JP2016207789A - Passivation processing method, semiconductor structure forming method, and semiconductor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the defect density of a surface of a germanium or group III-V material.SOLUTION: There is provided a passivation processing method comprising the steps of: mounting a germanium (Ge) or group III-V substrate on a mounting table in a processing chamber; and depositing a passivation film containing sulfur (S) or selenium (Se) on the germanium (Ge) or group III-V substrate by supplying a hydrogen sulfide (HS) gas or a hydrogen selenide (HSe) gas and an ammonia gas (NH) into the processing chamber.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a passivation processing method, a method for forming a semiconductor structure, and a semiconductor structure.

  Group III-V materials such as germanium (Ge) and indium gallium arsenide (InGaAs) have higher mobility than silicon (Si) materials. Therefore, it is expected to use germanium or the like instead of silicon as a substrate for the next generation integrated circuit. However, a high defect density at the interface between a substrate such as germanium and a dielectric film formed on the substrate is one of the factors that reduce the mobility of the manufactured semiconductor structure.

In order to reduce the defect density, a method of forming a passivation film on a substrate with hydrogen sulfide (H ₂ S) gas before forming a dielectric film on the substrate such as germanium has been proposed. (For example, see Patent Documents 1 and 2).

Japanese Patent No. 5224678 JP 2011-91394 A

  However, in the method of forming the passivation film, there is a problem that the substrate temperature needs to be set to a high temperature of 300 ° C. to 400 ° C. and the passivation film is formed for a long time, so that the production efficiency is deteriorated.

On the other hand, a method of reducing the defect density on the surface of the germanium substrate by wet etching using ammonium sulfide (NH ₄ ) 2S is conceivable. However, in this method, the germanium substrate is exposed to air after wet etching. For this reason, the surface of the germanium substrate is reoxidized, and a natural oxide film having a high defect density is formed on the surface of the germanium substrate.

  In one aspect, the present invention is directed to reducing the defect density on the surface of germanium or III-V materials.

In order to solve the above problems, according to one aspect, a step of placing a germanium (Ge) or III-V group substrate on a mounting table in a processing chamber, and a hydrogen sulfide (H ₂ S) gas or selenization A passivation film containing hydrogen (H ₂ Se) gas and ammonia (NH ₃ ) gas in the processing chamber and containing sulfur (S) or selenium (Se) on the germanium or III-V substrate. A passivation process method is provided.

  According to one aspect, the surface defect density of germanium or III-V materials can be reduced.

The figure which shows an example of the semiconductor structure concerning one Embodiment. The figure which shows an example of the defect density of the interface of a board | substrate and an oxide. 6 is a flowchart showing an example of a manufacturing process of a semiconductor structure according to an embodiment. The figure which shows an example of the relationship between the time exposed to air, and the thickness of the oxide on a board | substrate. The figure which shows the treatment (passivation film formation) result concerning one Embodiment. The figure which shows the presence or absence of the treatment concerning one Embodiment, and the composition of a substrate surface. The figure which shows the presence or absence of the treatment concerning one Embodiment, and the state of a board | substrate surface and a cross section. The figure which shows the temperature and pressure dependence of the treatment concerning one Embodiment. The figure which shows the temperature dependence of the treatment concerning one Embodiment. The figure which shows the temperature dependence of the passivation film concerning one Embodiment. The figure which shows the temperature and pressure dependence of the passivation film concerning one Embodiment. The figure which shows the flow volume dependence of the passivation film concerning one Embodiment. The figure which shows the presence or absence of the passivation film concerning one Embodiment, and the CV characteristic of a capacitor.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Example of semiconductor structure]
First, an example of a semiconductor structure according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of a semiconductor structure of a MOS transistor. In this embodiment, germanium (Ge) is used for the substrate. When the germanium substrate is P-type, n-type source and drain layers are formed. When the germanium substrate is n-type, p-type source and drain layers are formed. A gate layer is formed between the source and drain layers. A High-k film (high dielectric constant gate insulating film) is formed between the gate layer and the germanium substrate. In this embodiment, a passivation film is formed at the interface between the germanium substrate and the high-k film.

The germanium (Ge) material has higher mobility than the silicon (Si) material. For example, electron mobility (unit: cm ² / V · s) is 1400 for silicon, and 3900 for germanium. Group III-V materials such as gallium arsenide (GaAs), indium gallium arsenide (InGaAs), indium arsenide (InAs), gallium antimonide (GaSb), indium antimonide (InSb) are also more mobile than silicon materials. Is expensive. For example, the mobility of electrons is 8500 for gallium arsenide, 12000 for indium gallium arsenide, 40000 for indium arsenide, 3000 for gallium antimonide, and 77000 for indium antimonide. The group III-V material is a compound of a group III (group 13) element and a group V (group 15) element in the periodic table, and is not limited to the above-described materials such as gallium arsenide.

  It is expected that a high-performance semiconductor structure will be manufactured by using germanium or III-V group material instead of silicon as a substrate for the next generation integrated circuit. However, a high defect density at the interface between the germanium substrate and a dielectric film (gate insulating film) such as a high-k film is one of the factors that reduce the mobility of the manufactured semiconductor structure.

In the case of a silicon substrate, for example, a silicon oxide film (SiO ₂ ) is used for the gate insulating film. In the case of a germanium substrate, for example, alumina (Al ₂ O ₃ ) is used for the gate insulating film.

The defect density at the interface 100a between the silicon substrate 100 and the silicon oxide film 200 shown in FIG. 2A is on the order of 10 ¹⁰ . In contrast, the defect density at the interface 10a between the germanium substrate 10 and the germanium oxide film 20, 10 ¹³ of the order of, has three orders of magnitude higher than in the case of a silicon substrate.

Accordingly, in the present embodiment described below, the surface of the germanium substrate 10 is treated with hydrogen sulfide (H ₂ S) gas and ammonia (NH ₃ ) gas, and germanium sulfide (GeS _x ) passivation is performed on the surface of the germanium substrate 10. A film 30 is formed. As a result, the defect density on the surface of the germanium substrate 10 is on the order of 10 ¹¹ . Thus, in this embodiment, by reducing the defect density on the surface of germanium, the mobility of the manufactured semiconductor structure can be increased, and a high-performance transistor or other semiconductor structure can be manufactured.

[Example of semiconductor structure: Passivation method]
Next, an example of the manufacturing process of the semiconductor structure using the passivation processing method according to the present embodiment will be described with reference to the flowchart of FIG. The semiconductor structure according to the present embodiment, first, hydrochloric acid (HCL) or DHF: germanium substrate 10 is wet-etched by the liquid (Diluted hydrofluoric acid diluted hydrofluoric acid (a mixed solution of HF and _{H 2} O)) (step S10) . By this step, germanium oxide (GeO ₂ ) 20 on the germanium substrate 10 is removed.

  Next, in order to form a High-k film on the germanium substrate 10, the germanium substrate 10 is transferred to the film formation apparatus 1 (step S12). By this step, the germanium substrate 10 is exposed to air for a predetermined time. During this standing time, the surface of the germanium substrate 10 is reoxidized, and a natural oxide film (GeO) 40 is formed on the germanium substrate 10. Due to the natural oxide film 40, the surface of the germanium substrate 10 has a high defect density.

Therefore, the germanium substrate 10 is etched in an NH ₃ gas atmosphere using the same or different apparatus as the film forming apparatus 1 (step S14). By this step, the oxide film 40 on the surface of the germanium substrate 10 is substantially removed.

Next, hydrogen sulfide (H ₂ S) gas and ammonia (NH ₃ ) gas are supplied into the film forming apparatus 1 to treat the germanium substrate 10 (step S16). By this step, a GeS _x passivation film 30 is formed on the surface of the germanium substrate 10. Next, a high-k film 50 is formed (step S18). As the high-k film 50, alumina (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), hafnium aluminate (HfAlO), zirconia oxide (ZrO ₂ ), praseodymium oxide (PrO _x ), lanthanum oxide (LaO _x ) Gadolinium oxide (Gd ₂ O ₃ ) may be used.

  Finally, a metal film 60 that functions as an upper electrode is formed (step S20), and this process is terminated. As the metal film 60, tantalum (Ta), tantalum nitride (TaN), or titanium nitride (TiN) may be used.

(Natural oxide film)
In addition, the environment where the process after step S16 is performed in-situ is preferable. In an ex-situ environment, the surface of the germanium substrate 10 is exposed to air before forming the passivation film in step S16 and before forming the high-k film 50 in step S18. A natural oxide film 40 is formed on the surface of the substrate 10. For example, FIG. 4 shows an example of the relationship between the time of exposure to air (ie, the time for which the germanium substrate is left) and the thickness of the native oxide on the germanium substrate. The horizontal axis in FIG. 4 indicates the standing time, and the vertical axis indicates the thickness of the natural oxide film. 4 shows the paper `` Native Oxidation Growth on Ge (111) and (100) Surfaces '', Siti Kudnie Sahari, Hideki Murakami, Tomohiro Fujioka, Tatsuya Bando, Akio Ohta, Katsunori Makihara, Seiichiro Higashi, and Seiichi Miyazaki, Japanese. Citing Fig. 6 of Journal of Applied Physics 50 (2011) 04DA12.

  According to this, when the leaving times are the same, the thicknesses of the natural oxide films of the n-type germanium substrate (n-Ge) and the p-type germanium substrate (p-Ge) It is 4 to 5 times the thickness of the oxide film. That is, the germanium substrate is more easily oxidized than the silicon substrate.

Therefore, the longer the standing time, the more GeO _x bonds are increased on the germanium substrate 10 and the GeS _x bonds are decreased. Therefore, the longer the standing time, the lower the concentration of S on the germanium substrate 10 and the higher the O concentration. .

  As the O concentration on the germanium substrate 10 increases, the defect density at the interface between the germanium substrate 10 and the High-k film increases. That is, it can be seen that the germanium substrate 10 is more likely to be naturally oxidized than the silicon substrate, which increases the surface defect density and tends to decrease mobility.

The germanium oxide (GeO ₂ ) film 20 on the germanium substrate 10 can be almost removed by wet etching in step S10 of FIG. However, it is difficult to remove all the natural oxide film on the germanium substrate 10 by the wet etching. For this reason, it is preferable to make it difficult to form the natural oxide film 40 by shortening the time for which the germanium substrate 10 is left in step S <b> 12 (the transfer time or the like).

  Therefore, management of the standing time is important. In the present embodiment, the germanium substrate 10 is treated in step S16 of FIG. 3 to form and protect a passivation film on the surface of the germanium substrate 10, thereby preventing the surface of the germanium substrate 10 from being oxidized. To do. As a result, it is possible to prevent the defect density on the surface of the germanium substrate 10 from being increased and the device characteristics of the manufactured semiconductor structure from being deteriorated. For the above reason, it is more preferable that the processes after step S16 in FIG. 3 are performed in-situ in the film forming apparatus 1, for example. However, since a passivation film is formed on the surface of the germanium substrate 10 in step S16, an environment in which steps S18 and S20 are performed ex-situ may be used.

(Configuration example of film deposition system)
A configuration example of the film forming apparatus will be briefly described. The film forming apparatus 1 has a cylindrical processing chamber C made of aluminum whose surface is anodized (anodized). A mounting table 12 is provided inside the processing chamber C. The mounting table 12 mounts the germanium substrate 10.

  A gas shower head 11 is provided on the ceiling of the processing chamber C. Hydrogen sulfide gas and ammonia gas are introduced from the gas introduction port 14 of the gas shower head 11 and supplied into the processing chamber C through the gas buffer space 11b and from a large number of gas vent holes 11a. A passivation film 30 is formed on the germanium substrate 10 by the action of hydrogen sulfide gas and ammonia gas supplied into the processing chamber C.

(NH ₃ added)
In step S16 in FIG. 3, the germanium substrate 10 is treated, and hydrogen sulfide (H ₂ S) gas and ammonia (NH ₃ ) gas are used to form a passivation film on the surface of the germanium substrate 10. Next, a passivation film formed under five treatment conditions will be described with reference to FIG. FIG. 5A shows five treatment conditions.

  In the treatment condition A, the ratio of ammonia / hydrogen sulfide gas is 0/100.

  In the treatment condition B, the ammonia / hydrogen sulfide gas ratio is 60/140.

  In the treatment condition C, the ammonia / hydrogen sulfide gas ratio is 100/100.

  In the treatment condition D, the ammonia / hydrogen sulfide gas ratio is 140/60.

  In the treatment condition E, the ammonia / hydrogen sulfide gas ratio is 0/100.

  In the treatment condition F, the ammonia / hydrogen sulfide gas ratio is 100/100.

  That is, the treatment conditions A and E are different from the other conditions B to D and F in that ammonia gas is not added. Treatment conditions A to D are different from treatment conditions E and F in which the treatment time is as short as 2 minutes and the treatment time is as long as 20 minutes.

The common points of the treatment conditions A to F are as follows.
Hydrochloric acid (HCL) wet etching (10% solution, 10 minutes) is performed before treatment.
The pressure in the processing chamber is controlled to 100 Torr (13332 Pa), and the temperature is controlled to 100 ° C.

  FIG. 5 (b) shows the result of observation of S2p orbital electrons by XPS (X-ray Photoelectron Spectroscopy) measurement of a passivation film (that is, the surface of a germanium substrate) formed under five treatment conditions. The ratio of sulfur S is shown. For example, the treatment condition A indicates that 4% sulfur is present near the surface of the germanium substrate 10 on which the passivation film is formed.

  According to this, the conditions B, C, D, and F in which the ammonia gas was added to the hydrogen sulfide gas and the treatment were performed are more than the conditions A and E in which the treatment was performed without adding the ammonia gas to the hydrogen sulfide gas. It can be seen that the ratio of sulfur S contained in the material of the passivation film is large. In particular, when the treatment is performed for 20 minutes without adding ammonia gas to the hydrogen sulfide gas of Condition E, the ratio of sulfur S contained in the passivation film is 6%. On the other hand, when ammonia gas is added to the hydrogen sulfide gas under the conditions B to D and treatment is performed for 2 minutes, the ratio of sulfur S contained in the passivation film is about 10%. That is, when treatment is performed by adding ammonia gas to hydrogen sulfide gas, even if the treatment time is shortened to 1/10, the ratio of S contained in the passivation film increases, and the defect density on the surface of the germanium substrate 10 decreases. You can see that you can.

  However, the sulfur S contained in the passivation film shown in FIG. 5B includes sulfur S that is not bonded to germanium Ge in the film. Therefore, next, the component of sulfur S bonded to Ge in the germanium substrate 10 will be considered. FIG. 6 shows an example of the result of XPS measurement from the surface of the germanium substrate 10 on which the passivation film is formed. The horizontal axis represents the binding energy, and the vertical axis represents the composition state of the germanium substrate 10 surface. FIG. 6A shows a case where no treatment is performed (a case where a passivation film is not formed). FIG. 6B shows a case where treatment is performed without adding ammonia gas to hydrogen sulfide gas. FIG. 6C shows a case where treatment is performed by adding ammonia gas to hydrogen sulfide gas.

According to the measurement result of FIG. 6, in the treatment to which ammonia gas is added in FIG. 6 (c), the peak of GeS or GeS ₂ contained in the passivation film is performed without adding ammonia gas in FIG. 6 (b). It is significantly higher than the peaks of GeS and GeS _{2 in} the case of That is, in the present embodiment, it is shown that the passivation film when ammonia gas is added contains more sulfur S components bonded to Ge than when ammonia gas is not added. That is, it is presumed that the activation energy when forming GeS _x is lowered by performing treatment using hydrogen sulfide gas to which ammonia gas is added.

  From the above, by performing the treatment using hydrogen sulfide gas to which ammonia gas is added, the proportion of S bonded to germanium is increased in the passivation film, and the defect density on the surface of the germanium substrate 10 is reduced. I understand. As a result, the state of the interface between the germanium substrate 10 and the High-k film 50 is improved, and mobility is expected to increase.

When the treatment of FIG. 6A is not performed, the GeS and GeS ₂ peaks on the surface of the germanium substrate 10 are treated using hydrogen sulfide gas without adding the ammonia gas of FIG. 6B. It is even lower than the case.

As described above, in the passivation film formed by the passivation processing method according to the present embodiment, the content of sulfur S is high, and it is found that GeS or GeS ₂ is present in the film as a stable combination with germanium. It was. Thereby, the defect density in the surface of a germanium substrate can be reduced and the mobility of the manufactured semiconductor can be improved.

Moreover, treatment time can be shortened by adding ammonia gas to hydrogen sulfide gas. In addition, while a passivation film is usually formed using H ₂ S gas at a high temperature of 300 ° C. to 400 ° C., in this embodiment, ammonia gas is added to the hydrogen sulfide gas to lower the temperature to 100 ° C. A passivation film is formed at ° C. As a result, the treatment time can be shortened to about 1/10, and a passivation film can be formed by low-temperature treatment, and production efficiency can be improved.

  Note that the upper and lower SEM (scanning electron microscope) images in FIG. 7A show the surface and cross section of a germanium substrate that has not been treated. The upper and lower SEM images in FIG. 7B show the surface and cross section of a germanium substrate treated with hydrogen sulfide gas and ammonia gas. This proves that the surface roughness of the germanium substrate treated with hydrogen sulfide gas and ammonia gas is equivalent to the surface roughness of the germanium substrate not treated. In other words, it can be confirmed that even if treatment is performed with hydrogen sulfide gas and ammonia gas, the surface condition is not worse than the surface roughness of the germanium substrate before treatment.

[Temperature and pressure dependence]
Next, the temperature and pressure dependence of the processing chamber to which the passivation processing method according to the present embodiment is applied will be described with reference to FIGS. 8 to 11 show the results of analyzing the surface state of a germanium substrate on which a passivation film is formed by TOF-SIMS (Time-of-Flight Secondary Mass Spectrometry).

  In this embodiment, the temperature of the mounting table is shown as the temperature of the processing chamber.

Here, first, the germanium substrate 10 is wet-etched with a liquid containing hydrochloric acid (HCL) for 10 minutes. Next, an example of the result of treating the germanium substrate after wet etching with hydrogen sulfide gas and ammonia gas is shown. FIG. 8A shows the case where the pressure in the processing chamber is 3 Torr (400 Pa), and the number of GeO _{2 and} the number of GeS in the passivation film when the temperature in the processing chamber is 25 ° C., 50 ° C., and 100 ° C. It is the graph which showed. In FIG. 8C, the horizontal axis represents the temperature during treatment, and the vertical axis represents the ratio of GeO _{2 to} GeS. According to this result, the ratio of GeO _{2 to} GeS in the film is smaller at 50 ° C. and 100 ° C. than at 25 ° C.

FIG. 8B shows the case where the pressure in the processing chamber is 50 Torr (6667 Pa), and the number of GeO _{2 and} the number of GeS in the passivation film when the temperature in the processing chamber is 25 ° C., 50 ° C., and 100 ° C. It is the graph which showed. As shown in FIG. 8C, the ratio of GeO _{2 to} GeS in the film is less at 50 ° C. and 100 ° C. than at 25 ° C.

According to this, it can be seen that the ratio of GeO _{2 to} GeS decreases as the temperature increases in both cases where the pressure in the processing chamber is 3 Torr and 50 Torr, and as a result, the defect density decreases. From the above, when treatment is performed with hydrogen sulfide gas and ammonia gas, it is preferable to control the processing chamber to 50 ° C. or higher.

  Further, when the treatment is performed with hydrogen sulfide gas and ammonia gas, the pressure in the processing chamber is preferably controlled to 3 Torr or higher, and more preferably 50 Torr or higher.

FIG. 9 shows the number of GeO _{2 and} the number of GeS in the passivation film when the pressure in the processing chamber is controlled to 50 Torr and the temperature in the processing chamber is 25 ° C., 50 ° C., 100 ° C., 150 ° C., and 200 ° C. is a graph showing the ratio of GeO ₂ for GeS. According to this, when treatment with hydrogen sulfide gas and ammonia gas is performed, the temperature in the processing chamber is preferably 50 ° C. or higher because the O concentration on the surface of the germanium substrate can be reduced by controlling the temperature in the processing chamber to 50 ° C. or higher. I understand that. Further, when the temperature in the processing chamber is in the range of 100 ° C. to 200 ° C., it is in a saturated state, and the ratio of GeO _{2 to} GeS in the passivation film is almost the same.

FIG. 10 shows the number of GeO _{x and} the number of GeS _{x in} the passivation film when the pressure in the processing chamber is controlled to 50 Torr and the temperature in the processing chamber is 25 ° C., 50 ° C., 100 ° C., 150 ° C., and 200 ° C. And a ratio of GeO _x to GeS _x . In this example, the number of GeO _x is the total number of GeO and GeO ₂ , and the number of GeS _x is the total number of GeS and GeS ₂ . According to this, it is understood that when the treatment is performed with hydrogen sulfide gas and ammonia gas, it is preferable to control the temperature in the processing chamber to 50 ° C. or higher because the O concentration on the surface of the germanium substrate can be reduced. Further, in the range of 100 ° C. to 200 DEG ° C. is in the saturated state, the ratio of GeO _x is approximately the same for GeS _x in the passivation film.

In the experiment of FIG. 11, the pressure in the processing chamber is controlled to 50 Torr (6667 Pa), 100 Torr (13332 Pa), 300 Torr (39996 Pa), and 500 Torr (66670 Pa), and the temperature in the processing chamber is controlled to 100 ° C., 200 ° C., and 250 ° C. . FIG. 11 is a graph showing the number of GeO _{2 in} the passivation film, the number of GeS, and the ratio of GeO ₂ to GeS. According to this, when the treatment with hydrogen sulfide gas and ammonia gas is performed, if the pressure in the processing chamber is controlled to 100 Torr (13332 Pa) or more and the temperature is controlled to 100 ° C. or more, the concentration of O on the surface of the germanium substrate is generally reduced. It can be seen that this is preferable because it can be lowered.

Further, according to the result in the frame indicated by T, when the temperature is increased with the same pressure, the number of O contained in the passivation film increases. Further, according to the results in the frame indicated by P, when the pressure is increased at the same temperature, the number of O contained in the passivation film is reduced. However, considering the ratio of GeO _{2 to} GeS, the temperature of the mounting table may be controlled to 50 ° C. to 250 ° C. Further, the pressure in the processing chamber may be controlled to 3 Torr or more. The upper limit of the pressure is preferably about 200 Torr (26664 Pa). When adjusting the processing chamber by operating the APC (automatic pressure controller), the upper limit of the practical range of APC is about 200 Torr. Therefore, the processing chamber pressure should be controlled to 3 Torr to 200 Torr due to mechanical limitations. Is preferred. Further, the upper limit is considered to be about 200 Torr in reducing the amount of processing gas used.

[Indium gallium arsenide substrate and flow rate dependence]
Next, the gas flow rate dependency in the passivation processing method according to the present embodiment will be described with reference to FIG. Here, an indium gallium arsenide (InGaAs) substrate is used instead of a germanium substrate. The indium gallium arsenide substrate is an example of a group III-V substrate to which the passivation processing method according to the present embodiment is applied. As other III-V group materials, gallium arsenide (GaAs), indium arsenide (InAs), gallium antimonide (GaSb), indium antimonide (InSb), or the like can be used. FIG. 12 shows the result of analyzing the surface state of the germanium substrate on which the passivation film is formed by TOF-SIMS.

  Here, first, the germanium substrate 10 is wet-etched with a liquid containing dilute hydrofluoric acid (DHF) for 10 minutes. Next, the treatment chamber temperature is controlled to 50 ° C., the pressure is controlled to 50 Torr (6666 Pa), and treatment for 2 minutes is performed with hydrogen sulfide gas and ammonia gas. Through this process, a passivation film is formed.

In the case of a germanium substrate, the number of GeO _x and GeS _{x on} the surface of the germanium substrate was measured, and the characteristics of the passivation film were considered from their ratio. In contrast, in the case of an indium gallium arsenide (InGaAs) substrate, the number of InO _x , InS _x , GaO _x , GaS _x , AsO _x and AsS _{x on} the surface of the InGaAs substrate is measured. Then, the ratio of O and S with respect to indium (In), gallium (Ga), and arsenic (As) will be considered. FIG. 12 shows a case without treatment and a case with treatment. Here, “with treatment” is treatment of ammonia gas and hydrogen sulfide gas when the flow rate ratio of ammonia gas to hydrogen sulfide gas is 20/180. FIG. 12 shows the ratio of AsO and AsS, the ratio of GaO and GaS, and the ratio of InO and InS in the passivation film thus formed. According to this, as for the ratio of AsO and AsS, the ratio of GaO and GaS, and the ratio of InO and InS, the concentration of S on the surface of the InGaAs substrate is higher when the treatment is performed than when the treatment is not performed. It can be seen that it is higher than the concentration of. As a result, it is understood that the flow rate ratio of ammonia gas to hydrogen sulfide gas is preferably controlled to 10% (= 20 / (20 + 180) × 100) or more. In the results of FIG. 12, AsO / AsS <GaO / GaS <InO / InS.

  As described above, according to the passivation treatment method of the present embodiment, a passivation film having a high sulfur S content is formed on the surface layer of a substrate such as germanium by a treatment in which ammonia gas is added to hydrogen sulfide gas. . Thereby, the defect density on the surface of the substrate such as germanium (that is, the interface between the substrate and the High-k film) can be reduced.

  In addition, according to the present embodiment, the treatment speed of treatment is increased by about 10 times faster by adding ammonia gas to hydrogen sulfide gas than in the case of performing treatment with only hydrogen sulfide gas without adding ammonia. it can. In addition, according to the present embodiment, the passivation film can be formed at a low temperature of about 100 ° C. as compared with the case where the treatment is processed at a high temperature of about 300 ° C. As a result, production efficiency can be improved.

In the passivation treatment method of this embodiment, hydrogen sulfide gas and ammonia gas are used. However, hydrogen selenide (H ₂ Se) gas may be used instead of hydrogen sulfide gas. In this case, according to the passivation treatment method of the present embodiment, a passivation film having a high selenium Se content is formed on a germanium or III-V substrate by a treatment in which ammonia gas is added to hydrogen selenide gas. The Thereby, the defect density at the interface of germanium or a group III-V substrate can be reduced.

[Application to capacitors]
The passivation processing method according to the above embodiment was used for manufacturing a transistor. However, the passivation method according to the above embodiment can be applied to capacitors including germanium and III-V groups. With the passivation treatment method according to the above embodiment, the defect density at the interface between germanium or a group III-V semiconductor and an oxide film formed thereon can be reduced.

  FIG. 13 shows the presence or absence of a treatment (passivation film) according to this embodiment and the CV characteristics of the capacitor. FIG. 13A shows the characteristic of the capacitance C (CV characteristic) with respect to the voltage V of the capacitor when the treatment is not performed on the germanium substrate according to the present embodiment. FIG. 13B shows the CV characteristics of the capacitor when the treatment according to this embodiment is performed. Each frequency is a frequency of power applied to the capacitor in the IC chip.

  According to this, when the passivation film is formed by adding ammonia gas to hydrogen sulfide gas, the CV characteristic of the capacitor is improved by the passivation film. In particular, as indicated by W in FIG. 13B, good CV characteristics are obtained in the curve F1 (1 MHz), the curve F2 (500 kHz), the curve F3 (200 kHz), and the curve F4 (100 kHz). That is, when the defect density at the interface of the capacitor is low, good characteristics can be obtained even when the frequency is high (for example, 100 kHz, 200 kHz, 500 kHz).

  On the other hand, when the treatment according to the present embodiment is not performed, the CV characteristics of the capacitors vary as indicated by U in FIG. That is, in this case, it can be seen that the defect density at the interface of the capacitor is high and good characteristics are not obtained.

  From the above, according to the passivation treatment method of the present embodiment, a passivation film having a high sulfur S content is formed on a germanium or III-V group substrate by a treatment in which ammonia gas is added to hydrogen sulfide gas. . Thereby, the defect density in the interface of a germanium or a III-V group board | substrate can be reduced, and mobility can be improved.

  In addition, according to the passivation treatment method of the present embodiment, a passivation film having a high selenium Se content is formed on a germanium or III-V substrate by a treatment in which ammonia gas is added to hydrogen selenide gas. . Thereby, the defect density in the interface of a germanium or a III-V group board | substrate can be reduced, and mobility can be improved.

  As described above, the passivation processing method, the semiconductor structure forming method, and the semiconductor structure have been described in the above embodiments, but the passivation processing method, the semiconductor structure forming method, and the semiconductor structure according to the present invention are not limited to the above embodiments. Various modifications and improvements are possible within the scope of the present invention. Moreover, the matters described in the plurality of embodiments can be combined within a consistent range.

For example, the passivation film may be formed by adding an inert gas such as N 2 in addition to hydrogen sulfide (H ₂ S) gas or hydrogen selenide (H ₂ Se) gas and ammonia (NH ₃ ) gas. Good. However, it is preferable to control the partial pressure of hydrogen sulfide gas or hydrogen selenide gas higher than the partial pressure of other gases.

  The substrate to be processed according to the present invention is not limited to a wafer, and may be, for example, a large substrate for a flat panel display, a substrate for an EL element, or a solar cell. In the case of a substrate for a solar cell, a thin film of a power generation layer such as CIGS (CuInGaSe2) or CZTS (Cu2ZnSnS4) is in an atmosphere of hydrogen sulfide gas to which ammonia is added or hydrogen selenide gas to which ammonia is added, and 100 ° C. to 500 ° C. It is formed at a temperature of ° C. The power generation layer formed at this time has a crystal structure in which the band gap is adjusted.

1: Film forming apparatus 10: Germanium substrate 11: Gas shower head 12: Mounting table 20: Germanium oxide film 30: Passivation film 40: Natural oxide film 50: High-k film 60: Metal film C: Processing chamber

Claims (7)

Placing a germanium (Ge) or III-V group substrate on a mounting table in the processing chamber;
Hydrogen sulfide (H ₂ S) gas or hydrogen selenide (H ₂ Se) gas and ammonia (NH ₃ ) gas are supplied into the processing chamber, and sulfur (S) is deposited on the germanium or III-V substrate. ) Or a passivation film containing selenium (Se),
A passivation processing method comprising: Controlling the temperature of the mounting table to 50 ° C. to 250 ° C.,
The passivation processing method according to claim 1. Controlling the pressure of the processing chamber to 3 Torr to 200 Torr;
The passivation processing method according to claim 1 or 2. Controlling the flow rate ratio of ammonia (NH ₃ ) gas to hydrogen sulfide (H ₂ S) gas to 10% or more,
The passivation processing method as described in any one of Claims 1-3. Supplying an inert gas together with hydrogen sulfide (H ₂ S) gas or hydrogen selenide (H ₂ Se) gas and ammonia (NH ₃ ) gas;
The passivation processing method as described in any one of Claims 1-4. A method for forming a semiconductor structure, comprising:
Placing a germanium (Ge) or III-V group substrate on a mounting table in the processing chamber;
Hydrogen sulfide (H ₂ S) gas or hydrogen selenide (H ₂ Se) gas and ammonia (NH ₃ ) gas are supplied into the processing chamber, and sulfur (S) is deposited on the germanium or III-V substrate. ) Or a passivation film containing selenium (Se),
Forming a dielectric film on the passivation film;
Forming a metal film on the dielectric film;
A method for forming a semiconductor structure comprising: Germanium (Ge) or III-V substrate;
Passivation containing sulfur (S) or selenium (Se) formed on the substrate by hydrogen sulfide (H ₂ S) gas or hydrogen selenide (H ₂ Se) gas and ammonia (NH ₃ ) gas. A membrane,
A dielectric film formed on the passivation film;
A metal film formed on the dielectric film;
A semiconductor structure.