JP3313635B2 - Method for removing contaminated metal and method for treating bound product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing contaminant metals and a method for treating bonded products, and more particularly, to a method applicable to a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art For the purpose of improving the crystal quality of the surface layer of a CZ-Si substrate, a substrate obtained by subjecting a bare Si substrate to a heat treatment in a hydrogen or Ar gas atmosphere is used. However, these heat-treated substrates have a problem that the amount of metal contamination (particularly, Cu and Fe) is larger than that of a substrate that is not heat-treated. It has also been clarified that the amount of metal contamination depends on the composition of the gas in the heat treatment atmosphere, and the heat treatment in an Ar atmosphere is smaller than the heat treatment in a hydrogen atmosphere.

[0003] Further, a device for preventing a metal contamination of a substrate by exhausting heavy metal permeating through the furnace wall by supplying and discharging an inert gas into a space between each tube by forming a heat treatment furnace into a multi-tube structure has been put into practical use. However, the inert gas functions as a carrier gas and does not sufficiently prevent metal contamination. Although the source of metal contamination is not clear,
When metal outside the furnace tube such as a heater permeates the furnace wall, or when metal contained as an impurity in the furnace material diffuses, it is conceivable that the metal is mixed into the heat treatment gas as a metal oxide. It is also conceivable that oxygen atoms / molecules released from the Si substrate combine with metal atoms to form a metal oxide.

In a film forming apparatus or an etching apparatus, an inner wall of a processing tank, a transfer chamber or a load lock chamber is formed of a metal material such as aluminum, and the inner wall is polished and then coated with a metal oxide film or SiC. I have. This metal oxide film or SiC prevents dust, particularly heavy metals, from being released from the wall surface of the processing tank and adheres to the substrate surface. However, the control of the atmosphere focuses on the control of residual oxygen and residual H ₂ O for the purpose of preventing natural oxidation of Si and metal on the surface of the substrate to be processed, and is released from the inner wall of the processing tank. There is no atmosphere control intended to actively shield and remove heavy metals from the substrate.

[0005]

As described above, although it has been recognized that trace amounts of heavy metal contamination affect the device characteristics and reliability of semiconductor devices, particularly active devices such as transistors, Conventionally, it has not been possible to sufficiently prevent the contamination metal from reaching the semiconductor substrate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a method of removing a contaminated metal capable of preventing the contaminated metal from reaching a substrate to be processed. I do.

[0007]

According to the present invention, there is provided a method for removing a contaminated metal according to the present invention, wherein the contaminated metal causing the contamination of the substrate is positively ionized before reaching the substrate.
The method is characterized in that the positively ionized contaminated metal is reacted with a rare gas and discharged as a combined product (invention A).

A substrate to be processed is a semiconductor substrate such as Si, a contaminant metal is Fe or Cu, and a rare gas is Kr or Xe. As will be described later, by positively ionizing a contaminant metal such as Fe or Cu, the binding energy with a rare gas such as Kr or Xe is increased, and a bond product is easily formed. Therefore, by contaminating the contaminated metal in advance and reacting it with a rare gas such as Kr or Xe, the contaminated metal can be easily discharged as a combined product with the noble gas. Can be prevented. Therefore, when applied to the semiconductor device manufacturing process, the element characteristics and reliability of the semiconductor device can be improved.

When supplying a rare gas, a gas containing at least a rare gas may be supplied. That is, in addition to a single rare gas, a mixed gas of a rare gas and another gas, for example, O ₂ , N ₂ O, O ₃ , atomic oxygen, excited state O ₂ ,
A single gas of an oxidizing gas such as an excited state O atom or a mixed gas of a mixed gas of two or more of these and a rare gas may be used. Examples of the treatment performed on the substrate to be processed include an oxidation treatment, a diffusion treatment, a film formation treatment, and an etching treatment.

[0010] The method for positively ionizing a contaminated metal is roughly classified into the following two methods. First
In the method, a material for promoting the positive ionization of the contaminated metal is formed in a holding container holding the substrate to be processed therein, and the contaminated metal is passed through the material to promote the positive ionization of the contaminated metal.

[0011] In addition to the material for promoting the positive ionization of the contaminated metal, a material for suppressing the positive ionization may be laminated. In this case, the upper side of the material for suppressing the positive ionization (the substrate to be processed is held). It is preferable that a material that promotes positive ionization is formed on the side where the ionization is performed.

As the holding container, a processing container (a processing chamber, a reaction chamber, etc.) for performing a predetermined processing on a substrate to be processed, an evacuation container (a load lock chamber, etc.) for evacuating the substrate to be processed, a substrate to be processed, And a transportable storage container for storing the same. When these holding containers are used, a material that promotes positive ionization is formed on the inner wall of the container. Further, when the present invention is carried out using these, for example, a contaminated metal and a rare gas are allowed to react with each other in a state where a gas containing a rare gas is introduced into the container to generate a bond product, and the inside of the container is evacuated. At the time of exhausting, the combined product is discharged. Further, the holding vessel includes a vessel having a multi-layered vessel wall, for example, a vessel having a plurality of hollow-structured tubes (a reaction tube and a soaking tube). In this case, a material that promotes the positive ionization of the contaminated metal is formed on the inner wall of at least one container wall (tube), and the inner side (for example, the tube and the tube) of the container wall on which the material that promotes the positive ionization is formed. By flowing a gas containing a rare gas through the space between the pipes), the contaminated metal and the rare gas are reacted with each other, and the combined products generated by the reaction are discharged.

In the second method, before the contaminated metal reaches the substrate to be processed, energy is supplied to the contaminated metal by a predetermined method (irradiation of light or particles (irradiation of light beam or particle beam, etc.); (Application of a high-frequency electric field or the like) to promote the positive ionization of the contaminated metal. In particular, irradiation with light having an energy level higher than the ionization potential of the contaminant metal and lower than the ionization potential of the noble gas allows the contaminant metal to be selectively ionized and efficiently generates a bond product. be able to.

In the method for treating a bonded product according to the present invention, a predetermined process is performed on a discharged bonded product generated by a reaction between a contaminated metal causing a contamination of a substrate to be processed and a rare gas, thereby contaminating the contaminated metal. And the noble gas are dissociated, and the dissociated noble gas is reused for the generation of the combined product (invention B).

In order to dissociate the bond product into the contaminant metal and the rare gas, the bond product may be treated at a predetermined temperature or a predetermined gas atmosphere. Specifically, a gas containing at least a binding product is supplied to a path after the processing unit that performs processing on the substrate to be processed, and the binding product is treated at a predetermined temperature or a predetermined gas atmosphere, thereby contaminating the contaminated metal. What is necessary is just to dissociate with a noble gas. The predetermined temperature is preferably higher than the processing temperature in the processing unit. The predetermined gas atmosphere includes a reducing atmosphere, an oxidizing atmosphere,
A nitriding reaction atmosphere, a halogenation reaction atmosphere, and the like can be given, and it is more preferable to perform the heat treatment in these atmospheres. Further, when the combined product is processed at a predetermined temperature or a predetermined gas atmosphere, a high-frequency electric field may be further applied.

According to the invention B, for example, the combined product generated and discharged by the method of the above-described invention A is redissolved, the re-dissociated rare gas is recovered, and the generation and discharge of the combined product are performed again. The gas can be recycled and used effectively, and the rare gas can be efficiently used without waste. In particular, Kr and X
Since e is expensive, the cost can be reduced by such reuse.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing a specific embodiment, an interaction between a rare gas and a contaminated metal will be described. Here, the metal contamination (especially Cu, Fe) in the heat treatment of the bare Si substrate for the purpose of improving the crystal quality of the surface layer portion of the CZ-Si substrate is used as a motif, and a neutral metal atom, positive metal ion and The interaction between a metal oxide and a series of rare gas atoms (Ne, Ar, Kr, Xe) will be discussed from a theoretical and chemical viewpoint by ab initio (ab initio) molecular orbital calculation.

As a calculation method, Hartree-Fo
Assuming that the ck (Hartley Fock) wave function is a single reference electron configuration function, the electron correlation effect on this wave function is 1,
CCSD (T) (CCSD: Coupl) obtained by adding perturbation correction from the three-electron excitation configuration to the two-electron excitation cluster expansion method
ed Cluster Calculation wi
the Single Single and Doub
le) A method of evaluating at the level was adopted. The basis functions include Hay, Wadt for atoms other than O and Ne.
Effective core potential (ECP: Effective)
e Core Potential) spl
Dunning-Hay split-valley is used for O and Ne using the it-valance basis function.
Basis functions were used. At this calculation level, the molecular structure such as equilibrium structure and binding energy for various binding products
The ar properties were calculated and compared. The results are shown below.

(A) A series of rare gas atoms are neutral Cu, F
It has almost no chemical bonding interaction with the e atom. Therefore, only elastic / inelastic collisions occur, but no metal center cluster is formed.

(B) Each of the series of rare gas atoms forms a bond product with the metal positive ions ¹ Cu ⁺ and ⁶ Fe ⁺ .
However, the bonding strength greatly depends on the type of the rare gas.
The calculation results are shown in FIG.

It can be seen that the bonding force increases with increasing atomic number from Ne to Xe, and that the heavy noble gas atoms are more strongly bonded to metal positive ions. This is because Mulliken
(Mulliken) According to the electron density analysis result, it is understood that the electronic state of the bond changes as the heavy rare gas is reached. In the overlap charge between the metal and the rare gas, the overlap between the atomic orbitals increases as the heavy rare gas atom. Along with this, it can be seen from the change in the total electron density that the positive charges on the metal positive ions move toward the rare gas atoms as the heavy rare gas atoms. These indicate that the bond between the rare gas and the metal cation increases the covalent property as the heavy noble gas increases the bonding force. This can be explained from the frontier orbit theory. For example, the bond formation for ¹ Cu ⁺ ion is
¹ Cu ⁺ lowest vacancy atomic orbital (LUAO: Lowest Unocc)
4s orbital, which is an upied atomic orbital, and the highest occupied atomic orbital of a rare gas atom (HOAO: Highest Occupied Atomi)
c Orbital) orbital mixing due to orbital interaction between 2p to 5p orbitals, which is caused by stabilization. As can be seen from the orbital correlation diagram shown in FIG. 6, the HOAO energy level of the rare gas atom increases in order from Ne to Xe, approaches the ¹ Cu ⁺ LUAO level, and the orbital interaction becomes stronger in this order. In addition, ¹ Cu ⁺ and ⁶ Fe ⁺
FIG. 6 also shows that there is a clear difference in the bonding force.
LUAO has 4s orbitals in both ¹ Cu ⁺ and ⁶ Fe ⁺ , and the orbital energies are -0.2372 and -0.242, respectively.
4 hearttree (1 hearttree = 27.211e
And V), 0.005hartree only ⁶ Fe ⁺ it is low, the energy difference between HOAO orbital group of the rare gas is ⁶ F
e ⁺ is smaller. However, while ¹ Cu ⁺ has 0 4s electrons, ⁶ Fe ⁺ has 1 electron (commonly, 3d orbitals and less are occupied and exhausted). Therefore, electron repulsion interaction in trajectories involved in bond formation bonding force becomes larger in the ⁶ Fe ⁺ is weakened. It has been experimentally observed that Cr ⁺ and Co ⁺ ions form a cluster surrounded by a plurality of rare gas atoms (J. of Phys. Chem., Vol. 95, 10600).
(1991)).

(C) Each of the series of rare gas atoms forms a bond product with the metal oxides CuO and FeO. However, the bonding strength greatly depends on the type of the rare gas. The calculation results are shown in FIGS.

First, the characteristics of CuO and FeO will be considered.
In CuO and FeO, the doublet and the sevent are in the ground state, respectively. As a result of the electron density analysis, the polarization of the charge is larger in FeO than in CuO, and FeO has a Coulomb-coupling property compared to CuO. Although the overlapping charge between the rare gas and the metal is stronger in CuO, the binding energy is FeO> C
The fact that uO is used indicates that Coulomb bonding significantly contributes to the bonding force in the metal oxide. These metal oxides form a bond product having a series of noble gas atoms and a bond between the metal and the noble gas.
It can be seen that the bonding force increases as the atomic number increases up to e, and that the heavy noble gas atoms bond more strongly to the metal oxide. This is because, as in the case of the metal positive ions described above, the electronic state of the bond changes as the gas becomes heavy and rare gas. In other words, the overlap charge between the metal and the rare gas is such that the overlap between the atomic orbitals increases as the heavy rare gas atom increases. As a result, the positive charge on the metal that is more positively polarized as the heavy rare gas atom moves toward the rare gas atom. Moving. The difference from the metal positive ion is
That is, the binding energy is extremely small in the case of FeO. Therefore, the Fe-rare gas bonding distance is an extremely large value of 5 Å or more, and it is doubtful whether the bonding state has a finite life even at room temperature.

Next, the substance which promotes the positive ionization of metal will be described with reference to SiO ₂ as an example.
Consider whether ₂ is effective for positive ionization of metals. Si
One of the determinants of metal atom diffusion in O _{2 is} SiO 2
The solid solubility limits of metals in metals have been investigated (Journal Electroc
chemical Society vol.133 p.1242 1986). According to this, metal atoms are monovalent cations in SiO ₂ , so that the solid solubility limit is equal to the saturated concentration of monovalent cations. It is also stated that the saturation concentration is reduced when no impurities such as H ₂ O are present. In the process of converting a metal atom into a monovalent cation in SiO ₂ , it is important to stabilize the energy released by ionization in terms of energy, but this was not discussed. The stabilization of the released electrons depends on the level accepting the electrons, that is, the acceptor level, and the amount of the stabilized metal depends on the concentration of this level, that is, the acceptor concentration.
Therefore, it is possible to control the monovalent cation ionization process of metal atoms by changing the acceptor level and the concentration in SiO ₂ . This will be briefly described below.

The cation of the metal atom M is the ionization potential E _ion in a vacuum, E is in SiO _{2 ion} /
Energy of γ (γ is the relative dielectric constant of SiO ₂ ) is required. However, in SiO ₂ Unlike in vacuum, ionization reaction ^{"M → M + + e -} " - interaction energy (mainly Coulomb attraction between the at M ⁺ is generated, and negatively polarized in the SiO ₂ O ) Only E _{bind is} stabilized. Furthermore, S
When an acceptor level exists in iO ₂ , “M
→ M ^{+ +} e - ^"in the resulting e ^-, the acceptor level to be trapped it is only stabilized E _elec.

The above process will be considered with a model in which SiO ₂ is filled with an ideal gas of an electrically neutral metal M (concentration [M _gas ] atoms / m ³ ). As described above, the presence of the acceptor level promotes the cationization of the metal atom M, and the metal M is present mostly in the form of M ⁺ in SiO ₂ . The saturation concentration of e ^{− in} SiO ₂ is [e
^-] When electrons / m ^3, the saturation concentration of M ⁺ in the ^{_{SiO 2 [M ox +] atoms}} / m 3 ^{_{is, [M ox +] [e}} -] / [M gas] = (2πm e kT / h ² ) ^3/2 ×
It can be expressed as exp (-E _int / kT). Here, _me is the mass of electrons, k is Boltzmann's constant, T is temperature, and h is Planck's constant.
The total interaction energy E _int can be expressed as E _int = E _ion / γ-E _{bind in} the case of SiO ₂ containing no acceptor. Here, γ is the relative dielectric constant of SiO ₂ , which is about 3.9. On the other hand, when a sufficient acceptor is included, E _int = E _ion / γ-E _bind -E _elec , and the stabilization is increased by E _elec . The electrically neutral ^{_{condition, [M ox +] = [}} e -] So, after ^{_{all, [M ox +] = [}} M gas] 1/2 (2πm e kT / h 2) 3/4 × e
It can be expressed as xp (-E _int / 2kT).

The case of Cu and Fe will be exemplified. First, the saturation concentration [M _gas ] of the ideal gas of the metal M is determined by the temperature kT (J).
[M _gas ] = P where the saturated vapor pressure at
/ KT. P is log (P) = 5.006 + A + B / T + Clog T + D /
T ³ and can be approximated. At temperatures below the melting point, (A, B, C, D) = (9.123, -17748, −) for Cu.
0.7317, none), (A, B, C, D) =
(7.100, -21723,0.4536, -0.5
846). Among these parameters, B mainly gives Arrhenius-type dependence, and Cu and Fe are -1.529 and -1.872 eV, respectively.

The first ionization potential E _ion is Cu
And Fe are 7.726 eV and 7.902 eV, respectively.
Taking the binding energy of the diatomic molecule CuO and FeO shown in FIG. 8 as the interaction energy E _bind , they are 1.977 eV and 2.567 eV, respectively. Furthermore, Si
Examples of the acceptor level in O _2, Si-O (non-bridging oxygen defects: NBO) thinking, When this stabilization energy in the case of capturing electrons and E _elec, 2.24 eV
It is.

[0029] With the ^{_{above, [M ox +] = (}} kT) -1/2 (2πm e kT / h 2) 3/4 10
^{(5.006 + A) / 2} T ^{c / 2} × exp [-{E _int -k (B + D / T ² ) ln10} / 2k
T]. Considering that the pre-exponential factor is C to -0.5, it is approximately T ⁰ and may be independent of temperature. Furthermore, exponential factor since negligible D / T ² is above room temperature, exp - may be approximated by _{[{E int -kB ln10} /} 2kT].

After all, [M _ox ⁺ ] (atoms / m ³ ) is Cu
And Fe, respectively, are approximately as follows. When there is no acceptor, [Cu _ox ⁺ ] to 1.5 × 10 ²⁹ × exp (-1.763 / kT) [Fe _ox ⁺ ] to 1.5 × 10 ²⁸ × exp (-1.885 / kT). When NBO is sufficient as the acceptor level, [Cu _ox ⁺ ] 〜1.5 × 10 ²⁹ × exp (−0.643 / kT) [Fe _ox ⁺ ] 〜1.5 × 10 ²⁸ × exp (-0.765 / kT) Here, kT is in eV.

[M _ox ⁺ ] (atom) at 600 to 1000 ° C.
s / cm ³ ) is shown in FIG. This is because when no acceptor is present, the pp
This indicates that only heavy metals of the order of m can form a solid solution, that is, cannot be cationized, and when the acceptor concentration, which indicates stabilization by electron capture of about 2 eV, is sufficiently high, about 10 ^{-3 to 1} mol% of the metal is positively ionized. It shows that it can be ionized. For reference, amorphous SiO
The molar concentration of ₂ is approximately 2.2 × 10 ²² mol / cm ³ .

Next, FIG. 11 shows the change of the solid solubility limit when the stabilization energy E _elec at the time of electron capture by the acceptor level changes, taking Cu as an example. However, it is assumed that the acceptor concentration is sufficiently high. FIG. 11 shows that the larger the stabilization energy at the time of electron capture by the acceptor level, the higher the solid solubility limit of the metal, that is, the positive ionization concentration.

Considering that the molar concentration of amorphous SiO ₂ and the typical concentration of heavy metal which is a polluting source in the current semiconductor manufacturing process are about 10 ¹⁵ (atoms / cm ³ ) or more, [M _ox ⁺ ]> 1 × 10
¹⁵ (atoms / cm ^{3), _{i.e., (kT) -1/2 (2πm e}} kT / h 2) 3/4 10 (5.006 + A) / 2 T c / 2 × e
_{xp [- {E int -k (} B + D / T 2) ln10} / 2kT]> 1 × 10 15 electron capture by the temperature T and the acceptor level satisfying _{E int = E ion / γ-} E bind -E elec It can be seen that the metal can be cationized within the range of the stabilization energy E _elec at the time.

The highest charge trapping defect among currently used SiO ₂ is the so-called P-CVD SiO formed by plasma CVD (chemical vapor deposition).
₂ Tetraethoxysilane (Si (OC ₂ H ₅ )
₄₎ the most with O ₂ general P-CVD SiO ₂
When the film was analyzed by electron spin resonance (ESR),
Unpaired electron defects caused by impurities (mainly C) (up to 6 × 10
Defects due to SiO ₂ other than ¹⁷ cm ⁻³ ) were mainly three. Non-crosslinked oxygen hole center (Si-O ... O-
Si) and peroxide radicals (Si-O-O ...... -Si ) defect concentration due to the ~1.3 × 10 ¹⁷ cm ^-3, the defect concentration to 4 due to the E Center (Si ...... Si) × 10 ¹⁷
cm ^-3 ( ^note that the ends of each of the above Sis are back bonds). In addition, FIG. 12 shows the energy levels of various forms of the non-crosslinked hole center (J. A.
ppl. Phys. vol68 p.1212 (1990)). However, in the P-CVD SiO ₂ film or the thermally oxidized SiO ₂ film obtained by adding fluorine to this film, any defect was 1 × 10 ¹³ or less. That is, it can be seen that the type and concentration of the charge trapping defect level of SiO ₂ can be controlled by the film formation method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a horizontal diffusion furnace will be described as an example of the first embodiment with reference to FIG.

The diffusion furnace 100 having the double tube structure has two hollow cylindrical quartz tubes 101 and 102 having different diameters fitted in a loosely fitted state along the longitudinal direction. A heat equalizing tube 103 is provided so as to include the tubes 101 and 102, and an electric furnace 104 including a heater is provided on the outer surface of the heat equalizing tube 103.

The quartz tubes 101 and 102 are made of fused quartz, and the inner quartz tube 101 is a Si substrate 10 on which a diffusion process is performed.
A jig 107 capable of accommodating therein 6 is provided. Liner tube 103 is a material suppressing example SiC or manufactured SiN positive ions of heavy metals, are materials such as SiO ₂ on its inner surface to facilitate the positive ions of heavy metals (SiO ₂ that satisfies the conditions described above) Coated,
Outgassing from the wall surface of the soaking tube 103 and contamination of the substrate by heavy metals are prevented. Further, gas flows 108a, 108b and 108c are provided between the inner quartz tube 101, between the inner quartz tube 101 and the outer quartz tube 102, and between the outer quartz tube 102 and the soaking tube 103. It is being supplied. Furthermore, there is at least one space between the inner quartz tube 101 and the outer quartz tube 102 along the furnace tube.
A thermocouple 105 is provided.

Using the heat treatment furnace configured as described above,
If the i substrate 106 subjected to the impurity diffusion process such as source and drain layers formed, for example, BF ₂ ions are implanted S
The i-substrate 106 is placed on a jig 107 and the inner quartz tube 101
And the inside of the inner quartz tube 101 is set to an N ₂ atmosphere of 1 atm.
Heat treatment is performed at a temperature of about 1000 ° C. to obtain a desired diffusion length. Inner quartz tube 101 and outer quartz tube 102
, And between the outer quartz tube 102 and the soaking tube 103, a mixed gas of 0.2 atm O ₂ gas and 0.8 atm Kr gas was supplied and discharged at a flow rate of 10 slm.

[0039] Analysis of the Si substrate subjected to the heat treatment in the gas phase analysis method flameless atomic absorption spectrometry, 5 × 10 ¹⁵
atoms / cm ³ Fe and 1.5 × 10 ¹⁵ atoms
/ Cm ³ of Cu was detected. This metal impurity concentration is
The value in the heat treatment using the conventional heat treatment gas (5 × 10 ¹⁶ a
toms / cm ³ Fe, 3 × 10 ¹⁶ atoms / cm
³ was lower by one digit or more than that of Cu).

The composition of the gas supplied and discharged between the inner quartz tube 101 and the outer quartz tube 102 and that between the outer quartz tube 102 and the soaking tube 103 need not be the same. It need not be a mixed gas. For example, the outer quartz tube 1
02 and the soaking tube 103, a mixed gas of 0.5 atm O ₂ gas and 0.5 atm N ₂ gas is supplied and discharged at a flow rate of 10 slm, and the inner quartz tube 101 and the outer quartz tube 101 are supplied and discharged. If the fed exhaust a mixed gas of N ₂ gas of Kr gas and 0.5 atm 0.5 atm at a flow rate of 10slm between the quartz tube 102, or quartz tube 102 of the outer and soaking tube 103 Between 0 and 1.
A mixed gas of 8 atm O ₂ gas and 0.2 atm N ₂ gas is supplied and discharged at a flow rate of 10 slm, and 1 atm Xe is supplied between the inner quartz tube 101 and the outer quartz tube 102. Only gas 1
In the case of supplying and discharging at a flow rate of 0 slm, almost the same metal impurity shielding effect was obtained.

Next, a vertical oxidation furnace will be described as a second embodiment with reference to FIG. The oxidation furnace 200 having the double tube structure is composed of two hollow cylindrical quartz tubes 2 having different diameters.
01 and 202 are fitted in a loose fit state along the longitudinal direction. In addition, the heat equalizing tube 203 disposed so as to include the two quartz tubes 201 and 202 and the heat equalizing tube 20 are provided.
3 and an electric furnace 204 comprising a heater disposed on the outer surface.

The quartz tubes 201 and 202 are made of fused quartz, and the inner quartz tube 201 is a silicon substrate 20 to be oxidized.
A jig 207 capable of accommodating therein 6 is provided. Liner tube 203 is a material suppressing example SiC or manufactured SiN positive ions of heavy metals, are materials such as SiO ₂ on its inner surface to facilitate the positive ions of heavy metals (SiO ₂ that satisfies the conditions described above) Coated,
Outgassing from the wall of the soaking tube 203 and contamination of the substrate by heavy metals are prevented. Inner quartz tube 2
A plurality of gas flows 209a supplied between the inner quartz tube 201 and the outer quartz tube 202 are provided on the top of the upper lid 01 so that the gas flow 209a is uniformly supplied into the inner quartz tube 201. A pore 208 is provided. Further, a gas flow 209b is supplied between the outer quartz tube 202 and the soaking tube 203. Further, at least one thermocouple 205 is provided between the outer quartz tube 202 and the soaking tube 203 along the furnace tube.

Using the heat treatment furnace configured as described above,
When performing an oxidation process such as formation of a SiO ₂ film as a gate insulating film on the i-substrate 206, the process is performed as follows, for example. A Si substrate 206 that has been subjected to a pretreatment for obtaining a sufficiently clean Si surface to form a gate insulating film is placed on a jig 207, and an inner quartz tube 201 and an inner quartz tube 201 and an outer quartz tube 202 are placed. While supplying and discharging 1 atm of N ₂ gas, the inside is housed in the inner quartz tube 201 which has been heated and held to a uniform temperature of 650 ° C. in advance. After the temperature of the Si substrate 206 reaches the same temperature as the atmosphere in the heat treatment furnace 200, O ₂ gas at 1 atm is supplied to the inner quartz tube 201 and between the inner quartz tube 201 and the outer quartz tube 202. Then, the silicon substrate 206 is heated to 800 to 1200 ° C. by the electric furnace 204 to perform an oxidation process for a time to obtain a desired oxide film thickness. At this time, a mixed gas of 0.2 atm O ₂ gas and 0.8 atm Kr gas is placed between the outer quartz tube 202 and the soaking tube 203.
Supply and discharge were performed at a flow rate of 0 slm.

[0044] Analysis of the Si substrate subjected to the heat treatment in the gas phase analysis method flameless atomic absorption spectrometry, 5 × 10 ¹⁵
atoms / cm ³ Fe and 1.5 × 10 ¹⁵ atoms
/ Cm ³ of Cu was detected. This metal impurity concentration is
The value in the heat treatment using the conventional heat treatment gas (5 × 10 ¹⁶ a
toms / cm ³ Fe, 3 × 10 ¹⁶ atoms / cm
³ was lower by one digit or more than that of Cu).

The composition of the gas supplied and discharged between the inner quartz tube 201 and the outer quartz tube 202 and between the outer quartz tube 202 and the soaking tube 203 need not be the same. It need not be a mixed gas. For example, the outer quartz tube 2
02 and the discharge feed a mixed gas of N ₂ gas of O ₂ gas and 0.5 atm 0.5 atm at a flow rate of 10slm between the soaking tube 203, the inside of the quartz tube 201 and the outer side of When a mixed gas of 0.5 atm Kr gas and 0.5 atm O ₂ gas is supplied and discharged at a flow rate of 10 slm between the quartz tube 202 and the quartz tube 202 and the soaking tube 203 at the outer side Between 0 and 1.
The O ₂ gas and 0.6 atm mixed gas of Xe gas of 4 atm discharge feed at a flow rate of 10 slm, O 1 atm between the inside of the quartz tube 201 and an outer quartz tube 202 ₂ Only gas 1
In the case of supplying and discharging at a flow rate of 0 slm, almost the same metal impurity shielding effect was obtained.

Next, a third embodiment will be described with reference to FIG. This embodiment shows a processing apparatus system in which a plurality of processing apparatuses are connected, an atmosphere control of a substrate transfer system between the processing apparatuses, and the like.

The processing apparatus system 300 is roughly divided into a semiconductor processing apparatus 301 and a storage container 30 connected thereto.
The semiconductor processing apparatus 301 includes a processing chamber 303 and a load lock chamber 304. The processing chamber 303 and the load lock chamber 304 are connected by a gate valve 305. Further, the load lock chamber 304 and the storage container 302 have a cluster tool structure including a gate valve 306 provided therebetween, and the connection means 30 connected to the gate valve 306.
7 and a door 308 provided on the side wall surface of the storage container 302. Hereinafter, a more detailed configuration of the above device will be described.

The semiconductor processing apparatus 301 is an apparatus that performs an oxidation process, a diffusion process, a heat treatment, a film formation process, or an etching process on a substrate. Hereinafter, each of the processing chamber 303 and the load lock chamber 304 will be described in detail.

The processing chamber 303 is kept airtight by a processing container 309, and the substrate 31 to be processed is contained in the container 309.
There is provided a mounting table 310 on which the mounting table 1 is mounted. The processing container 309 is formed of a metal material, for example, an aluminum alloy. The inner wall made of an aluminum alloy is polished and then an oxide film is formed on the surface, and a material for suppressing the positive ionization of heavy metals, such as SiC or SiN, is further promoted on the surface. materials such as SiO ₂ to (SiO ₂ that satisfies the conditions described above) is covered, and is configured to prevent contamination of the substrate 311 surface by outgassing and heavy metals from the wall. In particular, with respect to heavy metals, a layer made of a material that suppresses positive ionization of heavy metals suppressed diffusion of heavy metals, and a layer made of a material that promoted positive ionization of heavy metals released heavy metals into the processing chamber 309 from the wall surface. In this case, the efficiency of heavy metal removal is improved.

At a position facing the mounting surface of the mounting table 310, a shower head 312 for mixing and supplying a plurality of process gases is provided. A plurality of gas supply units 313 for supplying a plurality of process gases for processing the substrate 311 are connected to the shower head via opening / closing valves 314 in the middle of the pipes connected to the respective gas. Further, an exhaust port 315 is provided on the bottom surface of the processing container 309, and the inside of the processing container 309 is several Torr to 1 × 10 ⁻ by exhaust means 316 (for example, a combination of a rotary pump and a turbo molecular pump) provided outside. ⁸ Tor
The vacuum evacuation is performed to a predetermined degree of r.

When plasma-assisted processing such as etching or film formation is performed in the processing chamber 303, the processing vessel 309 is electrically grounded, and the mounting table 310 is used as a lower electrode, for example, at 100 kHz to 500 kHz.
A high frequency electric field of KHz is applied through a matching circuit, and a high frequency electric field of 13.56 MHz, for example, is applied to the shower head 312 as an upper electrode through the matching circuit.

The processing chamber 303 configured as described above and the adjacent load lock chamber 304 can be connected to each other by a gate valve 305 that opens automatically when a workpiece is loaded.

The load lock chamber 304 has an airtight structure, in which the substrate 311 is transferred,
Transport means 3 for mounting the substrate 311 on the third mounting table 310
17 are provided. The transport means 317 is sealed by a magnetic rail at the bottom of the load lock chamber 304, and is connected to a drive means 318 provided outside with a drive shaft capable of rotating, moving up and down, and driving in the X-axis or Y-axis. By the driving force of the driving unit 318, the transporting unit 317 can move forward, backward, rotate, and move up and down.

An inert gas (for example, N ₂ or Ar) or Xe or Kr containing Xe or Kr is supplied into the load lock chamber 304 from a gas supply means 319 provided outside.
Is supplied through an opening / closing valve 320 and a filter 321 provided in the load lock chamber 304. This filter 321
For example, a porous body formed with a large number of fine holes similar to a gas shower head or a fine sintered body can be used.

At the bottom of the load lock chamber 304, exhaust means 324 (for example, a turbo pump and a rotary pump) is provided via an exhaust port 322 and a valve 323. This exhaust means 324 allows the load lock chamber 304
Is a predetermined degree of vacuum from atmospheric pressure, for example, several tens Torr to
The chamber is evacuated to 1 × 10 ⁻⁵ Torr. The load lock chamber 304 is formed of, for example, an aluminum alloy, the inner wall is coated with an oxide film after polishing, and the surface thereof is made of a material for suppressing positive ionization of heavy metals, for example, SiC or SiN.
But is covered, contamination by outgassing and heavy metals from the wall surface is prevented (SiO ₂ that satisfies the conditions described above) material such as SiO ₂ promotes positive ions of heavy metals and more its surface It has become. The function of these coating layers is the same as the function in the processing container 309.

The load lock chamber 30 configured as described above
4 and the connecting means 307 adjacent to the gate valve 306
And the storage container 302 is connected to the connection means 307 so as to be connectable.

Next, the configuration of the connection means 307 and the storage container 302 will be described. A door 308 provided on the storage container 302 is connected to a gate valve 306 provided on the side wall of the load lock chamber 304 by a connecting means 307. The connecting means 307 is provided with a transport means 317 provided in the load lock chamber 304.
A space capable of holding and transporting 1 is provided as a passage. Further, the connection means 307 is airtightly configured so that a communication space formed by the opening of the gate valve 306 and the door 308 is isolated from the outside to form an airtight clean space.

The connecting means 307 is provided with an inert gas containing Xe or Kr (for example, N ₂ or Ar) or Xe or Kr.
Clean air containing r is supplied. The non-movable part of the connection means 307 is formed of, for example, an aluminum alloy, the inner wall is coated with an oxide film after polishing, and a material for suppressing positive ionization of heavy metals, such as SiC or SiN, is further formed on the surface. materials such as SiO ₂ promotes positive ions of heavy metals (SiO ₂ that satisfies the conditions described above) is coated. The function of these coating layers is the same as the function in the processing container 309.

The storage container 302 has an airtight structure, and is provided with a cassette 325 capable of storing a plurality of substrates and holding means 326 for holding the cassette. Storage container 3
02, the cassette 325 and the holding means 326 are made of, for example, an aluminum alloy, the inner wall or the surface of the jig is coated with an oxide film after polishing, and the surface thereof is made of a material for suppressing positive ionization of heavy metals, for example, SiC or SiN.
There are further on the surface coating material such as SiO ₂ promotes positive ions of heavy metals (SiO ₂ that satisfies the conditions described above), is prevented from contamination by outgassing and heavy metals from the wall surface I have. The function of these coating layers is the same as the function in the processing container 309.

On the side wall surface of the storage container 302, a door 308 which can be opened and closed and has an airtight mechanism in a closed state is provided. The storage container 302 has a structure that can be transported separately from the semiconductor processing apparatus 301 while maintaining the internal atmosphere and cleanliness. The inside of the storage container 302 may be in a normal pressure state filled with an inert gas containing Xe or Kr (for example, N ₂ , Ar) or clean air containing Xe or Kr when transporting the container 302.
A reduced pressure atmosphere by the gas may be used.

An opening / closing valve 328 having an opening 327 is provided above the storage container 302 by piping.
Connected to a filter 329 in the inside. Open / close valve 3
28 is an external gas supply means (for example, gas supply means 31
It is opened only when the inert gas containing Xe or Kr or the clean air containing Xe or Kr is supplied into the storage container 302 from 9). A valve 331 is connected to the lower side of the storage container 302 via an exhaust port 330, and the valve 331 has an opening 332. The valve 331 is opened only when evacuating the storage container 302. The evacuation is performed by connecting an evacuation means (e.g., evacuation means 324) independently provided outside to the opening 332.

The storage container 302 contains a plurality of unprocessed substrates 3
The door 308 is closed in a state where 11 is stored, and the airtight state is established. After the inside of the storage container is evacuated to a predetermined degree of vacuum, an inert gas containing Xe or Kr or Xe
Clean air containing e or Kr is introduced and maintained at a predetermined degree of vacuum.

The operation of the substrate transport system configured as described above will be described below. Multiple substrates 31
The storage container 302 holding the cassette 325 storing therein the container 1 is conveyed by the automatic conveyance robot in a state where the door 308 is closed and the cleanness of the inside is maintained, for example, in class 1, and is provided adjacent to the load lock chamber 304. It is placed adjacent to the connected connecting means 307.

The inside of the load lock chamber 304 is provided with exhaust means 324.
After that, the gas supply means 319 supplies the inert gas containing Xe or Kr or the clean air containing Xe or Kr into the load lock chamber 304 until the pressure reaches a predetermined pressure. Subsequently, the gate valve 306 and the door 308 are opened to allow the load lock chamber 304 and the storage container 302 to communicate with each other.
Alternatively, the atmosphere is an inert gas containing Kr or a clean air atmosphere containing Xe or Kr. Next, the transfer means 317 in the load lock chamber 304 moves, and the storage container 3
The substrate 311 is taken out from the cassette 325 in the cartridge 02 and is transported into the load lock chamber 304.

Next, the gate valve 306 is closed, and the inside of the load lock chamber 304 has a predetermined degree of vacuum, for example, 1 × 10 ^−3.
It is evacuated to Torr. Next, the gate valve 305
Is opened, and the substrate 311 held by the transfer means 317 is placed on the placement table 310 in the processing chamber 303.

After the transfer means 317 retreats into the load lock chamber, the gate valve 305 is closed, and the inside of the processing chamber 303 is evacuated to a predetermined degree of vacuum. Next, a predetermined process is performed on the substrate 311 such as supplying a process gas into the processing chamber 303, performing a heat treatment, or exciting plasma.

After the predetermined process is completed, the inside of the processing chamber 303 is evacuated and then replaced with an inert gas containing Xe or Kr or a clean air atmosphere containing Xe or Kr. After that, the gate valve 305 is opened, and the substrate 311 is carried out into the load lock chamber 304 by the carrying means 317.

Further, the gate valve 305 is closed to replace the inside of the load lock 304 with an inert gas containing Xe or Kr or a clean air atmosphere containing Xe or Kr. After that, the gate valve 306 is opened, and the substrate 311 is returned to a predetermined slot of the cassette 325 held in the storage container 302 by the transfer means 317.

The transport system operates as described above. By repeating this operation for each branch and leaf sequentially from the cassette 325, the processing for all the substrates 311 in the cassette 325 is performed.

When a series of processing is completed, the gate valve 3
Reference numeral 06 is closed, the semiconductor processing apparatus 301 is returned to an airtight state, the door 308 of the storage container 302 is also closed, and the storage container 302 contains an inert gas containing Xe or Kr or Xe or Kr. Is maintained in a clean air atmosphere.

The storage container 302 storing the processed substrates 311 is maintained in an inert gas containing Xe or Kr or in a clean air atmosphere containing Xe or Kr, and is subjected to the next step of semiconductor manufacturing. It is transported to the device or semiconductor inspection device.

The substrate transfer system that operates as described above always operates except when processing is performed on the semiconductor substrate.
Inert gas containing Xe or Kr (eg, N ₂ , A
r) or a clean air atmosphere containing Xe or Kr. Therefore, the transport system can perform not only the substrate from dust, dust, and contamination in the external environment but also a series of processes having a shielding effect of heavy metal contamination throughout the entire process.

In this embodiment, the load lock chamber 3
Although only one processing chamber 303 is connected to 04, a plurality of processing chambers 303 may be connected to the load lock chamber 304 in order to sequentially perform a plurality of types of processing on the semiconductor substrate.

The pressure inside the storage container 302 can be set to an optimum value for the manufacturing process. For example, Xe or Kr
It is also possible to reduce the pressure in an inert gas containing Xe or a clean air atmosphere containing Xe or Kr to match the pressure (for example, 1 × 10 ⁻³ Torr) of the load lock chamber connected in advance.

Conversely, the inert gas containing Xe or Kr or the clean air atmosphere containing Xe or Kr is set at a positive pressure higher than the atmospheric pressure to prevent the air from entering the storage container 302 and to load the atmosphere. Prior to connection with the lock chamber, it is also possible to reduce the pressure inside the storage container 302 and bring it closer to the atmospheric pressure, and then communicate with the load lock chamber.

Next, as a fourth embodiment, a horizontal LPCV
This will be described with reference to FIG. 4 taking a furnace D as an example. In a horizontal LPCVD furnace 400 having a double-tube structure, two hollow cylindrical quartz tubes 401 and 402 having different diameters are fitted in a loosely fitted state along the longitudinal direction.
Heat equalizing tubes 403 arranged so as to include 1, 402
And an electric furnace 404 including a heater disposed on the outer surface of the heat equalizing tube 403.

The quartz tubes 401 and 402 are made of fused quartz, and the inner quartz tube 401 has a jig 407 capable of accommodating therein a Si substrate 406 on which a polycrystalline silicon film is deposited.
Is provided. The soaking tube 403 is made of a material that suppresses the positive ionization of heavy metals, such as SiC or SiN, and has a material that promotes the positive ionization of heavy metals, such as SiO ₂ , on its inner surface.
(SiO ₂ that satisfies the conditions described above) is coated so that gas emission from the wall surface of the soaking tube 403 and contamination of the substrate by heavy metals is prevented. Also,
Inner quartz tube 401, between inner quartz tube 401 and outer quartz tube 402, and outer quartz tube 402 and soaking tube 403
Are supplied with gas flows 408a, 408b and 408c. Furthermore, the inner quartz tube 40
At least one thermocouple 405 is provided between the first quartz tube 402 and the outer quartz tube 402 along the furnace tube.

When a polycrystalline silicon film deposition process is performed on the Si substrate 406 using the horizontal LPCVD furnace configured as described above, the process is performed, for example, as follows. The Si substrate 406 on which the gate oxide film is formed is placed on a jig 407 and transferred into the inner quartz tube 401 maintained at 620 ° C. in a nitrogen atmosphere. Then, 99.999 by the LPCVD method.
The Si substrate 406 is heated at 620 ° C. by the electric furnace 404 under a pressure of 30 Pa in an atmosphere of SiH _{4 having} a purity of 9% or more.
Then, the film is heated to about the temperature, and a film is formed for a time to obtain a desired polycrystalline silicon film thickness. At this time, between the inner quartz tube 401 and the outer quartz tube 402 and between the outer quartz tube 402 and the soaking tube 403, 0.2 atm O ₂ gas and 0.8 atm A mixed gas with Kr gas is supplied and discharged at a flow rate of 10 slm, and light irradiation 411 having an energy level higher than the ionization potential of the metal to be shielded is performed. Thereby, the metal to be shielded is ionized, but components having an ionization potential higher than the energy level of the irradiation light, for example, an inert gas such as Kr or Xe are not ionized. Therefore, only the metal element to be shielded can be selectively ionized (resonant ionization), and a metal heavy rare gas bonding product can be efficiently formed, and this can be removed outside the horizontal LPCVD furnace 400. Can be.

A preferable light irradiation means is an inner quartz tube 401.
Means for irradiating a single-frequency coherent light between the outer quartz tube 402 and the outer quartz tube 402 and the soaking tube 403 (preferably, a substantially single-frequency , For example, a laser light oscillating means capable of oscillating an ultraviolet laser light). Further, in order to shield and remove a plurality of types of metal elements, a laser light oscillation means,
Light intensity (light intensity) varying means for varying the irradiation intensity (irradiation intensity) of the laser light oscillated by the laser light oscillation means is used. When the wavelength variable light irradiation means having the light intensity (light intensity) variable means is adopted, the ratio between the fragment ions and the molecular ions can be adjusted by changing the irradiation light intensity of the laser light, and so-called soft / hard ionization adjustment Becomes possible. By appropriately selecting the light intensity and irradiating the irradiation target gas containing components having the same or close ionization potentials but different molecular weights with light, the ionization of each component can be clearly separated. As this wavelength variable means, a dye laser (D
and a YAG laser. When a dye laser is used, the wavelength of the emitted light is too long to obtain a necessary energy level. Therefore, it is desirable to provide a mechanism for converting the frequency to an integral multiple, for example, a frequency multiplier.

A preferable wavelength tunable light irradiation means has a configuration based on multi-photon ionization (MPI). One of the features of the MPI method is that the type of atom / molecule to be ionized can be selected according to the wavelength of irradiation light. This is because each gas atom / molecule has its own ionization potential,
The ionization potential is hν (h is Planck's constant, ν
Depends on the phenomenon that atoms / molecules lower than the frequency of irradiation light) are ionized, and atoms / molecules having an ionization potential higher than hν are difficult to ionize. Therefore, it is desirable that the light irradiated to the irradiation target gas be coherent light having a single frequency. According to the principle of MPI, there are three modes for exciting and ionizing gas molecules, namely, non-resonant MPI (NR).
MPI), Resonant Two-Photon
Ionization: R2PI) and two-photon resonance ionization (Two
Photon Resonant Ionization (TPRI).

In NRMPI, a large number of photon energies are instantaneously applied to atoms / molecules to excite the atoms / molecules from the ground level of the energy to an ionization potential at once. Therefore, in the wavelength tunable light irradiation means employing NRMPI, high energy laser light oscillation means is required. In other words, this NRMP
When I is adopted, it is necessary to irradiate a laser beam having a high energy level, that is, a laser beam having a short wavelength.
Therefore, a laser oscillator extending to the far ultraviolet region may be required.

In R2PI, a certain photon moves an atom / molecule from the ground level to an intermediate state (a level existing between the ground level and the ionization potential: Intermediate State).
To excite. This intermediate state is a metastable state, and the excited atoms / molecules return to the ground level from the intermediate state at a constant decay rate β. Therefore, by appropriately increasing the luminous intensity (light intensity) of the irradiation light, when the number of atoms / molecules excited to the intermediate state is larger than the number of atoms / molecules returning to the ground state at the attenuation rate β, the irradiation target is irradiated with the irradiation light. Most of the gas atoms / molecules will be excited to an intermediate state. If a second photon is irradiated during this time, this atom / molecule is further excited and gains energy exceeding the ionization potential to become an ion. Therefore, even if irradiation light having an energy level lower than the ionization potential of the atoms / molecules is irradiated, the atoms / molecules are efficiently ionized.

In TPRI, two or more photon energies are applied almost simultaneously to an atom / molecule to excite the atom / molecule from a ground state to an intermediate state. In this process, the ionization efficiency is lower than R2PI. This TPRI
Is adopted, a low-level laser, that is, a long-wavelength laser is sufficient, but the output needs to be increased.

In the present invention, any of non-resonant MPI, resonant two-photon ionization, and two-photon resonance ionization can be adopted. In consideration of the characteristics of each system, the metal element to be shielded is used. An appropriate method is adopted according to the ionization of

The Si on which the polycrystalline silicon film is deposited
When the substrate was analyzed by gas phase analysis flameless atomic absorption spectrometry, it was found that 5 × 10 ¹⁵ atoms / cm ³ Fe and 1.5 × 10 ¹⁵ atoms / cm ^3.
10 ¹⁵ atoms / cm ³ of Cu was detected. This metal impurity concentration is a value obtained by a conventional heat treatment using a heat treatment gas (5 × 10 ¹⁶ atoms / cm ³ Fe, 3 × 10 ¹⁶ atoms / cm ³ ).
atom / cm ³ of Cu). The oxygen concentration in this polycrystalline silicon film is
In the SIMS analysis, a very low value of less than the detection limit (1 × 10 ¹⁸ / cm ³ ) was obtained.

The composition of the gas supplied and discharged between the inner quartz tube 401 and the outer quartz tube 402 and between the outer quartz tube 402 and the soaking tube 403 need not be the same. It does not need to be a mixed gas. For example, the outer quartz tube 4
02 and the soaking tube 403, a mixed gas of 0.5 atm O ₂ gas and 0.5 atm N ₂ gas is supplied and discharged at a flow rate of 10 slm, and the inner quartz tube 401 and the outer quartz tube 401 are discharged. When a mixed gas of 0.5 atm of Kr gas and 0.5 atm of N ₂ gas is supplied and discharged at a flow rate of 10 slm between the quartz tube 402 and the outer quartz tube 402 and the soaking tube 403. Between 0 and 1.
A mixed gas of 8 atm of O ₂ gas and 0.2 atm of N ₂ gas is supplied and discharged at a flow rate of 10 slm, and 1 atm of Xe is supplied between the inner quartz tube 401 and the outer quartz tube 402. Only gas 1
In the case of supplying and discharging at a flow rate of 0 slm, almost the same metal impurity shielding effect was obtained.

The means for ionizing a metal element to be shielded is not limited to light irradiation, but may be, for example, particle beam irradiation or application of a high-frequency electric field. Next, the fifth
A horizontal LPCVD furnace will be described as an example of the embodiment with reference to FIG.

A horizontal LPCVD furnace 500 having a double tube structure is
Two hollow cylindrical quartz tubes 501 and 502 having different diameters
Are fitted in a play-fit state along the longitudinal direction, and are further disposed on the outer surface of the heat equalizing tube 503 disposed so as to include the two quartz tubes 501 and 502. And an electric furnace 504 including a heater.

The quartz tubes 501 and 502 are made of fused quartz, and the inner quartz tube 501 is provided with a jig 507 capable of accommodating therein an Si substrate 506 on which a silicon nitride film is deposited. The heat equalizing tube 503 is made of a material that suppresses the positive ionization of heavy metals, for example, SiC or SiN, and has a material that promotes the positive ionization of heavy metals, for example, SiO 2 on its inner surface.
₂ (SiO ₂ that satisfies the above-described conditions) is coated to prevent gas emission from the wall surface of the soaking tube 503 and contamination of the substrate by heavy metals. Further, the inner quartz tube 501, the inner quartz tube 501 and the outer quartz tube 502, and the outer quartz tube 502 and the soaking tube 5
03, gas flows 508a, 508b, and 508c are supplied, and an inner quartz tube 501 is provided.
At least one thermocouple 505 is provided between the quartz tube 502 and the outer side along the furnace tube.

When the silicon nitride film deposition step is performed on the Si substrate 506 using the horizontal LPCVD furnace configured as described above, for example, the following is performed. The Si substrate 506 having the gate polycrystalline silicon film formed thereon is placed on a jig 507, and the inner quartz tube 5 maintained at 400 ° C. in a nitrogen atmosphere.
01. And, SiH ₂ Cl ₂ 10 scc
m, the temperature is raised to 700 ° C. in an atmosphere of 100 sccm of NH ₃ , and a film is formed by LPCVD for a time to obtain a desired silicon nitride film thickness. The reaction pressure is 15P
a. At this time, between the inner quartz tube 501 and the outer quartz tube 502 and between the outer quartz tube 502 and the soaking tube 503, O ₂ gas of 0.2 atm and 0.8 atm of A mixed gas with Kr gas is supplied and discharged at a flow rate of 10 slm, and light irradiation having an energy level higher than the ionization potential of the metal to be shielded is performed. This allows
The metal to be shielded is ionized, but a component having an ionization potential higher than the energy level of the irradiation light, for example, an inert gas such as Kr or Xe is not ionized. Accordingly, only the metal element to be shielded can be selectively ionized (resonant ionization), and a metal heavy rare gas bonding product can be efficiently formed and can be removed outside the horizontal LPCVD furnace 500.

Thus, the horizontal LPCVD furnace 500
Gas 51 containing metal heavy rare gas binding products removed to the outside
8a is introduced into the decomposition processing chamber 511. Decomposition chamber 51
1 is a quartz tube 5 of, for example, two hollow cylindrical bodies having different diameters.
12 and 513 are fitted in a loose fit state along the longitudinal direction. In addition, a heat equalizing tube 514 arranged so as to include the two quartz tubes 512 and 513 and a heat equalizing tube 51 are provided.
4 and an electric furnace 515 composed of a heater disposed on the outer surface.

In the inner quartz tube 512, there is a quartz tube 512.
A shielding jig 516 is provided mainly for the purpose of meandering the gas flow inside and increasing the residence time of the gas. The soaking tube 514 is made of a material that suppresses the positive ionization of heavy metals, for example, SiC or SiN, and has an inner surface coated with a material that promotes the positive ionization of heavy metals, for example, SiO ₂ . In addition, the inner quartz tube 512 and the outer quartz tube 513
And between the outer quartz tube 513 and the soaking tube 514 are supplied with gas flows 518b, 518c, and the inner quartz tube 512 and the outer quartz tube 513 are connected to each other. At least one thermocouple 517 is provided therebetween along the furnace tube.

Gas 518 containing metal heavy rare gas combination product
a is a reducing gas (eg, H ₂ , a mixed gas of H ₂ and H ₂ O, a mixed gas of CO and CO ₂ ) and an inert gas (eg, N ₂ , He, Ne, Ar, Kr, Xe) ) Or is introduced into the inner quartz tube 512 by a separate gas supply system. The quartz tubes 512 and 513 and the soaking tube 514 are maintained at a temperature required for reduction / decomposition of the heavy metal rare gas bonding product, for example, 200 to 1000 ° C. by an electric furnace 515. This temperature is determined by the free energy of oxide formation of the metal to be removed and the composition of the reducing gas. The heavy metal elements to be removed by this reduction / decomposition treatment are quartz tubes 512,
513, captured by the soaking tube 514 or the shielding jig 516. On the other hand, since the heavy metal element is removed from the gas discharged from the decomposition processing chamber 511, the horizontal LPCVD furnace 500 is again subjected only to the separation and purification of the desired gas components.
It can be supplied inside the inner quartz tube 501, between the inner quartz tube 501 and the outer quartz tube 502, or between the outer quartz tube 502 and the soaking tube 503.

The Si substrate on which the silicon nitride film was deposited in this manner was analyzed by a gas phase analysis method using a flameless atomic absorption spectroscopy. As a result, 5 × 10 ¹⁵ atoms / cm ³ of Fe and 1.5 × 10 ¹⁵ atoms / cm ³ were measured. cm ³ of Cu was detected. This metal impurity concentration is a value obtained by a conventional heat treatment using a heat treatment gas (5 × 10 ¹⁶ atoms / cm ³ of Fe,
Compared with 3 × 10 ¹⁶ atoms / cm ³ of Cu), it is reduced by one digit or more. The oxygen concentration in this silicon nitride film was determined by SIMS analysis as the detection limit (1 × 10 ¹⁸ / c).
m ³ ) or less, very low values were obtained.

The composition of the gas supplied and discharged between the inner quartz tube 501 and the outer quartz tube 502 and between the outer quartz tube 502 and the soaking tube 503 need not be the same. It does not need to be a mixed gas. For example, the outer quartz tube 5
02 and the soaking tube 503, a mixed gas of 0.5 atm O ₂ gas and 0.5 atm N ₂ gas is supplied and discharged at a flow rate of 10 slm, and the inner quartz tube 501 and the outer When a mixed gas of 0.5 atm Kr gas and 0.5 atm N ₂ gas is supplied and exhausted at a flow rate of 10 slm between the quartz tube 502 and the quartz tube 502 and the soaking tube 503 at the outside. Between 0 and 1.
A mixed gas of 8 atm O ₂ gas and 0.2 atm N ₂ gas is supplied and discharged at a flow rate of 10 slm, and 1 atm of Xe is supplied between the inner quartz tube 501 and the outer quartz tube 502. Only gas 1
In the case of supplying and discharging at a flow rate of 0 slm, almost the same metal impurity shielding effect was obtained.

The decomposition treatment of the heavy metal and rare gas binding products in the decomposition treatment chamber 511 is not limited to the reduction treatment. An oxidation treatment for removing metal oxides that are more stable than bond products may be performed. In this case, the gas containing the metal heavy rare gas bonding product may be an oxidizing gas (for example, O ₂ , N ₂ O, O ₃ , atomic oxygen, excited state O ₂ , an excited state O atom alone gas or these gases). 2
Or more mixed gases) and an inert gas (eg, N ₂ , H
e, Ne, Ar, Kr, and Xe), or is introduced into the inner quartz tube 512 by a separate gas supply system. The quartz tubes 512 and 513 and the soaking tube 514 are heated at a temperature required for oxidation / decomposition of the heavy metal rare gas bonding product by the electric furnace 515, for example, 200 to 10
It is kept at 00 ° C. This temperature is determined by the free energy of oxide formation of the metal to be removed and the composition of the oxidizing gas. If the binding energy of the heavy metal rare gas bonding product is relatively small, oxidation, diffusion,
It is only necessary to keep the atmosphere at a temperature higher than the processing temperature in the processing part where each processing such as heat treatment, film deposition and dry etching is performed on the semiconductor substrate.

Further, when there is a metal compound having a free energy of formation equivalent to that of the oxide of the metal to be removed, typically 1/10 or more of the free energy of oxide formation, the reaction is promoted. The gas may be mixed, and the decomposition treatment may be performed in a reactive atmosphere such as a nitriding reactive atmosphere or a halogenating reactive atmosphere. Further, a high-frequency electric field may be applied to the decomposition treatment chamber 511 in order to promote the reduction, oxidation, or decomposition treatment in a reactive atmosphere. When a high-frequency electric field is applied, the heating temperature of the electric furnace 515 can be reduced.

Although the embodiments have been described above, the present invention is not limited to these embodiments.
Various modifications can be made without departing from the spirit of the invention.

[0099]

According to the present invention, the contaminant metal is positively ionized in advance and reacted with the noble gas, whereby the contaminant metal can be easily discharged as a combined product with the noble gas.
The substrate to be processed can be prevented from being contaminated by the contaminated metal.

Further, according to the present invention, the combined product of the contaminated metal and the rare gas is redissolved, and the redissolved rare gas is recovered and used again for producing and discharging the combined product. The gas can be used effectively.

[Brief description of the drawings]

FIG. 1 is a view showing a first embodiment of the present invention, showing a case where the present invention is applied to a horizontal diffusion furnace.

FIG. 2 is a view showing a second embodiment of the present invention, and is a view showing a case where the present invention is applied to a vertical oxidation furnace.

FIG. 3 is a diagram illustrating a third embodiment of the present invention, in which the present invention is applied to a processing apparatus system in which a plurality of processing apparatuses are connected and a substrate transfer system between the processing apparatuses. .

FIG. 4 is a view showing a fourth embodiment of the present invention, and is a view showing a case where the present invention is applied to a horizontal LPCVD furnace.

FIG. 5 is a view showing a fifth embodiment of the present invention, and shows a case where the present invention is applied to a horizontal LPCVD furnace and a decomposition apparatus.

FIG. 6 is a diagram showing an orbital correlation diagram between a metal ion and a rare gas.

FIG. 7 is a diagram showing the binding energy and the like between a metal ion and a rare gas.

FIG. 8 is a graph showing the binding energy and the like of a metal oxide.

FIG. 9 is a diagram showing the binding energy and the like between a metal oxide and a rare gas.

FIG. 10 is a diagram showing the saturation concentration of Cu and Fe ions in SiO ₂ .

FIG. 11 is a diagram showing a change in solid solubility limit of Cu when the stabilization energy at the time of electron capture by the acceptor level changes.

FIG. 12 shows energy levels for various forms of a non-crosslinked oxygen hole center.

[Explanation of symbols]

100: diffusion furnace 101, 201, 401, 501, 512 ... inner quartz tube 102, 202, 402, 502, 513 ... outer quartz tube 103, 203, 403, 503, 514 ... soaking tube 104, 204, 404, 504, 515: electric furnaces 105, 205, 405, 505, 517: thermocouples 106, 206, 406, 506: Si substrates 107, 207, 407, 507: jigs 108a to 108c, 209a to 209b, 408a to
408c, 508a to 508c, 518b to 518c ...
Gas flow 200 Oxidation furnace 208 Micropore 300 Processing system 301 Semiconductor processing apparatus 302 Storage container 303 Processing chamber 304 Load lock chamber 305, 306 Gate valve 307 Connection means 308 Door 309 Processing container 310 ... Mounting table 311 substrate to be processed 312 shower head 313, 319 gas supply means 314, 320, 328 opening / closing valve 315, 322, 330 exhaust port 316, 324 exhaust means 317 transport means 318 driving means 321 329 Filter 325 Cassette 327 Holding means 327 332 Opening 323 331 Valve 400 500 LPCVD furnace 411 Light irradiation 518a Gas containing metal heavy rare gas bonding product 511 Dispersion processing chamber 516 Shielding jig

Continuation of the front page (51) Int.Cl. ⁷ identification code FI H01L 21/68 H01L 21/68 A (56) References JP-A-62-244459 (JP, A) JP-A-5-144802 (JP, A) JP-A-8-128471 (JP, A) JP-A-7-78775 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/31 H01L 21/205 H01L 21 / 22 501 H01L 21/324 H01L 21/68

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the contaminating metal causing the contamination of the substrate to be processed is positively ionized before reaching the substrate.
A method for removing a contaminated metal, comprising reacting the positively ionized contaminated metal with a rare gas and discharging the contaminated metal as a combined product. 2. The method according to claim 1, wherein the contaminant metal causing the contamination of the substrate to be processed is positive.
The contaminated metal and the noble gas are dissociated by subjecting the bound product generated and discharged by being ionized to react with the noble gas to a predetermined treatment, and the dissociated noble gas is reused for generating the bound product. A method for treating a binding product, comprising: