JPH1022452A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which does not require precise control of the height of recess and protrusion steps and has a thin-film resistor enabling satisfactory laser trimming. SOLUTION: In this device, a step portion (4) having a tapered portion 4a inclined with respect to the direction of thickness of a semiconductor substrate is formed on the surface of the semiconductor substrate located under a region where a thin-film resistor 3 is to be formed. Then, an insulating film 2 is formed thereon and the surface is planarized. The thin-film resistor 3 is formed thereon. By carrying out laser trimming on this semiconductor device, the interference state between an incident light and a reflected light from the interface between the semiconductor substrate and the insulating film 2 is changed. Trimming is carried out in such a manner as to generate a laser energy amplifying region and a laser energy offsetting region in a direction perpendicular to the direction of thickness of the semiconductor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a thin film resistor which is trimmed by a laser.

[0002]

2. Description of the Related Art Conventionally, a resistive material such as CrSi is deposited on a semiconductor substrate via an insulating film or the like, patterned into a predetermined pattern, and then irradiated with a laser to blow a part thereof to obtain a desired resistance value. Is known.

[0003]

In this laser trimming, a laser irradiated on a thin film resistor passes through the thin film resistor, and the transmitted light is reflected at an interface between a lower oxide film and a semiconductor substrate to form incident light. Cause interference. This interference causes a problem that the thin film resistor cannot be trimmed stably.

To solve this problem, USP
No. 4,594,265 and US Pat. No. 4,708,747. These are semiconductor devices in which each semiconductor layer is insulated and separated by providing an insulating film for separation in a semiconductor substrate.In the former, an insulating film is formed on the surface of a semiconductor substrate, and a thin film resistor is formed thereon. The surface of the semiconductor layer at the interface between the isolation insulating film and the semiconductor layer in the substrate is formed with a notch by etching or the like, or a V-shaped groove is formed to form the interface between the isolation insulator and the semiconductor layer inside the semiconductor substrate. In the latter case, the reflected light is eliminated by controlling the thickness of the isolation insulating film formed inside the semiconductor substrate to be "transparent" to the laser.

[0005] However, the above two US Patents do not take any measures against the reflected light of the transmitted light of the laser at the interface between the insulating film immediately below the thin film resistor formed inside the semiconductor substrate and the surface of the semiconductor substrate. As a countermeasure in this regard, Nippon Denso Publication Technique No. 87-023 shown in FIG.
(Issued November 15, 1992). This is one in which an insulating film 2 is formed on a Si substrate 1 under a thin film resistor, and a thin film resistor 3 is formed thereon.
The interface between the i-substrate 1 and the insulating film 2 is 、 of the laser wavelength.
A step A having a height of the wavelength is provided so that the lasers reflected at the upper and lower steps of the unevenness cancel each other to prevent interference between the incident light and the reflected light near the thin film resistor. In this way, trimming is performed well.

However, this method has a problem that it is necessary to precisely control the height of the unevenness in order to cancel the reflected light. Accordingly, an object of the present invention is to provide a semiconductor device having a thin-film resistor capable of performing good laser trimming without requiring precise control of the height of the uneven step, and a method of manufacturing the same.

[0007]

In order to solve the above problems, according to the present invention, in a semiconductor device in which a thin film resistor requiring laser trimming is formed, an insulation under the thin film resistor is provided. At the interface between the film and the semiconductor substrate, an oblique area that is oblique to the thickness direction of the semiconductor substrate is formed so that the laser irradiated on the thin film resistor is reflected by the oblique area to reach the thin film resistor. I have.

Due to the reflected light in the oblique region, the interference with the incident light of the laser becomes complicated unlike the case where the interface between the insulating film and the semiconductor substrate is flat. Due to the complicated interference light, a region where the laser energy is intensified always exists in the region where the thin film resistor exists, whereby the thin film resistor can be trimmed satisfactorily. That is, the present invention does not eliminate the reflection at the interface between the insulating film and the semiconductor substrate as in the related art, but makes it possible to perform trimming of the thin film resistor by utilizing the reflection at the interface between the insulating film and the semiconductor substrate. ing.

Therefore, in the present application, it is not necessary to eliminate the reflected light unlike the prior art, so that it is not necessary to strictly control the height of the uneven steps for eliminating the reflected light. The state of interference between the incident light of the laser and the reflected light at the interface may be changed by the oblique region formed at the interface. Further, according to the present invention, there is also an effect that the trimming can be favorably performed without being affected by the thickness of the insulating film.

Further, in the semiconductor device according to the second aspect, the oblique region is set at an angle larger than 45 degrees and smaller than 90 degrees with respect to the thickness direction of the semiconductor substrate.
This ensures that the laser transmitted through the thin film resistor is reflected in the oblique region and reaches the thin film resistor without fail. Further, according to the semiconductor device of the third aspect or the method of manufacturing a semiconductor device of the fourteenth aspect, the oblique region is formed in a curved shape with respect to the cross section of the semiconductor device. The laser transmitted through the thin film resistor is reflected at various angles by the curved oblique region. Therefore,
It is considered that this also produces an action of alternately generating a region to be strengthened and a region to be weakened by laser interference in the lateral direction of the semiconductor device.

According to the semiconductor device described in claim 4 and the method for manufacturing a semiconductor device described in claim 15, a step portion is formed by the oblique region, and the step portion has an upper portion and a bottom portion. Therefore, it is considered that the laser transmitted through the thin film resistor changes the interference light of the laser as described above by reflection at the upper and lower portions of the step portion and the oblique region.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising:
Since at least one of the connection between the oblique area and the top of the step or the connection between the oblique area and the bottom of the step is curved, the laser transmitted through the thin film resistor is smoothed into this curve. The connection allows the light to be reflected at various angles. Therefore, it is considered that this also produces an effect of alternately generating a region to be strengthened and a region to be weakened by laser interference in the lateral direction of the semiconductor device.

Further, in the semiconductor device according to the present invention, a plurality of oblique regions exist with respect to the spot diameter of the laser to be irradiated, and the energy of the laser is reduced in the region where the thin film resistor is formed. Reinforcement areas are more reliably present. As a result, the thin film resistor can be more reliably trimmed. In the method for manufacturing a semiconductor device according to claim 7 or the method for manufacturing a semiconductor device according to claim 17, the oblique region is formed by a selective oxide film. By forming by selective oxidation, a smooth surface suitable for reflection can be formed in the oblique region. In addition, since it can be performed simultaneously with formation of a selective oxide film for dividing an element region such as a transistor formed on a semiconductor substrate, an oblique region can be formed without increasing the number of steps.

The oblique regions may be arranged in stripes as in the method of manufacturing a semiconductor device according to the present invention. That is, as in the semiconductor device according to the ninth aspect and the method for manufacturing a semiconductor device according to the nineteenth aspect, the upper portion and the lower portion of the step formed by the oblique region may be alternately arranged.

[0015] Incidentally, when the present inventors conducted an experiment,
When the laser is irradiated so as to cross the stripe vertically to the diagonal area formed in the stripe and the laser is irradiated in the parallel direction to the stripe, the laser is irradiated in the parallel direction. Trimming was performed well, but when laser irradiation was performed in the vertical direction, the trimming was not performed very well.

Therefore, as described in claim 8 or claim 18, by irradiating a laser in parallel to the stripe on the stepped portion arranged in a stripe shape, good trimming can be performed. Also, when trimming thin film resistors, the scanning direction of the laser is not
There is a case where trimming is performed by changing the direction like the letter "L" (hereinafter, referred to as an L-shaped cut). Therefore, as described in claim 5 or claim 12, when the oblique area is formed in a stripe shape. May not be able to perform an L-shaped cut satisfactorily.

Therefore, the inventors of the present application have conducted an experiment and found that the trimming can be stably performed even when the steps formed by the oblique regions are arranged in a mesh shape. Therefore, the semiconductor device according to claim 9 and the semiconductor device according to claim 1
According to the method for manufacturing a semiconductor device described in No. 9, it can be said that the L-shaped cut can be favorably performed. According to the semiconductor device of the eleventh aspect, the favorable trimming can be performed as described above by the reflected light of the laser on the oblique side of the trapezoidal step.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the present invention. In the semiconductor device shown in FIG. 1, a step 4 (trapezoidal step) is formed on the surface of a semiconductor substrate 1 made of Si, and boron (B) or phosphorus (P) is formed on the semiconductor substrate 1. An insulating film 2 such as a BPSG film containing Cr is deposited, the surface is flattened, and Cr is
A thin film resistor 3 of Si or the like is formed. Further, Al electrodes 5a and 5b are formed at both ends of the thin film resistor.
An insulating film 6 such as an oxide film and a protective film 7 such as a nitride film (SiN) are formed so as to cover the surfaces of the electrodes 5a and 5b and the thin film resistor 3.

The step portion 4 is a tapered portion 4a connecting the bottom 4b and the upper portion 4c of the step (a diagonal region in the present invention,
The tapered portion 4a is formed so as to form an angle α with respect to the substrate thickness direction indicated by A in FIG. 1, and the laser beam transmitted through the thin film resistor 3 during trimming. Is reflected by the tapered portion 4a and reaches the thin film resistor 3 again. The angle α is set to 45 ° <α <90 ° so that the laser transmitted through the thin film resistor is reflected upward again. Preferably 50
° ≦ α ≦ 70 °. The plane orientation of the semiconductor substrate 1 is the (100) plane.

A comparison between such a semiconductor device and a conventional semiconductor device having no step portion 4 in which trimming is performed is shown, and an experimental result is shown as to how the step portion 4 affects trimming. This will be described below. In the experiment, samples with different thicknesses of the insulating film 2 under the thin film resistor were prepared,
As shown in FIG. 2, a measuring device 51 for measuring the resistance value between the Al electrodes 5a and 5b is connected, and the laser output is varied to scan as indicated by arrows in the figure. When the resistance value indicated by the measuring device 51 becomes infinite, that is, when the thin film resistor 3 is
Was blown out, and the laser output when the space between the Al electrodes 5a and 5b was opened was examined. FIG. 2 is a top view of the semiconductor device on which the thin film resistor 3 is formed.

The apparatus used in the experiment was a trimming apparatus manufactured by ESi, and the laser used had a wavelength λ = 1.048 μm.
A YLF laser having a pulse width of about 50 ns and a pulse interval of 1.3 ms was used. The spot diameter of the laser on CrSi is 10μ.
m. FIG. 3 shows a detailed cross-sectional view of the sample actually measured. In the sample used in this experiment, as shown in FIG.
SG film 2a, plasma CVD (Chemical Vapor Depositi)
on) formed P-SiN film 2b, Tetraethyloxysil
TEOS film 2c, SOG (Sp
(In-On-Glass) film 2d, TEOS film 2e, and insulating film 6 on thin film resistor 3 is TEOS film 6a,
It is composed of a P-SiN film 6b and a TEOS film 6c.

FIG. 3A shows a semiconductor substrate 1 under a thin film resistor 3.
FIG. 3B shows a conventional semiconductor device having a flat interface between the semiconductor film 1 and the insulating film 2, and FIG. 3B shows a tapered portion 4 a shown in FIG. 1 at the interface between the semiconductor substrate 1 under the thin film resistor 3 and the insulating film 2. This is a semiconductor device provided with a step portion 4. Further, in the semiconductor device according to the present embodiment used in the experiment, the one in which the interval a of the step portion 4 shown in FIG. 3B was formed at an interval of 2 μm was used.

In the experiment, the laser output (trimming energy) that could be trimmed when the thickness of the BPSG film 2a in FIG. 3 was changed from 4000 ° to 7000 ° was examined. The experimental results are shown in FIG. In the figure, ■ indicates a measured value in the conventional semiconductor device shown in FIG. 3A, and ○ indicates a measured value in the semiconductor device according to the present invention in FIG. 3B. Note that ● will be described later.

As can be seen from FIG. 4, in the conventional case, the laser output required for trimming becomes larger when the thickness of the BPSG film 2a is around 4000 ° and around 7000 ° than when the other thicknesses are used, and the protective film becomes thicker. It exceeds 0.8 mW, which is the output that is destroyed. On the other hand, in this embodiment, even if the thickness of the BPSG film 2a changes, the laser output required for trimming is stable at around 0.3 mW, and it can be seen that trimming can be performed well. This will be described below based on simulation results.

FIGS. 5 and 6 show the insulating film 2 and the semiconductor substrate 1.
In the conventional case where the interface between the insulating film 2 and the semiconductor substrate 1 is flat.
Shows the results of a simulation of the state of laser interference with the case where the interface has the oblique region 4a. FIGS. 5A and 6A are partial cross-sectional views of a semiconductor device in which an insulating film 2, a thin film resistor 3 made of CrSi, an insulating film 6, and a protective film 7 are sequentially formed on a semiconductor substrate 1 made of Si. It shows. In FIG. 6, the width a of the simulation model is the same as the distance between the step portions 4 in FIG.
μm. These semiconductor devices have a wavelength of 1.048 μm.
FIG. 5B and FIG. 6B show the state of laser interference when the laser is irradiated.

In FIG. 5B and FIG. 6B, the same area of laser energy due to laser interference is shown by contour lines, and the numbers in the figures represent laser energy intensity due to interference. In FIG. 5B, since the surface of the semiconductor substrate 1 is flat, interference fringes occur parallel to the surface of the semiconductor substrate 1. That is, the regions where the laser is strengthened and the regions where the laser is weakened alternately appear in the thickness direction of the element shown in FIG. Therefore, in this case, the thin film resistor 3
If a region where the interference light of the laser is weakened occurs at the position where the laser beam exists, the thin film resistor cannot be trimmed. Therefore, in this case, whether the trimming can be performed or not depends on the thickness of the insulating film under the thin film resistor 3. However, even in such a case, the trimming can be performed by increasing the output of the laser, but the output of the laser is limited because the insulating film is destroyed.

On the other hand, in FIG. 6B, interference fringes different from those in FIG. 5B are generated. More specifically, FIG.
In the direction perpendicular to the thickness direction of the semiconductor device in FIG. 6A, that is, in the lateral direction in FIG. 6A, the region where the laser is strengthened and the region where the laser is weakened alternately appear. Therefore,
In this case, it is considered that a region where the laser is strengthened always occurs at the position where the thin film resistor 3 is present, so that the thin film resistor 3 can be surely trimmed.

That is, in the conventional structure shown in FIG. 5, the region where the laser is strengthened and the region where the laser is weakened due to interference appear alternately in the thickness direction of the semiconductor device (direction A shown in FIG. 1). Depending on the thickness of the insulating film 2 underlying the thin film resistor 3, there are cases where trimming can be performed and cases where trimming cannot be performed. However, by forming the tapered portion 4a at the interface between the semiconductor substrate 1 and the insulating film 2 as shown in FIG. This occurs not only in the direction, but also in the lateral direction of the semiconductor device, which is perpendicular to the thickness direction of the semiconductor device. As a result, the region where the laser is strengthened always exists in the region where the thin film resistor 3 is formed, and it is considered that the trimming can be surely performed.

FIG. 7 is a sectional view showing a transmission electron microscope (TEM) image of the semiconductor device after the thin film resistor 3 is trimmed. In this semiconductor device, the thin film resistor 3 is trimmed with a laser energy of 0.2 .mu.J which can or cannot be trimmed. A region indicated by M in the drawing is a region where the thin film resistor 3 is blown. From this figure, it can be seen that the thin film resistor 3 is actually blown at certain intervals in the horizontal direction. In the area indicated by M in FIG.
It is considered that the laser intensified due to the phenomenon shown in (b) and the thin film resistor 3 was blown.

Next, FIG. 8 shows a scanning electron microscope (SEM) image of a sectional view of the semiconductor device. In this embodiment, the step 4 is formed by forming the LOCOS oxide film 2L. In this figure, the tapered portion 4a has a curved shape, the connecting portion 4d connecting the tapered portion 4a and the bottom portion 4b of the step is also gently curved, and the bottom portion 4b of the step is also connected to the connecting portion 4d. It is curved. That is, the concave portions (the tapered portion 4a, the bottom portion 4b, and the connecting portion 4d) formed by the LOCOS oxide film are curved. Further, a connecting portion 4e between the tapered portion 4a and the upper portion 4c of the step is also smoothly curved.

Although the effect shown in FIG. 6B is considered to be caused by the tapered portion 4a, the bottom portion 4b, and the upper portion 4c of the step portion 4, the tapered portion 4a having a curved shape as shown in FIG. As a result, the laser transmitted through the thin film resistor 3 is reflected in a slightly different direction depending on the location, and it is considered that this also produces the above-described effect. Similarly, the connecting portion 4 between the tapered portion 4a and the bottom portion 4b
It is considered that the above-described effect is also produced by d and the connecting portion 4e between the tapered portion 4a and the upper portion 4c. In other words, the concave portion formed in a curved shape by the LOCOS oxide film has the above-described effect.

As described above, in the semiconductor device according to the present embodiment, the reflection at the interface between the insulating film and the semiconductor substrate is used instead of eliminating the reflection at the interface between the insulating film and the semiconductor substrate as in the related art. By changing the interference state between the incident light and the reflected light of the laser as described above, the thin film resistor can be trimmed. Therefore, in the present application, there is no need to eliminate the reflected light unlike the prior art, and it is not necessary to strictly control the height of the unevenness (T _{S in} FIG. 1) in order to eliminate the reflected light. What is necessary is just to change the interference state between the incident light of the laser and the reflected light at the interface by the tapered portion 4a formed at the interface with the semiconductor substrate.

(Second Embodiment) Next, as a second embodiment, an oxide film layer (SiO ₂ layer 1) is formed inside as shown in FIG.
A case in which laser trimming is performed on a semiconductor device using a semiconductor substrate 11 called an SOI (Silicon On Insulator) substrate on which 1b) is formed will be described.

When the semiconductor substrate 11 shown in FIG. 9 is used, the reflected light from the interface between the SiO ₂ layer 11b, the Si layer 11c thereon (having a (100) plane orientation) and the semiconductor substrate 11a therebelow. Interference between light and incident light causes a problem when trimming is performed. 9A shows a conventional semiconductor device in which the surface of a semiconductor substrate 11 is flat, and FIG.
The semiconductor device shown in FIG. 1 is the present embodiment in which the step portion 4 is formed on the surface of the semiconductor substrate 11. Note that the detailed configurations of the insulating film 2, the insulating film 6, and the protective film 7 shown in FIG. 9 are the same as those shown in FIG. The thickness of the SiO ₂ layer 11b in the semiconductor substrate 11 was 0.9 μm. A YAG laser having a wavelength λ = 1.06 μm (manufactured by Teradyne) was used as the trimmed laser.

The experiment was performed in the same manner as shown in FIG. 2, and the Si layer 1 on the SiO ₂ layer 11b in the semiconductor substrate 11 was formed.
In this figure, the laser output (laser energy per pulse) when the thin film resistor 3 is trimmed when the thickness 1c is changed. The result is shown in FIG.
Shown in In the figure, Δ indicates a measured value in the conventional semiconductor device shown in FIG. 9A, and ○ indicates a measured value in the semiconductor device according to the present invention in FIG. 9B.

As can be seen from FIG. 10, the semiconductor substrate 11
In the conventional device having a flat surface, the trimming energy greatly changes when the Si film thickness changes. In the present embodiment, the trimming energy is reduced to about 0.09 μJ even when the Si film thickness changes. It turns out that it is stable. That is, in the present embodiment, the tapered portion 4
a is refracted when transmitted through the tapered portion 4a, and changes the direction of the laser beam from the Si layer 11a.
c and the SiO ₂ layer 11b, the reflected light reflected at the interface is also reflected in a direction different from the laser incident direction, and the reflected light is further reflected by the tapered portion 4c. Will be refracted again when passing through. Therefore, the light reflected on the thin film resistor 3 is reflected by the substrate as shown in FIG.
Compared to the case of the semiconductor substrate 1 shown in (b), more reflected light traveling in different directions is mixed and mixed, so that the interference light formed by the incident light and the reflected light seems to be more complicated. As a result, it is considered that the present embodiment can also perform trimming satisfactorily by the operation described in the first embodiment.

(Third Embodiment) Next, as a third embodiment, the relationship between the step 4 and the laser irradiation direction will be described with reference to FIG.
This will be described with reference to FIGS. FIG. 11 shows that the step portion 4 having the tapered portion 4a shown in FIG.
FIG. 2 shows a configuration in which the electrodes 5a and 5b are arranged in a stripe shape parallel to a straight line connecting the electrodes. The step portion 4 is formed such that a cross-sectional view of the semiconductor device taken along the direction B in the drawing has the shape of the step portion 4 shown in FIG. In the hatched region shown in FIG. 11, the step portion 4 is formed by using a nitride film as a mask.
3 shows a mask pattern of a nitride film when formed by the OCOS oxidation method. Therefore, the tapered portion 4a formed by the so-called bird's beak formed at the end of the LOCOS oxide film.
Are formed at the boundary between the striped hatched area and the non-hatched area in FIG.

In such a semiconductor device, an experiment similar to that performed in FIGS. 3 and 4 was performed by scanning a laser in a direction A parallel to the stripe and a direction B perpendicular to the stripe. That is, the trimming energy when the thickness of the BPSG film 2a was changed was examined. FIG. 4 shows the results. In FIG. 4, ○ indicates the trimming energy when scanning the laser in the direction A, and ● indicates the trimming energy when scanning the laser in the direction B.

4, when the laser is scanned in the direction A, the trimming energy is stable irrespective of the thickness of the BPSG film 2a. However, when the laser is scanned in the direction B, the trimming energy is reduced by the thickness of the BPSG film 2a. It turns out that it changes greatly. Therefore, it can be seen that trimming can be favorably performed by scanning and irradiating a laser beam on the tapered portion 4a formed in a stripe shape in parallel with the direction in which the stripe extends.

The tapered portion 4 formed in a stripe shape
When the laser beam is irradiated by scanning the laser beam perpendicularly to the direction in which the stripe extends, the trimming energy varies depending on the thickness of the insulating film 2 under the thin film resistor 3. However, the trimming energy can be reduced as compared with the conventional case having no stepped portion 4 shown in FIG. That is, as shown in FIG. 4, in the conventional device, the trimming energy may be 0.8 mW or more which may cause the protection film to be destroyed depending on the BPSG film thickness. In the case of, it can be seen that trimming can be performed without exceeding 0.8 mW.

Here, in the trimming of the thin film resistor, the trimming is performed not only by scanning the laser in one direction but also by changing the laser scanning direction at a right angle.
A so-called L-shaped cut is often used. When performing this L-shaped cut, as described above, when performing trimming perpendicular to the stripe of the step portion 4 in a semiconductor device having the step portion 4 formed in a stripe shape and the thin film resistor 3 formed thereon. When the thickness of the insulating film under the thin film resistor varies, there is a possibility that the trimming energy cannot be stabilized to perform the trimming.

The inventors of the present application have conducted an experiment. As a result, the stepped portion 4 at the interface between the insulating film 2 under the thin-film resistor 3 and the semiconductor substrate 1 was found It has been found that trimming can be stably performed by forming a mesh-like pattern in which the bottom portion 4b and the upper portion 4c of the step connected by the tapered portion 4a of the portion 4 appear alternately.

FIG. 12 shows an example of this pattern. FIG.
In the pattern shown in FIG.
It shows a mask pattern of a nitride film in OS oxidation and substantially corresponds to the upper portion 4c of the step portion 4. FIG. 12 shows a state of the step portion 4 formed by such a mask pattern.
The cross-sectional view in the direction A and the cross-sectional view in the direction B are shown on the side of the mask pattern.

An insulating film 2 is formed on a step 4 formed by the mask pattern shown in FIG. 12, and a thin film resistor 3 is further formed thereon.
FIG. 13 shows the trimming energy required when the thin film resistor is trimmed by changing the thickness of the BPSG film 2a, which is a part of the insulating film 2, for the semiconductor device formed with. The hatched portion shown in FIG. 12 has a long side of 2 μm and a short side of 1 μm, and a YLF laser having a spot diameter of 10 μm was used as an irradiated laser. The laser was scanned in the direction of the arrow in the figure.

Comparing FIG. 13 with FIG. 4, in the semiconductor device in which the step portion 4 is formed in a stripe shape and the semiconductor device having the mesh step portion, the scanning direction of the laser is changed with respect to the stripe of the step portion 4. When the semiconductor device having the mesh-shaped step portion is slightly parallel, the trimming energy slightly changes, but the laser scanning direction is perpendicular to the stripe of the step portion 4. This indicates that the fluctuation of the trimming energy can be suppressed.

Therefore, in a semiconductor device in which a thin film resistor 3 requiring an L-shaped cut is formed, a step portion having a tapered portion is arranged in a mesh shape as shown in FIG. Trimming can be performed stably regardless of the film thickness. (Fourth Embodiment) Next, as a fourth embodiment, an example of a method for manufacturing a semiconductor device having the above-described step portion 4 and thin film resistor 3 will be described with reference to FIGS.

Although the semiconductor device described here is one in which each element region is insulated and separated by an insulating member, the present invention is also applicable to a semiconductor device in which each element region is insulated and separated by a conventional PN junction separation. It is. FIG.
As shown in (a), first, a semiconductor substrate 11 is prepared. This semiconductor substrate 11 is, for example, disclosed in
As described in Japanese Patent Publication No. 50, P-type single crystal Si
A substrate 11a having a silicon oxide film 11b formed thereon and N
After performing predetermined processing with the single-crystal Si substrate 11c of the mold,
At a temperature of about 1100 ° C., the single crystal Si substrate 11c is polished to a required thickness, a groove 11d called a trench is formed by dry etching or the like, and an oxide film 20 is formed on the side surface of the groove. It is formed by filling a trench with polysilicon 30 or the like. Thus, adjacent elements are insulated and separated by the oxide film 11b and the trench.

Next, as shown in FIG. 14B, an oxidation resistant mask 12 is formed on the surface of the semiconductor substrate 11. This oxidation resistant mask can be formed by depositing a nitride film (SiN) using a vapor phase growth method such as CVD and patterning it by a photo process. Thereafter, a selective oxide film 13 is formed on the trench and in a region where the step portion 4 is to be formed by an oxidation method called LOCOS oxidation. The selective oxide film 13 is formed on the surface of the semiconductor substrate 11 for the purpose of separating adjacent elements or semiconductor regions.

In the LOCOS oxidation, for example, the semiconductor substrate 11 on which the oxidation resistant mask 12 is formed is placed in a thermal oxidation furnace (not shown), and an oxygen (O ₂ ) + hydrogen (H ₂ ) atmosphere is
The thermal oxidation is performed at a temperature of about 1000 ° C. for about 5 to 6 hours. At the time of the LOCOS oxidation, oxidation also proceeds from the end of the oxidation-resistant mask 12, and a region called a bird's beak is formed at the end of the selective oxide film 13. Taper part 4
a is formed. The selective oxide film 1 for forming the step 4
The pattern 3 is formed into a pattern as shown in FIG. 11 or FIG. Further, the tapered portion 4 is formed by thermal oxidation.
Since a is formed, a smooth surface suitable for reflecting the laser transmitted through the thin film resistor 3 is formed on the surface of the tapered portion 4a. That is, although the surface of the semiconductor substrate 11 is a boundary surface, the tapered portion 4a is also substantially in the same state as the boundary surface.

Also, a semiconductor substrate 11 in which a semiconductor element such as a transistor is insulated and separated from other regions by a trench.
Is formed in the element region. In FIG. 14C, an N-type emitter 14, a P-type base 15, and an N-type collector 16 are shown.
Then, as shown in FIG. 15A, an insulating film 2 is deposited using a BPSG film, an SOG film or the like, and the surface of the substrate 11 is flattened. This insulating film 2 may be, for example, a multilayer film similar to the insulating film 2 shown in FIG.

Next, as shown in FIG.
The thin film resistor 3 is formed on the insulating film 2 in the region where the is formed. This thin film resistor 3 is, for example, applied to a sputtering apparatus as shown in FIG.
The semiconductor device shown in (a) is put therein, and CrSi is deposited on the insulating film 2 by sputtering in an inert gas atmosphere such as an argon (Ar) atmosphere or an argon + nitrogen (N ₂ ) atmosphere using a CrSi material as a target. Is formed by patterning into a desired pattern. still,
When nitrogen gas is mixed as an atmosphere during sputtering, nitrogen is taken into the thin film resistor.

Next, as shown in FIG. 15C, a contact hole is formed in the insulating film 2, an electrode wiring material such as Al is deposited and patterned to obtain desired patterns 5a to 5d.
To form FIG. 15C shows a state where the thin film resistor 3 is connected to the collector 16 of the transistor by the wiring pattern 5a. Then, an insulating film 6 such as an oxide film and a protective film 7 such as a nitride film for protecting the semiconductor device are formed. The insulating film 6 and the protective film 7 are made of, for example, T
The structure may be the same as that of the EOS film 6a or the protective film 7 shown in FIG.

The semiconductor device formed as described above is subjected to laser trimming of the thin film resistor 3 to adjust the resistance value. According to the present embodiment described above, since the step portion 4 is formed simultaneously with the formation of the selective oxide film 13,
The tapered portion 4a can be formed without increasing the number of steps.

The tapered portion 4a can be formed by a method other than selective oxidation, such as isotropic etching by wet etching or dry etching by CF ₄ gas or CCl ₄ gas. However, when the tapered portion 4a is formed by dry etching,
After dry etching, it is necessary to smooth the surface by thermally oxidizing the etched surface.

Although there is an anisotropic etching method as an etching method, usually, since a Si substrate uses a (100) plane as a surface as in this embodiment, a potassium hydroxide (KOH) solution (111) plane appears in anisotropic etching using an etching solution such as
Since the angle between the (100) plane and the (111) plane is about 54 °, the angle α shown in FIG. 1 is about 36 °, which is inappropriate.

Further, the surface of the silicon substrate may be slightly etched, and then a selective oxide film may be formed to form the tapered portion 4a. In this case, dry etching is also applicable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment.

FIG. 2 is a diagram showing a measurement test of trimming energy.

FIG. 3A is a cross-sectional view of a conventional sample used in an experiment. (B) is a cross-sectional view of the sample of the first embodiment used in the experiment.

FIG. 4 is a graph showing a measurement result of trimming energy.

FIG. 5A is a cross-sectional view of a semiconductor device having a conventional structure. (B) is a diagram showing a laser interference state by the structure of (a).

FIG. 6A is a cross-sectional view of the semiconductor device of the present embodiment. (B) is a diagram showing a laser interference state by the structure of (a).

FIG. 7 is a diagram showing a transmission electron microscope image of a cross section of the semiconductor device after trimming.

FIG. 8 is a diagram showing a transmission electron microscope image of a cross section of the semiconductor device of the present embodiment.

FIG. 9A is a cross-sectional view illustrating a conventional sample used in an experiment. (B) is a sectional view illustrating a sample of the second embodiment used in the experiment.

FIG. 10 is a graph showing a measurement result of a trimming energy.

FIG. 11 is a diagram illustrating a relationship between a scanning direction of a laser and a step portion 4;

FIG. 12 is a diagram showing a step portion 4 in a mesh shape.

FIG. 13 is a measurement diagram of the trimming energy when a mesh-shaped step portion 4 is formed.

FIGS. 14A to 14C are diagrams illustrating a manufacturing process of a semiconductor device.

FIGS. 15A to 15C are diagrams illustrating a manufacturing process of a semiconductor device.

FIG. 16 is a sectional view of a conventional semiconductor device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor substrate 2 insulating film 3 thin film resistor 4 step portion 4 a taper portion 5 electrode wiring 6 insulating film 7 protective film 11 SOI substrate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makio Iida 1-1-1, Showa-cho, Kariya-shi, Aichi

Claims (19)

[Claims] A semiconductor substrate, an oblique region formed on a surface of the semiconductor substrate, oblique to a thickness direction of the semiconductor substrate, and an insulating film formed on the semiconductor substrate including the oblique region. And a thin film resistor formed on the insulating film and above the oblique region, wherein the oblique region is formed by obliquely transmitting a laser beam transmitted through the thin film resistor when the thin film resistor is irradiated with a laser. A semiconductor device characterized by being set so as to be reflected at a region and reach the thin film resistor. 2. The semiconductor device according to claim 1, wherein the oblique region is set at an angle larger than 45 degrees and smaller than 90 degrees with respect to a thickness direction of the semiconductor substrate. . 3. The semiconductor device according to claim 1, wherein the oblique region has a curved shape when viewed in a cross section of the semiconductor device.
Alternatively, the semiconductor device according to 2. 4. The semiconductor device according to claim 1, wherein a step portion is formed by the oblique region, and the semiconductor device has an upper portion and a bottom portion of the step portion. 5. The semiconductor device according to claim 4, wherein at least one of a connection between the oblique region and the top or a connection between the oblique region and the bottom is gently curved. . 6. The semiconductor device according to claim 1, wherein a plurality of the oblique regions are formed within a spot diameter of the laser to be irradiated. 7. The semiconductor device according to claim 1, wherein said oblique region is formed by selective oxidation in which oxidation is performed using an oxidation-resistant mask. 8. The apparatus according to claim 1, wherein the oblique regions are arranged in a stripe shape when viewed in plan.
The semiconductor device according to any one of the above. 9. The semiconductor according to claim 1, wherein a step is formed by the oblique region, and upper and lower portions of the step are alternately arranged in a plan view. apparatus. 10. The semiconductor substrate, comprising: a first semiconductor layer;
The semiconductor device includes an insulating layer formed on the first semiconductor layer and a second semiconductor layer formed on the insulating layer, and the oblique region is formed on a surface of the second semiconductor layer. The semiconductor device according to claim 1, wherein: 11. A semiconductor substrate, an insulating film formed on the semiconductor substrate, a thin film resistor formed on the insulating film, and a semiconductor substrate and the insulating film located below the thin film resistor. A trapezoidal step formed at the interface, wherein the oblique side of the trapezoidal step is such that when the thin film resistor is irradiated with a laser, the laser transmitted through the thin film resistor is reflected at the oblique side and the thin film A semiconductor device which is set to reach a resistance. 12. A step of forming, on the surface of the semiconductor substrate, an oblique region that is oblique to the thickness direction of the semiconductor substrate; a step of forming an insulating film on the semiconductor substrate; Forming a thin film resistor on the oblique area, and irradiating the thin film resistor with a laser to adjust a resistance value of the thin film resistor, wherein the oblique area adjusts the resistance value. At
A method of manufacturing a semiconductor device, wherein a laser transmitted through the thin film resistor is formed so as to be reflected by the oblique area and reach the thin film resistor. 13. The semiconductor device according to claim 12, wherein the oblique region is formed at an angle larger than 45 degrees and smaller than 90 degrees with respect to a thickness direction of the semiconductor substrate. 14. The semiconductor device according to claim 12, wherein the oblique region is formed in a curved shape when viewed in a cross section of the semiconductor device. 15. The step of forming the oblique area is a step of forming a step on the surface of the semiconductor substrate, and the upper and lower parts of the step and the oblique area connecting these upper and bottom parts by this step. 15. The method for manufacturing a semiconductor device according to claim 12, wherein: 16. The method according to claim 16, wherein the step of forming the step forms at least one of a connection between the oblique region and the upper portion or a connection portion between the oblique region and the bottom portion in a curved shape. Item 16. A semiconductor device according to any one of Items 12 to 15. 17. The step of forming an oblique region includes forming an oxidation-resistant mask on a surface of the semiconductor substrate, and selectively oxidizing a surface of the semiconductor substrate that is not covered by the oxidation-resistant mask. The method of manufacturing a semiconductor device according to claim 12, wherein the semiconductor device is formed by a method. 18. The method according to claim 18, wherein the step of forming the oblique region is performed by forming a stripe in a plan view, and irradiating the laser by scanning the stripe in parallel. 18. The method for manufacturing a semiconductor device according to any one of 12 to 17. 19. The oblique region is formed by forming a step on the surface of the semiconductor substrate, and an upper portion and a bottom portion of the step are alternately arranged in a plan view. 19. The method for manufacturing a semiconductor device according to any one of 12 to 18.