JP2010045254A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device to which a cleaning method effective on a semiconductor substrate containing Ge is applied. <P>SOLUTION: A method of manufacturing a semiconductor device is characterized in that a semiconductor substrate containing Ge is cleaned with a halogenated gas containing at least one among an HCL gas, an HBr gas and an HI gas. A method of manufacturing a semiconductor device is characterized in that a semiconductor substrate containing Ge is cleaned with an HCL solution of 75 to 110°C. For example, the methods are applicable to preprocessing of a gate insulating film of MISFET, preprocessing of source-drain electrode formation, and preprocessing of metal plug formation for a contact. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which an effective cleaning process is applied to a semiconductor substrate containing Ge.

  The performance improvement of MISFET has been achieved by miniaturization so far. However, miniaturization is approaching the limit, and techniques for improving the performance of MISFETs other than miniaturization are being studied. As an example, the use of a substrate other than a Si substrate having higher electron and hole mobility than Si, for example, a semiconductor substrate containing Ge, such as a SiGe substrate or a Ge substrate, has been studied.

One of the problems with these Ge-containing substrates is that a pretreatment technique, which is an essential cleaning process at the time of device fabrication, has not been established. Since the physical properties of the Si oxide and the Ge oxide are different, the pretreatment of the Si element cannot be directly applied to the pretreatment of the Ge element. As an example of the different physical properties of oxides, in contrast to SiO ₂ which can only be etched with HF solutions, Ge oxides on Ge substrates are halogen acid solutions other than HF solutions, ie HCl solutions, HBr solutions, HI solutions. Can be etched (Non-patent Document 1).

In addition, as a pretreatment method other than a solution, vapor phase pretreatment used in a normal Si process, for example, Vapor HF treatment is effective in removing Ge oxide even in pretreatment of a semiconductor substrate containing Ge. Has been reported (Non-Patent Document 2). The initial oxide on the substrate surface contains various contaminants such as organic substances and metal elements. For this reason, it needs to be effectively removed from the substrate surface so as not to be reattached during the pretreatment process. Further, it has been reported that the pretreated Ge substrate is easily oxidized by moisture or oxygen in the air (Non-patent Document 3).
Onsia, B.M. , Et al. , “A Study of the Inflation of Typical Wet Chemical Treatments on the German Wafer Surface”, Diffus. Defect Data B, Solid State Phenom. (2005) 103-104, 27 Chui, C.I. O. , Et al. , “Germanium MOS Capacitors Intracoding Ultrathin High-k Gate Directive”, IEEE Electron Device Lett. (2002) 23, 473 Sakuraba, M .; , Et al. , "H-termination on Ge (100) and Si (100) by diluted HF dipping and by annealing in H2", Electrochemical Society Processings (1998) 97-35, 213.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a semiconductor device in which an effective cleaning process is applied to a semiconductor substrate containing Ge. .

  The semiconductor device manufacturing method according to the first aspect of the present invention is characterized in that a semiconductor substrate containing Ge is cleaned with a halogenated gas containing at least one of HCl gas, HBr gas, or HI gas.

  Here, in the first aspect, it is desirable that the temperature of the semiconductor substrate is equal to or higher than the boiling point of the Ge halide or Ge hydride formed by the cleaning process.

Here, in the first aspect, it is desirable that the temperature of the semiconductor substrate is equal to or higher than the boiling point of H ₂ O.

  Here, in the first aspect, it is desirable to supply a silylating agent to the surface of the semiconductor substrate during the cleaning process or after the cleaning process, and oxidize the surface of the semiconductor substrate after supplying the silylating agent.

  The semiconductor device manufacturing method according to the second aspect of the present invention is characterized in that a semiconductor substrate containing Ge is washed with an HCl solution at 75 ° C. or higher and 110 ° C. or lower.

  Here, in the second aspect, it is desirable that the HCl solution is 83 ° C. or higher and 110 ° C. or lower.

  Here, in the second aspect, it is desirable to form a metal film on the semiconductor substrate by a plating method in the same tank as the cleaning process after the cleaning process.

  Here, in the second embodiment, it is desirable that the HCl solution contains an alcohol.

  Here, in the second embodiment, it is desirable that the HCl solution contains a sulfide solution.

  Here, in the first and second embodiments, it is desirable to perform a rinse treatment with alcohol after the washing treatment.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of the semiconductor device by which the effective cleaning process was applied to the semiconductor substrate containing Ge.

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

(First embodiment)
In the semiconductor device manufacturing method according to the first embodiment of the present invention, a semiconductor substrate containing Ge is cleaned with a halogenated gas containing at least one of HCl gas, HBr gas, or HI gas. First, as an example of a pretreatment for forming a gate insulating film on a Ge substrate, a cleaning process using HCl gas will be described.

FIG. 2 is a process cross-sectional view illustrating the manufacturing method of the present embodiment. First, as shown in FIG. 2A, an element isolation region 22 embedded with SiO ₂ is formed on a Ge substrate 10 using a known process technique such as a lithography method, an RIE method, or a CVD method. In a region where Ge on the Ge substrate 10 is exposed on the surface, that is, an active region, a Ge oxide film 24 is formed as a natural oxide film, for example, about 0.1 to 1 nm. In general, the Ge oxide film 24 is made of GeO ₂ (Ge dioxide), GeO (Ge monooxide), or a mixture thereof.

Next, as shown in FIG. 2B, the Ge substrate 10 is pretreated with HCl gas in a known vapor phase etching apparatus. By this pretreatment, the Ge oxide film 24 is etched, and the surface of the Ge substrate 10 in the active region is exposed. Here, unlike HF gas or HF solution, HCl gas does not etch SiO ₂ . Therefore, the Ge oxide film 24 is selectively removed with respect to SiO _{2 in the} element isolation region 22 by this process.

FIG. 3 is a conceptual diagram showing an example of a vapor phase etching apparatus used in the pretreatment. HCl gas is generated from the solution tank 12 containing the HCl solution by bubbling with an inert gas such as N ₂ . Then, the generated HCl gas is introduced into the chamber 14 in which the Ge substrate 10 is placed. The Ge oxide film on the Ge substrate 10 is etched by the HCl gas.

  Here, it is desirable that the HCl gas does not contain water so that the Ge oxide film 24 is not etched and the surface of the Ge substrate 10 is not re-oxidized. Such a process is performed, for example, by an apparatus for dehydrating HCl gas between the chamber 14 and the chamber 12, or simply by supplying a HCl gas dried by interposing a desiccant to the Ge substrate 10 pretreatment chamber. 14 can be realized.

Next, a gate insulating film 26 is formed on the pretreated Ge substrate 10 as shown in FIG. The gate insulating film 26 can be formed, for example, by depositing about 3 nm of HfO ₂ that is a high dielectric film using a known ALD (Atomic Layer Deposition) apparatus. The transport from the pre-processing apparatus to the apparatus for forming the gate insulating film 26 is performed by a transport BOX sealed with an inert gas such as dry N ₂ gas or Ar gas in order to prevent oxidation of the surface of the Ge substrate 10. It is desirable to use (Environment BOX). In order to prevent oxidation of the surface of the Ge substrate 10, it is desirable to shorten the time from the end of the pretreatment to the formation of the gate insulating film 26 as much as possible.

  Next, as shown in FIG. 2D, for example, a metal gate electrode 28 is formed on the gate insulating film 26 by using a known process technique. In this way, a MIS device is formed on the Ge substrate 10.

According to the manufacturing method of the present embodiment, the Ge oxide on the Ge substrate can be effectively etched. In particular, not only GeO ₂ but also GeO can be effectively removed. This makes it possible to manufacture a MIS device that suppresses the intervention of Ge oxide at the interface between the Ge substrate and the gate insulating film. Therefore, when a MIS capacitor having a high dielectric constant film is formed on a Ge substrate, it is possible to suppress the presence of a Ge oxide layer having a relatively low dielectric constant. Therefore, it is possible to form a MIS capacitor having a high capacitance.

When the Ge oxide is etched with the HF solution, for example, a high concentration HF solution of about 20% by weight or more is required. According to the present embodiment, SiO _{2 in the} element isolation region is etched, which causes a problem. Further, since SiO ₂ is not etched by the pretreatment, the SiO ₂ film in the element isolation region does not recede. Therefore, it is possible to avoid the formation of an unnecessary base step which becomes a problem when forming the upper layer wiring or the like on the substrate, the deterioration of the element isolation withstand voltage accompanying the reduction in the thickness of the insulating film, and the like.

  Although the case of using HCl gas as the pretreatment gas has been described here, a halogenated gas containing at least one of HCl gas, HBr gas, or HI gas can be used. In addition to the Ge substrate, any semiconductor substrate containing Ge can be applied to, for example, a SiGe substrate.

  Next, the operation and effect of the present embodiment will be described in more detail. In general, oxidation near room temperature occurs when two conditions of water and oxygen are met. Conversely, if either water or oxygen is missing, it will not be oxidized. For this reason, the inventor paid attention to the fact that the gas phase treatment with a gas not containing water would be more effective in suppressing the oxidation of the Ge substrate than the solution treatment containing water, which is a necessary condition for oxidation.

Unlike Si oxide, Ge oxide is polymorphic. GeO (Ge monoxide) other than GeO ₂ (Ge dioxide) are also known to exist relatively stably. The possibility of etching GeO ₂ and GeO by vapor phase halogen acid was examined by examining the stability of Ge oxide from a thermodynamic viewpoint using Gibbs free energy. FIG. 4 is a diagram showing the results of examining the stability of Ge oxide.

In the following (Formula 1), X represents a halogen element F, Cl, Br or I, (g) represents a gas phase (gas) state, and Gibbs on the right side of (Formula 1) to (Formula 3) FIG. 4 shows ΔF obtained by subtracting Gibbs free energy ΔG ⁰ (left side) on the left side from free energy ΔG ⁰ (right side).
_{SiO 2 + 4HX (g) =} SiX 4 + 2H 2 O ··· ( Equation 1)
GeO ₂ + 4HX (g) = GeX ₄ + 2H ₂ O (Formula 2)
GeO + 4HX (g) = GeX ₄ + H ₂ + H ₂ O (Formula 3)

When ΔF in FIG. 4 is less than 0, it indicates that the reaction can occur thermodynamically, and when ΔF is greater than 0, it indicates that the reaction cannot occur thermodynamically. From this result, it is first confirmed that SiO ₂ is not etched by gas phase halogen acids other than HF. However, SiO ₂ HI etching was not calculated because there was no data.

Next, it was revealed for the first time by this calculation result that it is predicted thermodynamically that Ge oxide can be etched into all gas-phase halogen acids together with GeO ₂ and GeO. This Ge oxide etchability result is completely unexpected from the Si oxide results. It should be noted that all the HXs on the left side of (Expression 1) to (Expression 3) are calculated in the gas phase. There are no reports of calculation examples and experimental examples (excluding vapor HF) of the above (formula 1) to (formula 3) in gas phase HX.

In addition to the above (formula 2) and (formula 3), the removal of the Ge oxide is also caused by a reaction in which the following Ge hydride halide (in this case, GeHX ₃ ) is generated. Is expected.
2GeO ₂ + 6HX (g) = 2GeHX ₃ + 2H ₂ O + O ₂ (Formula 4)
GeO + 3HX (g) = GeHX ₃ + H ₂ O (Formula 5)

  FIG. 1 is a diagram showing a result of etching Ge oxide with HCl gas. The amount of Ge oxide on the Ge substrate before and after the treatment with HCl gas is evaluated by XPS (X-ray photoelectron spectroscopy). The XPS measurement conditions are measured using a monochromatic Al Kα as an X-ray source under a condition where TOA (take off angle) is 15 degrees, that is, the angle formed with the horizontal direction of the sample is 15 degrees. The measurement sample uses the substrate temperature of the Ge substrate during the cleaning process as a parameter, and the processing time is 5 minutes. In each spectrum, the peak of Ge—Ge bond derived from the Ge3d substrate is set to 29.3 eV, and the influence of charging the sample during X-ray irradiation is corrected. 1 that the Ge oxide on the surface of the Ge substrate is removed by the HCl gas cleaning process.

In addition, it is confirmed that the treatment at 90 ° C. or higher significantly reduces the Ge oxide amount as compared with the treatment at 70 ° C. or lower. As described below, since the boiling points of GeHCl ₃ and GeCl ₄ are 75 ° C. and 83 ° C., the Ge hydride and Ge halide produced by etching the Ge oxide are effectively used. This is thought to be removed.

For example, the above (formula 2) when the halogenated gas is HCl gas is the following (formula 6).
GeO ₂ + 4HCl (g) = GeCl ₄ + 2H ₂ O (Formula 6)
Here, the temperature of the semiconductor substrate is equal to or more than 83 ° C., the boiling point of GeCl _4, GeCl ₄ is a reactive product of etching is removed as a gas from the semiconductor substrate surface. Therefore, the reaction from the left side to the right side of (Expression 4) is promoted, and the reaction of Ge oxide on the surface of the semiconductor substrate is further promoted. The same applies to GeO in (Formula 3).

Similarly, the above (formula 4) when the halogenated gas is HCl gas becomes the following (formula 7).
_{2GeO 2 + 6HCl (g) =} 2GeHCl 3 + 2H 2 O + O 2 ··· ( Equation 7)
Here, the temperature of the semiconductor substrate is equal to or more than 75 ° C., the boiling point of GeHCl _3, is GeHCl ₃ is a reactive product of etching is removed as a gas from the semiconductor substrate surface. Therefore, the reaction from the left side to the right side of (Expression 7) is promoted, and the reaction of Ge oxide on the surface of the semiconductor substrate is further promoted. The same applies to GeO in (Formula 5).

Therefore, in this embodiment, the temperature of the Ge-containing semiconductor substrate is changed to a Ge halide formed by a cleaning process or a Ge hydride (Hydrohalides, GeH _y X _4-y , X = Cl). , Br, I, y = 1, 2, 3), the boiling point of which is desirable. That is, the temperature of the semiconductor substrate to be cleaned is the halide GeX _{4 on} the right side of (Formula 2) and (Formula 3) or the hydride halide GeHX _3, GeH on the right side of (Formula 4) (Formula 5). The boiling point of ₂ X ₂ or GeH ₃ X is desirable. It is further desirable that the temperature of the semiconductor substrate containing Ge is equal to or higher than the boiling points of both the Ge halide and the Ge hydrogen halide.

When halide gas is HBr gas, HI gas, halide produced in the reaction are each as GeBr _4, GeI ₄ Doo. Here, the boiling point of GeBr ₄ is 186 ° C., and the boiling point of GeBr ₄ is 400 ° C. Therefore, when the halogenated gas is HBr gas or HI gas, the temperature of the semiconductor substrate is preferably 186 ° C. or higher and 400 ° C. or higher, respectively.

In this embodiment mode, the temperature of the semiconductor substrate is preferably equal to or higher than the boiling point of H ₂ O. The boiling point of H ₂ O varies depending on conditions such as pressure, but is 100 ° C. at normal pressure. As apparent from the above (Formula 2), (Formula 3), (Formula 4), and (Formula 5), when the Ge oxide is removed by etching with a halogenated gas, H ₂ O is generated as a reaction product. Therefore, by making the temperature of the semiconductor substrate equal to or higher than the boiling point of H ₂ O, the reaction product H ₂ O is removed from the system. Thereby, the reaction from the left side to the right side proceeds, and the removal of the Ge oxide is further promoted. Further, re-oxidation of the Ge substrate due to the presence of H ₂ O on the substrate surface is also suppressed.

  Here, an example in which a cleaning process using a halogenated gas is applied as a pretreatment for forming a gate insulating film has been described. However, the application of the cleaning process using a halogenated gas according to the present embodiment is limited to this pretreatment. is not. For example, it is also effective as a pretreatment for forming a metal film when forming a germanide layer or a silicon germanide layer by reacting a metal film and a semiconductor substrate as source / drain electrodes of a MISFET. By effectively removing the Ge oxide by pretreatment, the contact resistance between the semiconductor substrate and the germanide layer or the silicon germanide layer can be reduced.

  Also, for example, it is effective to apply to a post-process for opening a contact hole or a pre-process for depositing a metal film to form a contact plug when forming a contact between a metal wiring of a semiconductor device and a semiconductor substrate containing Ge. It is. Also in this case, it is possible to reduce the contact resistance between the metal wiring and the semiconductor substrate by effectively removing the Ge oxide by the pretreatment.

(Second Embodiment)
In the method of manufacturing a semiconductor device according to the second embodiment of the present invention, after the silylating agent is supplied to the surface of the semiconductor substrate and after the silylating agent is supplied during or after the cleaning process of the semiconductor substrate containing Ge. This is the same as the first embodiment except that the surface of the semiconductor substrate is oxidized. Therefore, the description overlapping with the first embodiment is omitted.

In this example, Me ₃ SiNHSiMe ₃ (HMDS) is supplied as a silylating agent to the surface of the semiconductor substrate simultaneously with the HCl gas during the cleaning process as a pretreatment when forming the gate insulating film on the Ge substrate. Explained.

FIG. 5 is a process cross-sectional view illustrating the manufacturing method of the present embodiment. First, as shown in FIG. 5A, an element isolation region 22 embedded with SiO ₂ is formed. In a region where Ge on the Ge substrate 10 is exposed on the surface, that is, an active region, a Ge oxide film 24 is formed as a natural oxide film, for example, about 0.1 to 1 nm.

  Next, as shown in FIG. 5B, in a known vapor phase etching apparatus, HCl gas not containing water and HMDS are simultaneously supplied to preprocess the Ge substrate 10. By this pretreatment, the Ge oxide film 24 is etched, and the surface of the Ge substrate 10 in the active region is exposed. Then, Ge on the exposed surface of the Ge substrate 10 is terminated with Cl. Ge terminated with Cl is terminated with R (silyl group) -Si-O by HMDS supplied simultaneously with HCl gas, and a silyl group termination layer 30 is formed on the surface of the Ge substrate 10.

FIG. 6 is a conceptual diagram showing an example of a vapor phase etching apparatus used in this pretreatment. HCl gas and HMDS gas are generated by bubbling with an inert gas such as N ₂ from the solution tank 12 containing the HCl solution and the second solution tank 16 containing the HMDS, respectively. Then, the generated HCl gas is introduced into the chamber 14 in which the Ge substrate 10 is placed. The Ge oxide film on the Ge substrate 10 is etched by the HCl gas, and the silyl group termination layer 30 is formed on the surface of the Ge substrate 10.

  Next, as shown in FIG. 5C, for example, the R group bonded to Si is oxidized in the silyl group termination layer 30 by a known plasma oxidation process. As a result, the R group is released, and the Si oxide film 32 is formed on the surface of the Ge substrate 10. An oxidation process other than the plasma oxidation process may be applied.

Next, a high dielectric film 34 is formed on the Si oxide film 32 as shown in FIG. The high dielectric film 34 can be formed by depositing about 3 nm of HfO ₂ with a known ALD (Atomic Layer Deposition) apparatus, for example.

  Next, as shown in FIG. 5E, for example, a metal gate electrode 28 is formed on the high dielectric film 34 by using a known process technique. In this way, a MIS device is formed on the Ge substrate 10.

  According to the manufacturing method of the present embodiment, it is possible to suppress the presence of a Ge oxide layer having a relatively low dielectric constant, as in the first embodiment. Therefore, it is possible to form a MIS capacitor having a high capacitance.

Further, since the HMDS also does not etch SiO _2, the embodiment likewise the process in the first preferred, no retreat of the SiO ₂ film of the element isolation region. Therefore, it is possible to avoid the formation of an unnecessary base step, which is a problem in the formation of the upper wiring on the substrate, the deterioration of the element isolation withstand voltage accompanying the reduction in the thickness of the insulating film, and the like.

  Furthermore, according to the present embodiment, a highly uniform Si oxide film 32 is formed between the Ge substrate 10 and the high dielectric film 34. Therefore, there is an advantage that it is possible to provide a MIS device in which the characteristic deterioration caused by the interface state that occurs when the high dielectric film 34 is directly formed on the Ge substrate 10 is suppressed.

  Here, the pre-processing for supplying HCl gas and HMDS simultaneously has been described as an example. From the viewpoint of shortening the process time, it is desirable to simultaneously supply HMDS in the pretreatment with HCl gas. However, it is also possible to select a method for supplying HMDS after pretreatment with HCl gas.

Further, as the silylating agent, a silylating agent having a small R group (silyl group) is effective from the viewpoint of breaking the Si—R bond without breaking the Ge—O—Si bond on the Ge substrate surface later. This is because the smaller the R group, the smaller the average dissociation energy between Si and R groups. For example, the average dissociation energies of Si (CH ₃ ) ₄ and Si (C ₂ H ₅ ) ₄ are 317 and 356 (D / kJ / mol), respectively. From the viewpoint of easy dissociation of the R group, HMDS having a small R group is particularly effective. HMDS is also used for resist adhesion improving processing in a lithography process in a method for manufacturing a semiconductor device, and it is desirable that HMDS has high compatibility with the semiconductor device manufacturing process. However, depending on the degree of steric hindrance and hydrogen bond, a silylating agent having a large R group can also act effectively.

The silylating agent is not limited to HMDS. For _{example, Me 3 SiCl (KA-31} ), O = C- (NHSiMe 3) 2 (BTSU), CF 3 C- (OSiMe 3) = (NSiMe 3) (BSTFA), Me 3 SiOSO 2 CF 3 (TMST) Et ₃ SiCl (TESC), t-BuMe ₂ SiCl (TBMS), Cl (i-Pr) ₂ SiOSi (i-Pr) ₂ Cl (CIPS), etc. may be applied.

  FIG. 7 is a process flow diagram of a modification of the present embodiment. In this modification, heat treatment or plasma treatment is performed after treatment with HCl gas and HMDS. And the process which supplies HMDS further is performed after that. Then, after repeating these steps, an oxidation process is performed to form a Si oxide film on the Ge substrate.

As in this modification, by performing heat treatment or plasma treatment, the Si—R bond formed by the treatment with the immediately preceding HMDS is cut, and the steric hindrance due to the R group is removed. Thereafter, an R—Si—O bond is additionally formed by the next HMDS process. By repeating this process, a uniform silylated termination layer can be formed more effectively. As a result, a more uniform Si oxide film can be formed on the Ge substrate.

  In the second and subsequent HMDS processes, it is desirable to supply HCl gas at the same time. This is because it is possible to remove Ge oxide generated by heat treatment or plasma treatment by supplying HCl gas.

(Third embodiment)
The method of manufacturing a semiconductor device according to the third embodiment of the present invention is the first and second methods except that the pretreatment with the halogen gas and the subsequent formation of the insulating film and the metal film are performed in the same apparatus. This is the same as the embodiment. Therefore, the description overlapping with the first and second embodiments is omitted.

FIG. 8 is a conceptual diagram showing an example of a manufacturing apparatus used in the method for manufacturing a semiconductor device of the present embodiment. For example, the pretreatment HCl gas and HfCl _{4 serving} as the source gas of the HfO ₂ gate insulating film in the ALD method can be supplied into the chamber 40. In this way, the Ge substrate 10 is placed in the chamber 40 having resistance to Cl-based and HCl-based gas, and first, an HCl gas is flowed to remove the Ge oxide film on the surface of the Ge substrate 10. In this state, flowing HfCl ₄ is a source gas without exposing the Ge substrate 10 in an oxidizing atmosphere to deposit a HfO ₂ gate insulating film while avoiding the formation of Ge oxides by reoxidation.

  According to the present embodiment, it is possible to minimize the Ge oxide interposed between the Ge substrate 10 and the gate insulating film on the surface thereof. Therefore, an MIS capacitor having a high capacitance can be realized.

(Fourth embodiment)
In the method of manufacturing a semiconductor device according to the fourth embodiment of the present invention, a semiconductor substrate containing Ge is washed with an HCl solution at 75 ° C. or higher and 110 ° C. or lower. First, as an example of a pretreatment for forming a gate insulating film on a Ge substrate, a cleaning process using an HCl solution in which HCl is diluted with H ₂ O will be described.

FIG. 9 is a process cross-sectional view illustrating the manufacturing method of the present embodiment. First, as shown in FIG. 9A, an element isolation region 22 embedded with SiO ₂ is formed on a Ge substrate 10 using a known process technique such as a lithography method, an RIE method, or a CVD method. In a region where Ge on the Ge substrate 10 is exposed on the surface, that is, an active region, a Ge oxide film 24 is formed as a natural oxide film, for example, about 0.1 to 1 nm. Usually, the Ge oxide film 24 is GeO ₂ or GeO.

Next, as shown in FIG. 9B, the Ge substrate 10 is pretreated with an HCl solution at 75 ° C. or higher and 110 ° C. or lower in a known wet etching apparatus. By this pretreatment, the Ge oxide film 24 is etched, and the surface of the Ge substrate 10 in the active region is exposed. Here, unlike the HF gas and the HF solution, the HCl solution does not etch SiO ₂ . Therefore, the Ge oxide film 24 is selectively removed with respect to SiO _{2 in the} element isolation region 22 by this process.

Next, a gate insulating film 26 is formed on the pretreated Ge substrate 10 as shown in FIG. The gate insulating film 26, for example, in a known ALD (Atomic Layer Deposition) apparatus, it is possible to form by depositing an HfO ₂ about 3nm which is a high dielectric film. The transport from the pre-processing apparatus to the apparatus for forming the gate insulating film 26 is performed by a transport BOX sealed with an inert gas such as dry N ₂ gas or Ar gas in order to prevent oxidation of the surface of the Ge substrate 10. It is desirable to use (Environment BOX). In order to prevent oxidation of the surface of the Ge substrate 10, it is desirable to shorten the time from the end of the pretreatment to the formation of the gate insulating film 26 as much as possible.

  Next, as shown in FIG. 9D, for example, a metal gate electrode 28 is formed on the gate insulating film 26 using a known process technique. In this way, a MIS device is formed on the Ge substrate 10.

In the present embodiment, the etching of the Ge oxide by the HCl solution is expressed by the following (Expression 8), (Expression 9), (Expression 10), and (Expression 11).
GeO ₂ + 4HCl = GeCl ₄ + 2H ₂ O (Formula 8)
GeO + 4HCl = GeCl ₄ + H ₂ + H ₂ O (formula 9)
2GeO ₂ + 6HCl = 2GeHCl ₃ + 2H ₂ O + O ₂ (Formula 10)
GeO + 3HCl = GeHCl ₃ + H ₂ O (Formula 11)

In this embodiment, the temperature of the HCl solution is 75 ° C. or higher. In this case, since the boiling point of GeHCl ₃ which is the reaction product on the right side of (Equation 10) and (Equation 11) is 75 ° C., the produced GeHCl ₃ is removed from the semiconductor substrate surface as a gas. For this reason, the reaction from the left side to the right side is promoted, and the reaction of the Ge oxide on the surface of the semiconductor substrate is further promoted.

In this embodiment, to the temperature of the HCl solution and 110 ° C. or less, since the azeotropic temperature of HCl and _{H 2} O is about 110 ° C., HCl solution of the temperature above the HCl and _{H 2} O is This is because it cannot exist.

In this embodiment, it is desirable that the temperature of the HCl solution be 83 ° C. or higher. In this case, since the boiling point of GeCl ₄ which is the reaction product on the right side of (Equation 8) and (Equation 9) is 83 ° C., the produced GeCl ₄ is removed as a gas from the surface of the semiconductor substrate. For this reason, the reaction from the left side to the right side is further promoted, and the reaction of the Ge oxide on the surface of the semiconductor substrate is further promoted.

  According to the manufacturing method of the present embodiment, the Ge oxide on the Ge substrate can be effectively etched as in the first embodiment. This makes it possible to manufacture a MIS device that suppresses the intervention of Ge oxide at the interface between the Ge substrate and the gate insulating film. Therefore, when a MIS capacitor having a high dielectric constant film is formed on a Ge substrate, it is possible to suppress the presence of a Ge oxide layer having a relatively low dielectric constant. Therefore, it is possible to form a MIS capacitor having a high capacitance.

Further, since SiO ₂ is not etched by the pretreatment, the SiO ₂ film in the element isolation region does not recede. Therefore, it is possible to avoid the formation of an unnecessary base step which becomes a problem when forming the upper layer wiring or the like on the substrate, the deterioration of the element isolation withstand voltage accompanying the reduction in the thickness of the insulating film, and the like.

  FIG. 10 is a diagram showing a result of etching with an HCl solution of Ge oxide. XPS (X-ray photoelectron spectroscopy) evaluates the amount of Ge oxide on the Ge substrate before and after treatment with an HCl solution. The XPS measurement conditions are measured using a monochromatic Al Kα as an X-ray source under a condition where TOA (take off angle) is 15 degrees, that is, the angle formed with the horizontal direction of the sample is 15 degrees.

  The measurement samples are 4 samples whose HCl solution temperature is different from 20, 50, 95, 110 ° C., and the processing time is 5 minutes. In each spectrum, the peak of Ge—Ge bond derived from the Ge3d substrate is set to 29.3 eV, and the influence of charging the sample during X-ray irradiation is corrected.

From FIG. 10, it can be seen that GeO ₂ is removed from the Ge oxide on the surface of the Ge substrate because the Ge—O ₂ peak in the vicinity of 33 eV disappears due to the vapor phase HCl treatment. Further, the Ge—O peak decreases as the temperature increases. Thus, in this embodiment, it is clear that GeO is also effectively removed by etching.

In particular, in the 110 ° C. heat-treated sample, H ₂ O in the above reaction formula (Formula 6) is also removed from the Ge substrate surface as a gas, so that the substrate oxidation by H ₂ O is suppressed and the remaining amount of Ge oxide is higher than that in the 95 ° C. sample. It is thought that there were few. Such substrate oxidation suppressing effect, with H 2 _O of 100 ° C. or higher, the boiling point, becomes remarkable between 110 ° C. or less azeotropic temperature of between H 2 _O and HCl. When the HCl solution azeotropes, the HCl concentration and temperature are 20% and 110 ° C., and when the concentration is not 20%, HCl or water evaporates by boiling to 20% and azeotropes at 110 ° C. For example, in the case of an HCl solution thinner than 20%, water boils above 100 ° C., the concentration increases, and azeotropes at 110 ° C. Therefore, the temperature of the HCl solution is more preferably 100 ° C. or higher.

In the present embodiment, it is desirable that the HCl solution contains alcohol. When H ₂ O (water) is present in the HCl solution, H ₂ O may react with a halide in an atmosphere such as GeCl ₄ to form Ge oxide and generate particles on the Ge substrate. . For this reason, it is preferable to replace at least a part of water with an alcohol such as CH ₃ OH, and to effectively remove halides such as GeCl ₄ and H ₂ O that have a good affinity with the alcohol. It is more effective if the alcohol is used as a solvent instead of diluting HCl with water and washing is performed in a system not containing water.

(Fifth embodiment)
In the method of manufacturing a semiconductor device according to the fifth embodiment of the present invention, after a semiconductor substrate containing Ge is cleaned with an HCL solution, a metal film is formed on the semiconductor substrate by plating in the same bath as the cleaning process. Manufacturing method. Here, HCl was diluted with H ₂ O as a pretreatment for metal film deposition when forming a germanide layer by reacting a metal film and a semiconductor substrate as source / drain electrodes of a MISFET formed on a Ge substrate. An example in which the cleaning process using the HCl solution is performed will be described.

FIG. 11 is a process cross-sectional view illustrating the manufacturing method of the present embodiment. First, as shown in FIG. 11A, an element isolation region 22 embedded with SiO ₂ is formed on a Ge substrate 10. For example, a metal gate electrode 28 is formed on the Ge substrate 10 with a gate insulating film 26 interposed therebetween. The gate electrode 28 is covered with a silicon nitride film 46, for example. In a region where Ge on the Ge substrate 10 is exposed on the surface, so-called source / drain regions, a Ge oxide film 24 is formed as a natural oxide film, for example, about 0.1 to 1 nm. Usually, the Ge oxide film 24 is GeO ₂ or GeO.

Next, as shown in FIG. 11B, the Ge substrate 10 is pretreated with an HCl solution at 75 ° C. or higher and 110 ° C. or lower in a known plating apparatus. By this pretreatment, the Ge oxide film 24 is etched, and the surface of the Ge substrate 10 in the active region is exposed. Here, unlike the HF gas and the HF solution, the HCl solution does not etch SiO ₂ . Therefore, this Ge oxide film 24 is selectively removed with respect to SiO _{2 in the} element isolation region 22 by this process.

  Next, in the same tank of the plating apparatus that has been subjected to the pretreatment, for example, Ni (nickel) is formed on the Ge substrate 10 by plating using HCl as a plating solution. Ni has a standard electrode potential of −0.257 V, which is smaller than 0.000 V of hydrogen, and therefore exists as an ion in an acid solution such as HCl. Therefore, it is possible to form Ni as the metal film 42 on the Ge substrate 10 by plating.

  Here, by using HCl as the plating solution, the pretreatment and the formation of the metal film 42 can be performed as one process treatment. In addition, when different liquid temperatures are required for the pretreatment and the plating treatment for forming the metal film 42, the respective treatment temperatures may be changed to perform a continuous sequence. The plating method may be either electroless plating or electrolytic plating. Although it is desirable to use HCl as the plating solution from the viewpoint of simplifying the process, it is possible to replace the plating solution with another solution so that the Ge substrate 10 is not exposed to the oxidizing atmosphere after the pretreatment.

  Next, as shown in FIG. 11C, for example, heat treatment is performed at a temperature of about 250 to 600 ° C. to react the Ni metal film 42 with the Ge substrate 10 in the source / drain regions. Thereby, a NiGe (nickel germanide) layer 44 is formed in the source / drain regions.

  Thereafter, as shown in FIG. 11D, the unreacted Ni metal film 42 is selectively removed with, for example, a mixed solution of sulfuric acid and hydrogen peroxide. In this way, the MISFET on the Ge substrate 10 having the NiGe layer 44 on the source / drain electrodes is formed.

  According to the present embodiment, the Ge oxide is effectively removed by the pretreatment, and the metal film is formed by the plating method in the same tank where the pretreatment is performed. Therefore, the Ge substrate surface is not exposed to an oxidizing atmosphere before the metal film is formed. Therefore, re-oxidation of the Ge substrate surface hardly occurs. Therefore, the contact resistance between the Ge substrate and the germanide layer can be reduced. In this way, a high-performance MISFET with improved carrier channel mobility and reduced parasitic resistance of the source / drain electrodes is realized by the Ge substrate.

  Here, although Ni has been described as an example of the metal film formed in the source / drain electrode region, it is not necessarily limited to Ni, but Al, Li, K, Ca, Na, Mg, Zn, Fe, Sn, Pb Etc. can be applied.

  Although the Ge substrate has been described here as an example, the present embodiment can be applied to other semiconductor substrates as long as they are Ge-containing semiconductor substrates. Further, the present invention is not limited to the formation of the source / drain electrodes, and can be applied to, for example, a pretreatment for manufacturing a contact metal plug and a metal film formation treatment.

(Sixth embodiment)
The semiconductor device manufacturing method of the sixth embodiment of the present invention is the same as that of the fourth embodiment except that the HCl solution contains a sulfide solution. Therefore, description is abbreviate | omitted about the overlapping content.

Specifically, the Ge substrate is surface-treated with a mixed solution of (NH ₄ ) ₂ S solution and HCl solution, Ge oxide on the Ge substrate surface is etched with HCl, and Ge—S bond is formed with (NH ₄ ) ₂ S. Is formed on the surface of the Ge substrate. Here, it is also possible to place the HCl solution and the (NH ₄ ) ₂ S solution in separate treatment tanks and then perform the (NH ₄ ) ₂ S solution treatment after the HCl solution treatment.

  When a Ge—S bond is present at the interface between the gate insulating film and the semiconductor substrate in the semiconductor substrate containing Ge, the MIS characteristics are improved. According to the present embodiment, the effect of improving the MIS characteristics can be obtained by removing GeO at the interface and causing Ge—S bonds to exist at the interface.

(Seventh embodiment)
The manufacturing method of the semiconductor device according to the seventh embodiment of the present invention is the same as that of the first to sixth embodiments except that the Ge substrate surface is treated with HCl solution or HCl gas and then rinsed with alcohol. It is the same. Therefore, description is abbreviate | omitted about the overlapping content.

12 (a) and 12 (b) show the dependency of the rinse solution after treatment with an HCl solution at 110 ° C., that is, the amount of Ge oxide after pure water (H ₂ O), ethanol (ethanol), and isopropyl alcohol (IPA). Is an XPS Ge3d spectrum. The rinsing time is 10 minutes each. In the case of rinsing with alcohol (ethanol and isopropyl alcohol) as compared with normal pure water rinsing, the remaining amount of Ge oxide is small. This is thought to be because the dielectric constant of pure water is as high as 80, whereas the dielectric constants of ethanol and isopropyl alcohol are as small as 24 and 18, respectively, so that the Ge substrate is hardly reoxidized during rinsing.

  The embodiments of the present invention have been described above with reference to specific examples. The above embodiment is merely given as an example and does not limit the present invention. Further, in the description of the embodiments, the description of the parts and the like that are not directly required for the description of the present invention in the manufacturing method of the semiconductor device and the like is omitted. However, it is possible to appropriately select and use elements related to a required method for manufacturing a semiconductor device.

  For example, in the embodiment, the case where the material of the semiconductor substrate is mainly Ge (germanium) has been described. However, the present invention is applied to a semiconductor substrate containing other Ge, for example, SixGe1-x (0 ≦ x <1). It is also possible to apply to a semiconductor substrate made of a material.

  And it is desirable to apply to a semiconductor substrate having a Ge concentration of 85% or more in the SiGe substrate. This is because the band gap width is narrowed when the Ge concentration is 85% or more, and the superiority over the Si substrate when the Ge substrate is applied to a semiconductor substrate becomes remarkable.

  In addition, all methods of manufacturing a semiconductor device that include the elements of the present invention and whose design can be changed as appropriate by those skilled in the art are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

The figure which shows the etching result by HCl gas of Ge oxide of 1st Embodiment. Process sectional drawing which shows the manufacturing method of the semiconductor device of 1st Embodiment. The conceptual diagram which shows an example of the gaseous-phase etching apparatus of 1st Embodiment. The figure which shows the result of having examined stability of Ge oxide. Process sectional drawing which shows the manufacturing method of the semiconductor device of 2nd Embodiment. The conceptual diagram which shows an example of the gaseous-phase etching apparatus of 2nd Embodiment. The process flow figure of the modification of a 2nd embodiment. The conceptual diagram which shows an example of the manufacturing apparatus of 3rd Embodiment. Process sectional drawing which shows the manufacturing method of the semiconductor device of 4th Embodiment. The figure which shows the etching result by the HCl solution of Ge oxide of 4th Embodiment. Process sectional drawing which shows the manufacturing method of the semiconductor device of 5th Embodiment. The figure which shows the reoxidation suppression result of Ge board | substrate by the alcohol rinse of 7th Embodiment.

Explanation of symbols

10 Ge substrate 12 Solution tank 14 Chamber 16 Second solution tank 22 Element isolation region 24 Ge oxide film 26 Gate insulating film 28 Gate electrode 30 Silyl group termination layer 32 Si oxide film 34 High dielectric film 40 Chamber 42 Metal film 44 NiGe layer 46 Silicon nitride film

Claims (10)

  A method for manufacturing a semiconductor device, comprising: performing a cleaning process on a semiconductor substrate containing Ge with a halogenated gas containing at least one of HCl gas, HBr gas, and HI gas.   2. The method of manufacturing a semiconductor device according to claim 1, wherein a temperature of the semiconductor substrate is equal to or higher than a boiling point of Ge halide or Ge hydrogen halide formed by the cleaning process. The method of manufacturing a semiconductor device according to claim 1, wherein the temperature of the semiconductor substrate is equal to or higher than the boiling point of H ₂ O.   4. A silylating agent is supplied to the surface of the semiconductor substrate during or after the cleaning process, and the surface of the semiconductor substrate is oxidized after the silylating agent is supplied. A manufacturing method of a semiconductor device given in any 1 paragraph.   A method for manufacturing a semiconductor device, characterized in that a semiconductor substrate containing Ge is washed with an HCl solution at 75 ° C. or higher and 110 ° C. or lower.   The method for manufacturing a semiconductor device according to claim 5, wherein the HCl solution is at 83 ° C. or higher and 110 ° C. or lower.   7. The method of manufacturing a semiconductor device according to claim 5, wherein a metal film is formed on the semiconductor substrate by plating in the same tank as the cleaning process after the cleaning process.   The method for manufacturing a semiconductor device according to claim 5, wherein the HCl solution contains an alcohol.   The method for manufacturing a semiconductor device according to claim 5, wherein the HCl solution contains a sulfide solution. 10. The method for manufacturing a semiconductor device according to claim 1, wherein a rinsing process with alcohol is performed after the cleaning process.

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