TW202117063A - Apparatus and process of epitaxial growth (1) - Google Patents

Abstract

The present application provides an apparatus and a process of epitaxial growth. In the epitaxial growth apparatus, the growth chamber comprises a first inlet and a second inlet, wherein the first inlet feeds a reaction gas into the chamber for forming an epitaxial layer on a chip, and the second inlet feeds an etching gas into the chamber for preventing deposition of the epitaxial layer. On the chip, the edge area may be divided into faster regions and slower regions by different crystal orientations. To solve the problem that the epitaxial layer grows more rapidly in the faster region than that in the slower region, the second inlet provides the etching gas with a higher feeding rate to the faster region while the faster region passes by the second inlet during the chip rotation at the period of the epitaxial growth, and provides the etching gas with a lower feeding rate to the slower region while the slower region passes by the second inlet. Thereby, the epitaxial layer of the faster region can be removed by the etching gas with better efficiency, and the epitaxial growth of the faster region and the slower region can be regulated. Accordingly, the uniformity of thickness of the epitaxial layer can be enhanced, the SFQR (Site flatness front least-squares range) can be reduced, and the quality of the epitaxial chip can be improved.

Description

Epitaxy growth equipment and epitaxy growth method (1)

The present invention relates to the technical field of epitaxial growth, in particular to an epitaxial growth equipment and an epitaxial growth method.

Electronic component manufacturing requires very high flatness of the upper surface of the semiconductor wafer as the substrate. Nowadays, it is commonly used to add the focus ability of the stepping device on all areas of the wafer surface into consideration of the local flatness (site flatness front least-squares range, SFQR) (The least squares of the surface reference of the part/range) parameter to evaluate. The value of the maximum local flatness SFQR _max represents the maximum SFQR value of all considered electronic components on the semiconductor wafer. The reduction of the SFQR _max value is beneficial to solve the defocusing problems of photolithography methods that may be encountered when manufacturing electronic devices, the polishing uniformity problems of chemical mechanical polish (CMP) methods, and silicon on insulator (SOI) Poor bonding in bonding methods, etc. The local flatness of the silicon wafer can be optimized by methods such as grinding and polishing.

The semiconductor wafer commonly used as a substrate is a silicon epitaxial wafer, which is usually obtained by an epitaxial growth method, that is, an epitaxial layer is grown on a silicon wafer with the same crystal orientation and in a single crystal manner. Compared with silicon wafers that do not include the epitaxial layer, silicon epitaxial wafers have the advantages of lower defect density and better anti-latch-up capability, and are suitable for manufacturing height on the epitaxial layer. Integrated electronic components, such as microprocessors or memory chips. The local flatness of the silicon epitaxial wafer is related to the uniformity of the epitaxial layer deposited by the epitaxial growth method.

At present, silicon epitaxial wafers are manufactured by placing the silicon wafer in the chamber of the epitaxial device, using a heat source to heat it, and passing a reactive gas into the chamber. The reactive gas decomposes on the surface of the wafer at high temperature to form silicon, which is then deposited on the silicon. The surface of the wafer is grown to form an epitaxial layer. In this process, the wafer is usually rotated on a support (ie, susceptor or susceptor) at a set speed to make the epitaxial layer grow uniformly.

Studies have found that the growth rate of the epitaxial layer is related to the growth orientation, that is, the crystal orientation of the silicon wafer. According to the different crystal orientations, the growth rate of the epitaxial layer will increase or decrease, especially in the edge area of the wafer, resulting in epitaxial growth. The thickness of the crystal layer is different. Taking a silicon wafer with a diameter of 300 mm as an example, its upper surface is assumed to be a (001) crystal plane. Experimental data shows that in the edge area 149 mm away from the center of the wafer, it corresponds to a certain range of >110> crystal orientation of the wafer. The thickness of the epitaxial layer is larger in the entire wafer surface, and within a certain range corresponding to the >100> crystal orientation of the wafer, the thickness of the epitaxial layer is smaller in the entire wafer surface, and the local flatness of the edge area is SFQR Larger, this will make the maximum local flatness SFQR _{max of the} epitaxial silicon wafer larger, which will cause the quality of the epitaxial silicon wafer to deteriorate, and will also cause problems in the manufacture of electronic components.

For the above-mentioned problem of large local flatness SFQR of the epitaxial layer, most of the known methods are adjusted by changing the structure of the epitaxial growth device, such as changing the design of the air inlet or changing the design of the susceptor on which the wafer is installed in order to change airflow. However, adjusting the structure of the epitaxial growth device needs to consider the impact on the various functional components of the device, which is relatively complicated, and for the device in use, its structure is difficult to adjust in time according to actual method conditions, and its flexibility is poor.

The present invention provides an epitaxial growth equipment and an epitaxial growth method, aiming to adjust the uniformity of the thickness of the epitaxial layer formed on the wafer, so as to reduce the local flatness (SFQR) of the epitaxial wafer and improve the quality of the epitaxial wafer .

In one aspect, the present invention provides an epitaxial growth equipment. The epitaxial growth equipment includes a cavity and a susceptor located in the cavity. The susceptor is used to place the wafer and drive the wafer to rotate during the epitaxial growth process. The cavity The body is provided with a first air inlet and a second air inlet, the first air inlet allows the reaction gas used to form an epitaxial layer on the wafer to enter the cavity, and the second air inlet The opening allows the etching gas used to prevent the deposition of the epitaxial layer from entering the cavity; when the edge portion of the wafer has a faster region and a slower region with different crystal orientations, and the epitaxial layer is in the relatively When the fast region grows faster than in the slower region, during the epitaxial growth process, as the wafer rotates, the etching gas provided by the second gas inlet when the faster region rotates through The intake rate is greater than the intake rate of the etching gas provided when the slower zone rotates through.

If necessary, the gas inlet rate of the reaction gas provided by the first gas inlet remains unchanged during the epitaxial growth process.

If necessary, during the epitaxial growth process, as the wafer rotates, the first gas inlet provides a lower rate of reaction gas when rotating through the faster region than when rotating in the slower region. The feed rate of the reactant gas provided during the passage.

If necessary, the gas inlet rate of the etching gas provided by the second gas inlet varies with time in the form of pulses, and the gas inlet of the etching gas provided by the second gas inlet when rotating through the faster zone The rate is the peak value of the pulse.

If necessary, the faster zone and the slower zone are alternately distributed along the circumferential direction of the wafer at the edge portion of the wafer, and the edge portion of the wafer further includes a transition area, and the transition area is between the phases. Between the adjacent one of the faster zone and the one of the slower zone, and the crystal orientation of the transition zone makes the growth rate of the epitaxial layer in the transition zone be between the faster zone and the Between the slower zones.

If necessary, during the wafer rotation process, the gas inlet rate of the etching gas provided by the second gas inlet is rotated to the second gas inlet in turn along with the faster zone, the transition zone, and the slower zone. The two air inlets gradually decrease, and gradually increase as the slower zone, the transition zone, and the faster zone sequentially rotate to the second air inlet.

If necessary, the wafer is a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon wafer, or a strained silicon-on-insulator wafer.

If necessary, the faster area is located within a predetermined fan angle of the wafer >110> crystal orientation, and the slower area is located within a predetermined fan angle of the wafer >100> crystal orientation.

If necessary, the reaction gas includes _{at least one of SiH 4} , SiH ₂ Cl ₂ , SiHCl ₃ and SiCl ₄ ; the etching gas is gaseous HCl.

If necessary, the first air inlet and the second air inlet are located in the same horizontal plane, and the line connecting with the center of the wafer is perpendicular to each other.

If necessary, the rotation rate of the wafer is 40-60 revolutions per minute.

On the other hand, the present invention provides an epitaxial growth method, which includes the following steps: placing a wafer in a cavity of an epitaxial growth equipment, and the edge portion of the wafer has a faster region and a slower region with different crystal orientations. The crystal grows faster in the faster region than in the slower region, the cavity is provided with a first air inlet and a second air inlet; and the wafer is rotated and placed on the wafer Performing epitaxial growth, wherein a reactive gas is delivered into the cavity through the first air inlet to form an epitaxial layer on the wafer, and at the same time, etching is delivered into the cavity through the second air inlet The gas is used to prevent the deposition of the epitaxial layer. During the epitaxial growth process, the etching gas rotates in the faster region and passes through the second gas inlet at a higher inlet rate than when it rotates in the slower region. The air intake rate when passing through the second air intake port.

If necessary, during the epitaxial growth process, the feed rate of the reaction gas remains unchanged.

Optionally, during the epitaxial growth process, the gas flow rate of the reaction gas when rotating through the first gas inlet in the faster zone is smaller than when rotating through the first gas inlet in the slower zone Intake rate at time.

If necessary, the intake rate of the etching gas changes with time in the form of pulses, and the intake rate of the etching gas when rotating through the second intake port in the faster region is the peak of the pulse.

If necessary, the intake rate of the etching gas changes with time in the form of one or a combination of two or more of rectangular waves, sharp pulses, sawtooth waves, triangular waves, sine waves, and step waves.

If necessary, the gas inlet rate of the etching gas is 0-20 liters per minute (L/min).

The epitaxial growth equipment provided by the present invention can perform epitaxial growth on the wafers placed therein, and the cavity is provided with a first air inlet and a second air inlet, and the first air inlet is allowed to be used for forming on the wafer The reaction gas of the epitaxial layer enters the cavity, and the second gas inlet allows the etching gas used to prevent the deposition of the epitaxial layer from entering the cavity. When the edge of the wafer has a faster region and a slower region with different crystal orientations and the epitaxy When the crystal layer grows faster in the faster region than in the slower region, during the epitaxial growth process, as the wafer rotates, the second gas inlet provides a higher rate of etching gas when rotating through the faster region. The intake rate of the etching gas provided when rotating through the slower zone. Since the etching gas has a larger intake rate when rotating to the second air inlet in the faster region, that is, the input amount is larger, the etching gas has a greater removal efficiency for the epitaxial layer in the faster region, and has a faster adjustment region. And the effect of the thickness of the epitaxial layer in the slower zone helps to make the thickness of the epitaxial layer in the faster zone and the slower zone to be consistent, which is conducive to reducing the local flatness of the epitaxial wafer and improving the epitaxy The quality of the wafer.

In the epitaxial growth method provided by the present invention, a wafer is placed in a cavity of an epitaxial growth equipment, and the edge portion of the wafer has a faster region and a slower region with different crystal orientations, and the epitaxial growth is in the faster region Faster than in the slower zone, then the wafer is rotated and epitaxial growth is performed on the wafer, wherein the reaction gas is delivered through the first gas inlet on the cavity to form an epitaxial layer on the wafer, and at the same time The etching gas is delivered through the second air inlet on the cavity to prevent the deposition of the epitaxial layer. During the epitaxial growth process, the etching gas rotates in a faster region and passes through the second air inlet at a higher air inlet rate than in the process of epitaxial growth. The air intake rate when the slower zone rotates through the second air inlet. By adjusting the gas inlet rate of the etching gas, the epitaxial growth of the faster region and the slower region can be adjusted, which helps to improve the thickness uniformity of the epitaxial layer and reduce the local flatness of the epitaxial wafer , Improve the quality of epitaxial wafers. The epitaxial growth method provided by the present invention can improve the quality of the epitaxial wafer without changing the structure of the epitaxial growth device, and has good adjustment flexibility.

Further, during the epitaxial growth process, the gas inlet rate of the reaction gas may remain stable, or it may participate in the adjustment of epitaxial growth. Specifically, the reaction gas may rotate through the first inlet gas in a relatively fast region. The intake rate at the port is lower than the intake rate when rotating through the first intake port in the slower zone, combined with the intake of etching gas when the faster zone and the slower zone rotate to the second intake port The change of the rate can more flexibly adjust the thickness uniformity of the epitaxial layer on the surface of the wafer, especially the edge part, and improve the quality of the epitaxial layer, thereby improving the quality of the epitaxial wafer.

The epitaxial growth equipment and the epitaxial growth method of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and all use imprecise proportions, which are only used to conveniently and clearly assist in explaining the embodiments of the present invention.

In the manufacturing method of semiconductor wafers, the semiconductor wafers formed by cutting usually undergo a grinding step, such as grinding or grinding, to round the mechanically sensitive edges, then polishing and cleaning are carried out, and then the upper surface of the wafer is vaporized in the epitaxial growth equipment. Grow to form an epitaxial layer.

In the epitaxial growth method, a semiconductor wafer such as a silicon wafer is placed in an epitaxial growth equipment to rotate at a certain rate and heated, and a reactive gas (such as TCS, trichlorosilane) is delivered to the surface of the silicon wafer as a source gas. It is decomposed into silicon and volatile by-products at a temperature of about 600 to 1250°C, and is epitaxially grown on the silicon wafer to form an epitaxial layer of silicon. The epitaxial layer may be non-doped, or be doped with boron, phosphorus, arsenic, or antimony with a suitable doping gas to adjust the conductivity type and resistivity.

In order to improve the uniformity of the thickness of the epitaxial layer formed on the semiconductor wafer by epitaxial growth, especially to optimize the local flatness of the edge area to reduce the maximum local flatness value SFQR _{max of the} epitaxial wafer, an adjustment epitaxy is usually used For example, the structure of the crystal growth equipment is optimized by changing the design of the susceptor. However, adjusting the structure of the epitaxial growth equipment needs to consider the impact on the various functional components of the device, and it is difficult to adjust the structure of the device in time according to the actual method conditions during production. Design, this method is less flexible.

FIG. 1 is a schematic diagram of the crystal orientation of a silicon wafer in an embodiment of the present invention. 1, the upper surface of the silicon wafer is usually a crystal plane in the {100} crystal plane family, so the upper surface of the epitaxial layer formed after epitaxial growth on the silicon wafer is also the {100} crystal plane family In Figure 1, the upper surface of the silicon wafer is a (100) crystal plane as an example. According to the radial direction of the wafer, the different crystal orientations of the wafer are periodically distributed along the circumference. As shown in Figure 1, the crystal orientation >110> appears every 90 degrees, and the crystal orientation >110> rotates 45 degrees clockwise or counterclockwise. The crystal orientation is >100>.

Studies have shown that the growth rate of the epitaxial layer of semiconductor wafers such as silicon wafers is related to the crystal orientation. According to different crystal orientations (that is, the growth orientation of the epitaxial layer is different), the growth rate of the epitaxial layer will increase or decrease at intervals. This dependence is evident in the edge area of the upper surface of the wafer. Taking the silicon wafer shown in Figure 1 as an example, the epitaxial layer selectively grows faster in a certain angle including crystal orientation>110>, and grows slowly in a certain angle including crystal orientation>100>. In the crystal direction between >110> and crystal direction>100> (not shown in the figure), the growth of the epitaxial layer is slower than the growth in the crystal direction>110> angle, but is slower than the growth in the crystal direction>110> angle accelerate. The growth rate and crystal orientation of this epitaxial layer are not unique to the epitaxial growth method of silicon wafers, and it should also exist in the epitaxial growth of other semiconductor wafers. Therefore, although this embodiment is mainly described with a silicon wafer as an example, it should be understood that the concept and connotation of the present invention are also applicable to other semiconductor wafer epitaxial growth methods. For example, the semiconductor wafer described below may be a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon wafer, or a strained silicon-on-insulator wafer, etc. The material of the semiconductor wafer may also be a crystal of other elements such as germanium.

FIG. 2 is a schematic diagram of the distribution of the faster area and the slower area on the silicon wafer in an embodiment of the present invention. Referring to Figure 2, since the growth rate of the epitaxial layer on the edge of the silicon wafer is related to the crystal orientation of the wafer, that is, the growth orientation of the wafer, when the silicon wafer undergoes epitaxial growth in a rotating state, the memory at a certain angle corresponding to different crystal orientations The faster region I where the epitaxial layer grows faster along the circumferential direction, the slower region III where the epitaxial layer grows slowly, and the transition region II where the growth rate is between the faster region I and the slower region III. If no adjustment is made, due to the difference in the growth rate of the epitaxial layer at these positions at the edge, a significant difference in the thickness of the epitaxial layer will be caused, which will cause the flatness of the wafer to deteriorate and the quality and yield of the epitaxial wafer to decrease. . Therefore, it is necessary to adjust the difference in the growth thickness of the regions on the wafer where the epitaxial growth rate is different, especially the growth thickness of the faster region I and the slower region III.

The following first introduces the epitaxial growth equipment of this embodiment. The epitaxial growth equipment of this embodiment has the above-mentioned growth rate of the epitaxial layer due to the difference in growth crystal orientations. When the gas inlet provided on the cavity provides etching gas, the gas inlet rate is related to the rotation of the wafer. The purpose of adjusting the thickness of the epitaxial layer at the edge of the wafer is to obtain an epitaxial layer with a uniform thickness. The adjustment process does not change the design of the epitaxial growth equipment and the susceptor, so the adjustment flexibility is higher.

Fig. 3 is a schematic diagram of the positions of the first air inlet, the second air inlet and the wafer according to the embodiment of the present invention. Fig. 4 is a schematic partial cross-sectional view of an epitaxial growth device in an embodiment of the present invention. 3 and 4, the epitaxial growth apparatus of this embodiment includes a cavity 10 and a susceptor 20 located in the cavity 10, and the susceptor 20 is used to place the wafer 30 and drive the wafer 30 during the epitaxial growth process. When rotating, the susceptor usually drives the wafer 30 to rotate in a horizontal plane with its own centerline as the axis. The cavity 10 is provided with a first air inlet 11 and a second air inlet 12, and the first air inlet 11 allows the reaction gas used to form an epitaxial layer on the wafer 30 to enter the cavity 10, The second gas inlet 12 allows the etching gas used to prevent the deposition of the epitaxial layer from entering the cavity 10; and the edge portion of the wafer 30 has a faster region I and a slower region with different crystal orientations III. The faster region I and the slower region III have different epitaxial growth rates according to different growth directions. Specifically, the epitaxial layer grows faster in the faster region I than in the slower region III. During the epitaxial growth process of 30, as the wafer rotates, the second gas inlet 12 provides an etching gas at a higher rate of etching gas when rotating through the faster zone I than when rotating through the slower zone III. The intake rate of the etching gas.

In this embodiment, a silicon wafer is taken as an example. Referring to FIG. 1, since the growth rate of the epitaxial layer is related to the crystal orientation of the silicon wafer, according to the difference in crystal orientation growth, the edge portion of the silicon wafer includes the faster regions periodically distributed Ⅰ. Transition zone II, slower zone III, including one faster zone I, one slower zone III and two transition zones II in the same cycle, and the faster zone I, transition zone II, slower zone III and The sequence of transition zone II is connected in the circumferential direction, and the difference between two adjacent periods is 90 degrees. The faster zone I in the edge area of the wafer can be set to the predetermined fan angle range of the edge part of the wafer 30> 110> crystal orientation, and the slower zone III can be set to the predetermined fan angle range of the edge part of the wafer 30> 100> crystal orientation. The transition zone II can be set as the edge area of the upper surface of the wafer between the faster zone I and the slower zone III. The edge part can be set according to the specifications of the wafer and experimental data. For example, for a silicon wafer with a diameter of 300mm, the area between 145mm and 150mm from the center point can be used as the edge part of the wafer. The specific range of each interval can be set according to the experimental data of the conventional epitaxial growth method of the epitaxial device with similar structure (the method gas is input into the cavity at a stable gas inlet rate during the epitaxial growth process). For example, the wafer can be The range in the edge portion where the thickness exceeds 5% of the average thickness is defined as the faster zone I, and the range where the thickness is less than 5% of the average thickness is defined as the slower zone III. The thickness of the faster zone I and the slower zone III The difference is mainly due to the different crystal orientations. As an example, the faster zone I can be set within ±5 degrees with >110> crystal orientation as the center line, and the slower zone III can be set within ±5 degrees with >100> crystal orientation as the center line. Set within the range, that is, the fan angles of the faster zone I and the slower zone III can both be in the range of 0-10 degrees.

The susceptor 20 may be made of graphite, silicon carbide or quartz. In the epitaxial growth method, the wafer 30 is usually fixed in the groove 21 on the susceptor 20, and the upper surface of the edge of the groove 21 may be higher than or flush with the upper surface of the wafer 30. The shape of the groove 21 may also be a special shape after considering the factors of gas flow. For example, the bottom surface of the groove 21 may be designed as a slope with a certain slope to adjust the growth of the epitaxial layer by changing the resistance of the air flow. In addition, the epitaxial growth device may be provided with heating components above and below the cavity 10 to heat the wafer 30 and the reaction gas in the cavity 10 to promote the decomposition of the reaction gas and perform vapor deposition on the wafer 30 to form an epitaxial crystal. Floor. The susceptor and heating assembly of this embodiment can adopt conventional designs.

3, the cavity wall of the cavity 10 of the epitaxial growth apparatus is provided with a first air inlet 11 and a second air inlet 12, which can be arranged to be transported from the outside to the cavity 10 in the epitaxial growth method. Reactive gas and etching gas. Further, what the first gas inlet 11 allows to transport may be a mixed method gas including a reaction gas (that is, a source gas) and a carrier gas. The reactive gas used in the epitaxial growth method for silicon wafers can include silicon compounds such as silane (SiH ₄ ), dichlorosilane (SiH ₂ Cl ₂ ), trichlorosilane (SiHCl ₃ ) or tetrachlorosilane (SiCl ₄ ) Gas, H ₂ (hydrogen) or inert gas can be used as a carrier gas. The carrier gas mainly serves to dilute the reaction gas. The method gas can also include a trace amount of dopant gas, such as B ₂ H ₄ . In this embodiment, the reaction gas is, for example, trichlorosilane, or TCS for short, and the carrier gas is, for example, H ₂ . In another embodiment, the carrier gas and dopant gas in the method gas may also be delivered through gas inlets other than the first gas inlet 11 and the second gas inlet 12.

The second air inlet 12 can be arranged at a different position at the same level as the first air inlet 11, that is, the first air inlet 11 and the second air inlet 12 can follow the axis of the cavity 10 (or the center perpendicular to the wafer) They are arranged on the cavity wall at a certain angle to each other. As an example, as shown in Fig. 3, the connecting line between the first air inlet 11 and the second air inlet 12 and the center of the wafer 30 can be arranged perpendicular to each other, so that the first air inlet 11 The direction in which the gas is delivered from the second air inlet 12 is perpendicular to each other. Specifically, the horizontal distance L between the first air inlet 11 and the second air inlet 12 and the edge of the wafer 30 is in the range of about 5 cm to 15 cm, and the distance between the lower edge of the first air inlet 11 and the second air inlet 12 The vertical distance H between the upper surfaces of the grooves 21 of the susceptor 20 is, for example, about 1 mm to 10 mm. In practical applications, the arrangement of the first air inlet 11 and the second air inlet 12 mainly considers that the gas can be transported to the upper surface of the wafer more uniformly.

The etching gas delivered by the second air inlet 12 can prevent the deposition of the epitaxial layer. In this embodiment, the etching gas is, for example, gaseous HCl. Etching gas is often used in the epitaxy method to pre-treat the wafer placed on the susceptor to remove the natural oxide on the wafer surface before epitaxial growth, and after multiple epitaxial growth methods, the The susceptor is processed to remove excess deposits on its surface. In this embodiment, the etching gas is also applied to the epitaxial growth method, that is, the method gas including the reactive gas is delivered to the cavity 10 at the first gas inlet 11 so that the reactive gas is vapor-deposited on the surface of the wafer to form an epitaxial layer. During the process, the second air inlet 12 simultaneously transports the etching gas into the cavity 10. Taking silicon wafer epitaxy as an example, during the epitaxial growth process, the reactive gas entering the cavity 10 is decomposed under heating and forms silicon deposits on the surface of the silicon wafer, while the etching gas causes the silicon to leave the surface of the silicon wafer, and the silicon deposits and The removal reaction is carried out at a relatively high rate, which can be regarded as the movement of silicon on the surface of the silicon wafer. The amount of silicon deposition and the amount of silicon removed are affected by the ratio of the reaction gas and the etching gas in the corresponding area. It can be understood that in the epitaxial growth process of the epitaxial growth equipment mainly described in this embodiment, the etching gas is used to adjust the quality of the epitaxial layer. Therefore, the average deposition rate of silicon should be greater than the average removal rate, that is, during the entire epitaxial growth process Among them, the total deposition amount of silicon is greater than the total removal amount of silicon. In this embodiment, the gas inlet rates of the etching gas and the reaction gas are both in the range of 0-20 L/min. The rotation rate of the wafer is, for example, about 40-60 revolutions per minute, and the specific value can be determined according to actual equipment conditions.

According to the above description, at the edge of the wafer, according to the change of crystal orientation, the growth rate of the epitaxial layer growing along the crystal orientation is different. Among them, corresponding to the faster region I, the growth rate of the epitaxial layer is larger, and the corresponding In the slower zone III, the growth rate of the epitaxial layer is lower. In order to adjust the growth of the epitaxial layer, the deposition thickness of the epitaxial layer in the faster zone I, the slower zone III and the transition zone II tends to be uniform, so as to reduce the local flatness SFQR of the edge part. In this embodiment, During the rotation of the wafer 30 in the epitaxial growth method, the etching gas supplied by the second gas inlet 12 when rotating through the second gas inlet 12 in the faster zone I is greater than that of the etching gas when rotating through the second gas inlet 12 in the slower zone III. The gas inlet rate of the etching gas provided by the second gas inlet 12. That is, for the area where the edge area of the wafer 30 grows faster due to the crystal orientation (that is, the faster area I), the silicon removal reaction is relatively enhanced, while for the area where the edge area of the wafer 30 grows slower due to the crystal orientation (that is, the faster area) The slow zone III) relatively weakens the silicon removal reaction, thus has a reverse regulation effect on the growth difference of the epitaxial layer caused by the different crystal orientations, which is beneficial to make the epitaxial layer in the faster zone I and slower zone III The thickness difference is reduced, thereby helping to reduce the local flatness of the edge portion of the epitaxial wafer.

For the transition area II at the edge of the wafer, since the growth rate of the epitaxial layer in this area is between the faster area I and the slower area III, the second air inlet 12 provides etching when rotating through the transition area II. The gas intake rate can be selected to be between the values of the intake rate provided when the faster zone I and the slower zone III rotate through the second air inlet 12. Of course, if the transition zone II of the wafer 30 further has two or more smaller regions with different epitaxial growth rates according to different crystal orientations, the second air inlet 12 may also be in the two or more smaller regions. When rotating through the second gas inlet 12, the gas inlet rate of the etching gas is changed, so that the silicon deposition amount in the transition zone II tends to be uniform.

In order to make the etching gas provided by the second air inlet 12 rotate at a faster rate during the faster zone I, the rate of the etching gas may be controlled to vary with time in the form of pulses, and in the faster zone I When rotating through the second air inlet 12, the air inlet rate of the etching gas provided by the second air inlet 12 is the peak of the pulse. The specific pulse form that can be used can be one or a combination of two or more of rectangular waves, sharp pulses, sawtooth waves, triangle waves, sine waves, and step waves. Referring to FIG. 2, in this embodiment, the second air inlet 12 passes through four faster regions I, four slower regions III, and between them within a period of one revolution of the wafer 30 (that is, within one rotation period). There are eight transition zones II between the two, so that in each rotation cycle, the etching gas intake rate provided by the second air inlet 12 can be adjusted according to the time point when the faster zone I rotates to the second air inlet 12, respectively. Change in the manner of four pulses. The pulse frequency can vary from 1 Hz to 200 Hz, and the specific value can be determined according to the specifications and rotation rate of the wafer. In addition, considering the distance between the gas inlet and the wafer and the elapsed time of the etching gas from the gas inlet to the wafer, the start time of the transmission pulse of the etching gas provided by the second crystal port can be rotated faster than that of the wafer 30 in zone I. The second gas inlet is slightly advanced for a period of time (for example, about 0.05 second (s) to 1 second), and reaches the speed of the etching gas when the faster zone I rotates through the second gas inlet 12 The intake rate is the effect of the peak of the pulse.

In order to make the etching gas supplied in the faster zone I rotate through the second air inlet 12 at an air intake rate greater than the slow zone III when rotating through the second air inlet 12, the etching gas may also be in accordance with The transportation is carried out in a continuously changing manner. Specifically, during the epitaxial growth process, as the wafer 30 rotates, the faster zone I, the transition zone II, and the slower zone III rotate to the second The gas inlet 12 and the gas inlet rate of the etching gas provided by the second gas inlet 12 can be set to gradually decrease, and follow the slower zone III, the transition zone II, and the faster zone I to rotate to The second gas inlet 11 and the gas inlet rate of the etching gas provided by the second gas inlet 12 may be set to gradually increase. The gradual increase or decrease of the intake rate of the etching gas can be linear or non-linear.

Using the above epitaxial growth equipment, in the faster region I of the edge area of the wafer, the growth of the epitaxial layer is accelerated due to the crystal orientation on the one hand, but on the other hand due to the etching gas provided by the second gas inlet 12 The larger the rate and the decrease of the deposition rate, it helps to suppress the accelerated growth trend caused by the crystal orientation, so that the epitaxial layer grows at an average growth rate with a smaller change range. Similarly, in the slower zone III of the edge area of the wafer, the growth of the epitaxial layer will be slowed down due to the crystal orientation on the one hand, but on the other hand, the etching gas provided by the second gas inlet 12 has a lower inlet rate. The increase in the deposition rate is helpful to adjust the slowing trend of the growth caused by the crystal orientation, and helps the epitaxial layer grow at an average growth rate with a small change range.

Further, that is, during the epitaxial growth process, the gas inlet rate of the reaction gas provided by the first gas inlet 11 can be kept stable, or, according to the needs of adjusting the epitaxial layer, the first gas inlet can also be changed at the same time. The gas flow rate of the reactant gas provided by 11 is changed to adjust the deposition of the epitaxial layer. For example, the reactant gas provided by the first gas inlet 11 can be made to rotate through the first gas inlet 11 in the faster zone I. The air intake rate of is smaller than the air intake rate when the slower zone III rotates through the first air inlet 11, and combined with the second air inlet 12 to control the etching gas inlet rate, it can be adjusted more flexibly The thickness of the epitaxial layer on the surface of the wafer, especially the edge part, reduces the local flatness, and can also reduce the maximum local flatness of the epitaxial wafer, so that the thickness of the epitaxial layer is uniform, the defects are reduced, and the quality of the epitaxial wafer is improved.

FIG. 5 is a schematic flowchart of an epitaxial growth method according to an embodiment of the present invention. 1 to 5, this embodiment also includes an epitaxial growth method, including: First step S1: Place the wafer 30 in the cavity 10 of the epitaxial growth equipment. The edge portion of the wafer 30 has a faster region I and a slower region III with different crystal orientations, and the epitaxial growth is in the faster region. Zone I is faster than in the slower zone III, and the cavity 10 of the epitaxial growth equipment is provided with a first air inlet 11 and a second air inlet 12; The second step S2: rotating the wafer 30 and performing epitaxial growth on the wafer 30, wherein a reactive gas is delivered into the cavity 10 through the first gas inlet 11 to form an epitaxy on the wafer 30 At the same time, the etching gas is delivered into the cavity 10 through the second air inlet 12 to prevent the deposition of the epitaxial layer, wherein, during the epitaxial growth process, the etching gas is The air intake rate when the fast zone I rotates through the second air inlet 12 is greater than the air intake rate when the slow zone III rotates through the second air inlet 12.

Specifically, in the epitaxial growth method of this embodiment, the wafer 30 is placed on the susceptor 20 in the epitaxial growth device, and the wafer 30 is rotated with the susceptor 20, and then passes through the first inlet on the cavity 10 The gas port 11 delivers a reactive gas to the upper surface of the wafer 30 to deposit an epitaxial layer on the wafer 30. At the same time, it also delivers an etching gas to the upper surface of the wafer 30 through the second gas inlet 12 on the cavity 10 to prevent Deposition of epitaxial layer. Among them, since the wafer 30 rotates in the horizontal plane during the epitaxial growth, the crystal orientation toward the air inlet changes during the rotation, so that the faster regions I and the transition regions II with different epitaxial growth rates according to different crystal orientations And the slower zone III periodically passes through the first air inlet 11 and the second air inlet 12.

Furthermore, the epitaxial growth method of this embodiment adjusts the inlet rate of the etching gas according to the difference in the edge area of the wafer 30 facing the second air inlet 12, so that the faster region I where the crystal orientation grows faster is rotated through the second The corresponding etching gas inlet rate at the gas inlet 12 is greater than the corresponding gas inlet rate when rotating through the second inlet 12 in the slower zone III where crystal orientation growth is slower, in order to compensate for the growth caused by the different crystal orientations. The difference in the growth thickness of the crystal layer is adjusted.

In the epitaxial growth method, the traditional epitaxial growth method adopts the method of continuously conveying the reaction gas, and the epitaxial growth method of this embodiment, in the epitaxial growth process, as the wafer rotates, the second step is The gas inlet rate of the etching gas delivered by the gas port 12 is changed according to the specific area of the edge of the wafer rotating through the second gas port 12 to achieve the effect of adjusting the thickness uniformity of the epitaxial layer. In addition, the gas inlet rate of the reaction gas delivered from the first gas inlet 11 can also be changed according to the specific area of the edge of the wafer that reaches the first gas inlet 11, so that the faster regions I and of the edge of the wafer can be changed. The amount of deposition and removal of epitaxial materials (such as silicon) in the slower zone III is adjusted. On the one hand, it is beneficial to the migration of silicon, reduces surface defects, and makes the surface smooth, and also helps to reduce the local flatness of the edge of the epitaxial wafer. Straightness (SFQR) value, which helps to reduce the maximum local flatness (SFQR _max ) value of the epitaxial wafer surface and improve the quality of the epitaxial wafer. The epitaxial growth method provided by the present invention can achieve the effect of improving the quality of the epitaxial wafer without changing the structure of the epitaxial growth device, and because the main adjustment is the gas delivery, it has high flexibility in production Sex.

It should be noted that the embodiments of this specification are described in a progressive manner. For the methods disclosed in the embodiments, since the structures disclosed in the embodiments correspond to the structures disclosed in the embodiments, relevant points can be referred to each other.

The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any person skilled in the art can use the methods and technical content disclosed above to understand the present invention without departing from the spirit and scope of the present invention. The technical solution makes possible changes and modifications. Therefore, all simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention belong to the technical solution of the present invention. protected range.

10: Cavity 11: The first air inlet 12: The second air inlet 20: susceptor 21: Groove 30: chip

FIG. 1 is a schematic diagram of the crystal orientation of a silicon wafer in an embodiment of the present invention.

FIG. 2 is a schematic diagram of the distribution of the faster area and the slower area on the silicon wafer in an embodiment of the present invention.

Fig. 3 is a schematic diagram of the positions of the first air inlet, the second air inlet and the wafer according to the embodiment of the present invention.

Fig. 4 is a schematic partial cross-sectional view of an epitaxial growth device in an embodiment of the present invention.

FIG. 5 is a schematic flowchart of an epitaxial growth method according to an embodiment of the present invention.

Claims (17)

An epitaxial growth equipment, characterized in that the epitaxial growth equipment includes a cavity and a susceptor located in the cavity, the susceptor is used to place the wafer and drive the wafer to rotate during the epitaxial growth process, and the cavity is A first air inlet and a second air inlet are provided, the first air inlet allows the reaction gas used to form an epitaxial layer on the wafer to enter the cavity, and the second air inlet allows The etching gas used to prevent the deposition of the epitaxial layer from entering the cavity; when the edge portion of the wafer has a faster region and a slower region with different crystal orientations, and the epitaxial layer is in the faster region When the growth is faster than in the slower region, during the epitaxial growth process, as the wafer rotates, the second gas inlet provides an intake of etching gas when rotating through the faster region The rate is greater than the intake rate of the etching gas provided when the slower zone rotates through. For example, the epitaxial growth equipment of the first item in the scope of patent application is characterized in that the gas inlet rate of the reaction gas provided by the first gas inlet remains unchanged during the epitaxial growth process. For example, the epitaxial growth equipment of the first item in the scope of the patent application is characterized in that, during the epitaxial growth process, as the wafer rotates, the first air inlet is provided when the faster region rotates through. The feed rate of the reactant gas is smaller than the feed rate of the reactant gas provided when the slower zone rotates through. For example, the epitaxial growth equipment of the first item in the scope of the patent application is characterized in that the air intake rate of the etching gas provided by the second air inlet varies with time in the form of pulses, and the second air inlet is at the The intake rate of the etching gas provided when the faster region rotates through is the peak value of the pulse. The epitaxial growth equipment according to any one of items 1 to 4 in the scope of the patent application is characterized in that the faster area and the slower area are alternately distributed along the circumferential direction of the wafer at the edge portion of the wafer , The edge portion of the wafer further includes a transition region, the transition region is between the adjacent one of the faster region and the one of the slower region, and the crystal orientation of the transition region is such that the epitaxial crystal The growth rate of the layer in the transition zone is between the faster zone and the slower zone. For example, the epitaxial growth equipment of item 5 of the scope of patent application is characterized in that, during the rotation of the wafer, the gas inlet rate of the etching gas provided by the second gas inlet increases with the speed of the faster zone, the The transition zone, the slower zone sequentially rotate to the second air inlet and gradually decrease, and as the slower zone, the transition zone, and the faster zone rotate in turn to the second inlet The breath increases gradually. The epitaxial growth equipment according to any one of items 1 to 4 in the scope of the patent application is characterized in that the wafer is a single crystal silicon wafer, a silicon-on-insulator wafer, a strained silicon wafer, or a strained silicon-on-insulator wafer. For example, the epitaxial growth equipment of item 7 of the scope of the patent application is characterized in that the faster area is located within a predetermined fan angle of the wafer >110> crystal orientation, and the slower area is located at the >100> crystal orientation of the wafer. Within the predetermined fan angle. For example, the epitaxial growth equipment of item 7 of the scope of the patent application is characterized in that the reaction gas includes _{at least one of SiH 4} , SiH ₂ Cl ₂ , SiHCl ₃ and SiCl ₄ ; the etching gas is gaseous HCl. The epitaxial growth equipment according to any one of items 1 to 4 in the scope of the patent application is characterized in that the first air inlet and the second air inlet are located in the same horizontal plane and are located at the center of the wafer. The lines are perpendicular to each other. For example, the epitaxial growth equipment of any one of items 1 to 4 in the scope of the patent application is characterized in that the rotation rate of the wafer is 40-60 revolutions per minute. An epitaxial growth method, characterized in that it comprises: The wafer is placed in the cavity of the epitaxial growth equipment, the edge portion of the wafer has a faster region and a slower region with different crystal orientations, and the epitaxial growth is faster in the faster region than in the slower region , The cavity is provided with a first air inlet and a second air inlet; and The wafer is rotated and epitaxial growth is performed on the wafer, wherein a reactive gas is delivered into the cavity through the first gas inlet to form an epitaxial layer on the wafer, and at the same time, the first gas inlet The two air inlets deliver etching gas into the cavity to prevent the deposition of the epitaxial layer. During the epitaxial growth process, the etching gas rotates through the second air inlet in the faster region. The air intake rate is greater than the air intake rate when rotating through the second air inlet in the slower zone. For example, the epitaxial growth method of item 12 in the scope of the patent application is characterized in that, during the epitaxial growth process, the feed rate of the reaction gas remains unchanged. For example, the epitaxial growth method of item 12 of the scope of patent application is characterized in that, during the epitaxial growth process, the gas inlet velocity of the reaction gas when rotating through the first gas inlet in the faster zone is less than that in the epitaxial growth process. The air intake rate when the slower zone rotates through the first air inlet. For example, the epitaxial growth method of item 12 of the scope of patent application is characterized in that the gas inlet rate of the etching gas changes with time in the form of pulses, and the etching gas rotates through the second The intake rate at the intake port is the peak value of the pulse. For example, the epitaxial growth method of item 15 of the scope of the patent application is characterized in that the inlet rate of the etching gas is one or more of rectangular waves, sharp pulses, sawtooth waves, triangular waves, sine waves, and step waves. The combination form changes over time. For example, the epitaxial growth method of item 12 in the scope of patent application is characterized in that the gas inlet rate of the etching gas is 0-20 liters per minute (L/min).

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