US20020197828A1

US20020197828A1 - Method and apparatus for manufacturing a semiconductor device and processing a substrate

Info

Publication number: US20020197828A1
Application number: US10/106,234
Authority: US
Inventors: Masayuki Asai; Tsutomu Tanaka
Original assignee: Hitachi Kokusai Electric Inc
Current assignee: Hitachi Kokusai Electric Inc
Priority date: 2001-06-21
Filing date: 2002-03-27
Publication date: 2002-12-26
Also published as: US6687050B2; TW577123B; US20020196531A1; JP2003007697A; KR20020096860A

Abstract

A substrate processing apparatus includes a CVD (chemical vapor deposition) processing chamber and a RTO (rapid thermal oxidation) processing chamber. In the CVD processing chamber, a film growing process, in which thin amorphous film is deposited on a substrate, and an impurity removing process, in which specific impurities included in the grown amorphous film are removed, are repeatedly performed multiple times to provide an impurity removed amorphous film with good step coverage. Thus treated amorphous film on the substrate is then crystallized in the RTO process chamber to provide a crystalline film.

Description

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for manufacturing a semiconductor device and processing a substrate.

DESCRIPTION OF THE PRIOR ART

FIG. 5 shows a schematic view of a conventional chemical vapor deposition (CVD)

apparatus

50 for use in processing a substrate. As shown in FIG. 5, the apparatus 50 includes a heater 2 installed in a reactor chamber (hereinafter also referred to as a processing chamber) 1, a susceptor 3 positioned above the heater 2, a shower head 5 having shower holes 6 and installed above the susceptor 3, a gas inlet 7 jointed above the shower head 5, and an exhaust port 8 provided at the processing chamber 1.

In the

apparatus

50, a substrate 4 is mounted on the susceptor 3 positioned in the hermetically sealed processing chamber 1 and is heated by the heater 2. In the meantime, a reactive gas obtained by mixing an evaporated Penta Ethoxy Tantalum (Ta(OC₂H₅)₅, hereinafter referred to as PET), an oxygen gas and an inert gas is supplied to the substrate 4 after passing through the gas inlet 7 and the shower head 5. A tantalum oxide film is then formed on minute electrical circuit patterns positioned on the substrate 4 by the chemical reaction of the reactive gas that takes place on the substrate 4. Also, an exhausted gas is pumped out from the processing chamber 1 via the exhaust port 8.

Referring to FIG. 6, there is illustrated a

tantalum oxide film

11 grown on the substrate 4 with a step coverage (b/a), a and b representing a film thickness on the top surface of the substrate 4 and that on the bottom of a recess of the substrate 4, respectively. FIG. 7 shows the relationship between a step coverage (b/a) and the substrate temperature during the film growth (referred to as film growth temperature hereinafter).

In case the film growth temperature is low, the step coverage of the

tantalum oxide film

11 is good as shown in FIG. 7 and the tantalum oxide film 11 becomes an amorphous tantalum oxide film (TaO film). On the other hand, when the film growth temperature is high, the step coverage of the tantalum oxide film 11 is poor and the tantalum oxide film 11 becomes a crystalline tantalum oxide film (Ta₂O₅film). Also, if the film growth temperature is low, e.g., around 440° C., no significant stress is induced in the grown tantalum oxide film 11 and, therefore, the thus grown tantalum oxide film can be crystallized without much suffering from crack development therein during the subsequent recrystallization process.

For this reason, a crystalline tantalum oxide film having good step coverage is obtained by way of employing a two step process. That is, an amorphous

tantalum oxide film

11 is formed first on the substrate 4 at a relatively low film growth temperature, e.g., near 440° C., by using, e.g., the CVD apparatus 50 shown in FIG. 5. Thereafter, a rapid thermal oxidation (RTO) process is carried out on the thus grown amorphous tantalum oxide film at about 650° C. to 800° C. in an O₂atmosphere to obtain the crystalline tantalum oxide film with a good step coverage.

FIG. 8 depicts a relationship between the film growth temperature and the content of impurities, such as carbon and hydrogen, introduced in the

tantalum oxide film

11. In case where the film growth temperature is low, the growing tantalum oxide film 11 becomes amorphous and the content of impurities, such as carbon, hydrogen and the like introduced therein during the growth, increases.

In other words, when the amorphous tantalum oxide film is formed on the

substrate

4, a large amount of impurities such as carbon, hydrogen and the like originated from the organic source material, e.g., PET, is introduced into the growing amorphous tantalum oxide film. Therefore, it may be necessary to remove the thus introduced impurities simultaneously during the RTO process described above.

Since, however, the crystallization of the amorphous tantalum oxide film carried out by the RTO process is initiated at the surface of the amorphous tantalum oxide film and progresses into the inner portion thereof, the impurities such as carbon, hydrogen and the like may not be effectively removed from the film. In other words, as the amorphous tantalum oxide film becomes crystallized, a mean distance between atoms constituting the film gets reduced and further voids or vacancies among the atoms constituting the film also diminishes. Accordingly, impurity atoms included inside the film cannot readily pass through the atoms of the crystallized tantalum oxide film formed at the surface region. As a result, it becomes difficult to remove the impurities remaining inside the tantalum oxide film once the crystallization takes place at the surface region thereof and, therefore, insulation properties of the crystallized tantalum oxide film are deteriorated.

Therefore, it may be preferable to form a tantalum oxide film having a predetermined thickness, by repeatedly forming a relatively thin amorphous tantalum oxide film and carrying out the RTO process thereon sequentially multiple times.

Further, it may be more preferable to subject the amorphous tantalum oxide film grown in the

CVD apparatus

50 shown in FIG. 5 to a remote plasma oxidation (RPO) process to remove the impurities included in the film by oxygen radicals, followed by the RTO process described above.

FIG. 9 schematically shows a conventional

substrate processing apparatus

90 capable of performing the CVD process, the RPO process and the RTO process described above. As shown in FIG. 9, the substrate processing apparatus 90 is provided with a load lock chamber 21, a substrate transfer chamber 25, a CVD processing chamber (reaction chamber) 22 identical to that shown in FIG. 5, an RPO processing chamber 23 and an RTO processing chamber 24. Arrows represent various substrate transfer paths.

In the

substrate processing apparatus

90, the substrate 4 is transferred from the load lock chamber 21 to the CVD processing chamber 22 in which the amorphous tantalum oxide film is formed on the substrate 4. Thereafter, the substrate 4 having the amorphous tantalum oxide film thereon is transferred from the CVD processing chamber 22 to the RPO processing chamber 23. In the RPO processing chamber 23, the RPO process is carried out on the amorphous tantalum oxide film. The thus processed substrate 4 is then transferred from the RPO processing chamber 23 to the RTO processing chamber 24. After carrying out the RTO process in the RTO processing chamber 24, the substrate 4 is taken out from the substrate processing apparatus 90 via the load lock chamber 21. By employing such a substrate processing apparatus 90, a crystalline tantalum oxide film having a small amount of impurities such as carbon, hydrogen and the like can be formed on the substrate 4.

In case the amorphous tantalum oxide film formation and the RTO are carried out in a same reaction chamber, e.g., the

processing chamber

1 of the CVD apparatus 50 shown in FIG. 5, the amorphous tantalum oxide formed outside the substrate 4, e.g., on the wall of the processing chamber 1 or the shower head 5, during the amorphous tantalum oxide film deposition process may also be crystallized by the RTO process and then thus crystallized tantalum oxide may be peeled off to fall down on the substrate 4. Accordingly, the separate CVD and RTO processing chambers need be prepared as shown in FIG. 9.

Therefore, in case where a crystalline tantalum oxide film is formed by repeatedly performing the amorphous tantalum oxide film deposition process and the RTO process sequentially, the

substrate

4 need be repeatedly transferred between the CVD processing chamber and the RTO processing chamber and, therefore, the crystalline tantalum oxide film on the substrate 4 cannot be produced in an efficient manner.

Similarly, in the

substrate processing apparatus

90, the substrate 4 also need be repeatedly transferred among the CVD processing chamber 22, the RPO processing chamber 23 and the RTO processing chamber 24, lowering the system efficiency and deteriorating the throughput of the substrate processing apparatus.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a method and apparatus for manufacturing a semiconductor device and processing a substrate, capable of efficiently forming a film having low content of such impurities as carbon, hydrogen and the like on a substrate.

In accordance with one aspect of the invention, there is provided a method for manufacturing a semiconductor device, including the steps of: (a) forming an amorphous film on a substrate; (b) removing at least a portion of an impurity element included in the amorphous film; and (c) sequentially repeating the forming step (a) and the removing step (b) multiple times to provide an impurity removed non-crystalline film on the substrate.

In accordance with another aspect of the invention, there is provided a method for processing a substrate, including the steps of: (a) forming an amorphous film on a substrate; (b) removing at least a portion of an impurity element included in the amorphous film; and (c) sequentially repeating the forming step (a) and the removing step (b) multiple times to provide an impurity removed non-crystalline film on the substrate.

In accordance with still another aspect of the invention, there is provided an apparatus for processing a substrate, including: a processing chamber for processing a substrate; a gas supply unit for providing a reactive gas into the processing chamber; a plasma generation unit; and a control unit, wherein the control unit controls the substrate processing apparatus to sequentially repeat, in the processing chamber, a film forming process for depositing an amorphous film on the substrate through the use of the reactive gas and a plasma process for removing at least a portion of an impurity element included in the amorphous film through the use of the plasma generation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description given in conjunction with the accompanying drawings, in which: [0021]
FIG. 1 schematically illustrates a CVD apparatus in accordance with the present invention; [0022]
FIG. 2 depicts the relationship between the number of process cycles and the content of impurities included in an amorphous tantalum oxide film; [0023]
FIG. 3 presents the relationship between the number of process cycles and a leak current of a crystallized tantalum oxide film; [0024]
FIG. 4 schematically represents a substrate processing apparatus in accordance with the present invention; [0025]
FIG. 5 schematically shows a conventional CVD apparatus; [0026]
FIG. 6 sets forth a cross sectional view of a tantalum oxide film grown on a substrate; [0027]
FIG. 7 shows the relationship between the step coverage and the film growth temperature; [0028]
FIG. 8 depicts the relationship between the film growth temperature and the content of impurities included in a tantalum oxide film; and [0029]
FIG. 9 schematically shows a conventional substrate processing apparatus.[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically illustrates a [0031] CVD apparatus 10 in accordance with the present invention. As shown in FIG. 1, a heater 32 is installed in a reactor chamber (hereinafter also referred to as a processing chamber) 31. A substrate rotating unit 33 is installed outside the processing chamber 31. A susceptor 34 rotated by the substrate rotating unit 33 is installed in the processing chamber 31. The susceptor 34 is positioned on the heater 32.
Further, a [0032] substrate 35, e.g., wafer, is loaded on the susceptor 34. A shower head 36 having shower holes 37 is installed above the susceptor 34. A reactive gas supply unit 38 is installed outside the processing chamber 31. A gas supply line 39 connects the reactive gas supply unit 38 to the shower head 36 and has a valve 40. A reactive gas is supplied to the processing chamber 31 via shower holes 37 after passing through the gas supply line 39 and the shower head 36.
Further, a RPO unit (plasma generating apparatus) [0033] 41 is installed outside the processing chamber 31. A gas supply line 42 connects the RPO unit 41 with the shower head 36 and has a valve 43. Also, an exhaust line (exhaust port) 44 is installed at lower side wall of the processing chamber 31.
Additionally, a [0034] control unit 45 is provided outside the processing chamber 31. The control unit 45 serves to control the CVD apparatus 10 to repeatedly perform process cycles of a film forming process and a RPO process as many times as desired in the processing chamber 31. During the film forming process, an amorphous (non-crystalline) tantalum oxide film is grown on the substrate 35 and during the RPO process, specific elements such as carbon and hydrogen included in the thus grown amorphous tantalum oxide film are removed or reduced in their amount by the plasma process through the use of the RPO unit 41.
Referring to FIG. 1, there will be described a method for manufacturing a semiconductor device and processing a substrate by using the [0035] CVD apparatus 10 in accordance with the present invention. First, the substrate 35 is loaded on the susceptor. 34 positioned in the processing chamber 31. The susceptor 34 is then rotated by the substrate rotating unit 33 and the substrate 35 is heated at about 440° C. by the heater 32. While the substrate 35 is rotated and heated at about 440° C., the valve 40 is opened to supply the substrate 35 with a reactive gas containing the mixture of an evaporated PET, an oxygen gas and an inert gas via the gas supply line 39 and the shower head 36, thereby forming an amorphous tantalum oxide film having a thickness of about 20 Å grown on the substrate 35 (film growing process).
Subsequently, the [0036] valve 40 is closed to stop the reactive gas supply while maintaining the same condition in which the substrate 35 is rotated and heated at about 440° C. Thereafter, the valve 43 is opened to introduce oxygen radicals generated from the RPO unit 41 on the substrate 35 though the gas supply line 42 and the shower head 36 to thereby carry out the RPO process on the thus grown amorphous tantalum oxide film (impurity removing process). Consequently, the film growing process and the impurity removing process are sequentially carried out in one processing chamber, i.e., the processing chamber 31.
Further, it is preferable that both the film growing process and the impurity removing process are carried out at a substantially same temperature. That is to say, it is preferable that the setting temperature of the heater is maintained constant during the film growing process and the impurity removing process as well. By maintaining a constant temperature or greatly reducing a temperature variation in the processing chamber, particle generation due to thermal expansion of such parts as the shower head or the susceptor in the processing chamber can be suppressed and metal contamination originating from a metallic part in the processing chamber can also be prevented. In view of particulate generation discussed above, it is also preferable that both the film growing process and the impurity removing process are carried out at a constant pressure. [0037]
An amorphous tantalum oxide film having a thickness of about 80 Å can be formed by repeatedly performing four times the process cycle where one film forming process and one RPO process are carried out sequentially. That is, the film growing process and the impurity removing process are sequentially repeated a predetermined number of times by controlling the [0038] valves 40, 43 through the use of the control unit 45. Thereafter, the thus processed amorphous tantalum oxide film is treated to provide a crystalline tantalum oxide film by carrying out a RTO process thereon in a RTO process unit (not shown).
In the method and apparatus for manufacturing the semiconductor device and processing the substrate, the RPO process is carried out on the amorphous tantalum oxide film having a thickness of 20 Å, i.e., a quarter of the final thickness of 80 Å. Since such impurities as C and H can be removed or reduced more rapidly and uniformly from a thinner film by the RPO process, the amorphous tantalum oxide film having a predetermined final thickness with a low impurity content can be efficiently obtained by repeatedly performing the process cycles as described above. [0039]
Some of the advantages obtainable by repeatedly performing the film growing process and the impurity removing process will now be described. In case a thick amorphous tantalum oxide film having a thickness of, e.g., 80 Å with a good step coverage is formed on a substrate having a deep recess or groove, a large amount of impurities is included in the film due to its large thickness. Therefore, if the RPO process is carried out thereon, a possibility that the oxygen radicals are consumed by the reaction with the impurities included in the amorphous tantalum oxide film located at the entrance and the side wall of the deep groove is increased. Accordingly, the impurities such as C and H cannot be uniformly removed in a short time since sufficient oxygen radicals may not be provided to the amorphous tantalum oxide film formed at the bottom of the deep groove. [0040]
On the other hand, since the amorphous tantalum oxide film is thin and therefore has a reduced amount of impurities, when the RPO process is performed on the amorphous tantalum oxide film having the thickness of 20 Å, i.e., a quarter of the final thickness 80 Å, less oxygen radicals are consumed at the entrance and the side wall of the groove, so that the sufficient amount of oxygen radicals can be uniformly supplied to the amorphous tantalum oxide film located at the bottom portion of the deep groove. As a result, the amorphous tantalum oxide film having a predetermined target thickness with a low impurity concentration of C, H and the like can be readily formed since the impurities can be uniformly removed in a short time. [0041]
During the film growing process, the amorphous tantalum oxide film is also formed on an inner wall of the [0042] processing chamber 31 and the shower head 36. And as the film growing processes are repeated, the thickness of the accumulated film thereon becomes greater and so does the impurities such as C and H included in the accumulated film. As a result, more impurities are introduced in an amorphous tantalum oxide grown later, resulting in temporal variations in the amount of impurities contained in the amorphous tantalum oxide film formed on the substrate 35.
In contrast, since the growing process and the RPO process are carried out in a cyclic manner in the same processing chamber in accordance with the present invention, the impurities included in the thin film previously deposited outside the substrate can also be immediately removed by the subsequent RPO process. Resultantly, accumulation of the impurities in the ever thickening TaO film deposited inside the processing chamber can be effectively prevented and a content of the impurities included in the amorphous tantalum oxide film formed on the [0043] substrate 35 can be maintained rather uniformly, without suffering from temporal variations.
Instead of the CVD technique disclosed above, an ALD (atomic layer deposition) scheme can be employed, in forming the amorphous tantalum film on the substrate. The ALD differs from the conventional CVD in that in ALD atomic layers are formed one at a time at a lower substrate treating temperature (300° C. or below) and under a low inner pressure inside the processing chamber (10 Pa or below) and further only a surface reaction (adsorption reaction) is taking place. On the other hand, in the method and apparatus for manufacturing a semiconductor device and processing a substrate described above, the amorphous tantalum oxide film is formed by simultaneously growing tens of atomic layers, wherein the treating temperature of the [0044] substrate 35 is high (around 440° C.) and also the inner pressure of the processing chamber 31 is high (50 Pa or above) and further both the surface reaction and a vapor phase reaction are taking place. Further, since the film growing process and the impurities removing process are carried out with the substrate 35 being rotated, the film growth and the removal of the impurities can be uniformly accomplished throughout the substrate 35. Therefore, both the amorphous and the crystalline tantalum oxide film with the uniform film quality and low impurity concentration can be formed on the substrate 35. Also, it is possible to efficiently remove the impurities from the amorphous tantalum oxide film without incurring any damage thereon since the impurity removing process is carried out by using the RPO process.
Further, the crystallization process is carried out on the amorphous tantalum oxide film formed on the [0045] substrate 35 obtained by repeatedly performing the film forming process and the impurity removing process sequentially multiple times. Therefore, the crystalline tantalum oxide film having a good step coverage along with a low impurity concentration and good insulating properties can be efficiently formed on the substrate 35. Further, the amorphous tantalum oxide film can be efficiently crystallized since the RTO process is employed in the crystallization process.
FIG. 2 depicts a relationship between the number of process cycles and the total amount of impurities included in a crystalline tantalum oxide film, wherein in each process cycle one amorphous tantalum oxide film growing process and one RPO process have been sequentially carried out in the CVD apparatus described in FIG. 1. As shown in FIG. 2, the content of impurities included in the crystalline tantalum oxide film decreases as the number of process cycles increases. [0046]
FIG. 3 presents a relationship between the number of process cycles and a leak current (A/cm [0047] 2) of a crystallized tantalum oxide film. The leak current of the crystalline tantalum oxide film decreases as shown in FIG. 3 and the insulating properties thereof become improved as the number of process cycles increases.
Referring to FIG. 4, there is illustrated a [0048] substrate processing apparatus 40 in accordance with the present invention, including a load lock chamber 51, a substrate transfer chamber 55, CVD processing chambers 52 and 53 identical to that described in FIG. 1 and a RTO processing chamber 54. Arrows represent various substrate transfer paths.
In the [0049] substrate processing apparatus 40, the substrate 35 is transferred from the load lock chamber 51 to the CVD processing chamber 52 or 53, wherein the amorphous tantalum oxide film is formed on the substrate 35 by repeating the amorphous tantalum oxide film growing process and the RPO process sequentially a number of times. Thereafter, the substrate 35 having the amorphous tantalum oxide film thereon is transferred from the CVD processing chamber 52 or 53 to the RTO processing chamber 54. After carrying out the RTO process in the RTO processing chamber 54, the substrate 35 is taken out from the substrate processing apparatus 50 via the load lock chamber 51.
In such a [0050] substrate processing apparatus 40, the amorphous tantalum oxide film having a low impurity content of C, H and the like is formed on the substrate 35 by repeatedly performing the process cycles, in which the amorphous tantalum oxide film forming process and the RPO process are sequentially carried out multiple times. Further, the number of transfer processes per each substrate is three in the preferred substrate processing apparatus 40 shown in FIG. 4, while same is four in the conventional substrate processing apparatus 90 shown in FIG. 9. Therefore, the system efficiency and the throughput of product in accordance with the present invention can be improved, in comparison with the prior art substrate processing apparatus. Although the preferred embodiment of the present invention has been described with respect to the tantalum oxide film formed on the substrate 35 by using an organic liquid material, e.g., PET, the present invention can also be applied in cases where other types of films are formed on a substrate by using other types of source materials.
The present invention can be advantageously applied to the case where an organic material is used as the source material of a film since the amount of impurities introduced in the grown film becomes large by the use of the organic material. [0051]
Further, it is to be appreciated that other plasma process than the RPO process described above can also be employed in the impurity removing process. [0052]
Also, other crystallization process than the RTO process described in the preferred embodiment of the invention can also be equally employed in the crystallization process of the film. [0053]
While the present invention has been described with respect to certain preferred embodiments only, other modifications and variations may be made without departing from the sprit and scope of the present invention as set forth in the following claims. [0054]

Claims

What is claimed is:

1. A method for manufacturing a semiconductor device, comprising the steps of:

(a) forming an amorphous film on a substrate;

(b) removing at least a portion of an impurity element included in the amorphous film; and

(c) sequentially repeating the forming step (a) and the removing step (b) multiple times to provide an impurity removed non-crystalline film on the substrate.

2. The method of claim 1, wherein the forming step (a) and the removing step (b) are carried out in a same reaction chamber.

3. The method of claim 2, wherein the forming step (a) and the removing step (b) are carried out at the same temperature.

4. The method of claim 1, wherein the removing step (b) is carried out while rotating the substrate.

5. The method of claim 1, wherein the amorphous film is an amorphous tantalum oxide film.

6. The method of claim 1, wherein the removing step (b) is carried out by a plasma process.

7. The method of claim 1, further comprising, after the step (c), the step (d) of performing a crystallization process to crystallize the non-crystalline film formed on the substrate.

8. The method of claim 7, wherein the crystallization process is a rapid thermal oxidation process.

9. A method for processing a substrate, comprising the steps of:

(a) forming an amorphous film on a substrate;

10. A substrate processing apparatus, comprising:

a processing chamber for processing a substrate;

a gas supply unit for providing a reactive gas into the processing chamber;

a plasma generation unit; and

a control unit,

wherein the control unit controls the substrate processing apparatus to sequentially repeat, in the processing chamber, a film forming process for depositing an amorphous film on the substrate through the use of the reactive gas and a plasma process for removing at least a portion of an impurity element included in the amorphous film through the use of the plasma generation unit.