JPH0918021A - Semiconductor dynamic quantity sensor and its manufacturing method - Google Patents

Abstract

PURPOSE: To prevent a movable part from being fixed to a substrate in the case of etching a sacrifice layer. CONSTITUTION: Silicon oxide films 2, 3 and a silicon nitride film 4 are formed on the surface of a P type silicon substrate 1 while a movable part 5 made of a thin film is arranged above the silicon nitride film 4 at a specific interval, besides a movable gate electrode part to be displaced by acceleration is provided on a part of the movable part 5. On the other hand, fixed electrodes (source.drain parts) made of an impurity diffused layer are formed on the P type silicon substrate 1 so that the running current may be fluctuated by the fluctuation of the relative position to the movable gate electrode part by acceleration. The movable range limiting protrusions 17 are provided on the underface of the movable part 5 excluding the movable gate electrode part so as to form an interval narrower than that between the P type silicon substrate 1 1 and the movable gate electrode part. Incidentally, the ends of the movable range limiting protrusions are rounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to acceleration, yaw rate,
The present invention relates to a semiconductor mechanical quantity sensor for detecting a mechanical quantity such as vibration, and more specifically, a MISFET (Metal-Insu).
Later-Semiconductor Field
The present invention relates to an effect transistor type semiconductor dynamic quantity sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in order to prevent a sudden collision between a movable portion having a beam structure and a substrate, a protrusion is formed on the movable portion side or the substrate side, and a sudden force acts on the movable portion. Also, there is known a sensor in which the protrusion comes into contact with the movable portion first to bring the displacement amount of the movable portion within a predetermined value. As such a sensor, for example, US Pat.
There is No. 726. This is shown in FIG. 11
As shown in FIG. 2, after the sacrifice layer is formed, the portions where the protrusions are to be formed are etched, and FIG. As shown in FIG. 12, the groove for forming the protrusion also has a deep groove formed in a portion which will be a leg portion of the beam structure. As shown in FIG. 13, polysilicon, which is a movable part forming film, is embedded. After that, the sacrifice layer is etched to form a beam structure.

[0003]

However, in the step of removing the sacrificial layer by wet etching, a replacement liquid (pure water or the like) for the etching liquid enters between the movable portion and the substrate, and the replacement liquid (pure liquid) is added. When water (or the like) is dried, there is a problem that the movable portion is pulled toward the substrate due to the surface tension of the replacement liquid and the movable portion is fixed to the surface of the substrate.

There is also a problem in that etching is required a plurality of times in order to form protrusions and legs having different sizes in the vertical direction of the substrate. Therefore, the first aspect of the present invention
Is to provide a semiconductor dynamic quantity sensor capable of preventing the movable part from sticking to the substrate when etching the sacrificial layer, and the second purpose is to provide the movable part to the substrate. It is another object of the present invention to provide a method for manufacturing a semiconductor dynamical quantity sensor, which is capable of easily forming the movable range limiting protrusion and the leg portion of the movable portion in addition to preventing sticking.

[0005]

According to a first aspect of the present invention, there is provided a semiconductor substrate and a semiconductor substrate, which is disposed above the semiconductor substrate with a predetermined space therebetween and has a movable gate electrode portion in a part thereof. A movable part of a beam structure that is displaced by the action of quantity,
A source / drain portion configured by forming an impurity diffusion layer on the semiconductor substrate, in which a flowing current changes due to a change in a relative position with the movable gate electrode portion due to an action of the mechanical quantity; A semiconductor provided with a movable range limiting section provided between the semiconductor substrate and the movable section and having a pointed or rounded tip so as to form a distance narrower than the distance between the movable gate electrode section and the movable gate electrode section. The gist is a mechanical quantity sensor.

The invention according to claim 2 is a semiconductor substrate,
A movable part having a beam structure formed of a thin film, which is arranged at a predetermined interval above the semiconductor substrate by the legs and is displaced by the action of a mechanical quantity, and a movable part provided on the lower surface of the movable part. A method of manufacturing a semiconductor dynamical amount sensor, comprising: a movable range limiting protrusion that limits a displacement amount to the semiconductor substrate side, wherein a sacrificial layer having a substantially uniform thickness is formed on a main surface of the semiconductor substrate. A step of forming a resist on the sacrificial layer, a third step of exposing the resist with a photomask using an exposure device having a predetermined resolution, and a step of using the exposed resist And a fourth step of thinning the formation portion of the movable range limiting protrusion which is a part of the sacrificial layer, and a fifth step of forming a movable portion forming film made of a thin film on the remaining sacrificial layer. The sacrificial layer under the movable part forming film Leg is etched away, the movable portion,
A sixth step of forming protrusions for limiting the movable range, and the photomask in the third step has a pattern for forming a leg portion, and a fine pattern in which a protrusion formation region is finer than the resolution of the exposure device. The gist of the fourth step is to provide a method for manufacturing a semiconductor mechanical quantity sensor, in which a groove having a sharp tip or a rounded tip on the bottom surface side is formed in the projection formation region.

According to a third aspect of the present invention, in the invention according to the second aspect, the fine pattern in the protrusion forming region of the photomask in the third step is located on the center side of the protrusion forming region in the protrusion forming region. The gist is a method of manufacturing a semiconductor mechanical quantity sensor in which the amount of light transmission gradually changes.

[0008]

According to the invention described in claim 1, when the mechanical quantity acts, the relative position between the source / drain portion and the movable gate electrode portion changes, and the current flowing in the source / drain portion is changed by this positional change. It changes and the mechanical quantity is detected. At this time, in the movable range limiting portion, the distance is narrower than the distance between the semiconductor substrate and the movable gate electrode portion.
Therefore, when the movable portion is displaced in the direction approaching the semiconductor substrate due to an excessive mechanical amount, the movable range limiting portion contacts before the movable gate electrode portion contacts the semiconductor substrate, and the movable gate electrode portion is moved to the semiconductor substrate further than the movable gate electrode portion. Is prevented from approaching. In this way, contact between the movable gate electrode portion and the semiconductor substrate is avoided, and the MISFET type transistor characteristics do not change.

Further, even when liquid enters between the movable portion and the substrate at the time of manufacturing the sensor, due to the existence of the movable range limiting portion, droplets are formed only between the movable range limiting portion and the substrate,
It is possible to weaken the adhesive force between the movable part and the substrate due to the liquid droplets, and since the tip of the movable range limiting part is sharp or rounded, the contact area between the movable range limiting part due to the droplets and the substrate is reduced. The adhesive force between the movable portion and the substrate is further weakened to prevent the movable portion from sticking to the substrate.

According to the second aspect of the invention, the sacrificial layer having a substantially uniform thickness is formed on the main surface of the semiconductor substrate by the first step, and the resist is formed on the sacrificial layer by the second step. Then, in the third step, the resist is exposed using a photomask with an exposure device having a predetermined resolution. In the third step, a photomask having a pattern for forming the leg portion and a fine pattern in which the projection forming region is finer than the resolution of the exposure device is used as the photomask.

By the fourth step, the exposed resist is used to form a groove having a sharp tip or a rounded tip on the bottom surface side in the formation region of the movable range limiting protrusion which is a part of the sacrificial layer.

By the fifth step, on the remaining sacrificial layer,
A movable portion forming film made of a thin film is formed, and in the sixth step, the sacrificial layer under the movable portion forming film is removed by etching, so that the leg portion, the movable portion, and the protrusion for limiting the movable range having a pointed or rounded tip. Is formed.

Therefore, the movable range limiting protrusion can be manufactured without increasing the number of photomasks. As a result, a semiconductor dynamic quantity sensor is manufactured without increasing the number of processes. Further, since the leg portions and the protrusions are manufactured with one photomask, the sacrifice layer can be easily processed.

Further, even when liquid enters between the movable portion and the substrate during manufacturing of the sensor, a droplet is formed only between the protrusion and the substrate due to the presence of the protrusion, and the droplet causes the movable portion and the substrate to be separated from each other. In addition to weakening the adhesive force of the protrusion, the tip of the protrusion is sharp or rounded, so that the contact area between the protrusion and the substrate due to the droplets described above is reduced to further weaken the adhesive force between the movable part and the substrate. Sticking of the movable part to the substrate is avoided.

According to the invention described in claim 3, according to claim 2
In addition to the effect of the invention described in (3), since the fine pattern of the projection formation region of the photomask in the third step is such that the light transmission amount gradually changes toward the center of the projection formation region in the projection formation region. It is possible to easily form a predetermined projection shape.

[0016]

【Example】

(First Embodiment) A first embodiment in which the present invention is embodied in a semiconductor acceleration sensor will be described below with reference to the drawings.

FIG. 1 is a plan view of the semiconductor acceleration sensor of this embodiment. 2 shows a cross section taken along the line AA of FIG.
FIG. 3 shows a cross section taken along the line BB of FIG. 1, and FIG.
The C section is shown. This semiconductor acceleration sensor uses surface micromachining technology.

A silicon oxide film 2 as a gate insulating film is formed on a part of the P-type silicon substrate 1.
This silicon oxide film 2 is for reducing the leak current on the surface of the substrate and for suppressing the change in transistor characteristics over time. Similarly, an insulating isolation silicon oxide film 3 (LOCOS oxide film in this embodiment) having a predetermined thickness is formed on a part of the P-type silicon substrate 1. Further, a silicon nitride film (insulating film) 4 is formed on the silicon oxide film 2 and the silicon oxide film 3 for protecting the silicon oxide film 2 when etching a sacrifice layer described later. In this embodiment, the P-type silicon substrate 1, the silicon oxide film 2, the silicon oxide film 3 and the silicon nitride film 4 constitute a semiconductor substrate.

An anchor portions 6 as four legs are arranged on the silicon nitride film 4 in the formation region of the silicon oxide film 3, and the anchor portion 6 is movable above the formation region of the silicon oxide film 2 with the anchor portion 6 as a base end. The part 5 is installed.
The movable portion 5 is composed of four beam portions 7, a weight portion 8 and movable gate electrode portions 9 and 10, and has a beam structure. More specifically, a belt-shaped beam portion 7 extends from the anchor portion 6 and a square-shaped weight portion 8 is supported. Further, rectangular movable gate electrode portions 9 and 10 are provided on the weight portion 8 so as to project in opposite directions. The movable portion 5 and the anchor portion 6 are made of a polysilicon thin film having a thickness of about 2 μm. The movable portion 5 (beam portion 7, weight portion 8, movable gate electrode portions 9 and 10) is arranged above the silicon substrate 1 (silicon nitride film 4) at a predetermined interval. In this way, the movable part 5 is arranged above the substrate 1 by the anchor part (leg part) 6 at a predetermined interval, and can be displaced in the direction perpendicular to the surface of the silicon substrate 1. ing.

Further, the weight portion 8 has a rectangular opening 11 formed therein, which facilitates penetration of an etching solution at the time of sacrifice layer etching which will be described later. As shown in FIG. 4, the silicon substrate 1 below the movable gate electrode portion 10 of the movable portion 5
On the both sides of the movable gate electrode portion 10, fixed electrodes 12 and 13 as source / drain portions made of N-type impurity diffusion layers are formed. Similarly, as shown in FIG. 1, the silicon substrate 1 below the movable gate electrode portion 9 of the movable portion 5 has a source / drain portion formed of N-type impurity diffusion layers on both sides of the movable gate electrode portion 9. Fixed electrodes 14 and 15 are formed. As shown in FIG.
A channel region 16 is formed between the fixed electrodes 12 and 13 on the silicon substrate 1, and the channel region 16 is generated by applying a voltage between the silicon substrate 1 and the movable gate electrode portion 10. And the fixed electrode 1
By applying a voltage between 2 and 13, a drain current flows in this channel region 16. Similarly, a channel region (not shown) is formed between the fixed electrodes 14 and 15 on the silicon substrate 1, and the channel region is generated by applying a voltage between the silicon substrate 1 and the movable gate electrode unit 9. Things. When a voltage is applied between the fixed electrodes 14 and 15, a drain current flows through the channel region.

As shown in FIG. 2, a movable range limiting projection (movable range limiting section) that projects (displaces) toward the silicon substrate 1 is provided at a position close to the weight section 8 in each beam section 7 of the movable section 5. 17 are formed respectively. The movable range limiting protrusion 17 has a rounded tip. As shown in FIG. 4, the gap (distance) L1 between the movable range limiting protrusion 17 and the silicon nitride film 4 on the silicon substrate 1 is defined by the movable gate electrode portions 9 and 10 of the movable portion 5 and the silicon substrate 1. It is smaller than the gap (distance) L2 with the upper silicon nitride film 4. In this way, the movable range limiting protrusion 17
Is provided at a position close to the weight portion 8 in the beam portion 7, and is formed by displacing the movable portion 5 made of a polysilicon thin film downward.

On the surface of the silicon substrate 1, a movable part 5
The lower electrode 1 made of an N-type impurity diffusion layer in the region opposite to the fixed electrodes 12, 13, 14, 15
8 are formed. This lower electrode 18 is kept at the same potential as that of the movable portion 5, and the silicon substrate 1 and the movable portion 5 are kept at the same potential.
This is to suppress the electrostatic force generated between and.

Peripheral circuits (not shown) are formed around the area where the movable portion 5 is arranged on the silicon substrate 1. Then, the peripheral circuit and the movable portion 5 (movable gate electrode portions 9, 1
0) is electrically connected, the peripheral circuit and the fixed electrodes 12, 13, 14, 15 are electrically connected, and further, the peripheral circuit and the lower electrode 18 are electrically connected.

Next, the operation of this semiconductor acceleration sensor will be described. When a voltage is applied between the movable portion 5 and the silicon substrate 1 and between the fixed electrodes 12, 13 (14, 15), a channel region 16 is formed, and the fixed electrodes 12, 13 (1
Current flows between (4, 15). Here, the present semiconductor acceleration sensor receives acceleration and moves in the X ₊ direction (substrate 1) shown in FIG.
When the movable gate electrode portions 9 and 10 (movable portion 5) are displaced in the direction parallel to the surface of the fixed electrode 12, the area of the channel region between the fixed electrodes (the channel width in a transistor) changes, thereby causing the fixed electrode 12 to move. , 13 decrease,
The current flowing through the fixed electrodes 14 and 15 increases. Also, FIG.
When the movable gate electrode portions 9 and 10 (the movable portion 5) are displaced in the X _- direction (the direction parallel to the surface of the substrate 1) shown in FIG.
By changing the area of the channel region between the fixed electrodes (channel width in a transistor), the fixed electrodes 12 and 13 are changed.
The current flowing through the fixed electrodes 14 and 15 decreases, and the current flowing through the fixed electrodes 14 and 15 decreases. On the other hand, when the semiconductor acceleration sensor receives the acceleration, the Z ₊ direction (perpendicular to the surface of the substrate 1,
In addition, when the movable gate electrode portions 9 and 10 are displaced in the direction away from the substrate 1), the carrier concentration in the channel region 16 is reduced due to the change in the electric field intensity, so that the current is simultaneously reduced.

In this way, the movable gate electrode portions 9 and 10 and the fixed electrodes 12, 13 and 14, 1 due to acceleration
The current flowing between the fixed electrodes 12 and 13 and between the fixed electrodes 14 and 15 changes due to the change in the relative position with respect to 5, and two-dimensional acceleration is detected by the magnitude and phase of this current change.

Further, between the semiconductor substrate (P-type silicon substrate 1, silicon oxide films 2 and 3, silicon nitride film 4) and the movable portion 5 other than the movable gate electrode portions 9 and 10, that is, the beam portion 7. Providing a movable range limiting protrusion 17 on the lower surface, the distance (L) between the silicon nitride film 4 and the movable gate electrode portions 9 and 10 is reduced.
The distance (L1) is narrower than that of 2), and the moving range in the direction in which the movable portion 5 (movable gate electrode portions 9 and 10) approaches the substrate 1 (indicated by Z ₋ in FIG. 4) is limited. Therefore, within the normal acceleration range, the sensor normally functions as an acceleration sensor, but when excessive acceleration is applied in the direction in which the movable portion 5 is separated from the substrate 1, the movable portion 5 (the movable gate electrode portions 9, 1
0) tries to deform toward the substrate 1 due to the acceleration. At this time, before the movable gate electrode portions 9 and 10 come into contact with the silicon substrate 1 (silicon nitride film 4), the movable range limiting projections 17 come into contact with the silicon nitride film 4 and the movable gate electrode portions 9 and 10 Further approaching to the silicon substrate 1 side is blocked. That is, the excessive deformation can be suppressed. In this way, contact between the movable gate electrode portions 9 and 10 and the silicon substrate 1 (silicon nitride film 4) is avoided,
The transistor characteristics of the MISFET do not deteriorate.

Next, a manufacturing process of the semiconductor acceleration sensor of this embodiment will be described with reference to FIGS. First, as shown in FIG.
A type silicon substrate 1 is prepared, and a silicon oxide film 3 (LOCOS oxide film in this embodiment) is formed on a predetermined region of the main surface thereof. Then, a silicon oxide film 2 is formed on the surface other than the silicon oxide film 3 on the P-type silicon substrate 1 by thermal oxidation, and further below the lower electrode 18 made of an N-type impurity diffusion layer and the source of a MISFET not shown. Department (1
2) and (14) and the drain portions (13) and (15) are formed, impurities are simultaneously introduced by ion implantation or the like, and heat treatment is performed. Further, a silicon nitride film 4 is formed on the entire surface of the silicon oxide film 2 and the silicon oxide film 3 by low pressure CVD or the like.

Subsequently, as shown in FIG. 6, a silicon oxide film 19 serving as a sacrificial layer is formed on the entire surface of the silicon nitride film 4 by plasma CVD or the like. The silicon oxide film 19 has a substantially uniform thickness.

Thereafter, as shown in FIG. 7, a positive type resist 20 is applied on the entire surface of the silicon oxide film 19 by spin coating. Then, as shown in FIG. 8, the positive resist 20 is exposed and developed using the photomask 21 shown in FIGS. 12 and 13, and a portion M1 for removing all the positive resist 20 and the thickness direction of the positive resist 20. Part of which is partially removed (movable range limiting projection forming part) M2
Then, a portion M3 for leaving all the positive resist 20 is formed.

This processing will be described in detail. FIG.
Shows a photomask 21 for patterning the sacrificial layer shown by hatching in the formation region of the movable portion 5. FIG. 13 is an enlarged view of part D of the photomask 21. Here, the hatched portion indicates a light shielding portion formed of chrome or the like. As shown in part E in FIG. 13,
A distributed exposure unit 22 as a fine pattern finer than the resolution of the exposure machine is formed in a part of the portion corresponding to the beam portion 7 (movable range limiting projection forming portion). In the distributed exposure unit 22, a large number of small rectangular windows 23 through which light is transmitted are distributed and formed at a predetermined density as shown in FIG. The size of the rectangular window 23 is equal to or smaller than the resolution of the exposure machine that uses the photomask 21 for exposure. For example, if the exposure machine used is a reduction exposure machine of 10: 1 and the resolution is 1 micron, it is suitable that the size of one side of one rectangle is 10 times the reticle size and 1 micron or less. In FIG. 14, the distribution exposure part 22 of the photomask 21 of FIG. 13 is further enlarged, and the light transmission amount of the photomask 21 is correspondingly shown. The amount of light transmitted through the areas K1 and K3 other than the distributed exposure section 22 is zero.

On the other hand, the amount of transmitted light in the area K2 which is the distributed exposure section 22 is increased so that it goes to the center.
The density (number / unit area) of each window 23 is changed. Further, the light transmission amount in the region K2 which is the distributed exposure portion 22 increases toward the center, but the light transmission amount has a rounded peak in the center portion.

As described above, when the photomask 21 described with reference to FIGS. 12 to 14 is used for distributed exposure and then development, as shown in FIG. 8, the portion M1 through which light is completely transmitted is completely developed. Therefore, the resist 20 is completely removed.
Further, the resist 20 is completely left on the portion M3 where the light is completely shielded. On the other hand, the part M2 where the light is partially transmitted is
The film thickness of the resist 20 is reduced.

Next, as shown in FIG. 9, the developed resist 20 is used as a photomask to wet-etch or dry-etch the sacrificial silicon oxide film 19. Desirably, dry etching with CF ₄ and O ₂ is performed. CF ₄ etches the silicon oxide film 19, and O ₂ etches the resist 20. At this time,
When the flow rates and pressures of the respective gases are set so that the etching rate of the silicon oxide film 19 by CF ₄ and the etching rate of the resist 20 by O ₂ become equal,
The developed shape of the resist 20 is transferred as it is to the silicon oxide film 19 serving as a sacrifice layer. That is, in the silicon oxide film 19 serving as the sacrificial layer, a portion (groove) 19a having a partially reduced film thickness and a portion 19b having no change in film thickness are formed. The thinned portion (groove) 19a is the location where the movable range limiting projection 17 is formed, and the portion (groove) 1
The bottom end of 9a is rounded. In addition, a part of the region (deep groove) where the silicon oxide film 19 has disappeared becomes the location where the anchor portion 6 (leg portion) is formed.

Next, as shown in FIG. 10, a polysilicon thin film 24 as a movable part forming film is formed by low pressure CVD or the like. Next, as shown in FIG. 11, the polysilicon thin film 24 is patterned to form the anchor portion 6, the opening 11,
The beam portion 7, the weight portion 8, the movable gate electrode portions 9 and 10, and the movable range limiting protrusion 17 are collectively formed.

Finally, when the silicon oxide film 19 (sacrificial layer) is etched, as shown in FIG. 2, except for the anchor portion 6, the beam portion 7, the weight portion 8, the movable gate electrode portions 9 and 1 are formed.
0 and the movable range limiting protrusion 17 are separated from the underlying silicon nitride film 4 to form a movable structure.

The step of etching the silicon oxide film 19 (sacrificial layer) will be described in more detail. The substrate is placed in an etching solution to etch the silicon oxide film 19 (sacrificial layer), and then the substrate is taken out of the etching solution. In this state, since the etching liquid is attached to the surface of the substrate, the substrate is immersed in pure water to replace the etching liquid, and then the substrate is taken out of the pure water and dried. When the substrate is dried, pure water exists between the movable portion (beam portion 7, weight portion 8, movable gate electrode portions 9 and 10) and the substrate 1,
As the drying progresses, pure water becomes droplets, and the surface tension of the droplets causes the movable portions (beam portion 7, weight portion 8, movable gate electrode portions 9 and 10) to be fixed to the surface of the substrate 1 in a pulled form. In some cases, the movable structure cannot be formed. On the other hand, in the present embodiment, the presence of the movable range limiting projections 17 can prevent the above-mentioned fixation of the movable portion to the substrate surface. This is because the above-mentioned pure water droplet (indicated by W1 in FIG. 2) is formed between the movable range limiting protrusion 17 and the substrate 1, and this droplet is small.

More specifically, as shown in FIG. 15, the tip of the movable range limiting projection 17 shown in FIG. 2 is rounded as compared with the case where the tip of the movable range limiting projection 60 shown in FIG. 15 is flat. The size of the droplet becomes smaller than the size of the droplet (indicated by W2).

Therefore, the surface tension of the liquid droplets acting between the movable portion (the beam portion 7, the weight portion 8, the movable gate electrode portions 9 and 10) and the substrate 1 becomes small, and the movable portion is fixed to the substrate surface. It can be surely prevented. Moreover, even if the movable part is temporarily attached to the substrate surface due to the decrease in the surface tension of the droplet, the rigidity (restoring force) of the beam causes the movable part to separate from the substrate surface and return to the original state. In this way, the movable structure can be easily and reliably formed.

As described above, in this embodiment, the semiconductor substrate (P
A silicon oxide film 19 (sacrificial layer) having a substantially uniform thickness is formed on the main surfaces of the silicon substrate 1, the silicon oxide films 2, 3, and the silicon nitride film 4) (first step). A resist 20 is formed on the resist (second step), and the resist 20 is exposed to light using a photomask 21 with an exposure machine having a predetermined resolution (third step). The exposed resist 20 is used to form a silicon oxide film. A portion of the movable range limiting protrusion, which is a part of 19, is thinned (fourth step), and a polysilicon thin film 24 is formed on the remaining silicon oxide film 19.
(Moveable part forming film made of thin film) is formed (fifth step),
When the silicon oxide film 19 under the polysilicon thin film 24 is removed by etching to form the anchor portion 6 (leg portion), the movable portion 5, and the movable range limiting projection 17 (sixth step), the photomask in the third step Reference numeral 21 denotes a pattern for forming an anchor portion (leg portion formation) and a fine pattern in which the protrusion forming region is finer than the resolution of the exposure machine. In the fourth step, the tip on the bottom surface side in the protrusion forming region is formed. It forms a sharp or rounded groove (19a).

Therefore, the projection for limiting the movable range can be manufactured without increasing the number of photomasks, the semiconductor dynamic quantity sensor can be manufactured without increasing the number of processes, and the anchor portion (leg portion) can be formed with one photomask. Since the protrusions are manufactured, the sacrifice layer can be easily processed. Furthermore, since the tips of the protrusions are sharp or rounded, the contact area between the protrusions and the substrate due to liquid droplets is reduced during sensor manufacturing to weaken the adhesive force between the movable portion and the substrate, and the substrate of the movable portion is reduced. Can be prevented from sticking to.

Further, in the projection forming region of the photomask 21 in the third step, since the amount of light transmission gradually increases toward the center of the projection forming region, it is possible to easily form a predetermined projection shape.

Since the movable range limiting projections 17 are provided on each of the four beam portions 7, even if the movable portion 5 (beam portion 7) is twisted, the movable range provided on each beam portion 7 is increased. The limiting projection 17 can surely bring the movable range limiting projection 17 into contact before the movable gate electrode portions 9 and 10 come into contact with the silicon substrate 1 (silicon nitride film 4).

Further, since the movable range limiting projection 17 is provided at a position of the beam section 7 of the movable section 5 close to the weight section 8, even if the weight section 8 is deformed due to excessive acceleration, the movable range limiting projection is formed. The deformation can be prevented by 17.

Furthermore, since the movable range limiting protrusion 17 is formed by displacing the thin film forming the movable portion 5 downward, the protrusion 17 can be easily formed. (Second Embodiment) Next, a second embodiment will be described focusing on differences from the first embodiment.

In the first embodiment, the tip of the movable range limiting projection 17 is rounded, but in the present embodiment, the tip of the movable range limiting projection 17 is sharpened as shown in FIG. Even in this case, the same operational effects as those described in the first embodiment can be obtained.

Here, comparing the case where the tip of the movable range limiting projection 17 is rounded and the case where the tip of the movable range limiting projection 17 is sharpened, from the viewpoint of mechanical strength, the rounded tip is used. Can be said to be less likely to be damaged when it comes into contact with the substrate. (Third Embodiment) Next, a third embodiment will be described focusing on differences from the first embodiment.

FIG. 17 shows a cross section of the sensor of this embodiment.
As shown in FIG. 2, the movable range limiting protrusion 17 has the first
In the example, the movable portion 5 made of a polysilicon thin film was formed by displacing it downward, and the thickness was the same as that of the movable portion 5. On the other hand, in the sensor of the present embodiment, the movable range limiting projection 26 as the movable range limiting section is formed by increasing the film thickness of the movable section 5. In this case, the impact resistance is excellent when an excessive acceleration is applied. (Fourth Embodiment) Next, the fourth embodiment will be described focusing on the differences from the first embodiment.

FIG. 18 is a plan view of the sensor of this embodiment, and FIG. 19 is a sectional view taken along line GG of FIG. In the above-described first embodiment, the movable range limiting protrusions 17 are provided on each of the four beam portions 7.
However, in this embodiment, the installation position and the number of the movable range limiting projections 17 are changed.

As shown in FIGS. 18 and 19, two movable range limiting projections 17a to 17h are separately installed on each beam portion 7, and each movable range limiting projection 17a to 17h.
Is 50 μm or more. Furthermore, the weight portion 8
Also, in each of the quadrangular weight portions 8, two quadrangular movable range limiting projections 17i to 17q are installed separately from each side, and each movable range limiting projection 17i to 17q.
Is also 50 μm or more. The distance between the movable range limiting projections 17a to 17q is set to 50 μm or more because the total sum of the facing areas of the movable range limiting projections 17a to 17q and the substrate surface (lower electrode 18) is made smaller, and the sacrifice layer etching step is performed. The total surface tension of the liquid droplets (replacement liquid of the etching liquid) formed between the movable range limiting projections 17a to 17q and the substrate surface is reduced so that the movable portion is pulled and fixed to the substrate surface. This is to avoid.

18 and 19, the movable gate electrode portions 9 and 10 and the fixed electrodes 12, 13, 14 and 15 as the source / drain portions in FIG. A hole) 50 is provided to form a cantilevered movable gate electrode portion 51 extending in the X ₊ direction and a cantilevered movable gate electrode portion 52 extending in the X ₋ direction. That is, a pair of beam-shaped movable gate electrode portions 51 and 52 facing each other are formed by the opening 50. Further, fixed electrodes 53, 54, 55, 56 as source / drain portions are formed at positions facing the cantilevered movable gate electrodes 51, 52, similarly to the positional relationship of the transistors in FIG. In this way, the pair of beam-shaped movable gate electrode portions 51 and 52 can be arranged close to each other in the central portion of the weight portion 8. As a result, compared with the case where the movable gate electrode portions 9 and 10 are provided so as to project from the opposite sides of the weight portion 8 shown in FIG. 1, for example, the movable gate electrode portion 5 is also warped when the weight portion 8 is warped.
It is possible to make 1 and 52 less likely to contact the substrate, and to form two transistors close to each other in regions (regions) having the same crystal structure of the substrate, which makes it possible to achieve uniform element characteristics.

As an application example of this embodiment, the movable range limiting protrusion 17 may be formed only on the weight portion 8. In this case, when the area of the weight portion 8 is increased to increase the sensitivity, the weight portion 8 is deformed due to acceleration, but if the movable range limiting protrusions 17 are provided at the corners of the square weight portion 8. The deformation of the weight portion 8 can be prevented. Further, the weight portion 8 has a protrusion 17
Without providing the movable range limiting projection 1 for one beam 7.
A plurality of 7 may be provided. (Fifth Embodiment) Next, the fifth embodiment will be described focusing on the differences from the first embodiment.

FIG. 20 shows a sectional view of the sensor of this embodiment. In the first embodiment, the movable portion 5 has a protrusion 17 for limiting the movable range.
However, in the present embodiment, the movable range limiting projection 25 as the movable range limiting portion is formed on the upper surface of the P-type silicon substrate 1 (semiconductor substrate). This protrusion 25 is a LOCO
The movable range limiting projection 25 is formed of an S oxide film, and the tip is rounded.

As an application example of this embodiment, as shown in FIG. 21, a projection having a sharp tip may be used instead of rounding the tip. Further, the movable range limiting protrusion 17 may be provided on the movable portion 5, and the movable range limiting protrusion may be provided on the upper surface of the P-type silicon substrate 1 (semiconductor substrate). In this case, the first projection may be provided on the lower surface of the movable portion 5 and the second projection may be formed on the upper surface of the substrate facing the first projection.

The present invention is not limited to the above-mentioned embodiments, and the movable part 5 has a double-supported beam structure in the above-mentioned embodiments, but it may have a cantilever structure. Further, the movable range limiting projections (17, 25) as the movable range limiting portion may be a cone, a pyramid, or a ridge having a triangular cross section.

In addition to the semiconductor acceleration sensor, it may be embodied as a semiconductor yaw rate sensor, a vibration sensor, or the like.

[0056]

As described above in detail, according to the invention described in claim 1, when the sacrifice layer is etched, it is possible to prevent the movable portion from being fixed to the substrate, which is an excellent effect.

According to the second aspect of the present invention, in addition to preventing the movable portion from sticking to the substrate, the movable range limiting projection and the leg portion of the movable portion can be easily formed. According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, the projection can be easily formed into a desired shape.

[Brief description of the drawings]

FIG. 1 is a plan view of a semiconductor acceleration sensor according to a first embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

3 is a sectional view taken along line BB of FIG.

FIG. 4 is a sectional view taken along the line CC of FIG. 1;

FIG. 5 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 6 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 7 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 8 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 9 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor.

FIG. 10 is a cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor.

FIG. 11 is a cross-sectional view showing the manufacturing process of the semiconductor acceleration sensor.

FIG. 12 is a plan view of a photomask for patterning a sacrificial layer.

FIG. 13 is a partially enlarged view of the photomask.

FIG. 14 is an explanatory diagram showing a distributed exposure portion of a photomask and a light transmission amount.

FIG. 15 is a sectional view of a sensor for comparison.

FIG. 16 is a sectional view of a semiconductor acceleration sensor according to a second embodiment.

FIG. 17 is a sectional view of a semiconductor acceleration sensor according to a third embodiment.

FIG. 18 is a sectional view of a semiconductor acceleration sensor according to a fourth embodiment.

19 is a cross-sectional view taken along line GG of FIG.

FIG. 20 is a sectional view of a semiconductor acceleration sensor according to a fifth embodiment.

FIG. 21 is a sectional view of a semiconductor acceleration sensor of an application example of the fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate which comprises a semiconductor substrate, 2 ... Silicon oxide film which comprises a semiconductor substrate, 3 ... Silicon oxide film which comprises a semiconductor substrate, 4 ... Silicon nitride film which comprises a semiconductor substrate, 5 ... Movable part, 6 ... Anchor as a leg, 7
... Beam portion, 8 ... Weight portion, 9 ... Movable gate electrode portion, 10 ... Movable gate electrode portion, 12 ... Fixed electrode as source / drain portion, 13 ... Fixed electrode as source / drain portion,
14 ... Fixed electrodes as source / drain portions, 15 ... Fixed electrodes as source / drain portions, 17 ... Movable range limiting projections as movable range limiting portions, 19 ... Silicon oxide film as sacrificial layer, 19a ... Grooves , 20 ... Positive resist, 21 ... Photomask, 22 ... Distributed exposure portion as a fine pattern, 24 ... Polysilicon thin film as movable portion forming film, 25 ... Movable range limiting projection as movable range limiting section, 26 ... Projection for limiting movable range as movable range limiting section

Claims (3)

[Claims] A semiconductor substrate disposed at a predetermined interval above the semiconductor substrate;
A movable portion having a beam structure, which has a movable gate electrode portion in a part thereof and is displaced according to the action of a mechanical amount, and an impurity diffusion layer are formed on the semiconductor substrate. The semiconductor substrate is formed so as to form an interval narrower than an interval between the source / drain part in which a current flowing changes due to a change in relative position with the movable gate electrode part and the semiconductor substrate and the movable gate electrode part. And a movable portion, which is provided between the movable portion and the movable portion, and has a sharpened or rounded movable range limiting portion. 2. A semiconductor substrate, a movable part having a beam structure composed of a thin film, which is disposed above the semiconductor substrate with a leg portion at a predetermined distance from each other and is displaced according to the action of a mechanical quantity, and a movable part of the movable part. A method for manufacturing a semiconductor dynamic quantity sensor, comprising: a movable range limiting protrusion that is provided on a lower surface and limits a displacement amount of the movable portion to the semiconductor substrate side. A first step of forming a uniform sacrificial layer, a second step of forming a resist on the sacrificial layer, and a third step of exposing the resist with a photomask using an exposure device having a predetermined resolution. And a fourth step of thinning the formation portion of the movable range limiting protrusion which is a part of the sacrificial layer by using the exposed resist, and forming a movable portion made of a thin film on the remaining sacrificial layer. A fifth step of forming a film, And a sixth step of forming a leg portion, a movable portion, and a movable range limiting protrusion by etching away the sacrificial layer below the movable portion forming film, wherein the photomask in the third step is a leg portion. The pattern for formation and the protrusion formation region have a fine pattern finer than the resolution of the exposure machine, and the fourth step is to form a pointed or rounded groove on the bottom surface side tip in the protrusion formation region. A method for manufacturing a semiconductor dynamical quantity sensor which is to be formed. 3. The light transmission amount of the fine pattern in the protrusion formation region of the photomask in the third step gradually changes toward the center side of the protrusion formation region in the protrusion formation region. Manufacturing method of semiconductor dynamic quantity sensor.