JP3206435B2 - Semiconductor device and method of manufacturing the same - Google Patents

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-mentioned problems, according to the present invention , in a semiconductor device having a thin film resistor requiring laser trimming, an interface between an insulating film under the thin film resistor and a semiconductor substrate is provided. in the oblique area that diagonally with respect to the thickness direction of the semiconductor substrate, laser was irradiated to the thin film resistor is formed so as to reach the thin film resistor and reflected by the oblique area.

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.

[0010] Note that ensures more by setting the oblique area in an angle less than than 90 degrees than 45 degrees with respect to the thickness direction of the semiconductor substrate, the laser having passed through the thin film resistor is reflected by oblique area The thin film resistance is reached. Further, if 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 effect of alternately generating a region for strengthening and a region for weakening by laser interference in the lateral direction of the semiconductor device.

Further, a stepped portion is formed by the oblique area .
Thus, it is considered that the laser transmitted through the thin film resistor gives the above-described change to the interference light of the laser due to reflection at the upper and lower portions of the step portion and the oblique region.

Further, if at least one of gently curved connecting portion between the bottom portion of the connection or oblique area and the step portion between the oblique regions and the upper portion of the step portion, the laser transmitted through the thin film resistor in the curved Smooth connections allow for reflection at various angles. Therefore, it is considered that this also produces an effect of alternately generating a region for strengthening and a region for weakening by laser interference in the lateral direction of the semiconductor device.

Further, if there are a plurality of oblique regions with respect to the spot diameter of the laser to be irradiated, a region where the energy of the laser is strengthened more reliably exists in the region where the thin film resistor is formed. . As a result, the thin film resistor can be more reliably trimmed. Also, be such that more formed selectively oxidized oblique area
That it is, diagonal regions can be formed into a smooth surface suitable for reflecting. 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.

Further, the oblique region may be arranged in a stripe shape, a mesh shape in which the stripes are crossed, that is, the top and bottom of the step formed by the oblique area may be arranged alternately .

[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.

[0016] Therefore, with respect to the stepped portion disposed on the stripe-like, by irradiating the laser in parallel to the stripes, it is possible to perform good crop. In trimming a thin film resistor, trimming may be performed by changing the scanning direction of a laser beam in a direction other than one direction, such as a letter "L" (hereinafter, L-shaped cut). Therefore, when the oblique region is formed in a stripe shape, the L-shaped cut may not be performed well.

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 upper part of the step formed by the oblique region is
If the bottom and the bottom are arranged alternately, it can be said that the L-shaped cut can be performed well. Further, as described above by the reflected light of the laser in the oblique trapezoidal stepped perform a good crop.

[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 portion 4 ( trapezoidal step portion) is formed on the surface of a semiconductor substrate 1 made of Si, and a BPSG film containing boron (B) or phosphorus (P) is formed on the semiconductor substrate 1. The insulating film 2 is deposited and the surface is flattened, and a thin film resistor 3 such as CrSi is formed on the insulating film 2. Further, Al electrodes 5a and 5b are provided at both ends of the thin film resistor.
Are formed, and the Al electrodes 5a and 5b and the thin film resistor 3 are formed.
An insulating film 6 such as an oxide film and a nitride film (S
A protective film 7 such as iN) is formed.

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 type semiconductor device in which the interface between the semiconductor film 1 and the insulating film 2 is flat, and FIG. 3B shows a tapered portion 4a shown in FIG. 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 as shown in FIG. 1 at the interface between the semiconductor substrate 1 and the insulating film 2 as in this embodiment, the region where the laser is strengthened and the region where the laser is weakened by the interference are the thickness of the semiconductor device. 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. Thus now always exists a region constructive laser in the region formed of the thin film resistor 3, it is considered that the trimming can be performed reliably.

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 shows this embodiment in which a step portion 4 is formed on the surface of a 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. Further, the SiO 2 in the semiconductor substrate 11
The thickness of the _two layers 11b was 0.9 μm. In addition, YA having a wavelength λ = 1.06 μm is used as a trimmed laser.
G laser (made by Teradyne) was used.

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 4a. 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.
Than that of the semiconductor substrate 1 shown in (b), it appears to be something more complicated interference light formed by the incident light and reflected light by mix with a lot of reflected light from the proceeds in different directions . As a result, the present embodiment also has the first
It is considered that trimming can be favorably performed by the operation described in the embodiment.

Third Embodiment Next, as a third embodiment, the relationship between the step portion 4 and the laser irradiation direction will be described with reference to FIG . FIG. 11 shows an arrangement in which the stepped portion 4 having the tapered portion 4a shown in FIG. 1 and formed below the thin film resistor 3 is arranged in a stripe shape parallel to a straight line connecting the Al electrodes 5a and 5b. FIG. 1 is a sectional view of the step portion 4 when the semiconductor device is cut along a direction B in the drawing.
Is formed so as to have the shape of the step portion 4 shown in FIG. The shaded region shown in FIG. 11 shows a mask pattern of the nitride film when the step portion 4 is formed by the LOCOS oxidation method using the nitride film as a mask. Therefore, LOC
A tapered portion 4a formed by so-called bird's beak formed at the end of the OS oxide film is formed at the boundary between the stripe-shaped hatched region and the non-hatched region 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 with a laser beam in a direction perpendicular to the direction in which the stripe extends, the trimming energy varies depending on the thickness of the insulating film 2 below 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 Incidentally, there is shown a state of connecting the thin film resistor 3 in FIG. 15 (c) and the collector 16 of the transistor in 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 view showing a mesh-shaped step portion 4;

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 cross-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

Continuation of front page (72) Inventor Makio Iida 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-61-108150 (JP, A) JP-A-9-17877 ( JP, A) Hikaru Hei 2-92933 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/04 H01L 21/822 H01L 21/82 H01L 27/118

Claims (21)

(57) [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 diagonal region, wherein the diagonal region has a plurality of spots within the spot diameter of the laser when the thin film resistor is irradiated with a laser. It is formed, wherein a laser having passed through the <br/> thin film resistor is set to reach the thin film resistor is reflected at the oblique area. 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 step portion has an upper portion and a bottom 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. . Wherein said slant region, the semiconductor device according to any one of claims 1 to 5, characterized in that it is formed by selective oxidation performing oxidation using an oxidation-mask. Wherein said oblique regions, to claim 1, characterized in that it is arranged in stripes in plan view 6
The semiconductor device according to any one of the above. 8. and a step is formed by the oblique area, semiconductor according to any of claims 1 to 7, characterized in that the top and bottom of the step are alternately arranged in plan view apparatus. 9. The semiconductor substrate includes a first semiconductor layer, an insulating layer formed on the first semiconductor layer, and a second semiconductor layer formed on the insulating layer, the oblique region, the semiconductor device according to any one of claims 1 to 8, characterized in that it is formed on a surface of the second semiconductor layer. 10. A semiconductor substrate, an insulating film formed on the semiconductor substrate, a thin film resistor formed on the insulating film, and the 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. 11. A semiconductor substrate, Formed on the surface of the semiconductor substrate, the thickness direction of the semiconductor substrate
Diagonal area oblique to direction, with top and bottom
Step portion, An insulating film formed on the semiconductor substrate including the step portion
When, A thin film formed on the insulating film and above the step portion
Having a membrane resistance, The oblique region is formed by irradiating a laser to the thin film resistor.
The laser transmitted through the thin film resistor is reflected at the oblique area
To reach the thin film resistance
A semiconductor device characterized by the above-mentioned. 12. A semiconductor substrate, Formed on the surface of the semiconductor substrate, the thickness direction of the semiconductor substrate
An oblique area that is oblique to the direction, An insulating film formed on the semiconductor substrate including the oblique region
When, On the insulating film, formed above the diagonal region
Having a thin film resistor, The oblique regions are arranged in a stripe shape when viewed in plan.
When the thin film resistor is irradiated with a laser,
The laser transmitted through the thin film resistor is reflected at the oblique area
It is characterized that it is set to reach the thin film resistance.
Semiconductor device. 13. A semiconductor substrate, Formed on the surface of the semiconductor substrate, the thickness direction of the semiconductor substrate
An oblique area that is oblique to the direction, An insulating film formed on the semiconductor substrate including the oblique region
When, On the insulating film, formed above the diagonal region
Having a thin film resistor, A step is formed by the oblique area, and the upper part of the step
And the bottom are alternately arranged in a plan view, The oblique region is formed by irradiating a laser to the thin film resistor.
The laser transmitted through the thin film resistor is reflected at the oblique area
To reach the thin film resistance
A semiconductor device characterized by the above-mentioned. 14. 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. 15. The semiconductor device according to claim 14 , 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 . Manufacturing method . 16. The semiconductor device according to claim 1, wherein the oblique region is formed in a curved shape when viewed in a cross section of the semiconductor device.
16. The method for manufacturing a semiconductor device according to 14 or 15 . 17. The step of forming the diagonal region is a step of forming a step on the surface of the semiconductor substrate. In this step, an upper part and a lower part of the step part and the diagonal region connecting the upper part and the bottom part are formed. the method of manufacturing a semiconductor device according to any one of claims 14 to 16, characterized by forming a. 18. be smoothly formed on at least one of curved connecting portion between the bottom portion and the connection or the oblique region of the <br/> oblique area and the upper by the step of forming the stepped portion The method for manufacturing a semiconductor device according to claim 17 , wherein: 19. The step of forming the 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 for manufacturing a semiconductor device according to claim 14 , wherein the semiconductor device is formed by a method. 20. The step of forming the oblique region is performed in a stripe shape when viewed in a plan view, and the laser scans and irradiates the stripe in parallel. 20. The method of manufacturing a semiconductor device according to any one of 14 to 19 . 21. 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. 21. The method of manufacturing a semiconductor device according to any one of 14 to 20 .