Method and apparatus for depositing a SiC layer on a substrate

Abstract

A method for depositing a layer on a substrate (9), comprising: supplying a uniform first gas flow through a gas inlet member (6) to a process chamber (4) brought to a process temperature, the gas flow flowing in a flow direction (S) over the substrate (9) and comprising one or more reactive gases whose decomposition products form a layer; and supplying a second gas flow into the process chamber (4) through a gas outlet surface of gas outlet holes (10, 10', 10") arranged downstream of the gas inlet member (6) and upstream of the substrate (9), the second gas flow comprising at least one reactive gas that affects at least the composition of the layer or the dopant concentration in the layer.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for depositing a layer on a substrate. A uniform gas flow is supplied through a gas inlet member into a process chamber heated to a process temperature. The gas flow passes uniformly in a laminar flow across the cross-sectional area of ​​the process chamber with a uniform flow direction. The gas flow streamlines may be parallel to each other or radial to the center. The gas flow in that direction over the substrate contains one or more reactive gases, the decomposition products of which form a layer deposited on the substrate. A second gas flow enters the process chamber through additional gas outlet holes located downstream of the gas inlet member and upstream of the substrate or a substrate holder supporting the substrate. The second gas flow includes a reactive gas that affects the composition of the layer within the layer, e.g., a dopant. [Background technology]

[0002] Patent Document 1 describes an apparatus having a process chamber for depositing semiconductor layers. At its center is a gas inlet member that supplies process gas to the process chamber, and the process gas flows radially around the process chamber onto a substrate positioned around the gas inlet member. The substrate is supported by a substrate holder supported by a purge gas. The purge gas can not only set the substrate holder in a rotational motion, but also affect heat transport to the substrate holder by changing the purge gas flow. Upstream of each substrate holder is a gas inlet port through which compensation gas is supplied to the process chamber to compensate for fluctuations in the purge gas.

[0003] Patent Document 2 describes an apparatus and method for depositing SiC. The method is carried out at a process temperature of more than 1600 degrees Celsius. Silicon-containing and carbon-containing reactive gases are supplied as reactive gases to the process chamber through a gas inlet member, and a gaseous dopant in the form of nitrogen N2 is supplied through the gas inlet member.

[0004] A similar apparatus is described in US Pat. No. 5,699,499. In both apparatuses, the substrate is supported by a substrate holder mounted on a susceptor and kept suspended by a purge gas. Gases that affect the dopant concentration in the layer are mixed with the purge gas to affect the incorporation of dopants in the layer.

[0005] Patent Document 4 describes a CVD reactor for depositing SiC layers, which includes a gas inlet member arranged upstream of a substrate in the flow direction. The gas inlet member has a gas inlet / outlet surface with a width greater than the width of the substrate. The gas outlet surface is divided into three regions, through which a mixture of hydrogen, propane, monosilane, and nitrogen is supplied to the process chamber, and the mixtures in the three regions may be different.

[0006] The goal of the last mentioned method is to ensure that the SiC layer deposited on the substrate has as uniform a dopant concentration as possible. In SiC layers deposited without additional dopant added to the purge gas forming the gas cushion, an increasing dopant concentration was observed towards the edge of the layer. This dopant concentration non-uniformity can be reduced by the measures described above. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] DE 10 2018 124 957 A1 [Patent Document 2] U.S. Patent No. 8,052,794 [Patent Document 3] U.S. Patent No. 10,930,492 [Patent Document 4] U.S. Patent No. 10,858,758 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to further improve the uniformity of the dopant concentration within a layer, and in particular to provide a means by which the layer composition can be locally influenced within the layer in a targeted manner. [Means for solving the problem]

[0009] This object is achieved by the invention specified in the claims, the dependent claims being independent solutions of the object as well as advantageous developments of the invention specified in the independent claims.

[0010] Whereas in the prior art an additional gas flow is created which affects the dopant concentration in the layer and which includes gases exiting the gas outlet face which are wider than the width of the substrate transverse to the flow direction, the present invention proposes to reduce the width of the gas outlet face to be smaller than the width of the substrate, resulting in the formation of a gas flow which follows streamlines extending in the flow direction and which, for example, has a different dopant concentration from adjacent gas flows. Gas flow along streamlines can expand due to diffusion effects, which affect the incorporation of dopants in a layer on a locally limited area of ​​the substrate surface. The gas inlet member of the present invention has a gas outlet surface with gas outlet holes arranged to provide as uniform a gas flow as possible to the process chamber. The effective width of the gas inlet member is greater than the width of the substrate transverse to the flow direction, so that a laminar first gas flow emerges from the gas outlet surface of the gas inlet member and flows through the process chamber in a uniform flow direction. The streamlines of the first gas flow extending linearly from the gas inlet member to the substrate may be parallel to one another, or may exit the gas inlet member in a star-like pattern, e.g., radially from the center of the process chamber. The concentration of the first gas flow is uniformly distributed across the entire cross-sectional area. To achieve this, the gas inlet member preferably has a gas outlet surface with multiple gas passage holes evenly distributed thereon and having the same area as one another. For example, if different reactive gases are supplied at different horizontal levels, the concentration of the first gas flow may be different in the vertical direction. However, within these horizontal levels, the gas flow is uniform. According to the present invention, a second gas flow is supplied to this uniform first gas flow downstream of the gas inlet member and upstream of the substrate. For this purpose, gas outlet holes whose width is smaller than the width of the substrate are used. As a result, a localized gas flow of dopant is formed, affecting the substrate only at a partial surface. The location of the partial surface depends on where at least one gas outlet hole is located on a line extending transversely to the flow direction. For example, if a gas outlet hole is located on a midline extending through the center of the substrate in the direction of the first gas flow exiting the gas inlet member, the dopant incorporation in the layer at the center of the substrate will change. On the other hand, if the gas outlet hole is located away from the midline, the dopant incorporation will increase in regions of the layer away from the center of the substrate. The streamlines of the second gas flow generated by the gas outlet surface can pass over the substrate in a region extending between the center of the substrate and a point on the edge of the substrate located on a line passing through the center of the substrate and perpendicular to the flow direction. However, the streamlines can also extend outside the edge of the substrate, so that the second gas flow flows past the substrate. In this case, gases that affect the layer composition, particularly the dopant concentration, affect substantially only the edge of the substrate. In a CVD reactor with a central gas inlet member, the gas outlet holes may be positioned on a streamline at an angle relative to a midline extending through the center of the substrate in the direction of flow. The angle may be selected so that the gas flow over a partial area of ​​the substrate between the center and the edge of the substrate. However, the gas flow may also flow through the substrate. When multiple substrates are positioned next to each other, for example, in a circumferential line around the center of the process chamber, a second gas flow may flow through the gap between the two substrates. In a CVD reactor in which the first gas flow is linear rather than star-shaped, at least one gas outlet hole may be spaced a distance from a midline passing through the center of the substrate in the flow direction. Alternatively, the gas outlet hole may impel the second gas flow in a direction that deviates from the flow direction of the first gas flow. For example, the through-holes forming the gas outlet hole may extend at an angle to the normal to the susceptor surface. In the first case, the angle influences the effective location of the second gas flow, and in the second case, the separation distance influences the location of the effective location of the second gas flow on the substrate. In the third case, the direction of the outlet channel opening into the outlet hole influences the effective location of the second gas flow. In a preferred development of the invention, it is proposed that the width of the gas outlet surface of the gas outlet hole transverse to the flow direction is less than 1 / 2, 1 / 3, 1 / 4, 1 / 5, or 1 / 6 of the width of the substrate transverse to the flow direction. The smaller the width of the gas outlet surface of the gas outlet hole, the more precisely one or more gas outlet holes can influence the composition of the layer and, in particular, the dopant incorporation in the layer. However, the gas outlet surface may also consist of several partial openings with different individual surfaces. The composition of a layer composed of multiple components can be influenced locally using the above-mentioned method. This method is preferably used to influence the dopant incorporation. The width of the gas outlet holes can be used as a means for influencing the mass flow rate of the second gas flow, for example in the form of a throttle. For this purpose, a combination of different individual openings with the same or different opening areas can be provided. This makes it possible to influence the size and shape of the area of ​​the substrate affected by the second gas flow. The method according to the invention is preferably used for depositing a SiC layer on a substrate, for example a SiC substrate, at temperatures above 1500 degrees Celsius, as already described in the prior art cited above. At least one carbon-containing gas, such as methane or propane, and a silicon-containing gas, such as monosilane, disilane, or trichlorosilane, are used as reactive gases. However, it is also possible to use Si(CH3)4. The SiC layer is doped with nitrogen. Nitrogen-containing gases, such as ammonia or N2, may be used as gases that influence the dopant concentration in the layer. This method can be used not only for N-doping, but also for P-doping. Instead of nitrogen, other dopants, such as aluminum or boron, in the form of, for example, TMAl or TEB, or other suitable Al or B compounds, can also be used. However, it is also proposed to use carbon-containing gases, such as methane or propane, as gases that influence the dopant concentration in the layer. When a dopant-containing gas is used, the dopant concentration of the layer increases substantially proportionally to the partial pressure of the gas or dopant immediately above the substrate, whereas when a carbon-containing gas is used, the dopant incorporation into the layer decreases substantially inversely proportionally to the partial pressure of the gas or substance that inhibits dopant incorporation immediately above the substrate. The use of N2, for example, locally increases dopant incorporation. The use of methane or propane, for example, locally decreases dopant incorporation. To address the problem of higher dopant concentrations at the edge of the layer mentioned in the introduction, it is advantageous to position the gas outlet holes at an angle to the midline or at a distance from the midline so that the flow lines of the second gas flow passing through the outlet holes pass over the substrate between the midline and the edge of the substrate. This is particularly advantageous when the second gas flow includes N2 and the dopant concentration in the absence of the second gas flow has a W-shaped peak and trough across the diameter of the layer. In this case, the dopant concentration in the layer is greatest in the center and at the edge of the substrate, respectively. The dopant concentration is lowest between the center and the edge of the substrate. This angle or distance is selected so that the flow lines of the second gas flow pass through this minimum, thereby making dopant uptake particularly advantageous here. In the case of a rotating susceptor, the area affected by the gas flow due to rotation must also be considered. On the other hand, if the dopant concentration in the absence of the second gas flow has a U-shaped peak and trough across the diameter of the layer, i.e., a minimum in the central region and a maximum in the edge region, the second gas flow may contain a reactive gas that suppresses dopant incorporation, e.g., a carbon-containing gas. In this case, it is advantageous to limit the second gas flow only to the edge of the substrate. For this purpose, it may be beneficial to have the second gas flow flow directly through the substrate at the edge. It may also be advantageous to have the second gas flow flow through a gap, preferably intermediate, between two substrates. This reduces dopant incorporation in a targeted manner in the edge region of the substrate. The gas outlet holes may be located away from the substrate or the substrate holder supporting the substrate. The gas outlet holes may be circular through-holes in the susceptor connected to a supply line. In the case of a rotationally symmetric arrangement, the through-hole or through-holes respectively assigned to the substrates may be arranged in a ring surrounding the gas inlet member. If this ring is movable in the azimuth direction, the positions of the gas outlet holes can be changed. In a process chamber with linear flow, the through-holes may be arranged on a movable plate, whereby the distance between the gas outlet holes and the midline can be adjusted by moving the plate. The apparatus used to carry out this method may include a susceptor driven to rotate around its center. The susceptor may have pockets evenly distributed circumferentially about its center, each pocket containing a substrate holder. A purge gas flow containing only an inert gas, for example hydrogen, may be supplied to the bottom of the pocket. This purge gas serves to form a gas cushion that supports and rotates each substrate holder, the rotation speed of the substrate holder being greater than that of the susceptor. Rotation of the substrate holder results in the formation of a layer on the substrate that is rotationally symmetric in its properties. By selecting the angle and / or spacing, as well as the width of the gas outlet holes measured transversely to the flow direction, the dopant incorporation can be influenced in a targeted manner in the radial region. Only an inert gas, for example hydrogen, a carbon-containing gas, and a silicon-containing gas, may be supplied to the process chamber through the gas inlet member. The dopant is then incorporated into the layer solely by the reactive gas, exiting through one or more gas outlet holes of the type and arrangement described above. For this purpose, it is advantageous to arrange several gas outlet holes, preferably one for each substrate, in particular along a line running transverse to the flow direction, which may be straight or arc-shaped. The dopant incorporation can be locally influenced in a targeted manner through the various gas outlet holes. However, it may also be arranged so that different gas flows flow through different gas outlet holes, in particular through gas outlet holes assigned to different substrates, and the flows may differ in terms of mass flow rate. Preferably, the partial pressure of the reactive gas in the gas flow is the same in all flows. However, it is also possible to provide an additional reactive gas containing a dopant through the gas inlet member, so that the dopant incorporation is locally influenced by the second gas flow. For this purpose, it may be advantageous for the second gas flow to de-homogenize the previously homogenous gas flow. The apparatus may include a gas exhaust member located downstream of the substrate or substrate holder in the direction of the gas flow. In a rotationally symmetric arrangement of the susceptor and the gas inlet member, the gas exhaust member may surround the susceptor in a ring shape, with the edge of the susceptor extending along a circular arc adjacent to the gas exhaust member. A gas exhaust line may connect the gas exhaust member to a pump, thereby setting the total pressure in the process chamber to a negative pressure. The process chamber is preferably heated by a heating device. The heating device may be an RF coil that heats the susceptor, which may be made of graphite, or may generate eddy currents in the susceptor. The ceiling of the process chamber may be heated by thermal radiation from the susceptor. Alternatively, the ceiling of the process chamber may be actively heated. By supplying reactive gases to the process chamber, decomposition products, such as Si, C, and N, or intermediate products containing these elements, are generated by the elevated temperature and diffuse through the process gas boundary layer above the substrate to the substrate surface, where they react with the substrate surface or a layer already deposited thereon to form a nitrogen-doped SiC layer. Reactive gases that affect the layer composition can be supplied to the process chamber not only through the auxiliary gas outlet holes but also by other means. The reactive gas may also be supplied to the process chamber through a gas inlet member, so that the supply to the substrate surface can be locally adjusted by the gas flow from the gas outlet holes. The apparatus for carrying out the method may have six support positions for the substrates, evenly spaced around the center. The angle at which the flow lines deviate from the midline may be in the range of 5 to 10 degrees, with a preferred angle being 8.5 degrees. In this case, a circular substrate may be positioned at a sector angle of 70 degrees, so that a tangent line passing from the center to the edge of the substrate extends at an angle of 35 degrees relative to the midline.

[0011] The present invention further relates to the deposition of a layer on a substrate using a process chamber bounded below by a susceptor and above by a process chamber ceiling. Process gas is supplied to the process chamber through a gas inlet member. The process gas flows horizontally through the process chamber. The gas inlet member may have multiple gas inlet regions arranged vertically one above the other, allowing various reactive gases to enter the process chamber separately from one another. The reactive gas may include silicon and carbon, such as trichlorosilane or H2H4. Ammonia may be supplied to the process chamber as a dopant through one of the gas inlet regions, which may be through the upper gas inlet region. However, ammonia may also be supplied to the process chamber through other gas inlet regions, such as an intermediate gas inlet region located away from the ceiling and susceptor of the process chamber.

[0012] An additional doping gas may be supplied to the process chamber through gas outlet holes at the bottom of the process chamber, particularly the gas outlet holes described above, which have essentially the same properties as the gas outlet holes described above, but preferably introduce nitrogen (molecular nitrogen N2) through them, so that the nitrogen flows through the lowest region of the process chamber.

[0013] NH3 and N2 may be supplied from different locations. Two doping gases may be supplied to the process chamber through any of multiple gas inlet regions arranged one above the other. In particular, NH3, HCN, pyridine (C5H5N), hydrazine (N2H4), dimethylhydrazine (C2H8N2), or asymmetric dimethylhydrazine may be supplied to the process chamber through one or more gas inlet regions. Different doping gases may be supplied through different gas inlet regions.

[0014] In particular, NH3 or another of the above-mentioned doping gases may be provided to be supplied to the process chamber through gas inlet members, which may be at different vertical heights, for example through a top gas inlet member, through a middle gas inlet member, or through a bottom gas inlet member.

[0015] Additionally, NH2 may be supplied to the process chamber through gas outlet holes located at the bottom of the process chamber, i.e., in the susceptor.

[0016] However, it is also possible to feed NH3 through this gas outlet hole, in particular to simultaneously feed NH3 through the lowermost gas inlet region and NH3 through the gas outlet hole. [Brief explanation of the drawings]

[0017] Exemplary embodiments of the present invention will now be described with reference to the drawings. [Figure 1] FIG. 1 shows a schematic cross section through a CVD reactor for carrying out the method. [Figure 2] FIG. 2 shows a schematic plan view of the susceptor along section II-II. [Figure 3] FIG. 3 shows a part of the first embodiment, designated III in FIG. [Figure 4] FIG. 4 shows the portion shown in FIG. 3 from the second embodiment. [Figure 5] FIG. 5 shows the part shown in FIG. 3 from the third embodiment. [Figure 6] FIG. 6 shows a general schematic diagram of the progression of the dopant concentration in the layer on a line d extending through the center 12 of the substrate 9 in each case, where the second gas flow contains a gas that increases the dopant concentration. [Figure 7] FIG. 7 shows a general schematic diagram of the progression of the dopant concentration in the layer on a line d extending through the center 12 of the substrate 9 in each case, where the second gas flow contains a gas that reduces the dopant concentration. [Figure 8]FIG. 8 shows the portion shown in FIG. 3 from the fourth embodiment. [Figure 9] FIG. 9 shows a schematic cross section through a CVD reactor for carrying out the method from the fifth embodiment. [Figure 10] FIG. 10 shows a plan view of a susceptor of a CVD reactor according to a fifth embodiment. [Figure 11] FIG. 11 is a diagram of the sixth embodiment according to FIG. [Figure 12] FIG. 11 is a diagram of the seventh embodiment according to FIG. [Figure 13] FIG. 13 is a diagram according to FIG. 10 of the eighth embodiment. [Figure 14] FIG. 14 shows a view in which the gas outlet holes 10 according to FIG. 10 are arranged on a movable plate 25'. [Figure 15] FIG. 15 shows a view according to FIG. 3 of a tenth embodiment, in which two gas inlet holes with different diameters are provided. [Figure 16] FIG. 16 shows a ninth embodiment in a view according to FIG. 3, in which the three zones Z1, Z2, Z3 are marked by additional auxiliary lines. [Figure 17] FIG. 17 shows the dopant concentration in the layer depending on the angle α. [Figure 18] FIG. 18 is a diagram according to FIG. 9 of the eighth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The CVD reactor shown in Figures 1 and 9 has a housing and is part of a coating apparatus that additionally includes a control device 24 and a gas supply system.

[0019] The gas supply system comprises a number of supply lines 15, 16, 17, 18, 19 through which reactive gases supplied by gas sources 21, 22, 23, together with an inert gas, the source of which is not shown, are delivered to a process chamber 4 arranged within the housing 1. Gas source 21 supplies a carbon-containing gas, gas source 22 supplies a silicon-containing gas, and gas source 23 supplies a nitrogen-containing gas. These gases may be methane, propane, silane, disilane, trichlorosilane, nitrogen, ammonia, or the like. Valves (not shown) and mass flow controllers 20 are located in supply lines 15, 16, 17, 18, and 19, allowing the gas flows to be adjusted. For this purpose, controller 24 includes a programmable control computer capable of processing recipes stored in controller 24, which contain values ​​for the gas flows. The recipes allow several sequential process steps to be performed automatically. One or more layers containing SiC and doped with nitrogen are deposited on a substrate, e.g., a SiC substrate. However, the apparatus is also suitable for the deposition of other material systems.

[0020] The CVD reactor comprises a susceptor extending horizontally and heated to a process temperature of 1500°C or higher by a heating device 5 arranged below the susceptor 2. A gas inlet member 6 is provided, through which reactive gases can be supplied to the process chamber 4. Supply lines 15, 16, and 17 for gases containing carbon, silicon, and nitrogen open into the gas inlet member 6. The gas inlet member 6 has a gas outlet surface that is porous or has a large number of uniformly distributed and, in particular, uniformly sized holes through which the aforementioned gas mixture can enter the process chamber 4. In this embodiment, the gas inlet member 6 has a single gas outlet region through which a homogeneous mixture of gases flows into the process chamber, forming a homogeneous laminar flow. In an embodiment not shown, several gas inlet regions may be arranged one above the other, through which various gas mixtures flow into the process chamber 4 as homogeneous laminar flows, respectively.

[0021] The CVD reactor is operated to provide a homogeneous laminar flow profile across at least a portion of the height of the cross-sectional area of ​​the process chamber 4, preferably across the entire cross-sectional area of ​​the process chamber 4. In the embodiment shown in FIG. 1, the flow of the first gas flow exiting the gas inlet member 6 extends in a star shape about a center 13 located inside the gas inlet member 6. Here, the gas outlet surface extends on a cylindrical surface extending from the bottom of the process chamber 4 formed by the susceptor 2 to the ceiling 3 of the process chamber. In the embodiment shown in FIG. 9, the gas outlet surface may be a rectangular surface, and the width of the gas outlet surface extending in the flow direction S is greater than the diameter B2 of the substrate 9.

[0022] Downstream of the first gas flow, the susceptors 2 each have a storage space for one substrate 9. In this embodiment, the storage spaces are each formed by a substrate holder 8 which rests in a pocket of the susceptor 2. A supply line (not shown) for one purge gas flow, for example of an inert gas such as hydrogen, each opens into the bottom of the pocket. This purge gas flow creates a gas cushion below the substrate holder 8, lifting it and causing it to rotate about its axis 8'.

[0023] Radially outward from the edge 2' and opposite the gas inlet member 6 is a gas exhaust member 7, through which the process gas or decomposition products of the process gas supplied to the process chamber 4 via the gas inlet member 6 are conveyed out of the process chamber 4. This is achieved by a pump (not shown) which generates a negative pressure in the process chamber 4.

[0024] In a region downstream of the gas inlet member 6 and upstream of the substrate holder 8 and substrate 9, where the first gas flow preferably flows uniformly and homogeneously, gas outlet holes 10 are located, through which a second gas flow can be supplied to the process chamber. The location of the gas outlet holes 10 influences the effective location of a second gas flow, which flows through the gas outlet region of the gas outlet holes 10 into the process chamber 4 and includes a gas that affects the layer composition, preferably the dopant concentration in the layer. This second gas flow may be, for example, nitrogen or one of the carbon-containing reactive gases mentioned above. The second gas flow flows through the process chamber 4 along flow lines 14. The location of the flow lines 14 relative to a midline 11 extending in the flow direction S of the first gas flow through the center 12 of the substrate 9 influences the incorporation of dopants into the layer at different radial distances relative to the center 12. The flow lines 14 extend along the flow direction S of the first gas flow.

[0025] Supply lines 18, 19 are provided by which a second gas flow can be supplied to the process chamber 4. The supply lines 18, 19 are connected to a carbon gas source 21 or a nitrogen gas source 23. The supply lines 18, 19 open into one or more gas outlet holes 10, 10', 10''.

[0026] 2 shows a plan view of the susceptor 2 of the first embodiment, surrounded by an annular gas discharge member 7. Six substrates 9 are arranged around a center 13, evenly distributed circumferentially. In other embodiments, the number of substrates 9 may be fewer or greater. A notional midline 11 extends through the center 12 of the substrate 9 and runs parallel to the flow direction S of the first gas flow, and thus through the center 13. The star-shaped arrangement of streamlines extends symmetrically about the center 13.

[0027] In a first embodiment, shown in Figure 2 and enlarged in Figure 3, the gas outlet holes 10 are offset relative to the midline 11. A straight line extending through the center 13 and through the center of the gas outlet holes 10 forms a streamline 14 along which the second gas flow exiting the gas outlet holes 10 flows. The angle between the midline and the streamline 14 is selected such that the streamline 14 passes through one of the two halves of the substrate 9 where the midline 11 divides the substrate surface. Depending on the magnitude of the angle α, the radial position of the effective point of the second gas flow varies relative to the center 12 of the substrate 9.

[0028] The circular gas outlet hole in this embodiment has a diameter B1 that is significantly smaller than the diameter B2 of the circular substrate 9. The diameter of the gas outlet face of the gas outlet hole 10 is preferably smaller than ½, ⅓, ¼, ⅕, or ⅙ of the diameter of the substrate 9. However, the diameter of the gas outlet hole 10 may be smaller than 1 / 10 of the diameter of the substrate. The smaller the width B1 of the gas outlet face of the gas outlet hole 10 measured transversely to the flow direction S, the smaller the width of the second gas flow emerging therefrom, which spreads transversely to the flow direction as a result of diffusion or a star-shaped arrangement of the main stream lines. The smaller the ratio of the width B1 of the gas outlet face to the width B2 of the substrate 9 measured transversely to the flow direction S, the more precisely the second gas flow can locally influence the incorporation of dopants into the layer.

[0029] In the second embodiment shown in FIG. 4, the gas outlet holes 10 are located on the midline 11 so that the second gas flow emerging therefrom flows through the center of the substrate 9 .

[0030] 5, the gas outlet holes are located approximately on the angle bisector of two midlines 11 passing through the centers 12 of two adjacent substrates 9, so that a streamline 14 passes through the gap between the two substrates 9. A second gas flow is now directed precisely through the substrates 9, so that the gases contained in the second gas flow that affect the dopant incorporation act only in the region of the substrate's edge 9'.

[0031] FIG. 6 is a schematic diagram of the effect of the arrangement of the gas outlet holes 10 in the above-described embodiment.

[0032] The W-shaped curve A shows the dopant concentration along line d through the center 12 of a layer deposited on the substrate 9 without a second gas flow, where dopant is additionally supplied to the process chamber through the gas inlet member 6. Due to the rotation of the substrate 9 during deposition of the layer, the dopant concentration has rotational symmetry. However, there are maxima in the central region and in the edge regions of the substrate 9, with minima in between.

[0033] Curve B shows the effect on the radial dopant concentration of a second gas flow containing a reactive gas, e.g., nitrogen, that promotes dopant incorporation. The dopant incorporation is greatest in the region between the center 12 and edge 9' of the substrate 9, which is the active area in Figure 3. In this way, the minimum value shown by curve A can be compensated for.

[0034] 4, i.e., on the midline 11, the effect of a second gas flow containing a reactive gas that promotes dopant uptake is shown, where the effective location is intermediate and the maximum dopant concentration is formed in the central 12 region.

[0035] Curve D shows the effect of a second gas flow containing a reactive gas that promotes dopant incorporation when the gas outlet holes 10 are positioned according to the embodiment shown in Figure 5 and flow lines 14 are formed between the two substrates 9. Here, only the edge regions of the two substrates 9 are affected by the second gas flow, since the effective location is between the substrates 9. Here, a maximum value is found at the edge 9', while a minimum is formed in the central 12 region.

[0036] FIG. 7 is a schematic diagram of the effect of the placement of gas outlet holes 10 in the embodiment shown in FIGS. 3-5, where the second gas flow includes a reactive gas, e.g., a carbon-containing gas, that inhibits dopant incorporation.

[0037] Again, the W-shaped curve A shows the dopant concentration along line d through the centre 12 of a layer deposited on the substrate 9 without the second gas flow, but again with dopant supplied through the gas inlet member 6. Again, rotation of the substrate 9 during deposition of the layer results in rotational symmetry of the dopant concentration.

[0038] Curve B' shows the influence of the second gas flow on the arrangement of gas outlet holes 10 according to Figure 3. Here, a minimum is formed in the region between the center 12 and the edge 9'.

[0039] Curve C' shows the effect of the second gas flow on the arrangement of gas outlet holes 10 along Figure 4. Here, the reactive gas flow, which reduces the dopant incorporation, exhibits a minimum in the central region and a maximum in the edge 9' region.

[0040] Curve D' shows the effect of the second gas flow on the arrangement of gas outlet holes 10 according to Figure 5, where the reactive gas that reduces the dopant incorporation forms a maximum in the central 12 region and a minimum in the respective edge 9' regions.

[0041] By target selection of the angle α and / or the target ratio between the gas exiting the gas outlet holes 10 and the reactive gas exiting the gas inlet member 6 and influencing the dopant uptake, the respective curve A can be modified by the second gas flow to be as flat as possible, thereby increasing the curve in the minimum region or decreasing the curve in the maximum region.

[0042] It is also possible for the gas flow influencing the dopant concentration in the layer to flow both through the gas inlet member 6 and through the gas outlet holes 10. However, it is also possible for the gas flow influencing the dopant concentration to flow only through the gas outlet holes 10. In the embodiment shown in FIG. 8, multiple gas outlet holes 10, 10' are provided, which are arranged on different flow lines 14, 14' and through which the same or different gas flows can occur. These two second gas flows can influence the dopant incorporation at two different radial positions on the substrate 9. The angles α, α' can be the same or different.

[0043] 9 shows a second embodiment of a CVD reactor in which a first gas flow is horizontally linear through a process chamber 4 disposed in a housing 1. A substrate 9 is located in the center of a susceptor 2 and is equidistant from the two walls of the process chamber 4 in a direction perpendicular to the flow direction S. The midline 14 passes through the centre 13 of the gas inlet member 6 and through the centre 12 of the substrate 9 or substrate holder 8 supporting the substrate. The midline 14 has the direction of the flow direction S.

[0044] A uniform laminar main gas flow, which may or may not contain dopant, exits the gas inlet member 6. This gas flow flows through the process chamber 4 so that a SiC layer is deposited on the substrate 9. Further gas flows, which influence the dopant concentration, are supplied to the process chamber through the gas outlet face of additional gas outlet holes 10, which in the embodiment shown in FIG. 10 may have a distance α from the midline 11 so that flow lines 14, which run parallel to the midline 11, pass through one of the two halves of the substrate 9.

[0045] The embodiment shown in Figure 18 substantially corresponds to the embodiment shown in Figure 9. Gas source 23 may contain N2. Gas source 23' may contain ammonia. Mass flow controller 20 is adjusted to flow ammonia through gas inlet member 6 through the top gas inlet region into process chamber 4. In a SiC layer deposited on a substrate 9 mounted on a rotating substrate holder 8, the ammonia produces a bell-shaped dopant profile that tapers off toward the edge, as shown by line C in Figure 6.

[0046] N2 is supplied to the bottom of the process chamber 4 through supply line 18 and exits through gas outlet holes 10. Ammonia produces a valley-shaped dopant profile that rises towards the edges, as shown in curve A of Figure 6. By appropriate selection of the settings of the mass flow controller 20, i.e., by appropriate ratio of the mass flow rates of N2 and ammonia, a nearly flat dopant profile can be produced in the SiC layer deposited on the substrate 9.

[0047] In the embodiment shown in FIG. 11, the gas outlet hole 10 is located on the midline 11 .

[0048] In the embodiment shown in FIG. 12, two gas outlet holes 10 are provided, one gas outlet hole 10 being located on the midline 14 and a second gas outlet hole 10 ′ being offset from the midline 14 .

[0049] In the embodiment shown in Figure 13, three gas outlet holes 10, 10', 10" are provided and, as in the embodiment shown in Figure 12, they are located on a line extending transversely to the flow direction S. The flow lines 14', 14" passing through the gas outlet holes 10', 10" may extend above the edge 9' of the substrate 9.

[0050] Again, the dopant concentration in the layer can be influenced locally by the target selection of gases, which affects the dopant concentration, and the mass flow rate or its ratio to the mass flow rate of the gas entering through the gas inlet member, which affects the dopant concentration, where the position of the gas outlet holes 10, 10', 10" relative to the midline 11 and the effect of each secondary gas flow on the gas quality are shown in Figures 6 and 7. When multiple gas outlet holes 10, 10', 10" are provided, they need not lie along an exact line transverse to the flow direction S. They may also be at different distances from the gas inlet member 6 so that the gas flows from the gas outlet holes 10, 10', 10" fan out in different ways at the point of application on the substrate 9.

[0051] The embodiment shown in Figure 14 shows a plate 25' that can move transversely to the flow direction S and that can include gas outlet holes 10. By moving the plate 25, the distance of the streamlines 14 from the midline 11 can be individually adjusted.

[0052] 15 shows a tenth embodiment of the present invention. One gas outlet hole 10, 10' is positioned upstream of the substrate 9 on two flow lines 14, 14' that both pass through the substrate surface. The gas outlet hole 10' has a larger diameter than the gas outlet hole 10.

[0053] The eleventh embodiment shown in Figure 16 shows gas outlet holes 10 offset from midline 11 by an angle α of approximately 8-10 degrees. Here, substrate 9 has a diameter B2 such that a tangent applied to edge 9' and passing through center 13 subtends an angle of 70 degrees. In such an arrangement, angle α is advantageously between 5 and 10 degrees, preferably 8.5 degrees. Here, reference numeral 25 denotes a ring comprising a plurality of gas outlet holes 10. The angle α is adjusted by rotating ring 25 around center 13.

[0054] FIG. 17 shows the effect of angle α on dopant concentration C, plotted along radius R of substrate 9. As also shown in FIG. 16, regions Z1, Z2, and Z3 can be defined, in which dopant incorporation can be affected in a targeted manner. Region Z1, for example, extends from edge 9′ of the substrate to a first region of half of the substrate. Region Z2 extends over an angular range through the center of half of substrate 9. Region Z3 is adjacent to this and extends beyond the center of the substrate. The greatest effect on dopant incorporation is in region Z2, which extends over a region between 30 mm and 60 mm from center 12.

[0055] The minimum and maximum values ​​of curve A can be neutralized in a targeted manner. The arrangement and size of the gas outlet surface of the gas outlet holes according to the invention make it possible to use the gas flow leaving the gas outlet holes, which contains a gas that influences the dopant concentration, to particularly influence the dopant incorporation in the region located between the center of the substrate and the edge of the substrate.

[0056] This embodiment describes a local influence on the incorporation of dopants. However, the invention also includes methods in which ternary or quaternary semiconductor layers are deposited, where the layer composition can be influenced locally by a second gas flow. In this case, the dopant is not supplied to the process chamber through the gas outlet holes 10, 10', 10" but rather one of the starting materials for forming the crystal. Such a material system may be the material system GaInAsP.

[0057] The foregoing is intended to describe inventions covered by this application as a whole, each of which independently advances the prior art through at least the following combinations of features, two, some, or all of which may be combined:

[0058] Method, characterized in that the width B1 of the gas outlet holes (10, 10', 10'') extending transversely to the flow direction S is smaller than the width B2 of the substrate (9) extending transversely to the flow direction.

[0059] The method is characterized in that the flow lines 14 passing through the gas outlet holes 10, 10', 10" along the flow direction S are offset by an angle α or a certain distance with respect to the midline 11 passing through the center 12 of the substrate 9 in the flow direction S.

[0060] The method is characterized in that the streamlines 14 pass over the substrate between the center 12 and the edge 9' of the substrate 9, or the streamlines 14 pass over the substrate 9 outside the edge 9' of the substrate 9, or the streamlines 14 pass through a gap between two substrates arranged adjacent to each other.

[0061] 10. The method according to claim 1, wherein the width B1 of the gas outlet holes 10, 10', 10" extending transversely to the flow direction S is smaller than half, one-third, one-quarter, one-fifth or one-sixth of the width B2 of the substrate 9 extending transversely to the flow direction S.

[0062] The method is characterized in that the substrate 9 is placed on a substrate holder 8 that is driven to rotate around a rotation axis 8', and / or the substrate 9 is supported by a susceptor 2 that is heated to a process temperature by a heating device 5, and / or a gas inlet member 6 forms a center 13 of the susceptor 2 and generates a first gas flow that flows radially with respect to the center 13.

[0063] 10. The method of claim 9, wherein the first gas flow flows through the process chamber along parallel or star-shaped streamlines.

[0064] a first gas flow supplied through the gas inlet member (6) comprising at least one of a carbon-containing gas and a silicon-containing gas for depositing a SiC layer, and wherein the carbon-containing gas or the nitrogen-containing gas flows into the process chamber (4) through the gas outlet holes (10, 10', 10").

[0065] A method characterized in that a plurality of gas outlet holes (10, 10', 10'') are arranged in flow direction S between the gas inlet member (6) and the substrate (9).

[0066] Apparatus characterized in that the gas outlet holes (10) are connected to gas sources (23, 21) which influence the layer composition or the dopant concentration in the layer.

[0067] An apparatus characterized by a control device 24 having a control program for controlling the apparatus according to any one of claims 1 to 8.

[0068] All disclosed features are essential to the invention (both by themselves and in combination with one another). The disclosure of the present application includes in its entirety the disclosure content of the relevant / attached priority documents (copies and earlier applications), also for the purpose of incorporating the features of these documents into the claims of the present application. The dependent claims are characterized by an independent, inventive further development of the prior art, even without the features of the claims cited therein, in particular for the purpose of filing a divisional application based on these claims. The invention specified in each claim may additionally have one or more features specified in the preceding description, particularly those given reference signs and / or specified in the sign explanations. The present invention also relates in particular to embodiments in which individual features set forth in the preceding description are not implemented, insofar as they are clearly unnecessary for the respective intended use or can be replaced by other means having the same technical effect. [Explanation of symbols]

[0069] 1. Housing 2 susceptor 2' Edge 3 Process chamber ceiling 4 Process Chamber 5 Heating device 6 Gas inlet member 7 Gas exhaust member 8 PCB holder 8' rotation axis 9 Substrate 10 Gas outlet hole 10' gas outlet hole 10" gas outlet hole 11 Midline 12 center 13 center 14, 14', 14” streamline 15, 16, 17, 18, 19 Supply lines 20 Mass Flow Controller 21 Gas Source, Carbon 22 Gas source, silicon 23 Gas source, nitrogen 24 Control device 25 Ring 25' Plate d. Line passing through center 12 B1 Gas outlet hole 10, 10', 10" width B2 Width (diameter) of board 9 S flow direction A dopant concentration B, B', C, C', D, D' dopant concentrations S First gas flow direction

Claims

1. A method for depositing a layer on a substrate (9), comprising the steps of: a uniform first gas flow is supplied through a gas inlet member (6) to a process chamber (4) which is brought to a process temperature; the gas flow flows in a flow direction (S) over the substrate (9) and the gas flow contains one or more reactive gases, the decomposition products of which form a layer; a second gas flow is supplied to the process chamber (4) through a gas outlet surface of gas outlet holes (10, 10', 10") arranged downstream of the gas inlet member (6) and upstream of the substrate (9); The method, wherein the second gas flow includes at least one reactive gas that affects at least the composition of the layer or the dopant concentration within the layer, wherein the width (B1) of the gas outlet holes (10, 10', 10") extending transversely to the flow direction (S) is smaller than the width (B2) of the substrate (9) extending transversely to the flow direction.

2. 2. The method of claim 1, wherein a flow line (14) passing through the gas outlet holes (10, 10', 10") along the flow direction (S) is offset by an angle (α) or a distance (a) with respect to a median line (11) extending in the flow direction (S) through a center (12) of the substrate (9).

3. 3. The method of claim 2, wherein the flow lines (14) pass through the substrate (9) between the center (12) and an edge (9') of the substrate, or the flow lines (14) pass outside the edge (9') of the substrate (9), or the flow lines (14) pass through a gap between two substrates (9) arranged adjacent to each other.

4. 2. The method of claim 1, wherein the width (B1) of the gas outlet holes (10, 10', 10") extending transversely to the flow direction (S) is smaller than 1 / 2, 1 / 3, 1 / 4, 1 / 5 or 1 / 6 of the width (B2) of the substrate extending transversely to the flow direction (S).

5. 2. A method according to claim 1, characterized in that the substrate (9) is placed on a substrate holder (8) which is driven to rotate about an axis of rotation (8').

6. 2. A method according to claim 1, characterized in that the substrate (9) is supported by a susceptor (2) which is brought up to the process temperature by a heating device (5).

7. 2. The method of claim 1, wherein the gas inlet member (6) defines a center (13) of the susceptor (2) and generates a first gas flow that flows radially relative to the center (13).

8. 2. The method of claim 1, wherein the first gas flow flows through the process chamber (4) along parallel or star-shaped flow lines.

9. 2. The method of claim 1, wherein the first gas flow supplied through the gas inlet member (6) comprises at least one of a carbon-containing gas and a silicon-containing gas for depositing a SiC layer, and a carbon-containing gas or a nitrogen-containing gas flows into the process chamber (4) through the gas outlet holes (10, 10′, 10″).

10. 2. The method according to claim 1, characterized in that a plurality of gas outlet holes (10, 10', 10'') are arranged in the flow direction (S) between the gas inlet member (6) and the substrate (9).

11. Ammonia is supplied to the process chamber (4) through the gas inlet member (6), and N ２ 11. The method according to any one of claims 1 to 10, characterized in that is supplied through the gas outlet holes (10).

12. An apparatus for depositing a layer on a substrate (9), comprising: The apparatus includes a housing (1) in which a process chamber (4) is disposed, the housing (1) including a susceptor (2), a gas inlet member (6) for supplying a first process gas, and a gas exhaust member (7) for exhausting the process gas out of the process chamber (4); at least one gas outlet hole (10, 10', 10") is arranged in a region downstream of the gas inlet member (6) and upstream of the substrate holder (8); said gas outlet holes (10, 10', 10") having a gas outlet surface; a width (B1) of the gas outlet holes (10, 10', 10") extending transversely to a flow direction (S) of a first process gas through the process chamber (4) is smaller than a width of the substrate holder (8) or the substrate (9) extending transversely to said flow direction (S); and In the apparatus, further gas is introduced into the process chamber (4) through the gas outlet holes (10, 10', 10"); 10. An apparatus, characterized in that the gas outlet holes (10) are connected to gas sources (23, 21) that influence the composition of the layer or the dopant concentration in the layer.

13. A device according to claim 12, characterized by a control device (24) provided with a control program for controlling the device according to any one of claims 1 to 8.

14. A device or method characterized by one or more of the features characterized by any of claims 1 to 13.

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