WO2003043069A1

WO2003043069A1 - Apparatus of chemical vapor deposition for forming a thin film

Info

Publication number: WO2003043069A1
Application number: PCT/KR2002/002138
Authority: WO
Inventors: Pyung-Yong Um
Original assignee: Eugene Technology Co., Ltd.
Priority date: 2001-11-16
Filing date: 2002-11-15
Publication date: 2003-05-22
Also published as: KR100438491B1; KR20030039899A

Abstract

According to the present invention, a gas supply line of the CVD apparatus includes a regulator, a valve and an accumulator, thereby effectively controlling gas flowing into a chamber. Also, an opened portion of a heat element disposed on a heater is configured in the form of slant line, deeply bent line or gently curved line, and a wafer seating part is formed in the shape of wafer, thereby improving the thickness uniformity of the thin film. A metallic material is interposed thereby easily controlling the temperature of the heater. A vertically movable ceramic ring is mounted on a shower head, thereby preventing a thin film from being formed on a lateral or rear surface of the wafer. Besides, the chamber is set to perform a follow-up process after a remote plasma cleaning process by being clicked once, thereby reducing non-uniformity in thickness of each wafer and minimizing the generation of particles.

Description

APPARATUS OF CHEMICAL VAPOR DEPOSITION FOR FORMING A THIN FILM

Technical Field The present invention relates to an apparatus of

CVD(Chemical Vapor Deposition) for depositing a thin film on a surface of a wafer, and more particularly to an improved CVD apparatus for increasing thickness uniformity of a thin film.

Background Art

In general, with the number of design rules considerably decreasing along with a trend toward more decreased size and weight in a semiconductor-based apparatus, RC delay due to wiring becomes an important factor in determining an operation speed. Accordingly, a multi-layer metal structure is widely commercialized.

In case of a very large scale ICGntegrated circuit) device, such as a microprocessor, the number of metal layers required is increased from two or three in the past to four to five at the present time. In the future, it is expected that a larger scale IC would require more metal layers.

The routing layers are usually made of tungsten, which has superior step coverage and conductivity. A CVD is generally used as a method for depositing a tungsten film. Further, a thin film formed by the CVD is widely used in an oxide film which functions as an insulating film between conductive material films, such as Si02 films which employ various chemicals, and in a high-k film, such as a Si₃N₄ film, a Ta₂0₅ film, a BST film, a PZT film, a A1₂0₃ film, etc. used as a dielectric material in a memory, e.g., DRAMCdynamic random access memory) or a flash memory, as well as in the routing layer.

FIG. 1 is a cross-sectional view of a conventional CVD apparatus for depositing a CVD thin film on a wafer.

Referring to FIG. 1, the CVD apparatus includes a remote plasma generator 1, a process line 2, an inlet gas line 3, a shower head 4, a heater 5, a pumping line 6, a chamber 7, a bottom N2 nozzle 8, a heater support 9, and a bellows 10.

In the conventional CVD apparatus, when a CVD thin film is manufactured, the amount of reactive gas introduced into the chamber from a gas source is controlled by using an MFC(Mass Flow Controller) and two valves disposed on both ends of the MFC.

In this case, it is not difficult to control a large amount of influent reactive gas but it is fairly difficult to control a small amount of influent reactive gas. Accordingly, if the small amount of influent reactive gas is not completely controlled, a thin film deposition is impossible to be carried out or an unnecessary thin film is formed, thereby badly affecting a follow-up process or creating inferior elements.

FIG. 2 is a top view illustrating the alignment of a heat element in the conventional heater 5 illustrated in FIG. 1. Referring to FIG. 2, the heater 5 serves as a place where the wafer is seated, and has a power terminal 11 and a heat element 12 materialized of molybdenum(Mo) or tungstenC ) formed inside a ceramic or an ALN. In the conventional art, there exists an opened portion "A" in the heat element, namely, an area where the heat element is not positioned. Since the temperature in the opened portion A is much lower than that in other areas, when reactive gas for forming a thin film contacts the surface of the heater, uniformity of the thin film in the opened portion A is drastically deteriorated.

In the meantime, FIG. 3 is a top view illustrating a state in which a wafer is placed on a wafer seating part in the conventional heater 5.

Referring to FIG. 3, the wafer seating part 22 in which the wafer 21 is disposed is configured in a circular form. Therefore, when the CVD thin film is deposited, a low percentage of thin film deposition occurs in a flat zone "B" of the wafer 21 and thus overall uniformity is deteriorated.

FIG. 4 illustrates a state in which the conventional heater 5 and a TC(Thermo-Couple) are assembled in the CVD apparatus shown in FIG. 1. In general, the contact between the heater 5 and a TC sheath 32 of the TC 31 that measures the temperature of the heater 5 in a high vacuum environment is not a big problem. However, thermal resistance between the heater 5 and the TC sheath 32 in a low vacuum environment considerably varies with the contacted area and condition between the heater 5 and the TC sheath 32. Accordingly, heat transferred from the heater 5 to the TC sheath 32 significantly depends on the pressure of the chamber, i.e., whether or not reactive gas exists in the chamber, such that the range of the temperature sensed by the TC 31 accordingly varies. As a result, the temperature of the heater cannot be exactly controlled. In other words, when the chamber is under vacuum and there exists little reactive gas in the chamber, heat is primarily radiated from the heater 5 to the TC sheath 32. At this time, since the amount of heat transferred to the TC sheath 32 is small, the TC 31 measures the temperature of the heater lower than the actual temperature. However, when the pressure of the chamber is high, viz. there exists lots of reactive gas in the chamber, the heat is not only transferred by radiation but also transferred by convection of gas, from the heater 5 to the TC sheath 32. Therefore, a greater amount of heat is transferred than the amount of heat transferred in the case where the chamber is under vacuum. As a result, the TC

31 measures the temperature of the heater similar to the actual temperature of the heater, such that the range of the actual temperature of the heater varies widely.

Further, in the conventional CVD apparatus, to make the chamber's condition suitable for performing a follow-up process after a remote plasma cleaning process, respective steps, for example, temperature drop, remote plasma cleaning, temperature rise, cycle purge, pre-coating, cycle purge, etc., are individually executed in a manual manner. Thus, disadvantageously, the execution time is prolonged and the manipulation is complicated. Further, a dummy process is performed to reduce a variation in uniformity across each wafer, and an additional purge process is performed to control particles. Besides, an unnecessary thin film is formed on lateral surfaces and the bottom surface of the wafer and accordingly a post-treatment for removing the unnecessary thin film is required.

Disclosure of Invention

Accordingly, the present invention is directed to a CVD apparatus for depositing a thin film on a wafer that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a CVD apparatus for effectively controlling a small amount of gas when reactive gas for forming a thin film in a chamber is injected.

A further object of the present invention is to provide a CVD apparatus for preventing uniformity of a thin film deposited on a wafer from being deteriorated.

Another object of the present invention is to provide a CVD apparatus for preventing a thin film from being formed on lateral surfaces or the bottom surface of a wafer.

Still another object of the present invention is to provide a CVD apparatus for exactly controlling the temperature of a heater inside a chamber. To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a CVD apparatus comprising'- gas supply line including a main gas line having a regulator for adjusting gas pressure, an up-stream valve and a down-stream valve for controlling a stream of gas, and a mass flow controller mounted thereon, and an additional gas line having a regulator for adjusting gas pressure, an up-stream valve and a down-stream valve for controlling a stream of gas and an accumulator for determining the amount of gas mounted thereon; a heater including a heat element aligned thereon to apply heat to the wafer, and a wafer seating part where the wafer is seated, wherein an opened portion of the heat element is structured in such a manner as to prevent local decrease of temperature in the opened portion and the wafer seating part is configured in wafer shape; a TC sheath including a metallic material interposed between the hater and a TC for improving thermal conductivity between the heater and the TC; and a vertically movable shower head including a ring attached thereto for preventing reactive gas from being spread to lateral surfaces and the bottom surface of the wafer when the reactive gas is injected for the purpose of thin film deposition.

Brief Description of the Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a conventional CVD apparatus. FIG. 2 is a top view illustrating the alignment of a heat element in a conventional heater where a wafer is seated.

FIG. 3 is a top view illustrating a state in which a wafer is placed on a wafer seating part in the conventional heater.

FIG. 4 is a schematic view illustrating a state in which a conventional TC and a conventional heater are assembled.

FIG. 5 is a block diagram illustrating the configuration of a gas supply line according to a preferred embodiment of the present invention.

FIG. 6A is a diagrammatic view illustrating the configuration of a first embodiment of a gas control panel according to the present invention. FIG. 6A is a diagrammatic view illustrating the configuration of a second embodiment of a gas control panel according to the present invention.

FIG. 7A, 7B and 7C are schematic views illustrating examples of a heat element aligned on a heater where a wafer is seated according to the present invention.

FIG. 8 is a top view illustrating a state in which a wafer is placed on a wafer seating part according to a preferred embodiment of the present invention.

FIG. 9A is a schematic view illustrating a state in which a TC and a heater are assembled according to a first preferred embodiment of the present invention.

FIG. 9B is a schematic view illustrating a state in which a TC and a heater are assembled according to a second preferred embodiment of the present invention; FIG. 10A and 10B are cross-sectional views of a chamber according to a preferred embodiment of the present invention, in which the positions of the heater are changed. FIG. 11 is a flow chart illustrating a remote plasma cleaning process performed in a CVD apparatus according to a preferred embodiment of the present invention.

Best mode for Carrying Out the Invention

The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings. For reference, like reference characters designate corresponding parts throughout several views. FIG. 5 is a block diagram illustrating the configuration of a gas line

40 according to a preferred embodiment of the present invention. In general, various kinds of reactive gas are supplied to a chamber of a CVD apparatus to form a thin film on the upper surface of a wafer. Such gas, as shown in FIG. 5, passes through a gas source 41 and a gas control panel 42, and is fed to a process chamber 43.

In the conventional art, the amount of gas fed to the process chamber 43 is controlled by means of an Mass Flow Controller disposed in the gas control panel 42 and two valves disposed at both ends of the MFC. This has a limitation in controlling a small amount of gas. Thus, according to the present invention, a gas control structure of the gas control panel 42 is complemented such that the amount of gas supplied to the chamber to form a thin film is completely controllable. FIG. 6A and 6B are detailed views illustrating the configuration of an improved gas control panel 42.

FIG. 6A is a diagrammatic view illustrating the configuration of a first embodiment of a gas control panel according to the present invention. The gas control panel includes a main gas line 50, a first regulator 52a, a first up-stream valve 53a and a first down-stream valve 55a mounted thereon. An additional gas controller line 51, which includes an additional gas line 56, a second regulator 52b, a second up-stream valve 53b, an accumulator 57 and a second down-stream valve 55b mounted thereon, is connected to the main gas line 50.

The first and second regulators 52a and 52b adjust the pressure of reactive gas introduced into the chamber, and the valves formed at each gas supply line, that is to say, the up-stream valves 53a and 53b, and the down-stream valves 55a and 55b control the stream of reactive gas introduced into the chamber. The accumulator 57 functions to determine the amount of reactive gas introduced into the chamber.

FIG. 6B is a diagrammatic view illustrating the configuration of a second embodiment of a gas control panel according to the present invention.

Referring to FIG. 6B, the gas control panel includes a main gas line 60, a first regulator 62a, a first up-stream valve 63a, an MFC 64 and a first down-stream valve 65a. An additional gas controller line 61, which includes an additional gas line 66, a second regulator 62b, a second up- stream valve 63b, an accumulator 67 and a second down-stream valve 65b is connected to the main gas line 60 through a manual valve or an automatic air valve 68.

In the same manner as explained in FIG. 6A, the first and second regulators 62a and 62b adjust the pressure of reactive gas introduced into the chamber. The respective up-stream valves 63a and 63b and the down-stream valves 65a and 65b formed at each gas supply line control the stream of reactive gas introduced into the chamber. The accumulator 67 functions to determine the amount of reactive gas introduced into the chamber. As illustrated in FIG. 6A and 6B, the reactive gas introduced into the chamber of the CVD apparatus can be thoroughly controlled by virtue of the regulator for adjusting the amount of gas, the two valves for controlling the stream of gas, and the accumulator for determining the amount of gas. FIG. 7A is a top view illustrating a first example of a heat element 72 aligned on a heater 70 according to the present invention. The heater 70 serves as a place where a wafer is seated when a CVD thin film is manufactured. The heater 70 includes a power terminal 71 for supplying electric power, and the heat element 72 made of molybdenum or ceramic. According to the present invention, an opened portion, which is marked by a reference symbol "C", is configured in the form of slant line so that the temperature in the opened portion where the heat element doesn t exist can be compensated. As shown in FIG. 7a, since the opened portion of the heat element is configured in the slant line, although reactive gas for forming a thin film contacts the surface of the heater, the temperature of the opened portion is maximally compensated, thereby improving uniformity in the thin film.

FIG. 7B and 7C are schematic views illustrating other examples of the heat element aligned on the heater.

Referring to FIG. 7B, an opened portion "D" of the heat element 72 is configured in a steeply bent form. An opened portion "E" of the heat element 72 is configured in a gently curved form in FIG. 7C.

As shown in FIG. 7B and 7C, even when the heat element 72 is formed in the steeply bent form or gently curved form, local drop of temperature in the opened portion of the heat element 72 is minimized, similarly to the case of FIG. 7a, thereby improving uniformity of the thin film.

FIG. 8 is a top view illustrating a state in which a wafer is placed on a wafer seating part 82 according to a preferred embodiment of the present invention. Referring to FIG. 8, the wafer seating part 82 of a heater 80 where a wafer is seated when a CVD thin film is manufactured is identical in shape to a a wafer. In consequence, uniformity of the thin film in a wafer flat zone "F" can be enhanced.

Referring to FIG. 9A, to improve contact ability between a heater 90 and a TC sheath 91, a metallic material 92 is interposed between the heater 90 and the TC sheath 91. The upper portion of the heater 90 experiences a brazing process to form a brazed portion 93. Contact force between the heater 90 and the TC sheath 91 is improved with the help of the metallic material 92. Accordingly, thermal conductivity between the heater 90 and the TC sheath 91 is enhanced, and the temperature of the heater can be easily controlled even under a low vacuum environment without being affected by change in external conditions. FIG. 9B is a schematic view illustrating a state in which a TC and a heater are assembled according to a second preferred embodiment of the present invention.

Referring to FIG. 9B, the TC sheath 91 is partially formed of a metal screw 94 which is made of platinum(Pt) 95. The upper portion of the AIN heater 90 experiences a brazing process to form a brazed portion 93. As shown in FIG. 9B, since the metal screw 94 is formed on the one part of the TC sheath 91, contact force between the TC sheath 91 and the heater 90 is improved, and heat resistance between the TC sheath 91 and the heater 90 is accordingly reduced. Consequently, the temperature of the heater can be easily controlled even under a low vacuum environment without being affected by change in external conditions.

FIG. 10A and 10B are cross-sectional views of a chamber according to a preferred embodiment of the present invention, in which the positions of the heater are changed. FIG. 10A illustrates a state of a chamber in which a heater is located in a home position, and FIG. 10B illustrates a state of a chamber in which a heater is located in a process position.

In FIG. 10A and 10B, there are illustrated a chamber lid 100, a chamber 101, a shower head 102, a ring hanger 103, a ceramic ring 104, an align pin 105, a heater 106, a heater support 107 and a bellows 108. According to the present invention, the ceramic ring 104, which is vertically movable is coupled to the shower head 102 which injects reactive gas to a surface of a wafer. Herein, the ceramic ring 104 is coupled to the showerhead 102 in such a manner as to be caught by the ring hanger 103 of the showerhead 102. Conventionally, when a CVD thin film is deposited on the upper surface of the wafer, the heater 106 where the wafer is seated is upwardly moved toward the shower head 102 which injects the reactive gas as described in FIG. 10b until the heater reaches a position 106a. When the heater 106 which allows the wafer to be disposed therein becomes close to the shower head 102, in the conventional art, the reactive gas is spread to lateral surfaces and the bottom surface of the wafer, such that an unnecessary film is formed on the lateral surfaces and the bottom surface of the wafer. However, the present invention is characterized in that when the CVD thin film is manufactured, the align pin positioned on the surface of the heater 106 is inserted into an align hole of the ceramic ring 104 which is coupled to the shower head 102, so that the ceramic ring 104 is aligned to seal the edges of the wafer. After that, the reactive gas is injected from the showerhead 102, so that the reactive gas is prevented from being spread to the lateral surfaces and the bottom surface of the wafer. As a result, on the contrary to the conventional art, any unnecessary film is not deposited on the lateral surfaces and the bottom surface of the wafer, whereby a follow-up process is easily performed.

FIG. 11 is a flow chart illustrating a remote plasma cleaning process performed in a CVD apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 11, the temperature of a heater is compensated and the inside and outside regions of the heater are set to have the same temperature in step 200, thereby stabilizing the set temperature. Nitrogen(N2) gas is induced to the upper and lower sides of the heater so as to forcibly decrease the stabilized temperature of the heater in step 201. Thereafter, when the temperature of the heater reaches a target temperature, the target temperature is stabilized so as not to be decreased any further in step 202. A remote plasma cleaning process is performed in step 203, and the temperature of the heater is stabilized in step 204.

Next, the temperature of the heater is increased and a cycle purge are conducted in step 205. The increased temperature of the heater is stabilized in step 206. A pre-coating process is performed to deposit a thin film on the heater without any wafer in step 207. Then, a cycle purge is performed in step 208.

In the conventional art, in case of a single chamber for high temperature (600-800°C) deposition, accumulated thin films are formed on areas other than the wafer during the thin film manufacturing process according to process conditions. When the thickness of the accumulated thin films exceeds a predetermined level, it becomes a main cause of generation of run wafer particle. To eliminate such accumulated thin films, a remote plasma cleaning process is required. However, in case of the single chamber for high temperature(600-800°C) deposition, the temperature of the heater is further lowered to 400°C during the remote plasma cleaning process. To increase the temperature of the chamber to be a state in which the remote plasma cleaning process can be performed again, various works should be followed.

Therefore, according to the present invention, in order to combine the above steps and set the chamber to a state in which the remote plasma cleaning process can be performed and a follow-up process after the plasma cleaning process can be performed with one click in pictures which execute the processes, such respective steps as described in FIG. 11 are automatically carried out.

Furthermore, in case of the conventional single chamber for high temperature(600-800°C) deposition, a wafer run mode, i.e., how the chamber' s condition is maintained when the chamber is in an idle state becomes an important factor in determining a variation in uniformity of the thin film deposited on the wafer and controlling particles. Therefore, according to the present invention, if the chamber idle time is extended, there is checked whether or not the chamber' s condition meets conditions for performing an idle purge. In the affirmative, a previously prescribed purge recipe is automatically conducted. In accordance with the purge recipe, a chuck is properly moved, and nitrogen(N2) gas flow, pressure adjustment, a pumping process and so on are performed, so as to reduce a variation in uniformity across each wafer and minimize particle generation.

Industrial Applicability

As described above, the CVD apparatus according to the present invention has advantages as follows. First, since the gas supply line includes the regulator for adjusting gas pressure, the valves for controlling the stream of gas and the accumulator for determining the amount of gas, there can be effectively controlled a large amount of amount of gas as well as a small amount of gas introduced into the chamber to form a thin film. Second, since the opened portion in which the heat element doesn' t exist is configured in the form of slant line, deeply bent line or gently curved line when the heat element of the heater is aligned, the temperature decrease in the opened portion can be minimized and the uniformity of the thin film can be improved. Third, since the wafer seating part is identical in shape to the wafer, the thin film uniformity in the flat zone is prevented from being decreased.

Fourth, since the metallic material is interposed between the heater and the TC sheath to improve heat conductivity, the temperature of the heater can be easily controlled without being affected by external influence.

Fifth, since the vertically movable ceramic ring is coupled to the shower head through which the reactive gas is injected to form a thin film, an unnecessary film can be prevented from being formed on the lateral surfaces or the bottom surface of the wafer. Sixth, since the chamber of the CVD apparatus according to the present invention is set to start a follow-up process after the remote plasma cleaning process with just one click in pictures which execute the processes, the overall process time can be reduced. Besides, since the previously prescribed purge recipe is automatically conducted in chamber idle state, a variation in uniformity across each wafer can be reduced and particle generation can be minimized.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

What Is Claimed Is;

1. An apparatus of Chemical Vapor Deposition(CVD) for depositing a thin film on a wafer, the CVD apparatus comprising: a gas supply line including a main gas line having a regulator for adjusting gas pressure, an upstream valve and a down-stream valve for controlling a stream of gas, and a mass flow controller mounted thereon, and an additional gas line having a regulator for adjusting gas pressure, an up-stream valve and a down-stream valve for controlling a stream of gas and an accumulator for determining the amount of gas mounted thereon; a heater including a heat element aligned thereon to apply heat to the wafer and a wafer seating part where the wafer is seated, wherein an opened portion of the heat element is structured in such a manner as to prevent local decrease of temperature in the opened portion and the wafer seating part is identical in shape to the wafer; a Thermo Couple(TC) sheath having a TC embedded therein, the TC sheath including a metallic material interposed between the heater and the TC for improving thermal conductivity between the heater and the TC; and a vertically movable shower head including a ring coupled thereto for preventing reactive gas from being spread to lateral surfaces and the bottom surface of the wafer when the reactive gas is injected for the purpose of thin film deposition.

2. The CVD apparatus of claim 1, wherein the additional gas line is connected to the main gas line through a manual valve or an automatic air valve.

3. The CVD apparatus of claim 1, wherein the opened portion of the heat element is configured in the form of slant line, deeply bent line or gently curved line.

4. The CVD apparatus of claim 1, wherein the ring is materialized of ceramic.

5. The CVD apparatus of claim 4, wherein the ring is caught by a ring hanger of the shower head.

6. The CVD apparatus of claim 1, wherein an align pin mounted on a surface of the heater is inserted into an align hole of the ring when the reactive gas is injected.

7. The CVD apparatus of claim 1, wherein the upper portion of the heater is brazed.

8. The CVD apparatus of claim 1, wherein the TC sheath is partially formed of a metal screw which is made of platinum.

9. An apparatus of CVD for depositing a thin film on a wafer, characterized in that a chamber is automatically set such that a follow-up process is performed after a remote plasma cleaning process for removing thin films accumulated on areas other than a wafer when the thin film is formed, and the chamber' s condition is checked when the chamber is in an idle state so that a prescribed idle purge is automatically conducted.

10. The CVD apparatus of claim 9, wherein gas used in the chamber setting and the idle purge is nitrogen(N2) gas.