JP2001313265A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device capable of reducing a diffusing unevenness and a removing residue of an impurity by stably and uniformly forming a silicate glass layer by optimizing heat treating conditions in a predeposition. SOLUTION: The method for manufacturing the semiconductor device comprises the steps of introducing the impurity into a semiconductor substrate while depositing a layer to become an impurity diffusion source on a surface of the substrate, and then heat treating the substrate for a sufficient time to stabilize a quality of the deposited layer to become the impurity diffusion source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device including a heat treatment step for forming an impurity diffusion layer on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, when an impurity diffusion layer is formed on a silicon substrate which is a semiconductor substrate, pre-deposition for introducing the impurity into the silicon substrate and activation of the introduced impurity are performed. And a drive-in process of diffusing heat into a wider area is performed in two steps. This method is performed, for example, as follows.

First, when POCl ₃ is used as an impurity source, as a predeposition, a silicon substrate is placed in a heat treatment furnace, and POCl ₃ is introduced into the furnace together with oxygen gas. Thus, a phosphorus silicate glass layer (PSG layer) is formed on the silicon substrate by the following reaction, and phosphorus is introduced into the silicon substrate.
POCl ₃ + 3 / 4O ₂ → 1 / 2P ₂ O ₅ + 3 / 2Cl ₂ P ₂ O ₅ + 5 / 2Si → 2P + 5 / 2SiO ₂ Subsequently, the PSG layer formed on the silicon substrate is removed, and silicon is used as a drive-in. The substrate is heat treated to activate phosphorus and diffuse into a larger area. However, when the batch processing is repeated by such a method, there is a problem that the sheet resistance gradually shifts to a lower value, and finally the specification is deviated.

In the case where BBr ₃ is used as an impurity source, boron silicate glass (BSG layer) is formed on a silicon substrate and boron is introduced into the silicon substrate in the same manner as described above. BBr ₃ + 3 / 2O ₂ → 1 / 2B ₂ O ₃ + 3 / 2Br ₂ B ₂ O ₃ + 3 / 2Si → 2B + 3 / 2SiO ₂ Then, drive-in is performed in the same manner as described above. However, when the BSG layer formed on the silicon substrate is removed after the predeposition and before the drive-in, there is a problem that the BSG layer is not completely removed, and a contact failure often occurs.

[0005] In other words, in the predeposition by the above-mentioned method, the formation of the silicate glass layers such as the PSG layer and the BSG layer is not performed stably and uniformly.
Diffusion variation of impurities during drive-in increases,
In addition, since the removability is reduced, the reliability and the like of the finally obtained semiconductor device are reduced. Therefore, in order to improve the reliability of a semiconductor device, it is required to establish a heat treatment method capable of forming a silicate glass layer stably and uniformly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and by optimizing the heat treatment conditions in pre-deposition, a silicate glass layer is formed stably and uniformly, thereby reducing the diffusion variation of impurities and the removal residue. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can be used.

[0007]

According to the present invention, an impurity is introduced into a semiconductor substrate while a layer serving as an impurity diffusion source is deposited on the surface of the semiconductor substrate, and the film quality of the deposited impurity diffusion source layer is reduced. There is provided a method for manufacturing a semiconductor device, comprising heat-treating for a time sufficient for stabilization.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a method for manufacturing a semiconductor device, comprising forming an impurity diffusion layer on a semiconductor substrate by a so-called two-step diffusion method. Examples of the semiconductor substrate that can be used in the present invention include, for example, elemental semiconductor substrates such as silicon and germanium, GaAs, and In.
Various substrates such as a substrate made of a compound semiconductor such as GaAs, an SOI substrate, and a multilayer SOI substrate can be used. Among them, a silicon substrate is preferable.

According to the present invention, first, a semiconductor substrate is introduced into a diffusion furnace capable of heat treatment. Diffusion furnaces are usually those that can be used in the manufacture of semiconductor devices,
Any substance can be used as long as it can introduce a predetermined gas and can perform heat treatment at a high temperature. Next, a layer serving as an impurity diffusion source is deposited on the surface of the semiconductor substrate introduced into the diffusion furnace. At this time, impurities adsorbed on the surface of the semiconductor substrate are simultaneously introduced into the semiconductor substrate.

A source material that can be used for depositing a layer serving as an impurity diffusion source on the surface of a semiconductor substrate contains an impurity (element) that can function as an acceptor or a donor in a semiconductor device, and has a gaseous state. , Liquid or solid. Such impurities vary depending on the type of semiconductor substrate used.For example, when a silicon substrate is used, a group III or V element such as phosphorus, arsenic, antimony, boron, aluminum, gallium, or indium can be used. Of these, phosphorus or boron is preferred. Raw materials containing these impurities include, for example, POCl ₃ , PH ₃ , PCl ₃ , PB
_{r 3, P 2 O 5,} P 2 O 3, BBr 3, BCl 3, B 2 H 6, B 2
O ₃ , BN and the like can be mentioned, and among them, liquid or gaseous POCl ₃ or BBr ₃ is preferable.

As a method of depositing a layer serving as an impurity diffusion source using a raw material, a carrier gas (nitrogen gas or an inert gas such as argon or helium) is used when the raw material is liquid. The raw material (eg, PO
A method in which the raw material is vaporized by passing through (Cl ₃ ) (bubbling) and introduced into a diffusion furnace together with a carrier gas and / or an oxygen gas. At this time, the raw material is introduced into the diffusion furnace while the temperature inside the diffusion furnace is raised, preferably maintained at a constant temperature, and held for a predetermined time. The temperature in the diffusion furnace is, for example, about 800 to 1100 ° C, and further about 850 ° C to 1000 ° C. The holding time can be appropriately adjusted depending on the furnace temperature and the type of the raw material, for example, about 30 to 90 minutes, and more preferably about 40 to 90 minutes.
About 60 minutes. The flow rate of the gaseous raw material to be introduced can be appropriately adjusted depending on the furnace internal volume, the size of the impurity diffusion layer formed on the semiconductor substrate, the impurity concentration, the diffusion depth, and the like. For example, 100 to 180 mg / min. Degree.

When the raw material is solid, for example, BN wafers are alternately arranged together with semiconductor substrates in a furnace,
There is a method in which the substrate is kept at a high temperature for a predetermined time in an atmosphere of an oxygen gas, a nitrogen gas and / or an inert gas. On this occasion,
While raising the temperature in the furnace, preferably at a constant temperature, for example, at a temperature of about 900 to 1100 ° C, 180 to 60
It is appropriate to hold for about 0 minutes. The raw material to be introduced into the diffusion furnace can be appropriately adjusted in the same manner as described above, and examples thereof include a wafer-like material.

According to such a method, a layer serving as an impurity diffusion source is deposited on the surface of the semiconductor substrate, and at the same time, impurities adsorbed on the surface of the semiconductor substrate react on the surface of the semiconductor and can be introduced into a very shallow portion thereof. The thickness of the deposited layer serving as an impurity diffusion source is appropriately set depending on the processing conditions and the like. Examples of the layer serving as an impurity diffusion source include PSG, BSG, phosphorus-doped polysilicon, boron-doped polysilicon, and boron silicide.

Thereafter, heat treatment is performed for a time sufficient to stabilize the film quality of the deposited impurity diffusion source layer. The heat treatment here is preferably performed subsequent to the deposition of a layer serving as an impurity diffusion source on the surface of the semiconductor substrate. Conditions for the heat treatment include a temperature range of about 800 to 1100 ° C. and an atmosphere of oxygen gas, nitrogen gas and / or inert gas. Above all, except that the source material is not introduced, the same temperature (± 20 ° C.) as when depositing the layer serving as the impurity diffusion source on the surface of the semiconductor substrate is used.
It is preferably performed in an atmosphere or the like at a temperature of about 0 ° C., about ± 100 ° C., or about ± 50 ° C.). Further, the time sufficient to stabilize the film quality of the layer serving as the impurity diffusion source can be appropriately adjusted by the type, thickness, heat treatment atmosphere, heat treatment temperature, and the like of the deposited impurity diffusion source layer. About 0.5 to 1.5 times the time of depositing a layer serving as an impurity diffusion source on the surface of the semiconductor substrate, preferably about 0.9 to 1.1 times the deposition time, specifically 15 to 13 times.
5 minutes, preferably about 35 to 65 minutes, more preferably about 40 to 60 minutes.

The film quality of the deposited impurity diffusion source layer can be stabilized by, for example, the thickness distribution of a film (eg, a PSG film or a BSG film) after pre-deposition, the sheet resistance distribution, etc. It can be evaluated based on a film (for example, a silicon oxide film) distribution, a sheet resistance distribution, and the like. In addition, for example, the evaluation can be made using, as an index, the magnitude of variation in impurity diffusion into the semiconductor substrate, the removability of a layer serving as an impurity diffusion source deposited in a later step, and the like.
The film quality stabilization generally means a state that is not easily affected by external factors (for example, in the case of phosphorus diffusion, if the heat treatment in deposition is insufficient and the film quality is not stabilized, the furnace The sheet resistance tends to shift (decrease) depending on the atmosphere).

In the present invention, after this heat treatment, a heat treatment is preferably further performed in an oxygen gas atmosphere. Here, the oxygen gas atmosphere means an atmosphere under an oxygen gas atmosphere of almost 100%. The heat treatment is performed at a temperature in the range of about 800 to 1100 ° C., more preferably in the range of about 850 to 1000 ° C., and about 0.5 to 1 times, preferably about 0.6 to 0.8 times the deposition time of the layer serving as the impurity diffusion source. Specifically, for 15 to 90 minutes,
Preferably about 15 to 40 minutes, more preferably 15 to
Although about 25 minutes can be mentioned, it is preferable to carry out at a temperature similar to that for depositing a layer serving as an impurity diffusion source on the surface of the semiconductor substrate. In the present invention, after the above steps,
At a similar temperature or by gradually lowering the temperature, a layer serving as an impurity diffusion source deposited on the surface of the semiconductor substrate is removed under an atmosphere of oxygen gas, nitrogen gas and / or an inert gas (preferably under a nitrogen gas atmosphere), and the drive is performed. It is preferable to attach the in.

The method of removing the layer serving as an impurity diffusion source deposited on the surface of the semiconductor substrate is not particularly limited, and a usual method, for example, an appropriate etchant such as an acid, an alkali solution or a mixed solution thereof is used. Wet etching using: gas phase etching, plasma etching,
Dry etching such as RIE etching, sputter etching, ion beam etching, and optical etching can be given.

The drive-in is not particularly limited, and includes a usual method, for example, a heat treatment in an oxygen gas atmosphere. The conditions of the heat treatment can be appropriately adjusted depending on the type of the impurity, the depth of the impurity diffusion layer, the amount of the introduced impurity, and the like. For example, furnace annealing using a diffusion furnace, rapid heat treatment using a lamp annealing apparatus, or the like may be performed at a temperature range of about 1000 to 1200 ° C. for about 30 to 150 minutes. Hereinafter, embodiments of the method of manufacturing a semiconductor device according to the present invention will be specifically described.

Embodiment 1 First, when POCl ₃ is used as an impurity source, FIG.
As shown in (a), a silicon substrate is placed in a heat treatment furnace, and nitrogen gas and oxygen gas are respectively placed in the treatment furnace.
While introducing at about 10 slm and about 500 sccm,
The temperature in the processing furnace is raised to 850 ° C. (Step 2: temperature raising step), and the temperature in the furnace is stabilized by maintaining the temperature at 850 ° C. for about 10 minutes (Step 3: furnace temperature stabilizing step). Subsequently, as pre-deposition, POCl ₃ was placed in the furnace at 850 ° C.
A gas is introduced at a rate of about 150 mg / min for 40 minutes (step 4: impurity source introduction step). During this time, nitrogen gas and oxygen gas are also continuously introduced. This allows P on the silicon substrate
As the SG layer is formed, phosphorus is introduced into the silicon substrate.

With the PSG layer formed on the silicon substrate, heat treatment is performed for 45 minutes under the same conditions as in the previous step except that the introduction of the POCl ₃ gas is stopped to stabilize the film quality of the PSG layer (step 5: Stabilization step). Subsequently, the temperature in the processing furnace is gradually lowered to about 800 ° C. (Step 6: temperature lowering step), and then the PSG formed on the silicon substrate is cooled.
The layer is removed, the silicon substrate surface is covered with a silicon oxide film, and as a drive-in, to electrically activate phosphorus as an impurity introduced to the silicon substrate surface and diffuse phosphorus into a wider area. Then, the silicon substrate is heat-treated at 900 ° C. The impurity concentration on the surface of the obtained silicon substrate is 5.0 to 6.0 × 10
¹⁹ cm ^-3 and the depth of the diffusion layer is 1.059 μm
Met.

As described above, the phosphorus-diffused silicon substrate had a sheet resistance of about 30 Ω / □. Even if the above method was repeated for one month, no change in the sheet resistance of the obtained phosphorus-diffused silicon substrate was observed. In addition, as a comparative example, as shown in FIG. 1B, a stabilizing step 5 was performed for 5 minutes to diffuse phosphorus into the silicon substrate. Subsequently, drive-in was performed as described above. The impurity concentration on the surface of the obtained silicon substrate was almost unchanged at 5.0 to 6.0 × 10 ¹⁹ cm ⁻³ , but the depth of the diffusion layer was as shallow as 0.98 μm. The sheet resistance of the silicon substrate in this case was about 40Ω / □. In the method of the present invention as described above, the reason why the sheet resistance was lowered was that the stabilization step was performed for 45 minutes.
This is because the heat treatment progressed more than 5 minutes.

Embodiment 2 When BBr ₃ is used as an impurity source, as shown in FIG. 2A, a silicon substrate is placed in a heat treatment furnace, and nitrogen gas and oxygen gas are respectively placed in the treatment furnace. The temperature inside the processing furnace is raised to 1000 ° C. while introducing the solution at about 5 slm and about 20 sccm (step 2: heating step),
C. for about 10 minutes to stabilize the furnace temperature (step 3: furnace temperature stabilization step). Subsequently, as pre-deposition, 100 mL of BBr ₃ gas was introduced into the furnace at 1000 ° C.
It is introduced at about mg / min for 30 minutes (step 4: impurity source introducing step). During this time, nitrogen gas and oxygen gas are also continuously introduced. Thereby, a BSG layer is formed on the silicon substrate, and boron is introduced into the silicon substrate.

With the BSG layer formed on the silicon substrate, heat treatment is performed for 55 minutes under the same conditions as in the previous step except that the introduction of the BBr ₃ gas is stopped to stabilize the film quality of the BSG layer (step 5: Stabilization step). Next, it was oxidized at 1000 ° C. in a 100% oxygen atmosphere (Step 7: oxidation step). Subsequently, drive-in was performed as in the first embodiment.

In addition, apart from the above steps, as a comparative example,
As shown in FIG. 2B, drive-in was performed without performing the oxidation step in Step 7. In the embodiment of the present invention, the releasability was good due to the uniformization of the film quality of the BSG layer by the oxidation step.

[0025]

According to the present invention, an impurity is introduced into a semiconductor substrate while depositing a layer serving as an impurity diffusion source on the surface of the semiconductor substrate, and then the film quality of the deposited impurity diffusion source layer is stabilized. Since the heat treatment is performed for a sufficient time, it is possible to stabilize the film quality of the layer serving as the impurity diffusion source after the deposition, thereby suppressing the variation in the introduction of the impurity into the semiconductor substrate and achieving a uniform impurity. A diffusion layer can be formed. In addition, due to the stabilization of the film quality of a layer serving as an impurity diffusion source, it is possible to improve the peelability of such a layer thereafter, prevent a contact failure and the like, and manufacture a highly reliable semiconductor device. Becomes possible. In addition, in the case where the deposition of a layer serving as an impurity diffusion source on the surface of a semiconductor substrate and the heat treatment of the deposited layer serving as an impurity diffusion source are performed at the same temperature, the temperature can be easily increased without performing strict temperature control. A semiconductor device with high quality and high reliability can be manufactured.

In particular, the layer serving as the impurity diffusion source is a layer containing phosphorus or boron, and
In the case where the heat treatment is performed at 00 to 1100 ° C. for 40 to 60 minutes, variation in the introduction of impurities into the semiconductor substrate can be further suppressed, and the releasability can be improved. Further, when the heat treatment is performed in an atmosphere containing only oxygen gas, it is particularly advantageous when the layer to be the impurity diffusion layer is a layer containing boron.

[Brief description of the drawings]

FIG. 1 shows a method of manufacturing a semiconductor device according to the present invention;
is a diagram showing the heat treatment profile in Comparative Example and the heat treatment profile obtained by using the l _3.

FIG. 2 illustrates a method of manufacturing a semiconductor device according to the present invention.
FIG. 3 is a diagram showing a heat treatment profile when No. ₃ is used and a heat treatment profile in a comparative example.

Claims (4)

[Claims] An impurity is introduced into a semiconductor substrate while depositing a layer serving as an impurity diffusion source on the surface of the semiconductor substrate.
A method for manufacturing a semiconductor device, comprising: performing a heat treatment for a time sufficient to stabilize the film quality of a deposited impurity diffusion source layer. 2. The method according to claim 1, wherein the deposition of the impurity diffusion source layer on the surface of the semiconductor substrate and the heat treatment of the deposited impurity diffusion source layer are performed at the same temperature. 3. A layer serving as an impurity diffusion source is a layer containing phosphorus or boron.
The method according to claim 1 or 2, comprising heat-treating at 1100 ° C. for 40 to 60 minutes. 4. The method according to claim 1, further comprising heat-treating in an atmosphere containing only oxygen gas.
The method described in one.