JPH08250661A - Method for making polycrystalline silicon thin film amorphous and manufacture of polycrystalline silicon thin film resistor which uses the method - Google Patents

Abstract

PURPOSE: To effectively obtain an amorphous state by a little dosage, and restrain all the more the variation of a resistance value. CONSTITUTION: In the method for making a polycrystalline silicon thin film amorpbous by ion implantation, the amount of implantation energy of ions is set equal to the amount of energy wherein the projection range of implanted ions 4 becomes the distance reaching the half depth position 5 of the thickness of the polycrystalline silicon film, thereby forming a continuous amorphous region 6 in the polycrystalline silicon thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for effectively amorphizing a polycrystalline silicon thin film, and a method for producing a polycrystalline silicon thin film resistor with good reproducibility of a resistance value using this method.

[0002]

2. Description of the Related Art Polycrystalline silicon thin film resistors are widely used because of their desirable characteristics such as relatively high resistance values and constant resistance values with respect to changes in the bias of a semiconductor substrate. This polycrystalline silicon thin film resistor is manufactured through a process of forming a thin film of polycrystalline silicon on an insulator, ion-implanting an electrically active element, and then annealing.

At this time, it is known that even if the ion implantation conditions of the electrically active element are accurately controlled, the resistance value becomes non-uniform within the same wafer, or the resistance value varies among lots. . It is known that the main reason for this is that the crystal grain size in the formed polycrystalline silicon thin film varies within the same wafer, or the crystal grain size differs between lots.

In order to solve this problem, JP-A-57-
The technique described in Japanese Patent Publication No. 201061 is known. In this technique, an electrically inactive element is ion-implanted into the formed polycrystalline silicon thin film to once make it amorphous. This technique will be specifically described with reference to FIG. 7. First, the surface of the silicon wafer 100 is oxidized to form an insulating film (S
An iO ₂ layer) 110 is formed (FIG. 4A). in addition,
A polycrystalline silicon thin film 120 is formed by the CVD method (FIG. (B)). Then, an electrically inactive element, in this case silicon, is ion-implanted (130). The polycrystalline silicon thin film 120 is made amorphous. Then, in order to adjust the resistance value, an electrically active element, in this case As, is ion-implanted (150). Then, after that, it is annealed to recrystallize the amorphous silicon thin film,
A polycrystalline silicon thin film resistor 160 is obtained (FIG. (D)). When the polycrystalline silicon thin film 120 is once amorphized and then recrystallized, the recrystallized grain size is stabilized and variation in resistance value is suppressed.

[0005]

However, various researches conducted by the present inventor have revealed that when a sufficient amount of ions are implanted to amorphize, the variation of the resistance value is reduced, but if the ions are implanted more than necessary. It was found that this time, the phenomenon that the resistance value fluctuates due to the influence of implanted ions. The reason for this is presumed to be, for example, a phenomenon in which the inactive ions trap the active ions, or that the implantation of the inactive ions causes a defect that cannot be repaired by subsequent annealing.

Although the technique disclosed in Japanese Patent Laid-Open No. 57-201061 has succeeded in suppressing the variation in resistance value by making it amorphous, as compared with the case where it is not made amorphous, the above-mentioned research by the present inventor is carried out. In light of the above, as a result, excessive ion implantation is performed, and if it is more preferably made amorphous, there is still room for suppressing variation in resistance value. The present invention is intended to improve this knowledge after knowing the room for improvement.

Further, the present inventor has made various studies,
It was also found that the dose of ion implantation required for effective amorphization changes depending on the amount of implantation energy. According to the results of the study by the present inventors, the technique disclosed in Japanese Patent Laid-Open No. 57-201061 can be sufficiently amorphized if a more preferable implantation energy amount is selected. It was also found that the dose amount was much larger than the dose amount. As a result, the amount of implanted ions becomes excessive, which causes a large variation in the resistance value.

That is, although the conventional technique succeeds in significantly suppressing the variation in the resistance value as compared with the case of not amorphizing, according to the result of the research by the present inventor, excessive ion implantation is performed. Therefore, the variation in the resistance value is still larger than the degree of variation in the resistance value that should be obtained by more preferable ion implantation. The present invention makes it possible to effectively amorphize with a small dose amount, thereby further suppressing variation in resistance value.

[0009]

According to the invention of claim 1, in order to achieve the above object, in the method for amorphizing the polycrystalline silicon thin film by ion-implanting the polycrystalline silicon thin film, The implantation energy amount of the ion implantation is set to an energy amount such that the projected range of the implanted ions reaches a depth position which is half the film thickness of the polycrystalline silicon thin film. Created an amorphization method.

[0010]

When the implantation energy amount is set to the above relationship, the entire thickness of the polycrystalline silicon thin film is effectively made amorphous, and the variation in the resistance value of the polycrystalline thin film resistor manufactured thereafter is reduced. . If the implantation energy amount is smaller than this, the deep portion cannot be sufficiently amorphized. On the other hand, if the amount of implantation energy is larger than this, the action of implanted ions passing through the polycrystalline silicon thin film becomes strong, and the efficiency of amorphization becomes low. In the technique of Japanese Patent Laid-Open No. 57-201061 mentioned above, since the implantation energy amount is too large and the amorphization efficiency is low, the ion implantation dose amount which is sufficient for amorphization if the implantation is performed with the appropriate energy amount described above. Is ion-implanted to make it amorphous. By setting the above-mentioned ion implantation energy amount, an excessive amount of ion implantation can be made unnecessary.

[0011]

According to another aspect of the present invention, there is provided a method of alpha-converting a polycrystalline silicon thin film by ion-implanting fluorine into the polycrystalline silicon thin film, wherein the ion implantation is performed. And the ion implantation concentration calculated by the ion implantation dose / the thickness of the polycrystalline silicon thin film is 1.0 × 10 ²⁰ cm 2.
^A method for amorphizing a polycrystalline silicon thin film is characterized by setting the dose amount to be ^{−3 to} 2.5 × 10 ²⁰ cm ⁻³ .

[0012]

When the ion implantation dose amount is set to the above-mentioned relation, the polycrystalline silicon thin film is made sufficiently amorphous, but is not ion-implanted excessively, and the polycrystalline silicon to be manufactured thereafter. Variations in the resistance value of the thin film are reduced. If the ion implantation dose amount is smaller than the ion implantation concentration of 1.0 × 10 ²⁰ cm ⁻³ , amorphization is not sufficiently performed. On the other hand, if the ion implantation dose amount is larger than the ion implantation concentration of 2.5 × 10 ²⁰ cm ⁻³ , more ions than necessary for amorphization are implanted. But,
The trapping of electrically active ions or the excessive implantation of ions causes a phenomenon in which a defect that affects the resistance value develops, and the resistance value varies. Compared with the ion implantation of the technique disclosed in Japanese Patent Laid-Open No. 57-201061, when the ion implantation dose amount is appropriate as described above, the variation in resistance value can be further suppressed. Note that the ion implantation concentration is 1.8 in consideration of variations in resistance value when a resistance element is used.
It is preferably × 10 ²⁰ cm ^-3 or less, more preferably 1.5 × 10 ²⁰ cm ^-3 or less.

[0013]

According to a third aspect of the present invention, there is provided a step of forming a polycrystalline silicon thin film, and a step of amorphizing the polycrystalline silicon thin film by ion-implanting fluorine. In the method of manufacturing a polycrystalline silicon thin film resistor through a step of ion-implanting an electrically active element and a step of recrystallizing the ion-implanted silicon thin film by heat treatment, the ion implantation energy amount of fluorine is The projection range of the fluorine ions is set to an energy amount that is a distance to reach a depth position which is half the film thickness of the polycrystalline silicon thin film, and the ion implantation dose amount is calculated by the ion implantation dose amount / the film thickness. that ion implantation concentration is ^{1.0 × 10 20 ~2.5 × 10 20} cm -3 and manufacturing side of the polycrystalline silicon thin-film resistors and setting the dose comprising It is.

[0014]

According to this manufacturing method, since the implantation energy amount and the ion implantation dose amount are properly adjusted in the ion implantation for amorphization, the variation in the resistance value of the obtained polycrystalline silicon thin film resistance is suppressed. To be done.
Further, the ion implantation concentration is preferably 1.8 × 10 ²⁰ cm ⁻³ or less, more preferably 1.5 × 10 5.
²⁰ cm ^-3 or less.

The term "polycrystalline silicon thin film" as used herein refers to a polycrystalline thin film mainly composed of silicon and formed by a known thin film manufacturing method such as a CVD method or a PVD method. This polycrystalline silicon thin film may not contain an impurity element or may contain an impurity element. Examples of the thin film containing impurities include those in which impurities are introduced at the same time as film formation by the CVD method, or those in which impurities are introduced after the production of a polycrystalline Si thin film.

The projection range referred to in the present invention means the projection distance in the implantation direction of the total distance that ions travel to the thin film until they stand still. The projection range is LSS (Lindhar
It can be obtained from the calculated value or the measured value of the average projected range based on the d, Scharff, Schiott) theory.

The depth position of half the thickness of the polycrystalline silicon thin film means that, when ions are directly implanted into the surface of the polycrystalline silicon thin film, the projection range is half the thickness of the polycrystalline silicon thin film. It is a position. Even when implanting ions into the polycrystalline silicon thin film through another film such as an insulating film formed on the surface of the polycrystalline silicon thin film, the depth is half the thickness of the polycrystalline silicon thin film to be made amorphous. The position.

The amount of implantation energy at which the projected range is at a depth position of half the film thickness differs depending on the incident angle of ions. If the incident angle is normal to the thin film surface,
Since the projection range is along the film thickness direction, the average projection range is the amount of energy that is half the film thickness. Further, when the incident angle deviates from the normal direction, an implantation energy amount corresponding to an average projected range of a distance longer than half the film thickness is required.

Implanted ions for making the polycrystalline silicon thin film amorphous can be selected as required. In general, an element having a large mass can be more efficiently amorphized. Specifically, for example, an electrically inactive element such as fluorine (F) or argon (Ar), or silicon (Si) forming a semiconductor thin film can be used. Further, in the latter case, electrically active impurity elements such as phosphorus (P), boron (B), and arsenic (As) can be used.

The implantation energy amount at which the projected range coincides with the depth position which is half the film thickness of the polycrystalline silicon thin film is different for each ion. Table 1 shows an example of the average projection range based on the LSS theory and its standard deviation when various elements are ion-implanted into a silicon substrate. From this table, it is possible to determine the amount of implantation energy that makes the projected range half the depth of the film thickness.

[Table 1]

If ion implantation is performed with an implantation energy amount that can obtain a projection range that reaches a depth position half the thickness of the polycrystalline silicon thin film, a continuous amorphous region can be effectively formed in the thin film. In particular, since it can be made amorphous with one implantation energy amount regardless of the film thickness, it is not necessary to perform ion implantation a plurality of times with different energy amounts, and the ion implantation process for amorphization is simplified.

The ion implantation conditions (implantation energy amount, ion implantation dose amount) for amorphizing the polycrystalline silicon thin film according to the present invention are effective when the polycrystalline silicon thin film is formed as a resistor. However, without being limited to this, it can be widely applied to amorphization in the case of solid phase growth of silicon.

When an electrically active impurity element is ion-implanted to form a resistor, the electrically active element may be injected after recrystallization of the amorphized silicon thin film, The implantation may be performed before recrystallization of the amorphized silicon thin film, or further before the amorphization of the polycrystalline silicon thin film.

[0024]

According to the invention described in claim 1, by performing ion implantation with an appropriate amount of ion implantation energy,
The polycrystalline silicon thin film can be effectively amorphized without implanting an excessive amount of ions. Also,
According to the second aspect of the present invention, by performing the ion implantation with an appropriate ion implantation dose amount, the polycrystalline silicon thin film can be effectively amorphized without implanting an excessive amount of ions. Then, in any of these methods, when the thin film resistor is recrystallized after that, variation in resistance value is suppressed. Further, according to the invention as set forth in claim 3, the polycrystalline silicon thin film is made amorphous by ion implantation with an appropriate ion implantation energy amount and ion implantation dose amount, thereby varying the resistance value of the polycrystalline silicon thin film resistor. To prevent
A resistance element having a stable resistance value can be manufactured with good reproducibility.

[0025]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6. This example is an experimental example of an implantation energy amount and an implantation dose amount for amorphization according to the film thickness of a polycrystalline silicon thin film, and a step of forming a polycrystalline silicon thin film resistance element on a silicon wafer, and The evaluation of the obtained thin film resistance will be described. First, experimental results on the film thickness dependence of the amount of implantation energy will be shown. In FIG. 2, a silicon wafer (hereinafter, S
It is called an i-wafer. ) 1 on top of the fabrication process of polycrystalline silicon thin film resistors. First, Si shown in FIG.
The surface of the wafer 1 is oxidized as shown in FIG.
An insulating oxide film 2 having a desired film thickness was formed on the surface.

Si wafer 1 having an oxide film 2 formed on its surface
Was placed in a horizontal low pressure CVD apparatus, and a polycrystalline silicon thin film (referred to as a polycrystalline Si thin film) 3 having a predetermined film thickness was formed (see FIG. 2C). In the present example, the Si wafer 1 was divided into three parts, that is, the furnace opening, the furnace center, and the furnace interior in the low pressure CVD apparatus. In addition, 300 nm and 40 nm are set for each Si wafer 1 at these three film forming positions.
Polycrystalline Si thin film 3 having two kinds of film thickness of 0 nm was formed.

Next, as shown in FIG. 2 (d), fluorine 4 is ion-implanted under the following conditions along the direction substantially normal to the surface of the polycrystalline Si thin film 3 to form the polycrystalline Si thin film 3. Amorphous region 6 was formed. For each polycrystalline Si thin film 3 having a film thickness of 300 nm, the implantation energy amount is 40, 50,
There are four types, 60 and 80 keV, and the implantation dose amount for each of these implantation energy amounts is 3.75 × 10 ¹⁵ cm ^-2.
And For each polycrystalline Si thin film 3 having a film thickness of 400 nm, the implantation energy amount is 40, 60, 80 keV
The ion implantation dose amount was set to 5 × 10 ¹⁵ cm ^-2 with respect to these implantation energy amounts. In addition, 3.
The implantation doses of 75 × 10 ¹⁵ cm ⁻² and 5.0 × 10 ¹⁵ / cm ⁻² are proper doses determined as described below.

As is clear from Table 1, in the case of fluorine, the average projection range based on the LSS theory is 150 nm when the implantation energy amount is 60 keV. Therefore, as shown in FIG. 1, the thickness of the polycrystalline Si thin film 3 is 300 nm.
In this case, the average projected range corresponds to half depth position 5 of the thin film. Similarly, when the energy amount is 80 keV, the average projected range is 200 nm, and when the film thickness of the polycrystalline Si thin film 3 is 400 nm, the average projected range is at a depth position 5 which is half of the thin film. Correspond.

The amorphous region 6 thus formed is processed into a desired shape by photolithography and dry etching. Then, heat treatment is performed at 950 ° C. for 30 minutes in a dry O ₂ atmosphere to form an oxide film 7 on the surface.
And the amorphous region 6 was recrystallized to form the polycrystalline Si thin film 8 again. In this case, fluorine is desorbed from the amorphous region 6 by heating. The heat treatment is preferably 900 ° C. or higher. Also, N
Heat treatment may be performed in _two atmospheres to form the polycrystalline Si thin film 8 and then the oxide film 7.

Next, as shown in FIG. 2E, boron (B) 9 is doped as an impurity by ion implantation. In this case, for the polycrystalline Si thin film 8 having a film thickness of 300 nm, the ion implantation energy amount was 30 keV and the ion implantation dose amount was 3.6 × 10 ¹⁴ cm ^-2 . Also, the film thickness 40
For the 0 nm polycrystalline Si thin film 8, the ion implantation energy amount is 35 keV and the ion implantation dose amount is 4.0 × 10.
^{It was 14} cm ^-2 .

Next, as shown in FIG. 2 (f), an interlayer insulating film 11 is formed by CVD to a film thickness of 1.45 μm.
Annealing was performed in an OCl ₃ atmosphere at 950 ° C. for 30 minutes to 45 minutes also as a doping step by thermal diffusion of phosphorus (P) to electrically activate boron. Note that annealing can also be performed at 950 ° C. in a nitrogen atmosphere in the same manner. Furthermore, a resistance element was obtained through an Al wiring forming step and the like.

300 nm and 4 thus formed
3 and 4 show the results of measuring the sheet resistance of the resistive elements having two kinds of film thicknesses of 00 nm. Figures 3 and 4
Although there is a dependence of the sheet resistance on the implantation energy, it is clear from these that there is an implantation energy amount that reduces the variation in the sheet resistance value depending on the film formation position in the resistance element of any film thickness. It was That is, from FIG. 3, for the resistance element having a film thickness of 300 nm, the sheet resistance is 10 when the implantation energy amount is 60 keV.
Near 00Ω / □, the variation due to the film formation position is minimal. In other words, by ion implantation of fluorine at 60 keV,
Amorphous region 6 continuous over the entire polycrystalline Si thin film 3
As a result, the grain size corresponding to the heat treatment condition is obtained by the subsequent heat treatment, and the influence of the grain size at the time of forming the polycrystalline Si thin film 3 is eliminated. The average projected range with this implantation energy amount is about 150 nm, which corresponds to a half depth position of the polycrystalline Si thin film 3 having a film thickness of 300 nm in this embodiment.

With respect to the resistance element having a film thickness of 400 nm, when the implantation energy amount is 80 keV, the sheet resistance is close to 750 Ω / □ and the variation due to the film forming position is small. That is, by the fluorine ion implantation at 80 keV, a continuous amorphous region 6 was formed over the entire polycrystalline Si thin film 3, and the influence of the grain size at the time of film formation was eliminated. The average projected range with this implantation energy amount is about 200 nm, and in the present embodiment, 400 n
It corresponds to a half depth position of the polycrystalline Si thin film 3 having a film thickness of m.

As described above, if the ion implantation is carried out at the projection range corresponding to the depth position of half the film thickness, the grain size difference between the wafers, which occurs during the formation of the polycrystalline Si thin film, is reduced and the variation is caused. A polycrystalline Si thin film resistor having a reduced resistance value of can be manufactured.

Next, experimental results on the film thickness dependence of the implantation dose will be shown. In this experiment, a polycrystalline S on a Si wafer
The step of forming the i thin film resistance element and the evaluation of the obtained thin film resistance will be described. In addition, it demonstrates using FIG. 2 similarly to the experiment of the amount of implantation energy. In this experimental example,
After the oxide film 1 is formed on the Si wafer 1 by using the same process as the above experimental example, the polycrystalline Si thin film 3 having two kinds of film thicknesses of 300 nm and 400 nm is formed in the furnace in the horizontal low pressure CVD apparatus. Films were formed at three positions: the mouth, the center of the furnace, and the back of the furnace.

Next, the surfaces of these polycrystalline Si thin films 3 are
Ion-inject fluorine 4 under the following conditions, almost along the normal direction.
Then, an amorphous region 6 is formed on the polycrystalline Si thin film 3.
did. For each polycrystalline Si thin film 3 with a film thickness of 300 nm
Has an ion implantation dose of 60 keV.
1 x 10^Fifteencm^-23 x 10^Fifteencm^-25 x 10^Fifteencm
^-2And In addition, each polycrystalline Si thin film 3 having a film thickness of 400 nm
For, the implantation energy amount was set to 80 keV and ion implantation was performed.
Enter dose amount 1 × 10^Fifteencm^-23 x 10^Fifteencm^-24x
10^Fifteencm^-25 x 10^Fifteencm^-2, 7 × 10^Fifteencm^-210x
10^Fifteencm^-2And

Amorphous region 6 thus formed
Similarly to the experimental example, was processed into a desired shape by photolithography and dry etching, and dried O
Heat treatment was performed at 950 ° C. for 30 minutes in _two atmospheres to form an oxide film 7 on the surface and recrystallize the amorphous region 6 to form a polycrystalline Si thin film 8 again.

Further, as shown in FIG. 2 (e), when the film thickness of each polycrystalline Si thin film 8 is 300 nm, 30 keV
3.7k × 10 ¹⁴ cm ^-2 , film thickness 400 nm, 35 k
After boron ion implantation under the conditions of eV and 3.8 × 10 ¹⁴ cm ^-2 , an interlayer insulating film 11 is formed, and then annealing is performed by also performing a doping step by thermal diffusion of phosphorus (P) to electrically charge boron. Activated. Furthermore, a resistance element was obtained through an Al wiring forming step and the like.

300 nm and 4 thus formed
5 and 6 show the results of measuring the sheet resistance of the resistive elements having two kinds of film thicknesses of 00 nm. Figures 5 and 6
Although there is a dependence of the sheet resistance on the ion implantation dose amount, as is clear from these, there is an ion implantation dose amount in which the variation of the sheet resistance value depending on the film formation position becomes small for the resistive element of any film thickness. I understand. That is, from FIG. 5, in the case of a resistance element having a film thickness of 300 nm, when the ion implantation dose amount is 3 × 10 ¹⁵ cm ⁻² , the sheet resistance is around 950 Ω / □, and the variation due to the film formation position is minimal. . In other words, the ion implantation of 3 × 10 ¹⁵ cm ^-2 fluorine forms a continuous amorphous region 6 in the entire polycrystalline Si thin film 3, and as a result, the subsequent heat treatment results in a grain size corresponding to the heat treatment conditions. The influence of the grain size at the time of forming the polycrystalline Si thin film 3 is eliminated. Also, even at 5 × 10 ¹⁵ cm ^-2 , 1 × 10 ¹⁵ cm
The variation in sheet resistance is significantly reduced compared to the case of ^-2 , but the sheet resistance itself tends to increase due to carrier traps and the like.

When the ion implantation concentration is calculated by dividing the dose amount 3 × 10 ¹⁵ cm ^-2 that minimizes the variation in sheet resistance by the film thickness (300 nm), it becomes 1 × 10 ²⁰ cm ^-3 , which is 5 × 1.
The ion implantation concentration in the case of 0 ¹⁵ cm ^-2 is 1.67 × 10 ²⁰
cm ^-3 .

On the other hand, for the resistance element having a film thickness of 400 nm, the ion implantation dose amount is 4 × 10 ¹⁵ cm ⁻² to 5 ×.
At 10 ¹⁵ cm ^-2, the variation in sheet resistance due to the film forming position is the minimum. That is, by ion implantation of fluorine at an ion implantation dose of 4 × 10 ¹⁵ cm ^-2 , a continuous amorphous region 6 is formed over the entire polycrystalline Si thin film 3, and the influence of the grain size during film formation disappears. It is a thing. Also, 7 ×
3 x 10 even at 10 ¹⁵ cm ^-2 and 10 x 10 ¹⁵ cm ^-2
Compared with the case of ¹⁵ cm ^-2 or less, the variation in sheet resistance is smaller, but the sheet resistance tends to increase.

Dose that minimizes variations in sheet resistance
Quantity 4 × 10^Fifteencm^-2Is divided by the film thickness (400 nm)
Calculated injection concentration is 1 x 10²⁰cm^-3Becomes 5 × 1
0^Fifteencm^-2In this case, the ion implantation concentration is 1.25 × 10²⁰
cm^-3Becomes Also, 7 × 10 ^Fifteencm^-2When it was
1.75 x 10²⁰cm^-3Becomes 10 × 10^Fifteencm^-2When
2.5 × 10²⁰cm^-3Becomes

From these results, for any film thickness, if the ion implantation concentration is 1 × 10 ²⁰ cm ⁻³ or more,
Amorphous region 6 continuous in the polycrystalline Si thin film 3
Is clearly formed. Further, even when the ion implantation concentration is around 1.7 × 10 ²⁰ cm ⁻³ , a fairly stable resistance value is obtained, and further, the ion implantation concentration is 2.
It is possible to obtain a resistance value with reduced variations even up to 5 × 10 ²⁰ cm ^-3 . Therefore, to obtain a resistance element with reduced variation, 1 × 10 ²⁰ cm ^{−3 to} 2.5 ×
It has been found that the amorphization of the polycrystalline Si thin film 3 by ion implantation of fluorine at 10 ²⁰ cm ^-3 is preferable.

In these experimental examples, the case where the thickness of the polycrystalline Si thin film 3 is 300 nm and 400 nm has been described, but the thickness of the polycrystalline Si thin film to which the present invention can be applied is not limited thereto. The film thickness is 1 μm (1
The present invention can be applied up to about 000 nm). At the ion implantation dose amount, the average range is a polycrystalline silicon film thickness × 1/2 from the ion range of LSS theory,
This is because by selecting an ion implantation energy amount such that the film thickness <(average range + 3 × standard deviation), almost amorphous can be formed over the entire thickness of the polycrystalline silicon film.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which ion implantation is performed with an implantation energy amount such that a projection range reaches a depth position which is half the film thickness of a polycrystalline Si thin film in amorphization of the polycrystalline Si thin film.

FIG. 2 is a diagram showing manufacturing steps (a) to (f) of polycrystalline Si thin film resistors in Examples 1 and 2.

FIG. 3 is a graph showing a sheet resistance of a polycrystalline Si thin film resistor having a film thickness of 300 nm, as a function of fluorine ion implantation energy amount in an amorphization process.

FIG. 4 is a graph showing a sheet resistance of a polycrystalline Si thin film resistor having a film thickness of 400 nm, as a function of fluorine ion implantation energy amount in an amorphization process.

FIG. 5 is a graph showing the sheet resistance of a polycrystalline Si thin film resistor having a film thickness of 300 nm, as a function of fluorine ion implantation dose in the amorphization process.

FIG. 6 is a graph showing the dependency of sheet resistance of a polycrystalline Si thin film resistor having a film thickness of 400 nm on the fluorine ion implantation dose amount in the amorphization process.

FIG. 7: Manufacturing process (a) of a conventional polycrystalline Si thin film resistor
It is a figure which shows (d).

[Explanation of symbols]

 1 Si wafer 3 Polycrystalline Si thin film 6 Amorphous region

Claims (3)

[Claims] 1. A method for amorphizing a polycrystalline silicon thin film by implanting ions into the polycrystalline silicon thin film, wherein the implantation energy amount of the ion implantation is a projection range of the implanted ions of the polycrystalline silicon thin film. A method for amorphizing a polycrystalline silicon thin film, characterized in that the amount of energy is set to a distance that reaches a depth position of half the thickness. 2. A method of alphasing a polycrystalline silicon thin film by ion-implanting fluorine into the polycrystalline silicon thin film, wherein the ion implantation dose amount of the ion implantation is: ion implantation dose amount / the polycrystalline silicon thin film. The ion implantation concentration calculated from the film thickness is 1.0 × 10 ²⁰ cm
^A method for amorphizing a polycrystalline silicon thin film, characterized in that the dose amount is set to ^{−3 to} 2.5 × 10 ²⁰ cm ⁻³ . 3. A step of forming a polycrystalline silicon thin film, a step of amorphizing the polycrystalline silicon thin film by ion-implanting fluorine, a step of ion-implanting an electrically active element, and a heat treatment. In the method of manufacturing a polycrystalline silicon thin film resistor through a step of recrystallizing the ion-implanted silicon thin film by the method, the ion implantation energy amount of fluorine is set to the projection range of the fluorine ions of the film thickness of the polycrystalline silicon thin film. The energy amount is set to be a distance to reach the half depth position, and the ion implantation dose amount is determined by the ion implantation dose amount / the film thickness, and the ion implantation concentration is 1.0 × 10 ^{20 to} 2.5 ×. A method of manufacturing a polycrystalline silicon thin film resistor, characterized in that the dose amount is set to 10 ²⁰ cm ^-3 .