JP4978396B2 - Epitaxial wafer manufacturing method - Google Patents

Description

  The present invention relates to an epitaxial wafer manufacturing method in which an epitaxial layer is formed on a silicon single crystal wafer.

  Usually, as a silicon wafer for manufacturing a semiconductor device, a silicon wafer is used in which a wafer is cut out from a silicon single crystal rod grown by the Czochralski method (CZ method) and the surface is polished into a mirror surface. However, in many cases, silicon single crystals grown by the CZ method have so-called glow-in defects such as octahedral void defects called COP, which are formed by collecting silicon vacancies in the crystal, and this is the oxide film of a silicon wafer. It is a major cause of pressure breakdown.

  A silicon wafer manufactured by the CZ method contains supersaturated interstitial oxygen and a large number of oxygen precipitation nuclei formed during the cooling after the crystal pulling. When a semiconductor device is manufactured using this supersaturated interstitial oxygen and a silicon wafer containing a large number of oxygen precipitation nuclei, interstitial oxygen precipitates in the oxygen precipitation nuclei during the heat treatment in the device manufacturing process, and the inside of the silicon wafer. In addition, a large number of oxygen precipitates and minute defects resulting from this occur. When such oxygen precipitates and minute defects resulting from this are present in the bulk portion of the wafer, they become gettering sites (usually called the IG (Internal Gettering) effect) and are suitable for device manufacturing. However, it is known that the operation of the semiconductor device is hindered when it exists in the device manufacturing region near the wafer surface.

  In recent years, as a countermeasure against the above-mentioned COP defect, in order to make the device fabrication region near the surface of the silicon wafer defect-free, a CZ silicon mirror wafer was used as a base silicon wafer, and a silicon single crystal was epitaxially grown thereon by a CVD method. The demand for epitaxial wafers is increasing.

  However, the epitaxial wafer has a problem that the IG capability is low as compared with the silicon mirror wafer. That is, in the epitaxial wafer, the growth process of the epitaxial layer is at a high temperature of about 1050 ° C. to 1150 ° C., and the rate of temperature rise is high at that time. Nuclei decrease or disappear, and vacancy due to Si implantation (hereinafter also referred to as vacancies) is extinguished during the epitaxial layer growth process. Precipitates are not easily formed, and the IG capability is reduced as compared with a normal mirror wafer.

  Conventionally, as a manufacturing method for solving this problem and realizing an epitaxial wafer with high IG capability, a method of thermally treating a silicon single crystal wafer doped with nitrogen at the time of single crystal growth and then growing an epitaxial layer on the wafer surface (for example, Patent Document 1), a method of rapidly heating a silicon single crystal wafer doped with both nitrogen and carbon during single crystal growth, and then growing an epitaxial layer on the wafer surface (see, for example, Patent Document 2), carbon during single crystal growth A silicon single crystal wafer doped with a heat treatment by resistance heating, and then an epitaxial layer is grown on the wafer surface at a low temperature (less than 1000 ° C.) (see, for example, Patent Document 3), a silicon single crystal doped with carbon during single crystal growth Grow an epitaxial layer on the surface of the wafer, then A method of heat-treating (for example, see Patent Document 4) has been devised by rapid heating Eha.

  However, in the epitaxial wafer manufactured by the manufacturing method described above, oxygen gettering nuclei are not sufficient, so that proximity gettering in the vicinity of the epitaxial layer is weak, and a desired gettering ability cannot be obtained. In particular, a crystal doped with nitrogen and carbon has an advantage that the defect size is smaller than a crystal doped with carbon only, so that the defect easily disappears during epi-growth, but also has a disadvantage that oxygen does not easily precipitate. . Further, the defects that could not be eliminated during the epi growth changed into a plate shape, causing the epi defects.

JP 2001-274167 A JP 2005-515633 A JP 2001-237247 A JP 2006-40980 A

  The present invention provides an epitaxial wafer manufacturing method in which epitaxial defects are not formed in an epitaxial layer, and high density BMD is formed in a bulk portion, thereby manufacturing an epitaxial wafer having a strong gettering capability. It aims to provide a method.

In order to solve the above-mentioned problems, in the present invention, in the method for producing an epitaxial wafer, a Czochralski method is used to grow a silicon single crystal rod by doping only carbon except for a resistance control dopant. An epitaxial wafer characterized in that a rod is sliced and processed into a silicon single crystal wafer, followed by heat treatment using a rapid heating / rapid cooling (RTA) apparatus, and then an epitaxial layer is formed on the surface of the single crystal wafer. that provides a method of manufacturing.

  Thus, in the method for producing an epitaxial wafer of the present invention, at the time of growing a single crystal, only carbon is doped except for a dopant for resistance control, and heat treatment is performed by an RTA apparatus. As a result, holes are injected into the wafer, and a high-density hole injection layer is formed in the vicinity of the wafer surface. Even if interstitial silicon is injected into the wafer during the epi-growth process, the vacancies injected into the wafer surface capture the interstitial silicon, thus preventing interstitial silicon from being injected into the wafer bulk. Can do. Thus, even after the epitaxial layer is formed, oxygen precipitation nuclei in the wafer bulk portion can be secured. Therefore, the oxygen precipitation inherent in the wafer occurs during the heat treatment in the device process, and a sufficient amount of BMD is formed for gettering. be able to. Further, since nitrogen is not doped, no plate-like defects are generated, and no epi-defects are generated during the formation of the epitaxial layer. Therefore, an epitaxial wafer having high gettering capability and no epitaxial defects formed in the epitaxial layer can be manufactured.

Moreover, it is not preferable that the concentration of carbon doped in the silicon single crystal during growing by the Czochralski method or 1.0 ppma.
By growing the single crystal so that the carbon concentration in the silicon single crystal wafer is in the above range, the amount of oxygen precipitated during the heat treatment can be increased, thereby enhancing the gettering ability of metal impurities. Can do.

Furthermore, the RTA apparatus heat treatment using a can, the atmosphere non-oxidizing atmosphere, the heat treatment temperature in the range of 1150 to 1250 ° C., the treatment time have preferred to be at least 10 seconds.
By performing the heat treatment under such conditions, the heat treatment conditions can be set such that a sufficient amount of holes can be injected into the wafer in a short time.

  As described above, in the epitaxial wafer manufacturing method of the present invention, a high-density hole injection layer is formed in the vicinity of the wafer surface, and even if interstitial silicon is injected into the wafer during the epi-growth process, Capture interstitial silicon. Therefore, even after the epitaxial layer is formed, oxygen precipitation nuclei in the wafer bulk portion can be ensured. Therefore, the oxygen precipitation inherent in the wafer occurs during the heat treatment in the device process, and a necessary and sufficient amount of BMD can be formed for gettering. it can. Further, since nitrogen is not doped, no plate defects are generated, and therefore no epi defects are generated in the epitaxial layer. Therefore, an epitaxial wafer having high gettering capability and no epitaxial defects formed in the epitaxial layer can be manufactured.

Hereinafter, the present invention will be described more specifically.
As described above, there is no need to develop an epitaxial wafer manufacturing method having strong gettering ability by forming no epitaxial defect in the epitaxial layer and forming a high-density BMD in the bulk portion. It was.

  Therefore, the present inventors have found that oxygen precipitation nuclei disappear due to elements that do not form crystal defects on the wafer surface even when doped into a silicon single crystal wafer, and interstitial silicon implanted into the wafer during epi growth. We intensively investigated whether there was a treatment to prevent.

  As a result, the present inventors dope the process of injecting vacancies into a wafer prepared from the single crystal by doping only carbon except for the resistance control dopant during single crystal growth, and capturing interstitial silicon. Thus, the inventors have found that oxygen precipitation nuclei can be secured after the formation of the epitaxial layer and that no plate defects are formed, so that no epi defects are generated, and the present invention has been completed.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
The epitaxial wafer manufactured by the manufacturing method of the present invention is obtained by subjecting a silicon single crystal wafer doped only with carbon except for a resistance control dopant during the growth of the silicon single crystal to an epitaxial surface on the surface after heat treatment by an RTA apparatus. A layer is formed.

FIG. 1 shows a conceptual cross-sectional view of an epitaxial wafer manufactured by the manufacturing method of the present invention.
In the epitaxial wafer manufactured by the manufacturing method of the present invention, vacancies (V) are injected into the silicon single crystal wafer doped with carbon (C _s ) at the time of single crystal growth by RTA treatment, and the hole injection layer 13 And an epitaxial layer 11 is further formed on the wafer surface.

The RTA treatment injects vacancies (V) in the vicinity of the wafer surface, and carbon (C _s ) doped in advance during this heat treatment may become interstitial carbon (C _i ), These (C _s ) (C _i ) may form a carbon composite in the hole injection layer 13.
The vacancies (V) and the carbon composite capture the interstitial silicon (Si _I ) injected during the formation of the epitaxial layer 11, so that the vacancies (V) existing in the wafer bulk portion 12 can be converted into the epitaxial layer. 11 can be secured after formation, oxygen precipitation is promoted, BMD is formed in the bulk of the wafer during heat treatment in the device process, and the gettering ability can be enhanced.

  The manufacturing method of the epitaxial wafer of the present invention can be set as the following steps, and an example thereof is shown below, but the manufacturing method of the epitaxial wafer of the present invention is not limited to the following.

  In the present invention, a silicon single crystal rod doped with carbon is grown by the Czochralski method. In order to dope carbon into the single crystal rod, a general method may be used. When the seed crystal was brought into contact with the melt of the polycrystalline silicon raw material contained in the quartz crucible, and the silicon single crystal rod having a desired diameter was grown by rotating it slowly, the atmosphere gas contained carbon. A high-purity carbon powder can be added to the raw material melt as a dopant, and a carbon lump (block-like carbon) can be previously placed in a quartz crucible. Furthermore, carbon fibers and / or silicon carbide fibers can be used as the dopant.

At this time, the amount of carbon dope in the single crystal rod can be controlled by adjusting the carbon gas concentration or introduction time, and the amount of added carbon powder.
The carbon concentration doped during the growth of the single crystal rod can be 1.0 ppma or more. This makes it possible to sufficiently increase the density of oxygen precipitates that are deposited during the heat treatment in the device manufacturing process, thereby further enhancing the gettering ability of the wafer.
Here, it is desirable that the carbon concentration to be doped is 5.0 ppma as an upper limit. By setting the upper limit to 5.0 ppma, it is possible to suppress the single crystallization of the silicon single crystal.

Next, the grown silicon single crystal rod is sliced by a cutting device such as an inner peripheral slicer or a wire saw, and then a silicon single crystal wafer is manufactured through processes such as chamfering, lapping, etching, and polishing.
Here, the area of the glow-in defect of the silicon single crystal wafer is not particularly limited. For example, the OSF area may be used. This is because, since nitrogen is not doped, no defects on the plate are formed, and no epi defects are generated in the subsequent epitaxial growth.

Thereafter, heat treatment is performed on the produced silicon single crystal wafer. The heat treatment is performed using a rapid heating / rapid cooling (RTA) apparatus.
In this heat treatment, the atmosphere can be a non-oxidizing atmosphere, the heat treatment temperature can be in the range of 1150 to 1250 ° C., and the treatment time can be 10 seconds or longer.
By performing the heat treatment under such conditions, it is possible to achieve heat treatment conditions that allow a sufficient amount of holes to be injected into the silicon single crystal wafer in a short time. Therefore, the manufacturing cost can be reduced, and in addition, an epitaxial wafer having a strong gettering ability can be manufactured.

An epitaxial layer is formed on the surface of the silicon single crystal wafer after the heat treatment. General conditions can be used to form the epitaxial layer.
For example, a source gas such as SiHCl ₃ is introduced into the chamber using H ₂ as a carrier gas, and epitaxial growth is performed by CVD at about 1050 to 1250 ° C. on a wafer placed on the susceptor.

  Thus, according to the present invention, vacancies are injected into the silicon single crystal wafer by the RTA process, and a high-density vacancy injection layer is formed in the vicinity of the wafer surface. Therefore, even if interstitial silicon is implanted into the wafer during epi growth, the vacancies can capture the interstitial silicon and prevent the interstitial silicon from being implanted into the wafer bulk. This prevents interstitial silicon and vacancies from bonding and disappearance of oxygen precipitation nuclei, and ensures accelerated oxygen precipitation nuclei based on carbon doping in the wafer bulk even after the epitaxial layer is formed. Therefore, oxygen precipitation occurs during the heat treatment in the device process, and the BMD can be easily formed. Moreover, since nitrogen is not doped, no plate defects are formed, and no epi defects are generated in the epitaxial layer. Therefore, an epitaxial wafer having high gettering capability and no epitaxial defects formed in the epitaxial layer can be manufactured.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
First, a silicon single crystal rod having a diameter of 200 mm, an N type (phosphorus dope), and a crystal orientation <100> was grown by the Czochralski method. At this time, carbon was doped into the single crystal by previously putting carbon powder in a quartz crucible. As shown in Table 1 described later, the carbon concentration was controlled so that the carbon doping amount was a predetermined value in the range of 0.5 to 3.0 ppma. The grown silicon single crystal rod was 10 Ω · cm.
Thereafter, the silicon single crystal rod was sliced to produce a silicon single crystal wafer. The oxygen concentration of the produced silicon single crystal wafer was in the range of 16.5 to 16.8 ppma. Note that oxygen is not doped but is inevitably mixed from a quartz crucible in the CZ method.
The produced silicon single crystal wafer was subjected to a predetermined temperature and 10 seconds in a range of 1100 to 1300 ° C. as shown in Table 1 described later using an RTA apparatus in an argon atmosphere with an ammonia concentration of 3.0%. The heat treatment was performed under the following conditions.
Thereafter, an epitaxial layer was formed on the wafer surface under a processing condition of 1130 ° C. to produce an epitaxial wafer. The thickness of the formed epitaxial layer is about 6 μm.

The characteristics of the produced epitaxial wafer were evaluated as follows.
Epi defects on the surface of the epitaxial wafer were observed using a particle counter.
Moreover, oxygen precipitation heat processing was performed and BMD density was evaluated. Oxygen precipitation heat treatment conditions were 800 ° C. · 4 hours and 1000 ° C. · 16 hours. Then, the residual oxygen concentration change (ΔO _i: oxygen precipitation amount) of the wafer before and after the oxygen precipitation heat treatment was evaluated by FTIR.
Further, the epitaxial wafer after the oxygen precipitation heat treatment was cleaved and etched, and then the cross section of the epitaxial layer and the lower part of the epitaxial layer was observed to evaluate the BMD distribution and the BMD density.

(Comparative Example 1)
In the example, an epitaxial wafer was produced under the same conditions as in the example except that the single crystal was doped with carbon and also with nitrogen. The doping amount of nitrogen was 6 × 10 ¹³ atoms / cm ³ . And evaluation similar to the Example was performed about the produced wafer.

(Comparative Example 2)
In the examples, epitaxial wafers were produced under the same conditions as in the examples, except that the heat treatment after producing the silicon single crystal wafer was resistance heating. The resistance heating was performed at 1100 to 1200 ° C. for 10 minutes in a 100% nitrogen atmosphere. And evaluation similar to the Example was performed about the produced wafer.

  The results of evaluating the presence or absence of epi defects and the BMD density in Examples and Comparative Examples 1 and 2 are summarized in Tables 1, 2, and 3, respectively.

Here, FIG. 2 shows an example of the result of observing the cleavage plane of the epitaxial wafer after the oxygen precipitation heat treatment in the example.
From Table 1, the epitaxial wafer of an Example did not generate | occur | produce the epi defect in an epitaxial layer in any case irrespective of carbon concentration and RTA temperature. And when the carbon concentration doped was constant, it turned out that BMD density becomes high, so that RTA temperature is high. It was also found that when the RTA temperature is constant, the BMD density increases as the doped carbon concentration increases.
From FIG. 2, it was found that even when the RTA temperature was 1170 ° C., BMD was formed under the epitaxial layer as in the case of 1200 ° C.
It was also found that the higher the carbon concentration, the more the OSF of the crystal can be suppressed.

FIG. 3 is a diagram showing an example of an epi defect on the surface of the epitaxial wafer in Example and Comparative Example 1. In FIG.
From Table 2, it was found that the wafer of Comparative Example 1 doped with nitrogen together with carbon during single crystal growth had a lower BMD density than the wafer of Example doped with only carbon. Furthermore, it has been found that the occurrence of epi defects cannot be suppressed at all. This is considered to be because oxygen precipitation nuclei in the single crystal become smaller in the single crystal growth stage when nitrogen is also doped as compared with the case of doping only with carbon. As a result, when the precipitation nuclei disappear or do not disappear by RTA, the defect form changes to a plate shape, and as a result, there are few BMDs and epi defects (SF) are generated.
As shown in FIG. 3, when carbon and nitrogen are simultaneously doped into a single crystal, a large number of plate-like defects (stacking defects) are generated in the outer peripheral portion of the epitaxial layer, thereby causing epitaxial defects in the epitaxial layer. I understood that.

  On the other hand, as shown in Table 3, in the heat treatment by resistance heating of Comparative Example 2, since the supply amount of vacancies to the wafer is small, it is difficult to increase the BMD at a normal epi growth temperature. By heat treatment by resistance heating, OSF nuclei are formed on the wafer surface, and epi defects are generated in the epitaxial layer forming step. Moreover, it turned out that a BMD density becomes low also with respect to an Example and the comparative example 1. FIG.

(Comparative Example 3)
In the example, an epitaxial wafer was produced under the same conditions as in the example except that the order of the heat treatment step and the epitaxial layer forming step was changed. Then, in the same manner as in the Examples, an oxygen precipitation heat treatment was performed, and a change in residual oxygen concentration (ΔO _i : oxygen precipitation amount) of the wafer before and after the oxygen precipitation heat treatment was evaluated by FTIR.

FIG. 4 shows changes in residual oxygen concentration before and after the oxygen precipitation heat treatment (ΔO _i ) with respect to the carbon doping amount of each epitaxial wafer when the RTA condition is 1200 ° C. and the resistance heating condition is 1100 ° C. in Examples and Comparative Examples 2 and 3. : Oxygen precipitation amount).
From FIG. 4, it was found that Comparative Examples 2 and 3 had a smaller amount of oxygen precipitation than the Examples. In particular, it was found that in Comparative Example 3 in which the epi process and the RTA process were reversed, the amount of precipitated oxygen was considerably smaller than that of the example. From this, it was found that oxygen precipitation nuclei in the wafer bulk disappeared in the epi process, so that oxygen precipitation hardly occurred even when vacancies were injected by RTA.
In Comparative Example 3, it was found that depending on the RTA atmosphere, a film may be formed on the wafer surface, and the surface state may deteriorate in the etching process. Furthermore, it has been found that the vacancies introduced during the RTA process may not act as oxygen precipitation nuclei depending on the heat treatment conditions in the device process. It was also found that slip dislocations were introduced into the wafer by the RTA process after the epi process.

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

It is a conceptual sectional view of an epitaxial wafer manufactured by the manufacturing method of the present invention. It is a figure which shows an example of the result of having observed the cleavage surface of the epitaxial wafer after the oxygen precipitation heat processing in an Example. 5 is a diagram showing an example of epi defects on the surface of an epitaxial wafer in Examples and Comparative Example 1. FIG. It is a diagram _showing: (oxygen precipitates delta O.D. i) Example, the oxygen precipitation heat treatment before and after the remaining oxygen concentration change to carbon doping amount of the epitaxial wafers in Comparative Examples 2 and 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Epitaxial layer, 12 ... Wafer bulk part, 13 ... Hole injection | pouring layer.

Claims (3)

In the epitaxial wafer manufacturing method, the Czochralski method is used to grow a silicon single crystal rod by doping only carbon except for the resistance control dopant, and the silicon single crystal rod is sliced and processed into a silicon single crystal wafer. Then, RTA heat treatment is performed using a rapid heating / rapid cooling (RTA) apparatus to inject vacancies into the silicon single crystal wafer, and then an epitaxial layer is formed on the surface of the single crystal wafer. A method of manufacturing an epitaxial wafer.   2. The method for producing an epitaxial wafer according to claim 1, wherein the carbon concentration doped into the silicon single crystal at the time of growth is set to 1.0 ppma or more by the Czochralski method. The RTA heat treatment using the RTA apparatus is characterized in that the atmosphere is a non-oxidizing atmosphere, the heat treatment temperature is in a range of 1150 to 1250 ° C., and the treatment time is 10 seconds or more. The manufacturing method of the epitaxial wafer of description.

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