EP1899260A1

EP1899260A1 - Method for producing a micromechanical component and the thus obtained micromechanical component

Info

Publication number: EP1899260A1
Application number: EP06754905A
Authority: EP
Inventors: Hans Artmann; Arnim Hoechst; Andrea Urban
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-06-27
Filing date: 2006-04-27
Publication date: 2008-03-19
Also published as: JP2008543597A; WO2007000363A1; US8481427B2; US20100260974A1; DE102005029803A1

Abstract

The invention relates to a micromechanical method for producing a cavity in a substrate and, in particular a micromechanical component produced according to said method. The inventive method comprises a first step consisting in producing a first layer on a substrate or therein, in applying at least one second layer to the first layer and in producing an input hole in the said second layer in such a way that the first layer and substrate materiel is removable therethrough. Said second layer arranged above the cavity and can be subsequently used in the form of a membrane. It is also possible to apply other layers to the second layer, in such a way that they form a whole membrane, only. According to the main aspect of the invention, the first layer material is selected in such a way that a transition edge is produced in the first layer by removing the material thereof and is provided with an predeterminable angle between the substrate and the second layer.

Description

Method for producing a micromechanical component and micromechanical component

The invention describes a method for producing a micromechanical component which has a cavity in a substrate and a micromechanical component produced by this method.

State of the art

In microsystem technology, different membrane sensors are known. In this case, in a preferred production of such a membrane sensor, a membrane layer is first applied to a substrate before material is dissolved out of the substrate in order to produce a cavity below the membrane. Typically, processes of surface micromechanics (OMM) are used. For example, it is known to etch out the substrate material below the membrane region with an (isotropic) etching gas. Due to the isotropic etching process, this results in a vertical angle between the substrate material and the membrane.

Advantages of the invention

The present invention describes a micromechanical method for producing a cavity in a substrate or a micromechanical component produced by this method. In this method, a first layer is applied or deposited on a substrate in a first step. This can be done by one Deposition process done with in-situ doping. Alternatively, the layer may be created by implantation or doping of the substrate directly in the substrate surface. The doping can take place or be limited over the entire membrane region, so that the regions in which the etching front is to be found after the etching process have a doping which deviates from the substrate. In general, the doping in the first layer can be homogeneous or gradual. Subsequently, at least one second layer is applied to the first layer. An access hole is created in this second layer. Through this access hole, material of the first layer and of the substrate can be dissolved out, so that a cavity is produced below at least part of the second layer in the substrate. This second layer above the cavern can be used below as a membrane. In addition, however, it is also possible to deposit further layers on the second layer, which only form the membrane as a whole. The essence of the invention consists in the fact that the material of the first layer is chosen such that the dissolution of the material of the first layer creates a transitional edge in the first layer which has a predeterminable angle between the substrate and the second layer.

The advantage of a predeterminable angle of the transition edge is that a non-perpendicular angle between the substrate material and the second layer or membrane can be produced. Due to the non-perpendicular angle, the Schichtspannungseinkopplung can be changed and minimized in the membrane.

In one embodiment of the invention it can be provided that the angle of the transition edge is predetermined by the doping of the material of the first layer. In this case, it may be provided, for example, that the material of the first layer has a higher or lower doping level and / or a different doping type and / or a gradient compared to the material of the substrate.

Overall, a diaphragm sensor in surface micromechanics can be produced with the method according to the invention, wherein an isotropic etching process is used which predetermines the angle of the transition flank (= etching flank) between substrate and second layer or membrane by the choice of the materials of the substrate and the first layer.

Advantageously, the material is dissolved out by a gas phase etching. In particular, a gas phase etching with ClF ₃ or other halogen compounds such as XeF ₂ , BrF _{3 is} provided. A development of the invention generally uses an isotropic etching process for dissolving out the material.

Advantageously, a semiconductor material, in particular silicon, is provided as material for the substrate and for the first layer.

Advantageously, different layers can be applied to the first layer. Thus, under the second layer in a particular embodiment, a membrane layer can be understood. Furthermore, it is conceivable that one or more functional layers are applied to the first layer. Typical functional layers are, for example

Conductor tracks, layers with piezoresistive resistors, evaluation circuits and / or other electrical and / or mechanical layers which are customary in microsystem technology. In addition, however, it can also be provided that an insulating layer is applied to the first layer. Of course, it can also be provided that a plurality of said layers are deposited successively on the substrate or the first layer.

Further advantages will become apparent from the following description of exemplary embodiments or from the dependent claims.

drawings

Figures 1 to 3 show schematically the erfmdungsgemäße manufacturing method. FIG. 4 shows an alternative generation of two layers which react differently to an etching process.

embodiment

In a preferred embodiment, a silicon wafer 100 is used as the substrate for producing a micromechanical component. On this silicon wafer 100, a silicon layer 110 is epitaxially grown epi with a conventional micromechanical process, see FIG. 1. In order to achieve different etching rates in the substrate 100 and the first layer 110, it is provided that the material in the first layer 110 is covered by a silicon layer 110 - A -

Substrate 100 to provide different doping. It can be provided, for example, that the material of the first layer 110 can be provided with a higher doping, but also with a lower doping depending on the etching process used. A typical thickness of the first layer 110 is provided at 1 .mu.m to 10 .mu.m, although other layer thicknesses may well be used.

As shown in FIG. 2, a second layer 120 is applied to the first layer 110. This second layer 120 is then patterned so that at least access through the second layer 120 to the first layer 110 is possible through an access hole 130. By means of the second layer 120, for example, the membrane layer can be produced above the cavern 140 still to be produced. In addition, the second layer 120 is generally intended to stand for various layers that are mounted above the cavern 140. In this case, functional layers are conceivable, such as, for example, membrane layers, interconnects, evaluation circuits, piezoresistive resistors or other electrical and / or mechanical usable layers that can be produced using micromechanical production methods. However, it is also possible for an insulating layer to be applied first to the first layer 110, on which all further layers and functions necessary for the micromechanical component are deposited in the further manufacturing process.

The access holes 130 are used both for dissolving out the material from the first layer 110 and the material of the substrate 100. For extended cavities or to accelerate the etching process process can also be provided that a plurality of access holes 130 are arranged side by side. The distance between the access holes 130 to each other can be matched to the etching medium (gaseous or liquid), which is used to dissolve out the material.

In the next step for producing the cavern in the substrate, as shown in FIG. 3A, the material is removed from the substrate 100 and the first layer 110 through the access openings 130 by means of a gas-phase etching process. As a preferred gas phase etching process ClF _{3 has} proven itself. In general, however, any etching gases are suitable that used

Semiconductor material, or etch the silicon isotropically different for different dopants at different rates. Due to the different etch rates in the substrate 100 and the epitaxially deposited material of the first layer 110, an etch edge 150 is formed. In the detailed view of FIG. 3B, it can be seen that the different etching rates of the substrate 100 and the first layer 110 result in a transition edge 150 (= etching flank) which has an angle 160 to the perpendicular of the applied first layer 110. By suitable choice of the materials, the degree of doping, the doping type, the doping profile or the gradient, the etching gas and the etching conditions (eg temperature and concentration), this angle 160 of the etching flank or the transition flank 150 can be predetermined. By choosing the angle 160 of the transition edge 150, the layer voltage coupling into the second layer 120, or into the membrane, can be changed and minimized. Thus, a more stable embodiment of a micromechanical device with a cavern is possible.

Alternatively it can also be provided to introduce the first layer 112 directly into the substrate, as shown in FIG. In this case, an area 112 in the substrate 100 is initially produced by means of an implantation or a doping process. This region 112 can be present in the substrate 100 more or less extensively. The area 112, however, is characterized in that it forms part of the upper border of the later cavern 140 and has the transition edge 150 after the etching process. Preferably, the region 112 encloses the entire edge of the cavern 140, wherein it may also be provided that the region 112 consists of individual, non-interconnected partial regions. Importantly, however, the region 112 includes the subsequently created access holes through which the material of the substrate 100 is released.

Claims

claims

1. A micromechanical method for producing a cavity in a substrate with the steps

- Generating a first layer (110, 112) on or in a substrate (100), and

- applying at least one second layer (120) to the first layer (110, 112), and - creating an access hole (130) in the second layer (120) and

Dissolving material of the first layer (110, 112) and the substrate 100 through the access hole (130) to create a cavity (140), characterized in that by dissolving out the material of the first layer (110, 112) a transition edge (110) 150) is formed at a predetermined angle (160) between the second layer (120) and the substrate (100).

2. The method according to claim 1, characterized in that the angle is predetermined by the doping of the material of the first layer, in particular in relation to the substrate orientation, wherein it is provided in particular that the angle as a function of

Degree of doping and / or

- doping type and / or

- Doping profile or doping gradient is specified.

3. The method according to claim 1, characterized in that the first layer (112) is formed as a doped region in the substrate (100), wherein in particular it is provided that the transition edge (150) is formed after dissolution of the material in the first layer.

4. The method according to claim 1, characterized in that the material is dissolved out by a gas phase etching, wherein in particular a gas phase etching with ClF ₃ or another halogen compound such as XeF ₂ or BrF _{3 is} provided.

5. The method according to claim 1, characterized in that the material is dissolved out by an isotropic etching process.

6. The method according to claim 1, characterized in that a semiconductor material, in particular silicon, is provided as material for the substrate and for the first layer.

7. The method according to claim 1, characterized in that a membrane layer, a functional layer, a conductor, a piezoresistive resistor and / or an insulating layer is applied as the second layer.

8. Micromechanical device with

a substrate (100), a first layer (110),

a second layer (120) and

a cavern (140) delimited by the substrate (100), the first layer (110) and the second layer (120), characterized in that the first layer (110) forms a transitional edge (150) at an angle ( 160) between the second layer (120) and the substrate (100), wherein it is provided that the angle (160) depends on the material of the first layer (110) and the substrate (100).

9. The micromechanical component according to claim 7, characterized in that the material of the first layer and of the substrate has a different doping degree and / or a different doping type and / or a different doping profile or a different doping gradient.

10. Micromechanical component according to claim 7, characterized in that a semiconductor material, in particular silicon, is provided as the material for the substrate and for the first layer.

11. Micromechanical component according to claim 7, characterized in that the second layer has a membrane layer, a functional layer, a conductor track, a piezoresistive resistor and / or an insulation layer.