CN100452288C

CN100452288C - Method for removing cobalt contaminant on back side of silicon piece by wet method

Info

Publication number: CN100452288C
Application number: CNB2005101110404A
Authority: CN
Inventors: 刘须电; 仓凌盛
Original assignee: Shanghai Hua Hong NEC Electronics Co Ltd
Current assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corp
Priority date: 2005-12-01
Filing date: 2005-12-01
Publication date: 2009-01-14
Anticipated expiration: 2025-12-01
Also published as: CN1979761A

Abstract

The invention makes public a kind of eliminating the Co contamination from the back of silicon by wetting method, which is to use the mixed acid to clean the Co contamination from the back of silicon by rotating the etching device on the back, including the following procedures: Firstly, use the mixed acid solution to treat it 5~10 seconds, the temperature of the solution should be between 25~35DEG C; Secondly, wash it by deion water; thirdly, N2 dry. The method can eliminate the Co contamination from the back of the silicon quickly and efficiently, can reduce the metal contamination level of the back of silicon to 0.02*1010atoms/cm2 or below from 3000*1010atoms/cm2 or above, avoid the technical production line from being contaminated by metal Co, additionally the method has no effect to the front of the silicon.

Description

Wet method is removed the method for cobalt contaminant on back side of silicon piece

Technical field

The present invention relates to a kind of process of integrated circuit, be specifically related to a kind of wet method and remove the method that silicon chip back side cobalt (Co) stains.

Background technology

In the integrated circuit manufacturing process, adopt self-aligned metal silicate (Salicide) to reduce the contact resistance of polysilicon gate square resistance and source-drain area usually, thereby reduce power consumption and RC time delay.In the technology more than 0.25 micron, use titanium silicide (TiSi usually ₂) being used as self-aligned metal silicate (Salicide), its resistivity is about 10-16u Ω cm.But at 0.25um and following 0.18um, in the technological process of 0.15um and 0.13um, the dimension of picture of grid can become and compare TiSi ₂Crystallite dimension also little, TiSi ₂(C-54 structure) is difficult in the less zone of live width form.Therefore titanium silicide technology must be replaced by another kind of metal silicide-cobalt silicide.

Cobalt silicide (CoSi ₂) forming process: layer of metal cobalt (Co) film is by the surface of sputtering technology (Sputtering Process) at silicon chip, in source/drain region and the silicon at polysilicon gate top all contact with cobalt (Co), and all oxidized silicon fiml of other local silicon and cobalt (Co) is isolated.Carry out the rapid thermal treatment first time (RTP 1) then, chemical reaction at high temperature all takes place with cobalt (Co) and forms cobalt silicide-CoSi, the about 60u Ω of the resistivity of CoSi cm in the silicon at source/drain region and polysilicon gate top.Chemical reaction does not take place owing to stopping of silicon oxide film in other regional Co, and this part unreacted cobalt (Co) is used hydrochloric acid (HCl) and hydrogen peroxide (H in wet-etching technology ₂O ₂) admixing medical solutions or sulfuric acid (H ₂SO ₄) and hydrogen peroxide (H ₂O ₂) remove.And then carry out the rapid thermal treatment second time (RTP 2), form CoSi ₂, the about 10-16u Ω of its resistivity cm.

Because metallic cobalt (Co) is active higher, if metallic cobalt (Co) ion enters silicon oxide film, can cause the oxide-film puncture voltage to reduce, in the sputter procedure and residue cobalt (Co) wet-etching technology of metallic cobalt (Co), silicon chip back side portion is stained with cobalt (Co) impurity inevitably, if the cobalt at the silicon chip back side (Co) stains and remains in the subsequent technique process always, will cause intersection cobalt (Co) heavy metal pollution of equipment and other silicon chip.Especially require the highest gate oxide (Gate Oxide), slight beavy metal impurity all can cause coating mass to descend, the threshold voltage drift, even cause oxide-film to puncture, thus entire device was lost efficacy.In order to prevent cobalt pollution, before after silicide forms, entering miscellaneous equipment and handling, must be earlier with back side cobalt Ex-all.

Summary of the invention

The technical problem to be solved in the present invention provides the method that a kind of wet method is removed cobalt contaminant on back side of silicon piece, the cobalt that this method can be removed the silicon chip back side quickly and efficiently stains, avoid causing the metallic cobalt of production line to pollute, and this method is to the positive nothing influence of silicon chip.

For solving the problems of the technologies described above, a kind of wet method of the present invention is removed the method for cobalt contaminant on back side of silicon piece, and it uses nitration mixture to carry out cobalt contaminant on back side of silicon piece on rotation etching device overleaf and cleans, comprise the steps: the first step, the nitration mixture soup is handled 5-10 second, and fluid temperature is 25-35 ℃; In second step, wash with deionized water; The 3rd step, N ₂Dry.

Described nitration mixture is HNO ₃, H ₂SO ₄, H ₃PO ₄And HF.

The rotary speed of the first step is 1400-1600 rev/min, medicinal liquid flow be the 1-2 liter/minute.

The washing time in second step is 30-60 second, and rotary speed is 400-600 rev/min, and de-ionized water flow rate is 2 liters/minute.

Be 10-20 second the drying time in the 3rd step, and rotary speed is 1900-2100 rev/min, N ₂Flow be the 250-300 liter/minute.

The present invention uses nitration mixture (component: HNO on the rotation etching equipment overleaf ₃, H ₂SO ₄, H ₃PO ₄, HF) carry out back side cobalt (Co) and clean.It utilizes nitration mixture and metallic cobalt, and silicon and silicon nitride reaction are realized the purpose that back side cobalt is cleaned.This nitration mixture to the etch rate of cobalt is

Etch rate to silicon is 6-10um/min, to the etch rate of silicon nitride is

Wherein,

Rice.

Compare with prior art, the present invention has following beneficial effect: by the wet method of removing cobalt contaminant on back side of silicon piece of sending out provided by the invention, to the silicon chip of back metal cobalt contamination (back side state is POLY SILICON (polysilicon) or SILICON NITRIDE (silicon nitride)), can be with 3000 * 10 ¹⁰Atoms/cm ²The cobalt of level stains and is reduced to 0.02 * 10 ¹⁰Atoms/cm ²Below horizontal, reach the requirement that semiconductor is made.The silicon chip that this method is stain by metallic cobalt the back side has good clean efficient, can be widely used in integrated circuit and make the field.In addition, employed device of this method and soup all are semiconductor manufacturing industry equipment and chemicals commonly used, do not need special equipment or chemicals, are applicable to the needs of large-scale production.

Embodiment

The present invention is further detailed explanation below in conjunction with embodiment.

Embodiment 1

1. use equipment: the back side rotation etching device that SEZ company produces, model: FM203

2. chemical liquid: nitration mixture (N-D, component: 40wt%HNO ₃, 10wt%H ₂SO ₄, 20wt%H ₃PO ₄, 5wt%HF)

3. processing silicon chip

The back side is membranous: Poly Silicon (polysilicon) and Silicon Nitride (silicon nitride)

Contamination level: greater than 3000 * 10 ¹⁰At oms/cm ²

4. assay method: TXRF (total reflection fluorescence analyser)

5. treatment step

The first step: soup is handled

Nitration mixture (N-D) soup was handled 5 seconds, 30 ℃ of fluid temperature, 1500 rev/mins of rotary speeies, 1.5 liters/minute of medicinal liquid flows;

Second step: washing

Deionized water (DIW) was handled 45 seconds, 500 rev/mins of rotary speeies, 2 liters/minute of DIW flows;

The 3rd step: drying

Dry 15 seconds of N2,2000 rev/mins of rotary speeies, 300 liters/minute of N2 flows.

6. result

After the processing, the silicon chip back metal contamination level of two kinds of back side states (polysilicon and silicon nitride) is reduced to 0.02 * 10 ¹⁰Atoms/cm ²Below.

Embodiment 2

Use equipment, chemical liquid, processing silicon chip, assay method and result are with embodiment 1.

Treatment step is as follows:

The first step: soup is handled

Nitration mixture (N-D) soup was handled 10 seconds, 25 ℃ of fluid temperature, 1400 rev/mins of rotary speeies, 1 liter/minute of medicinal liquid flow;

Second step: washing

Deionized water (DIW) was handled 30 seconds, 400 rev/mins of rotary speeies, 2 liters/minute of DIW flows;

The 3rd step: drying

Dry 10 seconds of N2,1900 rev/mins of rotary speeies, 250 liters/minute of N2 flows.

Embodiment 3

Use equipment, chemical liquid, processing silicon chip, assay method and result are with embodiment 1.Treatment step is as follows:

The first step: soup is handled

Nitration mixture (N-D) soup was handled 7 seconds, 35 ℃ of fluid temperature, 1600 rev/mins of rotary speeies, 2 liters/minute of medicinal liquid flows;

Second step: washing

Deionized water (DIW) was handled 60 seconds, 600 rev/mins of rotary speeies, 2 liters/minute of DIW flows;

The 3rd step: drying

Dry 20 seconds of N2,2100 rev/mins of rotary speeies, 270 liters/minute of N2 flows.

Claims

1, a kind of wet method is removed the method for cobalt contaminant on back side of silicon piece, it is characterized in that, uses nitration mixture to carry out cobalt contaminant on back side of silicon piece overleaf on the rotation etching device and cleans, comprise the steps: the first step, the nitration mixture soup is handled 5-10 second, and fluid temperature is 25-35 ℃, and described nitration mixture is HNO ₃, H ₂SO ₄, H ₃PO ₄And HF; In second step, wash with deionized water; The 3rd step, N ₂Dry;

Wherein, the rotary speed of the first step is 1400-1600 rev/min, medicinal liquid flow be the 1-2 liter/minute; The washing time in second step is 30-60 second, and rotary speed is 400-600 rev/min, and de-ionized water flow rate is 2 liters/minute; Be 10-20 second the drying time in the 3rd step, and rotary speed is 1900-2100 rev/min, N ₂Flow be the 250-300 liter/minute.