Method for producing an isolation-diffused power semiconductor component

Abstract

A manufacturing method for a power semiconductor component is presented, comprising the following steps: diffusion from an aluminum source to form a separation diffusion region; application of an identical aluminum layer on the front and back sides and subsequent diffusion from these aluminum layers to form an aluminum diffusion region each, wherein a front-side and a back-side pn junction are formed; diffusion of gallium to form a gallium diffusion region each on the front and back sides with a smaller depth than the respective aluminum diffusion region; application of a structured phosphor layer on the front side and preferably simultaneous application of an unstructured phosphor layer on the back side; removal of a layer starting from the back side, wherein the aluminum source and the phosphor layer are completely removed and the gallium diffusion region is almost completely removed.

Description

The invention describes a method for producing a power semiconductor component, in particular a thyristor, in wafer assembly with an isolation diffusion region.DE 10 2016 124 669 B3 discloses a thyristor having a semiconductor body which has a first semiconductor body main side, a second semiconductor body main side and a semiconductor body edge which surrounds the semiconductor body and connects the first and second semiconductor body main sides, wherein the semiconductor body has a first semiconductor zone, wherein the first semiconductor zone extends in a semiconductor body edge region as far as the second semiconductor body main side and a second outer surface of the first semiconductor zone forms the semiconductor body edge and a third outer surface of the first semiconductor zone which adjoins the semiconductor body edge forms a first surface region of the second semiconductor body main side, wherein the semiconductor body has a second semiconductor zone which is arranged on the first semiconductor zone and does not extend as far as the semiconductor body edge, wherein the semiconductor body has a third semiconductor zone arranged on the second semiconductor zone and a fourth semiconductor zone arranged in the third semiconductor zone, wherein the semiconductor body has a recess, starting from a first surface of the second semiconductor body main side, running parallel to the semiconductor body edge and reaching as far as into the second semiconductor zone.With the knowledge of the prior art, the object of the invention is to provide a method for producing a power semiconductor component which is accessible for simple production.According to the invention, this object is achieved by a method for producing a power semiconductor component, in particular a thyristor, in a wafer composite, having the following production steps: a) providing a semiconductor body having a basic doping, preferably a weak n-doping, and having a front side and a rear side; b) local arrangement of an aluminum source, more generally a source for a first p-doping, in the edge region between two power semiconductor components and subsequent diffusion from this aluminum source, with formation of an isolation diffusion region; c) applying in each case an identical second aluminum layer, more generally a second source for a p-doping, over the front and rear sides and subsequent diffusion from these aluminum layers, forming in each case an aluminum diffusion region on the front and on the rear sides, a front-side and a rear-side p-n junction being formed; d) diffusing gallium, more generally from a third source for a p-doping, forming in each case a gallium diffusion region on the front side and on the rear side with a depth less than that of the respective aluminum diffusion region; e) applying a structured phosphorus layer, more generally a source for an n-doping, on the front side and applying, preferably simultaneously, an unstructured phosphorus layer on the rear side; f) removing a layer from the back side, wherein the aluminum source and the phosphorus layer are completely removed and the gallium diffusion region is approximately completely or completely removed; g) Further steps for completely forming the power semiconductor device.In particular, the step f), which is preferably carried out as a grinding process with a subsequent etching process, enables advantageous production of the power semiconductor component. As a result, materials applied or diffused in the preceding steps, which are not necessary or detrimental to the function of the power semiconductor component, are removed from the rear side. Without this step f), technically complicated masking of the rear side would have been required for these materials.It can be advantageous if the local arrangement of the aluminum source in step b) is carried out by planar application of a first aluminum layer and subsequent structuring of this aluminum layer.It may be preferred if, in step c), the arrangement of both first aluminum layers is carried out simultaneously.It may be preferred if gallium is provided in the gas phase in step d).It may be preferable that in the step g), a patterned portion of the phosphorus layer is diffused on the front side to form a phosphorus diffusion region.It may be preferred if in step g) a surface application of a boron layer, generally a further source for a p-doping, takes place on the rear side, followed by diffusion from this boron layer to form a boron diffusion region which extends into the aluminum diffusion region.It can be advantageous if, after step g), in a step h), a trench region is produced in the section of the isolation diffusion region from the front side, said trench region reaching as far as the isolation diffusion region and preferably being deeper than the aluminum diffusion region of the first side. It is particularly preferred if the trench region is formed as a, preferably two-stage, step trench.In this case, it is furthermore preferred if, after step h), a passivation, preferably a polyimide passivation, is introduced in the trench region, which preferably only partially closes the trench region, but in each case extends as far as the planar section of the front side.It is also advantageous if the ratio of the depth of the trench region to the depth of the front-side p-n junction is between 1.1:1 and 2:1, preferably between 1.2:1 and 1.4:1.Of course, unless explicitly excluded or apart from itself or contrary to the idea of the invention, the features mentioned in the singular can also be present several times in the method according to the invention or be carried out in the production method.It is understood that the various embodiments of the invention, regardless of whether they are mentioned in connection with the method, can be realized individually or in any combinations in order to achieve improvements. In particular, the features mentioned and explained above and below can be used not only in the combinations indicated, but also in other combinations or alone, without departing from the scope of the present invention.Further explanations of the invention, advantageous details and features will become apparent from the following description of the exemplary embodiments of the invention schematically illustrated in FIGS. 1 to 8 or of respective parts thereof. Figures 1 to 7 show different stages in the course of the process according to the invention. FIG. 8 shows a power semiconductor device at a stage of a method according to the invention.FIGS. 1 to 7 show different stages in the course of the method according to the invention in a illustration not to scale and in section through the wafer composite.FIG. 1 shows an embodiment of a power semiconductor component, here a thyristor, in wafer assembly during production step b) with a silicon semiconductor body 1 having a basic doping, here configured as a weak n-doping. The semiconductor body 2, i.e. the wafer, has a front side 3 and a rear side 4.In order to form the isolation diffusion region 412, an aluminum source having a thickness of approximately 2 μm was arranged locally on the rear side 4, and the isolation diffusion region 412 was produced therefrom in a diffusion process. The aluminum source itself was produced by structuring from a first aluminum layer.Shown here are full-surface second aluminum layers 320, 420 which are thinner compared to the first aluminum layers, which were applied simultaneously on the front side and the rear side 3, 4, respectively.FIG. 2 shows the power semiconductor device in wafer composite after the production step c), wherein an aluminum diffusion region 322, 422 has been produced in each case on the front side and on the rear side 3, 4 by a diffusion method of the second aluminum layers 320, 420. The aluminum diffusion region 322 on the front side 3 extends here, but not necessarily, as far as into the isolation diffusion region 412. At the respective boundaries of the aluminum diffusion regions 322, 422 with the semiconductor body 2, these respectively form a front-side and rear-side p-n junction.FIG. 3 shows the power semiconductor component in wafer composite after the production step d), wherein a gallium diffusion region 332, 432 has been produced in each case on the front side and on the rear side 3, 4 by a diffusion method from the gas phase. The penetration depth of the gallium here is about 60% of the penetration depth of the aluminum.FIG. 4 shows the power semiconductor component in wafer composite after the production step e), wherein a phosphorus layer 340 structured by methods customary in the art has been applied to the front side 3. At the same time, a planar phosphorus layer 440 which is explicitly not functionally necessary for the power semiconductor component was applied to the rear side 4.FIG. 5 shows the power semiconductor component in wafer assembly after the production step f), wherein the power semiconductor component according to FIG. 4 is shown purely for explanation in the left-hand part of the figure.In the right-hand part, it is shown that in the production step f) the aluminum source and the phosphorus layer 440 have been completely ablated, i.e. removed, and the gallium diffusion region 432 has been approximately completely ablated. The substantial portion of the removal of the layers was performed by a grinding process followed by an etching process.FIG. 6 shows the power semiconductor component in wafer assemblage after further production steps g customary in the art). Here, diffusion of a patterned portion of the phosphor layer 340 on the front surface 3 is performed to form a phosphor diffusion region 342. A boron layer is then applied over the surface of the rear side 4, followed by diffusion from this boron layer, forming a boron diffusion region 452 which extends into the aluminum diffusion region 422.FIG. 7 shows the power semiconductor component in wafer assemblage after further production steps h). In this case, a trench region 5 is produced in the section of the isolation diffusion region 412, symmetrically about its center, that is to say about the singulating line 6, from the front side 3. In a conventional manner, the wafer composite of the power semiconductor components is divided into the individual power semiconductor components 1 by sawing along this singulation line 6, cf. FIG. 8. In addition, in this embodiment, the trench region 5 is formed deeper than the aluminum diffusion region 322 on the front side 3.The trench region 5 is here formed as a two-stage, likewise customary in the art. After step h), a passivation 50, here a polyimide passivation, was furthermore introduced in the trench region 5. This passivation extends laterally as far as the respective planar section of the front side 3 and otherwise does not completely close.FIG. 8 shows a power semiconductor component 1 of a method according to the invention, after the singulation of the wafer composite, cf. FIG. 7, a power semiconductor component 1 is thus produced, the ratio of the depth 324 of the front-side p-n junction to the depth 424 of the rear-side being 2:1. Specifically, the depth 324 of the front-side p-n junction is 90 μm, while that of the rear-side is only 45 μm.In addition, the ratio of the depth 504 of the trench region 5 to the depth of the front-side p-n junction 3:4 results, since the depth of the trench region 5, of course without the passivation, is 50, 120 μm.

Claims

Method for producing a power semiconductor component (1), in particular a thyristor, in a wafer composite, having the following production steps: a) providing a semiconductor body (2) with a basic doping and with a front side (3) such as a rear side (4); b) locally arranging an aluminium source in the edge region between two power semiconductor components and subsequent diffusion from this aluminium source to form a separating diffusion region (412); c) applying in each case an identical second aluminium layer (320, 420) over a surface area on the front side and rear side (3, 4) and subsequent diffusion from these aluminium layers to form in each case an aluminium diffusion region (322, 422) on the front side and on the rear side (3, 4), wherein a front side and a rear side p-n junction are formed; d) Diffusion of gallium, forming a gallium diffusion region (332, 432) on the front and on the rear side (3, 4) each with a depth that is less than the respective aluminum diffusion region (322, 422); e) Application of a structured phosphorus layer (340) on the front side (3) and application, preferably simultaneously, of an unstructured phosphorus layer (440) on the rear side (3, 4); f) Removal of a layer starting from the rear side (4), wherein the aluminum source and the phosphorus layer (440) are completely removed and the gallium diffusion region (432) is approximately completely or completely removed; g) Further steps for completely forming the power semiconductor component (1).Method according to Claim 1, wherein the local arrangement of the aluminium source in step b) is carried out by planar application of a first aluminium layer and subsequent structuring of this aluminium layer.Method according to one of the preceding claims, wherein in step c) the arrangement of both first aluminium layers (320, 420) is carried out simultaneously.The process according to any one of the preceding claims, wherein in step d) gallium is provided in the gas phase.The method of claim 4, wherein the aluminum diffusion region (322) is partially retained.Method according to one of the preceding claims, wherein, in step g), a patterned portion of the phosphorus layer (340) is diffused on the front side (3) to form a phosphorus diffusion region (342).Method according to one of the preceding claims, wherein in step g) a surface application of a boron layer on the rear side (4) takes place, followed by diffusion from this boron layer to form a boron diffusion region (452) which extends into the aluminum diffusion region (422).Method according to one of the preceding claims, wherein, after the step g), in a step h), a trench region (5) is produced in the section of the isolation diffusion region (412) from the front side (3) and extends as far as into the isolation diffusion region (412).Method according to claim 8, wherein the trench region (5) is formed as a, preferably two-stage, stage trench.Method according to Claim 8 or 9, wherein after step h) a passivation (50), preferably a polyimide passivation, is introduced in the trench region (5), preferably only partially closing the trench region (5), but reaching as far as the planar section of the front side (3).Method for manufacturing a power semiconductor device according to any of claims 8 to 10, wherein the ratio of the depth (504) of the trench region (5) to the depth (324) of the front side p-n junction is between 1.1:1 and 2:1, preferably between 1.2:1 and 1.4:1.

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