JP2012044035A - Semiconductor manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor manufacturing apparatus which can improve in-plane uniformity of processing characteristics such as an etching rate on a wafer even when performing dry etching on a large-diameter wafer by electron cyclotron resonance (ECR) method.SOLUTION: The semiconductor manufacturing apparatus comprises a chamber 107, a power source 101 for generating plasma in the chamber 107, a waveguide 102 for guiding electric power from the power source 101 to the inside of the chamber and a power control unit controlling the power source 101. The semiconductor manufacturing apparatus further comprises an antenna 104 for introducing the power from a periphery to the inside of the chamber 107. The power control unit periodically repeats turning on the power for generating plasma and successively turning off the power before the plasma reaches a steady state.

Description

  The present invention relates to a semiconductor manufacturing apparatus, and more particularly to a semiconductor manufacturing apparatus that performs dry etching or the like using plasma.

  Japanese Laid-Open Patent Publication No. 59-47733 (Patent Document 1) discloses a technique for periodically turning on / off plasma with a dry etching apparatus using plasma. Here, a technique is described in which an off period is periodically provided in plasma to suppress an increase in sample temperature due to ion incidence, and at the same time, the ratio of electron temperature and radical type is controlled. JP-A-1-149965 (Patent Document 2) discloses that the plasma is periodically turned on and off, and that the composition of the plasma is different in the afterglow in the off period, so that ions, radicals and the like are temporally and spatially separated. Describes a method of arbitrarily controlling. The known example also describes that the pulse width is 1 ms or less and the period is 10 s or less. Japanese Patent Laid-Open No. 6-267900 (Patent Document 3) describes a technique for improving etching selectivity by controlling the radical generation rate by setting the repetition frequency to 10 KHz or more and the pulse-off time to 10 μs or less.

  As means for transmitting microwave power to the plasma, many holes on the slots are formed in the conductor plate in Japanese Patent Laid-Open No. 5-190501 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2009-259863 (Patent Document 5). Slot antennas that can be opened are known. High density plasma can be generated by this method.

JP 59-47733 A JP-A-1-149965 JP-A-6-267900 Japanese Patent Laid-Open No. 5-190501 JP 2009-259863 A

  The diameter of a Si wafer used for manufacturing a semiconductor element has been increased to increase the mass productivity and reduce the cost. Currently, the wafer is 300mm in diameter, but the transition to 450mm is being considered in the near future. On the other hand, in the semiconductor manufacturing apparatus, the uniformity of the processing characteristics within the wafer surface becomes an issue as the wafer diameter increases. In a dry etching apparatus using plasma, it is necessary to keep the etching rate and the processing shape uniform within the wafer surface, and the homogenization technique becomes more difficult as the wafer diameter increases.

  In order to improve uniformity with a dry etching apparatus, it is necessary to keep the plasma density in the chamber that directly affects the etching rate and shape uniform. As one of the methods for making the plasma density uniform, a method for optimizing the shape of the antenna described in Patent Document 5 is conceivable. For example, if the etching speed on the wafer peripheral side becomes slower compared to the vicinity of the center as the wafer diameter increases, the number of slots that radiate the electric field is increased in the outer peripheral portion, and the plasma density in the outer peripheral portion is increased. What is necessary is just to design.

  However, in an electron cyclotron resonance (hereinafter referred to as ECR) type etching apparatus, the distribution of plasma density could not be changed greatly even if the arrangement of the slot antennas was changed. The apparatus described in Patent Document 5 generates plasma using surface waves. This is a method in which the electromagnetic wave radiated from the slot generates strong plasma near the slot, and the electromagnetic wave energy is consumed mostly in the vicinity of the antenna and in the part very close to the surface. In this method, strong plasma is generated in the vicinity of the slot antenna, so that the plasma density distribution changes depending on the arrangement of the slot antenna.

  On the other hand, in an ECR system apparatus, a strong magnetic field is applied in plasma. The electric field is influenced by the magnetic field, propagates in the plasma, and is combined with the electric field reflected from the chamber side wall and the chamber bottom to form a standing wave in the chamber. At the same time, when plasma is generated with a 2.45 GHz microwave that is frequently used in commercial equipment, the frequency of the electron's cyclotron motion coincides with the frequency of the electric field to be introduced. Therefore, the plasma density is increased at this point. In the steady state, the plasma diffuses in the direction of the wall, collides with the wall, and ions and electrons recombine. By combining these phenomena, in the ECR apparatus, the plasma density distribution tends to be higher at the center and lower at the outer periphery of the chamber. For this reason, the distribution of the etching rate is also large at the central portion and tends to be low at the outer peripheral portion. The above is considered to be the reason why the plasma density is not greatly influenced by the antenna arrangement in the ECR system.

  An object of the present invention is to provide a semiconductor manufacturing apparatus capable of improving the in-wafer uniformity of processing characteristics such as an etching rate even when a large-diameter wafer is dry-etched by an ECR method. .

  In the present invention, in order to achieve the above object, in a semiconductor manufacturing apparatus that performs dry etching, a power introducing means for supplying power for generating plasma from the outer periphery of the chamber, and a control means for periodically turning on and off the power. Have. Further, the control means turns off the plasma by turning off the electric power before the plasma is generated and diffused to settle in a steady state.

  According to the present invention, it is possible to repeatedly illuminate only the state before the plasma generated in the outer periphery of the chamber diffuses to reach a steady state (density increases in the center), and increases in the center. Even in the ECR system having a tendency, the uniformity of the processing characteristics within the wafer surface can be improved.

1 is a schematic overall configuration diagram of a semiconductor manufacturing apparatus that performs dry etching according to a first embodiment of the present invention; FIG. 2 is a schematic plan view of a main part (antenna plate) of the semiconductor manufacturing apparatus shown in FIG. 1. It is a wafer surface distribution map of the etching rate when poly Si is etched using the semiconductor manufacturing apparatus shown in FIG. It is a schematic plan view of the antenna board used with the semiconductor manufacturing apparatus based on 2nd Example of this invention. FIG. 5 is a diagram showing a relationship between a slot installation range and plasma density uniformity in the antenna plate shown in FIG. 4. It is a schematic plan view of the other antenna board used with the semiconductor manufacturing apparatus based on the 2nd Example of this invention. It is a schematic plan view of the other antenna board used with the semiconductor manufacturing apparatus based on the 2nd Example of this invention. It is a general | schematic whole block diagram of the semiconductor manufacturing apparatus which performs the dry etching based on 3rd Example of this invention. It is a schematic plan view of the principal part (quartz plate part) of the semiconductor manufacturing apparatus shown in FIG.

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

A first embodiment will be described with reference to FIGS.
FIG. 1 and FIG. 2 are an overall configuration diagram of an ECR type dry etching apparatus according to the present embodiment and a plan view of a slot antenna plate used therefor. An electromagnetic wave emitted from the plasma power source 101 is emitted into a chamber (vacuum vessel) 107 through the waveguide 102, the cavity resonator 103, the antenna plate 104 and the quartz plate 106. As shown in FIG. 2, the antenna plate 104 has a slot 105 in the outer periphery.

  In the dry etching process, the etching gas is held in the chamber 107 at a constant pressure, and the etching progresses when the gas is turned into plasma by electromagnetic waves and reactive ions are incident on the wafer 110. Although the diameter of the wafer is 300 mm here, a wafer having a diameter larger than that can be used. A bias power supply 111 for accelerating incident ions is connected to the sample stage 109 that holds the wafer 110. In this apparatus, a magnetic field is generated in the chamber 107 by the electromagnetic coil 108. When the magnetic field strength is set so that the frequency of electron cyclotron motion in the plasma matches the frequency of the plasma power supply 101, electron cyclotron resonance occurs and power is efficiently absorbed into the plasma, maintaining a high plasma density at low pressure. can do. In the figure, a vacuum exhaust pump, a gas introduction system, a control unit for controlling the entire apparatus, and the like are omitted.

  A probe for plasma density measurement having a quick time response was installed on the sample stage 109, and the time change of the plasma density was measured. As a result, it was found that the plasma density reaches a steady value at about 50 ms at the outer periphery of the sample stage 109, but it takes about 150 ms to reach the steady value at the wafer center. In a steady state, the plasma density at the center of the wafer is higher than that at the outer periphery. Since microwave power is introduced from the outer periphery of the chamber, the plasma density instantaneously increases at the outer periphery, but after about 150 ms, the generated plasma diffuses across the magnetic field and becomes a steady state. It means that. On the other hand, when the microwave power was turned off, the plasma density at the outer periphery was reduced by half in about 4 ms and became 0 after 8 ms. At the center of the wafer, the density halved at 9 ms and became zero after 18 ms. It is desirable that 90% or more of the microwave power is introduced from the outer peripheral portion into the chamber.

  From the above results, if the microwave is introduced from the outer periphery, the plasma density is controlled by adjusting the pulse ON time and OFF time if the plasma is turned off before the steady state is reached and this blinking is repeated periodically. I understand that I can do it. Therefore, a control means (not shown) is provided that periodically turns on and off the power for generating plasma. In addition, the control means turns off the plasma by turning off the power before the plasma settles in a steady state after turning on the plasma. This control means is provided in the control section (not shown).

  Uniformity is improved by providing power introduction means for supplying power for generating plasma from the outer periphery of the chamber and control means for periodically turning on and off the power. Further, this control means can improve the uniformity by turning off the power and turning off the plasma before the plasma is generated and diffused and settles to a steady state.

  FIG. 3 shows the result of measuring the saturation ion current (Icf) distribution on the sample stage 109 of the apparatus shown in FIG. 1 with a probe. The radius of the sample stage 109 is 180 mm, which corresponds to a wafer having a diameter of 300 mm. The discharge gas was HBr 150 ml / min / O2 5 ml / min, and the pressure was 0.4 Pa. When the microwave power is compared with continuous 400W and pulse discharge with peak power 800W, repetition frequency 20Hz, duty ratio 50% (average microwave power 400W), uniformity is ± 35.5% during continuous discharge, pulse discharge Within 5% of the time. That is, the plasma density is not uniformed only by introducing the microwave power from the outer peripheral portion of the chamber 107, and is uniformed only when the microwave power is pulsed. Under this pulse condition, the on time of the microwave power is 50 ms and the off time is 50 ms. As described above, the plasma is turned off before the plasma reaches the steady state, and the expected effect is exhibited. Recognize. Further, from the measurement of the change in plasma density over time, it can be seen that the plasma on-time should be shorter than 150 ms and the off-time should be longer than the time required for the plasma density to fall to some extent. Experimentally, it has been found that if the off time is longer than the time when the plasma density is reduced to 50% or less, the effect of homogenization appears. After the power to generate the plasma is turned off, the control can be performed by the control means after the plasma density drops to less than half of the steady state. The time until the plasma reaches the steady state varies depending on the gas pressure and other conditions, but conceptually, the microwave power is introduced from the outer periphery and the plasma is turned on before the plasma reaches the steady state. If this is turned off and this is repeated, the uniformity can be improved. Further, the uniformity can be controlled by adjusting the on / off time. Further, the optimum on / off time at a certain gas type or pressure can be determined experimentally while monitoring the uniformity of the etching rate and the like with the above values as a guide.

  As described above, according to the present embodiment, the ECR system is used for the large-diameter wafer by providing the power introduction means for supplying the power for generating plasma from the outer periphery of the chamber and the control means for periodically repeating the power on / off. Even when dry etching is performed, a semiconductor manufacturing apparatus capable of improving in-wafer uniformity of processing characteristics such as etching rate can be provided. Further, the control means can turn off the power and extinguish the plasma before the plasma is generated and diffused and settles to a steady state, thereby improving the uniformity. In addition, it is effective for improving the uniformity that the control means turns on the power after the power is turned off after the plasma density falls to one-half or less of the steady state. Furthermore, when controlling these on / off operations, uniformity can be effectively improved by using data measured in advance.

  In the above embodiment, in the case of pulsing the μ-wave power, the case where the μ-wave is set to 0 W when turned off has been described, but it is not always necessary to set it to 0 W completely. Essentially, the microwave power at the time of off may be made smaller than the power at the time of on so that the plasma density is 50% or less of the peak. Under the conditions of this example, if the microwave at the time of OFF was set to 200 W or less with respect to the 800 μW of the μ wave at the time of ON, the same uniformity improvement as that of completely setting to 0 W was obtained. Since how much power should be set when turning off depends on conditions such as gas and pressure, uniformity data is acquired in advance under each condition, and a value may be determined based on the data.

  A second embodiment will be described with reference to FIGS. Note that the items described in the first embodiment and not described in the present embodiment can be applied to the present embodiment unless there are special circumstances. The semiconductor manufacturing apparatus used in this example is the same as that shown in Example 1 except for the antenna.

  In this embodiment, an example in which the installation range of slots provided in an antenna is changed will be described. FIG. 4 is a schematic plan view of an antenna. Slots 402 are arranged on an antenna plate 401 in a range of a radius r or more in a plurality of stages. FIG. 5 is a diagram showing the relationship between the radius r and the plasma density uniformity. The gas was Cl2 150 ml / min / O2 3 ml / min, the pressure was 0.6 Pa, and the microwave power was a pulse discharge with a peak power of 1000 W, a repetition frequency of 20 Hz, and a duty ratio of 50% (average microwave power of 500 W).

  The radius of the sample stage 109 is 180 mm, which corresponds to a wafer having a diameter of 300 mm. The uniformity was 10% or less, which is a standard applicable to dry etching when the radius r was 70 mm or more. That is, uniformity can be ensured by introducing microwaves from the outer peripheral portion of about one-half or more of the wafer radius. In an apparatus corresponding to a wafer diameter of 450 mm, microwave power may be introduced from a radius of 110 mm or more.

  FIG. 6 shows another embodiment of the antenna. An antenna plate 601 has a concentric slot 602. In FIG. 7, rectangular slots 702 are arranged in a concentric manner on the outer periphery of the antenna plate 701 in parallel. In any of the antennas, there are various other slot shapes and arrangements for introducing microwaves from the outer periphery, but the same effect can be obtained by installing the slots in a range of half or more of the wafer radius. .

  As described above, according to the present embodiment, even in the case where a large-diameter wafer having a diameter of 300 mm or more is dry-etched by the ECR method, the in-wafer uniformity of processing characteristics such as an etching rate is improved. The semiconductor manufacturing apparatus which can be provided can be provided. Moreover, practical uniformity can be obtained by installing the slot provided in the antenna within a range of one half or more of the wafer radius.

  A third embodiment will be described with reference to FIGS. Note that the matters described in the first or second embodiment and not described in the present embodiment can be applied to the present embodiment unless there are special circumstances.

  FIG. 8 is a schematic overall configuration diagram of a semiconductor manufacturing apparatus that performs dry etching according to the present embodiment, and shows another example in which microwave power is introduced into the outer periphery. FIG. 9 shows a schematic plan view of the quartz plate 106 used in this semiconductor manufacturing apparatus. Here, a microwave absorber 801 such as ferrite or graphite is disposed at the center of the quartz plate 106. In this structure, the microwave at the center is absorbed, so that the electric field strength is weakened, and the plasma density at the outer periphery is increased during discharge lighting. If the microwave absorption amount by the microwave absorber is 90% or more (transmission amount is 10% or less), it can be used practically. By using this microwave absorber, the uniformity of the plasma density can be improved by pulsing the discharge as in the first embodiment. In this case, the installation range of the microwave absorber may be set to a half or more of the wafer radius.

  As described above, according to the present embodiment, even when a large-diameter wafer is dry-etched by the ECR method, it is possible to improve the in-wafer uniformity of processing characteristics such as an etching rate. An apparatus can be provided.

  In the above embodiments, the ECR dry etching apparatus has been described as an example. However, the present invention is applied to a plasma source that propagates an electric field in plasma, such as a plasma source that uses propagation of helicon waves in plasma. Thus, the same effect can be obtained. Further, the frequency of the electromagnetic wave is not limited to 2.45 GHz, and the same effect can be obtained by using, for example, an electromagnetic wave in the UHF band. Further, the application range of the plasma source is not limited to dry etching, and the uniformity can be improved in the same manner even in a plasma source used for chemical vapor deposition (CVD) or the like.

Although the present invention has been described in detail above, the main invention modes are listed below.
(1) A chamber that can be evacuated, a power source for generating plasma in the chamber, a waveguide that guides power from the power source into the chamber, and a control that controls the entire apparatus including the power source. In a semiconductor manufacturing apparatus comprising a part,
Means for introducing the power from the outer periphery of the chamber into the chamber;
The semiconductor manufacturing apparatus according to claim 1, wherein the control unit includes control means for periodically turning on and off the power.
(2) A chamber capable of evacuating the interior, a power source for generating plasma in the chamber, a waveguide for guiding power from the power source into the chamber, and a control for controlling the entire apparatus including the power source In a semiconductor manufacturing apparatus comprising a portion and a sample stage provided in the chamber,
Further comprising power introduction means for introducing the power from the outer periphery of the chamber into the chamber;
The control unit includes control means for periodically turning on and off the power,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introduction means introduces the power from a portion outside a half of a radius of the semiconductor wafer placed on the sample stage.
(3) In the semiconductor manufacturing apparatus according to (1) or (2) above,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introduction means is an antenna plate having a slot provided in an outer peripheral portion.
(4) In the semiconductor manufacturing apparatus according to (1) or (2) above,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introducing means is a power absorber provided at an upper center of the chamber.
(5) In the semiconductor manufacturing apparatus according to any one of (1) to (4),
2. The semiconductor manufacturing apparatus according to claim 1, wherein the plasma is generated using a magnetic field and electron cyclotron resonance.
(6) In the semiconductor manufacturing apparatus according to any one of (1) to (5),
The semiconductor manufacturing apparatus according to claim 1, wherein the control means turns off the power after the power is turned on and before the generated plasma reaches a steady state.
(7) In the semiconductor manufacturing apparatus according to any one of (1) to (6),
The semiconductor manufacturing apparatus according to claim 1, wherein after the power is turned off, the control means turns on the power after the plasma density drops to one-half or less of a steady state.
(8) In the semiconductor manufacturing apparatus according to any one of (1) to (5),
2. The semiconductor manufacturing apparatus according to claim 1, wherein a time from turning on to turning off the power is shorter than 150 ms.
(9) In the semiconductor manufacturing apparatus according to any one of (1) to (5),
2. The semiconductor manufacturing apparatus according to claim 1, wherein a time from turning off the power to turning on is longer than 9 ms.
(10) In the semiconductor manufacturing apparatus described in (6) above,
The semiconductor manufacturing apparatus characterized in that the control means controls the power off using data acquired in advance.
(11) In the semiconductor manufacturing apparatus described in (7) above,
The semiconductor manufacturing apparatus according to claim 1, wherein the control means controls the power on using data acquired in advance.

101: Plasma power source, 102: Waveguide, 103: Cavity resonance part, 104, 401, 601, 701: Antenna plate, 105, 402, 602, 702: Slot, 106: Quartz plate, 107: Chamber, 108: Electromagnetic Coil, 109: sample stage, 110: wafer, 111: bias power source, 801: microwave absorber.

Claims (11)

A chamber capable of evacuating the interior; a power source for generating plasma in the chamber; a waveguide for guiding power from the power source into the chamber; and a controller for controlling the entire apparatus including the power source. In the semiconductor manufacturing apparatus provided,
Further comprising power introduction means for introducing the power from the outer periphery of the chamber into the chamber;
The semiconductor manufacturing apparatus according to claim 1, wherein the control unit includes first control means for periodically turning on and off the power. A chamber capable of evacuating the interior; a power source for generating plasma in the chamber; a waveguide for guiding power from the power source into the chamber; and a controller for controlling the entire apparatus including the power source; In a semiconductor manufacturing apparatus provided with a sample stage provided in the chamber,
Further comprising power introduction means for introducing the power from the outer periphery of the chamber into the chamber;
The control unit includes first control means for periodically turning on and off the power,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introduction means introduces the power from a portion outside a half of a radius of the semiconductor wafer placed on the sample stage. In the semiconductor manufacturing apparatus according to claim 1 or 2,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introduction means is an antenna plate having a slot provided in an outer peripheral portion. In the semiconductor manufacturing apparatus according to claim 1 or 2,
The semiconductor manufacturing apparatus according to claim 1, wherein the power introducing means is a power absorber provided at an upper center of the chamber. The semiconductor manufacturing apparatus according to any one of claims 1 to 4,
The semiconductor manufacturing apparatus, wherein the plasma is generated using a magnetic field and electron cyclotron resonance. The semiconductor manufacturing apparatus according to any one of claims 1 to 5,
The semiconductor manufacturing apparatus according to claim 1, wherein the control means turns off the power after the power is turned on and before the generated plasma reaches a steady state. The semiconductor manufacturing apparatus according to any one of claims 1 to 6,
The semiconductor manufacturing apparatus according to claim 1, wherein after the power is turned off, the control means turns on the power after the plasma density drops to one-half or less of a steady state. The semiconductor manufacturing apparatus according to any one of claims 1 to 5,
2. The semiconductor manufacturing apparatus according to claim 1, wherein a time from turning on to turning off the power is shorter than 150 ms. The semiconductor manufacturing apparatus according to any one of claims 1 to 5,
2. The semiconductor manufacturing apparatus according to claim 1, wherein a time from turning off the power to turning on is longer than 9 ms. The semiconductor manufacturing apparatus according to claim 6,
The semiconductor manufacturing apparatus characterized in that the control means controls the power off using data acquired in advance. The semiconductor manufacturing apparatus according to claim 7,
The semiconductor manufacturing apparatus according to claim 1, wherein the control means controls the power on using data acquired in advance.

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