 1 as shown in FIG. 2B. As shown in FIG. 2C, the oxide film 5 is patterned by using a photolithographic method to expose a part of the surface of the substrate 1 as shown in FIG.
Next, as a protective film forming step, as shown in FIG. 2 (d), a protective oxide film 2 made of a thermal oxide film is formed on the exposed portion of the substrate 1, and as shown in FIG. 2 (e). The injection process is performed in the same manner as in the first embodiment. Subsequently, as shown in FIG. 2F, the protective oxide film 2 and the oxide film 5 are removed by etching using an etchant such as hydrofluoric acid as the protective film removing step. Thereafter, as shown in FIG. 2G, the damage removing step is performed in the same manner as in the first embodiment.

As a result, a silicon substrate 1A ′ in which ions are partially implanted into a partial region in the substrate with a desired ion distribution / concentration and damage from the ion implantation is removed can be obtained.
Thereafter, as shown in FIG. 2H, the silicon wafer W ′ provided with the epitaxial layer 4 can be obtained by performing the epitaxial growth process in the same manner as in the first embodiment.
In the present embodiment, since the epitaxial layer 4 is grown on the silicon substrate 1A ′ that is very little damaged by ion implantation, the silicon wafer W ′ that has very few crystal defects detected when the epitaxial layer 4 is grown. Can be obtained.

  In addition, the ion-implanted silicon wafer manufactured in the present invention is preferable because it has very few crystal defects detected when an epitaxial layer is grown on the silicon wafer. This is also applicable to the case where the damage removal step is performed as the final step of the silicon wafer manufacturing, not when the damage is not grown, that is, when the damage removal step is performed during the silicon wafer manufacturing step.

"Experimental Example 1-Experimental Example 2"
An epitaxial silicon wafer was manufactured by the following method.
First, a substrate 1 made of a silicon single crystal is placed in an epi growth furnace, and boron is ion-implanted onto the substrate 1 with an implantation energy of 70 keV and an implantation amount of 1 × 10 ¹⁵ atoms / cm ^2. Formed (injection step). Then, the Gaussian distribution of the implanted ions in the depth direction of the substrate 1 into which ions were implanted was examined. The result is shown in FIG. As shown in FIG. 3, the maximum concentration depth Rp of the Gaussian distribution of implanted ions in the depth direction of the substrate 1 was 0.3 μm.

  Next, the damage caused by ion implantation on the ion-implanted substrate 1 was removed by etching by performing a heat treatment in a hydrogen atmosphere containing hydrogen chloride gas having a concentration shown in Table 1 and the heat treatment temperature and treatment time shown in Table 1 (damage removal). Process).

Table 1 shows the etching removal amount in the damage removal step. The etching removal amount here was determined by measuring the change (reduction amount) in the thickness of the epitaxial film before and after the etching using FT-IR (Fourier transform infrared spectroscopic analyzer).
Table 1 shows the amount of implanted ions remaining after the heat treatment in the damage removing step. Here, the amount of implanted ions was determined by measuring the ion current at the time of ion implantation and converting it to a previously determined implantation amount.

After the damage removing step, an epitaxial silicon wafer was obtained by growing the epitaxial layer 4 on the obtained silicon wafer in the epitaxial growth furnace under the following epitaxial conditions. Laser scattering is performed by irradiating the surface of the wafer with a laser beam having a size of 0.13 μm or more among the crystal defects on the surface of the obtained epitaxial silicon wafer and observing the state of the wafer surface by the intensity of the scattered light. Detected by meter.
The results are shown in Table 1.

"Conventional example"
An epitaxial silicon wafer was manufactured by the following method.
First, an implantation process was performed in the same manner as in Experimental Example 1 on the same substrate 1 as in Experimental Example 1. Thereafter, as shown in Table 1, in a hydrogen atmosphere containing no hydrogen chloride gas, heat treatment is performed at the same heat treatment temperature and treatment time as in Experimental Example 1, and in the same manner as in Experimental Example 1, the amount of etching removed in the heat treatment and after the heat treatment The amount of implanted ions remaining was determined. The results are shown in Table 1.
After the heat treatment, an epitaxial silicon wafer was obtained by growing an epitaxial layer on the obtained silicon wafer in the same manner as in Experimental Example 1. Then, the number of crystal defects on the surface of the obtained epitaxial silicon wafer was detected in the same manner as in Experimental Example 1. The results are shown in Table 1.

As shown in Table 1, in Experimental Examples 1 to 2 in which the etching removal amount in the damage removing process is 5 to 120% of the maximum concentration depth Rp, the heat treatment is performed in an atmosphere in which the number of crystal defects does not include hydrogen chloride gas. This is much less than the conventional example. Specifically, the number of defects was 1254 in the conventional example, but 20 in Example 1 and 7 in Example 2.
In Experimental Example 1 where the etching removal amount is 43% of Rp, the amount of implanted ions remaining after the heat treatment is 98%, and it can be confirmed that the amount of implanted ions removed by the damage removal step is very small. It was. In Experimental Example 2 where the etching removal amount was 117% of Rp, the amount of implanted ions remaining after the heat treatment was 23%.

FIG. 1 is a process cross-sectional view for explaining an example of the silicon wafer manufacturing method of the present invention. FIG. 2 is a process sectional view for explaining another example of the method for producing a silicon wafer of the present invention. FIG. 3 is a graph showing a Gaussian distribution of implanted ions with respect to the depth direction of the implanted substrate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Protective oxide film, 3 ... Diffusion layer, 4 ... Epitaxial layer, 5 ... Oxide film.

Claims (6)

An implantation step of performing ion implantation on a substrate made of silicon single crystal;
A damage removing step of etching the substrate surface in order to remove damage caused by ion implantation on the ion-implanted substrate by heat treatment in an etching gas atmosphere having a vacancy implantation effect;
An epitaxial process for forming an epitaxial layer by epitaxial growth, and a method for producing a silicon wafer.   The etching removal amount in the damage removal step is set to a thickness of 5 to 120% with respect to a depth Rp that is a maximum concentration position in the substrate depth direction distribution of ions implanted into the substrate. The method for producing a silicon wafer according to claim 1.   The silicon wafer production according to claim 1 or 2, wherein the etching gas atmosphere in the damage removing step includes hydrogen chloride gas, and the concentration of the hydrogen chloride gas is 1 to 50%. Method.   4. The method for producing a silicon wafer according to claim 1, wherein a processing time in the damage removing step is 30 to 120 seconds.   The process temperature in the said damage removal process is 1000-1210 degreeC, The manufacturing method of the silicon wafer in any one of Claim 1 to 4 characterized by the above-mentioned.   6. The method of manufacturing a silicon wafer according to claim 1, further comprising a protective film forming step of forming a protective oxide film for protecting the substrate from damage caused by ion implantation before the implanting step. .

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