JP6150075B2 - Epitaxial wafer manufacturing method - Google Patents

Description

  The present invention relates to an epitaxial wafer manufacturing method.

  A silicon epitaxial wafer in which an epitaxial layer is formed on the surface of a silicon single crystal substrate by a vapor deposition method is widely used for electronic devices. In recent years, improvement in surface quality (surface defects, roughness) of epitaxial wafers has become an important issue due to miniaturization of electronic devices.

  Crystal defects such as stacking faults may occur in the epitaxial layer depending on the growth conditions (film formation conditions). Defects generated by this epitaxial layer deposition are generally called epi defects. The occurrence of this epi defect is closely related to the growth temperature (film formation temperature) and the growth rate. Specifically, epi defects tend to occur when the growth rate is higher at a lower temperature, which is one of the factors that deteriorate the epi defect level when the growth conditions are changed.

  In relation to this epi defect, Patent Document 1 proposes a method in which two epitaxial layers having different growth conditions are grown, and the second layer is grown under growth conditions at a lower temperature and at a higher growth rate than the first layer. doing. According to this method, the first layer can prevent the crystal defect from the semiconductor substrate from propagating to the second layer.

Special Table 2003-505317

  By the way, there is a haze level as one of the indexes showing the surface roughness of the epitaxial layer. Haze is minute irregularities generated on the surface of the epitaxial wafer, and when the surface of the epitaxial layer is observed using a condensing lamp or the like in a dark room, light is irregularly reflected and appears white and cloudy. The evaluation of the haze level can be detected by measuring the scattered light of haze using, for example, a particle counter SP2 (light scattering measurement device) manufactured by KLA Tencor.

  The haze level is also closely related to the growth conditions, particularly the growth temperature and growth rate. Specifically, the haze level tends to decrease when the growth rate is high at a low temperature, and has an inverse relationship with epi defects. For this reason, there is a problem that the epi defect level deteriorates when trying to reduce the haze level, and conversely, when the epi defect level is reduced, the haze level deteriorates. In this regard, in Patent Document 1, the second layer is grown under conditions of a low temperature and a high growth rate, and this condition is a condition in which epi defects are likely to occur. Therefore, the epi defect level is deteriorated as compared with the single-layer epitaxial wafer under the growth condition of the first layer.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the method which can obtain the epitaxial wafer which reduced the haze level, suppressing the deterioration of an epi defect level.

In order to solve the above problems, an epitaxial wafer manufacturing method of the present invention includes a providing step of providing a semiconductor substrate,
A first growth step of growing a first epitaxial layer of semiconductor material on the surface of the semiconductor substrate provided in the providing step at a first growth temperature and a first growth rate;
A second epitaxial layer of semiconductor material on the first epitaxial layer, with a second growth temperature lower than the first growth temperature and a second growth rate lower than the first growth rate; Or a second growth temperature higher than the first growth temperature and a second growth rate higher than the first growth rate, or a second growth temperature equal to the first growth temperature and the first growth temperature. A second growth rate higher than a first growth rate, or a second growth temperature lower than the first growth temperature and a second growth rate equal to the first growth rate. The growth steps of the
It is characterized by including.

  In the present invention, after growing the first epitaxial layer at the first growth temperature and the first growth rate, the growth condition is switched to a growth condition that can improve the haze level while suppressing the deterioration of the epi defects to some extent. An epitaxial layer (second epitaxial layer) is grown. That is, the growth conditions of the second epitaxial layer are set to a second growth temperature lower than the first growth temperature and a second growth rate lower than the first growth rate, or higher than the first growth temperature. A second growth rate that is higher than the first growth rate and a second growth rate that is equal to the first growth temperature and a second growth rate that is higher than the first growth rate; The second growth temperature is lower than the first growth rate, and the second growth rate is equal to the first growth rate. Thereby, the haze level can be reduced while suppressing deterioration of the epi defect level as compared with the case where the single-layer epitaxial layer is grown under the growth conditions of the first epitaxial layer.

  In the present invention, the thickness of the second epitaxial layer is preferably 2 μm or less. The growth condition of the second epitaxial layer partially overlaps with the low temperature and high growth rate at which epi defects are likely to occur. Therefore, if the thickness of the second epitaxial layer is made too thick, the epi defect level is reduced. It will get worse. In the present invention, since the film thickness of the second epitaxial layer is 2 μm or less, deterioration of the epi defect level can be suppressed.

  More preferably, the thickness of the second epitaxial layer is 1 μm or less. As a result, the deterioration of the epi defect level can be further suppressed.

  Further, the second epitaxial layer can reduce the haze level while suppressing the increase rate of crystal defects in the epitaxial layer to 50% or less with reference to the case where only the first epitaxial layer is grown.

  Further, in the second growth step, after the growth of the first epitaxial layer, the second epitaxial layer may be grown through a period in which the growth of the epitaxial layer is stopped, or from the growth of the first epitaxial layer. The growth temperature and the growth rate are continuously changed from the growth condition of the first epitaxial layer to the growth condition of the second epitaxial layer so that the growth of the epitaxial layer continues during the switching to the growth of the second epitaxial layer. At least one of them may be changed.

  Further, the first growth step may be a step of growing the epitaxial layer once (step of growing one epitaxial layer), or a plurality of times of growing the epitaxial layer under different growth conditions each time. It may be a step to perform (a step of growing a plurality of epitaxial layers).

It is sectional drawing of the wafer in each process until it manufactures the silicon epitaxial wafer which concerns on 1st Embodiment and 3rd Embodiment. It is the figure which showed the 1st example of the time change of the wafer temperature which concerns on 1st Embodiment. It is the figure which showed the 2nd example of the time change of the wafer temperature which concerns on 1st Embodiment. It is the figure which showed the 3rd example of the time change of the wafer temperature which concerns on 1st Embodiment. It is the figure which showed the 4th example of the time change of the wafer temperature which concerns on 1st Embodiment. It is sectional drawing of the wafer in each process until manufacturing the silicon epitaxial wafer which concerns on 2nd Embodiment. It is the figure which showed the time change of the wafer temperature which concerns on 2nd Embodiment. It is the figure which showed the time change of the wafer temperature which concerns on 3rd Embodiment. It is the figure which showed the time change of the wafer temperature at the time of growing the single layer epitaxial layer as a comparative example.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are diagrams for explaining a first embodiment of a method for manufacturing a silicon epitaxial wafer by chemical vapor deposition (CVD: Chemical Vapor Deposition). Specifically, FIG. 1 shows a cross-sectional view of a wafer in each process until a silicon epitaxial wafer according to a first embodiment and a third embodiment described later is manufactured. 2 to 5 show the time change (temperature profile) of the wafer temperature. FIG. 2 shows a first example, FIG. 3 shows a second example, FIG. 4 shows a third example, and FIG. Shows a fourth example. 2 to 5, the temperature change up to Depo1 (first growth step) is the same between FIGS.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. First, as shown in the upper part of FIG. 1, a silicon single crystal wafer 1 (hereinafter sometimes simply referred to as a wafer) as a semiconductor substrate. Prepare (providing step). The characteristics (conductivity type, resistivity, crystal orientation, diameter, etc.) of the wafer 1 may be appropriately set according to the intended use of the silicon epitaxial wafer to be manufactured.

  Next, as shown in the middle part of FIG. 1, a silicon single crystal film 2 (hereinafter referred to as a first epitaxial layer) is vapor-phase grown on the surface of the prepared wafer 1. Specifically, for example, the wafer 1 is put into a reaction chamber of a single wafer type vapor phase growth apparatus. Thereafter, the wafer 1 is heated up to a predetermined heat treatment temperature T1 by a heater provided in the vapor phase growth apparatus, as indicated by a “Ramp” portion in FIGS. 2 to 5 show an example in which the heat treatment temperature T1 is the same as the growth temperature described later (the temperature at “Depo1” in FIG. 2), it may be different from the growth temperature. The heat treatment temperature T1 can be set to, for example, a temperature around 1100 ° C., specifically 1100 ° C. ± 50 ° C. Then, as shown by “Bake” in FIG. 2, hydrogen is introduced into the reaction chamber while maintaining the temperature of the wafer 1 at the heat treatment temperature T1 for a predetermined time, and is formed on the surface of the wafer 1 in a hydrogen atmosphere. A heat treatment (Bake) for removing the natural oxide film is performed.

  Thereafter, the temperature of the wafer 1 is set to a predetermined growth temperature T1 (same as the heat treatment temperature) as shown by a portion “Depo1” in FIGS. 2 to 5 and is used as a raw material for the silicon single crystal film in the reaction chamber. A reactive gas (specifically, a silane-based gas such as trichlorosilane (TCS)), a carrier gas (eg, hydrogen) for diluting the reactive gas, and a dopant gas (eg, boron or phosphorous) that imparts conductivity to the silicon single crystal film. A gas for vapor phase growth containing a gas containing a gas. Then, a first epitaxial layer 2 (silicon single crystal film) of a semiconductor material is grown on the surface of the wafer 1 by this vapor phase growth gas (first growth step).

  The characteristics (film thickness, resistivity, conductivity type, etc.) of the first epitaxial layer 2 may be set as appropriate according to the purpose of use of the silicon epitaxial wafer to be manufactured. Then, the growth conditions (growth temperature T1, growth rate GR1, growth time, etc.) of the first epitaxial layer 2 are set so that the first epitaxial layer 2 having desired characteristics can be obtained. Specifically, the growth time may be set so that a desired film thickness is obtained. The growth temperature T1 and the growth rate GR1 are preferably set to a growth temperature and a growth rate that can suppress the occurrence of epi defects in the first epitaxial layer 2, for example. Since epi defects tend to occur at a lower temperature and a higher growth rate, the growth temperature T1 is set to a region excluding the low temperature region (around 1000 ° C.), for example, around 1100 ° C. (range of 1100 ° C. ± 50 ° C.). it can.

  Further, the growth rate GR1 can be, for example, a region (for example, around 2 μm / min (range of 2 ± 1 μm / min)) excluding a region with a high growth rate (region of 3 μm / min or more). “2 μm / min” means the rate at which an epitaxial layer of 2 μm grows per minute. The growth rate may be adjusted according to the flow rate and concentration of the reaction gas introduced into the reaction chamber.

  After the growth of the first epitaxial layer 2, the introduction of the vapor phase growth gas into the reaction chamber is stopped to temporarily stop the growth of the epitaxial layer. During the stop period, the temperature of the wafer 1 is adjusted in advance so that the growth temperature of the epitaxial layer to be grown next is reached. After the stop period, in order to reduce the haze level (surface irregularity) of the epitaxial layer, the growth condition of the epitaxial layer is referred to as the growth condition of the first epitaxial layer 2 (hereinafter referred to as the first growth condition). ) To a predetermined growth condition (hereinafter referred to as a second growth condition), and then a silicon single crystal film 3 (hereinafter referred to as a first growth film) on the first epitaxial layer 2 as shown in the lower part of FIG. The second epitaxial layer is vapor-phase grown (second growth step).

  The second growth condition is a growth condition that can reduce the haze level as compared with a case where a single epitaxial layer is grown under the first growth condition (when only the first epitaxial layer is grown). The second growth condition is a growth condition that can suppress the occurrence of epi defects to some extent. Specifically, when a single epitaxial layer is grown under the first growth condition (see FIG. 9). ) Is a growth condition in which the increase rate from the number of occurrences of epi defects is 50% or less. FIG. 9 shows the temperature profile of the wafer when a single epitaxial layer is grown under the first growth condition. The second growth condition is any one of the first to fourth examples shown below.

(First example of second growth condition)
The first example of the second growth condition includes a growth temperature T2 (second growth temperature) lower than the growth temperature T1 (first growth temperature) in the first growth condition, and the first growth condition. The growth rate GR2 (second growth rate) lower than the growth rate GR1 (first growth rate) is included (see FIG. 2). That is, in the first example, the second epitaxial layer 3 is grown at a lower temperature and at a lower growth rate than when the first epitaxial layer 2 is grown.

  When the first growth temperature T1 is set near 1100 ° C., the second growth temperature T2 is set to a temperature of 1100 ° C. or lower (for example, 1050 ° C., 1000 ° C., etc.). When the first growth rate GR1 is set near 2 μm / min, the second growth rate GR2 is a growth rate of 2 μm / min or less (for example, 1.5 μm / min, 1 μm / min, 0.5 μm / min, etc.). ).

  Although the haze generally tends to decrease when the growth rate is high at a low temperature, the second growth temperature T2 in FIG. 2 is lower than the first growth temperature T1, so the first growth condition Compared with the case where a single-layer epitaxial layer is grown with (T1, GR1), the haze level can be reduced. On the other hand, epi defects are likely to occur in a low temperature region, but the second growth rate GR2 is a low growth rate at which epi defects are difficult to occur. Can be suppressed to 50% or less.

  However, if the thickness of the second epitaxial layer 3 is too large, the epi defect level may be deteriorated. Therefore, the smaller the thickness of the second epitaxial layer 3, the better. Specifically, the thickness of the second epitaxial layer 3 is preferably 2 μm or less, and more preferably 1 μm or less. The present inventor has obtained an experimental result that the increase rate of epi defects becomes 50% or less by setting the film thickness to 2 μm or less. Further, the growth time of the second epitaxial layer 3 is set so that a desired film thickness can be obtained.

(Second example of second growth condition)
The second example of the second growth condition includes a growth temperature T2 (second growth temperature) higher than the first growth temperature T1, and a growth rate GR2 (second second) higher than the first growth rate GR1. (See FIG. 3). That is, in the second example, the second epitaxial layer 3 is grown at a higher temperature and at a higher growth rate than when the first epitaxial layer 2 is grown.

  When the first growth temperature T1 is set near 1100 ° C., the second growth temperature T2 is set to a temperature of 1100 ° C. or higher (for example, 1150 ° C.). When the first growth rate GR1 is set near 2 μm / min, the second growth rate GR2 is a growth rate of 2 μm / min or more (for example, 2.5 μm / min, 3 μm / min, 3.5 μm / min, etc.). ).

  Since the second growth rate GR2 according to the second example is a high growth rate which is a region in which the haze tends to decrease, a single epitaxial layer is grown under the first growth condition (T1, GR1). Compared to the case, the haze level can be reduced. On the other hand, epi defects are likely to occur when the growth rate is high, but the second growth temperature T2 is a high temperature at which epi defects are difficult to occur. Can be suppressed. However, as in the first example, if the film thickness of the second epitaxial layer 3 is too large, the epi defect level may be deteriorated. Therefore, the film thickness of the second epitaxial layer 3 is more preferably 2 μm or less. Is preferably 1 μm or less.

(Third example of second growth condition)
A third example of the second growth condition includes a growth temperature T2 (second growth temperature) equal to the first growth temperature T1 and a growth rate GR2 (second second) that is higher than the first growth rate GR1. Growth rate) (see FIG. 4). That is, in the third example, the second epitaxial layer 3 is grown in a region having the same temperature and a high growth rate as compared with the growth of the first epitaxial layer 2.

  When the first growth temperature T1 is set near 1100 ° C., the second growth temperature T2 is kept at a temperature near 1100 ° C. When the first growth rate GR1 is set near 2 μm / min, the second growth rate GR2 is higher than 2 μm / min (for example, 2.5 μm / min, 3 μm / min, 3.5 μm / min, etc.). ).

  Since the second growth rate GR2 according to the third example is a high growth rate which is a region in which the haze tends to be reduced, a single epitaxial layer is grown under the first growth condition (T1, GR1). Compared to the case, the haze level can be reduced. On the other hand, epi defects tend to occur when the growth rate is high, but the second growth temperature T2 is equal to the first growth temperature T1 where the epi defects are hard to occur (normal temperature). Can be suppressed to some extent (increase rate is 50% or less). However, as in the first example and the second example, if the film thickness of the second epitaxial layer 3 is excessively increased, the epi defect level may be deteriorated. Therefore, the film thickness of the second epitaxial layer 3 is 2 μm. Hereinafter, it is more preferable that the thickness is 1 μm or less.

(Fourth example of second growth condition)
The fourth example of the second growth condition includes a growth temperature T2 (second growth temperature) that is lower than the first growth temperature T1 and that is equal to the first growth rate GR1 (the second growth temperature GR1). Growth rate) (see FIG. 5). That is, in the fourth example, the second epitaxial layer 3 is grown in a region at a low temperature and at an equal growth rate as compared with the growth of the first epitaxial layer 2.

  When the first growth temperature T1 is set near 1100 ° C., the second growth temperature T2 is set to a temperature of 1100 ° C. or lower (for example, 1050 ° C., 1000 ° C., etc.). When the first growth rate GR1 is set near 2 μm / min, the second growth rate GR2 is set to a growth rate near 2 μm / min that is equal to the first growth rate GR1.

  Since the second growth temperature T2 according to the fourth example is a low temperature which is a region where haze tends to be reduced, a single epitaxial layer is grown under the first growth conditions (T1, GR1). Compared with, the haze level can be reduced. On the other hand, epi defects tend to occur when the growth temperature is low, but the second growth rate GR2 is a growth rate (normal growth rate) equal to the first growth rate GR1 where epi defects are less likely to occur. The occurrence of epi defects can be suppressed to some extent (increase rate is 50% or less). However, as in the first example, the second example, and the third example, if the film thickness of the second epitaxial layer 3 is increased too much, the epi defect level may be deteriorated. The film thickness is preferably 2 μm or less, more preferably 1 μm or less.

  After the second epitaxial layer 3 is grown under the growth conditions of any of the first to fourth examples, the temperature in the reaction chamber (wafer temperature) is taken out and lowered to the temperature. Thereafter, the silicon epitaxial wafer is unloaded from the reaction chamber. Thereby, the silicon epitaxial wafer according to the present invention can be obtained.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with a focus on differences from the above embodiment. FIG. 6 shows a cross-sectional view of the wafer in each process until the silicon epitaxial wafer according to this embodiment is manufactured. FIG. 7 shows the time change of the temperature of the wafer according to this embodiment. In the first embodiment, an example in which two epitaxial layers are grown in total is shown. However, the present embodiment is an embodiment in which three epitaxial layers are grown in total.

  The second embodiment of the present invention will be described with reference to FIGS. 6 and 7. First, as shown in the first stage of FIG. 6, a silicon single crystal wafer 1 similar to the first embodiment is prepared (provided) Step). Thereafter, the prepared wafer 1 is put into the reaction chamber, and the wafer 1 is heat-treated (“Ramp” and “Bake” in FIG. 7). The heat treatment conditions are the same as in the first embodiment. Next, as shown in the second stage of FIG. 6, the first epitaxial layer 21 (silicon single crystal film) is grown on the surface of the wafer 1. The concept of the growth condition of the first epitaxial layer 21 is the same as the concept of the growth condition of the first epitaxial layer 2 (see FIG. 1) in the first embodiment. That is, the growth conditions (growth temperature T1, growth rate GR1, film thickness, etc.) of the first epitaxial layer 21 are appropriately set according to the purpose of use of the silicon epitaxial wafer, as in the growth of the epitaxial layer 2 in FIG. The growth conditions may be set, but the growth conditions are set such that the occurrence of epi defects can be suppressed. In the example of FIG. 7, the growth temperature T1 of the first epitaxial layer 21 is 1100 ° C., and the growth rate GR1 is 2.0 μm / min.

  After the growth of the first epitaxial layer 21, the growth of the epitaxial layer is once stopped. During the stop period, the temperature of the wafer 1 is adjusted to the next growth temperature, and then the growth conditions (growth temperature T2, growth rate GR2) different from the growth conditions of the first epitaxial layer 21 are switched to the first epitaxial layer. A second epitaxial layer 22 (silicon single crystal film) is grown on the layer 21 (see the third stage in FIG. 6). The growth conditions of the second epitaxial layer 22 may be set as appropriate according to the purpose of use of the silicon epitaxial wafer, similarly to the growth conditions of the first epitaxial layer 21, but the occurrence of epi defects is suppressed. Set to growth conditions that can be. Specifically, a region where an epi defect is likely to occur (low temperature and high growth rate region) is removed. In the example of FIG. 7, the growth temperature T1 of the second epitaxial layer 22 is 1050 ° C., and the growth rate GR2 is 1.5 μm / min.

  In the example of FIG. 7, the height relationship between the growth condition (T2, GR2) of the second epitaxial layer 22 and the growth condition (T1, GR1) of the first epitaxial layer 21 is T1> T2 and GR1. > GR2, but not limited thereto, T1 = T2 and GR1> GR2, or T1 = T2 and GR1 <GR2, or T1> T2 and GR1 <GR2, or T1 <T2 and GR1> GR2, or T1 <T2 and GR1 <GR2 or T1> T2 and GR1 = GR2 or T1 <T2 and GR1 = GR2 may be used.

  The first epitaxial layer 21 and the second epitaxial layer 22 correspond to the “first epitaxial layer” of the present invention. Further, the process of growing these epitaxial layers 21 and 22 corresponds to the “first growth step” of the present invention. Thus, in the present embodiment, the epitaxial growth process is performed twice under different growth conditions until the final epitaxial layer described later is grown. Note that three or more epitaxial growth steps may be performed to grow three or more epitaxial layers before the final epitaxial layer is grown.

  After the second epitaxial layer 22 is grown, the growth of the epitaxial layer is once stopped. During the stop period, the temperature of the wafer 1 is adjusted in advance so that the growth temperature of the epitaxial layer to be grown next is reached. After the stop period, the third epitaxial layer 31 is grown on the second epitaxial layer 22 after switching to a growth condition that can reduce the haze level of the epitaxial layer ( (See the fourth row in FIG. 6). The concept of the growth condition of the epitaxial layer 31 is the same as the concept of the growth condition of the second epitaxial layer 3 of the first embodiment (the first to fourth examples). Specifically, the relationship between the growth conditions (T3, GR3) of the third epitaxial layer 31 and the growth conditions (T1, GR1) (T2, GR2) of the epitaxial layers 21 and 22 grown before that is expressed as follows. For example, the growth temperature T3 is lower than the previous growth temperatures T1 and T2, and the growth rate GR3 is lower than both the previous growth rates GR1 and GR2 (in the first example of FIG. 2). Equivalent). Alternatively, the growth temperature T3 is higher than any of the previous growth temperatures T1 and T2, and the growth rate GR3 is higher than any of the previous growth rates GR1 and GR2 (corresponding to the second example of FIG. 3). ).

  Alternatively, the growth temperature T3 is equal to the previous growth temperature T2, and the growth rate GR3 is higher than both the previous growth rates GR1 and GR2 (corresponding to the third example in FIG. 4). Alternatively, the growth temperature T3 is lower than the previous growth temperatures T1 and T2, and the growth rate GR3 is equal to the previous growth rate GR2 (corresponding to the fourth example in FIG. 5). In the example of FIG. 7, the growth temperature T3 is 1000 ° C. and the growth rate GR3 is 1.5 μm / min, which corresponds to the fourth example.

  The film thickness of the third epitaxial layer 31 is preferably 2 μm or less, more preferably 1 μm or less, as in the first embodiment. The epitaxial layer 31 in FIG. 6 corresponds to the “second epitaxial layer” of the present invention. Further, the process of growing the epitaxial layer 31 corresponds to the “second growth step” of the present invention.

  After the third epitaxial layer 31 is grown, the temperature in the reaction chamber (wafer temperature) is taken out and lowered to the temperature. Thereafter, the silicon epitaxial wafer is unloaded from the reaction chamber. Thereby, the silicon epitaxial wafer according to the present invention can be obtained.

  As described above, in the present embodiment, the growth conditions of the final epitaxial layer 31 are the growth conditions that can suppress the occurrence of epi defects to some extent and can reduce the haze level as compared with the previous growth conditions. As a result, the number of occurrences of epi defects is increased with reference to the number of occurrences of epi defects when a single epitaxial layer is grown under the growth conditions of either the first or second epitaxial layers 21 and 22. A silicon epitaxial wafer with improved haze level can be obtained while suppressing the rate to 50% or less.

(Third embodiment)
Next, a third embodiment of the present invention will be described focusing on the differences from the above embodiment. FIG. 8 shows the time change of the temperature of the wafer according to the present embodiment. A third embodiment of the present invention will be described with reference to FIGS. 1 and 8. First, as shown in the upper part of FIG. 1, a silicon single crystal wafer 1 similar to the first embodiment is prepared (providing step). . Thereafter, the prepared wafer 1 is put into the reaction chamber, and the wafer 1 is heat-treated (“Ramp” and “Bake” in FIG. 8). The heat treatment conditions are the same as those in the first and second embodiments.

  Next, as shown in the middle part of FIG. 1, the first epitaxial layer 2 (silicon single crystal film) is grown on the surface of the wafer 1 under the same growth conditions (T1, GR1) as in the first embodiment ( First growth step). The first epitaxial layer 2 may be composed of a single layer as in the first embodiment, or may be composed of a plurality of layers as in the second embodiment.

  After the growth of the first epitaxial layer 2, the second epitaxial layer 3 is then grown under the same growth conditions (T 2, GR 2) as in the first embodiment, as shown in the lower part of FIG. 2 growth steps). At this time, the growth of the epitaxial layer is continued during the switching from the growth of the first epitaxial layer 2 to the growth of the second epitaxial layer 3. That is, while the introduction of the vapor phase growth gas is continued even after the growth of the first epitaxial layer 2, as shown in FIG. 8, the first growth condition (T1, GR1) to the second growth condition (T2, At least one of the growth temperature and the growth rate is continuously changed to GR2). That is, during the switching to the second growth condition, the temperature between the first growth temperature T1 and the second growth temperature T2, and the growth between the first growth rate GR1 and the second growth rate GR2. With the speed, the growth of the epitaxial layer is continued.

  Specifically, when the second epitaxial layer 3 is grown in the first example (T1> T2, GR1> GR2), after the growth of the first epitaxial layer 2, the first growth temperature T1 is increased. The growth temperature is continuously decreased to the growth temperature T2 of 2, and the growth rate is continuously decreased from the first growth rate GR1 to the second growth rate GR2. Further, when the second epitaxial layer 3 is grown in the second example (T1 <T2, GR1 <GR2), the second growth is started from the first growth temperature T1 after the first epitaxial layer 2 is grown. The growth temperature is continuously increased to the temperature T2, and the growth rate is continuously increased from the first growth rate GR1 to the second growth rate GR2.

  When the second epitaxial layer 3 is grown in the third example (T1 = T2, GR1 <GR2), the growth temperature is maintained at the first growth temperature T1 after the growth of the first epitaxial layer 2. In this state, the growth rate is continuously increased from the first growth rate G1 to the second growth rate GR2. Further, when the second epitaxial layer 3 is grown in the fourth example (T1> T2, GR1 = GR2), the growth rate is maintained at the first growth rate GR1 after the growth of the first epitaxial layer. The growth temperature is continuously decreased from the first growth temperature T1 to the second growth temperature T2.

  Thereby, the growth of the epitaxial layer can be continued even during the switching to the second growth condition (T2, GR2). The epitaxial layer grown during this switching also corresponds to the “second epitaxial layer” of the present invention.

  The film thickness of the second epitaxial layer 3 is preferably as small as possible. Specifically, as in the above embodiment, the second epitaxial layer 3 (including the epitaxial layer grown while continuously changing the growth temperature and growth rate) is 2 μm or less, more preferably 1 μm. The following is preferred. Since the epitaxial layer grows during the switching from the first growth condition to the second growth condition, the film thickness of the epitaxial layer after the switching is completed may be 0 μm. That is, the growth of the epitaxial layer may be stopped at the same time as the switching to the second growth condition (T2, GR2) is completed.

  Thus, in the present embodiment, the first epitaxial layer 2 and the second epitaxial layer 3 are grown in the same epitaxial growth step. In this sense, the first epitaxial layer 2 and the second epitaxial layer 3 can be considered as one epitaxial layer (single layer). However, in this specification, when grown under different growth conditions, it is described as a separate epitaxial layer.

  Also according to the present embodiment, it is possible to obtain a silicon epitaxial wafer having the same effect as the above-described embodiment, that is, an improved epitaxial haze level while suppressing the increase rate of epi defects to 50% or less. The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, these do not limit this invention.

Example 1
In a single wafer type vapor phase growth apparatus, a large number of P-type silicon single crystal wafers having a diameter of 300 mm and a surface orientation (100) of the main surface are prepared, and two layers are formed on the surface of each silicon single crystal wafer under different growth conditions. A silicon single crystal film was formed. Specifically, the film formation conditions for the first layer were a temperature of 1100 ° C., a growth rate of 2.0 μm / min, and a film thickness of 3 μm. The epi-defect level and haze level when the temperature and growth rate of the second layer were changed as follows were evaluated. Specifically, the growth temperature of the second layer is changed between 1150, 1100, 1050, and 1000 ° C., and the growth rate is 3.5, 3.0, 2.5, 2.0, 1.5, 1 0.0 and 0.5 μm / min. The film thickness of the second layer was 0.5 μm.

  Epi defects were evaluated in a DCO (Darkfield Composite Oblique) mode 42 nmup of a particle counter SP2 manufactured by KLA Tencor (evaluated with an epi defect having a size of 42 nm or more). Also, the haze level was evaluated in the DW (Darkfield Wide) mode of the particle counter SP2.

  Further, as a comparative example, a silicon single crystal wafer similar to that of the example was prepared, and a single layer was formed under the film formation conditions (temperature 1100 ° C., growth rate 2.0 μm / min, film thickness 3 μm) of the example. The epitaxial defect level and the haze level when the epitaxial layer was grown were evaluated. A temperature profile of the comparative example is shown in FIG. The epi defect level of the comparative example was 3.1 / wf (3.1 epi defects per wafer). Moreover, the haze level of the comparative example was 0.55 ppm. In addition, the value (3.1 piece / wf) of these epi defect levels, and the value (0.55 ppm) of haze level are the same conditions, manufacture several epitaxial wafers, the epi defect level of these several epitaxial wafers, Average value of haze level.

  Table 1 shows the epi defect level and haze level of the example together with the results of this comparative example. In Table 1, the result of the comparative example is shown in the column of the growth temperature of 1100 ° C. and the growth rate of 2 μm / min. Further, the deterioration rate (%) shown in Table 1 indicates the deterioration rate of the epi defect level of the example based on 3.1 / wf which is the epi defect level of the comparative example. In Table 1, the results of hatching indicate that the haze level is lower than the haze level of the comparative example, and the deterioration rate of the epi defect level is 150% or less (the increase rate is 50% or less). . In addition, each epi defect level and haze level of Table 1 are average values of the epi defect level and the haze level of a plurality of epitaxial wafers.

  As shown in the hatched portion of Table 1, the second layer in which the haze level is lower than the haze level of the comparative example and the deterioration rate of the epi defect level is 150% or less (the increase rate is 50% or less). The growth condition region is a region having a growth rate lower than the growth temperature of the first layer and lower than the growth rate of the first layer, or a region having a growth rate higher than the growth temperature of the first layer and higher than the growth rate of the first layer. Or a region having a growth temperature equal to the growth temperature of the first layer and a growth rate higher than the growth rate of the first layer, or a region having a growth rate lower than the growth temperature of the first layer and equal to the growth rate of the first layer. It was. In other regions (regions not hatched), the haze level was worse than that of the comparative example, or the deterioration rate of the epi defect level exceeded 150%.

(Example 2)
A large number of silicon single crystal wafers similar to those in Example 1 were prepared, and the first layer was grown on each silicon single crystal wafer under growth conditions of a growth temperature of 1100 ° C., a growth rate of 2.0 μm / min, and a film thickness of 3.0 μm. An epitaxial layer (silicon single crystal film) is formed, and a second epitaxial layer (silicon single crystal film) is formed under growth conditions (low temperature, low growth rate) at a growth temperature of 1000 ° C. and a growth rate of 1.5 μm / min. Filmed. At this time, the thickness of the second layer was changed between 0.5, 1.0, 1.5, 2.0, and 3.0 μm. Then, the epitaxial defect level and haze level of each obtained epitaxial wafer were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2. In Table 2, the results of the comparative example are also shown.

  As shown in Table 2, the haze level is improved from the comparative example at any film thickness, while the epi defect level is improved as the film thickness of the second layer is smaller. Specifically, when the film thickness of the second layer is 2 μm or less, the deterioration rate of the epi defect level is 150% or less (the increase rate is 50% or less). In addition, in the result of the film thickness of the second layer being 1 μm and 0.5 μm, the deterioration rate of the epi defect level is about 110% (increase rate is 10%), and if the film thickness of the second layer is 1 μm or less, It has been found that the deterioration of the epi defect level can be further suppressed.

(Example 3)
A silicon single crystal wafer similar to that of Example 1 was prepared, and the first layer epitaxial was grown on the silicon single crystal wafer under growth conditions of a growth temperature of 1100 ° C., a growth rate of 2.0 μm / min, and a film thickness of 3.0 μm. A layer (silicon single crystal film) is formed, and a second epitaxial layer (silicon single crystal film) is formed under the growth conditions of a growth temperature of 1050 ° C., a growth rate of 2.0 μm / min, and a film thickness of 0.5 μm. A third epitaxial layer (silicon single crystal film) was formed under the growth conditions (low temperature, low growth rate) of growth temperature 1000 ° C., growth rate 1.5 μm / min, and film thickness 0.5 μm. Then, the epitaxial defect level and the haze level of the obtained epitaxial wafer were evaluated in the same manner as in Example 1. The results are shown in Table 3. Table 3 also shows the results of the above comparative example and the results when the growth conditions of the second layer in Example 1 are a growth temperature of 1000 ° C., a growth rate of 1.5 μm / min, and a film thickness of 0.5 μm. ing.

  As shown in Table 3, the result of Example 3 in which three epitaxial layers were grown was the same as that in Example 1 in which two epitaxial layers were grown. Specifically, the epi defect level was 3.6 pieces / wf, the deterioration rate was 116%, and the haze level was 0.33. That is, the haze level was improved while suppressing the deterioration rate of the epi defect level with respect to the comparative example.

Example 4
A silicon single crystal wafer similar to that in Example 1 was prepared, and a film having a film thickness of 3 μm was formed on the silicon single crystal wafer under the conditions of a growth temperature of 1100 ° C. and a growth rate of 2.0 μm / min. After the film formation, the growth temperature and the growth rate were continuously changed to a growth temperature of 1000 ° C. and a growth rate of 1.5 μm while the growth of the epitaxial layer was continued. That is, film formation was performed as shown in FIG. And film-forming with thickness 0.0, 0.5, and 1.0 micrometer was performed on the growth conditions (2nd conditions) with the growth temperature of 1000 degreeC, and the growth rate of 1.5 micrometers. Then, the epitaxial defect level and the haze level of the obtained epitaxial wafer were evaluated in the same manner as in Example 1. The results are shown in Table 4. Table 4 also shows the results of the comparative example.

  As shown in Table 4, in any result of Example 4, the deterioration rate of the epi defect level could be suppressed to 110% to 123% with respect to the comparative example, and the haze level was improved. From this, it was shown that the effect of the present invention can be obtained even when the first and second layers are continuously formed. In addition, it can be shown that the effect of the present invention can be obtained even if the epitaxial layer growth is continued even during the switching to the second condition, even if the film thickness of the epitaxial layer under the second condition is 0.0 μm. It was.

1 Silicon single crystal wafer (semiconductor substrate)
2 First epitaxial layer 21 First epitaxial layer (first epitaxial layer)
22 Second epitaxial layer (first epitaxial layer)
3 Second Epitaxial Layer 31 Third Epitaxial Layer (Second Epitaxial Layer)

Claims (9)

A method of manufacturing an epitaxial wafer having no trench structure,
A providing step of providing a semiconductor substrate;
A first growth step of growing a first epitaxial layer of semiconductor material on the surface of the semiconductor substrate provided in the providing step at a first growth temperature and a first growth rate;
A second epitaxial layer of semiconductor material on the first epitaxial layer, in a pre-Symbol first growth temperature equal to the second growth temperature to the first higher than the growth rate second growth rate, Or a second growth step of growing at a second growth temperature lower than the first growth temperature and a second growth rate equal to the first growth rate;
Only including,
The method of manufacturing an epitaxial wafer, wherein the film thickness of the second epitaxial layer is 2 μm or less .   A method of manufacturing an epitaxial wafer having no trench structure,
  A providing step of providing a semiconductor substrate;
  A first growth step of growing a first epitaxial layer of semiconductor material on the surface of the semiconductor substrate provided in the providing step at a first growth temperature and a first growth rate;
  Growing a second epitaxial layer of semiconductor material on the first epitaxial layer at a second growth temperature lower than the first growth temperature and a second growth rate lower than the first growth rate. A second growth step,
  Including
  The film thickness of the second epitaxial layer is 2 μm or less,
  The semiconductor substrate is a silicon substrate;
  The first epitaxial layer and the second epitaxial layer are silicon epitaxial layers;
  The first growth temperature is 1050 ° C. or higher and 1150 ° C. or lower,
  The first growth rate is 1.5 μm / min or more and 2.5 μm / min or less,
  The method for producing an epitaxial wafer, wherein the second growth rate is lower than the first growth rate and is 1.0 μm / min or more.   A method of manufacturing an epitaxial wafer having no trench structure,
  A providing step of providing a semiconductor substrate;
  A first growth step of growing a first epitaxial layer of semiconductor material on the surface of the semiconductor substrate provided in the providing step at a first growth temperature and a first growth rate;
  Growing a second epitaxial layer of semiconductor material on the first epitaxial layer at a second growth temperature higher than the first growth temperature and a second growth rate higher than the first growth rate. A second growth step,
  Including
  The film thickness of the second epitaxial layer is 2 μm or less,
  The semiconductor substrate is a silicon substrate;
  The first epitaxial layer and the second epitaxial layer are silicon epitaxial layers;
  The first growth temperature is 1050 ° C. or higher and 1150 ° C. or lower,
  The first growth rate is 1.5 μm / min or more and 2.5 μm / min or less,
  The method for producing an epitaxial wafer, wherein the second growth rate is higher than the first growth rate and is 3.0 μm / min or more.   4. The method for manufacturing an epitaxial wafer according to claim 1, wherein a film thickness of the second epitaxial layer is 1 μm or less. 5.   The second epitaxial layer is characterized in that an increase rate of crystal defects in the epitaxial layer is 50% or less and a haze level is reduced with reference to a case where only the first epitaxial layer is grown. The manufacturing method of the epitaxial wafer of any one of 1-4.   6. The method according to claim 1, wherein, in the second growth step, after the growth of the first epitaxial layer, the second epitaxial layer is grown through a period in which the growth of the epitaxial layer is stopped. An epitaxial wafer manufacturing method according to claim 1.   In the second growth step, the growth conditions of the first epitaxial layer are set such that the growth of the epitaxial layer continues during the switching from the growth of the first epitaxial layer to the growth of the second epitaxial layer. The method for producing an epitaxial wafer according to claim 1, wherein at least one of a growth temperature and a growth rate is continuously changed from a growth temperature to a growth condition of the second epitaxial layer.   The method for manufacturing an epitaxial wafer according to claim 1, wherein the first growth step is a step of growing an epitaxial layer once.   The epitaxial wafer manufacturing method according to claim 1, wherein the first growth step is a step of growing the epitaxial layer a plurality of times under different growth conditions each time.

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