TWI226081B - Air-extracting system of an LPCVD reactor - Google Patents

Abstract

An air-extracting system of a low pressure chemical vapor deposition reactor is provided. The air-extracting system has a pump ring and an air-extracting apparatus. The pump ring surrounds around a susceptor, and has a plurality of pump holes. The pump holes are divided into at least a first group and a second group. The pump holes of the first group have different diameter and distance from the pump holes of the second group. The air-extracting apparatus is positioned in the reactor and facing the second group pump holes for extracting gases. The pump holes with different diameter and distance are for equalizing gas distribution such that the thickness uniformity of LPCVD process is increased.

Description

1226081 V. Description of the invention (1) Technical field to which the invention belongs The present invention provides a low pressure chemical vapor deposition (LPCVD) reactor extraction system. The prior art low pressure chemical vapor deposition reactor is a CVD reaction device that reduces the operating pressure of the reaction gas during the deposition reaction in the reactor to about 1 OOTorr or less. In advanced VLSI processes below 0.1 / zm, with the increase of wafer size, the traditional batch type LPCVD furnace tube has been gradually processed by a single wafer type (single wafer) ) Replaced by LPCVD to reduce thermal budget. The more common compounds deposited using a single wafer LPCVD reactor are Tungsten (W), Tungsten Silicide (Wsi 2), and silicon nitride (Si 1 icon ni tr ide (Si 3N4), so the use of a single wafer LPCVD deposition system at low temperatures has become an important semiconductor technology. Due to the decrease in the collision frequency between gas molecules of the batch furnace tube under low pressure, the vapor deposition reaction is less significant, and the film deposition rate is slower, so the deposited film has very good uniformity and step coverage. ) Capability; on the contrary, compared with the traditional batch LPCVD furnace official, for a single wafer LPCVD reactor,

1226081 V. Description of the invention (2) The yield and deposition rate will be greatly increased, which may cause problems such as low step coverage and uneven film thickness. Please refer to FIG. 1. FIG. 1 is a schematic diagram of a side structure of a single-wafer type LPCVD reactor 10. As shown in FIG. 1, a LPCVD chamber 10 includes a gas inlet 12 connected to the reaction chamber 11 for conveying process gas 14. A shower head 16 is disposed in the reaction chamber. The inner top of 11 is used to make the gas distribution uniform. A supporting member 18 is located at the bottom of the reaction chamber 11 to support the # crystal seat. A crystal seat 20 (susceptor) is located in the bottom branch of the CVD reaction chamber. On the object 18, a wafer 22 is placed, and a ring ring (pump ring) is read around the crystal seat 20, so that the gas in the reaction chamber 11 passes through the suction holes in the ring wall 24 ( pumph ο 1 e) 2 6 is drawn out, an extraction device 2 8 is connected to the extraction port 30 on one side of the reaction chamber 11 to maintain a low pressure state in the reaction chamber 11, and a heater 32 The wafer placed on the support is used to heat the wafer 22 on the wafer 20. During the LPCVD reaction, the deposited wafer 22 is first placed on the crystal base 20 heated by the heater 32, and then the process gas 14 is passed from the reaction to the gas inlet 12 above 10 and reacted to 1 1 through an air-jet head 16 covered with fine holes on its surface, so that the gas is evenly distributed and transmitted to the surface of the wafer 22. After the process gas 14 reaches above the heated wafer 22, a deposition reaction is performed on the surface of the wafer 22 at a predetermined temperature, pressure, and radio wave power. Finally, the remaining gas after the reaction

1226081 V. Description of the invention (3) and reaction by-products are drawn into the suction device 28 through the suction holes 26 in the annular wall 24. Please refer to FIG. 2. FIG. 2 is a schematic diagram showing the structure of the LPCVD reactor 10 of FIG. As shown in FIG. 2, the wafer 22 is placed on the wafer base 20, and the annular wall 24 surrounding the wafer base 16 has a plurality of exhaust holes 26 of equal size and even distribution. Among them, since most of the reaction chambers 11 are restricted to a single exhaust port 30 to connect the extraction device 28 to one side of the reaction chamber 1 1, during the LPCVD deposition, the gas flows through an extraction direction 34 by extraction. The portion of the wafer 22 near the pumping direction side 36 will have a faster flow rate than the four portions farther away from the pumping direction side 38, thus causing the wafer to be deposited thicker on the 36 side than the 38 side, and the wafer thickness status is inconsistent. Because the exhaust holes on the annular wall of the conventional single-wafer LPCVD furnace tube have the same diameter and size, when the gas flows in a single direction 34, a fixed flow rate distribution will inevitably be formed, thus causing the LPCVD process. The thickness distribution of the deposition is different, which further affects the yield of the wafer. SUMMARY OF THE INVENTION The objective of the present invention is to provide a pumping system of an LPCVD reactor capable of uniformly depositing thin films to solve the above problems.

1226081

The best practical learning gas seat includes the pore space distance of the surrounding area. The two groups of stomata are used to surround the current sinking. They are divided into a ring of the invention product reactor and the straight group. The first one is to draw a wall and a plurality of groups, and the second group is to draw the first group. The location of the extraction hole of the extraction device. The extraction system contains a wafer in the LPCVD process and the extraction system. The ring-shaped wall surrounds the suction holes of the crystal base, and the plurality of suction holes are at least, a second group, the suction holes of the first group have different diameters, and the diameter of the air holes between the discs is larger than that of the second group. The set-up is connected to the inside of the reactor and is used to extract the process gas. Since the present invention has more than two sets of suction holes with different diameters and spacings on the annular wall, the flow distribution of the process gas can be controlled, thereby increasing the deposition uniformity of the LPCVD process. Embodiments Please refer to Fig. 3 '. Fig. 3 is a schematic diagram of a single wafer LPCVD reactor 40 according to the present invention. As shown in FIG. 3, the LPCVD reaction chamber 41 includes a gas inlet 42 connected to the reaction chamber 41 for conveying process gas 44. A gas jet head 46 is provided at the top of the reaction chamber 41 and is a ceramic flat plate with a plurality of cloths on it Two 2mm holes can be used to make the gas distributed evenly. A support 48 is located at the bottom of the reaction chamber 41 to support the crystal base 50. The crystal base 50 is arranged on the support 48 in the CVD reaction chamber. For

Page 9 1226081 V. Description of the invention (5) A wafer 5 2 is placed, and a heater 54 is placed below the crystal base in the support, and is used to heat the wafer 52 on the crystal base 50. In addition, in order to enable the reaction to be performed at a low pressure range, the LPCVD equipment also includes a set of vacuum pumping systems to provide the vacuum required for the reaction. The pumping system includes a pumping device 56 made of a pumping motor or other agricultural equipment, which is arranged on one side of the reaction chamber 41 and is connected to the pumping port 60 and is used to maintain the inside of the reaction chamber 41. The low-pressure state, and an annular wall 58 surrounding the crystal seat 50, are used to allow the gas in the reaction chamber 41 to be drawn to the exhaust device 5 6 through the exhaust hole 6 2 in the annular wall 5 8. in. During the LPCVD reaction of silicon nitride, the deposited wafer 52 is placed on a wafer base 50 heated to 6 50 to 800 ° C by a heater 54. After mixing the process gas 44 of SiH4 and NH3 in advance, it enters the reaction chamber 41 from the gas inlet 4 2 above the reaction chamber 41, and through the air-jet head 4 6 covered with fine holes on the surface, the gas is evenly distributed and transferred to the wafer 5 2 surface. Under a pressure of 0.1 to ITorr, when the process gas reaches above the heated wafer 52, after obtaining sufficient energy, a deposition reaction is performed on the surface of the wafer 52. Among them, the present invention is not limited to the deposition of silicon nitride, and other depositions such as silicon dioxide or polycrystalline silicon are also applicable to the present invention. Please refer to FIG. 4, which is a schematic diagram of the structure of the LPCVD reactor of FIG. As shown in FIG. 4, the wafer 52 is placed on the base 50, and the annular wall 58 surrounding the base 50 has at least two groups of different diameters and sizes.

1226081 V. Description of the invention (6) The suction holes 64 and 66 at the same interval are distributed on the annular wall 58. Among them, since the reaction chamber 41 is connected to the exhaust device 5 6 with a single exhaust port 60, one of the reaction chamber 4 1 =, so when the LPCVD deposition is performed, the gas in the reaction chamber 41 will be the oxygen extraction device 5 6 Extraction and flow in an extraction direction 6 8, so the side 70 of the chip 5 2 near the extraction direction will have a faster flow rate than the one 72 that is far away from the extraction direction. Therefore, the present invention uses a smaller diameter and a longer distance between the extraction holes. = 4 is arranged on the annular wall 5 8 on the side of the pumping direction 6 8 to reduce the gas flow rate; and the larger-diameter and closer-spaced suction holes 6 6 are arranged on the ring on the side of the pumping direction 68 The wall 58 can increase the gas flow rate, so the gas distribution flow rate can be adjusted so that the deposition rates on the wafer 52 with respect to the two sides 70 and 72 near or away from the main pumping direction 68 are consistent, thereby forming a uniform thick deposition film. In addition, it is also possible to use more than two sets of suction holes with different f-spacings, which are symmetrically arranged on the% wall 58 near or away from the suction direction 68, and the closer to the suction direction 68, the larger the diameter of the suction holes to be arranged. The smaller the pitch, the greater. Compared with the extraction device of the conventional LPCVD reactor, the present invention has at least two sets of extraction holes with different diameters and spacings on the annular wall, which can improve the different conditions of the flow rate of the private gas, so LPCVD is increased. The deposition uniformity of the process and the yield of the semiconductor wafer. The above description is only a preferred embodiment of the present invention, and any equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the patent of the present invention. End of chapter

Page 11 1226081 Brief description of the drawings Brief description of the drawings Figure 1 is a schematic diagram of the side structure of a conventional single wafer LPCVD reactor. Figure 2 is a schematic diagram of the structure of a single-wafer LPCVD reactor shown in Figure 1. Figure 3 is a side view of the structure of a single-wafer LPCVD reactor of the present invention. Figure 4 is a schematic diagram of the structure of a single-wafer LPCVD reactor shown in Figure 3. Explanation of symbols ❶ 10 '40 tfte · Furnace tube 1 b 41 Reaction chamber 12' 42 Gas inlet Π 14, 44 Process gas 16 '46 Jet head 18 ^ 48 Support 20' 50 Crystal holder 22, 52 Wafer 24 '58 Ring Wall 26 ^ 62, 64, 6 6 28 ^ 56 Extraction device 30 > 60 Extraction π 32 ^ 54 Heater 34 '68 Extraction direction 36 ~ 70 Close to the extraction direction 38' 72 Keep away from the extraction hole in the extraction direction «

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Claims (1)

1226081 6. Scope of patent application 1. A pumping system of a low pressure chemical vapor deposition (LPCVD) reactor. The reactor contains a susceptor for placement. To perform a wafer in an LPCVD process, the pumping system includes: a ring wall surrounding the pedestal, the ring wall is provided with a plurality of pumping holes (pumph ο) 1 e), and the plurality of suction holes can be divided into at least a first group and a second group, and the suction holes of the first group and the suction holes of the second group have different diameters (diameter ) And distance, and the diameter of the suction holes of the first group is larger than the diameter of the suction holes of the second group; and a suction device connected to the inner surface of the reactor for the suction of the second group The position of the air holes is used to extract a process gas; the air holes of the different groups are used to control the flow distribution of the process gas to increase the uniformity of the LPCVD process. 2. The extraction system as described in the first item of the patent application, wherein the LPCVD reactor is used to deposit silicon nitride, silicon dioxide (Si02), or polycrystalline stone ( p〇iSiii con) thin film 03. The extraction system according to item 1 of the patent application scope, wherein the reactor is a single wafer reactor. Page 13 1226081 6. Scope of patent application 4. For the air extraction system of item 1 of the patent application scope, the distance between the exhaust holes in the first group is smaller than the distance between the exhaust holes in the second group. 5. An extraction system for a chemical vapor deposition (CVD) reactor, the reactor includes a crystal holder for placing a wafer to be subjected to a CVD process, the extraction system includes: a ring The wall is around the crystal base. The annular wall is provided with a plurality of exhaust holes, and the plurality of exhaust holes can be divided into at least a first group and a second group. The first group The suction holes and the suction holes of the second group have different diameters and spacings respectively; and a suction device is connected to the position of the inside of the reactor for the suction holes of the second group, and is used to separate a process gas. 6. The extraction system according to item 5 of the patent application, wherein the CVD reactor is a low-pressure chemical vapor deposition (LPCVD) reactor for depositing a nitride oxide and a dioxide oxide (SiO 2). Or a polysilicon film. 7. The extraction system as claimed in claim 5 in which the reactor is a single wafer reactor. 8. For the pumping system of item 5 of the patent application, the pumping holes of the different groups are used to control the flow distribution of the process gas to increase the deposition uniformity of the CVD process. Page 14 1226081 6. Scope of patent application 9. For the air extraction system of item 5 of the patent application scope, the diameter of the suction holes in the first group is larger than the diameter of the suction holes in the second group. 10. The extraction system according to item 5 of the scope of patent application, wherein the distance between the suction holes in the first group is smaller than the distance between the suction holes in the second group. ❿ Μ 1Β1 page 15