Chemical deposition chamber having gas seal

A chemical deposition apparatus having a chemical deposition chamber formed within the chemical isolation chamber includes a gas seal. The chemical deposition chamber includes a showerhead module having a faceplate with gas inlets to deliver reactor chemistries to a wafer cavity for processing a semiconductor substrate. The showerhead module includes primary exhaust gas outlets to remove reaction gas chemistries and inert gases from the wafer cavity. An inert gas feed delivers seal gas which flows radially inwardly at least partly through a gap between a step of the showerhead module and the pedestal module to form a gas seal. Secondary exhaust gas outlets withdraw at least some of the inert gas flowing through the gap to provide a high Peclet number.

FIELD OF THE INVENTION

This invention pertains to apparatuses and processes for conducting chemical depositions and for use in conducting plasma enhanced chemical depositions.

BACKGROUND

Plasma processing apparatuses can be used to process semiconductor substrates by techniques including etching, physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), pulsed deposition layer (PDL), plasma enhanced pulsed deposition layer (PEPDL) processing, and resist removal. For example, one type of plasma processing apparatus used in plasma processing includes a reaction or deposition chamber containing top and bottom electrodes. A radio frequency (RF) power is applied between the electrodes to excite a process gas into a plasma for processing semiconductor substrates in the reaction chamber.

SUMMARY

According to an embodiment, a chemical deposition chamber having a gas seal comprises a showerhead module and a pedestal module configured to support a semiconductor substrate in a wafer cavity beneath the faceplate. The faceplate includes a plurality of gas inlets configured to deliver process gas to the wafer cavity. The showerhead module includes primary exhaust gas outlets configured to remove reaction gas chemistries and inert gases from the wafer cavity. The showerhead module includes a step at an outer periphery of the wafer cavity and an inert gas feed configured to deliver an inert gas to form a gas seal in a gap between the step and the pedestal module. The showerhead module includes secondary exhaust gas outlets located radially outward of the main exhaust gas outlets, the secondary exhaust gas outlets configured to remove at least some of the inert gas which flows radially inward through the gap.

According to another embodiment, a method for containing reaction gas chemistries from escaping from the wafer cavity of the chemical deposition chamber described above includes the following steps: (a) supporting a semiconductor substrate on the pedestal module, (b) flowing process gas through the gas inlets of the faceplate, (c) withdrawing gases from the wafer cavity via the primary exhaust gas outlets, (d) maintaining a gas seal in the gap between the step and the pedestal module by flowing inert gas through the inert gas feed, and (e) withdrawing at least some of the inert gas flowing radially inward through the gap via the secondary exhaust gas outlets.

DETAILED DESCRIPTION

In the following detailed disclosure, exemplary embodiments are set forth in order to provide an understanding of the apparatus and methods disclosed herein. However, as will be apparent to those skilled in the art, that the exemplary embodiments may be practiced without these specific details or by using alternate elements or processes. In other instances, well-known processes, procedures, and/or components have not been described in detail so as not to unnecessarily obscure aspects of embodiments disclosed herein.

In accordance with an exemplary embodiment, the apparatuses and associated methods disclosed herein can be used for a chemical deposition such as a plasma enhanced chemical deposition. The apparatus and methods can be used in conjunction with a semiconductor fabrication based dielectric deposition process that requires separation of self-limiting deposition steps in a multi-step deposition process (for example, atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), pulsed deposition layer (PDL), or plasma enhanced pulsed deposition layer (PEPDL) processing), however they are not so limited.

As indicated, present embodiments provide apparatus and associated methods for conducting a chemical deposition such as a plasma enhanced chemical vapor deposition. The apparatus and methods are particularly applicable for use in conjunction with semiconductor fabrication based dielectric deposition processes which require separation of self-limiting deposition steps in a multi-step deposition process (e.g., atomic layer deposition (ALD), plasma enhanced atomic layer deposition (PEALD), plasma enhanced chemical vapor deposition (PECVD), pulsed deposition layer (PDL), or plasma enhanced pulsed deposition layer (PEPDL) processing), however they are not so limited.

The aforementioned processes can suffer from some drawbacks associated with nonuniform temperatures across a wafer or substrate receiving deposited material. For example, nonuniform temperatures may develop across a substrate when a passively heated showerhead, which is in thermal contact with surrounding chamber components, loses heat to the surrounding components. Therefore, the showerhead which forms an upper wall of a processing zone is preferably thermally isolated from the surrounding components such that an isothermal processing zone may be formed, thereby forming uniform temperatures across the substrate. The uniform temperatures across the substrate aid in the uniform processing of substrates wherein the substrate temperature provides activation energy for the deposition process and is therefore a control means for driving the deposition reaction.

Further, there are generally two main types of deposition showerheads, the chandelier type and the flush mount. The chandelier showerheads have a stem attached to the top of the chamber on one end and the faceplate on the other end, resembling a chandelier. A part of the stem may protrude the chamber top to enable connection of gas lines and RF power. The flush mount showerheads are integrated into the top of a chamber and do not have a stem. Present embodiments pertain to a flush mount type showerhead wherein the flush mount showerhead reduces chamber volume, which must be evacuated by a vacuum source during processing.

FIGS. 1A and 1Bare schematic diagrams showing a chemical deposition apparatus100in accordance with embodiments disclosed herein. As shown inFIGS. 1A and 1B, the chemical apparatus includes a chemical isolation chamber or housing110, a deposition chamber120, a showerhead module130, and a moving pedestal module140that can be vertically raised or lowered relative to the showerhead module130to raise and lower a substrate (or wafer)190position on an upper surface of the pedestal module140. The showerhead module130can also be vertically raised and lowered. Reactant material gases (or process gases)192(FIG. 3) are introduced into the sub-chamber (or wafer cavity)150via gas lines112through a central plenum202(FIG. 6) of the showerhead module130. Each of the gas lines112may have a corresponding accumulator (not shown), which can be isolated from the apparatus100using isolation valves (not shown). In accordance with an exemplary embodiment, the apparatus100can be modified to have one or more gas lines112with isolation valves and accumulators, depending on the number of reactant gases used. Also, reactant gas delivery lines112can be shared between a plurality of chemical deposition apparatuses or multi-station system.

In accordance with an exemplary embodiment, the chamber120can be evacuated through one or more vacuum lines160(FIG. 2) that are connected to a vacuum source (not shown). For example, the vacuum source can be a vacuum pump (not shown). In multi-station reactors, for example, those having multiple stations or apparatuses100that perform the same deposition process, a vacuum line160from another station may share a common foreline with the vacuum line160. In addition, the apparatus100can be modified to have one or more vacuum lines160per station or apparatus100.

In accordance with an exemplary embodiment, a plurality of evacuation conduits170can be configured to be in fluid communication with one or more exhaust outlets174within the faceplate136of the showerhead module130. The exhaust outlets174can be configured to remove process gases or reactor chemistries192from the wafer cavity150between deposition processes. The plurality of evacuation conduits170are also in fluid communication with the one or more vacuum lines160. The evacuation conduits170can be spaced circumferentially around the substrate190and may be evenly spaced. In some instances, the spacing of plurality of conduits170may be designed to compensate for the locations of the vacuum lines160. Because there are generally fewer vacuum lines160than there are plurality of conduits170, the flow through the conduit170nearest to a vacuum line160may be higher than one further away. To ensure a smooth flow pattern, the conduits170may be spaced closer together if they are further away from the vacuum lines160. An exemplary embodiment of a chemical deposition apparatus100including a plurality of conduits170including a variable flow conductor can be found in commonly-assigned U.S. Pat. No. 7,993,457, which is hereby incorporated by reference in its entirety.

Embodiments disclosed herein are preferably implemented in a plasma enhanced chemical deposition apparatus (e.g., PECVD apparatus, PEALD apparatus, or PEPDL apparatus). Such an apparatus may take different forms wherein the apparatus can include one or more chambers or “reactors”110, which can include multiple stations or deposition chambers120as described above, that house one or more substrates190and are suitable for substrate processing. Each chamber120may house one or more substrates for processing. The one or more chambers120maintain the substrate190in a defined position or positions (with or without motion within that position, e.g. rotation, vibration, or other agitation). In one embodiment, a substrate190undergoing deposition and treatment can be transferred from one station (e.g. deposition chamber120) to another within the apparatus100during the process. While in process, each substrate190is held in place by a pedestal, wafer chuck and/or other wafer holding apparatus of the pedestal module140. For certain operations in which the substrate190is to be heated, the pedestal module140may include a heater such as a heating plate.

FIG. 2is a cross-sectional view of a chemical deposition apparatus100having a gas based sealing system200in accordance with an exemplary embodiment. As shown inFIG. 2, the chemical deposition apparatus100includes a substrate pedestal module140, which is configured to receive and/or discharge a semiconductor substrate (or wafer)190from an upper surface142of the pedestal module140. In a lower position, a substrate190is placed on the surface142of the pedestal module140, which is then raised vertically upward towards the showerhead module130. In accordance with an exemplary embodiment, the distance between the upper surface142of the pedestal module140and a lower surface132of the showerhead module130, which forms a wafer cavity150can be about 0.2 inches (5 millimeters) to about 0.6 inches (15 millimeters). The upward vertical movement of the pedestal module140to close the wafer cavity150creates a narrow gap240between the pedestal module140and a step135around an outer portion131of the faceplate136(FIGS. 1A and 1B) of the showerhead module130.

In an exemplary embodiment, the temperature inside the chamber120can be maintained through a heating mechanism in the showerhead module130and/or the pedestal module140. For example, the substrate190can be located in an isothermal environment wherein the showerhead module130and the pedestal module140are configured to maintain the substrate190at a desired temperature. In an exemplary embodiment, the showerhead module130can be heated to greater than 250° C., and/or the pedestal module140can be heated in the 50° C. to 550° C. range. The deposition chamber or cavity150serves to contain the plasma generated by a capacitively coupled plasma type system including the showerhead module130working in conjunction with the pedestal module140.

RF source(s) (not shown), such as a high-frequency (HF) RF generator, connected to a matching network (not shown), and a low-frequency (LF) RF generator are connected to showerhead module130. The power and frequency supplied by matching network is sufficient to generate a plasma from the process gas/vapor. In an embodiment, both the HF generator and the LF generator can be used. In a typical process, the HF generator is operated generally at frequencies of about 2-100 MHz; in a preferred embodiment at 13.56 MHz. The LF generator is operated generally at about 50 kHz to 2 MHz; in a preferred embodiment at about 350 to 600 kHz. The process parameters may be scaled based on the chamber volume, substrate size, and other factors. For example, power outputs of LF and HF generators are typically directly proportional to the deposition surface area of the substrate. The power used on 300 mm wafers will generally be at least 2.25 higher than the power used for 200 mm wafers. Similarly, the flow rates, such as standard vapor pressure, for example, can depend on the free volume of the deposition chamber120.

Within the deposition chamber120, the pedestal module140supports the substrate190on which materials may be deposited. The pedestal module140typically includes a chuck, a fork, or lift pins to hold and transfer the substrate during and between the deposition and/or plasma treatment reactions. The pedestal module140may include an electrostatic chuck, a mechanical chuck, or various other types of chuck as are available for use in the industry and/or research. The pedestal module140can be coupled with a heater block for heating the substrate190to a desired temperature. Generally, the substrate190is maintained at a temperature of about 25° C. to 500° C. depending on the material to be deposited.

In accordance with an exemplary embodiment, the gas based sealing system200can be configured to help control and regulate flow out from the wafer cavity150during flow of process material or purge gas. In accordance with an exemplary embodiment, the evacuation or purging of the wafer cavity150uses an inert or purge gas (not shown), which is fed into the wafer cavity150through the showerhead module130. In accordance with an exemplary embodiment, one or more conduits170can be connected to the vacuum lines160via an annular evacuation passage176, which is configured to remove inert seal gas182(FIG. 2) from a zone below the pedestal module140.

In accordance with an exemplary embodiment, the showerhead module130is configured to deliver reactor chemistries to the wafer cavity (or reaction chamber)150. The showerhead module130can include a faceplate136having a plurality of inlets or through holes138and a backing plate139. In accordance with an exemplary embodiment, the faceplate136can be a single plate having a plurality of inlets or through holes138and the step135, which extends around the outer periphery137of the faceplate136. Alternatively, the step135can be a separate ring133, which is secured to a lower surface of the outer portion131of the faceplate136. For example, the step135can be secured to the outer portion131of the faceplate136with screws143. An exemplary embodiment of a showerhead module130for distribution of process gases including a faceplate136having concentric exhaust outlets174can be found in commonly-assigned U.S. Pat. No. 5,614,026, which is hereby incorporated by reference in its entirety. For example, in accordance with an exemplary embodiment, the exhaust outlets174surround the plurality of inlets138.

In accordance with an exemplary embodiment, the wafer cavity150is formed beneath the lower surface132of the faceplate136of the showerhead module130and the upper surface142of the substrate pedestal module140. The plurality of concentric evacuation conduits or exhaust outlets174within the faceplate136of the showerhead module130can be fluidly connected to the one or more of the plurality of conduits170to remove process gases or reactor chemistries192from the wafer cavity150between deposition processes.

As shown inFIG. 2, the apparatus100also includes a source180of inert gas or seal gas182, which is fed through the one or more conduits184to an outer plenum204of the gas based sealing system200. In accordance with an exemplary embodiment, the inert or seal gas182can be a nitrogen gas or argon gas. In accordance with an exemplary embodiment, the inert gas source180is configured to feed an inert seal gas182via one or more conduits184so as to flow radially inward through the narrow gap240, which extends outward from the wafer cavity150and is formed between a lower surface134of a step135around the outer periphery137of the faceplate136and the upper surface142of the pedestal module140. In accordance with an exemplary embodiment, the inert seal gas182communicates with process gases or reactor chemistries192(FIG. 3) from the wafer cavity150within the narrow gap240to form a gas seal during processing. As shown inFIGS. 3 and 4, the inert seal gas182only partly enters the narrow gap240, which forms a gas seal between the reactor chemistries192and the inert gas182within the narrow gap. Alternatively, as shown inFIGS. 5 and 6, the flow of the inert gas182can be to an outer edge of the wafer cavity150and removed from the wafer cavity150through the one or more exhaust outlets174within the showerhead module130.

In accordance with an exemplary embodiment, the annular evacuation passage176is fluidly connected to one or more of the plurality of evacuation conduits170. In accordance with an exemplary embodiment, the annular evacuation passage176has one or more outlets (not shown) and is configured to remove the inert gases182from the zone surrounding the periphery of the substrate190and the inert gases182traveling or flowing radially inward through the narrow gap240. The evacuation passage176is formed within an outer portion144of the substrate pedestal140. The annular evacuation passage176can also be configured to remove the inert gases182from underneath the substrate pedestal140. Further embodiments with multiple conduits similar to176can aid in withdrawing more inert gas182and enabling higher flow of inert gas into exhaust passages178and portion below the pedestal module140. The exhaust passages178can also aid in creating a higher pressure drop on the seal gas and lower diffusion of the seal gas into the wafer cavity150.

FIG. 3is a cross-sectional view of a portion of a deposition chamber120of a chemical deposition apparatus100having a gas based sealing system200in accordance with an exemplary embodiment. As shown inFIG. 3, the outer plenum204can be formed in the outer portion131of the faceplate136. The outer plenum204can include one or more conduits220, which are configured to receive the inert gas182from the inert gas source180. The inert gas182flows through the outer plenum204via the one or more conduits220to a lower outlet228. The lower outlet228is in fluid communication with the narrow gap240. In accordance with an exemplary embodiment, a distance from an outer edge152of the wafer cavity150to the outer periphery141of the faceplate136in communication with the outer plenum204is at a finitely controlled distance. For example, the distance (or width) from the outer edge152of the cavity150to the outer edge141of the faceplate136in communication with the outer plenum204can be from about 5.0 mm to 25.0 mm.

In accordance with an exemplary embodiment, the outer plenum204can be an outer annular recess222. The outer annular recess222is configured to be in fluid communication with the narrow gap240on an outer edge of the wafer cavity150via the one or more conduits220. The outer annular recess222can be configured to have an upper annular recess224and a lower annular recess226, wherein the upper annular recess224has a greater width than the lower annular recess226. In accordance with an exemplary embodiment, the lower outlet228is an annular outlet on a lower portion of the lower annular recess226, which is in fluid communication with the narrow gap240.

In accordance with an exemplary embodiment, as shown inFIG. 3, the inert gas182is fed through the outer plenum204at the outer edge of the wafer cavity150spaced at finitely controlled distances. The flow rate of the inert gas182flowing through the outer plenum204can be such that the Peclet number is greater than about 1.0, thus containing the reactor gas chemistries192within the wafer cavity150, as shown inFIG. 3. For example, if the Peclet number is greater than 1.0, the inert gas182and the reactor gas chemistries192can establish an equilibrium within an inner portion242of the narrow gap240. As a result, reactor gas chemistries192can be prevented from flowing beneath the substrate pedestal module140and contaminating portions of the deposition chamber120outside of the wafer cavity150.

In accordance with an exemplary embodiment, if the process is a constant pressure process, then a single (or constant) flow of the inert gas182in combination with the pressure from below the pedestal module140can be sufficient to ensure an inert gas seal between the reactor gas chemistries192within the wafer cavity150and the inert gas180flowing radially inward through the narrow gap240. For example, in accordance with an exemplary embodiment, the gas based sealing system200, can be used with ALD oxides of Si, which can be generally run in a relatively constant pressure mode. In addition, the gas based sealing system200can act as a means to control gas sealing across different processes and pressure regimes within the deposition chamber120and the wafer cavity150, for example, during an ALD nitride process by varying the flow rate of the inert gas182or pressure below the pedestal module140and/or a combination of both.

In accordance with an exemplary embodiment, the sealing gas system200as disclosed individually, or in combination with the pressures associated with the exhaust conduits174,176can help prevent flow and/or diffusion of reactor chemistries192out of wafer cavity150during processing. In addition, the system200individually, or in combination with the exhaust conduits174,176and pressure associated with the exhaust conduits174,176can also prevent the bulk flow of the inert gas182into the wafer cavity150and over onto the substrate190. The flow rate of the inert gas182into the narrow gap240to isolate the wafer cavity150can be adjusted based on the pressure produced by the exhaust outlets174. In accordance with an exemplary embodiment, for example, the inert gas or seal gas182can be fed through the outer plenum204at a rate of about 100 cc/minute to about 5.0 standard liters per minute (slm), which can be used to isolate the wafer cavity150.

In accordance with an exemplary embodiment, one or more evacuation cavities250can be located in an outer portion of the pedestal module140, which surrounds the wafer cavity150. The one or more evacuation cavities250can be in fluid communication with the narrow gap240and the lower outlet228, which can add to the pressure drop from the wafer cavity150to the inert or gas feed180. The one or more evacuation cavities250(or annular channel) can also provide an added control mechanism to enable gas sealing across various process and pressure regimes, for example, during ALD nitride processing. In accordance with an exemplary embodiment, the one or more evacuation cavities250can be equally spaced around the deposition chamber120. In an exemplary embodiment, the one or more evacuation cavities250can be an annular channel, which is concentric and of larger width than the lower outlet228.

FIG. 4is a cross-sectional view of a portion of the deposition chamber120of a chemical deposition apparatus100with a gas based sealing system200. As shown inFIG. 4, if the flow rate of the reactor chemistries192is greater than or about equal to the flow rate of the inert gas182, the flow of the reactor chemistries192may extend outside of the wafer cavity150, which may not be desirable.

As shown inFIG. 4, an annular evacuation passage176provides a secondary evacuation path in addition to the main evacuation path174in the faceplate136. The annular evacuation passage176is configured to remove the inert gases182from underneath the substrate pedestal140and from a zone surrounding a periphery of the substrate190. In accordance with an exemplary embodiment, the annular evacuation passage176has one or more outlets (not shown) and is configured to remove the inert gases182from the zone surrounding the periphery of the substrate190and the inert gases182flowing or diffusing radially inward through the narrow gap240.

FIG. 5is a cross-sectional view of a portion of the deposition chamber120of a chemical deposition apparatus100with a gas based sealing system200in accordance with an exemplary embodiment. The flow of inert gas182from outside the cavity150can be produced by reducing the flow rate of the reactor chemistries192and/or increasing the flow rate of the inert gas182. In accordance with an exemplary embodiment, the inert gas182from the outer plenum204will flow into the wafer cavity150and can be removed through the one or more exhaust outlets174within the showerhead module130.

FIG. 6is a cross-sectional view of a portion of the deposition chamber120of a chemical deposition apparatus100with a gas based sealing system300in accordance with an exemplary embodiment. In accordance with an exemplary embodiment, a central plenum202of the showerhead module130includes the plurality of inlets or through-holes138, which delivers the reactor chemistries192to the wafer cavity150. The wafer cavity150also includes concentric conduits or exhaust outlets174which remove reactor chemistries192and inert gases182from the wafer cavity150. The concentric conduits or exhaust outlets174can be in fluid communication with an intermediate plenum208between the backing plate139and an upper plate310. The intermediate plenum208is in fluid communication with one or more of the plurality of evacuation conduits170.

The showerhead module130can also include vertical gas passage370, which is configured to deliver an inert gas182around the outer periphery137of the faceplate136. In accordance with an exemplary embodiment, an outer plenum206can be formed between the outer periphery137of the faceplate136and an inner periphery or edge212of an isolation ring214.

As shown inFIG. 6, the system300includes the vertical gas passage370formed within an inner channel360within the upper plate310and an outer portion320of the backing plate139. The vertical gas passage370includes one or more conduits312,322, which are configured to receive the inert gas182from the inert gas source or feed180. In accordance with an exemplary embodiment, the inert gas182flows through the upper plate310and the outer portion320of the backing plate139via the one or more conduits312,322to one or more recesses and/or channels330,340,350to an outer edge of the wafer cavity150.

In accordance with an exemplary embodiment, the one or more conduits312can include an upper annular recess314and a lower outer annular recess316. In accordance with an exemplary embodiment, the upper recess314has a greater width than the lower recess316. In addition, the one or more conduits322can be within the upper plate310and the outer portion320of the backing plate139. The one or more conduits322can form an annular recess having an inlet326in fluid communication with an outlet318on the upper plate310and an outlet328in fluid communication with the narrow gap240. In accordance with an exemplary embodiment, the outlet328within the outer portion320can be in fluid communication with one or more recesses and/or channels330,340,350, which guides the flow of the inert gas182around an outer periphery of the faceplate136of the showerhead module130to an outer edge243of the narrow gap240.

In accordance with an exemplary embodiment, the inert gas182is fed through the vertical gas passage370to the outer plenum206, and radially inwardly at least partly through the narrow gap240towards the wafer cavity150. The flow rate of the inert gas182flowing through the one or recesses and/or channels330,340,350can be such that the Peclet number is greater than 1.0, thus containing the reaction gas chemistries192within the wafer cavity150. In accordance with an exemplary embodiment, if the Peclet number is greater than 1.0, the inert gas182and the reaction gas chemistries192establishes an equilibrium within the inner portion242of the narrow gap240, which prevents the reaction gas chemistries192from flowing beneath the pedestal module140and contaminating portions of the deposition chamber120outside of the wafer cavity150. In accordance with an exemplary embodiment, by containing the flow of the reaction gas chemistries192to the wafer cavity150, the system200can reduce the usage of process gas192. In addition, the system200can also reduce the fill time of the wafer cavity150with the process gas192during processing.

FIG. 7is a schematic of a gas based sealing system400in accordance with an exemplary embodiment. As shown inFIG. 7, the system400includes a source of an inert or seal gas180and source of a process gas19, which are configured to deliver an inert or seal gas182and a process gas192, respectively, to the wafer cavity150. The system400can also include a wafer-cavity or cavity pressure valve410and a lower chamber pressure valve412, which control a wafer-cavity or cavity pressure414, and a lower chamber pressure416, respectively.

FIG. 8is a chart500showing pressure and valve angle versus time for a gas based sealing system400in accordance with an exemplary embodiment. In accordance with an exemplary embodiment, as shown inFIG. 8, a process gas192in the form of helium is supplied to the wafer cavity150at flow rates of 0 to about 20 SLM (standard liters per minute). An inert or seal gas182in the form of nitrogen gas (N2) was provided to the cavity at about 2 SLM. In accordance with an exemplary embodiment, the cavity chamber414and the lower chamber pressure416was approximately 10 Torr. As shown inFIG. 8, at operating conditions of up to about 20 SLM of helium gas192and 2 SLM of nitrogen gas182, the helium gas192did not leak through the purge channel as evidenced by the Residual Gas Analyzer (RGA) measurements.

Also disclosed herein is a method of processing a semiconductor substrate in a processing apparatus. The method comprises supplying process gas from the process gas source into the deposition chamber, and processing a semiconductor substrate in the plasma processing chamber. The method preferably comprises plasma processing the substrate wherein RF energy is applied to the process gas using an RF generator, which generates the plasma in the deposition chamber.

According to an embodiment, the Peclet number can be greater than 100 along an outer periphery of the semiconductor substrate. Preferably, precursor gases are injected centrally into the reactor cavity with minimum inlet volume and axisymmetric flow while seal gas is injected circumferentially around an outer periphery of the reactor cavity. The precursor gases are reacted to deposit a film on the semiconductor and byproduct gases flow radially outward towards exhaust outlets distributed circumferentially around an outer periphery of the reactor cavity. At the same time, the seal gas flows radially inward through inlets distributed circumferentially around the outer periphery of the reactor cavity. In order to obtain a high Peclet number, gas pressures are controlled according to the following equation:
C2(Pvs−Pwc)={dot over (m)}wc>>0−Pvs>>Pwc.

FIG. 9illustrates an embodiment wherein a showerhead module400includes a faceplate402having gas outlets404, a backing plate406having a central gas passage408, and an isolation ring410having seal gas passages412distributed circumferentially around the reaction cavity so as to provide an inert gas seal with gas supplied through gas passages412. Process gas is withdrawn via main exhaust passages414distributed circumferentially around an outer portion of the faceplate402. InFIG. 9and the following equation, {dot over (m)}2and {dot over (m)}vsrepresent mass flow rate in kg/s, C2, C3and C4represent gas conductance in liters/second and Seffrepresents the effective pumping speed in liters/second. In order to obtain a high Peclet number it is desirable that {dot over (m)}wcshould not be so large that it overwhelms the effective pumping speed, {dot over (m)}vsshould be large, C2should be larger than C3, Seffshould be large and Pchcan be large (but creates issues with dilution) as shown below:
C2/C3(C3Pch+{dot over (m)}vs)−{dot over (m)}wc/Seff>>0 whereSeff=SC4/S+C4.

During wafer processing, pressures in the reactor cavity and main chamber are modulated whereas the seal gas flow rate is kept constant. If the reactor cavity pressure is maintained ±1 Torr in relation to main chamber pressure, it is possible to contain the precursor gases within the reactor cavity. With the virtual gas seal arrangement, it is possible to maintain desired pressure in the reactor cavity with the inert gas seal.

FIG. 10illustrates an embodiment wherein a showerhead module500includes a faceplate502having gas outlets504, a backing plate506having a central gas passage508, and an isolation ring510having seal gas passages512distributed circumferentially around the reaction cavity so as to provide an inert gas seal with gas supplied through gas passages512. Process gas is withdrawn via main exhaust gas passages514distributed circumferentially around an outer portion of the faceplate502and secondary exhaust gas passages distributed circumferentially around the isolation ring510at a location between the gas passages512and the main exhaust passages514. The secondary exhaust passages516remove gas through flow paths represented by flow conductances C5and C6, and the secondary exhaust gas path C5can provide a further increase in Peclet number according to the following equation:
C2/C3(C3Pch+{dot over (m)}vs)+{dot over (m)}wc(C1C4+C4C5/C1C5+C1C4+C4C5)>>0 whereSeff=SC6/S+C6.

As shown inFIG. 10, the seal gas is injected out of passages512into a small gap between the pedestal module (not shown) and showerhead module500at location Pvs, the seal gas flows radially inward along path C2and radially outward along path C3. The reacted precursor gases and inwardly flowing seal gas are pumped out of the reactor cavity150through the primary exhaust path located at C4. In addition, some seal gas is pumped out through the secondary exhaust path (exhaust passages516) at C5. The mass flow rates of the seal gas are shown by {dot over (m)}vs(seal gas flowing into the narrow gap), {dot over (m)}2(seal gas flowing radially inward towards the reactor cavity150), {dot over (m)}3(seal gas flowing radially outward and removed by vacuum pressure Pchof the vacuum source connected to the main chamber), {dot over (m)}1(seal gas flowing radially inward of the secondary exhaust outlets), and {dot over (m)}4(seal gas and process gases pumped out of the primary exhaust outlets). By keeping C5constant and high, the Peclet number can be made higher than a single-stage virtual gas seal. The secondary exhaust gas passages (secondary exhaust) are located between the seal gas entry point and the reactor cavity in order to provide the condition of making Seffand C5large. The secondary exhaust path is preferably connected downstream of a pressure control throttle valve to ensure constant exhaust and to provide the condition that C5be constant.FIG. 11illustrates how process gases PG flow radially outward, seal gas SG flows radially inward, a portion of the seal gas SG flows out the secondary exhaust gas passages and a portion of the inert sealing gas and process gas flows out the main exhaust gas passages.

FIG. 12illustrates a cut-away view of a showerhead module600which includes a faceplate602having gas inlets604, a backing plate606having a central gas passage608, an isolation ring610having an inner ring612and outer ring614. The inner ring612and outer ring614fit together such that a seal613around a lower portion of the inner ring612provides an annular plenum between opposed surfaces of the inner and outer rings. The inner ring612includes seal gas inlets616distributed circumferentially around an upper part of an inner surface618, horizontal passages620extending radially outward from the inlets616, vertical passages622extending downwardly from the horizontal passages620and seal gas outlets624distributed circumferentially around a lower surface626of the inner ring612.

The inner ring612includes primary exhaust outlets627comprising radially extending slots distributed circumferentially around a lower portion of the inner surface618and secondary exhaust outlets628distributed circumferentially around the lower surface626. The primary exhaust gas outlets627are connected to vertical passages630extending upward from the primary exhaust gas outlets627and inwardly extending horizontal passages having primary exhaust gas outlets632distributed circumferentially around the inner surface618at a location below the seal gas inlets616. The secondary exhaust gas outlets628are connected to vertical passages (not shown) and horizontal passages having secondary exhaust gas outlets629distributed circumferentially around an outer surface619of the inner ring612. The seal gas outlets624deliver seal gas to create a gas seal below the isolation ring610and some of the seal gas is withdrawn through the secondary exhaust gas outlets628during semiconductor substrate processing in the wafer cavity150.

FIG. 13illustrates how inner ring612fits around an outer periphery of the faceplate602and backing plate (gas distribution plate or GDP)606such that seal gas can be supplied from seal gas supply plenum650in an outer portion of the GDP606to radially extending seal gas passages652. The seal gas passages652open into an annular plenum658located between upper and lower gas seals654,656. The annular plenum658is in fluid communication with the seal gas inlets616in the inner surface618of the inner ring612to deliver seal gas through the seal gas outlets624in the lower surface626of the inner ring612.

The GDP606includes a primary exhaust gas plenum680connected to radially extending primary exhaust outlets682in an outer periphery of the GDP606. The outlets682open into an annular exhaust plenum684between the lower seal656and an annular seal686. The annular exhaust plenum684communicates with the primary exhaust gas outlets632on the inner surface618of the inner ring612. The primary exhaust gas outlets632connect with the vertical passages630and the slots627to allow primary gas to be exhausted from the wafer cavity150.

The outer ring614surrounds the inner ring612with a plenum between the outer surface619of the inner ring612and an inner surface615of the outer ring614. The secondary exhaust outlets628provide for secondary exhaust gas to be withdrawn through the secondary exhaust gas outlets629into the plenum between the inner ring612and the outer ring614. The GDP includes at least one opening670in an upper surface to allow the secondary exhaust gas to be withdrawn while bypassing the throttle vale pumping arrangement connected to the primary exhaust gas plenum680. Preferably, two opposed openings670are provided in the GDP for azimuthal uniformity of gas flow.

FIG. 14illustrates two gas seal connections630,632on the upper surface of the GDP606connected to the two openings670for secondary exhaust gas removal. The gas connections630,632are attached to two respective tubing sections634,636which are connected to a single tube638in fluid communication to an exhaust pump thereby bypassing the throttle valve connected to the primary exhaust outlets. Thus, a portion of the seal gs creating the gas seal can be withdrawn independently of the primary exhaust gas.

Moreover, when the words “generally”, “relatively”, and “substantially” are used in connection with geometric shapes, it is intended that precision of the geometric shape is not required but that latitude for the shape is within the scope of the disclosure. When used with geometric terms, the words “generally”, “relatively”, and “substantially” are intended to encompass not only features, which meet the strict definitions, but also features, which fairly approximate the strict definitions.

While the plasma processing apparatus including an isothermal deposition chamber has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.