JP2013258319A - Method for forming extremely shallow junction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a method for forming an extremely shallow junction, high in mass productivity.SOLUTION: A method for forming an extremely shallow junction includes: a first step of introducing phosphorous radicals 21 as impurities into a silicon substrate S to make the surface amorphous; and a second step of recrystallizing the silicon substrate surface 23 having been made amorphous by a solid phase epitaxial growth method to form an extremely shallow junction 24. In the first step, the surface of the silicon substrate S is exposed to plasma of gas mainly comprising neon.

Description

  The present invention provides an ultra-shallow junction forming method in which impurities are introduced into a processing object to make the surface of the processing object amorphous, and the surface of the amorphous processing object is recrystallized to form an ultra-shallow junction. About.

  In a field effect transistor that is one of semiconductor devices, it is known that when the gate length is shortened, a short channel effect in which a leakage current flows when the transistor is turned off occurs. In order to suppress this short channel effect, It is known to form an ultra-shallow junction (extension region) having a shallower depth from the substrate surface than the source / drain regions.

  Conventionally, as a method for forming an ultra-shallow junction, it is generally known that impurities are introduced into a substrate to make the substrate surface amorphous, and the amorphous substrate surface is recrystallized by heat treatment. As one of the impurity introduction methods, a so-called plasma doping method is known, for example, in Patent Document 1. In this method, a plasma of an impurity-containing gas is generated in a vacuum processing chamber in which the substrate is arranged, and a bias potential is applied to the substrate in conjunction with this, and ions of the impurity in the plasma are drawn toward the substrate. Impurities are introduced.

  On the other hand, as a recrystallization method, a solid phase epitaxial growth method is generally used instead of flash annealing or laser annealing. When using the solid phase epitaxial growth method, the recrystallization of the substrate surface can be performed at a lower temperature, and impurities introduced into the substrate can be prevented from diffusing in the depth direction. It is effective for. However, when impurities are introduced by plasma of a gas to which helium gas is added, helium atoms are also introduced into the substrate along with the impurities, and the introduced helium atoms significantly reduce the recrystallization rate. For this reason, there is a problem that the time required for recrystallization becomes long and mass productivity is lowered.

JP 2004-128210 A

  In view of the above points, an object of the present invention is to provide a method for forming an ultra-shallow junction with high mass productivity.

  In order to solve the above-mentioned problems, a method for forming an ultra-shallow junction according to the present invention includes a first step of introducing impurities into a processing object to make the surface amorphous, and solid-phase epitaxial growth of the amorphized processing object surface. And a second step of forming an ultra-shallow junction by recrystallization by a method, wherein the surface of the object to be processed is exposed to plasma of a gas mainly composed of neon in the first step. In the present invention, the gas plasma mainly composed of neon means a plasma in which the composition of neon ions in the plasma is 50% or more. Further, the amorphized processing target surface includes not only a strict processing target surface but also a surface layer in which impurities are implanted to break the crystal structure.

  According to the present invention, the case where the object to be processed is a silicon substrate and the impurity to be introduced is phosphorus will be described as an example. In the first step, for example, a gas mainly containing neon gas and containing phosphine gas containing phosphorus is used. The phosphorus is introduced into the silicon substrate while colliding with silicon atoms by introducing phosphorus into the silicon substrate. At this time, by exposing the silicon substrate surface to a plasma of a gas mainly composed of neon, the silicon substrate surface can be reliably amorphized. Then, the amorphous silicon substrate surface is recrystallized by solid phase epitaxial growth in the second step, thereby forming an n-type ultra-shallow junction.

  Here, in order to expose the silicon substrate surface to the plasma of gas mainly composed of neon in the first step, neon atoms are also introduced into the silicon substrate together with phosphorus. The introduced neon atoms are obtained by solid phase epitaxial growth. Since the recrystallization rate is hardly lowered, recrystallization of the silicon substrate surface by the solid phase epitaxial growth method can be achieved in a short time. Therefore, an ultra-shallow junction can be formed with high mass productivity.

  In the present invention, in the first step, a plasma of the gas containing the impurity is generated, radicals of the impurity are deposited on the surface of the object to be processed, a plasma of the gas mainly composed of neon is generated, It is preferable to draw neon ions into the surface of the object to be treated. According to this, the in-plane distribution of radicals deposited on the surface of the object to be processed and the in-plane distribution of neon ions drawn into the surface of the object to be processed can be controlled independently, and impurities can be uniformly distributed inside the object to be processed. Can be introduced. In addition, the time required for introducing the impurities can be shortened as compared with the case where the impurities are introduced in one process set to complicated conditions so as to uniformly introduce the impurities into the object to be processed. Then, when depositing impurity radicals, without using a dilution gas, only neon ions are drawn into the surface of the object to be processed, so that other than impurities and neon atoms are not introduced into the object to be processed, and recrystallization is performed. Since the time required for this can be shortened, combined with the fact that the impurity introduction time can be shortened, the mass productivity can be further improved.

  In the present invention, if the object to be treated is cooled to 10 ° C. or lower in the first step, it may be possible to prevent a part of the object to be crystallized during the introduction of impurities.

The figure which shows typically the structure of the plasma processing apparatus used for the formation method of the ultra-shallow junction of embodiment of this invention. 2A to 2C are diagrams illustrating a process of introducing impurities. 3A and 3B are STEM photographs showing the experimental results of the present invention. The figure which shows the experimental result of this invention. The figure which shows the experimental result of this invention.

  Hereinafter, referring to the drawings, a method for forming an ultra-shallow junction according to an embodiment of the present invention in which an object to be processed is a silicon substrate, phosphorus is introduced therein, and the introduced phosphorus is activated to form an ultra-shallow junction. explain.

  Referring to FIG. 1, M is an ICP (inductively coupled plasma) type plasma processing apparatus for introducing phosphorus into a silicon substrate. This plasma processing apparatus M is a vacuum chamber 1 capable of forming a vacuum atmosphere. It has.

  The upper part of the vacuum chamber 1 is constituted by a cylindrical part 2 made of a dielectric such as quartz, and this cylindrical part 2 functions as a plasma generating part. Three ring-shaped magnetic field coils 3, 4, and 5 that can form a magnetic neutral line (NLD) in the cylindrical portion 2 are disposed outside the cylindrical portion 2. Between the cylindrical portion 2 and the magnetic field coils 3 to 5, a loop-shaped antenna coil 6 is disposed. The antenna coil 6 is connected to a high frequency power source 8 via a capacitor 7 so that high frequency power for plasma generation can be input.

  The upper opening of the cylindrical portion 2 is closed by a top plate 9, and the top plate 9 is provided with a gas introduction port 10 for introducing gas into the vacuum chamber 1. The other end of the gas inlet 10 communicates with a gas source via a gas pipe and a mass flow controller (not shown). Thus, the gas can be introduced into the vacuum chamber 1 with the flow rate controlled. In the present embodiment, the first gas source is made of phosphine gas containing phosphorus, and the second gas source is made of neon gas.

  An electrode 12 is disposed on the bottom of the vacuum chamber 1 via an insulator member 11 so that the silicon substrate S transported using a transport robot (not shown) can be placed on the upper surface of the electrode 12 as a substrate placement surface. It has become. The electrode 12 is provided with a refrigerant circulation path (not shown) so that the silicon substrate S can be cooled to a predetermined temperature (for example, 10 ° C. or less). A high frequency power source 14 is connected to the electrode 12 via a blocking capacitor 13 so that a bias potential can be applied. An exhaust pipe 15 is connected to the side wall of the vacuum chamber 1 outside the electrode 12. The exhaust pipe 15 communicates with a vacuum exhaust means including a turbo molecular pump, a rotary pump, a conductance variable valve, etc. (not shown).

  When gas is supplied from the gas inlet 10 into the vacuum chamber 1, current in the same direction is passed through the upper and lower magnetic field coils 3, 5, and current in the opposite direction is passed through the intermediate magnetic field coil 4, An annular magnetic neutral wire 16 is formed therein. When high frequency power is supplied to the antenna coil 6 in this state, plasma is generated along the magnetic neutral line 16.

  Here, by appropriately adjusting the current value of the current flowing through the magnetic field coils 3 and 5 and the current value of the current flowing through the intermediate magnetic field coil 4, the horizontal spread of the magnetic neutral line 16 changes. The plasma spread distribution can be controlled. Hereinafter, with reference to FIG. 2 as well, in the ultra-shallow junction forming method of the present embodiment, phosphorus is introduced into the silicon substrate S using the plasma processing apparatus M to make its surface amorphous, and this amorphous silicon substrate. An example will be described in which the S surface is recrystallized by solid phase epitaxial growth to form an n-type ultra-shallow junction.

First, in a state where the vacuum evacuation means is operated and the vacuum chamber 1 is evacuated to a predetermined degree of vacuum (for example, 10 ⁻³ Pa or less), the silicon substrate S is transferred using a transfer robot (not shown). S is placed on the electrode 12. Then, phosphine (PH ₃ ) gas containing neon gas and phosphorus is supplied from the gas inlet 10 into the vacuum chamber 1. At the same time, a current in the same direction is supplied to the upper and lower magnetic field coils 3 and 5 and a current in the opposite direction is supplied to the intermediate magnetic field coil 4, thereby forming the magnetic neutral wire 16 in the cylindrical portion 2. Further, plasma is generated along the magnetic neutral line 16 by applying high frequency power from the high frequency power supply 8 to the antenna coil 6. At this time, since a negative bias potential is not applied to the electrode 12, ions (P ⁺ , PH _x ⁺ , Ne ⁺ ) in the plasma are not drawn into the silicon substrate S, and as shown in FIG. The deposition of 21 on the surface of the silicon substrate S becomes dominant.

  Here, the distribution of the phosphorus radicals 21 in the plasma can be controlled by adjusting the value of the current flowing through the magnetic field coils 3 to 5 to change the spread of the magnetic neutral line 16, thereby depositing on the surface of the silicon substrate S. The in-plane distribution of the phosphorus radical 21 to be improved can be improved. For example, the phosphorus radical 21 is deposited on the surface of the silicon substrate S under the following radical deposition conditions for a predetermined time (for example, 1 to 5 seconds), and then the supply of phosphine gas is stopped. Note that the phosphorus radical 21 may be deposited by supplying only the phosphine gas.

[Radical deposition conditions]
PH ₃ flow rate: 1 [sccm]
Ne flow rate: 100 [sccm]
Process pressure: 1 [Pa]
Antenna RF power: 400 [W]
Bias RF power: 0 [W]
Magnetic field coil current (up / down / middle): 9 [A] / 8 [A]

Next, a negative bias potential is applied from the high frequency power source 14 to the electrode 12 while the supply of neon gas from the gas inlet 10 into the vacuum chamber 1 and the application of the high frequency power to the antenna coil 6 are continued. Then, a plasma of gas mainly composed of neon is formed, and the surface of the silicon substrate S is exposed to this plasma. As a result, as shown in FIG. 2B, neon ions (Ne ⁺ ) 22 in the plasma are attracted to the silicon substrate S with a predetermined energy and collide with the phosphorus radicals 21, whereby the phosphorus radicals 21 become silicon substrates. The neon ions 22 are also introduced into the silicon substrate S along with being pushed into the S. The dose of phosphorus introduced into the silicon substrate S can be controlled by the drawing time of the neon ions 22 and can be set, for example, within a range of 5E14 cm ^{−2 to} 5E16 cm ⁻² . The phosphorus radicals 21 pushed into the silicon substrate S are introduced while losing energy by colliding with silicon atoms constituting the silicon substrate S, whereby the silicon substrate surface 23 becomes amorphous. The composition of neon ions in the plasma is set to 50% or more. If it is less than 50%, the amorphization of the silicon substrate surface 23 becomes insufficient. Further, as shown in FIG. 2B, some of the phosphorus radicals 21a are etched and scattered by the neon ions 22.

  Here, the distribution of the neon ions 22 in the plasma can be controlled by adjusting the value of the current flowing through the magnetic field coils 3 to 5 to change the spread of the magnetic neutral line 16, and the phosphorus radicals that are pushed into the silicon substrate S. 21 in-plane distribution can be improved. For example, by using the following ion attraction conditions, the spread of the magnetic neutral line 16 that is optimal for obtaining a uniform in-plane distribution of the neon ions 22 on the surface of the silicon substrate S is controlled.

[Ion pulling conditions]
PH ₃ flow rate: 0 [sccm]
Ne flow rate: 100 [sccm]
Process pressure: 1 [Pa]
Antenna RF power: 300 [W]
Bias RF power: 2500 [W]
Bias Vpp: 5.4 [kV]
Magnetic field coil current (up / down / middle): 9 [A] / 7 [A]
Substrate temperature: -20 ° C

  After the neon ions 22 are drawn into the surface of the silicon substrate S for a predetermined time (for example, 0.5 seconds to 10 seconds) under the above ion drawing conditions, the neon gas is supplied, the high frequency power is supplied to the antenna coil 6, and the electrode 12 The application of the bias potential to is stopped. Thereafter, the silicon substrate S is unloaded from the plasma processing apparatus M, and the unloaded silicon substrate S is loaded into a solid phase epitaxial growth apparatus (not shown). Since a solid-phase epitaxial growth apparatus having a known structure can be used, detailed description thereof is omitted here. In the solid phase epitaxial growth apparatus, the surface portion 23 of the amorphous silicon substrate S is recrystallized, thereby forming an n-type ultra-shallow junction 24 in the silicon substrate S as shown in FIG. The At this time, the phosphorus radical 21 introduced into the silicon substrate S is activated. The recrystallization temperature can be set within a range of 500 ° C to 600 ° C. When the temperature is higher than 600 ° C., impurities may be diffused or inactivated, and a shallow and low resistance ultra-shallow junction may not be formed.

  Here, not only phosphorus radicals 21 but also neon ions 22 are introduced into the silicon substrate S, but these neon ions 22 do not decrease the recrystallization rate by the solid phase epitaxial growth method. The recrystallization time can be shortened. Therefore, according to the present embodiment, an ultra-shallow junction can be formed with high mass productivity.

  Further, in this embodiment, since the neon gas is added to the phosphine gas when depositing the phosphorus radicals 21, after the phosphorus radicals 21 are deposited for a predetermined time, the supply of the phosphine gas is stopped, the neon gas supply and the antenna are performed. By applying a negative bias potential while continuously applying high-frequency power to the coil 6, the deposition of the phosphorus radicals 21 and the drawing of the neon ions 22 can be continuously performed. Further improvement.

In order to confirm the above effect, the following experiment was conducted. That is, in this experiment, a processing target is a silicon substrate S having a diameter of 300 mm, and the plasma processing apparatus M is used to deposit phosphorus radicals 21 for 3 seconds under the radical deposition conditions, and then neon ions 22 under the ion attraction conditions. Was carried out for 0.6 seconds (in this case, the dose was 3E15 cm ⁻² ), thereby introducing the phosphorus radical 21 into the silicon substrate S. At this time, by making the composition of neon ions 22 in the plasma 50% or more (100% in this experiment), the silicon substrate surface 23 can be reliably amorphized. A STEM photograph after amorphization is shown in FIG. According to this, it was confirmed that the surface of the silicon substrate was not rough and the surface of the silicon substrate could be made amorphous. Then, the amorphous silicon substrate surface 23 was recrystallized at a temperature of 550 ° C. for 300 seconds by the solid phase epitaxial growth method (invention product). A STEM photograph of the silicon substrate after the recrystallization is shown in FIG. According to this, it was confirmed that the amorphous silicon substrate surface was recrystallized. The phosphorus concentration after radical introduction (after amorphization) and after recrystallization of the product of the present invention was measured by SIMS (Secondary Ion-microprobe Mass Spectrometer), and the measurement results are shown in FIG. According to this, the depth at which the phosphorus concentration is 5E18 [atoms / cm ³ ] is about 19 nm, and it was confirmed that an extremely shallow junction can be formed. Moreover, it was confirmed that almost no phosphorus diffused in the depth direction of the substrate before and after recrystallization.

As another experiment, the neon ion irradiation dose was changed to 0 seconds by changing the drawing time of the neon ions 22 to 0 seconds, 0.6 seconds, 1.3 seconds, and 2.6 seconds under the radical deposition conditions. FIG. 5 shows the results of measuring the sheet resistance values by changing the sheet resistance value to 2.3 + 15 (cm ⁻² ), 5.0E15 (cm ⁻² ), and 1.0E16 (cm ⁻² ). According to this, it was found that there is an optimum neon ion irradiation dose amount that minimizes the resistance value.

The present invention is not limited to the above embodiment. For example, although the case where phosphorus is introduced has been described in the above embodiment, the present invention can also be applied to the case where arsenic or antimony that is an n-type impurity is introduced or boron that is a p-type impurity is introduced. In this case, in place of phosphine gas, by supplying arsine (AsH ₃ ) gas, stibine (SbH ₃ ) gas, diborane (B ₂ H ₆ ) gas, etc., as in the case of introducing phosphorus, ultra shallow junction Can be formed with high mass productivity.

  In the above-described embodiment, the case where impurities are introduced by performing radical deposition and ion attraction in two independent processes has been described as an example. However, the present invention can also be applied to the case where impurities are introduced in one process. In this case, plasma of gas mainly composed of neon gas may be generated. However, since it is necessary to perform the process under complicated process conditions in order to uniformly introduce the impurity into the silicon substrate, there is a demerit that the time required for introducing the impurity becomes longer than that in the above embodiment.

  Further, the deposition of the phosphorus radical 21 and the drawing of the neon ions 22 can be performed in separate chambers. However, as in the above-described embodiment, when the phosphorus radical 21 is deposited, plasma of phosphine gas and neon gas is generated and silicon is used. The bias potential is not applied to the substrate S, and when the neon ions 22 are drawn, the supply of phosphine gas is stopped and the bias potential is applied to the silicon substrate S, so that both steps are executed in the same vacuum chamber 1 continuously. It is preferable to do. According to this, mass productivity can be improved compared with the case where both processes are performed in separate chambers.

  In the above embodiment, the case where phosphorus is introduced into the substrate using an ICP type plasma processing apparatus has been described. However, for example, a parallel plate type plasma processing apparatus or the like may be used.

  S: silicon substrate (object to be processed), 21: phosphorus radical (impurities), 22: neon ions, 23: amorphized portion, 24: ultra shallow junction.

Claims (3)

A first step of introducing impurities into the object to be processed to make the surface amorphous; and a second step of recrystallizing the amorphized surface of the object to be processed by a solid phase epitaxial growth method to form an ultra-shallow junction. ,
A method of forming an ultra-shallow junction, wherein the surface of an object to be processed is exposed to plasma of a gas mainly composed of neon in a first step.   In the first step, a plasma of the gas containing the impurity is generated, radicals of the impurity are deposited on the surface of the object to be processed, a plasma of a gas mainly including the neon is generated, and neon ions in the plasma are generated. 2. The method for forming an ultra-shallow junction according to claim 1, wherein the surface is drawn into the surface of the object to be processed. The method for forming an ultra-shallow junction according to claim 1, wherein the object to be processed is cooled to 10 ° C. or lower in the first step.