JPH08273990A - Formatin of si substrate provided with groove - Google Patents

Abstract

PURPOSE: To shorten the total etching time and improve throughput by anisotropically etching a first recess forming area and a second recess forming area simultaneously to the same depth and then anisotropically etching the second recess forming area more. CONSTITUTION: After forming a mask 2 on a single crystal Si substrate 1 which has a (100) crystal orientation plane, a part equivalent to a first recess forming area 3 (area width: approximately 160μm) is removed to form an opening for forming the first recess and a part equivalent to a second recess forming area 8 (area width: approximately 800μm) is removed to form an opening for the second recess. Then, in the first recess forming area 3 and the second recess forming area 8, a first recess 4 and a recess 7 are simultaneously formed by the same depth by anisotropical etching. Then, a second mask 5 is formed so as to cover the opening equivalent to the first recess forming area 3 of the mask 2, the second recess forming area 8 is re-etched by anisotropical etching and a second recess 9 is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a Si substrate for a semiconductor module, and more particularly to a method for forming a grooved Si substrate.

[0002]

2. Description of the Related Art In a semiconductor module in which an optical semiconductor element is coupled with an optical fiber or an optical waveguide, or a semiconductor integrated circuit is mounted at a high density on a substrate, the relative position between the mounted element and member and the substrate. Greatly affects the characteristics of the entire module. Therefore, highly accurate positioning of individual parts is required, and for mounting optical elements, optical fibers, etc. on a substrate, positioning accuracy of several μm or less is often required.

Further, the use of so-called connector coupling, in which the semiconductor modules are coupled to each other or the semiconductor module and another optical coupling connector are coupled with each other by a guide pin, a ferrule or the like, has been actively studied. Must be kept below several μm. When performing such positioning, a technique of sandwiching and fixing a wire material such as an optical fiber or a guide pin in a V-shaped recess is often used (for example, Japanese Patent Laid-Open No. 4-66330).

As a method of forming the V-shaped recess, K
A wet etching method using an anisotropic etching solution such as an OH aqueous solution is considered to be advantageous in mass production over a forming method such as cutting because it is possible to form a large number of recesses with the same quality at one time. Has been done.

FIG. 5 shows a conventional V-shaped grooved Si for holding and fixing a wire used in a semiconductor module.
It is explanatory drawing of a board | substrate manufacturing process sequence. First, as shown in FIG. 5 (a), a mask 2 (SiO 2
₂ , after forming 1 μm), a portion corresponding to the first recess forming region 3 (region width 160 μm) is removed to form an opening. Thereafter, as shown in FIG. 5B, anisotropic etching using a KOH aqueous solution or the like is performed until the first recess 4 is formed in the first recess formation region 3 to a desired depth (depth 114 μm). Form. At this time, since the etching rate of the (111) crystal orientation plane is much slower than that of other crystal orientation planes, the shape of the first recess 4 after formation has four side surfaces having the (111) crystal orientation plane. And a bottom surface having a (100) crystal orientation plane.

Next, as shown in FIG. 5C, after removing the mask 2, the second mask 5 (SiO ₂ , 2 μm) is removed.
Are formed by thermal oxidation, a CVD method or the like, and a portion corresponding to the second recess forming region 8 (region width 890 μm) is removed to form an opening. After that, as shown in FIG. 5D, by anisotropic etching using a KOH aqueous solution or the like,
The second recess 9 is formed in the second recess forming region 8 at a desired depth (4
It is formed until it becomes 00 μm).

Since the side surface of the recess thus formed becomes a smooth (111) crystal orientation surface as described above, the opposing V-shaped side surfaces are used to fix an optical fiber in a semiconductor module or the like. Used for high-precision positioning. Further, in a connector-type semiconductor module using a guide pin or the like, the use of a recess having a wide groove width and a deep depth is actively studied as a groove for holding the guide pin.

However, this type of method has the following problems. That is, the step of forming the first concave portion 4 and the step of forming the second concave portion 9 are independent of each other, and the total etching time of both steps is the etching time of the first concave portion 4 and the second concave portion 9. It is the total of etching time. Depending on the conditions such as the etching temperature and the concentration, it takes a very long process time to form each concave portion, which causes a decrease in the throughput during mass production.

Further, in the step of forming the second recess 9 having a large depth, since the side wall of the second recess 9 has a large side etching because the etching is performed for a long time only with the second mask 5. 5 has a problem that the mask in the vicinity of the boundary between 5 and the second concave portion 9 is easily cracked due to the influence of the film stress and the water flow, the second concave portion 9 is etched, and the etching reproducibility is poor, and the concave width Was difficult to control.

[0010]

As described above, Si has conventionally been used.
When forming recesses having different depths on the substrate, the etching time is the sum of the etching times required to form the recesses, and there is a problem that the etching time becomes long and the throughput decreases.

The present invention has been made in view of the above circumstances, and an object thereof is to reduce the total etching time when forming recesses having different depths in a Si substrate by etching. An object of the present invention is to provide a method for forming a Si substrate with a groove which can be achieved and can improve the throughput.

[0012]

In order to solve the above problems, the present invention employs the following configurations. That is, according to the present invention (claim 1), in the method for forming a grooved Si substrate, an opening for forming a first recess and a dimension smaller than the opening are formed on a single crystal Si substrate having a plane orientation of (100). Big second
A step of forming a mask having an opening for forming the concave portion, and a step of anisotropically etching the first concave portion forming region and the second concave portion forming region to the same depth at the same time using the mask; After masking the opening for forming the first recess, further anisotropically etching the second recess forming region.

Further, according to the present invention (claim 2), a grooved Si
In the method for forming a substrate, a first mask having an opening for forming a first recess and a first opening for forming a second recess is formed on a single crystal Si substrate having a plane orientation of (100). A step of anisotropically etching the first recess forming region and the second recess forming region to the same depth at the same time using the first mask, and after removing the first mask, a first mask is formed on the substrate. Second step of forming a second mask having a second opening for forming the second recess having a size larger than that of the first opening for forming the recess; and a second mask using the second mask. And a step of further anisotropically etching the recess forming region.

[0014]

According to the present invention (claims 1 and 2), when the concave portions having different depths are formed by using anisotropic etching,
In the step of forming the shallow first concave portion by anisotropic etching, the second concave portion forming region is simultaneously etched halfway. Therefore, when the deep second recess is formed in the next step, etching for the depth of the shallow first recess has already been performed, so that the etching time for the deep second recess is shortened. Therefore, the etching time in the whole process is shortened, and the throughput can be improved.

According to the present invention (claim 2), the first
After the first recess formation region and the second recess formation region are etched halfway using the mask described above, the first mask is removed and a second mask is newly formed to form the second recess formation. The area is etched. That is, when the deep second recess is formed, the mask pattern boundary is reformed so as to cover the recess formed in the previous step and then etching is performed. It is possible to remove the effects of side etching, roughening of the etching surface, and the like. That is, etching with good reproducibility can be performed, and the recess width can be easily controlled.

Here, in the portion inside the second recess forming region and where the pre-process recess is not formed, etching proceeds in a direction other than the (100) direction, and the etching speed is (10
It is about 1.5 times the velocity in the 0) direction. Depending on the etching conditions, after etching the recess to a desired depth, a surface other than the (100) and (111) surfaces is formed at the boundary between the recess bottom (100) surface and the side surface (111) surface, and The cross section may have an arc shape, but the distance between the boundary of the second recess forming region and the boundary of the preceding process recess forming region is set to be half the difference between the second recess depth and the first recess depth. 1
If formed as follows, the formation of the second recess after etching will be composed of only four side surfaces having the (111) crystal orientation plane and the bottom surface having the (100) crystal orientation plane. Does not happen.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing a step of forming a grooved Si substrate according to a first embodiment of the present invention.

First, as shown in FIG.
0) A mask 2 (SiO ₂ , 2 μm) is formed on one main surface of the single crystal Si substrate 1 having a crystal orientation plane by thermal oxidation, a CVD method or the like.
Then, by photolithography and wet etching, the first recess formation region 3 (region width 160 μm) is formed.
Is removed to form the first recess forming opening, and the second recess forming region 8 (region width 800 μm is formed).
A portion corresponding to m) is removed to form a second recess forming opening.

Next, as shown in FIG. 1 (b), the first recesses are formed in the first recess formation region 3 and the second recess formation region 8 by anisotropic etching using a KOH aqueous solution or the like. Four
Then, the pre-process concave portion 7 which finally becomes the second concave portion is simultaneously formed in the same depth (114 μm).

Next, as shown in FIG. 1C, a second mask 5 is formed so as to cover the opening corresponding to the first recess forming region 3 of the mask 2. As the mask 5, SiO ₂ may be used as in the first mask, or SiO ₂ may be used.
It is also possible to use SiN, which has an etching selection ratio of ₂ .

Then, as shown in FIG. 1D, the second recess 9 is etched again by anisotropic etching to form the second recess 9 in a desired depth (400).
μm).

As described above, according to this embodiment, when the recesses having different depths are formed by using anisotropic etching,
In the step of forming the shallow first concave portion 4 by anisotropic etching, the etching in the second concave portion forming region 8 is also performed at the same time to form the pre-process concave portion 7 which finally becomes the second concave portion 9. For this reason, when forming the deep second concave portion 9 in the next step, since the etching of the depth of the shallow first concave portion 4 has already been performed, the depth is independently different as in the conventional example. Compared with the step of forming the concave portion, the etching time of the deep second concave portion 9 is shortened and the etching time of the entire step is shortened.

As the anisotropic etching liquid, KO is used.
In addition to the H aqueous solution, other anisotropic etching solutions such as KOH aqueous solution, isopropyl alcohol mixed solution, ethylene / diamine / pyrocaticol aqueous solution, tetraethylammonium hydroxide solution, hydrazine solution may be used. Further, as the masks 2 and 5, in addition to SiO ₂ , S
It may be iN, a metal film, or a multi-layered film thereof.

In addition, in the above-mentioned embodiment, the recesses having two kinds of depths are formed. However, even when the recesses having three kinds of depths or more are formed, the depths can be formed by repeating the above steps two or more times. It is obvious that the shallow recesses can be formed in order. (Embodiment 2) FIG. 2 is a sectional view showing a manufacturing process of a grooved Si substrate according to a second embodiment of the present invention.

First, as shown in FIG. 2 (a), (100)
The first mask 2 (SiO ₂ , 2 μm) is formed on one main surface of the single crystal Si substrate 1 having a crystal orientation plane by thermal oxidation or a CVD method.
After forming m), two types of openings are formed by photolithography and wet etching. That is, a portion corresponding to the first recess formation region 3 (region width 160 μm) is removed to form the first recess formation opening, and the pre-process recess formation region having a smaller size than the second recess formation region is formed. 6
A portion corresponding to (region width 800 μm) is removed to form a pre-process recess forming opening.

Then, as shown in FIG. 2B, the first recess 4 is formed in the first recess forming region 3 and the pre-process recess forming region 6 by anisotropic etching using a KOH aqueous solution or the like. The pre-process concave portion 7 is formed at the same depth (114 μm) at the same time.

Then, as shown in FIG. 2C, the first mask 2 is removed, and the second mask 5 (SiO ₂ , 2 μm) is removed.
m) is formed by thermal oxidation, a CVD method, or the like, and then the second recess formation region 8 (region width 890 μm) including the preprocess recess 7 is formed by photolithography and wet etching while the first recess 4 is masked. ) Is removed to form a second recess forming opening.

Then, as shown in FIG. 2D, the second recess 9 is etched again by anisotropic etching to form the second recess 9 in a desired depth (400).
μm).

As described above, according to this embodiment, when the recesses having different depths are formed by using anisotropic etching,
In the step of forming the shallow first concave portion 4 by anisotropic etching, the etching in the previous step concave portion forming region 6 is simultaneously performed. Therefore, when the deep second recess 9 is formed in the next step, etching is performed to the depth of the shallow first recess 4. Therefore, as in the first embodiment, the etching time of the deep second recess 9 can be shortened and the etching time of the entire process can be shortened.

Further, in the step of forming the deep second recess 9, the etching is performed after the mask pattern boundary is reformed so as to cover the recess 7 formed in the previous step. It is possible to remove the effects of cracking of the mask 2, side etching of the side surface of the recess 7 and roughness of the etched surface, and it is possible to perform etching with good reproducibility. Furthermore, the second formed finally
Since the width expansion of the concave portion 9 by the side etching depends only on the etching time of the second concave portion 9, the width of the concave portion is larger than that when the concave portion having the same depth as the second concave portion 9 is formed by one etching. Control becomes easy.

Further, in the portion inside the second concave portion forming region 8 and in which the pre-process concave portion 7 is not formed, etching progresses in a direction other than the (100) direction, and the etching speed is (1
This is about 1.5 times the velocity in the (00) direction. Depending on the etching conditions, after the second recess 9 is etched to a desired depth, the bottom surface (100) and side surfaces (11) of the recess are formed.
1) A surface other than the (100) and (111) surfaces is formed at the boundary with the surface, and the shape of the bottom cross-section may be an arc shape. If the distance from the boundary of the region 6 is set to be equal to or less than half the difference between the depth of the second recess 9 and the depth of the first recess 4, the shape of the second recess 9 after etching Is composed of only four side surfaces having a (111) crystal orientation plane and a bottom surface having a (100) crystal orientation plane, so that no problem occurs.

Further, the anisotropic etching solution and the masks 2 and 5 are used.
The material can be modified in the same manner as in the first embodiment. Further, in this embodiment as well, similar to the first embodiment, it is possible to form recesses having three or more kinds of depths. (Embodiment 3) FIG. 3 is a sectional view showing a manufacturing process of a grooved Si substrate according to a third embodiment of the present invention.

First, as shown in FIG.
0) A mask 2 (SiO ₂ , 0.25) is formed on one main surface of the single crystal Si substrate 1 having a crystal orientation plane by thermal oxidation or a CVD method.
μm) and a mask 5 (SiN, 0.5 μm) are formed, and then the following openings are formed by photolithography and wet etching.

That is, a portion corresponding to the first recess forming area 3 (area width 160 μm) of the second mask 5 is removed to form the first recess forming opening, and the second recess forming area 8 is formed. A portion corresponding to (region width 890 μm) is removed to form a second recess forming opening. Further, an opening corresponding to a region 10 (region width 100 μm) having a size smaller than that of the first recess forming region 3 is formed in the first mask 2, and a region having a size smaller than that of the second recess forming region 8 is formed. 6
An opening corresponding to (region width 800 μm) is formed.

Then, as shown in FIG. 3B, anisotropic etching using a KOH aqueous solution or the like is used for the first recess forming region 3 and the second recess forming region 8 to finally make the first recess. And the concave portion 7 which will eventually become the second concave portion.
Are simultaneously formed to the same depth (114 μm). afterwards,
The etching is continued, and the first mask 2 inside the first concave portion forming region 3 and the second concave portion forming region 8 is removed by etching.

Next, as shown in FIG. 3C, the second recess 9 is formed in the second recess forming region 8 by anisotropic etching.
To a desired depth (400 μm). At this time, the mask boundary of the first recess forming region 3 causes the recess 11
Are further etched to form the first recess 4.

In the third embodiment, the mask is formed in two steps, and the portion of the lower mask 2 which is not protected by the upper mask 5 is removed by etching with an anisotropic etching solution to attach the mask. It is possible to re-form the mask boundary and then perform etching without repairing.
Therefore, it is possible to remove the effects of cracking of the mask 2 near the mask boundary, side etching of the side surface of the recess 7 and roughness of the etched surface, which are caused by anisotropic etching using the mask 2, and the recesses 11 and 7 are removed. It is possible to perform etching with good reproducibility even when the two are simultaneously formed.

Further, the width expansion of the first concave portion 4 and the second concave portion 9 due to the side etching is irrelevant to the formation time of the concave portions 11 and 7, and thus the first concave portion 4 and the second concave portion 9 are formed. It depends only on the etching time. That is, the side surface is (1
Until the 11) or (100) crystallographic plane is exposed,
While the etching proceeds in a fast direction other than the (100) crystallographic plane such as (110) and (221), the etching proceeds on the bottom surface at a rate of (100). For this reason,
In the newly exposed first recess formation region 3 and second recess formation region 8, the etching proceeds in the depth method at the same speed as in the conventional method, and the (111) side surface is formed in the lateral direction. Until the etching, the etching proceeds faster than the conventional forming method, and after the (111) side surface formation, the side etching proceeds at the same rate as the conventional forming method.

Therefore, the side etching time becomes shorter than in the case of forming the recess having the same depth as the second recess 9 by one etching as in the conventional method.
The width of the recess can be easily controlled.

Further, depending on the thickness of the first mask 2 and the etching conditions such as temperature and concentration, the bottom cross-sectional shape may be an arc shape as described in the second embodiment. Is 0.2 μm or less, in a KOH aqueous solution having a concentration of 10 WT% or more and a temperature of 80 ° C., the distance between the boundary of the first mask 2 and the boundary of the second mask 5 is the depth of the second recess 9 and the first mask 2. If the recesses 4 are formed so as to be one third or less of the difference in depth, no problem will occur. (Embodiment 4) FIG. 4 is a sectional view showing a manufacturing process of a grooved Si substrate according to a fourth embodiment of the present invention.

First, as shown in FIG.
0) On one main surface of the single crystal Si substrate 1 having a crystal orientation plane,
A p-type region 12 (boron, 10 ²⁰ / cm ³ ) is diffused / ion-implanted into a region other than the first recess formation region 3 (region width 160 μm) and the second recess formation region 8 (region width 890 μm). Formed by. Subsequently, a mask 2 (SiO ₂ , 0.25 μm) is formed by thermal oxidation or a CVD method, and then the following openings are formed by a photolithography method and wet etching.

That is, a region 10 (region width 100 μm) having a diameter smaller than that of the first recess forming region 3 and the second recess forming region 8 are formed.
A region 6 having a smaller diameter (region width 800 μm) is removed so as to be located inside the first recess forming region 3 and the second recess forming region 8, respectively. After that, the regions 10 and 6 are etched by anisotropic etching using a KOH aqueous solution or the like. At this time, since the mask 2 is soluble in the etching liquid, the mask 2 is removed by etching during the etching.

Then, as shown in FIG. 4B, the etching is continued by using the p-type region 12 as a mask, and as shown in FIG.
As described above, the first recess forming region 3 and the second recess forming region 8 are formed.
Are etched to form the second recess 9 in the second recess forming region 8.
To a desired depth (400 μm).

In the fourth embodiment, the p-type region 12 and the mask 2 are used as a two-stage mask, and the upper mask 2 is removed by etching with an etching solution, so that the mask itself is not reattached. It becomes possible to perform etching after reforming the mask boundary. Therefore, it is possible to remove the effects of cracking of the mask 2 in the vicinity of the mask boundary caused by etching using the mask 2, side etching of the concave portion 7 and side etching, and roughening of the etched surface. Even if formed, etching with good reproducibility can be performed.

The width expansion of the first recess 4 and the second recess 9 due to side etching is independent of the etching time of the mask 2, and depends only on the etching time of the p-type region 12 as a mask. . That is, the side surface is (11
Until the 1) or (100) crystallographic plane is exposed,
While the etching progresses in a fast direction other than the (100) crystal orientation plane such as (110) and (221), the bottom surface is etched at a rate of (100), and thus the newly exposed first In the recess forming region 3 and the second recess forming region 8, the etching proceeds in the depth direction at the same speed as the forming method of the conventional technique, and the conventional technique is formed until the (111) side face is formed in the lateral direction. After the etching progresses faster than the method, after the (111) side face formation, the side etching progresses at the same speed as the conventional method. Therefore, as compared with the case of forming a recess having the same depth as the second recess 9 by one etching as in the conventional forming method, the side etching time becomes shorter and the width of the recess becomes easier to control. .

Further, depending on the thickness of the mask 2, the etching conditions such as the temperature and the concentration, the bottom surface cross-section may be arcuate as described in the second embodiment, but the mask thickness is 0.2 μm or less. In the case of concentration 10 WT% or more, temperature 8
In a KOH aqueous solution at 0 ° C., the boundary between the mask 2 and the p region 1
If the distance from the second boundary is formed to be one third or less of the difference between the depth of the second recess 9 and the depth of the first recess 4, no problem will occur.

The p-type region thus formed has a low resistivity,
Further, since the thermal oxide film also has a low insulating property, when it is used for a portion where electrical insulation is not required, the p-type region may be left as it is, but it is used for a portion where electrical insulation is required. In this case, it is preferable to use an oxide film, a nitride film or the like formed on the p-type region by plasma CVD or the like, or after removing the p-type region by polishing or the like.

In the third and fourth embodiments described above,
SiO ₂ as a mask 2, KOH as an etchant
Although an aqueous solution is used, it suffices that the mask 2 be removed during the etching. For example, even if SiN or the like formed by plasma CVD is used as the mask 2, a KOH aqueous solution / isopropyl alcohol mixed solution or the like is used as the etching solution. You can use it. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be carried out without departing from the scope of the invention.

[0049]

As described above, according to the structure of the present invention, it is possible to accurately form the recesses having different depths on the Si substrate in a short time, and shorten the process and reduce the yield. It becomes possible to manufacture a good Si substrate with a groove.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a grooved Si substrate according to a first embodiment.

FIG. 2 is a cross-sectional view showing a manufacturing process of a grooved Si substrate according to a second embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of a grooved Si substrate according to a third embodiment.

FIG. 4 is a cross-sectional view showing a manufacturing process of a grooved Si substrate according to a fourth embodiment.

FIG. 5 is a cross-sectional view showing a manufacturing process of a grooved Si substrate according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Single crystal Si substrate 2 ... 1st mask 3 ... 1st recessed part formation area 4 ... 1st recessed part 5 ... 2nd mask 6, 10 ... Pre-process recessed part formation area 7, 11 ... Pre-process recessed part 8 ... Second concave portion forming region 9 ... Second concave portion 12 ... P-type region

Claims (2)

[Claims] 1. A mask having an opening for forming a first recess and an opening for forming a second recess larger in size than the opening is formed on a single crystal Si substrate having a plane orientation of (100). And a step of anisotropically etching the first recess forming region and the second recess forming region simultaneously to the same depth using the mask, and masking the opening for forming the first recess of the mask. And a step of further anisotropically etching the second recess formation region. 2. An opening for forming a first concave portion and a first opening for forming a second concave portion on a single crystal Si substrate having a plane orientation of (100).
Forming a first mask having an opening of
Anisotropically etching the first recess forming region and the second recess forming region to the same depth at the same time by using the mask described above, and after removing the first mask, for forming the second recess on the substrate. Forming a second mask having a second opening for forming a second recess having a size larger than that of the first opening, and further forming a second recess forming region using the second mask. A method of forming a grooved Si substrate, which comprises the step of anisotropically etching.