EP1434897A1

EP1434897A1 - Method and device for depositing a plurality of layers on a substrate

Info

Publication number: EP1434897A1
Application number: EP02779322A
Authority: EP
Inventors: Markus Schumacher
Original assignee: Aixtron SE
Current assignee: Aixtron SE
Priority date: 2001-10-08
Filing date: 2002-09-07
Publication date: 2004-07-07
Also published as: US20040255856A1; WO2003031677A1; WO2003031677B1

Abstract

The invention relates to a method for depositing a plurality of layers on a substrate using gaseous starting materials, whereby the layers are deposited in one single process chamber in successive process steps. The gas phase composition and/or the substrate temperature is varied without the process chamber being opened in the interim, in such a way that layers of different quality can be deposited successively in one deposition chamber.

Description

Method and device for depositing a plurality of layers on a substrate

The invention relates to a method and a device for depositing a number of layers on a substrate by means of gaseous starting materials.

WO 01/14619 A1 describes a device for the deposition of, in particular, silicon carbide or silicon germanium carbite.

WO 01/61071 describes a device by means of which OLED "S or similar layer structures can be applied to a substrate.

WO 01/57289 A1 relates to a device for depositing one or more layers onto a substrate, liquid or solid substances being used as the starting material, which are introduced into the process chamber in gaseous form.

In the area of integrated MIM structures (metal-insulator-metal) in highly integrated CMOS components, deposition processes are used for the layer deposition of electrodes and dielectrics (here especially oxidic dielectrics), which usually run sequentially in different deposition systems (chambers) and usually also on different deposition methods (physical, such as PVD or chemical processes (MOD); here specifically chemical vapor deposition, CND for short, or MOCVO (metal-organic chemical vapor deposition)). In addition to the need for an extremely high degree of automation when transporting the substrates to be processed between the different process chambers, there is an increased disadvantage due to the complexity

obviously the process stability, but also the "cost of ownership" when maintaining the various deposition systems. When handling the substrates to be coated between the individual process chambers, high handling, cooling and heating times are normal today, but they have a significant negative impact on the minimum required wafer throughput in the large-scale production of components. In particular, a central component-related point is the problem that between the deposition of the bottom electrode and the dielectric or between the deposition of the dielectric and the top electrode (especially as is customary in the production of the so-called "gate stack" of the integrated MOS transistor) Change such as B. caused by ner contaminations of the surfaces during the wafer handling (wafer transport between the deposition steps) a negative influence on the electrical component properties by interface states.

The invention has for its object to develop an apparatus and a ner driving that reduces, bypasses and eliminates the disadvantages mentioned above.

The task is solved by depositing the layer structure without changing into other deposition systems or chambers.

The layers are deposited in a single process chamber in successive process steps by merely changing the gas phase composition and / or the substrate temperature. The layer sequence comprises in particular at least one oxide layer, on which a metal layer or a metal layer, on which an insulating layer and a metal layer is applied. The ner driving is also characterized in that the process chamber is pumped out between the individual process steps and / or is flushed with inert gas. This brings the pressure inside the process chamber to a value that is considerably lower than the process pressure. The walls of the process chamber can be tempered in different ways. When changing the gas phase, the process chamber can be flushed with noble gases, Ar, He, H ₂ or Ν ₂ . During this rinsing phase, the substrate holder on which the substrate is located and a gas inlet element arranged above the substrate holder can be brought to an optimal process temperature. The process chamber walls through which the gas can escape can also be brought to the required temperature in this way. This avoids condensation of the starting materials introduced in gaseous form into the gas phase, which can also disintegrate there.

The gas phase is individually tempered by the actively heated wall of the process chamber or by the wall of the process chamber heated by means of heat conduction, so that the required gas phase reactions between the starting materials or the decomposition of the starting materials is optimized. The gas inlet system can also be cooled in some areas so that pre-disassembly or pre-reactions are prevented. The deposited layers have different tasks. For example, the metallic layer serves as an electrode. There is an insulating layer between these two electrodes, so that a capacitor is built up from the metal-insulator-metal layer system. The metal layers are contacted in a known manner in the process steps following the coating step, in which, among other things, the substrate is divided. According to the invention, substrates are alternately coated with conductive and insulating layers in a multi-process chamber in a sequential, non-reactive CVD coating. The process chamber consists of a vacuum-tight chamber, a temperature-controlled substrate holder, a gas inlet element and a gas outlet element to which a pump is connected. The substrate holder, like the ceiling of the process chamber opposite the substrate holder, can be tempered. This can be done using an electrical resistor, infrared radiation or electromagnetic high frequency. A necessary cooling can be done with a liquid medium (H2O or similar). The process chamber walls can also be heated in this way. In a preferred embodiment, the substrate holder can also be driven in rotation via a rotary drive. The substrate holder itself can again have rotationally driven substrate carrier plates which circle like a planet around the center of the substrate holder. The temperature measurement in the substrate holder can be carried out by means of a thermocouple, the supply of which is carried out through the rotating union. The process chamber preferably has intermediate volumes in the region of the surfaces which define and delimit the geometry of the reaction chamber. There is a gas in each of these intermediate volumes. It can also be the process gas. The pressure in the intermediate volumes as well as the gas composition in the intermediate volumes can be adjusted. As a result, the thermal conductivity of the intermediate volumes can be set. This allows the temperature of the process chamber walls to be checked. The walls of the two volume can be very thin, inert quartz glass plates. It is also provided that such plates are thermally coupled to the walls. The gases in the intermediate volumes can have different gas compositions, for example hydrogen and nitrogen. Water cooling is also provided.

In a development of the invention it is provided that the process gases are introduced into the process chamber in a pulsed manner. The process gases can be generated from liquid or solid starting substances. For example, they can come from evaporators. There they are brought into a gaseous state by tempering. The transition from liquid starting materials into the gas phase is preferably carried out by non-contact evaporation. A gas stream can also flow through the liquid containers in which the liquid starting materials are located.

The carrier gas stream then saturates with the gas of the starting material. For temperature control, in particular for heating or also for cooling the process chamber walls and the process chamber ceiling, a thermal coupling of the process chamber ceiling or process chamber walls can be provided via a gas gap to a heat sink or to a heat source. Parasitic memory effects between different deposition sequences (dielectrics, electrodes; but also different dielectrics or electrodes) are avoided by pumping down the process chamber to a pressure below the process pressure. However, the pressure should not fall below the base pressure of the system. Residual contamination by chemical substances from previous process sequences is preferably monitored by measurement using a residual gas analyzer.

The layer thickness can be monitored in situ during the process using an optical method. In particular, it is provided to track the layer thickness growth using in situ ellipsometry.

To avoid the disadvantages described at the outset, the invention proposes a device and a method in which a complete MIM structure or at least parts of this structure can be produced in a single apparatus and in a single process step. The conductive (electrodes) and insulating layers (dielectrics, oxidic dielectrics) are produced here in particular according to the so-called sequential hetero wafer MOCVD process. The electrode / insulator layer system is applied in only one process chamber, in which the substrate to be coated remains in this one process chamber during the entire process flow without changing to other process chambers. In order to avoid parasitic memory effects between different process sequences, the process chamber is designed for minimal dead volumes. The contamination between the process sequences can be reduced to a minimum by pumping down the process chamber to a pressure lower than the process pressure (but minimally the base pressure of the process chamber). Residual impurities are monitored using a so-called RGA or residual gas analyzer. A continuous gas flow in a preferred direction is advantageous.

In the deposition of (oxidic) dielectrics and electrodes, organometallic starting substances (precursors) are usually used, which in the most general case are in the vapor pressure and also in the decomposition differentiate behavior. These precusors are either evaporated directly via so-called "bubblers" and introduced into the process chamber or introduced into one or more heated volumes (ina) (evaporator) via the solution of the precusors in a suitable solvent as a liquid / solid solution and introduced into the process chamber for reaction on the substrate to be coated. These precusors often have a very narrow process window between condensation and decay, which requires an exact temperature control of all bounding walls. However, in order to enable a quick adjustment of all wall temperatures when changing the process sequence, all the boundary surfaces defining the process chamber must have a low heat capacity, which is usually difficult to achieve. In order to avoid this problem, so-called intermediate volumes are introduced, which are adjustable in pressure and heat conduction, and are coupled to very thin, inert (eg quartz glass) walls facing the interior of the process chamber. The inner walls are thus tempered by heat transfer from the temperature-controlled process chamber outer wall via an intermediate thin volume which is adjustable in the heat conduction to the inner, thin inner wall facing the process chamber. The thermal conductivity properties of the intermediate volumes are set via a gas mixture of at least two gases with different thermal conductivity coefficients, which can also be freely adjusted in pressure. Different areas of the walls and the gas inlet can be tempered differently.

Embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

Fig. 1 A first embodiment of a CND system for performing the method. Fig. 2 shows a second embodiment of a CND system for performing the method.

The device shown in the drawings has a process chamber 6 which is enclosed on all sides. The process chamber 6 has a feed line which leads to a gas inlet element 7. This feed line can either be used to feed a process gas or a process gas mixed with a carrier gas into the process chamber 6 or a purge gas through the line 5.

The gas inlet member 7 consists of a flat cylindrical hollow body, the bottom of which has a plurality of openings arranged in a sieve shape, from which the gas can flow into the process chamber 6. In a spaced position parallel to the gas inlet element 7, there is a substrate holder 8 for receiving a substrate. Below the substrate holder 8, which can also be rotated by means not shown in the drawings, there is a heater 12. This heater can be an HF heater or an IR heater.

Not only the substrate holder 8 can namely be heated up to a temperature at which the process gases decompose. The walls of the process chamber housing 11 can also have heaters 13 in order to heat the walls. The wall temperature is lower than the temperature of the substrate holder 8.

A gas discharge line is located below the substrate holder 8. By means of this discharge, the unused gas is pumped out of the process chamber 6 by a pump 10. There is a residual gas analyzer 9 in the gas discharge line, which analyzes the composition of the gas pumped out of the process chamber 6 by mass spectrometry.

The two exemplary embodiments shown in the drawings differ essentially in the shape of the sources. For the sake of clarity, only a single source is shown in the drawings. A large number, in particular three sources, may be necessary for the deposition of metal-insulator-metal layers. A first source for providing an organometallic compound, for example an organometallic platinum compound for depositing the first metallization layer, a second source which contains a barium strontium titanium oxide, a so-called perovskite, for depositing a dielectric and a third source, for example a contains organometallic ruthenium compound for the deposition of the second metallization layer. Like the BST compound, the organometallic compounds can be dissolved in a solvent. You are then in a tank 1, into which carrier gas is introduced through a feed line 4. In the embodiment shown in Fig. 1, the tank acts as a wash bottle. In the exemplary embodiment shown in FIG. 2, the liquid in the tank is pressed through an ascending pipe into an evaporator 2. In both cases, the organometallic connection converted into a gas or the BST connection is fed to the gas inlet element 7 via a pipeline which can be closed by means of a valve 3.

The procedure is carried out as follows:

In a first process step, a metal layer is deposited on the substrate lying on the substrate holder 8 by a Solvent dissolved organometallic material containing platinum is brought into a gas form. The substrate is preferably made of silicon. The starting material is fed together with the solvent to the shower head-like gas inlet member 7 and brought into the process chamber 6 through the openings of the gas inlet member 7. A suitable gas phase transport (convection and diffusion) brings the gas to the hot substrate holder 8, where a decomposition reaction takes place on the surface. A platinum layer is formed on the substrate as a reaction product. As soon as the required layer thickness has been deposited, the valve 3 is closed and an inert gas is introduced into the process chamber through the line 5. During the purging of the process chamber 6 with the inert gas, the pump 10 can lower the internal pressure in the process chamber 6 several times, so that an increased gas exchange takes place. The residual gas fraction is measured spectrometrically by means of the residual gas analyzer 9. The concentration of the solvent and the concentration of the organometallic compound are measured. If the concentration of the measured residual gas falls below a limit, the purging process is completed.

The rinsing process is followed by a second process step in which, instead of the organometallic platinum compound, a barium-strontium-titanium-oxygen compound, a so-called perovskite, is introduced into the process chamber 6 through the gas inlet element 7. It is important that the process chamber 6 is essentially solvent-free before the introduction of this gas, which deposits a dielectric, since the BST compound reacts very sensitively to solvents in the gas phase.

The stoichiometry of the barium strontium titanium oxide can be set by means of a suitable temperature or by means of suitable other process parameters. The dielectric of the dielectric layer can thus be influenced. Instead of a dielectric material, a ferroelectric material can also be deposited. Here too, when the required layer thickness, which can be measured in situ during growth, is reached, the gas flow is closed by closing a valve. Thereafter, as described above, the process chamber 6 is flushed, the output of the pump also being able to be briefly increased in order to lower the total pressure within the process chamber 6.

The residual gas fraction is also examined here spectrometrically by means of the residual gas analyzer 9. Here the oxygen concentration in the gas phase is monitored. If this falls below a limit, the rinsing process is ended. The second process step is followed by a third process step, which is essentially carried out in the same way as the first process step, except that an organometallic compound containing ruthenium is chosen instead of an organometallic compound containing platinum. After the third process step, the process chamber 6 can also be rinsed.

All of the features disclosed are (in themselves) essential to the invention. The disclosure of the associated / attached priority documents (copy of the pre-registration) is hereby also included in full in the disclosure of the application, also for the purpose of including features of these documents in claims of the present application.

Claims

EXPECTATIONS

1. A method for depositing a plurality of layers on a substrate by means of gaseous starting materials, characterized in that the layers are deposited in a single process chamber in successive process steps by merely changing the gas phase composition in the process chamber and / or the substrate temperature.

2. Device for depositing a large number of layers on a substrate by means of liquid starting materials introduced into a process chamber, characterized in that the gas phase composition and / or the substrate temperature for depositing a large number of layers on a substrate can be deposited without opening the process chamber.

3. The method or device according to one or more of the preceding claims or in particular according thereto, characterized in that the layer sequence comprises at least one oxide layer and a metal layer deposited thereon.

4. The method or device according to one or more of the preceding claims or in particular according thereto, characterized in that the process chamber is pumped out between the individual process steps and / or flushed with inert gas.

5. The method or device according to one or more of the preceding claims or in particular according thereto, characterized in that that the walls of the process chamber can be tempered to different temperatures or are tempered.

6. The method according to any one of the preceding claims, characterized in that in a first process step, a metal layer is deposited on the substrate or on a layer previously deposited on the substrate such that an organometallic starting material which is optionally dissolved in a solvent is brought into the gas phase is brought into the process chamber (6) together with the solvent by means of a shower head-like gas inlet element (7) and, after the supply of this starting material has been switched off, the gas inlet element (7) and the process chamber (6) are flushed with inert gas (5) , The exhaust gas pumped out of the process chamber (6) being analyzed, in particular by mass spectrometry, for residual constituents of the starting material or the solvent, and the purging process is terminated first when the minimum gas concentration, in particular the solvent concentration, falls below a minimum value.

7. The method according to claim 6, characterized in that in a second process step, a dielectric layer is deposited on the metal layer in that a perovskite, optionally dissolved in a solvent, is brought into the gas phase as the starting material, and optionally together with the solvent by means of the shower head-like Gas inlet member (7) is brought into the process chamber (6) and after switching off the supply of this starting material, the gas inlet member (7) and the process chamber (6) are flushed with an inert gas (5), the exhaust gas pumped out of the process chamber (6) in particular mass spectrometry on residual components of the it is analyzed and the purging process is only ended when the minimum gas concentration, in particular the oxygen concentration, falls below a minimum value.

8. The method according to claim 7, characterized in that in a third process step, a metal layer is deposited on a previously deposited dielectric layer, that an organometallic starting material, which is optionally dissolved in a solvent, is brought into the gas form and, if appropriate, mediated together with the solvent of the shower head-like gas inlet member (7) is passed into the process chamber (6) and, after switching off the supply of this starting material, the gas inlet member (7) and the process chamber (6) are flushed with an inert gas (5), the process chamber (6) Pumped-off exhaust gas is analyzed, in particular, by mass spectrometry for residual constituents of the starting material or solvent, and the purging process is only ended when the residual gas concentration falls below a minimum value.

9. The method according to one or more of the preceding claims or in particular according thereto, characterized in that the flushing of the process chamber (6) with the inert gas (5) is accompanied by one or more pressure changes.

10. The method according to one or more of the preceding claims or in particular according thereto, characterized in that the first metal layer is a platinum layer.

11. The method according to one or more of the preceding claims or in particular according thereto, characterized in that the dielectric see layer consists of a barium-strontium-titanium-oxygen compound.

12. The method according to one or more of the preceding claims or in particular according thereto, characterized in that the second metal layer is a ruthenium layer.