JP2008124432A - Mask for ion implantation, method and apparatus for ion implantation using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion implantation mask which can form an impurity diffusion region in a predetermined region of a semiconductor substrate at a predetermined ion concentration and an ion implantation mask which can form an insular region or a plurality of implantation regions of different ion concentrations in a single ion implantation as well. <P>SOLUTION: A stencil mask for implanting ions into one or more regions of a semiconductor substrate from an ion source. A mask opening pattern, in which two or more openings and masked parts are aligned, is formed in the stencil mask. The openings and masked parts are arranged so that ion concentration of the semiconductor substrate after thermal diffusion can be approximately uniform. The opening pattern of the mask is shaped in an island. A plurality of mask opening patterns having the openings and masked parts of different area ratios are formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ion implantation mask used when ions are implanted into a predetermined position of a semiconductor substrate, an ion implantation method and an ion implantation apparatus using the mask, and particularly has a feature in an opening of the ion implantation mask. is there.

As a method for introducing impurities into a predetermined region of a semiconductor substrate, there is an ion implantation method. If ion implantation can be performed without using a photoresist during ion implantation, a photoresist coating process, an exposure process, a development process, a photoresist removal process after ion implantation, a semiconductor substrate cleaning process, and the like can be omitted. Shortening can be realized.
There exists patent document 1 as such a resistless ion implantation method. Patent Document 1 discloses that an impurity diffusion layer is formed by passing ions through an opening of a stencil mask positioned separately from a semiconductor substrate on a semiconductor substrate and implanting ions into the semiconductor substrate, and then performing a heat treatment. The method of doing is disclosed. According to Patent Document 1, various processes such as resist coating, pre-baking, exposure, post-baking, and resist removal can be reduced.

The stencil mask forms a through-hole in a substrate that is impermeable to ions, such as a silicon plate, and ions are implanted into the semiconductor substrate through the through-hole. Therefore, it is difficult to form an island pattern on the semiconductor substrate. is there. That is, the ion implantation blocking region must be held in the through hole of the stencil mask, but a holding portion for holding the ion implantation blocking region in the through hole is required. Therefore, the holding portion becomes a shadow at the time of ion implantation, and an island-like pattern cannot be formed accurately.
Therefore, conventionally, for example, as shown in FIG. 12A, a first mask 51 that forms a half of an island, and a second mask 52 that forms the other half of an island as shown in FIG. The island-shaped ion implantation region is formed by switching two masks and performing ion implantation twice into the semiconductor substrate 53 under the same conditions.
Alternatively, as disclosed in Patent Document 2, it is necessary to support the island-shaped implantation blocking region by a support portion that becomes a wavelength limit at the time of ion implantation.

When diffusion layers having different impurity concentrations are formed in a semiconductor substrate and wells having different thresholds are formed, ion implantation is performed in the first semiconductor substrate region 55a at the first impurity concentration as shown in FIG. First ion implantation is performed with the first stencil mask 56, and then, as shown in FIG. 13B, the second stencil mask is implanted with the second impurity concentration into the second semiconductor substrate region 55b. At 57, a second ion implantation is performed. In this way, a plurality of stencil masks are switched, and ion implantation is performed a plurality of times under different implantation conditions.
Alternatively, as disclosed in Patent Document 3, a specific mask is selected from a plurality of stencil masks in a vacuum chamber, a specific dopant ion is selected from a plurality of dopant ions, and a predetermined ion species is set in a predetermined region. There is a method of repeating the operation of injecting.
Japanese Patent Laid-Open No. 62-262421 JP 2003-109889 A JP-A-8-213339

As described above, since the stencil mask selectively implants ions into the semiconductor substrate through the ion transmission and non-transmission parts, the ion concentration in the ion transmission part is controlled by the dose of the ion source. Therefore, in order to form regions having different ion concentrations, it is necessary to perform an ion implantation operation by changing the dose amount of the ion source.
Further, when forming an island pattern as described above, it is necessary to switch between two masks and perform ion implantation twice under the same conditions. Alternatively, it is necessary to create a mask that supports the island-shaped implantation blocking region by a support portion that becomes the wavelength limit of ion implantation.
When a plurality of impurity diffusion layers having different concentrations are formed on a semiconductor substrate, it is necessary to switch a plurality of stencil masks and perform ion implantation a plurality of times under different implantation conditions.
As described above, the conventional technique has various restrictions in ion implantation and has a large number of processes.

In view of the above problems, the present invention provides an ion implantation mask capable of forming an impurity diffusion region with a desired ion concentration in a predetermined region of a semiconductor substrate. The present invention also provides an ion implantation method and an ion implantation apparatus using the ion implantation mask.
The present invention also provides an ion implantation mask capable of forming an island pattern by a single ion implantation operation.
Furthermore, the present invention provides an ion implantation mask capable of forming implantation regions having different concentrations by a single ion implantation operation.

  In order to solve the above problems, the present invention provides an ion implantation stencil mask disposed between an ion source and a semiconductor substrate, wherein an opening pattern is formed by arranging a plurality of openings and shielding portions, and the openings and shielding portions are formed. Is an ion implantation mask in which the area ratio is set so that the ion concentration after thermal diffusion of the semiconductor substrate becomes substantially uniform. Thus, an impurity diffusion region having a desired ion concentration can be formed at a predetermined position on the semiconductor substrate. Accordingly, the ion implantation region can be formed in an arbitrary shape.

Here, the area ratio may be determined based on thermal diffusion conditions in which the ion concentrations of the semiconductor substrate are substantially uniform. In this case, the thermal diffusion conditions are the thermal diffusion temperature and the thermal diffusion time, or one of them.
The area ratio may be determined based on implantation conditions that make the ion concentration of the semiconductor substrate substantially uniform. In this case, the implantation condition is a dose amount, ion species and implantation energy, or any one or more of these.

In the ion implantation mask of the present invention, it is preferable that one opening and one shielding part adjacent to the opening form a rectangle, a triangle, a hexagon, a rhombus, or a trapezoid. Thereby, the opening pattern of a mask can be formed with various shapes.
Moreover, it is preferable that the opening pattern of the mask has an island shape. Thereby, an island-like pattern can be formed by one ion implantation operation using one mask.
Further, it is preferable that a plurality of opening patterns are provided, and the plurality of opening patterns include an opening portion and a shielding portion having different area ratios. As a result, implantation regions having different ion concentrations can be formed by one ion implantation operation using a single mask.

According to another aspect of the present invention, there is provided an ion implantation method in which ions are implanted into a semiconductor substrate using any one of the above ion implantation masks. As a result, a method of forming an impurity diffusion region having a desired ion concentration at a predetermined position on the semiconductor substrate is realized, and an island-shaped implantation blocking region is formed by one ion implantation operation using one mask. Alternatively, implantation regions with different ion concentrations can be formed.
Moreover, this invention is an ion implantation apparatus provided with said mask for ion implantation.

  According to the present invention, an impurity diffusion region can be formed at a predetermined position on a semiconductor substrate with a desired ion concentration, and an ion implantation region can be formed in an arbitrary shape. Further, an island-like ion implantation pattern can be formed on the semiconductor substrate by one ion implantation operation using one ion implantation mask. In addition, implantation regions having different ion concentrations can be formed by one ion implantation operation using one ion implantation mask.

The present invention is a stencil mask for implanting ions from an ion source into a semiconductor substrate. The mask opening pattern of the stencil mask is formed by arranging a plurality of openings and shielding portions, and the openings and shielding portions are the heat of the semiconductor substrate. This is an ion implantation mask having an area ratio set so that ion concentrations after diffusion are substantially uniform.
The ion implantation mask of the present invention is used for a normal ion implantation apparatus. As shown in FIG. 1, such an ion implantation apparatus 1 includes an ion source 2 for generating ions, a mass separator 3 for removing unnecessary ions and taking out desired ions, and only dopant ions. Aperture 4 to pass through, a focusing lens 5 for focusing ions, a mask 7 for forming a predetermined ion implantation pattern in the semiconductor substrate 6, a focusing lens 8, an aperture 9, a projection lens 10, and a semiconductor The stage 11 is configured to hold the substrate 6. Such an ion implantation apparatus is well known, and the ion implantation mask of the present invention can be used for an ion implantation apparatus other than the ion implantation apparatus shown in FIG.

The ion implantation mask of the present invention is an ion implantation mask made of, for example, chromium formed on a silicon plate, a stainless steel plate, or a quartz glass plate, and formed by arranging a plurality of mask opening patterns with openings and shielding portions. In the present invention, in particular, the opening portion and the shielding portion have an area ratio set so that the ion concentration after thermal diffusion of the semiconductor substrate is substantially uniform. The basic concept of the present invention will be described below.
FIG. 2 shows one small opening 20 for forming an opening pattern in the ion implantation mask of the present invention. The opening small region 20 includes a first region 21 and a second region 22, the first region 21 forms an opening through which ions are transmitted, and the second shield 22 is a shield that blocks transmission of ions. Forming part. A plurality of small openings 20 composed of the first region 21 and the second region 22 are arranged side by side without any gap, and a mask opening pattern is formed in an arbitrary shape in the ion implantation mask. The ion implantation mask includes a plurality of such mask opening patterns.

The width direction dimension B of the second region 22 serving as the ion blocking part is set to 0 μm, 0.2 μm, 0.4 μm, and 0.5 μm, with respect to the width direction dimension A (1.0 μm) of the rectangular small opening 20 region. 5 types of 0.8 μm were set.
The opening small region 20 in which the width direction dimension B of the second region 22 forming the ion blocking portion is 0 μm does not include the second region forming the ion blocking portion, and the first region 21 forming the ion transmitting portion. Therefore, the aperture ratio of the small opening region 20 is 100%. In this case, the area ratio of the first region 21 and the second region 22 is 1 to 0.
Similarly, the aperture small region 20 in which the width direction dimension B of the second region 22 forming the ion blocking portion is 0.2 μm has an aperture ratio of 80%. In this case, the area ratio of the first region 21 and the second region 22 is 1: 4.
The aperture small area in which the width direction dimension B of the second area is 0.4 μm has an aperture ratio of 60%, and the area ratio of the first area 21 and the second area 22 is 3 to 2.
The aperture small area where the width direction dimension B of the second area is 0.6 μm has an aperture ratio of 40%, and the area ratio of the first area 21 and the second area 22 is 2 to 3.
The aperture small area where the width direction dimension B of the second area is 0.8 μm has an aperture ratio of 20%, and the area ratio of the first area 21 and the second area 22 is 1: 4.

As described above, using the five types of small openings 20, an impurity made of phosphorus ions is implanted into the P-type Si substrate 3 with an impurity concentration of 4.9 × 10 ¹⁵ cm ^{−3 at} an energy of 80 keV and a dose of 1.0 × 10 ^16. Ions were implanted at ions / cm ² and the surface concentration after thermal diffusion was examined.
Tables 1 to 3 show simulation results of ion implantation, and show the surface concentration of the impurity diffusion region on the silicon substrate after thermal diffusion.
As shown in Table 1, the result of thermal diffusion at 1000 ° C. for 1 hour in an N ₂ atmosphere is that the surface concentration at the center of the opening region and the center of the blocking region is 1.5 × 10 5 when the aperture ratio is 80%. ²⁰ / cm ³ , which are substantially equal, and the surface concentrations of the first region and the second region are flat. When heat treatment is performed after ion implantation in this way, there are an effect of rearranging the atomic arrangement disturbed by the implantation and an effect of diffusing atoms in the direction of thin concentration. The surface concentration of the first region and the second region can be flattened.
Note that the center of the opening region in each table indicates the impurity surface concentration at the center of the first region 21. More specifically, the impurity surface concentration at the center of the ion implantation region formed after the thermal diffusion is performed by ion implantation through the first region.
The center of the blocking region indicates the impurity surface concentration at the center of the second region 22. More specifically, the impurity surface concentration at the center of the semiconductor substrate region formed by diffusion of ions implanted by the first region by thermal diffusion is shown.

  However, when the aperture ratio is 60% or less, the concentration at the central portion of the blocking region is smaller than the concentration at the central portion of the aperture region, and the difference increases as the aperture ratio decreases. Therefore, it can be seen that when the aperture ratio is 60% or less, more specifically less than 80%, the concentration in the central portion of the blocking region is low, and an impurity layer having a flat concentration distribution is not formed. Therefore, it can be seen that a flat impurity layer can be formed if the aperture ratio is 80% or more under this thermal diffusion condition, that is, if the pattern dimension B of the second region 22 is 0.2 μm or less in this pattern.

Next, as shown in Table 2, in the thermal diffusion in an N ₂ atmosphere at 1000 ° C. for 2 hours, the surface concentration at the center of the opening region and the center of the blocking region is 1.0 × 10 ¹⁹ / cm at an opening ratio of 60%. ^{3 is} almost equal. Table 2 shows that the surface concentration at the center of the opening region and the center of the blocking region are substantially equal even when the aperture ratio is 80% or more.

However, when the aperture ratio is 40% or less, more specifically less than 60%, the concentration in the central portion of the blocking region is smaller than the concentration in the central portion of the aperture region, and the difference increases as the aperture ratio decreases. Under this thermal diffusion condition, it can be seen that a flat impurity layer can be formed when the aperture ratio is 60% or more, that is, the pattern dimension B of the second region 22 is 0.4 μm or less.
Further, as shown in Table 3, in the thermal diffusion in an N ₂ atmosphere at 1000 ° C. for 4 hours, the surface concentration at the center of the opening region and the center of the blocking region is 6.6 × 10 ¹⁹ / cm ³ at an aperture ratio of 40%. Is almost equal. Even if the aperture ratio is 60% or 80%, the surface concentration at the center of the opening region is equal to that at the center of the blocking region.

However, when the aperture ratio is 20% or less, more specifically less than 40%, the concentration in the central portion of the blocking region is smaller than the concentration in the central portion of the aperture region, and the difference increases as the aperture ratio decreases. Under this thermal diffusion condition, it can be seen that a flat impurity layer can be formed when the aperture ratio is 40% or more and the pattern dimension B of the second region 22 is 0.6 μm or less.
The above is the case where the thermal diffusion time is changed as the thermal diffusion condition. Even when the thermal diffusion temperature is changed, the ion concentration at the center of the opening region and the center of the blocking region is substantially equal when the aperture ratio is a certain value or more. Become. By changing both the thermal diffusion time and the thermal diffusion temperature, the ion concentration at the center of the opening region and the center of the blocking region can be made substantially equal. In addition, as ion implantation conditions, when the implantation energy, the dose amount, and the ion species, or any one or more of these are different, the aperture ratio at which the ion concentrations at the center of the opening region and the center of the blocking region are substantially equal can be obtained. Further, as the substrate conditions, even when the conductivity type and the impurity concentration are different, the aperture ratio at which the ion concentration at the center of the opening region and the center of the blocking region are substantially equal can be obtained.

As described above, according to the present invention, the aperture ratio is appropriately set based on the fact that the ion concentration at the center of the open area is substantially equal to that at the center of the shut-off area when the aperture ratio is a certain value or more due to the ion implantation condition or the thermal diffusion condition. Thus, an opening pattern of the ion implantation mask is formed.
In the above description, the aperture ratio at which the ion concentration in the opening region and the blocking region is equal is obtained. However, if the ion concentration in the opening region and the blocking region is not necessarily equal depending on the device type, standard, etc., the center of the opening region is used. The first region and the second region can be formed with an aperture ratio in a range in which the difference in ion concentration at the center of the blocking region is allowed.
Moreover, although the simulation result of the said Tables 1-3 is an ion implantation mask whose width direction dimension of the opening small area | region 20 is 1.0 micrometer, even if the width direction dimension of the opening small area | region 20 is 0.1-10.0 micrometers. Almost similar results were obtained. Further, Tables 1 to 3 show the results when the thermal diffusion is performed after the ion implantation. However, in the actual semiconductor manufacturing process, there are a plurality of heat treatment processes. It is sufficient that the density at the center is equal or within a range where there is a density difference within an allowable range.
As described above, the aperture ratio or the area ratio is substantially uniform in the present invention, including the aperture ratio in which the ion concentration at the center of the opening region and the center of the blocking region are equal and the aperture ratio having a concentration difference within an allowable range.

Also, the impurity concentration of 1 × 10 ¹⁶ cm ^{−3 is obtained} by using the seven types of small openings 20 of the five types of small openings 20 and the small openings 20 having the opening ratios of 5% and 10%. The N-type Si substrate 3 was ion-implanted with an impurity 1 made of boron at an implantation energy of 65 keV and a dose of 1 × 10 ¹³ ions / cm ² . That is, as shown in FIG. 3, a stencil mask having width-direction dimensions A and B was arranged on an N-type silicon wafer 25 having an impurity concentration of 1.0 × 10 ¹⁶ . The width-direction dimensions are A = 1 μm, B = 0.05 μm, 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, and 0.8 μm. Thereafter, the surface concentration of the P-type impurity concentration when the thermal diffusion was performed at 1150 ° C. for 25 hours was examined.
As a result, as shown in Table 4, when the aperture ratio is 20%, the surface concentration at the center of the opening region and the center of the blocking region is 1.5 × 10 ²⁰ / cm ³ , which are substantially equal. Furthermore, even when the aperture ratio is 5% or more, the surface concentration at the center of the opening region and the center of the blocking region are equal. Thus, at a high temperature such as 25 hours at 1150 ° C. for a long time, the surface concentration at the central portion of the blocking region and the central portion of the opening region are equal and uniform over a wide range of the aperture ratio of 5 to 80%. It can be seen that a flat impurity layer is formed.
Also in the case of Table 4, the aperture ratio at which the ion concentrations in the opening region and the blocking region are equal is obtained. However, if the ion concentrations in the opening region center and the blocking region center are not necessarily equal, A pattern can be formed when the difference in ion concentration at the center is within a predetermined range.

FIG. 4 is a diagram showing Table 4 as a graph. Using the small aperture regions having the above seven types of aperture ratios, the central region of the open region and the central region of the blocking region when thermal diffusion is performed after ion implantation. It is the result of examining the change of the surface concentration. However, the condition is that the surface concentration at the center of the opening region is equal to the surface concentration at the center of the blocking region, the impurity concentration on the substrate is uniform, and there is no unevenness in concentration. That is, in Tables 1 to 4, it is a graph showing a range in which the impurity concentration at the center of the opening region and the center of the blocking region is substantially constant.
From FIG. 4, in the thermal diffusion at 1150 ° C. for 25 hours indicated by the line a, in the case of the small opening area with the opening ratio of 20%, the surface concentration when the opening ratio is 100%. It was found that it can be reduced to about 40%. Furthermore, it has been found that in the case of an aperture small region with an aperture ratio of 5%, the surface density can be reduced to about 30% with respect to the surface concentration when the aperture ratio is 100%.
Further, in the case of thermal diffusion at 1000 ° C. for 4 hours indicated by the line b and 1000 ° C. for 2 hours indicated by the line c, in the case of the opening small region having the opening ratio of 60%, the opening small region having the opening ratio of 100% It was found that the surface concentration can be lowered to about 30%. Further, in the case of the thermal diffusion at 1000 ° C. for 1 hour indicated by the line d, in the case of the small aperture region with an aperture ratio of 80%, the surface concentration is about 30% with respect to the surface concentration in the small aperture region with an aperture ratio of 100%. It was found that it could be reduced.

The present invention is based on the fact that the ion concentration at the center of the opening region and the center of the blocking region becomes substantially equal at a certain opening ratio due to the thermal diffusion conditions after ion implantation as described above. When the thermal diffusion is performed after the implantation, it is formed by a blocking portion having an opening ratio at which the ion concentration becomes substantially uniform and an opening small region having the opening.
Then, by making this small opening region continuous, in the first embodiment, an ion implantation mask opening pattern is formed in an island shape, thereby forming an island shape pattern. In the second embodiment, implantation regions having different concentrations are formed. In addition to this embodiment, an ion implantation opening having an arbitrary shape is formed on a semiconductor substrate by forming an opening for ion implantation in an arbitrary shape by arranging an opening small region composed of a first region and a second region. can do. Moreover, the impurity concentration of the arbitrary shape can be partially varied.

(Embodiment 1)
FIG. 5 shows a P-type silicon wafer 31 having a (111) plane and a substrate resistance of 15 Ωcm, and an impurity 32 made of antimony is ion-implanted at an energy of 40 keV and a dose of 2.60 E15ions / cm ² , and heat treatment at 1200 ° C. for 180 minutes. And shows a substrate on which an N-type epitaxial layer having a sheet resistance of 1 Ωcm and a thickness of 3 μm is formed. A case will be described in which the ion implantation mask 30 of the present invention is used to form a deep collector on this substrate by a bipolar transistor manufacturing process. FIG. 5A shows a stencil ion implantation mask 30 having island-shaped ion implantation patterns 30 a on a silicon wafer 31.

FIG. 6 is a partially enlarged plan view of the stencil ion implantation mask 30, and the annular small region 20 composed of the first region 21 and the second region 22 shown in FIG. A pattern 25 is formed. Here, as shown in Tables 1 to 3, the aperture ratio of the first region 21 or the second region 22 with respect to the opening small region 20 is the surface concentration under certain substrate conditions, ion implantation conditions, and thermal diffusion conditions. Set to match. Alternatively, the opening is set within an allowable range.
Under this ion implantation condition, ion implantation is performed to form an island-shaped ion implantation pattern 34 as shown in FIG. Thereafter, a thermal diffusion process is performed under the set conditions to form an annular impurity diffusion layer 35 (FIG. 5C). Thereafter, an emitter and a base are formed, and a metal wiring is formed, thereby forming an NPN bipolar transistor having a collector saturation voltage of 0.2V.
FIG.5 (d) shows the impurity concentration of the AA line cross section of FIG.5 (c). FIG. 5E shows the impurity concentration in the cross section along the line BB in FIG.

The opening small area 20 shown in FIG. 6 has a first area 21 and a second area 22 formed by a rectangle, but the shape of the opening small area 20 is a rhombus as shown in FIG. As shown in FIG. 7B, it may be hexagonal. Then, the boundary line between the first regions 21a and 21b and the second blocking regions 22a and 22b is shown in FIG. 7A or FIG. 7B in the opening small region 20 having such a shape. It forms in a straight line. In addition, the boundary line between the first region and the second region may be formed in an arbitrary shape such as a diagonal line, a curve, or a waveform. In addition to this, the opening small region 20 may have any shape as long as the pattern can be continuously arranged without a gap like a triangle or a trapezoid.
Although Embodiment 1 showed island-like ion implantation patterns as shown in FIGS. 5 and 6, the present invention is not limited to island-like ion implantation patterns, and is rectangular, circular, elliptical, triangular, polygonal, It is possible to form a mask opening pattern having an arbitrary shape such as a circular shape, an elliptical shape, other curved surface shapes, or a combination of these shapes, and thus an ion implantation region having an arbitrary shape can be formed.

(Embodiment 2)
A case where diffusion layers having different impurity concentrations are formed on an N-type semiconductor substrate will be described.
FIG. 8 shows a manufacturing process. Ions were implanted into an N-type Si substrate 41 having an impurity concentration of 1 × 10 ¹⁶ cm ⁻³ using the stencil ion implantation mask 42 of the present invention (FIG. 8A). The left half 42l of the ion implantation mask 42 is an ion implantation mask in which the aperture ratio of the small opening area is 60% as shown in FIG. The right half 42r of the ion implantation mask 42 has a pattern in which the aperture ratio of the small opening portion is 20% as shown in FIG. 9B.
Using the stencil ion implantation mask 42, the boron impurity 1 was ion-implanted with an implantation energy of 65 keV and a dose of 1 × 10 ¹³ ions / cm ² (FIG. 8B). Thereafter, when thermal diffusion is performed at 1150 ° C. for 25 hours (FIG. 8C), as shown in Table 4, the surface concentration of the impurity diffusion layer 43r in the right half 42r is 2.3. 4 × 10 ¹⁶ / cm ³ , and the surface concentration of the impurity diffusion layer 43 l in the left half 42 l was 1.5 × 10 ¹⁶ / cm ³ . This impurity concentration distribution is shown in FIG. 8 (d).

In the well of the MOS transistor in which the two impurity diffusion layers 43r and 43l having different concentrations as described above are formed as described above, an electric insulating film 5000Å for element isolation is formed in a diffusion furnace by a well-known technique, and the channel portion is formed. Impurities made of boron are ion-implanted with an implantation energy of 35 keV and a dose of 2.90E12 ions / cm ² , a gate oxide film 160 Å is formed in a diffusion furnace, and a gate electrode metal wiring process is performed, thereby forming an impurity diffusion layer 43r. Two types of N-type MOS transistors having a threshold voltage (VTH) of 0.8 (V) and a threshold voltage (VTH) of 0.6 (V) could be formed in the impurity diffusion layer 43l.

FIG. 10 shows two small opening areas with different opening ratios, and FIG. 10A shows an opening small area 45 with an opening ratio of 100% and an opening small area 46 with an opening ratio of 20%.
FIG. 10B shows three aperture small regions having different aperture ratios, an aperture small region 47 having an aperture ratio of 100%, an aperture small region 48 having an aperture ratio of 20%, and an aperture ratio of 60. % Opening subregion 49.
FIG. 11 shows an ion implantation mask including all of the small openings 42l and 42r and 45 to 49 shown in FIGS. In an actual ion implantation mask, openings having various aperture ratios are formed in a complicated shape. By using such an ion implantation mask, an island shape is formed on a semiconductor substrate by a single ion implantation process. It is possible to simultaneously form regions having different impurity concentrations and the ion implantation pattern. Furthermore, the impurity concentration can be partially changed in part of the island-shaped opening.

The schematic block diagram of an ion implantation apparatus is shown. An explanatory view of an opening small area which has the 1st pattern field and the 2nd pattern field is shown. The arrangement plan of arrangement of a wafer and a stencil mask is shown. The relationship between the aperture ratio and the surface concentration at the center of the injection blocking region is shown by a characteristic diagram using the heat treatment condition as a parameter. FIG. 3 shows a process diagram of ion implantation in the first embodiment. The enlarged view of the opening part small area | region which has a 1st pattern area | region and a 2nd pattern area | region is shown. The other shape figure of an opening part small area | region is shown. FIG. 6 shows a process diagram of ion implantation in the second embodiment. The enlarged view of the mask for ion implantation used for Embodiment 2 is shown. The other shape figure of the mask for ion implantation used for Embodiment 2 is shown. An explanatory view of the pattern which changed the shape of an injection interception field and an opening field is shown. A process diagram of conventional ion implantation is shown. A process diagram of conventional ion implantation is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion implantation apparatus 2 Ion source 6 Semiconductor substrate 7,30 Mask 20 Small opening area | region 21 1st pattern area 22 2nd pattern area 30a Island-like pattern 35 Impurity diffusion layer

Claims (10)

  An ion implantation stencil mask arranged between an ion source and a semiconductor substrate has an opening pattern formed by arranging a plurality of openings and shielding portions, and the opening portions and shielding portions each have an ion concentration after thermal diffusion of the semiconductor substrate. An ion implantation mask characterized in that an area ratio is set to be substantially uniform.   2. The ion implantation mask according to claim 1, wherein the area ratio is determined based on a thermal diffusion condition in which an ion concentration of the semiconductor substrate is substantially uniform.   The ion implantation mask according to claim 2, wherein the thermal diffusion condition is a thermal diffusion temperature and a thermal diffusion time, or one of them.   2. The ion implantation mask according to claim 1, wherein the area ratio is determined based on implantation conditions in which the ion concentrations of the semiconductor substrate are substantially uniform.   The ion implantation mask according to claim 4, wherein the implantation condition is a dose amount, ion species and implantation energy, or any one or more thereof.   The said one opening part and one shielding part adjacent to this opening part form a rectangle, a triangle, a hexagon, a rhombus, or a trapezoid, The one of Claim 1-5 characterized by the above-mentioned. Ion implantation mask.   7. The ion implantation mask according to claim 1, wherein the opening pattern has an island shape.   8. The ion according to claim 1, wherein the stencil mask includes a plurality of the opening patterns, and the plurality of opening patterns include an opening portion and a shielding portion having different area ratios. Injection mask.   An ion implantation method comprising implanting ions into a semiconductor substrate using the mask according to any one of claims 1 to 8.   An ion implantation apparatus comprising the ion implantation mask according to claim 1.