JPH08162424A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To provide a manufacturing method capable of manufacturing a semiconductor device in which a plurality of impurity diffusion regions different in impurity concentration are formed, by using a small number of processes as compared with the conventional method. CONSTITUTION: Photoresist is not left on a high impurity concentration ion implanted region 34 turning to a region whose impurity concentration is the highest out of N-wells. On the middle impurity concentration ion implantated region 36 whose impurity concentration is the second highest, the photoresist is patterned in the manner in which the pattern width W is 1μm, the height H is 1μm, and the pattern interval L1 is 2μm. On the lowest impurity concentration ion implanted region 38, the photoresist is patterned in the manner in which the pattern width W is 0.5μm, the height H is 1μm, and the pattern interval L2 is 1μm. While an Si substrate 30 is rotated, oblique ion implantation of P<+> is so performed that an angle 45 deg. is kept to the surface of the Si substrate 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device in which a plurality of impurity diffusion regions are formed in which impurities of the same kind are diffused so as to have different impurity concentrations.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, for example, an impurity such as B or P is ion-implanted into a Si substrate and heat-treated to form a p-well (p-type impurity diffusion region) or an n-well (n-well) in the Si substrate. Form impurity diffusion regions), and transistors and the like are formed in these p wells and n wells. These p-wells and n-wells are sometimes used as resistors. In this case, it is convenient to make the impurity concentration different between the p-well to be a resistor and the p-well in which a transistor is formed. is there. Further, in order to change the characteristics of the plurality of transistors, the impurity concentrations of the plurality of p-wells may be changed.

A conventional method of forming a plurality of p wells or n wells having different impurity concentrations as described above will be described with reference to FIG. Here, a method of forming a plurality of n-wells in which phosphorus is diffused so as to have different phosphorus (P) concentrations will be described. First, the SiO ₂ film 12 is formed on the Si substrate 10, and a region of the Si substrate 10 excluding the high-concentration impurity region 14 in which the n-well having a high impurity concentration is formed (for example, an n-well having a low impurity concentration is formed). A photoresist 18 is formed on the low-concentration impurity region 16) via the SiO ₂ film 12 (FIG. 2A). Using this photoresist 18 as a mask, a high dose of phosphorus ions is ion-implanted into the high-concentration impurity region 14 from above the Si substrate 10 as shown by an arrow 20 (FIG. 2B). Next, the photoresist 18 is removed, and a photoresist 22 is formed on the high concentration impurity region 14 with the SiO ₂ film 12 interposed therebetween (FIG. 2C). Using this photoresist 22 as a mask, a low dose of phosphorus ions is ion-implanted into the low-concentration impurity region 16 from above the Si substrate 10 as shown by an arrow 24 (FIG. 2D). After the low dose phosphorus ion is ion-implanted, the photoresist 22 is removed.
The Si substrate 10 is annealed at a high temperature of about .degree. C. to activate the ions implanted in the high-concentration impurity region 14 and the low-concentration impurity region 16 to form the n-well 26 having a high impurity concentration and the n-well 28 having a low impurity concentration. (FIG. 2 (e)).

[0004]

According to the conventional method described above from the viewpoint of removing and removing the photoresist and ion implantation, when forming the high-concentration impurity region 14, S
A photoresist is applied to the i substrate 10, the applied photoresist is exposed and developed to form a photoresist 18 having a predetermined pattern, and then ion implantation is performed, and then the photoresist 18 having the predetermined pattern is removed. As described above, in order to form the high-concentration impurity region 14, three steps of forming a photoresist having a predetermined pattern, an ion implantation step, and a photoresist removing step are required. Therefore, in order to form the high-concentration impurity region 14 and the low-concentration impurity region 16, the above three steps are performed in two steps.
It is repeated each time, and a total of 6 steps are required.

In the above example, since there are two kinds of high and low impurity concentrations, there are six steps related to the formation and removal of the photoresist and the ion implantation. There are 9 steps, and when an impurity region having n kinds of impurity concentrations is formed, the number of these steps becomes 3 × n. That is, as the number of types of impurity concentration increases, the number of steps increases, and the manufacturing of the semiconductor device becomes complicated accordingly.

In view of the above circumstances, it is an object of the present invention to provide a semiconductor device manufacturing method capable of manufacturing a semiconductor device in which a plurality of impurity diffusion regions having different impurity concentrations are formed with a smaller number of steps than the conventional method. And

[0007]

According to a method of manufacturing a semiconductor device of the present invention for achieving the above object, a plurality of impurity diffusion regions are formed in which impurities of the same kind are diffused so as to have different impurity concentrations. In the method of manufacturing a semiconductor device comprising: (1) A photoresist having a different pattern depending on the impurity concentration is formed on the ion-implanted region into which the impurity ions are implanted to form the impurity-diffused region. Photoresist forming step (2) Oblique ion implantation step of obliquely ion-implanting an impurity of a dose amount corresponding to the impurity concentration into the ion-implanted region in which the photoresist is formed (3) Ion-implanted ion implantation A heat treatment step of activating the implanted impurity ions to form the impurity diffusion region by heat treating the region. It is characterized by including.

Here, the photoresist forming step is
It is preferable that the pattern interval and / or the pattern width of the photoresist is changed according to the level of the impurity concentration. Further, it is preferable that the oblique ion implantation step is one in which the dose amount is changed by changing the angle and performing ion implantation according to the level of the impurity concentration.

In the oblique ion implantation step, it is preferable to perform oblique ion implantation while rotating the substrate. Further, the photoresist pattern interval refers to the distance between adjacent portions of the photoresist that remains after being patterned by exposure or development, and the photoresist pattern width is defined by exposure or development. The width of the remaining photoresist.

[0010]

According to the method of manufacturing a semiconductor device of the present invention, a photoresist having a different pattern depending on the impurity concentration is formed on the ion-implanted region, and using this photoresist as a mask, the dose amount depending on the impurity concentration is formed. Since the impurity of (1) is obliquely ion-implanted into the ion-implanted region, a plurality of impurity-diffused regions having different impurity concentrations can be formed by performing the photoresist forming step and the ion-implanting step once and then performing heat treatment. Therefore, as in the past,
Since it is not necessary to repeat the photoresist forming step and the ion implantation step a plurality of times in order to form a plurality of impurity diffusion regions having different impurity concentrations, the number of steps can be significantly reduced as compared with the conventional manufacturing method.

Here, the photoresist forming step is
When the pattern interval and / or pattern width of the photoresist is changed according to the level of the impurity concentration, the dose amount can be adjusted relatively easily. Further, even in the case where the oblique ion implantation step is one in which the dose amount is changed by changing the angle according to the level of the impurity concentration and performing ion implantation, the dose amount can be adjusted relatively easily.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a semiconductor device of the present invention will be described below with reference to the drawings. 1A to 1C are cross-sectional views showing an outline of a method of manufacturing a semiconductor device in the order of steps. Here, a method of manufacturing a semiconductor device in which n wells having three types of impurity concentrations are formed will be described. First, p-type S is formed by a known method.
A SiO ₂ film 32 having a film thickness of about 500 Å is formed on the i substrate 30, and a photoresist 33 is uniformly applied on the SiO ₂ film 32 (in FIGS. 1A and 1B, it is already patterned. The photoresist 33 is shown), and the photoresist 33 is patterned. In patterning the photoresist 33, the pattern intervals L1 and L2 and the pattern width W of the photoresist are determined according to the impurity concentration to be finally obtained. The photoresist is not left on the high impurity concentration ion-implanted region 34, which is the region having the highest impurity concentration among the n wells of the three impurity concentrations. On the medium impurity concentration ion implantation region 36 where the impurity concentration is second highest, the pattern width W is 0.5 μm and the height H is H.
Of 1 μm and the pattern interval L1 is 2 μm. On the low impurity concentration ion implantation region 38 having the lowest impurity concentration, the photoresist is patterned so that the pattern width W is 0.5 μm, the height H is 1 μm, and the pattern interval L2 is 1 μm (FIG. 1A). ). The photoresist patterning is performed by a known exposure and development method.

The n-well thus formed is
Photoresist is patterned in different patterns depending on the concentration of pure substances.
After turning, while rotating the Si substrate 30, S
Keep the angle of 45 ° with respect to the surface of the i substrate 30,
As indicated by 40, for example, P ⁺ Oblique ion implantation
(FIG. 1 (b)). When performing this oblique ion implantation,
The dose is 1.4 × 10¹³/ Cm² , Acceleration voltage 100ke
Set to V. According to this oblique ion implantation, patterning
The photoresist 33 thus masked serves as a mask, and the impurity concentration
The impurity of a dose amount corresponding to the ion implantation regions 34, 3
6 and 38 are ion-implanted.

After the ion implantation, the photoresist 33 is removed and the Si substrate 30 is formed by using a thermal diffusion furnace (not shown).
Annealing was performed at 1100 ° C. for 16 hours. As a result, the high impurity concentration ion-implanted region 34 becomes an n well 44 having a surface impurity concentration of 6.0 × 10 ¹⁶ / cm ³ , and the medium impurity concentration ion-implanted region 36 has a surface impurity concentration of 3.9 × 10 ^16. / Cm ³ of the n well 46, and the low impurity concentration ion implantation region 38 has a surface impurity concentration of 2.5.
The n-well 48 has a density of × 10 ¹⁶ / cm ³ . As described above, the impurity concentration of the n-well can be changed in many ways by appropriately selecting the pattern interval and pattern width of the photoresist. Further, even if the pattern interval and pattern width of the photoresist are constant, the impurity concentration of the n-well can be changed in various ways by appropriately selecting the ion implantation angle.

The resist pattern is the same as that shown in FIG. 1, and the impurity concentration is 6.0 × 10 ¹⁶ / cm 3 when the implantation angle of the rotating oblique ion implantation is 60 ° with respect to the substrate surface.
³ , 4.5 × 10 ¹⁶ / cm ³ , 3.5 × 10 ¹⁶ / cm ³
Became. However, the heat treatment conditions are the same as in the above example. Although the n-well is described in the above embodiment, the p-well can be formed in the same manner, and other diffusion layers can be formed in the same manner as described above. After forming the n-well as described above, electrodes and wirings are formed by a known method to manufacture a semiconductor device. As a result, a semiconductor device in which a plurality of impurity diffusion regions having different impurity concentrations are formed can be manufactured with a smaller number of steps than the conventional method.

[0016]

As described above, according to the method for manufacturing a semiconductor device of the present invention, a photoresist having a different pattern depending on the impurity concentration is used as a mask to implant an impurity of a dose amount corresponding to the impurity concentration into the ion implantation region. Since a plurality of impurity diffusion regions having different impurity concentrations are formed by performing oblique ion implantation and then performing heat treatment, the number of steps can be significantly reduced as compared with the conventional manufacturing method.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a method of manufacturing a semiconductor device of the present invention in the order of steps.

FIG. 2 shows a plurality of p-wells and n-types having different impurity concentrations.
It is sectional drawing which shows the conventional method of forming a well in process order.

[Explanation of symbols]

 30 Si substrate 33 Photoresist 34 High impurity concentration ion implantation region 36 Medium impurity concentration ion implantation region 38 Low impurity concentration ion implantation region 44, 46, 48 n-well W Pattern width L1, L2 Pattern spacing

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device, comprising a plurality of impurity diffusion regions in which impurities of the same type are diffused so as to have different impurity concentrations from each other. A photoresist forming step of forming a photoresist having a different pattern depending on the impurity concentration on the ion-implanted region into which ions are implanted; and a step of forming a photoresist on the ion-implanted region where the photoresist is formed, depending on the impurity concentration. A diagonal ion implantation step of diagonally implanting a dose of impurities, and a heat treatment step of activating the implanted impurity ions to form the impurity diffusion area by heat treating the ion-implanted ion implanted area. A method of manufacturing a semiconductor device, comprising: 2. The semiconductor device according to claim 1, wherein the photoresist forming step changes a pattern interval and / or a pattern width of the photoresist according to the level of the impurity concentration. Production method. 3. The oblique dose ion implantation step according to claim 1, wherein the dose amount is varied by implanting ions at different angles according to the level of the impurity concentration. Manufacturing method of semiconductor device.