WO2002041377A1

WO2002041377A1 - Cvd thin film manufacturing apparatus

Info

Publication number: WO2002041377A1
Application number: PCT/KR2001/001945
Authority: WO
Inventors: Pyong Yong UM
Original assignee: Eugene Technology Co., Ltd.
Priority date: 2000-11-15
Filing date: 2001-11-15
Publication date: 2002-05-23
Also published as: KR20020037612A; KR100353578B1; AU2002224171A1

Abstract

Disclosed is a CVD apparatus for fabricating thin films capable of enhancing the uniformity, minimizing the formation of reaction products or by-products in the chamber, having a long cleaning ylcle of the chamber and increasing the yield of semiconductor fabricating processes. The CVD apparatus for fabricating thin films comprises a moveable shower head unit, a double heater unit and a vacuum channel unit, wherein the moveable shower head unit comprises a first shower head having a plate for secondly introducing the reaction gas from the first shower head after a predetermined period, the double heater unit comprises an inner heater and an outer heater for controlling temperature independently, and the vacuum channel unit comprises an inner vacuum plate unit having a dual nitrogen gas slit for preventing the nitrogen gas of the lower side from flowing into the upper side, a vacuum channel loop unit for preventing the gas introduced into a vacuum channel from flowing into the upper side of the heater; and a vacuum guide unit having a vacuum guide of a three-stage slope shape forming the flow passage of the introduced gas into a radial shape.

Description

CVD THIN FILM MANUFACTURING APPARATUS

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a chemical vapor deposition (CVD)

apparatus for fabricating thin fil s, more particularly to a CVD apparatus

capable of improving the uniformity of the thin films.

(2) Description of the Related Arts

In general, a method for forming thin films in semiconductor

manufacturing processes is roughly divided into a chemical vapor

deposition(CVD) and a physical vapor deposition(PVD). The CVD apparatus

for fabricating thin films is divided into a thermal CVD and a plasma

enhanced chemical vapor deposition(PECVD) according to the methods for

obtaining activation energy, and into an atmosphere pressure chemical vapor

deposition(APCVD), a sub-atmosphere chemical vapor deposition(SACVD),

low pressure chemical vapor deposition (LPCVD) and a high pressure

chemical vapor deposition(HPCVD) according to atmosphere pressure in a

chamber.

The CVD thin films, which are made of various materials on a wafer

by the CVD apparatus, perform various functions and roles in semiconductor

devices. There are various CVD thin films, for example, a poly silicon and metal(W, Cu, Tin and WSix) wire films for conducting electricity, SiO₂ insulating films for insulating between layers and wires, flat films such as boron phosphorous silica glass(BPSG) for flattening before wiring, high dielectric films such as Si₃N4, Ta₂O₅, BST, PZT and AL₂O₃ used for increasing a dielectric constant in forming capacitors, and passivation films such as SiON used for preventing impurities from permeating and protecting from external shocks.

As described above, the CVD apparatuses for fabricating thin films on silicon wafers are divided into a batch type for processing numbers of wafers at once after loading the wafers simultaneously and a single wafer chamber type for processing the wafers one by one.

With the high integration of semiconductor devices, the scaling down of design rule is more and more accelerated. In recent years, a photolithography process is realized up to the line width of 0.20-0.15 micron by using a KrF light source. It is expected that the high integration is continued and a next generation technology for light sources such as ArF, X- ray or laser is put to practical use. Owing to the high integration, from now on, it will be difficult to fabricate high-quality devices with the current furnace system. Since the current furnace exposes wafers to high temperature for a long time(4~6 hours), it will be difficult to obtain a processing margin in the next generation devices. Such a long time may cause a unnecessary diffusion and the seeping of impurities, so that a leakage current is generated in the devices, thereby deteriorating the electrical characteristics of the devices.

The conventional apparatuses for fabricating thin films have problem that the uniformity of the thin films may be deteriorated and reaction products or by-products may be formed in the undesired portion of the reaction chamber according to the method for fabricating the thin films. It must be followed that the cleaning cycle of the chamber should be shortened and the reaction products are functioned as particles on the substrate in progress, thereby deteriorating the yield of semiconductor fabricating processes.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved apparatus for fabricating semiconductor devices capable of solving the problems with the prior art.

It is another object of the present invention to provide an improved CVD apparatus for fabricating thin films capable of enhancing the uniformity. It is. still another object of the present invention to provide an improved CVD apparatus for fabricating thin films capable of minimizing the formation of reaction products or by-products in the chamber.

It is further another object of the present invention to provide an improved CVD apparatus for fabricating thin films capable of having a long cleaning cycle of the chamber and increasing the yield of semiconductor fabricating processes.

It is still further another object of the present invention to provide a CVD apparatus for fabricating thin films capable of minimizing the thermal damage due to high temperature atmosphere.

To achieve the above-mentioned objectives, according to one aspect of the present invention, there is provided a CVD apparatus for fabricating thin films comprising a moveable shower head unit, a double heater unit and a vacuum channel unit. The moveable shower head unit comprises a first shower head having a plate for firstly introducing the reaction gas and a second shower head having a plate for secondly introducing the reaction gas from the first shower head after a predetermined period. The double heater unit comprises an inner heater and an outer heater which can control temperature independently. The vacuum channel unit comprises an inner vacuum plate unit having a dual nitrogen gas slit for preventing the nitrogen gas of the lower side of the vacuum channel unite from flowing into the upper side of the vacuum channel unite; a vacuum channel loop unit for preventing the gas introduced into a vacuum channel from flowing into the upper side of the heater; and vacuum guide unit having a three-stage slope shaped vacuum guide for forming the flow passage of the introduced gas into a radial

shape.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an overall structural view showing a CVD apparatus for

fabricating thin films according to the present invention.

Fig. 2 is a structural view showing a vacuum channel unit of the CVD apparatus according to the present invention.

Fig. 3 is a view showing a laminar flow of gas by a shower head of the CVD apparatus according to the present invention.

Fig. 4a to 4c are structural views showing a heater unit of the CVD apparatus according to the present invention.

Fig. 5 is a plan view showing the upper part of the chamber of the CVD apparatus according to the present invention.

Fig. 6 is a side view and a plan view showing a flapper of the CVD apparatus according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to attaching the drawings, a CVD apparatus for fabricating thin films according to an embodiment of the present invention will be described in detail. It is noted that like parts are designated by like reference numerals throughout the accompanying drawings. Fig. 1 shows the whole structure of a CVD apparatus for fabricating thin films according to the present invention, and Fig. 2 shows a vacuum channel unit according to the present invention.

Referring to the figures, a process chamber is divided into five parts: a remote plasma unit 10, a shower head unit 30, 40, a chamber lid unit, a chamber body 50 and a chamber moving unit. A remote plasma cleaning kit 10 is arranged to clean without opening the chamber lid unit 202, and radical gas excited by the remote plasma is introduced through a gas line. The shower head unit 30, 40 having an improved structure are arranged in the upper part of the chamber so as to keep the quantity of the gas reached at the surface of a wafer uniform.

The shower head unit 30 is constructed such that the reaction gas firstly passes through the plate of the first shower head 30 having the predetermined number of holes from the external gas line, and secondly passes through the plate of second shower head 40 at a distance. The distance between the plates of the two shower heads is set to optimize the uniformity of processes. One of the plates is formed movable to maintain the distance optimally. Preferably, the number of the holes formed in the plate of the second shower head is greater than that of holes in the plate of the first shower head, and the size of the holes is different each other. Preferably, the shower heads are made of material such as inconel which stands at the high temperature more than 650 °C. Further, since the holes of the shower heads have the form of three stages, the introduced gas forms a laminar flowfsee Fig. 3).

Referring to the figures, the upper side of the chamber has the form of a chamber lid, which comprises the plates of two shower heads having the holes of a defined shape. The reaction gas introduces into the reaction chamber through the holes of the shower head, so that the uniformity of the gas reached on the surface of wafer is improved.

The lower part of the chamber is shaped as a cylinder having a predetermined volume from the upper part of the chamber. In the center of the bottom of the chamber, an inclined hole having a defined shape is formed at the position on which a heater is to be placed. In one side of the cylindrical chamber, a slit for loading/unloading the wafer is formed.

A vacuum guide for keeping vacuum inside the chamber is arranged on the sidewall of the chamber, and a vacuum port is formed on the opposite side of the slit. Further, an inner vacuum plate and an outer vacuum plate are arranged to keep the inside of the chamber vacuum and to make the reaction gas flowing from the upper part of the chamber into a stable flowing structure of a radial shape on the upper side of the heater. A vacuum channel loop 204 is arranged on the top side of the inner vacuum plate and the outer vacuum plate, so that the gas is uniformly distributed in the upper side of the heater. A vacuum guide support 206 is formed by making the vacuum guide 200 into two parts so as to decrease the damage caused by thermal expansion due to the difference in temperature between the upper side and the lower side of the vacuum guide 200.

In the inner vacuum plate 202, a dual nitrogen gas slit is arranged to prevent the nitrogen gas on the lower side of a heater unit 90 from flowing into the upper side of the heater unit and to improve the uniformity of the deposited film. Then, the size of the silts for controlling pressure and flow rate of the nitrogen gas in the lower side of the heater unit is varied, and the direction of the plate may be changed from side to side. Further, an inner vacuum plate hole is formed twofold to prevent the nitrogen gas and the reaction gas from mixing and to form a stable barrier. A lower nitrogen gas nozzle 110 is arranged to restrain the reaction gas from feeding to the bottom of the heater unit 90. A nitrogen gas slit is formed on the inner vacuum plate for controlling the passage of the nitrogen gas of the lower side, and an asymmetric vacuum guide of three-stage slopes shape is formed to guide the stream of the gas in radial direction.

Now, the heater unit 90 will be described referring to the Fig. 4a to 4c. Fig. 4a is a cross-sectional view of the heater unit, where an inner heater 301 is slightly smaller in diameter than the wafer. Since the peripheral of a heater block 305 is close to the chamber wall, the heat loss is heavy. To compensate the heat loss and keep the surface of the wafer at a uniform temperature, an outer heater 302 is arranged as another heat source. The temperature of the peripheral of the heater block is independently controlled by the outer heater 302, which is made of molybdenum(Mo). The heater block 305 enclosing the heaters therein is made of ceramic materials such as aluminum nitride. The heater block 405 transfers the heat generated from the heaters to a_upper susceptor_300 on which the wafer is placed. There is a lift pin hole 306 for loading/unloading the wafer on the upper side of the heater unit, and a lift pin is made of ceramic materials such as aluminum oxide. To control the temperature of the inside of the heater block, thermal couplers 303, 304 for measuring temperature are arranged on the center of the inside of the heater block and on the edge of the edge of the heater block, respectively.

Fig. 4b is a plan view showing a heating element 308 in the inner heater 301 , where the outer diameter of the inner heater is slightly smaller than the diameter 309 of the wafer. Fig. 4c is a plan view showing a heating element 310 in the outer heater 302, where the inner diameter of the outer heater is slightly larger than the diameter 309 of the wafer. Preferably, it is minimized that the inner heater affects the outer heater in its temperature by optimizing the distance between the outer diameter of the inner heater and the inner diameter of the outer heater under the condition of maintaining the uniformity. Since the heat loss generated in a portion close to the chamber wall is compensated with the outer heater 302, it is ensured that the temperature uniformity is optimized on the surface of the wafer.

As described above, the heater unit is a heat source for supplying thermal activation energy to form CVD thin films and comprises heating elements for transforming an externally applied electrical energy into the thermal energy. The heater block surrounding the heating elements, which is made of ceramic materials such as aluminum nitride(AIN), aluminum oxide(AI2O3) and the like, transfers the generated heat to its the upper side.

In order to measure temperature in the heat unit, the thermal couplers for measuring temperature are placed on a predetermined position in the inside of the heater unit. A heating zone is divided into an inner heater zone and an outer heater zone that are controlled independently, and the heating unit's surface temperature is controlled accurately and uniformly by using the thermal couplers. There is a step between the inner heater and the outer heater to compensate the temperature in the peripheral of the heater unit. That is to say, the outer heater is mounted higher than the inner heater and its temperature is also controlled slightly higher than that of the inner heater. The surface on the top of the heater on which the wafer is placed is called "susceptor", which comprises a susceptor guide for seating the wafer stably and a lift pin for moving the wafer, where a regular pattern of protrusions is formed on the surface of the susceptor so as to prevent the transferred wafer from sliding. Further, a heater moving up/moving down unit is arranged.

According to the present invention, there is a space for alleviating the stress between the heater block of ceramic materials and the chamber of aluminum materials. To prevent a vacuum part from moving due to the space, a fixing pin is arranged in the inside of the vacuum part. According to the present invention, a "ramp up(1 °C/10sec)" method is used to rise the temperature of the heater, so that the difference in temperature between the inside heater and the outside heater can be controlled stably. Further, an electric power for heating the inner and the outer heater is controlled by setting a power limits on temperature bands in order to minimize the damage of the heaters and to control the temperature stably in rising and controlling temperature.

Fig. 5 is a plan view of the upper part of chamber and shows an inner wall 52 of a Kettle-type chamber, the first and the second shower heads 30, 40 having holes of a defined shape, and a gas line 22 for introducing a gas from external into the chamber. The number, the diameter and the arrangement of the holes formed in the shower heads 30, 40 can be optimized to improve the consistency of processes, and the first shower head is different in shape from that of the second shower head according to the characteristics of the CVD thin film to be deposited. The gas line 22 for introducing the gas into the inside of the chamber is connected to the top of the shower head 30 via a chamber lid.

Fig. 6 is a side view and a plan view showing a flapper of the CVD apparatus according to the present invention. The conventional shuttle valve without sealing is a metal flapper. It is difficult to achieve the perfect sealing with the conventional shuttle valve because of needing a space between the shuttle valve and the sidewall of valve. Because of the imperfective sealing, it is impossible for the valve to control the pressure more than 100 Torr without increasing the quantity of gas, and more time for achieving a target pressure is needed. To solve above problem, a metal flapper 400 and a dual O-ring are formed to make the process possible in the pressure more than 100 Torr. The dual O-ring comprises an upper O-ring 402 and a lower O-ring 403. The flapper is formed rotatable on the dual O-ring. The dual O-ring is provided to prevent leakage from occurring with a O-ring and reduce the time for reaching the process pressure.

In case of using a single reaction gas to fabricate CVD thin films, generally, the reaction gas is introduced through the shower head in the upper part of chamber. The process for above case is divided into two cases. First, if SiH₄ or Si₂H₆ gas is introduced into the chamber and reacted at 450 °C to 650 °C, then amorphous silicon or polycrystalline silicon films may be deposited by a LPCVD process. Second, if SiH₄ or Si₂Hβ gas is introduced into the chamber and reacted at 450 °C to 650 °C with the pressure keeping in 10E-5 Torr, then a selective hemispherical silicon grain may be formed.

In case of using at least two reaction gases to fabricate CVD thin films, the first reaction gas and the second reaction gas are separately or simultaneously introduced into the chamber. Now, seven embodiments of above cases will be described.

First, a nitride film(Si₃N₄) is deposited from NH₃ and SiH₂CI₂ by introducing N₂O and then successively NH₃ and SiH₂CI₂ into the chamber with the internal temperature qf the chamber at 500 to 800 °C and the pressure of less than 300 Torr. Second, a nitride film is deposited from NH₃ and SiH₄ by introducing

N₂O and then simultaneously NH₃ and SiH₄ into the chamber with the internal temperature of the chamber at 500 to 800 °C and the pressure of less than 300 Torr.

Third, a nitride film is deposited from NH₃ and SiCI₄ by introducing N₂O and then simultaneously NH₃ and SiCI₄ into the chamber with the internal temperature of the chamber at 500 to 800 °C. and the pressure of

less than 300 Torr.

Fourth, a nitride film is deposited from NH₃ and SiCI₆ by introducing N₂O and then successively NH₃ and SiCI₆ into the chamber with the internal

temperature of the chamber at 500 to 800. °C and the pressure of less than 300 Torr.

Fifth, an oxide (SiO₂) film is deposited from O₂ and SiH₄ by introducing N₂O and then simultaneously O₂ and SiH into the chamber with the internal temperature of the chamber at 300 to 800 °C and the pressure of less than 300 Torr.

Sixth, an oxide film is deposited from N₂O and SiH₂CI₂ by introducing N₂O and then successively N₂O and SiH₂CI₂ into the chamber with the internal temperature of the chamber at 300 to 800 °C and the pressure of less than 300 Torr.

Seventh, an oxide film is deposited from N₂O and SiH₄ by introducing N₂O and then successively N₂O and SiH into the chamber with the internal temperature of the chamber at 300 to 800 °C and the pressure of

less than 300 Torr.

In case of using at least three reaction gases to form CVD films, one or two of the gases are firstly introduced before the rest(s) are introduced. It follows that the process induced particles are reduced and the flowing of the process gas is improved, so that the uniformity of the process is improved. The present invention has the effects as follows.

First, it is provided to inject gas stably with a radial form in the upper

side of the heater unit by forming the passages for the reaction gas and the

nitrogen gas in the upper and the lower sides of heater unit respectively with the dual nitrogen slit in the inner vacuum plate of the vacuum channel unit, thereby enhancing the uniformity of the deposited films.

Second, it is provided to prevent the gas introduced into the inside of the vacuum channel from flowing the upper side of the heater unit by forming the vacuum channel loop in the top of the vacuum channel loop, so that a radial flowing form is stably formed, thereby enhancing the uniformity of the deposited films.

Third, it is provided to enhance the uniformity of the deposited films by forming the shower heads with inconel which stands at the high temperature more than 650 °C and forming the hole of the second shower head into a multistage slope shape.

Fourth, it is provided to keep the surface of the wafer at a fixed temperature in processing by minimizing the heat loss from the chamber wall with the double heater whose temperature is controlled independently, thereby enhancing the uniformity of the deposited films. Further, it is provided to prevent the heater damage due to the difference in power or temperature between the inner heater and the outer heater by setting power limits by the temperature bands, and the thermal damage in increasing/decreasing the temperature of the heater by performing a ramp-up/down with a software system, thereby increasing the lift time of the heater.

Fifth, it is provided to control in the condition more than 1000 Torr by arranging two O-rings in the end of the flapper, and reduce the time for reaching the process pressure by preventing a leakage from occurring, thereby reducing the total processing time.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.

Claims

WHAT IS CLAIMED IS:

1. A chemical vapor deposition apparatus for fabricating thin films which comprises: a moveable shower head unit comprising a first shower head having a plate for firstly introducing the reaction gas and a second shower head having a plate for secondly introducing the reaction gas from the first shower head after a predetermined period; a double heater unit comprising an inner heater and an outer heater for controlling temperature independently; and a vacuum channel unit comprising an inner vacuum plate unit having a dual nitrogen gas slit for preventing the nitrogen gas in the lower part of a chamber from flowing into the upper part of the chamber, a vacuum channel loop portion for preventing the gas introduced into a vacuum channel from flowing into the upper side of the heater unit, and a vacuum guide unit having a vacuum guide of a three-stage slope shape for forming the flow passage of the introduced gas into a radial shape.

2. The chemical vapor deposition apparatus according to claim 1 , wherein the vacuum channel unit further comprises a vacuum guide support unit for reducing a damage caused by thermal expansion due to the difference in temperature between the upper side and the lower side of the vacuum guide.

3. The chemical vapor deposition apparatus according to claim 1 , wherein the shower head unit is formed from inconel materials with less thermal deformation, and having three-stage slope shaped hole for forming stably the introduced gas into a laminar flow.

4. The chemical vapor deposition apparatus according to claim 3, wherein power limits are set by temperature bands so as to prevent the damage of the heater unit due to the difference of power or temperature between the inner heater and the outer heater, and a ramping-up/down is performed with a software system to prevent the thermal damage in increasing/decreasing the temperature.

5. The chemical vapor deposition apparatus according to claim 3, further comprising a flapper unit which has a dual O-ring for a process in more than 100 Torr.