KR200454281Y1 - Temperature controlled showerhead - Google Patents

Abstract

Temperature controlled showerhead chambers for chemical vapor deposition (CVD) enhance the dissipation of heat to enable precise temperature control using electrical heaters. Heat is dissipated by radiation from the back plate and through the fluid passageway and showerhead stem. The temperature control system includes one or more temperature controlled showerheads in a CVD chamber having fluid passageways continuously connected to the heat exchanger.

Description

TEMPERATURE CONTROLLED SHOWERHEAD}

The present invention is directed to an apparatus and system for depositing a film on a substrate. In particular, the present invention relates to a chemical vapor deposition (CVD) apparatus for injecting gas into a reaction chamber. More particularly, the present invention relates to a temperature controlled showerhead and its temperature control system.

CVD showerhead reactors employ perforated or porous planar surfaces to distribute the reactant and carrier gases as consistently as possible over a second parallel planar surface. This shape can be used for continuous batch processing of multiple substrates or for single round wafer processing. The wafer is generally heated to a processing temperature at which a thin film is deposited on the wafer surface and the reaction gases interact.

Showerhead reactors or parallel plate reactors cause them to perform a plasma deposited process, for example plasma-enhanced chemical vapor deposition (PECVD). For most PECVD reactors, the top and bottom electrodes are the same size. The wafer electrode may be a substrate support and may be grounded and the showerhead may have an applied RF power. A bias RF power may be applied to the substrate support. RF applied in the showerhead may require insulating sections in the gas supply system to avoid the formation of parasitic discharges in the gas supply line to the chamber. RF power may be applied through the substrate support electrode while the showerhead is grounded.

Wafer-to-wafer uniformity can be influenced by varying the reaction temperature from wafer-to-wafer and changes in emissivity of showerhead components over time, processing conditions, cleaning cycles, and idling times. The time may affect both the substrate or the wafer as well as the gas reaction temperature. Although many wafers reach equilibrium temperature after continuous batch processing, these factors can affect the balance temperature or the number of deposition cycles before reaching the equilibrium temperature. In addition, the showerhead temperature in the multiple station chamber can vary from station to station. For example, cool incoming wafers at station 1 point can cause gradual cooling of the showerhead. The thermal cycle of the showerhead can form particles from the coating on the showerhead having different coefficients of thermal expansion from the showerhead itself.

Therefore, it is desirable to precisely control the temperature of each showerhead in the chamber to form valuable equipment to manufacture with good wafer to wafer uniformity. The showerhead can be produced at the lowest cost without reducing throughput or increasing footprint while maintaining good wafer to wafer uniformity and can be designed without the formation of small particles.

Temperature control systems with temperature controlled CVD showerheads and enhanced temperature dispersion can precisely control and stabilize temperature control with fast response. Precise temperature control reduces the wafer-to-wafer non-uniformity within a continuous batch with batch processing. Increased heat dissipation and heaters can allow for rapid recovery to a temperature set point when changes in operating environment disturb the system. Increased heat dissipation is realized by increased conduction through the showerhead stems, and additional convective cooling uses increased radiation from the back plate and fluid in the fluid passage. The temperature control system includes a heat exchanger that sequentially cools convective cooling flowing in the showerhead fluid passageway. In addition, the showerhead temperature may provide additional parameters for the optimization process.

In either aspect, the present invention provides a stem having a convection cooling fluid passageway, a rear plate thermally coupled to the stem, a heater physically attached to the rear plate, and a contact plate thermally coupled to the rear plate. A temperature controlled CVD showerhead comprising a temperature sensor for measuring the temperature of a face plate and a contact plate. The temperature sensor can be a thermocouple attached to a contact plate. Also non-contact methods for temperature measurement based on infrared radiation, fluorescence emission or pyrometry can be adopted. The back plate may be formed of aluminum or an aluminum alloy. The outer surface of the back plate may be coated with a material to increase the emissivity. The coating treatment may be anodized aluminum. The heater is an electrical resistance heater and may be enclosed in a back plate. The contact plate may be made of aluminum, anodized or coated aluminum or other metal designed to be high temperature, chemical and plasma resistant.

The stem receives a channel through which the reactant and carrier gas flow into the contact plate, which is distributed through holes or through holes in the contact plate. A baffle plate or some other distribution device may be located between the contact plate and the gas channel end to assist in evenly distributing the gas. The stem also receives a convective cooling fluid passageway through which cooling fluid can flow to cool the showerhead. A fluid passageway is constructed that is spaced apart from the reactant channels in the stem that carry the reactant and carrier gas to the showerhead. Convective cooling fluid enters the stem at the inlet and may exit the stem through one or more outlet channels. In the stem, both channels of the inlet or outlet channel or passageway can form a spiral path or some other serpentine path designed for conductive heat transfer between the fluid and the surface. The cooling fluid may wash dry air, argon, helium, nitrogen, hydrogen or mixtures thereof. Although not preferred, oil or water based liquid coolants may be used as the convective cooling fluid. In particular, CDA may be provided by silicon wafer fab facilities at a pressure of approximately 50-100 psi. The CDA can also be cooled by a heat exchanger connected in series with one or more showerheads. A series of cooling can be supplied by CDA to various showerheads with intermediate cooling by heat exchangers. For example, CDA can be supplied to the first showerhead cooled by a heat exchanger, can be supplied to a second showerhead cooled by a heat exchanger, and can be supplied to a third showerhead cooled by a heat exchanger. Can be supplied to a fourth showerhead cooled by a heat exchanger and then discharged. The device minimizes the amount of air used, eliminates safety hazards and ensures low temperatures of the discharge.

The contact plate includes holes or through holes through which gaseous reactants flow to the wafer. The contact plate may have various shapes of hole patterns of different sizes. The contact plate may be removably attached to the back plate to facilitate cleaning or changing the hole pattern. The temperature of the contact plate can be measured by thermal contact with the contact plate and by physical thermocouples or by any other means that may be less affected by RF interferences, such as optical temperature measurements. Can be. If a thermocouple is used, it can be connected to the contact plate via a standoff and stem between the back plate and the contact plate. A high frequency (RF) filter can be electrically coupled to the thermocouple to reduce or eliminate interference in the temperature signal from the applied RF to the showerhead.

The RF filter can also be electrically coupled to the heater. Either or both of the heater and the thermocouple may be separated from the RF power at a constant frequency used during the deposition process. A controller can be coupled to the thermocouple and the heater to maintain the desired temperature at the contact plate point.

In another aspect, the present invention is directed to a temperature control system for controlling one or more showerhead temperatures in a CVD chamber. The system includes a CVD chamber and a cooling system. The CVD chamber includes one or more temperature controlled showerheads. Each showerhead includes a thermocouple, stem, back plate, and contact plate for measuring the temperature of the contact plate. The stem includes a convective cooling fluid passageway and is thermally coupled to the back plate, which is thermally coupled to the contact plate. The cooling system is connected between the showerheads through each showerhead and heat exchanger to a convection cooling fluid passageway in each showerhead for a series of flow cooling fluids. The cooling system includes a connection to the liquid cooled heat exchanger and the convective cooling fluid passage. The temperature control system may also include a controller coupled to the thermocouple and a heater physically attached to the back plate.

The convective cooling fluid can be clean dry air (CDA), argon, helium, nitrogen, hydrogen or a combination thereof. The convective cooling fluid can be carried through the silicon fabrication plant connection and can be CDA. The CDA may be delivered at a pressure of approximately 50-100 psi and may be an ambient temperature for the first showerhead stem. The CDA may be continuously cooled between different cooling showerheads, which may or may not be formed in the same processing chamber on the same tool. Either heat exchanger may be used to cool the showerhead in one or more chambers for one or more tools. CDA may be finally discharged at ambient pressure and / or ambient temperature after final cooling. The liquid coolant in the heat exchanger may be promoted with water or another liquid coolant. The heat exchanger may be a cast metal block having an embedded coolant line and a convective cooling fluid line. The cast metal material may be aluminum. The cooling system may also include one or more bypass loops formed to space the one or more showerheads from the cooling system. The cooling system may also include flow modulators coupled to the controller to adjust or control the flow rate of cooling fluid to each showerhead to control the amount of cooling. have. In some embodiments, the CVD chamber may also include a chamber top having a coating with high emissivity. The coating may be formed on the inner surface of the top of the chamber and anodized aluminum may be formed.

In still another aspect, the present invention is directed to a temperature control system for controlling a CVD showerhead temperature. The system includes cooling means thermally coupled to the showerhead, heating means thermally coupled to the showerhead, temperature sensing means thermally coupled to the contacts of the showerhead, temperature sensing means and heating means. Electrically coupled RF filtering means and control means for controlling the temperature. The system may also comprise radial cooling means and convective cooling means.

In one aspect, the invention relates to a temperature controlled CVD showerhead comprising a stem having a convection cooling fluid passageway, a rear plate thermally coupled to the stem, and a contact plate thermally coupled to the rear plate. . The convective cooling fluid passage may be designed such that the cooling fluid exiting the passage is at the same temperature as the showerhead. The showerhead device may also include a temperature sensor for measuring the effluent cooling fluid located outside the plasma RF interference range. The temperature sensor may be a non-contact method or thermocouple for temperature measurement based on infrared radiation, fluorescence emission or pyrometers. The back plate may be made of aluminum or aluminum alloy. The outer surface of the back plate may be coated with a material to increase the emissivity. The coating can be anodized aluminum. In some embodiments, a heater can be attached to the back plate, which can be an electrical resistance heater and can be implemented within the back plate.

In another aspect, the present invention is directed to a temperature control system for controlling showerhead temperature in a CVD chamber. The system may include one or more temperature controlled showerheads, a cooling system fluidly coupled to the convective cooling fluid passage, and a CVD chamber having a controller. Each showerhead may include a stem having a convective fluid passageway, a rear plate thermally coupled to the stem, and a contact plate thermally coupled to the rear plate. The cooling system may include inlet and outlet to convective cooling fluid passages, a liquid cooling heat exchanger, a flow modulator, and a temperature sensor thermally coupled to the convective cooling fluid exiting the stem. The heat exchanger may remove heat from the convective cooling fluid that is mediated by the heat exchanger and flows continuously through the passages of one or more showerheads. The flow modulators may control the flow rate of the convective cooling fluid to each showerhead based on information received from the controller. The temperature sensor may measure the temperature of the fluid exiting the showerhead to allow the controller to determine the temperature of the contact plate. The controller can be coupled to the flow modulator and the temperature sensor to determine and control the contact plate temperature. In some cases, the heater may be attached to the back plate and coupled to the controller to provide heat.

In yet another aspect, the present invention relates to a temperature controlled showerhead contact plate for CVD. The contact plate includes a substantially flat and circular front and rear surface. The back surface may include many threaded blind holes and one or more mating features for attaching a contact plate to the back plate. The contact plate may also include a number of small through holes for gas flow from the showerhead stem to the treatment area on another side of the contact plate. The small through holes may form approximately 10 to 10,000, 2 to 5000, 3 to 4000 or 200 to 2000 holes having a diameter of approximately 0.01 to 0.5 inches or approximately 0.04 inches and form a hole pattern with non-uniform distribution. can do. The contact plate may have a thickness of approximately 0.25 to 0.5 inches, or approximately 0.125 to 0.5 inches, or approximately 0.25 to 0.375, and may be formed of aluminum, anodized or coated forming aluminum or other metals at which high temperatures and chemical and plasma resistances are formed. It can be prepared as. Also thermocouple contact holes may be included. The contact plate is formed to be removably attached to the back plate through one or more engagement engagement features. The engagement coupling feature may be formed with a peripheral side wall over the back surface, the recess, the plurality of threaded blind holes and the engaging jaw.

These and other features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

In the accompanying detailed description of the invention, many distinctive embodiments start to provide a thorough understanding of the invention. However, as will be apparent to one of ordinary skill in the art, the present invention may be practiced without the specific details or by using alternative elements or processes. In other instances, well known processes, procedures and components are not described in greater detail in order not to unnecessarily obscure the present invention.

In this application, the terms "substrate" and "wafer" may be used interchangeably. The following detailed description is performed in the semiconductor processing apparatus. However, the present invention is not limited. The apparatus can be used to process work pieces of various shapes, sizes and materials. In addition to semiconductor wafers, other articles of manufacture that utilize the present invention include a variety of articles, such as display surface planar printed circuit boards.

The showerhead temperature drifts over time and affects the deposition behavior in terms of reaction rate and thin film properties. 1 is a graph of four showerhead temperatures for a 50 wafer run without any temperature control, ie heating or cooling. Four showerheads in four station chambers are configured for 50 wafer runs in approximately 4000 seconds. Station 1 showerhead corresponds to line 102, station 2 corresponds to line 104, station 3 corresponds to line 106, and station 4 corresponds to line 108. Over time, the temperatures of stations 2-4 increase at approximately 3700 seconds until a steady state temperature is reached. The plasma condition is configured as a step function in line 110. Initially, the plasma remains in dummy deposition mode to preheat the showerhead and the wafer processing process begins after approximately 10 minutes. In station 1, as the wafer is preheated to the processing temperature, the temperature begins to decrease gradually after the wafer processing process begins because each incoming wafer in station 1 cools the chamber components including the showerhead. . Thus the temperature curve in the next station is gradually higher. The station 2 showerhead is cooler than the station 3 showerhead because the wafer entering the station 2 is cooler than the wafer entering the station 3. For all stations, the showerhead temperature reaches a balanced temperature after some time.

1 shows wafers processed in a multi-station chamber experimenting with different showerhead temperatures at each station. As such, when the showerhead temperature affects the deposited thin film properties, each layer deposited on the wafer has somewhat different properties. One embodiment of a CVD process that is sensitive to showerhead temperature is a silicon nitride spacer. Another example of a CVD process that is sensitive to showerheads is tetraethylorthosilicate (TEOS).

2A shows thin film thickness deposited below different showerhead temperatures. All other process parameters are the same, and moreover the thin film is deposited at higher showerhead temperatures. As such, the thin film thickness deposited at some idle time or at the beginning of a wafer run after chamber cleaning is formed to be less than the thin film thickness deposited after the showerhead temperature is balanced. Depending on the thin film, such thickness differences may or may not be affected by the performance of the fabricated device. 2B shows the showerhead temperature on silicon nitride spacer thin film characteristics-stress. As the showerhead temperature increases, the tension decreases. In particular, thin film tension deposited at the transistor level can have a significant impact on device performance. As such, the target tension may be implemented by manipulating the showerhead temperature. The function of showerhead temperature control provides another processing parameter and implements target thin film properties with the processing parameters and reduces wafer to wafer deformation (not uniform) in thin film properties and deposition thickness.

Temperature controlled showerhead

The temperature controlled showerhead improves wafer-to-wafer uniformity and eliminates non-processing delays for both individual sub-layers and bulk films. Increasing the particle size by reducing or eliminating thermal cycling and adding various processing parameters for t uning film properties. Thin film wafer-to-wafer uniformity is improved because it is less variable for continuous batches of wafers (within batch and within another batch, independent of tool conditions).

This reduces the difference in thin film properties between the first wafer in the batch when the showerhead is cooled and the final wafer in the batch when the showerhead reaches equilibrium temperature. By controlling all showerheads in the chamber to be formed at the same temperature, the uniformity of thin film properties in different sub-layers is improved. For example, non-processing time, which is a dummy deposition time for heating the showerhead, can be eliminated to increase yield. Thermal cycling may be reduced because the showerhead temperature is maintained while the station is idle or washed instead of allowing the showerhead to cool. The reduction in thermal cycling reduces the effect of different coefficients of thermal expansion between the coating on the component and the chamber component thereby reducing the small particles. As described above for some CVD processes, the desired thin film properties can be implemented by controlling the showerhead temperature along with other processing parameters. For example, low showerhead temperatures are desirable for high tension silicon nitride spacers.

There are two main types of CVD showerheads, usually chandeliers and flush mounts. Similar to a chandelier, the chandelier showerhead has a stem attached to a contact plate on one end and on top of the chamber. A portion of the stem may protrude from the chamber to enable connection of RF power and gas lines. The flush mount showerheads are integrally formed with the top of the chamber and do not have a stem. The present invention relates to the temperature at which the chandelier shaped showerhead is controlled.

To control the temperature, heat based on the showerhead temperature is added or removed. The showerhead temperature is such that (1) charged particles collide with the showerhead to split energy, (2) the applied RF energy is coupled to the showerhead, and / or (3) External heat is increased when the plasma is activated because it is intentionally added, for example by electrical energy from an electric heater. The showerhead temperature decreases as cooler material enters the chamber, for example a reactant gas at lower temperature or a wafer at ambient temperature, conducts heat conduction through the showerhead stem material up to the ceiling of the chamber and the showerhead surface The showerhead temperature decreases when heat is removed by radiation from the. Some of this heat is generated as part of normal chamber operation, and other heat can be used to control the showerhead temperature.

3A, 3B and 3C are cross-sectional views of a showerhead according to various embodiments of the present invention. In connection with FIG. 3A, the showerhead 300 includes a stem 304, a back plate 306 and a face plate 310. The stem 304 may be divided into upper and lower cross sections, which have different diameters. In one embodiment, the upper stem has a diameter of about 1.5 to 2 inches, preferably about 1.75 inches. The lower stem diameter is approximately 2-2.5 inches, preferably approximately 2.25 inches. The contact plate diameter may be formed somewhat larger or similar and somewhat larger than the wafer size, which is preferably approximately 100% to 125% of the wafer size. For example, in a 300 mm (12 inch) process chamber, the contact plate diameter may be formed to a size of approximately 13 inches or approximately 15 inches. The contact plate and the back plate may each have a thickness of about 0.25 to 0.5 inches or about 0.125 to 0.5 inches. The contact plate may be made of aluminum, anodized or coated aluminum, or other material designed to be resistant to high temperatures, chemicals, and plasma.

In one embodiment, the back plate is approximately 0.5 inches thick and the contact plate is approximately 3/8 inches. Reactant gases are introduced through the gas inlet channel 302 in the showerhead stem 304, flow past the back plate 306 and between the back plate 306 and the contact plate 310. Flows into region 308. In FIG. 3B, a baffle 312 distributes the gas evenly through the manifold region 308. The barrier 312 may be attached to the back plate 306 via a number of screws 344 and threaded holes 342 or threaded inserts in the barrier plate. The volume of the manifold region is formed by the gap between the back plate and the contact plate. The gap may be formed in approximately 0.5 to 1 inch, preferably approximately 0.75 inch. In order to maintain a constant gas flow in the gap, the gap is consistent with many separators / spacers 332 located between the rear plate and the contact plate at various locations, for example, 3, 6 or 10 positions. I can keep it. As shown, a screw 338 secures the back plate 306 through the separator / spacer 332 relative to the contact plate at threaded blind holes 328. In other embodiments, various types of bushings or spacers may be used, with or without internal screws. Although the illustrated screw introduces the rear plate and the screw into the contact plate, the reverse configuration can be used. For example, a screw may fit into the contact plate and enter the through hole in the back plate through the spacer. The screw can be secured to the back plate using nuts.

The gas enters the processing region through through holes or holes 334 in the contact plate 310 to cause deposition on the surface of the wafer. The through hole can be machined, milled or drilled. Each hole may be approximately 0.04 inches in diameter or 0.01 to 0.5 inches in diameter. Some holes may have different sizes. 100 to 10,000 or 2 to 5000 or about 3 to 4000 or about 200 to 2000 holes may be formed. The holes may be evenly distributed across the contact plate in various patterns, such as honeycomb patterns or larger circles. Depending on various factors, including desired thin film uniformity, thin film profile and gas flow, the holes may be distributed more densely at the center of the contact plate or relatively more uniformly at the edges of the contact plate. It can have various patterns of distribution. In one embodiment, the hole may have a circular pattern in which a space is constantly formed along with a hole disposed further and further spaced apart from the center. In general, various hole patterns and densities can be used.

In some cases, the contact plate 310 is detachably attached to the back plate 306 so that the through hole / hole shape can be more easily changed and the contact plate can be cleaned. The back surface of the contact plate 310 may include mating features for attaching and detaching from the back plate. As shown, the engageable features may be grooves 330 and screw blind holes 346. The recess 330 is engageable by engaging onto a corresponding lip on the rear plate. Screw holes 340 on the back plate or contact plate are located in the circumferential direction and matched with the holes 346. A screw attaches the back plate and the contact plate together. The number of screws located in the circumferential direction may be 4 or more, 10 or more, and may be about 24 or about 50. Other coupling features for the back plate and the contact plate can be used. For example, other fastening mechanisms may include straps or clips, or a simple friction formed based on engagement, wherein the dimensional shaping of the contact plate is matched with the dimensions of the corresponding receptacle in the back plate. Can be used in place. As shown in FIG. 3A, the contact plate may include a circumferential sidewall having a ledge. The back plate may be located on the ledge and the screw may be attached to the back plate. In one embodiment, the interlocking jaw mechanism is such that notches, particularly machined on the peripheral side wall edge of the contact plate or back plate, engage with the teeth on the counterpart. Used in place. The back plate and contact plate may be attached by friction when the showerhead is heated and the teeth and notches extend. The mechanism involving the non-moving part may be preferably screwed and the screws should be threaded and detached by detaching the particles. Yet another possible mechanism involves threads on the peripheral side walls of the back plate or contact plate, which can be threaded into their respective counterparts. Despite the coupling features and the fixing mechanism, the back plate and the contact plate are attached to maintain good electrical and thermal contact therebetween.

During operation, the showerhead contact plate may have stressful conditions in the chamber. For example, from a change to a very high temperature, for example 300 ° C., thermal stress can degrade the material and form a back plate or contact plate to warp. In operation, the plasma can corrode the surface material, causing small particles and weak spots. The reactant may also corrode the contact plate with a chemical attack, for example fluorine gas. When a thin film is formed on the surface or affects the plasma properties in the case of aluminum fluoride, undesired deposition of by products or reaction products may obstruct the gas flow holes that affect the performance of the treatment, It can cause particles. Cumulatively, this case can affect processing performance in terms of small particles, uniformity, and plasma performance. The ability to clean or replace the contact plate is cost effective without having to replace the entire showerhead assembly.

In FIG. 3A, a heater 314 may be thermally attached to the back plate 306. The heater 314 may be an electric heater and may be enclosed within the back plate 306. The heater may be attached by a vacuum brazing process. The heater coil 314 is controlled by heater wires 316 connected to the coil through the stem. Since the showerhead is subject to high RF energy during chamber operation, all or some heaters are insulated and spaced from the RF. The RF isolation may be performed through an EMI / RFI filter or other commercially available RF isolation device. In some embodiments, the heater is not used.

3C shows a somewhat different cross section of the showerhead to emphasize other elements. Thermocouple 318 makes thermal contact with contact plate 310 to measure the contact plate temperature. The thermocouple 318 is connected from the upper stem through a standoff 320 between the back plate 306 and the contact plate 310. At the point of contact plate 310, the thermocouple may contact the contact plate material in the thermocouple contact hole. Similar to the heater wire and element, the thermocouple is also spaced from and insulated from RF. The RF isolation may be performed through an RF filter at another frequency and an RF trap at another frequency. In other embodiments, other temperature sense devices may be used to measure the temperature of the contact plate. In particular, a non-contact temperature sensor can be used. Examples include pyrometry, temperature measurements based on fluorescence emission, and infrared temperature measurements.

The temperature controlled showerhead is reinforced with heat removal by conduction, convection and radiation. Heat is performed spaced apart through the showerhead stem itself, and the showerhead stem is connected to the top of the chamber. The stem diameter can be designed to maximize conductive heat loss to the top of the chamber. Heat is also removed by convection through the cooling fluid flowing in the convective cooling fluid passage in the stem 304. The embodiment of FIG. 3B includes a cooling fluid inlet 322 through which cooling fluid can flow, such as, for example, washing dry air (CDA), argon, helium, nitrogen, hydrogen or a mixture of these. The fluid may flow in a spiral path below the stem. The helical path is shown in FIG. 3B through the opening 324 of the convective cooling fluid passage. The cooling fluid exits the stem through one or more cooling fluid outlet channels 326. In one embodiment, two cooling fluid outlet channels are provided. Although the example herein uses a helical passageway and uses two outlet channels, those skilled in the art can design another meandering passageway to effectively transfer heat from the showerhead to the cooling fluid. .

The fluid cooling channel is designed such that the outflow fluid can be completely heated to the temperature of the showerhead stem. Since the contact plate temperature and the stem temperature are related to each other, it is possible to estimate the contact plate temperature by measuring the temperature of the effluent fluid. The effluent fluid temperature can be measured spaced from the electromagnetic interference caused by RF. This can avoid the use of thermocouples in the combined RF filter circuit of the showerhead inner portion and the showerhead.

In another scenario, the cooling fluid can be further adjusted to control the amount of cooling. A feedback loop based on the effluent fluid temperature can increase or decrease the flow to change the amount of cooling. Such cooling may add or replace heat on the back plate. To require less applications, the cooling can be used to control the showerhead temperature and the heater element and RF isolation device can be omitted. In more demanding applications, adjustment of the cooling fluid is an additional parameter for controlling the showerhead temperature.

In addition to conducting convection, heat may be radiated away from the showerhead from the back plate. In order to improve spinning cooling, the outer surface of the back plate may be coated with a high emissivity material. For example, the coating can be aluminum with an anode formed. The radiation can be absorbed by the top of the chamber. The chamber top may also be treated with high emissivity material to increase radiant heat transfer. The inner surface of the upper part of the chamber may be coated and assembled with aluminum having an anode formed thereon. The chamber top may be cooled independently with a heated cooling water line.

Conductive and radiant heat removal keeps the showerhead at a sufficiently low temperature so that the electric heater can accurately heat it from the rear. Without the heat removal, the showerhead temperature remains uncontrolled and at a high temperature. The heat removal forms a headroom for temperature control. In one embodiment, the heat removal causes the showerhead temperature to be present at approximately 200 ^° C. or less. The heater is a simple coil around the diameter of the back plate because most of the heat transfer between the contact plate and the back plate is around the parameter. More thermal contact between the showerhead and the back plate can improve temperature control because of increased conductive heat transfer and thus heat loss through the stem.

Control system

A cooling system connected to one or more showerhead stems cools the convective cooling fluid flowing through each showerhead stem. The cooling system includes a liquid cooled heat exchanger and includes a connection to the showerhead. 4 is a block diagram of a cooling system according to an embodiment of the present invention. In this embodiment, the heat exchanger 401 is connected to four showerheads 411, 413, 415 and 417. The convective cooling fluid flows continuously through the formalities of the heat exchanger 401 and through each showerhead. The convective cooling fluid enters the system at inlet 409 where fluid enters the first showerhead stem. After flowing through either showerhead, the convective cooling fluid is then cooled by a cooling coolant in the heat exchanger before flowing through the showerhead. After final cooling through the final compartment in the heat exchanger, the convective cooling fluid exits the cooling system at outlet 411. The convective cooling fluid may be wash dry air (CDA), argon, helium, nitrogen, hydrogen, or a mixture of one or more of these gases. In one embodiment, the convective cooling fluid is facilities provided with CDA at plant pressure. Different flow rates require different plant pressures. For example, 100 slm (standard liters per minute) of CDA can be used at a plant pressure of 80 psi. Emissions can be formed at approximately ambient temperature and pressure or at somewhat higher temperatures and pressures. Although the open system is shown in a position where the convective cooling fluid does not return to the system, the concept of intermediate cooling through a heat exchanger and a series of flow through the showerhead can be performed as a closed system. have.

In some embodiments, the outflow of cooling fluid temperature from the showerhead is measured and used to determine the showerhead temperature. Temperature sensors 441, 443, 445 and 447 may be thermally coupled to the effluent cooling fluid and may also be formed outside the range of RF interference. The shape can eliminate the need for an RF filtering device. As mentioned above, the convection cooling passage is designed such that the outlet cooling fluid temperature is equal to the temperature of the showerhead stem. Thus, one skilled in the art can design an algorithm to correlate the measured outlet fluid temperature to the showerhead temperature while noting the thermal properties of the various components.

In certain embodiments, the showerhead may not include a heater attached to the back plate. The showerhead temperature increases preheating and remote plasma cleaning during processing. In this embodiment, active cooling from the cooling fluid can be used to control the showerhead temperature. Control valves 421, 423, 425 and 427 control the flow of cooling fluid to the showerhead based on input from the controller. The cooling fluid may flow into the showerhead stem or may be diverted to a bypass loop 431, 433, 435, 437. Generally cooling may be performed based on the flow of cooling fluid to the showerhead. Only active cooling designs may be appropriate in less demanding applications where the range of acceptable showerhead temperatures is larger. In such embodiments, the showerhead temperature may be measured at the showerhead via contact thermocouple or non-contact heat sense means or determined based on the outlet cooling fluid temperature.

In one embodiment, four showerheads and four compartments are shown in FIG. 4, but the cooling system can be designed with another number of showerheads and compartments. In some cases, the cooling system may be provided to cool the showerhead for many semiconductor processing process tools. If each semiconductor processing process tool has any one multi-station chamber with four stations each, a cooling system with eight compartments connected to eight showerheads may be designed to provide two tools. Some semiconductor processing tools may have many multistation chambers. In that case the cooling system can be designed to provide all the showerheads in many chambers on a single tool. If a four compartment heat exchanger is used on a tool with many four station chambers, many heat exchangers per tool can be used.

In some cases one or more showerheads may be bypassed for convective cooling fluid flow as a whole. As such, each showerhead connection may comprise a bypass loop having a corresponding valve. For certain processing processes, not all stations are required to require a temperature controlled showerhead or to deposit material onto the wafer. In this case the bypass loop can be used at station 4.

Liquid coolant for the heat exchanger 401 flows into the coolant path 403 prior to entering the system at the inlet 405 and exiting the system at the outlet 407. Although only one loop is shown for the coolant path 403, the coolant path may consist of many loops depending on the required heat transfer, coolant temperature at the inlet and coolant temperature at the outlet, and diameter of the coolant path. Can be. The liquid coolant may be water or any other form of well known liquid coolant such as Freon. In one embodiment, the liquid coolant is a facility in which water is delivered. After exiting the heat exchanger, the liquid coolant may or may not be treated, for example prior to further removal to the drain. For example, facilities carried with water, such as liquid coolant, can be discharged directly. However, if other liquid coolant is used, the coolant may be compressed and recycled back to the heat exchanger, which is formed in a closed loop cooling system.

Different designs of the heat exchanger 401 can be used. 4 shows a cross flow heat exchanger whose flows flow approximately perpendicular to each other. However, counter flow or parallel flow heat exchangers can be used. One skilled in the art can design a heat exchanger with sufficient surface area to cause the intended heat transfer. In one embodiment, the heat exchanger 401 may be a cast metal surrounding the convective cooling fluid piping and the liquid coolant. The metal can be aluminum or any other metal having intended heat transfer properties. The cast metal design allows for dense heat exchangers with little footprint or space requirements.

Temperature control system

The showerhead temperature control system includes a controller, a cooling system, and one or more showerheads for controlling the temperature of each showerhead. 5 illustrates the main components of the temperature control system in relation to either showerhead. The showerhead graph in the figure includes an attachment portion to the top of the chamber. Convective cooling fluid flows from component 502 to the showerhead where it is heated in a processing process to cool the showerhead and exits to heat exchanger 506. In some embodiments, the cooling fluid flowing to the showerhead is regulated by a control valve or other flow regulator 522. By adjusting the flow, the cooling provided by the cooling fluid can be increased or decreased.

As mentioned above, convective cooling fluid from the heat exchanger may flow to another component, such as 504. If the showerhead is formed like a first station in the chamber, component 502 may be an air facility and component 504 may be another showerhead, such as a station showerhead. If the showerhead is not formed like a first station, components 502 and 506 can be the same component, a liquid cooled heat exchanger as described above. The cooling loop may not have a feedback back loop, which is generally the place where cooling is adjusted. The simple design may cool the showerhead sufficiently to allow the electric heater 518 to precisely heat the showerhead to a constant temperature.

Thermocouple 510 is in physical contact with the contact plate as described above. Thermocouple 510 is coupled to RF isolation device 512 to remove the effect of RF applied on the showerhead, such as an electrode, from the thermocouple signal. Typically, RF applied in PECVD has two frequencies, high frequency (eg 13.56 MHz) and low frequency (eg 400 kHz). The RF isolation device includes a high frequency filter and a low frequency filter. Without RF insulator, thermocouple measurements are useless because the RF interference is too large.

A schematic of the possible shape of the RF isolation device is shown in FIG. 6. The thermocouples 510/601 are surrounded by a stainless steel sheath. The sheath is wound into a coil 603 parallel to the capacitor 605. Coils such as inductors and capacitors form a tank circuit that blocks 13.56 MHz signals. The coil may have an inductance of approximately 1 microhenry and the capacitor 605 may have a capacitance of approximately 85 picofarads (pf, picofarads). Remaining 13.56 MHz RF is shortened to ground 609 with a second capacitor 607, which may have a capacitance of approximately 10000pf. In addition, the high frequency trapping together with the sheath blocks the RF in the thermocouple wire formed by fitting in the sheath. The 400 kHz frequency is not blocked by reference numerals 603/605, and due to its low frequency it is not formed short by the capacitor 607 to ground. There is still 400 kHz noise that is continuously filtered out by the low frequency filter 611 at the end of the 13.56 MHz filter. In either design, the low frequency filter may be an LC design similar to a two-stage low pass filter. Both stages can be LC designs similar to high frequency filters. The low frequency filter may be directly connected to the thermocouple wire, but the high frequency filter may be connected only to the sheath.

5, the filter element 518 is connected to an RF isolation device 508. RF isolation device 508 may be an RF filter or other available device for isolating the heater electrical signal from the effect of an applied RF. The temperature controller 516 obtains temperature information from the thermocouple 510 via an isolation device 512 and inputs to the heater 518 via the RF isolator 508 in a feed back loop. Adjust the input.

In yet another embodiment, the effluent cooling fluid temperature may be measured by a temperature sense device 520 located outside the range of RF interference. In this embodiment, an RF filter is required for the temperature sensor device 520. The controller is associated with the outlet cooling fluid temperature relative to the showerhead temperature.

The temperature controller 516 can also obtain feed forward information from the component 514. The feedforward information may be a time period until the plasma is activated. In some cases, the feedforward information may include other foreseeable cases that affect the showerhead temperature, such as gas flow flowing into the showerhead, wafer processing with cooling wafers. The controller can increase the input of the heater by foreseeing the case of cooling, for example a chamber purge, or reduce the input of the heater by predicting the case of active heating of the plasma. The controller can also increase the cooling by increasing the cooling fluid flow in anticipation of the case of heating or reduce the cooling by reducing the cooling fluid flow in anticipation of the case of cooling.

Various combinations of input and output components can be used in different control configurations. For example, active cooling (adjustment of cooling fluid flow) may use active heating (heater in the back plate) to precisely control the showerhead temperature. The showerhead temperature may be measured directly from the thermocouple attached to the contact plate or indirectly determined from the outlet cooling fluid temperature. In some cases, only active cooling or only active heating may be included in the control system. Other inputs may still be included, such as measuring the temperature of the cooling fluid at the inlet to precisely determine the heat removed from the showerhead.

In some embodiments, the temperature controller may be integrally formed with the system controller. In this case component 514 is not separated from controller 516.

Experiment

The showerhead temperature control system is performed according to the present invention. The control system carried out includes a controller using a feed back input (thermocouple only) and a temperature controlled showerhead as described above. The showerhead temperature for the four station chambers is measured over 50 wafer runs and is configured in FIG. 7. The temperature for each of the four of several showerheads is constructed on separate curves. The set point is 260 ° C. The temperature measured for station 1 is equal to line 701. The temperatures measured for stations 2-4 are very close to each other and are like line 703. As shown in FIG. 1, the plasma conditions are also configured by staged donation at 705.

The difference in showerhead temperature is sharp compared to FIG. 1 where the heater is off and the temperature is not controlled. During dummy deposition up to approximately 1800 seconds, the showerhead temperature operates similar to that of FIG. The temperature stabilizes rapidly after wafer deposition starts at approximately 1800 seconds. For at least the showerheads of stations 2-4, the temperature stabilizes faster. The temperature 701 of station 1 is inclined downward for approximately 500 seconds to the bottom of approximately 256 ° C., but recovered and maintained at the set remaining during the wafer processing.

 The data can be controlled using a temperature controlled plot so that the showerhead temperature exceeds approximately 4 ° C. within 50 wafer batches. Since the data is formed without using feedforward control, implementation involving feedforward control can improve response to a degree of less than approximately 4 ° C.

In another test, the wafer-to-wafer results of the deposition ratio for Tetraethylorthosilicate (TEOS) are studied using a temperature controlled showerhead and a standard showerhead according to the present invention. The standard showerhead does not include the temperature control feature of the present invention. The standard showerhead does not include a cooling mechanism or a heater. To test the responsiveness of the temperature controlled showerhead to changing conditions, 100 wafers were deposited with each showerhead under four conditions. Prior to each condition, the processing chamber is subjected to remote plasma clean (RPC), where the plasma is ignited from the gas into a chamber located remotely from the processing chamber. Plasma-activated species from the RPC chamber flow through the delivery line towards the treatment process chamber. As such, the RPC is performed before the wafers 1, 26, 51 and 76. In a first condition, TEOS is deposited for 12 seconds per wafer and the deposition thickness is measured. In a second condition, after the RPC the showerhead is cooled with nitrogen gas from the reaction channel for 20 minutes. After approximately 20 minutes of cooling forced with approximately nitrogen gas in a standard showerhead, the showerhead temperature reaches approximately 240 ° C. In a third condition, the process chamber is idle after RPC (be idled overnight). During this idle period, the pedestal is heated to approximately 350 ° C., so that within the standard showerhead the showerhead is balanced to a temperature less than 350 ° C. over the period. In a fourth condition, after the RPC the showerhead is heated to a high power plasma for 20 minutes. Nitrogen is used to generate the plasma at a flow rate of approximately 10 slm. The chamber pressure is maintained at approximately 1500 Watts of high frequency power and approximately 2.5 Torr.

8A and 8B show the configuration of the thickness deposited in angstroms for each measured wafer. Six wafers were measured for each condition. Region 801 matches for the first condition as described above. After the RPC, the showerhead temperature is raised because the heat dissipation at the showerhead surface detaches energy. The standard showerhead is kept at a higher temperature for as long as possible without additional cooling in the temperature controlled showerhead as shown by the thickness data. TEOS deposition rates are higher at higher showerhead temperatures. After some wafers, the deposition in the standard showerhead and the temperature controlled showerhead is increased slowly after reduction. The temperature controlled showerhead maintains a relatively stable deposition rate, but the deposition rate begins to decrease over the standard showerhead again. The second decrease in the standard showerhead station contributes to the effect of the cooling wafer entering the station, such as the temperature decrease shown on curve 102 of FIG. 1. The data shows that after the RPC sequence the temperature controlled showerhead is balanced to a constant temperature and therefore the deposition rate is faster than the standard showerhead.

Region 802 corresponds to the second condition. After the RPC sequence the process chamber is cooled with nitrogen. The deposition using a temperature controlled showerhead in this area is initially less affected and there is less drop in deposition thickness than the standard showerhead. Region 803 corresponds to the third condition. After overnight idling, deposition using a temperature controlled showerhead has the same characteristics as after the RPC sequence. The deposition initially dips and maintains a relatively constant value. Although the deposition parameters are the same, the standard showerhead maintains a lower deposition rate in the region 803 than in another region. Finally, region 804 corresponds to the fourth condition. After the RPC sequence, the high energy plasma heats the showerhead to a higher temperature than the RPC itself. In a standard showerhead, a high deposition rate is recorded in area 4. After the initial dip of deposition, the thickness can be balanced at higher values. For temperature controlled showerheads, high energy plasmas probably do not affect deposition except the first wafer.

In total, the thickness range measured for the standard showerhead is approximately 37 Angstroms and the thickness range measured for the temperature controlled showerhead is approximately 13 Angstroms. Wafer-to-wafer non-uniformity for the deposition is 3.7% for a standard showerhead and 1.3% for a temperature controlled showerhead. Better wafer-to-wafer uniformity for temperature controlled showerheads is 66% better than that of standard showerheads.

Although various descriptions have been omitted for clarity, various designs may be performed. Therefore, the present examples are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.

1 shows a graph of showerhead temperatures in four station chambers over time.

FIG. 2A shows a graph of silicon nitride spacers deposited at various showerhead temperatures. FIG.

FIG. 2B shows a graph of film stress for silicon nitride spacers deposited at various showerhead temperatures. FIG.

3A, 3B and 3C illustrate cross-sectional schematics of a temperature controlled showerhead in accordance with various embodiments of the present invention.

4 is a diagram illustrating a configuration of a cooling system according to an embodiment of the present invention.

5 is a diagram illustrating a configuration of a temperature control system according to an embodiment of the present invention.

6 shows a schematic diagram of one embodiment of an RF filter for reducing or removing RF noise.

7 shows a plot of showerhead temperature measured using a temperature controlled showerhead in accordance with the present invention.

FIG. 8A shows a chart showing TEOS thin film thickness versus 100 wafers using standard showerheads and having four different starting conditions.

FIG. 8B shows a chart showing TEOS thin film thickness versus 100 wafers using a temperature controlled showerhead and having the same four starting conditions.

Claims (26)

In a temperature controlled showerhead for chemical vapor deposition (CVD), the showerhead is (a) a stem comprising a convection cooling fluid passage, (b) a rear plate thermally coupled to the stem, (c) a heater physically attached to the back plate, (d) a contact plate thermally coupled to the back plate, (e) a temperature controlled showerhead for chemical vapor deposition comprising a temperature sensor for measuring the temperature of the contact plate. The showerhead of claim 1, wherein the temperature sensor is a thermocouple physically attached to the contact plate and further comprises a radio frequency (RF) filter electrically coupled to the thermocouple. 2. The showerhead of claim 1, further comprising an RF filter electrically coupled to the heater. The showerhead of claim 1, wherein the outer surface of the back plate comprises an aluminum coating with anodization. The showerhead of claim 1, wherein the heater is formed to fit within the rear plate. The showerhead of claim 1, wherein the contact plate is removably attached to the rear plate. The showerhead of claim 1, wherein the stem has a diameter of 1.5 inches to 2.5 inches. The showerhead of claim 1, wherein the contact plate and the back plate have a thickness of 0.25 inch to 0.5 inch. The showerhead of claim 1, wherein the gap between the back plate and the contact plate is between 0.5 inch and 1 inch. The showerhead of claim 1, wherein the contact plate has a diameter of 13 inches. 3. The showerhead of claim 2, further comprising a standoff between the back plate and the contact plate through which a thermocouple is attached to the contact plate. In a temperature controlled showerhead for chemical vapor deposition (CVD), the showerhead (a) a stem having a convection cooling fluid passage, (b) a rear plate thermally coupled to the stem, (c) a contact plate thermally coupled to the back plate, The convection cooling fluid passageway is configured such that the outlet cooling fluid temperature is equal to the stem temperature. 13. The showerhead of claim 12, further comprising a temperature sensor configured to measure the outflow cooling fluid temperature. 13. The showerhead of claim 12, wherein the outer surface of the back plate comprises an aluminum coating with anodization. 13. The showerhead of claim 12, wherein the contact plate is removably attached to the back plate. 13. The system of claim 12, wherein the stem has a diameter of 1.5 inches to 2.75 inches, the contact plate and the back plate have a thickness of 0.25 inches to 0.5 inches, and the gap between the back plate and the contact plate is from 0.5 inches to 1 inch and the contact plate has a diameter of 13 inches to 15 inches. In a temperature controlled showerhead contact plate for chemical vapor deposition (CVD), the contact plate is (a) a planar, circular anterior surface, (b) a planar and circular rear surface comprising a plurality of threaded blind holes and comprising a mating feature that engages against the rear plate, (c) a plurality of small through holes for gas flow, Contacting the rear plate of the showerhead including a stem having a passage of convective cooling fluid, a rear plate thermally coupled to the stem, a heater physically attached to the rear plate and a temperature sensor for measuring the temperature of the contact plate Showerhead contact plate, characterized in that the plate is attached. 18. The showerhead contact plate of claim 17, wherein the engagement feature comprises a peripheral side wall. 18. The joining feature of claim 17, wherein the engagement feature includes an interlocking jaw mechanism in which a notch machined on the peripheral side wall edge of the contact plate or rear plate engages and interlocks with the teeth on the counterpart. Showerhead contact plate. 18. The showerhead contact plate of claim 17, wherein the plurality of small through holes is between 100 and 10,000 through holes. 18. The showerhead contact plate as recited in claim 17, wherein the plurality of small through holes is between 3 and 4000 through holes. 21. The showerhead contact plate as recited in claim 20, wherein said small holes form a pattern of non-uniform distribution. 18. The showerhead contact plate of claim 17, wherein the plurality of small through hole diameters is between 0.01 inches and 0.5 inches. 18. The showerhead contact plate as recited in claim 17, wherein said contact plate has a thickness of 1/8 inch to 1/2 inch. 18. The showerhead contact plate of claim 17, further comprising a thermocouple contact hole. 18. The showerhead contact plate of claim 17, further comprising a plurality of spacers coupled to one or more screw blind holes.

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