JP3218362B2 - Semiconductor substrate processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the stabilization of processing characteristics on the surface of a semiconductor substrate.

[0002]

To form the Related Art Low-resistance ohmic contact is essential surface treatment of the high-concentration Si substrate before metal deposition (refer to what impurity concentration of about 1 × 10 ²⁰ / cm ³⁾ . Factors that increase the contact resistance include the adhesion of a polymer film at the time of opening the contact, the formation of an oxygen-containing layer, the introduction of crystal defects into the Si substrate, and the like. Re-formation of the natural oxide film is considered. Normally, in the pretreatment process, surface treatment such as ashing or chemical dry etching is performed to remove these deposits and altered layers, and in the final process before metal deposition, natural oxidation using a hydrofluoric acid-based treatment solution is performed. The removal of the film and the formation of a hydrogen-terminated surface are performed to reduce contamination due to transport in the atmosphere.

However, it is known that a high-concentration semiconductor substrate used for a metal contact is different from a low-concentration semiconductor substrate in cleaning characteristics, etching characteristics, and reaction characteristics between a source gas and a substrate during metal deposition. In the case of a low-concentration substrate, there is little difference in the above characteristics depending on whether the substrate type is a P-type or an N-type. In some cases, processing conditions with extremely small process margins have to be taken. In the following, conventional examples of each processing method will be described.

Prior to processing such as forming a metal film on a Si substrate, to obtain a hydrogen-terminated clean Si surface,
Washing with a diluted HF aqueous solution or a buffered diluted HF aqueous solution is often performed. This cleaning method is simple and the hydrogen-terminated surface is stable even in the atmosphere, so that it is extremely useful. However, in order to obtain near-complete hydrogen termination on the surface of the high-concentration substrate, it is necessary to perform treatment in the aqueous solution for a very long time, and this tendency is particularly remarkable in the case of a P-type high-concentration substrate. This characteristic is not found in an intrinsic or low-concentration substrate. For example, in a P-type Si substrate having an impurity concentration of about 1 × 10 ¹⁸ / cm ³ ,
As in the case of a substrate having a lower impurity concentration, a hydrogen-terminated surface that is stable for a long time in the air can be easily obtained.

If the surface treatment of a high-concentration substrate is sufficiently performed in the above-mentioned aqueous solution, the film thickness of an insulating film and the like mixed on the surface of the substrate is greatly reduced and the pattern edge is retreated. This is a problem in manufacturing. Also,
If the treatment time in the above aqueous solution is shortened so that the shape change of the insulating film or the like falls within an allowable range, cleaning of the surface of the high-concentration substrate becomes insufficient, and as a result, the metal film deposited on the substrate The electrical characteristics and adhesion of the bonding are deteriorated. In addition, in order to obtain a clean surface by washing in a short time, a buffer-diluted HF aqueous solution having a higher washing efficiency than a simple diluted HF aqueous solution or a commercially available buffer-diluted HF aqueous solution containing a surfactant may be used. The effect is not enough. further,
No matter how long the cleaning time is extended, there is a problem that an ideal hydrogen-terminated surface cannot be fundamentally obtained because fluorine easily remains on the surface of the P-type high concentration substrate.

Next, the etching of the surface of the high concentration substrate will be described. In the processing of a poly-Si gate used for a Si-MOS LSI having a heteropolar gate structure, it is necessary to etch amorphous Si or poly-Si doped with a P-type or N-type dopant at a high concentration at a constant rate. However, in practice, it is sometimes difficult to find such uniform etching conditions. At present, this problem is avoided by increasing the number of steps and devising processes other than etching. For example, a step of thinning the boron-doped poly-Si layer having a lower etching rate than the phosphorus-doped poly-Si layer before the etching step is provided. In addition, SiO
There is a method of performing sufficient over-etching using 2 as a stopping layer. These methods lead to an increase in the number of steps and deterioration of the crystallinity of the underlying substrate.

Finally, the deposition of a metal film on a Si substrate will be described. In the specific metal film deposition method, a method of improving the contact characteristics by incorporating the method of cleaning the surface of a high-concentration Si substrate into the deposition method and compensating for the incompleteness of the hydrofluoric acid-based wet treatment described above is attempted. I have been. As an example, a case of selective growth of tungsten (W) by tungsten hexaboride (WF6) will be described. Conventionally, in a selective growth technique in which W is grown only in a desired region on a Si substrate, W is grown by reducing WF6, which is a source gas, with a base Si (hereinafter referred to as Si reduction reaction).
i-reduction method, silane (SiH4) is supplied to the chamber simultaneously with WF6, and WF6 is reduced by this SiH4 (hereinafter referred to as SiH4 reduction reaction) to grow Si to grow W.
A method of depositing W by continuously performing two types of H4 reduction methods has been used.

In the Si reduction method, WF6 and the underlying Si react directly with each other to cause deposition of W, and at the same time, reaction consumption of the Si substrate (hereinafter referred to as Si consumption) occurs. (Hereinafter referred to as self-cleaning). Therefore, even if the hydrofluoric acid-based wet treatment is incomplete, it is easy to obtain a low-resistance ohmic contact. However, in the Si reduction method, the underlying Si substrate is etched by the consumption of the Si (that is, the underlying substrate is etched, and a W layer is cut into the etched portion).

In the case where the Si reduction reaction has surface contamination, a phenomenon occurs in which the start of the reaction is delayed for a certain time (hereinafter referred to as a latency time). Compared with the N-type high concentration substrate, the latency of the incompletely cleaned P-type high concentration substrate is much longer. Therefore, in a P-type and N-type mixed element, if the Si reduction method is performed until the P-type high-concentration substrate is cleaned, a large amount of Si is consumed in the N-type high-concentration substrate during that time. Nowadays,
The thickness of the active layer of a Si device is extremely thin for high performance of the device, and when depositing a metal on a highly doped active layer, the above Si consumption is not negligible because it degrades device characteristics. Becomes

[0010] The above-mentioned consumption of Si occurs at an early stage.
The problem can be solved by switching to the H4 reduction method. In the SiH4 reduction method, since a gas exhibiting a reducing property to WF6 is positively introduced, the direct reaction between Si and WF6 is suppressed, and the consumption of Si is smaller than in the Si reduction method. However,
Deposition by the SiH4 reduction method from the beginning consumes a small amount of Si, but since the Si reduction reaction is suppressed as described above, self-cleaning is incomplete, and good contact characteristics can be obtained with a P-type high concentration substrate. In many cases, W does not adhere, or W does not adhere, or even if it adheres, it peels off later.

Therefore, in order to form a good metal contact, it is necessary to combine the above two types of deposition methods. If these deposition methods can be used to form a contact with a high yield, the total Si consumption is , 3 × 10 ^-8 approximately m in N-type high concentration substrate 4 × 10 ^-8 m, P-type high-concentration substrate even if less is usually current situation is not be used for virtually shallow junction type device Met. As described above, even in a metal film deposition method incorporating a method of performing surface cleaning, surface cleaning of a high-concentration Si substrate before deposition, particularly a P-type high-concentration substrate, is indispensable and is usually used. There is a problem that it is difficult to form a good contact with the cleaning characteristics using a hydrofluoric acid-based treatment solution.

Next, an electrical inactivation method using hydrogen will be described. Conventionally, an electrical passivation method using hydrogen has been known, and the electric passivation is performed by exposing a semiconductor substrate to a hydrogen plasma atmosphere. In order to electrically inactivate 90% or more impurity levels by this method, for example, about 3 hours with P-type Si (Material Science Forum, Vol. 38-41, pp. 25-38, 1
989), about 10 hours with N-type Si (Applied Physics Letter, Vol. 59, 2841-22843, 1
It is empirically known that a plasma irradiation time of 991) is required.

However, in the electrical passivation method using hydrogen, when the substrate is made of Si, poly-Si, GaAs or InP, the etching of the substrate as shown in FIGS. Occurs in parallel with That is, FIG.
When the substrate 10 is irradiated with hydrogen plasma as shown in FIG.
Also in (b), the same etching occurs at a portion of the substrate 10 not masked by the mask 11. As a result, the region in which the impurity levels are inactivated is gradually lost from the substrate surface. For example, when a doped layer formed in a thin film is inactivated, the amount of etching with respect to the film thickness is It will not be ignored.

[0014]

As described above, in the conventional cleaning treatment using a hydrofluoric acid-based treatment liquid, if sufficient cleaning of a high-concentration semiconductor substrate is to be performed, the treatment time becomes longer, and the contamination occurs on the substrate surface. There is a problem that the film thickness of insulating film etc. is greatly reduced and the pattern edge retreats.In addition, if the processing time is short, the cleaning of the surface of the high-concentration substrate becomes insufficient and the metal film deposited on the substrate becomes However, even if the cleaning time is extended, fluorine is likely to remain on the surface of the P-type high-concentration substrate, so that an ideal hydrogen-terminated surface cannot be obtained. There was a problem.

In the conventional etching process for etching a high-concentration semiconductor substrate, it is difficult to find uniform etching conditions because the etching rate of a P-type high-concentration substrate is lower than that of an N-type high-concentration substrate. Since this problem is avoided by devising processes other than etching, there is a problem that the number of steps is increased and the crystallinity of the underlying substrate is deteriorated.

In a conventional process for forming a conductive layer on a high-concentration semiconductor substrate, for example, in a reduction method using a semiconductor substrate material as a reducing agent, such as a Si reduction method, the substrate is etched due to the consumption of the underlying substrate. There is a problem that happens
In a reduction method using no substrate material as a reducing agent, such as the SiH4 reduction method, self-cleaning is incomplete and only good contact characteristics cannot be obtained with a high concentration substrate, or a conductive layer does not adhere or adhere. Even then, there was a problem that it would come off later. Further, in the conventional electric deactivation method using hydrogen, there is a problem that etching of the substrate occurs in parallel with the deactivation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. A first object of the present invention is to alleviate the difference in processing characteristics between a P-type and an N-type high-concentration semiconductor substrate and to improve the cleaning characteristics of the high-concentration semiconductor substrate. It is an object of the present invention to provide a method for treating a semiconductor substrate, which can improve the etching characteristics and the reaction characteristics between the source gas and the substrate during metal deposition. Another object of the present invention is to provide a method for processing a semiconductor substrate, which can suppress etching when electrical inactivation by hydrogen is performed.

[0018]

According to the present invention, a step of exposing a semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited, as described in claim 1, comprises the steps of: The method includes a step of performing processing on the substrate surface on which the deactivation processing has been performed, and a step of heating the semiconductor substrate to activate the substrate surface on which the processing has been performed. In addition, as described in claim 2, an insulating film is formed on a semiconductor substrate and patterned.
Forming a portion of the insulating film where the semiconductor substrate is exposed; and exposing the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to remove the exposed surface of the substrate. Activating, and performing a processing process on the substrate surface that has been subjected to the inactivation process,
In order to activate the substrate surface where this processing was performed,
Heating the semiconductor substrate.

According to a third aspect of the present invention, the step of forming an insulating film on the semiconductor substrate includes exposing the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited. A step of inactivating the substrate surface, a step of patterning the insulating film and forming an opening in which a semiconductor substrate is exposed in a part of the insulating film, and a step of processing the substrate surface where the opening is exposed. And a step of heating the semiconductor substrate to activate the substrate surface on which the processing has been performed. Further, as described in claim 4, the processing step includes a step of cleaning the substrate surface. The processing step includes a step of etching the substrate surface into a predetermined pattern. Also,
As described in claim 6, the processing step includes a step of forming a conductive layer on the surface of the substrate.

Further, the semiconductor substrate is exposed to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to inactivate the substrate surface, and the inactivation treatment is performed. And a step of forming a conductive layer on the cleaned substrate surface. Further, as set forth in claim 8, a step of forming and patterning an insulating film on the semiconductor substrate and forming an opening exposing the semiconductor substrate in a part of the insulating film, wherein at least hydrogen atoms are contained. Exposing the semiconductor substrate to a plasma atmosphere in which a gas is excited to inactivate the substrate surface where the opening is exposed; cleaning the substrate surface on which the passivation process has been performed; Forming a conductive layer on the surface of the substrate. According to a ninth aspect of the present invention, the step of forming an insulating film on the semiconductor substrate includes exposing the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited, so that the surface of the substrate below the insulating film is not damaged. Activating, patterning the insulating film, forming an opening in which a semiconductor substrate is exposed in a part of the insulating film, cleaning the exposed substrate surface of the opening, Forming a conductive layer on the substrate surface of the portion.

According to a tenth aspect of the present invention, the heat treatment for activating the surface of the semiconductor substrate is performed after the cleaning step or after the conductive layer forming step. Further, as set forth in claim 11, the cleaning step is for cleaning the semiconductor substrate with a solution containing hydrofluoric acid. In the twelfth aspect, in the etching step, the substrate surface is dry-etched by plasma, sputter, or ion beam. According to a thirteenth aspect, in the conductive layer forming step, the conductive layer is formed on the substrate surface by a chemical vapor deposition method using a gas containing at least a compound of a metal and a halogen element.

According to a fourteenth aspect, in the conductive layer forming step, a tungsten layer is formed on a substrate surface by a chemical vapor deposition method using a gas containing at least a compound of tungsten and a halogen element. It is. Further, in the conductive layer forming step, the titanium layer is formed by a sputtering method.
Further, as set forth in claim 16, the deactivation treatment step exposes the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms and nitrogen atoms is excited. According to a seventeenth aspect of the present invention, in the deactivation treatment step, the semiconductor substrate is exposed to a plasma atmosphere in which a gas containing at least a hydrogen atom and an oxygen atom is excited.

[0023]

According to a first aspect of the present invention, there is provided a method for treating a semiconductor substrate, comprising exposing the semiconductor substrate to a plasma in which a gas containing at least hydrogen atoms is excited, thereby effectively doping the substrate. After the amount of the dopant is reduced, the substrate surface is processed. Claim 2
As described in the above, an opening for exposing the substrate is formed in a part of the insulating film on the semiconductor substrate, and the semiconductor substrate is exposed by exposing the semiconductor substrate to plasma excited with a gas containing at least hydrogen atoms. After reducing the effective doping amount,
Processing is performed on the substrate surface. Further, an insulating film is formed on the semiconductor substrate, and the effective doping amount of the substrate under the insulating film is obtained by exposing the semiconductor substrate to a plasma in which a gas containing at least hydrogen atoms is excited. Then, an opening is formed in the insulating film and the substrate surface is processed.

Further, the substrate surface is processed by cleaning the substrate surface. Further, the processing of the substrate surface is performed by etching the substrate surface into a predetermined pattern. In addition, as described in claim 6, the processing of the substrate surface is performed by forming a conductive layer on the substrate surface. Further, as described in claim 7, after exposing the semiconductor substrate to plasma in which a gas containing at least hydrogen atoms is excited to reduce the effective doping amount of the substrate, the substrate is subjected to a cleaning treatment, A conductive layer is formed on a substrate surface.

Further, an opening for exposing the substrate is formed in a part of the insulating film on the semiconductor substrate.
After reducing the effective doping amount of the exposed substrate by exposing the semiconductor substrate to plasma excited with a gas containing at least hydrogen atoms, the substrate is subjected to a cleaning process,
A conductive layer is formed on the substrate surface at the opening. Claim 9
After forming an insulating film on the semiconductor substrate and exposing the semiconductor substrate to plasma excited with a gas containing at least hydrogen atoms to reduce the effective doping amount of the substrate under the insulating film, as described in Then, the substrate is cleaned to form a conductive layer on the substrate surface in the opening. The heat treatment for activating the surface of the semiconductor substrate is performed after the cleaning step or after the conductive layer forming step. Further, the semiconductor substrate is washed with a solution containing hydrofluoric acid.

Further, as described in claim 12, the substrate surface is dry-etched by plasma, sputter or ion beam. Further, as described in claim 13,
A conductive layer is formed on a substrate surface by a chemical vapor deposition method using a gas containing at least a compound of a metal and a halogen element. Further, a tungsten layer is formed on a substrate surface by a chemical vapor deposition method using a gas containing at least a compound of tungsten and a halogen element. Further, a titanium layer is formed by a sputtering method. In addition, the substrate is deactivated by exposing the substrate to plasma in which a gas containing at least hydrogen atoms and nitrogen atoms is excited. Also, as described in claim 17,
The substrate is deactivated by exposing the substrate to plasma in which a gas containing at least hydrogen atoms and oxygen atoms is excited.

[0027]

【Example】

Embodiment 1 FIG. Hereinafter, as an example of a method for treating a semiconductor substrate according to an embodiment of the present invention, an example in which an electric passivation method using hydrogen is applied to cleaning of a high-concentration semiconductor substrate will be described. FIG.
FIG. 4 is a diagram showing the dependence of the contact angle on pure water on the treatment time of a dilute HF aqueous solution for explaining the effect of the present embodiment.

In FIG. 1A, Pa is a characteristic of a low-concentration boron-doped Si substrate having a carrier density of 2 × 10 ¹⁵ / cm ³ (hereinafter referred to as a low-concentration P-type Si substrate), and Pb is a carrier density of 2 × 10 ¹⁵ / cm ^3. Characteristics of a high-concentration boron-doped Si substrate of 10 ²⁰ / cm ³ (hereinafter referred to as a high-concentration P-type Si substrate);
Pc is a characteristic obtained when a similar high-concentration P-type Si substrate is irradiated with plasma to be electrically inactivated. FIG. 1 (b)
In the equation, Nb is a characteristic of a high-concentration arsenic-doped Si substrate having a carrier density of 2 × 10 ²⁰ / cm ³ (hereinafter referred to as a high-concentration N-type Si substrate), and Nc is a similar high-concentration N-type Si substrate irradiated with plasma. This is a characteristic when electrical inactivation is performed.

All substrates shown in FIGS. 1A and 1B have been cleaned with a 0.5% diluted HF aqueous solution.
However, the high-concentration P-type Si substrate and the high-concentration N-type Si substrate represented by Pc and Nc, respectively, are subjected to a passivation process by exposing to a plasma of a mixed gas of H ₂ and N ₂ , and are processed in one mode. A certain cleaning was performed. The conditions at this time are as follows: the substrate temperature is 120 ° C., and the hydrogen flow rate is 2000 sccm.
(Cm ³ / min), the flow rate of nitrogen is 6 sccm, the pressure in the reaction chamber is 0.5 Torr (mmHg), the applied high frequency power is 200 W, and the plasma irradiation time is 40 minutes. As a result of this plasma irradiation, the carrier density of these substrates is reduced to 2 × 10 ¹⁹ / cm ³ or less.

The carrier concentration of the substrate is 1 × 10 ¹⁴
In the range of 3 × 10 ²⁰ / cm ^{3 to} P type and n type S
By treating both for 40 minutes under the above plasma conditions, the carrier concentration near the substrate surface (up to a depth of about 20 nm) can be reduced to a value sufficiently lower than 1/10 of the initial value. In addition, in the passivation process of this embodiment, a nitrogen gas is added in addition to the hydrogen gas. However, as described in detail in a later-described embodiment, a semiconductor generated in parallel with the passivation is used. To suppress the etching of the substrate,
Since there is no relation to the passivation efficiency, it may not be added if etching is allowed.

The degree of surface cleaning by the diluted HF aqueous solution can be evaluated from the characteristics thus obtained in FIGS. 1A and 1B for the following reasons. On the surface of the low-concentration Si substrate, as the processing time in the diluted HF aqueous solution becomes longer, the hydrogen termination becomes closer to perfect, and the contact angle with pure water increases. If a sufficiently long processing time is allowed, the contact angle of both the P type and the N type is about 80 degrees.

The surface in such a state is called a cleaned surface, and only a very small amount of oxygen and carbon are detected from the substrate surface except for hydrogen. The dependence of the contact angle on the treatment time of the diluted HF aqueous solution is also unique. Therefore, it is possible to evaluate the degree of surface cleaning by using the contact angle with pure water.

Referring to FIGS. 1A and 1B, as shown by Pc and Nc, the high-concentration Si substrate which has been electrically inactivated by plasma irradiation has a low concentration for both P-type and N-type. Si
It shows a contact angle characteristic very close to that of the substrate, compared to a high-concentration Si substrate that is not inactivated by Pb and Nb.
It is understood that the formation of the hydrogen-terminated surface with the diluted HF aqueous solution is facilitated. The low-concentration Si substrate uses only the P-type, because there is no difference in characteristics between the P-type and the N-type at a low concentration.

The surface composition is completely the same as the surface composition of the low-concentration Si substrate, except for trace amounts of oxygen and carbon except hydrogen. As described above, the effective doping amount (the amount of activated dopant) of the high-concentration semiconductor substrate is reduced to about the same level as that of the low-concentration substrate by electrical inactivation by plasma irradiation, and the processing characteristics of the high-concentration substrate are reduced. Is converted to a material similar to a low-concentration substrate, thereby reducing the difference in cleaning characteristics between the P-type and N-type high-concentration substrates.

In this embodiment, the diluted HF aqueous solution treatment is performed. However, this treatment is a treatment for obtaining a so-called clean surface. Therefore, even if a buffer diluted HF aqueous solution or a buffer diluted HF aqueous solution containing a surfactant is used. Similar effects can be obtained. In addition, since the hydrogen atoms that have penetrated into the Si substrate are easily separated from the substrate by the heat treatment, if the heat treatment is performed at 200 ° C. or more after the cleaning, the carrier concentration and the mobility of the Si substrate become the values before the inactivation treatment. , So that the Si substrate can be reactivated.

In the case of boron-doped Si, diluted HF
The conventional processing characteristics for the aqueous solution processing gradually start to deteriorate from the vicinity where the carrier concentration exceeds 3 × 10 ¹⁸ / cm ³ . In particular, the processing characteristics are remarkably deteriorated in a range from 2 × 10 ¹⁹ / cm ³ to around 3 × 10 ²⁰ / cm ³ which is the upper limit of doping. As a result, the improvement in the treatment characteristics of the dilute HF aqueous solution by the passivation treatment of the present embodiment is due to the fact that the carrier density is 2%.
It is large in the range of × 10 ¹⁹ to 3 × 10 ²⁰ / cm ³ (that is, the increase in the contact angle saturation value by the treatment of this embodiment is 10 × 10 ²⁰ / cm ^3).
~ 50 °), slightly observed at 3 × 10 ¹⁸ to 2 × 10 ¹⁹ / cm ³ (increase in contact angle saturation value is 10 ° or less), 3 × 10
It is almost not seen below ¹⁸ / cm ³ .

On the other hand, in the case of arsenic-doped Si, the treatment characteristics of the dilute HF aqueous solution with respect to the carrier concentration are originally small. Therefore, the carrier density is 3 × 10 ¹⁸ to 3 × 10
In the range of ²⁰ / cm ^3, the improvement of dilute HF solution processing characteristics by inactivation process of this embodiment is seen slightly (less increase of 10 ° in contact angle saturation value) at 3 × 10 ¹⁸ / cm ³ or less Almost not seen.

Embodiment 2 FIG. Next, as a method of processing a semiconductor substrate according to another embodiment of the present invention, an example in which the present invention is applied to etching of a high-concentration semiconductor substrate will be described. In this embodiment, first, a high-concentration boron-doped poly-Si substrate having a carrier density of 3 × 10 ²⁰ / cm ³ (hereinafter, referred to as a high-concentration P-type poly-Si substrate), and a high-concentration phosphorus of 3 × 10 ²⁰ / cm ³ Each of the doped poly-Si substrates (hereinafter, referred to as a high-concentration N-type poly-Si substrate) is subjected to the same plasma irradiation as in the first embodiment for 40 minutes.

By this plasma irradiation, a film thickness of 3 × 10 ^{−7 is obtained.}
The average carrier density of the poly-Si film of m is 3 for both P-type and N-type.
× 10 ¹⁹ / cm ³ or less. Next, each of the electrically inactivated substrates is subjected to plasma etching of a mixed gas containing Cl ₂ , CF ₄ , O ₂ , and Ar, which is one mode of processing, using an ECR plasma etching apparatus. Do it. The etching rate at this time is 1.5 × 10 ⁻⁷ m / min for both P-type and N-type poly-Si substrates.
Becomes

On the other hand, in the case of the conventional method in which the same high-concentration P-type poly-Si substrate and high-concentration N-type poly-Si substrate as described above are etched using an ECR plasma etching apparatus, the etching rate is high. 1.3 × with Si substrate
1.9 × 10 ⁻⁷ m / min, high-concentration N-type poly-Si substrate
10 ⁻⁷ m / min. Therefore, in the conventional method, the etching rate is different between the P-type and the N-type, but in this embodiment, the processing characteristics of the high-concentration substrate are converted to those similar to the low-concentration substrate by electrical inactivation by plasma irradiation. Thereby, the difference in etching characteristics between the P-type and N-type high-concentration substrates can be reduced.

The above-mentioned etching can be performed with an etching gas containing at least one of fluorine-based or chlorine-based etching gas. After the etching, if annealing is performed at 550 to 600 ° C. for 20 minutes,
As in the first embodiment, the carrier density and the mobility of the poly-Si can be restored to the values before the passivation process.

In the case of boron-doped poly-Si, EC
The etching rate for R etching gradually starts to decrease near the carrier concentration exceeding 1 × 10 ¹⁸ / cm ³ , and continues to decrease monotonically to around 3 × 10 ²⁰ / cm ^3, which is the upper limit of doping. On the other hand, in the case of phosphorus-doped poly-Si, the etching rate for ECR etching starts to gradually increase from the vicinity where the carrier concentration exceeds 1 × 10 ¹⁸ / cm ³ , and is 3 × 10 ²⁰ / cm, which is the upper limit for doping.
^It continues to increase monotonically to around ³ . As a result, the improvement in the etching characteristics according to the present embodiment is achieved when the carrier density is 1 × 1
It is found in a wide range from 0 ¹⁸ to 3 × 10 ²⁰ / cm ³ .

Further, in this embodiment, an example is shown in which an ECR etching apparatus using Cl2 and CF4 as main etchants is used.
Since it is derived from inactivation of the substrate, it does not depend on an etching apparatus or an etching gas. Therefore,
It can easily be inferred that the improvement can be performed in the case of other etching apparatuses or etching gases.

Embodiment 3 FIG. Next, as a method of processing a semiconductor substrate according to another embodiment of the present invention, an example in which the present invention is applied to formation of a conductive layer on a high-concentration semiconductor substrate will be described. In this embodiment, each of the high-concentration P-type Si substrate and the high-concentration N-type Si substrate is subjected to plasma irradiation for 40 minutes in the same manner as in the first embodiment.
A W metal film is formed by a chemical vapor deposition method using F ₆ as a source gas. The condition at this time is that the WF ₆ gas flow rate is 10 scc.
m, hydrogen flow rate 1000 sccm, pressure 0.1 Torr
r, the substrate temperature is 150 ° C. for 60 seconds.

As a result of the formation of this tungsten layer, 3 × 10 ⁻⁸ m for a high-concentration P-type Si substrate and 5 for a high-concentration N-type Si substrate.
The etching of the base substrate of × 10 ⁻⁸ m is observed. On the other hand, a high-concentration P-type Si substrate without plasma irradiation and a high-concentration N-type
In the case of the conventional method in which a tungsten layer is formed on each of the type Si substrates under the same conditions as described above, 2.5 × 10 ⁻⁸ m for a high-concentration P-type substrate and 1 × 10 ⁻⁷ m for a high-concentration N-type substrate Of the base substrate can be seen. Under the same conditions, the density is 4 × 10 ⁻⁸ m for a low-concentration substrate.

Therefore, although the etching speed is different between the P-type and the N-type in the conventional method, in this embodiment, the processing characteristics of the high-concentration substrate are similar to those of the low-concentration substrate due to the electrical inactivation by plasma irradiation. By converting to a substrate, the difference in the etching speed between the P-type and N-type high-concentration substrates can be reduced. Can be dropped. Also,
When annealing is performed at 550 to 600 ° C. for 20 minutes after the formation of the tungsten layer, the carrier density and the mobility of the high concentration layer can be restored to the values before the passivation treatment by plasma irradiation.

In the case of boron-doped Si, the amount of Si etched by WF6 gas is such that the carrier concentration is 5 × 10 ¹⁸ /
It gradually starts to decrease from around ³ cm ³ and continues to decrease monotonically to around 3 × 10 ²⁰ / cm ³ which is the upper limit of doping. On the other hand, in the case of arsenic-doped Si, the etching amount of Si by the WF6 gas is such that the carrier concentration is 5 × 10 ¹⁸ / cm ^3.
, And gradually increases monotonically to around 3 × 10 ²⁰ / cm ^3, which is the upper limit of doping. As a result, the improvement of the Si etching amount according to the present embodiment is as follows.
The carrier density is found in a wide range from 5 × 10 ¹⁸ to 3 × 10 ²⁰ / cm ³ .

Embodiment 4 FIG. Next, as a method of processing a semiconductor substrate according to another embodiment of the present invention, an example in which the present invention is applied to formation of a conductive layer on a high-concentration semiconductor substrate will be described. FIG. 2 is a process sectional view showing a method of forming a conductive layer which is a method of processing a semiconductor substrate according to the present embodiment, wherein 1 is a high-concentration Si diffusion layer formed on a substrate not shown, and 2 is an insulating film made of SiO2 or the like. Reference numeral 3 denotes an opening provided in the insulating film 2, 4 denotes a passivation layer formed in the Si diffusion layer 1 by irradiation with hydrogen plasma, and 5 denotes a tungsten layer formed on the Si diffusion layer 1 in the opening 3. It is.

First, as shown in FIG. 2A, an insulating film 2 such as SiO2 is formed on a high-concentration Si diffusion layer 1 formed on a substrate, developed by pattern exposure, and then anisotropically. The opening 3 is formed by reactive etching. The Si diffusion layer 1
Are N-type Si substrates when the diffusion layer 1 is P-type, and P-type Si substrates when the diffusion layer 1 is N-type. Next, a mixed gas of hydrogen and nitrogen is introduced onto the substrate, a high frequency is applied to form hydrogen plasma, and a passivation layer 4 is formed near the surface of the high concentration Si diffusion layer 1 at the bottom of the opening 3. (FIG. 2B).

Here, the passivation is carried out when the substrate temperature is 0-17.
0 ° C., a hydrogen flow rate of 100 to 5000 sccm, a nitrogen flow rate of 0 to 100 sccm, and a pressure in the reaction chamber of 0.01 to 2
Torr and high frequency power in the range of 30 to 1000 W are possible. The processing time increases or decreases according to the doping amount of the high-concentration Si substrate 1, the type of the dopant, the gas conditions, and the method of applying a high frequency so that the dopant on the surface of the high-concentration Si substrate 1 is sufficiently inactivated. There is a need.

The conditions used in this embodiment are as follows.
℃, hydrogen flow rate 2000sccm, nitrogen flow rate 6scc
m, the pressure in the reaction chamber is 0.4 Torr, the applied high frequency power is 150 W, the high frequency application method is the cathode coupling mode, and the processing time is 60 seconds. The anode coupling mode requires about 10 times the processing time to obtain the same effect. Further, as in the above-described embodiment, the addition of nitrogen gas is for suppressing the etching of the high-concentration Si substrate 1 which occurs in parallel with the passivation. If it is present, it need not be added.

Next, the substrate is treated in a 0.5% diluted HF aqueous solution for 20 seconds. In this embodiment, a diluted HF aqueous solution was used, but this cleaning treatment is a process for obtaining a clean surface. Therefore, the same effect can be obtained by using a buffer diluted HF aqueous solution or a buffer diluted HF aqueous solution containing a surfactant. Needless to say, this is obtained. Ar, H2, CF4, C3F8, CCl4,
A clean surface can also be obtained by dry etching using plasma, sputtering or ion beam using various reaction gases such as BCl3.

Finally, as shown in FIG. 2C, a tungsten layer 5 is formed at the bottom of the opening 3 of the substrate by a selective growth method using a SiH4 reduction method. This tungsten layer 5
For the formation of the first, after heating the substrate to a predetermined temperature,
When a carrier gas (H2, N2, inert gas, etc.) is used, this gas is introduced into the reaction chamber, and then SiH4, WF
Gas is introduced in the order of 6. Selective growth is possible without using a carrier gas.

The selective growth here is performed when the substrate temperature is 200-3.
It is possible in the range of 50 ° C. The selective growth of the α-phase W is possible when the flow ratio of SiH4 and WF6 is 1: 2 ± 0.6, and the selective growth is possible when the total pressure is in the range of 0.01 to 1 Torr. The condition used in this example is that the substrate temperature is 3
00 ° C, carrier gas is 500 sccm of hydrogen, WF6
Is 10 sccm, SiH4 is 5 sccm,
2 seconds after the introduction of 4, WF6 was introduced into the reaction chamber, and W was deposited for 60 seconds.

Since a clean Si surface has already been obtained by the passivation treatment and the diluted hydrofluoric acid treatment shown in FIG. 2B, there is no need to perform self-cleaning by the conventionally used Si reduction method. , A low-resistance ohmic contact is formed with good yield by only a slight self-cleaning action.

FIG. 3A is a diagram showing a histogram of contact resistance values of metal contacts formed on a P-type high-concentration Si diffusion layer by the method of forming a conductive layer according to the present embodiment.
3B is a diagram showing a histogram of the contact resistance value of the metal contact similarly formed on the N-type high-concentration Si diffusion layer. In FIGS. 3A and 3B, the frequency of the vertical axis is standardized. Is a unit.

The contact diameter here is 0.85 μm, the contact resistivity is 0.3 μΩ · cm ^{2 for} the P-type high-concentration substrate in FIG. 3A, and the contact resistivity is 0.3 μΩ · cm ^{2 for} the N-type high-concentration substrate in FIG. 0.1 μΩ · cm ² . On the other hand, if W deposition is performed by the SiH4 reduction method without performing the passivation treatment according to the present embodiment, the contact resistivity of the P-type high-concentration substrate becomes about 10 times, and tungsten is often removed from the P-type high-concentration substrate. Peeling results. Thus, the contact bonding characteristics and the adhesion between tungsten and the semiconductor substrate can be improved.

[0058] Then, due to the use of low Si consumption SiH4 reduction method only, Si consumption N-type high concentration substrate ^{1.2 × 10 -8 m, 1.4 ×} 10 in the P-type high-concentration substrate ^{- 8} m
And slightly. As a result, the leak current flowing through the junction between the high-concentration Si diffusion layer 1 and the underlying low-concentration Si substrate does not increase at all even when compared with the leak current value inherently possessed by the junction.

In this embodiment, most of the passivation layer 4 is made of Si.
Lost by consumption. And the remaining passivation layer 4 is
Since the tungsten layer 5 is heated to 200 ° C. or more during growth, the dopant is reactivated without a special annealing step. However, if an annealing step at a temperature higher than the growth temperature of tungsten is specially provided, it is needless to say that the dopant is more completely reactivated, the adhesion between tungsten and Si is improved, and the contact characteristics are further improved. In fact, the annealing performed after tungsten growth reduces the contact resistance up to 550 ° C. in inverse proportion to the annealing temperature.

In this embodiment, the self-cleaning by the Si reduction method was not performed before the deposition of W by the SiH4 reduction method. However, if the consumption of some Si is allowed, the Si reduction method is performed as usual. Needless to say, this may be done. Further, although fluorine was used as the halogenating gas for W, the same selective growth can be performed by using chlorine instead of fluorine (that is, using WCl6), and the reducing gas is also SiH4.
Was used, but is not limited to SiH4. That is, H2 which shows a reducing property to WF6 or WCl6,
Si2H6, Si3H8, GeH4, Ge (CH3) 2H2,
Similar effects can be obtained even if one of Ge (C2H5) 2H2, B2H6 and AsH3 is used.

The improvement of the contact characteristics according to the present embodiment originates from the cleaning of the Si surface before the deposition of the high melting point metal, and therefore can be seen only when the effect of cleaning the surface of the underlying Si substrate can be obtained. It is. Therefore, Examples 1 and 2
As described above, the carrier concentration region (the former is 3 × 10 ¹⁸ to 3 × 10 ²⁰ / cm ³ , and the latter is 1 × 10 ¹⁸ to 3 × 10 ²⁰ / cm ³⁾ in which the above-mentioned hydrofluoric acid-based wet processing characteristics or dry etching characteristics are improved. × 10 ²⁰ / cm ³ ), good contact characteristics can be obtained. Further, needless to say, the same effect can be obtained even if other high melting point metals are deposited due to the above-mentioned origin.

Embodiment 5 FIG. Next, as a method of processing a semiconductor substrate according to another embodiment of the present invention, an example in which the present invention is applied to formation of a conductive layer on a high-concentration semiconductor substrate will be described. FIG. 4 is a process cross-sectional view showing a conductive layer forming method which is a method for processing a semiconductor substrate according to the present embodiment, and the same parts as those in FIG. 2 are denoted by the same reference numerals. In FIG. 4, reference numeral 6 denotes a Ti layer formed on the Si diffusion layer 1 in the opening 3, 7 denotes a TiN layer formed on the Ti layer 6, and 8 denotes a tungsten layer formed on the TiN layer 7.

First, as shown in FIG. 4A, an insulating film 2 such as SiO 2 is formed on a high-concentration Si diffusion layer 1 formed on a substrate, developed by pattern exposure and then anisotropically. The opening 3 is formed by reactive etching. Next, a mixed gas of hydrogen and nitrogen is introduced onto the substrate, a high frequency is applied to form hydrogen plasma, and a passivation layer 4 is formed near the surface of the high concentration Si diffusion layer 1 at the bottom of the opening 3. (FIG. 4B).

The conditions of the passivation in this embodiment are as follows: the substrate temperature is 100 ° C., the hydrogen flow rate is 2000 sccm, the nitrogen flow rate is 6 sccm, the pressure in the reaction chamber is 0.5 Torr, the applied high frequency power is 200 W, the processing time is 10 Minutes. By this passivation process, about 70% of the dopant inside the high-concentration Si diffusion layer 1 is deactivated by P-type,
About 50% is inactivated in the mold. Since the passivation proceeds from the surface side, the passivation seems to be further advanced on the outermost surface of the high-concentration Si diffusion layer 1, but the exact value is unknown.

As in the above-described embodiment, the addition of nitrogen gas is for suppressing the etching of the high-concentration Si substrate 1 which occurs in parallel with the deactivation. If it is, it may not be added.
In addition, when nitrogen is not added under the above inactivating conditions,
The high-concentration Si diffusion layer 1 is etched at a rate of 1 × 10 ⁻⁸ m / min. On the other hand, by adding nitrogen, the etching rate becomes 4 × 10 ⁻¹² m / min or less, and the etching of the high-concentration Si diffusion layer 1 can be suppressed.

Next, after treating the substrate in a 0.5% diluted HF aqueous solution for 20 seconds, a Ti layer 6 and a TiN layer 7 are formed in the opening 3 by a sputtering method (FIG. 4C). The tungsten layer 8 is deposited by the CVD method to form the opening 3.
And a metal contact was formed (FIG. 4).
(D)). After the formation of the metal contact, annealing for reactivating the inactivated dopant is necessary. However, when the tungsten layer 8 is deposited by the CVD method, the substrate is heated up to 450 ° C. Since the activation is performed, it is not necessary to perform annealing for reactivating the dopant.

In this embodiment, a diluted HF aqueous solution is used. However, this cleaning treatment is a treatment for obtaining a clean surface. Therefore, a buffer-diluted HF aqueous solution or a buffer-diluted HF aqueous solution containing a surfactant is used. Needless to say, the same effect can be obtained. In addition, a clean surface can be obtained by dry etching using plasma, sputtering or ion beam using various reaction gases such as Ar, H2, CF4, C3F8, CCl4, etc. as a cleaning treatment of the substrate surface.

FIG. 5A is a diagram showing a histogram of the contact resistance value of a metal contact formed on a P-type high-concentration Si diffusion layer by the method of forming a conductive layer according to the present embodiment, and FIG. FIG. 6 is a diagram showing a histogram of contact resistance values of metal contacts formed by the conductive layer forming method of FIG. Here, the contact diameter is 0.4 μm, and the frequency on the vertical axis and the contact resistance value on the horizontal axis are both standardized arbitrary units. The conventional process shown in FIG. 5B is exactly the same as the present embodiment except that the deactivation process is omitted.

By the passivation process of this embodiment, the contact resistance can be reduced by about 50% on average and the variation of the resistance can be reduced by about 30% in standard deviation as compared with the conventional process. FIG. 6 shows a chain pattern resistance value of 12,000 steps of 0.4 μm diameter contacts and a position (chip) on a 6-inch wafer.
position: position of the chip).
The chain pattern resistance value on the vertical axis is a standardized arbitrary unit. It can be seen that the passivation process according to the present embodiment provides a stable contact resistance value over the entire wafer as compared with the conventional process.

Similarly, in the case of the N-type high-concentration Si diffusion layer, the contact resistance value was improved by 10% and the standard deviation was improved by 15%. It is considered that the reason why the effect is smaller than that of the P-type diffusion layer is that there is little room for improvement because the cleaning property with respect to the hydrofluoric acid-based aqueous solution is originally better than that of the P-type diffusion layer. In addition, no increase in the leakage current from the diffusion layer to the substrate due to the adoption of this method was observed at all even when compared with the conventional process, indicating that the irradiation damage to the diffusion layer by hydrogen plasma was extremely small. ing.

Further, the improvement of the contact characteristics by the present method is derived from the Si surface cleaning method before the deposition of the high melting point metal.
It goes without saying that the same effect can be obtained even when the molybdenum is deposited by sputtering or chemical vapor deposition.

The improvement of the contact characteristics according to the present embodiment is derived from the cleaning of the Si surface before the deposition of the refractory metal, and is therefore only seen when the effect of cleaning the surface of the underlying Si substrate is obtained. It is. Therefore, Examples 1 and 2
As described above, the carrier concentration region (the former is 3 × 10 ¹⁸ to 3 × 10 ²⁰ / cm ³ , and the latter is 1 × 10 ¹⁸ to 3 × 10 ²⁰ / cm ³⁾ in which the above-mentioned hydrofluoric acid-based wet processing characteristics or dry etching characteristics are improved. × 10 ²⁰ / cm ³ ), good contact characteristics can be obtained.

Embodiment 6 FIG. In the fourth and fifth embodiments, the opening is provided in the insulating film 2 to inactivate the semiconductor substrate. However, the passivation may be performed through the insulating film 2 without providing the opening. This is because hydrogen atoms diffuse long distances at room temperature in a silicon oxide film or a silicon nitride film which is usually used as an insulating film, and even if the insulating film is formed, a part of the semiconductor film under the insulating film is partially removed. This is because it reaches the substrate. In this embodiment, after such inactivation, by performing processing such as formation of an opening, cleaning, formation of a conductive layer, and the like, the same effects as those of the fourth and fifth embodiments can be obtained. .

Embodiment 7 FIG. Next, as a method of processing a semiconductor substrate according to another embodiment of the present invention, a method of suppressing etching of a semiconductor substrate that occurs in parallel with deactivation will be described. The passivation in this embodiment is performed by exposing the Si substrate to a plasma of a mixed gas of H ₂ and N ₂ . The conditions at this time are as follows: the substrate temperature is 120 ° C., and the hydrogen flow rate is 2000 scc.
m, nitrogen flow rate is 6 sccm, reaction chamber pressure is 0.5 T
orr, applied high frequency power is 200W.

The etching depth of the Si substrate after performing such plasma irradiation for 12 hours is sufficiently lower than 2.5 × 10 ⁻⁹ m. That is, the etching rate is 4 × 10 ^-12
m / min or less. On the other hand, the substrate temperature was 120 ° C., the hydrogen flow rate was 2000 sccm, and the pressure in the reaction chamber was 0.5 T.
orr, in the case of the conventional method in which the Si substrate is exposed to pure hydrogen plasma under the condition that the applied high-frequency power is 200 W,
The etching rate is 9 × 10 ⁻⁹ m / min.

Therefore, the etching rate in this embodiment is 1/2000 or less of the conventional one, which is practically negligible. Since the efficiency of the electrical passivation is the same as the conventional method using only hydrogen plasma, it can be seen that the etching of the substrate can be suppressed without lowering the efficiency of the passivation.

The relationship between the flow rate of hydrogen and the flow rate of nitrogen generally indicates that increasing the flow rate of hydrogen increases the efficiency of deactivation and the etching rate, and increasing the flow rate of nitrogen increases the effect of suppressing etching. Therefore, by independently adjusting the amounts of the hydrogen gas and the nitrogen gas, it is possible to separately adjust the inactivation efficiency and the etching suppression effect. In this embodiment, an example in which N ₂ gas is mixed with H ₂ gas is described.
The same effect can be obtained even if NH ₃ is used in place of ₂ gas, and NH ₃ gas can be used alone without using H ₂ gas. In the case of using only NH ₃ gas, the apparatus used for deactivation is simplified Can be

The effect of suppressing the etching of the underlying substrate by adding the N ₂ gas or NH ₃ gas is as follows.
To 350 ° C., a hydrogen flow rate of 200 to 2000 sccm, a nitrogen gas flow rate of 1 to 40 sccm, and a pressure in the reaction chamber of 0.
1-2 Torr, carrier density of semiconductor substrate is P-type, N
Both types are obtained in the range of 1 × 10 ^{14 to} 3 × 10 ²⁰ / cm ³ .

Although the principle of the above-described etching suppression is not always clear, it is assumed that a thin nitride film is formed on the substrate by the action of nitrogen radicals, which prevents the etching of the base by hydrogen plasma. Can be inferred.

Other gases that suppress the etching of Si include oxygen. However, the etching rate of Si when oxygen is added does not become 4 × 10 ⁻¹⁰ m / min or less even when the amount of oxygen added is increased, and is less effective than nitrogen. However, since the surface after plasma irradiation is covered with an oxide film, there is an advantage that the surface is extremely stable in the air as compared with the case where nitrogen is added. Further, when mixing of nitrogen into Si becomes a problem, for example, when nitrogen is activated as an impurity and the doping effect becomes a problem, oxygen can be used.

Embodiment 8 FIG. In the above embodiment, the case of the Si substrate has been described. However, as a method of processing a semiconductor substrate according to another embodiment of the present invention, poly-Si, GaAs, In
Inactivation can also be applied to P. Poly Si, Ga
In the case of an As or InP substrate, similarly to the seventh embodiment, H ₂
The etching depth after performing plasma irradiation for 12 hours with a mixed gas of N ₂ and N ₂ is sufficiently less than 2.5 × 10 ⁻⁹ m.

The effect of suppressing the etching of the semiconductor substrate is as follows: the substrate temperature is 23 to 350 ° C., and the hydrogen flow rate is 200 to 2
000 sccm, a nitrogen gas flow rate of 1 to 40 sccm, and a pressure in the reaction chamber of 0.1 to 2 Torr.
Then, it and the efficiency of electrical inactivation is obtained equal to the method using only conventional hydrogen plasma, or using NH ₃ gas in place of N ₂ gas, or by using the NH ₃ gas alone, an oxygen Can be used as in the seventh embodiment. It goes without saying that the etching suppressing method according to the seventh and eighth embodiments can be applied to the first to sixth embodiments.

[0083]

According to the present invention, the effective doping amount of the substrate is reduced by exposing the semiconductor substrate to a plasma in which a gas containing hydrogen atoms is excited, and then the substrate is exposed to plasma. Since the processing is performed, the difference in processing characteristics between the P-type and N-type high-concentration substrates can be reduced, and the characteristics can be made closer to the low-concentration substrates. Further, by heating the processed semiconductor substrate, reactivation can be performed to restore the carrier density and the mobility of the substrate to the values before the inactivation treatment. Also, since an opening is formed in the insulating film and the effective doping amount of the substrate is reduced by electrical inactivation, and then the substrate surface is processed, the P-type and N-type high-concentrations are formed in the opening. The difference in the processing characteristics of the substrate can be reduced, and the characteristics can be made closer to a low-concentration substrate.

Before the opening is formed in the insulating film, the semiconductor substrate may be exposed to plasma to electrically inactivate the substrate under the insulating film. By performing the processing, the difference between the processing characteristics of the P-type and N-type high-concentration substrates in the opening can be reduced, and the characteristics can be made closer to that of the low-concentration substrate. Further, since the substrate is cleaned as one of the processing after the inactivation, the difference in cleaning characteristics between the P-type and N-type high-concentration substrates can be reduced, and the characteristics can be made closer to the low-concentration substrates. And an extremely clean substrate surface can be obtained. As a result, the number of steps required for processing can be reduced,
Stable processing with a large process margin becomes possible.

Further, since etching is performed as one of the processing after the passivation, the difference in etching characteristics between the P-type and N-type high-concentration substrates can be reduced, and as a result, the number of steps required for processing can be reduced. In addition, stable processing with a large process margin can be performed. In addition, since a conductive layer is formed on the substrate surface as one of the processing after the inactivation,
The difference in the etching speed between the P-type and N-type high-concentration substrates can be reduced, and the consumption of the semiconductor substrate can be close to the value for the low-concentration substrates, so that stable processing with a large process margin is possible. Becomes

Further, since the cleaning process and the formation of the conductive layer are performed after the deactivation, the conductive layer and the semiconductor substrate having few inclusions at the interface can be formed by realizing a clean substrate surface by improving the cleaning process characteristics. A high-performance contact with low resistance can be formed. In addition, after performing the inactivation by forming an opening in the insulating film, the cleaning and the formation of the conductive layer are performed.
By realizing a clean substrate surface by improving the cleaning treatment characteristics, a low-resistance and high-performance contact between the conductive layer having few inclusions at the interface and the semiconductor substrate can be formed on the substrate surface in the opening.

Before the opening is formed in the insulating film, the semiconductor substrate can be exposed to plasma to inactivate the substrate under the insulating film. By the treatment and the formation of the conductive layer, a low-resistance and high-performance contact between the conductive layer having few inclusions at the interface and the semiconductor substrate can be formed on the substrate surface in the opening. Also,
By performing the heat treatment after the cleaning step or the conductive layer formation step, reactivation can be performed to restore the carrier density and the mobility of the substrate to the values before the inactivation treatment. Further, by cleaning the semiconductor substrate with a solution containing hydrofluoric acid, the surface of the substrate can be easily cleaned. In addition, the substrate surface can be easily etched by dry-etching the substrate surface with plasma, sputtering, or ion beam.

Since the conductive layer is formed by chemical vapor deposition using a gas containing a compound of a metal and a halogen element after deactivation, the P-type and N-type high-concentration substrates are etched. The speed difference can be reduced. In addition, since the conductive layer is formed by a chemical vapor deposition method after performing the cleaning treatment, for example, in a reduction method using a semiconductor substrate material as a reducing agent such as a silicon reduction method, a P-type and an N-type high-concentration substrate are removed. Since the difference in the etching speed can be reduced and the consumption of the semiconductor substrate can be brought close to the value of the low-concentration substrate, stable processing with a large process margin can be performed. Further, by realizing a clean substrate surface by improving the cleaning treatment characteristics, good contact characteristics can be obtained only by a reduction method using no semiconductor substrate material as a reducing agent, such as a silane reduction method.

After the deactivation, a tungsten layer is formed by a chemical vapor deposition method using a gas containing a compound of tungsten and a halogen element.
The same effects as above can be obtained. Further, since the titanium layer is formed on the substrate surface after the inactivation, the difference in the etching speed between the P-type and N-type high-concentration substrates by titanium can be reduced. In addition, since the titanium layer is formed by a sputtering method after performing the cleaning treatment, the realization of a clean substrate surface by improving the cleaning treatment characteristics enables a low resistance between the titanium layer having few inclusions at the interface and the semiconductor substrate. Thus, a high-performance contact can be formed.

Further, since the semiconductor substrate is exposed to plasma excited with a gas containing hydrogen atoms and nitrogen atoms, the semiconductor substrate is electrically inactivated, so that the etching of the substrate can be performed without lowering the efficiency of the inactivation. Can be suppressed. In addition, since the semiconductor substrate is electrically inactivated by exposing the semiconductor substrate to plasma in which a gas containing hydrogen atoms and oxygen atoms is excited, etching of the substrate can be suppressed without lowering the efficiency of the inactivation. Can be.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method for processing a semiconductor substrate according to an embodiment of the present invention, which illustrates the effect of a dilute HF having a contact angle with respect to pure water.
It is a figure which shows the aqueous solution processing time dependency.

FIG. 2 is a process sectional view showing a conductive layer forming method as a method of processing a semiconductor substrate according to another embodiment of the present invention.

3 is a diagram showing a histogram of contact resistance values of metal contacts formed on a high-concentration Si diffusion layer by the method of processing the semiconductor substrate of FIG. 2;

FIG. 4 is a process sectional view showing a conductive layer forming method as a method for processing a semiconductor substrate according to another embodiment of the present invention.

5 is a diagram showing a histogram of contact resistance values of metal contacts formed on a P-type high-concentration Si diffusion layer by the processing method of the semiconductor substrate of FIG. 4 and a conventional processing method.

6 is a diagram showing the positional dependence on a wafer of the chain pattern resistance value of a metal contact formed on a P-type high-concentration Si diffusion layer by the processing method of the semiconductor substrate of FIG. 4 and the conventional processing method.

FIG. 7 is a cross-sectional view showing a conventional etching of a base substrate by hydrogen plasma irradiation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... High concentration Si diffusion layer, 2 ... Insulating film, 3 ... Opening, 4 ...
Passivation layer, 5: tungsten layer, 6: Ti layer, 7: T
iN layer, 8... tungsten layer.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-74846 (JP, A) JP-A-1-149423 (JP, A) JP-A-2-213125 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/304 641 H01L 21/285 H01L 21/302

Claims (17)

(57) [Claims] 1. A step of exposing a semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to inactivate the substrate surface, and processing the substrate surface on which the inactivation treatment has been performed. Process and in order to activate the substrate surface on which this processing has been performed,
Heating the semiconductor substrate. 2. A step of forming and patterning an insulating film on a semiconductor substrate, forming an opening in a part of the insulating film so that the semiconductor substrate is exposed, and a plasma in which a gas containing at least hydrogen atoms is excited. Exposing the semiconductor substrate to an atmosphere to inactivate the substrate surface where the opening is exposed; processing the substrate surface on which the deactivation processing has been performed; and performing this processing. To activate the substrate surface
Heating the semiconductor substrate. A step of forming an insulating film on the semiconductor substrate; and a step of exposing the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to inactivate a substrate surface under the insulating film. A step of patterning the insulating film to form an opening in a part of the insulating film where the semiconductor substrate is exposed; a step of performing processing on the surface of the substrate where the opening is exposed; To activate the substrate surface performed
Heating the semiconductor substrate. 4. The method of processing a semiconductor substrate according to claim 1, wherein the processing step includes a step of cleaning a surface of the substrate. 5. The method of processing a semiconductor substrate according to claim 1, wherein the processing step includes a step of etching the substrate surface into a predetermined pattern. 6. The method for processing a semiconductor substrate according to claim 1, wherein the processing step includes a step of forming a conductive layer on a substrate surface. 7. A step of exposing a semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to inactivate the substrate surface, and a step of cleaning the substrate surface subjected to the inactivation treatment. And a step of forming a conductive layer on the surface of the substrate on which the cleaning process has been performed. 8. A step of forming and patterning an insulating film on a semiconductor substrate and forming an opening in a part of the insulating film so that the semiconductor substrate is exposed, and a plasma in which a gas containing at least hydrogen atoms is excited. Exposing the semiconductor substrate to an atmosphere to inactivate the substrate surface where the opening is exposed; cleaning the substrate surface on which the passivation has been performed; Forming a conductive layer. 9. A step of forming an insulating film on the semiconductor substrate, and a step of exposing the semiconductor substrate to a plasma atmosphere in which a gas containing at least hydrogen atoms is excited to inactivate a substrate surface under the insulating film. Patterning the insulating film to form an opening in which a semiconductor substrate is exposed in a part of the insulating film; cleaning the substrate surface where the opening is exposed; Forming a conductive layer on a surface of the semiconductor substrate. 10. The method for processing a semiconductor substrate according to claim 7, wherein a heat treatment for activating the surface of the semiconductor substrate is performed after the cleaning step or after the conductive layer forming step. A method for processing a semiconductor substrate, comprising: 11. The method for processing a semiconductor substrate according to claim 4, wherein the cleaning step is a step of cleaning the semiconductor substrate with a solution containing hydrofluoric acid. 12. The method for processing a semiconductor substrate according to claim 5, wherein the etching step is a step of dry-etching the substrate surface by plasma, sputter, or ion beam. 13. The method for processing a semiconductor substrate according to claim 6, 7, 8 or 9, wherein the conductive layer forming step is performed by a chemical vapor deposition method using a gas containing at least a compound of a metal and a halogen element. A method for treating a semiconductor substrate, comprising a step of forming a conductive layer on a substrate surface. 14. The method for processing a semiconductor substrate according to claim 6, 7, 8 or 9, wherein the conductive layer forming step is performed by a chemical vapor deposition method using a gas containing at least a compound of tungsten and a halogen element. A method for treating a semiconductor substrate, comprising a step of forming a tungsten layer on a substrate surface. 15. The method for processing a semiconductor substrate according to claim 6, wherein the step of forming a conductive layer is a step of forming a titanium layer by a sputtering method. Method. 16. The method of processing a semiconductor substrate according to claim 1, 2, 3, 7, 8, or 9, wherein said deactivating step includes a step of exciting a gas containing at least a hydrogen atom and a nitrogen atom. A method for treating a semiconductor substrate, comprising exposing the semiconductor substrate to an atmosphere. 17. The method for processing a semiconductor substrate according to claim 1, 2, 3, 7, 7, or 9, wherein said deactivating step includes a step of exciting a gas containing at least a hydrogen atom and an oxygen atom. A method for treating a semiconductor substrate, comprising exposing the semiconductor substrate to an atmosphere.