JPH02251142A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To facilitate the unified formation of a cantilever structure and a stopper by removing the first semiconductor layer that is exposed from a window by electrochemical etching while impressing voltage to the second semiconductor layer as well as a semiconductor substrate. CONSTITUTION:The second semiconductor layer 3 is removed by etching from the window 42 of a mask film. When electrochemical etching is performed after causing the first semiconductor layer 2 to be exposed, both the second semiconductor layer 3 and a semiconductor substrate 1 are protected from electrochemical etching and only the first semiconductor layer 2 is removed because the second semiconductor layer 3 and the semiconductor substrate 1 each have a conductivity type that is opposite to that of the first semiconductor layer 2; besides, the above layer 3 and substrate 1 are impressed by voltage. As only the above layer 2 which is sandwiched between the layer 3 and the substrate 1 is in this way removed, etching goes crosswise and a cavity 21 is formed below the layer 3 and as a result, a cantilever structure made up by the second semiconductor layer 3 is formed. A stopper on the substrate side of a cantilever is easily formed to be integral with the cantilever.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device in which a cantilever and a stopper are integrally formed.

[Conventional technology]

In acceleration sensors, acceleration switches, and the like using semiconductors, it may be necessary to form a cantilever structure. In such a case, conventionally, the p-type portion of the two-layer structure of n-type and p-type single crystal silicon is removed by electrochemical etching to create a cantilever. That is, for example, as shown in FIG. 2, an n-type single crystal 9912 layer 3 is epitaxially grown on a p-type wheel crystal silicon substrate 7, and a mask film 4.5 is further formed on both the front and back surfaces.
will be established. Then, as shown in FIG. 2A, an etching window 42 is provided in the mask film 4, and a part of the silicon layer 3 is removed through this window by normal etching to expose the substrate 7.
The structure is as shown in FIG. 2B. Thereafter, only the p-type substrate 7 is etched from this etching window 42 by electrochemical etching to form an n-type substrate 7 as shown in FIG. 2C.
A cavity 71 is formed under the silicon layer 3 of the mold. By forming the cavity 71 in this manner, the n-type silicon layer 3 above the cavity 71 becomes a cantilever 10. In addition, there are cases where it is done as shown in FIG. First, as shown in FIG. 3A, an n-type single crystal 9932 layer 3 is epitaxially grown on a p-type crystalline silicon substrate 7, and a mask film 4.5 is provided on both the front and back surfaces of the layer 3, and then a mask film 4.5 is formed on the back surface. 5
An etching window 51 is provided in the. Next, as shown in FIG. 3B, a cavity 71 is formed in the p-type substrate 7 through the etching window 51 from the back side by electrochemical etching. Thereafter, as shown in FIG. 3C, a cantilever 10 can be formed by forming a hole 31 in a part of the 11-type silicon layer 3 (and mask film 4) by ordinary etching or CF4 plasma etching. When creating a cantilevered structure in this way, the silico formed in a sudden manner is very easily destroyed, so it is necessary to protect it from destruction by limiting the amount of amplitude. That is, stoppers are attached to both sides of the cantilever beam 10 to prevent the cantilever beam from being bent beyond a certain level, thereby preventing the cantilever beam from being destroyed. Conventionally, when the strength of the cantilever beam 10 is high or when the substrate 7
If the cantilever beam 10 is sufficiently thin, a lower stopper 1 is bonded to the back side of the substrate 7, and an upper stopper 12 is bonded to the upper side of the cantilever beam 10, as shown in FIG. In addition, if the cantilever beam 10 is thin or has low strength, the cantilever beam 10 as shown in Fig. 5 may be used to reduce the amplitude.
A lower stopper 11 having a shape corresponding to the lower cavity of 0 is glued to the back side of the substrate 7, and an upper stopper 1.2 made of glass or silicon is attached to the upper side of the cantilever beam 10 using adhesive 13. That's what I do. This adhesive 13 is made by anodic bonding when the upper stopper 12 is made of glass, and by Cr vapor deposited on the cantilever 10 side when the upper stopper 12 is made of silicon.
-Au etc. are used.

[Problem to be solved by the invention]

However, when providing stoppers on both sides of the cantilever in the amplitude direction, the stopper on the side opposite to the substrate (the upper stopper in the above example) can be attached relatively easily, but the stopper on the substrate side (in the above case, the upper stopper) can be attached relatively easily. Regarding the lower stopper), there are many problems when the strength of the cantilever is small. In other words, the lower stopper must have a shape that corresponds to the cavity on the board side of the cantilever beam as shown in Figure 5, which is difficult, and it is difficult to accurately determine the distance between the cantilever beam and the stopper. extremely difficult. This invention provides a method for manufacturing a semiconductor device in which a stopper on the substrate side of a cantilever beam can be easily formed integrally with the cantilever beam, and the distance between the cantilever beam and the stopper can be controlled very accurately. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, in a method for manufacturing a semiconductor device according to the present invention, a first semiconductor layer of a conductivity type opposite to that of the substrate is formed on one surface of a semiconductor substrate of one conductivity type, and a first semiconductor layer of a conductivity type of the same conductivity type as the substrate is formed on one surface of a semiconductor substrate of one conductivity type. a step of sequentially epitaxially growing a second semiconductor layer, a step of forming a mask film on the second semiconductor layer, and a step of etching the second semiconductor layer through a window of the mask film to form the first semiconductor layer. and a step of removing the first semiconductor layer exposed through the window by electrochemical etching while applying a voltage to the second semiconductor layer and the semiconductor substrate.

[For production]

When the second semiconductor layer is removed by etching through the window of the mask film and the first semiconductor layer is exposed, electrochemical etching is performed, so that the second semiconductor layer and the semiconductor substrate are of a conductivity type opposite to that of the first semiconductor layer. By applying a voltage and protecting the first semiconductor layer from electrochemical etching, only the first semiconductor layer is removed. Since only the first semiconductor layer sandwiched between the second semiconductor layer and the semiconductor substrate is removed in this way, the etching progresses laterally and a cavity is formed under the second semiconductor layer. A cantilever structure is formed by the second semiconductor layer, and a predetermined gap is formed between the second semiconductor layer and the substrate, which serves as a stopper for the cantilever. In other words, the thickness of the first semiconductor layer to be grown on the semiconductor substrate is the distance between the cantilever and the flange.
By controlling the thickness of the first semiconductor layer, it is easy to increase the precision of the distance between the cantilever and the stopper. [Example] Next, an example of the present invention will be described with reference to the drawings. First, as shown in FIG. 1A, after epitaxially growing p-type crystal wrinkles 3 on the surface of an n-type single crystal silicon substrate 1,
Mask films 4 and 5 are formed on the layer 3 and on the back surface of the substrate 1, respectively. These mask films 4 and 5 are, for example, Fll i
It is made by growing O 2 or SiN. At the same time, as shown in FIG. 1B, a resistant region 6 is formed which will serve as contacts 1 to 1 during electrochemical etching to be described later. Therefore, a diffusion window 41 is formed in a part of the mask film 4, and by diffusing an appropriate impurity from this window 41, the n+ region penetrates the n-type layer 3 and the n-type layer 2 and reaches the substrate. Form a region. After that, an etching window 42 is formed in another part of the mask film 4.
A window 42 is provided, and wet etching is performed from this window 42. This wet etching may be a conventional one using, for example, KOH or EDP (a mixed solution of ethylenediamine, pyrocatechol, and water) as an etchant (the mask film 4 is SiN in the former case, and SIN or 5i02 in the latter case). In this way, as shown in FIG. 1C, a portion of the uppermost n-type layer 3 is removed to expose the next layer, the n-type layer 2. Next, electrochemical etching is performed to remove only the n-type layer 2 from the front side through the window 42. The etchant in this case (and the combination with the material of the mask film 4) is the same as above. At this time, contact 1-
A voltage is applied to the Il type layer 3 and the n-type substrate 1 to prevent them from being etched by electrochemical etching, and only the n-type layer 2 is etched. Then, etching progresses laterally in the n-type layer 2, and a cavity 21 sandwiched between the substrate 1 and the n-type layer 3 is formed as shown in the first diagram. The n-type layer 3 above this cavity 21 becomes a cantilever beam 10. Here, the cantilever beam 10 is connected to the substrate 1 with a cavity 21 in between.
This substrate 1 functions as the lower part of the cantilever beam 10. That is, the cantilever beam 10 and the lower rib 10 can be formed at the same time by one step of electro-chemical etching. Since the width of this cavity 21, that is, the distance between the cantilever beam 10 and the surface of the substrate 1 exactly matches the p-type wheel crystal wrinkles 3, first the p-type wheel crystal wrinkles 3 are formed on the surface of the substrate 1. By controlling the thickness of the cantilever beam 10, it is easy to set the distance between the cantilever beam 10 and the lower stopper as desired. As a result, extremely precise spacing of a few μI11 can be easily achieved. Finally, after removing the mask films 4 and 5, an upper stopper 12 made of glass or silicon is attached using an adhesive 13 as shown in FIG. 5, thereby completing the chip of the acceleration sensor or acceleration switch. In this case, the adhesive 13 is anodic bonding ink when the upper stopper 12 is made of glass, and when the upper stopper 12 is made of silicon, it is made of Cr-Au etc. deposited on the n-type single crystal 9937 layer 3. use

【Effect of the invention】

According to the method for manufacturing a semiconductor device of the present invention, the cantilever structure and the ribs can be easily and integrally formed in the same process without providing a separate process for attaching the ribs. can. Additionally, the distance between the cantilever and the stopper can be controlled with high precision. As a result, even semiconductor devices with low cantilever strength can be manufactured with good yield.

[Brief explanation of drawings]

Figure 1 A. B, C, and D are cross-sectional views showing each step of an embodiment of the present invention, and FIGS. 2A, B, and C, and 3 A, B, and C are each step of the conventional cantilever manufacturing process. A cross-sectional view showing
FIGS. 4 and 5 are cross-sectional views showing the stopper mounting process in a conventional example. 1... N-type single crystal silicon substrate, 2... P-type single crystal silicon layer, 3... 1) type single crystal silicon layer, 4.5
. . . Mask film, 6 . . 11+ region, 7 . . . P-type wheel crystal silicon substrate, 10 . , 21.71...Cavity, 41...Diffusion window, 42.51
...Edge〉'g window.

Claims (1)

[Claims] (1) A step of sequentially epitaxially growing a first semiconductor layer of a conductivity type opposite to that of the substrate and a second semiconductor layer of the same conductivity type as the substrate on one surface of a semiconductor substrate of one conductivity type; forming a mask film on the semiconductor layer;
etching the second semiconductor layer through the window of the mask film to expose the first semiconductor layer; and applying a voltage to the second semiconductor layer and the semiconductor substrate to remove the first semiconductor layer exposed from the window. 1. A method for manufacturing a semiconductor device, comprising the step of removing the semiconductor material by electrochemical etching.